| seasonal variations in the renal cortical (na+ + k+)-atpase and mg2+-atpase of a hibernator, the ground squirrel (spermophilus richardsonii). | 1. the specific activity of renal cortical (na+ + k+)-atpase of the richardson ground squirrel is markedly reduced during hibernation, in contrast to the specific activity of the accompanying mg2+-atpase which is markedly increased. 2. the sensitivity of (na+ + k+)-atpase to inhibition by ouabain is unchanged by hibernation. 3. both the non-linear thermal dependence of (na+ + k+)-atpase and the linear thermal dependence of mg2+-atpase are also unchanged by hibernation. 4. the energy of activatio ... | 1978 | 233796 |
| serum t4 and t3 in active and torpid ground squirrels, spermophilus richardsoni. | | 1978 | 566236 |
| intranasal exposure of the richardson's ground squirrel to western equine encephalomyelitis virus. | adult richardson's ground squirrels were infected with western equine encephalomyelitis virus by intranasal instillation. mortality followed the instillation of a minimum threshold of 4.7 logs of virus while infection was produced by a dosage of 2.3 logs. the incubation period was from four to seven days, being preceded by a viremic phase. signs were depression, ataxia and paralysis of the limbs. highest titres of virus were recovered from the brain and histopathological changes involving the ce ... | 1978 | 667706 |
| subcutaneous exposure of the richardson's ground squirrel (spermophilus richardsonii sabine) to western equine encephalomyelitis virus. | both adult and suckling richardson's ground squirrels (spermophilus richardsonii) were susceptible to subcutaneous exposure with western equine encephalomyelitis (wee) virus, but the virus was more virulent for sucklings than adults. in sucklings, the incubation period was from 4 to 5 days, followed by apparent signs of central nervous system (cns) involvement. death occurred 10 to 13 days postexposure. in adults, infections were inapparent or acute with typical signs of cns involvement similar ... | 1976 | 933316 |
| reproduction, structure and host specificity of trypanosoma (herpetosoms) tamiasi sp. n. from the eastern chipmunk, tamias striatus. | trypanosoma (herpetosoma) tamiasi sp. n. is described from blood and organs of the eastern chipmunk, tamias striatus, and the least chipmunk, eutamias minimus. in experimentally infected tamias striatus and e. minimus, trypanosoma tamiasi reproduced by equal binary fission in the trypo-, sphaero-, epi-, or amastigote form, mainly in lymphoid organs. trypomastigotes developed from amastigotes through epimastigotes, or from sphaeromastigotes, mainly in the same organs. the mean lengths of body ... | 1975 | 1117439 |
| natural infections of richardson's ground squirrels with western equine encephalomyelitis virus, saskatchewan, canada, 1964-1973. | a survey (1964-1973) was conducted on naturally occurring western equine encephalomyelitis (wee) virus infections of richardson's ground squirrels (rgs) in agricultural areas of saskatchewan. the survey included both serology and virus isolation attempts on live-trapped wild squirrels. throughout the study, seropostive squirrels were found in the known enzootic regions of the province each summer. the infections rate was high (11.6% of 250) in the epidemic year of 1965 and low (less than 2% o ... | 1975 | 1148947 |
| prolonged stable hypothermia: effect on blood gases and ph in rats and ground squirrels. | richardson's ground squirrels [body temperature (tb) 7 degrees c] survive prolonged stable hypothermia for three times as long as do rats (tb 19 degrees c) (72 vs. 24 h). we have examined the changes in blood gases and acid-base state to assess whether these contribute to this difference in survival time. none of the variables (measured at ambient temperature of 25 degrees c) differed significantly between rats and ground squirrels before hypothermic induction. during cooling, neither hematocrit ... | 1992 | 1539726 |
| temperature dependence of electrophysiological properties of guinea pig and ground squirrel myocytes. | the effects of changing temperature on the electrophysiology of isolated cardiac myocytes of the guinea pig and richardson's ground squirrel were studied by patch-clamp techniques. in cells from both species, the resting membrane potential declined on cooling from 36 to 12 degrees c by approximately 6 mv. the duration of the plateau of the action potential in guinea pig cells increased monotonically on cooling. in contrast, the action potential of ground squirrel cells showed a biphasic response ... | 1992 | 1636784 |
| smooth muscle contractility and calcium channel density in hibernating and nonhibernating animals. | hibernating animals consistently survive prolonged periods of cold with body temperatures near the freezing point. previous studies have suggested that regulation of calcium influx may be a fundamental cellular mechanism for cold tolerance in hibernating species. the present study was undertaken to compare (i) the calcium dependence of contractility and (ii) [3h]nitrendipine binding in homogenates of ileal longitudinal smooth muscle from the nonhibernating guinea pig (cavia porcellus) and a hibe ... | 1990 | 2158386 |
| rapid quantitation of uncoupling protein in brown adipose tissue mitochondria by a dot immunobinding ("dot blot") procedure: application to the measurement of uncoupling protein in richardson's ground squirrel, rats, and mice. | a dot immunobinding ("dot blot") method for measuring uncoupling protein in brown adipose tissue mitochondria is described. mitochondrial proteins were solubilized in sodium dodecyl sulfate and applied directly to a nitrocellulose membrane housed in a 96-well microfiltration manifold. spare binding sites on the nitrocellulose membrane were blocked with bovine serum albumin and then anti-(uncoupling protein) serum was applied. the antigen-antibody complex was detected by the addition of 125i-labe ... | 1990 | 2397100 |
| evidence from immunoblotting studies on uncoupling protein that brown adipose tissue is not present in the domestic pig. | adipose tissues and other tissues of the pig have been examined for the presence of the mitochondrial "uncoupling protein," characteristic of brown adipose tissue, in order to assess whether brown fat is present in this species. mitochondria were prepared from various tissues and the proteins separated on the basis of molecular weight by sodium dodecyl sulphate--polyacrylamide gel electrophoresis. immunoblotting procedures were then used to probe for uncoupling protein, employing a rabbit anti-( ... | 1989 | 2627687 |
| gangrenous dermatitis caused by corynebacterium ulcerans in richardson ground squirrels. | gangrenous dermatitis caused by corynebacterium ulcerans developed in 63 of 350 wild richardson ground squirrels (spermophilus richardsonii). six squirrels died of toxemia and/or septicemia, but 57 responded to topical and parenteral administration of antibiotics. the epizo-otic was believed to be associated with fighting; infected and carrier ground squirrels most likely transmitted the c ulcerans through bite wounds. individuals handling ground squirrels should be cautioned that c ulcerans may ... | 1988 | 3182392 |
| melatonin synthesis in the pineal gland of the richardson's ground squirrel (spermophilus richardsonii): influence of age and insulin-induced hypoglycemia. | the nocturnal rises in pineal n-acetyltransferase (nat) activity and melatonin levels were compared in young (25-35 days old) and adult (at least 1 year old) richardson's ground squirrels. when expressed as nat activity per pineal gland, the nighttime rise in the activity of this enzyme was less in young than in the adult animals; conversely, the melatonin content of the pineal glands of young animals was higher at one point (4 a.m., 8 hours after darkness onset) when compared to that in adult s ... | 1987 | 3312493 |
