The quantification of testicular cells during the postnatal development in two Caviomorph rodents: the guinea pig (Cavia porcellus) and the cutia (Dasyprocta agouti)

ABSTRACT The germinative, Sertoli and Leydig cells of two caviomorph rodents (Cavia porcellus and Dasyprocta agouti) were counted as well as the estimation of the total volume of the testis and the total volume of seminiferous tubules and interstitium in prepubertal, pubertal and adult animals. The number of spermatogonia, spermatocytes and spermatids cells increased during the pubertal phase in both rodents, notably the spermatid cells. The spermatocyte and spermatid slightly decreased in the adult of both rodents, but the increment in spermatogonia cells number was seen, mainly in cutias. The number of Sertoli cells increased in pubertal rodents, but in the adult the number reduced. Substantial number of Leydig cells was counted in pubertal and adult guinea pigs. In cutias, the number of Leydig cells increased in pubertal phase and decline in adults. The design-based stereological method has proven to be unbiased and reliable to be applied in reproduction studies.

Morphometry of leydig cells in the collared peccary (Tayassu tajacu) / Morfometria das células de leydigem catetos (Tayassu tajacu)

This work aimed to determine total and individual volume of Leydigcells, leydigosomatic index and the number of Leydig cells per testisand per gram of testis in the collared peccary (Tayassu tajacu). Testeswere collected from sexually mature collared peccaries, destined forcommercial slaughter. Total and individual volumes of Leydig cellswere 2.02 ml and 1,202.74 x 10-12 ml, respectively. The leydigosomaticindex was 0.022%, and the number of Leydig cell per testis and pergram of testis was 1.7 billion and 92.12 million, respectively. Theseresults show that morphometric characteristics of Leydig cells incollared peccaries are similar to average results observed for most ofthe mammalian species studied.

Objetivou-se com esta pesquisa determinar o volume total e individual das células de Leydig, o índice leydigossomático e o número de células de Leydig por testículo e por grama de testículo em catetos. Utilizaram-se testículos de 10 catetos sexualmente maturos, destinados ao abate comercial. O volume total e individual das células de Leydig foi 2,02ml e 1202,74 x 10-12ml, respectivamente. O núcleo e o citoplasma ocuparam, respectivamente, 12,3% e 87,7% de cada célula de Leydig.O índice leydigossomático foi de 0,022%, enquanto que o número de células de Leydig por testículo e por grama de testículo foi, respectivamente, 1,7 bilhões e 92,12 milhões de células. Concluiu-se que os parâmetros morfométricos estudados para as células de Leydig de catetos estão inseridos na média relatada para a maioria das espécies de mamíferos.

Mouse model of male germ cell apoptosis in response to a lack of hormonal stimulation.

As a prerequisite for studies using mutant mice, we established a mouse model for induction of male germ cell apoptosis after deprivation of gonadotropins and intratesticular testosterone (T). We employed a potent long acting gonadotropin-releasing hormone antagonist (GnRH-A), acyline, alone or in combination with an antiandrogen, flutamide for effective induction of germ cell apoptosis in mice. Combined treatment with continuous release of acyline (3 mg/kg BW/day) with flutamide (in the form of sc pellets of 25 mg) resulted in almost the same level of suppression of spermatogenesis, as judged by testis weight and by germ cell apoptotic index, in 2 weeks as that reported for rats after treatment with 1.25 mg/kg BW Nal-Glu GnRH-A for the same time period. Within the study paradigm, the maximum suppression of spermatogenesis occurred after a single sc injection of high (20 mg/kg BW) dose of acyline with flutamide. The combined treatment resulted in complete absence of elongated spermatids. Germ cell counts at stages VII-VIII showed a significant (P < 0.05) reduction in the number of preleptotene (27.1%) and pachytene spermatocytes (81.9%), and round spermatids (96.6%) in acyline + flutamide group in comparison with controls. In fact, treatment with a single high (20 mg/kg BW) dose of acyline combined with flutamide in mice achieved same or greater level of suppression, measured by germ cell counts at stages VII-VIII, in two weeks when compared with those reported after daily treatment with Nal-Glu GnRH-A for 4 weeks in rats. Both plasma and testicular T levels were markedly suppressed after administration of acyline alone either by miniosmotic pump or by a single sc injection. Addition of flutamide to acyline had no discernible effect on plasma or intratesticular T levels when compared with acyline alone. These results demonstrate that optimum suppression of spermatogenesis through increased germ cell death is only possible in mice if total abolition of androgen action is achieved and further emphasize the usefulness of acyline + flutamide treated mice as a suitable model system to study hormonal regulation of testicular germ cell apoptosis.

