Publications
| Title | Abstract | Year Filter | PMID(sorted ascending) Filter |
|---|
| studies on sex chromosomes of four hamster species: cricetus cricetus, cricetulus griseus, mesocricetus auratus, and phodopus sungorus. | in this paper, we present an analysis of the sex chromosomes of four hamster species after application of different staining techniques. the mitotic x chromosomes show a striking similarity in g-banding pattern but rather great differences in their c-banding patterns. a presumably homologous euchromatic segment that exhibits two distinct g-bands appears in the x chromosome of each species. the y chromosome of cricetus cricetus is in contrast to those of the other species, because it reveals a re ... | 1977 | 67011 |
| pelage color cycles and hair follicle tyrosinase activity in the siberian hamster. | hair follicle tyrosinase levels and melanin content, together with serum tyrosine levels have been studied in relation to annual pelage color changes in the siberian hamster. tyrosinase levels were found to peak not only at the spring moult when pigmented hair is produced but also at the autumn moult when the hair produced is unpigmented. the melanin content of hair follicles was high in summer and low in winter but serum tyrosine levels did not differ at the spring and autumn moults. these resu ... | 2000 | 101597 |
| [damaging effect of 2 simian viruses on mammalian cell chromosomes]. | a green monkey myxovirus (sv5) causes chromosome breaks in embryonal diploid fibroblasts of man, cotton rats, striped hairy-footed hamster, and in cells of one heteroploid line of newborn lamb kidney. adenovirus sv15 is mutagenic for all cultures under study (diploid strains of human and cotton rat embryo fibroblasts and three continuous kidney cell lines from newborn lambs). the mutagenic activity of these viruses may be manifested without their undergoing a complete cycle of replication. | 1975 | 169630 |
| fine structural studies of the islets of langerhans in the djungarian hamster (phodopus sungorus). | a study of the pancreatic islets of langerhans in the djungarian hamster (phodopus sungorus) was initiated by the observation that 98 percent of the animals of a recently established colony showed ketoacidosis soon after birth, about ten percent of which later developed persistent hyperglycemia. the islets are made up of a centrally located mass of insulin-producing b-cells surrounded by a peripheral rim of a- and d-cells. most islets are richly supplied by unmyelinated nerve fibers which termin ... | 1978 | 354796 |
| a high incidence of abdominal pregnancy in the djungarian hamster (phodopus sungorus). | eight animals with abdominal fetuses were found in a relatively small colony of djungarian hamsters. all the fetuses were macerated. some had remains of an amniotic sac with an umbilical attachment to a placenta adherent to the peritoneum, but others were without placental remains. gross and histological examinations failed to reveal any ruptures of the uterus or oviducts. it was not possible to decide whether the abdominal pregnancies were primary or secondary. | 1979 | 480319 |
| photoperiodic control of androgen metabolism and binding in androgen target organs of hamsters (phodopus sungorus). | 1979 | 491657 | |
| photoperiodic effects in the djungarian hamster: one minute of light during darktime mimics influence of long photoperiods on testicular recrudescence, body weight and pelage colour. | in male djungarian hamsters (phodopus sungorus) short photoperiods (l/d 8/16) with additional 1- or 5-min light-pulses 8 h after light-off were as effective as long photoperiods (l/d 16/8) in stimulating testicular recrudescence, increase in body weight and moult into summer pelage. the results are discussed with regard to the hypothesis that the pattern of melatonin release from the pineal gland is important in mediating photoperiodic effects in mammals. | 1979 | 510511 |
| photoperiodic dependence of seasonal variations in melanocyte-stimulating hormone content of the pituitary gland in the siberian hamster (phodopus sungorus) [proceedings]. | 1979 | 521717 | |
| anatomy of the cecum of the dwarf hamster (phodopus sungorus). | the cecal anatomy of the dwarf hamster, phodopus sungorus, was investigated macroscopically and at the light, transmission electron microscopic and scanning electron microscopic levels. in addition, the arterial supply to the cecum and connecting mesenteries were elucidated. the cecum is divisible into an ampulla ceci and a corpus ceci. in the former, the differentiation of the ileocecal orifice and circumventing fold is described. scanning electron microscopically, the surface topography of the ... | 1979 | 525821 |
| chromosome replication patterns in the djungarian hamster (phodopus sungorus). | patterns of early and late replication in the individual chromosomes of the djungarian hamster (phodopus sungorus) have been studied using the techniques of giemsa staining suppression when bromodeoxyuridine is incorporated into the dna.--late replicating autosome regions correspond to g-band regions, early replication regions are less clearly demarcated but correspond to r-band regions plus some g-band zones. in part this reduction in sharpness of early replication bands may be due to the fact ... | 1978 | 567569 |
| circadian rhythm of plasma testosterone in the male djungarian hamster (phodopus sungorus). | a marked circadian rhythm of plasma testosterone was found in male djungarian hamsters. maximal values in the evening just prior to activity onset were about 12 times higher than minimum values in the early morning. the peak of serum testosterone concentration coincides with onset of oestrus in females. | 1977 | 578609 |
| post-natal development of the pineal organ in the hamsters phodopus sungorus and mesocricetus auratus. a fluorescence microscopic and microspectrofluorometric investigation. | 1978 | 657241 | |
| effects of short photoperiods on puberty, growth and moult in the djungarian hamster (phodopus sungorus). | male djungarian hamsters were raised from birth in either long (16l:8d) or short (8l:16d) photoperiods. in 16l:8d, testes were large (about 400 mg) and showed full spermatogenesis from 31 days of age, the cauda epididymidis contained motile spermatozoa from 35 days and the accessory glands were large and reached their final size at about 60 days of age. in 8l:16d, testes remained small (about 15 mg) and undeveloped up to an age of about 130 days; they then developed to reach normal size and full ... | 1978 | 712709 |
| new observations on the karyotype of the djungarian hamster, phodopus sungorus. | in this paper, the c-banding pattern of the karyotype of phodopus sungorus is presented and polymorphism is taken into consideration. | 1977 | 891798 |
| behavioral development in three hamster species. | the preweaning behavioral development was compared in 3 hamster species: the golden (mesocricetus auratus), chinese (cricetulus griseus), and djungarian (phodopus sungorus). differences in the age of appearance of action patterns could not be summarized by simply ranking species on either precocity or developmental speed, nor were they eliminated by measuring age from conception. problems in the interpretation of species differences in the age of appearance of action patterns are discussed. | 1976 | 955290 |
