Maintaining a high physiological rate of testosterone secretion in the adult ram by estradiol immunoneutralization partially prevents testicular regression

1991 ◽  
Vol 71 (4) ◽  
pp. 1099-1109 ◽  
Author(s):  
Lee M. Sanford ◽  
Donna G. Leggee ◽  
Peter M. Melnyk
Keyword(s):  
Pulse Amplitude ◽  
Base Line ◽  
Testis Size ◽  
Testosterone Secretion ◽  
Scrotal Circumference ◽  
Testicular Regression ◽  
Testicular Recrudescence ◽  
Hypothalamic Pituitary Axis ◽  
A Minor ◽  
Sperm Output

The seasonal testicular cycle of 10 adult Dorset × Leicester × Suffolk rams was entrained to alternating 4-mo periods of long-inhibitory (16 h light) and short-stimulatory (8 h light) day lengths. Beginning in the third month of a short-day period, when the testes were fully redeveloped, five rams were passively immunized with a low titre (1:200) of estradiol antiserum for 13 wk. During this time the testes of the remaining (control) rams regressed almost completely. Estradiol immunoneutralization reliably maintained most characteristics of testosterone secretion (mean and base-line concentrations, and pulse amplitude) at "breeding season" values and had a minor but persistent effect on the hypothalamic–pituitary axis. When both the immunization period and the following 6 mo were considered, LH pulses were 50% larger in the immunized rams than in the control rams. Testicular regression was partially prevented in the immunized rams. However, their 1.5- to 1.7-cm larger scrotal circumference during most of the regression stage was not associated with a greater daily sperm output (based on sperm voided in urine) early in the redevelopment stage. Mean LH and FSH concentrations were increased by 200% in all rams during testicular recrudescence, and maximum testis size was achieved 1 mo earlier in the immunized rams than in the control rams. Immunization of rams against estradiol effectively maintained a high physiological rate of testosterone secretion, but was not able to prevent the normal decline in quantitative spermatogenesis. Key words: Estradiol immunoneutralization, testicular regression, testosterone, adult ram

Seasonal changes in the endocrine responsiveness of the pituitary and testes of male sheep in relation to their patterns of gonadotropic hormone and testosterone secretion

1984 ◽  
Vol 62 (7) ◽  
pp. 827-833 ◽  
Author(s):  
L. M. Sanford ◽  
B. E. Howland ◽  
W. M. Palmer
Keyword(s):  
Seasonal Changes ◽  
Testis Size ◽  
Gonadotropic Hormone ◽  
Testosterone Levels ◽  
Testosterone Secretion ◽  
Testicular Regression ◽  
Serum Hormone ◽  
Lh Release ◽  
Circulating Levels ◽  
Male Sheep

Pituitary and testicular endocrine responses to exogenous gonadotropin releasing hormone (GnRH) and luteinizing hormone (LH), respectively, were assessed for adult rams in an investigation of the regulation of seasonal changes in the patterns of episodic LH and testosterone secretion. Concurrent variations in testis size and in circulating levels of follicle stimulating hormone (FSH) and prolactin (PRL) were also examined. On 10 occasions throughout the year, serum hormone levels were assessed over 6- to 8-h periods during which time rams were left untreated (day 1) or were injected (iv) with single doses of either 10 μg synthetic GnRH (day 2) or 30 μg NIH-LH-S18 (day 3); blood samples were collected from the jugular vein at 10- or 20-min intervals. Testicular redevelopment during the summer, as indicated by increasing testis diameter measurements, was associated with increases in mean FSH level and was preceded by a springtime rise in mean PRL level; "spontaneously" occurring LH pulses and those produced in response to GnRH treatment were relatively large during this period. Increases in the magnitude of testosterone elevations in response to both endogenously and exogenously produced LH pulses occurred in August. Mean testosterone levels were elevated fourfold in the fall as a consequence of relatively frequent and small LH pulses stimulating a more responsive testis to produce more frequent and larger testosterone elevations; endogenous LH pulses, however, did not appear to stimulate the testes maximally at this time. Testicular regression occurred during the winter months and was characterized initially by decreases in testosterone levels without obvious changes in the pattern of pulsatile LH release and subsequently by a decrease in testicular responsiveness to relatively infrequent LH pulses which led to further decreases in testosterone levels and smaller testes. Results demonstrate that alterations in pituitary and testicular responsiveness to stimulatory hormones account in part for seasonal changes in the magnitude of LH and testosterone secretory pulses in adult rams.

