Alkaline phosphatase in KB cells: influence of hyperosmolality and prednisolone on enzyme activity and thermostability

KB cells, derived from a human nasopharyngeal carcinoma, have high alkaline phosphatase (orthophosphoric monoester phosphohydrolase, EC 3.1.3.1) activity. Specific activity is 150 times higher than in HeLa S3 cells. Alkaline phosphatase activity in KB cells exhibits heterogeneity consisting of a large heat-labile and a small heat-stable component. Enzyme activity is modulated by the osmolality of the culture medium. Increasing the osmolality by the addition of NaCl results in reduction of activity. A similar effect is noted when KB cells are grown with prednisolone (Δ′-hydrocortisone). The activities of acid phosphatase, β-galactosidase and N-acetyl-β-glucosaminidase are not affected by hyperosmolality and/or prednisolone. The reduction in alkaline phosphatase activity is accompanied by an increase in the proportion of the heat-stable and a decrease of the heat-labile enzyme components. The alterations in specific activity and thermostability are independent of the basal culture medium employed. Enzyme stability at 56 °C is inversely related to the buffer concentration, but the differences in stability between the alkaline phosphatases of control cultures and of KB cells grown in hyperosmolar medium or with prednisolone can be recognized with various buffering mixtures.     

Goyazensolide,a schistosomicidal heliangolide from Eremanthus goyazensis

Isolation and structure determination of goyazensolide, a new heliangolide responsible for the schistosomicidal properties of Eremanthus goyazensis Sch.-Bip., is reported.     

Rotenoids from roots of Millettia pachycarpa

Roots of Millettia pachycarpa furnished retenone, cis-12a-hydroxyrotenone, rot-2′-enonic acid and cis-12a-hydroxyrot-2′-enonic acid.     

Protein expression in relation to the cell cycle of exponentially growing human prostatic epithelial cells

This report concerns the study of the relationship between protein expression and the cell cycle in exponentially proliferating benign and malignant human prostate epithelial cells in short-term cultures. Multiparameter flow cytometric measurements were performed to correlate the expression of prostate-specific acid phosphatase, epithelial membrane antigen and epitectin with cell cycle progression. The expression of the three proteins was heterogeneous in G1 cells. The early post-mitotic cells exhibited the lowest levels when compared with late G1 cells, wherein the expression was many times greater. There was no further increase as the cells progressed through S and G2 + M. These findings, corroborating prior observations in other systems, suggest the possibility that the levels of the proteins studied increase during the G1 phase of the cell cycle and drop during or immediately after cytokinesis. As an alternate explanation, the heterogeneity of protein expression characteristic of G1 cells may be due, at least in part, to an asymmetric apportionment of cell constituents at mitosis.