| 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 |
| [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 |
| 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 |
| post-natal development of the pineal organ in the hamsters phodopus sungorus and mesocricetus auratus. a fluorescence microscopic and microspectrofluorometric investigation. | | 1978 | 657241 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 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 |
| 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 |
| absence of specific luteinizing hormone-releasing hormone (lhrh) receptors in the ovaries of djungarian hamsters (phodopus sungorus). | high affinity binding sites for luteinizing hormone-releasing hormone (lhrh) were characterized in djungarian hamsters. scatchard analysis was used to demonstrate specific lhrh-binding in hamster and, serving as controls, rat pituitaries (dissociation constant, kd = 0.6 nm, binding capacity, bm = 2.5 +/- 0.7 fmol/mg tissue; kd = 0.6 nm, bm = 6.9 +/- 1.9 fmol/mg tissue, respectively). in contrast to results obtained with rat ovaries (kd = 0.9 nm, bm = 3.0 +/- 0.9 fmol/mg tissue), no specific lhrh ... | 1987 | 3036261 |
| morphological studies on the muscle cysts of sarcocystis dirumpens (hoare 1933) häfner and matuschka 1984 in several host species revealing endopolygeny in metrocytes. | muscle cysts from rodents (mastomys natalensis, mus musculus, rattus norvegicus, meriones unguiculatus, phodopus sungorus) experimentally infected with sarcocystis dirumpens were examined by light and electron microscopy. the corrugated primary wall showed a pattern of densely arranged invaginations surrounded by minute bleb-like evaginations. true protrusions were absent. the length of the blebs and the thickness of the primary wall varied insignificantly but not remarkable host-dependent morph ... | 1986 | 3092488 |
| effects of immunoneutralization of luteinizing hormone (lh)-releasing hormone on testicular prolactin and lh receptors in the golden hamster and on lh receptors in the djungarian hamster. | in male syrian hamsters, seasonal transitions between reproductive activity and quiescence are accompanied by major alterations in testicular binding of lh/hcg and prl. these alterations are believed to be due to the photoperiod-induced changes in prl secretion, but other adenohypophyseal hormones appear to be involved as well. to elucidate the role of lh and fsh in the control of testicular lh/hcg and prl receptors, we have examined the consequences of selective suppression of gonadotropin rele ... | 1987 | 3315633 |
| are the short-photoperiod-induced decreases in serum prolactin responsible for the seasonal changes in energy balance in syrian and siberian hamsters? | serum prolactin (prl) decreases in syrian (mesocricetus auratus) and siberian (phodopus sungorus sungorus) hamsters following short-photoperiod exposure. both species also exhibit short-photoperiod-induced changes in body and lipid mass, but in opposite directions; syrian hamsters increase and siberian hamsters decrease their body weight, changes reflected nearly exclusively in their carcass lipid content. the purpose of these experiments was to determine whether the photoperiod-induced changes ... | 1987 | 3443832 |
| pinealocyte projections into the mammalian brain revealed with s-antigen antiserum. | neural processes from mammalian pinealocytes have been discovered in several brain areas. these processes were visualized immunocytochemically in the djungarian hamster, phodopus sungorus, with an antiserum against bovine retinal s-antigen and traced as far as the region of the posterior commissure and habenular nuclei. this result indicates that pineal-to-brain connections exist in the mammal, and that the mammalian pineal gland, currently thought of only as a neuroendocrine organ, may communic ... | 1986 | 3454660 |
| 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 |
| [nomenclature of the metaphase chromosomes of the djungarian hamster]. | the proposed nomenclature of g-banded chromosomes of phodopus sungorus campbelli is based on requisites and principles of the international system for human cytogenetic nomenclature (iscn). | 1986 | 3705170 |
| change in duration of the nighttime melatonin peak may be a signal driving photoperiodic responses in the djungarian hamster (phodopus sungorus). | a regime of 14 h of light and 10 h of darkness (ld 14:10) induced regression of testes and accessory glands in adult djungarian hamsters maintained originally in ld 16:8, but recrudescence of these organs in hamsters maintained originally in ld 8:16. duration of the period of elevated nighttime melatonin levels in ld 14:10 was the same irrespective of whether hamsters had come from ld 16:8 or from ld 8:16. it is suggested that a change in duration of the nighttime melatonin peak and its directio ... | 1986 | 3725203 |
| follicular development in immature djungarian hamsters (phodopus sungorus) and the influence of exogenous gonadotropins. | this study evaluated follicular development and oocyte growth in ovaries of immature djungarian hamsters from 8 to 28 days of age and examined the influence of exogenous gonadotropins on follicular growth. an age-specific pattern of progressive follicular development was found, beginning with a compact, virtually undifferentiated ovary containing mostly small follicles on day 8 postpartum and progressing to an ovary with mature preovulatory follicles at the end of the fourth week. antral follicl ... | 1986 | 3768461 |
| comparative morphology and evolution of cheek pouches in rodents. | there are two types of cheek pouches in extant rodents. internal cheek pouches are evaginations of the oral cavity deep to m. platysma and m. sphincter colli profundus, and have evolved independently in some species of the superfamilies sciuroidea and muroidea. external, furlined cheek pouches open lateral to and separate from the oral cavity, (also deep to m. platysma and m. sphincter colli profundus), and occur in all species of the families geomyidae and heteromyidae. the presence of external ... | 1986 | 3783717 |