Increases in testosterone secretion in adult rams with immunoneutralization of endogenous estradiol occur in the absence of increases in pulsatile LH release or testicular LH receptors

1989 ◽  
Vol 120 (2) ◽  
pp. 180-186 ◽  
Author(s):  
Lee M. Sanford
Keyword(s):  
Binding Sites ◽  
Cell Function ◽  
Passive Immunization ◽  
Serum Testosterone ◽  
Experimental Period ◽  
Pulse Amplitude ◽  
Testicular Biopsy ◽  
Binding Activity ◽  
Testosterone Secretion ◽  
Lh Release

Abstract. The testes of the ram become more responsive to LH stimulation following immunoneutralization of endogenous estradiol. The possibility that testosterone secretion is facilitated by increased LH-binding activity in the testes was investigated in the present study conducted with adult Dorset × Leicester × Suffolk rams during the time of testicular recrudescence. Patterns of episodic LH release and testosterone secretion (days –5, 10 and 24) and LH-binding activity in testicular biopsy samples (days –1, 14 and 28) were assessed on the days indicated relative to the onset of passive immunization and the establishment of relatively low titres (~1:200) of estradiol antiserum. During the experimental period, mean serum testosterone concentration increased by approximately 150% for the immunized rams as basal concentration and pulse amplitude increased, while all characteristics of testosterone secretion remained unchanged for the nonimmunized rams. Characteristics of LH release and the concentration of LH-binding sites in the testes, however, were always similar for both groups of rams. Further, group differences in FSH and PRL secretion and in the concentration of testicular FSH-binding sites did not occur. These results provide evidence for an estradiol direct (gonadotropin independent) negativefeedback component in the regulation of Leydig cell function in the ram.

scholarly journals INFLUENCE OF SEASON AND SOCIAL ENVIRONMENT ON THE REPRODUCTIVE-ENDOCRINE STATUS OF THE ADULT LANDRACE BOAR

1990 ◽  
Vol 70 (1) ◽  
pp. 121-128 ◽  
Author(s):  
V. L. TRUDEAU ◽  
L. M. SANFORD
Keyword(s):  
Social Environment ◽  
Late Summer ◽  
Pulse Amplitude ◽  
Pulse Frequency ◽  
Social Environments ◽  
Blood Samples ◽  
Testosterone Secretion ◽  
Endocrine Status ◽  
Reproductive Endocrine ◽  
Basal Concentration

Seasonal variations in LH, FSH, and testosterone secretion were investigated for adult Landrace boars housed in different social environments for 1 yr. Socially nonrestricted boars (n = 4) were penned adjacent to ovariectomized gilts that were hormonally brought into estrus every 2 wk, while socially restricted boars (n = 4) were kept in pens with solid walls. Mean hormone concentrations were determined from the assay of single AM and PM blood samples collected from the jugular vein by venipuncture once a month. In November, February, May and August, blood samples were collected serially over 12 h from jugular catheters for assessment of pulsatile LH and testosterone secretion, and the LH response to a GnRH injection (1 μg kg−1 body weight). Mean LH and testosterone concentrations were relatively high in all boars during the late summer and fall, and often were greater for the socially nonrestricted versus the restricted boars (group × month), P < 0.05) in the winter (December and January). Mean FSH concentration also varied with month (P < 0.05). Pulse analysis indicated that higher mean testosterone concentrations in November and August were the result of increases (month, P < 0.05) in testosterone-pulse frequency and basal concentration. Maximal mean LH concentration in August was associated with maximal (month, P < 0.05) LH-pulse amplitude and basal concentration. The amplitude of the LH peak following GnRH injection increased (P < 0.05) between November and May, and remained high in August. Key words: Gonadotropins, testosterone, blood, season, social environment, boar

scholarly journals Biometric testicular and serum testosterone concentration of Brazilian Ponies stallions

2017 ◽  
Vol 18 (1) ◽  
pp. 204-210
Author(s):  
Miguel Alejandro Silva RUA ◽  
Celia Raquel QUIRINO ◽  
Wilder Hernando Ortiz VEJA ◽  
Aylton BARTHOLAZZI JUNIOR ◽  
Rosemary BASTOS ◽  
...  
Keyword(s):  
Analysis Of Variance ◽  
Rio De Janeiro ◽  
Reproductive Potential ◽  
Serum Testosterone ◽  
Testicular Volume ◽  
Testis Size ◽  
Testosterone Concentration ◽  
Important Trait ◽  
Sperm Output ◽  
Janeiro State

