Development Of Germinal Cells Research Articles

Barley Anther and Meiocyte Transcriptome Dynamics in Meiotic Prophase I.

In flowering plants, successful germinal cell development and meiotic recombination depend upon a combination of environmental and genetic factors. To gain insights into this specialized reproductive development program we used short- and long-read RNA-sequencing (RNA-seq) to study the temporal dynamics of transcript abundance in immuno-cytologically staged barley (Hordeum vulgare) anthers and meiocytes. We show that the most significant transcriptional changes in anthers occur at the transition from pre-meiosis to leptotene–zygotene, which is followed by increasingly stable transcript abundance throughout prophase I into metaphase I–tetrad. Our analysis reveals that the pre-meiotic anthers are enriched in long non-coding RNAs (lncRNAs) and that entry to meiosis is characterized by their robust and significant down regulation. Intriguingly, only 24% of a collection of putative meiotic gene orthologs showed differential transcript abundance in at least one stage or tissue comparison. Argonautes, E3 ubiquitin ligases, and lys48 specific de-ubiquitinating enzymes were enriched in prophase I meiocyte samples. These developmental, time-resolved transcriptomes demonstrate remarkable stability in transcript abundance in meiocytes throughout prophase I after the initial and substantial reprogramming at meiosis entry and the complexity of the regulatory networks involved in early meiotic processes.

The Role of Transcription Factors in Gonad Development and Sex Differentiation of a Teleost Model Fish—Guppy (Poecilia reticulata)

Simple SummaryThe research was carried out to determine differences in gonadal development in female and male guppies (Poecilia reticulata) at the molecular level. Fish from the Poeciliidae family is an excellent model for gonadal differentiation studies due to their fertility and the occurrence of sexual dimorphism. Due to exceptional exposure of the aquatic environment to xenobiotics and other pollutants released into water, it becomes necessary to consider their influence on fish and other aquatic organisms’ reproductive capacity. To better understand the processes occurring during gonadal development in guppies, we conducted our research on animals of different ages: 1, 60, and 360 dph (day post-hatching). By examining the basic mechanisms of sex determination in guppies, it will be possible to identify disorders in gonadal development caused by exposure to pollutants in the water.The guppy (Poecilia reticulata) is one of the world’s most popular ornamental fish. Due to lecithotrophic viviparous, it is commonly used in toxicological studies and environmental monitoring. This study aimed to investigate the molecular mechanisms of gonad development and differentiation during guppy ontogenesis. The study mainly focused on the role and localization of potential specific sex markers and transcription factors: Sox9, Dmrt1, Erβ. For histological analysis, guppies of both sexes were collected at 1, 60, and 360 dph (day post-hatching). The gonads morphology and immunohistochemistry detection of mentioned markers localization were performed. The expression of Sox9 protein was compared between sexes. Histological analysis revelated all types of male germinal cells in 60 dph guppy’s testes. Maturated oocytes were visible in the ovaries of 360 dph fish. The Sox9 expression varied in spermatocytes and spermatids, from cellular to nuclear localization, and was higher in ovaries. Dmrt1 was detected in all testes groups and 360 dph ovaries. The Erβ was observed in both sexes at 60 and 360 dph. For the first time, the localization of transcription factors in guppy during ontogenesis was traced. The Sox9 designation as a factor regulating the development of germinal cells in adult guppies may facilitate the analysis of xenobiotics’ influence on fish’s reproductive system.

Role of GnRH Isoforms in Paracrine/Autocrine Control of Zebrafish (Danio rerio) Spermatogenesis.

Abstract It is well established that hypothalamic GnRH (gonadotropin-releasing hormone) is one of the key peptides involved in the neuroendocrine control of testicular development and spermatogenesis. However, the role of GnRH as a paracrine regulator of testicular function has not been fully investigated. The present study demonstrates the presence of GnRH and its receptors in the zebrafish (Danio rerio) testis, and provides information on direct action of native GnRH isoforms (GnRH2 and GnRH3) on different stages of spermatogenesis in this model. Both GnRH2 and GnRH3 stimulated basal spermatogenesis by increasing numbers of type Aund spermatogonia, spermatozoa, and testosterone release, and in this study GnRH2 exerted higher relative activity than GnRH3. Next, we evaluated the effects of GnRH isoforms on human chorionic gonadotropin (hCG)- and follicle-stimulating hormone (Fsh)-induced spermatogenesis. The 2 GnRH isoforms were found to have different effects on Fsh- and hCG-induced response depending on the stage of spermatogenesis and concentration of the peptides. The results provide strong support for the hypothesis that locally produced GnRH2 and GnRH3 are important components of the complex multifactorial system that regulates testicular germinal cell development and function in adult zebrafish.

