Biochemical effects of pretreatment with vitamins E and C in rats submitted to intrastriatal hypoxanthine administration

We previously demonstrated that intrastriatal injection of hypoxanthine, the major metabolite accumulating in Lesch-Nyhan disease, inhibited Na+,K+-ATPase activity and induced oxidative stress in rat striatum. In the present study, we evaluated the action of vitamins E and C on the biochemical alteration induced by hypoxanthine administration on Na+,K+-ATPase, TBARS, TRAP, as well as on superoxide dismutase (SOD), catalase (CAT) and glutathione-peroxidase (GPx) activities in striatum of adult rats. Animals received pretreatment with vitamins E and C or saline during 7 days. Twelve hours after the last injection of vitamins or saline, animals were divided into two groups: (1) vehicle-injected group and (2) hypoxanthine-injected group. For all parameters investigated in this research, animals were sacrificed 30 min after drug infusion. Results showed that pretreatment with vitamins E and C prevented hypoxanthine-mediated effects on Na+,K+-ATPase, TBARS and antioxidant enzymes (SOD, CAT and GPx) activities; however the reduction on TRAP was not prevented by these vitamins. Although extrapolation of findings from animal experiments to humans is difficult, it is conceivable that these vitamins might serve as an adjuvant therapy in order to avoid progression of striatal damage in patients affected by Lesch-Nyhan disease.     

Antioxidant Effect of Cysteamine in Brain Cortex of Young Rats

Cysteamine is a cystine-depleting drug used in the treatment of cystinosis, a metabolic disorder caused by deficiency of the lysosomal cystine carrier. As a result, cystine accumulates within lysosomes in many tissues and organs, including the nervous system. Studies with cystine dimethyl ester loaded cells suggest that cystine might induce apoptosis through oxidative stress. Our objective was to investigate the effects of co-administration of cysteamine with the oxidant cystine dimethyl ester on several parameters of oxidative stress in the brain cortex of rats. Animals were injected with 1.6 μmol/g cystine dimethyl ester and/or 0.26 μmol/g body weight cysteamine. Cystine dimethyl ester induced lipoperoxidation, protein carbonylation, and stimulated superoxide dismutase, glutathione peroxidase and catalase activities, probably through the formation of free radicals. Cysteamine prevented those effects, possibly increasing cellular thiol pool and acting as a scavenger of free radicals. These results suggest that the antioxidant effect of cysteamine may be important in the treatment of cystinosis.     

The artiodactyl <Emphasis Type="Italic">APOBEC3</Emphasis> innate immune repertoire shows evidence for a multi-functional domain organization that existed in the ancestor of placental mammals

Background  

APOBEC3 (A3) proteins deaminate DNA cytosines and block the replication of retroviruses and retrotransposons. Each A3 gene encodes a protein with one or two conserved zinc-coordinating motifs (Z1, Z2 or Z3). The presence of one A3 gene in mice (Z2–Z3) and seven in humans, A3A-H (Z1a, Z2a-Z1b, Z2b, Z2c-Z2d, Z2e-Z2f, Z2g-Z1c, Z3), suggests extraordinary evolutionary flexibility. To gain insights into the mechanism and timing of A3 gene expansion and into the functional modularity of these genes, we analyzed the genomic sequences, expressed cDNAs and activities of the full A3 repertoire of three artiodactyl lineages: sheep, cattle and pigs.     

Intraspecific DNA sequence variation of the mitochondrial control region of white sturgeon (Acipenser transmontanus)

Intraspecific sequence variation in the D-loop region of mtDNA in white sturgeon (Acipenser transmontanus), a relict North American fish species, was examined in 27 individuals from populations of the Columbia and Fraser rivers. Thirty-three varied nucleotide positions were present in a 462-nucleotide D-loop sequence, amplified using the polymerase chain reaction. Bootstrapped neighbor-joining and maximum- parsimony trees of sequences from 19 haplotypes suggest that the two populations have recently diverged. This is consistent with the hypothesis that the Columbia River, a Pleistocene refugium habitat, was the source of founders for the Fraser River after the last glacial recession. On the basis of a divergence time of 10-12 thousand years ago, the estimated substitution rate of the white sturgeon D-loop region is 1.1-1.3 x 10(-7) nucleotides/site/year, which is comparable to rates for hypervariable sequences in the human D-loop region. Furthermore, the ratio of mean percent nucleotide differences in the D- loop (2.27%) to that in whole mtDNA (0.54%, as estimated from restriction-enzyme data) is 4.3, which is similar to the fourfold-to- fivefold-higher substitution rate estimated for the human D-loop. The high nucleotide substitution rate of the hypervariable region indicates that the vertebrate D-loop has potential as a genetic marker in molecular population studies.      

