Male and female genotype mediate pheromonal regulation of the mouse estrous cycle

Estrous cyclicity was studied to examine the possibility that strain differences in the regularity of the mouse estrous cycle are the result of different olfactory signals produced by the male. Females with regular estrous cycles (lines E and S1) were housed in the olfactory presence of males from a line with irregular cycles (line CN-) or in the presence of males of their own line (used as a control). Females with irregular cycles (line CN-) were housed in the presence of males from a line with regular cycles (line E) or were exposed to males of their own line. The regularity of the estrous cycle decreased in line E females (regular cycles) when exposed to line CN- males (irregular cycles). The decreased regularity of line E cyclicity resulted from an increased period of diestrus, i.e., lengthening of the cycle. In contrast, line S1 females (regular cycles) did not show any change in estrous cyclicity when exposed to line CN- males. The period of diestrus increased in line CN- females when they were exposed to line E males. These results provide evidence that 1) the genotype of the male can influence the regularity of the estrous cycle, and 2) the genotype of the female regulates her responsiveness to environmental factors (e.g., male odor).     

温度对四纹豆象生长发育与繁殖的影响

四纹豆象CallosobruchusmaculatusFabricius是一种世界性分布害虫,危害多种豆类因而具有重要的经济学意义。为准确掌握四纹豆象的生物学特性,并为其综合防治提供一定的理论依据,以绿豆为食料,在20,25,28,32,35和37℃等6个温度和相对湿度75%的条件下,通过逐日观察法对四纹豆象各虫态的发育历期、存活率、成虫寿命及产卵量等生物学特性进行研究。结果表明:四纹豆象卵期、豆内幼虫及蛹期、未成熟期发育点温度分别为12.67,13.86和13.53℃;温度与世代存活率及周限增长率均呈二次抛物线关系,根据相应抛物线方程可知,四纹豆象理论最适生存温度和最适种群增长温度分别为30.2℃和33.7℃,其生长发育繁殖的最适温区为30~34℃。     

Apoptosis in endometrium of mouse during estrous cycle

The present study was carried out to evaluate apoptosis in endometrium and to correlate these changes with the circulating levels of estradiol and progesterone in the mouse. Apoptosis was observed in various compartments of mouse uterus i.e. stroma, glandular epithelium and luminal epithelium depending on the stage of cycle. Stromal cell apoptosis was observed during various stages of cyclicity except on estrus day. Luminal epithelial cells showed apoptotic changes during all stages of cyclicity except on diestrus day. During metestrus, apoptosis was observed in glandular and luminal epithelia as well as stromal cells. Steroid antagonists such as tamoxifen and onapristone altered the apoptotic changes in the uterus. The results suggest that epithelial cell apoptosis is regulated by estrogen while stromal cell apoptosis is under the control of progesterone.     

Metabolism and temperature regulation during daily torpor in the smallest primate, the pygmy mouse lemur (Microcebus myoxinus) in Madagascar

Thermoregulation, energetics and patterns of torpor in the pygmy mouse lemur, Microcebus myoxinus, were investigated under natural conditions of photoperiod and temperature in the Kirindy/CFPF Forest in western Madagascar. M. myoxinus entered torpor spontaneously during the cool dry season. Torpor only occurred on a daily basis and torpor bout duration was on average 9.6 h, and ranged from 4.6 h to 19.2 h. Metabolic rates during torpor were reduced to about 86% of the normothermic value. Minimum body temperature during daily torpor was 6.8 °C at an ambient temperature of 6.3 °C. Entry into torpor occurred randomly between 2000 and 0620 hours, whereas arousals from torpor were clustered around 1300 hours within a narrow time window of less than 4 h. Arousal from torpor was a two-step process with a first passive climb of body temperature to a mean of 27 °C, carried by the daily increase of ambient temperature when oxygen consumption remained more or less constant, followed by a second active increase of oxygen consumption to further raise the body temperature to normothermic values. In conclusion, daily body temperature rhythms in M. myoxinus further reduce the energetic costs of daily torpor seen in other species: they extend to unusually low body temperatures and consequently low metabolic rates in torpor, and they employ passive warming to reduce the energetic costs of arousal. Thus, these energy-conserving adaptations may represent an important energetic aid to the pygmy mouse lemur and help to promote their individual fitness. Accepted: 2 November 1999     

Expression of insulin-like growth factor binding protein-4, insulin-like growth factor-I receptor, and insulin-like growth factor-I in the mouse uterus throughout the estrous cycle