| characterization of lipid accumulation in the gallbladder mucosa of the ground squirrel fed a lithogenic diet. | richardson's ground squirrels (spermophilus richardsonii) of both sexes were fed a 2 per cent cholesterol-enriched diet for intervals of 12, 18, and 24 h; 3, 5, and 7 days; and 2, 3, 10, and 20 weeks. it was shown that free (unesterified) cholesterol, phospholipid, and cholesterol ester accumulated in specific regions of the gallbladder mucosa during cholelithiasis. electron microscopy revealed the presence of lipids inter- and intracellularly as early as 12 h after ingestion. by 7 days, lipids ... | 1988 | 3351664 |
| thyroid hormone resistance in hibernating ground squirrels, spermophilus richardsoni. i. increased binding of triiodo-l-thyronine and l-thyroxine by serum proteins. | thyroid function was examined during the annual cycle of richardson's ground squirrel, spermophilus richardsoni. a number of facets were measured to facilitate comparison of thyroid function in active, dormant, and aroused animals. this report discusses changes in the serum thyroid hormone and binding as assessed by radioimmunoassay, equilibrium dialysis, and competitive binding assays. during the hibernation phase (both dormant and aroused), total serum t3 (trioodo-l-thyronine) and t4 (l-thyrox ... | 1988 | 3360293 |
| thyroxine 5'-deiodination in brown adipose tissue and pineal gland: implications for thermogenic regulation and role of melatonin. | t4 type ii 5'-deiodinase (5'-d ii) activity was studied in wild-captured richardson's ground squirrels. as previously reported for other species, 5'-d ii activity was detected in frontal cortex, cerebellum, pineal gland, and brown adipose tissue (bat); in the median eminence the levels of 5'-d ii activity were undetectable with our methodology. when pineal gland, frontal cortex, and cerebellum nyctohemeral profiles were studied, none of them showed variations. cold exposure for 4 h led to an inc ... | 1988 | 3396504 |
| morphological observations on the gallbladder of ground squirrels fed a lithogenic diet. | richardson's ground squirrels (spermophilus richardsonii) of both sexes were fed a 2 per cent cholesterol-enriched rat chow diet for intervals of 1, 2, 10 and 20 weeks. light microscopy and 3h-thymidine autoradiography revealed an increase in cell proliferation prior to the occurrence of macroscopically visible stones, but in the presence of crystals and microliths. transmission electron microscopy studies showed that columnar epithelial cells undergo mitosis rather than basal cells and that oed ... | 1987 | 3625395 |
| ultrastructural observations on the gallbladder of richardson's ground squirrel (spermophilus richardsonii). | the gallbladder of richardson's ground squirrel shares many structural similarities with numerous other species, including the mouse, rabbit and man. dark cells exhibit a condensed cytoplasm but contain all the typical organelles of light cells, although their total complement appears reduced. edematous cells extruded from the epithelial lining were replaced through mitosis or had their space occupied by adjacent cells. specializations of the basal plasma membrane and underlying basal lamina for ... | 1987 | 3661109 |
| resistance to adipocyte hyperplasia in ground squirrels given high-fat diets. | mammalian hibernators prepare for the winter by depositing fat in existing fat cells. there is little, if any, production of new fat cells. this is curious because equivalent fat deposition in rats is associated with substantial fat cell production. to determine whether degree of weight gain, diet composition, or some special mechanism militating against adipocyte hyperplasia may underlie the absence of adipocyte hyperplasia in hibernators, male richardson's ground squirrels, spermophilus richar ... | 1987 | 3661751 |
| experimental cholelithiasis in the ground squirrel. | richardson's ground squirrels of both sexes were fed a 2% cholesterol-enriched rat chow diet for various intervals from 6 hours through 20 weeks. bile was withdrawn from the organs and analyzed biochemically to obtain a lithogenic index. the remaining luminal contents were rinsed from the resected organs and examined by light and scanning electron microscopy. gallbladder tissue was fixed and examined in a similar fashion to observe the luminal aspect of the epithelial sheet. scanning electron mi ... | 1987 | 3807311 |
| experimental colorado tick fever virus infection in colorado mammals. | one hundred and twenty-four small mammals of six species were inoculated with three strains of colorado tick fever (ctf) virus to define viremia and neutralizing (n) antibody responses. adult eutamias minimus and eutamias embrinus, and juvenile peromyscus maniculatus and spermophilus lateralis, were highly susceptible to development of viremic infection. adult s. lateralis and p. maniculatus were moderately susceptible (greater than or equal to 50% viremic). five sylvilagus nuttalli did not beco ... | 1981 | 6259958 |
| the ecology of colorado tick fever in rocky mountain national park in 1974. ii. infection in small mammals. | field studies of colorado tick fever (ctf) in small mammals in rocky mountain national park (rmnp) in 1974 established that eutamias minimus and spermophilus lateralis were the most important hosts for ctf virus and were the source of virus for immature stages of the tick vector, dermacentor andersoni. other species (peromyscus maniculatus, spermophilus richardsonii, eutamias umbrinus) are secondary hosts. the intensity of viral activity in rodents varied greatly from locality to locality. highe ... | 1981 | 6263122 |
| changes in serotonin levels, n-acetyltransferase activity, hydroxyindole-o-methyltransferase activity, and melatonin levels in the pineal gland of the richardson's ground squirrel in relation to the light-dark cycle. | pineal serotonin and melatonin levels and the activities of hydroxyindole-o-methyltransferase (hiomt) and n-acetyltransferase (nat) were studied over a 24-hour period in the pineal gland of the diurnally active richardson's ground squirrel (spermophilus richardsonii). under alternating light-dark conditions (light:dark hours 14:10), pineal serotonin and melatonin levels exhibited a rhythm with high values occurring either during the day (serotonin) or during the night (melatonin). nat activity w ... | 1984 | 6493447 |
| influence of light irradiance on hydroxyindole-o-methyltransferase activity, serotonin-n-acetyltransferase activity, and radioimmunoassayable melatonin levels in the pineal gland of the diurnally active richardson's ground squirrel. | when richardson's ground squirrels were kept under light:dark cycles of 14:10 h there was no nocturnal rise in pineal hydroxyindole-o-methyltransferase (hiomt) activity. conversely, the 10 h dark period was associated with large nocturnal rises in both pineal serotonin-n-acetyltransferase (nat) activity and radioimmunoassayable melatonin levels. the nighttime rises in pineal nat and melatonin were not suppressed by the exposure of the animals to a light irradiance of 925 mu w/cm2 during the norm ... | 1983 | 6686468 |
| the neuroendocrine system in hibernating mammals: present knowledge and open questions. | the present review describes the distribution and the function-dependent reactivity pattern of those peptidergic and aminergic components of the neuroendocrine system of hibernating mammals that have been studied by histological, pharmacological and physiological techniques. particular attention has been paid to the intrinsic connectivity of the peptidergic apparatus and its input systems. since the reactivity patterns of the neuroendocrine system show remarkable fluctuations in relation to the ... | 1995 | 7553762 |
