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Biomedical subjects

G Wilcox

Publications and source records attributed to G Wilcox.

At least 55 records · Page 3Linked to original sources
PubMed1985

Evidence that polygalacturonase is a virulence determinant in Erwinia carotovora.

Polygalacturonase (PG) was purified from Erwinia carotovora EC. A hybrid cosmid, pSH711, that encodes PG activity but not pectate lyase activity was identified from an E. carotovora genomic library by an immunological screening method. A cell extract of Escherichia coli cells containing pSH711 was able to produce plant tissue maceration when spotted on carrot, potato, or turnip slices. In addition, the E. coli strain containing this plasmid was able to macerate carrot, potato, and turnip slices. Our results suggest that PG plays an important role in soft-rot disease.

Cloning, Molecular↗
PubMed1985

Laterality of cerebral function: relations with anxiety, repression, and perception.

Based on two factor analyses of data from 67 right-handed undergraduates, a laterality quotient based on forward memory spans, spatial minus digit, divided by their sum, was devised. The hemispheric balance factor for which this quotient served as the principal marker had significant positive loadings by the laterality quotient for the Edinburgh Handedness Questionnaire and by a measure of repressive tendencies, the Marlowe-Crowne Social Desirability Scale. Scores from this factor were positively related to global as opposed to analytic perception as measured by the Navon tachistoscopic task. This factor was unrelated to the trait anxiety and working short-term memory factors which also emerged. Trait anxiety was negatively related to global perception. The results raise the possibility that greater degrees of right-handedness may be related to the release of the nondominant right hemisphere from inhibition and that working short-term memory may not be lateralized.

Adult↗
PubMed1984

Regulation of the araC gene of Escherichia coli: catabolite repression, autoregulation, and effect on araBAD expression.

The araC gene encodes a positive regulatory protein required for L-arabinose utilization in Escherichia coli. Transcription from the araC promoter has been shown to be under positive control by cAMP receptor protein and under negative control by its protein product (autoregulation). This work describes the identification of the region of the araC promoter that interacts with the cAMP receptor protein to mediate catabolite repression. A 3-base-pair deletion centered 60 base pairs from the transcriptional initiation site results in a mutant araC promoter that, in the absence of araC protein, reduces transcriptional activity when compared with the wild-type promoter and is unresponsive to various concentrations of intracellular cAMP in vivo. The same deletion results in a lowered affinity of the araC promoter for cAMP receptor protein in vitro. However, this lowered affinity for the mutant araC promoter does not result in substantial reduction of intracellular araC protein because autoregulation of the araC gene dominates catabolite repression. The 3-base-pair deletion in the cAMP receptor protein binding site of the araC promoter does not affect catabolite repression of the adjacent araBAD operon. The implications of these results on current models for expression of the araBAD operon and the araC gene are discussed.

Arabinose↗
PubMed1984

Functional limits of the araIc promoter suggest an additional regulatory site for araBAD expression.

The araBAD promoter is defined, in part, by two types of cis-acting constitutive mutations, araIc at position -35 and araXc at position -10. Subcloning experiments demonstrated that the araIc and araIcXc promoters require DNA sequence information out to position -53 to -56 for maximum constitutive expression. This is 8 to 10 base pairs more DNA than is generally thought to be necessary for RNA polymerase interaction. The -53 to -56 region is required for glucose repression, suggesting that an additional factor interacts in this region and is necessary for maximum expression.

Arabinose↗
PubMed1984

Genetic characterization of Salmonella typhimurium LT2 ara mutations.

Seventeen independently isolated L-arabinose utilization-deficient mutants of Salmonella typhimurium LT2 were characterized. Four complementation groups (araA, araB, araC, and araD) were identified and were equivalent to the same genes in the ara system in Escherichia coli. The order of the four genes was determined to be araD-araA-araB-araC-leu. Two transcription units were found: the araBAD operon was transcribed counterclockwise, and the araC gene was transcribed clockwise.

Arabinose↗
PubMed1984

Positive control of the L-rhamnose genetic system in Salmonella typhimurium LT2.

A total of 28 L-rhamnose-negative mutants in Salmonella typhimurium LT2 were all linked by P22 transduction and were classified into five groups on the basis of genetic and biochemical experiments. Deletion mapping showed that the gene order was rhaD rhaA rhaB rhaC rhaT . rhaA mutants lacked an inducible L-rhamnose isomerase, rhaB mutants lacked an inducible L- rhamnulokinase , and rhaD mutants were probably defective in L- rhamnulose -1-phosphate aldolase. Mutants that were unable to accumulate L-[14C]rhamnose but could grow on 1% L-rhamnose were designated rhaT to indicate a defect in L-rhamnose transport. Genetic evidence supports the hypothesis that the rhaC gene is a positive regulator of rha gene expression. (i) Pleiotropically negative mutants in the rhaC gene were isolated at a high frequency. (ii) Mutants containing an insertion or deletion within the rhaC gene had a pleiotropically negative phenotype. (iii) Complementation tests indicated that rhaC + was dominant to rhaC -. (iv) Rha+ revertants of deletion and Tn10 insertion mutations in the rhaC gene were isolated.

