Implantation involves the attachment of the blastocyst to the wall of the uterus with, in some cases, the embedding of the entire ovum in the uterine wall. Associated with it are very profound and characteristic changes in the endometrium both during preparation for implantation and following attachment of the blastocyst. In this chapter, the uterine changes that take place during preparation will be considered first and then the changes during the process of implantation. The former occur regularly and frequently throughout the life of most female mammals, whereas the latter are rarer events, especially in women. This division of the subject is also convenient for the consideration of the control mechanism involved. Whereas the preparative changes are largely directed by the varying levels of the hormones secreted by the ovary, once the implantation process has been initiated hormones play a largely permissive role.

The Implantation Reaction

Once found throughout the Rocky Mountains and forests of the northern states, the lynx now hides in pockets of its former range while feeding mostly on small animals like snowshoe hares A team of government and university scientists review the newest scientific knowledge of this unique cat's history, distribution, and ecology The chapters on this web site provide information for current scientific and public debates regarding the fate of the lynx in the United States Chapters look at the relationships among lynx, its habitat, and its prey The attributes of northern versus southern lynx populations are compared and contrasted The authors caution against making decisions without enough knowledge and show where we lack information While the authors present the latest preliminary research results on lynx and offer some qualified insights into lynx management, the book's intent is to assess the current state of knowledge regarding lynx

https://www.fs.fed.us/rm/pubs/rmrs_gtr030.pdf

Ecology and Conservation of Lynx in the United States

Ecological conditions, feeding and ranging behaviour as well as physical condition of female Hanuman langurs (Presbytis entellus) were studied in order to analyse the major influences on the timing of reproductive events. The langurs inhabited a semi-evergreen forest dominated by Sal trees (Skorea robusta). The climate was dominated by the summer monsoon lasting from May to September. Availability of plant phytophases was markedly seasonal, with fruiting as well as flushing of the six main food plants during the monsoon. Feeding and ranging behaviour of the females varied with food availability and its distribution. High dietary quality was only obtained during a short period from May to July. Physical condition of the females varied in accordance with dietary quality and energy expenditure, with a good physical condition during the second half of the year. Births occurred from January until June, with most births around the energetically worst period of the year. The results indicate that, in contrast to several other non-human primates, most females of this population gave birth too early to meet the optimum lactation requirements. Complete weaning mainly took place during an energetically bad time of the year (October to December). However, it can be inferred that the reduction of suckling bouts prior to the next conception took place when high quality food was available. Conceptions were confined to the months of July to November, coinciding with the time of best physical condition. Moreover, females who conceived were in a better physical condition than those who failed to conceive, suggesting a primary influence of nutrition on the probability of conception. Seasonality and timing of births may be the result of a regular seasonal shortfall of resources influencing the ability of the females to ovulate and to conceive.

Ecology, nutrition, and timing of reproductive events in an Asian primate, the Hanuman langur (Presbytis entellus)

Seasonally recurring patterns in physiology and behavior are pervasive in nature. These often reflect adaptive, anticipatory responses to annual energetic constraints. This chapter reviews biological timekeeping mechanisms that allow mammals to engage seasonal phenotypic transitions. The overwhelming majority of research into mammalian seasonality has focused on the reproductive system. This chapter not only emphasizes lessons learned from the study of seasonal reproduction, but also considers mechanisms of seasonal changes in aggression, immune function, and cognition. In a species- and trait-specific manner, the exegesis of seasonality invokes measurement of day length (photoperiodism), the induction of photorefractoriness, and the activity of endogenous self-sustained circannual oscillators. Formal models of seasonal timekeeping are elaborated, and the phenomenology of seasonality in rodents and primates is reviewed. Evidence toward the critical nature of photoperiodic changes in nocturnal melatonin production is presented, the neural substrates that participate in responsiveness to melatonin, and the neuroendocrine events occurring downstream of melatonin signaling are also reviewed.

Mammalian Seasonal Rhythms: Behavior and Neuroendocrine Substrates

To date, it is not known whether the seasonal occurrence of sexual behavior and mating in free-ranging Hanuman langurs at Ramnagar, Nepal, is correlated with seasonal changes in female ovarian function, and, if so, which factor(s) triggers the onset of the reproductive period. Using non-invasive fecal hormone analysis in combination with behavioral observations, this study was carried out to: 1) investigate and characterize seasonal patterns of ovarian cyclicity and timing of conception in wild langur females living in a highly seasonal habitat; and 2) examine the relationship between seasonal patterns of ovarian cyclicity, behavioral estrus, and female physical condition. Behavioral data and fecal samples were collected during a total period of 14 months from nine females living in a multi-male group. Physical condition of the females was assessed monthly by visual inspection, using a seven-fold scale. Ovulatory cycles and timing of conceptions were identified by the measurement of immunoreactive pregnanediol glucuronide (iPdG) in extracted feces. Hormone profiles in individual females revealed a clearly seasonal distribution in the occurrence of ovulatory cycles, which were restricted to the period from July to October. The distribution of female estrus behavior showed a similar seasonal pattern, and in total 88.2% of all estrus periods observed in the focal females were accompanied by ovulation. Onset of ovarian cycles as well as mating activities were strongly correlated with the onset of the rainy season. Females conceived, on average, in their second ovulatory cycle (pregnancy length: 211.6 ± 3.4 days), with timing of conception being confined to the months when animals showed an improved physical condition. Collectively the present data clearly suggest that in seasonally-breeding langurs at Ramnagar, ecological conditions (rainfall, food availability, and quality) influence the onset of ovulations and timing of conceptions. Am. J. Primatol. 51:119–134, 2000. © 2000 Wiley-Liss, Inc.