Reproductive Cycle of Females and Reproduction of the Siberian Salamander (Salamandrella keyserlingii, Caudata, Hynobiidae) on the Coast of the Sea of Okhotsk

The sexual cycle of Siberian salamander females (Salamandrella keyserlingii Dybowski 1870) has been studied in the tundra of the northern coast of the Sea of Okhotsk. Spawning starts soon after the end of wintering (in the second half of May) and ends up in the first half of June. At the end of June, the ovaries show obvious features of a new ovogenic cycle; i.e., pigment starts accumulating in large vitellogenic oocytes. By the end of July, the ovaries in most individuals are already filled with pigmented follicles and the oviduct epithelium is restored. The time from spawning to the appearance of a new generation of mature oocytes lasts a little more than two months (i.e., half of the whole activity season). In the second half of August, the state of the genital system is identical to that in spring before spawning, this proving their annual reproduction. The average fecundity in the studied water bodies varies from 102 to 123 eggs and is comparable to that in other parts of the distribution range. Oogenesis both in the vast majority of females that reach pubescence (subadultus) and in those that spawn in spring occurs simultaneously, but in some subadults it is completed almost a month or a month and a half earlier. By this phenological feature, the female subadults differ considerably from the male subadults, in which completion of spermatogenesis extends much more strongly into the season. A study of the ecology of the Siberian salamander in the conditions of a short season of activity with low temperatures allows for the coast of the Sea of Okhotsk to be considered not as extreme, but, in contrast, rather favorable for its habitation. Many population characteristics in this area are typical for the species in general. The main features of the male and female sexual cycles appear to be similar to those observed in species of the same family that live in the south of the region. The short period of germinal cell development, coupled with the outstanding winter cold hardiness of the species, partially accounts for its unique adaptive potential, which allows it to colonize vast territories of northern Eurasia and successfully thrive in the territories with short and cold summer period.

Stage-Specific Gene Profiling of Germinal Cells Helps Delineate the Mitosis/Meiosis Transition.

In flowering plants, germ lines are induced from somatic meristems within reproductive organs. Within anthers, germinal cell initials first undergo several rounds of mitotic proliferation before synchronously entering meiosis. Our understanding of the progression and the molecular basis of this mitosis to meiosis transition is still limited. Taking advantage of the correlation between anther length and premeiotic germinal cell development in maize (Zea mays), we studied the transcriptome dynamics of germinal cells at three sequential stages, mitotic archesporial cells, enlarging pollen mother cells at the premeiosis interphase, and pollen mother cells at the early prophase of meiosis, using laser microdissection-based expression profiling. Our analysis showed that cells undergoing the mitosis-meiosis switch exhibit robust transcriptional changes. The three stages are distinguished by the expression of genes encoding transcription factor subsets, meiotic chromosome recombination proteins, and distinct E3 ubiquitin ligases, respectively. The transcription level of genes encoding protein turnover machinery was significantly higher in these three stages of germinal cells than in mature pollen, parenchyma cells, or seedlings. Our experimental results further indicate that many meiotic genes are not only transcribed, but also translated prior to meiosis. We suggest that the enlarging pollen mother cells stage represents a crucial turning point from mitosis to meiosis for developing germinal cells.

Molecular cloning and expression analysis of five heat shock protein 70 (HSP70) family members in Lateolabrax maculatus with Vibrio harveyi infection

Heat shock proteins 70 (HSP70s) are molecular chaperones that aid in protection against environmental stress. In this study, we cloned and characterized five members of the HSP70 family (designated as HSPa1a, HSC70-1, HSC70-2, HSPa4 and HSPa14) from Lateolabrax maculatus using rapid amplification cDNA ends (RACE). Multiple sequence alignment and structural analysis revealed that all members of the HSP70 family had a conserved domain architecture, with some distinguishing features unique to each HSP70. Quantitative real-time (qPCR) analysis revealed that all members of the HSP70 family were ubiquitously and differentially expressed in all major types of tissues, including testicular tissue. This indicated that HSP70s have vital and conserved biological functions, and may also function in the development of germinal cells. The expression of mRNA of the five HSP70 family members mRNA expression was significantly increased in the head kidney, intestine and gill after Vibrio harveyi challenge, suggesting that HSP70s play an important role in the immune response.

