An electron microscopic correlation of structure with function in the isolated perfused cow adrenal, preliminary observations

Ultrastructural zonation of adrenocortex in the rat

The fine structure of the different zones in the adrenal cortex of the adult rat has been studied under the electron microscope. Four regions mainly differentiated by the mitochondrial morphology, the lipid droplets, and the structure of the ground cytoplasm were recognized. In the glomerular zone mitochondria are thin and elongated with an abundant matrix. The inner structure is characterized by the presence of tubules of 300 A that are straight or bend at an angle and which may be grouped in parallel array giving a pseudocrystalline pattern. The wall of each tubule is a finger-like projection of the inner membrane and its cavity corresponds to the outer chamber of the mitochondrion. In the intermediary zone mitochondria are larger and irregular. The matrix is filled with convoluted tubules and vesicular elements. The lipid droplets are larger and irregular in the glomerulosa and and small in the intermedia. The ground substance is dense and contains free ribosomes in the glomerulosa and starts to be vacuolated in the intermedia. In the fasciculata mitochondria are round or oval and are filled with vesicular elements with a mean size of 450 A. Larger vesicles and more clear elements (vacuoles) are seen near the edge as if their content was diluted. Some of these vacuoles protrude on the surface. In the reticular zone mitochondria are also vesicular but frequently show signs of alteration and disruption. Dense elements recognized as microbodies are observed in the fasciculata but they increase in number in the reticularis. These results are discussed on the light of the so called zonal theory of the adrenal cortex. Two stages in the differentiation of the mitochondria are postulated. The tubular structure of the glomerulosa undergoes a process of disorientation and dilatation of the tubules to form the tubulo-vesicular elements of the intermediary zone. In a second stage of differentiation, by fragmentation of the tubules, the vesicular structure of fasciculata is formed. These findings are discussed from the viewpoint of the relationship between mitochondria and synthesis of steroid hormones. A secretory process that starts within mitochondria by the formation of vesicles and proceeds into the ground cytoplasm, as extruded and more clear vacuoles, is postulated.

Isolation and properties of tumor-derived endothelial cells from rat KMT-17 fibrosarcoma

Rat KMT-17 fibrosarcoma-derived endothelial cells were isolated by Percoll gradient centrifugation with an attaching-speed separation technique, and their properties in culture were examined. The primary cultured tumor-derived endothelial cells (TEC) showed angiotensin-converting enzyme activity, positivity for Factor VIII-related antigen staining, and typical capillary-like formation on Matrigel. The primary cultured TEC monolayer showed greater permeability than normal tissue-derived endothelial cell (aorta, vena cava and epididymal fat capillary) monolayers on FITC-dextran diffusion (molecular weight 70,000). Leukocyte adhesion to TEC was reduced compared to that to fat-derived capillary endothelial cells. These characteristics resembled those of tumor vascular endothelium, and were observed both in the primary and first-passage cell cultures, but not in the fourth-passage cell cultures. Our findings indicate that primary or subcultured TEC are applicable for studies of the physiological characteristics of tumor endothelial cells.

The formation of fenestrations and channels by capillary endothelium in vitro

Microvascular endothelial cells isolated from fenestrated capillaries have been shown to form tubes in vitro, thereby demonstrating that they retain the ability to express some degree of their in vivo differentiated phenotype. However, some of their physiologically important structural features, such as transendothelial openings (i. e., diaphragmed fenestrations and transendothelial channels) are lost or are greatly reduced in number. In this study, cloned bovine adrenal cortex endothelial cells were cultured on plastic or on a basal lamina produced by Madin-Darby canine kidney (MDCK) cells for up to 17 days postconfluence. All cultures were then routinely fixed and processed for electron microscopic morphometry. For cells grown on plastic for 17 days postconfluence, the linear density of transendothelial openings in endothelial profiles less than 400 nm thick was found to be 0.007 openings per micron. On MDCK matrix, however, the linear density of transendothelial openings in endothelial profiles less than 400 nm thick was found to be 0.157 per micron. Occasionally some cells formed "tube-like" structures that also contained diaphragmed fenestrations and transendothelial channels on both sides of the tubes. These findings suggest that the substrate on which endothelial cells are grown can affect their differentiation.

The microcirculation of cerebral arteries: a morphologic and morphometric examination of the major canine cerebral arteries

A morphologic and morphometric examination of the major cerebral blood vessels in the dog was carried out to determine whether there were vasa vasorum in these arteries and what features might be associated with them. True vasa vasorum confined to the media were not seen in any of the vessels examined. Microvessels confined to the adventitia, however, were found in the internal carotid and vertebral arteries but not in the basilar, middle cerebral, or anterior spinal arteries. Animal size, vessel size as determined by adventitial and medial area, and the number of smooth muscle cell lamellae were not associated with the presence of these adventitial vessels; they occurred only in arteries with both an intra- and extradural portion. It therefore appears that most canine cerebral arteries do not have vasa vasorum.