| effects of hypothermia on energy metabolism in rat and richardson's ground squirrel hearts. | glycolysis, glucose oxidation, palmitate oxidation, and cardiac function were measured in isolated working hearts from ground squirrels and rats subjected to a hypothermia-rewarming protocol. hearts were perfused initially for 30 min at 37 degrees c, followed by 2 h of hypothermic perfusion at 15 degrees c, after which hearts were rewarmed to 37 degrees c and further perfused for 30 min. functional recovery in ground squirrel hearts was greater than in rat hearts after rewarming. hypothermia-rew ... | 1997 | 9104858 |
| ca2+ uptake by cardiac sarcoplasmic reticulum at low temperature in rat and ground squirrel. | the ca2+ uptake by isolated cardiac sarcoplasmic reticulum (sr) was compared between richardson's ground squirrels and rats at 37, 25, 15, and 5 degrees c. the rate of sr ca2+ uptake in ground squirrels was significantly higher than in rats over the temperature range. this marked species difference was observed over a ca2+ concentration range from 0.1 to 10 microm. the arrhenius plot for ca2+ uptake was linear for ground squirrels between 37 and 5 degrees c but showed a depression from linearity ... | 1997 | 9140010 |
| camp-dependent protein kinase from brown adipose tissue: temperature effects on kinetic properties and enzyme role in hibernating ground squirrels. | arousal from hibernation requires thermogenesis in brown adipose tissue, a process that is stimulated by beta-adrenergic signals, leading to a rise in intracellular 3',5'-cyclic adenosine monophosphate amp (camp) and activating camp-dependent protein kinase a (pka) to phosphorylate a suite of target proteins and activate lipolysis and uncoupled respiration. to determine whether specific adaptations (perhaps temperature-dependent) facilitate pka kinetic properties or protein-phosphorylating abili ... | 1998 | 9810716 |
| evidence for rodent-common and species-typical limb and digit use in eating, derived from a comparative analysis of ten rodent species. | order rodentia comprises a vast portion of mammalian species (1814 species), which occupy extremely diverse habitats requiring very distinct motor specializations (e.g. burrowing, hopping, climbing, flying and swimming). although early classification of paw use ability suggests rodents are impoverished relative to primates and make little use of their paws, there have been no systematic investigations of paw use in rodents. the present study was undertaken to describe limb/paw movements in a var ... | 1998 | 9821545 |
| comparisons of the effects of temperature on the liver fatty acid binding proteins from hibernator and nonhibernator mammals. | hibernating mammals rely heavily on lipid metabolism to supply energy during hibernation. we wondered if the fatty acid binding protein from a hibernator responded to temperature differently than that from a nonhibernator. we found that the kd for oleate of the liver fatty acid binding protein (1.5 microm) isolated from ground squirrel (spermophilus richardsonii) was temperature insensitive over 5-37 degrees c, while the rat liver fatty acid binding protein was affected with the kd at 37 degrees ... | 1998 | 10099779 |
| glutamate dehydrogenase from liver of euthermic and hibernating richardson's ground squirrels: evidence for two distinct enzyme forms. | glutamate dehydrogenase (gdh) was purified to homogeneity from the liver of euthermic (37 degrees c body temperature) and hibernating (torpid, 5 degrees c body temperature) richardson's ground squirrels (spermophilus richardsonii). sds-page yielded a subunit molecular weight of 59.5+/-2 kda for both enzymes, but reverse phase and size exclusion hplc showed native molecular weights of 335+/-5 kda for euthermic and 320+/-5 kda for hibernator gdh. euthermic and hibernator gdh differed substantially ... | 2001 | 11235914 |
| experimental infection of nontarget species of rodents and birds with brucella abortus strain rb51 vaccine. | the brucella abortus vaccine strain rb51 (srb51) is being considered for use in the management of bnucellosis in wild bison (bison bison) and elk (cervus elaphus) populations in the greater yellowstone area (usa). evaluation of the vaccines safety in non-target species was considered necessary prior to field use. between june 1998 and december 1999, ground squirrels (spermophilus richardsonii, n = 21), deer mice (peromyscus maniculatus, n = 14), prairie voles (microtus ochrogaster, n = 21), and ... | 2001 | 11504226 |
| mammalian hibernation: lessons for organ preparation? | the adaptations to low environmental temperatures exhibited in mammalian hibernation are many and varied, and involve molecular and cellular mechanisms as well as the systematic physiology of the whole organism. natural torpidity is characterised by a profound reduction in body temperature and other functions lasting from a few hours to several weeks. controlled reduction of heart rate, respiration and oxygen consumption is followed by the fall in body temperature. however, thermoregulation pers ... | 2000 | 12148053 |
| rodent-associated bartonella in saskatchewan, canada. | six species of wild rodents were sampled at 10 sites in 2002 and 2003 to determine the prevalence of bartonella infections in rodent communities near saskatoon, saskatchewan, canada. isolates were characterized genotypically and compared with isolates found at other locations. of 104 wild rodents examined, 57% were infected with bartonella and prevalence within species varied from 49% for richardson's ground squirrels (spermophilus richardsonii) to 90% for franklin's ground squirrels (s. frankli ... | 2005 | 16417436 |
| diversity of bartonella genotypes in richardson's ground squirrel populations. | the diversity and dynamics of bartonella genotypes found in wild richardson's ground squirrels (rgs), spermophilus richardsonii were monitored at multiple sites in saskatchewan, canada from 2002 to 2004. based on sequence analysis of a portion of the bartonella citrate synthase (glta) gene, four different genotypes were detected in 233 isolates from 176 animals. the majority (87%) of sequences were identified as genotype h, with genotypes i, j, and k accounting for 8%, 4%, and 1% of sequences, r ... | 2006 | 17187575 |
| demographic features of bartonella infections in richardson's ground squirrels (spermophilus richardsonii). | the epidemiology of bartonella infections in richardson's ground squirrels (spermophilus richardsonii) was studied at multiple sites in saskatchewan, canada, from 2002 to 2004. the overall prevalence of bartonella infection was 48%. juvenile squirrels were significantly more likely to be infected with bartonella than were adults (58% and 37%, respectively), and juvenile animals also were significantly more likely to have high levels of bacteremia compared to adult animals. prevalence of bartonel ... | 2006 | 17255440 |
| effect of experimental ectoparasite control on bartonella infections in wild richardson's ground squirrels. | the purpose of this study was to investigate the role of ectoparasites in transmitting bartonella infections in wild richardson's ground squirrels (spermophilus richardsonii). richardson's ground squirrels were trapped, examined for fleas, and tested for bartonella bacteremia once monthly, at six sites, from april to september 2004. after the initial trapping session in april, burrows at three sites were treated with deltamethrin insecticide. richardson's ground squirrels trapped on treated site ... | 2006 | 17255441 |
| experimental infection of richardson's ground squirrels (spermophilus richardsonii) with attenuated and virulent strains of brucella abortus. | a previous investigation of the safety of brucella abortus strain rb51 (srb51) in various nontarget species suggested that richardson's ground squirrels (spermophilus richardsonii) may develop persistent infections when orally inoculated with the vaccine. in the present study, srb51, b. abortus strain 19 (s19), and virulent b. abortus strain 9941 (s9941) were administered orally to richardson's ground squirrels to further characterize b. abortus infection in this species. six groups of nongravid ... | 2009 | 19204348 |