| location of nucleolar organizing regions on the chromosomes of the syrian hamster (mesocricetus auratus) and the djungarian hamster (phodopus sungorus). | terminal chromosome associations ("satellite associations") in asg-banded preparations have been used to determine the number and location of staellites in the syrian hamster (mesocricetus auratus) and the djungarian hamster (phodopus sungorus). five pairs of satellites are found in the former and four in the latter. nucleolar organizing regions (nors) were visualized with the ag-as silver precipitation technique, and their number and position corresponded exactly with the number and position of ... | 1976 | 975935 |
| pinealectomy inhibits stimulation of testicular development by long photoperiods in a hamster (phodopus sungorus). | 1975 | 1112305 | |
| [characteristics of the reproduction of djungarian hamsters in captivity and spontaneous tumors]. | breeding behavior and fertility of the djungarian hamster (d. h.) -- phodopus sungorus campbelli th-during 8 years (1966-1973) have shown that this hamster species is a suitable laboratory animal. the decline of breeding in winter months, observed in the first years of maintaining d. h. in our laboratory, became less pronounced in the last three years. d. h. seems to be resistant to common infections of laboratory animals. the only infection observed in d. h. was on outbreak of trichophytosis wh ... | 1975 | 1198984 |
| diurnal variation in 5-hydroxyindole-acetic acid output in the suprachiasmatic region of the siberian hamster assessed by in vivo microdialysis: evidence for nocturnal activation of serotonin release. | in vivo brain microdialysis was used to characterize the daily pattern of 5-hydroxyindole-acetic acid (5-hiaa) release in the region of the suprachiasmatic nuclei (scn) in freely behaving male siberian hamsters housed under 16l:8d. a marked diurnal variation in the concentration of extracellular 5-hiaa was apparent, with peak levels (147 +/- 5% of the daily mean; p < 0.05) occurring 2-3 h after lights-off. smaller nocturnal rises in extracellular 5-hiaa were observed in the posterior hypothalamu ... | 1992 | 1282219 |
| vitamin d nuclear binding to neurons of the septal, substriatal and amygdaloid area in the siberian hamster (phodopus sungorus) brain. | autoradiographic experiments were performed on brains of siberian hamsters (phodopus sungorus) injected with tritiated 1,25-dihydroxycholecalciferol. nuclear labeling was prevented in the presence of excess unlabeled hormone. strong nuclear concentration of radioactivity was observed in neurons of the nucleus basalis of meynert, the medial septal nucleus, the nucleus of the diagonal band of broca and the central amygdaloid group. the latter has been defined as consisting of the central nucleus o ... | 1992 | 1321365 |
| effects of short photoperiod on atpase activities in the testis of the immature siberian hamster. | the effects of changes in photoperiod length upon body weight; spleen, thymus, and testis weights; testis protein content; testis cation pump enzyme activities; and plasma testosterone were studied in the developing siberian hamster, phodopus sungorus. male hamsters were exposed to a cycle of 16l:8d (long-day), until day 18 when half were switched to a 10l:14d (short-day) cycle, until killed 0, 2, 4, 7, 10, 12, or 15 days later. body weight and relative testis weight (expressed as percentage of ... | 1992 | 1327208 |
| choroid plexus, ependyma and arachnoidea express receptors for vitamin d: differences between "seasonal" and "non-seasonal" breeders. | autoradiographic studies with [3h]1,25-dihydroxyvitamin d3 demonstrated nuclear high affinity binding sites (receptors) in epithelial cells of choroid plexus, ependyma and arachnoid in "seasonal" breeders of various vertebrate phyla, namely xiphophorus helleri, hyla crucifer, xenopus laevis, bufo woodhousei, chrysemys scripta, anolis carolinensis, nerodia sipedon and phodopus sungorus, but vitamin d receptors were undetectable in these tissues in non-seasonal breeders, such as zebra finch, labor ... | 1992 | 1329147 |
| nuclear receptor sites for vitamin d-soltriol in midbrain and hindbrain of siberian hamster (phodopus sungorus) assessed by autoradiography. | autoradiograms were prepared from midbrains and hindbrains of male and female siberian hamsters (phodopus sungorus), kept under short-day or long-day illumination, after injection of tritium-labeled 1,25-dihydroxycholecalciferol (vitamin d, soltriol). concentration and retention of radioactivity was noted in nuclei of certain neurons, glial cells, and ependymal cells, and in choroid epithelium. labeled neurons of varying intensity were found throughout the brainstem in distinct populations at ch ... | 1992 | 1333462 |
| serotonin content and melatonin production in the pineal gland of the male djungarian hamster (phodopus sungorus). | diurnal variations in serum melatonin levels and pineal concentrations of serotonin (5-ht), n-acetylserotonin (nas), 5-hydroxyindole acetic acid (5-hiaa), and melatonin were estimated in adult male djungarian hamsters kept under long-day (ld 16:8) or short-day (ld 8:16) photoperiods. the nocturnal increase in melatonin production was accompanied by a marked drop in pineal serotonin concentrations. serotonin levels, however, decreased approximately 4 hr before pineal melatonin increased. correlat ... | 1992 | 1380550 |
| maternal transfer of photoperiodic information in siberian hamsters. v. effects of melatonin implants are dependent on photoperiod. | photoperiodic information is transferred from female siberian hamsters to their fetuses during gestation. although maternal melatonin is known to be essential for the transfer of prenatal photoperiodic information, its specific role is not well defined. the duration of the daily melatonin signal, expressed as an elevation of serum melatonin levels in the maternal circulation, has been hypothesized to convey day length information to the fetus. if this hypothesis is valid, it predicts that identi ... | 1992 | 1391334 |
| isolation and culture of testicular macrophages from a seasonally breeding species, phodopus sungorus. evidence for functional differences between macrophages from active and regressed testes. | we have developed an isolation and cultivation protocol for testicular macrophages from the seasonally breeding siberian hamster, phodopus sungorus which allows serum-free culture. macrophages were isolated from the active testes of adult phodopus kept in long photoperiod (ld, 18hl:6hd), and from the inactive testes of animals with gonadal regression induced by exposure to a short photoperiod (sd, 6hl;18hd; for 10 weeks). the isolated cells were identified as macrophages by (a) electron microsco ... | 1992 | 1399090 |
| interruption of nocturnal pineal melatonin synthesis in spontaneous recrudescent djungarian hamsters (phodopus sungorus). | the duration of nighttime synthesis of the pineal hormone melatonin is believed to determine the breeding season in many mammalian species. hamsters exposed to short days undergo gonadal involution followed by a return to normal function, suggesting a developed insensitivity to regressive photoperiods. this recrudescence may be due to either exhaustion of the pineal or to target-desensitization. both theories have been tested previously but failed to explain this phenomenon. we performed an expe ... | 1992 | 1432575 |
| absence of a daily neuronal rhythm in the suprachiasmatic nuclei of acircadian djungarian hamsters. | the suprachiasmatic nuclei (scn) in mammals generate and maintain a variety of daily rhythms. in nocturnally active rodents, scn electrical activity is high during the subjective day (that time of locomotor inactivity) and low during the subjective night. the present experiment examines the relationship between scn neuronal activity and the expression of overt circadian behavior in the djungarian hamster (phodopus sungorus). wheel-running locomotor activity was measured in 2 groups of hamsters h ... | 1992 | 1454212 |