SUMMARY Evaluation of the testis size is very important in stallions’ selection, since it is an indirect determinant of their reproductive potential. The aim of this study was to evaluate the biometric testicular traits, calculate the volume testicular and analyze the serum testosterone concentration of the stallion. During six months were measured the tests of adults Brazilian Ponies stallions from northern of Rio de Janeiro State, Brazil. The length, the width and the height of the testicles (TL, TW and TH) were measured. From these measurements, the total testicular volume (TTV) was calculated. The serum testosterone concentration was also evaluated. The data were studied by analysis of variance and were calculated the correlations among the traits. The average of the testis biometry were TL 5.8 ± 0.6 cm; TW 3.8 ± 0.5 cm; TH 4.7 ± 0.4 cm and 111.2 ± 27.7 for TTV. Mean of serum testosterone concentration was 0.89 ± 0.52 ng/dl. High correlations between biometry testicular traits with testicular volume were observed and low to moderate correlations were observed for testicular traits, testosterone and sperm output. The testis size could be an important trait that assists to the prediction of stallion's reproductive potential of the Brazilian ponies stallions. It is suggested that there would be no fluctuation in serum testosterone concentration in Brazilian ponies stallions that coult afect on its fertility.

Exercise inhibits reproductive quiescence induced by exogenous melatonin in hamsters

1988 ◽  
Vol 255 (5) ◽  
pp. R718-R723 ◽  
Author(s):  
D. R. Pieper ◽  
K. T. Borer ◽  
C. A. Lobocki ◽  
D. Samuel
Keyword(s):  
Luteinizing Hormone ◽  
Reproductive System ◽  
Voluntary Exercise ◽  
Melatonin Secretion ◽  
Gonadotropin Secretion ◽  
Estrous Cycles ◽  
Exogenous Melatonin ◽  
Serum Luteinizing Hormone ◽  
Testicular Regression ◽  
Testicular Recrudescence

Voluntary exercise inhibits the reproductive regression associated with a short photoperiod in male or female hamsters. The question addressed by the present study was whether exercise would also attenuate the reproductive regression associated with injection of exogenous melatonin. In male hamsters exercise inhibited the testicular regression, decline in gonadotropin secretion, and reduction in testosterone release associated with two daily injections (15 micrograms) of melatonin in pinealectomized hamsters on long days. After the reproductive system of the sedentary melatonin group had regressed, one-half of these hamsters were placed in cages with exercise wheels. Access to the exercise wheels stimulated testicular recrudescence and restored gonadotropin secretion to levels found in vehicle-injected hamsters. Sedentary female hamsters injected with melatonin tended to go into a state of constant diestrus associated with daily afternoon increases in serum luteinizing hormone, whereas most exercising hamsters injected with melatonin generally continued having regular estrous cycles with proestrus luteinizing-hormone surges. The ability of exercise to inhibit the effect of exogenous melatonin in pinealectomized hamsters suggests that exercise acts, at least in part, by mechanisms other than altering melatonin secretion.

scholarly journals Prolactin regulation of testosterone secretion and testes growth in DLS rams at the onset of seasonal testicular recrudescence

Reproduction ◽  
2010 ◽  
Vol 139 (1) ◽  
pp. 197-207 ◽  
Author(s):  
L M Sanford ◽  
S J Baker
Keyword(s):  
Peripheral Blood ◽  
Entire Period ◽  
Testosterone Levels ◽  
Testosterone Secretion ◽  
Testicular Recrudescence ◽  
The Times ◽  
Transition Stages

Our objective was to test the hypothesis that prolactin (PRL) acts at both the pituitary and testis levels to regulate testosterone secretion in the adult ram. The focus was on the mid-regression to mid-redevelopment stages of a photoperiod-condensed ‘seasonal’ testicular cycle. DLS rams (six per group) were given daily s.c. injections of bromocriptine (4 mg) or vehicle during the entire period. Serum PRL concentration in control rams peaked at 103.4±22.1 ng/ml in late regression and then steadily declined (P<0.01) to 19.5±4.3 ng/ml, whereas PRL in treated rams was always ≤4.0 ng/ml. Suppression of PRL tended (P<0.10) to increase the amplitude of natural LH pulses (transition stages) or reduce the number of LH receptors in the testis (regressed stage), although neither change disturbed testosterone levels in peripheral blood. These subtle changes were accompanied by significant (P<0.05) alterations in the capability of the pituitary to release LH (85% more) and of the testes to secrete testosterone (20% less). These effects of PRL were unmasked when rams were given highly stimulative i.v. injections of GNRH (single 3 μg dose) and NIH-oLH-S24 (three 5 μg doses given 20 min apart) respectively. PRL insufficiency also appeared to slow down the ‘seasonal’ rise in FSH secretion and slightly delayed (2 weeks) the times when the testes began to grow and were first significantly (P<0.05) enlarged from the regressed state. We conclude that PRL is an important part of the intricate regulation of the pituitary–gonadal system in moderately seasonal DLS rams.

