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Biomedical subjects

M Tavassoli

Publications and source records attributed to M Tavassoli.

At least 181 records · Page 10Linked to original sources
PubMed1984

Pure red blood cell aplasia associated with paraproteinemia: in vitro studies of erythropoiesis.

Pure red cell aplasia (PRCA) and monoclonal gammopathy were detected simultaneously in a 57 year old man with severe anemia. While erythroid burst forming units (BFU-E) were absent from blood, his bone marrow contained a high normal number of BFU-E in the absence of morphologically recognizable erythroid precursors. Serum from the patient did not inhibit the growth of BFU-E from normal blood suggesting that his PRCA was not antibody mediated. These studies suggest that in the patient the inability to produce erythrocytes was due to a block in the maturation of BFU-E; however, they do not indicate an etiology for this block. The absence of blood BFU-E and their abundance in the marrow may result from selective trapping of these cells by the marrow-blood barrier.

Blood Transfusion↗
PubMed1984

Measurement of antibody to poly (adenosine diphosphate-ribose): its diagnostic value in systemic lupus erythematosus.

Poly (ADP-ribose) and dsDNA binding activity have been measured in sera from 61 patients with systemic lupus erythematosus (SLE) and 188 control sera from 20 normal individuals, 144 patients with clinically similar diseases and 24 patients with drug-induced anti-nuclear antibodies (ANA). Elevated poly (ADP-ribose) binding was not observed with normal sera. Five of 144 samples from diseases entering the differential diagnosis of SLE gave raised poly (ADP-ribose) binding compared with 12 in the 125I-dsDNA binding. Only two of these false positive samples gave elevated binding in the 14C-dsDNA assay. The apparent high specificity of the poly(ADP-ribose) assay was not observed with samples containing drug-induced ANA where 62% had elevated binding values. The frequency with which the poly(ADP-ribose) assay was positive with SLE sera (sensitivity) was lower than either of the dsDNA assays. This low sensitivity and the high rate of false positives in patients with drug-induced ANA limit the value of the poly(ADP-ribose) assay as a diagnostic test for SLE. However the restriction of poly(ADP-ribose) antibody to SLE and patients with drug-induced ANA together with the known role of poly(ADP-ribose) in DNA excision repair suggest that the antibody may be of fundamental significance.

Adult↗
PubMed1984

Characterization of human monocytes maintained in long-term culture with functional and morphological homogeneity.

We recently reported a method for long-term in vitro culture of human monocytes with maintenance of functional and morphological homogeneity. We have now used microexudate-coated flasks to improve both the plating efficiency and the purity of these cultures. The technique is based on pregrowth of BHK cells that presumably produce large amounts of fibronectin, thus coating the flask with this substance, for which monocytes have receptors. We have further characterized the monocytes obtained with this culture technique by scanning electron microscopy (SEM), transmission electron microscopy (TEM), cytochemistry, surface markers, lectin receptors, and phagocytic functions. All these methods show the cultured cells to consist of a pure, functionally and morphologically homogeneous population of nontransformed monocytes.

Acid Phosphatase↗
PubMed1984

Lodgement of haemopoietic cells in the course of haemopoiesis on cellulose ester membrane: an experimental model for haemopoietic cell trapping.

Intraperitoneally implanted cellulose ester membrane in mice was used as a model to study the lodgement of haemopoietic cells into haemopoietic organs. A heterogeneous cellular coat developed on the membrane. Its upper layer ( epilayer ) thinned out and formed a veil over the cellular coat. Numerous microvilli developed on its free surface. They were randomly oriented. A week after implantation, mice were given total body irradiation (400 cGy) and were infused intraperitoneally with 10(5) marrow cells. Two days after infusion round cells were penetrating the epilayer . Extensive interaction was noted between the surface of the penetrating cells and the microvilli of the epilayer . Penetration was through a single cell in the epilayer and not at the junction of two cells. These observations suggest specific interaction between haemopoietic cells and the supporting tissue leading to lodgement of haemopoietic cells. Intraperitoneally implanted cellulose ester membrane may provide an experimental model for haemopoietic cell trapping.