| central sites mediating reproductive responses to melatonin in juvenile male siberian hamsters. | juvenile male siberian hamsters received infusions of varying doses of melatonin (mel), or saline vehicle, via microdialysis probes implanted in brain regions which have previously been shown to contain mel receptors. daily infusions were 10 h in length and occurred during exposure to constant light on days 22-34 of age. all animals were sacrificed on day 35 and paired testis weights recorded prior to preparation of the brain tissue for histological evaluation of the infusion site. some animals ... | 1992 | 1486507 |
| daily torpor in the absence of the suprachiasmatic nucleus in siberian hamsters. | siberian hamsters express torpor spontaneously after several weeks of exposure to short days. in long days, torpor is expressed only when food intake is restricted. hamsters maintained in a long photoperiod (16 h light/day) at 15 degrees c expressed daily torpor during food restriction both before and after bilateral ablation of the suprachiasmatic nucleus (scn). hamsters housed in short days (8 h light/day, ambient temperature 15 degrees c) and fed ad libitum displayed torpor before, but not af ... | 1992 | 1510174 |
| effects of thyroxine on the photoperiodic control of energy balance and reproductive status in siberian hamsters. | siberian hamsters (phodopus sungorus sungorus) exhibit a variety of seasonal responses when exposed to short days (sd), including decreases in body weight and fat, gonadal regression, and changes in several nonsteroid serum hormone concentrations. one such sd-induced hormonal change is a modest decrease in serum thyroxine (t4) concentrations. in an attempt to determine any underlying hormonal influences for the sd-induced decreases in body weight and fat, we investigated the possible role of t4 ... | 1992 | 1523252 |
| pattern of pineal melatonin concentrations during prolonged exposure to short photoperiods in photosensitive and photoinsensitive djungarian hamsters. | in the djungarian hamster (phodopus sungorus) there is strong evidence that the nightly decompression or lengthening, respectively, of the pineal melatonin pattern is involved in conveying the inhibitory influence of short photoperiods. some hamsters, however, are insensitive to photoinhibitory influences; other late-responding hamsters show a delayed reaction of several months. the daily pattern of pineal melatonin proves that the mechanisms determining long- or short-day patterns become effect ... | 1992 | 1578338 |
| rapid gonadal recrudescence and body and lipid mass increases with hypothalamic lesions in photoregressed siberian hamsters. | the effects of lesions (x) of the suprachiasmatic nucleus (scn) or paraventricular nucleus (pvn), or pinealectomy (pinx) on gonadal recrudescence, body and fat pad weights, and food intake were examined in photoregressed male siberian hamsters (phodopus sungorus sungorus). blood was sampled weekly for serum follicle-stimulating hormone (fsh) and prolactin (prl) measurement. lesions were classified as complete if greater than 80% of the nuclei were destroyed and designated as 'hits', whereas inco ... | 2006 | 1584338 |
| evidence for genetic variation in the occurrence of the photoresponse of the djungarian hamster, phodopus sungorus. | the djungarian hamster generally responds to a short-day photoperiod with a complex syndrome of physiological and behavioral changes; however, not all hamsters are photoresponsive. the phenotypic difference is, in part, genetically determined. parent-offspring regression on a number of continuous and discontinuous measures indicated significant heritability for photoresponsiveness. four generations of replicated bidirectional selection on a photoresponse index (pi) resulted in significant shifts ... | 1992 | 1611131 |
| effects of age, photoperiod and follicle-stimulating hormone on lactate production by cultured sertoli cells from prepubertal siberian hamsters (phodopus sungorus). | to define a functional difference in sertoli cells of animals exposed to different photoperiodic conditions, we isolated sertoli cells from the testes of juvenile siberian hamsters and cultured them in serum-free medium. in all age groups studied, sertoli cells isolated from hamsters with delayed and normal puberty responded to follicle-stimulating hormone (fsh) with an increase in lactate production. the increase in lactate production induced by 1000 ng fsh ml-1 was significantly greater in ser ... | 1992 | 1625253 |
| melatonin receptors and signal transduction during development in siberian hamsters (phodopus sungorus). | maternal melatonin communicates daylength information to the fetus in siberian hamsters. fetal sensitivity to melatonin declines near birth. in this report, we describe melatonin receptor distribution and a second messenger response to melatonin in siberian hamsters during the perinatal period. the sites of high-affinity 2-[125i]iodomelatonin ([125i]mel) binding were generally similar throughout the perinatal period. the non-hydrolyzable gtp analog, guanosine-5'-o-(3-thiotriphosphate) (100 micro ... | 1991 | 1645629 |
| tumours in russian hamsters (phodopus sungorus) | 1991 | 1648281 | |
| appearance of melatonin receptors during embryonic life in siberian hamsters (phodopus sungorous). | maternal melatonin readily crosses the placenta to provide the fetus with time-of-day and day length information. to determine if melatonin could have a broader role during development than is currently recognized, melatonin receptor expression was examined in somatic sites during siberian hamster embryogenesis. using 125i-labeled-2-iodomelatonin ([125i]mel), melatonin receptor expression was examined in whole fetuses by in vitro autoradiography. [125i]mel binding sites were first apparent at ge ... | 1991 | 1667620 |
| development of phodopus sungorus brown preadipocytes in primary cell culture: effect of an atypical beta-adrenergic agonist, insulin, and triiodothyronine on differentiation, mitochondrial development, and expression of the uncoupling protein ucp. | a new cellular model for the study of brown adipocyte development and differentiation in vitro is presented. preadipocytes isolated from brown adipose tissue (bat) of the djungarian dwarf hamster phodopus sungorus are able to proliferate and differentiate in vitro into true brown adipocytes able to express the bat marker protein the uncoupling protein (ucp). whereas basal ucp expression is very low, its mrna levels as well as the ucp detected by immunoblotting are highly increased by beta-adrene ... | 1991 | 1684582 |
| brain ca2+/mg(2+)-atpase activity and seasonal adaptation of the djungarian dwarf hamster phodopus sungorus. | 1. of three sets of djungarian dwarf hamster, two groups were raised during winter under greatly differing circumstances. one winter group was raised within a climate controlled cage in which the ambient temperature was maintained at 22 degrees c and whereby conditions of light vs darkness were maintained in a constant 12 hr cycle. the second winter group was raised out of doors whereby the hamsters were subjected to prevailing seasonal environmental conditions. a third group was studied under s ... | 1991 | 1685389 |
