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Biomedical subjects

S Waxman

Publications and source records attributed to S Waxman.

At least 145 records · Page 8Linked to original sources
PubMed1982

DNA ligase and DNase activities in mouse erythroleukemia cells during dimethyl sulfoxide-induced differentiation.

DNA ligase and DNase levels were measured in cell-free extracts from untreated mouse erythroleukemia (MEL) cells and from cells treated with dimethyl sulfoxide (Me2SO) to induce erythroid differentiation. The DNase activity present in the extracts was sensitive to inhibition by G-actin and was, therefore, presumed to be DNase I. When the MEL cells were induced to differentiate by culturing in the presence of 1.8% Me2SO for 3 or 4 days, the apparent activity of the DNA ligase decreased to approximately 12% of the value in untreated MEL cells. In contrast, the apparent DNase I activity of the extracts from Me2SO-treated cells increased over that in extracts from untreated cells by a factor of 2. The activity of acid phosphatase, a lysosomal enzyme, remained unchanged. When strain DR-10, a mutant of the MEL cells which does not undergo Me2SO-induced differentiation, was treated with Me2SO, the DNA ligase and DNase activities of extracts from these cells remained unchanged as compared to extracts from untreated DR-10 cells. Therefore, the marked increase in the level of DNA ligase activity appeared to be related to the process of differentiation in the Me2SO-treated MEL cells.

Animals↗
PubMed1981

Effect of a folate-binding protein on the plasma transport and tissue distribution of folic acid.

Folic acid (3H-pteroylglutamic acid or 75Se-selenofolate) administered free or bound to folate-binding protein (FABP) was rapidly cleared from the plasma but the plasma survival when bound to FABP was longer than unbound during the initial 5 min. 75Se-folate bound to FABP is more rapidly taken up by the liver than when administered as free 75-Se-folate. 125I-labeled FABP was rapidly cleared from the plasma (90% in 5 min). The rapid uptake of FABP, a sialoglycoprotein, was inhibited by the preadministration of desialyzed fetuin. Following the hepatic uptake of 75Se-folate/FABP, only free 75Se-folate was found in the bile. The total biliary secretion of 75Se-folate over 240 min was 63% when administered bound to FABP and 33% when administered as free 75Se-folate. The liver retained 33.5% of the 125I activity 5 min following the administration of 125I-FABP, while only 4.46% of the 125I activity was secreted into the bile over 180 min. This data suggests that FABP may play an important role in the enterohepatic circulation of folates by directing nonmethylated folates to the liver.

Animals↗
PubMed1981

Cryoprotected Lactobacillus casei: an approach to standardization of microbiological assay of folic acid in serum.

Folate-depleted, cryoprotected preparations of Lactobacillus casei are stable for at least eight months at -18 degrees C, capable of reproducible growth and suitable as a ready source of inoculum for measurement of folates in physiological fluids. Cryoprotected microorganisms can be a commercially available laboratory reagent, thus simplifying and further standardizing the microbiological assay of various nutriments. Standard folate growth curves of cryoprotected L. casei, prepared at intervals over eight months, are superimposable, have a low blank, and should eliminate the variations encountered with the continuous passages of microorganisms required for the classic microbiological assays. Serum folate values obtained by use of the cryoprotected L. casei fall into the same diagnostic groups as determined by the classic microbiological assay.

Biological Assay↗
PubMed1980

12-O-tetradecanoyl-phorbol-13-acetate release of glycosyltransferases from human blood cells.

The mononuclear cells separated from human blood by Ficoll-Hypaque centrifugation contained and released sialyltransferase, galactosyltransferase, and fucosyltransferase. Granulocytes contained and released lesser amounts of glycosyltransferases, whereas platelets released more fucosyltransferase than sialyltransferase or galactosyltransferase. When mononuclear cells were incubated with 12-O-tetradecanoyl-phorbol-13-acetate (TPA), the release of these three glycosyltransferases increased two- to six-fold, and cell suspension glycosyltransferase activities decreased 10-50%. Mononuclear cells were fractionated into lymphocytes and monocytes using baby hamster kidney cells microexudate-coated flasks. TPA stimulated the release of glycosyltransferases from lymphocytes but not from monocytes. The release of glycosyltransferases by TPA-treated mononuclear cells was not further stimulated by reincubation with TPA and was not affected by puromycin, cAMP, or cGMP. Concanavalin A, a mitogenic stimulator of lymphocytes, also stimulated the release of glycosyltransferases from mononuclear cells, but to a lesser extent. TPA did not stimulate the release of 5'-nucleotidase or decrease its activity on the cell pellet. Triton X-100 (0.2%) stimulated the release of glycosyltransferases to the same extent as TPA, but also caused the release of 5'-nucleotidase. [(3)H]TPA bound specifically and reversibly to mononuclear cells. The possible relationship between glycosyltransferase release and TPA effect on the plasma membrane is discussed.

Cell Separation↗
PubMed1980

Clinical pharmacologic effects of thymidine plus 5-FU.

