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R M Singer

Publications and source records attributed to R M Singer.

35 records · Page 2Linked to original sources
PubMed1976

Carcinoplacental alkaline phosphatase. Base level and hormone-induced activity associated with events in the cell cycle.

Using HeLa TCRC-1, a cell line which is monophenotypic with respect to the Regan isoenzyme of alkaline phosphatase, we have examined the factors which influence its expression in relation to events of the cell cycle. DNA synthesis is not required for hormone induction of the Regan isoenzyme as in the presence of hydroxyurea, a specific inhibitor of DNA synthesis, we found induction to occur. Additionally, when partially synchronised cells were allowed to leave the S period prior to hormone treatment, and hydroxyurea was added to prevent cells from entering the next S period, hormone induction of the Regan isoenzyme was still observed. This indicates that initiation of expression of hormone-induced carcinoplacental alkaline phosphatase occur prior to the DNA synthetic phase of the cell cycle. We propose a hypothetical two-step mechanism of hormone induction to interpret the present findings in relation to previous results.

Alkaline Phosphatase↗
PubMed1976

Coproduction of Regan isoenzyme and carcinoembryonic antigen in HCT-8 cells.

The presence of the Regan isoenzyme of alkaline phosphatase was demonstrated in the carcinoembryonic antigen-producing human cell line HCT-8 Biochemical, histochemical, immunologic, and electrophoretic methods were used as criteria for the identification and characterization of this isoenzyme.

Carcinoembryonic Antigen↗
PubMed1976

Plasma membrane localization of alkaline phosphatase in HeLa cells.

The localization of alkaline phosphatase in HeLa cells was examined by electron microscopic histochemistry and subcellular fractionation techniques. Two monophenotypic sublines of HeLa cells which respectively produced Regan and non-Regan isoenzymes of alkaline phosphatase were used for this study. The electron microscopic histochemical results showed that in both sublines the major location of alkaline phosphatase is in the plasma membrane. The enzyme reaction was occasionally observed in some of the dense body lysosomes. This result was supported by data obtained from a subcellular fractionation study which showed that the microsomal fraction rich in plasma membrane fragments had the highest activity of alkaline phosphatase. The distribution of this enzyme among the subcellular fractions closely paralleled that of the 5'-nucleotidase, a plasma membrane marker enzyme. Characterization of the alkaline phosphatase present in each subcellular fraction showed identical enzyme properties, which suggests that a single isoenzyme exists among fractions obtained from each cell line. The results, therefore, confirm the reports suggesting that plasma membrane is the major site of alkaline phosphatase localization in HeLa cells. The absence of any enzyme reaction in the perimitochondrial space in these cultured tumor cells also indicates that the mitochondrial localization of the Regan isoenzyme reported in ovarian cancer may not be a common phenomenon in Regan-producing cancer cells.

Alkaline Phosphatase↗
PubMed1976

Evidence for altered gene regulation in HeLa cells returned to culture after growing in immunosuppressed rats.

HeLa TCRC-1, is a monophenotypic cell line for the production of the carcinoplacental Regan isoenzyme of alkaline phosphatase. It has been previously reported that, when this cell line is grown in immunosuppressed rats, there is an alteration of phenotypic expression in that an isoenzyme that is referred to as oncoamnion (FL) becomes the dominant enzyme form. This report describes the isoenzyme regulation after these cells are returned to culture for at least three months. These cells in culture demonstrate a density-dependent alteration in isoenzyme profiles. The Regan isoenzyme is the dominant isoenzyme form in new, sparsely populated cultures, while the oncoamnion isoenzyme predominates in the later high-density stages of growth. Prednisolone induction of enzyme activity is found to be most effective in the early stages of growth, and the previously reported specificity of hormone action on isoenzymes produced by cancer cells is maintained. Enzyme induction is restricted to the Regan isoenzyme, while hormone-mediated diminution in enzyme activity is confined to the oncoamnion (FL) isoenzyme.

Alkaline Phosphatase↗
PubMed1976

Regulatory controls of oncotrophoblast proteins and developmental alkaline phosphatases in cancer cells.

The two oncotrophoblast proteins, Regan isoenzyme (placental-type alkaline phosphatase) and human chorionic gonadotrophin, are readily studied oncodevelopmantal gene products in human cancer patients and in three experimental model systems. The latter consists of (a) HeLa sublines TCRC-1 and TCRC-2, which produce Regan and non-Regan isoenzymes, (b) HEp-2 and FL amnion cell lines as models for the reciprocal expression of developmental genes, and (c) modulation in vivo of developmental gene expression in HeLa cells. In the case of the third model, for example, HeLa TCRC-1 cells grow in immunosuppressed rats to form a tumor nodule, which expresses a new oncoamnion (FL) isoenzyme, while the Regan isoenzyme disappears. Return of the tumor cells to cell culture medium results in a disappearance of the oncoamnion (FL) species and the reappearance of Regan isoenzyme. This interesting model is expected to bridge the interpretation of experiments done in cell culture with observations made on tumors of cancer patients. Most helpful in interpretation of all these studies has been a chronology of early development. It appears that the counterparts of a number of tumor proteins appear as early as gametogenesis and as late as 10 weeks of gestation.

Alkaline Phosphatase↗
PubMed1975

The psychological differentiation of male myopes and nonmyopes.

A comparison of 140 male myopes and 118 male nonmyopes of the entering class of Virginia Military Institute cadets in 1968 demonstrated that there are a number of Strong Vocational Interest Inventory test items which will clearly differentiate myopes from nonmyopes so that it is possible to identify 76% of the individuals falling into either class on the basis of a stepwise discriminant analysis based almost entirely on the Strong Vocational Interest Blank. The items which discriminate in favor of the myopes are essentially those which require academic achievement and individual creative performance, whereas the items which are in favor of the nonmyopes are those which require business and selling skills as well as outdoor types of activities. Further, the myopes are significantly more likely to achieve officer status and win more academic awards than the nonmyopes.

Factor Analysis, Statistical↗
PubMed1975

The release of high-molecular-weight alkaline phosphatase and leucine aminopeptidase into the media of cultured human cells.

Using exclusion from Sepharose 4B as our criterion, we have found a high-molecular-weight form of alkaline phosphatase and of leucine aminopeptidase which are released into the culture media by the FL amnion cell line. A low-molecular-weight form of leucine aminopeptidase is also found to contribute to the total levels of this enzyme in the media. The levels of these enzymes increased during the growth cycle of the culture, paralleling the increase in cell density, suggesting that the two events may be related. This phenomen in culture suggests a possible explanation for the appearance of similar enzyme forms in patient serum and fluids originating from diseased tissue.

Alkaline Phosphatase↗
PubMedDate not supplied

Neurobehavioral changes among shipyard painters exposed to solvents.

Painters in three shipyards, exposed to a wide variety of solvents, were examined. A short battery of performance tests, a detailed occupational history, and a special questionnaire to assess acute (prenarcotic, transitory) and chronic (persistent) neurologic symptoms was administered. The results of the neurobehavioral performance tests demonstrated decrements in central nervous system function in painters when compared with a control group matched for age, sex, race, and education. The prevalence of reported acute neurological symptoms among painters was increased significantly compared to other occupational groups in the same yards; for chronic, persistent symptoms the difference was not statistically significant. Performance test scores were significantly, negatively correlated with chronic symptoms but not with acute symptoms. No significant correlations between performance test scores and duration of solvent exposure or between symptoms and duration of solvent exposure were observed. The reversibility of such symptoms and of decrements in central nervous system function after cessation of exposure is still uncertain.

Acute Disease↗