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The morphology and function of the apical mitochondria-rich cells in the mammalian ductus epididymidis epithelium are revised. These cells are similar in all mammalian species studied. Apical mitochondria-rich cells are scarce (1-5 cells/100 principal cells) and are mainly found in the initial epididymal segments. Their morphology varies from slender cells that extend from the basal lamina to the epididymal lumen, to round cells that protrude into the lumen and are not in contact with the basal lamina. Their cytoplasm is more electron-dense than that of principal cells and contains more mitochondria which, in some species, are surrounded by rough endoplasmic reticulum cisternae. The adluminal cytoplasm displays a few short microvilli and contains many acid phosphatase positive vesicles. Apical mitochondria-rich cells differ from the principal cells in some histochemical features such as: (a) different lectin-staining pattern; (b) more intense reaction to the enzymatic activities: carbonic anhydrase, Ca(2+)-ATPase, peanut-agglutinin-sialidase, NADP dehydrogenase, succinate dehydrogenase, alpha-galactosidase and beta-galactosidase; (c) more intense immunoreaction to several cytokeratin types and to estradiol-related receptor protein; (d) weaker immunoreaction to epithelial membrane antigen and to retinol-binding protein. Although the function of the apical mitochondria-rich cells is still unknown, the following possible functions have been suggested: holocrine secretion; cooperation with the principal cells in epididymal reabsorption of testicular fluid; and acidification of epididymal fluid. Experimental results suggest that differentiation and maintenance of apical mitochondria-rich cells are not under androgen control and that these cells are sensitive to estrogen stimulation.

A semi-quantitative study of the extra-parenchymal Leydig cells in the tunica albuginea testis and spermatic cord was performed on histological sections immunostained with anti-testosterone antibodies in the testes and spermatic cords obtained from human foetuses, adults and elderly men without testicular or related diseases (autopsy specimens), as well as from adult men with cryptorchidism (surgical specimens). The albugineal Leydig cells appeared in small groups in the vicinity of blood vessels. The Leydig cells of the spermatic cord usually appeared inside or around nerve trunks. The percentages of testes and spermatic cords with extra-parenchymal Leydig cells were higher in the cryptorchid testis group than in the normal male groups. The number of Leydig cells per mm2 in the tunica albuginea testis was higher in normal adult males than in foetuses. This number decreased in elderly men and increased markedly in cryptorchidism. The number of Leydig cells per mm2 in the spermatic cord was also higher in normal adults than in foetuses and it did not change with either advancing age or cryptorchidism. In foetuses, the percentage of cells intensely immunostained by anti-testosterone antibodies in the tunica albuginea and spermatic cord did not differ significantly from that found in the testicular parenchyma, whereas in the other three groups (adult, elderly, and cryptorchid men) the percentages of these cells in the tunica albuginea and spermatic cord were significantly lower than in the testicular parenchyma.

A cytophotometric quantification of DNA in tumor cells was performed in histological sections of orchidectomy specimens from 36 men with testicular germ cell tumors (TGCT), 7 of them showing more than one tumor type. Among the variants of seminoma (classic and spermatocytic) the lowest DNA content were in spermatocytic seminoma. With respect to non-seminomatous tumors (yolk sac tumor, embryonal carcinoma, teratoma, and choriocarcinoma), choriocarcinomas showed the highest DNA content, and the lowest value was found in teratomas. No significant differences were found between the average DNA content of seminomas (all types) and non-seminomatous tumors (all types). Both embryonal carcinoma and yolk sac tumor showed similar DNA content when they were the sole tumor and when they were found associated with other tumors. In this study, except for the 4 cases of teratoma and the case of spermatocytic seminoma, all TGCT examined did not show modal values of DNA content in the diploid range. Such an elevated frequency of aneuploidism in these tumors may be helpful for their diagnosis.

The histological and ultrastructural study of the ductuli efferentes in epididymides from 40 adult men revealed the occurrence of multinucleate epithelial cells in all specimens. These cells appeared in the luminal protrusions of epithelial folds and correspond to either principal or ciliated cells. The ultrastructure of their cytoplasm did not differ from that of their respective mononucleate cells. Multinucleate cells contained 3-20 closely juxtaposed nuclei, thus appearing much more irregularly outlined than those of the mononucleate epithelial cells. Multinucleation four times more frequent in the principal cells than in the ciliated cells. The number of multinucleate cells increased progressively from the age of 60 years onwards. The average number of nuclei per cell increased in the fourth decade of life, was maintained up to the eighth decade, and then increased again.