| lipid synthesis and deposition by adult richardson's ground squirrels in the natural environment. | adult male richardson's ground squirrels, spermophilus richardsonii, were estimated to have emerged from hibernation in late february to early march, and adult females in mid to late march. half of the females trapped in late march were not pregnant, as against 10% after that time. in late march males and all females had similar wat (white adipose tissue) deposits. between late march and early june, wat deposits in males increased from 14 g to 64 g (a rate of 5.6 g per week). in non-parous femal ... | 2011 | 3170826 |
| measurement of free glucocorticoids: quantifying corticosteroid-binding globulin binding affinity and its variation within and among mammalian species. | plasma glucocorticoids (gcs) are commonly used as measures of stress in wildlife. a great deal of evidence indicates that only free gc (gc not bound by the specific binding protein, corticosteroid-binding globulin, cbg) leaves the circulation and exerts biological effects on gc-sensitive tissues. free hormone concentrations are difficult to measure directly, so researchers estimate free gc using two measures: the binding affinity and the binding capacity in plasma. we provide an inexpensive satu ... | 2015 | 27293705 |
| hepatocellular carcinoma in richardson's ground squirrels (spermophilus richardsonii): evidence for association with hepatitis b-like virus infection. | during studies of seasonal obesity, a high frequency of hepatic neoplasms was observed in richardson's ground squirrels. of 12 richardson's ground squirrels examined thoroughly, 7 had mild or moderate degrees of chronic portal hepatitis and 6 (50%) had hepatocellular carcinoma. serological tests for hepadnavirus surface antigen, anti-core antibody and virion dna that recognize the ground squirrel hepatitis virus of california ground squirrels (spermophilus beecheyi) were uniformly negative. sout ... | 1991 | 1646762 |
| ground squirrel hepatitis virus (gshv) infection and hepatocellular carcinoma in the canadian richardson ground squirrel (spermophilus richardsonii). | sera and livers from 40 richardson ground squirrels were examined for evidence of ground squirrel hepatitis virus (gshv) infection and hepatocellular carcinoma. twenty-five sera were obtained from fully grown adult ground squirrels and 15 from young ground squirrels estimated to be between 6-8 weeks of age. all animals had been caught in the wild and had spent less than 1 month in captivity. sixteen sera (40%) had at least one serologic marker of gshv (2 with gshv surface antigen, 3 gshv core an ... | 1986 | 3033421 |
| mutation scanning-based identification of larval and nymphal ticks (acari: ixodidae) from richardson's ground squirrels (spermophilus richardsonii). | the objective of this study was to identify the tick species parasitizing richardson's ground squirrels (spermophilus richardsonii) in southern saskatchewan (canada). morphological examination of the adult ticks revealed the presence of three tick species, ixodes sculptus, ixodes kingi and dermacentor andersoni. however, given the difficulties in identifying some of the larval and nymphal (immature) ticks using this approach, pcr-based single-strand conformation polymorphism (sscp) and dna seque ... | 2014 | 24075866 |
| effects of hibernation on somatostatin-like immunoreactivity in the brain of the ground squirrel (spermophilus richardsonii) and european hedgehog (erinaceus europaeus). | the localization of the somatostatin system in the brains of richardson's ground squirrels (spermophilus richardsonii) and european hedgehogs (erinaceus europaeus) was described by use of immunocytochemical methods. in addition, (i) chemically differing types of somatostatin and (ii) different activity phases of the somatostatin system during the hibernation cycle were investigated in the ground squirrel by means of high pressure liquid chromatography (hplc) and radioimmunoassay (ria). in both s ... | 1986 | 2868793 |
| trypanosoma (herpetosoma) kuseli sp. n. (protozoa: kinetoplastida) in siberian flying squirrels (pteromys volans). | all trypanosome species classified in the subgenus herpetosoma in sciurid hosts have been recorded from ground and tree squirrels to date, but not from any flying squirrels. we describe in this paper a novel trypanosome species, trypanosoma (herpetosoma) kuseli sp. n., from siberian flying squirrels (pteromys volans) imported from china, and compare it with t. (h.) otospermophili in richardson's ground squirrels (spermophilus richardsonii) and columbian ground squirrels (spermophilus columbianus ... | 2007 | 17334786 |
| relative abundance of american badger (taxidea taxus) and red fox (vulpes vulpes) in landscapes with high and low rodenticide poisoning levels. | over the past decade, extensive poisoning campaigns have been conducted in southern saskatchewan to control richardson's ground squirrel spermophilus richardsonii (sabine, 1822) populations. such campaigns might impact on predator abundance by decreasing prey levels, and also through secondary poisoning. using spotlighting, we investigated the relative abundance of american badgers taxidea taxus (schreber, 1777) and red fox vulpes vulpes (linnaeus, 1758) in 2 study areas with road access and cro ... | 2012 | 22405447 |
| a new species of subulura (nematoda: subuluroidea) from ground squirrels, spermophilus spilosoma bennett, 1833, in new mexico. | a description is presented of a new species of subulura molin, 1860, subulura novomexicanus, collected from the spotted ground squirrel, spermophilus spilosoma bennett, 1833, in new mexico. the males are 24 to 29 mm long, precloacal sucker 1.7-2.0 mm from posterior end, spicules subequal 0.83-1.0 long, and gubernaculum y-shaped 0.21-0.39 mm long. females are 34-39 mm long, vulva near middle of body 14.06-22.00 mm from anterior end, and eggs 0.04-0.05 mm long by 0.03-0.04 mm wide. the new species ... | 2007 | 18163357 |
| eimerian guilds (apicomplexa: eimeriidae) in richardson's (spermophilus richardsonii) and wyoming (spermophilus elegans) ground squirrels. | feces of richardson's ground squirrels (spermophilus richardsonii) were examined to determine occurrence and prevalence of eimerian species and to compare guilds in these hosts to previously described guilds from wyoming ground squirrels (spermophilus elegans). six species of eimeria were collected from 100 richardson's ground squirrels: eimeria beecheyi (36% infected); eimeria bilamellata (13%); eimeria callospermophili-eimeria morainensis complex (41%); eimeria lateralis (6%); and eimeria sper ... | 1993 | 8277397 |
| sarcocystis campestris from naturally infected 13-lined ground squirrels, spermophilus tridecemlineatus tridecemlineatus, from nebraska. | grossly visible sarcocysts were seen in the skeletal muscles of 1 of 12 13-lined ground squirrels, spermophilus tridecemlineatus tridecemlineatus, collected in nebraska. the tissue cyst wall was up to 5.0 microm thick and contained spikelike projections. transmission electron microscopy of tissue cysts revealed they were similar to sarcocystis campestris cawthorn, wobeser, and gajadhar, 1983, previously known only from experimental infections in richardson's ground squirrel spermophilus richards ... | 2000 | 11128502 |
| pathology of sarcocystis campestris infection in richardson's ground squirrels (spermophilus richardsoni). | richardson's ground squirrels were infected with 1500 or 9000 sporocysts of sarcocystis campestris from badgers. no lesions were found in animals killed one to three days postinfection (pi). hepatitis and phlebitis of hepatic veins were present in animals killed between four and eight days pi. no meronts were detected in these animals, but the lesions suggested that a generation of merogony occurred in the hepatic veins. meronts were found in endothelial cells in many tissues beginning on day 9 ... | 1983 | 6411306 |
