Follicular Kinetics Research Articles

The Potential role of Eugenol and Ocimum sanctum extract on female rats: a focus on infertility efficacy

Objectives The aim of the present study was to evaluate the infertility effect of Eug and OS extract administrations in female albino rats.
 Methods Healthy female albino rats are provided with EUG (99% pure) with a dose of 0.4 ml/ day/ rat and OS Linn. Leaf extract with a dose of 500 mg/kg body weight/ day/ rat orally for 20 days. The control group received saline (vehicle). On day 20 of gestation, maternal and foetal, Antifertility and Antiimplantation, ovarian follicular kinetics and Estrogenic activity parameters. ANOVA Analysis One-way with Dunnett comparison tests used to analyze data. Ocimum Sanctum also gets an antifertility effect. 
 Results Oral administration of the extract from days 1 to 19 of gestation showed a reduction (p<0.05) in the number of corpora lutea of pregnancy and number of live fetuses. The foetal and placental weights were also significantly (P < 0.05) decreased in Eug and OS extract compared with the control. The results revealed that Antiimplantation activity were 87.17% and 79.48% in Eug and OS extract administration. Antifertility activity was 83.33 % in in Eug and OS extract administration.
 Conclusion The results of this study concluded the evidence for the antifertility activity of the administration of Eug and OS extract in female rats. Administration can induce the effects of inhibition on reproductive function in female albino rats.

Melatonin-induced changes in ovarian function in the freshwater fish Channa punctatus (Bloch) held in long days and continuous light

It is possible to manipulate fish gonadal function through exogenous melatonin. However gonadal responses to melatonin vary and depend on time, mode and duration of the administration of the hormone. The present study describes the effects of different photoperiods and melatonin treatments on the ovarian kinetics of the fish Channa punctatus. Fish held in long days (LD 14:10) were injected melatonin daily (10 μg im) either at 08.00 or 17.00 h, respectively or immersed in melatonin water (100 μg/l) for 24 or 15 h daily. In another experiment fish held in long days or continuous light (LL; LD 24.00) were immersed in melatonin water (100 μg/l) either for 24 or 15 h daily. Both experiments had appropriate controls. The GSI (Gonadosomatic index = gonadal wt./100 g body weight) increased ( P < 0.01) in fish immersed in melatonin water daily for 24 h when compared either with the GSI of control fish or with fish held in melatonin water daily for 15 h (17.00–08.00 h). The GSI decreased ( P < 0.01) in fish that received melatonin daily by injection mode. Data from follicular kinetics largely corroborate the GSI data. Fish exposed to melatonin water daily for 24 h had more vitellogenic follicles (VF) and fewer atretic follicles (AF). There was a general decrease ( P < 0.01) in previtellogenic follicles (PVF) in all treated groups. Melatonin by injection mode did not affect the number of VF but it significantly increased ( P < 0.01) the AF. In the other experiment, the GSI increased ( P < 0.01) in fish held in long days and immersed in melatonin water 24 h daily. However, the GSI decreased in fish held in long days and immersed in melatonin water for a restricted period (between 17.00 and 08.00 h). The GSI of fish held in LL and immersed in melatonin water daily for 24 h increased ( P < 0.01), whereas it decreased ( P < 0.01) in fish that were immersed in melatonin water daily for 15 h. The data from follicular kinetics revealed a decrease in PVF of fish held in LL and in all the melatonin-exposed groups irrespective of the duration of exposure to melatonin. However the VF increased markedly in fish held in LL and immersed in melatonin water daily for 24 h. VF of fish held in LL but immersed in melatonin water daily for restricted period decreased. In fish held in long days and immersed in melatonin water daily either for 24 or 15 h the VF number increased ( P < 0.01). Marked increase in AF was seen fish held in LL and exposed to melatonin-containing water daily for restricted period. The effect of melatonin on reproduction seems to depend on the photoperiod and duration of exposure to melatonin. In fish held either in long days or LL, daily restricted exposure to melatonin tends to inhibit gonads, whereas continuous exposure to melatonin either stimulate or has no effect. The results apparently support the view that duration of exposure to melatonin signals darkness.

