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Hyperglycemia (experimental diabetes) was induced in adult male rats by destruction of the pancreatic beta cells with a single intravenous injection of streptozotocin (STZ). Testes from diabetic, from insulin-treated diabetic, and from sham-injected normal rats were fxed by vascular perfusion. The fine structure of Leydig cells was examined at two, three, and four weeks after the STZ injection in the untreated diabetic animals, and at four weeks in the controls and insulin-treated diabetic rats. A number of morphological changes was observed in Leydig cells of untreated diabetic animals. Most obvious of these was an accumulation of lipid droplets, not normally present in Leydig cells in adults of this species. Smooth endoplasmic reticulum (SER) was markedly reduced in Leydig cells of the hyperglycemic rats. Several types of intracellular bodies were seen exclusively in Leydig cells of the untreated diabetic animals. Many resembled secondary lysosomes or dense bodies, while others appeared to be autophagic vacuoles. In addition, a small, granule-containing lamellar structure was seen either within a typical dense body or free in the cytoplasm. Myelin-like structures were commonly observed within the cytoplasm of the Leydig cell or within mitochondria. The appearance of the mitochondria in diabetic rats was otherwise normal. The extracellular spaces surrounding Leydig cells from untreated hyperglycemic rats also contained large accumulations of myelin-like material. These structural changes appear to be direct consequences of the diabetic state of the animals, since the ultrastructure of insulin-treated diabetic rats did not differ from that of the controls. These findings may reflect an alteration or breakdown of Leydig cell components normally involved in the synthesis of androgen, and correlate with previous reports of lowered circulating levels of testosterone in diabetic rats.
Anat Rec 1979 Nov
PMID:Ultrastructural changes in Leydig cells of streptozotocin-induced diabetic rats. 22 65

Data are presented on the size, Leydig cell content and seminiferous tubule dimensions of the normal bull testis. A method of estimating total tubule length, requiring only the measurement of testis volume and the number of tubule cross-sections in a unit area is described, and its applicability to the bull established. The average bull testis contains about 5.2 km of tubules.
Vet Rec 1979 May 12
PMID:Tubule length and Leydig cell volume in the normal bull testis. 38 6

A Friesian bull with bilateral testicular hypoplasia was diagnosed as having a pure 61XXY karyotype. The bull displayed normal sexual behaviour but was azoospermic. At 17 months, the animal's peripheral plasma androgen levels appeared to be lower than normal, and one testicle removed one month later showed small seminiferous tubules totally lacking in germ cells. The Leydig cell volume of this testis was well within the normal range but the tubule length was rather short. At 33 months of age an increase in peripheral plasma androgen levels was noted. In the remaining testis there had been both a considerable rise in Leydig cell volume and a fall in tubule length. These findings may be explained by the interaction of three factors; the effects of the abnormal karyotype, the increased maturity of the animal at 33 months and the reaction of the remaining testis to unilateral castration.
Vet Rec 1979 Jun 02
PMID:Hormonal and histological studies in a 61XXY bull. 48 39

The time of onset of brain regulation of the pituitary-Leydig cell system in fetal rats was assessed by fetal encephalectomy, which allowed the pituitary to persist in situ. The effects of encephalectomy were compared with those of fetal hypophysectomy (surgical decapitation). The parameter for interpretation of these effects was the collective volume of Leydig cells, measured by the method of Chalkley ('43). The normal increase in the collective volume of Leydig cells in fetuses encephalectomized on day 17 of gestation and autopsied on day 18 was not retarded, whereas that in decapitated fetuses of the same age was retarded. In all other one-day experimental periods (day 18-19, 19-20, 20-21, and 21-22), the increase in volume was retarded to approximately the same extent in encephalectomized as in decapitated fetuses. The collective volume of Leydig cells continued to increase to some extent without the brain until day 20, after which it ceased to increase. The results suggest that in fetal rats, the brain control of the pituitary-Leydig cell system begins to operate from day 18 of gestation, when the day following overnight mating was designated as day 1 of gestation.
Anat Rec 1978 Mar
PMID:Development of the fetal pituitary-testicular system based on the observation of Leydig cells in encephalectomized, hypophysectomized and control fetal rats. 63 19

