The length of the cycle of seminiferous epithelium in goats (Capra hircus).

This is the first report in literature showing the length of the seminiferous epithelium cycle in goats. In the present study, the duration of spermatogenesis was estimated using intratesticular injections of tritiated thymidine. Animals were castrated at 4 h, 7 days, and 11 days after injections. The duration of each spermatogenic cycle in goats is 10.6 +/- 0.5 days (SEM). Considering that the total duration of spermatogenesis takes about 4.5 cycles of seminiferous epithelium, spermatogenesis was estimated to last 47.7 days. The approximate primary spermatocytes life span is 14.1 days, while spermiogenesis in goats lasts 14.9 days. Staging in goats was based on the tubular morphology, where 8 stages of the cycle are yielded for all species. The relative stage frequencies in goats, based on 400 seminiferous tubule cross sections for each animal were as follows: stage 1: 15.8 +/- 1.0%; stage 2: 12.8 +/- 0.5%; stage 3: 20.5 +/- 0.9%; stage 4: 10.7 +/- 0.7%; stage 5: 11.6 +/- 0.6%; stage 6: 9.3 +/- 1.1%; stage 7: 7.6 +/- 0.4%; stage 8: 11.7 +/- 0.6%. The pre-meiotic, meiotic and post-meiotic phases' relative frequencies were 49.1%, 10.7% and 40.2%, respectively. The duration of spermatogenesis in goats is very similar to that found in rams.     

Synchronization of the seminiferous epithelium after vitamin A replacement in vitamin A-deficient mice

The effect of vitamin A deficiency and vitamin A replacement on spermatogenesis was studied in mice. Breeding pairs of Cpb-N mice were given a vitamin A-deficient diet for at least 4 wk. The born male mice received the same diet and developed signs of vitamin A deficiency at the age of 14-16 wk. At that time, only Sertoli cells and A spermatogonia were present in the seminiferous epithelium. These spermatogonia were topographically arranged as single and paired cells and as clones of 4, 8 and more cells. A few mitoses of single, paired, and clones of 4 A spermatogonia were found, which were randomly distributed over the seminiferous epithelium. When vitamin A-deficient mice were treated with retinol-acetate combined with a normal vitamin A-containing diet, spermatogenesis restarted again synchronously. Only a few successive stages of the cycle of the seminiferous epithelium were present up to at least 43 days after vitamin A replacement. After 20 days, 98.3% of the seminiferous tubules were synchronized, showing pachytene spermatocytes as the most advanced cell type, mostly being in epithelium stages IX-XII. After 35 and 43 days, spermatogenesis was complete in 99.6% of the tubular cross sections, and most tubular cross sections were in stages IV-VII of the cycle of the seminiferous epithelium. The degree of synchronization was comparable or even higher than found in rats. The rate of development of the spermatogenic cells between 8 and 43 days after vitamin A replacement seemed to be similar to that in normal mice. Assuming that the rate of development of the spermatogenic cells is also normal during the first 8 days after vitamin A replacement, it can be deduced that the preleptotene spermatocytes, present after 8 days, were A spermatogonia in the beginning of stage VIII at the moment of vitamin A replacement. These results indicate that the mouse can be used as a model to study epithelial stage-dependent processes in the testis.     

Spermatogenesis in white-lipped peccaries (Tayassu pecari)

We describe here morphological and functional analyses of the spermatogenic process in sexually mature white-lipped peccaries. Ten sexually mature male animals, weighing approximately 39 kg were studied. Characteristics investigated included the gonadosomatic index (GSI), relative frequency of stages of the cycle of seminiferous epithelium (CSE), cell populations present in the seminiferous epithelium in stage 1 of CSE, intrinsic rate of spermatogenesis, Sertoli cell index, height of seminiferous epithelium and diameter of seminiferous tubules, volumetric proportion of components of the testicular parenchyma and length of seminiferous tubules per testis and per gram of testis. The GSI was 0.19%, relative frequencies of pre-meiotic, meiotic and post-meiotic phases were, respectively 43.6%, 13.8% and 42.6%, general rate of spermatogenesis was 25.8, each Sertoli cell supported an average 18.4 germinative cells, height of seminiferous epithelium and diameter of seminiferous tubules were, respectively, 78.4 microm and 225.6 microm, testicular parenchyma was composed by 75.8% seminiferous tubules and 24.2% intertubular tissue, and length of seminiferous tubules per gram of testis was 15.8m. These results show that, except for overall rate of spermatogenesis, the spermatogenic process in white-lipped peccaries is very similar to that of collared peccaries, and that Sertoli cells have a greater capacity to support germinative cells than most domestic mammals.     