| purification and properties of glycerol-3-phosphate dehydrogenase from the liver of the hibernating ground squirrel, urocitellus richardsonii. | cytosolic glycerol-3-phosphate dehydrogenase (g3pdh, ec 1.1.1.8) is an important branch point enzyme connecting lipid metabolism and carbohydrate metabolism. we investigated the dynamic nature of g3pdh by purifying the enzyme from the liver of richardson's ground squirrel (urocitellus richardsonii), a hibernating species, and analyzing its structural and functional changes during hibernation. kinetic parameters of purified g3pdh from ground squirrel liver were characterized at 37, 22 and 5°c and ... | 2016 | 27521690 |
| one plus one: binary alarm calls retain individual signature for longer periods than single-note alarms in the european ground squirrel (spermophilus citellus). | ground squirrels emit species-specific alarm calls that, among other characteristics, differ by the number of elements. unlike some species that produce single-element calls, e.g., the speckled ground squirrel (spermophilus suslicus), individual european ground squirrels (s. citellus) frequently emit binary-element calls in addition to single-element calls. we tested the hypothesis that the time stability of individuality encoded in alarm calls might be better retained by complicating their acou ... | 2017 | 28219730 |
| day-night differences in the number of pineal "synaptic" ribbons in two diurnal rodents, the chipmunk (tamias striatus) and the ground squirrel (spermophilus richardsonii). | daytime numbers of pineal "synaptic" ribbons higher than reported in the pineal gland of any other mammalian species were observed in two diurnal rodents, the eastern chipmunk and richardson's ground squirrel. the number of "synaptic" ribbons was lower during the daytime and higher at night in both of these species. | 1982 | 6889463 |
| evolutionary relationships among colonies of columbian ground squirrels as shown by mitochondrial dna. | mitochondrial dna (mtdna) from 71 columbian ground squirrels (spermophilus columbianus) collected in 12 locations in western canada were assayed for restriction-site variation with 10 endonucleases. five of these endonucleases revealed variant patterns, and the composite genotypes were used to develop a linear transformation series among the mtdna genotypes. two of the four clones had a wide distribution, while the remaining two clones were geographically restricted. the mtdna of columbian groun ... | 1987 | 28564362 |
| impact of live trapping on stress profiles of richardson's ground squirrel (spermophilus richardsonii). | researching the physiological ecology of natural populations requires an understanding of the impact of capture-induced stress because of its numerous effects on physiological processes. in many cases, initial blood samples to which comparisons are made are obtained well after capture and may differ markedly from free-ranging conditions. we examined the extent to which stress profiles of male richardson's ground squirrels (spermophilus richardsonii) were affected by short-term responses to live ... | 2009 | 19059261 |
| purification and characterization of skeletal muscle pyruvate kinase from the hibernating ground squirrel, urocitellus richardsonii: potential regulation by posttranslational modification during torpor. | ground squirrel torpor during winter hibernation is characterized by numerous physiological and biochemical changes, including alterations to fuel metabolism. during torpor, many tissues switch from carbohydrate to lipid catabolism, often by regulating key enzymes within glycolytic and lipolytic pathways. this study investigates the potential regulation of pyruvate kinase (pk), a key member of the glycolytic pathway, within the skeletal muscle of hibernating ground squirrels. pk was purified fro ... | 2017 | 28918505 |
| the size of non-hippocampal brain regions varies by season and sex in richardson's ground squirrel. | sex- and season-specific modulation of hippocampal size and function is observed across multiple species, including rodents. other non-hippocampal-dependent behaviors exhibit season and sex differences, and whether the associated brain regions exhibit similar variation with sex and season remains to be fully characterized. as such, we examined the brains of wild-caught richardson's ground squirrels (rgs; urocitellus richardsonii) for seasonal (breeding, non-breeding) and sex differences in the v ... | 2015 | 25595988 |
| maternal gestational cortisol and testosterone are associated with trade-offs in offspring sex and number in a free-living rodent (urocitellus richardsonii). | the adaptive manipulation of offspring sex and number has been of considerable interest to ecologists and evolutionary biologists. the physiological mechanisms that translate maternal condition and environmental cues into adaptive responses in offspring sex and number, however, remain obscure. in mammals, research into the mechanisms responsible for adaptive sex allocation has focused on two major endocrine axes: the hypothalamic pituitary adrenal (hpa) axis and glucocorticoids, and the hypothal ... | 2014 | 25353347 |
| the effects of season and sex on dentate gyrus size and neurogenesis in a wild rodent, richardson's ground squirrel (urocitellus richardsonii). | sex and reproductive status affect hippocampal neurogenesis and dentate gyrus (dg) size in rodents. relatively few studies, however, address these two effects simultaneously and even fewer studies address this issue in wild populations. here, we examined seasonal and sex differences in neurogenesis and dg size in a wild, polygynous and social rodent, richardson's ground squirrel (uriocitellus richardsonii). based on the behavioral ecology of this species, we predicted that both neurogenesis and ... | 2014 | 24813432 |
| litter sex ratios in richardson's ground squirrels: long-term data support random sex allocation and homeostasis. | when costs of producing male versus female offspring differ, parents may vary allocation of resources between sons and daughters. we tested leading sex-allocation theories using an information-theoretic approach and bayesian hierarchical models to analyse litter sex ratios (proportion males) at weaning for 1,049 litters over 24 years from a population of richardson's ground squirrels (urocitellus richardsonii), a polygynandrous, annually reproducing mammal in which litter size averages from six ... | 2014 | 24385085 |
| effects of hibernation on regulation of mammalian protein phosphatase type-2-a. | hibernation is used by many small mammals for winter survival. animals undergo cycles of deep torpor characterized by strong reductions in metabolic rate, body temperature, and all physiological activities. one prominent biochemical mechanism involved in regulating coordinated transitions to and from the hypometabolic state is reversible protein phosphorylation, a dynamic covalent modification maintained by the actions of protein kinases and protein phosphatases. the present study characterizes ... | 2013 | 23499617 |
| seasonal and sex differences in the hippocampus of a wild rodent. | studies across and within species suggest that hippocampus size is sexually dimorphic in polygamous species, but not in monogamous species. although hippocampal volume varies with sex, season and mating system, few studies have simultaneously tested for sex and seasonal differences. here, we test for sex and seasonal differences in the hippocampal volume of wild richardson's ground squirrels (urocitellus richardsonii), a polygamous species that lives in matrilineal, kin-based social groups and h ... | 2013 | 22974551 |
