Effect of HCG on resorption and fetal weight in the hamster (Mesocricetus auratus)

Female hamsters were given either low (10 i.u.) or high (100 i.u.) doses of HCG on day 6, 7, or 8 of gestation. Maternal weight at breeding was found to have a significant effect on litter size and the number of resorptions, but not on mean fetal weight, in both control and treatment groups. Treatment regimens produced significant changes in litter size, number of resorptions, mean fetal weight, and resorption site by position within the uterine horns. No teratogenic effects were produced as judged by gross morphological examination.     

Microsatellites for diversity studies in the golden hamster (Mesocricetus auratus)

Ten polymorphic microsatellites were developed for the golden hamster (Mesocricetus auratus), a widely used model organism in biological and medical researches. All loci were used to analyse the microsatellite variability in wild golden hamsters from Syria and in a sample of domestic animals comprising different strains. Average mean expected heterozygosity (H_E) and mean allele number (A) of domestic hamsters measured 0.279 ± 0.058 and 2.6 ± 0.306, respectively, compared to 0.809 ± 0.019 and 8.3 ± 1.075 found for wild hamsters. Cross‐species application in other Mesocricetus species proved conservation of most loci throughout the genus.     

Effects of hypoxia and hypercapnia on circadian rhythms in the golden hamster (Mesocricetus auratus).

This study was designed to determine whether respiratory stimuli can influence the mammalian circadian timing system. Three-hour pulses of hypoxia (inspired O(2) concentration = 8%) or hypercapnia (inspired CO(2) concentration = 11%) were presented for 7 days at mid-subjective day (circadian time 6-9) under constant darkness. Hypoxic and hypercapnic pulses caused cumulative phase delays of 46. 4 +/- 6.9 and 25.9 +/- 12.3 min, respectively. Distance run per day was significantly reduced on hypoxic and hypercapnic pulse days, compared with nonpulsed days. Phase shifts were correlated with the reduction in daily running activity (multiple r(2) = 0.521, P = 0.036), metabolic depression (multiple r(2) = 0.772, P < 0.001), and reduction in body temperature (multiple r(2) = 0.539, P = 0.027), but not lung ventilation (multiple r(2) = 0.306, P = 0.414) during pulses. We conclude that hypoxia and hypercapnia can influence the phase and quantity of activity in free-running hamsters.     

Sex differences in odor-stimulated flank marking in the golden hamster (Mesocricetus auratus).

To determine whether sex differences exist in the frequency of odor-stimulated flank marking, intact male and female hamsters were exposed to the recently vacated home cages of male stimulus hamsters for a 10-min test on 4 consecutive days. Females were found to mark at significantly higher levels than males. To investigate the role of gonadal hormones in the sex differences in flank marking, gonadectomized male and female hamsters were implanted with Silastic capsules containing estradiol or testosterone. Females exhibited twofold higher levels of odor-stimulated flank marking than males, and the amount of flank marking was significantly higher when the hamsters were administered testosterone than when they were administered estradiol. These data demonstrate that sex differences exist in the frequency of flank marking stimulated by the odors of male hamsters, and that these sex differences do not appear to result from the typical sex-specific patterns of circulating levels of estradiol and testosterone.     

The development of the Chondrocranium in the golden hamster, Mesocricetus auratus (Waterhouse).

3 -stages of development of the chondrocranium of the golden hamster have been described. The chondrocrania of the gerbil, mouse and white rat have been compared with the chondrocranium of the golden hamster and the main differences noted. In several respects, the chondrocranium of the golden hamster is primitive.     