Enhanced testosterone secretion in adult rams after establishment of a high-frequency, low-amplitude pattern of LH pulses in the nonbreeding season occurs without changes in the number or binding affinity of testicular LH receptors

1990 ◽  
Vol 122 (1) ◽  
pp. 55-61 ◽  
Author(s):  
Lee M. Sanford ◽  
Susan J. Baker
Keyword(s):  
Binding Affinity ◽  
Binding Sites ◽  
High Frequency ◽  
Leydig Cells ◽  
Jugular Vein ◽  
Pulse Amplitude ◽  
Nonbreeding Season ◽  
Testosterone Secretion ◽  
Low Amplitude ◽  
Amplitude Pattern

Abstract When the LH signal in the ram is changed from one of large and infrequent pulses to one of small and frequent pulses, the testes quickly become more responsive to LH and testosterone secretion is elevated, perhaps because the number and (or) binding affinity of testicular LH receptors have increased. An experiment was undertaken in the nonbreeding season (July) with 10 adult Dorset × Leicester × Suffolk rams that were about 3.5 years of age and 69 ± 2 kg in body weight. Rams were given injections into the jugular vein of either 5 μg NIH-LH-S24 (in 1 ml saline) or vehicle every 80 min for 6 days. LH treament produced a series of LH pulses that occurred three times more frequently and were 70% less in amplitude than pulses in the control rams, without causing mean LH concentration to increase. Endogenously produced LH pulses were not evident in the treated rams after LH injection began. The modified LH-pulse pattern elevated mean testosterone concentration by 150% (assessed on days 2 and 5), and caused the cumulative testosterone response to LH pulses, estimated by multiplying testosterone-pulse amplitude by frequency per 6 h, to increase progressively by 180% (days −2 through 5). Enhanced testicular steroidogenic activity, presumably due to greater enzymatic activity and cholesterol availability within Leydig cells, was not associated with increases in either the concentration or affinity of LH-binding sites in the testis (assessed on days 3 and 6).

scholarly journals TESTICULAR SIZE AND SPERM OUTPUT IN HOLSTEIN-FRIESIAN AND N'DAMA BULLS

2021 ◽  
Vol 10 ◽  
pp. 114-118
Author(s):  
L. N. Nwakalor ◽  
B. I. Orji
Keyword(s):  
Body Weight ◽  
Testicular Volume ◽  
Regression Equations ◽  
Scrotal Circumference ◽  
Holstein Friesian ◽  
Testicular Size ◽  
Sperm Output ◽  
The Relationship ◽  
Artificial Vagina

Records collected over a period of four months from October 1978 to January 1979 from four Holstein-Friesian and four N'dama hulls, were used to study the relationship between testicular size and sperm output. Semen samples were collected from the bulls twice a week using the artificial vagina and non-oestrous female teasers. The means (± s.e.) of testicular measurements for Holstein-Friesian and N'danta, respectively, were 35.6 ± 1.8 and 7.9 ± 0.3cm. for scrotal cir­cumference, 12.6 ± 0.3 and 7.7 ± 0.8cm for testis length, 6.7 ± 0.3 and 3.7 ± 0.2em for testis diameter. Calculated mean testicular volumes were 296.8 I 22.2 and 57.4 ± 10.1m1 respectively for Holstein-Friesian and N'dama bulls. T-he mean total sperm per ejaculate were 8.80 t 3.045 x 109 for (be Holstein-Friesian and 3.03 ± 0.905 x 109 for the N'dama bulls. Simple correla­tions for Holstein-Friesian and N'damn in the same order, were between body weight and scrotal dr. rumference 0.49 and 0.66, body weight and sperm output/einculate 0.48 and 0.88, scrotal cir­cumference and testicular volume 0.74 and 0.60. scrotal circumference and sperm outpuilejactilete 0.18 and 0.69, and testicular volume and sperm out­put/ejaculate —.45 and 0.84. Regression equations for predicting sperm oat­put/ejaculate from testicular volume are given as Y = .13.458 — .031 X and Y' = - .650 + 0,038 x respectively, for holstein-Friesian and N'dania bulls.

