Morphological findings in varicocele: an ultrastructural study of 30 bilateral testicular biopsies

Varicocele and testicular cord torsion: immune testicular microenvironment imbalance

The main functions of the testis, steroidogenesis and spermatogenesis, depend on the endocrine axis and systemic and local tolerance mechanisms. Infectious or non-infectious diseases may disturb testicular immune regulation causing infertility. Literature has illustrated that bacterial and viral infections lead to autoimmune infertility: either sperm antibodies or autoimmune epidydimo-orchitis. However, little is known about the association between non-infectious testicular pathologic diseases and autoimmunity. Here we review the novel aspect of varicocele and testicular cord torsion pathology linked to inflammation and discuss how immune factors could contribute to or modulate autoimmunity in ipsi- and contralateral testis.

Effects of liver-regulating herb compounds on testicular morphological and ultrastructural changes in varicocele rats through SCF/C-KIT pathway

Liver-regulating herb compound (LRHC) has good effects on improving sperm quality and male fertility of varicocele (VC) patients. But the mechanism of LRHC on VC is still not clear. This study explored the effects of LRHC on histomorphological and ultrastructural changes and expression of stem cell factor (SCF) and C-KIT of VC rat testis. Twenty-four male rats were divided into three groups with eight rats in each group as sham, varicocele and LRHC groups. Testis specimens were collected for light microscopy and transmission electron microscopy respectively. The expression of SCF/C-KIT was detected with Western blot. Results showed that seminiferous tubules in VC rats were damaged and cell numbers were decreased. Ultrastructural alterations were observed, such as increased thickness of lamina propria, vacuolation in Sertoli cells, spermatocytes and spermatids, and abnormal head and mitochondria in spermatozoa. While in LRHC-treated rats, the architectures of seminiferous tubules were as organised and compact as that of sham animals, and ultrastructure of Sertoli, Leydig and germ cells developed well. LRHC ameliorated histological appearance and ultrastructure by VC. In addition, the abnormal expression of SCF and C-KIT were observed in testicular tissues from rats with VC, which were brought back to normal level by LRHC.

Varicocele and testicular function

Testicular varicocele, a dilation of the veins of the pampiniform plexus thought to increase testicular temperature via venous congestion, is commonly associated with male infertility. Significant study has clarified the negative impact of varicocele on semen parameters and more recent work has shed light on its detrimental effects on the molecular and ultrastructural features of sperm and the testicular microenvironment, as well as more clearly defined the positive impacts of treatment on couples’ fertility. The relationship between varicocele and testicular endocrine function, while known for some time based on histologic evaluation, has become more apparent in the clinical setting with a growing link between varicocele and hypogonadism. Finally, in the pediatric setting, while future study will clarify the impact of varicocele on fertility and testicular function, recent work supports a parallel effect of varicocele in adolescents and adults, suggesting a re-evaluation of current treatment approaches in light of the progressive nature of the condition and potential increased risk of future disease.

Ultrastructure of the seminiferous tubules in oligoasthenoteratozoospermic men associated with varicocele

Varicocele is associated with venous reflux that may cause increased heat and interstitial pressure within the testes, with variable pathological effects on spermatogenesis. This study aimed to study the ultrastructural testicular changes in the seminiferous tubules of 20 infertile severe oligoasthenoteratozoospermia (OAT) men associated with varicocele and five patients with obstructive azoospermia without varicocele as controls. They were subjected to testicular biopsy which was evaluated by transmission electron microscopy. Ultrastructurally, the seminiferous epithelium in the testicular biopsies of infertile severe OAT men associated with varicocele was variably affected in the form of thickening of the peritubular connective tissue, vacuolation of Sertoli cell and germ cell cytoplasm, presence of degenerated and apoptotic cells among the germinal epithelium, altered spermatids and abnormal spermatozoa. It is concluded that varicocele in severe OAT men is associated with ultrastructural changes in the seminiferous tubule.

Varicocele repair: does it still have a role in infertility treatment?

PURPOSE OF REVIEW

To review the role of varicocele repair in the treatment of male infertility.