Synaptic ribbons during postnatal development of the pineal gland in the golden hamster (Mesocricetus auratus)

Summary Synaptic ribbons, functionally enigmatic structures of mammalian pinealocytes, were studied during the postnatal development of the pineal gland in the golden hamster (Mesocricetus auratus). On day 4 post partum, synaptic ribbons appear in cells that have already started to differentiate into pinealocytes. Between days 4 and 9, an increase in the number of synaptic ribbons occurs, concomitant with the continuing differentiation of the pineal tissue. Between days 9 and 16, when differentiation of this tissue is almost completed, the number of synaptic ribbons decreases and approaches that characteristic of the adult pineal gland. During development, the synaptic ribbons increase in length, and dense core vesicles are frequently found in the vicinity of these structures. It is assumed that a functional relationship exists between dense core vesicles and the synaptic ribbons, which are considered to be engaged in a certain form of secretory activity of the mammalian pineal gland.Supported by the Deutsche Forschungsgemeinschaft     

Retinotopic organization of striate and extrastriate visual cortex in the golden hamster (Mesocricetus auratus).

The visual topography within striate and lateral extrastriate visual cortices was studied in adult hamsters. The cortical areas 17 and 18a in the left hemisphere were electrophysiologically mapped upon stimulation of the right eye, correlating receptive field positions in the visual field with cortical recording sites. Reference lesions were placed at selected cortical sites. Like in rats and other mammals, the lateral extrastriate cortex contained multiple representations of the visual field. Rostral area 18a contained the rostrolateral maps, with medial and lateral divisions. More caudally and sharing a common border with V1, maps in lateromedial, posterolateral and posterior areas were found. More laterally and forming a "third tier" of visual maps, anterolateral, laterolateral-anterior, laterolateral and laterolateral-posterior areas were found. There was also an indication of a possible pararhinal map. The plan so defined is virtually identical to that of rats. The results may be useful to understand a basic mammalian plan in the organization of the visual cortex.     

Effect of castration and testosterone therapy on harderian gland protein patterns of the golden hamster (Mesocricetus auratus).

1. Sodium dodecyl sulphate 7-12% gradient polyacrylamide gel electrophoresis of male and female hamster Harderian gland whole homogenate shows a clear-cut sexual dimorphism, which consists of the presence of two male-specific glycoproteins (168 and 116 kDa) and two specific female proteins (210 and 190 kDa). 2. In the male, castration causes a significant decrease in the concentration of the two glycoprotein fractions. 3. Replacement therapy with testosterone propionate (T) restores the intact male pattern.     

Chromosome replication in fibroblasts of the Syrian hamster (Mesocricetus auratus)

The BrdU/Hoechst 33258/Giemsa method for sub-dividing S-phase in asynchronous cell populations has been re-evaluated and modified to give better definition and more even distribution of sub-phases. A reference pattern of early-relicating euchromatic bands is given for all chromosomes at Sk2 in primary cultures of skin fibroblasts. The overall band patterns at each sub-phase have allowed more objective definitions of early and late replication for these cells, and show that in both classes of chromatin light G-bands preceed dark G-bands. Asynchrony between homologous bands is observed at all stages of S, albeit with a variable frequency. The observed in vitro replication patterns and programme for the chromosomes of skin fibroblasts does not appear to be affected by the age or sex of the source.     

The formation and cytochemical characterization of cortical granules in ovarian oocytes of the golden hamster (Mesocricetus auratus).

The formation and cytochemical characterization of cortical granules in the ovarian oocytes of the golden hamster have been investigated by use of light and electron microscopical techniques. Particular emphasis is given to the changing population of organelles associated with cortical granule formation. Our observations indicate that cortical granules are produced by the participation of both the Golgi complex and the rough endoplasmic reticulum. Ultrastructural cytochemistry reveals that the cortical granules are composed of glycoprotein. The cortical granules are released at fertilization by a merocrine-type of secretory process.     

Predictors of dominance in the male golden hamster (Mesocricetus auratus)

The outcome of social interactions between four male hamsters was significantly related to body weight (r_s=0·66) and to the size and pigmentation of their lateral flank glands (r_s=0·82). Weight was held constant in a second experiment and variations in gland size and pigmentation remained significantly related to the outcome of social encounters (r_s=0·77). In a third experiment, castrate hamsters of uniform weight receiving either no hormone, 0·1 mg, 0·50 mg, or 1·00 mg testosterone propionate exhibited flank gland variations significantly related to social rank (r_s=0·81). These experiments demonstrate that the state of the flank gland, which is related to endogenous androgen levels, can be used as a predictor of social rank in male hamsters.