| different in vivo metabolic activities of suprachiasmatic nuclei of turkish and golden hamsters. | the 14c-labeled 2-deoxy-d-glucose technique was used to measure in vivo glucose utilization of the suprachiasmatic nuclei (scn) of turkish and golden hamsters during the middle hours of the light phase of the 12:12 h light-dark cycle. the nuclei were clearly visible on autoradiographs made from the brains of turkish hamsters, and their rate of glucose utilization (69 +/- 6 mumol.100 g-1.min-1) was similar to that previously measured in other rodents, whereas the nuclei were hardly visible on aut ... | 1990 | 2240268 |
| comparative anatomy of the retino-hypothalamic tract in photoperiodic and non-photoperiodic rodents. | this study examined whether the nearly symmetrical input from each eye to each suprachiasmatic nucleus previously reported in syrian hamsters (mesocricetus auratus) is a universal feature of retino-hypothalamic projections in photoperiodic rodents. intraocular injections of horseradish peroxidase (hrp) were used to trace the retino-hypothalamic tract in three species of photoperiodic rodents, turkish hamster (mesocricetus brandti), deer mouse (peromyscus maniculatus bairdi) and white-footed mous ... | 1986 | 2430681 |
| termination of gonadal refractoriness in turkish hamsters, mesocricetus brandti. | the turkish hamster (mesocricetus brandti) is a photoperiodic species. in this investigation, we characterized the photoperiodic requirements for termination of gonadal refractoriness, defined as the inability of the animal to respond to short-day treatment with gonadal regression. paired testes weights were reduced to less than 20% of their original weight by 10 wk of 12l:12d treatment. this was followed by spontaneous testicular recrudescence (completed by week 25 of 12l:12d treatment), the ov ... | 1988 | 3378077 |
| effects of exogenous and endogenous melatonin on gonadal function in hamsters. | in this article we review the functions of the pineal gland and of pineal melatonin in regulating gonadal activity in three species of hamster, the golden (syrian) hamster (mesocricetus auratus), the turkish (brandt's) hamster (mesocricetus brandti), and the djungarian (siberian, or hairy-footed) hamster (phodopus sungorus sungorus). some experimental treatments elicit the same response in all three species; this is especially true for the regulation of the nocturnal elevation of pineal melatoni ... | 1986 | 3462343 |
| pinealectomy and constant release of melatonin or 5-methoxytryptamine induce testicular atrophy in the european hamster (cricetus cricetus, l.). | the role of the pineal and of photoperiod in the regulation of gonadal activity has been studied in the european hamster, a wild hamster commonly found in the vicinity of strasbourg, france. besides the presence of a probable endogenous circannual rhythm in reproductive capacities, it appears that, as in all other hamster species studied to date, the sexual activity of this animal is directly regulated by changes in the photoperiodic environment. pinealectomy as well as a constant release of mel ... | 1987 | 3470503 |
| a mathematical method for estimating paired testes weight from in situ testicular measurements in three species of hamster. | linear regression analysis was used to determine the correlation between testicular volume (calculated from measurements of length and width) and weights of paired testes. line equations that can be used to predict weights of paired testes from the volume of one or both testes are given for three species of hamster (mesocricetus auratus, mesocricetus brandti, and phodopus sungorus sungorus). because these parameters are highly correlated (r greater than or equal to 0.97), the line equations prov ... | 1985 | 4073579 |
| pineal is required for testicular maintenance in the turkish hamster (mesocricetus brandti). | the effect of pinealectomy on reproductive function was examined in the turkish hamster, mesocricetus brandti. pinealectomy resulted in testicular regression in this species. this result was unexpected since pinealectomy prevents short day-induced regression of the gonads in the closely related syrian hamster, mesocricetus auratus. decentralization of the superior cervical ganglia and exposure to continuous illumination also caused testicular regression in the turkish hamster. these manipulation ... | 1982 | 6809448 |
| non-agonistic familiarity decreases aggression in male turkish hamsters, mesocricetus brandti. | in laboratory studies, hamsters (mesocricetus spp.) exhibit intense male-male aggression, thus making them an excellent model system for studies of the functional and mechanistic bases of aggression. in a field study of golden hamsters (m. auratus) in the wild, however, the few documented male-male interactions were not highly aggressive. thus, we tested the hypothesis that familiarity modulates aggression in hamsters. previous investigations of the effects of familiarity on aggression have most ... | 2009 | 20126280 |
