The preference of Syrian hamsters (Mesocricetus auratus) for different in-cage shelters was tested. First, 15 males and 15 females were made to choose between a cage with a shelter and one without. Different shelters were tested consecutively: short (10-cm) or medium (15-cm) pipes made of black acrylonitrile butadiene styrene (ABS), 7.6 cm in diameter and open at both ends; and short or medium boxes made of black acrylic panels and open at only one end. The strongest use of the shelter cage for nesting (about 75% of days) was in the case of the medium, open pipe, for both males and females. The strongest use of the shelter itself for nesting was also in the case of the medium open pipe (52% of days). A second experiment gave a choice between pairs of shelters (of seven different types) to 10 males and 10 females. Both sexes nested significantly more in a medium pipe closed at one end than under a wheel, and tended to nest more in that medium, semi-closed pipe than in a medium, open pipe. Also, females tended to nest more in the medium, semi-closed pipe than under an aluminium cover. Other pairings did not yield significant differences. Direct use of the shelters for nesting was rather low, except for the medium, semi-closed pipe (about 50% of days). Semi-closed ABS pipes are inexpensive, easy to clean, and do not interfere with running wheels, and they could be recommended as environmental enrichment for hamsters.

The Deleted in AZoospermia (DAZ) gene family regulates the development, maturation and maintenance of germ cells and spermatogenesis in mammals. The DAZ family consists of two autosomal genes, Boule and Dazl (Daz-like), and the Daz gene on chromosome Y. The aim of this study was to analyze the localization of DAZL and BOULE during testicular ontogeny of the seasonal-breeding Syrian hamster, Mesocricetus auratus. We also evaluated the testicular expression of DAZ family genes under short- or long-photoperiod conditions. In the pre-pubertal and adult testis, DAZL protein was found mainly in spermatogonia. BOULE was found in the spermatogonia from 20 days of age and during the pre-pubertal and adult period it was also detected in spermatocytes and round spermatids. DAZL and BOULE expression in spermatogonia was strictly nuclear only in 20-day-old hamsters. We also detected the novel mRNA and protein expression of BOULE in Leydig cells. In adult hamsters, Dazl expression was increased in regressed testis compared with non-regressed testis and DAZL protein expression was restricted to primary spermatocytes in regressed testis. These results show that DAZL and BOULE are expressed in spermatogonia at early stages in the Syrian hamster, then both proteins translocate to the cytoplasm when meiosis starts. In the adult regressed testis, the absence of DAZL in spermatogonia might be related to the decrease in germ cell number, suggesting that DAZ gene family expression is involved in changes in seminiferous epithelium during photoregression.

We studied the morphology of the aortic valves of 1,036 Syrian hamsters belonging to two families subjected to high endogamous pressure. Most (n=955) specimens were examined using a corrosion-cast technique. In the remaining 81 specimens, valvar morphology was assessed by means of a stereomicroscope, and in 18 of these cases a histologic study was also performed. In one of the families, a high proportion (30.5%) of hamsters had aortic valves with two leaflets, the aortic sinuses being oriented ventrodorsally. The percentage of such anomalous valves was found to be positively correlated with the inbreeding coefficient of specimens. In the other family, the occurrence of an aortic valve with two leaflets was a sporadic event. Stereoscopic and histologic observations demonstrated that, in 52 of 63 aortic valves with three leaflets, the ventral commissure between the right and left leaflets was partially fused, while in 10 other cases this commissure was completely fused. In addition, in nine of 18 aortic valves with two leaflets, there was a more or less well-developed raphe located in the ventral aortic sinus, approximately where the true ventral commissure would have been. Our observations suggest the existence of a continuous spectrum of aortic valvar morphology, ranging from a valve with three leaflets and no fusion of the ventral commissure to an aortic valve with two leaflets devoid of any raphe. This spectrum seems to be the result of the interaction of genetic and intrauterine environmental factors. Results of crosses between both related and unrelated hamsters suggest that the observed morphology in individuals is the result of quantitative inheritance.

Adult male Syrian hamsters were fed on a high-fat diet with or without access to boiled coffee. Plasma total, low-density-lipoprotein- and high-density-lipoprotein-cholesterol and triacylglycerol concentrations were increased by the coffee and very-low-density-lipoprotein-cholesterol concentrations were lowered. It is concluded that the Syrian hamster is a suitable animal model in which to study the hypercholesterolaemic effect of coffee