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.     

Detection and regulation of δ-aminolevulinic acid synthetase activity in rat skeletal muscle

The presence of δ-aminolevulinic acid synthetase (ALAS) in mitochondria obtained from rat skeletal muscles has been observed. Optimal conditions for the meausurement of this activity are described. The activity of skeletal muscle ALAS was investigated under conditions known to affect the activity of this enzyme in other tissues. ALAS activity in skeletal muscle mitochondria was decreased 55% by a 48-h fast. Treatment with dexamethasone did not reverse the effect of starvation on ALAS activity and did not change the activity in the fed controls. ALAS activity was decreased 56% in skeletal muscle mitochondria obtained from rats in which diabetes mellitus had been induced by streptozotocin. Administration of insulin to the diabetic animals partially reversed the effect of diabetes on skeletal muscle ALAS; however, administration of insulin to control animals caused a 21% decrease in skeletal muscle ALAS activity. By contrast, treatment with inducers of hepatic ALAS such as allylisopropylacetamide or 3,5-dicarbethoxy-1,4-dihydrocollidine had no effect on skeletal muscle ALAS. These results confirm our previous suggestion that ALAS activity is regulated in a tissue-specific manner.     

Secretion of N-glycosylated interleukin-1 beta in Saccharomyces cerevisiae using a leader peptide from Candida albicans. Effect of N-linked glycosylation on biological activity

Human interleukin-1 beta (IL-1 beta) is expressed in activated monocytes as a 31-kDa precursor protein which is processed and secreted as a mature, unglycosylated 17-kDa carboxyl-terminal fragment, despite the fact that it contains a potential N-linked glycosylation site near the NH2 terminus (-Asn7-Cys8-Thr9-). cDNA coding for authentic mature IL-1 beta was fused to the signal sequence from the Candida albicans glucoamylase gene, two amino acids downstream from the signal processing site. Upon expression in Saccharomyces cerevisiae, approximately equimolar amounts of N-glycosylated (22 kDa) and unglycosylated (17 kDa) IL-1 beta protein were secreted. The N-glycosylated yeast recombinant IL-1 beta exhibited a 5-7-fold lower specific activity compared to the unglycosylated species. The mechanism responsible for inefficient glycosylation was also studied. We found no differences in secretion kinetics or processing between the two extracellular forms of IL-1 beta. The 17-kDa protein, which was found to lack core sugars, does not result from deglycosylation of the 22-kDa protein in vivo and does not result from saturation of the glycosylation enzymatic machinery through overexpression. Alteration of the uncommon Cys8 residue in the -Asn-X-Ser/Thr-glycosylation site to Ser also had no effect. However, increasing the distance between Asn7 and the signal processing site increased the extent of core N-linked glycosylation, suggesting a reduction in glycosylation efficiency near the NH2 terminus.     

Evolution of ruminant hemoglobins. Thermodynamic divergence of ox and buffalo hemoglobins.

The ligand-binding properties of hemoglobins from two homozygote phenotypes (AA and BB) of water buffalo (Bubalus bubalis) have been characterized by equilibrium and kinetic techniques. In the case of the BB phenotype, the two constituent hemoglobins have been purified and separately analysed. Buffalo hemoglobins display the reduced sensitivity to organic phosphates characteristic of ruminant hemoglobins, their physiological effector probably being the chloride ion. In contrast to the other known hemoglobins from ruminants, all the hemoglobins from the water buffalo display a significant temperature sensitivity, the delta H for oxygen binding in the presence of physiological effectors approaching that of human hemoglobin (delta H = -30.5 kJ/mol O2). This discrepancy with the other ruminant hemoglobins (e.g. ox, delta H = -10.4 kJ/mol O2), whose primary structure is very similar to that of buffalo, hemoglobins might be correlated to the different habitat and phylogenetic history of the two subfamilies (Bos and Bubalus) of Bovidae.     

Vascular endothelial growth factor (VEGF) induces plasminogen activators and plasminogen activator inhibitor-1 in microvascular endothelial cells.

Extracellular proteolysis is believed to be an essential component of the angiogenic process. The effects of VEGF, a recently described angiogenic factor, were assessed on PA activity and PA and PAI-1 mRNA levels in microvascular endothelial cells. u-PA and t-PA activity were increased by VEGF in a dose-dependent manner, with maximal induction at 30 ng/ml. u-PA and t-PA mRNAs were increased 7.5- and 8-fold respectively after 15 hours, and PAI-1 mRNA 4.5-fold after 4 hours exposure to VEGF. At equimolar concentrations (0.5 nM), VEGF was a more potent inducer of t-PA mRNA than bFGF, while bFGF was a more potent inducer of u-PA and PAI-1 mRNAs. In addition, VEGF induced u-PA and PAI-1 mRNAs with kinetics similar to those previously demonstrated for bFGF. These results demonstrate the regulation of PA and PAI-1 production by VEGF in microvascular endothelial cells and are in accord with the hypothesis that extracellular proteolysis, appropriately balanced by protease inhibitors, is required for normal capillary morphogenesis.     

5,8,11,14-Eicosatetraynoic acid-induced destruction of mitochondria in human prostate cells (PC-3)

Summary Culturing human prostate PC-3 cells for 4, 24, or 72 h in the presence of 5,8,11,14-eicosatetraynoic acid (ETYA), an inhibitor of arachidonic acid metabolism and cholesterol biosynthesis, markedly altered the morphology and reduced the number of mitochondria in the treated cells. Using quantitative electron microscopic morphometry, we documented changes in the number, form, area, matrix density, and integrity of the cristae and limiting membranes of mitochondria in cells cultured with ETYA. The inhibition of cholesterol synthesis or the substitution of ETYA for polyunsaturated fatty acids in the inner membrane may participate in the disruption of the mitochondria, which resembles the morphologic sequelae of oxidative stress. If sufficiently extensive, these changes could contribute to the inhibition of cellular proliferation by ETYA.     

Gene structure of mouse cathepsin B

The structure of a genomic DNA fragment encoding mouse cathepsin B was characterized. The genomic insert spans 15 kbp and contains 9 exons encoding the 339 amino acid residues of mouse preprocathepsin B. Intron break-points are not found at the junctions of the pre-peptide, pro-peptide and mature enzyme. Like other cysteine proteinase genes, the region around the cysteinyl active site is split by an intron, but in contrast with cathepsins L and H the intron break-point is located immediately after the active site.     

Revision and affinities ofGalium (Rubiaceae) in Madagascar

The only representatives ofRubiaceae-Rubieae in Madagascar are five species ofGalium. G. thunbergianum andG. chloroionanthum are essentially afromontane species, ± widely distributed in both the African mainland and Madagascar. The new speciesG. andringitrense andG. ankaratrense are endemic to Madagascar but show close affinities to two afromontane—afroalpine groups from the African mainland, theG. simense—G. ruwenzoriense andG. glaciale complex respectively.G. polyacanthum (new combination) exhibits certain primitive morphological traits and appears to be an old Madagascan endemic without close allies. New chromosome counts for populations from the African mainland demonstrate thatG. chloroionanthum andG. simense are 4x (x=11). Distribution patterns and origins of theGalium species in Madagascar and their relationships with African taxa are discussed.