Molecular biology of testicular germ cell tumors

Testicular germ cell tumors (TCGT) comprise a heterogeneous group of neoplasms, although all of them are originated from common precursors related to germ cell lineage. Understanding of normal development of germinal cells is essential to define new markers for diagnosis, prognostic subgroups and targeted therapies. Recent advances related to cytogenetic and molecular features have established the role of immunohistochemistry of c-kit, OCT-3/4 and determination of gain of chromosome 12 in the daily workup of premalignant lesions and invasive tumors. This review summarizes the current knowledge in the field of molecular biology of TGCT.

An insulin-like system involved in the control of Pacific oyster Crassostrea gigas reproduction: hrIGF-1 effect on germinal cell proliferation and maturation associated with expression of an homologous insulin receptor-related receptor

The putative involvement of insulin-like peptides in the control of the reproduction of the Pacific oyster Crassostrea gigas was investigated using different approaches. In conjunction with a monthly histological analysis of the oyster reproductive cycle, in vitro biological effects of the human recombinant IGF-1 (hrIGF-1) on dissociated germinal cells were mesured over 1 year using [ 3H]-thymidine and [ 14C]-amino acid mixture as tracers for DNA and protein synthesis. DNA synthesis was stimulated by hrIGF-1 in November (114 ± 11% for 10 − 7M), December (46 ± 6% for 10 − 7 M) and January, which was identified as the highest gonial mitosis period. A clear dose–effect was observed in January with a maximum activation of 68 ± 7% for 10 − 12 M. Germinal cell protein synthesis was also stimulated in March (20 ± 1% for 10 − 10 M), April (41 ± 5% for 10 − 13 M), May (25 ± 4% for 10 − 13 M), and by almost all of hrIGF-1 doses in June (21.5 ± 2% for 10 − 13 M) and July (34 ± 1% for 10 − 13 M). This suggests the involvement of insulin-like substances in gonadal tubule rebuilding (December), as well as in the development of germinal cells (March, April), and in the summer maturation of gametes (May, June, July). These insulin-like effects conform with the expression pattern of the recently identified C. gigas insulin receptor-related receptor (CIR): It appeared highly expressed in the gonadal area during gonial mitosis phase, but also in maturating oocytes, suggesting the involvement of an insulin-like system in gonial proliferation and maturation. Moreover, CIR showed differential expression during embryogenesis and larval developmental stages. The expression of maternal CIR during the embryonic and early larval development, followed by the increasing zygotic CIR expression from D larvae to 11-day-old veliger larvae, then a decrease until metamorphosis, also suggest that insulin-like peptide is involved in organogenesis.

Cytogenetic studies on Mepraia gajardoi (Heteroptera: Reduviidae). Chromosome behaviour in a spontaneous translocation mutant

We analysed the chromosome complement and male meiosis in a natural population of Mepraia gajardoi (Hemiptera: Reduviidae: Triatominae). The normal karyotype of this species is 20 autosomes plus X1X2Y in males and X1X1X2X2 in females. We confirmed that M. gajardoi is cytogenetically strikingly different from M. spinolai (with which it was previously included), which supports the taxonomic separation of these two species. For the first time in the holocentric chromosomes of the subfamily Triatomi- nae, a structural rearrangement was detected. Observations made during meiosis and mitosis indicated that one of eleven individuals had undergone a fusion between two non-homologous chromosomes, probably before germinal cell development. This autosomal translocation resulted in chromosomal irregularities such as an autosomal trivalent, autosomal univalents and chromosomal frag- ments, which altered the normal segregation of both autosomes and sex chromosomes. The chromosomal fragments resemble super- numerary or B chromosomes, which supports the idea that these chromosomes are remnants of structural rearrangements. The genetic consequences of translocations in holokinetic chromosomes and their role in the evolution of chromosomes in triatomines are also discussed.