| topographical mapping of the thalamocortical projections in rodents and comparison with that in primates. | the general topographical organization of the thalamo-cortical projection of two rodents, the siberian hamster (phodopus sungorus) and the guinea pig (cavia aperta) was investigated with the hrp-method and compared with that of the new world primate marmoset (cal-lithrix jacchus) as shown in a companion study by brysch et al. (1990). hrp was injected into various regions of the cortex in different animals and hemispheres, and plots were made of the retrogradely stained thalamic projection neuron ... | 1991 | 1722758 |
| prolactin-dependent seasonal changes in pelage: role of the pineal gland and dopamine. | the siberian hamster displays seasonal changes in pelage that are dependent upon fluctuations in circulating prolactin levels. pinealectomy prevented the decrease in serum prolactin and molt to the winter pelage displayed by castrated males housed under a short-day photoperiod. a dopaminergic antagonist, pimozide, enhanced prolactin levels in both pinealectomized and sham-operated animals under both long and short photoperiods. in the short-day animals, this effect of pimozide was associated wit ... | 1992 | 1729383 |
| expression of circadian rhythmicity in djungarian hamsters under constant light: effects of light intensity and the circadian system's state. | djungarian hamsters (phodopus sungorus), were exposed to constant light with increasing intensities (20, 60, 350 lux), and wheel running activity was recorded. with increasing light intensity the percentage of hamsters showing a split in their daily activity pattern increased and the free running period was lengthened for both the unsplit and the split state. the fact that the free running period of both states depended on the light intensity together with the observation that the highest incide ... | 1991 | 1748975 |
| evidence for independence of circadian characters and extent of photoresponsiveness in the djungarian hamster, phodopus sungorus. | djungarian hamsters (phodopus sungorus) exposed to a short-day photoperiod generally respond with a syndrome of physiological and behavioral changes, such as body weight loss and molt to a white pelage. the extent of the short-day-induced responses differs among individuals. furthermore, some hamsters show no photoresponse. in this study, we sought to determine whether variation in the photoresponse would be associated with circadian function: whether phase angle or free-running period (tau) wou ... | 1991 | 1773088 |
| in vitro electrical activity in the suprachiasmatic nucleus following splitting and masking of wheel-running behavior. | djungarian hamsters (phodopus sungorus sungorus) were chronically exposed to constant light (60 lux) in order to generate a split rhythm of wheel-running behavior. the animals were killed and coronal hypothalamic slices prepared for extracellular recording from the left and right suprachiasmatic nuclei (scn). nine hamsters which exhibited a split in overt behavior also had bimodal peaks (280 cells) of scn firing frequency (5.4 +/- 1.1 and 5.8 +/- 0.7 hz); these peaks were about 180 degrees antip ... | 2004 | 1782563 |
| expression of vasopressin receptors in hamster hypothalamus is sexually dimorphic and dependent upon photoperiod. | the distribution of vasopressin receptors was studied in the brain of a photoperiodic animal, the siberian hamster. attention was focused on [3h]vasopressin binding sites located in the hypothalamic ventromedial nucleus, medial tuberal nucleus, and ventral premammillary nucleus in males or females kept in long or short photoperiod conditions. displacement experiments with structural analogs suggested that vasopressin receptors in the hamster hypothalamus are of the vasopressor (v1) type. quantit ... | 1991 | 1837144 |
| melatonin receptors and signal transduction in photorefractory siberian hamsters (phodopus sungorus). | in seasonally breeding mammals, seasonal alterations in day length are perceived via the pineal hormone melatonin. when exposed to short day lengths, hamsters and other long-day breeders undergo gonadal regression. with chronic exposure (greater than 20 weeks) to short days, however, the animals become photorefractory, or insensitive to the inhibitory influence of short-day melatonin patterns, and gonadal recrudescence occurs. in this report, we examined photorefractory siberian hamsters and lon ... | 1991 | 1846576 |
| circadian differences in neuronal activity of the suprachiasmatic nucleus in brain slices prepared from photo-responsive and photo-non-responsive djungarian hamsters. | the suprachiasmatic nucleus (scn) of the hypothalamus, as the putative generator of circadian rhythmicity, plays an important role in mammalian photoinduction. to determine if scn function differs in photo-non-responsive djungarian hamsters, we defined the pattern of spontaneous neuronal discharge of single cells from scn slices in vitro of photo-responsive and photo-non-responsive phenotypes. responsive hamsters exhibited a peak neuronal discharge rate (4.8 +/- 0.5 hz) during the mid day which ... | 1991 | 1855138 |
| effects of temperature, steroids and castration on daily torpor in the djungarian hamster (phodopus sungorus). | 1. in phodopus sungorus the frequency and characteristics of daily torpor were not affected by a decrease in temperature. the seasonal cycle of daily torpor is essentially under photoperiodic control. 2. testicular regression is a necessary condition for daily torpor occurrence. testosterone and 5 alpha-dihydrotestosterone administration totally inhibited daily torpor in hamsters which were exposed to short days. the temporal inhibition of torpor by steroids had no effect on the seasonal time me ... | 1991 | 1865387 |
| parameters of the circadian rhythm of pineal melatonin secretion affecting reproductive responses in siberian hamsters. | the major function of the mammalian pineal gland appears to be its central role in photoperiodism. the pineal hormone, melatonin, is synthesized and secreted primarily at night, under the control of a circadian oscillator that is entrained to the light-dark cycle. both the circadian phase and the duration of the nocturnal peak of melatonin secretion are established primarily by interactions between the endogenous circadian oscillator and the daily photic cycle. the duration of the melatonin peak ... | 2007 | 1877061 |
| scn lesions block responses to systemic melatonin infusions in siberian hamsters. | the role of the suprachiasmatic nuclei (scn) in the response to short-day melatonin (mel) signals was examined in long-day-housed pinealectomized (pinx) siberian hamsters. five- or ten-hour mel infusions that mimicked the peak nocturnal durations of serum mel levels in long or short days, respectively, or control saline infusions were given for 5 wk. half the hamsters in each infusion group also received bilateral electrolytic scn lesions. the 10-h mel infusions reduced testes weight, body and f ... | 1991 | 1899543 |
| suprachiasmatic and paraventricular control of photoperiodism in siberian hamsters. | the effects of lesions of the suprachiasmatic (scn) and paraventricular nuclei (pvn) of the hypothalamus on photoperiodic responses were examined in adult siberian hamsters. scn lesions reduced nocturnal water intake in long days, whereas pvn lesions increased body weight and food intake in both short and long days. scn or pvn lesions blocked short-day-induced decreases in body, fat pad, and testes weights and in food intake. serum prolactin (prl), but not follicle-stimulating hormone, levels we ... | 1991 | 1899544 |
