β-Linked disaccharides stimulate,but do not act as primer for,β(1–3)glucan synthase activity ofNeurospora crassa

-Linked disaccharides (laminaribiose and cellobiose) stimulated(1–3)glucan synthase activity ofNeurospora crassa by reducing the K_{m app} for the substrate while not changing the V_max. Laminaribiose and cellobiose werelinear activators with a K_{a app} of 0.32 mM and K_{a app} of 1.7 mM, respectively. Laminaribiose was not found to be incorporated into product, i.e., did not act as a primer covalently bound to product.     

Permeabilization ofNeurospora crassa hyphae with toluene-ethanol and filipin

Young hyphae ofNeurospora crassa were made permeable to UDP-glucose and trypan blue by treatment with toluene-ethanol and filipin. Less than 2% of treated cells survived treatment with 8% and 16% toluene-ethanol, while 25% survived treatment with 4% toluene-ethanol. Similarly, 98% of treated cells were killed by treatment with 16 g/ml filipin. Electron microscopy revealed that toluene-ethanol-treated cells lost pieces of plasma membrane and contained a number of vacuole-like structures; filipin-treated cells were less affected. Both filipin- and toluene-ethanol-treated cells were able to incorporate UDP-glucose into insoluble material (likely glycogen and glucan).     

Viability of Cururbita pepo pollen: biophysical and structural data

During ageing of the short-lived pollen grains of Cucurbita pepo L., water loss was examined in relation to viability using biophysical (¹H-nuclear magnetic resonance, NMR) and cytological methods (fluorochromatic reaction test, freezefracture and scanning electron microscopy). A semi-logarithmic representation of the pollen weight loss demonstrated the complexity of the dehydration process. A the study of proton loss using ¹H-NMR indicated that two major releases water of had taken place, each with different flux rates. Pulse ¹H-NMR experiments showed the occurrene of non-exponential signal decay as a function of time, indicating the existence of different fractions of water in a pollen grain sample. These fractions leave the pollen grain at different times during pollen dehydration, and one of them (that of the so-called vital water) can be related to pollen viability. The quantity of protons giving a signal during pulse ¹H-NMR experiments was very low when the pollen grains were judged to be dead according to the fluorochromatic test. Freeze-fracture replicas of these dead pollen grains (less than 25% water content) showed that the plasma membrane had become detached from the intine surface; this ultrastructural feature might therefore be involved in the loss of pollen viability.Abbreviations A initial amplitude of the NMR signal - A₂ quantity of water charcterized by T_2-2 - A₅ quantity of water characterized by T_2–5 - FCR fluorochromatic reaction - NMR nuclear magnetic resonance - T₂ transverse relaxation time - T_2-2 T₂ measured with 2 ms between each pulse of radiofrequency - T_2–5 T₂ measured with 5 ms between each pulse of radiofrequency     

Effect of HCO - 3 concentration in the absorption solution on the energetic coupling of H+-cotransports in roots of Zea mays L.

The effect of HCO ₃ ^- on ion absorption by young corn roots was studied in conditions allowing the independent control of both the pH of uptake solution and the CO₂ partial pressure in air bubbled through the solution. The surface pH shift in the vicinity of the outer surface of the plasmalemma induced by active H⁺ excretion was estimated using the initial uptake rate of acetic acid as a pH probe (Sentenac and Grignon (1987) Plant Physiol. 84, 1367). Acetic acid and orthophosphate uptake rates and NO ₃ ^- accumulation were slowed down, while ⁸⁶Rb⁺ uptake and K⁺ accumulation rates were increased by HCO ₃ ^- . These effects were similar to those induced by 4-(2-hydroxyethyl)-1-piperazineethane sulfonic acid/2-amino-2-(hydroxymethyl)-1,3-propanediol (Hepes-Tris). They were more pronounced when the H⁺ excretion was strong, were rapidly reversible and were not additive to those of Hepes-Tris. The hypothesis is advanced that the buffering system CO₂/H₂CO₃/HCO ₃ ^- accelerated the diffusion of equivalent H⁺ inside the cell wall towards the medium. This attenuated the surface pH shift in the vicinity the plasma membrane and affected the coupling between the proton pump and cotransport systems.Abbreviations FW fresh weight - Hepes 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid - J_aa acetic acid influx - J_K ⁺ K⁺ influx - J_Pi orthophosphate influx - Mes 2-(N-morpholino)ethanesulfonic acid - pCO₂ CO₂ partial pressure - Tris 2-amino-2-(hydroxymethyl)-1,3-propanediol     

