Evolution of testosterone metabolism during neonatal life in the guinea pig]

The neonatal period is characterized in the male Guinea-Pig by a steady increase in the metabolic clearance rate of testosterone and by a decrease in the conversion rate of testosterone to androstenedione. The transient rise in testosterone production rate on day 3 is concomitant with the neonatal peak in plasma testosterone.     

Plasma, testicular, and adrenal cortex levels of androgens in the perinatal period and determination of neonatal hypertestosteronemia in guinea pigs]

The perinatal period is characterized in the male faetus and new-born Guinea-Pig by a prenatal increase in testis testosterone and by a neonatal peak in plasma testosterone. This transient rise in plasma testosterone is testis dependent and light dependent at birth.     

Seasonal variations in the nyctohemeral rhythm of plasma testosterone in the European badger Meles meles L

In the badger a seasonal sexual rhythm of the plasma testosterone is observed. There is also a nycthemeral rhythm of the testosterone secretion; during the regressed period of the testis this rhythm is bimodal with testosterone peaks during the light phase of the day; during the active period and "activity rhythm" with many transitorys peaks during the dark phase is added.     

Annual cycle of plasma testosterone and thyroxine in the European badger (Meles meles L.)]

In the male European Badger there are important variations in the plasma testosterone and thyroxine levels during the annual cycle. During the summer, plasma testosterone concentrations are low while plasma thyroxine rises to a very high level. In winter, when the thyroid activity is minimal, testicular activity increases. From February to May, the plasma testosterone remains at a high level, and then, after a sudden fall, a second peak occurs in June at which time the concentration of thyroxine is low.     

Combined effects of testosterone and estradiol on the ventral lobe of the rat postate in organ culture]

After organ culture without hormone, the epithelial gland cells of Rat veantral prostate undergo atrophic changes, whereas the interstitial stroma components tend to increase. Estradiol (1-1,000 nM),added to the culture medium, is ineffective. On the contrary, testosterone (1-100 nM) maintains epithelial cells and prevents the increase of interstitial stroma. When estradiol (1-1,000 nM) is combined with a physiological concentration of testosterone (1-4 nM), the epithelial cells are well maintained, but the inhibitory action of testosterone on the stroma is counteracted so that the glandular epithelium and the interstitial stroma are both stimulated. However, when testosterone is used at supraphysiological (10-100 nM) concentrations, estradiol is completely ineffective and the structure of the prostate is identical to the one given by the androgen alone.     

Effect of testosterone on the kinetics of the development of suppressor cells in adjuvant arthritis

The induction of unresponsiveness to mycobacterial adjuvant took a longer time in male DA rats than in female rats. A shift in the induction time of unresponsiveness in males toward the female type was brought about by castration, but could be reverted to the male type by the application of testosterone. The transfer study revealed that cells capable of preventing arthritis required a longer incubation time for their development in males than in females. This suggests that testosterone inhibits the development of suppressor cells in adjuvant arthritis.     

Ontogenic development of the renal ornithine decarboxylase response to testosterone

Summary In neonatal mice, renal ornithine decarboxylase was not altered by testosterone injection, in contrast to adult mice in which the enzyme was greatly elevated following treatment with testosterone.     

Inhibition of the testosterone effect on the submaxillary gland by actinomycin-d

Riassunto La somministrazione di testosterone in topi femmina produce notevoli modificazioni della ghiandola sottomascellare, che acquista i caratteri di tipo maschile. Actinomicina-D, somministrata contemporaneamente all'ormone maschile, inibisce tale effetto sulla ghiandola sottomascellare. I risultati suggeriscono che l'azione del testosterone si svolga al livello della sintesi di RNA nucleare.     

Effect of testosterone on the kinetics of the development of suppressor cells in adjuvant arthritis

Summary The induction of unresponsiveness to mycobacterial adjuvant took a longer time in male DA rats than in female rats. A shift in the induction time of unresponsiveness in males toward the female type was brought about by castration, but could be reverted to the male type by the application of testosterone. The transfer study revealed that cells capable of preventing arthritis required a longer incubation time for their development in males than in females. This suggests that testosterone inhibits the development of suppressor cells in adjuvant arthritis.Acknowledgments. We are grateful to The Naito Foundation Research Grant for 1983.     

Effect of light on variations in blood testosterone in the ram: demonstration of a photosensitive phase in diurnal rhythm]

6 groups each of 5 adult rams were subjected in light controlled pens to a pretreatment of normal variations in daylength during May and June. Then one group followed the normal daylength and the other five different "skeleton photoperiods" of 8 hrs of light per day consisting of: 7 hrs continuous light (7 L) + 1 hr light (1 L) situated at different times of the dark period (D) according to groups. Blood samples were taken once each week and hourly during one 24 hr period in June, July and September. Peripheral plasma testosterone measured by radio-immunoassay was used as an index of testicular activity. There was increase in the level of testosterone resuting from a rise in the number of peak release during the 24 hrs. In the different light treatments tested, only the treatment (7L+9D+1L)+7D) stimulated testosterone secretion with the pattern of testosterone of this group being similar to that of the control group. This indicates that there exists a photosensitive phase at 16 to 17 hrs after the beginning of the principal light (the subjective dawn).     

