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At least 19 recordsLinked to original sources
PubMedDate not supplied

[A comparative study of the osmoregulating system in the hamsters Phodopus roborovskii and Phodopus sungorus].

The hamster Phodopus roborovskii is adapted to live in desert, Phodopus sungorus in less arid regions. Hamsters of both species have rather close values of blood serum osmolality and ion concentration, after dehydration the value of urine osmolality is found to be equally high. The microdissection of the kidney did not reveal any difference in the structure and arrangement of nephrons in cortex and medulla. According to the results of immunocytochemical analysis of the hypothalamo-hypophyseal neurosecretory system of hamster Phodopus roborovskii, compared to Phodopus sungorus, has a smaller quantity of vasopressin-positive neurons, which is likely to be a result of a release of larger quantities of vasopressin in long-term dehydration. It is suggested that of importance in the animal adaptation to life in arid condition may be not only morphofunctional reorganization of kidney but also of the hypothalamo-hypophyseal system which is involved in permanent secretion of vasopressin.

Animals↗
PubMed1994

Photoperiodic differences during development in the dwarf hamsters Phodopus sungorus and Phodopus campbelli.

The dwarf hamsters Phodopus sungorus and to a lesser extent Phodopus campbelli are widely used to study pineal physiology and seasonal reproduction because of their marked responses to photoperiod in adulthood. These species are frequently confused, partly because the common names "Siberian hamster" and "Djungarian hamster" are applied to both, often interchangeably. The current study examines whether the effects of photoperiod on reproductive maturation and prolactin secretion differ between these closely related species. Both male and female P. sungorus and P. campbelli were gestated and raised in long days (LD) of 16 hr light: 8 hr dark or in short days (SD) of 8 hr dark: 16 hr light. They were raised in pairs of the same sex after weaning at 21 days of age. Reproductive organ weights and serum prolactin concentrations were studied at 35 and 70 days of age. Whereas reproductive development proceeded rapidly in LD in both male and female P. sungorus, SD photoperiod completely inhibited growth of the gonads during this study. There were also marked differences in serum prolactin concentrations in both sexes of P. sungorus at all ages: levels were approximately 10-fold higher in LD than in SD. In P. sungorus of both sexes, SD also significantly decreased body weight relative to conspecifics raised in LD. In P. campbelli, reproductive maturation in LD occurred even more rapidly than in P. sungorus. Although significant effects of photoperiod were still apparent, the magnitude of its effect was less marked than in P. sungorus, and a substantial degree of reproductive development was observed in SD-reared males and females.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

[The attraction of Campbell (Phodopus campbelli) and Djungarian (Phodopus sungorus) hamster pups to the odor of the secretion from specific complexes in the corners of the mouth of the mother].

The hamsters, Phodopus campbelli and Ph. sungorus have additional sacculi at the opening of the cheek pouches. The secretion of additional sacculi is very important for normalization of some aspects of the hamsters' physiology, as well as growth and development of pups, and also for chemical communication. We studied the role of the mother's additional sacculi secretion in mother-youngs interaction. It was shown that this secretion is most attractive for pups of both species from 6th to 11th day after the birth. During this period the pups begin to consume solid food but their own complexes only begin to form. Hence, pups may use the mother's additional sacculi as an additional (and may be the main) source of the secretion at this time. The difference in behavioral patterns of pups of the two studied species suggests some specific features of postnatal ontogenesis of additional sacculi.

Animal Communication↗
PubMed1999

[Characteristics of the first meiotic division in hamster hybrids obtained by backcrossing Phodopus sungorus and Phodopus campbelli].

Spermatocytes of fertile, subfertile, and sterile hamster hybrids obtained by backcrossing Phodopus sungorus and Ph. campbelli were analyzed under light and electron microscopes. Light microscopy showed that early meiosis was blocked in pachitene in the spermatocytes of sterile hybrids. The X and Y chromosomes were dissociated in metaphase I in several fertile and subfertile animals. Electron microscopic analysis of the synaptonemal complex (SC) revealed a disturbed synapsis of sex chromosomes and autosomes in all hybrids. Dissociation of the sex chromosomes, terminal and interstitial asynapsis, and interlocking of autosomes were observed. Disturbed synapsis in hybrids was assumed to result from the difference between Ph. sungorus and Ph. campbelli in not only their chromosomes, but their genes as well.

Animals↗
PubMedDate not supplied

[The ontogeny of additional saccules in the orifice of the cheek pouches in hamsters (Phodopus campbelli Thomas, 1905 and Phodopus sungorus Pallas, 1773): a morphometric analysis].

