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Biomedical subjects

A A Stein

Publications and source records attributed to A A Stein.

At least 19 recordsLinked to original sources
PubMed2000

Tension-dependent collective cell movements in the early gastrula ectoderm of Xenopus laevis embryos.

Ventral ectodermal explants taken from early gastrula embryos of Xenopus laevis were artificially stretched either by two opposite concentrated forces or by a distributed force applied to the internal explant's layer. These modes of stretching reflect different mechanical situations taking place in the normal development. Two main types of kinematic response to the applied tensions were detected. First, by 15 min after the onset of concentrated stretching a substantial proportion of the explant's cells exhibited a concerted movement towards the closest point of the applied stretching force. We define this movement as tensotaxis. Later, under both concentrated and distributed stretching, most of the cell's trajectories became reoriented perpendicular to the stretching force, and the cells started to intercalate between each other, both horizontally and vertically. This was accompanied by extensive elongation of the outer ectodermal cells and reconstruction of cell-cell contacts. The intercalation movements led first to a considerable reduction in the stretch-induced tensions and then to the formation of peculiar bipolar "embryoid" shapes. The type and intensity of the morphomechanical responses did not depend upon the orientation of a stretching force in relation to the embryonic axes. We discuss the interactions of the passive and active components in tension-dependent cell movements and their relations to normal morphogenetic events.

Animals↗
PubMed2000

Breast cancer: importance of spiculation in computer-aided detection.

PURPOSE: To determine the prevalence of spiculation in a large series of screening-detected breast cancers appearing as masses on mammograms and to assess the sensitivity of a computer-aided detection (CAD) algorithm that uses spiculation measures in the detection of such lesions. MATERIALS AND METHODS: Six hundred seventy-seven consecutive cases of breast cancers detected as masses on mammograms were independently reviewed by three radiologists who determined if the lesions were spiculated. All cancers were then analyzed by the CAD system. RESULTS: All three radiologists interpreted 375 (55%) of the 677 masses as being spiculated on at least one view. The CAD algorithm correctly marked 322 (86%) of the 375 clearly spiculated masses, with a mean of 0.24 additional mass mark per image. With a looser definition of spiculation, 585 (86%) of the 677 masses were called spiculated by at least one radiologist on one view. The algorithm correctly marked 464 (79%) of the 585 lesions that were spiculated or possibly spiculated. CONCLUSION: Spiculation was clearly present in a majority (55%) of consecutive screening-detected breast cancer masses found on mammograms in a large clinical trial. Incorporation of spiculation measures is, therefore, an important strategy in the detection of breast cancer with CAD. A present-generation CAD algorithm correctly identified a large proportion (86%) of spiculated breast cancers.

Algorithms↗
PubMed1996

Chronic inhalation exposure of rats to nitromethane.

Male and female Long-Evans rats were housed in inhalation chambers and exposed to vapors of nitromethane (NM) at either 100 or 200 ppm. The animals were exposed 7 hr per day, 5 days per week for 2 years. Control groups of rats were also housed in a similar inhalation chamber, but NM was not introduced into the chamber. The animals were observed daily for signs of pharmacologic or toxicologic effect and body weights were recorded periodically. At the 2-year termination of the exposure period, clinical laboratory examinations (serum chemistry and hematology) were performed on selected animals and all surviving animals were sacrificed. All animals were necropsied and subjected to a thorough histopathologic examination. During the study there were no pharmacologic effects from exposure to NM at either 100 or 200 ppm. There was no effect on mortality on either sex at either exposure level. Body weights of male rats exposed to NM were not significantly different from those of control rats, but the body weights of female rats of both exposure groups were slightly less than their controls. There was no effect of exposure of rats of either sex to either level of NM on hematology. There were no clinically significant effects on serum chemistry. There were no effects of exposure to NM on organ weights. There were no significant differences in the nonneoplastic or neoplastic pathology related to exposure to NM.

Administration, Inhalation↗
PubMed1996

[The interaction of a root growing vertically with a rigid barrier].

Bending root tip that grows outside the soil is investigated. The decrease of growth rate due to increasing compressive stress leads to the destabilization of uniform solution, whereas differential growth that is controlled by root cap gravitropism is a stabilizing factor. The interplay of both processes leads to diverse behaviour types.

Gravitropism↗
PubMed1988

Chronic inhalation exposure of rats to vapors of nitroethane.