| social mediation of puberty: an adaptive female strategy? | females of two hamster species with contrasting degrees of gregariousness were tested for social influences on the timing of sexual maturation. when female dwarf hamsters (phodopus sungorus campbelli), a gregarious species, were housed with an adult male at weaning, they began estrous cycles significantly earlier than when they were housed alone or with their family. females housed with one or two female siblings at weaning matured significantly later than did all other females. once mature, fem ... | 1986 | 3814041 |
| photoperiodic control of seasonal body weight cycles in hamsters. | syrian (mesocricetus auratus) and siberian (phodopus sungorus sungorus) hamsters exhibit seasonal changes in body weight mainly by altering their carcass lipid stores. these seasonal changes are triggered largely by the photoperiod. although both species exhibit gonadal regression when exposed to short photoperiods ("winterlike") daylength), they show opposite body weight changes. syrian hamsters gain weight, but siberian hamsters lose weight following short photoperiod exposure. syrian hamsters ... | 1985 | 3909016 |
| [characteristics of the distribution of dna repetitive sequences in the sex chromosomes of 4 species of rodent]. | four rodent species with very large heterochromatic regions on the sex chromosomes have been studied using in situ dna/dna hybridization techniques. repetitious dna fractions were obtained at c0t 0-0.01. heterochromatic regions of x and x chromosomes of cricetulus barabensis and phodopus sungorus, and the heterochromatic long arm of the y chromosome of mesocricetus auratus do not contain disproportionately high amounts of repeated dna sequences. heterochromatic regions on sex chromosomes of micr ... | 1985 | 3911513 |
| photic influences on the developing mammal. | in adult mammals, the daily light-dark cycle acts via the retinohypothalamic pathway to entrain the circadian clock in the suprachiasmatic nuclei (scn) and to communicate information about daylength to photoperiodic species. studies in rats show that during late fetal and early neonatal life, before the retinohypothalamic pathway has innervated the scn, the maternal circadian system entrains the timing of the developing clock to prevailing lighting conditions. although the nature of the maternal ... | 1985 | 3915455 |
| the role of ozone/oxygen in clindamycin-associated enterocolitis in the djungarian hamster (phodopus sungorus sungorus). | rectal and oral ozone-o2 gas insufflations prevented a fatal clindamycin-induced enterocolitis in djungarian dwarf hamsters. in spite of no gross lesions in the colon of these species, the term 'colitis' is justified because of intracellular degenerative changes of colon epithelial cells. dwarf hamsters are omnivores and are, therefore, more relevant to man than other animal species as an animal model for studying colitis. | 1986 | 3951192 |
| effects of diet and photoperiod on ne turnover and gdp binding in siberian hamster brown adipose tissue. | this experiment examined the effects of diet and photoperiod on food intake, body weight, and brown adipose tissue (bat) activity in female siberian hamsters (phodopus sungorus sungorus). bat function was assessed by measuring both the sympathetic nervous system activity of bat [estimated by the rate of norepinephrine (ne) turnover] and bat thermogenic activity (estimated by gdp binding to bat mitochondria). nineteen weeks of high-fat feeding in long photoperiod [16:8 light-dark cycle (ld)] caus ... | 1986 | 3953850 |
| stereological analysis of daily variation in the ultrastructure of the pars intermedia of the pituitary gland of the djungarian hamster (phodopus sungorus). | a stereological analysis has been made of the daily changes occurring in the ultrastructure of the melanotrophs of the pars intermedia of the pituitary gland of the djungarian or siberian hamster, phodopus sungorus, maintained in long day photoperiods. the rough endoplasmic reticulum, golgi apparatus and lysosomes all declined in fractional volume throughout the photophase reaching minima at mid-scotophase and rising to reach their maxima at about the time of onset of the photophase. the mitocho ... | 1985 | 4040814 |
| preferential nondisjunction of specific bivalents in oocytes from djungarian hamsters (phodopus sungorus) following colchicine treatment. | in an attempt to study the mechanisms leading to nondisjunction during meiosis i, djungarian hamster females were treated with colchicine (3 mg/kg), which binds specifically to tubulin. the number of ovulated oocytes per female was significantly reduced following colchicine treatment (8.2 +/- 5.3, compared to 10.6 +/- 5.9 in controls receiving saline solution only). application of colchicine rather late during oocyte maturation (ie, 5.5 h after injection of human chorionic gonadotrophin) caused ... | 1985 | 4042684 |
| 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 |
| body weight, food intake and energy regulation in exercising and melatonin-treated siberian hamsters. | the coupling among energy intake, storage, and expenditure was examined in male siberian hamsters (phodopus sungorus sungorus) given access to running wheels for 14 weeks. half of the hamsters were injected with melatonin in a schedule that mimics the effects of short photoperiods by decreasing body weight, carcass lipid content, and testis weight. the exercise-induced body weight increases which are seen in syrian hamsters (mesocricetus auratus) were not found in siberian hamsters. instead, the ... | 1985 | 4080844 |
| trichophyton mentagrophytes infection of the djungarian hamster (phodopus sungorus). | | 1974 | 4826198 |