Lead Intoxication in Gestational and Lactation Periods Alters the Development of Male Reproductive Organs

The effect of lead (Pb) intoxication during pregnancy and lactation on the male reproductive system was studied to evaluate the alterations caused by Pb in the development of pups. The investigations covered the effect of lead on the course of spermatogenesis and the development of the epididymis and reproductive glands. For this purpose, dams were intoxicated with 300 mg/L Pb during the gestational period and through lactation. Pups were sacrificed on Postnatal (PN) Days 12 and 21. Blood lead (PbB) and plasma iron concentrations were measured, and blood cells counted. Biochemical studies as well as histochemical analyses were performed on testes and accessory glands of the reproductive system. Lead intoxication resulted in a decrease in testis and seminal vesicle weights and an increase in DNA and RNA levels on PN Day 21. Total protein was significantly decreased by the toxicant, and alkaline and acid phosphatase levels of the gonads were reduced. Effects were also reflected in the reduction of the thickness of epithelium and of seminiferous tubule diameter (STD) as a consequence of the action of lead in the reduction in numbers of prospermatogonia and spermatocytes. Results indicate that the reproductive system targets of lead intoxication are not only the testes; lead intoxication results in the inhibition of testicular, epididymal, and seminal vesicle function, altering the biochemical composition of these organs, and consequently, affecting the normal development of germinal cells.

Validation of Immunotoxicology Techniques in Passerine Chicks Exposed to Oil Sands Tailings Water

Avian species, through their trophic relationships, may represent ideal indicators for assessing environmental health. In this study several assays of immune function in young passerines are validated and compared. From 6 to 10 days of age, zebra finch nestlings (Taeniopygia guttata) were given daily oral doses of Oil Sands tailings water (CT), an immunosuppressant dexamethasone, or phosphate-buffered saline. At 9–10 days of age, a phytohemagglutinin (PHA) skin test of immune function was conducted; at 11 days of age, five chicks from each group were euthanized for gross and histopathologic examination of immune system organs. The remaining birds were vaccinated with sheep red blood cells (srbc) to evaluate antibody-mediated immunity. The main findings were that in 10-day-old nestlings, T lymphocytes were sensitive to PHA stimulation, while B lymphocytes were unable to respond to srbc; that hematocrit was approximately 30% lower than in mature birds; that precision of leucocrit determination was heavily technique-dependent; that endogenous steroids increased the total leucocrit, while exogenous steroids increased heterophil and decreased lymphocyte counts, thus increasing H:L; that dexamethasone exposure temporarily reduced growth rate; that CT exposure stimulated germinal cell development in the bursa of Fabricius; and that dexamethazone and CT exposure were associated with decreased splenic white pulp formation.

Cell‐Cell Interactions and the Regulation of Testis Function

Regulatory interactions have been shown to occur between all the testicular cell types considered. The paracrine factors mediating these interactions generally influence either cellular growth or differentiation. The regulation of cellular growth is essential in the developing testis and is required for the maintenance of spermatogenesis in the adult testis. The rapid rate of germinal cell proliferation and the continuous but slowed growth of the peritubular cells and Leydig cells requires the presence of specific growth factors in the adult. Therefore, cell-cell interactions have evolved that involve growth factors such as IGF, TGF-alpha, TGF-beta and NGF. Other growth factors such as FGF or less characterized components like the seminiferous growth factor (SGF) also may be involved in the paracrine regulation of testis cell growth. An alternate cellular parameter to cell growth to consider is the regulation of cellular function and differentiation. A number of endocrine agents and locally produced paracrine factors have been shown to control and maintain testis cell function and differentiation. Cell-cell interactions mediated by factors such as androgens, POMC peptides, and PModS are all primarily directed at the regulation of cellular differentiation. Therefore, the agents which mediate cell-cell interactions in the testis can generally be categorized into factors that regulate cell growth or those which influence cellular differentiation. The specific cell-cell interactions identified will likely be the first of a large number of cellular interactions yet to be investigated. Although a number of potentially important cell-cell interactions have been identified, future research will require the elucidation of the in vivo physiological significance of these interactions. The existence of different cell types and potential cell-cell interactions in a tissue implies that the actions of an endocrine agent on a tissue will not simply involve a single hormone and single cell. The endocrine regulation of testis function will have effects on cell-cell interactions and be affected by local cell-cell interactions. The ability of LH to influence Leydig cell androgen production promotes a cascade of interactions mediated through several cell types to maintain the process of spermatogenesis. FSH actions on Sertoli cells also promote cell-cell interactions that influence germinal cell development, peritubular myoid cell differentiation and Leydig cell function. Therefore, elucidation of the endocrine regulation of testis function requires an understanding of the local cell-cell interactions in the testis.

Function of vitamin A in normal and synchronized seminiferous tubules.

