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Biomedical subjects

M Tavassoli

Publications and source records attributed to M Tavassoli.

At least 253 records · Page 14Linked to original sources
PubMed1978

Structural analysis of hemopoiesis in S1/S1d anemic mice.

This study is an ultrastructural analysis of hemopoiesis in S1/S1d anemic mice. The anemia in this strain is caused by a defect in hemopoietic microenvironment which fails to support hemopoiesis. Marrow cellularity is reduced and vascular channels are dilated. Coverage of sinus endothelium by adventitial cells is nearly twice as in normal mice, suggesting a reduced rate of cell traffic into the circulation. Central macrophages are small with little or no interdigitation with erythroid cells and no crystalloid inclusions as seen in normal littermates. The findings suggest that a fundamental abnormality in the central macrophage may be responsible for the defect in hemopoietic microenvironment.

Anemia↗
PubMed1978

Membrane characteristics of cultured endothelial cells: identification of gap junction.

Membrane characteristics of cultured endothelial cells derived from the superior vena cava of the rabbit were studied in freeze-fracture replicas. Gap junctions were identified, but tight junctions were not seen. In addition to pinocytic vesicles, fenestrations of plasma membrane which are not normally seen in the endothelium of vena cava in situ were found. This finding may be explained by the absence of platelets in the culture medium and is consistent with the current concept of endothelial-platelet interaction.

Animals↗
PubMed1977

Platelet-derived acid phosphatase isoenzyme in the serum in thrombocythemia.

Acid phosphatase is present in platelets and is released during the clotting process. In thrombocythemic conditions, this may increase serum enzymatic activity. An illustrative case in which the determination of plasma enzymatic activity suggested a platelet origin of elevated serum levels, confirmed by isoenzyme fractionation on disk polyacrylamide gel electrophoresis is presented. It is concluded that in the presence of thrombocytosis a plasma sample is preferable to a serum sample for determination of acid phosphatase activity.

Acid Phosphatase↗
PubMed1977

Adaptation of marrow sinus wall to fluctuation in the rate of cell delivery: studies in rabbits after blood-letting.

The extent of marrow sinus wall coverage by perisinal adventitial cells was measured before and after removing 25% of the calculated blood volume in rabbits. A marked reduction in the area covered by adventitial cells was recorded coinciding with the early reticulocyte response to phlebotomy. In control animals, only scattered microfilaments were occasionally observed in the cytoplasmic process of adventitial cells. After phlebotomy, these filaments were more frequently observed and appeared as band-like structures, raising the possibility of an active role for perisinal adventitial cells in response to fluctuations in the magnitude of cell traffic. Perisinal adventitial cells may, therefore, translate the body's demand for cell delivery by regulating the rate of transmural cell migration from the marrow. Such an adaptive mechanism may depend on the incompleteness of the adventitial layer of the sinus wall and the absence of endothelial-adventitial cell junctions, permitting separation of the two layers of the wall, so that the reticulocyte can gain access to more endothelial surface and the pores.

Adaptation, Physiological↗
PubMed1977

Fatty acid composition of adipose cells in red and yellow marrow: A possible determinant of haematopoietic potential.

The fatty acid composition of whole bone marrow and that of isolated, disaggregated adipose cells from red and yellow marrow was examined by gas chromatography. Consistent and significant shifts from myristic and palmatic acids (in red marrow) to their respective monounsaturated derivatives myristoleic and palmitoleic acids (in yellow marrow) were found. These differences in the fatty acids correlate with histochemical studies and lend further support to the concept that the composition of lipid in the adipose cells of bone marrow may determine their relative stability in relation to haematopoietic requirements.

Adipose Tissue↗
PubMed1976

Differences in susceptibility of tissues to revascularization studied in ectopic implants.

The survival rate of implanted marrow is reduced when the tissue is transferred from one site to another within the first 24 hours but not more than 48 hours after the initial implantation. Splenic implants can be transferred at any time after implantation without affecting the survival rate. The observation suggests a difference in the sensitivity of the two tissues to the avascular period that they experience prior to initiation of angiogenesis.

Animals↗
PubMed1976

The spleen in Friend leukemia. II. Nonleukemic nature of spleen stroma.

Pieces of Friend leukemic spleens implanted sc into mice regenerated into normal-appearing spleens if animals were protected against the leukemia. In unimmunized animals, the implant regenerated normally, but was subsequently infiltrated by leukemia cells. This leukemia cell infiltration required at least 30% stromal regeneration of the implant. The hematopoietic regeneration was primarily a repopulation with cells from the host animal, not with cells indigenous to the donor spleen. The development of the implant, whether normal or leukemic, was retarded by the presence of the host spleen, whether leukemic or normal. These studies strongly suggested that the stromal cells of the spleen are not directly involved in the virus-induced leukemic process but acted as supporting structure for the malignant cells.