| regulation of the pineal melatonin concentration in the rat (rattus norvegicus) and in the djungarian hamster (phodopus sungorus). | 1. rapid changes of melatonin concentration in pineals of rats (rattus norvegicus) after isoproterenol administration or in the course of a day were accompanied by parallel changes of n-acetyltransferase but not of hydroxyindole-o-methyltransferase activity. 2. in pineals of djungarian hamsters (phodopus sungorus) the evening and morning melatonin changes were also parallel with n-acetyltransferase changes. 3. in both species, melatonin concentration during its rise had approached the maximum ea ... | 1983 | 6130878 |
| acrosin in the spermiohistogenesis of mammals. | using the indirect immunofluorescence staining technique, the developmental pattern of acrosin during spermatogenesis of boar, ram, rabbit, mouse, rat, and russian hamster (phodopus sungorus) was studied. specific antibodies against purified boar acrosin raised in rabbits cross-reacted with the acrosin of all species investigated thus suggesting that the antigenic determinants of the acrosin molecule cross-reacting with anti-boar acrosin antiserum have been highly conserved in mammalian evolutio ... | 1983 | 6354818 |
| [laboratory animal infection in modeling intestinal schistosomiasis]. | a comparative efficiency of different regimes for infecting laboratory animals has been determined in order to find out optimal conditions under which an experimental model of intestinal schistosomiasis (infection with schistosoma mansoni) can be maintained. when evaluating the results of laboratory definitive hosts infection we took into account the character of schistosoma distribution in animals, which with high probability rate was modelled by means of negative binomial distribution. the mai ... | 1984 | 6493803 |
| effects of photoperiod and gonadectomy on food intake, body weight, and body composition in siberian hamsters. | two experiments examined the effects of gonadectomy, photoperiod, and melatonin treatment on food intake, body weight, and carcass composition in male and female siberian hamsters (phodopus sungorus sungorus). gonadectomy caused small decreases in body weight in both sexes but did not affect food intake. in males the weight reduction was due to small (nonsignificant) decreases in all carcass components. ovariectomy caused a significant reduction in carcass lipid but did not affect lean body mass ... | 1984 | 6696099 |
| melanotrophin-potentiating factor (mpf) potentiates msh-induced melanogenesis in hair follicle melanocytes. | melanotrophin-potentiating factor (mpf) is a fragment of human beta-lipotrophin (lph 88-91) which potentiates the action of alpha-msh on anolis skin. in the present study, we investigated the effect of mpf on msh-induced melanogenesis. pooled hair follicle scrapings from siberian hamsters (phodopus sungorus) were incubated for 48 hours with or without alpha-msh and/or mpf. melanogenesis was monitored by measuring tyrosinase activity and melanin accumulation. 10-8 m mpf potentiated the effect of ... | 1981 | 6794009 |
| comparative dna/dna reassociation kinetics in three hamster species. | 1. three major dna repetition classes can be distinguished in the genomes of three hamster species mesocricetus auratus, cricetulus griseus, and phodopus sungorus sungorus: a very fast reassociating fraction of about 13% of the dna, a fast reassociating fraction comprising 10-23% of the dna, and a slowly reassociating fraction containing single-copy sequences of 63-78% of hamster dna. 2. in the dna of the syrian and djungarian hamster 43%-53%, and in the dna of the chinese hamster 80% of the sin ... | 1982 | 7128102 |
| ontogeny of the pineal melatonin rhythm in the syrian (mesocricetus auratus) and siverian (phodopus sungorus) hamsters and in the rat. | the ontogeny of the pineal melatonin rhythm was determined in three rodent species. pineal glands were obtained either during the day or during the expected peak in melatonin at night. in all species the rhythm was first detected during the second week of life. investigations of the photic regulation of pineal melatonin revealed that light could inhibit the nocturnal increase in melatonin in all species by the end of the second week of life. these studies indicate that for these species the deve ... | 1980 | 7408759 |
| developmental changes of tachykinins in the hypothalamus and anterior pituitary of female siberian hamsters from prepuberty to adulthood. | the developmental changes of hypothalamic and anterior pituitary tachykinin concentrations were studied in female siberian hamsters kept either under short (sd) or long (ld) daily photoperiods. the animals were killed between 15 and 70 days of age. hypothalamic nka sharply increased starting at 15 days up to 50 days in ld animals, and between 20 and 60 days in sd animals. hypothalamic sp levels increased in a similar manner in sd animals, but in ld animals the increment was less pronounced, with ... | 1995 | 7479322 |
| photoperiod affects the expression of neural cell adhesion molecule and polysialic acid in the hypothalamus of the siberian hamster. | immunohistochemical and immunoblot procedures were used to examine the effects of inhibitory short day (sd) photoperiod on the expression of neural cell adhesion molecule (ncam) and its polysialylated form (psa-ncam) in the hypothalamus and preoptic area (poa) of the adult male siberian hamster. in animals that had undergone sd-induced gonadal regression, immunoblot analyses revealed significant reductions in the content of immunoreactive psa in anterior hypothalamic (ah) and mediobasal hypothal ... | 1995 | 7496808 |
| photoperiodic exposure and time of day modulate the expression of arginine vasopressin mrna and vasoactive intestinal peptide mrna in the suprachiasmatic nuclei of siberian hamsters. | in hamsters, changes in ambient photoperiod lead to alterations in the circadian rhythm of pineal melatonin secretion and subsequent changes in reproductive function. the present study examined whether photoperiod also alters 24-h rhythms in neuropeptide mrna levels in the scn of siberian hamsters. in situ hybridization and quantitative autoradiography were used to assess messenger rna levels for vasopressin (avp) and vasoactive intestinal peptide (vip) in the scn of hamsters sacrificed at six t ... | 1995 | 7500829 |
