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Biomedical subjects

S R Greenberg

Publications and source records attributed to S R Greenberg.

At least 19 recordsLinked to original sources
PubMed1992

Cardiac anaphylaxis in the Sprague-Dawley rat.

Anaphylactic shock was induced in pentobarbital-anesthetized, mechanically ventilated Sprague-Dawley rats that had been sensitized 21 days earlier to crystallized ovalbumin. The sensitization was confirmed by passive cutaneous anaphylaxis test. Antigen challenge produced an immediate reduction in mean aortic pressure from 168 to 67 mm Hg within 1 minute after intravenous injection of ovalbumin. Plasma histamine increased from 4.5 to 128 ng/ml within 5 minutes after injection of antigen. There were no changes in airway or esophageal pressures after antigen challenge. Left ventricular diastolic pressure was increased, and contractility, as measured by the rate of change of left ventricular pressure (dP/dt), was decreased over an interval exceeding 90 minutes. When isolated, constant flow--perfused hearts from sensitized Sprague-Dawley rats were challenged with antigen, decreases in left ventricular function were observed associated with decreased positive and negative maximum rate of change of left ventricular pressure (dP/dtmax). This experimental model in the rat therefore demonstrated selective myocardial impairment with reduced inotropism and lusitropism after anaphylaxis.

Anaphylaxis↗
PubMed1990

The histopathology of tissue lead retention.

An experimental murine model of chronic lead retention is established. This model excludes joint communication and synovial fluid solubility of lead ions recognized in human gunshot injury. Degenerative changes in the visceral organs and bone appear in these mice 30 days after implantation of lead spheres in the subcutaneous tissues of the posterior body wall. Degeneration, necrosis and interstitial fibrosis of the lung, kidney and remodeling of femoral bone are noted during the course of the experiment (120 days). It is concluded that the systemic diffusion of lead ions from a central focus is related to the development of an absorptive circulatory mechanism around the retained peripheral lead mass.

Absorption↗
PubMed1989

The confined space. A review of a recently discerned medical entity.

This paper presents an extensive review of the literature relating to the industrial confined space. It defines the various types of confined spaces, classifies their associated noxious atmospheres, and identifies the potential hazards of each. A newly recognized confined space, the environment of the surgical amphitheater in which the surgical patient undergoes general anesthesia, has been added. Pathological alterations bearing upon these hazards and the forensic principles of confined space injuries are examined in depth. In addition, recent methods are described for prevention and control of the perils of the confined space.

Accidents, Occupational↗
PubMed1987

Seat belts and human rights: an appraisal.

Mandatory seat belt legislation has been passed in 15 states. Accompanying this action has been a deluge of information concerning the lives saved and the injuries prevented by the wearing of seat belts by the front seat passengers in automobiles. This study presents data relating to the injuries and deaths attributable to their usage. There is virtually no major area of the adult body that has escaped such involvement. Mechanisms by which seat belt injury is effected are described in relation to the restraint systems currently available in the United States and abroad.

Abdominal Injuries↗
PubMed1986

Response of the renal supporting tissues to chronic fluoride exposure as revealed by a special technique.

The effects of chronic fluoride excess in the mouse were studied by means of polarizing microscopy in combination with a special staining technique employing Sirius red F3B, a dye which renders collagen fibrils sharply visible. It was observed that changes occur in three renal areas: the interstitium, the intrinsic vasculature and Bowman's capsule. The collagen content of each area increases after about 100 days of the total fluoride exposure of 280 days had elapsed. Although Bowman's capsule was thickened, the glomerular tufts and the nephrons showed edematous swelling and degeneration. A concept is developed to illustrate how early inflammatory response to the chemical effects of fluoride excess leads to vascular injury, parenchymal ischemia and fibrosis.

Animals↗
PubMed1986

The association of medial collagenous tissue with atheroma formation in the aging human aorta as revealed by a special technique.

