PubMed Health⌕ Search

Biomedical subjects

M M Schwartz

Publications and source records attributed to M M Schwartz.

16 recordsLinked to original sources
PubMed1979

Regional membrane specialization in the thin limbs of Henle's loops as seen by freeze-fracture electron microscopy.

Rat thin limbs of Henle were studied by freeze-fracture electron microscopy. Thin limb segments in both short- and long-looped nephrons were identified by previously developed ultrastructural criteria, continuity with known thick segments, and architectural relationships in the outer medulla. Intramembrane particle (IMP) density and the number of intramembrane fibrils comprising the zonula occludens were determined for each morphologically identifiable thin limb segment. The IMP density on the protoplasmic faces of both the luminal and abluminal membranes of the upper portion of the descending thin limb (DTL) of the long-looped nephron is quantitatively greater than in the short-looped thin limb, lower portion of the long-looped DTL, and in the ascending thin limb. The zonulae occludens in the long-looped upper DTL consists of a single fibril; the long-looped lower DTL contains 3.13 +/- 0.14 fibrils; the ascending thin limb contains 1.31 +/- 0.09 fibrils; and the short-looped DTL contains 3.75 +/- 0.19 fibrils. These studies further support the contention that there is anatomic heterogeneity among the thin limb segments. Because direct physiologic studies in the thin limbs are incomplete and conflicting, the need for correlative physiologic studies on anatomically characterized structures is indicated.

Animals↗
PubMed1978

Isolated dissecting aneurysm of the renal artery.

We report two cases of an unusual cause of the acute onset of hypertension, a spontaneous dissecting aneurysm localized to the renal artery. Also reviewed are 16 reported cases from the literature. The mean age of the 18 patients was 52 years. The majority of these patients were males (78%). Hypertension was a presenting sign in 14 (78%), but was not usually a pre-existing feature. Loin pain, often severe, occurred in eleven patients (61%), whereas gross hematuria was recorded only in two (11%). The right renal artery was involved in ten cases (55%), the left in three (17%), and both in five cases (28%). Atherosclerosis of the renal arteries and the aorta was absent in 69%, and mild in 23%. There has been no report of renal artery rupture; however, vascular occlusion occurs frequently. Medical and surgical approaches to the management of this phenomenon have been reported and are reviewed.

Adult↗
PubMed1978

Pulmonary hemorrhage in systemic lupus erythematosus.

The clinicopathological features of four patients with systemic lupus erythematosus and pulmonary hemorrhage are described. Our study confirms that pulmonary hemorrhage may be a dominant clinical expression of lung involvement in this disease. Its clinical manifestations are usually quite characteristic. However, hemoptysis may be absent. Radiographically, bilateral alveolar infiltrates resembling pulmonary edema or infection may be seen. Pulmonary hemorrhage was a major contributing factor to the death of three of our patients. The possible pathogenetic mechanisms responsible for pulmonary hemorrhage in our patients and other patients previously recorded in the literature are reviewed. Evidence supporting an immune complex pathogenesis is presented. Our immunopathological and ultrastructural studies demonstrate deposition of immune aggregates in the lungs in the alveolar septa, large blood vessels, and bronchioles in a manner similar to that which has been observed in the experimental serum sickness model of immune complex mediated pulmonary injury. The histological abnormalities, although nonspecific, are consistent with this interpretation, and collectively show diffuse alveolar lining cell and endothelial cell injury. However, an immune complex pathogenesis may not completely explain the occurrence of pulmonary hemorrhage in SLE. Other factors, including bleeding disorders, pulmonary infection, oxygen toxicity, and the "shock lung" syndrome, may also have contributed to lung hemorrhage in some of these patients.

Adolescent↗
PubMed1978

Endocytosis: a property of the glomerular visceral epithelial cell.

