Ultrasonographic characteristics of the preovulatory follicle preceding and during ovulation in mares

Changes in appearance of preovulatory follicles were observed with real-time ultrasonography prior to and during ovulation in mares. Preovulatory follicles of 15 mares were scanned at < 1 hr intervals for 12 hr or more frequently if displaying signs of impending ovulation. If ovulation was not imminent at the end of 12 hr (n = 2), mares were removed from the trial. Mean follicular diameter decreased 13% from 30 minutes prior to ovulation until the beginning of ovulation. Fifteen to 77 minutes (mean = 41 min) prior to ovulation, a break in or a protrusion of the follicular wall toward the ovulation fossa was visualized in all follicles and was a consistent indicator of impending ovulation. A rapid decrease in size of follicles (ovulation) occurred within a period of 5 to 90 seconds (mean = 42 sec). Little or no fluid remained in the antrum following ovulation. An increase in echogenicity (whiteness) of the follicular wall and echogenic “spots” within the follicle were frequently visualized (13/13, 100% and 7/13, 54% respectively) prior to ovulation; however, prediction of time of ovulation could not be based solely on these individual changes.     

Ovulation of the preovulatory follicle originating from the first-wave dominant follicle leads to formation of an active corpus luteum

The objective of our study was to compare the characteristics of the corpus luteum (CL) formed after ovulation of the dominant follicle (DF) of the first follicular wave (W1) and those of the CL formed after ovulation of the DF of the second (induced) follicular wave (W2). Non-lactating Holstein cows were used for this study. In Experiment 1, cows were treated with PGF2α and GnRH on days 6 and 8 (day 0 = day of follicular wave emergence) for W1 (n = 6) and W2 (n = 6), respectively. Dominant follicles were aspirated on day 9 to quantify the amounts of mRNA (VEGF120, VEGF164, FGF-2, StAR, P450-scc and 3β-HSD) in granulosa cells (GC). In Experiment 2, the size and blood flow area of the CL formed after ovulation of the DF in W1 (W1CL; n = 6) and W2 (W2CL; n = 6) (the day of DF ovulation in W1 and W2 was day 10) were evaluated on days 12, 15, 18 and 21. The plasma P4 concentration was measured on days 10 to 21. The amounts of VEGF164, P450-scc and 3β-HSD mRNA were higher (P < 0.05) in the DF in W1, and those of VEGF120,FGF-2 and StAR mRNA tended to be higher (P < 0.1) in the DF in W1. The size of the CL was greater in the W1CL on days 15, 18 and 21. The blood flow area of the CL was greater in the W1CL on days 12 and 15. The plasma P4 concentrations were higher in the W1CL. These results indicate that the CL formed after ovulation of the DF in W1 was greater in terms of size, blood flow and plasma P4 concentration.     

In vivo evidence that local cortisol production increases in the preovulatory follicle of the cow

The aim of the present in vivo study was to monitor real-time fluctuations of cortisol (Cr) in the wall of preovulatory follicles using a microdialysis system (MDS) implanted in the theca layer as well as changes in ovarian venous plasma (OVP) and jugular venous plasma (JVP). Seven cows were superovulated using FSH and prostaglandin F2alpha injections. Dialysis capillary membranes were surgically implanted into the theca layer of mature follicles and connected to a microdialysis system. Fractions of the perfusates were collected from Day -1 (Day 0=LH surge) to Day 3. No difference in the concentrations of Cr between JVP and OVP was detected throughout the experiment. Circulating concentrations of Cr ranged from 20 to 35 ng/ml 8 h after surgery in ovulatory and anovulatory cows. In five ovulatory cows, the Cr concentration decreased to basal levels (<10 ng/ml) between 12 and 24 h after surgery, however, two anovulatory cows retained high Cr levels (>10 ng/ml) up to 42 h after surgery. There was a clear increase in the local concentration of Cr from 13.3+/-2.1 pg/ml at -24 h to 27.5+/-1.7 pg/ml at 0 h (peak of the LH surge) within the wall of ovulatory follicles. This increase was not detected in anovulatory follicles. This transient increase in Cr occurred only in the follicle wall, but not in the OVP or JVP, indicating that the presence of a local regulatory mechanism for Cr production/conversion in ovulatory follicles, and this mechanism may modulate the inflammatory-like reaction induced by LH surge in the follicle wall. The present results demonstrate that the glucocorticoid environment in the follicular wall adjusts at the local level in bovine ovulatory follicles. This mechanism may protect follicles from the adverse effects of glucocorticoid, and it may prevent excess inflammatory reactions associated with ovulation by temporarily increasing local concentrations of glucocorticoid, thus forming an integral part of the regulatory mechanism in ovarian physiology.     