Existing evidence suggests that the aging human male experiences a gradual decline in testosterone production, a phenomenon that should be reflected in the Leydig cell population of the testis. It has been proposed that Leydig cells diminish in number with increasing age, but conflicting claims characterize reports of this topic. We have reinvestigated this possibility by histometric analysis of perfused testes from 25 men ranging from 18 to 87 years of age. Average single Leydig cell volume (2,943 +/- 623 micrometer 3, X +/- S.D.) did not change significantly with increasing age (r = 0.24, P greater than 0.2), suggesting that surviving cells remain active. Total testis weight (43.5 +/- 13.9 g) also did not change with age (r = 0.04, P greater than 0.5). However, both total Leydig cell volume and the absolute number of Leydig cells per individual decreased significantly as functions of age (r = -0.71, P less than 0.002, and r = -0.61, P less than 0.005, respectively). Analysis of relationship between these two parameters indicates that the total volume of Leydig cell cytoplasm contained within the human testis is determined by the number of cells present. Our results show that a pair of young adult testes endowed with more than 700 million Leydig cells at 20 years of age may be expected to undergo an attrition rate of approximately 80 million cells per subsequent decade of life. Thus, Leydig cell attrition is an important correlate of declining androgen status in aging men.
Anat Rec 1978 Dec
PMID:Attrition of the human Leydig cell population with advancing age. 73 71

The interstitial tissue of the testis of the nine-banded armadillo is composed of blood vessels, clusters of Leydig cells, the usual connective tissue elements, and a network of lymphatic sinusoids. The endothelial walls of the sinusoids are separated from the peritubular contractile cell layer surrounding the seminiferous tubules by a thin layer of collagen. The pertibular contractile cell is characterized by filaments and dense bodies within the cytoplasm, whereas the endothelial cells lack these structures. Within each cluster, several Leydig cells surround one or more blood vessels. Adjacent Leydig cells are jointed by 2- to 3-nm wide gap junctions and desmosome-like specializations. The Leydig cell is polygonal in shape with an ovoid nucleus. The cell is characterized by an abundance of smooth endoplasmic reticulum which appears as sheets of membranes, concentric whorls around vacuoles, and a random tubular network. Only a few short cisternae of rough endoplasmic reticulum are observed. Centrioles are closely associated with the Golgi apparatus. Rod-like mitochondria with tubular cristae are scattered throughout the cytoplasm. In addition, the cells contain vacuoles resulting from lipid extraction, filaments, microtubules, and glycogen. The surface of the cell exposed to the intercellular spaces exhibit numberous pinocytotic vesicles and cell processes which indicate active movement of material across the plasma membrane. In comparison to other mammalian species, the ultrastructural organization of the interstitium and the fine structure of Leydig cell of the armadillo resemble those of the guinea pig.
Anat Rec 1977 Jan
PMID:The fine structure of the interstitial tissue of the testis of the nine-banded armadillo. 83 39

The effect of tunicamycin (TM) on testicular cord organization in the fetal mouse was examined in vitro at light and electron microscopic levels, with special reference to the glycoprotein functions during Sertoli cell differentiation. In testicular explants treated with TM, testicular cord organization was inhibited. TM treatment affected basal lamina formation by Sertoli cells, resulting in a discontinuous basal lamina or none at all in certain areas. The disorganized Sertoli cells were amorphous in shape, exhibited poor epithelial polarity, and were irregularly arranged in the testicular parenchyma. Extracellular matrix and collagen fibers were often observed in the intercellular spaces between the disorganized Sertoli cells. Lectin histochemical observation revealed that the number of wheat germ agglutinin binding sites on the plasma membrane and basal lamina of disorganized Sertoli cells was significantly decreased by TM treatment. However, junctions were normally observed in the plasma membrane between disorganized Sertoli cells. Leydig cells showed a normal differentiation in the testicular parenchyma in the presence of TM. These observations suggest that basal lamina formation of Sertoli cells and/or the expression of their cell surface glycoconjugates may be crucial for the establishment of Sertoli cell polarity and/or the Sertoli-Sertoli cell interactions required for proper testicular cord formation. Sertoli cell organization into testicular cords and Leydig cell differentiation may be controlled by different regulatory mechanisms.
Anat Rec 1991 Jun
PMID:Effect of tunicamycin, an inhibitor of protein glycosylation, on testicular cord organization in fetal mouse gonadal explants in vitro. 186 96

