The Experts below are selected from a list of 264 Experts worldwide ranked by ideXlab platform

M D Calderón - One of the best experts on this subject based on the ideXlab platform.

  • Stress induced changes in Testis Function.
    The Journal of steroid biochemistry and molecular biology, 1991
    Co-Authors: A López-calderón, C Ariznavarreta, M I González-quijano, J A Tresguerres, M D Calderón
    Abstract:

    The mechanism through which chronic stress inhibits the hypothalamic-pituitary-testicular axis has been investigated. Chronic restraint stress decreases testosterone secretion, an effect that is associated with a decrease in plasma gonadotropin levels. In chronically stressed rats there was a decrease in hypothalamic luteinizing hormone-releasing hormone (LHRH) content and the response on plasma gonadotropins to LHRH administration was enhanced. Thus the inhibitory effect of chronic stress on plasma LH and FSH levels seems not to be due to a reduction in pituitary responsiveness to LHRH, but rather to a modification in LHRH secretion. It has been suggested that beta-endorphin might interfere with hypothalamic LHRH secretion during stress. Chronic immobilization did not modify hypothalamic beta-endorphin, while an increase in pituitary beta-endorphin secretion was observed. Since we cannot exclude that changes in beta-endorphin secreted by the pituitary or other opioids may play some role in the stress-induced decrease in LHRH secretion, the effect of naltrexone administration on plasma gonadotropin was studied in chronically stressed rats. Naltrexone treatment did not modify the decrease in plasma concentrations of LH or FSH. These findings suggest that the inhibitory effect of restraint on the testicular axis is exerted at hypothalamic level by some mechanism other than opioids.

  • Stress induced changes in Testis Function
    The Journal of Steroid Biochemistry and Molecular Biology, 1991
    Co-Authors: A López-calderón, C Ariznavarreta, M I González-quijano, J A Tresguerres, M D Calderón
    Abstract:

    Abstract The mechanism through which chronic stress inhibits the hypothalamic-pituitary-testicular axis has been investigated. Chronic restraint stress decreases testosterone secretion, an effect that is associated with a decrease in plasma gonadotropin levels. In chronically stressed rats there was a decrease in hypothalamic luteinizing hormone-releasing hormone (LHRH) content and the response on plasma gonadotropins to LHRH administration was enhanced. Thus the inhibitory effect of chronic stress on plasma LH and FSH levels seems not to be due to a reduction in pituitary responsiveness to LHRH, but rather to a modification in LHRH secretion. It has been suggested that β-endorphin might interfere with hypothalamic LHRH secretion during stress. Chronic immobilization did not modify hypothalamic β-endorphin, while an increase in pituitary β-endorphin secretion was observed. Since we cannot exclude that changes in β-endorphin secreted by the pituitary or other opioids may play some role in the stress-induced decrease in LHRH secretion, the effect of naltrexone administration on plasma gonadotropin was studied in chronically stressed rats. Naltrexone treatment did not modify the decrease in plasma concentrations of LH or FSH. These findings suggest that the inhibitory effect of restraint on the testicular axis is exerted at hypothalamic level by some mechanism other than opioids.

Luiz R Franca - One of the best experts on this subject based on the ideXlab platform.

  • Foxn1 and Prkdc genes are important for Testis Function: evidence from nude and scid adult mice
    Cell and Tissue Research, 2020
    Co-Authors: Carolina Fa Oliveira, Luiz R Franca, Nathália Lm Lara, Samyra Msn Lacerda, Rodrigo R Resende, Gleide F Avelar
    Abstract:

    Mutations in Foxn1 and Prkdc genes lead to nude and severe combined immunodeficiency (scid) phenotypes, respectively. Besides being immunodeficient, previous reports have shown that nude mice have lower gonadotropins and testosterone levels, while scid mice present increased pachytene spermatocyte (PS) apoptosis. Therefore, these specific features make them important experimental models for understanding Foxn1 and Prkdc roles in reproduction. Hence, we conducted an investigation of the testicular Function in nude and scid BALB/c adult male mice and significant differences were observed, especially in Leydig cell (LC) parameters. Although the differences were more pronounced in nude mice, both immunodeficient strains presented a larger number of LC, whereas its cellular volume was smaller in comparison to the wild type. Besides these alterations in LC, we also observed differences in androgen receptor and steroidogenic enzyme expression in nude and scid mice, suggesting the importance of Foxn1 and Prkdc genes in androgen synthesis. Specifically in scid mice, we found a smaller meiotic index, which represents the number of round spermatids per PS, indicating a greater cell loss during meiosis, as previously described in the literature. In addition and for the first time, Foxn1 was identified in the Testis, being expressed in LC, whereas DNA-PKc (the protein produced by Prkdc ) was observed in LC and Sertoli cells. Taken together, our results show that the changes in LC composition added to the higher expression of steroidogenesis-related genes in nude mice and imply that Foxn1 transcription factor may be associated to androgen production regulation, while Prkdc expression is also important for the meiotic process.