Hormonal correlates of reproductive seasonality in wild female hanuman langurs (Presbytis entellus).

An experiment was designed to examine the effect of season on frequency of ovulation and to estimate the proportion of ovulatory cycles during the summer and winter months in feral rhesus monkeys housed under conditions of controlled light and temperature. The frequency of ovulatory menstrual cycles was determined for 9 monkeys in the summer months of June July and August and again during December January and February. Occurrence of ovulation was determined by observations of the ovary at laparotomy. 5 of 24 menstrual cycles during the summer and 30 of 31 cycles during winter were ovulatory. The 5 ovulatory summer cycles were distributed among only 2 of the animals; the other 7 animals did not ovulate during the summer. The proportion of monkeys which ovulated during the summer months was 22%. Summer menstrual cycles showed greater variability in length than those occurring during the winter. The data suggest that some monkeys maintain a seasonal anovulatory season even in the absence of seasonal light and temperature variations. Other monkeys do ovulate during the summer presenting the possibility of selecting these animals for breeding colonies.(Authors modified)

/pdf/the-effect-of-season-on-occurrence-of-ovulation-in-the-4eynbucb11.pdf

The Effect of Season on Occurrence of Ovulation in the Rhesus Monkey

The reprodutive performance of PMSG-pnimed immature female rats (8 lU PMSG at 30 days of age)was studiedto determinewhether theyaresuitablemodelsorsubstitutes foradultanimalsin studies of reproduction. Pseudopregnancy, induced by cervical stimulation on day 33, lasted 12 days as indicated by leukocytic vaginal smears. Decidual cell reaction was elicited by uterine trauma on day 5 of pseudopregnancy, and resulted in a fifteen-fold increase in the mean weight of the traumatized horn within 4 days. PMSG-treated immature rats can conceive, maintain viable fetuses to term, and deliver live pups in a normal mannner (mean length of gestation: 24.2 days; mean litter size: 7.1 pups). Serum levels of progesterone, 20o-dihydroprogesterone (20�-DHP), LH, and FSH were measured by radioimmunoassay in samples taken at 3-day intervals between days 6 and 21 of pregnancy. Progesterone decreased from 86.7 ng/ml on day 6 to 69.7 ng/ml on day 9, was elevated to 111.4 ng/ml on day 12, and decreasedto 64.4ng/mlon day 21.20a-DHP increasedfrom 7.2ng/mlon day 6 to a peak of 14.5 ng/ml on day 15, and decreased significantly to 5.8 ng/ml on day 18. Serum LU and FSH did not vary significantly. These hormone profiles are similar to those reported by others in adult pregnant rats. Implantation was delayed in PMSG-pnimed pregnant rats by bilateral ovariectomy on day 3 and

/pdf/reproductive-biology-of-pmsg-primed-immature-female-rats-ra1dfb5ztc.pdf

Reproductive Biology of PMSG-Primed Immature Female Rats

The Effect of Daylength on Pituitary FSH and LH and Gonadal Development of Snowshoe Hares

Polycystic ovarian syndrome (PCOS) is characterized by hyperandrogenemia, polycystic ovaries, and menstrual disturbance and a clear association with insulin resistance. This research evaluated whether induction of insulin resistance, using dexamethasone (DEX), in a monovular animal model, the cow, could produce an ovarian phenotype similar to PCOS. In all of these experiments, DEX induced insulin resistance in cows as shown by increased glucose, insulin, and HOMA-IR (homeostasis model assessment of insulin resistance). Experiment 1: DEX induced anovulation (zero of five DEX vs. four of four control cows ovulated) and decreased circulating estradiol (E2). Experiment 2: Gonadotropin-releasing hormone (GnRH) was administered to determine pituitary and follicular responses during insulin resistance. GnRH induced a luteinizing hormone (LH) surge and ovulation in both DEX (seven of seven) and control (seven of seven) cows. Experiment 3: E2 was administered to determine hypothalamic responsiveness after induction of an E2 surge in DEX (eight of eight) and control (eight of eight) cows. An LH surge was induced in control (eight of eight) but not DEX (zero of eight) cows. All control (eight of eight) but only two of eight DEX cows ovulated within 60 h of E2 administration. Experiment 4: Short-term DEX was initiated 24 h after induced luteal regression to determine if DEX could acutely block ovulation before peak insulin resistance was induced, similar to progesterone (P4). All control (five of five), no P4treated (zero of six), and 50% of DEX-treated (three of six) cows ovulated by 96 h after luteal regression. All anovular cows had reduced circulating E2. These data are consistent with DEX creating a lesion in hypothalamic positive feedback to E2 without altering pituitary responsiveness to GnRH or ovulatory responsiveness of follicles to LH. It remains to be determined if the considerable insulin resistance and the reduced follicular E2 production induced by DEX had any physiological importance in the induction of anovulation. dexamethasone, follicle, follicular development, glucocorticoid, hypothalamus, ovary, ovulation

Effect of Glucocorticoid-Induced Insulin Resistance on Follicle Development and Ovulation 1

/pdf/embryonic-survival-and-development-in-unilaterally-4xark24tzh.pdf

Embryonic survival and development in unilaterally ovariectomized rats.

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