Changes In Testicular Size Research Articles

Determinants of the annual pattern of reproduction in mature male Merino and Suffolk sheep: modification of responses to photoperiod by an annual cycle in food supply.

Rams of a 'Mediterranean breed' (Merino) and a 'temperate breed' (Suffolk) were compared to determine how much of the differences between their reproductive seasons is owing to variation in their responses to photoperiodic and nutritional cues. In a previous study, both nutritional and photoperiodic inputs were held constant, and it was found that the two breeds show similar endogenous rhythms and, when the animals are challenged with a Mediterranean photoperiodic cycle, these endogenous rhythms are similarly modified. The present study tested whether an annual cycle in the supply of forage might modify the patterns that are generated by the interaction between photoperiod and endogenous rhythms. Both breeds were subjected to a simulated 'Mediterranean' annual cycle in photoperiod (10L:14D to 14D:10L) and provided with either constant food supply or a simulated 'Mediterranean' annual cycle in food supply. In Merino rams, testicular growth responded to photoperiod, but nutrition dominated those responses. In Suffolk rams, changes in testicular size can be completely out of phase with changes in body mass because they are driven primarily by photoperiod, with only subtle responses to changes in diet. The cycle of testicular growth in the Suffolk was driven by changes in the secretion of gonadotrophins (follicle-stimulating hormone concentrations and luteinizing hormone pulse frequency). By contrast, in the Merino, the nutritionally driven seasonal cycle of testicular growth was associated primarily with changes in body mass and this relationship could not always be explained by changes in gonadotrophin secretion. Melatonin secretion was not affected by food supply. Thus, the 'Mediterranean' and 'temperate' genotypes have similar endogenous rhythms that are similarly modified by photoperiod but, with respect to seasonal changes in nutrition, they differ in both the nature of their reproductive response and the physiological mechanisms that mediate those responses.

Aspects of reproduction in the eastern rufous mouse lemur (Microcebus rufus) and their implications for captive management

AbstractThe eastern rufous mouse lemur is one of the smallest primate species. It inhabits the eastern rain forest of Madagascar. Its reproductive biology has not been examined because of its rarity in laboratories. We present the first data on reproduction and variation in reproductive success from a breeding colony of wild‐caught Microcebus rufus. The eastern rufous mouse lemur shows a seasonal change in testicular size and in the occurrence of estrus. Females had 2.5 cycles (range, one to four) per season. The estrous cycle length was 59 days (range, 51–66), the duration of vaginal opening during estrus was 7.5 days (range, 5–8), receptivity occurred on the third day of estrus, gestation length was 56.5 days (range, 56–57), litter size was two neonates (range, one to three). The frequency and duration of mating behavior varied widely among the pairs. Copulation seemed to occur on a single day per estrus within the first to fourth hour after light change to red light. In four cases (three pairs), copulation lasted between 15 and 240 seconds. Breeding success can be increased by choosing mates carefully. Microcebus rufus seems to be a seasonal breeder like its sibling species Microcebus murinus. In wild‐caught animals, males seemed to adapt quickly (first season) to the conditions of captivity, whereas in the females, individual variation (first to third season) in reproductive activity was observed. Air humidity of >60% seems to facilitate the breeding success in wild‐caught pairs. First pregnancy and successful rearing of offspring occurred in the second and fourth year of captivity in two of three females. Wild‐caught eastern rufous mouse lemurs seemed to demonstrate variation in adapting to the conditions of captivity with regard to sex and individuality. Zoo Biol 20:157–167, 2001. © 2001 Wiley‐Liss, Inc.