  • slow increase of sertoli cell efficiency and daily sperm production causes delayed establishment of full sexual maturity in the rodent chinchilla lanigera
    Theriogenology, 2009
    Co-Authors: Marcelo C Leal, Luiz R Franca
    Abstract:

    Abstract Puberty in the male Andean rodent Chinchilla lanigera occurred ∼3 mo after birth, whereas full sexual maturity was established much later. The objective of the present study was to investigate Testis Function in postpubertal chinchillas, with an emphasis on the estimation of seminiferous epithelium cycle length ( n  = 6) and Sertoli cell (SC) and spermatogenic efficiencies ( n  = 26). Samples of testes were collected between May and November. Each spermatogenic cycle lasted 10.2 d and the total duration of spermatogenesis was ∼46 d. The SC efficiency (spermatids/SC) and the daily sperm production per Testis gram increased markedly ( P P  > 0.05) from 5 to 30 mo. Therefore, efficiency of the spermatogenic process increased equally during all phases of spermatogenesis. In conclusion, based on the gradual and striking postpubertal increases for SC and sperm production, we inferred that more undifferentiated spermatogonia and/or spermatogonial stem cells were produced and therefore, that the chinchilla might represent a good experimental model to investigate regulation of this crucial aspect of spermatogenesis.

  • Testis morphometry duration of spermatogenesis and spermatogenic efficiency in the wild boar sus scrofa scrofa
    Biology of Reproduction, 2006
    Co-Authors: Fernanda F L Almeida, Marcelo C Leal, Luiz R Franca
    Abstract:

    Abstract The wild boar is a natural inhabitant of Europe, Asia, and North Africa and is phylogenetically the ancestor of the domestic pig. Because of its phylogenetic and economic importance, this species is an interesting model for studying Testis Function in boars. Therefore, the present study was performed to investigate the Testis structure, spermatogenic cycle length, and Sertoli cell (SC) and spermatogenic efficiencies in eight adult wild boars. Each spermatogenic cycle lasted 9.05 days, and the total duration of spermatogenesis was estimated as lasting approximately 41 days. The percentages of Testis volume occupied by seminiferous tubules and by Leydig cells were 87% and 6%, respectively. The mean number of SCs per gram of Testis was 42 million. The SC (round spermatids per SC) and spermatogenic (daily sperm production per gram of Testis) efficiencies were 6.6 cells and 28.6 million, respectively. In general, the Testis structure, overall germ cell associations at the different stages of the semin...

Marcelo C Leal - One of the best experts on this subject based on the ideXlab platform.

  • Zebrafish primary Testis tissue culture: An approach to study Testis Function ex vivo
    General and comparative endocrinology, 2009
    Co-Authors: Marcelo C Leal, Paul P. De Waal, Ángel García-lópez, Shi Xi Chen, Jan Bogerd, Rüdiger W. Schulz
    Abstract:

    To develop new tools to study the regulation of Testis physiology in teleost fish, a medium-term ex vivo organ culture system was adopted for zebrafish Testis tissue. The addition of 100 nM 11-ketotestosterone to the system supported complete spermatogenesis, as determined by morphological, molecular and immunohistochemical analyses. Under basal conditions, however, the development of differentiated spermatogonia, spermatocytes, and spermatids was seriously disturbed, probably related to the rapid (within 2 days) down-regulation of the steroidogenic system. Forskolin (0.5 μM) stimulated acute androgen release from freshly removed tissue and partially prevented down-regulation of the steroidogenic system. The present ex vivo culture system can serve as a tool to evaluate effects of a wide range of substances on the two main Functions of the Testis, spermatogenesis and hormone production.

