Preparation of internally labelled rat pituitary somatotropin (growth hormone).

Rat somatotropin (growth hormone) was labelled biosynthetically by incubating anterior pituitary lobes with radioactive amino acids for 24 h in a simple buffered salts medium containing glucose. The labelled hormone was isolated by preparative polyacrylamide-gel electrophoresis or by chromatography on Sephadex G-100 and then DEAE-cellulose. The labelled material was pure by several criteria and cross-reacted immunologically with unlabelled rat somatotropin. When a mixture of 14C-labelled amino acids was used for labelling the protein, label could be introduced into these same amino acids of somatotropin, though relative specific radioactivities varied considerably. Somatotropin labelled by the procedures described in the present paper was suitable for structural studies and could be used for a variety of other biochemical experiments.     

Breakdown of aberrant protein in rabbit reticulocytes decreases with cell age.

1. The lower regions of the stem of celery (Apium graveolens L.) contain a soluble enzyme that hydrolyses phosphatidylinositol. 2. The lipoidal product of hydrolysis is diacylglycerol, and the water-soluble products are 1:2-cyclic phosphoinositol and phosphoinositol in the approximate proportions of 60% and 40% respectively: this indicates that a phosphodiesterase (phospholipase C-like) activity is cleaving the phosphatidylinositol. 3. The enzyme requires a bivalent cation, Ca2+ being the most effective activator. 4. The enzyme has a pH optimum, depending on conditions of assay, of pH 5.9-6.6 and in this pH range shows no detectable activity against phosphatidylcholine or phosphatidylethanolamine. 5. The activity is stimulated by phosphatidic acid and slightly inhibited (30% at concentrations equimolar with phosphatidylinositol) by phosphatidylcholine. 6. The phosphodiesterase was also detected (but not quantified) in the tips of the flowers in cauliflowers, in outer leaves of onion and in the elongating stem of daffodils. 7. The enzyme's properties are compared with equivalent mammalian enzymes, and its possible role in the catabolism of phosphatidylinositol in higher plants is discussed.     

Identifying sites of simultaneous DNA replication in eukaryotes by N-methyl-N''-nitro-N-nitrosoguanidine multiple mutagenesis.

Summary N-methyl-N-nitro-N-nitrosoguanidine (NG) induces certain classes of multiple mutations in yeast at high frequency. By selecting for mutation at one locus (his4 or leu1) one frequently obtains double mutants where another mutation to temperature sensitivity has also been induced. This multiple mutagenesis exhibits a considerable specificity: for mutation at one particular locus there is a high chance that another mutation will be found in the same cell at one of a restricted number of other loci. For any given locus (e.g. his4) there is a spectrum of sites at which temperature-sensitivity mutations are coinduced. This spectrum differs for different loci, such that the spectrum of sites co-mutating with leul differs completely from that for sites co-mutating with his4. This NG-induced co-mutation is interpreted in terms of NG acting to enhance mutagenesis at sites of simultaneous DNA replication within the cell. The results so obtained indicate a very strict control over the order and timing of gene replication in Saccharomyces cerevisiae, and it is suggested that it is now possible to use NG double mutagenesis to try and locate origins of replication in yeast.     

hobo transposable elements in Drosophila melanogaster and D. simulans.

Genomic patterns of occurrence of the transposable element hobo are polymorphic in the sibling species Drosophila melanogaster and D. simulans. Most tested strains of both species have apparently complete (3.0 kb) and smaller hobo elements (H lines), but in both species some strains completely lack such canonical hobo elements (E lines). The occurrence of H and E lines in D. simulans as well as in D. melanogaster implies that an hypothesis of recent introduction in the latter species is inadequate to explain the phylogenetic occurrence of hobo. Particular internally deleted elements, the approximately 1.5 kb Th1 and Th2 elements, are abundant in many lines of D. melanogaster, and an analogous 1.1 kb internally deleted element, h del sim, is abundant in most lines of D. simulans. Besides the canonical hobo sequences, both species (and their sibling species D. sechellia and D. mauritiana) have many hobo-hybridizing sequences per genome that do not appear to be closely related to the canonical hobo sequence.     

