Melatonin: its inhibition of pineal antigonadotrophic activity in male hamsters

Exposure of male hamsters to short daily photoperiods (1 hour of light and 23 hours of darkness daily for 9 weeks led to total involution of the testes and accessory sex organs (seminal vesicles and coagulating glands). Pituitary levels of immunoreactive prolaction also decreased by about 60 percent after dark exposure. The inhibitory effects of darkness on the reproductive organs were prevented either by pinealectomy or by the subcutaneous implantation of a melatonin-beeswax pellet into the animals each week. Both pinealectomy and melatonin treatment also returned pituitary levels of prolactin toward normal. The results suggest that melatonin is not the pineal antigonadotrophic factor in the male golden hamster.     

Circadian oscillations in rodents: a systematic increase of their frequency with age

The circadian activity rhythms of golden hamsters and two species of deermouse, when released from a light-dark cycle of 12 hours light and 12 hours of darkness into constant darkness, had progressively shorter periods as the animals became older. A possible bearing of this fact on the aging process is briefly outlined.     

A mutation of the circadian system in golden hamsters

A mutation has been found that dramatically shortens the period of the circadian locomotor rhythm of golden hamsters. The pattern of inheritance of this mutation suggests that it occurred at a single, autosomal locus (tau). Wild-type animals have rhythms with free-running periods averaging about 24 hours; animals heterozygous for the mutation have periods of about 22 hours, whereas homozygous animals have rhythms with periods close to 20 hours. Animals that carry the mutant alleles exhibit abnormal entrainment to 24-hour light:dark cycles or are unable to entrain.     

Chromosomal aberrations in a population of ground squirrels

Chromosomes were analyzed from a population of Spermophilus beldingi that included an adult female and three juveniles from the same burrow. All animals had a diploid number of 30. The adult and a juvenile female from the burrow had identical aberrant karyotypes containing an unpaired submetacentric and a minute metacentric chromosome. A familial aberration involving an X chromosome, without phenotypic alteration, is most probable.     

Pineal gland: influence on gonads of male rats treated with androgen 3 days after birth

Either blinding or the injection of 1 milligram of testosterone propionate into male Sprague-Dawley rats, 3 days old, results in testes and accessory organs (seminal vesicles and coagulating glands) that are smaller than normal when the rats are 72 days old. The response to blinding is prevented by removal of the pineal gland, whereas the response to treatment with testosterone is unaffected by pinealectomy. Combination of the two treatments in 3-day- old rats causes testes to be less than one-third their normal size at 72 days of age; pinealectomy in these rats permits the reproductive organs to grow to the same size as those in the androgen-treated animals.     

一种有效分离及在体外扩增成年小鼠精原干细胞的方法

尝试建立一种简便有效的成年小鼠精原干细胞分离培养及扩增的方法。从单只成年小鼠的睾丸中经过两步酶消化法分离精原干细胞,并在去除间质细胞、纯化后的支持细胞饲养层上培养与扩增,获得稳定增殖的精原干细胞系。此方法可显著提高建系成功率,保证细胞系的单一基因型,显著降低体外培养精原干细胞的成本。为成体基因来源的转基因动物的制作和疾病模型的建立提供技术支持。     

Light pulses that shift rhythms induce gene expression in the suprachiasmatic nucleus

Lighting cycles synchronize (entrain) mammalian circadian rhythms by altering activity of cells in the suprachiasmatic nucleus (SCN) of the hypothalamus, a circadian pacemaker. Exposure of hamsters and rats to light pulses at those phases of the circadian rhythm during which light can shift the rhythm caused increased immunoreactivity for the product of the immediate-early gene c-fos in cells in the region of the SCN that receives retinal fibers. Light pulses also increased messenger RNA for the Fos protein and for the immediate-early protein NGFI-A in the rat SCN. Similar increases in mRNA for NGFI-A were seen in the SCN of hamsters. Thus cells in this portion of the SCN undergo alterations in gene expression in response to retinal illumination, but only at times in the circadian cycle when light is capable of influencing entrainment.     

Chronic infection of rodents by Machupo virus

Machupo virus, the etiologic agent of human hemorrhagic fever in Bolivia, induced chronic asymptomatic infection in laboratory hamsters and colonized individuals of the peridomestic, wild, South American rodent, Calomys callosus. Viruria was detected for more than 500 and 150 days, respectively, in the two species. Chronic viremia was shown only for Calomys. Virus-neutralizing substances were present in parenterally infected adult animals, but not in animals born to, and in contact with, an infected female. Chronic infection in wild rodents may be an important mechanism in the natural history of Machupo and related virus infections.     

