PHOTOPERIODIC CONTROL OF GONADOTROPHIN SECRETION IN THE RAM: A DETAILED STUDY OF THE TEMPORAL CHANGES IN PLASMA LEVELS OF FOLLICLE-STIMULATING HORMONE, LUTEINIZING HORMONE AND TESTOSTERONE FOLLOWING AN ABRUPT SWITCH FROM LONG TO SHORT DAYS

1977 ◽  
Vol 74 (3) ◽  
pp. 355-367 ◽  
Author(s):  
G. A. LINCOLN ◽  
M. J. PEET
Keyword(s):  
Plasma Levels ◽  
Photoperiodic Response ◽  
Plasma Testosterone ◽  
Short Term ◽  
Artificial Lighting ◽  
Lighting Conditions ◽  
Gonadotrophin Secretion ◽  
Low Levels ◽  
Lh Rh ◽  
Short Days

SUMMARY Six adult Soay rams were housed under artificial lighting conditions of long days (16 h light: 8 h darkness) for 4 months and this caused the animals to lapse into a state of reproductive quiescence with low levels of gonadotrophins in the circulation and regressed testes secreting very low amounts of testosterone. The photoperiod was changed abruptly to short days (8 h light: 16 h darkness) to induce a resurgence of sexual activity, and a detailed study was made of the pituitary and testicular responses over the first 100 days. Plasma levels of LH and FSH first began to increase between days 6 and 12 of short days, and rose progressively until days 33–54 before declining again. Testicular growth of the rams began on days 19–26 and continued for most of the remaining period of study. Plasma testosterone levels rose in parallel with the growth of the testes, and were greatly increased by day 100 when gonadotrophin levels were reduced. At most stages there were short-term fluctuations in the plasma levels of FSH, LH and testosterone indicative of episodic secretion. Peaks in plasma levels of LH were especially conspicuous and from the changes in frequency and amplitude of these peaks it was possible to predict the way in which photoperiod influenced gonadotrophin secretion by its effect on hypothalamic LH-RH secretion. A slight 24 h rhythm in the plasma levels of all three hormones was observed, and the significance of this in relation to the photoperiodic response is discussed.

SEASONAL VARIATION IN THE EPISODIC SECRETION OF LUTEINIZING HORMONE AND TESTOSTERONE IN THE RAM

1976 ◽  
Vol 69 (2) ◽  
pp. 213-226 ◽  
Author(s):  
G. A. LINCOLN
Keyword(s):  
Plasma Testosterone ◽  
Domestic Sheep ◽  
Testis Size ◽  
Short Term ◽  
Artificial Lighting ◽  
Short Intervals ◽  
Lighting Conditions ◽  
Lh Releasing Hormone ◽  
Dynamic Interplay

SUMMARY Rams of an ancient breed of domestic sheep (Soay) were housed under artificial lighting conditions to study the way in which the secretion of LH and testosterone changes in relation to the mating season. Conspicuous changes were found in the short-term fluctuations in plasma LH concentrations related to the cycle of testis growth and regression; serial blood samples collected at short intervals revealed episodic peaks in plasma LH at all times, but there were changes in the frequency (lowest when the testes were regressed and highest when fully active), amplitude (lowest at the peak of testis activity, and highest during the developing phase), and duration of the peaks (shortest when the testes were regressed). In addition, the basal levels changed from being lowest in the regressed phase of the testis cycle, and highest when the gonads were most active. Plasma testosterone concentrations changed in parallel with the cycle of testis size and were correlated with the fluctuating levels of LH. Each episodic peak in plasma LH was associated with an increase in the level of testosterone, beginning after 0–30 min and rising to a peak at 60–90 min; the speed and magnitude of the response being greatest when the testes were largest, but was not correlated with the magnitude of the LH change. Injections of LH releasing hormone (5 μg) stimulated an increase in plasma LH and testosterone proportional to the endogenous fluctuations in the hormones at the various stages of the seasonal cycle; LH concentrations were raised to supra-physiological levels after the injections, while testosterone concentrations seldom exceeded the normal peak values at any stage. These observations are used to discuss the role of the hypothalamus in the control of male seasonality with emphasis on the dynamic interplay between the hypothalamus, pituitary and testis.

