Testicular Regression Syndrome: Two Case Studies.

Testicular agenesis, also called testicular regression syndrome (TRS), is a rare disease. It is defined by the complete absence of testicular tissue associated with a 46,XY karyotype. The phenotype is variable depending on when gonadal regression occurs in utero. Several etiologies have been identified. Here, we report two cases of TRS with an initial diagnosis of cryptorchidism and bilateral impalpable testes. The hormonal assessment showed an undetectable anti-Müllerian hormone (AMH) level and high gonadotropins. Also, radiological exploration did not show the testicles in a normal position, which was confirmed by a negative laparoscopy, establishing the diagnosis of TRS. Androgen replacement therapy along with psychological support to the patient is recommended is such cases.

Abdominal Cryptorchidism with Complete Dissociation between the Testis and Deferent Duct Mimicking Testicular Regression Syndrome.

Complete separation of the deferent duct from the epididymis in cryptorchid testes residing in the abdomen is an extremely rare variant of developmental disorders of the testis and epididymis. Available sources mention only three clinical cases similar to our observations. The unique anatomic aspects of this disorder hamper the correct diagnosis of an intra-abdominal cryptorchid testis. Two boys with nonpalpable left-sided cryptorchidism underwent diagnostic laparoscopy, revealing an intra-abdominally located testis. The epididymis was completely separated from the deferent duct, and the epididymis and testis were supplied by testicular vessels. Exploration of the inguinal canal revealed blind-ending deferent ducts. The testis was brought down through the inguinal canal and fixed in the scrotum in both boys. The follow-up examination at 6 months revealed no signs of testicular atrophy or malposition of the testis in either patient. With our observations in mind, the exclusive use of a transscrotal or transinguinal approach as the initial surgical exploration in the treatment of patients with nonpalpable forms of cryptorchidism may be inappropriate. Careful laparoscopic examination of the abdominal cavity is indispensable in children with suspected testicular regression syndrome or nonpalpable forms of cryptorchidism.

Testicular regression syndrome: A retrospective analysis of clinical and histopathological features in 570 cases.

This study aimed to analyze the clinical features and pathological findings of the largest reported case series of testicular regression syndrome (TRS). Data, including age, affected side, color Doppler ultrasound results, surgical methods, intraoperative conditions, and pathological examinations, of children with unilateral TRS who were treated in our center from December 2012 to November 2021 were retrospectively analyzed. A total of 570 patients were included in this study. The mean age at surgery was 38 (range, 5-193) months. There were 457 cases (80.2%) of left TRS. Preoperative color Doppler ultrasonography found nubbins in 172 cases (30.2%). The long diameter of the contralateral testis was 17.11 (±4.22) mm, and the volume was 0.81 (±1.15) ml. The long diameter was ≥1.6 cm in 62.0% of the patients (240/387) aged ≤3 years. Laparoscopy was performed as the initial surgical step in 513 cases, of which 96.7% of the children had closed internal rings. One or more lesions of fibrosis, hemosiderin, and calcification were found in 92.4% (474/513) of the excised remnants. Germ cells were present in 16 cases (3.1%). In conclusion, TRS is more common on the left side and is usually accompanied by a closed internal ring and compensatory hypertrophy of the contralateral testis. Germ cells are only present in cases where the spermatic vessels enters the internal ring. We recommend that further exploration and excision of the remnants may not be applicable in cases where only the vas deferens has entered the internal ring.

Cellular Modifications in Spermatogenesis during Seasonal Testicular Regression: An Update Review in Mammals.