The sequential intravenous injections of protamine and heparin into rats results in the deposition of protamine-heparin aggregates along the lamina rara externa of the glomerular basement membrane. Morphologic studies indicate that these foreign aggregates are removed from the glomerular basement membrane by virtue of phagocytic activity by the glomerular visceral epithelial cells. We have studied the disappearance rate of protamine-heparin aggregates from the glomerular basement membrane in animals given a single dose of these compounds and in animals receiving chronic administration. The disappearance rate was measured utilizing a computerized morphometric technique to determine the numerical density of protamine-heparin aggregates per 100 micrometer glomerular basement membrane in sequential biopsy specimens taken from 15 to 600 min post-injection. The disappearance rate described a linear function in both acute and chronic animals, with a half-disappearance time of approximately 120 min. Disappearance of the aggregates appeared to be due to epithelial cell phagocytosis. This model provides a method of studying this function in the intact glomerulus in both normal and disease states.

Animals↗
PubMed1978

Interpersonal managerial skills in the training of dental students.

Responsibilities of the dental practitioner impose stress situations similar to those of any manager. These deal with elements of interpersonal behavior and skills not customarily taught to the dental practitioner. In an effort to train dentists so that they may better cope with these managerial situations a method was devised using as the primary instrument the Dental Managerial Situation Study (DMSS). The DMSS employs a variety of problem situations that the dentist is likely to encounter as a means of eliciting his or her managerial tendency (Managerial Profile). A managerial profile is then applied for diagnostic and training purposes. In group discussions, most appropriate behavior (i.e. normative responses) is determined and new ways to behave are learned as each student witnesses advantages and disadvantages of certain responses. The method described in this paper imparts a lexicon (knowledge) of alternative coping or non-coping behaviors to managerial situations. The dental practitioner is able to apply this knowledge in future situations in a way that is more coping and thus he or she may alleviate some managerial stress.

Aggression↗
PubMed1978

Hereditary C2 deficiency and systemic lupus erythematosus associated with severe glomerulonephritis.

Although an unusually high incidence of immunological diseases has been described in patients with hereditary C2 deficiency, the severity of these illnesses has been relatively mild, suggesting that blocking complement activation beyond C4 may protect against significant complement-mediated inflammation. This report describes studies in a C2-deficient patient with severe systemic lupus erythematosus (SLE) and diffuse proliferative glomerulonephritis. An immunopathological study of the kidney revealed the deposition of properdin, properdin factor B, C3 and C5 in a pattern similar to immunoglobulin G deposits. Serum properdin and properdin factor B levels were low at various times during the patient's course. In vitro complement fixation studies showed C3 fixation by glomerular deposits could occur via the alternative pathway. Studies of the immune deposits in the patients' skin revealed similar results. These studies suggest that inflammation may be effectively mediated via the alternative complement pathway in the C2 deficiency-lupus syndrome.

Adolescent↗
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↗
PubMed1976

Acute renal failure following halothane anesthesia.

Acute renal failure was observed postoperatively in a patient after halothane anesthesia. The clinical and pathologic findings in this case were remarkably similar to those found in patients with renal failure after methoxyflurane anesthesia.

Acute Kidney Injury↗
PubMed1976

Ultrastructural differences between rat inner medullary descending and ascending vasa recta;.

The ultrastructure of rat inner medullary vasa recta was studied by both conventional transmission and freeze-fracture electron microscopy. The identify of descending and ascending vasa recta in the inner medulla was established by tracing outer medullary descending vasa recta and ascending vasa recta into the inner medulla, as well as by the incomplete carbon labeling technique to identify isolated descending vessels or loops. As in the outer medulla, descending vessels possess thick continuous endothelium with pinocytotic vesicles budding off the luminal and basal plasma membranes (more numerous in the latter location), but no fenestrae. Ascending vasa show thin, attenuated endothelium with numerous (500 to 800 A fenestrae bridged by 40 A thick fenestral diaphragms. Intercellular junctions in both vessels are zonulae occludens with usually one, and uncommonly two or three zones of outer leaflet membrane fusion. Intramembranous particles are numerous in endothelial plasma membranes of descending vasa recta; similar particles are much fewer in corresponding ascending vasa recta endothelial plasma membranes. The ultrastructural differences between descending vasa recta and ascending vasa recta may reflect markedly different permeability properties, particularly to macromolecules, and may be relevant to recent functional studies on rat inner medullary vasa recta.

Animals↗