Biological Transport↗
PubMed1983

Characterisation, experimental infection and serological response to caprine retrovirus.

A virus (151) isolated from synovial membrane explant cultures from a goat with arthritis-synovitis was characterised with respect to cytopathic effect in synovial membrane cell cultures, virus morphology, buoyant density and presence of RNA dependent DNA polymerase. Virus 151 was shown to be a retrovirus with similar properties to caprine arthritis-encephalitis virus in the United States of America. Inoculation of the virus into uninfected goats caused the development of arthritis-synovitis lesions and the virus was recovered from affected joints and lung 361 days post-inoculation. The development of antibody to virus 151 was detected using an enzyme linked immunosorbent assay (ELISA). Other goats with arthritis-synovitis, progressive pneumonia or viral leukoencephalomyelitis all had antibody that reacted in this ELISA. Viruses similar to virus 151 were recovered from a number of cases. Goats inoculated with one of the viruses produced serum antibody that cross-reacted in ELISA using maedi-visna virus and virus 151 as antigens.

Animals↗
PubMed1983

Effect of colostrum deprivation of goat kids on the natural transmission of caprine retrovirus infection.

An investigation was conducted to determine if depriving goat kids of colostrum and rearing them away from the herd would prevent transmission of caprine retrovirus infection. Twenty-four newborn goat kids were deprived of colostrum and reared on cow's milk away from their dams from an endemically infected goat herd. Twenty-three colostrum-deprived kids had no evidence of retrovirus infection at birth. One kid had sucked briefly and obtained some colostrum resulting in passive transfer of antibody but it did not develop evidence of infection. Nineteen showed no serological evidence of infection over the 370 days of the study. One colostrum-deprived, segregated goat was subsequently found to be infected and developed arthritis-synovitis. Three had doubtful positive response in one or 2 serological tests during the period but no evidence of infection in leucocyte co-cultures. Cells centrifuged from colostrum of infected goats were co-cultivated with foetal goat synovial membrane cultures. Caprine retrovirus was isolated from cells in the colostrum from the 3 goats examined.

Animals↗
PubMed1983

Five mutations in the promoter region of the araBAD operon of Escherichia coli B/r.

Five mutations that result in reduced expression of the araBAD operon were cloned onto the plasmid pBR322. The position of each mutation was determined by DNA sequence analysis. Three of the mutations were located in the RNA polymerase binding site of the araBAD promoter. The first, ara-1016, was a one-base-pair deletion at position -35; the second, ara-1036, was a transversion at position -13; the third, ara-1027, was a nine-base-pair deletion from +5 to +13. S1 nuclease mapping showed that mutations ara-1016 and ara-1036 greatly reduced transcription and that mutation ara-1027 had little, if any, effect on transcription. Two other mutations resulted from the transposition of the insertion element, IS1, downstream from the transcriptional start site of the operon. Molecular mechanisms for all of the mutations are discussed.

Arabinose↗
PubMed1982

Regulation of L-arabinose transport in Salmonella typhimurium LT2.

The inducible L-arabinose transport system was characterized in Salmonella typhimurium LT2. Only one L-arabinose transport system with a Km of 2 X 10(-4) M was identified. The results suggested that araE may be the only gene which codes for L-arabinose transport activity under the conditions tested. An araE-lac fusion strain was used to study the induction of the araE gene. No araE expression was detected when the L-arabinose concentration was lower than 1 mM. The expression of araE reached a maximum in the presence of 50 mM L-arabinose, and was significantly reduced in the presence of 50 mM L-arabinose, and was significantly reduced in the presence of D-glucose. Expression of the araBAD and araE genes was coordinately regulated. The concentration of L-arabinose that allowed maximum araBAD gene expression was 50-fold lower in an araE+ strain compared to an araE strain.

Arabinose↗
PubMed1982

Tail pinch behavior and analgesia in diabetic mice.

Mild tail pinch induced "consummatory" behaviors in mice. The major tail pinch behavior appeared to be chewing with food ingestion occurring possibly as an epiphenomenon. All tail pinch behaviors were obliterated by the dopamine antagonist haloperidol; and the opiate antagonist, naltrexone, decreased eating without altering chewing. The combination of dopamine blockade and tail pinch induced jumping behavior in mice. Diabetic mice showed increased tail flick latencies to radiant heat and to the induction of tail pinch behaviors, displaying these behaviors less commonly than their homozygote and heterozygote littermate controls.