Testicular regression occurs during the non-breeding season in many mammals. This affects spermatogenesis, resulting in decreased or arrested activity. Both lead to a decrease or cessation in sperm production. In recent years, the cellular mechanisms that lead to infertility in males in non-reproductive periods have been studied in very different species of mammals. At the start of the present century, the main mechanism involved was considered as an increase in the apoptotic activity of germ cells during the regression period. The loss of spermatogonia and spermatocytes causes not only a decrease in spermatogenesis, but an arrest of the seminiferous epithelium activity at the end of regression. Recently, in some mammal species, it was found that apoptosis is the usual mechanism involved in epithelium activity arrest, although it is firstly atrophied by massive desquamation of the germ cells that are released from their binding with the Sertoli cells, and which are shed into the lumen of the seminiferous tubule. In other species, it has been shown that not only germ cell apoptosis, but also Sertoli cell apoptosis, including decreased proliferative activity, spermatophagy or autophagy, are involved in testicular regression. Furthermore, the most recent studies indicate that there are multiple patterns of seminiferous epithelium regression in seasonally breeding animals, which may not only be used by different species, but also by the same ones to reproduce in the best conditions, ensuring their survival. In conclusion, at this time, it is not possible to consider the existence of a paradigmatic cellular mechanism in the involution of the seminiferous epithelium applicable to all male mammals with seasonal reproduction, rather the existence of several mechanisms which participate to a greater or lesser extent in each of the species that have been studied to date.

Genetics of cryptorchidism and testicular regression.

Cryptorchidism, i.e., undescended testis, is one of the most common genital malformations in newborn male babies. The birth rate of cryptorchidism varies from 1.6 to 9.0 %. Etiology of disrupted testicular descent is complex and predisposing causes include genetic, hormonal, environmental, lifestyle and maternal factors. Testicular descent occurs in two major steps and testicular hormones and normal function of hypothalamic-pituitary-testicular axis are important for normal descent. Several gene mutations are associated with syndromic cryptorchidism but they are rarely found in boys with isolated undescended testis. Testicular regression can also cause an empty scrotum. Normal male genital phenotype indicates that the boy has had functioning testis during development. Torsion of the testis can cause testicular regression but in many cases the reason for vanishing testis remains elusive. In this narrative review we discuss genetics of cryptorchidism and testicular regression.

Is Routine Excision of Dysplastic Testicular Remnants/Nubbins Associated with Nonpalpable Testis Necessary? Is Routine Fixation of Contralateral Solitary Testis Indicated? A Survey on the Prevalent Practice among Indian Pediatric Surgeons.

Background and Aims: Dysplastic nubbin also referred to as testicular regression syndrome (TRS) is found in 5% of cases of the Non palpable testis (NPT). There is no consensus on the excision of the above and fixation of the contralateral solitary testis. We aimed to survey the prevalent practice of the same among members of the Indian Association of Pediatric Surgeons (IAPS). Methods: A structured questionnaire was sent through group e-mail and social media platforms to IAPS members to identify their practices in management. Results: A total of 132 surgeons responded to the questionnaire. Excision of intra-abdominal and inguinoscrotal TRS remnants was practiced by 84% (95% confidence interval [CI] 77%-89%) and 82% (95% CI 74%-87%). Fixation of contralateral solitary testis was practiced by 62% (95% CI 53%-70%) in the above scenario. Among the respondents, 30% reported encountering torsion of solitary testis during their career and this experience was a significant factor (P = 0.01) in deciding contralateral orchidopexy. Scrotal infection/necrosis was not encountered by a majority (72%) and it was not a deterrent factor in preventing contralateral orchidopexy (P = 0.68). Conclusions: The majority of pediatric surgeons favored the removal of intra-abdominal/inguinoscrotal TRS remnants identified during laparoscopy for NPT. A majority favored sutureless fixation of the contralateral solitary testis.

DHX37 gene heterozygous variant—a frequent cause of embryonic testicular regression syndrome / 中华内分泌代谢杂志