Time changes in functional activity of the recently described additional sacs in the orifice of cheek pouches (AS) has been studied in one-month-old and adult Phodopus sungorus and P. campbelli. The most intense AS growth and increase in their secretory activity falls on the second decade of the first month. It coincide with transition to their own feeding by coarse crust. Although there is no sexual dimorphism in the AS mass or the amount of their secret, time pattern of growth is different in males and females. Stabilization of the main indices of AS functional activity, their relative mass and amount of secret, at the adult level occurs in females earlier than in males. Adults of both species do not show sexual dimorphism by the both studied indices, but breeding females have both absolute and relative mass of AS and its secret significantly increased. As a whole the obtained data agree well with the previous studies (Vasil'eva, Feoktistova, 1993) that have demonstrated the importance of AS secret in survival, normal growth and development during the first month of P. campbelli. The described time pattern of the AS activity in ontogenesis seem to reflect the real need in the secret at the early age in small hamsters, and the increased AS activity in lactating females can be considered as a functional adaptation that compensate the secret deficit.

Aging↗
PubMed1987

Male-female interactions across the female estrous cycle: a comparison of two species of dwarf hamster (Phodopus campbelli and Phodopus sungorus).

Recent studies in our laboratory have suggested that monogamy may be the preferred mating system in the Djungarian hamster (Phodopus campbelli), whereas the available evidence for the closely related Siberian hamster (P. sungorus) does not show the same pattern. Here we examine the behavior of male-female dyads of both species interacting during 1-hr tests in large, familiar habitats containing defensible nest boxes, food, and water. Levels of aggression within pairs were low, compared with those seen during brief intrasexual encounters, whereas affiliative behaviors, such as sniffs, were high. P. campbelli scent marked more than twice as frequently as P. sungorus. Females of both species scent marked at a constant rate irrespective of their location in the habitat, whereas males scent marked at a higher rate in the female's home area. Two major features of the copulatory pattern differed between the two species: (a) The duration of the ejaculatory lock was five times longer in P. sungorus than in P. campbelli. (b) Both species had approximately the same number of mounts in each ejaculatory series, but the intromission/mount ratio was significantly higher in P. sungorus.

Agonistic Behavior↗
PubMed1989

Differential effects of paternal presence on pup survival in two species of dwarf hamster (Phodopus sungorus and Phodopus campbelli).

The effect of the presence or absence of the male, and of decreased ambient temperature (21 degrees C vs. 4 degrees C) on litter survival, pup survival and pup growth was measured from birth through day 18 after birth in Siberian (P. sungorus) and Djungarian (P. campbelli) hamsters. Siberian hamsters were not significantly affected by the experimental manipulations. In contrast, whereas 100% of litters and 95% of pups were successfully raised to weaning at 21 degrees C by paired Djungarian hamsters, survival fell to 47% when the mate was absent and even further, to 32%, when the ambient temperature was lowered. No significant differences in litter size or pup weight at birth were detected between species at the warmer temperature. However, P. sungorus pups gained weight significantly faster through day 12 after birth (while dependence upon the mother for food was absolute) than P. campbelli pups under all experimental conditions. Although the species are closely related, these data show that male Djungarian hamsters are essential to offspring survival under conditions where Siberian hamsters do not require conspecific help. Species differences in metabolism and thermoregulation may account for the differential pup survival.

Animals↗
PubMed1992

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 microscopy, (b) non-specific phagocytosis, and (c) the presence of Fc-receptors. Treatment of the cultures with oFSH (at 0.5 and 1 micrograms ml-1 for 1 and 4 days) significantly stimulated lactate secretion by testicular macrophages from LD hamsters, as expected from studies in the rat. In marked contrast, oFSH did not affect lactate secretion by testicular macrophages from SD hamsters, or by peritoneal macrophages. To test possible macrophage-Leydig cell interactions, the influence of testicular macrophage-conditioned medium (TM-CM) from FSH-responsive LD macrophage cultures was assessed and compared with the effect of peritoneal macrophage-conditioned medium (PM-CM) on testosterone production by testicular parenchyma from LD hamsters. Unexpectedly, and in contrast to previous reports in rats, testosterone production by testes was inhibited significantly by TM-CM from cultures pretreated with either 0.1 or 0.5 micrograms FSH ml-1. FSH alone stimulated testosterone production (due either to LH contamination or to possible paracrine effects). PM-CM from cultures pretreated with FSH did have an inhibitory effect. It is concluded that: (i) There is indirect evidence for the presence of functional FSH receptors on macrophages from the active testes of Phodopus. (ii) Testicular macrophages from inactive testes of Phodopus are not responsive to FSH, implicating impaired macrophage function in the regressed testes of Phodopus exposed to SD. (iii) Testicular macrophages produce a factor which can inhibit testosterone production by incubated testicular tissue.