Severe internal hemorrhage resulting from transvaginal ultrasound-guided follicle aspiration in a mare

Transvaginal ultrasound-guided follicle aspiration (TVA) is becoming a more widely utilized procedure for obtaining oocytes from mares for both research and clinical applications because it is practical, repeatable and minimally invasive. Although the incidence of complications associated with TVA is low, the risk of serious complications cannot be completely eliminated. In this report, we present a case in which severe internal hemorrhage occurred as a result of TVA in a mare.     

Histologic and histochemical studies of the prenatal development of the wool follicle in Egyptian fat-tailed sheep]

Thickness of epidermis, diameter and density of follicles as well as the ratio of secondary to primary follicles went up with significance (P less than 0.01) along with development. Medium concentrations of neutral and acid mucopolysaccharides were histochemically recorded from the corium, while high levels were present in basal stratum and hair pivots. High concentrations of alkaline phosphatase were recorded from basal stratum, hair pivots, and papillae and moderate concentrations from sweat and sebaceous glands, with the latter containing also glycogen and lipids.     

Effects of low-dose follicle-stimulating hormone administration on follicular dynamics and preovulatory follicle characteristics in dairy cows during the summer

The well-documented phenomenon of reduced conception rate in dairy cows during the hot season involves impaired functioning of the ovarian follicles and their enclosed oocytes. Three experiments were performed to examine the administration of low doses of follicle-stimulating hormone (FSH) to induce turnover of follicles that are damaged upon summer thermal stress and to examine whether this FSH administration has beneficial effects on preovulatory follicles. In experiment 1, synchronized heifers were treated with 100 mg of Folltropin-V (n = 7) or 4.4 mg of Ovagen (n = 6) on day 3 of the estrous cycle. Treatment with both FSH sources resulted in greater (P < 0.05) numbers of follicles than in control animals (n = 12) on day 6 of the estrous cycle, indicating that low doses of FSH can increase the number of emerging follicles in a follicular wave. In experiment 2, milking cows were assigned to a control group (n = 4) or treated with 2.2 mg (FSH-2.2; n = 6) or 4.4 mg (FSH-4.4; n = 5) Ovagen. Follicle-stimulating hormone was administrated on day 3 or 4 and day 10 or 11 of the estrous cycle, coinciding with emergence of the first and second follicular waves, respectively. The number of follicles emerging during the first wave tended to be higher (P < 0.1) in FSH-4.4-treated cows than in controls. The second-wave dominant follicles emerged 2 d later in the treated cows and were smaller in diameter (P < 0.05) than controls, 2 d before aspiration. Despite being younger, the preovulatory follicles of FSH-4.4 cows expressed a steroidogenic capacity that was similar to controls with a tendency toward greater insulin concentrations (P < 0.09). In experiment 3, milking cows were assigned to a control group (n = 6) or treated with 4.4 mg Ovagen (FSH-4.4; n = 6). Follicle-stimulating hormone was administrated on day 3 and day 12 or 13 of the estrous cycle. The number of emerging follicles was higher (P < 0.05) in the treated vs control cows. However, the features of the preovulatory follicle developed in the subsequent cycle did not differ between groups. In summary, low doses of FSH can efficiently induce follicular turnover accompanied by a modest effect on the preovulatory follicle of the treated cycle. It appears that the administration of low doses of FSH, precisely timed to synchronize with the emergence of follicular waves, might have a beneficial effect on the preovulatory follicle and its enclosed oocyte.     

Immunohistological studies of the local immune system in the reproductive tract of the mare

The immunoperoxidase technique was adapted for the identification of free immunoglobulin and immunoglobulin producing cells in equine tissues. Staining specific for free IgG, IgA and IgM was detected at all levels of the reproductive tract, and secretory component staining was present in the uterine epithelium but not in the oviduct, cervix or vagina. Immunoglobulin producing cells were present at all levels of the tract, with IgG and IgA cells at equivalent concentrations, but with fewer IgM cells. There was no cyclical trend in free immunoglobulin staining, or plasma cell numbers. IgG and IgM plasma cell numbers declined from uterus to vagina, as did epithelial staining, and the ratio of IgG:IgA cells declined from oviduct to vagina.     