Leydig cells, thyroid hormones and steroidogenesis.

Leydig cells are the primary source of androgens in the mammalian testis. It is established that the luteinizing hormone (LH) produced by the anterior pituitary is required to maintain the structure and function of the Leydig cells in the postnatal testis. Until recent years, a role by the thyroid hormones on Leydig cells was not documented. It is evident now that thyroid hormones perform many functions in Leydig cells. For the process of postnatal Leydig cell differentiation, thyroid hormones are crucial. Thyroid hormones acutely stimulate Leydig cell steroidogenesis. Thyroid hormones cause proliferation of the cytoplasmic organelle peroxisome and stimulate the production of steroidogenic acute regulatory protein (StAR) and StAR mRNA in Leydig cells; both peroxisomes and StAR are linked with the transport of cholesterol, the obligatory intermediate in steroid hormone biosynthesis, into mitochondria. The presence of thyroid hormone receptors in Leydig cells and other cell types of the Leydig lineage is an issue that needs to be fully addressed in future studies. As thyroid hormones regulate many functions of Sertoli cells and the Sertoli cells regulate certain functions of Leydig cells, effects of thyroid hormones on Leydig cells mediated via the Sertoli cells are also reviewed in this paper. Additionally, out of all cell types in the testis, the thyrotropin releasing hormone (TRH), TRH mRNA and TRH receptor are present exclusively in Leydig cells. However, whether Leydig cells have a regulatory role on the hypothalamo-pituitary-thyroid axis is currently unknown.

Testosterone productivity and histostructural changes of autotransplanted rat Leydig cells

To investigate the possibility of in vivo transplantation of Leydig cells as a new biologic androgen replacement therapy, the Leydig cells procured from 6 week-old male Sprague-Dawley rats were autotransplanted, and the level of testosterone secretion and histostructural changes were observed. The renal subcapsular and intraperitoneal transplant showed higher levels of testosterone compared to subcutaneous or scrotal counterparts, and the number of transplanted cells was correlated with the level of measured testosterone. Furthermore, if the Leydig cells were transplanted intraperitoneally after the uptake on synthetic collagen, testosterone levels were higher than the ones simply transplanted without synthetic collagen uptake, resulting in 27 fold increase at 3 months. The activity of 125I-hCG decreased 20 to 40% at each month after transplantation compared to the normal levels, but no statistical significance was noted among different periods. The histologic examination revealed neovascularized capillaries and well demarcated sheet-like group of eosinophilic Leydig cells were observed at 4 weeks. But the evidence of destructive changes such as a focal inflammation with central dystropic ossification could be noted after 3 month. On electron microscopy, the marked indentation of nucleus and presence of lipochrome pigment were seen, and the number and size of smooth endoplasmic reticulum and mitochondria were reduced after 3 month. In conclusion, testosterone output could be increased to the physiologic range by increasing the number of transplant cells or utilizing collagen uptake but further effort is necessary on delaying or preventing the structural and functional decrement of Leydig cells.