Objective:To report embryonic testicular regression syndrome(ETRS) caused by DHX37 heterozygous variant for the first time in China and summarize the clinical manifestations of ETRS as to improve the understanding of doctors for this disease.Methods:The clinical data and whole exome sequencing results of five cases of ETRS from Shenzhen Children′s Hospital were collected. The reported cases of DHX37 heterozygous variant were reviewed.Results:Five patients with ETRS visited the doctors at the age of 2 months to 5 years and 5 months. Three patients raised as males came to hospital due to virilition and 2 female patients visited a doctor due to clitoral hypertrophy. No uterus was detected by ultrasound in all patients. The gonadal pathologies from 4 cases displayed no testicular tissue or gonadal dysgenesis, complicated with gonadoblastoma in one case. The genetic testing revealed that the heterozygous variant(c.923G>A, p. R308Q) in DHX37 was found in 2 cases, without variant in other 3 cases. According to the review, ETRS and 46, XY gonadal dysgenesis due to DHX37 herozygous variant was firstly reported in 2019. A total of 40 cases, including 21 cases of ETRS, presented with the virilition or female phenotype, with the disappearance of testicular tissue as the main pathologies. There is no report in China.Conclusion:The article summarized the clinical manifestations and whole exome sequencing results of 5 patients with ETRS, among which two cases were caused by DHX37 variants and one was complicated with gonadoblastoma.

Expanding DSD Phenotypes Associated with Variants in the DEAH-Box RNA Helicase DHX37.

Missense variants in the RNA-helicase DHX37 are associated with either 46,XY gonadal dysgenesis or 46,XY testicular regression syndrome (TRS). DHX37 is required for ribosome biogenesis, and this subgroup of XY DSD is a new human ribosomopathy. In a cohort of 140 individuals with 46,XY DSD, we identified 7 children with either 46,XY complete gonadal dysgenesis or 46,XY TRS carrying rare or novel DHX37 variants. A novel p.R390H variant within the RecA1 domain was identified in a girl with complete gonadal dysgenesis. A paternally inherited p.R487H variant, previously associated with a recessive congenital developmental syndrome, was carried by a boy with a syndromic form of 46,XY DSD. His phenotype may be explained in part by a novel homozygous loss-of-function variant in the NGLY1 gene, which causes a congenital disorder of deglycosylation. Remarkably, a homozygous p.T477H variant was identified in a boy with TRS. His fertile father had unilateral testicular regression with typical male genital development. This expands the DSD phenotypes associated with DHX37. Structural analysis of all variants predicted deleterious effects on helicase function. Similar to all other known ribosomopathies, the mechanism of pathogenesis is unknown.

Annual reproductive cycle of males of the bat Molossusmolossus: Seasonal bimodal polyestry, testicular regression, and some aspects of the hormonal control.

Bats are mammals that play a fundamental role in the regulation of the ecosystems by, for example, controlling the insect populations. Therefore, insectivorous species, such as Molossusmolossus, have become the target of great scientific interest. Despite the different studies that exist on the species, there is still no consensus regarding its reproduction. Thus, this study aimed to analyze the morphophysiology and some aspects of the hormonal control of the testes of M. molossus (Chiroptera: Molossidae), by evaluating its morphological and morphometric variations throughout the annual reproductive cycle. Sixty sexually adult males of M. molossus were used in the study, with five specimens collected each month for one year, forming 12 sample groups. The testes of each bat were submitted to morphological, morphometric, and immunohistochemical analyses. Molossusmolossus presented an annual reproductive cycle with two peaks of spermatogenic activity, one in April and the other in September, and a period of total testicular regression in December, which has never been described. The cycle appeared to be regulated by rainfall and was, at least partially, controlled by the expression of the androgen receptor in Sertoli cells, which has agonist effects on cell proliferation.

Severe Degenerative Changes in Cryptorchid Testes in Japanese Black Cattle.

This is a histopathologic and endocrinologic study of 6 calves diagnosed with cryptorchidism. Cases 1-3 were diagnosed as resembling testicular regression syndrome. In cases 1 and 2, the extracted tissue was a small, firm, gray-white mass, and there was lack of obvious testicular tissue in case 3. Histopathologically, the excised tissue in cases 1-3 was a fibrotic testicular remnant with inflammation, mineralization, hemosiderin-laden macrophages or lipofuscin-laden macrophages, and lack of germ cells and interstitial endocrine cells. These findings were compared with cases 4-6, which were diagnosed as testicular hypoplasia due to cryptorchidism. These cases had small but otherwise grossly unremarkable intra-abdominal testicular tissue and histologically had a few germ cells and sustentacular cells with arrested spermatogenesis and an increase in interstitial endocrine cells. Cases 1-3 had more severe degenerative changes compared with cases 4-6. In case 2, the average diameter of the seminiferous tubules was much smaller than in cases 4-6, and there were few tubule cross sections. Anti-Müllerian hormone (214 pg/ml) was detected in the plasma of case 2. Based on the macroscopic and histopathologic findings as well as endocrinologic profiles, the testicular degeneration in cases 1-3 was considered similar to that of testicular regression syndrome. In this condition, it is thought that a normally developing intra-abdominal testis undergoes degeneration due to heat or a vascular disorder such as torsion.

