Effect of carbon sources on the synthesis of pectinase by Aspergilli

The synthesis of pectinase is investigated using six species of Aspergillus, with five media differing either in their carbon sources or level of carbon source(s). Five of the six species used, synthesized appreciable amounts of pectinase in the media containing sugars. Pectinase synthesis was highest for A. niger, NCIM 548, with all the sugar containing media. A. foetidus, NCIM 510, was the only one among the organisms studied, that responded well to the medium containing pectin in the absence of additional sugars supplied in the medium.     

Expression of plasmid-encoded aad in Clostridium acetobutylicum M5 restores vigorous butanol production.

Mutant M5 of Clostridium acetobutylicum ATCC 824, which produces neither butanol nor acetone and is deficient in butyraldehyde dehydrogenase (BYDH), acetoacetate decarboxylase, and acetoacetyl-coenzyme A:acetate/butyrate:coenzyme A-transferase activities, was transformed with plasmid pCAAD, which carries the gene aad (R. V. Nair, G. N. Bennett, and E. T. Papoutsakis, J. Bacteriol, 176:871-885, 1994). In batch fermentation studies, aad expression restored butanol formation (84 mM) in mutant M5 without any acetone formation or any significant increase in ethanol production. The corresponding protein (AAD) appeared as a ca. 96-kDa band in a denaturing protein gel. Expression of AAD in M5 resulted in restoration of BYDH activity and small increases in the activities of acetaldehyde dehydrogenase, butanol dehydrogenase, and ethanol dehydrogenase. These findings suggest that BYDH activity in C. acetobutylicum ATCC 824 resides largely in AAD, and that AAD's primary role is in the formation of butanol rather than of ethanol.     

Effects of Nerve Growth Factor on Glutathione Peroxidase and Catalase in PC 12 Cells

Abstract: Nerve growth factor (NGF) is a member of the neuro- trophin family and is required for the survival and maintenance of peripheral sympathetic and sensory ganglia. In the CNS, NGF regulates cholinergic expression by basal forebrain cholinergic neurons. NGF also stimulates cellular resistance to oxidative stress in the PC12 cell line and protects PC12 cells from the toxic effects of reactive oxygen species. The hypothesis that NGF protection involves changes in antioxidant enzyme expression was tested by measuring its effects on catalase and glutathione per- oxidase (GSH Px) mRNA expression in PC12 cells. NGF increased catalase and GSH Px mRNA levels in PC 12 cells in a time- and dose-dependent manner. There was also a corresponding increase in the enzyme activities of catalase and GSH Px. Thus, NGF can provide cytoprotection to PC12 cells by inducing the free radical scavenging enzymes catalase and GSH Px.     

Effects of Two Strains of Tobacco Mosaic Virus on Photosynthetic Characteristics and Nitrogen Partitioning in Leaves of Nicotiana tabacum cv Xanthi during Photoacclimation under Two Nitrogen Nutrition Regimes

Photoacclimation was studied in tobacco leaves (Nicotiana tabacum cv Xanthi) infected with two strains of tobacco mosaic virus (TMV) and grown under different light and nitrogen nutrition regimes. Photosynthetic acclimation measured by the quantum yield and the maximum rate in saturating light of CO2-saturated photosynthesis was impaired to a greater extent in tobacco leaves infected with TMV strain PV230 than in those infected with TMV strain PV42. Infection with TMV strain PV230 severely impaired photosynthetic acclimation at high light/low nitrogen and during transfer from low to high light. Expanding leaves showing chlorotic-mosaic symptoms had greatly reduced capacity to acclimate to high light compared with controls and with developed leaves without visible symptoms. We conclude that the failure of expanding leaves to acclimate was largely due to the destruction of chloroplasts in yellow areas of the tissue, accompanied by severe reduction in ribulose-1,5-bisphosphate carboxylase/oxygenase levels, and corresponding reduction in photosynthesis on a leaf-area basis. When corrected for areas of healthy green tissue, photoacclimation of infected leaves was the same as that of controls. Visible symptom development was greatest in high light/low nitrogen treatments. In developed leaves without visible symptoms, virus accumulation, which was as extensive as in expanding leaves, accelerated senescence and impaired photoacclimation during transfer from low light to high light. Generally, infection with TMV strain PV42 did not impair photosynthetic acclimation and even enhanced it in some treatments, even though virus accumulated to the same concentration as in PV230-infected leaves. These data show that TMV does not simply impair photoacclimation in tobacco by competing with chloroplasts for leaf nitrogen reserves. Rather, specific properties of severe strains, such as PV230, which lead to visible symptom development and patchy loss of photosynthetic activity in expanding leaves as well as general acceleration of chloroplast senescence in developed leaves, contribute to impaired photoacclimation, which is generally exacerbated by low nitrogen nutrition.     

