Analysis of Slow Hyperpolarizing Potentials in Frog Taste Cells Induced by Glossopharyngeal Nerve Stimulation

Chemical Senses, 29,     

Physiological evaluation of temperature effect on the growth processes of the mysid, Neomysis intermedia Czerniawsky

Ingestion, respiration, and molting loss rates were measuredover the 3 – 29°C range in Neomysis intermedia. Weightspecific rates of these physiological processes ranged from2 to 140% body C day^–1 for ingestion, from 2 to 15% bodyC day^–1 for respiration, and from 0.1 to 5% body C day^–1for molting loss. All weight-specific rates showed a logarithmicdecrease with a logarithmic increase in body weight, and a logarithmicincrease with a linear increase in temperature below 20 or 25°C.The effect of temperature, however, was different between thephysiological rates, with a large temperature dependency foringestion (Q₁₀ = 2.6 –3.9) and molting loss (Q¹⁰ = 2.9– 3.6) and a moderate temperature dependency for respiration(Q₁₀ = 1.9 – 2.1). Calculated assimilation efficiencychanged with body size, but was constant over the temperaturerange examined. Allocation of assimilated materials varied witha change in temperature, reflecting the different temperaturedependence between physiological processes. It was deduced thatthe strong temperature dependency of the growth rate in N. intermediaobserved in the previous studies resulted from the large temperatureeffect on ingestion and assimilation rates, superimposed bythe different allocation of assimilated materials. ¹Present address: Department of Botany, University of Tokyo,Hongo, Tokyo 113, Japan     

Effects of Exogenous Amino Acids on Iron Uptake in Relation to their Effects on Photoperiodic Flowering in Lemna paucicostata 6746

The flowering of Lemna paucicostata 6746 grown on 14-h photoperiodwas enhanced by the addition of high concentrations of ironto the medium, which also increased the endogenous iron concentration.The addition of asparagine, aspartate, glutamate, -alanine,glycine or serine to the medium also increased the endogenousiron level, resulting in the promotion of flowering. In contrast,the addition of cysteine, cystine, glutamine, arginine, threonineor phenylalanine lowered the endogenous iron level, resultingin the inhibition of flowering. Glycine and asparagine added to the medium during an inductive96-h dark period did not promote iron uptake and had no effecton flowering, but when added during the subsequent 120-h lightperiod, they promoted both iron uptake and flowering response.The increase in the endogenous iron level seems to favor floraldevelopment rather than induction of photoperiodic floweringof Lemna paucicostata 6746. (Received September 8, 1986; Accepted March 31, 1987)     

Selective growth of a mutant in continuous culture of Bacillus caldolyticus for production of α-amylase

Summary In a continuous culture of Bacillus caldolyticus strain SP, which requires maltose as an inducer for production of -amylase in batch culture, a predominant mutant strain M1 which produced high amounts of -amylase in the absence of maltose in batch culture, developed. The change of cell population from strain SP to strain M1 in maltose-casitone medium was linear with time in the transient state after the change from batch to continuous culture at a dilution rate of 0.17 h^-1, and was completed in about 11 generations of bacterial growth. The dilution rate effect of continuous culture on -amylase activity was almost the same with both strains SP and M1. The maximum -amylase activity of 380 units/ml was observed at an intermediate dilution rate that was 11.5 times higher than -amylase activity at the end of a batch culture using the same medium. It was deduced that the enhancement of -amylase production in continuous culture was attributed partly to the predominant growth of a mutant strain with higher -amylase productivity.     

Isolation and Characterization of an Enterobacter cloacae Strain That Reduces Hexavalent Chromium under Anaerobic Conditions

An Enterobacter cloacae strain (HO1) capable of reducing hexavalent chromium (chromate) was isolated from activated sludge. This bacterium was resistant to chromate under both aerobic and anaerobic conditions. Only the anaerobic culture of the E. cloacae isolate showed chromate reduction. In the anaerobic culture, yellow turned white with chromate and the turbidity increased as the reduction proceeded, suggesting that insoluble chromium hydroxide was formed. E. cloacae is likely to utilize toxic chromate as an electron acceptor anaerobically because (i) the anaerobic growth of E. cloacae HO1 accompanied the decrease of toxic chromate in culture medium, (ii) the chromate-reducing activity was rapidly inhibited by oxygen, and (iii) the reduction occurred more rapidly in glycerol- or acetate-grown cells than in glucose-grown cells. The chromate reduction in E. cloacae HO1 was observed at pH 6.0 to 8.5 (optimum pH, 7.0) and at 10 to 40°C (optimum, 30°C).     

Cloning and sequence analysis of a cDNA encoding the Rieske iron-sulfur protein of rat mitochondrial cytochrome bc1 complex

We have isolated a cDNA clone for the Rieske iron-sulfur protein of rat cytochrome bc1 complex, by screening a rat liver cDNA expression library using antiserum directed against the corresponding protein of bovine. The amino acid sequence deduced from the nucleotide sequence of the cDNA indicated that the mature polypeptide of the rat protein consists of 196 amino acid residues with a molecular weight of 21,465, and that it is formed as a precursor with an amino-terminal extension. Northern blot analysis indicated that rat liver possibly contains different sizes of mRNAs for the Rieske iron-sulfur protein, and Southern blot analysis demonstrated that rats and mice possess a single gene for this protein.     

