Variations of Equine Urinary Volatile Compounds during the Oestrous Cycle

Ma, W. and Klemm, W.R., 1997. Variations of equine urinary volatile compounds during the oestrous cycle. Veterinary Research Communications, 21 (6), 437-446Equine urine was analysed by capillary gas chromatography. The volatile profiles from oestrous and dioestrous samples were compared to establish any qualitative or quantitative difference that may have potential value in olfactory communication. Forty-five different volatile compounds were detected. Of these, 17 major compounds were common to all chromatograms. The chemical profile of oestrous urine was distinguished by the presence of a unique peak that was not present in dioestrous samples. Numerous constituents exhibited endocrine dependence: while the concentrations of seix peaks increased at oestrus, the concentrations of another five peaks decreased at the same time. Since oestrous urine, but not dioestrous urine, has been shown to elicit sexual behaviour in the stallion, the unique peak, together with the peaks that were present in increased concentrations at oestrus, may represent important chemical signals that stallions use to detect urinary oestrous odours. Statistical analyses also indicated that the relative ratios (normalized peak areas) of many peaks changed significantly across the oestrous cycle: the ratios increased in nine peaks, decreased in six peaks, and remained constant in two peaks at oestrus.     

Changes in Ovarian Follistatin Levels During the Oestrous Cycle in Sheep may Serve as an Intraovarian Regulator

The expression and concentration of follistatin and activin change during oestrous cycle suggesting their involvement in the regulation of follicular development. The aim of this study was to determine the level, source and potential role of follistatin in the sheep ovary. Follistatin in ovarian venous blood, measured by radioimmunoassay, remained at its low level from follicular phase (day ?1 and 0) to mid‐luteal phase (days 11–13) phase but were significantly elevated during the late luteal phase (days 14 and 15) when corpora lutea underwent regression. Western blot analyses of follicular fluid at day 15 of the cycle showed two strong bands at 42 and 45 kDa and weakly stained bands at 39 and 31 kDa. At day 0, these bands became weaker and the 39 kDa band became undetectable. However, there were no differences in follistatin concentrations between ovaries with and without functional corpus luteum (CL) during the whole luteal phase. In addition, although the ovaries of Booroola ewes normally contain more corpora lutea than those of normal merino ewes, follistatin concentrations in both jugular and ovarian venous blood were similar in Booroola and normal merino ewes. It is concluded that the secretion of follistatin from the ovary is not related to the formation of CL or high ovulation rate of Booroola ewes. The elevation in follistatin concentration in follicular fluid and ovarian blood during late luteal phase may indicate a dual role of follistatin in the luteolysis of existing CL and development of new follicle cohort.     

Some Endocrinological Aspects of corpora lutea and of Follicles during the Oestrous Cycle in Sheep.

Inhalt Die Konzentration von 17-β-Östradiol im liquor folliculi und Pregnenolon im lutealen Gewebe wurde während des Brunstzyklus bei 63 Schafen bestimmt. Die Konzentration von 17- β-Östradiol erreichte ein Maximum am Tag 16. Bei Eintritt des Östrus fiel die Konzentration um mehr als 50 %. Während der progestativen Phase wurden in der Regel geringe Konzentrationen gemessen, obwohl einige Follikel um Tag 8 hohe Konzentrationen zeigten. Bei Eintritt der Brunst war die Pregnenolon-Konzentration 20mal höher als die von Progesteron. Nach der Ovulation fiel die Pregnenolon-Konzentration, während die Progesteron-Konzentration am dritten Tag ein Maximum erreichte, um dann bis zum Tag 6 abzufallen und erneut am Tag 12 einen Höhepunkt zu erreichen. Die Pregnenolon-Konzentration begann ab Tag 6 anzusteigen, um am Tag 14 einen Höhepunkt zu erreichen. Die Ergebnisse Lassen vermuten, daβ während der ersten 4 Zyklustage Pregnenolon der limitierende Faktor ist in der Progesteron-Synthese, wäbrend vom Tag 12 an die Konversion von Pregnenolon in Progesteron allmäblich gehemmt wird. Contents The concentration of oestradiol-17 β in follicular fluid and of progesterone and pregnenolone in luteal tissue were determined throughout the oestrous cycle in 63 ewes. The concentration of oestradiol-17 β reached a maximum on day 16. At oestrus the concentration was reduced by more than 50%. During dioestrous generally low concentrations were determined although some follicles showed high concentrations around day 8. At oestrous the concentration of pregnenolone was 20 times higher than that of progesterone. After ovulation the concentration of pregnenolone dropped whereas the concentration of progesterone increased to a maximum on day 3, then decreased until day 6 when it again increased to a peak on day 12. The concentration of pregnenolone gradually increased from day 6 reaching a peak on day 14. The results suggest that during the first four days of the cycle pregnenolone may be the limiting factor in the progesterone synthesis while from day 12 onwards the conversion of pregnenolone in progesterone is gradually inhibited.     

