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R S Cotran

Publications and source records attributed to R S Cotran.

At least 73 records · Page 4Linked to original sources
PubMed1981

Influence of molecular charge upon the endocytosis and intracellular fate of peroxidase activity in cultured arterial endothelium.

The molecular charge of the macromolecule, horseradish peroxidase (HRPase, 40 000 mol. wt), was modified to yield highly anionic (PI less than 3.68) and cationic (PI = 9.5-10.5) derivatives. The effects upon the interactions between HRPase and arterial endothelium were then studied in vitro. The net rate of uptake of HRPase into endocytic vesicles and vacuoles of confluent endothelium was influenced by its molecular charge, there being less internalization of the anionic HRPase than of the native (pI = 7.9-8.2) and cationic derivatives. The molecular diameter was not significantly different between the cationic (Ae = 28.8 A), anionic (Ae = 31.2 A) and native (Ae = 29.6 A) HRPase. The rate of uptake of [U-14C]sucrose, a tracer of bulk fluid endocytosis, was unaffected by the presence of the differently charged HRPase, indicating that the volume of vesicles formed per cell per hour remained constant. The intracellular fate of HRPase of different charge was investigated biochemically and morphologically. The rate of loss of internalized HRPase activity in the endothelial cells approximated first-order kinetics. The rate of disappearance of intracellular HRPase activity was much greater for cationic (t1/2 = 8 h) and native (t1/2 = I 8 h) than for anionic HRPase (t1/2 = 80-100 h). By electron microscopy, all 3 forms of HRPase were restricted to intracellular membrane-bounded vesicles and vacuoles consistent with a vesicle-lysosomal pathway. Studies with purified lysosomal cathepsin D indicated that the differences in the intracellular half-lives of HRPase may be attributable in small part to decreased and increased rates of lysosomal proteolysis of anionic and cationic HRPase, respectively, in comparison with native HRPase. Pre-labelling of endothelial secondary lysosomes by inhibitors of phagosome-lysosome fusion (dextran sulphate, polyglutamate) lengthened the intracellular half-life of native HRPase, while introduction of cationic ferritin to cells pulsed with anionic HRPase greatly decreased its half-life. Thus an influence of molecular charge upon endosome-lysosome fusion cannot be excluded. The studies indicate that the net charge carried by exogenous HRPase influences both its internalization in endocytic vesicles and its subsequent intracellular fate, which in turn may be modified by the introduction of other differently charged macromolecules. These results are discussed in relation to macromolecular transport by vascular endothelium in vivo.

Animals↗
PubMed1981

Stimulation of nonlymphoid mesenchymal cell proliferation by a macrophage-derived growth factor.

Cultured mouse peritoneal macrophages secrete a growth-promoting activity that stimulates 3 types of nonlymphoid mesenchymal cells in vitro: fibroblasts, vascular smooth muscle, and vascular endothelium. Production of this macrophage-derived growth factor (MDGF) is directly related to the number of viable macrophages and their time in culture, and is independent of platelet- or plasma-derived serum growth factors. Treatment of cultured macrophages with latex, bacterial lipopolysaccharide, or phorbol myristate acetate results in increased growth factor activity. Preliminary biochemical characterization of MDGF indicates that it is a heat labile (100 degrees C, 2 min), non-dialyzable protein, which contains at least 1 essential disulfide bond. Growth-promoting activity is not adsorbed by CM-Sephadex chromatography, under conditions that effectively remove platelet-derived growth factor(s). Serine protease activity is not required for the action of MDGF. Secretion of macrophage-derived growth factor may be relevant to the function of mononuclear phagocytes in several pathologic processes, including the neovascularization and fibroplasia of wound healing, smooth muscle hyperplasia in atherosclerosis, and proliferative glomerulonephritis.

Animals↗
PubMed1979

Distribution and movement of anionic cell surface sites in cultured human vascular endothelial cells.

Cell surface anionic sites on primary and transformed cultures of human vascular endothelium were studied using cationized ferritin (CF) as an ultrastructural marker. The native distribution of anionic sites on the upper (free) surfaces of cells, fixed in situ with glutaraldehyde, was uniform. Binding of the polycationic ligand, CF, in unfixed cells induced redistribution of anionic sites. Rapid formation of discrete patches of CF particles was followed by reappearance of binding between patches, movement of surface-bound CF into intercellular clefts, and endocytosis, over the next 30 min. Aldehyde-fixed cells, detached from the culture surface, bound CF on both upper and lower surfaces. The distribution and mobility of negatively charged membrane components in vascular endothelium may have relevance for thrombosis, atherogenesis, and vascular permeability.