RECENT FINDINGS

Since the advent of technologies bypassing boundaries of natural selection, this question may seem outdated. Over the past 20 years, fertility has decreased, and testicular damage (cryptorchidism, tumors) has increased. Thus the exploration of the infertile male is still unavoidable. However, what should be done and assigned to the discovery of a varicocele?The issue raised is whether varicocele found during the review of the infertile couple should be treated or 'ignored'.This study will update significant findings with regards to the pathophysiology of varicocele-induced infertility, such as oxidative stress and role of varicocele in bilaterality of testicular damage. Benefits of varicocele repair in semen analysis and simplifications of assisted reproductive techniques are reported. But reviews of randomized clinical trials have raised doubts about the benefit of varicocele treatment in infertile men.

SUMMARY

We conclude that varicocele repair may be effective in men with subnormal semen analysis, a clinical varicocele and otherwise unexplained infertility. Deleterious cofactors, like obesity or smoking, could also be reduced for the benefit of general health and fertility.

Radiologically assessed testicular changes in infertile males with varicocele

The aim of this study was to assess vascular disturbances in the testis of infertile males associated with varicocele. In total, 124 consecutive male subjects were divided into the following groups: healthy fertile controls (n = 10), Gp1 (n = 28); infertile males with subclinical varicocele, Gp2 (n = 26); infertile males with grade I left varicocele, Gp3 (n = 28); infertile males with grade II left varicocele and Gp4 (n = 32); infertile males with grade III left varicocele. They were subjected to colour duplex for pampiniform plexus and scrotal scintigraphy. There was significant decrease in arterial blood velocity, testicular arterial diameters and testicular perfusion especially in high grade varicocele compared with healthy controls. The mean vein diameter demonstrated significant negative correlation with arterial diameter, arterial blood velocity, perfusion index, testicular size and significant positive correlation with perfusion index. The mean testicular size demonstrated significant positive correlation with arterial blood velocity, perfusion index and nonsignificant correlation with arterial diameter. It is concluded that there are significant decreases in testicular volume, testicular perfusion, blood velocity and testicular artery diameter in infertile males with varicocele.

Morphological changes in varicocele veins: ultrastructural study

BACKGROUND

Varicocele consists of dilatation of the pampiniform venous plexus and the internal spermatic veins. It is present in 15% of male population and is a common cause of male infertility.

OBJECTIVE

To describe the normal structure of the internal spermatic vein and the morphological changes in grade 3 varicocele.

METHODS

The authors dissected and analyzed a 2- to 3-cm tract of the pampiniform venous plexus of 20 patients undergoing varicocelectomy for left varicocele and of 10 consecutive patients undergoing surgery for left inguinal hernia. The histological examination was performed with hematoxylin–eosin and Masson trichrome stains. The ultrastructural evaluation was done using both scanning and transmission electron microscopy.

RESULTS

Compared with normal internal spermatic veins, varicocele veins showed narrowing and/or obliteration of the lumens, destruction of the endothelial cells, invagination of the intima, and deposition of collagen bundles in the media (light microscopy). The ultrastructural changes in varicocele veins included elongation of the endothelial cells with features of cellular damage, loss of the internal elastic lamina, and the appearance of ghost bodies and degenerative vacuoles in the subendothelial layer.

CONCLUSIONS

The authors believe this is the first report analyzing ultrastructual changes in normal human internal spermatic vein samples and in varicocele. The underlying molecular mechanisms of these changes await further studies.

Varicocele-Induced Testicular Dysfunction May Be Associated with Disruption of Blood-Testis Barrier

The objective of this study was to examine E-cadherin and alpha-catenin expression at the junctions between adjacent Sertoli cells in testicular specimens from patients with varicocele in order to determine the presence of a possible link between blood-testis barrier and pathophysiology of varicocele. A total of 51 testicular biopsies were obtained from 28 infertile men with unilateral or bilateral varicocele. Twenty-three patients had bilateral and 5 had unilateral varicocele, Grade I varicocele was detected in 30 (59%), grade II in 15 (29%) and grade III in 6 (12%) patients. Abnormal expression of E-cadherin and alpha-catenin at the junctions between adjacent Sertoli cells was demonstrated in 100% and 90% of the patients with varicocele, respectively. In those with grade I-III varicocele, the mean E-cadherin and alpha-catenin expression were 7.6 +/- 11.4 and 39 +/- 36; 7.6 +/- 0.0 and 49 +/- 30; 8.3 +/- 9.3 and 58 +/- 33, respectively, but the difference was not significant. Reduced E-cadherin and alpha-catenin expression at the junctions between adjacent Sertoli cells may be associated with disruption of blood-testis barrier in varicocele.