A new technique which brilliantly colors collagen fibers in a field of polarized light reveals that during mid-life the smooth muscle cells in the tunica media of the human aorta begin to disappear. The connective tissue is divided between two regions; one below the subintimal layer and the other under the adventitia. Fine collagen fibers extend upward from the former into the subintima and beyond into the intima and the overlying atheromatous plaques of the aging aorta. Thus, the source of fibrous thickening of the vessel is not confined solely to the intimal layer; at least, a portion of the total collagen content arises deep within the aortic wall.

Adolescent↗
PubMed1985

Thresholds for primary auditory fibers using statistically defined criteria.

The discharge behavior of auditory-nerve fibers near "threshold" was investigated in anesthetized cats using low-intensity sinusoidal stimuli presented at the respective characteristic frequencies. Particular attention was paid to fibers with "low" and "medium" rates. Estimates of threshold derived from statistically significant increases in discharge rate indicate that the average threshold values for low-spontaneous fibers are only slightly higher (ca. 5 dB) than the averages for the corresponding high-spontaneous fibers, with the medium-spontaneous fibers having intermediate averages. The difference between these average values is considerably less than the more than 20-dB difference obtained using threshold criteria based on an absolute increment in discharge rate [e.g., M. C. Liberman, J. Acoust. Soc. Am. 63, 442-455 (1978)]. The main reason for the difference between the results of the two techniques is the fact that the slopes of the rate-intensity functions for the high-spontaneous fibers are considerably steeper near "threshold" than those for fibers of the other two classes. The results are taken as supportive of a recent model of primary-fiber discharge [C. D. Geisler, Brain Res. 212, 198-201 (1981)].

Animals↗
PubMed1980

Hormonal influences on chemical carcinogenesis: studies with the aflatoxin B1 hepatocarcinoma model in the rat.

The role of adrenocorticotropin, cortisol, and corticosterone on chemical carcinogenesis was investigated using the rat aflatoxin B1 hepatocarcinoma model. The animals were divided into untreated controls and various experimental groups receiving the carcinogen alone or the carcinogen with a hormone. Animals lost during the treatment period died mostly of massive hepatic necrosis. The results following 65 weeks of observation show that: (1) hormones decrease the toxicity of aflatoxin B1; (2) adrenocorticotropin possibly exerts its influence on aflatoxin B1 hepatocarcinogenesis through adrenal stimulation, and (3) in aflatoxin B1-adrenocorticotropin treated animals, hepatocellular carcinoma, cholangiocarcinoma, and malignant lymphoma may be observed.

Adenoma, Bile Duct↗
PubMed1979

Morphologic effects of metallic copper and cadmium directly implanted into the rat kidney.

The discovery of increasing amounts of copper and cadmium in public drinking water supplies has prompted an exploration of the effects of these elements upon the kidney. Markedly different responses are observed during the 6 months after the surgical implantation of copper and cadmium wires into kidneys of Sprague-Dawley rats. Those organs which contained copper showed only mild fibrosis near the site of injury and some pelvic distortion. The cadmium-containing kidneys revealed striking parenchymal destruction and pyraminal distortion. The coexistence of persistent foci of mononuclear cells in the cadmium kidneys and widespread parenchymal destruction is accepted as evidence for the actuality of a tissue hypersensitivity to this metallic element.

Animals↗
PubMed1975

The pathogenesis of hypophyseal fibrosis in aging: its relationship to tissue iron deposition.

An investigation was made of 101 hypophyses from male and female human subjects dying from unrelated diseases. Careful microscopic examination revealed that fibrous replacement of the gland begins after the fourth decade. There is a gradual increase in iron deposition in this connective tissue after the 4th decade. It is suggested that the fibrous replacement of the hypophysis is a consequence of repeated bouts of passive congestion with diapedesis of red cells through the walls of anoxic capillaries. This pattern is akin to that of brown induration of the lung. In this manner, the active cells of the hypophysis may gradually be replaced by collagenous tissue. Because of the inherent slowness of this process, the gland seems to adapt quite well to a reduction in functional elements, thus circumventing significant clinical effects.

Adolescent↗