Neonatal growth of testosterone propionate-treated embryos

Studies on birds treated in ovo with testosterone (TP) indicate that while food conversion of the birds was essentially the same, control birds grew significantly faster. Growth rate was improved when the TP birds were fed a penicillin‐supplemented ration. Penicillin also improved the growth rate of control birds but not to the same extent. These findings indicate that the immunological incompetence of TP birds may be contributing to the slow growth but this is not the sole contributory factor.

Blood glucose levels at hatching were similar in TP and control birds. Analyses when the birds were consuming basal or penicillin‐supplemented ration ad libitum revealed significantly lower blood sugar levels in the TP birds. According to a glucostatie theory, a higher blood sugar level might have depressed the appetite. However, since the TP birds have lower blood sugar levels and eat less, it was not affecting the appetite. Conversely, a significant correlation between weight gains and blood sugar levels was interpreted as indicating that food consumption probably influenced the blood sugar levels. The development of the feeding centres in the hypothalamus may have been influenced by the TP treatment.     

Genetic parameters for testosterone production in boars

Data were collected in 1982 through 1989 from 66 sires and 358 Duroc boars. Testosterone production was measured from peripheral blood samples before (PRE) and after (POST) GnRH challenge. Additionally, data were collected on testes length at 168 d (TL168), testes width at 168 d (TW168), testes volume at 168 d (TVOL), birth weight (BWT), average daily gain (ADG), days to 104 kg (DAYS104), and backfat adjusted to 104 kg (FAT). Overall means for these traits were 24.6 ng.ml-1.h-1, 75.7 ng.ml-1.h-1, 12.3 cm, 11.6 cm, 422.0 cm3, 1.5 kg, .5 kg, 189.3 d, and 18.5 mm, respectively. Son-sire regressions were used to calculate genetic parameters. Heritabilities for PRE, POST, TL168, TW168, TVOL, BWT, ADG, DAYS104, and FAT were .37, .26, .33, .34, .33, .21, .42, .35, and 0, respectively. Moderately favorable genetic correlations were obtained for PRE and POST with growth measurements. Large positive genetic correlations were present for both PRE and POST with TL168, TW168, and TVOL, and testes measurements had large positive genetic correlations with growth traits. Selection for testes size or testosterone production should be equally effective. However, it seems that selection for testes size would result in larger changes in measures of growth than selection for testosterone. This study suggests that testes measurements are good predictors of both basal and challenge testosterone levels. Selection for increased testis size or increased testosterone levels would be expected to enhance growth.     

Effects of testosterone on rat placental development

We investigated the morphological effects of testosterone on placental development in a rat model of polycystic ovarian syndrome (PCOS). Testosterone propionate (TP), which was subcutaneously administered to pregnant rats with 5 mg/animal from gestation day (GD) 14 to GD 18, induced a maternal weight reduction without mortality or clinical signs from GD 19 onwards. A decrease in fetal and placental weight, an increase in intrauterine growth retardation (IUGR) rates, and histological changes in the placenta were observed on GD 21 but not on GD15 or 17. Histopathologically, on GD 21, the trophoblast septa thickened, and the maternal sinusoids were narrowed in the labyrinth zone, resulting in a small placenta. Additionally, the placental weight, thickness, and histological morphology in the labyrinth zone on GD 21 in the TP-treated group were nearly identical to those on GD 17 in the control and TP-treated groups. Therefore, it was assumed that the testosterone-induced small placenta was induced in association with the developmental inhibition of the fetal part of the placentas from GD 17 onwards.     

Blood plasma concentrations of oestradiol-17beta,testosterone and testosterone/oestradiol ratio in dogs with neoplastic and degenerative testicular diseases

Oestradiol-17beta and testosterone blood plasma concentrations were measured in dogs with Leydig-cell tumours (n=20), Sertoli-cell tumours (n=6), seminomas (n=9), unilateral inguinal cryptorchidism (n=7), abdominal cryptorchidism (n=9, one bilateral), degenerate scrotal testicles (n=6, two bilateral), and animals with normal scrotal testicles (n=20). The testosterone/oestradiol ratio (testosterone concentration [ng/mL]x100/oestradiol concentration [pg/mL]) was calculated.A considerably higher oestradiol concentration was found in dogs with Sertoli-cell tumours (29.0, 14.4-48.3 pg/mL; median, minimum-maximum; P=0.0256, Mann-Whitney test) and lower oestradiol levels were found in animals with seminomas (12.0, 3.4-17.6 pg/mL; P=0.0025) compared to the healthy control group (18.0, 8.6-31.5 pg/mL). Testosterone concentration was decreased in dogs with Sertoli-cell tumours (0.08, 0.03-0.77 ng/mL) when compared to the control group (1.95, 0.05-3.70 ng/mL; P=0.0012). Testosterone/oestradiol ratios differed from the control (9.6, 0.58-35.8) only in dogs with Sertoli-cell tumours (0.32, 0.06-2.80; P=0.0005). Clinical signs of feminization were observed in five dogs with Sertoli-cell tumour and one dog with a Leydig-cell tumour, and were more often associated with decreased testosterone/oestradiol ratios than with an increased oestradiol-17beta concentration.     