Aldehydes↗
PubMed1978

A mononuclear cell component in experimental immunological glomerulonephritis.

An accelerated form of nephrotoxic serum nephritis in the rat was examined. The experimental model consisted of preimmunization of the rat with rabbit IgG 5 days before injection of subnephrotoxic doses of rabbit anti-rat kidney serum. The immunized rats developed proteinuria during the first 24 h, increasing by 48-96 h. The early 24-h proteinuria correlated with a neutrophilic infiltration of glomeruli and with deposition of rat Ig and C. The 48- to 96-h proteinuria was associated with a glomerular infiltration by mononuclear cells and proliferation of intrinsic glomerular cells. Many of the mononuclear cells were morphologically identical to monocytes and macrophages. [3H]thymidine labeling experiments indicated that the mononuclear cells originated from dividing precursors localized outside the kidney. Preimmunized rats given systemic irradiation (the kidney being protected by a shield) showed loss of the mononuclear cell infiltrate and absence of 48- to 96-h proteinuria. We conclude that mononuclear phagocytes can infiltrate the kidney in immunological glomerular disease and might contribute to the functional abnormalities.

Animals↗
PubMed1978

Pathologic localization of Tamm-Horsfall protein in interstitial deposits in renal disease.

Interstitial periodic acid-Schiff positive deposits of amorphous or fibrillar material were observed in 32% of kidneys with a variety of tubulointerstitial diseases, including medullary cystic disease (60%), chronic pyelonephritis (20%), and hydronephrosis (33%). Immunofluorescent staining for Tamm-Horsfall protein showed interstitial localization of this protein which was identical in distribution, shape, size, and fine detail with the periodic acid-Schiff positive deposits. The deposits appeared to originate from disrupted tubules and were sometimes surrounded by inflammatory infiltrate. The intrarenal localization of Tamm-Horsfall protein outside of distal tubules in pathologic states indicates that this protein may have a role in the pathogenesis of renal disease.

Fluorescent Antibody Technique↗
PubMed1978

The effects of leukocyte depletion on corneal neovascularization.

The role of leukocytic infiltration in the initiation and maintenance of corneal neovascularization was studied in rats. Vascular ingrowth was induced by central cauterization of the cornea with silver nitrate and assessed after intraarterial perfusion of colloidal carbon. In normal rats, the mean vascular length was 0.33 mm. at 3 days and 0.63 mm. at 4 days. Whole-body x-irradiation with 800 rads depressed peripheral blood leukocyte counts to 1% of normal, prevented infiltration of monocytes, and reduced infiltration of neutrophils, but did not alter the neovascular response at 4 days. Combined treatment with radiation (800 rads) and repeated injections of antineutrophil serum (ANS) reduced peripheral leukocyte counts to nearly zero and eliminated infiltration of both monocytes and neutrophils. Despite the absence of leukocytes, neovascularization occurred in all corneas. However, the mean vascular length was reduced to 67% of control at 3 days and to 33% at 4 days. The results indicate that vascular growth can be initiated in the absence of leukocytic infiltration. The reduced neovascularization in totally leukopenic animals might be due to either the ability of neutrophils to facilitate or augment vascular growth or the nonspecific effects of treatment with radiation and antineutrophil serum.

Animals↗
PubMed1978

Endothelial proliferation in inflammation. II. Autoradiographic studies in x-irradiated leukopenic rats after thermal injury to the skin.

The effect of leukocyte depletion on endothelial proliferation in the microvasculature of skin sites of acute inflammation was studied. Leukocytes were suppressed by 800 rad of whole-body irradiation 2 or 4 days prior to producing necrotizing thermal injuries (60 C, 20 seconds) on a shielded area of skin. Endothelial proliferation was assayed 3 days after thermal injury by quantitating the labeling index after injection of 3H-thymidine. Circulating mononuclear cells were depressed to 1.3% of pre-irradiation levels by 2 days and remained at similar levels at 5 days. Lesions developing over this interval were devoid of mononuclear infiltrate, although neutrophils emigrated as usual. Three-day lesions without mononuclear infiltrate had a mean endothelial-labeling index of 8.97%, and this was not significantly different control controls (9.42%). Lesions induced at 4 days, when circulating neutrophils were also suppressed, had reduced infiltration of neutrophils, but endothelial-labeling indexes were similar to those of controls. The results indicate that infiltration by monocytes is not a necessary stimulus for endothelial proliferation of new vessel growth in sites of nonimmunologic acute inflammation.