Susceptibility of Tobacco Leaves to Photoinhibition following Infection with Two Strains of Tobacco Mosaic Virus under Different Light and Nitrogen Nutrition Regimes

Sensitivity to photoinhibition under high light stress (2000 [mu]mol photons m-2 s-1 for 2 h in air) and recovery from this stress were examined in leaves of control, uninfected tobacco (Nicotiana tabacum cv Xanthi) leaves and in leaves in tobacco plants infected with tobacco mosaic virus (TMV) when grown under low light (150-200 [mu]mol photons m-2 s-1) or high light (1200 [mu]mol photons m-2 s-1) with high (8.0 mM) or low (0.5 mM) nitrate supply. Photoinhibition was monitored using the dark-adapted fluorescence parameters variable fluorescence/maximum fluorescence, an indicator of photosynthetic efficiency that correlated well with the quantum yield of photosynthetic oxygen evolution, and initial fluorescence, potentially an indicator of photoinhibitory damage. Susceptibility to photoinhibition was greater in low light- and low nitrogen-grown control plants than in high light- or high nitrogen-treated plants. Compared with uninfected controls, infection with the masked strain PV42 increased susceptibility to photoinhibition only in plants grown under low light/low nitrogen conditions. In expanding leaves, infection with severe strain TMV PV230 markedly accelerated photoinhibition under these conditions and under high light/low nitrogen conditions, even before visible symptoms were evident. High nitrogen levels during growth protected against this accelerated photoinhibitory response to virus infection during light stress and generally promoted recovery, at least prior to symptom development. As symptoms developed, the yellow regions provided evidence for chronic photoinhibitory damage, prior to and during the stress treatment, irrespective of growth conditions. Green regions of leaves showing visible symptoms were generally indistinguishable from control, uninfected plants during photoinhibitory stress and recovery. In developed leaves that remained free of visible symptoms during the experiments, in spite of the accumulation of about the same amounts of virus protein (S. Balachandran, C.B. Osmond, A. Makino [1994] Plant Physiol 104: 1043-1050) infection led to an acceleration of photoinhibition during stress treatments, especially in low light/low nitrogen treatments, in which chronic photoinhibitory damage was evident. These studies suggest a role for photoinhibitory damage in the acceleration of visible symptom development following TMV PV230 infection of expanding leaves, as well as in acceleration of senescence in developed leaves without visible symptoms.     

Characterization and Plasmid Profile of Xanthomonas campestris pv. Glycines from Maharashtra, India

Xanthomonas campestris pv. glycines , (Xcg), the causative agent of the bacterial pustule disease of soybean was isolated and characterized. On susceptible soybean the pathogenic isolates displayed characteristic chlorotic lesions around the site of infection within 48 h of inoculation. The pathogenic isolates were found to contain two cryptic plasmids. A smaller plasmid of 1.5 kb and a larger one of size about 25 kb. SDS-PAGE profile of the soluble proteins of the pathogenic isolatess, howed a different pattern compared to that of the non-pathogenic isolates.     

