Androgenic control of porphyrin in the harderian glands of the male syrian hamster is modulated by the photoperiod,which suggests that the sexual differences in porphyrin concentrations in this gland are important functionally

Background: The porphyrin concentrations of the Harderian glands of Syrian hamsters show marked sexual differences, with male levels being much lower than those of females. Porphyrinogenesis is inhibited by androgens, so orchidectomy leads to elevated male porphyrin concentrations; however, a number of other procedures (some of which also lower androgen levels) prevent this. We studied the effects of short-day photoperiods and melatonin on Harderian porphyrin concentrations. Methods: Intact, castrated, or pinealectomized hamsters of both sexes were exposed to long-day or short-day photoperiods. Intact or castrated hamsters were given melatonin injections in the morning or the afternoon, or were given beeswax pellets containing melatonin. After a variable period, Harderian glands were dissected and porphyrins were measured. Results: Prolonged short-day exposure (13 weeks) led to increased Harderian porphyrin concentrations and this rise was prevented by pinealectomy. The rise in Harderian porphyrins following short-day exposure was small, compared with that following castration. Short-day photoperiods also prevented the rise in porphyrin levels associated with castration and this effect was prevented by removal of the pineal. Melatonin injections, whether given in the morning or in the afternoon, had no effect on Harderian porphyrin concentration of castrated male hamsters. Continuous release melatonin pellets reduced the postcastrational rise in porphyrin levels in one experiment, while having no effect in another. In female hamster, neither short photoperiods nor melatonin pellets influenced Harderian porphyrin concentrations. Conclusions: These results suggested that a factor from the pineal gland helps maintain the low levels of porphyrin which are characteristic of male Harderian glands, despite the decrease in androgen levels which typically results from exposure to short days. Morning and afternoon injections of melatonin and continuous release melatonin pellets failed to resolve the question of whether this pineal factor is melatonin. Our results demonstrated that low male and high female porphyrin levels are maintained in Syrian hamsters, despite seasonal variations in the hormonal milieu, suggesting that these sexual differences are important for the (still unestablished) function of the Harderian glands in this species. © 1994 Wiley-Liss, Inc.     

高温致神经管畸形相关基因CDK109克隆及其致畸相关性分析

目的通过筛选高温致畸金黄地鼠胚胎神经管cDNA文库,克隆高温致畸相关基因CDK109。方法利用本室构建的高温致畸胚胎神经管cDNA文库,采用噬菌斑原位杂交方法,用寡核苷酸探针筛选cDNA文库,挑取阳性噬菌斑,将其转化为质粒,再通过限制性酶切鉴定阳性克隆并测序,将该基因标记探针与孕8.5 d高温致畸胚胎神经管组织和正常对照胚胎神经管组织总RNA进行NORTHERN杂交,以便确认该基因在高温致神经管畸形中的异常表达。结果成功地从高温致畸金黄地鼠胚胎神经管cDNA文库中筛选出高温致畸相关基因CDK109全长,其在高温致畸组的表达明显高于对照组。结论 CDK109在神经管中的高表达与高温致神经管畸形密切相关。     

Thermal effects on long-term potentiation in the hamster hippocampus

Extracellular CA1 pyramidal cell activity was measured at different temperatures in hippocampal slices from the Syrian hamster (Mesocricetus auratus), a hibernator. Control records taken before and after tetanic stimulation of Schaffer collateral/commissural pathways were compared to determine if long-term potentiation (LTP) was established. LTP (an enhancement of the population spike amplitude or population synaptic response following tetanus) was elicited in slices at temperatures above 22 °C, but not in slices at temperatures of 20 °C. When LTP was established at temperatures above 24 °C, however, lowering the temperature to 20 °C did not abolish the LTP. Furthermore, when a tetanus was delivered at 20 °C and the bath temperature was then raised above 22 °C, LTP was established. These results for step changes in temperature suggest that the sequence of cellular mechanisms leading to LTP is activated, but then arrested in slices maintained at a constant temperature of 20 °C. Assuming this type of activity in the slice parallels in vivo hippocampal activity, it follows that the ability to elicit LTP in CA1 hippocampal pyramidal cells is lost when the core temperature of an animal entering hibernation falls to 20 °C.     

Arsenite exposure compromises early embryonic development in the Golden hamster

The toxicity of arsenite to 8-cell stage hamster embryos was evaluated. Females were superovulated and mated; embryos were collected and grown for 72 h in culture medium containing vehicle control, 25, 50, 250, 500, or 750 nM arsenite. Morphological observations were taken at 0 and 24 h increments. A TUNEL assay was used for determining DNA damage. Survival was expressed by the ability to undergo zona escape. The control group had 78% survival and no evidence of deformities. Embryos in the 25, 50 and 250 nM groups had survival rates of 63%, 55% and 27%, respectively. Arsenite exposure caused total embryo lethality, major deformities, complete failure to undergo zona lysis, and significantly higher number of cells with fragmented DNA in embryos at the 500 and 750 nM concentrations. The study underscores the sensitivity of preimplantation stage embryos to the presence of even relatively small amounts of arsenic in luminal fluid.     