PHOTOPERIODIC MODULATION OF GONADOTROPHIN SECRETION IN CASTRATED JAPANESE QUAIL

1982 ◽  
Vol 92 (1) ◽  
pp. 73-83 ◽  
Author(s):  
H. F. URBANSKI ◽  
B. K. FOLLETT
Keyword(s):  
Japanese Quail ◽  
Plasma Levels ◽  
Time Course ◽  
Neural Mechanisms ◽  
Gonadal Steroids ◽  
Photoperiodic Control ◽  
Gonadotrophin Secretion ◽  
Lh Secretion ◽  
Sexually Mature ◽  
Short Days

Male Japanese quail were castrated when sexually immature and immediately exposed to one of the following stimulatory lighting regimes for 52 days: 11 h light: 13 h darkness/day (11L : 13D), 12L : 12D, 13L : 11D, 14L : 10D, 15L : 9D, 16L : 8D, 20L : 4D or 23L : 1D. One group was retained on short days (8L : 16D). Clearcut differences in the plasma levels of LH and FSH emerged between the various groups. Levels remained very low in castrated quail on 8L : 16D but were much greater in those on 14L : 10D, 15L : 9D, 16L : 8D, 20L : 4D and 23L : 1D, eventually becoming 15 to 20 times higher. Less pronounced castration responses developed on 13L : 11D, 12L : 12D or 11L : 13D. Alterations in photoperiod after day 52 caused an appropriate rise or fall in LH secretion. Photoperiodically induced suppressions were rapid, being highly significant within 4 days, but increases usually had a slower time course. When sexually mature quail (on 16L : 8D) were castrated and transferred to 8L : 16D they also exhibited a rapid suppression in LH secretion. Thus in quail, unlike some mammals, the photoperiodic control over gonadotrophin secretion is independent of the reproductive status of the animal at the time of castration. The results confirm the view that changes in sensitivity of the hypothalamo-pituitary axis to gonadal steroids are not a primary factor in the neural mechanisms underlying photoperiodism in quail.

LIGHT-INDUCED RHYTHMS OF PROLACTIN SECRETION IN THE RAM AND THE EFFECT OF CRANIAL SYMPATHECTOMY

1979 ◽  
Vol 91 (3) ◽  
pp. 421-427 ◽  
Author(s):  
G. A. Lincoln
Keyword(s):  
Prolactin Secretion ◽  
Plasma Prolactin ◽  
Hormone Concentration ◽  
Short Term ◽  
Seasonal Rhythms ◽  
Artificial Lighting ◽  
Long Term Changes ◽  
Cervical Ganglia ◽  
Short Days

ABSTRACT Four Soay rams cranially sympathectomised by removal of the superior cervical ganglia were housed alongside 4 control rams in an artificial lighting regime of alternating 16 week periods of short days (8L: 16D) and long days (16L: 8D) for 2 years. The variations in the plasma prolactin concentration revealed that while the control animals adjusted both the short term (diurnal) and long term (seasonal) rhythms in prolactin secretion in response to the changes in daylength, the ganglionectomised rams failed to respond. These sympathectomised animals continued to show long term changes in the circulating level of prolactin however and during the periods of hypersecretion a conspicuous diurnal rhythm in the hormone concentration was apparent.

PHOTOPERIODIC CONTROL OF SEASONAL BREEDING IN THE RAM: PARTICIPATION OF THE CRANIAL SYMPATHETIC NERVOUS SYSTEM

1979 ◽  
Vol 82 (1) ◽  
pp. 135-147 ◽  
Author(s):  
G. A. LINCOLN
Keyword(s):  
Nervous System ◽  
Sympathetic Nervous System ◽  
Reproductive Activity ◽  
Seasonal Breeding ◽  
Photoperiodic Control ◽  
Artificial Lighting ◽  
Lighting Conditions ◽  
Sympathetic Nervous ◽  
Cervical Ganglia ◽  
Short Days

SUMMARY Four mature Soay rams, cranially sympathectomized by removal of the superior cervical ganglia, were housed alongside four normal rams in controlled lighting conditions of alternating 16 week periods of short days of 8 h light: 16 h darkness (8L: 16D) and long days (16L: 8D). The changes in the concentration of FSH, LH, prolactin and testosterone in the plasma, the size of the testes, the intensity of the sexual flush and the sexual and aggressive behaviour of the animals were recorded. While the control rams were able to respond to the artificial lighting conditions with synchronized cycles of reproductive activity, the ganglionectomized animals failed to respond. The treated rams had well-developed testes and relatively high levels of gonadotrophins and testosterone in the blood throughout the experiment. It is concluded that the cranial sympathetic nervous system is involved in the photoperiodic control of seasonal breeding in the ram, probably through its role in the innervation of the pineal gland.

