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 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.

Possible role of prolactin in the inhibitory effect of testosterone on the hypothalamic-pituitary-testicular axis in the rat

1985 ◽  
Vol 105 (3) ◽  
pp. 423-427 ◽  
Author(s):  
J. A. F. Tresguerres ◽  
L. F. Perez Mendez ◽  
A. Lopez-Calderon ◽  
A. I. Esquifino
Keyword(s):  
Inhibitory Effect ◽  
Plasma Testosterone ◽  
Plasma Prolactin ◽  
Intact Male ◽  
Testosterone Levels ◽  
Basal Plasma ◽  
Male Wistar Rats ◽  
Lh Releasing Hormone ◽  
Acute And Chronic Treatments

ABSTRACT To study the role of testosterone on the regulation of the hypothalamic-pituitary-testicular axis, young intact male Wistar rats were given acute (24 h) or chronic (5 days) subcutaneous treatments of 500 μg testosterone propionate (TP) or vehicle alone. Plasma LH, prolactin and testosterone levels were measured both basally and after administration of LH-releasing hormone (LHRH) or human chorionic gonadotrophin (hCG) by means of specific radioimmunoassay systems using materials supplied by the NIADDK. After acute treatment with TP there was an increase in basal plasma testosterone concentrations and no modification in the hCG response when compared with vehicle-treated animals. No difference could be detected in basal plasma testosterone levels after the chronic treatment, but a significant reduction in the hCG response was observed. Both acute and chronic treatments with TP resulted in a significant decrease of basal plasma LH levels. A reduced LH response to LHRH in acutely treated rats and no response in the chronically treated rats was detected. Plasma prolactin levels showed an increase after both acute and chronic treatments. To evaluate the possible role of the increased plasma prolactin levels on the above modifications during TP treatment, another group of animals was treated with TP and bromocriptine (dopamine agonist) simultaneously to avoid the increase in plasma prolactin levels. In this situation, neither basal plasma LH levels nor the response to LHRH were altered when compared to vehicle-treated rats; a normal testosterone response to hCG stimulation was observed in spite of the high basal plasma testosterone levels. All these observations suggest that increased prolactin levels may exert a modulatory role on the negative feedback effect of testosterone both at the testicular and central levels. J. Endocr. (1985) 105, 423–427

Prolonged exposure to ethylene stimulates the negative gravitropic responses of Arabidopsis inflorescence stems and hypocotyls

2002 ◽  
Vol 29 (8) ◽  
pp. 989 ◽  
Author(s):  
Bingwen Lu ◽  
Ho Yan Yu ◽  
Lai Kwan Pei ◽  
Man Yu Wong ◽  
Ning Li
Keyword(s):  
Prolonged Exposure ◽  
Plant Tissues ◽  
Wild Type ◽  
Inhibitory Effects ◽  
Short Term ◽  
Gravitropic Response ◽  
Inflorescence Stems ◽  
Opposing Effects ◽  
Dynamic Interplay

The actual effect of ethylene on shoot gravitropic response has been controversial. To elucidate the role of ethylene in the modulation of shoot gravitropic response, Arabidopsis inflorescences and light-grown seedlings were pretreated with 0.1-10 -1 of ethylene for either a long (12-48 h) or short term (0.5 h). When the gravicurvature was measured either in air or in ethylene, it was found that prolonged exposure to various levels of ethylene stimulated both inflorescence stem and hypocotyl gravicurvature in air, while the continued presence of ethylene immediately following reorientation of plant tissues inhibited gravicurvature of both tissues. Both stimulatory and inhibitory effects existed in inflorescence stems and hypocotyls when the plant tissues were exposed to a chosen concentration of ethylene. Stimulation by ethylene was stronger than its inhibition in inflorescence stems, while the reverse was true for the hypocotyls. Therefore, the continued presence of high levels of naturally produced ethylene in eto1-1 did not suppress the faster gravicurvature of inflorescence stems, whereas the removal of exogenously applied ethylene was necessary to observe faster gravicurvature of both the wild-type and eto1-1 hypocotyls. Both effects acted through the known ethylene receptor complex. These results strongly suggest that ethylene of a chosen concentration has opposing effects on the negative gravitropic responses of both inflorescence stems and hypocotyls. The ultimate negatively gravitropic behaviour of a plant tissue, when exposed to ethylene, depends on the dynamic interplay between these two opposing effects.

Daily illuminance levels affect pituitary prolactin in male rats

1989 ◽  
Vol 120 (4) ◽  
pp. 429-434 ◽  
Author(s):  
Maija-Liisa Laakso ◽  
Tarja Porkka-Heiskanen ◽  
Aino Alila ◽  
Susanna Kajander ◽  
Dag Stenberg ◽  
...  
Keyword(s):  
Serum Levels ◽  
Causative Factor ◽  
Male Rats ◽  
Adaptation Period ◽  
Artificial Lighting ◽  
Natural Lighting ◽  
Lighting Conditions ◽  
Illuminance Level ◽  
Pituitary Prolactin

Abstract. The 24-h patterns of melatonin, PRL, and gonadotropins in male rats maintained under natural lighting conditions have been found to differ from the patterns in rats kept under artificial lighting. In the present experiments we studied the role of different daily illuminances as a possible causative factor for the variation of the hormonal patterns. Three groups of male rats were kept under artificial lighting conditions (12 h on/12 h off), where the daily illuminance was 550, 110 or 25 lux. After a 7-day adaptation period the pineal content of melatonin, the serum levels of LH, FSH and PRL, and the pituitary content of these hormones were measured by RIAs in samples taken at 10.00, 13.00, 22.00 and 01.00 h. The patterns of pineal melatonin were equal in all three groups. The variation of daily illuminance did not change the serum levels of LH, FSH and PRL or the pituitary content of the gonadotropins. However, the pituitary content of PRL during the light phase was inversely related to the illuminance. The results suggest that the intensity of daily lighting in the studied range does not affect the patterns of melatonin or gonadotropins, but the synthesis of prolactin may be significantly regulated by the daily illuminance level.

