gltF, a member of the gltBDF operon of Escherichia coli, is involved in nitrogen-regulated gene expression

We report here the construction and analysis of insertional mutations in each of the three genes of the gltBDF operon and the nucleotide sequence of the region downstream from gltD. Two open reading frames were identified, the first of which corresponds to gltF. The gltB and gltD genes code for the large and small subunits, respectively, of the enzyme glutamate synthase (GOGAT). gltF codes for a protein, with a molecular mass of 26,350 Da, which is required for Ntr induction. Histidase synthesis was determined as a measure of Ntr function. First, insertions in gltB, gltD or gltF all prevent Ntr induction. Second, complementation analysis indicates that high-level expression of both the gltD and gltF genes is required for the induction of the Ntr enzymes under nitrogen-limiting conditions, indicating that the phenotype of the gltB insertion probably results from polarity on gltD and gltF. Third, glutamate-dependent repression of the glt operon appears to be mediated by the product of the gltF gene. Thus, the gltBDF operon of Escherichia coli is involved in induction of the so-called Ntr enzymes in response to nitrogen deprivation, as well as in glutamate biosynthesis.     

Biological control of Pythium damping‐off by seed‐treatment with pseudomonas putida: Relationship with ethanol production by pea and soybean seeds

The relationship between biocontrol activity of Pseudomonas putida strain N1R against Pythium ultimum on pea and soybean seeds and the reduction in ethanol evolution by imbibed seeds was investigated under different treatment conditions, including temperature and numbers of seed‐applied cells of the bacterium. Treatment with strain N1R increased emergence at all temperatures, except for soybean at 12 °C and reduced ethanol concentration in the spermosphere of imbibed seeds at several temperatures. The concentration of bacterial cells in the seed treatment suspension also significantly affected biocontrol efficiency and reduced ethanol production, especially in pea seeds. In contrast, the duration (0–7 h) of submergence of seeds in bacterial suspension had little effect on biocontrol activity of N1R, although submergence of soybean seeds reduced their emergence even in the absence of the pathogen or biocontrol agent. Competition for seed‐derived compounds, including ethanol, is suggested to be one possible mechanism of biocontrol of Pythium by strain N1R, which is not known to produce antifungal antibiotics.     

Glutamic acid decarboxylase of embryonic avian retina cells in culture: Regulation byγ-aminobutyric acid (GABA)

1. Retina-cell aggregate cultures expressed glutamate decarboxylase activity (L-glutamate 1-carboxylase; EC 4.1.1.15) as a function of culture differentiation. 2. Glutamic acid decarboxylase (GAD) activity was low in the initial phases of culture and increased eight-fold until culture day 7, remaining high up to day 13 (last stage studied). 3. The addition of GABA to the culture medium 24 h after cell seeding almost totally prevented the expression of GAD activity. 4. In association with decreased enzyme activity, aggregates exposed to GABA did not display immunoreactivity for GAD, suggesting that GAD molecules were either lost from GABAergic neurons or significantly altered with GABA treatment. 5. Control, untreated aggregates showed intense GAD immunoreactivity in neurons. Positive cell bodies were characterized by a thin rim of labeled cytoplasm with thickest labeling at the emergence of the main neurite. 6. Heavily labeled patches were also observed throughout the aggregates, possibly reflecting regions enriched in neurites. 7. The GABA-mediated reduction of GAD immunoreactivity was a reversible phenomenon and could be prevented by picrotoxin.     

An electron microscopy study of wall expansion during Candida albicans yeast and mycelial growth using concanavalin A-ferritin labelling of mannoproteins

Depending upon growth temperature, Candida albicans can exhibit two different morphologies, a budding yeast or a mycelium. By studying the distribution of concanavalin A-ferritin particles on the cell wall surface during bud and germ tube formation, we have elucidated the way cell wall extension occurs. Both processes initially require the localized lysis of the wall in order to allow the incorporation of the newly synthesized material. Later on, the cell wall behaves as an elastic structure, allowing extension by an intosusception process and, as a consequence, cell growth.Abbreviation Con A concanavalin A     

CFC syndrome: a syndrome distinct from Noonan syndrome

We report two children with a common pattern of birth defects. Both have very sparse, curly hair, nystagmus and mental retardation. The first one has Noonan syndrome habitus associated with keratosis plantaris and nystagmus; the second one has a slightly Noonan-like face, macrocephaly, keratosis pilaris, and hypertrophic cardiomyopathy. They represent the extreme of a spectrum of congenital defects recently reported independently as CFC syndrome by Reynolds and as "Noonan-like short stature syndrome with sparse hair" by Baraitser and Patton. The clinical features are reviewed and the autonomy of the syndrome with regards to Noonan syndrome, is disputed, since every sign seems to occur independently in Noonan syndrome. The father of the second case probably has a minor syndrome expression, pointing to probable autosomal dominant inheritance.     

A comparison of the effect of three fungicides on growth and roridin E production by Myrothecium roridum

Three fungicides, chlorothalonil, dichloran and mancozeb were studied to determine the effects on growth and production of roridin E by Myrothecium roridum in vitro. With increasing concentrations of fungicides, both growth and production of roridin E were inhibited. Of the three fungicides, chlorothalonil was much more effective in the inhibition of growth and production of roridin E, than dichloran and mancozeb.     

Morphological comparison ofSqualus blainvillei andS. megalops in the Eastern Atlantic,with notes on the genus

Morphological comparisons are made from the study of 64 specimens belonging to the following species:Squalus acanihias, S. blainvillei, S. megalops andS. acutirostris. The results suggest conspecificity betweenS. acutipinnis andS. megalops. The differences betweenS. blainvillei andS. megalops in the E-Atlantic are stressed. The Indo-Pacific species calledS. blainvillei by Chen et al. (1979) is regarded in this paper as probably an undescribed species. Some consideration on the status of several nominal species and the species grouping withinSqualus are also made.     

Histamine Stimulation of Cyclic AMP Accumulation in Astrocyte-Enriched and Neuronal Primary Cultures from Rat Brain

Histamine stimulates cyclic AMP accumulation in astrocyte-enriched and neuronal primary cultures from rat brain in the presence of the phosphodiesterase inhibitor isobutylmethylxanthine. The response in the astrocyte cultures (Emax = 304 +/- 44% over basal, EC50 = 43 +/- 5 microM) was much higher than in neuronal cultures (Emax = 24 +/- 2%, EC50 = 14 +/- 7 microM). The histamine effect in astrocytes was competitively inhibited by the H2 antagonists cimetidine (Ki = 1.1 +/- 0.2 microM) and ranitidine (Ki = 46 +/- 10 nM) but was insensitive to the H1 antagonist mepyramine (1 microM). The two selective H2 agonists impromidine and dimaprit behaved as partial agonists and showed relative potencies (139 and 0.5, respectively) consistent with an interaction with H2 receptors. The more selective H1 agonist 2-thiazolylethylamine (0.01-1 mM) did not potentiate the response to impromidine (10 microM). Thus, in contrast to what is generally observed in intact cell preparations from brain, the histamine-induced cyclic AMP accumulation in astroglial cells is mediated solely by H2 receptors. The small effect shown in neuronal cultures also appears to be mediated by H2 receptors.