| avoidance of interspecific mating in female syrian hamsters is stronger toward familiar than toward unfamiliar heterospecific males. | adult syrian hamster females (mesocricetus auratus) learn to discriminate against familiar heterospecific males (turkish hamster, m. brandti). we investigated whether females learn to avoid any heterospecific male after exposure to just one heterospecific male. we predicted that, after being exposed to one heterospecific male, a female would avoid mating not only with that familiar male but also with any unfamiliar heterospecific male. we exposed females to a heterospecific male across a wire-me ... | 2011 | 21347669 |
| unique state of sexual dimorphism of crossing-over in diplotene spermatocytes and oocytes of mesocricetus brandti, a species with neonatal oogenesis. | sexual dimorphism of recombination has been held by classic genetic theory to disfavor the heterogametic sex. assessment of chiasma frequencies at the diplotene stage of meiosis has been used as a valid measure of this concept and in many species has revealed, as expected, an increased frequency in female vs. male germ cells. mesocricetus brandti, a species currently used in investigations of gonadal regression, photoperiods, and hibernation, was found by this measure to be an exception to this ... | 2006 | 1782293 |
| laguna negra virus infection causes hantavirus pulmonary syndrome in turkish hamsters (mesocricetus brandti). | laguna negra virus (lnv) is a new world hantavirus associated with severe and often fatal cardiopulmonary disease in humans, known as hantavirus pulmonary syndrome (hps). five hamster species were evaluated for clinical and serologic responses following inoculation with 4 hantaviruses. of the 5 hamster species, only turkish hamsters infected with lnv demonstrated signs consistent with hps and a fatality rate of 43%. clinical manifestations in infected animals that succumbed to disease included s ... | 2016 | 25722219 |
| the circadian system of the turkish hamster, mesocricetus brandti: responses to light. | the circadian system of the turkish hamster controlling wheel-running activity responded to single 1-hr light pulses and to repeated 1-hr pulses in a similar way as that of syrian hamsters studied previously. at constant light of 100 lx, the period length (tau) of the freerunning activity rhythm of turkish hamsters was longer and the activity time (alpha) was shorter than that of syrian hamsters. among individuals, the ability of the system to be entrained by one 1-hr light pulse per cycle was r ... | 1985 | 2863051 |
| daily rhythms of follicle-stimulating hormone in adult anestrous and prepubertal female turkish hamsters (mesocricetus brandti). | we tested the hypothesis that daily fsh surges are correlated with the anestrous condition in adult turkish hamsters. blood samples were collected from anestrous hamsters on short (12l:12d) and long photoperiods (16l:8d) by cardiac puncture. both photoperiod-induced anestrous (pia) and spontaneously anestrous adult turkish hamsters had a daily rhythm of fsh secretion with maximum hormone concentrations occurring late in the afternoon. we also hypothesized that daily fsh and progesterone surges a ... | 1992 | 1536903 |
| the pachytene chromomere map of the oocyte of the turkish hamster (mesocricetus brandti). | a study of the chromomere maps of the sex and twenty autosomal bivalents of turkish hamster pachytene oocytes was carried out. the average total number of chromomeres in early/mid pachytene autosomes was 280 with 91 on the p (short arm) and 189 on the q (long arm). the submetacentric x1 chromosome had 20 chromomeres and the metacentric x2 had 27. comparisons of the number and location of oocyte chromomeres are made with the pachytene spermatocyte chromomere maps of this species. | 1991 | 1868000 |
| seasonal regulation of neuroendocrine activity in male turkish hamsters (mesocricetus brandti): role of the hypothalamic paraventricular nucleus. | male turkish hamsters received horizontal knife cuts within the hypothalamus to investigate the role of afferent and efferent projections of the paraventricular nucleus (pvn) in seasonal regulation of endocrine function. following surgery, the animals were exposed to either a long (16 h light/8 h dark) or a short (8 h light/16 h dark) photoperiod. similar to pinealectomy, knife cuts placed ventral to the pvn, so as to disrupt transfer of photic information to the pineal gland, resulted in a rapi ... | 1992 | 1565210 |