Role of affect in short-term memory for paired associates.

1968 ◽  
Vol 78 (3, Pt.1) ◽  
pp. 494-501 ◽  
Author(s):  
Calvin F. Nodine ◽  
James H. Korn
Keyword(s):  
Short Term Memory ◽  
Short Term ◽  
Term Memory ◽  
Paired Associates

The capacity of short term memory from an evolutionary perspective

2019 ◽  
Author(s):  
Majid Manoochehri
Keyword(s):  
Short Term Memory ◽  
Memory Span ◽  
Critical Role ◽  
Experimental Studies ◽  
Cognitive System ◽  
Evolutionary Approach ◽  
Evolutionary Perspective ◽  
Short Term ◽  
Term Memory

Memory span in humans has been intensely studied for more than a century. In spite of the critical role of memory span in our cognitive system, which intensifies the importance of fundamental determinants of its evolution, few studies have investigated it by taking an evolutionary approach. Overall, we know hardly anything about the evolution of memory components. In the present study, I briefly review the experimental studies of memory span in humans and non-human animals and shortly discuss some of the relevant evolutionary hypotheses.

Impact of FII’s and FDI’s on Indian Stock Market

2016 ◽  
Vol 1 (1) ◽  
Author(s):  
Dr. Kamlesh Kumar Shukla
Keyword(s):  
Stock Market ◽  
Financial Markets ◽  
Global Economy ◽  
Short Term ◽  
Earnings Growth ◽  
The Past ◽  
Bull Market ◽  
Indian Stock Market

FIIs are companies registered outside India. In the past four years there has been more than $41 trillion worth of FII funds invested in India. This has been one of the major reasons on the bull market witnessing unprecedented growth with the BSE Sensex rising 221% in absolute terms in this span. The present downfall of the market too is influenced as these FIIs are taking out some of their invested money. Though there is a lot of value in this market and fundamentally there is a lot of upside in it. For long-term value investors, there’s little because for worry but short term traders are adversely getting affected by the role of FIIs are playing at the present. Investors should not panic and should remain invested in sectors where underlying earnings growth has little to do with financial markets or global economy.

Introduction: Kinship Bereavement in Later Life

1997 ◽  
Vol 35 (1) ◽  
pp. 1-7 ◽  
Author(s):  
Brian De Vries
Keyword(s):  
Adult Child ◽  
Later Life ◽  
Short Term ◽  
Traumatic Grief ◽  
Death Of A Parent ◽  
De Vries ◽  
Longitudinal Effects ◽  
Analysis Of Variation

This article introduces a volume devoted to the examination of later-life bereavement: an analysis of variation in cause, course, and consequence. Six articles address and represent this variation and comprise this volume: 1) Prigerson et al. present case histories of the traumatic grief of spouses; 2) Hays et al. highlight the bereavement experiences of siblings in contrast to those spouses and friends; 3) Moss et al. address the role of gender in middle-aged children's responses to parent death; 4) Bower focuses on the language adopted by these adult children in accepting the death of a parent; 5) de Vries et al. explore the long-term, longitudinal effects on the psychological and somatic functioning of parents following the death of an adult child; and 6) Fry presents the short-term and longitudinal reactions of grandparents to the death of a grandchild. A concluding article is offered by de Vries stressing both the unique and common features of these varied bereavement experiences touching on some of the empirical issues and suggesting potential implications and applications.

Role of Nitric Oxide in Short-term and Prolonged Effects of Angiotensin II on Renal Hemodynamics

Hypertension ◽  
1996 ◽  
Vol 27 (5) ◽  
pp. 1173-1179 ◽  
Author(s):  
Xiaolin Deng ◽  
William J. Welch ◽  
Christopher S. Wilcox
Keyword(s):  
Nitric Oxide ◽  
Angiotensin Ii ◽  
Renal Hemodynamics ◽  
Short Term

Literalism and Moral Status

2018 ◽  
Author(s):  
Carrie Figdor
Keyword(s):  
Moral Status ◽  
Moral Standing ◽  
Short Term ◽  
Long Run ◽  
Moral Boundaries ◽  
Psychological Capacities

Chapter 9 presents the idea that Literalism undermines current social and moral boundaries for moral status. Possession of psychological capacities, moral standing, and respectful treatment are a standard package deal. So either many more beings enjoy moral status than we now think, or the relative superiority of human moral status over other beings is diminished. It introduces the role of psychological ascriptions in drawing social and moral boundaries by examining dehumanization and anthropomorphism. It argues that in the short term Literalism does not motivate us to do more than make minor adjustments to current moral boundaries. We can distinguish the kinds of psychological capacities that matter for moral status from the kinds that best divide nature at its joints. In the long run, however, Literalism prompts us to reconsider the anthropocentric standards that govern current moral boundaries.

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