The cycle of the seminiferous epithelium in the Japanese quail (Coturnix coturnix japonica) and estimation of its duration

A regular, well defined spermatogenic cycle was found in the Japanese quail by examining thin sections of isolated lengths of seminiferous tubules embedded in epoxy resin to resolve the structure of developing spermatids. The stages of the cycle initially were identified in studies using a preparatory method for fixation which separated adjacent cellular associations. The cycle was divided into 10 stages with relative frequencies (%) of Stages I to X respectively of: 11.9, 14.8, 24.1, 10.3, 8.2, 6.4, 9.4, 5.5, 3.8 and 5.4. The duration of one cycle was 2.69 +/- 0.08 days (mean +/- s.e.m.) as determined by intraventricular injection of [3H]thymidine and autoradiographic examination of the testes 1-4 days later. It was estimated that lifespans were 2.01 days for type B spermatogonia, 3.86 days for primary spermatocytes, 0.15 days for secondary spermatocytes, and 4.54 days for spermatids. The results suggest that the kinetics of spermatogenesis in the quail are fundamentally similar to the pattern in mammals.     

Stability of spermatogenic synchronization achieved by depletion and restoration of vitamin A in rats

Studies of synchronization of spermatogenesis following vitamin A deficiency have suggested that this may provide an in vivo model for the study of stage-dependent changes in hormonal action and protein secretion within the seminiferous epithelium. However, until now, no information on the stability or durability of this condition has been available. In this study, 200 seminiferous tubules from each of 40 rats (including controls) were classified according to their spermatogenic stage after withdrawal and replenishment of vitamin A. Following 15 wk withdrawal and subsequent replenishment of vitamin A, spermatogenesis was initiated in a synchronous fashion. This synchrony remained stable for more than 10 cycles of the seminiferous epithelium (2.5 spermatogenic cycles). In association with the extended period of vitamin A deficiency, a proportion of tubules (30%) showed morphological characteristics of either Sertoli cells only or Sertoli cells plus spermatogonia with occasional pachytene spermatocytes. During the 11-wk period of observation in this study, no significant change in proportions of damaged tubules were observed. Testicular testosterone concentrations, although elevated with respect to controls, showed no correlation with the stage of the cycle of the seminiferous epithelium observed, whereas pituitary and serum follicle-stimulating hormone levels were elevated, probably due to the number of damaged tubules observed. The persistence of synchrony in spermatogenesis following vitamin A treatment suggests that this model is applicable for studies of paracrine actions within the testis. However, the decreased ratio of synchrony observed with time may provide evidence that duration of the individual stages of the cycle of the seminiferous epithelium might be subject to temporal variation, leading to a progressive desynchronization of spermatogenesis in this model system.     

The cycle of the seminiferous epithelium in Landrace boars

The present study describes the morphological features of the eight stages of the seminiferous epithelium in Landrace boars according to the tubular morphology method, as well as their relative frequency, length, and duration. In Landrace boars the pre-meiotic stages occupied the 31.9 +/- 19.9% of the spermatogenic cycle and had a total length of 1788.8 +/- 1153.0 microm and a duration of 2.78 days; they were mainly characterised by the presence of leptotene and pachytene spermatocytes and round spermatids. Meiotic stages, with a relative frequency of 16.4 +/- 6.8%, a length of 787.1 +/- 603.1 microm and a duration of 1.41 days, contained spermatocytes in advanced meiosis I and/or in meiosis II and elongating spermatids grouped in bundles. Post-meiotic stages occupied the 50.6 +/- 20.4% of the spermatogenic cycle and had a length of 2096.8 +/- 1175.0 microm and a duration of 4.37 days; the most important event of these stages was the spermiation, which included the complete remodelling of sperm head and tail and the releasing of spermatozoa into the lumen, as well as the formation of residual bodies. From data obtained we concluded that both germ cell associations of the stages maintain constant among Landrace boars, and that the relative frequency, length and duration of the stages were directly dependent of the cytological transformations on the seminiferous tubules.     