| patterns of immunocytochemically detected z-dna in the recrudescing testicular epithelium of the turkish hamster (mesocricetus brandti). | z-dna has been considered a labile but essential structural form of dna in recombination and gene expression, two significant activities in mammalian seminiferous epithelium. the present study has utilized the recrudescing testes of mesocricetus brandti to study in detail the potential z-dna sites in specific testicular cell types as detected by an immunoprobe. testicular regression was physiologically induced by modifying environmental photoperiods and/or temperature. partial atrophy of seminif ... | 1992 | 1499879 |
| a single injection of adrenergic agonists enhances pineal melatonin production in turkish hamsters. | the purpose of this study was to determine whether the pineal gland of turkish hamsters (mesocricetus brandti) responds to adrenergic agonists with an increase in melatonin production, and, if it does, whether the sensitivity of the pineal gland to agonists would differ throughout the dark phase. adult turkish hamsters weighting 110-210 g received a subcutaneous injection of isoproterenol (iso, 1 mg/kg b.w.) or norepinephrine (ne, 1 mg/kg b.w.) at different times of night. animals exposed to ld ... | 1993 | 8336275 |
| a melatonin-independent seasonal timer induces neuroendocrine refractoriness to short day lengths. | the duration of nocturnal pineal melatonin secretion transduces effects of day length (dl) on the neuroendocrine axis of photoperiodic rodents. long dls support reproduction, and short dls induce testicular regression, followed several months later by spontaneous recrudescence; gonadal regrowth is thought to reflect development of tissue refractoriness to melatonin. in most photoperiodic species, pinealectomy does not diminish reproductive competence in long dls. turkish hamsters (mesocricetus b ... | 2008 | 18487416 |
| elimination of short-day melatonin signaling accelerates gonadal recrudescence but does not break refractoriness in male turkish hamsters. | long days stimulate and short days (sds) inhibit the reproductive axis of photoperiodic rodents. in long-day turkish hamsters, unlike most other rodents, elimination of pineal melatonin secretion by constant light or pinealectomy initiates a cycle of gonadal involution and recrudescence outwardly similar to that induced by short days. the present study assessed whether short days and constant light induce the seasonal reproductive cycle via common or different interval timing mechanisms. male ha ... | 2011 | 21454293 |
| hibernation patterns of turkish hamsters: influence of sex and ambient temperature. | turkish hamsters (mesocricetus brandti) are a model organism for studies of hibernation, yet a detailed account of their torpor characteristics has not been undertaken. this study employed continuous telemetric monitoring of body temperature (t(b)) in hibernating male and female turkish hamsters at ambient temperatures (t(a)s) of 5 and 13 °c to precisely characterize torpor bout depth, duration, and frequency, as well as rates of entry into and arousal from torpor. hamsters generated brief inter ... | 2013 | 22983485 |
| the effects of day length, hibernation, and ambient temperature on incisor dentin in the turkish hamster (mesocricetus brandti). | dentin is deposited on a circadian basis, and daily layers manifest as bands on the medial surfaces of rodent incisors. hibernation alters dentin deposition, and a distinct hibernation mark has been described on incisor surfaces of several rodent species; the factors that influence the morphology of this mark are poorly understood. we tested the effects of day length, torpor expression, and ambient temperature on incisor surface morphology in turkish hamsters housed in one of four conditions: lo ... | 2013 | 23233167 |
| effects of pinealectomy and short day lengths on reproduction and neuronal rfrp-3, kisspeptin, and gnrh in female turkish hamsters. | long days (lds) stimulate and short days (sds) inhibit reproduction in photoperiodic rodents by modifying nocturnal pineal melatonin secretion. in ld turkish hamsters, unlike other rodents, pinealectomy induces reproductive quiescence comparable to that produced by sds. we assessed whether sds and pinealectomy induce similar or different patterns of kisspeptin and gonadotropin-inhibitory hormone (also known as rfamide-related peptide-3 [rfrp-3] in mammals) expression, important mediators of seas ... | 2014 | 24916391 |
| asymmetric learning to avoid heterospecific males in mesocricetus hamsters. | if a female mates with a male of a closely related species, her fitness is likely to decline. consequently, females may develop behavioral mechanisms to avoid mating with heterospecific males. in some species, one such mechanism is for adult females to learn to discriminate against heterospecific males after exposure to such males. we have previously shown that adult, female syrian hamsters (mesocricetus auratus) learn to discriminate against male turkish hamsters (mesocricetus brandti) after ex ... | 2012 | 22658324 |
