Feedback inhibition of homoserine dehydrogenase and threonine deaminase in the genusBifidobacterium

Feedback inhibition of crude and purified extracts of homoserine dehydrogenase and threonine deaminase activities in the genusBifidobacterium was studied. Homoserine dehydrogenase was partially or completely inhibited byl-threonine, and a marked inhibitory effect byl-isoleucine on threonine deaminase was observed. In the speciesBifidobacterium cuniculi high levels ofl-valine reversed the inhibitory effect ofl-isoleucine. The -aminobutyric acid-resistant mutant Ru 326/106 of the speciesB. ruminale, overproducer ofl-isoleucine, had a derepressed homoserine dehydrogenase and a lesser feedback inhibition byl-threonine. Homoserine dehydrogenase appeared to be in bifids specifically NAD dependent. The regulatory mechanisms of aspartate family amino acid biosynthesis in bifidobacteria was discussed.     

Hybrids between tobacco crown gall cells and normal somatic cells of Atropa belladonna

Protoplast fusion of Nicotiana tabacum (B6S3) crown gall cells and Atropa belladonna leaf mesophyll cells was carried out. Hybrids were selected for their capacity to grow on hormone-free media and to green in light. Shoots incapable of rhizogenesis were regenerated on the same media and grafted onto normal plants of different species. 57 hybrid cell lines differing in their genetic constitution were produced. Analysis of hybrid lines involved the determination of the lysopine dehydrogenase (LpDH) activity and the molecular forms of esterase and amylase, a restriction analysis of chloroplast DNA and a cytogenetic study.Abbreviations LS-H Linsmaier and Skoog (1965) hormone-free medium - LpDH lysopine dehydrogenase     

Volume-dependent regulation of ion transport and membrane phosphorylation in human and rat erythrocytes

Summary Osmotic swelling of human and rat erythrocytes does not induce regulatory volume decrease. Regulatory volume increase was observed in shrunken erythrocytes of rats only. This reaction was blocked by the inhibitors of Na⁺/H⁺ exchange. Cytoplasmic acidification in erythrocytes of both species increases the amiloride-inhibited component of²²Na influx by five- to eight-fold. Both the osmotic and isosmotic shrinkage of rat erythrocytes results in the 10- to 30-fold increase of amiloride-inhibited²²Na influx and a two-fold increase of furosemide-inhibited⁸⁶Rb influx. We failed to indicate any significant changes of these ion transport systems in shrunken human erythrocytes. The shrinking of quin 2-loaded human and rat erythrocytes results in the two- to threefold increase of the rate of⁴⁵Ca influx, which is completely blocked by amiloride. The dependence of volume-induced²²Na influx in rat erythrocytes and⁴⁵Ca influx in human erythrocytes on amiloride concentration does not differ. The rate of⁴⁵Ca influx in resealed ghosts was reduced by one order of magnitude when intravesicular potassium and sodium were replaced by choline. It is assumed that the erythrocyte shrinkage increases the rate of a nonselective Ca _o ²⁺ (Na _i ⁺ , K _i ⁺ ) exchange. Erythrocyte shrinking does not induce significant phosphorylation of membrane protein but increases the³²P incorporation in diphosphoinositides. The effect of shrinkage on the³²P labeling of phosphoinositides is diminished after addition of amiloride. It is assumed that volume-induced phosphoinositide response plays an essential role in the mechanism of the activation of transmembrane ion movements.     

Characterization of a pollen-specific gene family from Brassica napus which is activated during early microspore development

In this paper we describe the isolation and characterization of a genomic clone (Bp4) from Brassica napus which contains three members of a pollen-specific multigene family. This family is composed of 10 to 15 closely related genes which are expressed in early stages of microspore development. The complete nucleotide sequence of the clone Bp4 and of three homologous cDNA clones is reported. One of the genes (Bp4B) contained in the genomic clone is believed to be non-functional because of sequence rearrangements in its 5 region and intron splicing sites. The remaining genes (Bp4A and Bp4C), as well as the cDNA clones, appear to code for small proteins of unique structure. Three different types of proteins can be predicted as a result of the deletion of carboxy or amino terminal portions of a conserved core protein. These proteins all share a common alternation of hydrophobic and hydrophilic domains. A fragment of the genomic clone containing the gene Bp4A, as well as the non-functional gene Bp4B, was introduced into tobacco plants via Agrobacterium-mediated transformation. The functional gene Bp4A is expressed in transgenic tobacco plants and shows spatial and temporal regulation consistent with the expression patterns seen in Brassica napus.     

