Histological and steroidogenic changes in dominant ovarian follicles during oestradiol-induced atresia in heifers

Treatment alternatives to induce follicular wave emergence for timed-AI in lactating dairy Cows

Two experiments evaluated the effect of different hormonal treatments to synchronize follicle wave emergence on follicle dynamics and pregnancies per AI (P/AI) in estradiol (E2)/progesterone (P4) timed-AI (TAI) protocols in lactating dairy cows. In Experiment 1, lactating, primiparous Holstein cows (n = 36) received a P4 releasing device (Day 0) and were allocated at random to one of the following three treatment groups: Group EB received 2 mg E2 benzoate (EB) intramuscularly (i.m.), Group EB + GnRH received 2 mg EB+20 μg buserelin (GnRH) i.m., or Group EB + P4 received 2 mg EB + 100 mg of injectable P4 (iP4) in oil i.m. All cows received 0.150 mg D-Cloprostenol on Days 7 and 8 followed by P4 device removal, 400 IU eCG and 1 mg ECP on Day 8. Daily ultrasound examinations revealed that although the interval from P4 device removal to ovulation was not affected by treatment, cows that received EB + GnRH had an earlier (P < 0.05) emergence of the new follicular wave (Day 2.6 ± 0.2) than the other two treatment groups (Days 3.5 ± 0.3 and 6.1 ± 0.3, for EB and EB + P4, respectively). In Experiment 2, 808 lactating cows were assigned randomly to the three treatments evaluated in Experiment 1, and all the cows were TAI to determine P/AI. Cows in the EB + GnRH group had greater P/AI (57.4 %, P < 0.01) than those in the EB (44.6 %) or EB + P4 (45.7 %) groups. In conclusion, the administration of GnRH, but not iP4, on the day of insertion of a P4 device improves P/AI in lactating dairy cows synchronized for TAI with an estradiol/P4-based protocol.

Impact of a timed-release FSH treatment from 2 to 6 months of age in bulls I: Endocrine and testicular development of beef bulls

In prepubertal males, FSH facilitates Sertoli cell proliferation and testis maturation. The study aimed to determine the effect of an exogenous FSH treatment on hormone secretion and testis development in Angus bulls. Bulls (n = 22) weaned at 53 ± 3.8 days of age were randomized into two treatment groups based on age and pedigree. Beginning at Day 59, bulls were injected im every 3.5 days with either 30 mg FSH (Folltropin-V; NIH-FSH-P1 units) in a 2% hyaluronan solution (FSH-HA, n = 11) or saline (control, n = 11) until Day 167.5. Blood samples to assess FSH, activin A, and testosterone were collected prior to each treatment. To determine how FSH profiles surrounding treatment were affected, three intensive blood sampling periods, each encompassing two treatment administrations, began at Day 66, 108, and 157, and blood was collected at 0, 6, 12, 18, 24, 36, 60, and 84 h respective to time of treatment. Scrotal circumference (SC) and BW were measured monthly. Bulls were castrated at Day 170 to measure testis size, seminiferous tubule diameter, and the number of Sertoli and germ cells per tubule cross-section. During intensive FSH sampling, FSH-HA bulls experienced an increase (P < 0.05) in FSH over control bulls for at least 18 h post-injection in all instances. In blood collected every 3.5 days, FSH concentrations in FSH-HA bulls were increased (P < 0.05) over initial Day 59 concentration from Day 97.5-167.5. FSH concentrations did not differ between treatments from Day 59-90.5, but were greater (P < 0.05) in FSH-HA from Day 94-167.5. Concentrations of activin A assessed for Day 59, 83.5, 94, 129, and 167.5 were greater (P < 0.05) in FSH-HA than control bulls on Day 83.5 and 94. The treatments did not differ (P > 0.1) in testosterone, BW, SC, testis size, tubule diameter, or number of germ cells per tubule. However, the number of Sertoli cells per tubule was greater in FSH-HA than control bulls (45.2 ± 1.4 vs. 41.6 ± 0.9 cells, P < 0.05). In summary, FSH-HA treatment every 3.5 days from Day 59-167.5 maintained elevated FSH for a minimum of 18 h post-injection, likely attributable to the addition of HA. We propose the exogenous FSH-HA treatment initiates a positive feedback loop that includes an increased density of Sertoli cells per tubule cross-section, which is related to increased activin A concentrations on Day 83.5 and 94. Furthermore, this activin A increase preceded an increase in endogenous FSH from Day 94-167.5 in FSH-HA bulls.