Male and female Long-Evans rats were exposed in inhalation chambers to vapors of nitroethane at concentrations of 100 or 200 ppm, 7 hr per day, 5 days per week for 2 years. During the study, general observations were made daily and body weights were obtained weekly for the first 6 months of the study and biweekly thereafter. Any rats that were found dead or sacrificed moribund during the 2-year exposure phase of the study were given a thorough gross examination and tissues were retained for microscopic examination. After 2 years of inhalation of nitroethane, all surviving rats were sacrificed and subjected to the same thorough gross examination. Blood samples were obtained from representative groups of animals for hematology and serum chemistry studies. All rats were examined histopathologically. Exposure of the rats to nitroethane had no pharmacologic effects nor were there any effects on mortality of rats of either sex at either level of exposure. Throughout most of the investigation, body weights of both sexes of both exposed groups were slightly less than those of respective controls, but lack of a well-defined dose-response relationship suggested the involvement of factors other than just exposure to nitroethane. There were no effects of exposure to nitroethane on hematology nor were there any biologically significant effects of exposure to nitroethane on clinical chemistry or on organ weights. No significant nonneoplastic or neoplastic pathology was found as a consequence of exposure of the rats to nitroethane.

Administration, Inhalation↗
PubMed1983

Pasteurella multocida septicemia. Experience at a cancer hospital.

Pasteurella multocida most commonly infects patients with animal contacts. Life-threatening systemic disease is distinctly uncommon in otherwise healthy persons and usually occurs in patients with chronic predisposing disease. Two cases of sepsis occurred in a cancer hospital, and we surmise that specific predisposing factors existed in our patients as in prior reported cases of sepsis in patients without cancer. These factors include animal contact, open wounds, and, most important, advanced hepatic disease.

Adult↗
PubMed1976

The centrineurogenic etiology of the respiratory distress syndrome: induction by isolated cerebral hypoxemia and prevention by unilateral pulmonary denervation.

Twenty-eight anemic control dogs were subjected to isolated cerebral hypoxemic (PO2,35+/-5 mm Hg) perfusion for 2 hours. All were found to have functional pulmonary impairment. Two hours later, twenty were sacrificed and found to have the bilateral anatomic complex of the respiratory distress syndrome (RDS). All those not sacrificed expired within 20 hours with progressive respiratory distress and at autopsy had the bilateral anatomic complex. Twenty-three beagles with chronic denervation (autotransplantation) of the left lung also were subjected to the 2 hour isolated cerebral arterial hypoxemic perfusion. Minimal pulmonary functional impairment was measurable in all. Ten of sixteen were long-term survivors. The six that succumbed did not appear to suffer respiratory deaths. These six, as well as seven sacrificed 2 hours after perfusion, had the anatomic complex of RDS in the normally innervated right lungs. However, the denervated left lungs were anatomically normal. These findings are offered as additional evidence that RDS has a centrineurogenic etiology. We postulate the following sequence: "shock" causes cerebral (probably hypothalamic) cellular oxygen deprivation and dysfunction; there is autonomically mediated, increased resistance of the pulmonary venules ("postcapillary sphincters"); this leads to capillary hypertension, congestion, hemorrhage, edema, surfactant inactivation, and atelectasis. Pulmonary denervation blocks this sequence and protects the lung.

Animals↗
PubMed1976

The centineurogenic etiology of the respiratory distress syndrome. Protection afforded by anemia and pulmonary denervation against lung lesions of oxygen toxicity.

For beagles respiring 100 per cent oxygen at ambient pressure, anemia protected against the development of the lung lesions of oxygen toxicity. Similarly, unilateral pulmonary denervation was protective of the affected lung but not of the normally innervated, contralateral lung. This indicates that the lung lesions are triggered by the toxic effect of elevated PO2 at a remote site, most likely the sensitive central nervous system.

Anemia↗
PubMed1976

The centrineurogenic etiology of the respiratory distress syndrome: protection by unilateral chronic pulmonary denervation in hemorrhagic shock.

Anemic beagles were subjected to 40 mm Hg hemorrhagic shock for 2 hours, which uniformly induced the pulmonary lesions of the "respiratory distress syndrome" (RDS) bilaterally in all six controls. For six subjects with complete denervation of the left lung 2 months previously, the shock regimen induced the lesions in the normally innervated right lungs; all reimplanted, denervated left lungs remained anatomically intact. This is presented as additional evidence for a centrineurogenic etiology for RDS.

Animals↗
PubMed1975

Cerebral etiology of the acute respiratory distress syndrome: diphenylhydantoin prophylaxis.

Beagles and rats were subjected to hemorrhage regimens that induced the pulmonary complex of the Acute Respiratory Distress Syndrome (ARDS) in 6:6 dogs and 7:8 rats. Pretreatment with diphenylhydantoin (DPH), 5 mg/kg 1-2 hours preceding hemorrhage, resulted in complete prevention of the lung lesions in 8:8 dogs. (P smaller than 0.005). It also provided significant (P smaller than 0.01) protection to 8:11 rats. We offer this as circumstantial evidence that the ARDS has a centrineurogenic etiology.

Animals↗