Effect of edifenphos on compensatory ovarian hypertrophy, follicular kinetics and estrous cycle in hemicastrated rats.

Edifenphos, an organophosphate fungicide, was administered to hemicastrated albino rats intraperitoneally for 15 consecutive days in graded doses of 2 to 8 mg/kg body weight. In the oil-treated hemicastrated control group, ovarian weight and total number of healthy and atretic follicles were significantly higher than the same parameters in sham-operated control animals, and the estrous cycle was normal. Treatment with 2, 4, 6, or 8 mg/kg/d edifenphos significantly decreased ovarian weight (-6.75, -9.79, -18.71, and -34.13 percent, respectively) below that of the controls. Although treatment with 2 or 4 mg/kg/d edifenphos did not change the number of healthy and atretic follicles, a dosage of 4 mg/kg/d significantly decreased the number and duration of estrous cycles. Treatment with 6 or 8 mg/kg/d, however, significantly decreased the number and duration of different phases of the estrous cycle as well. In all treated groups, the weights of the thymus and uterus were significantly reduced when compared with those of hemicastrated oil-treated control animals.

Proliferative activity of follicles and serum steroid concentration in Scotophilus heathi (vespertilionid bat) during periods of delayed ovulation

Follicular kinetics were studied using immunocytochemical localization of proliferating cell nuclear antigen (PCNA) and changes in circulating steroid concentrations to investigate the cause of prolonged survival of Graafian follicles and delayed ovulation in the vespertilionid bat Scotophilus heathi. PCNA immunoreactivity was limited to the granulosa cells and varied with stage of follicular development and reproductive phase. Two waves of follicular growth appear to be initiated in October and February. The first wave resulted in the appearance of some late antral follicles in November. These antral follicles grew slowly and differed from typical mammalian Graafian follicles, as the cells of their cumulus oophoricus were large and hypertrophied. The second wave of follicular development resulted in fresh recruitment and selection of dominant follicles in February. The steroid-hormone profile showed an unusually high concentration of circulating androstenedione from October to December. The estradiol concentration showed two peaks coinciding with two peaks of PCNA immunoreactivity. The results show that the unusually high androstenedione concentration might be responsible for the development of non-ovulatory Graafian follicles with hypertrophied granulosa cells, which survive for a prolonged period. The decline in androstenedione concentration allows the development of ovulatory follicles in S. heathi.

Melatonin Counteracts the Stimulatory Effects of Blinding or Exposure to Red Light on Reproduction in the Skipper Frog Rana cyanophlyctis

An earlier study reported that blinding or exposure to red light stimulates reproduction in R. cyanophlyctis. The present study investigates whether melatonin counteracted blinding- or red-light-induced ovarian stimulation. The study consisted of two experiments carried out during the prebreeding (March/April) and breeding phase (August/September) of the reproductive cycle of this species. In experiment 1, exposure to red light for 30 days increased (P<0.01) the gonadosomatic index (GSI) and oviductal weights, whereas exposure to continuous darkness for the same duration decreased (P<0.01) the GSI. Data on follicular kinetics revealed an increase in vitellogenic oocytes and decrease in previtellogenic oocyte numbers following exposure to red lights. Exposure to continuous dark on the other hand increased previtellogenic oocyte and decreased vitellogenic oocyte numbers. In experiment 2, the GSI and the number of vitellogenic oocytes increased in blinded and red-light-exposed frogs. However, treatment with melatonin (15 μg sc) for 30 days to both these groups of frogs reduced the GSI, oviductal weights, and the number of vitellogenic oocytes. The results both confirm earlier finding that blinding and exposure to red light stimulate ovarian growth and also demonstrate that melatonin counteracts blinding or red-light-induced stimulation of ovarian activity. This apart, the findings from experiment 1 demonstrate for the first time that exposure to continuous dark inhibits ovarian growth in this species. Ocular melatonin seems to play an important role in regulation of reproduction in this species.

