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181.
Eighteen German families with a history of paramyotonia congenita (PC) were characterised by genetic und mutational analysis at the SCN4A locus, which encodes the -subunit of the adult skeletal muscle sodium channel. We concentrated our analysis primarily on these families to test the hypothesis that a predominance of one common mutation occurs in all German PC families and that this mutation arose in a common ancestor originating in the North-West of the country. The present eighteen PC families exhibit two different mutations (R1448C and R1448H) on various SCN4A dinucleotide repeat haplotypes and therefore the majority of the mutations probably occurred independently. However, the R1448H mutation is extremely frequent in the North-West of Germany (Ravensberger Land) on a specific SCN4A microsatellite haplotype, indicating a founder effect within this subpopulation. Our results suggest that the R1448C/R1448H mutations are by far the most common to be associated with the PC phenotype in the German population.This paper is dedicated to Professor Dr. Dr. Peter Emil Becker on the occasion of this 85th birthday 相似文献
182.
Relationship between osmoprotection and the structure and intracellular accumulation of betaines by Escherichia coli 总被引:2,自引:0,他引:2
Barbara A. Peddie Michael Lever Colin M. Hayman Kelly Randall Stephen T. Chambers 《FEMS microbiology letters》1994,120(1-2):125-131
Abstract Naturally occuring betaines, especially glycine betaine and proline betaine, were accumulated by Escherichia coli from urine. In synthetic hyperosmotic medium, with an homologous series of added betaines, (CH3 )3 N+ -(CH2 ) n -COO− , osmoprotective activity and intracellular accumulation decreased monotonically as n increased from 1 to 5. In contrast, α -substituted glycine betaines were accumulated in a similar manner to glycine betaine, but with different osmoprotective activities. Arsenobetaine, with a quaternary arsonium group, was also accumulated but amino acids which can become negatively charged in a chemically basic environment were not. 相似文献
183.
The oxidative stress response in Bacillus subtilis 总被引:9,自引:0,他引:9
Barbara C.A. Dowds 《FEMS microbiology letters》1994,124(3):255-263
Abstract Bacillus subtilis undergoes a typical bacterial stress response when exposed to low concentrations (0.1 mM) of hydrogen peroxide. Protection is thereby induced against otherwise lethal, challenge concentrations (10 mM) of this oxidant and a number of proteins are induced including the scavenging enzymes, catalase and alkyl hydroperoxide reductase, and a putative DNA binding and protecting protein. Induced protection against higher concentrations (10–30 mM) of hydrogen peroxide is eliminated in a catalase-deficient mutant. Both RecA and Spo0A influence the basal but not the induced resistance to hydrogen peroxide. A regulatory mutation has been characterized that affects the inducible phenotype and is constitutively resistant to high concentrations of hydrogen peroxide. This mutant constitutively overexpresses the proteins induced by hydrogen peroxide in the wild-type. The resistance of spores to hydrogen peroxide is partly attributable to binding of small acid soluble proteins by the spore DNA and partly to a second step which coincides with the depletion of the NADH pool, which may inhibit the generation of hydroxyl radicals from hydrogen peroxide. 相似文献
184.
The nucleotide (nt) and deduced amino acid (aa) sequences were determined for polymorphic arylamine N-acetyl-transferase (NAT2) and its gene, NAT2, from homozygous rapid and slow acetylator congenic Syrian hamsters. The slow acetylator (NAT2s) allele contained three point mutations which differed from the rapid acetylator allele (NAT2r); two mutations were silent, and the third mutation resulted in a premature stop codon. The NAT2r allele contained a truncated open reading frame of 726 nt encoding a 242-aa protein, which is 48-aa shorter than NAT2r. 相似文献
185.
Kumar B. Reddy Barbara A. Hocevar Philip H. Howe 《Journal of cellular biochemistry》1994,56(3):418-425
Transforming growth factor β1 (TGFβ1) inhibits epithelial cell proliferation late in the G1 phase of the cell cycle. We examined the effect of TGFβ1 on known late G1 cell cycle regulators in an attempt to determine the molecular mechanism of growth inhibition by this physiological inhibitor. The results demonstrate the TGFβ1 inhibits the late G1 and S phase specific histone H1 kinase activity of p33cdk2. This inhibitiion is not dur to TGFβ1's effect on p33cdk2 synthesis, but rather due to its negative effect on the late G1 phosphorylation of p33cdk2. It is also shown that TGFβ1 inhibits both late G1 cyclin A and cyclin E associated histon H1 kinase activities. The inhibitor has no effects on the synthesis of cyclin E but to inhibit the synthesis of cyclin A protein in a cell cycle dependent manner. If TGFβ1 is added to cells which have progressed futher than 8 hours into G1, then it is without inhibitory effect on cyclin A synthesis. These effect on TGFβ1 on late G1 cell cycle regulators correlate well with its inhibitory effects on cellular growth and suggest that these G1 cyclin dependent kinases might serve as targets for TGFβ1-mediated growth arrest. 相似文献
186.