| the benefits of baseline glucocorticoid measurements: maximal cortisol production under baseline conditions revealed in male richardon's ground squirrels (urocitellus richardsonii). | wildlife capture methods can make it impractical or impossible to obtain baseline plasma glucocorticoid (gc) levels, and the time of capture of individual animals is often unknown so there may be little uniformity in the duration of capture-stress prior to blood collection. although baseline samples are preferred, if seasonal changes in capture-stress gc levels closely reflect seasonal baseline changes, then capture-stress gc levels can be used to infer at least the direction of change in baseli ... | 2012 | 22814333 |
| suppression of mapkapk2 during mammalian hibernation. | metabolic signaling coordinates the transition by hibernating mammals from euthermia into profound torpor. organ-specific responses by activated p38 mitogen activated protein kinase (mapk) are known to contribute to this transition. therefore, we hypothesized that the mapk-activated protein kinase-2 (mapkapk2), a downstream target of p38 mapk, would also be active in establishing the torpid state. kinetic parameters of mapkapk2 from skeletal muscle of richardson's ground squirrels, spermophilus ... | 2012 | 22771537 |
| regulation of liver glutamate dehydrogenase by reversible phosphorylation in a hibernating mammal. | glutamate dehydrogenase (gdh) is a key enzyme that links amino acid and carbohydrate metabolism in cells. regulation is likely most important when organisms are confronted with extreme stresses such as the low environmental temperatures and lack of food associated with winter. many small mammals, such as richardson's ground squirrels, spermophilus richardsonii, cope with these conditions by hibernating. animals enter long periods of profound torpor where metabolic rate is greatly suppressed, bod ... | 2010 | 20674762 |
| spontaneous cutaneous mast cell tumor with lymph node metastasis in a richardson's ground squirrel (spermophilus richardsonii). | a 4-year-old female richardson's ground squirrel (spermophilus richardsonii) presented with multicentric nodules arising from the skin of the middle of the tail and lumbosacral regions. histologically, the nodules were composed of a proliferation of spindloid to pleomorphic cells that sometimes formed sheets and fascicular to storiform patterns. diffuse infiltration of eosinophils was also noted. the results of immunohistochemistry indicated positive labeling for vimentin, mast cell tryptase, c- ... | 2009 | 19139521 |
| skeletal muscle hexokinase: regulation in mammalian hibernation. | skeletal muscle hexokinase (hk) from richardson's ground squirrels was analyzed to determine how the enzyme is regulated during hibernation, a state of cold torpor. the hk ii isozyme dominated in muscle and ~15% of total hk was bound to the insoluble fraction. hk maximum activity was 33% lower in hibernator muscle and the enzyme showed a significantly higher k ( m ) atp (by 80%) and a lower k ( i ) for glucose-6-p (by 40%) than euthermic hk (assayed at 22 degrees c). however, 5 degrees c assay s ... | 2008 | 18642117 |
| spontaneous adenocarcinoma immunoreactive to cyclooxygenase-2 and transforming growth factor-beta1 in the buccal salivary gland of a richardson's ground squirrel (spermophilus richardsonii). | the ground squirrel is used as an experimental animal because of its unique biological nature. a 3-year-old female richardson's ground squirrel developed a mass, 1.5 cm in diameter, in the buccal mucosa. the mass consisted of neoplastic epithelial cells showing acinar, ductular, intraductal papillary, solid, and lobular growth patterns; the cells were immunoreactive to cytokeratin, cyclooxygenase-2 (a marker of malignancy) and tgf-beta1. after resection, the tumor recurred with increased area ha ... | 2007 | 18075199 |
| regulation of akt during hibernation in richardson's ground squirrels. | akt (or protein kinase b) plays a central role in coordinating growth, survival and anti-apoptotic responses in cells and we hypothesized that changes in akt activity and properties would aid the reprioritization of metabolic functions that occurs during mammalian hibernation. akt was analyzed in skeletal muscle and liver of richardson's ground squirrels, spermophilus richardsonii, comparing the enzyme from euthermic and hibernating states. akt activity, measured with a synthetic peptide substra ... | 2008 | 17983605 |
| the effect of hibernation on protein phosphatases from ground squirrel organs. | protein phosphorylation has been identified as a reversible mechanism for the regulated suppression of metabolism and thermogenesis during mammalian hibernation. the effects of hibernation on the activity of serine/threonine and tyrosine protein phosphatases (pp1, pp2a, pp2c and ptps) were assessed in five organs of richardson's ground squirrel. each phosphatase subfamily responded differently during torpor, and each showed organ-specific patterns of activity changes. the distribution of pp1 cat ... | 2007 | 17964276 |
| regulation of skeletal muscle creatine kinase from a hibernating mammal. | control over skeletal muscle energetics is critical in hibernation to sustain viability over weeks of cold torpor and to support shivering thermogenesis during arousal. creatine kinase (ck) has a key role in muscle energetics and this study analyzes muscle ck from ground squirrels, spermophilus richardsonii. ck activity was approximately 20% lower during hibernation than in euthermia, as was ck protein whereas ck mrna was reduced by approximately 70%. hibernator ck showed reduced affinity for at ... | 2007 | 17888865 |
| variation in litter size: a test of hypotheses in richardson's ground squirrels. | we studied litter size variation in a population of richardson's ground squirrels (spermophilus richardsonii) in alberta, canada, from 1987 to 2004. litter size at first emergence of juveniles from the natal burrow ranged from 1 to 14; the most common litter sizes, collectively accounting for 41.0% of 999 litters, were 6 and 7. the number of offspring surviving to adulthood (attained on emergence from hibernation as yearlings) increased with increasing litter size, a result that was not predicte ... | 2007 | 17479749 |
| mitogen-activated protein kinases and selected downstream targets display organ-specific responses in the hibernating ground squirrel. | the responses of mitogen-activated protein kinase (mapk) family members, including the extracellular signal-regulated kinases (erks), the c-jun nh2-terminal kinases (jnks) and p38mapk, during mammalian hibernation were analyzed in five organs of richardson's ground squirrels, spermophilus richardsonii. each kinase subfamily responded differently in torpor and each showed organ-specific patterns of response. erk1/2 activities increased significantly in muscle and brain during hibernation but decr ... | 2005 | 15618024 |
| animal communication: ground squirrel uses ultrasonic alarms. | apart from echolocation and the pursuit of prey by bats, the function of ultrasound in animal communication is poorly understood. this is mainly because of the broad range of responses that it can evoke and the widely varied contexts in which it is used (for example, in rodents of the muridae family it may indicate distress in infants or a sexual or predatory encounter in adults). here we find that a purely ultrasonic signal is produced in the wild by a rodent of the sciuridae family, richardson ... | 2004 | 15282596 |
| reproductive status of four species of fleas (insecta: siphonaptera) on richardson's ground squirrels (rodentia: sciuridae) in manitoba, canada. | to test the hypothesis that oogenesis in 4 species of fleas is dependent on the reproductive cycle of their monoestrous host spermophilus richardsonii, 6,416 oropsylla (oropsylla) rupestris (baker), 5,893 oropsylla (opisocrostis) bruneri (baker), 813 neopsylla inopina (rothschild), and 223 rhadinopsylla (actenophthalmus) fraterna (baker) females were collected from active hosts at 3 locations in manitoba during 1987, 1988, and 1989 and dissected. based on morphological changes in the ovaries, fe ... | 1998 | 9701922 |