Impact of aggressive encounters on reproductive behaviour in the Indian desert gerbil,Meriones hurrianae (Jerdon)

The gerbils were exposed to daily I min aggressive encounters for 30 days, to study the effect of social stress on reproduction. The encounters were induced by introduction of an adult male or female gerbil into the cage of a male retired breeder living in isolation. In the male gerbils the encounters decreased (P < 0.001) gonadal weight and sperm counts. The accessory sex organs responded variedly to the encounters. The surface areas of abdominal scent glands decreased (P < 0.001). The results suggest that exposure to aggressive encounters had a negative influence on male reproduction in the gerbil. Contrary to the results in male gerbils, encounters with males had a positive influence on reproduction in females. This was evidenced by data on ovarian and uterine weights, follicular kinetics and the estrous cycle. The ovarian and uterine weights increased (P < 0.001) in gerbils exposed to the encounters. The number of estruses increased (P < 0.001) whereas the diestruses decreased. Study of follicular kinetics revealed an increase in the number of growing follicles and a decrease in the number of regressive follicles. The mechanism(s) by which the encounters influence reproduction is not known. Adrenal gland weights increased (P < 0.001) in both male and female gerbils exposed to the encounters. The pinealocyte cell and nuclear diameters decreased (P < 0.01) in males and increased (P < 0.001) in female gerbils after the encounters. Presumably the adrenal and pineal glands may play an important role mediating the effects of the encounters.

Changes in Ovarian Follicular Kinetics in Intact Blinded and Parietal Shielded Frogs Exposed to Different Spectra of Light

Ovarian follicular kinetics and gravimetric changes in the ovary and oviduct were studied in intact, blinded (BL), and parietal shielded (PS) skipper frogRana cyanophlyctisexposed to different light spectra. The gonadosomatic index (GSI) increased (P<0.01) in intact and PS frogs, held in green, yellow, and red light. The maximum increase was in red light followed by yellow and green. The GSI of BL frogs also increased (P<0.001) in white, green, yellow, and red light. However, the GSI of blinded and parietal shielded (BLPS) frogs increased (P<0.001) in white and all the colored lights compared with controls. The percentage changes of oviductal weights were similar to the ovarian weights. Data on follicular kinetics revealed a decrease in previtellogenic oocytes in intact and PS frogs placed in blue, green, yellow, and red lights. The previtellogenic oocytes of BL and BLPS frogs decreased in white light, while their number did not vary significantly in other spectra. The vitellogenic oocytes of intact and PS frogs increased in all the spectra, with a maximum increase in red. The vitellogenic oocyte count increased in both BL and BLPS frogs held in white light. The green, yellow, and red spectra stimulated vitellogenic oocyte count of BL frogs. The response of BPLS frogs was similar except for a slightly decreased oocyte count in red light. The pattern of vitellogenic oocyte counts in general exhibited a negative correlation with previtellogenic oocyte counts in all the frogs. The atretic follicular numbers did vary significantly in all of the groups. Red light stimulated ovarian activity maximally, followed by yellow and green. As the ovary exhibited varied response to the different spectra of light even in BL frogs, it may be concluded that extraretinal perception of colored light occurs in this species.