Animals↗
PubMed1977

The effect of propranolol on microvascular injury in acute myocardial ischemia.

The purpose of this study was to determine whether propranolol, which has been shown to reduce the extent of myocardial infarction, reduces microvascular injury which may play a role in exacerbating ischemia. Saline (10 dogs) or propranolol (2 mg/kg i.v., 7 dogs) was injected prior to a one hour occlusion of the left anterior descending coronary artery. Carbon black (1 ml/kg), which labels damaged and leaky vessels, was injected 5 min after release of the occlusion and allowed to circulate for two hours. By morphometric analysis of 1 micron thick sections, 75 +/- 12% of vessels and 84 +/- 7% of myocardial cells showed damage in untreated dogs; only 2 +/- 1% of vessels and 9 +/- 8% of myocardial cells showed damage in the propranolol-treated dogs (P less than 0.001). The number of carbon black-labeled vessels/10 fields/biopsy from comparable areas of ischemic tissue was 55 +/- 7 in untreated dogs and 27 +/- 3 in propranolol-treated dogs (P less than 0.001). The results suggest that propranolol not only protects the ischemic myocardial cell, but also significantly decreases the ischemic microvascular changes.

Acute Disease↗
PubMed1977

Pathogenesis of polycation-induced alterations ("fusion") of glomerular epithelium.

Perfusion of rat kidneys with polycations (protamine sulfate, poly-L-lysine), resulted in glomerular epithelial alterations very similar to those observed in proteinuric states, particularly rat aminonucleoside nephrosis. Such changes did not occur after exposure to neutral or anionic macromolecules (poly-DL-alanine, myoglobin, heparin, poly-L-glutamic acid and ovalbumin). Morphigenetic factors in the polycation-induced lesion included retraction and flattening of foot processes, narrowing of filtration slits, formation of occluding junctions between foot processes and cell swelling. The associated suppression of histochemically demonstrable glomerular polyanion suggested that neutralization of cell surface anionic sites was an important factor in the causation of the lesion, which was reversible by reperfusion with heparin. Observations by freeze-fracture confirmed the similarity of the polycation-induced lesion to the epithelial changes in rat aminonucleoside nephrosis. Following exposure to polycations there was also "staining" of anionic sites on epithelial and endothelial cell membranes and glomerular basement membrane. Reperfusion of protamine-treated kidneys with heparin resulted in restoration of previously suppressed colloidal iron staining and the formation of spherical, electron-dense (heparin-protamine) complexes within the glomerular filter.

Animals↗
PubMed1977

Cellular migration and replication in endothelial regeneration: a study using irradiated endothelial cultures.

Cellular migration and replication were studied during repair of mechanical injuries produced in cultured monolayers of vascular endothelium. Human endothelial cells were obtained by collagenase perfusion of term umbilical cord veins and were grown on glass cover slips in replicate primary cultures. Following standardized mechanical denudation ("wounding") of narrow linear areas in postconfluent cultures, cellular migration and DNA synthesis were assessed at intervals after terminal 3H-thymidine incubation. Migration of cells from the edges of the wound into the denuded area was consistently underway by 12 hours, and by 24 hours there was considerable repopulation of the wound. A significant increase in 3H-thymidine labeling was not observed in the wound area until 36 hours. When cultures were exposed to 1500 rads of x-rays 1 hour prior to wounding, labeling was nearly abolished at 48 and 72 hours despite continuous incubation with 3H-thymidine. However, migration occurred as usual and resulted in repopulation similar to that in nonirradiated replicate cultures. These studies indicate that small endothelial defects can be significantly repaired by migration of adjacent viable cells. Thus, factors influencing both migration and replication should be considered in studies dealing with endothelial regeneration in vivo.

Cell Division↗
PubMed1977

Reversible inner medullary vascular obstruction in acute experimental hydronephrosis.