| hypothalamic npy and prepro-npy mrna in djungarian hamsters: effects of food deprivation and photoperiod. | two catabolic states leading to loss of body weight were compared in the djungarian hamster (phodopus sungorus campbelli). hypothalamic neuropeptide y (npy) and gene expression for npy and corticotropin-releasing factor (crf) were examined after withdrawal of food for 48 h or exposure to short photoperiod for 10 or 20 wk. food deprivation was accompanied by increases in both npy and prepro-npy mrna in the hypothalamic arcuate nucleus (arc). increases in gene expression were limited compared with ... | 1995 | 7503297 |
| immunoreactive substance p and neurokinin a in the hypothalamus and anterior pituitary gland of siberian and syrian hamsters and of rats. | in this investigation the concentrations of immunoreactive substance p and neurokinin a in the hypothalamus and anterior pituitary of the siberian hamster were compared with those in the rat and syrian hamster. the concentrations of immunoreactive neurokinin a in the hypothalamus of siberian hamsters were significantly higher than those of rats and syrian hamsters, while male siberian hamsters had similar amounts of substance p in the hypothalamus to those of male syrian hamsters, but had higher ... | 1994 | 7523668 |
| regional distribution of iodomelatonin binding sites within the suprachiasmatic nucleus of the syrian hamster and the siberian hamster. | the pineal hormone melatonin is a potent regulator of seasonal and circadian rhythms in vertebrates. in order to characterize potential target tissues of melatonin, the distribution of iodomelatonin (imel)-binding sites was examined within neurochemically and anatomically defined subdivisions of the suprachiasmatic nucleus (scn), a structure necessary for seasonal and circadian rhythms in mammals. studies were carried out in both the adult syrian (mesocricetus auratus) and siberian (phodopus sun ... | 1995 | 7606248 |
| ontogeny of a photic response in the suprachiasmatic nucleus in the siberian hamster (phodopus sungorus). | the ontogeny of photic responsiveness in the suprachiasmatic nucleus of the siberian hamster (phodopus sungorus) was studied using the enhanced expression of the immediate early gene c-fos as a marker of neuronal activation. c-fos expression was assessed by immunocytochemical localization of its protein product. hamsters were kept on a 16 h light:8 h dark photocycle. the adult siberian hamster showed a marked increase in the number of c-fos-immunoreactive (c-fos-ir) cells within the suprachiasma ... | 1995 | 7613614 |
| ovulated oocytes collected from pmsg/hcg-treated and cycling djungarian or siberian hamsters (phodopus sungorus) are structurally similar with no evidence of polar body formation, indicating arrest in meiosis i. | this study was undertaken (1) to devise a method of inducing multiple follicular development and subsequent ovulation in the djungarian or siberian hamster (phodopus sungorus) and (2) to assess the quality of ovulated oocytes collected from pmsg/hcg treated animals in comparison to naturally ovulating animals. hamsters (4-5 weeks; n = 70) received 5 iu pmsg followed 50-52 hr later by 10 iu hcg. ovulated oocytes were collected 14-20 hr after hcg injection. ovulated oocytes were flushed from ovidu ... | 1995 | 7619509 |
| effects of food deprivation and metabolic fuel utilization on the photoperiodic control of food intake in siberian hamsters. | unlike rats, siberian hamsters exhibit seasonal changes in energy balance that are controlled by the photoperiod (daylength). in siberian hamsters, body weight and fat, and food intake peak in long, summer-like days and reach nadirs in short, winter-like days. the purpose of the present experiments was to test whether metabolic challenges that increase food intake in laboratory rats also increase feeding in siberian hamsters. specifically, we asked the questions: (a) is food intake increased fol ... | 1995 | 7710560 |
| isolation and culture of sertoli cells from the testes of adult siberian hamsters: analysis of proteins synthesized and secreted by sertoli cells cultured from hamsters raised in a long or a short photoperiod. | in the present study, we describe two procedures for isolation and culture of sertoli cells from the testes of adult siberian hamsters. in procedure i, collagenase and pancreatin were used for differential enzymatic digestion of the tissue at 32 degrees c, and effects of several attachment factors were examined. sertoli cells isolated from adult hamsters were not affected by addition of na selenite, epidermal growth factor, insulin, and transferrin, with or without 5% fetal bovine serum, to dulb ... | 1995 | 7756459 |
| early embryonic development in the djungarian hamster (phodopus sungorus) is accompanied by alterations in the distribution and intensity of an estrogen (e2)-dependent oviduct glycoprotein in the blastomere membrane and zona pellucida and in its association with f-actin. | the luminal environment of the estrogen (e2)-dominated mammalian oviduct generates and sustains the environment in which the first embryonic cleavages take place. the objective of this study was to determine, by use of an antiserum against an e2-dependent sheep oviduct secretory glycoprotein (m(r) 90,000-92,000), whether the e2-dominated and pregnant oviduct of the djungarian hamster (phodopus sungorus) releases an antigenically related protein. if the protein was present, a secondary objective ... | 1994 | 7888491 |
| the timed infusion paradigm for melatonin delivery: what has it taught us about the melatonin signal, its reception, and the photoperiodic control of seasonal responses? | this review summarizes the evidence showing that the duration of the nocturnal secretory profile of pineal melatonin (mel) is critical for eliciting seasonally appropriate reproductive physiological and behavioral responses in mammals. we review experiments using the timed infusion paradigm (tip) to deliver mel either systemically or centrally to pinealectomized hamsters and sheep. in this paradigm, mel is infused, usually once daily, for a specific number of hours and at a predetermined time of ... | 1993 | 8120796 |