Animals↗
PubMed1984

Hairy-cell leukemia with the appearance of mixed cryoglobulinemia and vasculitis.

Hairy-cell leukemia has been associated with a number of disorders of the immune system. At least 13 cases of vasculitis and hairy-cell leukemia have been reported. However, the occurrence of cryoglobulinemia and hairy-cell leukemia is rare. We report a case of a patient with the unusual combination of hairy-cell leukemia, vasculitis, and cryoglobulinemia. This case illustrates that hairy-cell leukemia should now be included in the differential diagnosis of patients with the appearance of vasculitis and cryoglobulinemia. The association presents a therapeutic challenge and emphasizes the need for individualized treatment in such patients.

Cryoglobulinemia↗
PubMed1983

Isolation and purification of poly(ADP-ribose) glycohydrolase from pig thymus.

Poly(ADP-ribose) glycohydrolase has been purified about 12 300-fold from pig thymus with a recovery of 8.5%. The specific activity of the purified enzyme is 13.8 mumol min -1 mg protein -1. The molecular weight was estimated to be 59 000 by gel filtration through Sephadex G-100 in a non-denaturing solvent. Analysis of the final preparation by sodium dodecyl sulphate gel electrophoresis reveals two protein bands of molecular weight, 61 500 and 67 500. The Km value for poly(ADP-ribose) is estimated to be 1.8 microM monomer units. The enzyme preparation is free from phosphodiesterase, NADase and ADP-ribosyltransferase activities. The purified enzyme is inhibited by cyclic AMP, ADP-ribose, naphthylamine, histones H1, H2A, H2B, H3, polylysine, polyarginine, polyornithine and protamine. The inhibition by histone is relieved by an equal mass of DNA. Single-stranded DNA, poly(A), poly(I) and polyvinyl sulphate were inhibitory, but double-stranded DNA was not inhibitory.

Animals↗
PubMed1983

Effect of the substratum on the growth of CFU-c in continuous marrow culture.

The effect of the substratum on the maintenance of granulocyte-macrophage progenitors (CFU-c) was studied in continuous mouse marrow culture. Glass and decalcified eggshell membrane were found preferable to plastic, providing better adherence of stromal cells. Eggshell membrane consists of a meshwork of branching fibers suitable for the adherence of stromal cells. The glass surface with its high surface pH may provide an electrostatic attraction for the negatively charged surface of stromal cells.

Animals↗
PubMed1983

Distribution of insulin receptors in liver cell suspensions using a minibead probe. Highest density is on endothelial cell.

The distribution of insulin receptors was studied in rat liver cell suspensions using a latex minibead covalently bound to insulin. This probe can be visualized by electron microscopy (EM). Using this visual probe, the highest density of the receptor was found on endothelial cells in the cell suspension, with hepatocytes having only few receptors and Kupffer cells having none. Fractionation of liver cell suspensions on metrizamide gradients yielded two populations of cells; large cells (hepatocytes) and small cells which consisted mostly of Kupffer cells and endothelial cells, distinguishable by their surface and cytoplasmic features. Again, by the use of an insulin-minibead probe, the highest density of receptors was found on endothelial cells. It is suggested that the endothelium has a crucial role in the uptake and transport of the hormone across the tissue-blood barrier.

Animals↗
PubMed1983

Mapping of the bone marrow sinus endothelium with lectins and glycosylated ferritins: identification of differentiated microdomains and their functional significance.