Melatonin and Exposure to Constant Light/Darkness Affects Ovarian Follicular Kinetics and Estrous Cycle in Indian Desert GerbilMeriones hurrianae(Jerdon)

Melatonin mediates photoperiodic influence on reproduction and constant light and darkness affect pineal biosynthesis of melatonin. The present study was undertaken to assess the effects of melatonin and drastic photoperiodic changes on reproduction in a tropical desert species with a fossorial lifestyle. Ovarian follicular kinetics and estrous cycle were studied in the Indian desert gerbilMeriones hurrianae,after treatment with melatonin and exposure to constant light (LL) and darkness (DD) regimes. Melatonin treatment increased (P<0.001) ovarian weights without changing the uterine weights. While exposure to LL decreased (P<0.001) both ovarian and uterine weights, exposure to DD had no effect on these weights. Follicular kinetics of growing and regressing follicles revealed that ovaries of melatonin-treated and DD-exposed animals had significantly more growing follicles. Melatonin treatment increased all types of growing follicles, especially antral and Graafian follicles. Exposure to DD increased all types of growing follicles, with the medium sized antral and Graafian follicles being significant (P<0.01). In contrast to stimulation of follicular growth by melatonin and DD, LL caused regression of all stages of follicular growth and also reduced the number of small preantral follicles. Melatonin treatment increased (P<0.001) the length of estrous cycle (5.08 to 7.29 days). Gerbils treated with melatonin, exposed to LL and DD, had a longer (P<0.001) metestrus. Animals held in LL, had the least number (P<0.001) of estrous smears (1 in 30 days). The results suggest that melatonin is involved in growth of ovarian follicles in the Indian desert gerbil.

Follicular growth and kinetics in the Indian gerbil (Tatera indica) ovary during oestrous cycle

The growth of the follicle and oocyte in the Indian gerbil (Tatera indica) was a continuous process. The relationship between follicle and oocyte or its nucleus was log linear, represented by the equation logY =a +b logX.A linear relationship (Y =a +bX)existed between the oocyte and its nucleus. The number of stages I and II follicles varied significantly during the oestrous cycle. Maximum percentage of stage I follicles was observed during oestrus and metoestrus, while stage II follicles were abundant during dioestrus, metoestrus and pro-oestrus. These follicles were significantly more in number than other types of the follicles. The occurrence of comparatively larger follicles during pro-oestrus and the presence of newly formed corpora lutea at oestrus, indicated ovulation in the early oestrus.

Effect of exposure to continuous light and melatonin on ovarian follicular kinetics in the skipper frog, Rana cyanophlyctis.

Ovarian follicular kinetics and gravimetric changes in the ovary and oviducts were studied in the skipper frog, Rana cyanophlyctis, following exposure to continuous light and melatonin treatment during the breeding season. Daily late-afternoon injections of melatonin (15 micrograms subcutaneous) for 30 days decreased the gonadosomatic index (GSI), whereas continuously available melatonin from subcutaneous implants did not influence the GSI compared to those of controls. Exposure to continuous light for 30 days stimulated the GSI, and melatonin given as daily injections prevented the continuous-light induced increase in GSI. Oviductal weights decreased only in the melatonin-injected groups. Data on follicular kinetics revealed a decrease in first-growth-phase (FGP) oocytes and an increase in medium-sized second-growth-phase (MSGP) and large-sized second-growth-phase (LSGP) oocytes following continuous-light exposure. Melatonin administered to continuous-light-exposed frogs did not change the FGP oocyte number; however, it reduced both the MSGP and LSGP oocytes. Melatonin administration to frogs held in a light and dark cycle increased FGP oocytes and decreased MSGP and LSGP oocytes. Atretic follicles increased in all melatonin-treated groups. The results suggest that continuous light stimulates and melatonin inhibits reproductive function in this species.

