Concentrations of plasma luteinising hormone,prolactin, progesterone and androgens during the ovulatory cycle of the Turkey

1. Changes in the concentrations of plasma luteinising hormone (LH), prolactin, androgen and progesterone were measured during the ovulatory cycle of the turkey.

2. Single pre‐ovulatory peaks of plasma LH, androgen and progesterone were observed which took 8, 8 and 12 h respectively, to increase and return to base‐line values. The concentration of plasma prolactin tended to be elevated between 6 h before and 6 h after the LH peak with the maximum values occurring after the peak.

3. The changes in the concentrations of plasma LH and progesterone were 3‐ and 7‐fold respectively while 2‐fold changes were observed in the concentrations of plasma androgen and prolactin.

4. The pre‐ovulatory concentration of plasma progesterone and prolactin began to decrease 4 and 6 h respectively, after the pre‐ovulatory peak of LH.

5. Ovulation and oviposition occurred 6 to 8 h and 36.10+ 0.57 h (SEM) ( n= 11) respectively after the pre‐ovulatory peak of LH.

6. In birds kept on 14 h light/d, pre‐ovulatory peaks of LH were initiated only during a 10 to 11‐h period starting within 2 h after the onset of darkness.

7. A comparison between these data and those from the fowl suggest that the egg is retained in the turkey's oviduct for about 3 to 4 h longer than in the fowl.     

Effect of luteinising hormone releasing hormone and its analogues on plasma luteinising hormone concentrations in incubating bantam hens

The ability of synthetic vertebrate luteinising hormone releasing hormones (LHRHs) and their long-acting analogues to maintain elevated plasma luteinising hormone (LH) concentrations and to stimulate ovarian growth was investigated in incubating bantam hens. Chicken LHRH-II (pGlu1-His2-Trp3-Ser4-His5-Gly6-Trp7-Tyr8-Pro9-G ly10-NH2) was more effective than chicken LHRH-I (pGlu1-His2-Trp3-Ser4-Tyr5-Gly6-Leu7-Gln8-Pro9-Gly10-N H2) or porcine LHRH (pGlu1-His2-Trp3-Ser4-Tyr5-Gly6-Leu7-Arg8-Pro9-Gly10-N H2) in stimulating the release of LH. Long-acting analogues of chicken LHRHs (chLHRHs) were created by substituting D-amino acids in position 6. An intravenous injection (10 micrograms/bird) of D-Arg6-chLHRH-II or of a long-acting mammalian analogue of LHRH (buserelin) resulted in a sustained release of LH for up to 8 h. Less sustained releases of LH were observed after the same doses of D-Ala6-chLHRH-I or of D-Trp6-chLHRH-I. Repeated subcutaneous injections of D-Arg6-chLHRH-II or buserelin at 7 to 9 h intervals for 9 d resulted in loss of pituitary gland responsiveness to these analogues. For this reason, the treatment failed to maintain elevated plasma LH concentrations and did not stimulate the growth of the ovary or oviduct.     

Pubertal changes in the secretion of gonadotropic hormones, testicular gonadotropic receptors and testicular function in the ram

Developmental changes in pituitary content and secretory patterns of luteinizing hormone (LH), follicle-stimulating hormone (FSH) and prolactin (PRL), testicular size and steroidogenic function, testicular LH- and FSH-binding activity, and growth of the accessory sex organs were examined for 24 Dorset X Leicester X Suffolk rams (born in March) every 30 days from 30 to 150 days of age, and again at 200 days. Pituitary LH and FSH contents increased between 30 and 60 days of age and remained constant until 150 days, when contents were somewhat greater than on either 120 or 200 days. LH-pulse amplitude and frequency, and mean FSH concentration, were highest at 60 and (or) 90 days of age. Testicular growth increased dramatically between 90 and 150 days of age in association with increases in the number of LH- (100-fold) and FSH- (33-fold) binding sites in the testis and a small increase in blood testosterone concentration (1 ng/ml). During the same period, pituitary content and blood concentration of PRL increased to maximal values, epididymal, vesicular gland and bulbourethral gland weights increased 6-fold, and body weight doubled. Between 150 and 200 days of age, testosterone concentration increased considerably (8 ng/ml), as did LH-pulse frequency and the amount of LH- and FSH- binding in the testis; the reproductive organs continued to grow at a rate faster than that of the body as a whole. Testicular development of ram lambs was accompanied by increases in the secretion of all three pituitary hormones with gonadotropic properties, and in the number of LH and FSH receptors.     