Impact of a timed-release FSH treatment from 2 to 6 months of age in bulls II: Endocrinology, puberty attainment, and mature sperm production in Holstein bulls

The use of genomic testing in the cattle industries has renewed an interest in hastening bull puberty. In prepubertal males, FSH facilitates Sertoli cell proliferation and testis maturation. The aim of this study was to determine the effect of prepubertal administration of a timed-release FSH (delivered in a hyaluronan solution) on hormone secretion, puberty attainment, and mature sperm production in Holstein bulls in an AI center. Bulls (n = 29) were randomly assigned to one of two treatment groups based on birth date and pedigree. Beginning at 62 days of age (Day 62), bulls were injected im every 3.5 days with either 30 mg FSH (Folltropin-V; NIH-FSH-P1 units) in a 2% hyaluronan solution (FSH-HA, n = 17) or saline (control, n = 12) until Day 170.5. Blood samples to assess FSH, activin A, and testosterone were collected prior to each treatment. Scrotal circumference (SC) and BW were measured monthly. Puberty assessment (ability to ejaculate 5 × 10⁷ sperm, 10% motile) was initiated at Day 244. Average mature daily sperm production (3× wk collection, combined 2 ejaculates) was assessed from Day 571-627. In blood collected every 3.5 days, FSH concentrations within FSH-HA bulls were increased (P < 0.05) over initial Day 62 concentration from Day 93.5-170.5. Concentrations of FSH did not differ between treatments from Day 62-93.5, but were greater (P < 0.05) in FSH-HA than control bulls from Day 97-170.5. Concentrations of activin A assessed for Day 62, 86.5, 107.5, 139, and 170.5 were greater (P < 0.05) in FSH-HA than control bulls on Day 86.5 and 107.5. Treatments did not differ (P > 0.1) in testosterone, BW, or SC. FSH-HA bulls attained puberty at a younger age than control bulls (278 ± 7.7 vs. 303 ± 9.1 days of age, P < 0.05), but mature daily sperm production was not different when measured from Day 571-627 (average 5.84 ± 0.11 billion cells/day, P = 0.5). In summary, FSH administration every 3.5 days from Day 62-170.5 resulted in an increase in FSH concentration beginning at 97 days of age and a hastened age of puberty. We propose this exogenous FSH delivered in hyaluronan initiates a positive feedback loop that includes an increase in activin A production observed on Day 86.5 and 107.5. However, differences in mature sperm production were not realized in this experiment.

Impact of a timed-release follicle-stimulating hormone treatment from one to three months of age on endocrine and testicular development of prepubertal bulls

In prepubertal bulls, FSH facilitates testis maturation and a transient proliferation of Sertoli cells. Two experiments examined the effects of exogenous FSH on hormone secretion and testis development in Angus bulls. Exogenous FSH treatment consisted of an intramuscular injection (i.m.) of 30 mg FSH (Folltropin-V) in a 2% hyaluronic acid solution (FSH-HA). In Exp. 1, bulls (50 ± 6.5 d of age) received either FSH-HA ( = 5) or saline (control; = 5) on d 50 and 53.5. Blood samples were collected via jugular venipuncture to assess FSH concentrations every 6 h for 24 h after treatment and every 12 h until 84 h. After each treatment, peripheral FSH concentrations were greater ( < 0.05) in the FSH-HA-treated bulls than in the control bulls 6 h after treatment and tended to be greater ( ≤ 0.08) 12 h after treatment. The FSH concentration from 18 to 84 h after treatment did not differ between treatments. In Exp. 2, bulls were treated with FSH-HA ( = 11) or saline (control; = 11) every 3.5 d from 35 to 91 ± 2 d of age. Blood samples were collected before each treatment to quantify FSH, testosterone, and activin A concentrations. Scrotal circumference (SC) and BW were measured weekly. Bulls were castrated at 93 ± 2 d of age. Seminiferous tubule diameter, testis composition, and the number of Sertoli cells per tubule cross section (GATA-4 positive staining) were determined from fixed and stained histological sections. Follicle-stimulating hormone concentrations within the FSH-HA-treated bulls increased ( < 0.05) on d 70 from prior sampling and remained elevated. The FSH concentration did not differ between treatments from 35 to 66.5 d of age but were greater ( < 0.05) in the FSH-HA-treated bulls than in the control bulls from 70 to 91 d of age. Serum concentration of activin A on d 35, 70, and 91 did not differ between treatments. The FSH-HA and control bulls did not differ ( > 0.1) in BW, SC, testis weight, testis volume, percent of parenchyma composed of tubules, tubule diameter, and concentration of testosterone. The number of Sertoli cells per tubule cross section was greater in the FSH-HA-treated bulls than in the control bulls (33.35 ± 0.9 vs. 28.27 ± 0.9 cells; ˂ 0.05). In summary, the FSH-HA treatment from 35 to 91 d of age resulted in increased endogenous FSH from 70 to 91 d and increased numbers of Sertoli cells at 93 d of age. Exogenous FSH altered endocrine mechanisms regulating endogenous FSH secretion and augmented Sertoli cell proliferation in young bulls, but this effect was apparently not caused by increased activin A concentration in the FSH-HA-treated bulls.