Ovarian Follicular Kinetics in Response to Enucleation and Parietal Shielding inRana cyanophlyctis

Ovarian follicular kinetics, gravimetric changes in the ovary and the oviduct, were studied in the skipper frog,Rana cyanophlyctis,following enucleation (ENX) and parietal shielding (PS), during the breeding reason. PS was to prevent extraoptic photoreception by the pineal via the frontal organ. The gonadosomatic index (GSI) was high in ENX and PS frogs (P<0.01). The highest GSI occurred in frogs that were both ENX and PS (P<0.01). Percentage of oviductal weight decreased (P<0.01) in PS frogs and increased (P<0.01) in those subjected to both ENX and PS. Oviductal weight of ENX frogs was unchanged. Data on follicular kinetics revealed a decrease (P<0.01) in the ENX group in the number of first growth phase (FGP) oocytes and atretic follicles (AF), whereas the number of medium-sized secondary growth phase (MSGP) oocytes and large-sized secondary growth phase (LSGP) oocytes increased (P<0.01). There was a similar pattern of follicular kinetics in ENX+PS frogs. However, following PS, the number of FGP oocytes and AF increased (P<0.01) and decreased (P<0.01) in the MSGP and LSGP oocytes. The lower oviductal weight in PS frogs correlated with reduced SGP oocytes, the major source of estrogen. The importance of lateral eyes and the frontal organs in the transduction of environmental signals to the neuroendocrine–reproductive axis is indicated in this species. That recruitment of FGP to SGP is inhibited only in the PS group suggests that the frontal organ plays an important role in ovarian follicular kinetics.

Age related changes in ovarian follicular kinetics in the Indian skipper frogRana cyanophlyctis (Schn.)

Changes in ovarian follicular kinetics were studied in relation to aging in the Indian skipper frog Ran a cya noph ly cti s. Age was determined by skeletochronology, by counting the number of growth rings and lines of arrest of growth from the cross sections of 4th phalange of 4th toe. For follicular kinetics study oocytes were counted under binocular using 10% of Bouin's fixed ovary and they were classified into first growth phase, medium-sized second growth phase, large-sized second growth phase and atretic follicles. Analysis of phalangeal cross sections indicated that frogs ranging 14-54 g in body weight and 4·9-8·9 cm in body size showed 1-7 year rings. Frogs that weighed 14-16 g showed 1 year ring, and contained immature ovaries; those with 18 g body weight had one to two year rings, in which second growth phase oocytes appeared for the first time in the primiparous ovary. Frogs with 20-54 g body weight showed 2-5 year rings in which ovary contained 5-24% of second growth phase oocytes. Further, body weight, body size, ovarian weight, number and size of second growth phase oocytes and total number of oocytes showed a significant (P < 0·05) positive correlation, while, the number of first growth phase and atretic follicles showed a poor correlation with age. The results suggest that in nature, the age of Rana cyanophlyctis ranges between 1-7 years. Phalangeal growth rings are formed annually. Females attain sexual maturity in 2nd year. Frogs with 2-5 years of age may constitute breeding females. Body weight, body size, ovarian mass, number of second growth phase and total oocytes, and egg size increase with age up to 5 years.

Proliferative activity in the different ovarian compartments in cycling rats estimated by the 5-bromodeoxyuridine technique.

The ovary is one of the most active proliferating tissues, and several methods for assessing cellular proliferation have been used to study follicular kinetics during the estrous cycle in the rat. In this study, we have estimated the proliferative activity of the different ovarian tissue compartments by using the 5-bromodeoxyuridine (BrdU) technique. Adult cyclic rats were studied 1 h after pulse-labeling with BrdU. Follicles were divided by size as small (mean diameter < 275 micrograms) or large (mean diameter > or = 275 micrograms). Small follicles were recorded into five classes: 1) primordial follicles (formed by flattened pre-granulosa cells), 2) unilaminar primary follicles (which ranged from having at least one enlarged pre-granulosa cell up to having a complete layer of cuboidal granulosa cells), 3) multilaminar class a (having 1-2 layers of granulosa cells and measuring up to 75 micrograms in diameter), 4) multilaminar class b (76-150 micrograms), and 5) multilaminar class c (151-274 micrograms). Large follicles were recorded into classes 1-5 according to previous classifications [Osman P. J Reprod Fertil 1985; 73:261-270]. Primordial follicles and about 70% of unilaminar primary follicles were unlabeled, whereas all of the remaining classes of small and large follicles were labeled. The labeling index (percentage of BrdU-positive cells) increased in parallel with follicle size but showed a progressive decrease in large preovulatory follicles and a centripetal pattern of cell proliferation. Atretic follicles showed a significantly lower number of labeled cells than healthy follicles of the same size. The number of proliferating cells was not related to follicle size but was inversely correlated with the degree of atresia. Cyclic CL showed intense proliferative activity that was well correlated with functional activity. The number of labeled cells was maximal in metestrus, decreased in the succeeding days, and was very low in proestrus. Proliferating cells seemed to correspond to vascular cells lining blood vessels. These results indicate that the BrdU technique is a useful, accurate, and sensitive method for assessing cellular proliferation in the rat ovary.