Spermatozoal sensitive biomarkers to defective protaminosis and fragmented DNA

Human sperm DNA damage may have adverse effects on reproductive outcome. Infertile men possess substantially more spermatozoa with damaged DNA compared to fertile donors. Although the extent of this abnormality is closely related to sperm function, the underlying etiology of ensuing male infertility is still largely controversial. Both intra-testicular and post-testicular events have been postulated and different mechanisms have been proposed to explain the presence of damaged DNA in human spermatozoa. Three among them, i.e. abnormal chromatin packaging, oxidative stress and apoptosis, are the most studied and discussed in the present review. Furthermore, results from numerous investigations are presented, including our own findings on these pathological conditions, as well as the techniques applied for their evaluation. The crucial points of each methodology on the successful detection of DNA damage and their validity on the appraisal of infertile patients are also discussed. Along with the conventional parameters examined in the standard semen analysis, evaluation of damaged sperm DNA seems to complement the investigation of factors affecting male fertility and may prove an efficient diagnostic tool in the prediction of pregnancy outcome.

Ultrastructural nuclear defects and increased chromosome aneuploidies in spermatozoa with elongated heads

BACKGROUND

Cellular and molecular mechanisms leading to elongated sperm heads are not known. We have analysed the nuclear status of spermatozoa with elongated heads.

METHODS

Fourteen men with at least 30% of spermatozoa with an elongated nucleus were studied and compared with five fertile men as controls. Sperm morphology was analysed by a quantitative ultrastructural analysis. Sperm chromosomal content was assessed by three-colour fluorescence in-situ hybridization (chromosomes X, Y, 18). Y chromosome microdeletion and karyotype were analysed.

RESULTS

Elongated sperm head rates of the patients were 46.9% (30-75 versus 0-2% in the control group) by light microscopy and 34.4% by electron microscopy. In all patients, the chromatin was poorly condensed in elongated sperm heads (50% of elongated nuclei). No anomalies of sperm biochemical markers were found. All the men showed normal karyotype (46,XY) and absence of Y chromosome microdeletion. Aneuploidy rates of gonosomes and chromosome 18 were significantly increased in patients (1.64- and 3.6-fold, P = 0.006 and 0.026, respectively).

CONCLUSIONS

This study demonstrates that impaired chromatin compaction and slightly increased chromosome aneuploidies are found in spermatozoa with an elongated head, suggesting possible mechanisms such as meiotic non-disjunctions or spermiogenesis anomalies.

Beneficial effect of microsurgical varicocelectomy on human sperm DNA integrity

BACKGROUND

Human sperm DNA damage may adversely affect reproductive outcomes, and the spermatozoa of infertile men possess substantially more DNA damage than that of fertile men. To date, there is no available treatment for men with high levels of sperm DNA damage. The objective of this study was to examine the effect of varicocelectomy on sperm DNA denaturation (DD, an index of sperm DNA damage) in infertile men with a clinical varicocele.

METHODS

We reviewed the reports of 37 men who underwent microsurgical varicocelectomy at our institution from September 2001 to July 2002. Standard semen parameters and the percentage of spermatozoa with DD (monitored by flow cytometry analysis of acridine orange-treated spermatozoa) were assessed before and 6 months after varicocelectomy.

RESULTS

The percentage of spermatozoa with DD decreased following varicocelectomy compared with pre-operatively (27.7 versus 24.6%, respectively, P < 0.05). Sperm concentration and the percentages of motile sperm and normal forms (WHO criteria) increased following varicocelectomy, but the difference did not reach statistical significance.

CONCLUSIONS

Our data suggest that varicocelectomy can improve human sperm DNA integrity in infertile men with varicocele. These data represent the first report of improved sperm DNA integrity after therapy and further support the beneficial effect of varicocelectomy on human spermatogenesis.

Does the gonadotropin-releasing hormone stimulation test predict clinical outcomes after microsurgical varicocelectomy?

OBJECTIVES

To examine the predictive value of the gonadotropin-releasing hormone (GnRH) stimulation test in a large cohort of infertile men undergoing varicocelectomy.