Inhibition of Immune Complex-Induced Inflammation by A small Molecular Weight Selectin Antagonist

The anti-inflammatory effect of a small molecular weight antagonist of P- and E-selectin-dependent cell adhesion was examined. The glycolipid sulphatide was shown to block the adherence of thrombin-activated rat platelets to HL-60 cells. This interaction is known to be dependent on P-selectin. The rat dermal reverse passive Arthus reaction was used to assess the effect of sulphatide on a neutrophil dependent inflammatory response. Sulphatide dosedependently blocked both the vascular permeability increase and cell infiltration after intraperitoneal administration. These results show that a small molecular weight compound which blocks P- and E-selectin dependent adhesion in vitro can effectively block the inflammation due to immune complex deposition. A compound with this type of profile may have therapeutic potential in the treatment of immune complex mediated diseases.     

Cloning of ODAP Degrading Gene and Its Expression as Fusion Protein in Escherichia coli

A gene responsible for the degradation of ß-N-Oxalyl diaminopropionic acid (ODAP) was fused to the maIE gene, which codes for maltose binding protein, by cloning into an expression vector pMAL c2. The gene has been expressed as fusion protein of mol wt approximately 62 kD. It has been purified by affinity chromatography. The fusion protein has been cleaved by an endoprotease factor Xa and the presence of maltose binding protein and the product of the cloned gene confirmed. SDS-PAGE has shown that the product of the ODAP degrading gene is a single polypeptide of mol wt of about 20.7 kD.     

Epidemic isolates of Vibrio cholerae 0139 express antigenically distinct types of colonization pili

Abstract Vibrio cholerae belonging to the recently described serogroup 0139, which are responsible for the current cholera epidemics in India and Bangladesh, were shown to express pilus-like structures partially cross-reacting with the toxin-coregulated pilus of V. cholerae strain (0395) belonging to the 01 serogroup and classical biotype. The 0139 pili were composed of 20 kDa subunit proteins which were antigenically related to the 20 kDa pilus protein of another diarrhoeagenic non-01 V. cholerae strain (serogroup 034) isolated earlier. The pili described in this study were found to be involved in the intestinal colonization process and, therefore, may contribute towards the virulence of the 0139 epidemic isolates.     

Poliovirus-induced intracellular alkalinization involves a proton ATPase and protein phosphorylation

We reported previously that poliovirus infection induces alkalinization in HeLa cells and that an alkaline intracellular pH (pHi) promoted viral replication. Additional experiments were carried out to understand the underlying mechanism. Virus-infected or control monolayer cultures were incubated with nominally bicarbonate-free Eagle's minimal essential medium (MEM) buffered with N-2-hydroxyethylpiperazine-N-3-ethanesulfonic acid (HEPES), and immediately following preincubations, changes in pHi were monitored via benzoic acid uptake around 2 h postinfection. The absence of pH increase in cells infected with ultraviolet light-inactivated virus (UV-virus) indicated that viral gene expression was required for this effect. On the other hand, lack of effect of 3 mM guanidine, an inhibitor of poliovirus-specific RNA but not protein synthesis, suggested that translation of input viral genome RNA is sufficient for the pH increase. Activation of Na⁺/H⁺ exchange, Cl^?HCO^?₃ exchange, or H⁺-ATPase was considered as possible mechanisms by which alkalinization occurs in virus-infected cells. Na⁺/H⁺ exchange was excluded because the pH effect occurred in a Na⁺/H⁺ exchange deficient HeLa cell mutant. Similarly, Cl^?/HCO^?₃ exchange was excluded because virus-specific alkalinization was evident in the presence of Cl^? or bicarbonate deficient medium and was not associated with an increase in HCO^?₃ uptake or a decrease in Cl^? uptake. Lack of dependence on Na⁺, abrogation by 10 μM 7-chloro-4-nitrobenz-2-oxa-1,3-diazole (NBD-Cl), and resistance to 1 mM vandate suggested that this effect was due to the activation of a vacuolar-type (V) proton ATPase. Studies using protein kinase inhibitors indicated that activation of the ATPase in virus-infected cells probably involved protein kinase C-mediated phosphorylation. © 1993 Wiley-Liss, Inc.