Endothelial Cells Of Microvessels Research Articles

A saturable mechanism for transport of immunoglobulin G across the blood-brain barrier of the guinea pig

The existence of an immunological blood-brain barrier to homologous blood-borne immunoglobulin G (IgG) was investigated in the guinea pig using a vascular brain perfusion technique in situ. Cerebrovascular unidirectional transfer constants ( K in) for 125I-labeled IgG (2.5 μg/ml) estimated from the multiple-time brain uptake data, ranged from 0.53 to 0.58 ml min −1 g −1 × 10 3 in the parietal cortex, hippocampus, and caudate nucleus, the transfer rate being some 10 times higher than that for [ 3H]dextran (MW 70,000). In the presence of 4 mg/ml unlabeled IgG, unidirectional blood to brain transfer of 125I-IgG was markedly inhibited. Immunohistochemical analysis of the brain tissue after vascular perfusion with unlabeled IgG revealed a distribution of the blood-borne immunoglobulin in the endothelial cells of microvessels and in the surrounding perivascular tissue. It is concluded that there is a specific transfer mechanism for IgG at the blood-brain barrier in the guinea pig, which is saturated at physiological plasma levels of IgG.

Active proliferation of telangiectases in skin of patients with progressive systemic sclerosis (PSS).

The labeling index of endothelial cells as measured by in vitro autoradiography with 3H-thymidine and the electron microscopic structure of microvessels were studied in telangiectases. The telangiectases of eight patients with progressive systemic sclerosis (PSS) were compared with the cherry angiomas of six healthy controls subjects. The ultrastructural features of telangiectases were similar in the two groups and were characteristic of capillaries and postcapillary venules of the dermis, with multilayering of the vascular basement membrane. However, a significant difference existed between these two groups in an autoradiographic study: in PSS telangiectases, the average labeling index was 5.9%, whereas in cherry angiomas it was around 0.8%. Thus, the telangiectases in PSS are structures with accelerated endothelial proliferation, as are the other endothelial cells of microvessels anywhere in dermis in this disease. However, the great heterogeneity of the labeling index (varying from 0.5% to 27%) must be emphasized in telangiectases.

Enzymhistochemical identification of microglial cells in the rat retina: Light and electron microscopic studies

We used the method of thiamine pyrophosphatase (TPPase) enzyme histochemistry and flat-mounted and transverse-sectioned retinas to identify microglial cells. Light microscopically, TPPase activity was demonstrated on the outer surfaces of glial cells located in the inner plexiform layer (IPL) and the ganglion cell layer (GCL) of the entire retinal regions, and also on the outer surfaces of blood vessels. Electron microscopically, TPPase activity was observed on the plasma membranes of the glial cells, the endothelial cells of microvessels and the pericytes. The TPPase-positive glial cells had a dark nucleus with large clumps of chromatin beneath the nuclear envelope. These findings strongly suggest that the glial cells with TPPase activity observed in the IPL and the GCL of the rat retina were microglial cells.

Insulin binding to microvascular endothelium of intact heart: a kinetic and morphometric analysis.

We have studied insulin binding to blood vessels of the intact, beating heart. The beating hearts were perfused with [125I]iodoinsulin (3 X 10(-10) M) followed by perfusion with unlabeled insulin. The unlabeled insulin displaced the bound [125I]iodoinsulin in direct proportion to the concentration of the unlabeled hormone. Perfusion with unlabeled insulin at 10(-11) M elicited a significant displacement of [125I]iodoinsulin, with a maximal effect at 10(-6) M. Unlabeled proinsulin also displaced [125I]iodoinsulin in a dose-dependent manner, being 1% as potent as insulin. Perfusion with unrelated peptides had no effect. Radioautographic counting of 125I grains indicated that greater than 95% of the grain counts over blood vessels were within the microvessels. When [125I]iodoinsulin perfusion was followed by perfusion with unlabeled insulin at 10(-6) M, there was a 50% decrease in grain counts over the microvessels (versus perfusion with [125I]iodoinsulin alone); with coperfusion of [125I]iodoinsulin and 10(-6) M unlabeled insulin, an 80% decrease in grain counts occurred. Electron microscopic radioautography indicated that the 125I grains were associated with the vascular endothelial cells. We conclude that specific insulin receptors are present on endothelial cells of microvessels in the intact heart.

Plasmalemma-bound nucleoside diphosphatase as a cytochemical marker of central nervous system (CNS) mesodermal cells.

Nucleoside diphosphatase (NDPase) activity, using inosine-5'-diphospbate (IDP) as a substrate, was studied by light and electron microscope cytochemistry in brain and spinal cord of normal mouse. After cytochemical incubation for the enzyme, neurons, astroglial and oligodendroglial cells contained reaction product in the cisternae of endoplasmic reticulum (ER) and/or in the trans elements of the Golgi apparatus. In contrast, reaction product for NDPase was concentrated on the outer surface of the plasmalemma of microglial cells, endothelial cells of microvessels, pericytes, and smooth muscle cells of the arteriole wall. An occasional microglial cell contained sparse reaction product in the flattened saccules of the Golgi apparatus. The pattern of enzyme distribution for these cell types was the same for all parts of the nervous system examined in this study. These data suggest that in cells of ectodermal origin, NDPase is intracellular in location, whereas in cells of mesodermal origin, this enzyme is bound to the plasmalemma. The usefulness of this cytochemical reaction for NDPase as a marker of microglial and other cells in brain pathology is discussed.