Testicular damage after surgical groin exploration for elective herniorrhaphy

Background/Purpose: Controversy exists whether to explore the contralateral groin in boys during unilateral herniorrhaphy. Proponents claim there is minimal risk of injury to the cord structures and developing testicle with contralateral exploration. However, findings have shown testicular atrophy occurred in 1% to 2% of patients after herniorrhaphy, and vasal damage is possible after routine manipulation of the spermatic cord. This study investigated the effect of routine surgical exploration of the prepubertal groin on testicular development and future fertility.Methods: Twenty-four prepubertal Wistar rats were divided equally into 2 groups. Group 1 (sham) rats underwent unilateral inguinoscrotal incision only. Group 2 (experimental) rats underwent unilateral inguinoscrotal exploration with manipulation of the cord structures as in human inguinal exploration. At maturation, the fertility and fecundity of the males were assessed. After mating, testes were examined for mass, volume, mean seminiferous tubule diameter (MSTD), and mean testicular biopsy score (MTBS). The vasa were examined for histological injury and vasal diameter. Statistical comparisons were made by paired t test and Mann-Whitney rank sum test.Results: There was a difference between the volumes of the testes when comparing the operative and nonoperative side of the 2 groups (experimental, Δvol = −0.063 ± 0.123; sham, Δvol = +0.067 ± 0.137; P = .029). There also was a trend toward a smaller testicular mass when comparing the two sides (experimental, Δmass = −0.045 ± 0.101; sham, Δmass = +0.048 ± 0.123; P= .057) but did not reach significance. The MSTD and MTBS were similar between the ipsilateral and contralateral testes in both groups. Likewise, the MSTD and MTBS were similar when comparing the 2 groups. All male rats in both groups were fertile. The number of offspring produced and the number of female rats impregnated were similar between the 2 groups. There was no histological evidence of vasal injury in any of the experimental spermatic cords. The vasal diameters were similar between the 2 groups.Conclusion: Surgical manipulation of the prepubertal spermatic cord imparts a small, but statistically significant morphological change in testicular size without a deleterious effect on testicular development, fertility, or fecundity.

Seasonal changes in day-light intensity as a potential zeitgeber of circannual rhythms in equatorial Stonechats

The annual rhythms of reproduction and molt of equatorial Stonechats in East Africa (Saxicola torquata axillaris) are controlled by an endogenous circannual rhythmicity. This has been demonstrated in previous experiments in which birds from Africa were kept in a seasonally constant environment: the annual cycles of gonadal size and molt were found to persist for up to 10 years. Since in such constant environmental conditions the period of the rhythms tended to deviate from 12 months, we postulate that seasonally changing factors in the normal environment of these birds normally synchronize the rhythms with the natural year. In the present study we examined the possibility that annual variations in daytime light intensity that occur as a result of changing cloud cover associated with the dry and rainy seasons may provide a circannual zeitgeber. An experimental group consisting of 6 male Stonechats was kept for 25 months in a light-dark cycle in which the light period had a constant duration of 12.5 hours and an intensity alternating between high and low in a 300-day rhythm. Changes in testicular size and molt of these birds were compared with those of a control group of 6 birds that were exposed to the same photoperiod but with bright daylight throughout the experiment. In the control group, only one bird went through 2 testicular cycles and two birds went through one cycle. All these birds showed a molt rhythm, but periods were highly variable among individuals. In contrast, all experimental birds went through two testicular cycles and exhibited rather synchronous molt rhythms (Fig. 1). These findings support the hypothesis that changing light intensity during daytime may provide synchronizing stimuli for circannual rhythms. Nevertheless, premature conclusions should be avoided; possible shortcomings of the experiment are discussed.

Peripuberal sexual development of pantaneiro stallions

Pantaneiro horses are a breed native to flood plains of Brazil, where they thrive with little human interference. The aims of this study were to characterize age-associated changes in testicular size, serum testosterone and sexual behavior and to determine age at puberty as well as to evaluate daily sperm production in the Pantaneiro stallion. After weaning the males were kept in bachelor groups away from the females, in a separated area in the natural environment of flood plains. Infantile period ended at approximately 14.4 mo of age. Sexual interest and breeding capability first appeared between the ages of 15.6 to 27.5 mo. The transition from prepuberal to postpuberal histological stage, occurred at approximately 27.8 mo of age. All animals were in the postpuberal period at 38.5 mo of age. Daily sperm production estimated with testicle homogenate, at 38.5 mo of age was low (1.4603 ± 0.48X10 9 sperm) and serum testosterone levels were similar to adult levels by 27.8 mo. In conclusion the 2 y old Pantaneiro stallions showed full sexual behavior and had adult testosterone levels, but at this age, the stage of development of the seminiferous epithelium was variable and the efficiency of sperm production was still low.