Production of alkaline phosphatase by immobilized growing cells of Escherichia coli excretory mutants

Summary In continuous cultures, alkaline phosphatase was synthesised and excreted for more than 250 h by immobilized growing cells in contrast to free cells for which the excretion decreased after 150 h of culture. This observed increase in alkaline phosphatase synthesis and excretion by immobilized cells may have resulted from growing conditions within the gel beads.Offprint requests to: C. Manin     

Molecular characterization of ataxia telangiectasia T cell clones

Summary To delimit the 14q32.1 recurrent breakpoint of ataxia telangiectasia clones, we performed an in situ hybridization study with various probes located on the 14q32 band. We thus mapped this breakpoint between the D14S1 and Pi loci. Furthermore, an interstitial duplication including D14S1 and a part of the IgH locus was demonstrated on a t(14;14) clone.     

Electron cytochemistry of mycobacteria: Evidence that strongly acidic sulfate groups are present on the surface of H37Rv (virulent) strain ofMycobacterium tuberculosis

Cytochemical characterization of mycobacterial surfaces was carried out on virulent (H37Rv) and avirulent (H37Ra) strains ofMycobacterium tuberculosis. The results were quantified and compared with those obtained with three colony types of the opportunistic pathogenMycobacterium avium. Mycobacterium aurum, a rapidly growing, nonpathogenic species, served as a model for the cytochemical methods. Concanavalin A (ConA) reacted with -d-mannose and -d-glucose residues, whereas negative charged residues were detected with either the ionized ferritin (CF) or the colloidal ferric hydroxide (CIH) method. Strongly acidic sulfate groups were detected by their selective blockage with alcian blue (AB) at pH 1 prior to the CIH labeling at pH 1.8. Weakly acidic groups were demonstrated by AB blockage at pH 2.5 prior to staining with CF stain. Except forM. aurum, all other strains showed a marked heterogeneity in regard to the abundance of their surface labeling. Accessible sulfate groups were present on the cell surface of the virulent H37Rv strain ofM. tuberculosis, but not on the avirulent strain H37Ra. Distribution of ConA receptors, on the other hand, was unrelated to the virulence or pathogenicity of the bacterial strain.     

Lampetra (Eudontomyzon) gracilis,a synonym of Eudontomyzon danfordi

Synopsis Evidence is presented which suggests that the nonparasitic lamprey, Lampetra (Eudontomyzon) gracilis Kux, 1965, is conspecific with the parasitic lamprey Eudontomyzon danfordi Regan, 1911. The diagnostic characters of the holotype and of the non-type material of E. gracilis are features found in E. danfordi specimens in their second and final year of adult life, thereby making the former a junior synonym of the latter.     

Properties of the 12-O-Tetradecanoylphorbol-13-Acetate-Stimulated S6 Kinase from Rat Astroglial Cells

The S6 kinase activity of astroglial cells in primary culture stimulated by 12-O-tetradecanoylphorbol-13-acetate (TPA) has been studied. This activity was eluted as a single peak at 0.15 M NaCl from a DEAE-Sephacel column. The chromatography of this peak on phosphocellulose revealed an activity eluted at 0.15 M NaCl. This partially purified enzyme had a sedimentation coefficient of 3.7S; Km values were 2 X 10(-5) M for ATP and 10(-6) M for 40S ribosomal subunits. The optimal Mg2+ concentration requirement was 2-3 mM. Mn2+ and Co2+ could substitute for Mg2+ (optimum concentrations 1.5 and 0.8 mM, respectively), but these cations were strong inhibitors in the presence of Mg2+. The enzyme was inhibited by N-ethylmaleimide, indicating that it contained thiol groups. This S6 kinase used ATP, but not GTP, as a phosphate donor, and exhibited great specificity for S6 as phosphate acceptor. Whole histones and protamine were slightly phosphorylated whereas phosvitin, histone H1, and surprisingly the peptide Arg-Arg-Leu-Ser-Ser-Leu-Arg-Ala were not phosphorylated. The TPA-stimulated S6 kinase resembles the insulin-, fibroblast growth factor- and cyclic AMP-stimulated enzymes, suggesting that several pathways might activate the same entity.