| cold prevents the light induced inactivation of pineal n-acetyltransferase in the djungarian hamster, phodopus sungorus. | in the djungarian hamster seasonal acclimatization is primarily controlled by photoperiod, but exposure to low ambient temperature amplifies the intensity and duration of short day-induced winter adaptations. the aim of this study was to test, whether the pineal gland is involved in integrating both environmental cues. exposure of hamsters to cold (0 degrees c) reduces the sensitivity of the pineal gland to light at night and prevents inactivation of n-acetyltransferase (nat). the parallel time ... | 1991 | 1920160 |
| photoperiod effects on bombesin- and cholecystokinin-like immunoreactivity in the suprachiasmatic nuclei of the djungarian hamster (phodopus sungorus). | the immunocytochemical distribution of the putative satiety peptides bombesin (bbs) and cholecystokinin (cck) were studied in the hypothalamic suprachiasmatic nuclei (scn) of male and female djungarian hamsters (phodopus sungorus) held under either long (light/dark, ld 16:8 h) or short (ld 8:16) photoperiod. the animals were killed by perfusion with a fixative at the middle of the light period and the tissue was processed by routine immunohistochemical methods. perikarya exhibiting bbs- or cck-l ... | 1991 | 1922941 |
| the influence of lh and/or fsh on leydig and sertoli cell morphology after testicular involution in the djungarian hamster, phodopus sungorus, induced by hypophysectomy or short photoperiods. | in the djungarian hamster, phodopus sungorus, the morphological alterations of sertoli and leydig cells were investigated under the influence of gonadotropins (lh and/or fsh) after testicular regression induced either by hypophysectomy or photoinhibition. stimulation with lh or lh/fsh lead to a redifferentiation of morphological features of leydig cells such as nuclear structure, smooth endoplasmic reticulum and size of cell and nucleus area within 7 days of hormone treatment. similarly, stimula ... | 2006 | 1952128 |
| effects of melatonin agonists and antagonists on reproduction and body weight in the siberian hamster. | this study examined whether melatonin-induced inhibition of testicular weight and body weight in vivo could be antagonized by luzindole, a competitive melatonin receptor antagonist, or methysergide, a competitive serotonin receptor antagonist. adult male siberian hamsters were exposed to a long photoperiod (16l:8d) and given daily injections of drugs 3 h before lights off for 7 weeks. hamsters treated with melatonin (0.375 mg/kg) exhibited testicular regression and loss of body weight. these eff ... | 1990 | 1965726 |
| neuroendocrine and endocrine correlates of pair bonds and parental care in the seasonal reproductive cycle of the siberian hamster (phodopus sungorus). | 1990 | 1974360 | |
| maternal programming of the fetal brain dictates the response of juvenile siberian hamsters to photoperiod: dissecting the information transfer system. | development of neuroendocrine mechanisms regulating reproduction results from the interaction between genetic and environmental factors. for the developing fetus, the environment includes the maternal system. our work with siberian hamsters examines mechanisms by which prenatal photoperiods influence neuroendocrine functions regulating postnatal reproductive development. the maternal system has two effects on the young: 1) to program a reproductive growth pattern in the young and 2) to influence ... | 1990 | 1974794 |
| long terminal repeats of dwarf hamster endogenous retrovirus are highly diverged and do not maintain efficient transcription. | recently we described a new endogenous proretrovirus of dwarf hamster phodopus sungorus (mrs-ps). its sequence possesses evident homology with the endonuclease domain of the mouse mammary tumor virus pol gene. here we present nucleotide sequence data on three clones of retroviral long terminal repeats. as many as 15% of substituted, deleted, and inserted base pairs were found while comparing these sequences. hence, mrs-ps seems to be rather an old genetic element which originated about 30 millio ... | 1991 | 1994585 |
| immunohistochemical localization of testicular sulphydryloxidase during sexual maturation of the djungarian hamster (phodopus sungorus). | immunohistochemical localization of sulphydryloxidase was examined in the testis of the djungarian hamster from day 0 to day 31 of post-natal development. the sulphydryloxidase antibody labelled prespermatogonia and the first population of spermatogonia type a within the seminiferous epithelium. additionally, sertoli cells exhibited immunoreactivity from day 2 to day 11 after birth. from day 11 onwards, sulphydryloxidase immunoreactivity was found in germ cells after the initiation spermatogenes ... | 1991 | 1995854 |
| daily torpor in the djungarian hamster (phodopus sungorus): photoperiodic regulation, characteristics and circadian organization. | 1. the daily torpor was measured by oxygen uptake in djungarian hamsters during adaptation to a short photoperiod (sp: 10l, 14d) at 20 degrees c. in these constant conditions the torpor presented metabolic characteristics and a daily time course independent of the duration of adaptations to sp. 2. the frequency of torpor bouts increased during sp exposure and its maximum was reached after about 130 days. the frequency of torpor was greater in males than in females. 3. the incidence of torpor was ... | 1991 | 2033564 |
| effects of diabetes and insulin on photoperiodic responses in siberian hamsters. | short day pineal melatonin secretion patterns cause gonadal regression in siberian hamsters, an effect due to alterations in gonadotropin secretion that ultimately affects the gonads. an analogous endocrine response sequence may underlie short day (melatonin)-induced decrease in body weight (fat) in this species. a potential mediating hormone for this effect of melatonin may be insulin. the purpose of the present experiments was to determine whether alterations in insulin status might affect the ... | 1991 | 2062939 |
| early embryo development in the siberian hamster (phodopus sungorus). | development of preimplantation embryos of the siberian hamster (phodopus sungorus) in vivo and in vitro was examined. the timing of early development in vivo was found to be slower than that reported for the golden hamster. progression through the cleavage stages, cavitation, and hatching from the zona pellucida occurred later, with blastocyst formation beginning on the afternoon of day 4 and uterine attachment occurring early on day 5. in vitro, morulae, and early blastocysts collected on day 4 ... | 1990 | 2078338 |
| species-specific changes in the metabolic control of food intake: integrating the animal with its environment. | research on the metabolic control of feeding has been almost exclusively restricted to the study of laboratory rats. this poses no problem if all animals respond to metabolic challenges similarly; however, they do not. unlike rats, syrian, turkish, and to a lesser degree, siberian hamsters do not increase their food intake following food restriction. it has been argued that hamsters do not increase their food intake following a fast in laboratory tests because in their natural habitat they presu ... | 1990 | 2086506 |
| distribution pattern of testicular sulphydryloxidase immuno-activity in the djungarian hamster (phodopus sungorus) during photoperiodically induced involution and recrudescence. | the distribution pattern of testicular sulphydryloxidase (sox) immuno-activity was investigated in the djungarian hamster during photoperiodically induced testicular involution and recrudescence. sox immuno-activity, indicating functional integrity of labelled cells, did not change in pachytene spermatocytes and spermatids as long as these cells were present in the seminiferous epithelium. its disappearance coincided with the degeneration of spermatocytes in phases iv and v of involution and rea ... | 1990 | 2096112 |