Animals↗
PubMed1982

The use of synthetic oligodeoxyribonucleotides to produce specific deletions in the araBAD promoter of Escherichia coli B/r.

Two oligodeoxyribonucleotides were chemically synthesized and used to specifically mutate the regulatory region of the araBAD operon in Escherichia coli B/r. One oligodeoxyribonucleotide introduced a 3-bp deletion in the araC activator binding site, the other a 3-bp deletion in the CRP-cAMP binding site. The mutations were introduced onto an ara insert cloned in an M13 vector using the synthetic oligodeoxyribonucleotides as primers and the (+) strand of an M13 mp2::ara hybrid phage as a template in an in vitro polymerization reaction. Hybridizations using the original synthetic oligodeoxyribonucleotide as a radioactive probe identified phage containing the desired deletion. The mutant ara inserts were subcloned into a stable plasmid for functional analysis. Transcription studies performed on strains containing the mutant ara plasmids demonstrated that both mutations reduced the amount of araBA mRNA synthesized in the presence of L-arabinose.

Arabinose↗
PubMed1982

The nucleotide sequence of the araC regulatory gene in Salmonella typhimurium LT2.

The nucleotide sequence of the araC regulatory gene of Salmonella typhimurium LT2 has been determined. This sequence and the predicted araC translational product are compared to their counterparts in Escherichia coli. The two genes code for similar products although the S. typhimurium protein is eleven amino acids shorter than the E. coli protein. The predicted amino acid sequences are 92% conserved and the DNA sequences are 82% conserved for the common regions of the two genes.

Amino Acid Sequence↗
PubMed1981

DNA sequence of the araBAD-araC controlling region in Salmonella typhimurium LT2.

The araB and araC genes of Salmonella typhimurium have been cloned onto the plasmid pBR322. Restriction analysis and subcloning of restriction fragments localized these genes to a 4.4 kb DNA fragment. Complementation analysis revealed that the cloned araB and araC genes from S. typhimurium complemented araB and araC mutant strains of escherichia coli. Conversely, cloned araB and araC genes from E. coli complemented araB and araC mutant strains of Escherichia coli. Conversely, cloned araB and araC genes from E. coli complemented araB and ara C mutant strains of S. typhimurium. The DNA sequence was determined for the S. typhimurium araB and araC controlling region and for the initially translated portions of these genes. The nucleotide sequence of the araB promoter was 87% homologous with the same region in E. coli and contained no deletions or insertions relative to the E. coli sequence. The presumed AUG codon corresponding to the amino terminus of the S. typhimurium araC protein was in the same location as in E. coli. There was, however, considerable divergence for the E. coli sequence preceding the translation start site. The nucleotide sequence of the initial 237 bp in the open reading frame of the S. typhimurium araC gene was 78% homologous with the same sequence in E. coli. By comparison, the amino acid sequence for this region was 91% conserved.

Arabinose↗
PubMed1981

Characterization of a site-specific restriction endonuclease from Streptomyces aureofaciens.

A new type II sequence-specific restriction endonuclease, SauI, was isolated from Streptomyces aureofaciens IKA18/4. The purified enzyme was free of contaminating exonuclease and phosphatase activities. SauI cleaved lambda DNA at two sites, but did not cleave pBR322, simian virus 40, or phi X174 DNA. SauI recognized the septanucleotide sequence 5'-CCTNAGG-3' and cleaved at the position indicated by the arrow, producing a trinucleotide 5'-terminal extension.

Base Sequence↗
PubMed1981

Genetic characterization of the araE gene in Salmonella typhimurium lt2.

Six L-arabinose transport-deficient mutants of Salmonella typhimurium LT2 were isolated on the basis of their inability to ferment low concentrations of L-arabinose. The mutations were localized between serA and lys on the S. typhimurium genetic map and assigned to the araE locus. An araE-lac fusion strain was constructed and used to determine that the direction of araE transcription was counterclockwise on the S. typhimurium genetic map. beta-Galactosidase activity was induced by L-arabinose in the araE-lac fusion strain, suggesting that araE expression is controlled at the level of transcription.

Arabinose↗
PubMed1981

The araIc mutation in Escherichia coli B/r.

The araIc allele is a cis-acting mutation which has been used to define the araBAD promoter in Escherichia coli B/r. Nineteen araIc mutants were originally isolated by Englesberg and co-workers as Ara+ "revertants" of an araC deletion mutant (Englesberg et al. J. Mol. Biol. 43:281-298, 1969). The mutants constitutively expressed araBAD gene products in the absence of functional araC activator protein. Eight of the araIc mutations have been cloned by in vivo recombination onto pBR322-ara hybrid plasmids. Restriction and DNA sequence analysis of these araIc mutations showed that they result from a single base-pair change located at -35 in the araBAD promoter.

Aldose-Ketose Isomerases↗