Chicken liver fatty acid synthetase dimer: Evidence of asymmetrical structure from iodoacetamide inhibition studies

The condensing component of chicken liver fatty acid synthetase is inhibited by a sulfhydryl reagent, iodoacetamide, with a second-order rate constant of 0.23 M^–1 sec^–1 at pH 7.0 and 0. Complete inactivation requires the modification of approximately 8-SH groups per dimer of the enzyme. Quantitation of the extent of inactivation in the presence of i mM acetyl CoA (which completely protects the enzyme against inactivation) and in its absence shows that complete inactivation results from the binding of approximately 1.1 tool of carboxamidomethyl residues per dimer. These data are consistent with the proposed functional asymmetry of the enzyme.     

Changes in soluble amino nitrogen,protein, nitrate reductase activity and abscisic acid during development of wheat grain

Trends in the time course, changes in the moisture, soluble amino acids, proline, abscisic acid contents and nitrate reductase activity determined byin vivo method in the developing seeds of wheat were studied. Maximum dry matter augmentation in the seed took place in the period between 10–30 days after anthesis. Per cent moisture and moisture content started declining 15 days and 25 days after anthesis, respectively. Levels of soluble amino acids, proline and nitrate reductase activity were higher during initial stages of seed development, but decreased with increasing magnitude of dehydration and accumulation of abscisic acid (ABA) in the maturing seeds.     

Selection for malathion-resistance in Drosophila melanogaster

Results from a long-term selection experiment for malathion-resistance in Drosophila melanogaster are described. A polled population of 40 locally-caught, iso-female lines was exposed to increasing concentrations of malathion in the food at both a high selection intensity (MH) and a lower intensity (ML). The response was consistent with a polygenic system. Both adult and larval resistance increased in parallel. Changes in the dose-response curve of adults could be approximately described by a dose-modification factor. Larval resistance was more complex; both selected populations showed a maternal effect which could not be explained by sex-linked genes. Larval resistance in the selected populations behaved as a co-dominant trait with respect to the susceptible controls. Adult resistance was dominant in the ML and co-dominant in the MH population, suggesting that different genes conferring resistance were selected. The selection procedure also produced a developmental delay in both populations, dependent on malathion concentration, but present even in its absence.     

Population biology of Avena XI. Variation in peripheral isolates of A. barbata

Data on genetic polymorphism, scored at two morphological loci, showed peripheral, isolated roadside colonies of slender oat (Avena barbata) to be significantly less polymorphic than the large central populations in continuous stands. The role of random drift (founder effect) was evident in the genetic structure of such roadside colonies which were, however, not monomorphic. Multilocus associations also suggested large Hill-Robertson effect in generating gametic disequilibria. Such isolates with varying amounts of elapsed time since the founder events could offer useful material for a study of evolutionary processes including the selection-drift balance.     

Aquatic oligochaeta from among the roots of eichhornia crassipes solms

The paper records the presence of sixteen species of aquatic oligochaetes, belonging to the Aeolosomatidae (1 species). Naididae (13 species) and Tubificidae (2 species), living in association with the floating roots of the water hyacinth, Eichhornia crassipes Solms., from a tank in Vizianagaram town in Andhra Pradesh, India. Of these, Aeolosoma hyalinum Bunke, 1967 and Dero obtusa D'Udekem, 1855 are new records for the Indian sub-continent.     

Induction of N-acetylmannosamine catabolic pathway in yeast.

N-Acetylmannosamine kinase activity is absent from yeast cells grown on N-acetylmannosamine. However, other enzymes of the catabolic pathway, namely, N-acetylmannosamine-2-epimerase, N-acetylglucosamine kinase and glucosamine-6-phosphate deaminase are induced. In addition, a high affinity uptake system (permease) for the uptake of N-acetylglucosamine is synthesized under these conditions. The presence of either N-acetylmannosamine or N-acetylglucosamine as inducer is essential for the induced synthesis of these enzymes. The enzyme synthesis stops and their concentration in the cells declines rapidly as soon as inducer is removed from the medium. N-Acetyl-D-galactosamine can also induce all these enzymes except for N-acetylmannosamine-2-epimerase, suggesting the convergence of catabolic pathways for both the aminosugars at N-acetyl-D-glycosamine. Experiments with inhibitors of macromolecule synthesis suggest that the snythesis of RNA and protein is necessary for the induction of these cyzymes whereas the synthesis of DNA is not.     

The action of tributyltin chloride on the uptake of proline and glutamine by intact cells of Escherichia coli.

Tributyltin chloride inhibits growth and uptake of glutamine and proline into intact cells of Escherichia coli. It causes efflux of the accumulated amino acids. A pH gradient generated in intact cells and everted membrane vesicles is dissipated by this compound. These effects do not require lipoic acid but are dependent on the presence of chloride, bromide, or iodide ions. We conclude that tributyltin chloride can catalyse a transmembrane OH- -anion exchange exchange reaction and that this is its mode of inhibition of the uptake of these amino acids. The response of proline and glutamine uptake to the inhibitor is similar and is consistent with the transport of both amino acids requiring an electrochemical gradient of protons.