Isolation, structure elucidation and biological activities of trichofumins A, B, C and D, new 11 and 13mer peptaibols from Trichoderma sp. HKI 0276W.

Trichofumins A-D were isolated from cultures of Trichoderma sp. HKI 0276 as new 11 and 13mer peptaibols. Similar to 15mer peptaibols they promote morphogenesis of the fungus Phoma destructiva and cause hypothermia in mice as a characteristic of neuroleptic activity. Membrane measurements using a synthetic BLM model showed that A, B, C and D increased membrane permeability for cations in a similar manner as was shown for larger peptaibols but with comparably lower efficiency.     

Susceptibility to fluconazole and amphotericin B in clinical Candida isolates.

Susceptibility to fluconazole and amphotericin B in 84 clinical isolates of Candida was determined by a macrodilution method (NCCLS). Amphotericin B was very active (CMI < 1.25 microg/ml) against C. tropicalis and C. parapsilosis. Less than 5% of C. albicans and/or C. glabrata isolates presented low susceptibility to the drug (CMI 80 > 2.50 microg/ml). Fluconazole was less active against C. glabrata and C. krusei (CMI 80 > 100 microg/ml). The susceptibility profile for fluconazole indicated the importance to the treatment of identification to species level.     

Protection against activated oxygen following re-aeration of hypoxically pretreated wheat roots. The response of the glutathione system

This paper shows the effects of re-aeration on the glutathionepool following a prolonged period of root hypoxia. An increased content of total glutathione has been measuredin roots of wheat seedlings (Triticum aestivum L. cv. Alcedo),grown in a nitrogen-flushed nutrient solution (HI) with theirshoots in air compared with roots of aerobically grown plants(C). Re-aeration of hypoxically pretreated roots causes oxidativeinjury indicated by the oxidation of reduced glutathione (GSH),decrease of total thiol-groups and increased formation of TBAreactive material (lipid peroxidation). Re-admission of oxygen results in a 50% rise in oxygen uptakeover the whole 16 h re-aeration period compared with the control.During this time the overall glutathione pool of HI treatmentincreases to almost double that of the control, essentiallyreflected in the amount of oxidized glutathione (GSSG). Hypoxically pretreated roots showed lower glutathione reductaseactivity (GR) than the control. Immediately following re-aerationthe activity was further decreased to a limiting value whichseems to prevent full reduction of the newly formed glutathione.Therefore, the capacity to reduce the GSSG pool is below thecapacity for net glutathione synthesis. This results in a declineof the GSH/GSSG ratio which reflects oxidative stress. The enzymeactivity recovers slowly after re-aeration exceeding the valuesof aerobically grown roots only after 16 h correlating witha high reduction state of the glutathione pool. Copper, known to induce the formation of reactive oxygen species,strengthened the effect of re-aeration and enhanced the post-anoxicinjury irreversibly. The importance of the glutathione system in roots to cope withvarying oxygen tension is discussed. Key words: Hypoxia, re-aeration, glutathione system, glutathione reductase, wheat     

The Mutator Gene Swi8 Effects Specific Mutations in the Mating-Type Region of Schizosaccharomyces Pombe

The swi8(+) gene of Schizosaccharomyces pombe appears to be involved in the termination step of copy synthesis during mating-type (MT) switching. Mutations in swi8 confer a general mutator phenotype and, in particular, generate specific mutations in the MT region. Sequencing of the MT cassettes of the h(90) swi8-137 mutant revealed three altered sites. One is situated at the switching (smt) signal adjacent to the H1 homology box of the expression locus mat1:1. It reduces the rate of MT switching. The alteration at the smt signal arose frequently in other h(90) swi8 strains and is probably caused by gene conversion in which the sequence adjacent to the H1 box of mat2:2 is used as template. This change might be generated during the process of MT switching when hybrid DNA formation is anomalously extended into the more heterologous region flanking the H1 homology box. In addition to the gene conversion at mat1:1, two mutations were found in the H3 homology boxes of the silent cassettes mat2:2 and mat3:3.     