FemalePhoturis versicolor fireflies attempt to capture males by responding to heterospecific flash patterns. A mating-dependent switch occurs which affects response timing and frequency of female flashes. We examined the switch using females of known age, mating status, and flash experience to assess how accurate mimicry is, what factors influence it, and what mechanism produces it. Presentations of simulated male flash patterns before and after mating revealed elements of an entrainment mechanism controlling female responsiveness. Unmated females preferentially answered conspecific patterns with variable latencies, averaging 1 s. Mating induced changes in both response frequency and response latency: Females answered heterospecific patterns more frequently, and latencies elicited by conspecific patterns shifted away from the unmated range. Heterogeneity in mean and variance of response latency among individuals indicates that females do not share a discrete reply to a given pattern. Little correspondence exists between latencies of sympatric species andP. versicolor females, suggesting that the flash response mechanism produces entriainment to any rhythmic pattern, not a one-to-one matching between prey and predator latencies. Different selective scenarios underlie strict mimicry versus entrainment mimicry. 相似文献
187.
Barbara L. Randolph-Anderson John E. Boynton Nicholas W. Gillham Elizabeth H. Harris Anita M. Johnson Marie-Pierre Dorthu René F. Matagne 《Molecular & general genetics : MGG》1993,236(2-3):235-244
Summary The respiratory deficient dum-1 mutant of Chlamydomonas reinhardtii fails to grow in the dark because of a terminal 1.5 kb deletion in the linear 15.8 kb mitochondrial genome, which affects the apocytochrome b (CYB) gene. In contrast to the wild type where only mitochondrial genomes of monomer length are observed, the dum-1 genomes are present as a mixture of monomer and dimer length molecules. The mutant dimers appear to result from head-to-head fusions of two deleted molecules. Furthermore, mitochondrial genomes of dum-1 were also found to be unstable, with the extent of the deletion varying among single cell clones from the original mutant population. The dum-1 mutant also segregates, at a frequency of ca. 4% per generation, lethal minute colonies in which the original deletion now extends at least into the adjacent gene encoding subunit four of NAD dehydrogenase (ND4). We have used the dum-1 mutant as a recipient to demonstrate stable mitochondrial transformation in C. reinhardtii employing the biolistic method. After 4 to 8 weeks dark incubation, a total of 22 respiratory competent colonies were isolated from plates of dum-1 cells bombarded with C. reinhardtii mitochondrial DNA (frequency 7.3 × 10–7) and a single colony was isolated from plates bombarded with C. smithii mitochondrial DNA (frequency 0.8 × 10–7). No colonies were seen on control plates (frequency < 0.96 × 10–9). All transformants grew normally in the dark on acetate media; 22 transformants were homoplasmic for the wild-type mitochondrial genome typical of the C. reinhardtii donor. The single transformant obtained from the C. smithii donor had a recombinant mitochondrial genome containing the donor CYB gene and the diagnostic HpaI and XbaI restriction sites in the gene encoding subunit I of cytochrome oxidase (COI) from the C. reinhardtii recipient. The characteristic deletion fragments of the dum-1 recipient were not detected in any of the transformants. 相似文献
188.
189.
Identification of a nucleo-cytoplasmic ionic pathway by osmotic shock in isolated mouse liver nuclei
Summary The observation that the nuclear envelope outer mem brane contains ion channels raises the question of whether these conductances
communicate between the cytosol and the nuclear envelope cisternae or between the cytosol and the cytoplasm. Failure to detect
large, nonselective holes using the patch-clamp technique has led to the speculation that ion channels and nuclear pores are
in fact the same.
In this paper we present evidence that the ionic channel, recorded in isolated liver nuclei with the patch-clamp configura
tion of “nucleus-attached,” spans the double membrane of the envelope, providing a direct contact between nucleoplasm and
cytoplasm. 相似文献
190.
Abstract: A possible role for protein kinases in the regulation of free cytosolic Ca2+ levels in nerve endings was investigated by testing the effect of several kinase inhibitors on the increase in cytosolic Ca2+ (monitored with the Ca2+ -sensitive dye fura-2) induced by depolarization with 15 or 30 mM K+ . The ability of various drugs to inhibit the cytosolic Ca2+ response appeared to correlate with their reported mechanism of action in inhibiting protein kinases. W-7 and trifluoperazine, drugs reported to inhibit calmodulin-dependent events, were effective inhibitors of the increase in cytosolic Ca2+ induced by high K+ depolarization, as was sphingosine, a drug that inhibits protein kinase C by binding to the regulatory site, but which also inhibits calcium/calmodulin kinase. On the other hand, drugs that inhibit protein kinases by binding to the catalytic site, such as H-7 (1 m/W ), staurosporine (1μ M ), and K252a (1μ M ), were ineffective. Activation of protein kinase C, which is blocked by each of these drugs, does not appear to be essential to the maintenance of elevated cytosolic Ca2+ in depolarized synaptosomes. All of the drugs, including sphingosine, that functionally inhibit the depolarization-induced elevation in cytosolic Ca2+ have in common the ability to bind to calmodulin. Because the drugs that inhibit protein kinases by competing with ATP binding at the active catalytic site did not block the response in this system, we suggest that a calmodulin or a calmodulin-like binding site participates in the regulation of Ca2+ increases after depolarization. 相似文献