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.     

L-lysine production at 65°C by auxotrophic-regulatory mutants ofBacillus stearothermophilus

Summary The amino acid L-lysine was produced from auxotrophic-regulatory mutants ofBacillus stearothermophilus at a temperature of 60–65°C. One of the mutants (AEC 12 A5, S-(2-aminoethyl)-cysteine^r, homoserine^–), produced L-lysine at the concentration of 7.5 g/l in shaken flasks in minimal medium containing 5% glucose. Culture conditions for optimizing L-lysine production were not investigated. The aspartokinase activity of the wild strainB. stearothermophilus Zu 183 was inhibited by lysine alone and by threonine plus lysine. AEC resistant mutants showed an aspartokinase activity genetically desensitized to the feedback inhibition. Optimal temperature and pH of aspartokinase were 45°C and 9.5, respectively. The data provide significant evidence that mutants of the speciesB. stearothermophilus have a potential value for amino acid production.     

Aphyllophorales del Bosco della Mesola (Ferrara)

Abstract

Aphyllophorales from Mesola Forest (Ferrara) Italy—The present check-list is the first contribution to the knowledge of Aphyllophorales growing in the area of the Mesola Forest. The paper deals with 72 species of Aphyllophorales collected during the years 1980-1983. A further contribution will complete the picture of the Aphyllophorales flora which is particularly interesting and abundant in the forest.

Some of the species listed in the present paper are quite interesting since they are uncommon: Meruliopsis hirtellus and Oxyporus latemarginatus are new to Italy; Flaviporus semisupiniformis is the first European finding and the second world collection.     

A HERG current sustains a cardiac-type action potential in neuroblastoma S cells

From the adrenergic SH-SY5Y human neuroblastoma clone, we isolated a subclone (21S) endowed with a glial-oriented phenotype. At difference from the parental clone, 21S cells responded to depolarizing stimuli with overshooting action potentials, whose repolarization phase was composed of an initial rapid episode, followed by a long-lasting plateau and a slow return to the resting potential (V(REST)). The action potential depolarization phase was sustained by a TTX-sensitive Na(+) current, while the first repolarizing episode was produced by the scanty delayed rectifier potassium current (I(KDR)) expressed in 21S cells. The bulk of repolarization, including the after-hyperpolarization, was sustained by the human eag related (HERG) potassium current (I(HERG)) that also governs V(REST) in 21S cells. This double role of I(HERG), together with the poor expression of I(KDRs), represents a novel finding in electrophysiology, as well as gives a clue to identify a new excitable element of the complex cellular population of neuroblastoma.     

Pim-1 regulates cardiomyocyte survival downstream of Akt

The serine-threonine kinases Pim-1 and Akt regulate cellular proliferation and survival. Although Akt is known to be a crucial signaling protein in the myocardium, the role of Pim-1 has been overlooked. Pim-1 expression in the myocardium of mice decreased during postnatal development, re-emerged after acute pathological injury in mice and was increased in failing hearts of both mice and humans. Cardioprotective stimuli associated with Akt activation induced Pim-1 expression, but compensatory increases in Akt abundance and phosphorylation after pathological injury by infarction or pressure overload did not protect the myocardium in Pim-1-deficient mice. Transgenic expression of Pim-1 in the myocardium protected mice from infarction injury, and Pim-1 expression inhibited cardiomyocyte apoptosis with concomitant increases in Bcl-2 and Bcl-X(L) protein levels, as well as in Bad phosphorylation levels. Relative to nontransgenic controls, calcium dynamics were significantly enhanced in Pim-1-overexpressing transgenic hearts, associated with increased expression of SERCA2a, and were depressed in Pim-1-deficient hearts. Collectively, these data suggest that Pim-1 is a crucial facet of cardioprotection downstream of Akt.     