Effects of nutrition on testicular growth in mature Merino rams actively immunized against GnRH

Nutrition-induced changes in testicular size in Merino rams appear to involve both GnRH-dependent and -independent pathways. This hypothesis was tested by feeding mature Merino rams that had been actively immunized against BSA or GnRH conjugated to BSA a diet that maintained initial body weight or the same diet supplemented daily with 1.5 kg of lupin grain. Blood was sampled every 20 min for 24 h on days-1, 19 and 70 relative to the change in diet. The plasma was used to assess the effects of treatments on changes in LH, FSH and testosterone concentrations. In the group immunized against BSA, FSH increased in lupin-supplemented rams compared with maintenance-fed rams, while LH and testosterone were not affected by diet. In comparison, the concentrations of LH, FSH and testosterone were significantly lower in the group immunized against GnRH than in rams immunized against BSA, but none of these endocrine variables was affected by nutrition. With both immunization treatments, the testes were significantly larger in lupin-supplemented than in maintenance-fed rams. In the group immunized against BSA, this difference was caused by testicular growth in lupin-supplemented rams, whereas in the group immunized against GnRH, lupin supplementation effectively maintained testicular mass, rather than allowed the regression observed in maintenance-fed rams. In conclusion, differences in testicular growth that were induced by dietary treatments in rams immunized against GnRH were not associated with changes in gonadotrophin or testosterone secretion. This supports the hypothesis that part of the effect of nutrition on testicular growth is independent of changes in GnRH secretion. The differences in testicular size observed in control rams were of similar magnitude to those observed in treated rams, but associated with large differences in plasma FSH concentrations, suggesting that this hormone plays an important role in this effect.

Androstenedione and Testosterone Levels in Peripheral Plasma of Male Shiba Goats during Development.

Developmental changes in testicular size and plasma androgen levels in male Shiba goats were studied during 2-12 months of age. Scrotal circumference increased rapidly until 5 months of age (18.6±0.9 cm; mean±SEM). Plasma androstenedione and testosterone reached peak levels of 0.23-0.50 ng/ml and 5.47-9.69 ng/ml, respectively as testicular size increased, and then showed a tentative decline with nadirs of 0.01-0.04 ng/ml and 0.26-0.94 ng/ml, respectively after full growth in testicular size. The fluctuation of androstenedione was in parallel with that of testosterone but the androstenedione levels were only 1-10% those of testosterone. Thus, the results indicated that testosterone was the predominant androgen starting from 2-3 months of age through puberty in male Shiba goats.

Seasonal changes in LH, androgens and testes in the male Angora goat

Six adult Angora bucks, housed under natural photoperiod for 15 months in a temperate southern hemisphere environment, were examined for seasonal changes in testicular size and secretion of LH and androgens. The pattern of testicular growth and regression lagged behind the photoperiod by 9 weeks over which time the continuing development due to maturation of the animals was superimposed. The seasonal secretion of androgens was parallel to, but lagged behind, the photoperiod by 16 weeks. Blood sampling over 24 hours every second month revealed that the mean LH and androgens levels were respectively 47 and 876% higher in March than at their lowest levels at the end of the breeding season (July), and the secretion of both hormones remained low from July to January. There appeared to be no diurnal pattern for the secretion of either hormone at any time of the year.

Seasonal changes in testicular size, plasma testosterone concentration and body weight in captive flying foxes (Pteropus poliocephalus and P. scapulatus)

Adult male flying foxes Pteropus poliocephalus and P. scapulatus were captured in south-east Queensland and kept in outdoor enclosures. Testicular size (TS), plasma testosterone concentrations (PTC) and body weight (BW) were measured over 1-year periods. Testicular recrudescence in P. poliocephalus began before the summer solstice and TS was greatest during mid-March (autumn) and lowest from July to September. Large increases in PTC were observed in all individuals approximately 1 month after the peak in TS. BW also increased around the time of the mating season, changes being correlated significantly with changes in TS. Mating occurred between April and June, and births from late October to late November. In P. scapulatus, TS was greatest in the spring (October) and least in the autumn (February to May); PTC fluctuated throughout the year in this species but, unlike P. poliocephalus, did not show a single large increase in the mating season. BW showed a similar seasonal pattern to that seen in P. poliocephalus, being greatest at the time of greatest TS. Mating occurred in October to November, and births in autumn. In captivity, in outdoor enclosures, these species maintained the seasonal reproductive patterns observed in the wild. The 2 species respond differently to the same environmental cues in terms of regulation of the timing of their breeding seasons.