Animals↗
PubMed1976

Marrow cell uptake by megakaryocytes in routine bone marrow smears during blood loss.

In studying smears of marrow aspirates, we have encountered the presence of normal appearing haemopoietic cells within megakaryocytes. We have then searched routine marrow smears from 125 patients seen in our service during 3 years. The presence of marrow cells (granulocytic, erythroid, and lymphoid cells) within megakaryocytes was seen in 16 cases of whom 9 had documented bleeding and 5 had carcinoma. 3 patients were suspected of bleeding but this was not documented. 56% of patients with bleeding and 83% of patients with carcinoma seen during this period displayed this pehnomenon. A search for this phenomenon in routine marrow smears may reveal unsuspected blood loss.

Adult↗
PubMed1976

Gelatinous transformation of bone marrow in prolonged self-induced starvation.

In bone marrow from 3 patients with prolonged, severe self-induced starvation, fat atrophy, hypoplasia of haemopoietic cells and characteristic gelatinous transformation of marrow were noted. The gelatinous substance appeared amorphous and stained pink with the Wright-Giemsa stains. Histochemical and ultrasturctural studies indicated that it consisted of acid mucopolysaccharides and was extracellular in nature. Similar marrow abnormalities were produced in rabbits by limitating their food intake for 4 months. These marrow abnormalities in the experimental animals could be reverted to normal by restoring their nutritional status. It is proposed that the gelatinous transformation of marrow is caused by excessive production of mucopolysacchrides of the ground substance to compensate for the mobilization of marrow fat which occurs to meet the energy requirement. It is further postulated that excessive production of acid mucopolysaccharides may provide a microenvironment unsuitable for haemopoietic proliferation. The relevance of these findings to other conditions associated with marrow aplasia, is discussed.

Animals↗
PubMed1976

Ultrastructural development of bone marrow adipose cell.

The postnatal development of bone marrow adipose cells was studied by sequential examination of marrow tissue obtained from the tibia and femur of 1- to 8-week-old rabbits. The bone marrow adipocyte begins to develop 2 weeks after birth. Its cellular origin differs from the "fibroblast-like" cell that is the progenitor of the extramedullary adipocyte. The marrow pre-adipocyte is associated with the sinus endothelium and adventitial cells, but is not associated with collagen and does not contain abundant organized rough endoplasmic reticulum. Unlike the extramedullary adipocyte, the course of differentiation of the medullary adipocyte is not characterized by the appearance of glycogen; furthermore, during the coalescence of lipid droplets to form larger fat globules, cytoplasmic organelles, such as mitochondria and ribosomes, are trapped within the lipid substance to form intralipid vacuoles containing degraded cytoplasmic organelles. The possible significance of these morphologic differences between the developing bone marrow adipocyte and that of its extramedullary counterpart is discussed.

Adipose Tissue↗
PubMed1976

Simultaneous occurrence of myeloma and Hodgkin's disease.

A patient in whom lymphocyte-depleted Hodgkin's disease and multiple myeloma were diagnosed simultaneously is reported. There was no prior history of irradiation or chemotherapy, the significance of which is discussed in relation to previously documented patients with Hodgkin's disease and myeloma.

Clinical Trials as Topic↗
PubMed1976

Marrow adipose cells. Histochemical identification of labile and stable components.

Two histochemically distinct populations of fat cells are present in the bone marrow with a topographic distribution paralleling that of hemopoiesis. Fat cells of red marrow stain positively with performic acid-Schiff (PFAS) whereas those of yellow marrow do not stain with this technique. When hemopoietic tissue expands in response to experimentally induced hemolysis, PFAS-positive cells of red marrow disappear whereas the PFAS-negative cells of yellow marrow remain stable. This differential staining indicates a difference in lipid composition of fat cells in red and yellow marrow and may relate to their relative stability during the expansion of hemopoiesis.

Adipose Tissue↗
PubMed1976

Experimental induction of erythroblastemia using intravenous carbonyl iron particles.

An experimental model is presented whereby erythroblastemia, the appearance of nucleated red cells in circulation, was induced reproducibly in rabbits by intravenous injection of 0.5 to 1 g/kg carbonyl iron particles (CIP). The phenomenon reached a peak in 24 to 48 hours and disappeared after a week. Erythroblastemia was associated with evidence for disseminated intravenous coagulation; both could be aborted by administration of heparin. Repeated injection of CIP was always followed by recurrence of erythroblastemia. For a period as long as 7 months, the animals tolerated repeated injections without evidence of lasting sequelae. Electron microscopic studies of marrow tissue indicated alterations in the red cell nuclei but no alterations in the endothelium of marrow sinuses into which the red cells migrate to reach the circulation. This model provides a means to study the mechanisms involved in nuclear elimination by mammalian red cells.

Animals↗