Concentrations of luteinising hormone and progesterone in pregnant and non-pregnant heifers

An experiment was conducted to determine if concentrations of luteinising hormone or progesterone were different in pregnant or non-pregnant heifers for seven days before and 20 days after a successful or non-successful insemination. Heifers with an oestrous cycle length of 18 to 24 days only were used and they were bled at 08.00, 16.00 and 24.00 each day for seven days before and for 20 days after insemination with thawed semen (treatment 1) or semen diluent (treatment 2). Animals allocated to treatment 3 had the embryo nonsurgically flushed from the uterus at days 10 to 12 while animals allocated to treatment 4 were inseminated with semen diluent and then had a viable embryo transferred to the uterus between days 10 and 12. All animals were slaughtered between 19 and 21 days after insemination and pregnancy rate determined. There were no differences in basal luteinising hormone levels between treatments. Blood concentrations of progesterone were not different before insemination and for 16 days after insemination for pregnant (11 out of 15) and non-pregnant heifers (14) allocated to treatments 1 and 2. Between days 17 and 20, progesterone concentrations declined in non-pregnant heifers. Transfer of an embryo to non-pregnant heifers on day 10 to 12, did not affect progesterone concentrations, but non-surgical flushing of the embryo caused a decline in blood concentrations of progesterone. It was concluded that basal blood concentrations of luteinising hormone and progesterone, in samples taken three times daily were not different in pregnant or non-pregnant heifers before and for 16 days after insemination.     

The influence of photoperiod on gonadotrophin-releasing hormone stimulated luteinising hormone release in the anoestrous mare

The transition from anoestrus to oestrus in mares is controlled by photoperiod. The present study examined whether additional daylength would accelerate the mares' response to gonadotrophin-releasing-hormone (GnRH). Nine anoestrous mares were placed under ambient or artificial long lighting on 7th January. The four month experimental period was divided into a three-day sequence which was repeated at 21 day intervals. Ovaries were palpated rectally on Day 1; saline was injected (1 ml intravenously [iv]) on Day 2; GnRH was administered (0.59 microgram/kg bodyweight iv) on Day 3. Blood was taken at -60, 0, 15, 30, 60 and 120 mins relative to saline or GnRH treatment. Serum luteinising hormone (LH) was determined by a homologous equine radioimmunoassay (RIA). Several criteria were employed to define a positive response to GnRH and the results were analysed by Fisher's exact probability test. Treatment with artificial light allowed a response to GnRH within six weeks whereas the mares in ambient lighting took 12 weeks to respond to GnRH. The advancement in the time of response to GnRH under the long photoperiod could be related to changes in pituitary LH content, accelerated follicular activity or alterations in other brain-pituitary hormone levels.     

Developmental changes in the regulation of plasma growth hormone concentrations in Holstein calves

A study was initiated to determine whether development of a functional ruminant digestive system was associated with alterations in plasma growth hormone (GH) concentration. Holstein bull calves were fed milk or milk with grain until studied at the age of 1 month (n = 12). Calves placed on pasture with some grain supplementation were studied at the age of 3 months (n = 6) to determine plasma GH concentration in an animal with fully developed ruminant metabolism. Blood samples were taken at 10-minute intervals for 5 hours, followed by administration of bovine GH-releasing factor (0.075 micrograms/kg of body weight) and subsequent blood sample collection for 1 hour. On the following day, a blood sample was collected via jugular cannula, clonidine (10 micrograms/kg) was administered, and blood samples were subsequently obtained. Data indicated that milk-fed calves had higher mean plasma GH concentration than did either milk/grain-fed or older calves. The difference in mean plasma GH concentration was related to higher secretory pulse amplitude. Pituitary responses to bovine GH-releasing factor did not differ among the 3 groups, but response to clonidine were greater in milk-fed calves than in calves of the other groups. These data indicate that the change from a nonruminant to a ruminant-type gastrointestinal tract, perhaps attributable to subsequent changes in metabolism, may induce changes in hypothalmic function to decrease GH concentration.     