Ten patients with advanced cancer were given 24 courses of thymidine (TdR) plus 5-FU. In the initial part of the study, TdR was given by continuous infusion at a dose of 8 g/m2/24 hrs x 5 days, and 5-FU was given as an iv bolus daily x 5. During the continuous TdR infusion, TdR serum levels ranged from 10(-6) to 10(-5) M, and thymine serum levels ranged from 10(-5) to 10(-4) M. 5-FU serum decay on Day 1 was rapid, and serum decay on Day 5 was slightly prolonged in two of three patients studied. The optimal dose of 5-FU with continuous infusion of TdR seemed to be between 200 and 400 mg/m2 daily x 5 in heavily pretreated patients. In the second part of the study, rapid infusion of TdR at a dose of 8 g/m2/2 1/2 hrs followed by 5-FU resulted in markedly prolonged 5-FU serum decay (initial serum half-life, approximately 240 mins) and definite increase in clinical toxicity. The dose-limiting toxic effect of both schedules was myelosuppression. Administration of TdR in one tenth of the initial infusion time resulted in a nearly 100-fold increase in peak TdR levels. Thymine was the major metabolite of TdR. 5-FU did not influence TdR blood levels. The protracted 5-FU serum decay appears to account at least in part for the increased toxicity of 5-FU when administered following TdR.

Adult↗
PubMed1979

The specific release of sialytransferase activity by human hepatoma cell lines.

Sialyltransferase (EC 2.4.99.1) is released in large amounts by two hepatoma cell lines (SK-H-MA and CLH) established from patients with hepatocellular carcinoma (hepatoma). This release requires protein synthesis and glycoprotein synthesis, but not cell division. In contrast, sialyltransferase is released in minimal amounts by a cell line derived from normal human liver (Chang). The hepatoma cells also contain more surface and cellular sialyltransferase activity than Change cells. Hepatoma sialyltransferase has properties similar to other sialyltransferases. Using a calibrated Sephadex G-200 column, it is resolved into two forms with molecular weights of 65 000 and 80 000.

Carcinoma, Hepatocellular↗
PubMed1978

Catabolism of 2-deoxyglucose by phagocytic leukocytes in the presence of 12-O-tetradecanoyl phorbol-13-acetate.

We have found that phagocytic leukocytes exposed to the tumor-promoting agent, 12-O-tetradecanoyl phorbol-13-acetate, efficiently release carbon-1 of 2-deoxyglucose in the form of CO2 with concurrent intracellular accumulation of a phosphorylated 5-carbon intermediate. In the absence of 12-O-tetradecanoyl phorbol-13-acetate, these cells release barely detectable amounts of CO2 from 2-deoxyglucose. 12-O-Tetradecanoyl phorbol-13-acetate, at a concentration of 1 ng/ml, has an immediate effect on CO2 release, which is temperature-dependent and linear with time and cell number. The ability of a number of phorbol ester-like compounds to enhance this catabolic pathway for 2-deoxyglucose correlates with their ability to act as tumor promotors and inflammatory agents. Although this effect of phorbol esters appears to be restricted to granulocytes, monocytes, and macrophages, the possibility arises that other mammalian cells are capable of catabolizing or can be induced to catabolize-2-deoxyglucose. Thus, 2-deoxyglucose decarboxylation should be considered whenever this analog of mannose and glucose is used as an indicator for sugar transport, especially when pharmacodynamic agents are present.

B-Lymphocytes↗
PubMed1978

Measurement of serum folate by 75Se-selenofolate radioassay. Results of a multi-institutional clinical trial.

The authors report the multi-institutional evaluation of a radioassay for serum folate utilizing a gamma-labeled folate analog (75Se-pteroyl-L-methylselenocysteine). The assay is run as a one-step simultaneous addition at ambient temperature and is completed within 45 minutes. The assay data were reproducible within four study centers and correlated with both the Lactobacillus casei diagnostic groups and the clinical pictures.

Biological Assay↗
PubMed1977

The clinical and physiological implications of hepatoma B12-binding proteins.

A serum B12-binding protein with increased sialic acid content (termed hepatoma B12-binding protein) that causes elevations of serum B12 and unsaturated B12-binding capacity has been found in some patients with hepatocellular carcinoma (hepatoma). We now report another patient with hepatoma with initial near-normal, unsaturated B12-binding capacity that increased 400-fold as the disease progressed and then fell 50% with response to chemotherapy. A perfusate of the tumor in the liver had 5 times more B12-binding protein than did the serum and was immunologically the same as the serum hepatoma B12-binding protein isolated from previous cases. A cell line derived from hepatoma produced significant amounts of B12-binding protein similar to hepatoma B12-binding protein, whereas cell lines from normal liver and other neoplasia did not. The hepatoma sera, perfusate, and media from the hepatoma cell line contained elevated sialyltransferase activity. These data suggest that some hepatomas produce increased hypersialylated B12-binding protein that is cleared slowly from the plasma and accumulates there as hepatoma B12-binding protein.

Adolescent↗
PubMed1975

The purification and characterization of the low molecular weight human folate binding protein using affinity chromatography.

The low molecular weight folate binding protein (FABP) has been purified 1000-fold to a specific activity of 7.2 gamma g of pteroylglutamic acid (PGA) bound per mg of protein. This purified FABP represents two protein bands that bind PGA on polyacrylamide disc gel electrophoreis, elutes from DEAE-cellulose in 0.001 M phosphate buffer, stains positive with PAS, Elutes from concanavalin A Sepharose affinity columns with methyl alpha-mannoside, and shows three major peaks (pl =6.8, 7.5, 8.2) by isotric focusing. The binding of PGA to purified FABP dependent on pH and is inhibited by urea...

Carrier Proteins↗