Concentrations of Oestrone and Oestradiol-l 7β in the Peripheral Plasma of the Nanny Goat during the Oestrous Cycle, Gestation and Puerperium

The changes in the plasma levels of oestrone sulphate and oestradiol-17β during the oestrous cycle, gestation and puerperium in the goat are described. The oestrone sulphate concentrations remained fairly constant (250–350 pg/ml) throughout the oestrous cycle until day 20 when a sharp increase of the oestrone sulphate plasma levels occurred in pregnant goats which became significantly different at day 38 of gestation from nonpregnant values. Oestradiol-17β plasma levels were significantly lower at days 17–20 in pregnant than in nonpregnant does. Oestrone sulphate and oestradiol-17β concentrations rose until the 12th week of gestation and then declined to about 50% of the former ranges of concentrations before rising again to high values at weeks 17–20 of gestation. Increasing plasma levels of oestrone sulphate and oestradiol-17β were determined during the last ten days preceding parturition. The concentrations of oestrone sulphate returned to basal levels by the 2nd—4th day post partum whereas oestradiol-17β values reached base values 24 hours after parturition. Both oestrogen concentrations remained constant during the puerperium until day 51 post partum .     

Ion,Protein, Phospholipid and Energy Substrate Content of Oviduct Fluid During the Oestrous Cycle of Buffalo (Bubalus bubalis)

The aim of this research was to analyse the composition of oviduct fluid (ODF) in buffalo cows at different oestrous cycle phases to fulfil the requirements of buffalo embryos in vitro. ODF was collected by chronic cannulation from three cows that were synchronized by administering a synthetic prostaglandin. Based on hormonal profiles, the pre‐ovulatory, ovulatory, post‐ovulatory and luteal phases of the oestrous cycle were defined. The volume of ODF produced (ml/24 h) was influenced by the oestrous cycle, with values (mean ± SE) around ovulation (1.0 ± 0.2) greater (p < 0.05) than in both the luteal (0.4 ± 0.1) and the post‐ovulatory phases (0.5 ± 0.1), but not different from the intermediate values in the pre‐ovulatory phase (0.8 ± 0.2). Among cycle phases, no differences were found in sodium, potassium, calcium and magnesium concentrations (130.0 ± 1.1, 5.1 ± 0.3, 2.8 ± 0.1 and 0.59 ± 0.04 mmol/l respectively). Interestingly, the chloride secretion (μm /24 h) was higher (p < 0.05) at ovulation (150.2 ± 16.5) than during both the luteal (73.7 ± 22.0) and the post‐ovulatory phases (63.7 ± 11.2), with intermediate values in the pre‐ovulatory phase (113.4 ± 23.5). Glucose concentration (mmol/l) was higher (p = 0.056) in the pre‐ovulatory phase (0.06 ± 0.02) than in the luteal (0.02 ± 0.01) and post‐ovulatory (0.02 ± 0.01) phases but not different from values in the ovulatory phase (0.04 ± 0.02). Concentrations of pyruvate and lactate among oestrous cycle phases were similar (0.08 ± 0.01 and 1.0 ± 0.1 mmol/l respectively). The total quantity of phospholipids (μmol/24 h) was greater (p < 0.05) at ovulation (0.21 ± 0.02) compared with the luteal, pre‐ovulatory and post‐ovulatory phases of the cycle (0.09 ± 0.02, 0.13 ± 0.02 and 0.09 ± 0.01 respectively). No differences were found in either the protein concentration (1.8 ± 0.3 mg/ml) or the quantity of proteins secreted in 24 h (1.8 ± 0.4 mg) among oestrous cycle phases. In conclusion, this study provides the first characterization of buffalo ODF during the oestrous cycle, showing species‐specific differences that may be useful for developing suitable media for buffalo in vitro embryo production.     