Meiotic crossing-over in nondisjoined chromosomes of children with trisomy 21 and a congenital heart defect.

We have used DNA polymorphisms to study meiotic crossovers of chromosome 21q in 27 nuclear families. Each family had a child with Down syndrome and a congenital heart defect. Twenty DNA polymorphisms on chromosome 21 were used to determine parental and meiotic origin of nondisjunction and to identify crossovers. Twenty-four cases were of maternal origin, and three were of paternal origin. Twenty-two unequivocal crossover events were identified. Sixteen crossovers were observed in 22 chromosome pairs nondisjoining at the second meiotic division. Fifty percent of crossover events in MI nondisjunction are detectable by molecular genetic means. Thus, the results suggest that, in this sample, each nondisjoined chromosome 21 pair has been involved in at least one crossover event.     

Neuromuscular modulation in Limulus by both octopamine and proctolin

Both octopamine and proctolin potentiate nerve-evoked skeletal muscle contractions in the horseshoe crab, Limulus. The threshold concentration for octopamine was 10^?9 to 10^?8M, while for proctolin it was 3 × 10^?9M. Norepinephrine and dopamine produced effects similar to octopamine but at higher thresholds; tyramine and serotonin were ineffective. Octopamine caused significant increases in amplitudes of excitatory postsynaptic potentials (epsps) of muscle fibers, but had little effect on muscle fiber input resistance or membrane potential. Also, octopamine did not affect depolarization of muscle fibers and subsequent contraction due to the direct action of exogenously applied glutamate. These results suggest that octopamine potentiates nerve-evoked contractions primarily by facilitating release of neuromuscular transmitter. At concentrations above 10^?7M, however, octopamine sometimes caused muscle spikes in response to motoneuron stimulation, a finding that suggests that octopamine may also have some postsynaptic action. Proctolin potentiated the muscle contractions evoked by glutamate but had little effect on glutamate-evoked muscle fiber depolarization, muscle fiber input resistance, or membrane potential. Thus, proctolin appears to act directly on skeletal muscle to enhance contractility. The proctolin-induced potentiations of contraction were sometimes accompanied by modest increases in epsp amplitude, so that unlike lobster skeletal and Limulus cardiac neuromuscular preparations, proctolin may have a secondary direct synaptic effect. Both octopamine and proctolin have been found in Limulus cardiac ganglion. This potential access to the hemolymph and the relatively low threshold concentrations needed for physiological action suggest that octopamine and proctolin could function as hormonal modulators of neuromuscular function in Limulus.     

Biosynthesis, translocation, and accumulation of betaine in sugar beet and its progenitors in relation to salinity

Like other halophytic chenopods, sugar beet (Beta vulgaris L.) can accumulate high betaine levels in shoots and roots. N,N,N-trimethylglycine impedes sucrose crystallization and so lowers beet quality. The objective of this research was to examine the genetic variability and physiological significance of betaine accumulation in sugar beet and its relatives. Three cultivated genotypes of B. vulgaris and two genotypes of the wild progenitor B. maritima L. were grown with and without gradual salinization (final NaCl concentration = 150 millimolar). At 6 weeks old, all five genotypes had moderately high betaine levels in shoots and roots when unsalinized (averages for all genotypes: shoots = 108 micromoles per gram dry weight; roots = 99 micromoles per gram dry weight). Salinization raised betaine levels of shoots and roots 2- to 3-fold, but did not greatly depress shoot or root growth. The genotype WB-167—an annual B. maritima type—always had approximately 40% lower betaine levels in roots than the other four genotypes, although the betaine levels in the shoots were not atypically low.