Role of fat bodies in oocyte growth and recruitment in the frog Rana cyanophlyctis (Schn.)

AbstractEffects of 30‐day bilateral fat body excision in February and November and replacement with 10 or 20 mg fresh aqueous fat body homogenate 6 days a week for 30 days, unilaterally or bilaterally fat body excision plus 20 IU human chorionic gonadotrophin (HCG) in February, and long‐term (60 days) fat body excision in March—April were studied in Rana cyanophlyctis. In addition, the effect of ovariectomy on fat body weights in February and November was also studied. The frogs were fed 6 days a week with live guppies and libitum. The ovarian follicular kinetics was studied by estimating the numbers of first growth phase (FGP), medium and large second growth phase (MSGP and LSGP) oocytes and atretic follicles. Regardless of season, 1‐month fat body ablation caused a significant reduction in LSGP oocytes, gonadosomatic index, and increase in atretic follicles. Administration of 20 mg fat body homogenate to fat‐body‐excised frogs prevented the fall in the number of LSGP oocytes and the gonadosomatic index. In fact, there was a significant increase in the LSGP oocytes and percentage weight of ovaries in these frogs. Follicular atresia was greatly reduced due to fat body homogenate (10 or 20 mg) administration. In 30‐day unilaterally fat‐body‐extirpated frogs, the mean weight of the ipsilateral ovary was reduced to 50% compared to that of the shamoperated frogs due to increased follicular atresia and associated decrease in LSGP oocytes. The administration of HCG increased recruitment of SGP oocytes in unilaterally as well as bilaterally fat‐body‐ablated frogs. This was accompanied by a reduction in atresia of oocytes and elevation of the gonadosomatic index. Interestingly, in long‐term fat‐body‐ablated frogs, ovarian weight recovered and follicular kinetics in them was identical to that found in shamoperated control frogs. Furthermore in 30‐day ovariectomized frogs, in both seasons there was a significant rise in fat body weights. The above findings in R. cyanophlyctis suggest that fat bodies have a role in vitellogenesis, and they serve as immediate sources of lipid energy needed for follicular growth. If adequate food is provided to fat‐body‐excised frogs, after an initial setback, ovarian growth commences by drawing lipids from other sources. It is concluded that fat bodies in the frog have a supporting and possibly not an obligatory role in vitellogenic growth of oocytes.

Variations in patterns of follicle development in prolific breeds of sheep.

