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Biomedical subjects

H George

Publications and source records attributed to H George.

At least 19 recordsLinked to original sources
PubMed2000

RuvAB-mediated branch migration does not involve extensive DNA opening within the RuvB hexamer.

The Escherichia coli RuvA and RuvB proteins promote the branch migration of Holliday junctions during the late stages of homologous recombination and DNA repair (reviewed in [1]). Biochemical and structural studies of the RuvAB-Holliday junction complex have shown that RuvA binds directly to the Holliday junction [2] [3] [4] [5] [6] and acts as a specificity factor that promotes the targeting of RuvB [7] [8], a hexameric ring protein that drives branch migration [9] [10] [11]. Electron microscopic visualisation of the RuvAB complex revealed that RuvA is flanked by two RuvB hexamers, which bind DNA arms that lie diametrically opposed across the junction [8]. ATP-dependent branch migration occurs as duplex DNA is pumped out through the centre of each ring. Because RuvB possesses well-conserved helicase motifs and RuvAB exhibits a 5'-3' DNA helicase activity in vitro [12], the mechanism of branch migration is thought to involve DNA opening within the RuvB ring, which provides a single strand for the unidirectional translocation of the protein along DNA. We have investigated whether the RuvB ring can translocate along duplex DNA containing a site-directed interstrand psoralen crosslink. Surprisingly, we found that the crosslink failed to inhibit branch migration. We interpret these data as evidence against a base-by-base tracking model and suggest that extensive DNA opening within the RuvB ring is not required for DNA translocation by RuvB.

Adenosine Triphosphate↗
PubMed2000

Evidence for transmission of pertussis in schools, Massachusetts, 1996: epidemiologic data supported by pulsed-field gel electrophoresis studies.

In 1996, 18 of 20 pertussis outbreaks reported in Massachusetts occurred in schools. Pertussis surveillance data were reviewed and a retrospective cohort study was conducted in a high school that experienced an outbreak. Bordetella pertussis isolates from 9 school cases and from 58 cases statewide were examined by use of pulsed-field gel electrophoresis (PFGE). Statewide incidence rates were highest among children aged <1 year, 10-14 years, and 15-19 years (106, 117, and 104 cases per 100,000, respectively). Among 34 confirmed and 20 probable cases at the school, 61% had cough onset within 8 weeks of school opening. Five different PFGE types were identified among the 58 B. pertussis isolates from throughout the state. All 9 isolates from the affected high school were the same PFGE type. School-aged children may play an important role in pertussis epidemics. Consideration should be given to use of acellular pertussis vaccines among school-aged children.

Adolescent↗
PubMed2000

Recovery of Bordetella holmesii from patients with pertussis-like symptoms: use of pulsed-field gel electrophoresis to characterize circulating strains.

A 4-year retrospective study showing that we isolated Bordetella holmesii, but not Bordetella pertussis, from patients with pertussis-like symptoms was performed. From 1995 through 1998, we isolated B. holmesii from 32 nasopharyngeal specimens that had been submitted from patients suspected of having pertussis. Previously, B. holmesii had been associated mainly with septicemia and was not thought to be associated with respiratory illness. A study was undertaken to describe the characteristics of the B. holmesii isolates recovered and why we were successful in detecting the organism in nasopharyngeal specimens. B. holmesii isolates were characterized for drug sensitivities and for genetic relatedness by pulsed-field gel electrophoresis (PFGE). These isolates, an additional strain of B. holmesii isolated from a blood culture and previously confirmed by the Centers for Disease Control and Prevention, Atlanta, Ga., and 14 other clinical isolates of Bordetella spp., including 4 of B. bronchiseptica, 5 of B. parapertussis, and 5 of B. pertussis, were studied. They were all separately inoculated on three Bordet Gengou (BG) selective media containing either 0.625 microgram of oxacillin per ml, 40 microgram of cephalexin per ml, or 2.5 microgram of methicillin per ml, on BG agar with no antibiotic (control), and on charcoal agar (CA) with and without 40 microgram of cephalexin per ml. We found that cephalexin, the antibiotic commonly incorporated in both CA and BG agar for the recovery of Bordetella spp., is inhibitory to the growth of B. holmesii. In addition, the genotypic analysis of the 32 B. holmesii isolates by PFGE following restriction with XbaI and SpeI identified the dominant strains circulating during the study period.