The Cycle of the Seminiferous Epithelium of the Turkish Hamster (Mesocricetus brandti)

The Turkish hamster ( Mesocricetus brandti ) has become a desirable species for experimentation in testicular function, photoperiod, reproductive hormones and hibernation. Basic data on the kinetics of the seminiferous epithelium have not yet been published. In the present study, the cycle of the seminiferous epithelium was divided into eight stages based on the overall cellular associations of 1540 cross sections of tubules. The mean relative frequencies for stages 1 through 8 were 5.9, 3.3, 11.7, 6.7, 7.2, 28.5, 21.6 and 15.1%, respectively. The absolute duration of the cycle of the seminiferous epithelium was determined by administration of ³H-thymidine, removal of testes at intevals after injection and autoradiography. The mean duration of one cycle was estimated at 8.0 days and the duration of stages 1 through 8 was 0.5, 0.3, 0.9, 0.5, 0.6, 2.3, 1.7 and 1.2 days, respectively. The duration of meiotic prophase was 11.5 days and of spermiogenesis was 13.8 days. The life span of preleptotene cell was estimated at 1.21 days, leptotene, 0.73 days, zygotene, 0.94 days and pachytene, 7.37 days. The total cycle length of spermatogenesis as usually calculated was 32.0 days.     

Comparative testis morphometry and seminiferous epithelium cycle length in donkeys and mules

The mule (Equus mulus mulus) is a sterile hybrid domestic animal that results from the breeding of a male donkey (Equus asinus) to a female horse (Equus caballus). Usually, spermatogenesis in mules does not advance beyond spermatocytes. In the present study, we performed a comparative and more accurate morphometric and functional investigation of the testis in donkeys and mules. Due to the smaller testis size, lower seminiferous tubule volume density, and fewer germ cells, the total length of seminiferous tubules in mules was significantly smaller than in donkeys. However, the percentage of seminiferous tubules containing germ cells (spermatogonia and spermatocytes) in mules was approximately 95%. The total number of Sertoli cells per testis observed in donkeys and mules was very similar. However, the total number of Leydig cells in mules was approximately 70% lower than in donkeys. At least in part, this difference was probably related to the lower number of germ cells present in mule seminiferous tubules. Although spermatogenesis in mules did not advance beyond secondary spermatocytes/newly formed round spermatids, germ cell associations in the seminiferous epithelium and pachytene spermatocytes nuclear volume in donkeys and mules were similar. The duration of spermatogenesis was estimated using intratesticular injections of tritiated thymidine. Each spermatogenic cycle in donkeys lasted 10.5 days. A similar value was found in mules ( approximately 10.1 days). Considering that the entire spermatogenic process takes approximately 4.5 cycles to be completed, its total duration in donkeys was estimated to last 47.2 days. The results found for mules suggest that the mechanisms involved in the determination of testis structure and function are probably originated from donkeys. Also, the data found for mules suggest that their seminiferous tubules are able to sustain complete spermatogenesis. In this regard, this species is a potential model for transplants of germ cells originated from donkeys and horses or other large animals.     

The cycle of the seminiferous epithelium in the Australian Swamp buffalo

The relative frequencies of stages and substages of the Swamp buffalo seminiferous epithelium were determined using a morphological classification. Duration of one cycle of the seminiferous epithelium was determined from radiolabelling studies using tritiated thymidine. Mean (+/-SD) duration of the cyle of the seminiferous epithelium of five Swamp buffalo was 8.74 +/- 0.18 d. Mean (+/-SEM) relative frequencies of stages and substages of the seminiferous epithelial cycle in ten bulls were Stage 1a, 7.27 +/- 0.72; Stage 1b, 8.11 +/- 0.85; Stage 1c, 8.54 +/- 1.13; Stage 2a, 5.9 +/- 0.79; Stage 2b, 7.49 +/- 0.78; Stage 3a, 9.05 +/- 0.66; Stage 3b, 9.69 +/- 1.11; Stage 4a, 5.04 +/- 0.44; Stage 4b, 4.8 +/- 0.69; Stage 5, 1.86 +/- 0.23; Stage 6, 8.81 +/- 0.84; Stage 7, 10.64 +/- 1.2; Stage 8a, 6.87 +/- 0.96; and Stage 8b, 5.93 +/- 0.72.     