Thyroxine treatment induces changes in hypothalamic gonadotrophin-releasing hormone characteristic of photorefractoriness in starlings ( Sturnus vulgaris)

Photosensitive intact male starlings were transferred from short days (8L: 16D) to 11 L:13D for 16 weeks, and were therefore sexually mature. Experimental groups were (i) held under 11L:13D and given exogenous thyroxine dissolved in the drinking water for 6 weeks or (ii) given thyroxine for 6 weeks and then transferred from 11L:13D to long days (18L:6D) for a further 6 weeks, while control groups were transferred to long days (18L:6D) either (iii) for 6 or (iv) for 12 weeks, or were (v) maintained under 11L:13D throughout. Changes in testicular size and plumage molt were monitored at regular intervals during the 12-week period. At the end of the experiment, the birds were killed and hypothalamic gonadotropin-releasing hormone (Gn-RH) content and testicular mass were measured. Treatment with exogenous thyroxine caused rapid testicular regression followed by plumage molt, and after 6 weeks hypothalamic Gn-RH content was much reduced, to an even greater extent than that in control birds exposed to long days for 6 weeks. After 6 weeks of thyroxine treatment, withdrawal of exogenous thyroxine and exposure to long days for a further 6 weeks caused no increase in testicular size, and caused a further reduction in hypothalamic Gn-RH content to a level similar to that in controls after 12 weeks of exposure to long days. The results confirm previous findings that thyroxine induces a state of photorefractoriness in sexually mature starlings and show for the first time that the treatment mimics the effect of long days in reducing Gn-RH content in the hypothalamus.

Pharmacological doses of thyroxine simulate the effects of increased daylength, and thyroidectomy, decreased daylength on the reproductive system of European starlings

AbstractIntact male starlings, thyroidectomized male starlings, and intact male starlings treated chronically with pharmacological doses of L‐thyroxine were kept on four different daylengths, 8 hr of light : 16 hr of darkness per day (8L : 16D), 9.5L : 14.5D, 11L : 13D, or 13L : 11D. Changes in testicular size, molt, and plasma thyroxine concentrations were monitored for 18 weeks. In all three treatments, initial testicular growth rates increased with daylength. On all four daylengths, treatment with thyroxine increased initial testicular growth rates above those of intact birds. Thyroidectomy decreased testicular growth rate on 13L : 11D. Intact birds on 13L : 11D, and thyroxine‐treated birds on 13L : 11D, 11L : 13D, and some on 9.5L : 14.5D, became photorefractory and molted. The results demonstrate that treatment with thyroxine simulates a long day and, conversely, that thyroidectomy simulates a short day. This may be due to an effect on the photoperiodic clock. However, the changes in plasma thyroxine concentration necessary for this far exceed the normal physiological range. Thus, photoperiodically induced changes in reproductive function are not mediated by thyroxine.

Extragonadal Germ Cell Tumor: The Preoperative Urological Evaluation

Primary extragonadal germ cell tumors were diagnosed in 4 patients in whom surgical or postmortem examination of the testis failed to reveal germ cell tumor. A fifth patient underwent serial examination with testicular ultrasound without evidence of any abnormalities and he remains free of disease following chemotherapy. Based on our experience and a literature review, it is our opinion that orchiectomy is not indicated unless there is a palpable testicular abnormality, recent change in testicular size or consistency, abnormal testicular ultrasound or history of cryptorchidism, or if the primary tumor is choriocarcinoma.

Seasonal changes in testicular size and in plasma follicle-stimulating hormone and prolactin concentrations in thyroidectomized male and thyroidectomized castrated starlings ( Sturnus vulgaris)

Testicular size and plasma concentrations of FSH and prolactin were measured frequently in thyroidectomized male and thyroidectomized castrated starlings kept in outdoor aviaries during 1 year. In thyroidectomized males, testes increased from minimal to maximal size during March, remained large until June, and then decreased slowly during the next 6 months. Plasma FSH increased to a peak in April (126 μg/litre) and then declined slightly. Plasma FSH in thyroidectomized castrates was very high (360–760 μg/litre) and did not change significantly during the year. In both groups of birds, plasma prolactin concentration remained low (<5 μg/litre) and there was no molt. These results demonstrate that while thyroidectomy prevents the onset of photorefractoriness in starlings, short days nevertheless cause gonadal regression. However, this regression is not analogous to the short-day-induced gonadal regression shown by species, such as quail, which do not exhibit absolute photorefractoriness.