Respuesta del testiculo no descendido a la administración de gonadootrofina corionica humana / Non descended testis response to the administration of human gonadothrophin

Se estudiaron a 31 varones prepuberales del Servicio de Endocrinología Infantil del Hospital de Niños no descendidos de los cuales 7 tenían criptorquidia unilateral, 14 eran bilaterales y 10 testículos retráctiles que no permanecen la mayor parte del tiempo en el escroto. El motivo fué evaluar la respuesta tanto clínica como hormonal a la administración de Gonadotrofina Corionica Humana a 15.000 Uds. por m2 sc por dosis siendo el total 9 dosis y determinar la posibilidad de su uso terapéutico de rutina en testículos no descendidos. La respuesta hormonal fué evidenciada por el aumento de los niveles de testosterona por estimulación con G lo cual demostró integridad funcional de las células de Leydig en el 100% de los casos estudiados. En cuanto el éxito de descenso testicular no fué muy significativo sin embargo se recomienda utilizarse en niños de edad preescolar y que la dosis total supere a las 10.000 Uds. para lograr un mejor efecto terapéutico

Effect of LH, FSH, LH + FSH and homoplastic pituitary extract on developing testis and epididymis of pigeon Columba livia.

Ovine LH is needed for differentiation of juvenile Leydig cells and for their maintenance and steroidogenic potential, while FSH is necessary for Sertoli cell activity and spermatogonial multiplication suggesting that LH is steroidogenic hormone and FSH is gametogenic in the developing pigeon, C. livia. Homoplastic pituitary extract is more potent than ovine LH + FSH in stimulating gametogenic and endocrine components of the developing testis.

Célula de Leydig: ultra-estrutura e síntese de testosterona / Leydig cell: ultrastucture and testosterone synthesis

A Gonadotrofina LH prende-se a receptores específicos, localizados em microvilos da membrana citoplasmática, formando o complexo hormonio-receptor, que ativa o sistema adenilato ciclase e consequente sintese de AMPc. O nucleolite ativa fosfoquinases que fosforilam e sintetizam proteinas, necessárias para que seja produzida a testosterona. Gotículas de lipídeos, situadas no citoplasma da CL contêm a maior parte do colesterol esterificado que, após hidrólise, sob a forma de colesterol livre, é transportado por proteinas até a mitocôndria e nela, depois de ser levado até a membrana interna da crista, entra em contato com enzimas, que fazem a clivagem da cadeia lateral, transformando-o em pregnenolona. A pregnenolona é transportada para o REA, onde nova bateria de enzimas a transformará em testosterona, se o animal for adulto e suas células, consequentemente, maduras, ou em hormônios reduzidos, se a célula for imatura. Cada etapa do processo tem seus próprios mecanismos de autocontrole, secretando quantidades exatas de testosterona necessária à manutençäo da espermatogênese e caracteres sexuais secundários.

Respuesta testicular a la gonadotropina coriónica humana en pacientes infértiles atendiendo al patrón histológico testicular / Testicular response to human chorionic gonadotropin in infertile patients. According to testicular histology standard

Se estudió la respuesta testicular a 6,000 UI de HCG intramuscular determinando testosterona (T) y estradiol (E2) plasmáticos, en pacientes infértiles, de acuerdo al patrón histológico testicular y se compararon sus resultados con los obtenidos en hombres normales. En los normales la T presentó un incremento inicial a las 2-4 horas y un incremento máximo entre 48-96 horas post-HCG. El E2 presentó un incremento máximo a las 24 horas post-HCG, regresando al nivel basal a las 192 horas. En los pacientes infértiles con hipoespermatogénesis y aplasia germinal, la T repondió a la HCG en forma similar a los normales, pero el E2 disminuyó más rápido en los últimos, lo que sugiere una disminución de la capacidad de sintetizar y/o liberar E2. Aquellos con hialinización tubular no presentaron la respuesta bifásica de T y los incrementos de T y E2 se encontraron disminuidos significativamente. Finalmente, los pacientes con Síndrome de Klinefelter no respondieron a la estimulación con HCG. Se concluye que los pacientes infértiles presentan una respuesta diferente a la HCG si son clasificados según el patrón histológico de los testículos