The pattern of ovulation in the southern African spiny mouse (Acomys spinosissimus)

The pattern of ovulation in mammals is generally considered to be either spontaneous or induced by coitus. The present study aimed to assess the pattern of ovulation in the southern African spiny mice (Acomys spinosissimus). Females were divided into three treatments differing in the degree of contact with a male. Control females had no contact with males, separated females had only chemical, auditory and visual contact with a male as the sexes were separated with wire mesh and paired females had full contact with a vasectomized male and copulations were possible. Each treatment consisted of seven females and the ovarian mass, the number of primary, secondary/tertiary and Graafian follicles as well as presence of corpora lutea were compared between the three treatments. Faecal progestagen metabolite (FPM) concentrations were analyzed for every second day throughout the experiment and they were used to determine luteal phases and oestrous cycles. Corpora lutea were found in both the control and the paired treatment indicating that ovulation also occurred in the absence of coitus. There was also no effect of treatment on ovarian mass or follicle numbers. In contrast, only females in the separated and paired treatments exhibited luteal phases and oestrous cycles. Especially at the beginning of the experiment, FPM concentrations were higher in those two groups than the control. The results indicate that A. spinosissimus appears to ovulate spontaneously, although physical as well as olfactory male cues appear to be of great importance to enhance reproductive efforts of females.     

Short-lived corpora lutea syndrome in anoestrous ewes following 17β-oestradiol or MAP treatments applied before an allogenic sexual stimulation with rams and oestrous ewes

When induced to ovulate during anoestrus, ewes, does and cows frequently develop a short-lived corpora lutea (SLCL) syndrome associated to lack of previous progesterone. Exogenous progesterone precludes SLCL by blocking oxytocin endometrial receptors, thus inducing normal life-span CL (NLCL). Paradoxically, circa 50% of unprimed ewes do not develop SLCL. We report results from 3 trials assessing follicular, oestrous, ovulatory, and luteal end-points after 17β-oestradiol or MAP treatments. Oestradiol benzoate (50 μg) induced follicular turnover, provoked ovulation in 40% (24/60) of ewes treated (93% of which developed SLCL), but did not affect the incidence of SLCL (26/53) after an allogenic sexual stimulation (ASS) by rams and oestrous ewes. By the onset of the ASS, most NLCL ewes (26/27) had already experienced turnover of their largest follicle, had smaller largest and second largest follicles, and ovulated their largest follicle more frequently than SLCL ewes did. Most SLCL ewes (19/25) did not ovulate their largest follicles, ovulating instead smaller follicles of identical size to those of NLCL ewes. Priming (40 mg of MAP for 12 days) was partially effective at preventing SLCL even when terminated 14 days in advance of an ASS, but failed at completely preventing SLCL when terminated 6 or more days in advance. The coupling of a timed acquisition of full steroidogenic capability before ovulation with a system of endometrial oestradiol–progesterone–oxytocin receptors linked in an unstable equilibrium controlling the amplification of the luteolytic feed-forward loop of oxytocin and prostaglandin F₂α explains occurrence and relative incidences of both NLCL and SLCL, and links proximate and ultimate causes of the SLCL syndrome.     

Histology,histochemistry and morphometry of the ovary of the adult plains viscacha (Lagostomus maximus) in different reproductive stages

Lagostomus maximus is a South American Hystricognathi rodent whose reproductive behaviour shows characteristics unusual for mammals, such as polyovulation (200–800 oocytes) and a high rate of embryo mortality. Thirty‐six mature females captured in the province of Buenos Aires showed different physiological reproductive stages. Most of them presented a postpartum oestrus in August–September. This characteristic is different from that reported in other geographical areas. The stages considered were: anoestrus, follicular phase, early pregnancy and late pregnancy. The ovaries were light‐pink and smooth and presented a tortuous cord‐like aspect. Many primordial follicles were found in all the females studied. Follicles in different states of maturation and primary and accessory corpora lutea were observed in the cortex. These structures were smaller than those present in other related species. Follicles did not project into the surface of the organ. Calcified follicles of diverse size were found in all the ovaries. Atretic follicles were found in all the stages analysed. Interstitial tissue surrounding the follicles and the corpora lutea was also observed. The number and proportion of different cortical structures varied in the physiological stages analysed. The ovaries of the viscacha have differential characteristics in comparison to other Hystricognathi, some of them related to polyovulation.     