Physico-chemical characterization and transfection efficacy of cationic liposomes containing the pEGFP plasmid

Cationic liposomes-DNA complexes (lipoplexes) are largely used in gene delivery. Deciphering specific chemical and physical properties of lipoplexes is a necessary step to unravel the mechanisms underlying transfection and to improve transfection efficacy in each experimental model. In the present paper we investigated the physico-chemical features of lipoplexes containing a plasmid encoding for the GFP protein, in order to correlate these results with transfection efficacy. Cationic unilamellar vesicles (mean diameter 100 nm) were prepared, from the cationic DC-Chol lipid and the zwitterionic phospholipid DOPE. The two components of the liposome bilayer were used at molar ratio close to unity. ESR spectra were recorded and zeta potential zeta was measured on liposomes complexed with the plasmid. One of the main points of interest in this paper resided in the fact that both kinds of measurements were carried out in the same conditions (i.e. lipid concentration, medium composition, and pH) employed for cell transfection experiments. Transfection was performed on CHO cells; the percentage of fluorescent cells was evaluated and compared with the above physico-chemical features. It emerged that the composition and pH of the medium, the lipoplex/cell ratio, as well as the amount of lipoplex added to the cell culture were critical parameters for transfection efficacy. Finally, lipoplex surface charge played a fundamental role to achieve a high transfection level.     

Yeast Flora during the Fermentation of Wines Made from Vitis viniferaL. cv. Emir and Kalecik Karasi Grown in Anatolia

Summary A study was conducted of the growth of Saccharomyces (S.) and non-Saccharomyces populations during alcoholic fermentation of Emir and Kalecik karasi grape varieties in the 1998 and 1999 vintages. Kloeckera (Kl.) apiculata, Kluyveromyces (K.) thermotolerans, S. cerevisiae and Candida (C.) pulcherrima were the dominant yeasts in fermentation of the 1998 vintage in Emir must. Kl. apiculata and K. thermotolerans proliferated at the beginning of the fermentation. The number of these yeasts eventually decreased when S. cerevisiae appeared as the dominant yeast on day four. But they remained until the end of the fermentation. Kl. apiculata, C. dattilla, C. pulcherrima, C. krusei and S. cerevisiae were found during the fermentation of the 1999 vintage Emir must. The count of S. cerevisiae was very high in the juice, but after skin fermentation and cold treatment, it disappeared and could not be isolated until day six of the fermentation. Kl. apiculata and C. dattilla were the dominant yeasts until S. cerevisiae started proliferation after the middle of the fermentation. Kl. apiculata, Metschnikowia (M.) pulcherrima, S. cerevisiae, C. holmii, C. valida, C. guillermondii and Candida sp. were isolated during the fermentation of Kalecik karasi must in 1998. Kl. apiculata, C. pulcherrima, S. cerevisiae, C. holmii and C. valida were identified in fermentation of must in the 1999 vintage. An erratum to this article is available at .     

In vivo effects of dexamethasone on blood gene expression in ataxia telangiectasia

The effect of estrogens is mediated by activation of estrogen receptors (ERs). Because ER-α gene polymorphisms may exert different effects in childhood, we analyzed the associations between the IVS1 ?397T>C (PvuII) polymorphism and systemic inflammatory state, proangiogenic factors, frequency of monocyte subsets, lipid profile, blood pressure, and vascular complications in girls with type 1 diabetes mellitus (DM1). We examined 180 young girls with DM1 and 120 healthy age-matched controls. The analysis concerned PvuII polymorphism of the ER-α gene as well as the levels of serum inflammatory markers (CRP, IL-6, TNF-α), proangiogenic factors (VEGF, angiogenin), 17β-estradiol, values of monocyte subsets (CD14⁺⁺CD16^? and CD14⁺CD16⁺), lipid profile, and blood pressure. In our study, girls with CC genotype had lower level of inflammatory and angiogenic factors and lower frequencies of CD14⁺CD16⁺ monocytes in comparison to CT or TT carriers. Simultaneously, the CC carriers had a greater population of CD14⁺⁺CD16^? monocytes, increased blood pressure, and serum levels of: estrogen, total cholesterol, triglycerides, and low-density lipoprotein cholesterol than girls bearing CT or TT genotype. Our study suggests a pleiotropic effect of PvuII polymorphic CC variant on diabetic vasculopathies. Although the CC genotype carriers demonstrate less inflammatory and angiogenic activity, they seem to display less favorable cardiometabolic features. Based on our study, we cannot distinguish PvuII ER-α genotype that could be useful in identification of DM1 girls that are more prone to develop of late vascular complications, before the occurrence of first clinical symptoms.