Induction of protective immunity in a Syrian hamster model against a cytopathogenic strain of Andes virus

Andes virus (ANDV) is responsible for the Hantavirus Pulmonary Syndrome cases in Argentina and neighboring countries, with moderate to high case-fatality rates. ANDV has some particular features, which make it unique among other members of the Hantavirus genus such as person-to-person transmission and causing a disease similar to Hantavirus Pulmonary Syndrome in the hamster as an animal model. The kinetics of replication in Vero E6 cells of an ANDV strain isolated in Argentina, called Andes/ARG, was studied. Cytopathic effect and the formation of clear plaques were observed and therefore Andes/ARG could be quantified by classic plaque assay. The Andes/ARG strain was found to be highly lethal in Syrian hamsters allowing experiments to demonstrate the protective potential of vaccines. A recombinant nucleocapsid protein of ANDV induced a long lasting antibody response and protective immunity against a homologous challenge, but to a lower extent against heterologous challenge by the Seoul virus.     

Lack of detectable diffuse or neuritic plaques and neurofibrillary tangles in the brains of aged hamsters

Syrian golden hamsters (Mesocricetus auratus) are facultative hibernators with a life expectancy of approximately 2 years. Previous investigations showed a hyperphosphorylation of the tau protein during hibernation and aging and raised hopes that Syrian hamsters might represent a useful animal model to study pathogenetic mechanisms of Alzheimer's disease. Brain and spinal cord transversal sections of 190 hamsters 1-36 months of age were investigated using histology and immunohistochemistry to detect neurofibrillary tangles and/or diffuse as well as neuritic plaques. Summarized, amyloid deposition, neurofibrillary tangles, and diffuse as well as neuritic plaques were absent indicating that the Syrian golden hamster does not develop changes characteristic of Alzheimer's disease even at advanced age and does not represent an appropriate animal model for this disease.     

The formation of the allantoic placenta in the golden hamster (Mesocricetus auratus)

Summary The processes of attachment, implantation and placentation in the golden hamster (Mesocricetus auratus) have been re-examined. Blastocyst attachment occurs at 4.0 days P.C. and complete interstitial implantation is attained by 5.5 days P.C. At 6.15 days P.C. the trophoblast of the träger breaks into the uterine lumen which becomes filled with blood clot. The advancing träger uses this blood clot as a bridge to reach the decidua basalis, lying on the opposite side of the uterine cavity, at 8.5 days P.C. Thus the uterine lumen becomes obliterated opposite each conceptus by the formation of the allantoic placentas which are vascularised by 8.5 days P.C. Non-glandular extensions of the glandular interlocular lumina penetrate between the decidua capsularis and the muscularis of the antimesometrial wall of the uterus from the 8th day P.C. onwards. On the 14th day P.C. the parietal wall of the yolk sac and its thin covering layer of decidua capsularis disappear to form a completely inverted yolk sac placenta. This places the yolk sac cavity in continuity with the non-glandular extensions of the uterine lumen and re-establishes complete continuity of the uterine lumen.     

天麻细粉和天麻素降血脂作用的实验研究

目的研究天麻细粉、天麻素的降血脂作用。方法采用金黄地鼠饲喂高脂饲料,分为正常对照组、高脂对照组(HF)、阳性对照组(舒降之)5.0mg/kg,天麻细粉125mg/kg、250mg/kg、500mg/kg、天麻素12.5mg/kg、25.0mg/kg、50.0mg/kg组,口服给药14d取血清测定总胆固醇(TC)、甘油三脂(TG)、高密度脂蛋白胆固醇(HDL-C)和低密度脂蛋白胆固醇(LDL-C)含量。结果天麻细粉和天麻素各剂量组均能降低高脂血症金黄地鼠血清中TC、TG、LDL-C含量,LDL-C/HDL-C比值、动脉硬化指数AI减小,均有显著性差异(P0.01及P0.05)。结论天麻细粉、天麻素具有降血脂作用。     

Increased Ifng and Il10 Expression Correlate with Disease in Rodent Models Experimentally Infected with Modoc Virus

Flaviviruses present an ongoing threat to global public health, although the factors that contribute to the disease remain incompletely understood. We examined an acute Modoc virus (MODV) infection of two rodent models. Viral RNA was detected in the kidneys, spleen, liver, brain, urine, and sera of experimentally infected deer mice, a reservoir host of MODV, and Syrian hamsters, a known disease model. As expected, clinical outcomes differed between species, and the levels of viral RNA recovered from various tissues demonstrated signs of differential replication and tissue tropism. Multivariate analysis indicated significance in the profile of expressed genes between species when analyzed across tissues and over time (p = 0.02). Between-subject effects with corrected models revealed a significance specific to the expression of Ifng (p = 0.01). the expression of Ifng was elevated in hamsters as compared to deer mice in brain tissues at all timepoints. As the over-expression of Ifng has been shown to correlate with decreased vascular integrity, the findings presented here offer a potential mechanism for viral dissemination into the CNS. The expression of IL10 also differed significantly between species at certain timepoints in brain tissues; however, it is uncertain how increased expression of this cytokine may influence the outcome of MODV-induced pathology.