Microvasculature of human colorectal epithelial tumors. An electron microscopic study

The ultrastructure of the microvasculature in human colorectal adenomas and carcinomas was studied, and compared with that of normal tissue. Blood vessels in adenomas were generally of normal structure, whereas carcinoma vessels displayed a variety of structural alterations. Endothelial proliferation was frequently observed in all the eleven carcinomas examined, which confirms the reports of new vessel formation in experimental malignant tumors. The presence of fenestrations in obviously abnormal endothelium was tentatively attributed to hypoxia, vascular regression or immaturity of the cells, in spite of the fact that normal capillaries in colonic mucosa are fenestrated. Some vessels showed multilayered basement membranes, various types of activated cells containing numerous lysosomal granules, and thickened perivascular tissue. These features may be a vascular response to repeated damage or a manifestation of vascular remodelling. Dilated thin-walled vessels, which were usually found at the periphery of carcinomas, were identified as venules. Small vessels located between the closely apposed carcinoma tubules were not obviously abnormal. They were nevertheless considered to be tumor-induced vessels which had undergone differentiation. The differences in vascular morphology between adenomas and carcinomas were considered to be due to their different growth patterns, growth rates and degrees of maturity.

The fine structure and electrophysiology of heart muscle cell injury

Injured frog heart cells electrically uncouple from their uninjured neighbors within 30 min after injury. This uncoupling process can be shown by the disappearance of an injury potential measured between such injured and uninjured cells. In the present study, the time course of the decline of injury potentials, and thus of electrical uncoupling, in bullfrog atrial trabeculae was determined. Tissue was fixed with glutaraldehyde and osmium tetroxide at various times after injury to determine the morphological changes which accompany this uncoupling process. In some cases, ruthenium red was included in the fixatives. Normal atrial cells are long and narrow, with intercellular junctions located along the lateral surfaces of the cells. Two types of intercellular junctions have been observed: cardiac adhesion plaques (CAPs), and close junctions. Close junctions occur only infrequently. Ruthenium red penetrates all around the cells, leaving only small areas within the CAPs unstained. After injury, the cells are very dense and the myofilaments disarranged. Both types of intercellular junction remain intact, and only slight changes within CAPs are observed. The results are discussed in relation to current concepts of intercellular communication.

Studies in cryo-immunology. I. The production of antibodies to urogenital tissue in consequence of freezing treatment

Experimental cryosurgery has been found to result in the formation of circulating antibodies, directed against antigenic material of the tissue frozen. These antibodies were detected by passive haemagglutination and immunodiffusion. The tissue that was subjected to destructive freezing by means of this surgical procedure was the coagulating gland and seminal vesicle of rabbit. A probe carrying liquid nitrogen and a thermocouple assembly for measuring temperature changes was utilized. Control rabbits were manipulated in the same way but with no freezing.

A large number of rabbits subjected to tissue freezing exhibited the development of a rapid antibody response, achieving a maximum titre in 7–10 days, followed by a decline. This antibody response has been compared to that seen following isoimmunization by injection. As an additional comparison, several rabbits were autoimmunized by injection of homogenate from their own accessory tissue; these rabbits also produced antibodies. It was found that the time sequence in the antibody production was quite similar for auto- and isoimmunization, but was quite distinctive for cryo-stimulation.

By several means of evaluation, it was shown that the antibody response to the freezing of tissue was an autoantibody. It was not, however, an antibody against serum γ-globulin.

The consequences of the freezing of tissue are thus seen to simulate the effects of incorporating adjuvant. This method of producing autoantibodies and investigating the nature of the response has been termed cryo-immunology.

Cytological alterations related to stimulation of the zona glomerulosa of the adrenal gland

The structure of the zona glomerulosa of the rat adrenal gland stimulated by sodium restriction has been studied by light and electron microscopy. The major changes observed during the course of the experiment in stimulated glands involve cytoplasmic droplets, mitochondria, and the endoplasmic reticulum. There is a progressive decrease in the number of cytoplasmic droplets of low electron opacity. Numerous, greatly elongated mitochondria containing parallel arrays of tubules are noted. These tubules extend from within the mitochondria through gaps in the mitochondrial-limiting membranes into the cytoplasm. In addition, amorphous intramitochondrial deposits, possibly aldosterone precursors, are seen. Increased amounts of smooth-surfaced endoplasmic reticulum, often showing complex arrangements, are another feature of the stimulated zona glomerulosa. Other alterations include the presence of large numbers of dense bodies as well as cytoplasmic droplets of high electron opacity. These observations are discussed in relation to the biosynthesis of aldosterone.