Geometry of the projection of the visual field onto the superior colliculus of the wallaby (Macropus eugenii). II. Stability of the projection after prolonged rearing with rotational squint

At about the time of eye opening, one eye of seven tammar wallaby pouch young was surgically rotated about the optic axis by approximately 90°. In adulthood the projection of the visual field through the rotated eye onto the contralateral superior colliculus was mapped electrophysiologically. Although apparently distorted, the projection could be coherently rerotated mathematically to a reasonable copy of the normal projection from the opposite eye of the same animal, including details such as regional variations of the magnification factor. The same was true of three adult animals in which the eye rotation was done after anaesthesia immediately before the electrophysiological mapping. In animals in which the visual field seen through one eye, the other being normal, was rotated for the entire period of visual experience, there was no sign of compensation or rearrangement of the topographic map. Retinocollicular synaptic connections appear unmoved by such discordant visual experience.     

Cohesin component dynamics during meiotic prophase I in mammalian oocytes

Cohesins are chromosomal proteins that form complexes involved in the maintenance of sister chromatid cohesion during division of somatic and germ cells. Three meiosis-specific cohesin subunits have been reported in mammals, REC8, STAG3 and SMC1 beta; their expression in mouse spermatocytes has also been described. Here we studied the localization of different meiotic and mitotic cohesin components during prophase I in human and murine female germ cells. In normal and atretic human fetal oocytes, from leptotene to diplotene stages, REC8 and STAG3 colocalize in fibers. In murine oocytes, SMC1beta, SMC3 and STAG3 are localized along fibers that correspond first to the chromosome axis and then to the synaptonemal complex in pachytene. Mitotic cohesin subunit RAD21 is also found in fibers that decorate the SC during prophase I in mouse oocytes, suggesting a role for this cohesin in mammalian sister chromatid cohesion in female meiosis. We observed that, unlike human oocytes, murine synaptonemal complex protein SYCP3 localizes to nucleoli throughout prophase I stages, and centromeres cluster in discrete locations from leptotene to dictyate. At difference from meiosis in male mice, the cohesin axis is progressively lost during the first week after birth in females with a parallel destruction of the axial elements at dictyate arrest, demonstrating sexual dimorphism in sister chromatid cohesion in meiosis.     

洱源县小兽类哺乳动物种群结构研究

目的　调查大理州洱源县小兽类哺乳动物种群结构。方法　 2 0 0 1～ 2 0 0 3年春季 ,在不同环境下采用捕鼠笼、鼠夹、电子捕鼠器等工具捕捉小兽 ,研究小兽种群结构。结果　捕获小兽 3目 5科 8属 17种共 661只。野外生境捕获小兽 3目 17种 ,以大绒鼠和齐氏姬鼠为常见种 ,分别占 3 2 .71%和 2 3 .5 9%。室内生境捕获小兽 2目 4种 ,褐家鼠为优势种 ,占 77.43 % ,黄胸鼠次之 ,占 18.75 %。结论　野外生境小兽种群丰富 ,室内较单一。     

Biology of tooth replacement in amniotes

Tooth replacement is a common trait to most vertebrates, including mammals. Mammals, however, have lost the capacity for continuous tooth renewal seen in most other vertebrates, and typically have only 1–2 generations of teeth. Here, we review the mechanisms of tooth replacement in reptiles and mammals, and discuss in detail the current and historical theories on control of timing and pattern of tooth replacement and development.     

The endogenous rhythm of plasma melatonin and its regulation by light in the highveld mole-rat (Cryptomys hottentotus pretoriae): a microphthalmic, seasonally breeding rodent

Abstract:  The day- and night-time levels of plasma melatonin were measured in adult male and female highveld mole-rats, Cryptomys hottentotus pretoriae . This study aimed to assess whether melatonin secretion in this nocturnal, strictly subterranean but seasonally breeding rodent has a day-night rhythm and whether that rhythm is circadian and can be modified by photoperiod. In experiment 1, a day-night rhythm of plasma melatonin was found in all animals housed on a 12L:12D schedule, with significantly higher concentrations in the dark (D) compared with the light (L) phase. The increment of plasma melatonin concentration at night was the same on days 1 and 2 for animals in the control group and animals transferred to constant dark. The animals transferred to constant light substantially reduced the amplitude of the melatonin rhythm on day 2. This suggests that the endogenous melatonin rhythm in C. h. pretoriae has a circadian pattern, which can be synchronized by photoperiod and inhibited by exposure to light at night. In experiment 2, the concentration of plasma melatonin in animals kept under 14L:10D (long day, LD) conditions differed significantly from animals on 10L:14D (short day, SD). This finding supports the notion that C. h. pretoriae is sensitive to changes in day length.     