Regulation of testosterone production in fetal testicular cells: effect of androgens

Summary Pre-incubation of dispersed testicular cells from 18-day-old mouse fetuses in presence of testosterone or dihydrotestosterone resulted in a significant decrease of the hCG-stimulated testosterone production. These results suggest that during late fetal life testosterone production may be inhibited by an ultra-short loop feedback of androgens.     

Pituitary-testicular relationships in the rat embryo]

LH given to the Rat embryo at the time of hypophysectomy by decapitation (18 days of intrauterine life) will prevent the drop in androgen synthesis which normally ensues. This is regarded as definite proof that androgen synthesis is under pituitary control in the rat embryo at late gestational stages. On the other hand, the decrease in androgen synthesis following testosterone injection to the pregnant female points to the fact that there is a negative feedback of testosterone on pituitary LH secretion.     

The effects in vivo of some sex hormones on the growth of tibias of normal and chondrodystrophic (Creeper) chick embryos]

Various sex hormones (testosterone, oestradiol, dehydroepiandrosterone), in the form of suspensions in oil, are injected into the allantois of normal and chondrodystrophic (Creeper) chick embryos of 6 days 1/2 incubation. Observations made on each of the phenotypes on the 12th day of incubation show that oil injected alone causes a significant decrease in the dry weight of the tibiae. This inhibitory effect is partially abolished when the oil is injected together with the sex hormones, testosterone being the most effective.     

Inhibition of post-hemicastration hypertrophy of the remaining testis by testosterone or aqueous testicular extract treatments in the young rat]

In the 10 day old hemicastrated Rat daily injections of testosterone (total doses of 0.04 to 4 mg/Rat) or of proteinaceous extract of Rat testis (4 mg/Rat) inhibit compensatory hypertrophy of the remaining testis. Both testosterone and testicular proteinaceous extract could be involved in the growing processes of the testis, locally or by means of modification of gonadotropin secretion. Results have been analysed by covariance analysis to eliminate the influence of body weight variations.     

Evolution of testosterone and dihydrotestosterone in plasma, testicle and ovary of the guinea pig throughout fetal life]

High testosterone concentrations were found in the plasma of male fetus at the stage of sexual differentiation. Then the fetal testis is the principal source of circulating testosterone; its action on the Wolffian duct would occur by the systemic pathway. In female fetus, androgens were synthesized by the gonad and the relatively high levels found in the plasma have probably another source.     

The effect of gonadotropic hormones and the fetal hypophysis on testosterone production by the testis of 18 day mouse fetuses in organ culture]

The production of testosterone (measured by radioimmuno-assay) by the 18-day-old mouse fetal testis may be stimulated specifically by ovine LH (1 ng, p less than 0.005) and HCG in organ culture. A stimulation by FSH is observed only with high doses (10 mug, p less than 0.0005). Prolactin and ACTH have no effect. Age-matched fetal pituitaries increase significantly the testosterone production in the culture medium (p less than 0.0005).     

Effect of testosterone on the hypothalamic-pituitary-gonadal axis of pinealectomized and pineal-intact male rats.

Previous studies indicate that steroid hormones alter pineal biochemistry, and it has been suggested that at least part of the negative feedback effect of steroid hormones on pituitary gonadotropin release may be mediated by the pineal gland. In this study, pinealectomy did not alter the inhibitory effect of testosterone on neuroendocine-gonadal activity in the male rat, suggesting that the pineal gland does not mediate the response of the rat hypothalamic-pituitary axis to testosterone.     

Effects of photoperiod, temperature and testosterone-treatment on plasma T3 and T4 levels in the Djungarian hamster, Phodopus sungorus

The effects of photoperiod, temperature and testosterone treatment on plasma T3 and T4 levels were investigated in the Djungarian hamster. Plasma T3 level was affected by temperature (25 degrees C less than 7 degrees C) but not by photoperiod. Plasma T4 level was affected by photoperiod (short day less than long day) at 25 degrees C. Administration of testosterone increased plasma T4 level under short photoperiod at 25 degrees C. Thus, higher plasma T4 level under long photoperiod at 25 degrees C might be induced by testosterone.     

Trans-4-hydroxy-3-methoxycinnamic acid (ferulic acid) inhibits the effect of androgens on the rat prostate.

Trans-4-hydroxy-3-methoxycinnamic acid (ferulic acid, FA) antagonized the effect of exogenous androgens on the ventral prostate (VP) in castrated rats as well as the effect of endogenous androgens in intact rats. FA, however, had no effect on the seminal vesicles (SV) and levator ani muscle (LAM), nor oestrogenic effect in female rats and mice. FA did not antagonize the receptor binding of testosterone nor inhibit the conversion of testosterone into 5 alpha-dihydrotestosterone (DHT).     

Comparison of estradiol benzoate and dihydrotestosterone propionate with testosterone propionate on the induction of male-like sexual behavior in female sheep ovariectomized as adults]

Daily I/M injections of 200 microgram of oestradiol benzoate induce in female Sheep, ovariectomized as adults, male-like sexual reactions similar to what is obtained with 10 mg testosterone propionate per day. Simultaneously, a permanent female sexual receptivity is observed. Oestradiol benzoate at the dose of 20 microgram/day, and dihydrotestosterone propionate (10 mg/day) are both totally ineffective. The result support the hypothesis of the necessity of the aromatization of testosterone for the action on sexual behaviour.