Oxidative Protective Mechanisms and Resistance to the Dicarboximide Fungicide, Iprodione, in Alternaria alternata

The free radical scavengers α-tocopherol and butylated hydroxytoluene, but not ascorbate, diminished the growth-inhibiting effects of the dicarboximide fungicide, iprodione in Alternaria alternata. Growth of A. alternata in the presence of iprodione increased the activities of superoxide dismutase and glutathione reductase while catalase was unaffected. Four iprodione sensitive and four iprodione resistant isolates of A. alternata were compared for activity of free radical enzymes. The isolates of A. alternata resistant to iprodione had more catalase activity than those which were sensitive, but did not differ in superoxide dismutase of glutathione reductase, activities. 3-Amino-1.24.-triazole, a specific inhibitor of catalas, reduced the ability of DAR 69775, a dicarboximide resistant isolate of A. alternata. to grow in the presence of iprodione. In A. alternata dicarboximide resistance appeats to be at least partially mediated by enhanced activitiesof, catalase.     

L1 (LINE-1) retrotransposable elements provide a "fossil" record of the phylogenetic history of murid rodents

The single most difficult problem in phylogenetic analysis is deciding whether a shared taxonomic character is due to common ancestry or one that appeared independently due to convergence, parallelism, or reversion to an ancestral state. Mammalian L1 retrotransposons undergo periodic amplifications in which multiple copies of the elements are interspersed in the genome. Because these elements apparently are transmitted only by inheritance and are retained in the genome, a shared L1 amplification event can only be an inherited ancestral character. We propose that L1 amplification events can be an excellent tool for analyzing mammalian evolution and demonstrate here how we addressed several refractory problems in rodent systematics using L1 DNA as a taxonomic character.      

One short well conserved region of Alu-sequences is involved in human gene rearrangements and has homology with prokaryotic chi.

Alu elements have repeatedly been found involved in gene rearrangements in humans. Although these elements have been suggested to stimulate gene rearrangements, sparse information is available for the possible mechanism(s) of these events. Here we present a compilation of Alu elements that have been involved in recombinational events leading to gene rearrangements, indicating the presence of a common 26 bp core sequence at or close to the sites of recombination. Besides the obvious possibility of retrotransposition, gene rearrangements may be induced by sequences that stimulate genetic recombination. We suggest that the core sequence stimulates recombination and may thereby cause the frequent involvement of these elements in gene rearrangements. Curiously, the core sequence contains the pentanucleotide motif CCAGC, which is also part of chi, an 8 bp sequence known to stimulate recBC mediated recombination in Escherichia coli.     

The interaction of decorin core protein fragments with type I collagen.

To further define the molecular interaction between decorin and type I collagen we generated a 20 kD fragment containing the N-terminal half of the core protein by Endoproteinase Arg C digestion and a 40 kD fragment including all leucine-rich repeats in the central part of decorin core by cleavage with 2-nitro-5-thiocyanobenzoate. The fragments did not influence collagen fibril formation, even at high concentration, and radioactive fragments showed little binding to collagen fibrils. Our observations suggest that neither the N-terminal half nor the central leucine-rich repeats of the decorin core protein can, by itself, interact fully with fibrillar collagen.     

Characterization of the pH-mediated solubility of Bacillus thuringiensis var. san diego native delta-endotoxin crystals.

Native crystals of Bacillus thuringiensis var. san diego, a coleopteran-specific delta-endotoxin, were metabolically labelled with [35S]methionine. Specific activity was 82,000 CPM/micrograms (2.44 Ci/mmol). Using a universal buffer formulated with the same ionic strength at every pH, we determined that native crystals dissolve above pH 10 and below pH 4. At the acidic pH, the rate of solubilization was substantially slower than at the alkaline pH. Recrystallization rates for the toxin were similar regardless of solubilization conditions. The banding patterns in denatured polyacrylamide gel electrophoresis were unaffected by solubilization conditions. Toxicity was higher for soluble toxin compared to crystal toxin, but virtually identical for the acidic and alkaline produced solutions. Acid solubilization is significant because of the acidic midgut of susceptible Coleoptera.     

Modulation of transient type K channel cloned from rat heart.

We have cloned a transient type K channel from rat heart (RH10) and coexpressed a metabotropic glutamate receptor (mGluR5) to study the functional modulation of RH10 coupled to the phosphatidylinositol (PI) hydrolysis. Stimulation of mGluR5 suppressed peak amplitude of RH10 current and affected voltage dependence of activation and inactivation of the channel.     

Effect of coenzymes on the quaternary structure conformation of glyceraldehyde-3-phosphate dehydrogenases of mung beans and rabbit muscle.

Kinetics of thermal inactivation of glyceraldehyde-3-phosphate dehydrogenases of mung beans and rabbit muscle have been studied under different pH conditions in the absence and presence of various concentrations of NAD+ and NADH. The data have been discussed with respect to the effect of the coenzymes on the quaternary structure symmetry of the two enzymes and their binding isotherms. Both the (homo-tetrameric) apo-enzymes exhibit biphasic kinetics of thermal inactivation, characteristic of C2 symmetry, at lower pH values and a single exponential decay of enzyme activity, characteristic of D2 symmetry, at higher pHs. In each case, NAD+ has no effect on the biphasic kinetic pattern of thermal inactivation at lower pH values, but NADH brings about a change to single exponential decay. At higher pH values, NADH does not affect the kinetic pattern (single exponential decay) of any enzyme, but NAD+ alters it to biphasic kinetics in each case. The data suggest that NAD+ and NADH have higher affinity for the C2 and D2 symmetry conformation, respectively. With mung beans enzyme, the effect of NAD+ on the two rate constants of biphasic inactivation at pH 7.3 is consistent with a Kdiss equal to 110 microM. The NAD(+)-dependent changes in the kinetic pattern of thermal inactivation of this enzyme at pH 8.6 suggest a positive cooperativity in the coenzyme binding (nH = 3.0). In the binding of NADH to the mung beans enzyme, a weak positive cooperativity is observed at pH 7.3.(ABSTRACT TRUNCATED AT 250 WORDS)     

Bivariate flow cytometry of farm animal chromosomes: a potential tool for gene mapping

Bivariate flow karyotypes of chromosomes from sheep, cattle and pig lymphocytes and from a cattle-mouse somatic cell hybrid line were obtained using a dual laser fluorescence-activated cell sorter (FACS). Pig chromosomes were resolved into 19-20 peaks, indicating that most, if not all, pig chromosomes could be separated by this technique. Sheep chromosomes showed incomplete separation but three clear peaks, presumably representing the three large metacentric chromosomes, plus five other clusters were obtained. Cattle chromosomes showed poor separation but about four peaks could be distinguished, indicating that certain chromosomes could be sorted in this species. The use of cattle-mouse hybrids may enable other individual cattle chromosomes to be obtained. It is concluded that FACS separation will be a useful additional tool for gene mapping.     

Facile and stereoselective synthesis of 2'-5'-oligothioadenylate by UO2(2+) ion catalyst.

The synthesis and characterization of 2'-5'-oligothioadenylate by UO2(2+) ion catalyst are described. The polymerization of imidazole-activated thioadenylate or thioinosylate yielded oligomers containing mainly 2'-5'-internucleotidyl blond and Rp configuration at phosphorous atom.