Plasma Levels of Immunoreactive Parathyroid Hormone in Relation to Starvation Hypocalgaemia in Dairy Cows

The hypocalcaemia caused by parturition and onset of lactation in high-production dairy cows was mimicked by subjecting cows to starvation periods before and after partus. The changes in plasma calcium, phosphate and magnesium were followed and compared with immunoreactive parathyroid hormone (iPTH) in 2 cows. During the starvation periods before partus, the cows developed hypocalcaemia with no or only small changes in the plasma concentration of magnesium. After the onset of hypocalcaemia, the concentration of iPTH increased on the average 3–4-fold and the raised hormone levels lasted about 24 h after start of refeeding. An increase in plasma phosphate occurred somewhat later than the rise in iPTH and lasted longer. After partus hypocalcaemia developed, together with smaller increases in iPTH concentration (about 2-fold). The post-partum starvation period again resulted in hypocalcaemia and raised iPTH concentrations.In conclusion, starvation and parturition induced inverse changes in plasma calcium and iPTH in dairy cows. The increases in plasma iPTH were reversible and considered secondary to the hypocalcaemia. Through the effect of paratyroid hormone, plasma calcium was normalized and phosphate concentration increased. Therefore, fatal hypocalcaemia which may occur following the course of parturition and onset of lactation is not due to impaired PTH secretion.     

鲁西黄牛发情周期和产后期外周血浆孕酮水平

在鲁西黄牛母牛的发情周期和产后期（产犊至产后６０ｄ）收集颈静脉血样，用放射免疫分析法测定血浆孕酮（Ｐ４）水平。结果表明，母牛的发情周期平均为（２１．２±１．６）ｄ，发情当天（０ｄ）外周血浆孕酮水平为（０．５２±１．４）μｇ／Ｌ，在周期的９～１５ｄ，孕酮水平较高，其峰值为（４．６２±１．５６）μｇ／Ｌ（ｎ＝１５），在周期的约１８ｄ以后，孕酮水平迅速下降，至周期的２１ｄ降至发情开始时的水平；母牛产后１０．６～１３．６ｄ以后，外周血浆孕酮水平开始升高，出现黄体周期，约有一半的母牛产后第１个黄体周期为（８．４±０．５）ｄ，显著短于正常周期（２０．１±３．２）ｄ（Ｐ＜０．０１）；在短周期中，孕酮峰值为（１．５２±０．７１）μｇ／Ｌ，亦显著低于正常周期孕酮峰值（３．８４±１．２５）μｇ／Ｌ（Ｐ＜０．０５）。除短周期外，产后发情周期中的孕酮水平变化与通常的发情周期基本相同     

大鼠发情周期中主要生殖激素的变化

动物的生殖过程是由生殖激素严格调控的,深入研究生殖激素对畜牧生产具有重要的指导意义。然而发情周期中生殖激素的变化非常复杂,虽然人们在这方面做了许多的研究,但仍有许多问题仍不明了,对许多问题的认识还存在分歧。文章基于最近十几年的研究成果,以大鼠为对象,在综述了促性腺激素释放激素、促卵泡素、促黄体素、雌二醇及孕酮等几种重要的生殖激素的来源、生物学特性的基础上,着重介绍了这几种生殖激素在大鼠发情周期中的变化,并对影响生殖的因素进行了总结。     