| increased nonshivering thermogenesis, brown fat cytochrome-c oxidase activity, gdp binding, and uncoupling protein mrna levels after short daily cold exposure of phodopus sungorus. | in their natural environment, burrowing rodents experience rather fluctuating ambient temperatures and are acutely cold exposed only for short periods outside their burrows. the effect of short daily cold exposure on basal metabolic rate, nonshivering thermogenesis, brown fat thermogenesis, and uncoupling protein mrna was studied in the djungarian hamster, phodopus sungorus. they were kept at 23 degrees c and exposed to 5 degrees c daily either for one 4-h period or twice for 2 h (in 12-h interv ... | 1990 | 2155691 |
| on the ultrastructure of the male reproductive tract in the siberian hamster (phodopus sungorus campbelli). i. the ductuli efferentes. | the efferent ducts of the siberian hamster were studied using transmission electron microscopy. structural evidence indicates the presence of three cell types. first, in the nonciliated cell, the apical cytoplasm was replete with coated vesicles and pits and several classes of tubular profiles. dense fields of microvilli characterize the apices of these cells. populations of dense bodies were present together with large nonmembrane-bound structures containing membrane fragments and amorphous, ho ... | 1990 | 2282646 |
| fenestrated capillaries in the ventral sebaceous gland of the djungarian hamster, phodopus sungorus. | the ventral sebaceous gland of the djungarian hamster is a macroscopically visible organ situated in the midventral area of the abdominal wall. it consists of densely packed acini arranged in lobules with common excretory ducts. the rich vascular network of the gland is characterized by fenestrated capillaries. fenestrated endothelium has not yet been reported as a characteristic and regular finding within sebaceous glands. results are discussed with regard to proliferation rate of sebocytes and ... | 1990 | 2288188 |
| sustained reproductive responses in djungarian hamsters (phodopus sungorus) exposed to a single long day. | male and female djungarian hamsters maintained from birth in a short photoperiod (8 h light per day; 8l:16d) showed substantial testicular and uterine growth in response to a single long photoperiod or a 15-min light pulse that interrupted the 16-h dark period at 18 days of age. these light regimens resulted in heavier testes and uteri at 30 and 35 days of age when compared with those of control animals. similar results were obtained in hamsters maintained from birth to day 18 in a long photoper ... | 1990 | 2325022 |
| maternal transfer of photoperiodic information in siberian hamsters. iv. peripubertal reproductive development in the absence of maternal photoperiodic signals during gestation. | peripubertal reproductive development of siberian hamsters is influenced by photoperiodic information received during gestation; the maternal pineal is important for this process. we observed that in the absence of the maternal pineal, the fetus appears to receive no information about gestational photoperiods. this is not the equivalent of receipt of a long-day signal by the fetus. pinealectomized and sham-operated pregnant females were exposed to photoperiods of 12l:12d, 14l:10d, 16l:8d, or con ... | 1990 | 2340330 |
| in vitro fertilization of siberian hamster oocytes. | siberian hamsters were superovulated and various media were tested in an effort to fertilize the recovered oocytes in vitro. the highest percentage of fertilized ova was achieved by using a modified tyrode's medium, designated mt (bavister, j. reprod. fertil., 18:544-545, '69), previously formulated to fertilize syrian hamster ova in vitro. spermatozoa incubated in this medium in a concentrated state overnight (14 hr) and then diluted (1 hr) fertilized 39% of the ova. similar results (40%) were ... | 1990 | 2345347 |
| sites of action of soltriol (vitamin d) in hamster spleen, thymus, and lymph node, studied by autoradiography. | siberian hamsters (photopus sungorus) were injected with 3h dihydroxycholecalciferol (vitamin d, soltriol). autoradiograms of spleen, thymus, and lymph nodes revealed nuclear concentration of the hormone in a select population of cells in all of these organs. in the spleen, labeled cells were abundant in the red pulp, but sparse in the white pulp. in the periarterial lymphatic sheath (pals) labeled cells were found predominantly at the outer rim, with a few scattered labeled cells in the inner p ... | 1990 | 2358370 |
| [the functional capacities of the kidneys in hamsters of the genus phodopus]. | studies have been made on total osmolarity and concentration of na and k in the urine, as well as on the level of diuresis in three species of the hamsters (phodopus sungorus, ph. campbelli, ph. roborovskii) under the conditions of presence or absence of wet food and during water and salt loading. mean value of osmotic concentration of the urine at free access to wet food varied within 2,600-3,500 mosmol, under the condition of dry-eating--within, 5,600--6,400 mosmol, which indicates the existen ... | 2015 | 2360381 |
| nucleolus-like bodies in the pineal gland of the djungarian hamster (phodopus sungorus). | light- and electron-microscopic observations on the pineal gland of phodopus sungorus revealed intracytoplasmic inclusions resembling nucleolus-like bodies similar to those found in other regions of the central nervous system. bernhard's edta method was used to confirm that these inclusions were nucleolus-like bodies. these structures were rarely found in pinealocytes of sexually active long-day animals, whereas large numbers of them were observed in pinealocytes of sexually quiescent short-day ... | 1986 | 2418977 |
| post-natal patterns of plasma androgen-binding activity in djungarian (phodopus sungorus) and golden (mesocricetus auratus) hamsters. | the binding of sex steroids to plasma proteins was examined in post-natal djungarian and golden hamsters. with dihydrotestosterone or testosterone as ligands, steady-state polyacrylamide gel electrophoresis revealed 2 androgen binding components in the plasma of young djungarian hamsters of both sexes. the fast-moving component exhibited a low affinity and high capacity for androgens and corresponded to albumin in stained gels. in contrast, the slow moving component was a beta-globulin with high ... | 1989 | 2502624 |
| an enzyme histochemical study on phosphatases and glycosidases in the ductus epididymidis and ductus deferens of phodopus sungorus under different photoperiods. | 1989 | 2505314 | |
| differential effects of follicle-stimulating hormone and luteinizing hormone on leydig cell function and restoration of spermatogenesis in hypophysectomized and photoinhibited djungarian hamsters (phodopus sungorus). | effects of pure human follicle-stimulating hormone (hfsh) and ovine luteinizing hormone (olh) on testicular function were investigated in long-term hypophysectomized or photoinhibited djungarian hamsters. hfsh (5 iu) or olh (5 micrograms) or a combination of fsh and lh (5 iu and 5 micrograms, respectively) were injected s.c. twice daily for 7 days to hypophysectomized and photoinhibited hamsters. other photoinhibited hamsters were treated for 14 and 21 days with fsh and lh (3 iu and 3 micrograms ... | 1989 | 2516470 |