Effects of luteinising hormone on embryo production in superovulated cows

Equivalent doses of follicle stimulating hormone (FSH) produced the same number of embryos and ova from a single flush irrespective of the luteinising hormone (LH) content of the superovulating drug (P less than 0.108). As the LH content of the FSH increased, the proportion of transferable embryos decreased (P less than 0.001) because the proportion fertilised decreased (P less than 0.001) and the degeneration rate of the fertilised embryos increased (P less than 0.002). FSH-W free from detectable luteinising hormone produced 8.8 embryos per flush of which 5.7 were transferable, representing 7.6 fertilised embryos of which 21 per cent had degenerated. The addition of a very small quantity of LH (FSH/LH ratio more than 500) resulted in 5.8 transferable embryos from a total of 10.6, of which 9.0 had been fertilised and 34 per cent of those fertilised had degenerated. Commercial FSH-P (FSH/LH less than 100) produced 3.3 transferable embryos from a total of 8.1, of which six had been fertilised and 39 per cent of those fertilised had degenerated. The luteinising hormone content of FSH-P has to be controlled and limited for optimum superovulation in cattle.     

Comparison of the basal and luteinising hormone-releasing hormone induced luteinising hormone release by perifused hypophyses from turkey hens (Meleagris gallopavo) at different physiological stages.

1. An experiment was performed to investigate the weight of the ovary, the oviduct, the pituitary gland, the plasma concentrations of luteinising hormone (LH), progesterone, oestradiol and the responsiveness of the pituitary gland in vitro to doses of Luteinising Hormone-Releasing Hormone (LH-RH) ranging from 10(-10) to 10(-5) M in laying (L), incubating (I) and out-of-lay (OL) turkey hens. 2. Pituitary weights did not differ between the groups but the weights of the ovary and oviduct and the plasma concentrations of progesterone and oestradiol were lower in I and OL than in L hens. The plasma concentrations of LH were lower in I than in L hens. 3. In vitro, the basal release of LH was similar in L and I hens, but significantly higher in OL hens. A slow and linear increase in basal LH release by the glands from I and OL hens was observed throughout the experiment. 4. No clear dose-response relationship was found in any of the reproductive states with respect to LH release in vitro following LH-RH stimulation, probably as a result of partial cell desensitisation. On the other hand, the amount of LH released over basal level in responses to stimulation with different doses of LH-RH were not significantly different between L and I hens, but they were between 5- to 10-fold higher in OL hens, except at the lowest dose. 5. These findings confirm that there is no correlation between circulating LH in turkey hens and the capacity of the hypophysis to release LH in vitro passively or in response to LH-RH. Therefore, the low circulating concentrations of LH in I and OL turkey hens cannot be accounted for by decreased adenohypophyseal responsiveness to LH-RH. They may indicate a low level of hypothalamic secretion of LH-RH and/or to the existence of an inhibitory mechanism on LH secretion in vivo in both OL and I hens.     

Serial percutaneous testicular biopsy in the Beagle dog

The effects of serial percutaneous testicular biopsy on testicular size, semen characteristics and plasma testosterone have been assessed. Testicular atrophy occurred in one dog after the first biopsy, but apparently there were no permanent deleterious effects on semen characteristics or testosterone concentrations. The histological changes 72 hours and 14 days after bilateral testicular biopsy were examined in one dog. Initial haemorrhage and necrosis with subsequent fibrosis and atrophy occurred at the biopsy site. The surrounding tissue remained normal in appearance. The technique may be worthwhile for establishing diagnostic criteria in cases of male canine infertility. Not enough tubules are obtained in circular cross-section to allow detailed histomorphometric analysis of spermatogenesis under laboratory conditions.     