Vitamin A is clearly an important factor in spermatogenesis. Some of the new data on metabolism of retinoids in the testis has contributed to our understanding of the mechanism(s) involved in the action of vitamin A. It is probable that the requirement of the testis of vitamin A deficient rats for retinol but not retinoic acid involves access of the retinoids to various testicular compartments. Retinol may be required by germinal cells because of a requirement for esterification in order to be successfully transported by the Sertoli cells. Existing evidence suggests that both the Sertoli cells and the germinal cells have specific requirements for retinoids. In the vitamin A deficient rat there appears to be a developmental block at preleptotene spermatocyte and type Al spermatogonia stages. This block is removed by retinol and germinal cell development reinitiates in a synchronous manner. The synchronous testis model offers a number of advantages for the study of molecular events associated with the cycle of the seminiferous epithelium and the development of germinal cells as well as for investigations into the mechanism of action of the retinoids.

Infestation of Palaemonetes argentinus (Crustacea: Palaemonidae) with Probopyrus cf. oviformis (Crustacea: Bopyridae): Observations on the habitat of cryptoniscus larvae

Several Probopyrus ssp. produce ecto- and endoparasitic (tissue) larvae. The purpose of this paper is to evaluate the colonization and distribution of cryptoniscus larvae in shrimp of both sexes and to perform a microanatomical analysis of the larvae-bearing tissue in order to typify the tissues involved and their eventual reaction. The following conclusions are drawn: (1) ecto- and endoparasitic cryptoniscus colonize the various body areas of Palaemonetes argentinus at random, affecting young shrimp, maturing shrimp, and sexually mature shrimp; (2) only the ectoparasitic larvae that reach the branchial chamber become actually integrated to the consortium; (3) the tissue larvae are erratic guests of the shrimp's connective-hemolymphatic tissue and no tissue reaction leading to the isolation of the larvae occurs and this is not the result of a systemic immunological depression in the host; (4) the tissue cryptonisci located next to the gonad of shrimp of either sex do not have any effect on the normal development of germinal cells.

Biological regulation of testicular angiotensin I-converting enzyme.

Angiotensin I-converting enzyme (ACE) from rat testes and lung was purified to homogeneity and partially characterized with respect to physicochemical parameters. Additionally, the biological regulation of testicular ACE by gonadotropins and androgens was investigated was investigated and the cell type with which ACE is associated in testes was identified. Rat testicular ACE is a lower molecular weight, isozymic version of the lung enzyme. Partial proteolysis of each isozyme produces different peptide maps, suggesting unique primary structures for each protein. The sensitivity of each isozyme to Co2+, chelators and thermal denaturation is different, a finding that further supports the hypothesis that structural differences exist between the two isozymes. The pituitary gland is essential for the development during puberty and maintenance during adulthood of testicular ACE. In hypophysectomized mature rats, gonadotropins or androgen can maintain ACE activity to near sham-operated levels. ACE activity in testes appears to be associated almost entirely with various stages of germinal cell development. The function(s) of testicular ACE awaits definition. The mechanism of androgen-maintenance of testicular ACE is unclear. Whether androgen specifically induces gene expression of testicular ACE or simply allows for ACE activity to develop in parallel with spermatogenesis is an unresolved question.

Effects of 6-hydroxydopamine-induced norepinephrine depletion on cerebellar development.

In order to investigate the possible influence of norepinephrine (NE) on neuronal development, the effects of neonatal NE depletion on postnatally developing cell populations were characterized in (1) the normal mouse cerebellum, and (2) a cerebellar model system with delayed germinal cell development produced by neonatal methylazoxymethanol acetate (MAM) administration. Reduction in NE content was achieved by neonatal 6-hydroxydopamine (6-OHDA) injections. In the MAM-treated groups, 6-OHDA did not produce significant changes in external germinal layer (EGL) reconstitution. In the other groups, 6-OHDA treatment produced a reduction in the vermis area, alterations in foliation, and changes in the schedule of EGL development. These results support a role for NE in regulation of neuronal development in the cerebellum.

Microelectrophoretic analysis of basic protein changes during spermiogenesis in the dogfish Scylliorhinus caniculus (L.)