毫米波局部照射的远位效应

目的探讨毫米波局部照射后,除局部效应外。对动物神经系统、内分泌器官、免疫及其他内脏、生殖器官、胚胎发育及子代有无远位效应。方法选用不同频率、不同功率密度的毫米波辐照小鼠、大鼠、豚鼠,并于照后不同时间,应用先进的技术方法,(光镜、电镜、DNA定量分析、组化、免疫组化、细胞培养、高效液相(HPLC)、RIA、RBA、TAS、畸形学分析、精神行为学分析等)从功能、形态、代谢等不同角度对实验动物进行观察分析。结果系列实验研究证明,在毫米波局部照射后确可引起远位组织、器官发生许多变化(骨髓中多核巨细胞核固缩,睾丸精管中出现多核巨细胞,肝细胞中糖原含量有变化,肝中cAMP、cGMP有起伏,G-6-P酶活性有变化,血液细胞成分有变化)。小鼠孕早期(1～2d)局部受照射,可见胚卵细胞表面一些酶活性有改变,导致胚卵着床减少;小鼠孕后期(5～15d)局部皮肤受照射,其胚胎虽未发生畸形,但其生下之后一代,学习记忆能力有所降低。结论毫米波局部照射确有远位效应。本项研究为临床毫米波的应用和防护标准的制定奠定了理论基础。     

梁河县不同地区小型兽类的种群组成及分布

目的了解不同海拔地区小型兽类的种类及分布,为研究人兽共患病提供科学依据。方法在不同海拔区采用夹夜法调查小型兽类数量及分布。结果布放鼠夹2 120个次,捕获小兽155只,密度7.31%,其中高海拔区捕获动物12种,捕获率8.24%,以锡金小鼠为优势种;中海拔区捕获动物10种,捕获率7.79%,以斯氏家鼠为优势种;低海拔区捕获动物12种,捕获率6.05%,以黄胸鼠为优势种。结论不同地区小兽的种类、数量及分布不同,小兽密度随海拔升高而增高,黄胸鼠密度随海拔升高而降低。     

云南省大理洱海周边地带小兽体表恙螨群落结构

目的了解大理洱海周边地带小兽体表恙螨寄生状况、恙螨物种多样性及群落结构特点.方法选择云南省大理洱海周边的不同地理方位作为野外抽样调查地点,用鼠笼（夹）加食饵诱捕小兽.以小兽耳窝作为固定采集部位,用手术刀片刮取耳窝的全部恙螨,70%酒精保存,Hoyer＇s液封片后于显微镜下鉴定螨种.群落结构用丰富度（S）、Shannon-Wiener多样性指数（H＇）、均匀度（J＇）及优势度指数（C＇）描述.结果捕获小兽3 313只,经鉴定隶属7科14属21种.从3 313只小兽双侧耳窝共采获恙螨56 150只,经鉴定隶属3亚科13属109种.8种优势螨种占全部恙螨的74.42%.多数小兽体表恙螨种类丰富（8种以上）,最多达58种.多数恙螨种类可同时寄生于不同宿主（5种以上）,最多可寄生15种小兽.优势螨种在相应宿主寄生其染螨率（2.06%～59.02%）和螨指数（0.462 7～68.560 6）差异很大.在17种主要小兽中,有13种小兽体表恙螨群落的物种丰富度超过10,最高可达58;有15种小兽体表恙螨群落的多样性指数超过1,最高达2.583 4.结论大理洱海周边地带小兽体表恙螨寄生普遍,恙螨物种多样性高、群落结构比较复杂.多数恙螨的宿主范围广泛,宿主特异性较低.