PITUITARY LH AND FSH AND TESTOSTERONE SECRETION IN INFANTS WITH UNDESCENDED TESTES

1977 ◽  
Vol 85 (3) ◽  
pp. 644-649 ◽  
Author(s):  
Jean-Claude Job ◽  
Dominique Gendrel ◽  
Anne Safar ◽  
Marc Roger ◽  
Jean-Louis Chaussain
Keyword(s):  
Leydig Cell ◽  
Plasma Levels ◽  
Leydig Cells ◽  
Plasma Testosterone ◽  
Normal Range ◽  
Undescended Testes ◽  
Cell Axis ◽  
Testosterone Secretion ◽  
Basal Plasma ◽  
Lh Rh

ABSTRACT Twelve male infants with undescended testes (5 bilaterally, 7 unilaterally) were studied between the ages of 1 week and 11 months. As in older pre-pubertal cryptorchid boys, a significant decrease of the LH response to LH-RH test was found, while basal plasma levels of gonadotrophins and FSH response to LH-RH were normal. Plasma testosterone levels were in the normal range, and Leydig cells responded to stimulation by HCG, the degree of this response being significantly and positively correlated to the LH peak elicited by LH-RH. It may be concluded that some early defect of the pituitary-Leydig cell axis is associated with undescended testes.

SEXUAL DIFFERENTIATION OF THE PHOTOPERIODIC RESPONSE IN JAPANESE QUAIL

1982 ◽  
Vol 92 (2) ◽  
pp. 279-282 ◽  
Author(s):  
H. F. URBANSKI ◽  
B. K. FOLLETT
Keyword(s):  
Japanese Quail ◽  
Sexual Differentiation ◽  
Plasma Levels ◽  
Photoperiodic Response ◽  
Breeding Cycle ◽  
Response System ◽  
Female Quail ◽  
The Difference ◽  
Short Days

Plasma levels of LH are generally higher in male than in female quail. This dimorphism was found to persist in quail which had been through a breeding cycle and then gonadectomized. Under long daylengths (12 h light: 12 h darkness (12L : 12D) or 16L : 8D) ovariectomized quail had plasma levels of LH that were 55–70% of those seen in castrated birds. The difference was reduced after transfer to short days (8L : 16D) when LH concentrations fell to basal levels, but again became more pronounced when the quail were restimulated with long photoperiods. Thus, the photoperiodic response system is sexually differentiated.

EFFECT OF LUTEINIZING HORMONE RELEASING HORMONE ON PLASMA LEVELS OF LUTEINIZING HORMONE, OESTRADIOL AND TESTOSTERONE IN THE MALE DOG

1976 ◽  
Vol 68 (3) ◽  
pp. 469-474 ◽  
Author(s):  
GWYNETH E. JONES ◽  
KAY BAKER ◽  
DIAN R. FAHMY ◽  
A. R. BOYNS
Keyword(s):  
Luteinizing Hormone ◽  
Plasma Levels ◽  
Plasma Testosterone ◽  
Progressive Decline ◽  
Luteinizing Hormone Releasing Hormone ◽  
Releasing Hormone ◽  
Lh Rh ◽  
Plasma Oestradiol

SUMMARY An injection of luteinizing hormone releasing hormone (LH-RH) increased plasma LH and testosterone concentrations in the male dog, but no significant increase in plasma oestradiol-17β levels was observed. Repeated injections of LH-RH produced an increase in plasma LH levels but there was a progressive decline in the response with each injection. The concentration of plasma testosterone reached a maximum within 40 min of the first injection of LH-RH and remained constant thereafter while plasma oestradiol concentration gradually increased with successive injections of LH-RH.

Effect of stress administered during pregnancy on the development of fetal testes and their subsequent function in the adult rat

1985 ◽  
Vol 107 (2) ◽  
pp. 241-245 ◽  
Author(s):  
I. Pollard ◽  
S. L. Dyer
Keyword(s):  
Plasma Testosterone ◽  
Adult Males ◽  
Critical Periods ◽  
Short Term ◽  
Plasma Progesterone ◽  
Adult Rat ◽  
Stressed Group ◽  
Gonadotrophin Secretion ◽  
Basal Plasma ◽  
Circulating Levels

ABSTRACT When maternal stress, containing a large anxiety component, was administered during pregnancy there was a significant decrease in 3β-hydroxysteroid dehydrogenase (3β-HSD) activity in the fetal testis from days 16 to 20 of gestation, but not at birth nor in the first week after birth. However, persistent effects were found in adult males of 90 days of age. Basal testosterone concentrations in both plasma and testes and testicular 3β-HSD activity were significantly lower whilst basal plasma progesterone concentrations were significantly higher in the stressed group. When the stressed offspring were subjected to short-term stress (one session), their plasma testosterone concentration was significantly below that of the controls. It is suggested that suppressed gonadotrophin secretion during critical periods of development alters fetal testicular function, and that raised circulating levels of stress-induced hormones such as β-endorphin may be responsible for changes in gonadotrophin secretion. J. Endocr. (1985) 107, 241–245