| interactions with heterospecific males do not affect how female mesocricetus hamsters respond to conspecific males. | reproductive interference includes any interspecific interaction that reduces the fitness of one or both species involved. there are several types of reproductive interference, but they normally involve the direct cost of interacting or mating with heterospecifics. an indirect cost of interacting with heterospecific individuals is a consequent reduction in successful interactions with conspecifics. we tested the hypothesis that being aggressive towards a heterospecific individual will diminish s ... | 2013 | 23439800 |
| the chromomere map of the pachytene spermatocyte of the turkish hamster (mesocricetus brandti). | the chromomere map of the early to mid pachytene spermatocyte of the turkish hamster (mesocricetus brandti) is described. each autosomal bivalent was identified and a total of 304 chromomeres was found. a sex bivalent with a despiralized xq protruding from the sex vesicle and a small number of the polymorphic 16q bivalents were observed. | 2001 | 1783302 |
| adult female hamsters require long and sustained exposures to heterospecific males to avoid interspecific mating. | interspecific mating normally decreases female fitness. in many species, females avoid heterospecific males innately or by imprinting on their parents. alternatively, adult females could learn to discriminate against heterospecific males after exposure to such males. for example, syrian hamster (mesocricetus auratus) females learn to discriminate between conspecific males and turkish hamster (m. brandti) males during adulthood by exposure to males of both species. adult females not previously ex ... | 2011 | 21572573 |
| adult female hamsters avoid interspecific mating after exposure to heterospecific males. | when females mate with a heterospecific male, they do not usually produce viable offspring. thus, there is a selective pressure for females to avoid interspecific mating. in many species, females innately avoid heterospecific males; females can also imprint on their parents to avoid later sexual interactions with heterospecific males. however, it was previously unknown whether adult females can learn to discriminate against heterospecific males. we tested the hypothesis that adult females previo ... | 2010 | 20676390 |
| hibernation in the female turkish hamster (mesocricetus brandti): an investigation of the role of the ovaries and of photoperiod. | the possible role of the ovaries in hibernation was examined by comparing patterns of hibernation in intact and ovariectomized turkish hamsters (mesocricetus brandti). ovariectomy had little, if any, effect on hibernation in these studies. however, females which were anovulatory prior to cold exposure entered hibernation more rapidly as compared to cycling females. most females (both intact and ovariectomized) maintained in short days returned to a second phase of hibernation several months afte ... | 1982 | 6890852 |
| lipofuscin accumulation and hibernation in the turkish hamster, mesocricetus brandti. | this report is based on previous data that showed that turkish hamsters that hibernated lived longer than nonhibernating controls. fluorescent microscopy was used to measure the lipofuscin content of brain and heart of hamsters that hibernated for various fractions of their lives. according to regression data the 13 animals that hibernated 11 to 37% of their lives had a slower accumulation of lipofuscin than 11 animals that hibernated 0 to 7% of their lives. it was calculated that the total amou ... | 1982 | 7086076 |
| hibernation and longevity in the turkish hamster mesocricetus brandti. | a positive correlation was found between the length of life of 288 turkish hamsters and the amount of time spent in hibernation, suggesting that the process of aging is slowed during hibernation. | 1981 | 7221552 |
| [discovery of a new focus of zoonotic plague in the eastern azarbaidjan region of iran]. | the surveillance of territories surrounding the plague focus of kurdistan province in iran, by inspection of wild rodent burrows, permit to reveal the existence of an epizootic in a new focus located in the eastern azarbaidjan province, where plague was never reported. 14 strains of y. pestis were isolated from meriones vinogradovi, m. persicus mesocricetus brandti and from the fleas: xenopsylla conformis and nosopsylla iranus iranus. the eventual relationship between these two areas separated b ... | 2013 | 7418121 |
| karyotypes of mesocricetus brandti and hybridization within the genus. | | 2005 | 5031316 |
| [effect of prolonged sleep (hibernation) on the appearance and growth of malignant tumors in mesocricetus brandti]. | | 1952 | 14926621 |