SEASONAL VARIATION IN CIRCULATING GONADOTROPIN AND TESTOSTERONE LEVELS AND IN TESTIS SIZE OF YEARLING RAMS DURING AND SUBSEQUENT TO IMMUNONEUTRALIZATION OF ESTRADIOL OR TAMOXIFEN TREATMENT IN THE NONBREEDING SEASON

1987 ◽  
Vol 67 (2) ◽  
pp. 391-404 ◽  
Author(s):  
LEE M. SANFORD
Keyword(s):  
Endocrine Function ◽  
Tamoxifen Treatment ◽  
Feedback Signal ◽  
Testis Size ◽  
Testosterone Levels ◽  
Nonbreeding Season ◽  
Lh Pulsatility ◽  
17Β Estradiol ◽  
Hypothalamic Pituitary Axis ◽  
Baseline Levels

Seasonal variations in endocrine function and testis size with manipulation of the estrogen negative-feedback signal were assessed for yearling rams. Groups of three rams were passively immunized against estradiol-17β (estradiol) or injected with the antiestrogen tamoxifen (30 mg d−1) for 8 wk (July and August). In comparison with a group of four control rams, seasonal changes in many reproductive parameters were different for treated rams (group × period, P < 0.01). Immunized rams had higher mean LH levels at weeks 2 and 8, and higher baseline levels of LH and more frequent releases at week 8. Mean testosterone levels were increased between weeks 4 and 8 to values that were twice those of the breeding season as a consequence of higher baseline levels and larger episodic secretions. This was not associated with enhanced testicular regrowth, although regression in early winter occurred at a faster rate. Estradiol immunoneutralization was also associated with elevated levels of FSH. Tamoxifen had an inhibitory estrogen-like action on the hypothalamic-pituitary axis. Treatment suppressed LH pulsatility consistently and lowered testosterone to near undetectable values during the first 4 wk; this was associated with progressive decreases in testis size which were reversed with cessation of treatment. During the last month of tamoxifen treatment, the magnitude of the LH and FSH responses to exogenous GnRH was reduced. Key words: Estrogen immunization, tamoxifen, testosterone, gonadotropins, testis, ram

scholarly journals An Essential Role for Insulin and IGF1 Receptors in Regulating Sertoli Cell Proliferation, Testis Size, and FSH Action in Mice

2013 ◽  
Vol 27 (5) ◽  
pp. 814-827 ◽  
Author(s):  
Jean-Luc Pitetti ◽  
Pierre Calvel ◽  
Céline Zimmermann ◽  
Béatrice Conne ◽  
Marilena D. Papaioannou ◽  
...  
Keyword(s):  
Signaling Pathway ◽  
Essential Role ◽  
Testis Size ◽  
Sperm Production ◽  
Igf System ◽  
Igf1 Receptor ◽  
Sperm Output ◽  
And Function ◽  
Igf Signaling

Abstract Testis size and sperm production are directly correlated to the total number of adult Sertoli cells (SCs). Although the establishment of an adequate number of SCs is crucial for future male fertility, the identification and characterization of the factors regulating SC survival, proliferation, and maturation remain incomplete. To investigate whether the IGF system is required for germ cell (GC) and SC development and function, we inactivated the insulin receptor (Insr), the IGF1 receptor (Igf1r), or both receptors specifically in the GC lineage or in SCs. Whereas ablation of insulin/IGF signaling appears dispensable for GCs and spermatogenesis, adult testes of mice lacking both Insr and Igf1r in SCs (SC-Insr;Igf1r) displayed a 75% reduction in testis size and daily sperm production as a result of a reduced proliferation rate of immature SCs during the late fetal and early neonatal testicular period. In addition, in vivo analyses revealed that FSH requires the insulin/IGF signaling pathway to mediate its proliferative effects on immature SCs. Collectively, these results emphasize the essential role played by growth factors of the insulin family in regulating the final number of SCs, testis size, and daily sperm output. They also indicate that the insulin/IGF signaling pathway is required for FSH-mediated SC proliferation.

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