Modulating effect of cystamine and unsaturated fatty acids on gamma-glutamyl transpeptidase: Relation to cellular oxidative status

Summary Cell surface gamma-glutamyl transpeptidese activity in cultured neoplastic astrocytes was significantly increased upon treatment of the cells with the hepatoprotective disulfide, cystamine. The cystamine effect was sensitive to cycloheximide and could be significantly depressed by exogenous glutathione. Surface gamma-glutamyl transpeptidase activity was also modulated by the presence in the culture medium of the unsaturated fatty acids, linoleic acid and arachidonic acid. Metabolism of the fatty acids via the cyclooxygenase pathway was not a prerequisite for their modulation of the glycoprotein ectoenzyme. Lipoxygenase, however, was found to potentiate the unsaturated fatty acid effect in neoplastic astrocytes. Lipoxygenase is reported to catalyze the conversion of unsaturated fatty acids to their corresponding peroxides. The data indicate an oxidative influence on the control of gamma-glutamyl transpeptidase activity.     

Immunocytochemical study of seminal γ-glutamyltransferase using monoclonal antibodies

We produced three monoclonal antibodies, SG1, SG2 and SG3, specific for human seminal -glutamyltransferase when characterized by enzyme-linked immunosorbent assay and immunoblotting. Seminal -glutamyltransferase was localized, by immunostaining, to the epithelial cells of the ductus epididymidis, seminal vesicle and prostate gland with SG1, those of the prostate gland with SG2, and those of the seminal vesicle with SG3. Rabbit polyclonal anti-seminal -glutamyltransferase serum reacted with the proximal convolution of the kidney and the bile capillaries of the liver, and with the epithelial cells of the reproductive organs. However, immunoreactivity was not observed in the kidney or liver with the monoclonal antibodies. Thus, these monoclonal antibodies are probably all specific to seminal -glutamyltransferase but recognize different epitopes.     

Influence of carbon and nitrogen sources on glutathione catabolic enzymes inCandida albicans during dimorphism

The effect of carbon sources, glucose and sucrose, and nitrogen sources such as ammonia, glutamate andl-citrulline on the activities of glutathione metabolic enzymes has been studied. Yeast and mycelial cells were used to identify changes in activity levels of glutathione reductase (GSSGR), glutathione transferase (GST), glutathione peroxidase (GPX) and -glutamyl transpeptidase (GGT). Enzyme activities from cells grown in sucrose media were lower than in glucose media regardless of the enzyme tested, morphological form, or the growth interval. In all enzymes except GST, activity was higher in yeast form than in mycelia, regardless of nitrogen source, with lower activity from 24 to 72 h than at 96 h. In citrulline media, yeast form showed the maximum GST, GGT, and GPX activity. In ammonia-amended media, mycelia showed maximum activity in GGT, whereas in glutamate media, mycelia showed the maximum activity in GST. Also, the type of nitrogen source had no effect on GPX activity in the mycelial form. Finally, changing the nitrogen source showed no significant effect on GSSGR activity, either in the yeast or mycelial form.     

Chromosomal analyses in vinyl chloride-exposed workers

Chromosomal morphology from cultured peripheral lymphocytes was studied in 81 men; 57 of the men were employed on plants manufacturing vinyl chloride or polyvinylchloride, 19 were on-site controls and 5 were off-site controls. There was a significant increase in chromosomal abnormalities in the exposed workers when compared with the controls. The greatest statistically significant increase in total B and total C cells occurred in autoclave operators, with smaller increases in other job categories. The increase in chromosomal aberrations was correlated with the length of exposure and with a history during the year prior to sampling (1973–1974) of exposure to excursion levels of vinyl chloride. Information on smoking habits was obtained 18 months after blood sampling and a positive correlation between these and total C cell abnormalities was found. There was no positive correlation with various other parameters (bilirubin, platelets, γ-glutamyltranspeptidase, alkaline phosphatase, alanine transaminase and aspartate transaminase). It was not possible to estimate which of the three parameters (smoking history, length of employment or exposure to excursion levels) was the most important.     

Studies on the properties of the variants of gamma-glutamyl transpeptidase in human urine

Both the high molecular weight and the low molecular weight variants of urinary Y-glutamyl transpeptidase, displayed transpeptidase (pH optimum 8.6) and autotrans-peptidase (pH optimum 9.4) activities. Iodoacetamide inhibited the transpeptidase activity more efficiently than the autotranspeptidase activity with respect to both variants of Y-glutamyl transpeptidase. The high molecular weight form utilized L-glutamine as a better acceptor than L-cystine during the transpeptidation reaction whereas the reverse was the case with the low molecular weight variant. While phenylmethylsulphonyl fluoride-treated enzymes retained full activitiesper se, addition of maleic acid to the modified enzyme was found to inhibit the catalytic activities indicating a maleic acid-induced conformational change of the modified enzyme.     

Properties of Wilms' tumor line (TuWi) and pig kidney line (LLC-PK1) typical of normal kidney tubular epithelium

Summary Two stable epithelial-like cell lines, the pig kidney strain (LLC-PK₁) and a Wilms' tumor line (TuWi), previously established in other laboratories, were found to exhibit a number of properties characteristic of kidney proximal tubular epithelium. Electron micrographs of LLC-PK₁ monolayers revealed cells forming rosettes reminiscent of tubules. Numerous elongated microvilli and an amorphous basal laminar material surrounded the cell membranes. Cell junctions were located between cell membranes at regions adjacent to the patent lumens. Wilms' cells in culture were similar in appearance to the pig kidney cells; they exhibited numerous microvilli, a thin basal laminar coating on the membrane, and desmonsomes between cells. No rosette formation was evident. Neither cell line was found to produce extracellular reticulin fibers when grown in the presence ofl-ascorbic acid for 1 week. Absence of stainable reticulin in cell monolayer culture after ascorbicacid treatment has been noted only in cell lines of apparent epithelial origin. Histochemically, both lines reacted positively for activities of a number of enzymes found in high amounts in normal kidney tubular epithelium. Pig kidney cells were highly positive for γ-glutamyl transpeptidase activity and moderately active for acid phosphatase and leucine aminopeptidase activities. Wilms' tumor cells were markedly active for γ-glutamyl transpeptidase, 5′-nucleotidase, ATPase, glucose-6-phosphatase, and acid phosphatase activities. These findings in conjunction with the ultrastructural observations indicate that these two lines in culture maintain many of the properties typical of proximal kidney tubular epithelium.     

Organelle contacts: Sub‐organelle zones to facilitate rapid and accurate inter‐organelle trafficking of lipids

When one person wants to communicate securely with another, he/she should contact the other person directly. This rule applies not only to human society, but also to the intracellular micro‐society. In the past two decades, it has become increasingly clear that the sub‐organelle regions called membrane contact sites (MCSs) are pivotal for inter‐organelle transport of lipids in cells, as highlighted in the thematic review series “Interorganelle trafficking of lipids” held in Traffic in 2014–2015. In this commentary, we will describe how the currently prevailing model for lipid trafficking at MCSs was generated, and comment on three important issues that have not been explored: (a1) the principles guiding the generation of an asymmetrical inter‐organelle flow of lipids in cells, (b2) the advantages in lipid trafficking at organelle contacts, and (c3) the dynamic network of inter‐organelle lipid trafficking.