Pathogenic variants in the DEAH-box RNA helicase DHX37 are a frequent cause of 46,XY gonadal dysgenesis and 46,XY testicular regression syndrome.

PURPOSE: XY individuals with disorders/differences of sex development (DSD) are characterized by reduced androgenization caused, in some children, by gonadal dysgenesis or testis regression during fetal development. The genetic etiology for most patients with 46,XY gonadal dysgenesis and for all patients with testicular regression syndrome (TRS) is unknown. METHODS: We performed exome and/or Sanger sequencing in 145 individuals with 46,XY DSD of unknown etiology including gonadal dysgenesis and TRS. RESULTS: Thirteen children carried heterozygous missense pathogenic variants involving the RNA helicase DHX37, which is essential for ribosome biogenesis. Enrichment of rare/novel DHX37 missense variants in 46,XY DSD is highly significant compared with controls (P value = 5.8 × 10-10). Five variants are de novo (P value = 1.5 × 10-5). Twelve variants are clustered in two highly conserved functional domains and were specifically associated with gonadal dysgenesis and TRS. Consistent with a role in early testis development, DHX37 is expressed specifically in somatic cells of the developing human and mouse testis. CONCLUSION: DHX37 pathogenic variants are a new cause of an autosomal dominant form of 46,XY DSD, including gonadal dysgenesis and TRS, showing that these conditions are part of a clinical spectrum. This raises the possibility that some forms of DSD may be a ribosomopathy.

Is excision of testicular nubbin necessary in vanishing testis syndrome?

BACKGROUND/PURPOSE: Vanishing Testes Syndrome1 (VTS) is one of the most common causes of impalpable testes in children. The role of removal of testicular nubbins owing to malignant potential in VTS is unclear. We sought to evaluate whether testicular nubbins need to be excised owing to this potential. METHODS: We conducted a retrospective review of children with a clinical diagnosis of impalpable testes aged 0-18 who presented to our tertiary hospital between 2007 and 2017. VTS was defined as the presence of hypoplastic vas entering a closed internal inguinal ring or remnants of gonadal tissue distally. Data collected included: age at operation, need for laparoscopy, location of nubbin and histopathological findings. RESULTS: We identified 50 consecutive children (mean age 2.4 years, range: 7 months to 12 years) with a clinical diagnosis of impalpable testis. Forty-eight of the 50 underwent laparoscopy with no testicle palpable when examined under anesthesia. Thirty-three children had VTS confirmed at laparoscopy and testicular nubbins identified with three of these being bilateral. Thirty-two children had these nubbins excised with histopathology available for 31 individual testes. Thirty were confirmed testicular nubbins with no viable testicular tissue. No malignancies were identified. CONCLUSION: Results from this study show that testicular nubbins do not have viable germ cells and therefore do not need to be excised on the basis of malignant potential of residual testicular tissue. LEVEL OF EVIDENCE: Level IV treatment study.

Presence of viable germ cells in testicular regression syndrome remnants: Is routine excision indicated? A systematic review.