The site and pathway of betaine synthesis were investigated in young, salinized sugar beet plants by: (a) supplying 1 micromole [¹⁴C]ethanolamine to young leaf blades or to the taproot sink of intact plants; (b) supplying tracer [¹⁴C]formate to discs of leaf, hypocotyl, and taproot tissues in darkness. Conversion of both ¹⁴C precursors to betaine was active only in leaf tissue. Very little ¹⁴C appeared in the phospholipid phosphatidylcholine before betaine was heavily labeled; this was in marked contrast to the labeling patterns in salinized barley. Phosphorylcholine was a prominent early ¹⁴C metabolite of both [¹⁴C]ethanolamine and [¹⁴C]formate in all tissues of sugar beet. Betaine translocation was examined in young plants of sugar beet and WB-167 by applying tracer [methyl-¹⁴C]betaine to a young expanded leaf and determining the distribution of ¹⁴C after 3 days. In all cases, extensive ¹⁴C translocation to young leaves and taproot sink occurred; neither in the fed leaf nor in sink organs were any ¹⁴C metabolites of betaine detected.

     

Alkali Cation/Sucrose Co-transport in the Root Sink of Sugar Beet

The mechanism of sucrose transport into the vacuole of root parenchyma cells of sugar beet was investigated using discs of intact tissue. Active sucrose uptake was evident only at the tonoplast. Sucrose caused a transient 8.3 millivolts depolarization of the membrane potential, suggesting an ion co-transport mechanism. Sucrose also stimulated net proton efflux. Active (net) uptake of sucrose was strongly affected by factors that influence the alkali cation and proton gradients across biological membranes. Alkali cations (Na⁺ and K⁺) at 95 millimolar activity stimulated active uptake of sucrose 2.1- to 4-fold, whereas membrane-permeating anions inhibited active sucrose uptake. The pH optima for uptake was between 6.5 and 7.0, pH values slightly higher than those of the vacuole. The ionophores valinomycin, gramicidin D, and carbonyl cyanide m-chlorophenylhydrazone at 10 micromolar concentrations strongly inhibited active sucrose uptake. These data are consistent with the hypothesis that an alkali cation influx/proton efflux reaction is coupled to the active uptake of sucrose into the vacuole of parenchyma cells in the root sink of sugar beets.     

Allelic mutations in acetyl-coenzyme A carboxylase confer herbicide tolerance in maize

Summary The genetic relationship between acetyl-coenzyme A carboxylase (ACCase; EC 6.4.1.2.) activity and herbicide tolerance was determined for five maize (Zea mays L.) mutants regenerated from tissue cultures selected for tolerance to the ACCase-inhibiting herbicides, sethoxydim and haloxyfop. Herbicide tolerance in each mutant was inherited as a partially dominant, nuclear mutation. Allelism tests indicated that the five mutations were allelic. Three distinguishable herbicide tolerance phenotypes were differentiated among the five mutants. Seedling tolerance to herbicide treatments cosegregated with reduced inhibition of seedling leaf ACCase activity by sethoxydim and haloxyfop demonstrating that alterations of ACCase conferred herbicide tolerance. Therefore, we propose that at least three, and possible five, new alleles of the maize ACCase structural gene (Acc1) were identified based on their differential response to sethoxydim and haloxyfop. The group represented by Acc1-S1, Acc1-S2 and Acc1-S3 alleles, which had similar phenotypes, exhibited tolerance to high rates of sethoxydim and haloxyfop. The Acc1-H1 allele lacked sethoxydim tolerance but was tolerant to haloxyfop, whereas the Acc1-H2 allele had intermediate tolerance to sethoxydim but was tolerant to haloxyfop. Differences in tolerance to the two herbicides among mutants homozygous for different Acc1 alleles suggested that sites on ACCase that interact with the different herbicides do not completely overlap. These mutations in maize ACCase should prove useful in characterization of the regulatory role of ACCase in fatty acid biosynthesis and in development of herbicide-tolerant maize germplasm.Cooperative investigation of the Minnesota Agriculture Experiment Station and the U.S. Department of Agriculture, Agricultural Research Service. Supported in part by a grant from BASF Corporation and a University of Minnesota Doctoral Dissertation Fellowship to LCM. Minnesota Agricultural Experiment Station Publication No. 19,056Mention of a trademark, vendor, or proprietary product does not constitute a guarantee or warranty of the product by University of Minnesota or the USDA, and does not imply its approval to the exclusion of other products or vendors that may also be suitable