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Biomedical subjects

R Weinstein

Publications and source records attributed to R Weinstein.

At least 73 records · Page 4Linked to original sources
PubMed1992

Noninvasive carotid duplex ultrasound imaging for the evaluation and management of carotid atherosclerotic disease.

Renewed interest in surgical management of atherosclerotic disease of the carotid bifurcation underscores the necessity for accurate and efficacious means for diagnostic evaluation of patients with suspected carotid disease. Noninvasive testing by carotid duplex ultrasound, which combines high-resolution B-mode imaging with pulsed Doppler spectral analysis, is the method of choice. Noninvasive testing permits identification of potentially significant carotid stenosis, occlusion, or unstable plaque morphology with virtually no significant morbidity from the testing itself. Symptomatic patients, or patients with asymptomatic carotid bruits, can be evaluated serially to determine disease progression or response to medical management. In patients who are surgical candidates, substitution of noninvasive duplex ultrasound evaluation for carotid arteriography is controversial. Noninvasive testing is highly technique-dependent and probably requires at least 1 year of experience for acquisition of a sufficient "learning curve" for diagnostic reliability. This applies not only to the technical performance of the test but to interpretation of results. Proper training of technicians and quality assurance in individual vascular laboratories are crucial elements with respect to accuracy and reliability of results obtained in noninvasive testing.

Arteriosclerosis↗
PubMed1992

[The use of digital techniques with storage phosphors for orthopantomography. Preliminary note].

Digital panoramic tomographies with light-emitting phosphors were obtained in 39 patients, during a study on the clinical applications of digital imaging. Performing digital panoramic radiographies required the preliminary adaptation of the imaging plates to the cassette holder of the radiographic equipment. The digital images were post-processed according to two different protocols, both of which were recorded for each patient. The former image was quite similar to standard X-ray films and was called "analogic-like". The latter, called "xeroradiographic-like", featured a flattening of the overall contrast together with detail contrast enhancement due to the presence of an edge effect, as it occurs in xeroradiography. Digital panoramic tomography allows a marked reduction in patient's exposure to X-rays. In addition, this technique offers constant high-quality results, due to the possibility of recovering over- or under-exposed images during post-processing. Xeroradiographic-like digital films may reduce the sharp contrast that is often present between the anterior and the lateral portions of the maxillary and mandibular arches, thus improving the diagnostic reliability of the examination. Other modalities of digital post-processing may be helpful to depict gingival soft tissues, with obvious advantages for the study of periodontal diseases.

Adolescent↗
PubMed1991

[Special care in dentistry. The therapeutic relationship].

Psychological relationship dentist-patient and psychological education of the dentist are in special dental care very important. In fact the patients with medically complex conditions--patients at risk--often present an altered perception of the reality and behavior, therefore they seldom can co-operate during the operating session. It is then very important to carry-out a psycho-pathological diagnosis, which can avoid a dentist's wrong behavior. Anxiety rate, pathological personality and comprehension level are finally studied.

Aged↗
PubMed1990

Sickle erythrocytes inhibit human endothelial cell DNA synthesis.

Patients with sickle cell anemia experience severe vascular occlusive phenomena including acute pain crisis and cerebral infarction. Obstruction occurs at both the microvascular and the arterial level, and the clinical presentation of vascular events is heterogeneous, suggesting a complex etiology. Interaction between sickle erythrocytes and the endothelium may contribute to vascular occlusion due to alteration of endothelial function. To investigate this hypothesis, human vascular endothelial cells were overlaid with sickle or normal erythrocytes and stimulated to synthesize DNA. The erythrocytes were sedimented onto replicate monolayers by centrifugation for 10 minutes at 17 g to insure contact with the endothelial cells. Incorporation of 3H-thymidine into endothelial cell DNA was markedly inhibited during contact with sickle erythrocytes. This inhibitory effect was enhanced more than twofold when autologous sickle plasma was present during endothelial cell labeling. Normal erythrocytes, with or without autologous plasma, had a modest effect on endothelial cell DNA synthesis. When sickle erythrocytes in autologous sickle plasma were applied to endothelial monolayers for 1 minute, 10 minutes, or 1 hour and then removed, subsequent DNA synthesis by the endothelial cells was inhibited by 30% to 40%. Although adherence of sickle erythrocytes to the endothelial monolayers was observed under these experimental conditions, the effect of sickle erythrocytes on endothelial DNA synthesis occurred in the absence of significant adherence. Hence, human endothelial cell DNA synthesis is partially inhibited by contact with sickle erythrocytes. The inhibitory effect of sickle erythrocytes occurs during a brief (1 minute) contact with the endothelial monolayers, and persists for at least 6 hours of 3H-thymidine labeling. These results indicate that interaction between sickle erythrocytes and the endothelium may result in altered endothelial function. This altered endothelial function may contribute to the development of vascular occlusive phenomena in patients with sickle cell anemia.

Anemia, Sickle Cell↗
PubMed1990

Coexistence of low secretion of gonadotropins and ACTH in a patient with gonadal dysgenesis and pituitary tumor.

A 56-year-old woman with gonadal dysgenesis and pituitary adenoma is described. The unusual feature in this patient was the coexistence of a low gonadotropin level with secondary ACTH deficiency rather than the high gonadotropin level usually found in gonadal dysgenesis. Secretion of the other pituitary hormones was normal. Several hypotheses for such an unusual combination are presented.