| effects of food deprivation and restriction, and metabolic blockers on food hoarding in siberian hamsters. | syrian hamsters do not increase their food intake following several metabolic challenges, including food deprivation and blockade of metabolic fuel utilization, in contrast to the response of other small rodents to these challenges. perhaps hamsters respond to such challenges differently, for example by altering hoarding. in the present experiments, we have begun to question the role of food hoarding in the total energy balance of siberian hamsters. therefore, we developed a simulated burrow sys ... | 1994 | 8184952 |
| assessment of the role of follicle-stimulating hormone and prolactin in the control of testicular endocrine function in adult djungarian hamsters (phodopus sungorus) exposed to either short or long photoperiod. | exposure of adult male djungarian hamsters (phodopus sungorus) to a short photoperiod induces testicular atrophy. to evaluate the role of fsh and prolactin (prl) in the control of testicular endocrine function, adult djungarian hamsters were exposed to either a long photoperiod (16l:8d per day) or a short photoperiod (6l:18d per day) for 11 wk. after 11 wk, hamsters housed in each of these photoperiods were placed into three groups and treated s.c. daily for 7 days with 50% polyvinylpyrrolidone ... | 1994 | 8312454 |
| catecholamines stimulate testicular steroidogenesis in vitro in the siberian hamster, phodopus sungorus. | we have examined direct effects of catecholamines on testicular testosterone production in a seasonally breeding species, the siberian hamster, phodopus sungorus. testicular parenchyma from gonadally active long photoperiod (ld)-exposed and gonadally regressed short photoperiod (sd)-exposed animals was incubated for 6 h with norepinephrine, epinephrine, beta-adrenoceptor agonist isoproterenol, or alpha-adrenoreceptor agonist phenylephrine (all at 10 microm), as well as with various concentration ... | 1993 | 8485254 |
| an in vitro circadian rhythm of melatonin sensitivity in the suprachiasmatic nucleus of the djungarian hamster, phodopus sungorus. | past studies in the rat and syrian hamster show that metabolic and electrical activity of the suprachiasmatic nuclei (scn) is inhibited by melatonin (mel) at about circadian time (ct) 8-11 h. the present experiment examined the effect of mel on the firing frequency of scn cells in brain slices prepared from long day (ld 16:8) djungarian hamsters to determine the timing of mel sensitivity and if sensitivity persists in vitro. pressure ejection of mel (2 mm in 165 mm nacl) suppressed the firing ra ... | 1993 | 8508320 |
| control of secretory lipid droplets in the harderian gland by testosterone and the photoperiod: comparison of two species of hamsters. | harderian glands of mammals secrete lipid. they are markedly sexually dimorphic in syrian (golden) hamsters (mesocricetus auratus): female glands consist almost entirely of one cell type (type i) with small lipid droplets, whereas glands of males have both type i and type ii cells, with large lipid droplets. siberian (djungarian) hamsters (phodopus sungorus) have sexually monomorphic harderian glands, with both type i and type ii cells. we used a morphometric technique to quantify the proportion ... | 1995 | 8536934 |
| the impact of dietary fats, photoperiod, temperature and season on morphological variables, torpor patterns, and brown adipose tissue fatty acid composition of hamsters, phodopus sungorus. | we investigated how dietary fats and oils of different fatty acid composition influence the seasonal change of body mass, fur colour, testes size and torpor in djungarian hamsters, phodopus sungorus, maintained from autumn to winter under different photoperiods and temperature regimes. dietary fatty acids influenced the occurrence of spontaneous torpor (food and water ad libitum) in p. sungorus maintained at 18 degrees c under natural and artificial short photoperiods. torpor was most pronounced ... | 1995 | 8576453 |
| the effects of anterior hypothalamic lesions on short-day responses in siberian hamsters given timed melatonin infusions. | the suprachiasmatic nucleus (scn) of the hypothalamus is an area of dense 2-[125i]iodomelatonin binding in siberian hamsters (phodopus sungorus sungorus) that is suggestive of a possible role in the reception and/or relaying of melatonin (mel) signals. indeed, in pinealectomized male siberian hamsters given short day (sd) mel signals (long-duration mel infusions), lesions of the scn (scnx) block testicular regression and decreases in body and fat pad masses seen in identically treated hamsters w ... | 1996 | 8695888 |
| daylength and body mass affect diet self-selection by siberian hamsters. | siberian hamsters exhibit a decrease in peak body mass/fat and caloric intake when they are exposed to short winter-like days (sds) compared with hamsters exposed to long summer-like days (lds). we hypothesize that the photoperiod may directly or indirectly mediate alterations in gustatory processing that may account for shifts in the preferences for specific food types and/or macronutrients. two experiments lasting 14 days each were conducted to: 1) identify photoperiod-related differences in d ... | 1996 | 8737891 |
| development of a specific radioimmunoassay for neuropeptide k: its application to siberian hamster tissues. | in this report we describe the development of a radioimmunoassay for neuropeptide k (npk) that is not influenced by the presence of free neurokinin a (nka) or neuropeptide gamma (npg). the antisera for the radioimmunoassay were obtained by immunizing rabbits with beta-preprotachykinin a fragment 69-91. this fragment contains the sequence 1-20 of npk and has only the sequence 18-20 (gly-his-gly) in common with npg. two antisera were obtained, neither cross-reacting with nka or npg. the specificit ... | 1996 | 8822521 |