| nematodes of rodents of armenia | this review summarizes known data on the species composition of nematodes in 24 species of rodents inhabiting the territory of armenia (south of lesser caucasus). the studied rodents include members of some cosmopolitan species (mus musculus, rattus norvegicus, rattus rattus), as well as endemic and narrow-areal species (meriones vinogradovi, spermophilus xanthoprymnus, microtus schidlovskii, mesocricetus brandti, sciurus anomalus). the taxonomical identity of the nematode species reported by pr ... | 2019 | 30316207 |
| fluoxetine does not prevent interspecific mating between two hamster species. | in a recent study we showed that female syrian hamsters (mesocricetus auratus) from a laboratory stock readily mated with male turkish hamsters (m. brandti). we hypothesized that captivity and/or unconscious selection of the most receptive females by researchers or animal caretakers results in heightened female sexual receptivity and reduces the tendency to reject heterospecific males. to test this hypothesis, we decided to decrease female receptivity by injection of fluoxetine, which increases ... | 2010 | 20149811 |
| absence of functional short-wavelength sensitive cone pigments in hamsters (mesocricetus). | studies of syrian golden hamsters (mesocricetus auratus) have yielded contradictory evidence as to whether the retina of this species supports a population of cones containing short-wavelength sensitive pigments. we undertook a re-examination of this issue by (a) measuring lens transmission, (b) determining complete spectral sensitivity functions using electroretinogram (erg) flicker photometry, (c) employing a sensitive chromatic-adaptation paradigm in conjunction with erg measurements to condu ... | 2008 | 18259758 |
| similarity in the qualities of individual odors among kin and species in turkish (mesocricetus brandti) and golden (mesocricetus auratus) hamsters. | in this investigation, the authors used habituation techniques to explore similarities and differences in the qualities of individual odors from hamsters. in experiment 1, male turkish hamsters (mesocricetus brandti) treated flank-gland odors of 2 males from 1 litter as similar compared with the odor of a male from another litter, whether the odor donors were familiar or unfamiliar. at the same time, the turkish hamsters discriminated between the subtle differences in the individual odors of the ... | 1999 | 10497798 |
| effect of hamster pregnancy on female protein, a homolog of serum amyloid p component. | pentraxins such as human serum amyloid p component (sap) and c reactive protein (crp) represent an ancient family of proteins that are ubiquitous in nature and have evolved with little change in structure or regulation. the pentraxin in the syrian hamster (mesocricetus auratus) is unique because it is preferentially expressed in the female at high constitutive levels and accordingly called female protein (fp) or fp(sap) due to its close homology with human sap. the high levels of fp in female se ... | 1999 | 10460699 |
| the impact of photoperiods and melatonin on gonadal development in juvenile turkish hamsters (mesocricetus brandti). | the reproductive response of both intact adult and juvenile turkish hamsters has been thoroughly studied and shown to be similar, unlike the golden hamster where juveniles remain aphotoperiodic until approximately 8 weeks of age. unstudied to date, however, is the role of the pineal and its hormone melatonin in generating the testicular response to photoperiod in juvenile turkish hamsters. therefore, in this study we examined the reproductive response of prepubertal male turkish hamsters, subjec ... | 1998 | 9885988 |
| female protein, amyloidosis, and hormonal carcinogenesis in turkish hamster: differences from syrian hamster. | the syrian hamster (mesocricetus auratus) has been widely used as an experimental animal and is a unique model for three sex hormone-regulated events: 1) estrogen-initiated renal carcinogenesis, 2) sex-limited expression of amyloidosis, a ubiquitous disease, and 3) sex hormone control of a serum amyloid p component (sap) called female protein (fp). in this study, we evaluated the closely related turkish hamster (mesocricetus brandti) for these three events and found some very different responses ... | 1997 | 9321870 |
| histamine enhances synaptic transmission in hippocampal slices from hibernating and warm-acclimated turkish hamsters. | the effects of histamine on synaptic transmission were studied at 37 degrees c and 22 degrees c with extracellular recordings of stimulus-induced population action potentials in area ca1 of hippocampal slices prepared from hibernating (hth) and warm-acclimated turkish hamsters (wth) and rats. in rat slices, application of 50 microm histamine had no effects on population spikes and field excitatory postsynaptic potentials (epsps). in hth as well as wth slices, 50 microm histamine generally increa ... | 1996 | 8783287 |
