MJ Karnovsky

Bio: MJ Karnovsky is an academic researcher. The author has contributed to research in topics: Glutaraldehyde & Fixative. The author has an hindex of 1, co-authored 1 publications receiving 8378 citations.

Culture of Human Endothelial Cells Derived from Umbilical Veins. IDENTIFICATION BY MORPHOLOGIC AND IMMUNOLOGIC CRITERIA

Abstract: Endothelial cells were isolated from freshly obtained human umbilical cords by collagenase digestion of the interior of the umbilical vein. The cells were grown in tissue culture as a homogeneous population for periods up to 5 mo and some lines were subcultured for 10 serial passages. During the logarithmic phase of cell growth, cell-doubling time was 92 h. Light, phase contrast, and scanning electron microscopy demonstrated that cultured human endothelial cells grew as monolayers of closely opposed, polygonal large cells whereas both cultured human fibroblasts and human smooth muscle cells grew as overlapping layers of parallel arrays of slender, spindle-shaped cells. By transmission electron microscopy, cultured endothelial cells were seen to contain cytoplasmic inclusions (Weibel-Palade bodies) characteristic of in situ endothelial cells. These inclusions were also found in endothelial cells lining umbilical veins but were not seen in smooth muscle cells or fibroblasts in culture or in situ. Cultured endothelial cells contained abundant quantities of smooth muscle actomyosin. Cultured endothelial cells also contained ABH antigens appropriate to the tissue donor's blood type; these antigens were not detectable on cultured smooth muscle cells or fibroblasts. These studies demonstrate that it is possible to culture morphologically and immunologically identifiable human endothelial cells for periods up to 5 mo.

The early stages of absorption of injected horseradish peroxidase in the proximal tubules of mouse kidney: ultrastructural cytochemistry by a new technique.

Abstract: The early stages of absorption of intravenously injected horseradish peroxidase in proximal tubules of mouse kidney were studied with a new ultrastructural cytochemical technique. In animals killed as early as 90 sec after injection, reaction product was found on the brushborder membranes and in the apical tubular invaginations. From the latter structures it was transported to the apical vacuoles, in which it was progressively concentrated to form protein absorption droplets. The method, which employs 3,3'-diaminobenzidine as oxidizable substrate, gives sharp localization and is sensitive. This system is advantageous in studying the early stages of renal tubular protein absorption, since small amounts of protein on membranes and in tubules and vesicles can be detected easily. The method also appears promising for studying protein transport in a variety of other cells and tissues.

Fine structural localization of a blood-brain barrier to exogenous peroxidase

Abstract: Horseradish peroxidase was administered to mice by intravenous injection, and its distribution in cerebral cortex studied with a recently available technique for localizing peroxidase with the electron microscope. Brains were fixed by either immersion or vascular perfusion 10–60 min after administration of various doses of peroxidase. Exogenous peroxidase was localized in the lumina of blood vessels and in some micropinocytotic vesicles within endothelial cells; none was found beyond the vascular endothelium. Micropinocytotic vesicles were few in number and did not appear to transport peroxidase while tight junctions between endothelial cells were probably responsible for preventing its intercellular passage. Our findings therefore localize, at a fine structural level, a "barrier" to the passage of peroxidase at the endothelium of vessels in the cerebral cortex. The significance of these findings is discussed, particularly with reference to a recent study in which similar techniques were applied to capillaries in heart and skeletal muscle.

Junctions between intimately apposed cell membranes in the vertebrate brain

Abstract: Certain junctions between ependymal cells, between astrocytes, and between some electrically coupled neurons have heretofore been regarded as tight, pentalaminar occlusions of the intercellular cleft. These junctions are now redefined in terms of their configuration after treatment of brain tissue in uranyl acetate before dehydration. Instead of a median dense lamina, they are bisected by a median gap 20–30 A wide which is continuous with the rest of the interspace. The patency of these "gap junctions" is further demonstrated by the penetration of horseradish peroxidase or lanthanum into the median gap, the latter tracer delineating there a polygonal substructure. However, either tracer can circumvent gap junctions because they are plaque-shaped rather than complete, circumferential belts. Tight junctions, which retain a pentalaminar appearance after uranyl acetate block treatment, are restricted primarily to the endothelium of parenchymal capillaries and the epithelium of the choroid plexus. They form rows of extensive, overlapping occlusions of the interspace and are neither circumvented nor penetrated by peroxidase and lanthanum. These junctions are morphologically distinguishable from the "labile" pentalaminar appositions which appear or disappear according to the preparative method and which do not interfere with the intercellular movement of tracers. Therefore, the interspaces of the brain are generally patent, allowing intercellular movement of colloidal materials. Endothelial and epithelial tight junctions occlude the interspaces between blood and parenchyma or cerebral ventricles, thereby constituting a structural basis for the blood-brain and blood-cerebrospinal fluid barriers.