Follicle Dynamics and its Relation with Plasma Concentrations of Progesterone, Luteinizing Hormone and Estradiol during the Egg-Laying Cycle in Ostriches

The aims of this study were (i) to describe the changes in the volume of large ovarian follicles (diameter >3 cm) during the 48 h egg laying cycle in farmed ostriches, and (ii) to quantify factors affecting the volume of the largest measured follicle and the plasma concentrations of progesterone (P₄) and estradiol‐17β (E₂β). In eight egg‐producing birds, which all ovulated during the study period, transcutaneous ultrasound scanning and blood sampling was performed at 3 h intervals. The average volume of the total number of visualized large follicles (V_total), the largest measured follicle (V_F1), the second largest follicle (V_F2) and of all follicles smaller than F2 (V_F3–Fn) were each higher before than after oviposition. V_total, V_F2 and V_F3–Fn nearly doubled in the 24‐h period before oviposition, while V_F1 remained at an equal, rather high level until oviposition. Immediately after oviposition V_total, as well as the volume of the other follicle categories, decreased within 6 h, i.e. around the moment of ovulation. By performing statistical analysis on the basis of linear mixed‐effects modelling, we quantified that: (i) V_F1 was 13.2% higher before than after oviposition and increased with 6.5% when LH increased with 1 ng/ml; (ii) P₄ levels were 93.2% higher before than after oviposition and increased with 43.1% for every 3 h closer to oviposition; when LH and E₂β levels and V_F1 increased with 1 ng/ml, 10 pg/ml and 10 ml, respectively, P₄ increased with 116.6%, 50% and 6.1%; and (iii) E₂β levels were 35.6% higher before than after oviposition, increased with 2.7% for every 3 h closer to oviposition and increased with 14.6% when LH increased with 1 ng/ml. It is concluded that during the egg‐laying cycle in ostriches: (i) follicular mass, as estimated by the volume of visualized follicles larger than 3 cm, increases before and decreases after ovulation, and (ii) follicular dynamics and its accompanying endocrine plasma hormone profiles during the egg‐laying cycle in ostriches follow a pattern similar to that in chickens.     

The Concentration of Faecal Progestins during the Oestrous Cycle in Nkone Cows and the Effect of Duration of Storage of Faecal Samples at Room Temperature on Faecal Progestin Levels

The objectives of this study were to determine whether ovarian function in Nkone cows could be monitored by measuring progestin concentrations in faeces and to assess the effect of duration of storage at room temperature on faecal progestin concentrations. Faecal and blood samples were obtained once a day for 26 days from 21 Nkone cows whose oestrous cycles had been synchronized. Faecal samples from each cow were divided into five portions that were kept at room temperature for 0, 6, 12, 24 and 48 h, respectively, and then frozen. After centrifuging the blood to recover plasma and extracting steroids from the faeces, analysis of progesterone (P₄) was carried out using solid-phase radioimmunoassay. The faecal progestin and plasma progesterone profiles corresponded well and were positively correlated (r = 0.70, p>0.01). Faecal progestin concentrations decreased with increasing duration of storage at room temperature during both the follicular and luteal phases (p>0.01). In both cases, the decline in faecal progestin concentrations followed an exponential pattern. The progestin concentrations in faeces after 48 h of storage at room temperature were higher (p>0.05) during the peak luteal phase than in the follicular phase.     