Adenoma↗
PubMed1989

Impacted molars.

Explore the source record for details and available documents.

Humans↗
PubMed1989

The protracted effect of o,p'-DDD in Cushing's disease and its impact on adrenal morphogenesis of young human embryo.

We hereby present a patient with Cushing's disease who became pregnant while being treated with o,p'-DDD and underwent a therapeutic abortion in view of the known embryotoxicity and placental transfer of this drug. Biopsy of adipose tissue in this patient showed it to be the storage site of considerable quantities of o,p'-DDD. Serum levels of o,p'-DDD determined in this patient initially four months after withdrawal of treatment and in another similar case three months after withdrawal were about 20 times higher than those found in untreated patients and reached control values only about 20 months later. Repeated evaluation of plasma and urinary free cortisol failed to reveal any correlation with the serum levels of o,p'-DDD, suggesting that the drug blood values cannot be used as a reliable indicator of the therapeutic effect on the adrenal gland. The histopathological examination of the embryo, aged about 42 days, revealed a dysmorphogenic event in the cortical primordia characterized by pycnotic sympathoblasts. It is suggested that such a toxic effect of o,p'-DDD on the embryonic cortical cells may act indirectly, affecting the viability of the migrating sympathoblasts.

Abortion, Therapeutic↗
PubMed1989

Dual role of fibronectin in hematopoietic differentiation.

The adhesive glycoprotein fibronectin provides anchorage for fibroblasts and hematopoietic progenitor cells in vitro. Fibronectin also demonstrates growth factor activity for fibroblasts; however, there is no available information regarding its role as a hematopoietic growth factor. To distinguish growth factor activity of fibronectin from its anchorage activity for hematopoietic progenitors, we assessed the ability of purified human plasma fibronectin to promote human bone marrow erythroid, granulocyte-macrophage (GM) and mixed granulocyte-erythroid-macrophage-megakaryocyte (GEMM) colony formation in liquid suspension, methylcellulose, and fibrin clots under serum-free conditions. Addition of fibronectin to methylcellulose cultures, or to cultures formed in fibrin clots, using fibrinogen depleted of fibronectin by preadsorption over gelatin-Sepharose and clotted with thrombin, resulted in up to a twofold enhancement of proliferation of erythroid burst-forming units (BFU-E), erythroid colony-forming units (CFU-E), and CFU-GEMM. This effect was concentration-dependent up to a fibronectin supplement of 100 micrograms/mL. By contrast, CFU-GM proliferation was not affected by the addition of fibronectin to the cultures. Fibronectin-adherent marrow cells overlaid with liquid medium formed both early and late-appearing erythroid colonies, whereas similarly cultured plastic-adherent marrow cells did not. Erythroid colony formation was observed in cultures of fibronectin-adherent marrow cells overlaid with methylcellulose but not in cultures of plastic-adherent marrow cells under the same conditions. Finally, the erythroid growth-promoting activity of fibronectin was inhibited by arginyl-glycyl-aspartyl-serine (RGDS), a tetrapeptide that competitively blocks the interaction of fibronectin with its receptor. We conclude that fibronectin plays a dual role in hematopoiesis: providing (a) anchorage for erythroid and primitive progenitors, and (b) as a proliferative stimulus for these hematopoietic cells. Both activities may be mediated by the cell adhesion domain of the molecule.

Adult↗
PubMed1988

Cell attachment to thrombospondin: the role of ARG-GLY-ASP, calcium, and integrin receptors.

Thrombospondin is a 420,000-D glycoprotein that has recently been shown to have several properties in common with the members of a class of adhesive proteins. To characterize further the adhesive properties of thrombospondin, we have studied its ability to support cell attachment. Thrombospondin adsorbed to plastic dishes supports the attachment of human endothelial and smooth muscle cells and the monocyte-like cell line (U937) as well as normal rat kidney cells. The majority of attached cells do not spread on the solid-phase thrombospondin. The attachment of all four cell types to thrombospondin is abolished if the assay is performed in the presence of EGTA, although the cells still attach to fibronectin. If thrombospondin is adsorbed to the dishes in the presence of EGTA and then washed with buffer containing calcium before addition of the cells, attachment is still markedly inhibited, indicating that calcium affects the conformation and function of thrombospondin. Attachment of all four cell types is also markedly inhibited by the synthetic peptides gly-arg-gly-asp-ser-pro (GRG-DSP) and gly-arg-gly-asp-ala-cys (GRGDAC) but not by the control peptide gly-arg-gly-glu-ser-pro (GRG-ESP). Affinity chromatography of n-octylglucoside extracts of surface-labeled endothelial cells or smooth muscle cells on thrombospondin-Sepharose and GRG-DSP-Affigel columns was used to identify an integrin complex related to glycoprotein IIb-IIIa as an RGD-dependent receptor for thrombospondin. In addition, a monoclonal antibody (LM609) that blocks attachment of endothelial cells to vitronectin, fibrinogen, and von Willebrand factor also inhibits attachment of endothelial cells to thrombospondin. These data indicate that the attachment of cells to thrombospondin is mediated by RGD and calcium-dependent mechanisms and is consistent with the hypothesis that the GRGDAC sequence in thrombospondin is a site for interaction with an integrin receptor of the beta 3 subclass.

Amino Acid Sequence↗