哺乳动物卵泡发育过程中的超微结构变化

目前 ,动物腔前卵泡的体外培养正日益受到重视 ,并已取得了较大进展 ,已建立的培养体系可成功地使腔前卵泡发育到有腔阶段 ,猪、山羊等已可实现腔前卵泡卵母细胞体外成熟 ,体外受精并发育至囊胚阶段。但有关腔前卵泡体外成熟的机制仍不明了。本文通过对体内发育与体外培养之卵泡及其卵母细胞超微结构进行比较 ,从微细结构上客观评定体外培养卵泡的形态、活力、代谢状况及功能完整性 ,界定体外生长卵泡所处发育阶段 ,从而为确立和完善腔前卵泡体外培养体系并最终选择高质量的卵母细胞进行体外受精提供可靠的理论依据。1　体内发育卵泡及其卵…     

Preliminary studies of mammary secretions in the mare to assess foetal readiness for birth

The status of the mare and foetus in relation to readiness for birth was assessed by measurement of the electrolytes sodium, potassium and calcium in mammary secretions pre-partum. Sixteen Thoroughbred mares were allowed to foal spontaneously and the ionic status of their mammary secretions was measured over three to five weeks pre-partum. From these measurements, a scoring system was developed where an ionic score of 35 points or more suggested that the mare was within 24 h of foaling. On the basis of this ionic score, 10 pony mares were induced with either oxytocin or fluprostenol and assessment of foal maturity was made by physical, behavioural and physiological criteria. Eight pony mares, induced when the ionic score was 35 points or more, delivered full term foals; two mares were induced when their scores were 30 and 20 points and delivered a full term and slightly immature foal respectively. These results suggest that foetal maturity may be related to electrolyte concentrations in mammary secretions and that an ionic score of 35 points or more may indicate that induction would be successful in terms of maturity of the newborn foal.     

Relationship of the conception rate and the side (left or right) of preovulatory follicle location at artificial insemination in dairy heifers

In this study, we examined the locational effect (left or right ovary) of the preovulatory follicle (PF) on fertility in dairy heifers. In total, 1,111 artificial inseminations (AI) were analyzed. At AI, PF locations were examined using rectal palpation, and heifers were divided into two groups on their PF locations: (i) the PF located in the left ovary (L‐PF); and (ii) the PF located in the right ovary (R‐PF). Pregnancy was diagnosed by rectal palpation 60 days after AI. The conception rate was 50.7% in all heifers. Conception rate was significantly higher in the L‐PF (60.1%) than in the R‐PF (46.2%). The conception rate was significantly lower by sexed semen (48.6%) than conventional semen (59.1%). Conception rates divided by the semen type (sexed: n = 896, conventional: n = 215) were significantly higher in the L‐PF than in the R‐PF for both semen types (sexed; L‐PF vs. R‐PF: 57.3% vs. 44.4%, conventional; L‐PF vs. R‐PF: 72.3% vs. 53.3%). In addition, season, age, AI number, and the number of re‐inseminations at the same estrus did not affect conception rates. In summary, PF development in the left ovary was associated with increased conception rates in dairy heifers.     

Endometritis in the mare caused by a Coryneform organism--a case report and experimental studies

Persistent purulent endometritis in a mare was attributed to an unclassified species of Corynebacterium. Following intrauterine infusions of 20% betadine for 5 days the purulent vulval discharge ceased and the mare appeared clinically normal. Based on histological examination of endometrial biopsy samples, the severe acute inflammatory reaction had largely resolved 2 days after therapy. Three maiden mares considered resistant to bacterial endometritis received single intrauterine inoculations of 1.8 X 10(9) colony-forming units of the Corynebacterium species. The uterine response was followed by vaginal speculum examinations, uterine cultures and cytology, and endometrial histology. After an acute inflammatory reaction, each mare had recovered completely within 2 weeks. Most rapid recovery occurred in the mare in estrus at the time of inoculation. Subsequent secondary infections were detected in two mares. The uncertainty of correlations between results obtained by various diagnostic techniques emphasized the problems associated with each. This report illustrates the concept that endometritis in individual mares may relate more to as yet unidentified "mare factors" controlling uterine defense than to primary invasion by bacteria.     