| effect of melatonin infusion duration and frequency on gonad, lipid, and body mass in pinealectomized male siberian hamsters. | the goal of this study was to discriminate between two hypotheses regarding how the circadian rhythm of pineal melatonin (mel) production transmits photoperiodic information: (1) a circadian rhythm of sensitivity to mel regulates the hormone's effect; (2) the duration of the mel signal, rather than its circadian timing, is the critical parameter of the mel rhythm. the experiment examined the response of pinealectomized (pinx) male siberian hamsters to 10-hr (short-day-type) versus 6-hr (long-day ... | 1989 | 2519605 |
| a comparison of some photoreceptor characteristics in the pineal and retina. ii. the djungarian hamster (phodopus sungorus). | a rod-specific antiserum was used to immunolabel elements within the retina and pineal of the adult djungarian hamster and welsh mountain sheep. in the retina immunostaining was localized to the outer segments and perikarya of photoreceptor cells, while in the pineal limited numbers of labelled pinealocytes were scattered throughout the gland. an enzyme-linked immunosorbent assay (elisa) was then used to obtain a quantitative measure of rod opsin in total eye and pineal extracts from the djungar ... | 1989 | 2527978 |
| non-random karyotypic changes in djungarian hamster tumors induced by 3-methylcholanthrene. | the karyotypes of 30 tumors (sarcomas and adenocarcinomas) induced with methylcholanthrene in djungarian hamsters (phodopus sungorus campbelli) have been investigated. in 23 tumors structural changes of the short arm of x-chromosome (xp+ or xp = type) were revealed. non-random rearrangements of 3p, 7q and 8q were also observed. other structural or numerical changes of the karyotype were accidential. for majority of tumors the presence of chromosome markers with long homogeneously staining region ... | 1989 | 2596955 |
| regional differences in fat pad responses to short days in siberian hamsters. | siberian hamsters exhibit decreased body weight and fat after initial exposure to short photoperiods and increased body weight and fat after extended short photoperiod exposure. the purpose of the present experiments was to determine if uniform changes in white adipose tissue (wat) pad weights and lipid metabolism correspond to these short photoperiod-induced changes in body fat. carcass lipid content and testes and fat pad weights [retroperitoneal wat (rwat), epididymal wat (ewat), and inguinal ... | 1989 | 2604008 |
| reception of photoperiodic information by fetal siberian hamsters: role of the mother's pineal gland. | the rate of reproductive development in juvenile male siberian hamsters is strongly influenced by daylength (photoperiod). recent studies indicate that reception of photoperiodic cues begins during fetal life. the present experiments yielded a further demonstration that developing male siberian hamsters receive information about the photoperiod to which their mother is exposed during pregnancy. the possibility that photoperiodic information is transmitted from mother to young after birth was inv ... | 1989 | 2607327 |
| immunohistochemical localization of neuropeptide y in nerves of the male genital tract of the photoperiodically responsive djungarian hamster, phodopus sungorus. | neuropeptide y (npy) was demonstrated by immunohistochemistry in nerves of the male genital tract of phodopus sungorus at long (ld 16:8) und short (ld 8:16) photoperiods. no immunoreactive nerve fibres could be demonstrated in the testis, caput and corpus epididymidis and the ventral prostate gland. dense networks of npy-containing nerve fibers were demonstrated in the smooth muscle layer of the sperm-transporting duct, beginning in the cauda epididymidis with increasing density towards the dist ... | 2005 | 2619101 |
| photoperiodic influence on the innervation of the ductus epididymidis and ductus deferens of the djungarian hamster, phodopus sungorus: electron-microscopic and biochemical results. | the influence of long (light:dark 16:8) and short (light:dark 8:16) photoperiods on the autonomic innervation of the ductus epididymidis and the ductus deferens of phodopus sungorus was studied using electron microscopy with morphometric analyses, and biochemical methods. at short photoperiods, only the large smooth muscle cells in the ductus deferens became atrophic, the number of mainly adrenergic varicosities in the smooth muscle layer decreased, and the mean distance between varicosity and s ... | 1989 | 2713891 |
| ultrastructural localization of thyrotropin (tsh)-like immunoreactivity in specific secretory cells of the hypophyseal pars tuberalis in the djungarian hamster, phodopus sungorus. | specific secretory cells in the hypophyseal pars tuberalis of djungarian hamsters maintained under different photoperiods were investigated immunocytochemically by means of the colloidal gold technique using antibodies against rat thyrotropin (tsh). secretory cells of animals kept under long photoperiods (ld16:8) showed positive staining of secretory granules (diameters 90-130 nm), whereas other intracellular structures were free of immunoreactivity. in animals kept under short photoperiods (ld8 ... | 1989 | 2743401 |
| control of torpor and body weight patterns by a seasonal timer in siberian hamsters. | two experiments were designed to assess whether the short-day-induced patterns of shallow daily torpor, body weight, and other seasonal responses (food intake and pelage pigmentation) exhibited by siberian hamsters (phodopus sungorus sungorus) are under the control of a "seasonal timekeeping mechanism" that is independent of reproductive status [testosterone, (t)]. we examined whether the patterning and expression of these seasonal responses were altered by decreases in serum t that accompany go ... | 1989 | 2750957 |
| suprachiasmatic nuclei influence torpor and circadian temperature rhythms in hamsters. | siberian hamsters were maintained in a short-day photoperiod (8 h light-day) at 15 degrees c; body temperature (tb) and locomotor activity were telemetrically recorded at 10-min intervals over the course of 5 mo. animals manifesting repeated torpor bouts (tb less than 30 degrees c for several hours) were subjected to lesions of the suprachiasmatic nuclei (scn), pinealectomy, or sham operations. in the 15 wk after surgery, none of the animals with bilateral lesions of the scn exhibited torpor; ci ... | 1989 | 2750960 |
| differential effects of paternal presence on pup survival in two species of dwarf hamster (phodopus sungorus and phodopus campbelli). | the effect of the presence or absence of the male, and of decreased ambient temperature (21 degrees c vs. 4 degrees c) on litter survival, pup survival and pup growth was measured from birth through day 18 after birth in siberian (p. sungorus) and djungarian (p. campbelli) hamsters. siberian hamsters were not significantly affected by the experimental manipulations. in contrast, whereas 100% of litters and 95% of pups were successfully raised to weaning at 21 degrees c by paired djungarian hamst ... | 1989 | 2756037 |
| maternal transfer of photoperiodic information in siberian hamsters. ii. the nature of the maternal signal, time of signal transfer, and the effect of the maternal signal on peripubertal reproductive development in the absence of photoperiodic input. | peripubertal reproductive development of siberian hamsters is controlled by maternally derived photoperiodic information and the ambient photoperiod present after weaning. previous experiments suggested that the maternally derived information is transferred during gestation, not during lactation. development was examined in several photoperiods following manipulation of gestational and lactational photoperiods; development was influenced by the gestational, but not lactational, photoperiod. seco ... | 1989 | 2758085 |