Neisseria gonorrhoeae: experimental infection of laboratory animals

Experimlental Neisseria gonorrhoeae infections were established in five species of small laboratory animals (rabbits, guinea pigs, hamsters, mice, and rats) after subcutaneolusly implanted chambers were inioculated with gonococci. The chamber fluid was easily available for study or culture. A systemic immune response was indicated by hemnagglutination assay.     

Colobus guereza: Territoriality and Group Composition

Troops of the black and white colobus Colobus guereza in the Bueclongio Forest, Uganda, average eight animals with a typical composition of one adult male, four adult females, two subadults, one juvenile, and one infant. Solitary males and small all-male groups also occur. Troops of mixed sexes have well-defined territories which coincide roughly with the home range. Territories of five groups averaged 0.062 square mile (0.137 kmn(2)) in area agreeing closely with territory-sizes of Asian Colobine monkeys. Adult males have a roar that is concerned with maintaining territorial spacing, but not with actual territorial defense. The territories of these arboreal, forest animals are much smaller than the home ranges of more terrestrial and nonterritorial open-country primaes.     

非洲淡水鳉鱼的生存要素及日常管理研究——以贡氏假腮鳉为例

[目的]探讨非洲淡水鳉鱼的生存要素和日常管理。[方法]以贡氏假腮鳉为例,从水质、水温、光照和日常管理等方面来探讨贡氏假腮鳉的生存要素和日常管理。[结果]贡氏假鳃鳉幼鱼对水质和水温的要求很高。若水温过低,幼鱼的生病几率会大大增加,还可能出现畸变情况。另外,光照对成鱼的色彩也有很大影响。[结论]在贡氏假鳃鳉的日常饲养中,水中的溶氧量一般保持在6 mg/L以上。     

Antiphase oscillation of the left and right suprachiasmatic nuclei

An unusual property of the circadian timekeeping systems of animals is rhythm "splitting," in which a single daily period of physical activity (usually measured as wheel running) dissociates into two stably coupled components about 12 hours apart; this behavior has been ascribed to a clock composed of two circadian oscillators cycling in antiphase. We analyzed gene expression in the hypothalamic circadian clock, the suprachiasmatic nucleus (SCN), of behaviorally "split" hamsters housed in constant light. The results show that the two oscillators underlying the split condition correspond to the left and right sides of the bilaterally paired SCN.     

A specialized forebrain circuit for vocal babbling in the juvenile songbird

Young animals engage in variable exploratory behaviors essential for the development of neural circuitry and adult motor control, yet the neural basis of these behaviors is largely unknown. Juvenile songbirds produce subsong-a succession of primitive vocalizations akin to human babbling. We found that subsong production in zebra finches does not require HVC (high vocal center), a key premotor area for singing in adult birds, but does require LMAN (lateral magnocellular nucleus of the nidopallium), a forebrain nucleus involved in learning but not in adult singing. During babbling, neurons in LMAN exhibited premotor correlations to vocal output on a fast time scale. Thus, juvenile singing is driven by a circuit distinct from that which produces the adult behavior-a separation possibly general to other developing motor systems.     

Symbiont recognition and subsequent morphogenesis as early events in an animal-bacterial mutualism

Bacterial colonization of the developing light organ of the squid Euprymna scolopes is shown to be highly specific, with the establishment of a successful association resulting only when the juvenile host is exposed to seawater containing one of a subset of Vibrio fischeri strains. Before a symbiotic infection the organ has elaborate epithelial structures covered with cilia and microvilli that are involved in the transfer of bacteria to the incipient symbiotic tissue. These structures regressed within days following infection; however, they were retained in uninfected animals, suggesting that the initiation of symbiosis influences, and is perhaps a prerequisite for, the normal developmental program of the juvenile host.     

Lymphocytic-choriomeningitis virus in hamster tumor: spread to hamsters and humans

A passage line of a spontaneous hamster fibrosarcoma is contaminated by the virus. of lymphocytic choriomeningitis. Tumors from animals receiving implants when newborn contain high titers of infectious lymphocytic-choriomeningitis virus and complement-fixing antigen, and hamsters receiving implants when weanlings develop high titers of complement-fixing antibody against lymphocytic-choriomeningitis virus. In contrast with the specific reactions of tumorous hamsters to the initiating virus in virus-induced tumors, the development of complement-fixing antibody to lymphocytic-choriomeningitis virus does not depend on the development of tumors. Infant hamsters bearing the tumor have a generalized subclinical infection and seem able to spread virus to other hamsters and to humans.     