Infertility in the brood mare

This communication describes the methods used and results obtained with a 21-year-old Standardbred sire bred, using artificial insemination techniques, to a book of 108 mares during the period 11th September to 16th March, 1979-80. A positive pregnancy test rate of 93.5% was achieved. Those mares becoming pregnant averaged 4.6 inseminations per pregnancy (range 1-13). Barren mares, maiden mares and wet mares, irrespective of age, all achieved highly satisfactory pregnancy rates and it was noted that breeding through the January/February period improved the ultimate success rate markedly. When the official returns for the breeding season under review were returned the sire had a live foal success rate of 84%.     

Melatonin supplement induced the hair follicle development in offspring rex rabbits

Previous studies have shown that the administration of melatonin (MT) to early post-natal fur-bearing animals increases the numbers of hair follicles (HFs). In this study, the effect of maternal MT supplementation on the HF development in offspring was investigated. To explore the potential underlying mechanisms, the expression of the melatonin receptor 1A (MTNR1A) gene was determined in the offspring. The Rex rabbit was the animal model, and 79 same-day-pregnancy females were randomly assigned to either a control (n = 39) or MT treatment (n = 40) group, and 10 mg MT microcapsules was implanted at the base of the neck of rabbits in the treatment group. Skin, lung, liver, muscle, kidney, heart and duodenum samples were collected from the newborn rabbits. The results showed that MT improved fur quality in the offspring rabbits by reducing the diameter of primary and secondary HFs, and increasing the HF population. MT did not affect the reproductive performance of female rabbits, and it did affect the blood levels of thyroid-stimulating hormone, prolactin and MT. In the offspring rabbits, MT significantly stimulated MTNR1A gene expression in the skin and heart (p < .01), whereas MTNR1A gene expression was significantly suppressed in the liver and kidney (p < .05). These results revealed that maternal MT supplementation increased HF density, reduced hairiness and improved the fur quality in Rex rabbit offspring. Maternal MT supply may modulate the responses of HFs in the offspring by upregulating the expression of MTNR1A in the skin. In this study, implantation of low-dose MT did not affect the reproductive performance of female rabbits or on the growth of their offspring.     

Proteolysis of insulin-like growth factor binding proteins during preovulatory follicular development in cattle

The present study was conducted to evaluate changes in follicular fluid (FF) insulin-like growth factor binding protein (IGFBP) proteolytic activity and levels of steroids and IGFBP during follicular development in cattle. Estrous cycles of cows were synchronized with two injections of prostaglandin F2alpha (PGF) 11 d apart and follicular growth monitored via daily rectal ultrasonography in order to identify the dominant follicle. All cows were ovariectomized 48 hr after the second injection of PGF. Follicular fluid was collected individually for all follicles > 5 mm and pooled for small (1 to 5 mm) follicles. Follicular fluid estradiol and androstenedione levels were greater (P < 0.05) and progesterone and IGFBP-3 levels not different (P > 0.10) in large dominant than in small (1 to 5 mm) or large (>5 mm) subordinate follicles, whereas IGFBP-2, -4 and -5 levels were less (P < 0.05) in large dominant than in small or large subordinate follicles. To evaluate proteolysis of IGFBPs, FF was incubated with recombinant human (125) I-labeled IGFBP-2, -3, -4, and -5 and proteins separated by 12% SDS-PAGE. Follicular fluid caused little or no proteolysis of (125)I-lableled IGFBP-2 or -3. However, cleavage of (125)I-labeled IGFBP-4 and -5 by FF from large dominant follicles was greater (P < 0.05) than by FF from small or large subordinate follicles indicating that a protease to IGFBP-4 and -5 exists in estrogen dominant follicles. We conclude that lower levels of IGFBP-2 in estrogen dominant follicles of cattle are not due to increased proteolysis, whereas decreases in IGFBP-4 and -5 levels are likely due, in part, to increased protease activity. Changes in IGFBP may alter levels of bioavailable IGFs that stimulate steroidogenesis and mitogenesis in developing bovine follicles.