The Normal Fine Structure of Opossum Testicular Interstitial Cells

Abstract

The interstitial tissue of the opossum testis includes interstitial or Leydig cells, macrophages, and small cells which morphologically resemble mesenchymal cells. The latter are thought to give rise to mature interstitial cells. The most prominent feature of the interstitial cell cytoplasm is an exceedingly abundant agranular endoplasmic reticulum. This reticulum is generally in the form of a meshwork of interconnected tubules about 300 to 450 A in diameter, but occasionally it assumes the form of flattened, fenestrated cisternae resembling those of pancreatic acinar cells, except for the lack of ribonucleoprotein particles on the surface of the membranes. The interstitial cells vary considerably in their cytoplasmic density. The majority are quite light, but some appear extremely dense, and in addition usually have a more irregular cell surface, with numerous small pseudopodia. These differences may well reflect variations in physiological state. Cytoplasmic structures previously interpreted as "crystalloids" consist of long bundles of minute parallel tubules, each about 180 A in diameter, which seem to be local differentiations of the endoplasmic reticulum. The mitochondria are rod-shaped, and contain a moderately complex internal membrane structure, and also occasional large inclusions that are spherical and homogeneous. The prominent juxtanuclear Golgi complex contains closely packed flattened sacs and small vesicles. The results of the present study, coupled with biochemical evidence from other laboratories, make it seem highly probable that the agranular endoplasmic reticulum is involved in the synthesis of the steroid hormones produced by the interstitial cell. This finding therefore constitutes one of the first functions of the agranular reticulum for which there is good morphological and biochemical evidence.

THE ABSORPTION OF FAT BY INTESTINE OF GOLDEN HAMSTER IN VITRO

“…There are indications, too, that this form of the reticulum may be involved in the handling of lipid in other ways than merely as a pathway directing its movement to the Golgi region and to the lateral surface of the cell. Agranular reticulum has been found to be well developed in a variety of other cell types active in biosynthesis of steroids (17)(18)(19) and in other types of lipid metabolism (20,21). Moreover biochemical studies have demonstrated, in the microsome fraction of intestinal mucosa, a thiokinase for activation of long-chain fatty acids (22).…”

Electron Microscopic Study on the Testicular Interstitial Cells in the Mouse

“…Around the microbodies, the cisternae of the whorl partially form annulate lamellae was proposed by CHRISTENSEN (1965), CHRISTENSEN andFAWCETT (1966) andCHRISTENSEN (1975) that the SER membranes of the Leydig cell might be the site of emzymes necessary for the conversion of pregnenolone to testosterone.…”

“…There was also indication that cholesterol biosynthesis might be associated with the SER membranes and that the latter might serve as a reservoir for cholesterol (CHRISTENSEN and FAWCETT, 1966). The majority of the previous authors supported the view that the smooth membranes of the interstitial cells formed a network of interconnected tubules extended throughout the cytoplasm, which could transform into flattened, sometimes fenestrated cisternae (FAWCETT and BURGOS, 1960;CHRISTENSEN and FAWCETT, 1961;CRABO, 1963;LEESON, 1963;CHRISTENSEN, 1965CHRISTENSEN, , 1970CHRISTENSEN, , 1975NAGANO, 1965;CHRISTENSEN and FAWCETT, 1966;BELT andCAVAZOS, 1967, 1971;AOKI, 1968AOKI, , 1970MERKOW et al, 1968b;BLACK and CHRISTENSEN, 1969;PELLINIEMI and NIEMI, 1969;GONDOS et al, 1974;CONNELL and CHRISTENSEN, 1975;WEAKER, 1977;WING and LIN, 1977).…”

“…MUROTA et al (1965) demonstrated in mouse interstitial cell homogenates that the conversion of progesterone to testosterone took place in a microsomal fraction, therefore probably in the ER of the cell. BURGOS (1960) andCHRISTENSEN andFAWCETT (1961) had assumed that important stepes in the biosynthesis of steroid might be associated with the SER membranes.…”

“…A mitotic figure of the macrophage has been detected. CHRISTENSEN and FAWCETT, 1961;LEESON, 1963;CRABO, 1963;CHRISTENSEN, 1965CHRISTENSEN, , 1970MURAKAMI, 1966;DE KRETSER, 1967a, b;CONNELL, 1972;USUI, 1976). CHRISTENSEN (1965) assumed that the occurrence of dark and light cells might be an artifact induced by unsuitable fixation.…”