Animals↗
PubMed1997

Length of delay to birth of a second litter in dwarf hamsters (Phodopus): evidence for post-implantation embryonic diapause.

In Phodopus, all first litters are born after an 18 (or 19) day gestation. Birth of subsequent litters conceived during a postpartum estrus is routinely, but not always, delayed beyond 18 days. With an interval from first mating to birth of a second litter of as little as 36 days, Phodopus have the most compressed reproductive cycle of any eutherian mammal. Although pups of the Siberian hamster P. sungorus gain thermal independence from maternal care faster than pups of the Djungarian hamster P. campbelli, no species difference in the extent of delay to second litters was found. However, poor growth of first litter pups as a result of unintentional limitation of water bottle access increased delays before birth of a second litter in P. sungorus. Weight of pups in the first litter was a good predictor of the length of delay. In P. campbelli, females with large pups early in lactation were the only ones to deliver a second litter without delay, and short delays enhanced weaning weights for pups in the first litter. Patterns in P. sungorus were similar. The timing of the delay in second litters was investigated in P. campbelli. Delayed implantation during second pregnancies was common. Postimplantation embryonic diapause occurred in 43% of females following unilateral ovariohysterectomy on day 8 of a first pregnancy. As pup growth curves also implicated a postimplantation embryonic diapause, Phodopus may be the only known mammalian genus outside the order Chiroptera in which postimplantation diapause can occur.

Animals↗
PubMed2002

Male-induced estrus synchronization in the female Siberian hamster (Phodopus sungorus sungorus).

Olfactory cues play an integral role in the organization of events that mediate reproductive success. In a variety of species, priming pheromones, in particular, are important for ensuring reproductive fitness. To date, very little research has focused on how male-emitted priming pheromones, such as those that regulate the onset of puberty and estrus synchronization in females, affect the reproductive physiology of the female Siberian hamster (Phodopus sungorus sungorus). This lack of research may be due to the physiology of the Phodopus genus; vaginal cytology cannot be used as a reliable indicator of estrus or ovulation. Using a jugular cannulation technique to determine estrous stage by blood analysis of prolactin and luteinizing hormone, we sought to determine if male priming pheromones affect estrous cyclicity in the female Siberian hamster and, if so, whether the production of these priming pheromones is androgen dependent. Our results showed that females exposed to bedding from mature, intact males showed a significantly higher incidence of proestrus 3 days later than did females exposed to the bedding of mature, gonadectomized males. Therefore, we found that not only do male Siberian hamsters emit chemical signals that induce estrus synchronization, but also that this ability is likely to be androgen dependent.

Androgens↗
PubMed1998

Maternal and pup contributions to different patterns of pup growth in Phodopus species.

A cross-fostering approach was used to compare and quantify patterns of pup growth in Phodopus sungorus and P. campbelli. Standard litters of five pups were reared by a foster mother of the same or the opposite species. Individual pups were weighed daily, and maternal and pup body condition were quantified. Studies were conducted at an ambient temperature of 23 degrees C, which constrains maternal contact with pups in P. campbelli but not P. sungorus, to maximize the difference in pup growth curves between the species. Results confirmed that the similar Day 18 weights in the two species of Phodopus were a complex result of laboratory conditions that masked different patterns of pup growth. The primary determinants of that pup growth were 1) constraints on maternal investment by P. campbelli mothers, which arose from the thermoregulatory stresses of a 23 degrees C ambient temperature and may have involved different milk energetic value or water content; 2) an intrinsic pup difference in the threshold weight for independent thermoregulation, which increased energetic expenditures for P. sungorus pups several days earlier than for P. campbelli pups; and 3) a longer lactation in P. campbelli, which improved access to dry food. Results also confirmed that within-litter variation in pup weights was considerably larger in P. campbelli, but forced rejection of the hypothesis that the difference arose from different maternal investment strategies during lactation. Species-typical patterns of variation were already established on Day 1 after birth.

Adipose Tissue↗
PubMed1999

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 evidence for resumption of pituitary PRL surges in late pregnancy, P4 concentrations during the differentiation of the corpus luteum on day 2 of pregnancy are higher (as opposed to lower) than concentrations on the comparable day of an unmated estrous cycle (diestrus 1), P4 concentrations increase throughout pregnancy, PRL surges are common during the estrous cycle, including a reliable surge on proestrus, and P4 plays an important role in facilitating the expression of behavioral receptivity. We conclude that 'novel' P. campbelli reproductive endocrinology has evolved since a common ancestor was shared with P. sungorus. With a time frame (the available time since the divergence of the two species) and an ecological context (known niches and behavior in the wild) these species offer the opportunity to study endocrinological evolution in progress.