| purification and characterization of the sex hormone-binding globulin in serum from djungarian hamsters. | a high-affinity sex hormone-binding globulin (shbg) was purified from the serum of prepubertal djungarian hamsters (phodopus sungorus). a purification of more than 2000-fold with an overall yield of 23% was achieved without the use of androgen affinity chromatography. two predominant variants (51 and 55 kda) were resolved by denaturing polyacrylamide gel electrophoresis. both variants participated in the binding of dihydrotestosterone (dht) and had identical amino-terminal sequences. the sequenc ... | 1996 | 8829809 |
| diurnal changes in the content of indoleamines, catecholamines, and methoxyindoles in the pineal gland of the djungarian hamster (phodopus sungorus): effect of photoperiod. | previous studies in syrian hamster have shown that the correlations between the daily fluctuations in the contents of pineal indoleamines and methoxyindoles are influenced by the photoperiod, and that dopamine may play a role in the regulation of pineal function. the present study investigated the 24 hour changes in the content of 5-hydroxytryptophan (5-htp), serotonin (5-ht), 5-hydroxyindoleacetic acid (5-hiaa), n-acetylserotonin (nas), melatonin, 5-methoxytryptophol (5-mt), noradrenaline (na), ... | 1996 | 8836959 |
| pharmacokinetics of extracellular melatonin in siberian hamster forebrain. | in vivo brain microdialysis was used to characterize the pharmacokinetics of subcutaneously injected melatonin in the anterior hypothalamic-preoptic area (ah-poa) of the male siberian hamster. animals with a microdialysis probe implanted in the ah-poa were treated with a subcutaneous melatonin injection at 0900 h (3 h after lights-on) or 2000 h (2 h prior to lights-off). treatment with 2.5 or 0.25 mg/kg dosages of melatonin in saline vehicle induced peak concentrations of melatonin in ah-poa mic ... | 1996 | 8891318 |
| fosb in the suprachiasmatic nucleus of the syrian and siberian hamster. | the suprachiasmatic nucleus (scn) generates circadian rhythms of behavior and hormone secretion in mammals, and integrates responses to light and nonphotic stimuli to synchronize such rhythms with the external environment. previous studies have demonstrated a close association between the induction of the immediate early gene (ieg) c-fos in the scn by light and phase shifts of circadian rhythms induced by light, but nonphotic stimuli (e.g., arousal), which also cause phase shifts, do not increas ... | 1996 | 8924036 |
| daily and photoperiodic melatonin binding changes in the suprachiasmatic nuclei, paraventricular thalamic nuclei, and pars tuberalis of the female siberian hamster (phodopus sungorus). | using quantitative autoradiography, 2-(125)i-melatonin binding was investigated throughout the light:dark cycle in the suprachiasmatic nuclei (scn), paraventricular nuclei (pvt), and pars tuberalis (pt) of adult female siberian hamsters kept for 10 weeks in either long or short photoperiods (lp or sp, respectively). plasma melatonin concentrations were measured by radioimmunoassay, and the sexual status of the animals was established by visual inspection of vaginal smears and by weighing uteri a ... | 1996 | 8946260 |
| photoperiodism in hamsters: abrupt versus gradual changes in day length differentially entrain morning and evening circadian oscillators. | in studies of photoperiodism, animals typically are transferred abruptly from a long (e.g., 16 h light per day [16l]) to a short (8l) photoperiod, and circadian oscillators that regulate pineal melatonin secretion are presumed to reentrain rapidly to the new photocycle. among rats and siberian hamsters, however, reentrainment rates vary depending on whether additional darkness is added to morning or evening, and a subset of hamsters (nonresponders) fails ever to reentrain normally to short photo ... | 1997 | 9090566 |
| neuroendocrine correlates of separation stress in the siberian dwarf hamster (phodopus sungorus). | siberian dwarf hamsters form monogamous male-female pair bonds. disruption of the pair bond results in increases in body mass and behavioral alterations similar to profiles seen in human atypical depression. we examined behavioral and neuroendocrine correlates associated with separation of the male from his mate. animals were paired (n = 28 pairs) for 3 weeks, then 15 pairs were separated and 13 pairs remained as controls. behaviors of the males were observed in a novel environment following 3 w ... | 1997 | 9108564 |
| secretoneurin: a new neuropeptide in the rodent pineal gland. | the pineal gland of mammals is richly innervated by nerve fibres containing various peptides of central or sympathetic origin. in this study, we have investigated the presence, regulation and effect of secretoneurin (sn), a 33-amino-acid peptide discovered recently in the central and sympathetic nervous systems. the rat pineal gland contains about 34 fmol sn/pineal, although only 20% of the secretoneurin immunoreactivity (sn-ir) is the free peptide. sn-ir is localised in only a few nerve fibres ... | 1997 | 9134856 |
| effect of a light pulse on melatonin receptor density and mrna expression in siberian hamster suprachiasmatic nuclei. | melatonin receptors located in the suprachiasmatic nuclei (scn) have been cloned in mammals hypothalamus. we previously reported a scn melatonin receptor photic regulation in the rat. the present study's aim was to investigate whether a photic regulation of both melatonin receptor density and mrna expression takes place in the scn of a highly photoperiodic species, the siberian hamster. to achieve this goal, we first set up an in situ hybridization protocol without rnase treatment to allow a hig ... | 1997 | 9324237 |
| in vitro fertilizing capacity of sperm from fsh-treated photoinhibited djungarian hamsters (phodopus sungorus). | in hypogonadal male djungarian hamsters fsh alone can induce normal spermatogenesis. however, for the induction of mating behavior, supplementation with testosterone is necessary. we have here investigated, by in vitro fertilization, whether sperm produced by photoinhibited hamsters treated with fsh alone can fertilize without testosterone. photoinhibited hypogonadal male djungarian hamsters were injected daily with human fsh (10 iu; fertinorm) for 5-7 weeks. the hormone stimulated regrowth of t ... | 1997 | 9379125 |