SEASONAL AND CIRCADIAN CHANGES IN THE EPISODIC RELEASE OF FOLLICLE-STIMULATING HORMONE, LUTEINIZING HORMONE AND TESTOSTERONE IN RAMS EXPOSED TO ARTIFICIAL PHOTOPERIODS

1977 ◽  
Vol 72 (3) ◽  
pp. 337-349 ◽  
Author(s):  
G. A. LINCOLN ◽  
M. J. PEET ◽  
R. A. CUNNINGHAM
Keyword(s):  
Plasma Levels ◽  
Activity Cycle ◽  
Maximum Size ◽  
Progressive Increase ◽  
Seasonal Development ◽  
Plasma Testosterone ◽  
Dark Phase ◽  
Blood Samples ◽  
Circadian Changes ◽  
Short Days

SUMMARY Six rams of an ancient breed of domesticated sheep (Soay) were subjected to an artificial light régime of alternating periods of long days (16 h light:8 h darkness) and short days (8 h light: 16 h darkness) which induced seasonal development and regression of the testes during a period of 36 weeks. Over 2000 blood samples were taken, and the changes in plasma levels of FSH, LH and testosterone were related to the cycle of testicular activity. During long days plasma levels of gonadotrophins became very low and the testes regressed to about 20% of their maximum size; there was a corresponding reduction in plasma testosterone levels. When the rams were returned to short days reproductive development was again stimulated after 2–3 weeks with a progressive increase in plasma FSH and LH levels and consequent hypertrophy of the testes. It took about 16 weeks of short days for testicular activity to become maximal. Blood samples collected at hourly intervals for 24 h on ten occasions during the study revealed transitory peaks in plasma FSH and LH levels indicative of episodic release. Changes in gonadotrophin secretion were modulated primarily by alterations in the frequency of episodic release; < 1 spike per 24 h during long days increased to a maximum of 10 spikes/24 h under short daylengths. The peaks of FSH release were of smaller amplitude than those of LH, although during periods of frequent episodic release basal levels of FSH were increased to a greater extent than those of LH. A circadian rhythm was observed in the plasma levels of FSH, LH and testosterone, which was related to increased gonadotrophin release during the dark phase of the 24 h cycle; changes in blood haematocrit were also observed. The circadian changes appeared to be correlated with the activity cycle of the animals which in turn was dictated by daylight. A possible interrelationship between the circadian cycle and the seasonal cycle is discussed.

LUTEINIZING HORMONE RELEASE IN ENTIRE AND CASTRATED RAMS FOLLOWING INJECTION OF SYNTHETIC LUTEINIZING HORMONE RELEASING HORMONE, AND EFFECT OF TESTOSTERONE PROPIONATE PRE-TREATMENT

1975 ◽  
Vol 64 (1) ◽  
pp. 7-16 ◽  
Author(s):  
D. B. GALLOWAY ◽  
J. PELLETIER
Keyword(s):  
Luteinizing Hormone ◽  
Peak Level ◽  
Plasma Testosterone ◽  
Total Response ◽  
Short Term ◽  
Luteinizing Hormone Releasing Hormone ◽  
Testosterone Treatment ◽  
Releasing Hormone ◽  
Lh Rh

SUMMARY Plasma luteinizing hormone (LH) levels and LH responses to intravenous administration of 100 μg luteinizing hormone releasing hormone (LH-RH) were studied in entire rams, long-term castrated animals (operation performed six months previously), long-term castrated animals treated with testosterone for the two preceding weeks and short-term castrated animals (castrated 3 h before LH-RH injection). LH was measured by radioimmunoassay in samples taken at 5 or 15 min intervals. Basal LH levels were lower in entire rams (0·9 ng/ml) than in long-term castrated animals (6·0 ng/ml). After LH-RH treatment the LH response was much smaller (peak level 9·6 ng/ml, total response 13·3 ng/ml/1 h) and slower (120 min to peak) in entire than in long-term castrated animals (peak level 61·8 ng/ml, total response 141·2 ng/ml/1 h, 29 min to peak). Testosterone treatment after long-term castration depressed the basal LH level and delayed the peak LH response after LH-RH to values similar to those for entire rams. After short-term castration the response to LH-RH was already as great (peak level 70·1 ng/ml, total response 133·6 ng/ml/1 h) as after long-term castration. The latency to peak LH level (82 min) was intermediate between that for untreated and testosterone-treated long-term castrated animals (130 min). Testosterone treatment was considered to have acted on the hypothalamus to depress basal levels. The results provided evidence for the presence of two inhibitory actions of the testis at the pituitary level in the ram: a qualitative delaying action of testosterone and a quantitative inhibitory action of the testis on LH release after LH-RH injection. The latter may also be related to plasma testosterone levels.

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