The distribution of lectin binding sites and sugar-recognizing systems (lectin-like substances) was studied on the luminal side of the bone marrow sinus endothelium in rats. Ferritin-conjugated lectins (Con A, PHA, RCA, WGA, UEA) and glycosylated ferritins (mannosyl, fucosyl, chitobiosyl) were used as probes. With the exception of UEA, all lectins bound to the endothelial surface. The binding was heavier on the plasmalemma proper of the nuclear region (PP-N) compared to that of the tapered region (PP-T). Lectin mapping also identified differentiated microdomains with less or no bindings. These domains related to the transport organelles in the endothelium: luminal vesicles (LV) and diaphragmmed fenestrae (DF). The relative density of binding for these four domains demonstrated the following spectrum PP-N greater than PP-T greater than LV greater than DF. The relation of this binding pattern to the transport function of marrow sinus endothelium for various cells and molecules has been discussed. Lectin mapping also identified heavily labeled microvilli and microprojections from the membrane. These organelles may have a function in recognizing cells and molecules for the transport. The absence of binding for UEA, also absent in liver endothelium, may differentiate sinus endothelia from other endothelia. This lectin is thought to be endothelium-specific in other systems. No binding was observed with glycosylated ferritins suggesting the absence of lectin-like substances on marrow sinus endothelium.

Affinity Labels↗
PubMed1983

Internalization of iron-transferrin complex by murine L1210 leukemia cells and rat reticulocytes demonstrated by a minibead probe.

To determine if the cellular uptake of iron is associated with internalization of iron-transferrin (TF) complex by the cell, we synthesized a visual probe in which TF is covalently bound to amide-modified latex minibead, submicrometer in size (0.345 micron). Incubation of the probe with L1210 leukemia cells and rat reticulocytes led to the binding of the probe to the cell surface visualized and semiquantified by scanning and transmission electron microscopy. The binding was inhibited by preincubation with nonderivatized iron-TF complex. Internalization of the probe occurred through clathrin-coated pits and vesicles. Minibeads derivatized by nontransport proteins or glycine as well as nonderivatized minibeads did not appreciably bind to the cells and were not internalized. Ethylamine, an inhibitor of receptor-mediated endocytosis abolished the internalization but not the binding of the probe which, then, accumulated on the cell surface. These findings provide direct evidence for internalization of TF during the iron uptake.

Animals↗
PubMed1983

Modulation of insulin receptors in cultured adipocytes as studied by a latex minibead probe.

In monolayer cultures, adipocytes transform into spindle-shaped cells, morphologically similar to buccal submucosa-derived fibroblasts. Insulin receptors were searched for on the surface of these cells using a visual probe which consisted of latex minibeads covalently bound to insulin. Adipocyte-derived cells showed clusters of insulin receptors not observed on the surface of fibroblasts derived from submucosa. The finding indicates that despite their fibroblastic morphology and the loss of their lipid inclusions in culture, these adipocytes do not lose their state of differentiation and therefore should be considered lipid-depleted adipocytes rather than fibroblasts. Moreover, quantitative analysis demonstrated a significant increase in the number of insulin receptors in cultured cells as compared to isolated but not cultured cells. This may reflect the low concentration of insulin in the culture medium as compared to the in vivo environment and indicates that the cells are subject to regulatory mechanisms of adipocytes.

Adipose Tissue↗
PubMed1983

A method for processing polymeric beads for critical point drying.

Polymeric beads are increasingly being used for surface studies. Processing of these beads for critical point drying (CPD) poses a problem since these beads must be handled in suspension. For this processing, a method has been described here which relies on a capsule made by an ordinary micropipette tip covered on the end by parafilm and on the other by a filter paper which permits the exchange of fluid without the loss of beads.

Histological Techniques↗
PubMed1983

Evidence of hyposplenism in the presence of splenomegaly.

Evidence of hyposplenism (Howell-Jolly bodies, Pappenheimer bodies and nucleated red cells in the blood) was found in a patient with splenomegaly and Hb C disease. Splenic haemangiosarcoma was found at operation. Evidence of hyposplenism in the presence of a normal size or enlarged spleen should alert the physician to the possibility of a complicating factor.

Erythrocyte Inclusions↗