黄花牛耳朵(苦苣苔科)的传粉生物学

通过野外观察和繁育系统的实验,对黄花牛耳朵(Chirita lutea Yan Liu et Y.G.wei)的传粉生物学进行了研究.结果表明,黄花牛耳朵的花期从7月初至8月底,单株花期约35～47 d,单花化期约6～10 d,花的开放无固定的时间.在花期内花粉活性约80%,柱头可授性约75%～90%.花粉/胚珠比率(P/O)为1 215.73±266.13.柱头在花药散粉时已生长至花筒口部,明显高于花药,便于接受异花花粉.黄花牛耳朵不存在无融合生殖,高度白交亲和,但较难发生自动的白花授粉,产生种子主要依靠传粉媒介.自然授粉的结实率明显低于人工授粉的结实率,存在传粉限制,蜜蜂(Apidae sp.)、方头泥蜂(Crabro sp.)、无垫蜂(Ameglla sp.)是主要的传粉者.     

琼东海域橙黄滨珊瑚骨骼生长特性及其主要影响因素

基于珊瑚骨骼X射线照片,使用CoralXDS软件,对海南岛(琼)东部海域的橙黄滨珊瑚生长特性进行研究,获取了百年来的年生长率(ER)、骨骼密度(D)和钙化速率(CR) 3种生长参数.结果表明: 该橙黄滨珊瑚ER的变化范围为0.49～1.10 cm·a^-1,年均值0.76 cm·a^-1;D的变化范围1.11～1.35 g·cm^-3,年均值1.22 g·cm^-3;CR的变化范围为0.55～1.41 g·cm^-2·a^-1,年均值0.94 g·cm^-2·a^-1.统计分析表明,研究海区表层水温(SST)是橙黄滨珊瑚骨骼生长参数变化的主要环境影响因素,对ER和CR的控制较强,对D的影响较弱,但总体上3项生长参数都随SST升高而增大.光照、盐度和水动力条件等是次要影响因素.台风和强热带风暴对琼东海域橙黄滨珊瑚骨骼密度条带分布的影响也较为显著.复杂的气候环境,赋予了橙黄滨珊瑚骨骼多变的生长模式.过去一个世纪以来,琼东海域年平均表层水温显著上升,气候倾向率为0.15 ℃·(10 a)^-1,SST上升分为两个阶段,20世纪40年代初和80年代初,人类活动加剧和全球气候变暖是导致琼东海域SST显著上升的原因.     

草芍药,野牡丹和黄牡丹的核型研究

本文报道了国产芍药属(Paeonia L.)植物草芍药、野牡丹和黄牡丹的染色体数目及核型,均为2n=10=6m 2sm 2st,它们分别具2、3和4对次缢痕,所具次缢痕的数目和位置可以作三种核型的区别特征。     

Cloprostenol induced luteal regression in the beef cow. II. Histological evaluation of corpora lutea and correlation with luteal progesterone

Forty-two cycling, multiparous beef cows (percentage-Brahman) were injected twice at 11-d intervals with 500mug Cloprostenol (a prostaglandin F(2alpha) analog) to induce luteolysis. Cows were randomly assigned for ovariectomy at 12 hr intervals from 0 to 72 hr post-injection. Corpora lutea were excised and one-half of the corpus luteum was stored in phosphate-buffered formalin until mounting and staining with hematoxylin and eosin. The other half of the CL was snap-frozen for determination of progesterone content and concentration. Luteal cell density increased following Cloprostenol injection and was significantly correlated with a shift from predominantly healthy Type I cells to predominantly degenerating Types III and V cells. Cell mitosis tended to decrease by 12 hr and was lower by 24 hr post-injection. Cell pyknosis increased by 24 hr post-injection and was correlated with the decrease in percentage of healthy luteal cells. No pattern was detectable in cell karyorrhexis. Histological regression of the CL was inversely correlated with CL progesterone content. Therefore, we conclude that a reduction in cell mitosis is the earliest morphological sign of degeneration of the CL and that the CL follows a well-defined sequence of regression which is accompanied by a decrease in progesterone content.     

Variation in the oxytocin content of caprine corpora lutea across the breeding season

Ovarian tissues were obtained from cyclic goats during the early, mid and late breeding season. Immunoreactive oxytocin was measured by RIA in tissue extracts after chromatography on octadecylsilica cartridges. Luteal oxytocin concentrations were significantly greater during the early breeding season than during the mid or late breeding season. Oxytocin is luteolytic in goats. High concentrations of luteal oxytocin may be related to the high incidence of short estrus at the onset of the breeding season.