| acetyl-coa carboxylase control of fatty acid oxidation in hearts from hibernating richardson's ground squirrels. | although mammalian hibernators rely on stored body fat as a source of energy, direct measurement of energy substrate preference in heart tissue during hibernation, as well as potential mechanisms controlling fatty acid oxidation has not been examined. in order to determine whether an increase in fatty acid utilization occurs during hibernation, glucose and palmitate oxidation were measured in isolated working hearts from hibernating and non-hibernating richardson's ground squirrels. hearts were ... | 1998 | 9518540 |
| juvenile richardson's ground squirrels, spermophilus richardsonii, discriminate among individual alarm callers | richardson's ground squirrels, spermophilus richardsonii, issue vocal alarm responses to avian and terrestrial predators. recipients of those calls presumably benefit from enhanced detection and subsequent avoidance of predators. if receivers of alarm calls differentiate among callers, they could use that information to tailor their behavioural response to the perceived level of threat. a neighbour's call may indicate more imminent danger than that of a non-neighbour; with individual recognition ... | 1998 | 9480711 |
| ground squirrel model for cholelithiasis: role of epithelial glycoproteins. | the cholesterol-fed richardson's ground squirrel (spermophilus richardsonii) has proven to be an effective animal model in which to study factors that influence cholesterol gallstone formation and associated alterations in the gallbladder epithelium. ground squirrels of either sex, fed a 2% cholesterol-enriched diet, exhibit cholesterol monohydrate crystal precipitation within 24 hours and macroscopically visible cholesterol stones by 3 weeks. data on bile chemistry, biliary cholesterol precipit ... | 1997 | 9329018 |
| alpha 2-macroglobulin gene expression during hibernation in ground squirrels is independent of acute phase response. | alpha 2-macroglobulin, a major acute phase reactant in many species, increases in the richardson's ground squirrel (spermophilus richarsonii) during hibernation at the level of both mrna and protein. to determine if the pattern of liver gene expression known as the acute phase response is elicited as a normal part of the physiological adaptation of hibernation, acute phase reactants were identified in the richardson's ground squirrel and were then assayed for changes in mrna expression in the li ... | 1995 | 7541965 |
| synonymy of eimeria larimerensis with eimeria lateralis. | oocysts of eimeria lateralis were isolated from feces of spermophilus richardsonii and compared to published descriptions of e. lateralis and eimeria larimerensis from other spermophiline rodent hosts. a comparison from other spermophiline rodent hosts. a comparison of these 2 eimerian species, combined with an examination of host specificity of spermophiline eimerians and host and parasite distributions, suggests that e. larimerensis is synonymous with e. lateralis. | 1993 | 8277396 |
| the modulatory effects of mu and kappa opioid agonists on 5-ht release from hippocampal and hypothalamic slices of euthermic and hibernating ground squirrels. | to elucidate the role of opioids in regulating hibernation, the modulatory effects of different opioids on 35 mm k(+)-stimulated [3h]-5-ht release from brain slices were examined in the richardson's ground squirrels. dago ([d-ala2,n-me-phe4,gly-ol5]-enkephalin), a specific mu agonist, evoked a significant dose-dependent (10(-7)-10(-5) m) inhibition of k(+)-stimulated 5-ht release from hippocampal slices of the non-hibernating squirrels. the inhibitory effect of dago was attenuated by either the ... | 1993 | 8255158 |
| sexual differences in over-winter torpor patterns of richardson's ground squirrels in natural hibernacula. | over-winter torpor patterns of richardson's ground squirrels hibernating in southern alberta were monitored with temperature-sensitive radiocollars to determine if these patterns differed between males and females in a manner related to the greater costs of mating effort by males than females. the hibernation season (from immergence to emergence) was composed of three periods: post-immergence euthermy, heterothermy, and pre-emergence euthermy. the hibernation season was shorter for juveniles tha ... | 1992 | 28313089 |
| seasonal variations in the rate and capacity of cardiac sr calcium accumulation in a hibernating species. | the rate of calcium uptake and the level of calcium accumulation was measured in cardiac muscle sr from hibernating and nonhibernating richardson's ground squirrels. in whole heart homogenates, the rate of calcium uptake was higher (p less than 0.05) in hibernating animals than it was in active animals. further purification of homogenates into sacroplasmic reticulum (sr) preparations showed that the hibernating animals had the highest rate of calcium uptake and the greatest level of calcium accu ... | 1991 | 1834435 |
| cardiac mechanical restitution in active and hibernating richardson's ground squirrel. | the cardiac mechanical restitution was compared in papillary muscles between the active and the hibernating richardson's ground squirrels at 0.1, 2.8, and 5 mm external ca2+ concentration [( ca2+]o). the amplitude of the restitution was significantly higher in hibernating animals between 37 and 7 degrees c at all [ca2+]o. the first postrest contraction (f1) was highest at 20 degrees c and lower at 37 and 7 degrees c in both groups. the pause duration for maximum f1 was 30 s in active but 10 s in ... | 1991 | 1996722 |
| pineal sensitivity to nighttime swimming stress changes during the active season in richardson's ground squirrels (spermophilus richardsonii). | melatonin synthesis in the pineal gland, which is primarily regulated by the environmental lighting regime, can also be influenced by other factors that elicit modifications in sympathetic tone. the objectives of this study were to determine if forced swimming alters the normal pattern of melatonin production in the pineal gland of the richardson's ground squirrel (spermophilus richardsonii). in early june, the squirrels were forced to swim for 10 min during the photophase or during the scotopha ... | 1989 | 2760576 |
| the serotonin-immunoreactive system of the suprachiasmatic nucleus in the hibernating ground squirrel, spermophilus richardsonii. | in the suprachiasmatic nucleus (nsc) of hibernating and non-hibernating ground squirrels, the distribution of serotonin-immunoreactive (5ht-ir) fibers was studied by the use of the peroxidase-antiperoxidase technique. the cytology of perikarya giving rise to these suprachiasmatic 5ht-ir fibers was investigated in the anterior raphe nuclei. differences in the immunoreactivity of suprachiasmatic fibers between hibernating and non-hibernating ground squirrels were determined by digital image analys ... | 1989 | 2743396 |
| reproductive effort during gestation and lactation by richardson's ground squirrels. | reproductive effort by yearling and older female richardson's ground squirrels was studied over a 4-year period in southern alberta by obtaining serial weight records from marked individuals to compare the mother's mass at critical points in the annual cycle (emergence from hibernation, estrus, parturition, and litter emergence) with her litter's mass at birth and weaning. yearlings weighed only 80% of older adults at emergence from hibernation, but they mated at the same time as older females, ... | 1989 | 28311904 |
| brown fat thermogenesis during hibernation and arousal in richardson's ground squirrel. | the thermogenic activity [mitochondrial guanosine 5'-diphosphate (gdp) binding] and capacity (uncoupling protein concentration, cytochrome oxidase activity) of brown adipose tissue have been investigated at different phases of the seasonally linked hibernation cycle in richardson's ground squirrel. the amount of axillary brown adipose tissue and the total mitochondrial content of the tissue were substantially greater in hibernating squirrels than in squirrels caught posthibernation in april or m ... | 1989 | 2912224 |