There is no consensus in the literature about the necessity for excision of testicular remnants in the context of surgery for an impalpable testis and testicular regression syndrome (TRS). The incidence of germ cells (GCs) within these nubbins varies between 0 and 16% in previously published series. There is a hypothetical potential future malignancy risk, although there has been only one previously described isolated report of intratubular germ-cell neoplasia. Our aim was to ascertain an accurate incidence of GCs and seminiferous tubules (SNTs) within excised nubbins and hence guide evidence-based practice. The systematic review protocol was designed according to the PRISMA guidelines, and subsequently published by the PROSPERO database after review (CRD42013006034). The primary outcome measure was the incidence of GCs and the secondary outcome was the incidence of SNTs. The comprehensive systematic review included articles published between 1980 and 2016 in all the relevant databases using specific search parameters and terms. Strict inclusion and exclusion criteria were ultilised to identify articles relevant to the review questions. Twenty-nine paediatric studies with a total of 1455 specimens were included in the systematic review. The mean age of the patients undergoing nubbin resection was 33 months and the TRS specimen was more commonly excised from the left (68%). The incidence of SNTs was 10.7% (156/1455) and the incidence of GCs, 5.3% (77/1455). Histological analysis excluding the presence of either SNTs or GCs was consistent with TRS, fibrosis, calcification or haemosiderin deposits. There is limited evidence on subset analysis that GCs and SNTs may persist with increasing patient age. This systematic review has identified that 1 in 20 of resected testicular remnants has viable GCs and 1 in 10 has SNTs present. There is insufficiently strong evidence for the persistence of GCs and SNTs with time or future malignant potential. Intra-abdominal TRS specimens may contain more elements and, therefore, require excision, although this is based on limited evidence. However, there is no available strong evidence to determine that a TRS specimen requires routine excision in an inguinal or scrotal position.

Comb, cloaca and feet scores and testis morphometry in male broiler breeders at two different ages / Escores de crista, cloaca e de pé e morfometria testicular em galos de matriz pesada em duas diferentes idades

In broiler breeder roosters, the weight of the testes is positively associated with daily sperm production and fertility. In birds, the testes are located in the coelomic cavity, not being accessible to reproductive evaluation as mammalian testes. The reproductive evaluation of roosters is based on phenotypic traits. Any changes on testes will be reflected on fertility levels. The aim of this paper was to evaluate the potential of association of phenotypic traits as body weight (BW), comb scores (COS), cloaca scores (CLS) and feet scores (FS) with testicular morphometric parameters in adult Cobb® Mx roosters in two ages (25 and 45 weeks of age). The low BW roosters had lower testes weight (TW), smaller seminiferous tubule diameter (STD) and lower comb and cloaca scores than the medium and high BW roosters (P≤0.05). Heavy roosters had the highest COS and bigger seminiferous epithelium height (SEH). There was no statistical difference between the BW categories in FS and volumetric proportion of seminiferous tubule (ST) and interstitial tissue (IT). Considering the age effect, roosters with 45 weeks of age had lower TW and ST than 25-week roosters. Positive, moderate and significant correlation was found between testes weight and phenotypic characteristics as BW, COS and CLS in 45week roosters. A positive, moderate and significant correlation was found between body weight and histologic testicular characteristics as STD and SHE in both evaluated ages. In conclusion, there is a regression in the testes weight with age and it is more intense in Cobb® Mx roosters with lower BW. Furthermore, it is concluded that the BW positively influences the testes weight and histological quality of the testes. COS and CLS can be used with moderate potential prediction to identify roosters with low testes weight at 45 weeks of age.(AU)

Em galos de matriz pesada sabe-se que o peso dos testículos pode ser associado positivamente com a produção diária de espermatozoides e que alterações nos testículos irão refletir na fertilidade. Nas aves, os testículos estão localizados dentro da cavidade celomática, e, portanto, não são acessíveis para exame andrológico direto, como em mamíferos. A avaliação reprodutiva de galos se baseia principalmente em características fenotípicas. Buscou-se avaliar o potencial de associação de alguns parâmetros fenotípicos, como peso corporal (PC), escores de crista (ECR), escores de cloaca (ECL) e escores de pés (EP), com parâmetros morfológicos de testículos em galos Cobb® Mx em duas idades (25 e 45 semanas de idade). Galos leves apresentaram menor peso testicular (PT), menor diâmetro de túbulo seminífero (DT), e menores ECR e ECL que galos médios e pesados (P≤0.05). Galos pesados apresentaram os maiores ECR e maiores valores para altura do epitélio seminífero (AE), e DT. Não houve diferença estatisticamente significativa entre as categorias de peso para escores de pé e proporções de túbulo seminífero (TS) e interstício (INT). Considerando-se o efeito da idade, galos com 45 semanas de idade apresentaram menores PT e TS que galos com 25 semanas de idade. Correlação positiva, moderada e significativa foi encontrada entre peso de testículo e características fenotípicas como ECR, ECL e PC em galos de 45 semanas de idade. Foi encontrada correlação positiva, moderada e significativa entre PC e características testiculares como DT e AE nas duas idades avaliadas. Conclui-se que em galos Cobb® Mx ocorre regressão do testículo com o avanço da idade, e ela é mais intensa em galos com menor peso corporal. Conclui-se que o PC tem influência positiva no peso e índices histomorfométricos dos testículos, e que escores de crista e de cloaca podem ser utilizados com potencial moderado de predição para identificar galos com baixo peso de testículos em galos com 45 semanas de idade.(AU)

