Regulation of proliferation of LLC-MK2 cells by nucleosides and nucleotides: the role of ecto-enzymes.

1. Using the incorporation of [methyl-3H]thymidine as a proliferation marker, the effects of various nucleosides and nucleotides on endothelial LLC-MK2 cells were studied. We found that ATP, ADP, AMP and adenosine in concentrations of 10 microM or higher stimulate the proliferation of these cells.

Inhibition studies on calf pregastric esterase: the enzyme has no functional thiol group.

Pregastric esterase (PGE) (EC 3.1.1.

Autoradiography-based cytochemical detection of ecto-ATPase, ecto-ADPase, 5'-nucleotidase, and extracellular adenosine production, employing 141Ce3+ as a capturing agent.

A method for the visualization of the ecto-nucleotidase enzyme activities present on the cell surface, employing 141Ce3+ as a capturing and labelling agent, is described. Phosphate ions precipitated at the cell surface can be detected by coating the cells with an autoradiographic emulsion, followed by light microscopical inspection of the formed silver grains. The activities of ecto-ATPase, ecto-ADPase and 5'-nucleotidase were detected by this approach in four different cell lines.

Identification and partial purification of (Ca2+ or Mg2+)-ATPase in renal brush-border membranes.

The protein responsible for the (Ca2+ or Mg2+)-ATPase activity in brush-border membranes from pig kidney tubular cells was characterized to distinguish this enzyme from the N-ethylmaleimide-sensitive Mg(2+)-ATPase, also present in renal brush borders. Both enzymes are clearly different in their pH optimum and their sensitivity to divalent cations, nucleoside 5'-triphosphates and inhibitors. Solubilization of the (Ca2+ or Mg2+)-ATPase from brush-border membrane vesicles was accomplished with Nonidet P-40 or dodecylmaltoside.

The cDNA sequence encoding bovine pregastric esterase.

The polymerase chain reaction (PCR) was used to amplify specific parts of the gene encoding calf pregastric esterase (PGE). Primers based on conserved regions in human gastric lipase (HGL) and rat lingual lipase (RLL) were used to screen a cDNA library prepared from calf tongue tissue. This resulted in the cloning of the entire coding sequence for PGE, which exists as a mature 378-amino-acid (aa) polypeptide with a molecular mass of 42,960 Da.

The localization of (Ca2+ or Mg2+)-ATPase in plasma membranes of renal proximal tubular cells.

Basolateral and brush-border vesicles from pig kidney cortex were prepared by differential centrifugation followed by free-flow electrophoresis. A low-affinity (Ca2+ or Mg2+)-ATPase which co-migrated with alkaline phosphatase was demonstrated. A considerable enrichment (by a factor of 10) of this ATPase activity was only observed in the brush-border and not in the basolateral membrane fractions.

Evaluation of sample work-up methods and internal standards for the determination of 5-hydroxytryptamine and 5-hydroxyindoleacetic acid in brain by HPLC with electrochemical detection.

A high-performance liquid chromatographic method with electrochemical detection is described for the determination of 5-hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) in brain. Results of studies on sample work-up methods and on the use of various internal standards are reported. The reproducibility of determination of 5-HT and 5-HIAA in two regions of rabbit brain has been evaluated.

An azide-insensitive low-affinity ATPase stimulated by Ca2+ or Mg2+ in basal-lateral and brush border membranes of kidney cortex.

Basal-lateral and brush border membranes from pig kidney cortex were prepared by differential centrifugation followed by free-flow electrophoresis. In each type of membrane, azide-insensitive, low-affinity Ca2+-ATPase and Mg2+-ATPase activities are demonstrated. A comparative study for both membranes further reveals the following analogies between these ATPases: (a) they show maximal activity between pH 8 and 8.

Corneal ultrastructural changes in Fabry's disease.

A case of Fabry's disease is reported. The findings of the corneal alterations with the light microscope as well as with the electron microscope are described. The diffuse corneal haziness seems to be due to small intracellular osmiophilic inclusions of the epithelium.

Characterization of different plaque-forming and defective temperate phages in Agrobacterium.

Four Agrobacterium tumefaciens temperate phages (PB2A, PB6(omega), PV-1(LV-1) and PS8), were shown to have the same genome size. Moreover hybridization experiments by the heteroduplex method and electron microscopy showed a 100% homology between these four phage genomes. Indications for lysogeny were found by direct means for the Agrobacterum timefaciens strain 396, Agrobacterium radiobacter strain 8149 and Agrobacterium species 0362 and by the electron microscope negative staining technique for the A.

Electron microscopy of the intracellular development of bacteriophage MS2 in Escherichia coli.

The developmental cycle of bacteriophage MS2 in Escherichia coli was studied by means of ultramicrotomy and transmission electron microscopy. Application of a special fixation method made it possible to discern the individual phage particles from cellular ribosomes in the early infection stages and to follow the further development of the phage in the host bacterium. By means of the same techniques we have tried to obtain a better insight in the process of lysis of the infected cells.