| effects of adenosine on synaptic transmission in hippocampal slices from hibernating and warm-acclimated turkish hamsters and rats. | the effects of adenosine on synaptic transmission were studied with extracellular recordings of stimulus-induced population action potentials in area ca1 of hippocampal slices prepared from hibernating (hh) and warm-acclimated turkish hamsters (wh) and rats. in hh as well as wh and rat slices, adenosine generally reduced the population spike amplitude and the slope of the field epsp. the sensitivity for adenosine was significantly lower in hh slices than in wh and rat slices. the results are dis ... | 1995 | 7753495 |
| long-term potentiation at low temperature is stronger in hippocampal slices from hibernating turkish hamsters compared to warm-acclimated hamsters and rats. | tetanus-induced long-term potentiation (ltp) of population action potentials at 22 degrees c was investigated in area ca1 of hippocampal slices prepared from hibernating (hh) and warm-acclimated turkish hamsters (wh) and rats. ltp elicited at this temperature was significantly stronger in hh slices compared to wh and rat slices. hibernation-related improvement of the ability to develop long-lasting enhancement of synaptic transmission at low temperatures is interpreted as supporting hippocampal ... | 1995 | 7478194 |
| functional maturation of the gonads of turkish hamsters under various photoperiods. | the golden hamster, mesocricetus auratus, is the only photoperiodic rodent to date that has been shown to fail to respond to inhibitory (i.e., short, less than 12.5 h/day) photoperiods until after pubertal onset. in other photoperiodic hamsters, mice, and voles, short photoperiods greatly retard gonadal maturation. the turkish hamster, mesocricetus brandti, is a photoperiodic rodent that as an adult is reproductively competent only on photoperiods of 15-17 h of light per day; photoperiods of les ... | 1986 | 3814699 |
| some characteristics of oogenesis in the female turkish hamster subjected to modified environments. | the hibernating female turkish hamster (mesocricetus brandti) was utilized for a study of possible in vivo effects of cold on oocyte maturation. such a physiologic model offered an opportunity to analyze the ability of oocytes exposed to prolonged periods of reduced core temperature and/or light to subsequently mature to metaphase ii. detailed observations of core temperatures, torpor/arousal, serum estradiol, and ovarian histology were made. an average incidence of 37.7% binuclearity was found ... | 1992 | 1600958 |
| effects of high fat diets on hibernation and adipose tissue in turkish hamsters. | the effects of dietary fat saturation and fat content on hibernation and several properties of white and brown adipose tissue (wat and bat, respectively) were investigated in turkish hamsters (mesocricetus brandti). male hamsters were housed in a long photoperiod (ld 16:8) at 23 degrees c and fed one of three diets: (1) chow (6.5% fat per weight), (2) chow + 13.5% vegetable oil (oil, 20% fat per weight [largely unsaturated fat]) and (3) chow + 13.5% vegetable shortening [(shortening, 20% fat per ... | 1991 | 1744246 |
| the timing of gonadal refractoriness in the female turkish hamster (mesocricetus brandti) is not dependent on the timing of gonadal regression. | when prepubertal female turkish hamsters are reared on 12l:12d, individuals respond reproductively in two ways; the majority exhibit a delay in the onset of regular vaginal estrous cyclicity (first vaginal estrus; fve), and some individuals exhibit fve at a time not different from females reared on 16l:8d. soon, however, these females also become reproductively quiescent. this study addresses the following questions: (1) at what age do these two subpopulations become refractory to 12l:12d? (2) i ... | 2006 | 2383607 |
| uterine steroid hormone receptors during the estrous cycle and during hibernation in the turkish hamster (mesocricetus brandti). | the turkish hamster is a long-day breeder that hibernates for 4-5 mo if exposed to a short-day, cold environment. the objective of this study was to assess the uterine responsiveness of the hibernating animal to ovarian steroids. our approach was 1) to characterize and determine uterine estrogen (e) and progesterone (p) receptors (r) during hibernation as compared to the levels observed in cycling females that had terminated hibernation, and 2) to assess the responsiveness of the uterus to e dur ... | 1988 | 3378072 |
| the primary structure of the hemoglobin beta-chain of the turkish hamster (mesocricetus brandti). | | 1988 | 3384704 |
| effects of photoperiod on hibernation in castrated turkish hamsters. | hibernation and circulating reproductive hormones [luteinizing hormone, follicle-stimulating hormone, and prolactin (lh, fsh, and prl)] were studied for greater than 40 wk in castrated male turkish hamsters (mesocricetus brandti) housed in either a long-day cold or short-day cold environment. a significantly greater percentage of short-day animals hibernated than did long-day animals, indicating that short-day exposure can predispose turkish hamsters to enter hibernation and that this photoperio ... | 1987 | 3113271 |