Resveratrol, an effective regulator of ovarian development and oocyte apoptosis

Resveratrol, a phytopolyphenol compound found chiefly in grapes and wine, has been reported to have a variety of anti-inflammatory, anti-platelet, and anti-carcinogenic effects. However, little is known about the effects of resveratrol on ovarian development and oocyte apoptosis. We investigated the effects of resveratrol on ovarian development in rats with different ages [from post-natal day (PD) 1 to 15 months], as well as on oocyte apoptosis in PD1 and PD2 rat ovaries. We show that: a) ip injection of resveratrol (20 mg/kg/day) increased the percentage of unassembled follicles and the total number of oocytes in PD1 and PD2 rat ovaries. Similar results were obtained when mothers were treated with resveratrol (20 mg/kg/day) by intragastric administration from day 11, after the detection of vaginal plug, until delivery. In PD4 rat ovaries, the total number of oocytes was significantly increased in the groups treated with resveratrol. Moreover, more unassembled follicles and fewer primary follicles were present in the groups treated with resveratrol than in the controls; b) in 15-month-old rat ovaries, resveratrol increased the number of resting follicles and total oocytes, and decreased the number of developing follicles and atretic follicles; 3) the percentage of TUNEL-positive oocytes decreased in PD1 and PD2 rat ovaries after resveratrol treatment, and the number of oocytes positive for Foxo3a, Bim, and p27KIP1 in PD2 rat ovaries was lower in the resveratrol treatment group than in controls. These results suggest that resveratrol may delay oocyte nest breakdown and inhibit both the primordial-to-developing-follicle transition and apoptosis by decreasing the activation of Foxo3a, Bim, and p27KIP1, thus augmenting the resting follicle reserves, maintaining regular estrous cycles of early aged rats and delaying climacterium.

Changes in the glucose-6-phosphate dehydrogenase activity in granulosa cells during follicular atresia in ewes

Apoptosis of granulosa cells during follicular atresia is preceded by oxidative stress, partly due to a drop in the antioxidant glutathione (GSH). Under oxidative stress, GSH regeneration is dependent on the adequate supply of NADPH by glucose-6-phosphate dehydrogenase (G6PD). In this study, we analyzed the changes of G6PD, GSH, and oxidative stress of granulosa cells and follicular liquid and its association with apoptosis during atresia of small (4–6 mm) and large (>6 mm) sheep antral follicles. G6PD activity was found to be higher in granulosa cells of healthy small rather than large follicles, with similar GSH concentration in both cases. During atresia, increased apoptosis and protein oxidation, as well as a drop in GSH levels, were observed in follicles of both sizes. Furthermore, the activity of G6PD decreased in atretic small follicles, but not in large ones. GSH decreased and protein oxidation increased in follicular fluid. This was dependent on the degree of atresia, whereas the changes in G6PD activity were based on the type of follicle. The higher G6PD activity in the small follicles could be related to granulosa cell proliferation, follicular growth, and a lower sensitivity to oxidative stress when compared with large follicles. The results also indicate that GSH concentration in atretic follicles depends on other factors in addition to G6PD, such asde novosynthesis or activity of other NADPH-producing enzymes. Finally, lower G6PD activity in large follicles indicating a higher susceptibility to oxidative stress associated to apoptosis progression in follicle atresia.