Duration of spermatogenesis and daily sperm production in the jaguar (Panthera onca)

The jaguar, like most wild felids, is an endangered species. Since there are few data regarding reproductive biology for this species, our main goal was to investigate basic aspects of the testis and spermatogenesis. Four adult male jaguars were utilized; to determine the duration of spermatogenesis, two animals received an intratesticular injection of H(3)-thymidine. Mean (+/-SEM) testis weight and the gonadosomatic index were 17.7+/-2.2g and 0.05+/-0.01%, respectively, whereas the seminiferous tubules and the Leydig cells volume density were 74.7+/-3.8 and 16.7+/-1.6%. Eight stages of spermatogenesis were characterized, according to the tubular morphology system and acrosome development. Each spermatogenic cycle and the entire spermatogenic process (based on 4.5 cycles) lasted approximately 12.8+/-0.01 and 57.7+/-0.07 d. The number of Sertoli and Leydig cells per gram of testis was 29+/-4x10(6) and 107+/-12x10(6). Based on the number of round spermatids per pachytene spermatocyte (2.8+/-0.3:1; meiotic index); significant cell loss (30%) occurred during the two meiotic divisions. There were approximately eight spermatids for each Sertoli cell (Sertoli cell efficiency), whereas the daily sperm production per gram of testis was 16.9+/-1.2x10(6). We expect that in the near future, the knowledge obtained in the present investigation will facilitate, utilizing germ cell transplantation, preservation of the germinal epithelium and the ability to generate sperm from jaguars in testes of domestic cats.     

Stages and duration of spermatogenesis in the domestic ferret (Mustela putorius furo)

Classification of seminiferous tubules is the basis for understanding normal and abnormal spermatogenesis. The aim of the present study was to determine spermatogenic stages and the duration of the cycle in the domestic ferret using bromodeoxyuridine (BrdU) as a tracer. Eleven adult male ferrets that were maintained in a breeding condition were used. Testicular sections were stained with the periodic acid-Schiff reaction for light microscopy. To determine the cycle duration, six ferrets were injected intraperitoneally with BrdU, and testes were collected 3h later and 10 days and 3h later. BrdU was detected by immunohistochemistry. Seminiferous tubules were classified into eight stages, and frequencies of stages I-VIII were 10.6, 2.2, 7.9, 13.1, 22.3, 21.9, 14.0 and 8.0%, respectively. The most advanced BrdU-labeled cells at 3h post-injection were leptotene spermatocytes in stage VI and those at 10 days and 3h were pachytene spermatocytes in stage V. From differences in stage frequency and BrdU staining frequency between two time points, the duration of one cycle was estimated to be 13.0 days. The present observations indicate that stages and the cycle duration of the ferret spermatogenesis are similar to those reported in other carnivores.     

Cycle and duration of the seminiferous epithelium in puma (Puma concolor)

Puma or sussuarana (Puma concolor) is the second largest feline in the American continent and has an ample latitudinal distribution in very diverse habitats. In relation to its conservation status, the puma is considered an extinction-threatened species. The study of the testis morphology and the spermatogenic process in a species is fundamental for establishing the physiologic patterns that will make possible the selection of the protocols for assisted reproduction. A number of peculiarities associated with the reproductive biology of specific species such as the duration of spermatogenic process can be used to determine the frequency of sperm collection. Nine adult male pumas maintained in captivity were used to determine the relative frequency of stages in the seminiferous epithelium cycle. Three of them received intra-testicular injections of 0.1ml tritiated thymidine to determine the duration of the seminiferous epithelium cycle, and were subjected to biopsy 7 days later. The cycle of the seminiferous epithelium in puma was didactically described into eight stages by the tubular morphology method. The total duration of one seminiferous epithelium cycle in puma was calculated to be 9.89 days, and approximately 44.5 days are required for development of spermatozoon from spermatogonia. The duration of spermiogenesis, prophase and other events of meiosis were 14.08, 15.20 and 1.79 days, respectively. The relative frequency of the pre-meiotic, meiotic and post-meiotic phases were 3.98, 1.79 and 4.12 days, respectively.     