Involvement of juvenile hormone in the regulation of pheromone release activities in a moth

Juvenile hormone has been implicated in the mediation of several reproduction-related events in adult insects, but had previously been found to play no role in the regulation of sex pheromone production and release behavior ("calling") in moths. In females of the true armyworm moth, Pseudaletia unipuncta, juvenile hormone is shown to be essential to the initiation of both calling behavior and pheromone production. Females without corpora allata, the source of juvenile hormone, do not call and do not produce pheromone, but injection of juvenile hormone into allatectomized females restored these activities. The armyworm's control system has likely evolved in response to the adults' migratory behavior which may necessitate that mating be restricted to the period following migration.     

己烯雌酚对成年仓鼠睾丸生精的影响

 探讨环境内分泌干扰物己烯雌酚(DES)对成年动物睾丸生精的影响。将DES皮下注射给成年仓鼠(剂量为1 mg·kg-1·d-1)，用光镜和电镜观察睾丸和生精细胞形态结构的变化，并用甲基绿-哌咯宁和脱氧核糖核酸末端转移酶介导的dUTP缺口末端标记法（TUNEL）检测生精细胞的凋亡。结果表明，DES处理后睾丸萎缩，曲精小管变细。曲精小管内的细胞排列紊乱，大量的精母细胞和精子细胞凋亡，少见长形精子细胞。电镜下，这些退化的精母和精子细胞的胞浆内有大量髓样或空泡状结构。DES诱发生精细胞凋亡是造成成年动物睾丸生精障碍的重要原因。     

镉暴露家兔睾丸和肝脏中小分子金属结合蛋白的分离与比较

 【目的】通过对镉暴露家兔睾丸和肝脏中小分子金属结合蛋白分离与比较,揭示动物睾丸组织镉高敏感性的机制。【方法】6月龄雄性青紫兰家兔经皮下染镉,9 d后将兔子杀死,制备睾丸和肝脏匀浆超离上清液,用Sephadex G-75凝胶层析法进行蛋白分离,经双波长（280 nm和254 nm）测定紫外吸收和原子吸收分光光度法测定Cd、Zn元素含量两种方法确定洗脱液小分子量金属结合蛋白峰管;通过试验比较它们的紫外扫描特性、热稳定性、镉锌元素比值和氨基酸组成。【结果】肝脏分离蛋白分子量为6.0～10.0 kD,有254 nm特征紫外吸收峰,OD250nm/OD280nm的值为13.13,有较好的热稳定性,不被无水乙醇抽提,每摩尔物质中Cd与Zn的摩尔比为4.7﹕2,半胱氨酸相对比例为32.89%、不含芳香族氨基酸、氨基酸组成与MT的理论值非常接近。睾丸分离蛋白无254 nm特征紫外吸收峰,Cd结合能力低,半胱氨酸相对含量只有2.36%,氨基酸组成与MT的理论组成相差较大。【结论】雄性动物睾丸对镉暴露敏感性高的原因是睾丸中不能被诱导产生能够拮抗重金属镉毒性作用的特殊蛋白质——金属硫蛋白。     

Estradiol shortens the period of hamster circadian rhythms

Continuous administration of estradiol benzoate by means of subcutaneously implanted capsules shortened the free-running circadian period of locomotor activity of blind hamsters (Mesocricetus auratus) that had had their ovaries removed. Estradiol also advanced the phase of the wheel running of sighted female hamsters without ovaries that were entrained to a photoperiod with 12 hours of light and 12 of darkness. These results, and findings from hamsters undergoing natural estrous cycles, indicate that endogenous estradiol is involved in the regulation of circadian periodicity.     

Melatonin induction of gonadal quiescence in pinealectomized Syrian hamsters

Pinealectomized Syrian hamsters were injected thrice daily with 25 micrograms of melatonin per injection. The injections were administered at 3-hour intervals either during the day or during the night of a photoperiodic cycle of 14 hours of light and 10 hours of darkness. After 6 weeks of treatment with melatonin during the night, both pinealectomized and intact hamsters had reduced testis weight, and pinealectomized hamsters showed decreased levels of serum gonadotropins. Injection of melatonin during the day for 7 weeks either once (75 micrograms) a day or thrice (25 micrograms per injection) daily caused a reduction in testis weight in pinealectomized hamsters. Both pinealectomized and intact females injected with melatonin thrice daily during the day became anovulatory by week 7 of treatment. These results are similar to those observed when hamsters are exposed to a short photoperiod, suggesting that melatonin may be acting as a hormone in mediating the effects of photoperiod on the reproductive system of the Syrian hamster.