The pathogenesis of experimental unilateral hydronephrosis was studied in the rat, with emphasis on the role of medullary vascular obstruction. The medullary circulation was evaluated after increasing periods of ureteral obstruction (up to 48 hours) using in vivo perfusion of silicone rubber or colloidal carbon. Evidence of inner medullary hypoperfusion was seen after 1 hour, and by 6 hours, the entire papilla was ischemic. Papillar hypoperfusion was still present at 24 and 48 hours, but significant recirculation occurred in the presence of continued obstruction. Release of ureteral obstruction caused rapid reversal of the perfusion defect. Histologic studies of the renal parenchyma adjacent to the pelvis showed increasing vascular congestion, focal interstitial edema, and extravasation of erythrocytes; these changes were also diminished after release of obstruction. Endothelial swelling or thrombosis in inner medullary blood vessels was not observed. Inner medullary tubules showed degenerative changes in kidneys that had been obstructed for 6 hours or more; at later periods (18 hours or more) focal necrosis was seen, but it never involved the entire papilla. Thus, reversible collapse of inner medullary blood vessels occurs in acute unilateral hydronephrosis and may provide the basis for the development of ischemic tubular damage. The findings suggest that the vascular obstruction may be due to increased intrapelvic pressure, rather than endothelial swelling or thrombosis. The vascular-tubular defect may be relevant to the altered medullary physiology observed in this condition.

Acute Disease↗
PubMed1977

Endothelial proliferation in the delayed hypersensitivity reaction: an autoradiographic study.

The time-sequence of endothelial proliferation in the delayed hypersensitivity reaction was examined in the skin of guinea pigs. Animals were sensitized to tuberculin (PPD) and dinitrochlorobenzene (DNCB) and skin lesions were examined 12 hr to 7 days after challenge. Thirty minutes before sacrifice 3H-thymidine (3H-T) was injected i.p. and endothelial labeling was assessed in autoradiographs of 1.5-mu thick methacrylate sections. Endothelial labeling became manifest at 24 hr (PPD) and 12 hr (DNCB) after challenge, reaching a peak at 48 to 72 hr in PPD-sensitized animals and 36 to 48 hr in DNCB-sensitized animals. Peak labeling indices were 7.88 and 15.08%, respectively. Labeling indices for nonsensitized control groups were always less than 1%. Endothelial labeling was associated, in time of occurrence, distribution, and magnitude with mononuclear cell infiltration of the lesions. These findings thus document the occurrence of significant endothelial cell proliferation in delayed hypersensitivity responses and suggest that the events leading to the expression of hypersensitivity also result in endothelial replication.

Animals↗
PubMed1977

Endothelial proliferation in inflammation. I. Autoradiographic studies following thermal injury to the skin of normal rats.

Endothelial prolifertion was studied in sites of acute inflammation induced by necrotizing (60 C for 20 seconds) or mild (54 C for 20 seconds) thermal injury to the skin of rsts. DNA synthesis in endothelial cells was assayed 6 hours to 10 days following injury by quantitation of the (3)H-thymidine labeling indices on 2-mu Epon section autoradiographs. In lesions induced at 60 C for 20 seconds, increase in DNA synthesis in small vessels around the necrotic tissue began at 1 day and became significant at 2 and 3 days (10 to 12% for endothelial cells, 9% for perivascular cells). This increased endothelial replication resulted in the formation of new blood vessels by 5 to 7 days. Endothelial labeling diminished progressively after 3 days, as the epidermis regenerated. Foci completely covered by new epidermis consistently showed lower labeling indices than those which were not reepithelialized. Mild thermal injury (54 C for 20 seconds) also resulted in significant increases in endothelial labeling (6%), but the labeling was present mainly in superficial vessels and was not followed by neovascularization. The findings with mild injury are consistent with data that vascular leakage from superficial vessels is due to direct, albeit delayed, endothelial damage. Electron microscopic studies confirmed labeling in endothelial cells and indicated that ultrastructural alterations that were previously ascribed to activation, recovery, or regenerative transformation of endothelium represent, in the main, endothelial proliferation.

Animals↗
PubMed1976

Endothelial DNA synthesis in themicrovasculature of rat skin during the hair growth cycle.

Earlier studies of the vascular patterns around hair follicles revealed that actively growing follicles have an extensive microvasculature relative to that around quiescent follicles. In order to determine whether the establishment of the active perifollicular vascular pattern involves replication of endothelial and perivascular cells, we studied the 3H-thymidine labeling indices of these cells in autoradiographs of rat skin from regions containing either actively growing follicles or recently inactive follicles. In skin containing inactive follicles, the endothelial labeling index was 0.22%, a figure similar to those reported for the endothelium of small blood vessels in several other non-stimulated adult tissues. However, skin containing actively growing follicles displayed an endothelial labeling index of 2.35%. The labeling indices of perivascular cells paralleled those of the endothelial cells. Thus, endothelial and perivascular cells in vessels associated with actively growing follicles undergo significantly more DNA synthesis than those in vessels associated with inactive follicles. Replication of these cells apparently contributes to the extension of the microvascular network around growing follicles.

Animals↗