The effect of scrotal insulation on spermatozoal morphology and the rates of spermatogenesis and epididymal passage of spermatozoa in the bull

In five beef bulls spermatogenic cells labelled with (3)H-thymidine were used to estimate the duration of one cycle of the seminiferous epithelium (S.E.) and epididymal passage (E.P.) of spermatozoa after 10 or 20 hr of scrotal insulation designed to increase testicular temperature. From six autoradiographic estimates in three bulls, the mean value for 1 S.E. cycle was 13.4 days (range 12.9 to 13.6 days). Two estimates of E.P. were both 13.5 days. Scrotal insulation altered both semen quality (lowered percentage live and motile spermatozoa, raised percentage abnormal spermatozoa and lowered concentration per ml spermatozoa) and the histological appearance of the seminiferous epithelium. However, the rate of spermatogenesis and epididymal transport was unchanged.     

Cycle of the seminiferous epithelium and its duration in the zebu, Bos indicus

The cycle of the seminiferous epithelium was studied in Nelore zebu bulls 4–6 years old. The stages of the cycle were determined according to the shape and position of spermatid nuclei and the presence of meiotic divisions in cross-sections of seminiferous tubules. The relative frequencies of stages 1 to 8 were, respectively: 31.3 ± 0.5, 12.2 ± 0.7, 21.2 ± 0.5, 8.8 ± 0.6, 4.2 ± 0.4, 5.7 ± 0.6, 6.3 ± 0.5 and 10.3 ± 0.5. The duration of the cycle was estimated by autoradiography using tritiated thymidine injected directly into the testes. The mean duration of one cycle was estimated to be 14.0 ± 0.4 days.     

The seminiferous epithelium cycle length in the black tufted-ear marmoset (Callithrix penicillata) is similar to humans

Marmosets are New World small primates phylogenetically close to humans and are commonly used in biomedical research. Although the reproductive biology of the common marmoset Callithrix jacchus is fairly well investigated, there are few data available for testis function for its close relative, Callithrix penicillata. In this regard, the present study was performed to investigate testis structure, spermatogenic cycle length, and spermatogenic and Sertoli cell efficiencies in eight captive C. penicillata. These animals received (3)H-thymidine injections and had their testes perfused-fixed with glutaraldehyde and embedded in plastic at different time periods after (3)H-thymidine injections, for histomorphometric and autoradiographic evaluation. The analysis of the different germ cell associations showed that two or more stages were observed in about 30% of the seminiferous tubule cross sections investigated. The values found for spermatogenic cycle length and for total duration of spermatogenesis in the marmoset C. penicillata, 15.4 and 69.3 days respectively, were very close to those cited in the literature for humans. However, the results observed for Sertoli cell efficiency (number of round spermatids per Sertoli cell; 8:1) and spermatogenic efficiency (daily sperm production per gram of testis; 18.4 million) were substantially higher than those observed for humans. The results found in the present investigation suggest that the black tufted-ear marmoset C. penicillata might represent an alternative and useful experimental model to perform comparative studies regarding the spermatogenic process, particularly in investigations related to the expansion of spermatogonial stem cells and the establishment of spermatogenic waves.     

Testis morphometry,seminiferous epithelium cycle length,and daily sperm production in domestic cats (Felis catus)