| the detection of thyrotropin-releasing hormone (trh) and trh receptor gene expression in siberian hamster testes. | thyrotropin-releasing hormone (trh) from the hypothalamus is the major regulator of tsh synthesis and secretion. most recently, trh and trh receptors (trh-r), as well as their mrnas, have been identified in rat testis. to expand our knowledge on the testicular trh and trh receptor gene expression in different species, in the present study the mrna levels of testicular trh and trh-r were investigated in siberian hamsters. to further localize the cellular sites of the gene expression, the animal m ... | 1997 | 9396064 |
| characterization and developmental expression patterns of testicular androgen-binding protein in the djungarian hamster (phodopus sungorus). | studies were conducted to characterize djungarian hamster androgen-binding protein and examine its expression during development. the cdna encoding the full length testicular androgen-binding protein was cloned and, except for two suspected polymorphisms, shared a common primary sequence with hepatic sex hormone-binding globulin. a single androgen-binding protein/sex hormone-binding globulin gene was identified and a 1.7 kb mrna encoding androgen-binding protein/sex hormone-binding globulin was ... | 1997 | 9462298 |
| non-photic signalling in the suprachiasmatic nucleus. | scheduled arousal by handling and sub-cutaneous saline injection entrains the free-running clock of the adult syrian hamster and outbred (id(icr)) but not inbred (c57b16) mice. syrian hamsters bearing lesions of the intergeniculate leaflet of the thalamus remain able to entrain and phase-shift to light, but the lesions block completely entrainment by serial arousal, even though lesioned animals continue to respond acutely to the arousing cue. this suggests that the innervation from the igl to th ... | 1997 | 9618899 |
| evolutionary change in the endocrinology of behavioral receptivity: divergent roles for progesterone and prolactin within the genus phodopus. | siberian (phodopus sungorus) and djungarian (p. campbelli) hamsters are phenotypically similar and were long considered subspecies. progesterone (p4) and prolactin (prl) changes (determined by repeated sampling of individuals) during the behavioral receptivity of both an ovulatory cycle and a postpartum mating, as well as the hormonal requirements for behavioral receptivity, were determined. changes in p. sungorus were similar to well-described hormonal changes in rats, mice, and golden hamsters ... | 1998 | 9674990 |
| central nervous system origins of the sympathetic nervous system outflow to white adipose tissue. | white adipose tissue (wat) is innervated by postganglionic sympathetic nervous system (sns) neurons, suggesting that lipid mobilization could be regulated by the sns [t. g. youngstrom and t. j. bartness. am. j. physiol. 268 (regulatory integrative comp. physiol. 37): r744-r751, 1995]. a viral transsynaptic retrograde tract tracer, the pseudorabies virus (prv), was used to identify the origins of the sns outflow from the brain to wat neuroanatomically. prv was injected into epididymal or inguinal ... | 1998 | 9688991 |
| evidence for melatonin synthesis in rodent harderian gland: a dynamic in vitro study. | melatonin content and release from harderian glands (hgs) has been measured by an in vitro perifusion technique in three rodent species: wistar rat, syrian hamster, and siberian hamster. melatonin immunoreactive concentrations in hgs of animals killed at 10.00 hr were 0.31 +/- 0.031 pg/mg gland in male wistar rat, 0.54 +/- 0.026 pg/mg gland in male siberian hamster, 0.17 +/- 0.070 and 0.20 +/- 0.059 pg/mg gland in male and female syrian hamster, respectively. in all species examined, isolated hg ... | 1998 | 9694405 |
| expression of the gene for the retinal protein peripherin in the pineal gland of humans and djungarian hamsters (phodopus sungorus). | this study investigated whether the gene for peripherin, a protein previously considered to play only a role in the retina, may also be expressed in the pineal gland of both djungarian hamsters (phodopus sungorus) and humans. after extraction of mrna from pooled pineal glands of hamsters and from one human pineal gland, mrna was transcribed into cdna followed by pcr amplification with specific primers. clear signals were obtained at the expected sizes of the pcr products. an additional experimen ... | 1998 | 9885962 |
| cone receptor variations and their functional consequences in two species of hamster. | results from earlier experiments indicate that different species of rodent vary both in the number of cone types found in their retinas and in the spectral sensitivities of the cone pigments. these features have now been examined in two types of hamster commonly used for research purposes: syrian golden hamsters (mesocricetus auratus) and siberian dwarf hamsters (phodopus sungorus). electroretinogram (erg) flicker photometry, behavioral discrimination tasks, and opsin antibody labeling were used ... | 1999 | 10022478 |
| anatomical and functional characterisation of a dopaminergic system in the suprachiasmatic nucleus of the neonatal siberian hamster. | in altricial rodents, maternal influences entrain the developing circadian system in the perinatal period before the capacity to respond directly to photic cues develops. the aim of these studies was to investigate the potential role of dopamine in this process in the siberian hamster. an initial study investigated the ontogeny of retinal innervation of the suprachiasmatic nuclei (scn) by using cholera toxin b subunit as a tracer. this revealed that retinal fibres first innervate the scn on post ... | 1999 | 10331581 |