Size Distribution of Dispersed Luteal Cells During Oestrous Cycle in Angora Goats

The present study examines the size distribution of the goat steroidogenic luteal cells throughout the oestrous cycle. Corpora lutea (CL) were collected after laparatomy on days 5, 10 and 16 of the oestrous cycle. Luteal cells were isolated from CL by collagenase digestion. Steriodogenic luteal cells were identified by staining of the cells for 3beta-hydroxysteroid dehydrogenase activity, a marker for steroidogenic cells. Luteal cells having steroidogenic capacity covered a wide spectrum of sizes, ranging from 5 to 37.5 microm in diameter. There was a significant increase in mean cell diameters (p < 0.01) as CL aged. The mean cell diameter on day 5 was 11.55 +/- 0.12 microm, which was significantly increased and reached up to 19.18 +/- 0.24 mum by day 16 of the oestrous cycle. The ratio of large to small luteal cells was 0.06:1.0 on day 5 of the oestrous cycle. This ratio increased to 0.78:1.0 by day 16 of the oestrous cycle. Luteal cell size on days 5, 10 and 16 of the oestrous cycle reached its maximum at 7.5, 10 and 35 microm in diameter, respectively. Development of CL is associated with an increase in luteal cell size in goats. It is likely that small luteal cells could develop into large luteal cells as CL becomes older during oestrous cycle in goats.     

Endometrial Phospholipase A2 Activity During the Oestrous Cycle and Early Pregnancy in Mares

The aim of this study was to determine phospholipase A2 (PLA2) kinetics and activity in the mare’s endometrium during the oestrous cycle and early pregnancy. Phospholipase A2 is responsible for the liberation of arachidonic acid from phospholipids, which is the first limiting step in prostaglandins synthesis. Phospholipase A2 activity was measured using an assay based on the liberation of oleic acid from 1‐palmitoyl‐2‐[¹⁴C] oleoyl phosphatidylcholine. The enzyme was shown to be calcium dependent, to have an optimum pH of 8 and an apparent Michaelis constant of 127 μm . Enzyme activity was low in the endometrium of early luteal phase tissue but increased significantly (p < 0.001) during the late luteal phase (5.39 ± 0.16; 3.48 ± 0.33, 6.85 ± 0.59, and 9.96 thinsp;± thinsp;1.23 thinsp;nmol oleic acid released/mg protein at oestrus, and Days 3, 8 and 14 after ovulation, respectively). The mean PLA2 activity in endometrial tissue from pregnant mares (4.23 ± 0.74) was significantly lower (p < 0.01) than from cyclic animals during late dioestrus (9.96 ± 1.23). The results indicate that PLA2 activity in equine endometrium changes with the stage of the oestrous cycle and thus may be influenced by systemic hormone concentrations. The inhibitory effects of conceptus products on secretion of prostaglandin during early pregnancy were associated with a competitive inhibitor that decreased endometrial PLA2 activity.     

The Role of the Endometrium in Endocrine Regulation of the Animal Oestrous Cycle

A critical analysis of the results of research in the function of the endometrium was carried out and a view point presented. The role of the endometrium in endocrine regulation of the oestrus cycle can be summarized as follows: 1. The transfer of prostaglandin F_2α (PGF_2α) from the uterus to an ovary, which causes luteolysis, occurs mainly via the lymphatic pathways. 2. The system of retrograde transfer of PGs enables PGF_2α and PGE₂ to reach the myometrium and endometrium with arterial blood at high concentration. In the luteal phase, PGF_2α, together with the increasing concentration of progesterone, constricts the arterial vessels of the uterus; in the follicular phase and in early pregnancy, PGE₂ together with oestrogen and embryonic signals, relaxes the arterial vessels. In addition, this system protects the corpus luteum from premature luteolysis during the cycle and luteolysis during early pregnancy. 3. In days 10–12 of the cycle, the blood flow in the uterus decreases by 60–70% in pigs and around 90% in sheep. This causes ischaemia and local hypoxia confirmed by the presence of hypoxia inducible factor and thus remodelling of the endometrium commences. 4. The pulsatile elevations in PGF_2α concentration occurring in the blood flowing out of the uterus during the period of luteolysis and the next few days, do not result from increased PGF_2α synthesis as suggested in numerous studies. They are the effect of excretion of PGF_2α and its metabolites together with lymph and venous blood and tissue fluids in which prostaglandin accumulates.