Bacterial Typing Techniques↗
PubMed1999

Helicase-defective RuvB(D113E) promotes RuvAB-mediated branch migration in vitro.

In Escherichia coli, the RuvA and RuvB proteins interact at Holliday junctions to promote branch migration leading to the formation of heteroduplex DNA. RuvA provides junction-binding specificity and RuvB drives ATP-dependent branch migration. Since RuvB contains sequence motifs characteristic of a DNA helicase and RuvAB exhibit helicase activity in vitro, we have analysed the role of DNA unwinding in relation to branch migration. A mutant RuvB protein, RuvB(D113E), mutated in helicase motif II (the DExx box), has been purified to homogeneity. The mutant protein forms hexameric rings on DNA similar to those formed by wild-type protein and promotes branch migration in the presence of RuvA. However, RuvB(D113E) exhibits reduced ATPase activity and is severely compromised in its DNA helicase activity. Models for RuvAB-mediated branch migration that invoke only limited DNA unwinding activity are proposed.

Adenosine Triphosphatases↗
PubMed1999

Purification and cloning of aggrecanase-1: a member of the ADAMTS family of proteins.

We purified, cloned, and expressed aggrecanase, a protease that is thought to be responsible for the degradation of cartilage aggrecan in arthritic diseases. Aggrecanase-1 [a disintegrin and metalloproteinase with thrombospondin motifs-4 (ADAMTS-4)] is a member of the ADAMTS protein family that cleaves aggrecan at the glutamic acid-373-alanine-374 bond. The identification of this protease provides a specific target for the development of therapeutics to prevent cartilage degradation in arthritis.

ADAM Proteins↗
PubMed1999

Escherichia coli RuvBL268S: a mutant RuvB protein that exhibits wild-type activities in vitro but confers a UV-sensitive ruv phenotype in vivo.

The RuvABC proteins of Escherichia coli process recombination intermediates during genetic recombination and DNA repair. RuvA and RuvB promote branch migration of Holliday junctions, a process that extends heteroduplex DNA. Together with RuvC, they form a RuvABC complex capable of Holliday junction resolution. Branch migration by RuvAB is mediated by RuvB, a hexameric ring protein that acts as an ATP-driven molecular pump. To gain insight into the mechanism of branch migration, random mutations were introduced into the ruvB gene by PCR and a collection of mutant alleles were obtained. Mutation of leucine 268 to serine resulted in a severe UV-sensitive phenotype, characteristic of a ruv defect. Here, we report a biochemical analysis of the mutant protein RuvBL268S. Unexpectedly, the purified protein is fully active in vitro with regard to its ATPase, DNA binding and DNA unwinding activities. It also promotes efficient branch migration in combination with RuvA, and forms functional RuvABC-Holliday junction resolvase complexes. These results indicate that RuvB may perform some additional, and as yet undefined, function that is necessary for cell survival after UV-irradiation.

Adenosine Triphosphatases↗
PubMed1998

Coordinated actions of RuvABC in Holliday junction processing.

The RuvA, RuvB and RuvC proteins of Escherichia coli process Holliday junctions during genetic recombination and DNA repair. Biochemical studies have shown that RuvA and RuvB promote branch migration whereas RuvC resolves junctions by endonucleolytic cleavage. Here we show that RuvAB stimulate Holliday junction resolution by RuvC. Elevated RuvC activity was dependent upon RuvAB-mediated ATP-hydrolysis. These results show that the three Ruv proteins work in a coordinated manner to promote Holliday junction resolution, and account for the resolvase-defective phenotype exhibited by ruvA, ruvB or ruvC mutant strains.

Adenosine Triphosphate↗
PubMed1998

Pulsed-field gel electrophoresis of genomic digests demonstrates linkages among food, food handlers, and patrons in a food-borne Salmonella javiana outbreak in Massachusetts.