| cns origins of the sympathetic nervous system outflow to brown adipose tissue. | brown adipose tissue (bat) plays a critical role in cold- and diet-induced thermogenesis. although bat is densely innervated by the sympathetic nervous system (sns), little is known about the central nervous system (cns) origins of this innervation. the purpose of the present experiment was to determine the neuroanatomic chain of functionally connected neurons from the cns to bat. a transneuronal viral tract tracer, bartha's k strain of the pseudorabies virus (prv), was injected into the intersc ... | 1999 | 10362733 |
| isolation method of leydig cells from mature male djungarian hamsters (phodopus sungorus) and their steroidogenic activity in vitro. | for studies addressing the functions of leydig cells, isolated cells are often better suited than intact animals. here, the isolation procedure of leydig cells from adult male djungarian hamsters (phodopus sungorus) is described. cells were isolated using a procedure involving enzymatic dissociation and percoll-gradient centrifugation. for each experiment, approximately 4.4 x 10(6) leydig cells from six animals were obtained. the cells showed high steroidogenic responsiveness to physiological (o ... | 1999 | 10363120 |
| aging and photoperiod regulate glutamic acid decarboxylase(67) messenger rna expression. | aging and short photoperiod exposure both induce similar long-term changes in circadian rhythms, including alterations in the timing and the amplitude of rhythms. furthermore, these chronic conditions affect the function of the circadian pacemaker in the suprachiasmatic nuclei (scn) by altering rhythmic expression of neuropeptide messenger rnas (mrnas). because gaba modulates scn neuronal activity, and gabaergic neurons innervate peptidergic neurons in the scn, the present study investigated whe ... | 1999 | 10521586 |
| role of photoperiod and the pineal gland in t cell-dependent humoral immune reactivity in the siberian hamster. | the present study tested the hypothesis that antibody production in response to xenoantigen is modulated by daylength and dependent upon the pineal gland. alter injection of sheep erythrocytes (srbc), serum immunoglobulin (ig) concentrations were 5-fold lower in hamsters in short versus long days. pinealectomy (pinx) abolished the nocturnal melatonin rhythm, blocked short-day-mediated testis regression, and eliminated the short-day reduction in ig production after srbc treatment. antibody titers ... | 1999 | 10551773 |
| divergent reproductive endocrinology of the estrous cycle and pregnancy in dwarf hamsters (phodopus). | progesterone (p4) and prolactin (prl) in peripheral circulation of siberian hamsters (phodopus sungorus) throughout an estrous cycle and pregnancy were determined by repeated, small volume sampling from individuals housed in modified home cages. as predicted, the endocrinology of p. sungorus reproduction is similar to the rat, mouse and golden hamster and shows none of the eight distinctive features known for djungarian hamsters (phodopus campbelli). specifically, in p. sungorus there is no evid ... | 1999 | 10605068 |
| differential regulation of pituitary gonadotropin subunit messenger ribonucleic acid levels in photostimulated siberian hamsters. | fsh levels begin to rise 3-5 days after male siberian hamsters are transferred from inhibitory short photoperiods to stimulatory long photoperiods. in contrast, lh levels do not increase for several weeks. this differential pattern of fsh and lh secretion represents one of the most profound in vivo examples of differential regulation of the gonadotropins. the present study was undertaken to characterize the molecular mechanisms controlling differential fsh and lh synthesis and secretion in photo ... | 2000 | 10611080 |
| photoperiod, but not a high-fat diet, alters body fat in shaw's jird. | many animal species living in temperate zones show annual body fat cycles. in an apparent regulation of total body fat, species showing naturally occurring decreases in adiposity in the fall (e.g., meadow voles and siberian hamsters) are resistant to high-fat diet (hfd)-induced obesity in short, "winter-like" days (sds), and in long, "summer-like" days (lds) at their peak adiposity. sd-exposed shaw's jirds (meriones shawi) show sd-induced decreases in body fat; therefore, we predicted they also ... | 1999 | 10627066 |
| diet self-selection and food hoarding after food deprivation by siberian hamsters. | siberian hamsters (phodopus sungorus) increase food hoarding, but not food intake, after a fast. because the physiological mechanisms underlying these changes in food hoarding are virtually unknown, we sought insight into these mechanisms by allowing hamsters to self-select their diet from food sources varying in macronutrient composition and caloric density ("dietary wisdom"). therefore, the effects of food deprivation length on diet self-selection were tested in adult female hamsters after ada ... | 1999 | 10627080 |
| metabolic influences on circadian rhythmicity in siberian and syrian hamsters exposed to long photoperiods. | calorie restriction and other situations of reduced glucose availability in rodents alter the entraining effects of light on the circadian pacemaker located in the suprachiasmatic nuclei. siberian and syrian hamsters are photoperiodic species that are sexually active when exposed to long summer-like photoperiods, while both species show opposite changes in body mass when transferred from long to short or short to long days. because metabolic cues may fine tune the photoperiodic responses via the ... | 2000 | 10692145 |
| modulation of leptin sensitivity by short photoperiod acclimation in the djungarian hamster, phodopus sungorus. | during seasonal acclimation, djungarian hamsters spontaneously exhibit a reduction in food intake, body mass and body fat stores, which is externally cued by shortening of day length in autumn and controlled by a sliding set-point. we investigated the function of the leptin adipostatic feedback system in the photoperiodic control of seasonal acclimation. in response to mouse recombinant leptin injections for 10 days, long day photoperiod (ld) and short day photoperiod (sd)-acclimated hamsters de ... | 2000 | 10707323 |