Prolific breeds of sheep (Romanov, Finn and Booroola Romanov crosses heterozygous for the Booroola gene (F+) were compared with breeds of lower prolificacy (Ile-de-France, Finn X Scottish Blackface, Merino X Blackface and Booroola X Romanov not carrying a copy of Booroola gene (++] by in-vivo monitoring of follicular kinetics by ink labelling during the late luteal phase and follicular phase of the oestrous cycle followed by histological examination of the ovaries or follicle dissection. At each of 3 successive laparotomies, the 3 largest follicles of each ovary were measured and ink labelled. At the final laparotomy, around the beginning of oestrus, all ewes were ovariectomized. High ovulation rate was not associated with the total number of antral follicles in any of the breeds. However, there were more follicles greater than 2 mm in diameter in Romanov and Booroola X Romanov crosses (F+) compared to their respective controls. Such a feature was not observed in Finnish Landrace compared to Finn X Blackface and Merino X Blackface ewes. A more numerous population of recruitable follicles, together with a similar incidence of selection through atresia, were the features associated with the high ovulation rate of Romanov compared to Ile-de-France ewes. The high ovulatory potential of the Finn ewes resulted from a markedly reduced incidence of selection through atresia. Booroola X Romanov ewes carrying a copy of the Booroola gene (F+) appeared to possess features of both parental breeds, including high numbers of recruitable follicles, smaller follicular size when recruitment occurs and an extended time for recruitment. Booroola X Romanov (++) ewes, not carrying the gene, appeared to have lost part of the 'Romanov characteristics' of a more numerous population of recruitable follicles. The variability in the kinetics of preovulatory enlargement, seen in these breeds of sheep, demonstrates that there are a number of pathways through which high ovulation rate can be achieved and hence through which ovulation rate might be manipulated.

Ovarian cycle in the frog Rana cyanophlyctis: A quantitative study of follicular kinetics in relation to body mass, oviduct, and fat body cycles.

In Rana cyanophlyctis, all stages of oocyte development are present throughout the year owing to continuous and asynchronous gametogenetic activity, but quantitative differences occur in the frequency distribution of the first growth phase (FGP) and second growth phase (SGP) oocytes. The number of SGP oocytes influences ovarian weight; therefore, seasonal changes in the number of SGP oocytes and ovarian mass are correlated. Mean ovarian weight and gonadosomatic index follow comparable changes during the annual cycle. The body mass of the frog undergoes only minor seasonal variations. Also, the body mass does not influence the number of oocytes in the frog. Small FGP oocytes always formed the dominant type in the ovary. Only 20-0% of FGP oocytes were recruited to SGP stage during the prebreeding months (March-April). The breeding season extends over 2- months (July-September) and an adult R. cyanophlyctis spawns 3,000-,500 eggs of 1,300-1,350 μm diameter in size. The breeding is not followed by any resting period, and therefore oogonial proliferation and recruitment of FGP oocytes start soon after the breeding months (October-December). Atretic oocytes are present in all months but their number is greatest during prebreeding and breeding months. The frequency distribution of oocytes in the right and the left ovaries is identical. The oviducts undergo seasonal changes that are correlated with ovarian weight, whereas the fat body cycle is inversely related to ovarian weight.

Follicle population dynamics in sheep with different ovulation rate potentials

To investigate the factors contributing to the different ovulation rates observed in two strains of sheep (Booroola 5.2, Merino, 1.2) and after immunization against androstenedione (Immunized 1.8, Control 1.3), in vivo monitoring of follicular kinetics followed by histological examination of the ovaries was performed during the late luteal and follicular phases. Ewes had the three largest follicles of each ovary ink-labelled at days 13 and 15 and were ovariectomized after the beginning of oestrus. High ovulation rate was not associated with a more numerous antral follicle population in either Booroola ewes or immunized ewes. Furthermore, in Booroola ewes ( r = 0.22) and in immunized ewes ( r = −0.02), there was no correlation between the number of antral follicles per ovary and the ovulation rate. The reasons for the high ovulation rate became clear when preovulatory enlargement was followed by ink-labelling. An extended period of time during which recruitment of ovulatory follicles takes place, together with a low incidence of selection through atresia and the ability of fully grown follicles to wait for ovulation are the features involved in the high ovulation rate of the Booroola ewes. A lower incidence of selection together with an unaltered recruitment leads to the increased ovulation rate noticed after immunization.

An enzymatic method for dissociation of intact follicles from the hamster ovary: histological and quantitative aspects.