Animals↗
PubMed1993

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 concentrations of norepinephrine (10 nM-10 microM), and 10 microM norepinephrine with or without hCG (0.7, 3.1, and 12.5 mIU/ml). In addition, effects of alpha-adrenoreceptor antagonist prazosin and beta-adrenoreceptor antagonist propranolol (50 microM) were tested in the incubations containing 10 microM norepinephrine. In the incubations of testes from both LD and SD Siberian hamsters, norepinephrine was most effective in stimulating testosterone production, followed by epinephrine and phenylephrine, while isoproterenol failed to increase testosterone accumulation. The stimulatory effects of norepinephrine were dose-dependent and were prevented by coincubation with prazosin, but not affected by coincubation with propranolol. In combination with various doses of hCG, norepinephrine failed to stimulate testosterone production above the levels obtained with hCG alone. These data indicate that the testicular receptors mediating the action of catecholamines on testicular steroidogenesis in Phodopus sungorus are of the alpha 1-subtype, a result in accordance with a previous study in the golden hamster. However, the results of the present study are strikingly different from the findings obtained in the golden hamster in terms of the effects of photoperiod on the responsiveness of testicular steroidogenesis to catecholamines.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1999

Effects of 60 Hz magnetic field exposure on the pineal and hypothalamic-pituitary-gonadal axis in the Siberian hamster (Phodopus sungorus).

Experiments using the dwarf Siberian hamster Phodopus sungorus were carried out to determine possible neuroendocrine consequences of one-time and repeated exposures to 60 Hz magnetic fields (MF). Animals were maintained in either a short-light (SL, 8 h light:16 h dark) or long-light (LL, 16 h light:8 h dark) photoperiod. Acute (one-time, 15 min) exposure of male SL animals to a linearly polarized, horizontally oriented, 60 Hz MF (0.1 mT) gave rise to a statistically significant (P < .005) reduction in pineal melatonin content as determined 3 and 5 h after onset of darkness. In LL animals, acute exposure to 0.10 mT resulted in a significant decrease in pineal melatonin as measured 4 h after onset of darkness, whereas acute exposure to 50 microT showed no effect compared with sham exposure. In SL animals, an increase in norepinephrine was observed in the medial basal hypothalamus (including the suprachiasmatic nucleus) after acute exposure (P < .01). Daily MF exposure of SL animals to a combination of steady-state and on/off 60 Hz magnetic fields (intermittent exposure) at 0.1 mT for 1 h per day for 16 days was associated with a reduction in melatonin concentrations at 4 h after onset of darkness and an increase in blood prolactin concentrations (P < .05). Exposure of SL animals to a steady state 60 Hz MF for 3 h/day for 42 days resulted in a statistically significant reduction in body weight (ANOVA: P > .05), compared with sham-exposed SL animals. At 42 days, however, no significant changes in overnight melatonin or prolactin levels were detected. In both repeated exposure experiments, gonadal weights were lowest in the MF-exposed groups. This difference was statistically significant (P < .05) after 42 days of exposure. These data indicate that both one-time and repeated exposure to a 0.1 mT, 60 Hz MF can give rise to neuroendocrine responses in Phodopus.

Adrenergic alpha-Agonists↗
PubMed1988

Distributional pattern of oxytocin- and vasopressin-immunoreactivity in the neurohypophysis of the Djungarian hamster (Phodopus sungorus).

The topography of oxytocin (OT)- and vasopressin (VP)-containing axons of the hypothalamo-neurohypophyseal system was studied in the neurohypophysis of the Djungarian hamster (Phodopus sungorus) by means of immunohistochemistry. Compared with other mammalian species, the neurohypophysis of Phodopus shows some peculiarities. Accumulations of OT-immunoreactivity around the distal vessels of the primary portal plexus can be observed in the distal median eminence and neural stem. This staining pattern indicates that OT is secreted into portal blood. In the neural lobe, OT- and VP-immunopositive fibers terminate in different areas. The vast majority of the OT-containing axons is distributed in the dorsal part of the neural lobe. In contrast, VP-containing axons are mainly found in the centre of the neural lobe up to the pars intermedia.

Animals↗
PubMed1976

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 satellites in Phodopus, where positive chromosome identification can be made in the absence of banding. Numerical agreement is exact in Mesocricetus as well, and the morphology of the silver-tagged NOR-bearing chromosomes strongly suggests that corrrespondence also occurs in this species.

Animals↗