METHODS

We examined the records of 144 consecutive infertile couples in whom the man underwent microsurgical varicocelectomy between September 1998 and December 2002. All men underwent a GnRH stimulation test before surgery. Data on the preoperative and postoperative semen parameters, pregnancy outcome, and follicle-stimulating hormone (FSH) and luteinizing hormone increase after GnRH stimulation were recorded.

RESULTS

The mean (+/-SE) sperm concentration and motility 6 months after varicocelectomy were significantly greater than the preoperative values (25.3 +/- 2.4 versus 19.7 +/- 2.1 x 10(6)/mL and 29.2% +/- 1.4% versus 25.3% +/- 1.3%, respectively, P <0.05). Overall, 28% of the couples achieved a spontaneous pregnancy at a mean of 22 months of follow-up. The median elevation in the FSH and luteinizing hormone value 60 minutes after GnRH administration was 1.8 and 5.6 times the baseline level, respectively. No statistically significant relationship was found between the FSH or LH response to GnRH stimulation and improvement in the semen parameters or positive pregnancy outcome in our population.

CONCLUSIONS

Our data showed that the FSH response to bolus GnRH stimulation does not predict improvement in semen parameters or unassisted pregnancy outcome in couples in whom the man undergoes varicocelectomy (for treatment of varicocele). The study was the largest of its type and sufficiently powered to validate these findings. The results indicate that the bolus GnRH stimulation test is of no clinical value in the treatment of infertile men with varicoceles.

Varicocele is associated with abnormal retention of cytoplasmic droplets by human spermatozoa

OBJECTIVE

To determine whether varicocele is associated with retention of sperm cytoplasmic droplets in infertile men.

DESIGN

Retrospective study.

SETTING

University infertility clinic.

PATIENT(S)

Nonazoospermic men with idiopathic (n = 69) and varicocele-associated infertility (n = 73), and 20 fertile controls presenting for vasectomy.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURES(S)

Standard semen parameters and percentage of spermatozoa with cytoplasmic droplets on Papanicolaou smears.

RESULT(S)

No statistically significant differences were found between the fertile and infertile groups with respect to semen volume. Fertile controls had significantly greater mean percent sperm motility and normal morphology than infertile men. The mean percentage of sperm with residual cytoplasm was statistically significantly different in all three groups. Infertile men with varicocele had the highest percentage of sperm with cytoplasmic droplets, the next highest level being in men with idiopathic infertility and the lowest level in fertile controls (11.7 +/- 1.0, 8.1 +/- 0.9 and 3.2 +/- 0.4%, respectively, P<.0001).

CONCLUSION(S)

Our data show that idiopathic and even moreso, varicocele-related male infertility are conditions associated with impaired disposal of residual sperm cytoplasm by the testis and/or epididymis. These data provide a possible mechanism for the observed semen abnormalities and reduced fertility potential associated with varicocele and idiopathic male infertility.

Effect of varicocelectomy on the abnormal retention of residual cytoplasm by human spermatozoa

Abnormal retention of cytoplasmic residues by human spermatozoa is associated with the generation of reactive oxygen species (ROS) in semen and defective sperm function. We have examined the effect of varicocelectomy on the retention of residual cytoplasm by human spermatozoa. Clinical reports of 43 men who underwent microsurgical varicocelectomy at our institution during a 1 year period beginning July 1996 were reviewed. Standard semen parameters (concentration, motility and morphology) and residual cytoplasm retention (monitored by Papanicolaou stain) were assessed before and 6 months after varicocelectomy. The percentage of spermatozoa with residual cytoplasm decreased significantly following varicocelectomy compared to pre-operatively (25.8 versus 18.1% respectively). The percentages of motile spermatozoa and normal forms increased significantly (P = 0.0003, P = 0.005 respectively) following varicocelectomy (22.6 versus 32.9% and 46.4 versus 54.4% respectively). Our data suggest that varicocelectomy can improve the disposal of residual sperm cytoplasm by the testis and/or epididymis in infertile men with varicocele. These data also suggest that varicocelectomy reduces the potential for ROS generation by human spermatozoa in these men.

Recent concepts in the management of male infertility

This review outlines the current treatment of many causes of male infertility, including idiopathic spermatogenic disorder, varicocele, obstruction of the seminal tract, and emission disorders. Recommendations regarding future treatments are presented.