Plasma testosterone in functionally castrated cockerels with hypothalamic lesions

Two types of modified cockerels were produced by lesioning the hypothalamus: (1) functionally castrated, obese, with atrophied testes and combs, bearing lesions in the mammillary nuclei and posterior part of the ventromedial nuclei (FC) and (2) functionally castrated, obese, with atrophied testes, but with large combs, bearing lesions in the posterior part of the mammillary nuclei and part of the arcuate nuclei (FCLC).

Semen could not be obtained from either type of bird. Plasma testosterone concentrations, determined by radio‐immunoassay, were 25.5 ± 5, 125 ± 20 and 508 ± 272 ng/100 ml plasma, for the FC, FCLC and control birds respectively. Correlations were not found between comb weight and testosterone concentration within each of the different groups. Neuroendocrine aspects and some physiological effects of androgenic activity are discussed in the light of previous studies with similarly lesioned cockerels.     

A possible role for testosterone during luteolysis in the ewe

Increased peripheral plasma concentrations of testosterone were detected at the commencement of luteolysis and at oestrus in sheep. Daily subcutaneous administration of spironolactone (10 mg kg-1) between days 10 and 16 of the oestrous cycle suppressed testosterone secretion and delayed luteolysis and oestrus. In pregnant ewes no increases in testosterone concentrations occurred between days 10 to 16 after mating and luteal regression, monitored by peripheral progesterone concentrations, was inhibited. It is suggested that aromatisation of testosterone to oestrogens is needed for luteolysis in sheep.     

Seasonal changes of testicular weight, sperm production, serum testosterone, and in vitro testosterone release in Korean ring-necked pheasants (Phasianus colchicus karpowi)

To study the biology of reproduction of male Korean ring-necked pheasants kept under natural conditions of temperature and photoperiod, testicular weight, serum testosterone concentrations, testosterone release from the luteinizing hormone (LH)-stimulated testis in vitro and sperm production were measured. Significant changes associated with seasonal cycles were found. Testis weight decreased dramatically in August, remained low until February, rapidly increased from March to high levels to June, and decreased subsequently. Serum testosterone concentrations remained little from August until February, but increased sharply in March to reach the highest levels in April. Thereafter, the concentrations decreased significantly from June. The testosterone release was low from August to February, increased abruptly in March to reach the highest levels in May, and showed rapid decrease thereafter. Sperm production decreased to nondetectable levels from August to February, increased markedly in March, reached a peak in May, and sharply decreased thereafter. Thus, the pheasants breed from late March to late June. These results indicate that the Korean ring-necked pheasant, under natural conditions, exhibits characteristics of a seasonal cycle in reproduction.     

Effect of bilateral orchidectomy on serum testosterone levels in boars]

Bilateral orchidectomy caused a marked decrease in the concentration of testosterone in the bood plasma of boars already in the early post-castration stage of three hours after the operation. In the period from 3 to 207 days after castration, the pre-operation levels of plasma testosterone decrease by 84.4%, on an average. Adreno-cortical compensation of the concentration of the hormone did not occur in the post-castration period. The conclusion is that the levels of testosterone in the blood of boars are mostly of testicular origin and can be considered as the main criterion of the incretion function of the testes. The discussion concerns the practical importance of the determination of testosterone levels in the blood of boars for clinical evaluation of the hormonal function of the testes and for diagnostics of incretion hypogonodism.     

Preparation of a bovine monoclonal antibody to testosterone by interspecies fusion

This communication reports the first successful attempt to produce a hybridoma cell line secreting bovine immunoglobulin to a small hapten, starting with peripheral blood lymphocytes, rather than spleen or lymph node cells. A heteromyeloma line, sensitive to selective media, was made by fusing NS1/1-Ag4-1 mouse myeloma cells with bovine peripheral blood lymphocytes. This cell line was then fused with blood lymphocytes from a steer immunised with a testosterone immunogen. Cell cultures were screened using an ELISA specific for bovine antibodies to testosterone. Following repeated cloning, a cell line was established which secretes moderate levels of a specific, high affinity antibody to testosterone. This particular cell line has significant potential for veterinary application and the successful fusion demonstrates the possibilities of heteromyelomas for the development of non-murine monoclonal antibodies.     

Concentration of plasma testosterone in adult roosters of a low-weight strain

The levels of blood-plasma testosterone were studied in the adult light bodied strain cocks. Blood was sampled (1 ml) from the wing vein by means of a heparinized syringe six times within a 24-hour interval. The plasma obtained by centrifugation was kept in a refrigerator at a temperature of --18 degrees C. Testosterone was determined by the radioimmunological method. The testosterone levels were significantly higher (P less than 0.001), 18.8 nmol/l on the average, in the blood samples taken during the dark period of the day (10 o'clock p.m., 2 and 6 o'clock a.m.) than in the samples taken in the light part of the day (8 and 10 o'clock a.m., 2 o'clock p.m.) when the average concentration of the studied hormone was 10.7 nmol/l of plasma. the lowest levels of testosterone were recorded in the morning and the highest values were recorded late in the evening (10 o'clock p.m.). The differences in the levels of the hormone between sampling terms indicate that the testosterone level in adult animals shows diurnal variances. It was found by the study of the concentration of testosterone in the blood plasma of the same individuals within short intervals of time (30-60 min) that testosterone secretion in adult cocks had a pulsatory manner. The evaluation of hormone levels should include not only the diurnal variances but also the pulsatory manner of testosterone secretion.