| antigonadal activity of the melatonin analogs 2-iodomelatonin and 2-chloromelatonin in the juvenile djungarian hamster, phodopus sungorus campbelli. | the antigonadal effects of daily (20 micrograms, s.c.) injection of melatonin and two analogs, 2-iodomelatonin and 2-chloromelatonin, were compared in juvenile djungarian hamsters housed under long photoperiod (l:d 16:8). melatonin, 2-iodomelatonin, and 2-chloromelatonin injected 3 h before lights off for 16 days (17-34 days of age) significantly inhibited testis growth compared to vehicle-injected hamsters. in addition, melatonin and both analogs significantly reduced body weight gain. these 2- ... | 1989 | 2769572 |
| photoperiodic influence on the innervation of the ductus epididymidis and ductus deferens of phodopus sungorus--light microscopic studies. | the influence of long (ld 16:8) and short (ld 8:16) photoperiods on the autonomic innervation of the ductus epididymidis and ductus deferens of phodopus sungorus was studied using the glyoxylic acid-induced catecholamine fluorescence and acetylcholinesterase (ache) histochemical methods. ache-positive nerve fibres could be demonstrated in the smooth muscle layer along the whole sperm transporting duct, in the lamina propria and within the epithelium of the ductus deferens. the extent and intensi ... | 1989 | 2782610 |
| maternal transfer of photoperiodic information in siberian hamsters. iii. melatonin injections program postnatal reproductive development expressed in constant light. | in siberian hamsters, transference of photoperiodic information from dam to fetus influences pubertal testicular development of the young when reared either in constant light (ll) or postnatal photoperiods of intermediate length (i.e. 14l:10d). the effects of short photoperiods during gestation can be mimicked by administering melatonin to pregnant females. this experiment examined whether there exists a daily pattern of sensitivity to melatonin when it is administered to pineal-intact pregnant ... | 2009 | 2804208 |
| pineal and pituitary involvement in the photoperiodic regulation of body weight, coat color and testicular size of the djungarian hamster, phodopus sungorus. | hypophysectomy of 40-day-old male hamsters kept under long photoperiods resulted in a change in coat color from the brownish summer coat to the whitish winter coat, within 5 wk of the surgery, cessation of growth, and, most frequently, an additional loss in body weight. the testes of the hypophysectomized animals were involuted within 14 days after surgery. continuous substitution of prolactin by implantation of two anterior pituitaries under the kidney capsule was able to reverse partly or tota ... | 1988 | 2846085 |
| circadian locomotor activity rhythm under the influences of temperature cycle in the djungarian hamster, phodopus sungorus, entrained by 12 hour light-12 hour dark cycle. | effects of temperature cycle (25 degrees c during light and 10 degrees c during dark) on circadian locomotor activity rhythm entrained by 12 hr light-12 hr dark cycle were studied in the dark active djungarian hamster. the amounts of activity per 24 hr were significantly greater under temperature cycle than under constant temperature of 25 degrees c. phase angle difference between activity onset and light off was always more positive under temperature cycle than under constant temperature. these ... | 1985 | 2864167 |
| ventilation and metabolism of the djungarian hamster (phodopus sungorus) and the albino mouse. | metabolic rates (o2 consumption and co2 production) were similar in the djungarian hamster and the white mice. the djungarian hamster had a decreased tidal volume, an increased frequency of breathing (due to a lengthened expiratory time) and a decreased minute ventilation compared to that of the mouse. although the relative ventilatory increase in response to hypercapnia or hypoxia was similar in the hamster and the mouse, the breathing patterns during exposures differed. | 1985 | 2865035 |
| seasonal changes of heart weight and erythrocytes in the djungarian hamster, phodopus sungorus. | djungarian dwarf hamsters (phodopus sungorus) show an annual cycle in weight-specific metabolic rate with a high level during winter. these seasonal changes in oxygen demand are met by hematological adjustments, primarily based on an increased number of erythrocytes, but a decreased erythrocyte volume during winter. subsequently, the diffusion area for blood gas exchange is increased during this time of high metabolic capabilities. blood oxygen capacity (hemoglobin, 2,3-diphosphoglycerate (2,3-d ... | 1986 | 2873924 |
| metabolism and thermoregulation in two races of djungarian hamsters: phodopus sungorus sungorus and p. s. campbelli. | two races of djungarian hamsters (phodopus sungorus sungorus and p. s. campbelli) differ in their responses to low ambient temperatures. the lowest temperature tolerated is 6-10 degrees c higher in p. s. campbelli than in p. s. sungorus, both in summer and in winter, but the highest (vo2-max) and lowest (bmr) metabolic rates are similar in both subspecies. body temperature and overall conductance in the cold appear to be more variable in p. s. campbelli than in nominative sp. | 1987 | 2882893 |
| seasonal changes in circulating levels of thyroid hormones are not dependent on the age in djungarian hamsters phodopus sungorus. | 1. plasma levels of total and free thyroxine (t4; ft4) and triiodothyronine (t3; ft3) were measured by radioimmunoassay in adult and senescent djungarian hamsters at different times of the year. 2. seasonal changes of both hormones were found in adult and senescent hamsters. 3. however, except for total thyroxine, the patterns were different in both groups of hamsters. 4. these results suggest, that in djungarian hamsters age-related changes of thyroid function do not affect the secretory activi ... | 1987 | 2889578 |
| thyroid medullary carcinoma of the djungarian hamster phodopus sungorus. ultrastructural evidence for the production of normal and atypical intracellular granules. | we have carried out an electron microscopic and immunocytochemical study of thyroid medullary carcinoma arising spontaneously in the djungarian hamster, phodopus sungorus. at the ultrastructural level the cytoplasm of tumor cells contained numerous round to slightly elongated, dense-cored secretory granules. the number of secretory granules differed from cell to cell in the tumor, being scanty in some cells but more or less abundant in most. electron microscopic-immunocytochemistry demonstrated ... | 1988 | 2895541 |
| effects of photoperiod, temperature and testosterone-treatment on plasma t3 and t4 levels in the djungarian hamster, phodopus sungorus. | the effects of photoperiod, temperature and testosterone treatment on plasma t3 and t4 levels were investigated in the djungarian hamster. plasma t3 level was affected by temperature (25 degrees c less than 7 degrees c) but not by photoperiod. plasma t4 level was affected by photoperiod (short day less than long day) at 25 degrees c. administration of testosterone increased plasma t4 level under short photoperiod at 25 degrees c. thus, higher plasma t4 level under long photoperiod at 25 degrees ... | 1989 | 2912765 |