Varicocele in the rat: a new experimental model. Effect on histology, ultrastructure and temperature of the testis and the epididymis

With no consistent animal prototype for the study of varicocele, we set out to create a model in the rat by complete ligation of the main branch of left spermatic vein (MBSV) or by partial ligation of the left renal vein. Three months later, the histology, ultrastructure and temperature of the testis and epididymis were studied. Microscopically, spermatogenic arrest was the most frequent anomaly seen. The most frequently noted ultrastructural change of the testis was distension of smooth endoplasmic reticula in Sertoli cells. The microvilli of columnar epithelia in epididymis were sparse and showed local defects. Lesions and increased temperatures in the testis and epididymis induced by the ligation of the left MBSV were similar to those seen in partial ligation of the left renal veins, with no significant differences between left and right. Significant differences were found, however, on comparison with the controls.

The effects of unilateral, experimental varicocele are not mediated through the ipsilateral testis

Unilateral varicocele has been associated with diminished male fertility in humans and with bilateral physiologic and histologic changes in the testis of humans and laboratory animals. In particular, left varicocele in Sprague-Dawley rats results in bilateral increases in testicular temperature and blood flow. The mechanism by which unilateral varicocele can cause testicular changes is not known. The purpose of the present study was to determine whether or not the presence of either the ipsilateral or contralateral testicle is necessary for these effects of the varicocele to occur in the opposite testis. Varicoceles were created in adult, male rats by partial constriction of the left renal vein. Bilateral testicular blood flow was measured by a radiolabelled microsphere distribution technique and testicular temperature was taken with a needle probe thermometer. Right or left orchiectomies were performed on selected animals at the time of surgery to establish the unilateral left varicocele. Animals were studied 30 days after surgery. Mean testicular blood flow was significantly increased (P less than 0.01) in all animals having a left varicocele when compared with animals not having a varicocele regardless of whether a unilateral orchiectomy was performed. Likewise, the mean difference between intraabdominal temperature and intratesticular temperature (delta T) was significantly decreased in all groups of animals having varicoceles when compared with groups without varicoceles whether or not an orchiectomy had been performed. Thus, the studied bilateral effects of left-sided, experimental varicocele in the rat are not dependent upon the presence of a left testicle.

The value of testicular biopsy in patients with varicocele

With the use of semi-thin sections of 88 testicular biopsies from 44 patients, we were able to separate a relatively uniform group of patients with idiopathic left varicocele and infertility into 4 groups with different pathophysiological conditions. Group 1 patients had atrophy of the Leydig cells, decreased Leydig cell ratio, low plasma testosterone, and normal luteinizing and follicle-stimulating hormone levels. Surgery resulted in a significant improvement in sperm count. Group 2 patients had undergone attempted repair of Leydig cells, and had a normal Leydig cell ratio, and normal testosterone, luteinizing hormone and follicle-stimulating hormone plasma values. Group 3 patients demonstrated hyperplasia and an increased Leydig cell ratio, high luteinizing and follicle-stimulating hormone values, and relatively high testosterone values. Group 4 patients had an increased Leydig cell ratio but severe atrophy of the Leydig cells and tubuli, indicating burned out testes with high luteinizing and follicle-stimulating hormone but low testosterone levels. A successful operation failed to increase the sperm count in the latter groups. The technique used should allow better patient selection for medical treatment, as well as lead to a better understanding of the etiopathogenesis of infertility in varicocele patients. Therefore, the histological technique has an important role in the evaluation of patients suffering from infertility in general.

An ultrastructural study on the presence of various types of crystals in the infertile human testis

Testicular biopsies obtained from 23 infertile outpatients, found to be normal except for oligospermia, were investigated using a Zeiss electron microscope. Ultrastructural changes in the Sertoli cells were encountered frequently, whilst most of the spermatogenic cells were degenerative. Sertoli cells exhibited abundant microfilaments which were seen to form small clusters leading to the formation of Charcot-Böttcher crystals, whilst the Leydig cells of the same specimens revealed the presence of small microtubular arrays and numerous small sized crystals. Fusion of small sized crystals resulted in the formation of typical Reinke crystals in the Leydig cells. Crystalloid structures similar to those seen in the Sertoli cells were also observed in the cytoplasm of type-A-spermatogonia and in a number of multinucleated cells with cytoplasmic characteristics of spermatogonia and Sertoli cells. Similar crystallization processes in both Sertoli and Leydig cells imply a close relationship between crystallization processes and impairment of spermatogenesis.

