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Biomedical subjects

L T Yam

Publications and source records attributed to L T Yam.

At least 127 records · Page 7Linked to original sources
PubMed1977

Impaired marrow granulocyte reserve and leukocyte mobilization in leukemic reticuloendotheliosis.

Cytotoxic chemotherapy often induces sustained, severe granulocytopenia in patients with leukemic reticuloendotheliosis. Many of the patients so treated subsequently develop serious infections. Poor marrow reserve has been implicated but lacks supporting evidence as the cause of the granulocytopenia. In six patients we studied with leukemic reticuloendotheliosis, bone marrow showed severe granulocytopenia, blood neutrophil response after intravenous hydrocortisone injection was poor, and leukocyte migration to the site of inflammation showed suboptimal neutrophilia and poor or no mononuclear response. Splenic hypersequestration and pooling were probably not important factors in causing neutropenia, since similar results were seen in patients without spleens. These findings suggest that in this disease the marrow granulocyte reserve and leukocyte mobilization are impaired and the neutropenia is due to poor granulocyte production and not to increased migration of leukocytes to tissues. Cytotoxic chemotherapy should be used with caution in patients with this disease.

Adult↗
PubMed1977

Biochemical characterization of the tartrate-resistant acid phosphatase of human spleen with leukemic reticuloendotheliosis as a pyrophosphatase.

A tartrate-resistant acid phosphatase was isolated from a human leukemic spleen by freeze-thawing in saline and purified by repeated chromatography on carboxymethyl-cellulose. The purified enzyme has a molecular weight of 64 000. It catalyzes the hydrolysis of inorganic and organic pyrophosphate as well as the phenolic ester of monoorthophosphate, with optimal activity between pH 5 and 6. However, there is no activity toward mono-orthophosphate esters of aliphatic alcohols. The present data have identified its catalytic function as a pyrophosphatase. However, it has properties different from the pyrophosphatase previously observed in normal animal tissues.

Acid Phosphatase↗
PubMed1976

Studies of intracellular distribution of acid phosphatase 5 in the spleen cells of leukemic reticuloendotheliosis by isopycnic gradient centrifugation.

A fresh spleen sample obtained from a patient with leukemic reticuloendotheliosis was homogenized and subjected to centrifugation on a sucrose density gradient. A major portion of acid phosphatase band 5 was observed in the lysosome, confirming that the elevated phosphatase activity in the neoplastic spleen is a lysosomal enzyme. However, a significant amount of brand 5 was also observed in the microsome. The microsomal and lysosomal enzymes have different affinity to CM-cellulose. The relationship between lysosomal and microsomal enzymes has not been established.

Acid Phosphatase↗
PubMed1976

Histogenesis of splenic lesions in Hodgkin's disease.

Histochemical markers were used to identify the various cellular and structural components of the human spleen, and to investigate the histogenesis of the splenic lesions of Hodgkin's disease. The early lesions appear in areas near the central artery (periarterial lymphatic sheath) in the white pulp. The white pulp becomes hypertrophic. The lesions enlarge, extend into the red pulp, and compress the sinuses and the cords of Billroth. The derivations of various "histiocytes" contained with the lesions are differentiated by using cytochemical stains for lysosomal enzymes and for granulocytes. The epithelioid cells in the granulomas are rich in those lysosomal enzymes typically seen in phagocytic histiocytes, suggesting that they are indeed true histiocytes. The malignant "histiocytes," including the mononuclear Hodgkin cells, the binucleated Sternberg-Reed cells, and the multinucleated giant cells, do not contain significant amounts of lysosomal enzymes and more closely resemble stimulated lymphocytes. The splenic lesions in Hodkin's disease may be the result of a lymphocytic and histiocytic cellular response to an unknown agent, which reaches the spleen through the central artery in the white pulp.

Acid Phosphatase↗
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↗
PubMed1975

Differential characterization of the "reticulum cell" in lymphoreticular neoplasms.

Differential characterization of the "reticulum cell" in lymphoreticular neoplasms. Am J Clin Pathol. 64: 171-179, 1975. The term "reticulum cell" is confusing, having been applied to the cells involved in many hematopoietic neoplasms, such as reticulum-cell sarcoma, histiocytic medullary reticulosis, leukemic reticuloendotheliosis, and monocytic or histiocytic leukemias. In histologic sections, even the cells from poorly differentiated extramedullary lesions of chloroma or myeloblastic leukemia have been called "reticulum cells."A combined morphologic and cytochemical approach has been used to study "reticulum cells"in smears and tissue sections of neoplasms involving "histiocytes" or "reticulum cells."The cytochemical markers are: chloracetate esterase for neutrophilic granulocytes; nonspecific esterase and fluoride-resistant esterase for monocytes and histiocytes (phagocytes); tartrate-resistant acid phosphatase for the reticulum cells of leukemic reticuloendotheliosis; pyronin for the lymphatic reticulum cells (germinal center cells). The morphology of these cells is very well appreciated in smears, and the locations of these marked cells in tissue sections are easily recognized. The use of cytochemical and immunochemical methods and functional studies, in addition to simple morphology, may be useful in subclassification of lymphoreticular neoplasms.

Cell Differentiation↗