Preparation ofN-acetylneuraminic acid from delipidated egg yolk

Egg yolk, a large proportion of the egg, was studied for the preparation ofN-acetylneuraminic acid (Neu5Ac). The delipidated hen egg yolk (DEY; 500 kg containing 0.2% w/w, Neu5Ac) was hydrolysed with HCl (pH 1.4) at 80 °C and neutralized with NaOH (pH 6.0). The mixture was filtered and electrodialysed until the conductivity was 240 µS cm^–1. The filtrate was applied on a column of Dowex HCR-W2 (20–50 mesh), followed by a column of Dowex 1-X8 (200–400 mesh). The latter column was washed with water, and then eluted with a linear gradient of HCO₂H (0–2m). The eluates containing Neu5Ac were concentrated using a reverse osmosis membrane and, finally, rotary evaporated at 40 °C. The residue was then lyophilized to yield 500 g Neu5Ac. The purity of Neu5Ac was >98% (TBA method). HPLC, NMR spectroscopy and TLC chromatography of the product obtained from the DEY showed that Neu5Ac was the sole derivative present in egg yolk. The DEY, a byproduct from egg processing plants, was found to be an excellent source for the large-scale preparation of Neu5Ac.Abbreviations Neu5Ac N-acetylneuraminic acid - Neu5Gc N-glycolylneuraminic acid - DEY delipidated egg yolk - HPLC high performance liquid chromatography - TLC thin layer chromatography - NMR nuclear magnetic resonance - IR infrared spectroscopy Presented at the 11th International Symposium on Glycoconjugates, Toronto, Canada.     

Cloning and sequencing of a cDNA for human mitochondrial ubiquinone-binding protein of complex III

The ubiquinone-binding protein (QP-C) is a nuclear-encoded component of ubiquinol-cytochrome c oxidoreductase in the mitochondrial respiratory chain and plays an important role in electron transfer as a ubiquinone-QP-C complex. We obtained a partial cDNA for rat liver QP-C by screening a lambda gt11 rat liver cDNA library using antiserum directed against bovine heart QP-C. Using this cDNA as a probe, a cDNA clone was isolated from a human fibroblast cDNA library by colony hybridization. The total length of the cloned cDNA was 518 base pairs with an open reading frame of 333 base pairs. The 111-amino acid sequence deduced from the nucleotide sequence of the cDNA is 85% homologous to that of bovine QP-C and contains only a single additional amino-terminal methionine. This implies that the human QP-C is synthesized without a presequence which is required for import of most nuclear-encoded mitochondrial proteins into mitochondria.     

Effect of base substitutions in the colicin E1 gene on colicin E1 export and bacteriocin activity

Summary Base substitutions have been introduced into the segment of the colicin E1 gene corresponding to the polypeptide region between the 404th and the 502nd residues which was considered to participate in colicin E1 export and bacteriocin activity. The methods used were in vitro localized mutagenesis with sodium bisulphite and in vivo mutagenesis using either nitrosoguanidine or ethyl methane sulphonate. Cells carrying mutagenized plasmids were screened by their inability to form a clear zone on a lawn of colicin E1 sensitive cells. Mutation sites were determined from the nucleotide sequence analysis and the altered amino acid residues were reduced. The mutant proteins were analysed for their ability to be exported to the periplasmic space and for their bacteriocin activity. Out of eight mutants obtained, three had a single amino acid replacement. Mutant proteins that had Ser and Glu in place of Pro-462 and Gly-502, respectively, showed a decrease in both the export and the bacteriocin activity. A mutant protein having Arg in place of Gly-439 showed a decrease only in the bacteriocin activity. These results suggest that the target region of colicin E1 contributes to the export as well as the bacteriocin activity but the two functions are supported in part by different amino acid residues of the protein.     

Plasmodium falciparum: Attenuation by irradiation

The effect of irradiation on the in vitro growth of Plasmodium falciparum was investigated. The cultured malarial parasites at selected stages of development were exposed to gamma rays and the sensitivity of each stage was determined. The stages most sensitive to irradiation were the ring forms and the early trophozoites; late trophozoites were relatively insensitive. The greatest resistance was shown when parasites were irradiated at a time of transition from the late trophozoite and schizont stages to young ring forms. The characteristics of radiosensitive variation in the parasite cycle resembled that of mammalian cells. Growth curves of parasites exposed to doses of irradiation upto 150 gray had the same slope as nonirradiated controls but parasites which were exposed to 200 gray exhibited a growth curve which was less steep than that for parasites in other groups. Less than 10 organisms survived from the 10⁶ parasites exposed to this high dose of irradiation; the possibility exists of obtaining radiation-attenuated P. falciparum.