Stagnation of blood in the microcirculatory vessels in the testes of men with varicocele

This study reports on the stagnation of blood within the microcirculatory vessels of the testes of patients with varicocele. Both fine structural and quantitative studies were carried out on testicular biopsies from 14 men with varicocele and a control group of three men. Arterioles, capillaries, and venules were completely filled with blood in all affected testes. Enlarged pores were also noticed between the endothelial cells of these affected vessels. Lumen diameters of the arterioles were significantly decreased in the affected testis compared to controls. No change in the overall diameter of the arterioles and venules was noted. Significant thickening of the limiting membrane was also noted in the affected testis. It was concluded that the stagnation of blood in the microcirculatory vessels may cause local hypoxia and ischemia, which lead to spermatogenic disorders.

Ultrastructural lesions in testes from hyperprolactinemic men

Testicular tissue from eight men with prolactinomas and elevated serum prolactin were evaluated by light (LM) and transmission electron microscopy (TEM). A semiquantitative assessment of testicular morphology was employed to provide a morphology index for each tissue specimen. Although in each biopsy specimen germ cell exfoliation was evident, as was abnormal structural change in the seminiferous epithelium, there was no apparent correlation with the overall degree of tissue pathology (morphology index) and the serum level of prolactin. All of the tissue displayed variably thickened seminiferous tubule walls which, when viewed by TEM, were composed of thickened laminae propriae and redundant and involuted basal laminae. Likewise, all tubules contained Sertoli cells with overt cytoplasmic degeneration, principally in the apical (adluminal) region of the cell. This was visualized, in part, as a retraction of the apical cytoplasm from periluminal spermatids and degeneration or absence of Sertoli-germ cell junctional specializations. Sertoli-Sertoli cell junctional complexes appeared structurally intact. Leydig cell ultrastructure was typical of normal cells and contained a variable amount of lipid and smooth endoplasmic reticulum. This also was without positive correlation with the overall degree of tissue pathology or level of serum prolactin. Our results demonstrate the variable degree of testicular pathology associated with hyperprolactinemia in man, and suggest that abnormal tubule walls and altered Sertoli cell ultrastructure are consistent findings in this abnormal endocrine condition.

Testicular arterial perfusion in varicocele: the role of rapid sequence scintigraphy with technetium in varicocele evaluation

Rapid sequence scintigraphy was used to study testicular arterial perfusion and venous stasis in 53 patients with varicocele-associated infertility, 17 with idiopathic testicular failure and 9 treated for varicocele. Arterial blood supply to the diseased testicle was decreased in 63 per cent of the patients with subclinical or low grade varicocele compared to 18 per cent with idiopathic testicular failure. In the majority of cases the disturbance of perfusion disappeared immediately after interruption of retrograde blood flow in the internal spermatic vein by transcatheter embolization, whereas persistently impaired perfusion was found in a few cases with no improvement of semen quality after treatment. Venous stasis was found in only 18 per cent of the patients with low grade varicocele compared to 88 per cent with large varicoceles. It is suggested that impaired arterial blood supply rather than venous stasis is the pathogenic factor in epididymo-testicular dysfunction associated with low grade varicocele.

Ultrastructural study of seminiferous tubules in the rat after prenatal irradiation

Is the presence of germinal cells necessary for the Sertoli cells to acquire normal features? To respond to this question we have studied the development of the Sertoli cells in rats irradiated at the end of the foetal life. In the prenatal irradiated rats, the lumen of the seminiferous tubules appears later than in the control rats. The Sertoli cells show numerous flexuose apical processes, with central microtubule bundles. These processes regress progressively after the 40th day of life when the tubular lumen appears; numerous junctional complexes differentiate with the same structure as those of control animals. There are important dilatations of the intercellular spaces. The cytoplasmic organelles show a normal development up to the 40th day of life. After this period, the rough endoplasmic reticulum and the Golgi apparatus clearly regress while important dilatations appear in the smooth endoplasmic reticulum and persist in the adult animal. From the 35th day on, the basal lamina of the seminiferous tubules is irregular and multilayered. The differentiation of the Sertoli cells seems to be independent of the presence of germinal cells until the 40th day of life and presents several particularities; thereafter the Sertoli cells show signs of regression.