Effects of tea polyphenols on ovarian development in rats

Tea is the most consumed beverage in the world. Tea polyphenols are the major constituents of tea leaves and have shown many potential healthy benefits. However, whether tea polyphenols influence ovarian follicle assembly and development and ovarian life span is unknown. To study the effect of tea polyphenols on ovarian follicle development and oocyte apoptosis, we investigated rat ovarian development of different ages [from postnatal day (PD)1 after birth to 10 months] after treatment with tea polyphenols. Our data showed that the percentage of unassembled follicles increased in the ovaries of 1- and 2-day-old rats which were ip injected with tea polyphenols (50 mg/kg/d) or whose mothers were treated with tea polyphenols (100 mg/kg/d) by intragastric administration from the day 11 after the detection of vaginal plug till delivery. The percentage of primordial follicles increased, while that of developing follicles decreased in the ovaries of 4- and 8-day-old rats following peritoneal injection with tea polyphenols compared with controls. The ratio of terminal deoxynucleotidyltransferase-mediated dUTP nick-end labeling (TUNEL)-positive oocytes decreased in the ovaries of neonatal rats following tea polyphenol treatment. In the 3- and 10-month-old rat ovaries, the number of primordial follicles augmented, whereas that of atretic follicles decreased after the treatment for 4 weeks. These data suggest that tea polyphenols may inhibit the transition from primordial to developing follicles, extend the entire growth phase of a follicle, and reduce dominant follicle numbers per cycle to increase the reserve of germ cells, inhibit oocyte apoptosis and follicle atresia during ovarian development from birth to early aged, and retard climacterium in rats. Drinking even a small cup of tea per day may benefit to extent the productive life of ovary.

Mês de parição, condição corporal e resposta ao protocolo de inseminação artificial em tempo fixo em vacas de corte primíparas

No experimento I, foi avaliada a alteração da condição corporal (CC) pré e pós-parto em 155 novilhas inseminadas para parir de setembro a dezembro. A CC foi avaliada mensalmente no pré e pós-parto, de junho a fevereiro. No experimento II, 538 vacas primíparas foram sincronizadas com o protocolo de inseminação artificial em tempo fixo (IATF) que usou estradiol junto ao dispositivo intravaginal de progesterona (CIDR®). As taxas de ciclicidade, sincronização e concepção foram avaliadas por ultra-som. No experimento I, os animais que pariram primeiro tiveram maior (P<0,001) redução na CC pós-parto. No experimento II, foi observado maior CC (P<0,0001) nos animais com menor número de dias pós-parto, maior (P<0,05) taxa de sincronização nas vacas de melhor CC e aumento (P<0,0001) na taxa de concepção proporcional ao aumento na CC (incremento médio na concepção de seis pontos percentuais para cada 0,25 ponto na CC). Não se deve antecipar a parição de novilhas de corte quando se pretende realizar IATF no início da estação de monta subseqüente.

Steroidogenic changes and steady state amount of messenger RNA encoding steroidogenic enzymes, gonadotropin receptors and cell-death signalling in the dominant ovarian follicle during estradiol-induced atresia in cattle

Changes in steroidogenic function and associated gene expression were characterized in dominant ovarian follicles (DF) of cattle where follicles were induced to become atretic by systemic administration of estradiol benzoate (EB). In experiment 1, follicular fluid (FF) steroid concentrations in the DF were measured at 12-hourly time points for 48 h in heifers treated with 1 mg EB i.m./500 kg body weight (EB; n=20) as compared with untreated controls (C; n=19). Treatment with EB promoted a transient reduction in circulating FSH, a rapid (12 h) and sustained reduction in FF estradiol, a rapid (12 h) but transient reduction in FF progesterone and a delayed (36 h) increase in FF testosterone concentrations. In experiment 2, whole follicular wall tissue was collected from DF of mature non-lactating cows allocated to a 0 h control group (0 HC: n=7), a 24h control group (24 HC; n=7) or an EB-treated group where tissue was collected 24 h after administration of 1 mg EB i.m./500 kg body weight (EB; n=8). As for experiment 1, EB promoted a transient reduction in circulating FSH, a pronounced reduction in FF estradiol and a smaller but significant reduction in FF progesterone concentrations. Semi-quantitative RT-PCR on follicular wall tissue revealed that the loss in estrogen activity at 24 h after EB was associated with two-fold reduction in aromatase mRNA, with an apparent acceleration in loss of 17alpha-hydroxylase mRNA. Expression of genes for gonadotropin receptors (LHR and FSHR) and a cell-death signalling pathway (Fas antigen and Fas ligand) were unchanged during the initial 24h of EB-induced atresia. These results suggest that EB initiates atresia in dominant ovarian follicles through a rapid suppression of follicular estradiol synthesis, an effect associated with down-regulation of the aromatase gene. A transient suppression in circulating FSH following administration of EB appears to have initiated these events, and it is suggested that subsequent processes involved in atresia follow this loss in estrogenic function.