  • slow increase of sertoli cell efficiency and daily sperm production causes delayed establishment of full sexual maturity in the rodent chinchilla lanigera
    Theriogenology, 2009
    Co-Authors: Marcelo C Leal, Luiz R Franca
    Abstract:

    Abstract Puberty in the male Andean rodent Chinchilla lanigera occurred ∼3 mo after birth, whereas full sexual maturity was established much later. The objective of the present study was to investigate Testis Function in postpubertal chinchillas, with an emphasis on the estimation of seminiferous epithelium cycle length ( n  = 6) and Sertoli cell (SC) and spermatogenic efficiencies ( n  = 26). Samples of testes were collected between May and November. Each spermatogenic cycle lasted 10.2 d and the total duration of spermatogenesis was ∼46 d. The SC efficiency (spermatids/SC) and the daily sperm production per Testis gram increased markedly ( P P  > 0.05) from 5 to 30 mo. Therefore, efficiency of the spermatogenic process increased equally during all phases of spermatogenesis. In conclusion, based on the gradual and striking postpubertal increases for SC and sperm production, we inferred that more undifferentiated spermatogonia and/or spermatogonial stem cells were produced and therefore, that the chinchilla might represent a good experimental model to investigate regulation of this crucial aspect of spermatogenesis.

  • Testis morphometry duration of spermatogenesis and spermatogenic efficiency in the wild boar sus scrofa scrofa
    Biology of Reproduction, 2006
    Co-Authors: Fernanda F L Almeida, Marcelo C Leal, Luiz R Franca
    Abstract:

    Abstract The wild boar is a natural inhabitant of Europe, Asia, and North Africa and is phylogenetically the ancestor of the domestic pig. Because of its phylogenetic and economic importance, this species is an interesting model for studying Testis Function in boars. Therefore, the present study was performed to investigate the Testis structure, spermatogenic cycle length, and Sertoli cell (SC) and spermatogenic efficiencies in eight adult wild boars. Each spermatogenic cycle lasted 9.05 days, and the total duration of spermatogenesis was estimated as lasting approximately 41 days. The percentages of Testis volume occupied by seminiferous tubules and by Leydig cells were 87% and 6%, respectively. The mean number of SCs per gram of Testis was 42 million. The SC (round spermatids per SC) and spermatogenic (daily sperm production per gram of Testis) efficiencies were 6.6 cells and 28.6 million, respectively. In general, the Testis structure, overall germ cell associations at the different stages of the semin...

A López-calderón - One of the best experts on this subject based on the ideXlab platform.

  • Stress induced changes in Testis Function.
    The Journal of steroid biochemistry and molecular biology, 1991
    Co-Authors: A López-calderón, C Ariznavarreta, M I González-quijano, J A Tresguerres, M D Calderón
    Abstract:

    The mechanism through which chronic stress inhibits the hypothalamic-pituitary-testicular axis has been investigated. Chronic restraint stress decreases testosterone secretion, an effect that is associated with a decrease in plasma gonadotropin levels. In chronically stressed rats there was a decrease in hypothalamic luteinizing hormone-releasing hormone (LHRH) content and the response on plasma gonadotropins to LHRH administration was enhanced. Thus the inhibitory effect of chronic stress on plasma LH and FSH levels seems not to be due to a reduction in pituitary responsiveness to LHRH, but rather to a modification in LHRH secretion. It has been suggested that beta-endorphin might interfere with hypothalamic LHRH secretion during stress. Chronic immobilization did not modify hypothalamic beta-endorphin, while an increase in pituitary beta-endorphin secretion was observed. Since we cannot exclude that changes in beta-endorphin secreted by the pituitary or other opioids may play some role in the stress-induced decrease in LHRH secretion, the effect of naltrexone administration on plasma gonadotropin was studied in chronically stressed rats. Naltrexone treatment did not modify the decrease in plasma concentrations of LH or FSH. These findings suggest that the inhibitory effect of restraint on the testicular axis is exerted at hypothalamic level by some mechanism other than opioids.