There is very little information regarding the testis structure and function in domestic cats, mainly data related to the cycle of seminiferous epithelium and sperm production. The testis weight in cats investigated in the present study was 1.2 g. Compared with most mammalian species investigated, the value of 0.08% found for testes mass related to the body mass (gonadosomatic index) in cats is very low. The tunica albuginea volume density (%) in these animals was relatively high and comprised about 19% of the testis. Seminiferous tubule and Leydig cell volume density (%) in cats were approximately 90% and 6%, respectively. The mean tubular diameter was 220 microm, and 23 m of seminiferous tubule were found per testis and per gram of testis. The frequencies of the eight stages of the cycle, characterized according to the tubular morphology system, were as follows: stage 1, 24.9%; stage 2, 12.9%; stage 3, 7.7%; stage 4, 17.6%; stage 5, 7.2%; stage 6, 11.9%; stage 7, 6.8%; and stage 8, 11 %. The premeiotic and postmeiotic stage frequency was 46% and 37%, respectively. The duration of each cycle of seminiferous epithelium was 10.4 days and the total duration of spermatogenesis based on 4.5 cycles was 46.8 days. The number of round spermatids for each pachytene primary spermatocytes (meiotic index) was 2.8, meaning that significant cell loss (30%) occurred during the two meiotic divisions. The total number of germ cells and the number of round spermatids per each Sertoli cell nucleolus at stage 1 of the cycle were 9.8 and 5.1, respectively. The Leydig cell volume was approximately 2000 microm3 and the nucleus volume 260 microm3. Both Leydig and Sertoli cell numbers per gram of testis in cats were approximately 30 million. The daily sperm production per gram of testis in cats (efficiency of spermatogenesis) was approximately 16 million. To our knowledge, this is the first investigation to perform a more detailed and comprehensive study of the testis structure and function in domestic cats. Also, this is the first report in the literature showing Sertoli and Leydig cell number per gram of testis and the daily sperm production in any kind of feline species. In this regard, besides providing a background for comparative studies with other fields, the data obtained in the present work might be useful in future studies in which the domestic cat could be utilized as an appropriate receptor model for preservation of genetic stock from rare or endangered wild felines using the germ cell transplantation technique.     

Testis morphometry, duration of spermatogenesis, and spermatogenic efficiency in the wild boar (Sus scrofa scrofa)

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 seminiferous epithelium cycle, and duration of spermatogenesis in the wild boar were similar to those in domestic pigs. Probably because of the small size of Leydig cells (400 microm3), their number per gram of testis (157 million) was the highest among investigated mammalian species. Although the SC efficiency in wild boars was low, their spermatogenic efficiency was comparable to that observed in domestic pigs, mainly because of the higher number of SCs per gram of testis in wild boars. These data suggest that SCs became more efficient during evolution, genetic selection, and domestication in pigs.     

Ultrastructural changes in the spermatogenic epithelium and in the basic components of the blood-testis barrier in adult rats following repeated administration of estradiol dipropionate]

Electron microscopic studies of the testes were conducted in intact adult Wistar rats and in rats given repeated injections of a 0.1% solution of estradiol-dipropionate-0.3 mg week for 10 weeks. Administration of the hormone caused focal inhibition of spermatogenesis (6 weeks) accompanied by development of destructive changes in the spermatogenic cells. These pathological changes were reversible and disappeared two months after the cessation of the hormone injection, and the spermatogenesis was restored. Development of the pathological changes in the spermatogenic epithelium was accompanied by disturbances of the fine structure of the main components of the blood-test is barrier (Sertoli cells, tunica propria of the seminiferous tubules).     

Expression of connexin 43 in human testis

In order to further characterize the Sertoli cell state of differentiation, we investigated the expression of connexin 43 (cx43) protein in the testis of adult men both with normal spermatogenesis and associated with spermatogenic impairment, since cx43 is first expressed during puberty. Cx43 protein was found as a single 43-kDa band on western blots of extracts of normal human testicular material. Cx43 immunoreactivity was generally present between Leydig cells. Within the normal seminiferous epithelium cx43 immunoreactivity was localized between adjacent Sertoli cells, except at stages II and III of the seminiferous epithelial cycle when primary spermatocytes cross from the basal to the adluminal compartment suggesting a stage-dependent Sertoli cell function. While testes with hypospermatogenesis and spermatogenic arrest at the level of round spermatids or spermatocytes revealed a staining pattern similar to that of normal adult testis, the seminiferous tubules showing spermatogenic arrest at the level of spermatogonia and Sertoli-cell-only syndrome were completely immunonegative. We therefore assume that severe spermatogenic impairment is associated with a population of Sertoli cells exhibiting a stage of differentiation deficiency. Accepted: 10 June 1999     

Slow increase of Sertoli cell efficiency and daily sperm production causes delayed establishment of full sexual maturity in the rodent Chinchilla lanigera

Puberty in the male Andean rodent Chinchilla lanigera occurred approximately 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 10.2d and the total duration of spermatogenesis was approximately 46 d. The SC efficiency (spermatids/SC) and the daily sperm production per testis gram increased markedly (P<0.05) from 5 to 17-22 mo of age, whereas the conversion rates of type A1 spermatogonia to preleptone and the number of spermatids per pachytene remained stable (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.