An angiographic study of the fox testis in various stages of sexual activity.

The arteries and veins of the fox testis were studied using an angiographic technique. The postnatal development of the testis involved only minor modification of the vasculature. In the non-breeding season both the arteries and veins of the adult fox testis undergo extensive spiralization which completely disappears during the breeding season. When the sequence of morphological changes in blood vessels are related to available data on changes in testicular size, blood flow and connective tissue content, it is obvious that the vascular spiralization is passive and related to shrinkage of the organ and dose not primarily influence the testicular blood flow.

Hormonal changes in puberty. I. Correlation of serum luteinizing hormone and follicle stimulating hormone with stages of puberty, testicular size, and bone age in normal boys.

Extract: The concentration of luteinizing hormone (LH) and follicle stimulating hormone (FSH) in serum was determind using a double antibody radioimmunoassay method in each of 106 normal boys aged 5-16 years. The boys were grouped according to the stage of puberty (P1-P5) using the classification of TANNER. The serum LH and FSH, LH/FSH ratio, and testicular volume index (TVI) for boys prepuberty (P1) and at different stages of puberty (P2-P5) are shown in figure l and table. The mean value of LH in prepubertal boys was 4.2 ng/ml, which steadily rose to a concentration of 5.3 ng/ml at P4-5. The differences between the values for LH in early puberty (P2) and at a more advanced stage of puberty (P4-5) were statistically significant. The mean value for serum FSH in the prepubertal boy was 1.4 ng/ml. Serum FSH rose steadily through the early stages of puberty (P1-P3) with no further rise from P3 to P4-5. These changes were reflected in the LH/FSH ratio which fel between P1 and P2, but increased between P2 and P4. Tesricular size (TVI) showed a gradual increase from P1 through P4-5. A comparison of serum LH and FSH, LH/FSH ratio. and TVI with chronological age is indicated in table II. A slight increase in the mean levels of serum LH and FSH was observed from age 9 to age 12 with a continued rise to 15 years and older. Serum LH and FSH was obsereved from age 9 to age 12 with a continued rise to 15 years and older. Serum LH seemed to rise at an earlier age than serum FSH. The TVI showed a definite increase from chronologic age 8 through 11. A pronounced change in testicular size from age 11 through 15 was observed during the period of sharp rise in serum FSH. The correlation of bone age with concentrations of LH and FSH in serum, LH/FSH ratio, and TVI is shown in table III. A significant rise in LH was seen in boys with a bone age of 9-10 years, with a further increase at a bone age of 13-15 years and older. Serum FSH showed a steady increment from a bone age of 11 to 14 years. The most pronounced increase in TVI was seen at a bone age of 11 through 15 years. The relation of concerntrations of LH and FSH in serum and LH/FSH ratio to the TVI is presented in table IV. Mean LH and FSH showed a gradual rise from a TVI of <2 to 10.1-12. Serum LH rose and serum FSH fell, however, with the increase in TVI from 10.1-12 to 12.1-16. In four patients with chromatin-positive seminiferous tubular dysgenesis (Klinefelter's syndrome), the mean serum LH concentration was 11.3 ng/ml and the mean serum FSH concerntration was 21.6 ng/ml. The mean serum LH in 14 patients with multiple pituitary hormone deficiencies was 2.1 ng/ml and the mean serum FSH was 1.5 ng/ml. The small diffrences in the concentration of LH and FSH in prepubertal boys compared with that observed in children with hypopituitarism stress the need for further definition of the sensitivity of the assay for serum samples. The serum values reported are of relative not absolute significance. Speculation: The detection of serum FSH and LH prior to puberty, and the increase in serum FSH and LH coincident with advancing puberty suggests 1) that the hypothalamic-pituitary-testicular axis is functional befor puberty, and 2) that the onset of puberry may be associated with a change in sensitivity of the hypothalamus to feedback by testicular steriods.