| patterns of reproductive hormone secretion in hibernating turkish hamsters. | changes in gonadal state and in circulating reproductive hormones [follicle-stimulating hormone (fsh), prolactin (prl), and testosterone] were studied for 30 wk in male turkish hamsters (mesocricetus brandti) induced to hibernate by exposure to a short-day, cold environment [10:14-h light-dark (ld) cycle, 6 +/- 1 degree c]. similar measures were compared in hamsters maintained under short-day warm conditions (10:14-h ld, 21 +/- 2 degrees c). a decrease in testicular size and in hormone levels wa ... | 1987 | 3113270 |
| circadian pacemaker does not arrest in deep hibernation. evidence for desynchronization from the light cycle. | a freerunning rhythm of locomotor activity was observed between hibernation bouts in turkish hamsters (mesocricetus brandti) kept in 10l:14d light-dark cycles at 10 +/- 1 degree c. the data further indicate an influence of natural hypothermia upon the circadian system and its ability to entrain to light-dark cycles. | 1987 | 3556522 |
| detailed diurnal rhythm of sensitivity to melatonin injections in turkish hamsters, mesocricetus brandti. | a diurnal rhythm of sensitivity to exogenous melatonin was defined in adult male turkish hamsters, mesocricetus brandti. melatonin was administered daily by subcutaneous injections (15 micrograms in 0.1 ml 10% ethanolic saline) for 10 weeks in animals exposed to 16 l:8 d. as in golden and djungarian hamsters, two periods of melatonin sensitivity were identified. the first, in late afternoon, persisted for 6 hr, from 7 hr to 1 hr before lights off. the second period was briefer, of only 2 hr dura ... | 1987 | 3559888 |
| pineal melatonin rhythms in female turkish hamsters: effects of photoperiod and hibernation. | daily rhythms of pineal and serum melatonin content were characterized for adult female turkish hamsters (mesocricetus brandti) exposed to long days (16l:8d, 22 degrees c) or after transfer to short days (10l:14d, 22 degrees c). the nocturnal peak of pineal melatonin content was found to be approximately 3 b greater in duration on short than on long days. changes in levels of serum melatonin closely paralleled those of pineal melatonin. thus, an effect of photoperiod on synthesis and secretion o ... | 1986 | 3741956 |
| maintenance of testicular function in turkish hamsters: interaction of photoperiod and the pineal gland. | adult male turkish hamsters maintained testicular function when exposed to photoperiods of 15, 16, or 17 h of light per day. photoperiods of less than 15 or greater than 17 h of light per day induced a rapid and complete testicular regression. as pinealectomy had been shown by others to induce testicular regression in long-day turkish hamsters, we thought that regression on 18 or more h of light might be based on the inability of the pineal to generate a daily rhythm of melatonin in production a ... | 1986 | 3697467 |
| lithium suppresses hibernation in the turkish hamster. | daily uptake of lithium salt (licl) in the drinking water at a rate of over 100 micrograms/g b.wt (or 2.4 meq/kg) reduced or suppressed natural torpidity (hibernation) in the turkish hamster (mesocricetus brandti). the data indicate a direct influence of lithium on clock-related functions controlling the hibernation process rather than indirect effects by preventing gonadal regression and thereby also hibernation. | 1985 | 2998859 |
| circadian organization of locomotor activity in the turkish hamster (mesocricetus brandti). | the circadian organization of locomotor activity was examined in turkish hamsters while exposed to a light-dark (ld) cycle, constant illumination (ll), and following blinding and gonadectomy. under ld 16:8 the activity rhythm of all hamsters became well entrained with activity beginning approximately 30 min after dark onset. in contrast, when activity rhythms free-ran as the result of exposure to ll or blinding, a variety of spontaneous perturbations in the period and/or phase of the activity rh ... | 1983 | 6626095 |
| role of the testis in regulating the duration of hibernation in the turkish hamster, mesocricetus brandti. | the effect of castration on hibernation was studied in male turkish hamsters (mesocricetus brandti). in the first study the animals were exposed to a long-day photoperiod from birth and throughout the period of hibernation. hibernation was induced by exposure to cold (10 degrees c). intact males usually hibernated for approximately 6-7 months and then became euthermic. males which had been castrated prior to cold exposure continued to hibernate for a longer period. none of the 6 surviving castra ... | 1982 | 7171666 |