  • Stress induced changes in Testis Function
    The Journal of Steroid Biochemistry and Molecular Biology, 1991
    Co-Authors: A López-calderón, C Ariznavarreta, M I González-quijano, J A Tresguerres, M D Calderón
    Abstract:

    Abstract The mechanism through which chronic stress inhibits the hypothalamic-pituitary-testicular axis has been investigated. Chronic restraint stress decreases testosterone secretion, an effect that is associated with a decrease in plasma gonadotropin levels. In chronically stressed rats there was a decrease in hypothalamic luteinizing hormone-releasing hormone (LHRH) content and the response on plasma gonadotropins to LHRH administration was enhanced. Thus the inhibitory effect of chronic stress on plasma LH and FSH levels seems not to be due to a reduction in pituitary responsiveness to LHRH, but rather to a modification in LHRH secretion. It has been suggested that β-endorphin might interfere with hypothalamic LHRH secretion during stress. Chronic immobilization did not modify hypothalamic β-endorphin, while an increase in pituitary β-endorphin secretion was observed. Since we cannot exclude that changes in β-endorphin secreted by the pituitary or other opioids may play some role in the stress-induced decrease in LHRH secretion, the effect of naltrexone administration on plasma gonadotropin was studied in chronically stressed rats. Naltrexone treatment did not modify the decrease in plasma concentrations of LH or FSH. These findings suggest that the inhibitory effect of restraint on the testicular axis is exerted at hypothalamic level by some mechanism other than opioids.

Paolo Vitti - One of the best experts on this subject based on the ideXlab platform.

  • effects of radioiodine treatment for differentiated thyroid cancer on Testis Function
    Clinical Endocrinology, 2015
    Co-Authors: D Canale, Claudia Ceccarelli, Carolina Caglieresi, Agnese Moscatelli, Silvia Gavioli, P Santini, Rossella Elisei, Paolo Vitti
    Abstract:

    SummaryObjective To evaluate the effects of radioactive iodine (RAI) treatment for differentiated thyroid cancer (DTC) on Testis Function. Design A prospective longitudinal single-centre study was performed. A comprehensive andrological evaluation including hormonal assessment, semen analysis and scrotal ultrasound was undertaken in male patients undergoing RAI treatment for DTC. Methods Hormonal assessment of FSH, LH, testosterone (T), sperm concentration and motility and Testis volume were determined in 20 patients in basal conditions, 6 and 12 months after RAI. Results were analysed in the whole group of patients and then separately in those who received one single ablative treatment (‘Single’ group, n = 10) and those who received multiple treatments (‘Multiple’ group, n = 10). Results In basal conditions, 3 of 20 (15%) patients had a reduced sperm count and belonged to the ‘Multiple’ group. After RAI, an increase of FSH (8·8 ± 1·2 UI/l vs 5·2 ± 1·2, P < 0·005) and a decrease in sperm concentration (28·8 ± 7·7 millions/ml vs 54·5 ± 7·1, P < 0·005) and Testis volume (15·2 ± 3·1 vs 13·7 ± 0·8 ml, P < 0·005) occurred at 6 months in the whole group. One year after RAI, seven patients had oligozoospermia (five from the ‘Multiple’ group and two from the ‘Single’ group). Permanent impairment of one or more Testis Function parameters was observed in patients who underwent multiple RAI treatments: 50% for sperm count, 40% for FSH levels and Testis volume and, respectively, in 20 and 10% of those who received one single RAI treatment. Conclusions The single ablative RAI treatment in cancer patients is better tolerated respect multiple RAI treatments regard Testis Function. Multiple treatments for recurrent or metastatic disease may cause a permanent impairment of one or more parameters related to the reproductive potential of male patients.

  • Effects of radioiodine treatment for differentiated thyroid cancer on Testis Function
    Clinical endocrinology, 2014
    Co-Authors: D Canale, Claudia Ceccarelli, Carolina Caglieresi, Agnese Moscatelli, Silvia Gavioli, P Santini, Rossella Elisei, Paolo Vitti
    Abstract:

    SummaryObjective To evaluate the effects of radioactive iodine (RAI) treatment for differentiated thyroid cancer (DTC) on Testis Function. Design A prospective longitudinal single-centre study was performed. A comprehensive andrological evaluation including hormonal assessment, semen analysis and scrotal ultrasound was undertaken in male patients undergoing RAI treatment for DTC. Methods Hormonal assessment of FSH, LH, testosterone (T), sperm concentration and motility and Testis volume were determined in 20 patients in basal conditions, 6 and 12 months after RAI. Results were analysed in the whole group of patients and then separately in those who received one single ablative treatment (‘Single’ group, n = 10) and those who received multiple treatments (‘Multiple’ group, n = 10). Results In basal conditions, 3 of 20 (15%) patients had a reduced sperm count and belonged to the ‘Multiple’ group. After RAI, an increase of FSH (8·8 ± 1·2 UI/l vs 5·2 ± 1·2, P