Embryonic Testicular Regression Syndrome Presenting as Primary Amenorrhea: A Case Report and Review of Disorders of Sexual Development.

BACKGROUND: Sex development depends on the synchronous interaction of complicated genetic and hormonal events. Sex differentiation begins with sex determination, which is the assignment of the embryonic bipotential gonads as either testes or ovaries on the basis of transcriptional regulation. Hormonal regulation then directs the development of the male or female phenotype. Disruptions of this intricate cascade of events result in disorders of sexual development. CASE: A 16-year-old female adolescent presented with primary amenorrhea. Evaluation revealed female external genitalia, XY karyotype, absent gonadal tissue, and rudimentary Müllerian structures. On the basis of her constellation of findings, the most logical diagnosis was the rare embryonic testicular regression syndrome. SUMMARY AND CONCLUSION: A careful understanding of embryonic sexual development is critical to the evaluation of patients with disorders of sexual development.

Is routine excision of testicular remnants in testicular regression syndrome indicated?

BACKGROUND: Undescended testicles are a common finding in full-term male infants. In the majority of these infants, the testicle spontaneously descends in the first year of life. However, in others, it remains impalpable in an abnormal position or there may only be a small abnormal testicular remnant present. For these infants there is still controversy surrounding inguinal exploration and/or excision of these testicular remnants at the time of operative intervention. The controversy centres on their potential future malignant potential. AIM: The aim of the study was to ascertain the incidence of the presence of either germ cells (GCs) or seminiferous tubules (SNTS) in the excised testicular remnants. This was performed at a paediatric surgical tertiary centre and contributes to the evidence base for this condition. METHOD: A retrospective data analysis occurring over a 15-year period of all excised testicular remnants. The testicular remnants were analysed for age, laterality, histological analysis and clinical diagnosis. Subset analysis included subdivision into both intra-abdominal or inguinal positions, and age ranges. Statistical analysis was using Fisher's exact test and a P-value of <0.05 was considered to be significant. RESULTS: A total of 140 paediatric male patients were identified as having had a testicular remnant excised during the study period. Their demographics and also the main results are summarised in the overall summary Table. The mean age at intervention was 3.5 years (range: 3 months to 17 years). A total of 132/140 of the boys underwent excision of an inguinal testicular regression syndrome (TRS) remnant and 8/140 an intra-abdominal remnant. Comparison of these two groups revealed no significant difference for the presence of GCs (12 (9%) vs 2 (25%), P = 0.18). However, intra-abdominal TRS remnants were much more likely to contain SNTs (27 (21%) vs 7 (88%), P = 0.0002). There was no decreased incidence of either GCs or SNTs with increased patient age. DISCUSSION: The main reason for the debate over the management of boys with TRS is the variable incidence of viable germ cells reported in different studies: it has been reported between 0 and 16%. The incidence of GCs (10%) and also SNT (24%) in the present series therefore contributes to this evidence base and is in the middle of this range. It is still unclear as to whether these remnants have a future malignancy risk, as there is only one case of intratubular germ cell neoplasia (ITGCN) in a testicular remnant reported in the literature and this was not immunohistochemically supported. The presence of ITGCN, although considered as a precursor to the development of a testicular germ cell tumour in adult patients, has also not been established in paediatric patients. The natural history of the GCs in TRS specimens is also unknown. In the present series, however, there was no decreased incidence demonstrated with increased patient age, although older patient numbers limited this subset analysis. Despite this controversy, as these patients were already under general anaesthetic, an inguinal exploration and excision of any TRS remnant that was present did not significantly increase the operative procedure or time, and removed any potential malignancy risk. CONCLUSION: This evidence supports the exploration and excision of inguinal testicular remnants, as one in ten boys have GCs present and one in four have SNTs, which may have a potential future malignant transformation risk.