A total of 66 isolates of Salmonella javiana isolated from food, food handlers, and patrons that were epidemiologically linked to an outbreak of gastroenteritis were analyzed by pulsed-field gel electrophoresis. Analysis with restriction endonucleases XbaI and SpeI supported the epidemiologic association and suggested a pathway of transmission among food, food handlers, and patrons.

DNA, Bacterial↗
PubMed1997

The vrille gene of Drosophila is a maternal enhancer of decapentaplegic and encodes a new member of the bZIP family of transcription factors.

We report here the genetical and molecular characterization of a new Drosophila zygotic lethal locus, vrille (vri). Vri alleles act not only as dominant maternal enhancers of embryonic dorsoventral patterning defects caused by easter and decapentaplegic (dpp) mutations, but also as dominant zygotic enhancers of dpp alleles for phenotypes in wing. The vri gene encodes a new member of the bZIP family of transcription factors closely related to gene 9 of Xenopus laevis, induced by thyroid hormone during the tadpole tail resorption program, and NF-IL3A, a human T cell transcription factor that transactivates the interleukin-3 promoter. NF-IL3A shares 93% similarity and 60% identity with Vri for a stretch of 68 amino acids that includes the bZIP domain. Although all the alleles tested behave like antimorphs, the dominant enhancement is also seen with a nonsense mutation allele that prevents translation of the bZIP domain. Because of the strong domainant enhancement of dpp phenotypes by vri alleles in both embryo and wing, and also the similarity between the wing vein phenotypes caused by the vri and shortvein dpp alleles, we postulate that vri interacts either directly or indirectly with certain components of the dpp (a TGF beta homologue) signal transduction pathway.

Alleles↗
PubMed1992

Effects of selenium supplementation in cattle on aquatic ecosystems in northern California.

The potential impact on aquatic ecosystems of supplementing the diets of beef cattle with selenium (Se) was studied on 4 northern California ranches. All study sites included an area of concentrated use by cattle that had diets supplemented with Se. In each case, a stream flowed through the site and provided a control sampling area upstream and a treated sampling area downstream. Specimens of water, sediment, algae, aquatic plants, aquatic invertebrates, and fish were analyzed fluorometrically for total Se content. Significant differences in Se concentration were not found between specimens from upstream control areas and those from downstream areas subjected to use by Se-treated cattle. Evidence was not found that Se supplementation in cattle at maximal permitted concentrations caused Se accumulation in associated aquatic ecosystems.

Analysis of Variance↗
PubMed1991

Calcium inhibition of efrotomycin production by Nocardia lactamdurans.

Efrotomycin is a modified polyketide antibiotic of the elfamycin family that has use in the area of pig husbandry. Optimization of the fermentation medium for production of efrotomycin by Nocardia lactamdurans revealed that the fermentation is sensitive to hard water and certain lots of cottonseed flour used to prepare a complex fermentation medium. A limited metal ion analysis of the hard water indicated that calcium ions are present at concentrations found to be inhibitory by the addition of calcium chloride to medium prepared with distilled water. Similarly, a correlation between lots of cottonseed flour that poorly supported the fermentation and high calcium levels is presented. Further experimentation revealed that by altering the sterilization conditions of the cottonseed flour, the inhibitory effect of poor lots could be prevented.

Anti-Bacterial Agents↗
PubMed1991

cDNAs encoding members of a family of proteins related to human sterol carrier protein 2 and assignment of the gene to human chromosome 1 p21----pter.

Sterol carrier protein 2 (SCP2) is believed to play a key role in intracellular lipid movement. Here we report the cloning and nucleotide sequences of cDNAs encoding SCP2-related proteins of 58.85 kD and 30.8 kD and the assignment of the SCP2 gene to human chromosome 1 p21-pter. The SCP2-related proteins share common deduced carboxyl amino acid sequences with SCP2 and the cDNAs have a common 3' untranslated nucleotide sequence. The mRNAs encoding these proteins increased in a coordinate fashion as human placental cytotrophoblasts differentiated into syncytiotrophoblasts in culture. Our observations document the existence of a family of related proteins encoded by the human SCP2 gene.

Amino Acid Sequence↗
PubMed1990

Transfer of long-stay psychiatric patients: a preliminary report of inter-institutional relocation.