| fatty acid synthetase in control, starved and refed richardson's ground squirrels. | 1. starvation for 6 days reduced whole body mass and total body lipids to 76 and 71%, respectively, of pre-starvation levels in weight-gain phase ground squirrels. after 4 days of refeeding, body mass increased to 86% of pre-starvation level but total body lipids had not changed from starvation levels. 2. compared to the fed state, fatty acid synthetase (fas) activity in white adipose tissue (wat) was 15 and 31% in starved and refed 4-day animals, respectively, and in liver was 26 and 21% in sta ... | 1989 | 2569377 |
| the "hibernation induction trigger": specificity and validity of bioassay using the 13-lined ground squirrel. | even though the existence of the blood-borne "hibernation induction trigger" has been reported in the 13-lined ground squirrel, transfusion of plasma from hibernating rodents with other hibernating species as the recipients failed to induce the occurrence of summer hibernation. in order to verify whether the response to the "trigger" substance is species specific, the present study was carried out to compare the effect of plasma from hibernating richardson's ground squirrels on the incidence of ... | 1988 | 3409709 |
| calorimetric and spectroscopic studies of lipid thermotropic phase behavior in liver inner mitochondrial membranes from a mammalian hibernator. | arrhenius plots of various enzyme and transport systems associated with the liver mitochondrial inner membranes of ground squirrels exhibit changes in slope at temperatures of 20-25 degrees c in nonhibernating but not in hibernating animals. it has been proposed that the arrhenius breaks observed in nonhibernating animals are the result of a gel to liquid-crystalline phase transition of the mitochondrial membrane lipids, which also occurs at 20-25 degrees c, and that the absence of such breaks i ... | 1988 | 3167006 |
| thyroid hormone resistance in hibernating ground squirrels, spermophilus richardsoni. ii. reduction of hepatic nuclear receptors. | hepatic nuclear triiodo-l-thyronine (t3) receptors were studied to investigate the mechanism of thyroid hormone resistance in richardson's ground squirrels, spermophilus richardsoni, during the hibernation phase of the annual cycle. the cycle is divided into an active phase and a hibernation phase, the latter composed of alternating dormancy and arousal bouts. in addition to animals in these three states, a group of cold-exposed animals was also examined (those animals held at 6 degrees which sh ... | 1988 | 3360294 |
| mucus hypersecretion in the gallbladder epithelium of ground squirrels fed a lithogenic diet for the induction of cholesterol gallstones. | this study identified mucus granules, determined mode of release and quantified their volume in the gallbladder epithelium of richardson's ground squirrels (spermophilus richardsonii) fed a lithogenic diet of 2% cholesterol to experimentally induce gallstone formation. tissue was examined using light microscopy histochemistry, scanning and transmission electron microscopy, as well as autoradiography and morphometry at the electron microscopic level. autoradiography demonstrated incorporation of ... | 2006 | 3679091 |
| reduced synthetic activity as a contributing factor to weight-loss in the circannual cycle of richardson's ground squirrels. | 1. glycogen concentrations in richardson's ground squirrels of the weight-loss phase were 1/4-1/2 those in animals of the weight-gain phase. white adipose lipid content was similar in animals in the two phases when total body weight was similar. 2. specific activity of 14c in muscle glycogen of fed, starved and refed ground squirrels in the weight-loss phase was similar to that in starved weight-gain phase animals. activity in adipose lipids of fed, starved, and refed ground squirrels in the wei ... | 1987 | 2887372 |
| anesthesia in the richardson's ground squirrel: comparison of ketamine, ketamine and xylazine, droperidol and fentanyl, and sodium pentobarbital. | a combination of ketamine and xylazine (88.9 mg of ketamine/ml and 11.1 mg of xylazine/ml) given im (85.5 +/- 3.4 mg of ketamine/kg of body weight and 10.6 +/- 0.5 mg of xylazine/kg) or subcutaneously (85.6 +/- 4.0 mg of ketamine/kg and 10.7 +/- 0.7 mg of xylazine/kg) induced effective surgical anesthesia for 20 to 30 minutes in richardson's ground squirrels. use of ketamine alone (86 +/- 7 mg/kg, im), a droperidol and fentanyl combination (2.6 +/- 0.4 mg of droperidol/kg and 52 +/- 8 micrograms ... | 1986 | 3505921 |
| insulin and central regulation of spontaneous fattening and weight loss. | insulin binding to receptors in a partially purified hypothalamic membrane preparation is altered by prolonged starvation. to define further the relationship between hypothalamic insulin binding and energy balance, we studied the richardson's ground squirrel, a hibernator that exhibits spontaneous 6- to 8-mo body weight cycles when kept in constant conditions. isolated pancreatic islets from squirrels killed during the weight gain phase had greater glucose-stimulated insulin secretion than those ... | 1985 | 3895985 |
| radioglucose metabolism by richardson's ground squirrels in the weight-gain and weight-loss phases of the circannual cycle. | captive fed, starved, and refed richardson's ground squirrels in the weight-gain and weight-loss phases of the circannual cycle were injected with radioglucose and the activity of the label in skeletal muscle proteins and white adipose tissue lipids four hours after injection was used to determine if lean body mass and white adipose tissue would be rapidly restored when starved animals were refed. starvation for six days reduced carcass mass 27-31% and white adipose tissue mass 23-24% (table 1). ... | 1985 | 3836232 |
| seasonal variations in drug response and staircase phenomena in atrial muscle from a hibernating rodent (spermophilus richardsonii). | 1 electrically driven atrial muscle from a hibernating rodent (spermophilus richardsonii) showed marked seasonal variations in inotropic responsiveness to both the cardiac glycoside actodigin and to raised extracellular calcium concentration. in contrast, glycoside toxicity was apparent and comparable in all tissues. 2 these variations were accompanied by changes in force-frequency ('staircase') characteristics of the tissues. 3 in contrast, no seasonal variation was observed in either positive ... | 1983 | 6297645 |
| thyroidal iodine and thyroglobulin in hibernating and active richardson's ground squirrels spermophilus richardsoni. | thyroidal iodine, protein and thyroglobulin (tg) were investigated in a hibernator, spermophilus richardsoni, sampled in the field and from laboratory-held winter colonies. in field animals, thyroidal iodine and protein contents were similar at onset of hibernation and at terminal arousal. iodine content was increased in laboratory-held animals, a function of alimentary supply, but no differences were observed between hibernators and non-hibernators. density sucrose gradients showed that approx. ... | 1983 | 6135544 |
| seasonally-related physiological and behavioural changes in captive richardson's ground squirrels (spermophilus richardsoni). | 1. this study reveals the interrelationship among body weight, food intake and activity for a one-year period in two different year groups of captive juvenile richardson's ground squirrels (spermophilus richardsoni). 2. an increase in body weight during initial captivity and during the post-hibernation period related to an increase in food intake and in activity. 3. high and constant body weights during the pre-hibernation seasons were associated with a "voluntary" reduction in food intake, a de ... | 1983 | 6131779 |