Vanishing testis syndrome: report of two cases.

Vanishing testis syndrome or Testicular regression syndrome (TRS) is defined as the absence or an incomplete development of the testis of varying degrees in 46XY patients with normal external genitalia.TRS or vanishing testis syndrome may be seen in less than 5% of all patients of cryptorchidism. We report two cases of TRS who underwent surgical exploration with an initial diagnosis of cryptorchidism with impalpable testis. Grossly testicular tissue was not identified and the vas deferens was ending into a nubbin in both the cases. The presumed testicular remnants were sent for histological examination. The histological sections in both the cases showed vascularised fibrous nodule, structure of the spermatic cord and calcification, supporting the diagnosis of TRS.

Ultrastructure of spermatogenesis, spermatozoon and processes of testicular regression and recrudescence in Eptesicus furinalis (Chiroptera: Vespertilionidae).

Studies have shown that the annual reproductive cycle of Eptesicus furinalis includes at least one period of total testicular regression. Thus, this study aimed to evaluate their reproductive cycle ultrastructurally. The annual reproductive cycle was divided into four periods: active, regressing, regressed and recrudescence. The active period was similar to that of other bats, including the completion of spermatogenesis with three main types of spermatogonia (Ad, Ap and B) and 12 steps in the process of spermatid differentiation. However, its spermatozoa differed in that outer dense fibers 1, 5, 6 and 9 are larger than the others and due to the presence of what is likely a probably genera-specific bulging in the anterior portion. In the regressing period, Sertoli cell nuclei migrate to the basal compartment with the nuclei close to the basal lamina. The basal compartment had a more compact appearance than the adluminal compartment, with relaxed cellular connections. In the regressed period, spermatogenesis ceased; the seminiferous epithelium was composed only of Sertoli cells and three types of spermatogonia: types Ad, 1 and 2. In the recrudescence period, spermatogenesis restarted, with the process of reactivation divided into three phases: early, medial and late recrudescence. In conclusion, our study described the process of spermatogenesis and the ultrastructure of the spermatozoa and confirmed the presence of a process of total testicular regression in the annual cycle of E. furinalis. We characterize distinct morphologic variations in the ultrastructure of the testicular cells during the four different periods of the annual reproductive cycle.

Ultrastructural characteristics of the spermatogenesis during the four phases of the annual reproductive cycle of the black myotis bat, Myotis nigricans (Chiroptera: Vespertilionidae).

Myotis nigricans is an endemic species of vespertilionid bat, from the Neotropical region, that resembles temperate zone bats in their reproductive cycle; presenting an annual reproductive cycle with two periods of testicular regression, which are not linked to the apoptotic process and seems to be not directly linked to any seasonal abiotic variation. Thus, this study aimed to ultrastructurally evaluate their reproductive cycle. The process of testicular regression could be divided into four periods: active; regressing; regressed and recrudescence; with all presenting distinct characteristics. The active period was similar to that of other bats, presenting the complete occurrence of spermatogenesis, with three main types of spermatogonia (A(d), A(p), and B) and 12 steps in spermatid differentiation; however, it differed in having the outer dense fibers 1, 5, 6, and 9 larger than the others. These three types of spermatogonia undergo considerable morphologic changes from regressing to the regressed period, and in the recrudescence, they return to the basic morphology, which reactivates spermatogenesis. In conclusion, our study described the process of spermatogenesis, the ultrastructure of the spermatozoa and the distinct morphologic variations in the ultrastructure of the testicular cells of M. nigricans during the four different periods of its annual reproductive cycle.