A histological study of 23 testicular biopsies or surgical specimens from adult cryptorchid testes revealed the presence of multi-vacuolated Leydig cells in 12 cases. These cells showed abundant lipid inclusions and scarce secondary lysosomes as well as liprofuchsin pigment granules. Some of these cells contained crystals of Reinke but others had only microcristalline inclusions. This Leydig cell alteration may be related either to heat or to congenital lesions.

The testicular biopsy study of a 17-year-old male with Noonan's syndrome revealed seminiferous tubules of reduced diameter with hypospermatogenesis. Many spermatocytes underwent degeneration and many spermatids developed abnormal. The Sertoli cells were similar to immature Sertoli cells. Fully differentiated Leydig cells were rare while precursor Leydig cells were numerous. Both gonadotropin and testosterone levels were low, and a lack of response to LH-RH as well as to clomiphene was found. The testicular biopsy performed at 20 years of age revealed a certain maturation of the seminiferous tubules which increased the germ cell number. The abnormalities in the spermatogenesis as well as the immature appearance of Sertoli cells continued. Leydig cells were more numerous and showed a certain development without reaching the normal pattern. Gonadotropin levels were normal while testosterone levels low. The response to LH-RH was increased and the absence of response to clomiphene persisted. These features suggest a delayed puberty.

Two brothers have spermiograms with a similar pattern: absolute teratozoospermia with round-headed spermatozoa. The familial trait only has been previously one time in the literature. The spermatozoa show several abnormalities in the head. They lack acrosome and postacrosomal sheath. The nuclei are small and the chromatin is distributed in small groups. The nuclear envelope has abundant pores and is loosely attached to the chromatin. All the nuclei have brown inclusions, refringent when they are observed under the light microscope, vesicular and laminar under the electron microscope. Other abnormalities less frequently observed are: irregularities in the mitochondrial sheath, loss of parallelism of the dense fibres and duplication and angulation of the sperm tail. The hormonal assays and the biochemical tests are normal in both patients.

The number of mononucleate and multinucleate Leydig cells per unit area of the testis was determined in normal adult men using the peroxidase-anti-peroxidase method for testosterone detection. The results of this study indicate that the number of multinucleate Leydig cells increases markedly with age, whereas the total Leydig cell population decreases.

Examination of testicular biopsy from a patient with 47,XXY Klinefelter's syndrome revealed a diffuse hyalinization of seminiferous tubules as well as absence of mature Leydig cells. Ultrastructural findings showed some immature Leydig cells in the testicular interstitium. Hormone assays revealed low serum FSH and LH levels. The association of both, hormone assays and testicular morphologic pattern, suggests the presence of a Klinefelter's syndrome with hypogonadotropic hypogonadism.

Light microscope and ultrastructural studies of normal infants and children testes revealed the presence of primary spermatocytes and occasional spermatids at 4, 8, 9, 11, 12 and 13 years of age, but not in all the boys of these ages. When they were found they appeared in both testes, but only in a 5-25% of the seminiferous tubules. These spermatocytes undergo degeneration or progress to abnormal spermatids which degenerate in turn. Spermatozoa were never found.

In order to elucidate the ultrastructural characteristics of the precursor cell of Leydig cells and its subsequent differentiation, testicular biopsies from two patients with hypogonadotropic hypogonadism, obtained prior to and after treatment with HCG and HMG, were studied in comparison with those of prepubertal, pubertal and postpubertal testes. Prior to HCG and HMG stimulation, the testicular interstitium of both patients showed the following spindle-cell-types: Fibroblasts, myofibroblasts and a cell-type similar to the myofibroblast but differing from it by the arrangement of microfilaments and the development of the smooth endoplasmic reticulum as well as lipid droplets. It may be considered the precursor of Leydig cells. In the following stages of differentiation observed in the biopsies after treatment, there is a progressive involution of microfilaments and rough endoplasmic reticulum, a transient period of hyperplasia of the Golgi complex, and the definitive development of cell components involved in steroid biosynthesis, such as the smooth endoplasmic reticulum, polymorphic mitochondria with tubular cristae, lipid droplets and diverse lysosomal bodies. From early stages of differentiation, gap junctions occurred between the cells. Numerous axon profiles were also present among the cells. Only in a small percentage of cells did vesicle-bearing axons closely appose the Leydig cell membrane.