An enzymatic method was developed to collect intact follicles at different stages of development from cyclic hamsters to study ovarian folliculogenesis under various circumstances. Ovaries from 6 adult hamsters on each day of the cycle (Day 1 = ovulation) were collected, corpora lutea and large preantral and antral follicles were dissected, and follicles saved. Minced ovaries were then incubated with a mixture of collagenase, DNAse and pronase at 37 degrees C for 20 min to disperse intact follicles. Histological studies with 2191 isolated follicles revealed 10 different stages of follicular development (depending on the number of granulosa cell layers surrounding the oocyte and development of the antrum). Of the total follicular population, 14% showed signs of atresia, with 50% of those having 1-3 layers of granulosa cells (Stages 1-3); a second peak of 18% was observed in antral follicles (Stages 8-10). No signs of thecal cells were evident until the follicles reached Stage 6 (7-8 layers of granulosa cells), which possibly accounts for reduced atresia in this class and beyond. Ultrastructural study revealed that there were no signs of morphological damage to the basement membrane or to other subcellular organelles in the small preantral follicles. The presence of subnuclear lipid droplets in follicles with 3 layers of granulosa cells provided evidence for potential steroidogenesis by small follicles. The number of Stage 1-10 follicles was remarkably constant throughout the estrous cycle (460 +/- 34 per animal on Day 1 vs. 492 +/- 66 on Day 4). The usefulness of this method in analyzing follicular kinetics is illustrated in experiments involving hypophysectomy and the effects of unilateral ovariectomy. This procedure offers an improved method to study the factors responsible for the growth and the differentiation of small preantral follicles in the mammalian ovary.

Ovarian follicular populations and preovulatory enlargement in Booroola and control Merino ewes

To investigate the factors contributing to the different ovulation rates observed in two strains of sheep (Booroola 5.2, Merino 1.2), in-vivo monitoring of follicular kinetics followed by histological examination of both ovaries was performed during the late luteal and follicular phases. Ewes of both strains were either ovariectomized at Day 13, or had the 3 largest follicles of each ovary ink-labelled at Day 13 and were ovariectomized at Day 15, or had the 3 largest follicles of each ovary ink-labelled at Days 13 and 15 and were ovariectomized 16 h after the beginning of oestrus (N = 6 per time per strain). In another experiment, the age effects on the follicular populations of these two strains were also studied. There were 2-4 times more primordial follicles and 1.5-2 times more preantral follicles in the ovaries of Booroola than in control Merino ewes, although the number of antral follicles was the same. The percentage of normal follicles in this population was higher in Merino than Booroola ovaries. In Booroola ewes, there was no correlation between the number of antral follicles per ovary and the ovulation rate at the previous cycle (r = 0.22). This suggests that follicle numbers do not play a key role in the high ovulation rate of the Booroola strain. The number of follicles initiating growth from the primordial pool, the number of growing follicles disappearing at the preantral stage, the pattern of antrum development, granulosa cell multiplication and appearance of atresia differed between strains. The reasons for the high ovulation rate of the Booroola strain became clear when preovulatory enlargement was followed by ink labelling. An extended period of time during which recruitment of ovulatory follicles takes place, together with a low incidence of selection and the ability of the follicles to wait for ovulation are the features involved in this high ovulation rate.

Seasonal effects on ovarian follicular development in pony mares.

To define ovarian follicular kinetics in the equine ovary during anestrus and the breeding season, the follicular population of pony mares was investigated at mid-anestrus and at the beginning and end of the breeding season. There was a clear effect of season on the exit of reserve (primordial and initiated) follicles since at the beginning of the breeding season we noticed a higher mitotic index for the smaller preantral follicles, leading to an accumulation of small and medium antral follicles. In contrast, the ovaries sampled during anestrus or at the end of the breeding season were very similar; only preovulatory development was lacking in anestrous ovaries. However, atresia was unaffected by season.