Parasagittal hypothalamic knife cuts in male chicks: advancement of reproductive function and changes in plasma concentrations of luteinising hormone and androgen

Advancement of reproductive function occurred in male domestic chicks after lateral hypothalamic deafferentation (bilateral knife cuts extending from the preoptic to the mamillary region) at 2 weeks of age. Five out of 24 chicks showed sexual precocity as shown by accelerated comb growth after surgery. The 5 chicks had significantly higher concentrations of plasma luteinising hormone (LH) and androgen (A) than 5 sham-operated controls. Maximum concentrations of plasma LH and A were observed 3 and 4 weeks respectively after surgery. It is concluded that in the male domestic chick gonadotropin secretion is inhibited by extrahypothalamic influences.     

Follicle stimulating hormone, luteinising hormone and progesterone concentrations in the blood of thoroughbred mares exhibiting single and twin ovulations

The concentrations of follicle stimulating hormone, luteinising hormone and progesterone were measured in serial blood samples taken throughout one or more oestrous cycles from 12 Thoroughbred mares, some of which exhibited single and others twin ovulations. The resulting profiles clearly demonstrated that no simple relationship exists between circulating gonadotrophin levels and subsequent ovulation rate in the mare. However, plasma progesterone concentrations during dioestrus are, as expected, higher following twin than single ovulations. The findings suggest that the underlying cause of twin ovulation in some mares may exist at the ovarian end of the pituitary-ovarian axis which controls follicular development and ovulation.     

The effects of androgens and gonadotropins on testicular development in the prepubertal rat.

Treatment of male rat pups from five to 34 days of age with dihydrotestosterone or 5 alpha-androstane-3 alpha, 17 beta-diol, resulted in reduced testicular size at 35 days of age. This appeared to be due to decreased tubular diameters and reduced spermatocyte numbers, especially late pachytene cells in stages X to XIII. In rat pups treated with dihydrotestosterone or 5 alpha-androstane-3 alpha, 17 beta-diol, treatment with luteinizing hormone resulted in some restoration of tubular diameter and spermatocyte numbers. In 5 alpha-androstane-3 alpha, 17 beta-diol treated rat pups partial restoration of testes size resulted from follicle-stimulating hormone treatment, but tubular diameter and spermatocyte numbers were depressed. Single serum samples collected at 35 days of age were analysed for luteinizing and follicle-stimulating hormone concentrations. These data indicated that the effects of administered androgens were due primarily to depression of circulating gonadotropin concentrations but a direct inhibition at the level of the testis could not be ruled out.     

Cytologic features of testicular tumours in dog

In this paper, we report on our experience of cytology of fine needle biopsies performed on 92 dogs with testicular tumours during the period from 1998 to 2002. Cytological diagnosis was consistent with seminoma in 20 cases, sertolioma in 16 cases, Leydig cell tumours in 50 cases and mastocytoma in one case. Five cases could not be diagnosed by cytology. Cytological observations were confirmed after surgery by histopathological examination in 87 cases. Cytology provided a sensitivity of 95% for seminoma, 88% for sertolioma and 96% for Leydig cell tumours. The specificity was 100% for all three tumour types. In our experience cytology of fine needle aspirations of testicular tumours is a very reliable technique.     

Relationship between plasma concentration of luteinising hormone and intensity of lay in the domestic hen

1. The concentration of plasma luteinising hormone (LH) in samples taken at frequent intervals from 6 weeks of age until the onset of lay, and also at 9 months after the onset of lay, was significantly greater in hens with a high rate of egg production than in comparatively poor layers.

2. The difference was most marked during the period 7 to 9 weeks of age when there was a transient increase in plasma LH in hens that subsequently had a high rate of egg production, while LH concentration remained stable in comparatively poor layers.

3. The concentration of LH in plasma, particularly at 7 to 9 weeks of age, before gonadal growth, or during the prepubertal peak of LH secretion, at about 2 to 4 weeks before the onset of lay, may be a useful criterion in the selection of laying strains.     

Relationship between ultrasonographic appearance, testicular size, spermatozoal output and testicular lesions in the dog

The ultrasonographic appearance of the dog testis and epididymis was examined in vivo and in vitro. The relationship between specific testicular and epididymal dimensions was studied in normal animals. Assessment of testicular volume using ultrasound compared favourably to the volume calculated by water displacement. The correlation between testicular volume, epididymal cross-sectional area and semen parameters was, however, poor. Changes in the normal testicular architecture were identified in a variety of pathological conditions including testicular cysts and neoplasia.