Spermatogenesis in the dogfish is characterized by the synchronous development of germinal cells inside follicles. This particularity has permitted studies on precise stages of cell differentiation, especially on the evolution of chromatin structure. A microelectrophoretic method has been devised for the determination of the basic nuclear protein content of accurately identified homogeneous stages of spermatid differentiation. No significant difference was observed during the first stages of spermiogenesis, i.e., in round spermatids, where a typical histone complement was present. At the beginning of nuclear elongation, two new basic protein fractions appeared and coexisted for some time with typical histones; they replaced somatic histones progressively. Later, during elongation, four proteins of high electrophoretic mobility appeared and gradually replaced the intermediary basic proteins. In elongated spermatids, DNA was found tightly packed by these four proteins: three are arginine- and cysteine-rich (Z1, Z2 and S4), the fourth is arginine-rich (Z3). At first, these fractions are all soluble in 0.25 M HCl but during sperm maturation only one (Z3) remains acid-soluble, the others being extractable only after reducing and alkylating treatments. This modification of solubility of Z1, Z2 and S4 corresponded to the oxidation of cysteine residues to form SS crosslinks in chromatin of mature sperm cells. Thus spermiogenesis of the dogfish shows two basic nuclear protein transitions which both occur during nuclear elongation.

The results of 100 small tissue biopsies of testis in male infertile patients.

The value of testicular biopsy in male infertility has recently been emphasized by Meinhard, McRae and Chisholm (1973), and the present authors agree with them that a biopsy is essential for the following reasons: (1) to establish a firm diagnosis; (2) to rationalize therapy on the basis of histological findings; (3) new developments in drug therapy and electronmicroscopic techniques will help to clarify many areas of doubt and uncertainty in this difficult field; (4) the diagnosis of 'sloughing' by itself may mask changes in germinal cell development which may be amenable to hormone therapy.

Hormonal requirements of the different cycles of the seminiferous epithelium during reinitiation of spermatogenesis in long-term hypophysectomized rats.

Restoration of testicular function in long-term hypo-physectomized rats given different hormonal treatments during the various cycles of the seminiferous epithelium was evaluated on the basis of the weights of testes, epididymides, and other accessory sexual glands, histological examination of testes, and determination of the numbers of spermatozoa/epididymis. The staput fractionation technique for the separation of classes of germinal cells was employed to provide a measure of the advancing front of pulse-labelled cells following the intratesticular administration of (3-H)thymidinemthe results suggested that during the first two cycles, in which spermatogonia develop into pachytene spermatocytes, either LH or testosterone alone was sufficient for partial restoration. During the third cycle of the seminiferous epithelium, LH and FSH were required to allow previously labelled pachytene spermatocytes to progress efficiently to stage 7 spermatids. Administration of LH alone during the final cycle was sufficient to permit stage 7 spermatids to develop into spermatozoa, provided LH plus H had been given during the previous three cycles. Injection of LH during the entire period and of FSH during the third cycle of the seminiferous epithelium was required to achieve Staput profiles characteristic of a normal advancing front of pulse-labelled cells, and to allow partial restoration of spermatogenesis. More complete restoration was obtained in rats given FSH and LH during the first three cycles but, with the doses employed, the number of spermatoza/testis remained subnormal. Efficient completion of each cycle of the seminiferous epithelium appeared to be hormone-dependent. The data are discussed in relation to the possibility that hormones may affect the general development of germinal cells in an indirect manner by their influence on Sertoli cell function.

A morphological and histochemical study of sertoli cells in normal and XX sex‐reversed mice

AbstractMorphological and histochemical studies on the testes of mice with XX sex‐reversal demonstrates several profound differences in the ultracytology and oxidative enzyme activity of Sertoli cells as compared to the normal. Membranous structures, cytoplasmic inclusions, and certain dehydrogenases in Sertoli cells of normal mice are described in relation to a possible role in steroid synthesis. In XX sex‐reversed mice, two types of Sertoli cells are observed in the seminiferous tubules which are devoid of germ cells. One type is the randomly dispersed cells, which reveal the following ultrastructural alterations when compared with the normal cells: large spherical nuclei with prominent nucleoli, reduced smooth endoplasmic reticulum, pleomorphic mitochondria with no apparent cristae, and decreased lipid droplets. The other type is clustered cells which appear similar to immature Sertoli cells. These cells have small nuclei with poorly developed nucleoli, small profiles of rough endoplasmic reticulum, pleomorphic mitochondria, decreased lipid droplets, and an absence of specialized inter‐Sertoli cell junctions.The results of this study suggest that functional and ultrastructural alterations of Sertoli cells in XX sex‐reversed mice may result from degeneration or absence of germinal cells, and that steroidogenesis by Sertoli cells in mice may be associated with the development of germinal cells. It is also suggested that Sertoli cells may secrete a steroid which controls follicle‐stimulating hormone secretion.