Recent evidence suggests that a regulated insulin-like growth factor (IGF) system mediates the effects of estrogen, promoting the proliferation and differentiation of specific uterine cell types throughout the estrous cycle and during gestation in the rodent. Previous studies have shown that IGFs are differentially expressed in the mouse uterus during the periimplantation period. In the current study, we examined the expression of IGF binding protein-4 (IGFBP-4), IGF-I receptor (IGF-IR), and IGF-I in the mouse uterus throughout the estrous cycle. Ligand blot analysis was conducted on uterine homogenates using [125I]IGF-I. IGFBP-4 was detected in all uterine homogenates, varying in intensity throughout the estrous cycle. In situ hybridization studies at metestrus and diestrus demonstrated an intense IGFBP-4 mRNA signal in antimesometrial stromal cells between the luminal epithelium and the myometrium, but at proestrus and estrus, no IGFBP-4 signal was detected. No IGF-I mRNA was detected at any stage of the estrous cycle by in situ hybridization. However, by RT-PCR analysis, IGF-I mRNA was detected at all stages of the estrous cycle. RT-PCR analysis also showed IGF-IR mRNA throughout the estrous cycle. Using immunohistochemistry, IGF-IR immunostaining was detected throughout the estrous cycle and on days 2-7 of gestation, but was restricted to the glandular epithelium. These results suggest that uterine IGFBP-4 expression may not be dependent on uterine IGF-I expression. They also suggest that IGFBP-4 may play a role in uterine physiology independent of the inhibition of IGF-I action, and that IGF-IR is constitutively expressed in the mouse uterus.     

Expression and regulation of insulin-like growth factor binding protein-1 in the rat uterus throughout estrous cycle

The role of Ca²⁺-stimulated adenosine 5-triphosphatase (Ca²⁺-ATPase) in Ca²⁺ sequestering of rat liver nuclei was investigated. Ca²⁺-ATPase activity was calculated by subtracting Mg²⁺-ATPase activity from (Ca²⁺–Mg²⁺)-ATPase activity. Ca²⁺ uptake and release were determined with a Ca²⁺ electrode. Nuclear Ca²⁺-ATPase activity increased linearly in the range of 10–40 M Ca²⁺ addition. With those concentrations, Ca²⁺ was completely taken up by the nuclei dependently on ATP (2 mM). Nuclear Ca²⁺-ATPase activity was decreased significantly by the presence of arachidonic acid (25 and 50 M), nicotinamide-adenine dinucleotide (NAD⁺; 2 mM) and zinc sulfate (2.5 and 5.0 M). These reagents caused a significant decrease in the nuclear Ca²⁺ uptake and a corresponding elevation in Ca²⁺ release from the nuclei. Moreover, calmodulin (10 g/ml) increased significantly nuclear Ca²⁺-ATPase activity, and this increase was not seen in the presence of trifluoperazine (10 M), an antogonist of calmodulin. The present findings suggest that Ca²⁺-ATPase plays a role in Ca²⁺ sequestering by rat liver nuclei, and that calmodulin is an activator. Moreover, the inhibition of Ca²⁺-ATPase may evoke Ca²⁺ release from the Ca²⁺-loaded nuclei.     

Lectin histochemistry of mouse vagina during the estrous cycle

Estrous cycle-related histochemical changes in the vaginal epithelium of sexually mature female mice were studied with 30 fluorescein isothiocyanate (FITC)-labeled lectins. On the basis of the staining pattern the lectins were divided into five groups: I, seventeen lectins that reacted with mucinous surface layer of proestrus. This group comprised two subgroups: Ia, seven lectins that reacted exclusively with the mucinous layer, and Ib, ten lectins that reacted with mucinous cells and the underlying squamous epithelium of proestrus; II, two lectins that reacted with squamous epithelium of proestrus only but were unreactive with mucinous cells; III, three lectins that reacted in a phase-specific manner with squamous epithelium; IV, six lectins that showed increased luminal surface reactivity in diestrus and/or metestrus; and V, eleven lectins that were unreactive with vaginal epithelium. These data indicate that the cyclic changes in the morphology of the vaginal epithelium are accompanied by distinct lectin reactivity patterns.     

Cell cycle regulation in hair cell development and regeneration in the mouse cochlea

Cell cycle inhibitors play important roles in the development of mammalian cochleae. Loss of function of those factors in mice at various developmental stages results in distinct phenotypes characterized by overproduction or loss of cochlear sensory cells. Our recent study showed that acute deletion of the retinoblastoma protein (Rb) induces rapid cell cycle reentry and subsequent loss of postnatal cochlear hair cells in mice. Clearly, these regulators play multiple roles in cell cycle exit and differentiation of hair cell and supporting cell progenitors. They are also crucial in maintenance of postmitotic states and survival of differentiated hair cells and supporting cells. In mammals, lost hair cells cannot be spontaneously replaced, leading to permanent deafness. However, lower vertebrates such as birds and fish can naturally regenerate damaged hair cells from the underlying supporting cells through proliferation and transdifferentiation. Thus, manipulating cell cycle inhibitors in mammalian cochleae could provide a new avenue to restore hearing in deaf people caused by a variety of genetic mutations and environmental insults.     

