Membrane excitability expressed in human neuroblastoma cell hybrids

The voltage-sensitive Na+ channel is responsible for the action potential of membrane electrical excitability in neuronal tissue. Three methods were used to demonstrate the presence of neurotoxin-responsive Na+ channels in two hybrid cell lines resulting from the fusion of excitable human neuroblastoma cells with mouse fibroblasts. Only one of the two electrically active hybrid cell lines maintained the sensitivity of the neuroblastoma parent to tetrodotoxin (TTX). The other hybrid, although electrically active, was not responsive to TTX or scorpion venom. Comparisons of the patterns of expression of membrane excitability and of chromosome complements in these human neuroblastoma cell hybrids suggest that the phenotype of membrane excitability is composed of genetically distinct elements.     

Characterization and expression of collagen-like genes in Drosophila melanogaster

We have used a cloned chicken collagen cDNA sequence to help identify hypothetic members of the collagen gene family from Drosophila melanogaster. Several experimental evidences have been obtained which indicate that the Drosophila genome contains numerous collagen-like sequences. We have characterized in more detail ten distinct DNA sequences that hybridized strongly to the heterologous collagen probe. By in situ hybridization we have shown that these sequences are dispersed throughout the Drosophila genome. Two of them are shown to originate from the previously described DCg 1 and DCg 2 collagen genes. In other respects, we show that in addition to DCg 1 and DCg 2, at least five putative collagen genes are expressed during the Drosophila lifetime. These genes are unique, and some of them are seen to be transcribed into different size classes of mRNAs. Additionally, the data presented so far demonstrate that the expression of these genes is regulated temporally and/or quantitatively during the Drosophila life cycle.     

FAST (Flexible Analysis by Software Tool) and CHAMP (CHemico-physical AMinoacidic Parameter data bank): a new tool to investigate protein structure

A flexible package designed to study protein structure is described.The package is devoted to the analysis of protein sequencesby drawing structural profiles of specific structure-relatedamino acid parameters. An Aminoacidic Parameters Data Bank (CHAMP)containing 32 different series of physico-chemical parametersof amino acids is available. Sequences can be loaded from anyASCII format data bank or from keyboard. The program possessesa routine which enables easy updating of the protein data bankand CHAMP Data Bank. FAST reads statistical correlations betweentwo plots in order to identify structural similarities. Plotscan be printed, saved or used for correlation, comparison orgraph overlap by using common spreadsheets (e.g. Lotus 123).Plots can be smoothed by a running mean or a running median.The program also has a special feature—a global flexibilityanalysis of proteins. The package runs on IBM or compatiblesand requires DOS 3.0 or later. Received on June 20, 1989; accepted on August 2, 1989     

Conservation of the alternative oxidase and enhancement of cyanide-resistant respiration in suspension-cultured pear fruit cells by inhibitors of macromolecular synthesis

The contribution of the alternative pathway to the respiration of suspension-cultured pear ( Pyrus communis cv. Passa Crasanne) cells was enhanced, often severalfold, within 2 to 4 days following the addition of cycloheximide, actinomycin D, or 2-(4-methyl-2,6-dinitroanalino)- N -methyl propionamide (D-MDMP). Concomitant inhibition of cellular protein synthesis by cycloheximide and actinomycin D was transient and incomplete. However, inhibition by D-MDMP was virtually complete (>97%) and persisted over several days. [³⁵S]-labelling and polyacrylamide gel separation indicated that cycloheximide precluded the appearance of discernable new proteins in mitochondria. Probes with monoclonal antibodies revealed a conservation of alternative oxidase protein levels in the mitochondria of inhibitor-treated cells. The data, appraised within the complexities of cell-culture dynamics, lead to the conclusion that the observed increases in capacity for cyanide-resistant respiration are the consequence, likely indirect, of inhibited protein synthesis with resultant retention and activation of constitutive alternative oxidase.