Diethyldithiocarbamate Potentiates the Neurotoxicity of In Vivo l-Methyl-4-Phenyl-1, 2, 3, 6-Tetrahydropyridine and of In Vitro 1-Methyl-4-Phenylpyridinium

Diethyldithiocarbamic acid (DDC) potentiates in vivo neurotoxicity of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and in vitro neurotoxicity of 1-methyl-4-phenylpyridinium (MPP+). Male C57B1/6 mice were given two or five injections of MPTP (30 mg/kg i.p.) preceded 0.5 h by DDC (400 mg/kg i.p.). The mice were tested for catalepsy, akinesia, or motor activity during and after the period of dosing. Striatal and hippocampal tissues were obtained at 2 and 7 days following the last injection and evaluated for dopamine and norepinephrine levels, respectively. These same tissues were also analyzed for the levels of glial fibrillary acidic protein (GFAP), an astrocyte-localized protein known to increase in response to neural injury. Pretreatment with DDC potentiated the effect of MPTP in striatum and resulted in substantially greater dopamine depletion, as well as a more pronounced elevation in GFAP. In hippocampus, the levels of norepinephrine and GFAP were not different from controls in mice receiving only MPTP, but pretreatment with DDC resulted in a sustained depletion of norepinephrine and an elevation of GFAP, suggesting that damage was extended to this brain area by the combined treatment. Mice receiving MPTP preceded by DDC also demonstrated a more profound, but reversible, catalepsy and akinesia compared to those receiving MPTP alone. Systemically administered MPP+ decreased heart norepinephrine, but did not alter the striatal levels of dopamine or GFAP, and pretreatment with DDC did not alter these effects, but did increase lethality. DDC is known to increase brain levels of MPP+ after MPTP, but our data indicate that this is not due to a movement of peripherally generated MPP+ into CNS.(ABSTRACT TRUNCATED AT 250 WORDS)     

Ecophysiology of Bacteriophage S5100 Infecting Halobacterium cutirubrum

Increasing salinity reduces burst size and increases the latent period of infection of Halobacterium cutirubrum by lytic bacteriophage S5100. Cells become reversibly and persistently infected at saturation-level concentrations of NaCl. We propose that high salinity provides a natural refuge for sensitive host bacteria and that phage S5100 acts as a scavenger, proliferating when host viability is threatened by dilution of the environment.     

An investigation of the immune response of homozygotes for the Rh haplotype --D-- and related haplotypes. Using cells of rare Rh phenotypes

Immune sera from people homozygous for the "deleted" gene complexes --D--, cD--, CwD--, . D . and (C)Div-- as well as heterozygous --D--/--- --- --- were studied by their reactions, and in some cases by absorption-elution tests, with cells of the following rare Rh types: two unrelated examples of homozygous . D .; three unrelated examples of Rhmod; homozygous R33; cDe with a very weak e; apparent CwD(e)/--D--. The results showed that these immune sera are clearly heterogeneous: this heterogeneity was not entirely due to the strength of the antibody (as determined by titration against CDe/cDE cells) or to the phenotype of the antibody maker. Absorption and elution tests using two of the immune sera and . D ./. D . cells demonstrated a "new" antibody, anti-Dav, for a high frequency Rh antigen in addition to anti-Rh17.     

Origin of hydrogen in methane produced by Methanobacterium thermoautotrophicum.

The production of deuterated methane by Methanobacterium thermoautotrophicum in H2O-D2O mixtures was examined by high-resolution mass spectrometry. The hydrogen in the methane arose solely from water and not from hydrogen gas. Hydrogen gas served only as an electron source in methanogenesis. A whole-cell product isotope discrimination of 1.5 favoring hydrogen over deuterium was observed in methane production in 81 atom% deuterated water. The distribution of deuterated methane species is described by a simple model of the overall reaction.     

Alpha glucosidases in white blood cells, with reference to the detection of acid alpha 1-4 glucosidase deficiency.

The iron-containing violet acid phosphatases from beef spleen and pig allantoic fluid have been purified to homogeneity. Molecular weight determinations by zonal gel filtration, SDS-gel electrophoresis, and ultracentrifugation support values close to 40,000 for both enzymes, necessitating reappraisal of literature values. Similarly, the equivalent weight for iron is close to 20,000 for both enzymes, indicating the presence of two iron atoms per molecule of enzyme. The enzymes also have very similar ultraviolet and visible spectra, with λ_max values close to 550 nm, and ?₅₅₀ values(in terms of iron) of 2.04 × 10³ and 2.00 × 10³ for the beef spleen and pig allantoic fluid enzymes respectively.