Ratios as a size adjustment in morphometrics

Simple ratios in which a measurement variable is divided by a size variable are commonly used but known to be inadequate for eliminating size correlations from morphometric data. Deficiencies in the simple ratio can be alleviated by incorporating regression coefficients describing the bivariate relationship between the measurement and size variables. Recommendations have included: 1) subtracting the regression intercept to force the bivariate relationship through the origin (intercept-adjusted ratios); 2) exponentiating either the measurement or the size variable using an allometry coefficient to achieve linearity (allometrically adjusted ratios); or 3) both subtracting the intercept and exponentiating (fully adjusted ratios). These three strategies for deriving size-adjusted ratios imply different data models for describing the bivariate relationship between the measurement and size variables (i.e., the linear, simple allometric, and full allometric models, respectively). Algebraic rearrangement of the equation associated with each data model leads to a correctly formulated adjusted ratio whose expected value is constant (i.e., size correlation is eliminated). Alternatively, simple algebra can be used to derive an expected value function for assessing whether any proposed ratio formula is effective in eliminating size correlations. Some published ratio adjustments were incorrectly formulated as indicated by expected values that remain a function of size after ratio transformation. Regression coefficients incorporated into adjusted ratios must be estimated using least-squares regression of the measurement variable on the size variable. Use of parameters estimated by any other regression technique (e.g., major axis or reduced major axis) results in residual correlations between size and the adjusted measurement variable. Correctly formulated adjusted ratios, whose parameters are estimated by least-squares methods, do control for size correlations. The size-adjusted results are similar to those based on analysis of least-squares residuals from the regression of the measurement on the size variable. However, adjusted ratios introduce size-related changes in distributional characteristics (variances) that differentially alter relationships among animals in different size classes. © 1993 Wiley-Liss, Inc.     

The two catalytic components of the 2-oxoglutarate dehydrogenase complex in rat cerebral synaptic and nonsynaptic mitochondria: Comparison of the response to in vitro treatment with ammonia,hyperammonemia, and hepatic encephalopathy

The effects of in vitro treatment with ammonium chloride, hepatic encephalopathy (HE) due to thioacetamide (TAA) induced liver failure and chronic hyperammonemia produced by i.p. administration of ammonium acetate on the two components of the multienzyme 2-oxoglutarate dehydrogenase complex (OGDH): 2-oxoglutarate decarboxylase (E1) and lipoamide dehydrogenase (E3), were examined in synaptic and nonsynaptic mitochondria from rat brain. With regard to E1 the response to ammonium ions in vitro (3 mM NH₄Cl) was observed in nonsynaptic mitochondria only and was manifested by a 21% decrease of Vmax and a 35% decrease of Km for 2-oxoglutarate (2-OG). By contrast, both in vivo conditions primarily affected the synaptic mitochondrial E1: TAA-induced HE produced an 84% increase of Vmax and a 38% increase of Km for 2-OG. Hyperammonemia elevated Vmax of E1 by 110% and Km for 2-OG by 30%. HE produced no effect at all in nonsynaptic mitochondria while hyperammonemia produced a 35% increase of Vmax and a 30% increase of Km for 2-OG of E1. Both in vivo conditions produced a 20% increase of E3 activity in synaptic mitochondria, but no effect at all in nonsynaptic mitochondria. The preferential sensitivity of E1 to ammonium chloride in vitro in nonsynaptic mitochondria and hyperammonemic conditions in vivo in synaptic mitochondria may play a crucial role in the compartmentation of OGDH responses under analogous conditions. These results confirm the intrinsic differences between the OGDH properties in the synaptic and nonsynaptic brain compartments.     

Molecular basis of streptomycin resistance in Mycobacterium tuberculosis: alterations of the ribosomal protein S12 gene and point mutations within a functional 16S ribosomal RNA pseudoknot

Multidrug-resistant strains of Mycobacterium tuberculosis have resulted in several recent outbreaks. Recognition of drug resistance is important both for treatment and to prevent further transmission. Here we use molecular biology techniques to study the basis of streptomycin resistance in single and multi-drug-resistant M. tuberculosis. We demonstrate that streptomycin resistance is associated with mutations implicated in ribosomal resistance. The mutations found either lead to amino acid changes in ribosomal protein SI2 or alter the primary structure of the 16S rRNA. The 16S rRNA region mutated perturbs a pseudoknot structure in a region which has been linked to ribosomal S12 protein.     

Chromosome G—banding in plants by inducing with trypsin and urea

Clear G-bands were revealed by applying the TUG method on chromosomes of 5 species of higher plants(Lilium davidii,Viciafaba,Hordeum vulgare,Ginkgo biloba and Triticum monococcum).Some details of the TUG method which consisted of treating chromosomes with both trypsin and urea were also studied.The mechanisms that might account for the presence of G-bands in plants were discussed.     

Effects of Light and Temperature on the Association between Zea mays and Spirillum lipoferum

Zea mays was grown on a low N nutrient solution under 16 conditions of light and temperature in a crossed-gradient room in an attempt to determine whether or not variation in climatic conditions influences N₂ fixation by the association between maize and Spirillum lipoferum. Temperatures were 28, 32, 36, and 40 C and 10 C lower at night; light intensities were 500, 1,250, 2,400, and 3,000 ft-c. Plants harvested after 94 days showed no significant benefit from association with S. lipoferum either in dry weight production or in total N content; variations in temperature and light had only a small influence on N₂ fixation under the conditions tested. Measurements of total N, together with designated assumptions, indicated that less than the equivalent of 0.5 kilogram of N was fixed/hectare during the entire growing period by the maize-S. lipoferum association. Rates of C₂H₂ reduction by replicate root samples generally were low and variable and did not correlate with the measurements of total N.