Waves of follicle development during the estrous cycle in sheep

The pattern of ovarian follicle development in maiden cyclic lambs was characterized using the definition of a follicle wave as the changes in the number of follicles among the days of the estrous cycle, as originally defined in cattle by Rajakoski in 1960. We also examined the steroid content relationships among follicles on Days 5 (Wave 1) and 14 (Waves 2 and 3) of the estrous cycle. In Experiment 1, the ovaries of 20 cyclic lambs (40 to 45 kg) were examined daily using transrectal ultrasonography for 1 or 2 estrous cycles (n = 31 cycles). The number of small (2 and 3 mm in diameter), medium (4 and 5 mm) and large (> or = 6 mm) follicles were aligned with the beginning and end of the average length estrous cycle and then compared among days. Identified follicles were defined as those that grew to > or = 4 mm and remained at > or = 3 mm for > or = 3 d. The number of identified follicles emerging (retrospectively identified at 2 or 3 mm) per ewe per day was also aligned with the average length estrous cycle. In Experiment 2, ewe lambs were ovariectomized on Day 5 (n = 6) or 14 (n = 5) of the estrous cycle, then follicle diameters and follicular fluid concentrations of estradiol and progesterone were compared among follicles. Data were analyzed by repeated measures ANOVA and compared among days using Fisher's LSD. In Experiment 1, either 2 (n = 10 cycles), 3 (n = 20 cycles) or 4 (n = 1 cycle) periods of emergence of identified follicles occurred during individual cycles, with estrous cycle lengths of 15.6 +/- 1.6, 16.1 +/- 1.1 and 17 d respectively. In animals with 2 or 3 periods of emergence of identified follicles, the total number of small, medium and large follicles differed (P < 0.05) among days of the estrous cycle showing a wave-like pattern. In Experiment 2, a single follicle collected on each of Days 5 and 14 of the cycle (6.2 +/- 0.2 and 3.9 +/- 0.2 mm in diameter) had a higher (P < 0.05) concentration of follicular fluid estradiol (36.2 +/- 4.4 and 50.9 +/- 21.6 ng/mL) than other follicles collected on the same day (next largest follicle: 4.3 +/- 0.3 and 3.5 +/- 0.4 mm; 4.3 +/- 0.9 and 18.2 +/- 6.7 ng/mL estradiol). The results showed that 1) there was a synchronous emergence of follicles associated with fluctuations in the number and size of follicles during the estrous cycle; 2) within a wave there was a hierarchy among follicles for diameter and steroid content; 3) ovarian follicle growth in ewe lambs occurred in 2 or 3 organized waves during the estrous cycle.     

The effect of atrophy, hyperplasia, and keratinization accompanying the estrous cycle on Langerhans' cells in mouse vaginal epithelium

The morphology and numbers of Langerhans' cells vary in epithelia with different patterns of hyperplasia and keratinization. Langerhans' cells stained for ATPase were compared at five phases of the estrous cycle in murine vaginal epithelium. The cells were more dendritic and sparsely distributed with hyperplasia and were less dendritic and more densely distributed with atrophy. Greater numbers of the cells did not accompany keratinization at estrus. Ultrastructurally, three types of Langerhans' cells were discriminated. The first type, active in protein synthesis and phagocytosis, was commonest in sloughing and atrophic epithelium. The second type, containing accumulated and dispersed, electron-dense bodies presumed to be lysosomes, predominated in hyperplastic epithelium. The third, a mature resting cell, was found only after keratinization was complete. This study shows that Langerhans' cells in murine vaginal epithelium vary in morphology and numbers with the epithelial changes of the estrous cycle which may relate to their immunological role, but does not support the contention that their distribution is important for keratinization.     

Effects on reproduction of estrous cycle variations, rectal temperatures and liveweights in mated Brahman cross heifers

Estrous cycle variations and the association of rectal temperature with reproductive measurements and liveweight were examined in 25-month-old 1 2 and 3 4 Brahman heifers (n = 88). The mean cycle length was longer in the 1 2 Brahmari (24.3 days) than in the 3 4 Brahman heifers (21.3 days) due to the length of estrus-metestrus, but the overall difference was not statistically significant. Cycle length was not influenced by cycle number or liveweight. Cycles were classified into 6 types: normal, short, long, anovulatory and those involving embryonic nortality and prolonged diestrus. Only 33.6% of 1 2 Brahman cycles and 36.1% of 3 4 Brahman cycles were of normal duration (18 to 24 days), and 13.3% of 1 2 Brahman and 11.6% of 3 4 Brahman cycles were classified as embryonic mortality cycles. On an individual animal basis, 25.0% and 31.8% of 3 4 Brahman heifers, respectively, had cycles in which embryonic mortality was suspected. Heifers that became pregnant were significantly (P < 0.01) heavier throughout mating and had significantly (P < 0.05) lower mean rectal temperatures. Heifers in which embryonic mortality had occurred were lighter and had significantly (P < 0.01) higher rectal temperatures than heifers in which embryonic mortality had not occurred. Correlations between rectal temperature and ambient temperature were nonsignificant after eliminating the effect of genotype, but rectal temperature was significantly (P < 0.01) negatively correlated with liveweight.