Interstitial cells of Leydig characteristically occur in clusters around blood vessels. Often these clusters remain intact when interstitial tissues are mechanically separated from other components of the testis. The presence of strong intercellular attachments is most likely one of the factors responsible for maintaining the integrity of Leydig cell clusters. In many tissues, actin associated adhesion junctions commonly provide intercellular attachment. To determine if actin associated adhesion junctions are present between Leydig cells, we have used 1) immunofluorescence to probe for two components that characterize these junctions in other tissues and 2) electron microscopy to examine areas of intercellular contact for evidence of microfilament related adhesion junctions. Isolated clusters of unsectioned cells, which had been fixed and detergent extracted, were probed with the F-actin specific strains rhodamine phalloidin and NBD-phallacidin and with an affinity purified primary antibody raised against human platelet vinculin. In regions of intercellular contact, fluorescence staining with the actin probes was intense and appeared as a solid linear band. Similar regions also stained with the vinculin probe. In double label experiments, actin and vinculin probes were co-distributed at sites of intercellular contact. Zones of intercellular contact, apparently similar to those detected with fluorescence microscopy, were observed at the ultrastructural level. At these sites, subsurface filaments, interpreted by us as actin, formed a dense carpet adjacent to the plasma membrane on each side of the junction. These filaments appeared to be organized into networks rather than discrete bundles.(ABSTRACT TRUNCATED AT 250 WORDS)
Anat Rec 1991 Aug
PMID:Evidence for the presence of actin-associated intercellular adhesion junction between interstitial cells of Leydig in the ground squirrel testis. 192 52

The neonatal period in male development is characterized by an acute rise in serum testosterone, which peaks at 2 to 3 months of age. The purpose of this study is to examine the neonatal human testicular interstitium at 4 months for evidence of Leydig cell maturation, as well as any morphological criteria relating to the fate of Leydig cells during this period, specifically, for signs of cell regression. Leydig cells are described with impressive development of the steroid secreting apparatus, which are consistent with the mature Leydig cells found during early fetal development and in the adult. The outstanding feature of these cells is the "organelle association" of extensive, anastamosing tubules of smooth endoplasmic reticulum (SER), pleomorphic mitochondria with a component of tubular cristae, and abundant microperoxisomes associated with the SER. Well-developed Golgi elements, regionalized RER, and diverse cell inclusions are also characteristics of these cells. Reinke crystals and paracrystalline inclusions are absent. Gap junctions are common in this system and are notable in the asymmetric nature of the adjacent cytoplasmic components. These findings provide a morphologic correlate to the reported neonatal phase of testosterone production in man. Intermediate forms of Leydig cells are described with "organelle associations" including decreased SER with increased lipid droplets, and decreased SER with prominent cytoplasmic filaments and/or dramatic mitochondrial changes supportive of mitochondrial involution. Cells consistent with immature Leydig cells are also present. The rather impressive diversity in cell morphology present during this time frame of 4 months, slightly past the peak in testosterone production, provides evidence of Leydig cell regression and a continuity of the mature neonatal Leydig cells with the immature Leydig cells of childhood (Prince, 1984). There is also some evidence of cell degeneration. Although the developmental history of Leydig cells has been described for years as biphasic, it is time to view Leydig cell development in man as a triphasic event, fetal, neonatal, and pubertal.
Anat Rec 1990 Dec
PMID:Ultrastructural evidence of mature Leydig cells and Leydig cell regression in the neonatal human testis. 217 25

In an effort to further understand the basis for the changes in steroidogenesis known to occur during sexual maturation in the rat, we examined by quantitative morphologic methods the number and ultrastructure of Leydig cells in fetal rats (days 18-20 of gestation) and in rats from days 2 to 3 of age through adult. Quantitative light microscopic analyses indicated that Leydig cell number, when expressed per unit volume of testis, was very high in fetal rat testes, fell significantly in testes of days 2 to 3 rats, and subsequently rose significantly. When Leydig cell number was expressed per testis rather than per unit volume of testis, the results indicated that testes of fetal rats and rats of days 2 to 3 contained the same number of Leydig cells; after the neonatal period, significant increases in Leydig cell number per testis occurred in concert with increases in testis weight. Quantitative electron microscopic studies revealed significant differences in the ultrastructure of fetal and adult populations of Leydig cells. For example, Leydig cells of fetal and neonatal rats contained abundant lipid, whereas Leydig cells of weeks 7 to 8 and adult rats contained little. Stereological analyses also revealed dramatic changes in smooth endoplasmic reticulum and inner mitochondrial membrane surface areas during sexual maturation, both per cell and per testis. These findings are discussed with respect to the steroidogenic capacity of the testis during sexual maturation.
Anat Rec 1987 Oct
PMID:Leydig cell differentiation during maturation of the rat testis: a stereological study of cell number and ultrastructure. 368 69


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