Metabolic activities in germinated ancient lotus seeds

Seeds of Taizi lotus (Nelumbo nucifera Gaertn cv. Taizi) wereunearthed in a western suburb of Beijing in 1984, and determinedto be 58070-years-old by radiocarbon dating. Pretreatment withconcentrated sulphuric acid for 6 h promoted 75% of the seedstested to germinate. Over 3 weeks of incubation after the additionof water, storage starch, total soluble sugar and globulin inthe cotyledons decreased whereas albumin and soluble -aminonitrogen increased. These changes in cotyledonary componentswere similar to the changes seen in four present-day Indianlotus varieties, although the content of reducing sugar in Taizilotus was significantly lower. The polypeptide compositionsin extracts from the cotyledons and embryonic axis of Taiziseeds, as analysed by SDS-PAGE, were similar to those of present-dayJiangxi seeds. Taizi lotus also showed the ability to incorporateradioactive leucine into the trichloroacetic acid (TCA)-insolublefraction of a cotyledonary extract during the 24 h post-imbibitionperiod. The incorporation was inhibited when seeds of Taizilotus were allowed to rehydrate for 24 h in the presence of-amanitin or cycloheximide. Key words: Ancient lotus, Nelumbo nucifera, protein synthesis, seed germination, seed viability     

Production of (R)-1-phenylethanol through enantioselective oxidation of (S)-isomer from their racemic mixture by Pachysolen tannophilus IFO 1007

Summary Stereoselective oxidation of (S)-isomer of rac-1-phenylethanol (1-PA) by the yeast Pachysolen tannophilus IFO 1007 immobilized into calcium-alginate gels was investigated to produce (R)-isomer. Continuous production of (R)-isomer was accomplished for more than 80 h with an enantiomeric excess of > 90% using a bioreactor of a fluidized-bed type.     

A preliminary report on the use of transfer factor for treating stage D3 hormone-unresponsive metastatic prostate cancer

As conventional treatments are unsuccessful, the survival rate of stage D3 prostate cancer patients is poor. Reports have suggested the existence of humoral and cell-mediated immunity (CMI) against prostate cancer tumour-associated antigens (TAA). These observations prompted us to treat stage D3 prostate cancer patients with an in vitro produced transfer factor (TF) able to transfer, in vitro and in vivo, CMI against bladder and prostate TAA. Fifty patients entered this study and received one intramuscular injection of 2–5 units of specific TF monthly. Follow-up, ranging from 1 to 9 years, showed that complete remission was achieved in 2 patients, partial remission in 6, and no progression of metastatic disease in 14. The median survival was 126 weeks, higher than the survival rates reported in the literature for patients of the same stage.     

THE LASER TOMOGRAPHICAL METHOD USINGMINIMUM OF PROJECTION FOR BIOLOGICAL OBJECT STRUCTURE STUDY

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Effect of infusing branched-chain amino acid during incremental exercise with reduced muscle glycogen content

The aim of this study was to investigate whether, when muscle glycogen is reduced, a pre-exercise infusion of branched-chain amino acids (BCAA) modifies exercise performance or the metabolic and respiratory responses to incremental exercise. Six moderately trained volunteers took part in the following protocol on two occasions. On day 1, at 9 a.m. in the postabsorptive state, they performed a graded incremental exercise (increases of 35 W every 4 min) to exhaustion (Ex-1). A meal of 1,000 kcal (4,200 kJ; 60% protein, 40% fat) was consumed at 12 p.m. No food was then allowed until the end of the experiment (20–21 h later). A 90-min period of exercise at alternating high and moderate intensities, designed to deplete muscle glycogen, was performed between 6 p.m. and 7.30 p.m. The morning after (day 2), the subjects randomly received either a mixed solution of BCAA (260 mg × kg^–1 × h^–1 for 70 min), or saline. They then repeated the graded incremental exercise to exhaustion (Ex-2). Metabolic and respiratory measurements suggested a muscle glycogen-depleted state had been achieved. No significant differences were observed in total work performed, maximal oxygen uptake or plasma ammonia, alanine, and blood pyruvate concentrations in the two treatments. After BCAA infusion, higher blood lactate concentrations were observed at maximal power output in comparison with those during saline [BCAA 4.97 (SEM 0.41) mmol × l^–1, Saline 3.88 (SEM 0.47) mmol × l^–1,P < 0.05]. In summary, in conditions of reduced muscle glycogen content, after a short period of fasting, BCAA infusion had no significant effect on the total work that could be performed during a graded incremental exercise.