A large mental hospital closed in November 1986. Twenty-eight female patients formed the first group to be transferred to a second psychiatric hospital. Patients in the receiving hospital were identified as controls. Both transfer and control groups were studied before the move and at six- and 12-month follow-ups. No differences in mortality or morbidity were found between groups, but the transferred patients increased in behavioural dependency. Within the transfer group, patients became more positive towards the move over time. Results are discussed with reference to previous studies of relocation effects on elderly people.

Adaptation, Psychological↗
PubMed1989

The nucleotide sequence of a mouse renin-encoding gene, Ren-1d, and its upstream region.

The renin-encoding genes have been cloned from high (Ren-1d, Ren-2d)- and low (Ren-1c)-renin-producing strains of mice (DBA/2J and C57BL/10). Each of the genes is approx. 9.6 kb in length and consists of nine exons and eight introns. The entire nucleotide sequence of the Ren-1d gene has been determined and the 5'-flanking regions of the three genes, Ren-1c, Ren-1d and Ren-2d, have been compared. The significance of several potential regulatory signals found in the DNA is discussed.

Amino Acid Sequence↗
PubMed1989

Use of a cutoff range in identifying mycobacteria by the Gen-Probe Rapid Diagnostic System.

Commercial DNA probes (Gen-Probe Corp., San Diego, Calif.) for Mycobacterium tuberculosis complex Mycobacterium avium, and Mycobacterium intracellulare were compared with conventional methods for accuracy, applicability, and speed for the identification of putative isolates of the M. tuberculosis and M. avium complexes. Results are expressed as percent hybridization. Values of greater than 15% were considered positive, and values of less than 5% were negative. Cultures having hybridization values within an indeterminate range of 5 to 15% were repeated. Mycobacterial isolates resembling M. tuberculosis and M. avium complex from cultures of 589 specimens, representing 432 patients, were entered into this study; 294 cultures were tested with the M. tuberculosis complex probe, and 326 cultures were tested with the M. avium probe. In all cases, probe results agreed with our biochemical identification of the isolates. The M. intracellulare probe was used with 117 isolates morphologically resembling M. avium complex, and one false-negative result was observed. Seventy-two cultures gave initial hybridization results that fell within the indeterminate range and were repeated. If the manufacturer's recommended 10% cutoff value had been used, the original hybridization values would have resulted in 27 misidentified cultures, 16 false-negatives and 11 false-positives.

DNA Probes↗
PubMed1987

Phadebact Monoclonal GC OMNI Test for confirmation of Neisseria gonorrhoeae.

The Phadebact Monoclonal GC OMNI Test (Pharmacia Diagnostics, Piscataway, N.J.) is used for the definitive identification of Neisseria gonorrhoeae. In this test, boiled organisms are examined by using a 1-min coagglutination technique. A total of 776 Neisseria strains, confirmed to the species level by patterns of acid production from carbohydrates incorporated in cysteine-tryptose agar or morphologically consistent with Neisseria meningitidis and fluorescent antibody negative, were tested by the coagglutination technique. Of the 516 isolates of N. gonorrhoeae, 8 (1.6%) were negative with the OMNI Test. Of the 260 isolates of Neisseria spp. other than N. gonorrhoeae, none showed a positive coagglutination reaction. The Phadebact Monoclonal GC OMNI Test provided rapid, accurate identification of N. gonorrhoeae (sensitivity, 98.4%; specificity, 100%).

Agglutination Tests↗
PubMed1985

Comparative evaluation of the Optimate and TDX analyzers using NCCLS guidelines.

A comparative simultaneous evaluation of the Optimate and the TDX analyzers was performed according to guidelines proposed by the National Committee for Clinical Laboratory Standards. Statistically significant (P less than 0.05) better precision was demonstrated for the TDX analyzer with both commercial controls and patient pools. No statistically significant difference was found between the analyzers in terms of linearity, accuracy, and curve stability. Technologists judged the TDX to be superior in ease of start-up and shutdown procedures, loading and unloading, test changeover, time for a stat specimen, and time for an average run. In general, the TDX analyzer required less operator interaction for routine performance, but its consumable expenses were about 50% greater than those for the Optimate analyzer.

Autoanalysis↗