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Biomedical subjects

L M Hall

Publications and source records attributed to L M Hall.

At least 73 records · Page 4Linked to original sources
PubMed1996

Genetic relatedness within and between serotypes of Streptococcus pneumoniae from the United Kingdom: analysis of multilocus enzyme electrophoresis, pulsed-field gel electrophoresis, and antimicrobial resistance patterns.

A collection of 54 isolates of invasive Streptococcus pneumoniae of serotypes 3 and 14 and serogroups 6, 9, 19, and 23 was investigated. Multilocus enzyme electrophoresis and pulsed-field gel electrophoresis suggested that two clones were represented in the collection, one of serotype 14 isolates, most of which were resistant to erythromycin, and one of serotype 9V isolates, in which resistance to penicillin (MIC, 1 microgram/ml), cefotaxime, and co-trimoxazole was common. Among other isolates there were only a limited correlation between genetic relatedness measured by multilocus enzyme electrophoresis and expression of the same capsule type. However, isolates with highly related pulsed-field gel electrophoresis patterns always shared the same serotype and highly related allele profiles. Calculation of the index of association suggests a freely recombining population structure with epidemic spread of successful clones.

Child↗
PubMed1995

Cloning and functional analysis of TipE, a novel membrane protein that enhances Drosophila para sodium channel function.

Voltage-dependent sodium channels are involved in the initiation and propagation of action potentials in many excitable cells. Here we report that tipE, a gene defined by a temperature-sensitive paralytic mutation in Drosophila, encodes a novel integral membrane protein that dramatically stimulates functional expression in Xenopus oocytes of the Drosophila sodium channel alpha subunit encoded by the paralytic (para) locus. Using a heat shock promoter to control tipE+ gene expression in transgenic flies, we demonstrate that tipE+ gene expression is required during pupal development to rescue adult paralysis. In addition, we demonstrate a role for the tipE gene product in adults.

Amino Acid Sequence↗
PubMed1995

Metalloregulation of the cyanobacterial smt locus: identification of SmtB binding sites and direct interaction with metals.

The smtB gene of Synechococcus PCC 7942 encodes a trans-acting repressor of the metal-regulated smtA gene that encodes a class II metallothionein. Recombinant SmtB has been expressed in Escherichia coli and purified. Electrophoretic mobility shift assays using recombinant SmtB or a protein extract from Synechococcus PCC 6301 reveal the concentration-dependent formation of three specific complexes with the smt operator/promoter. SmtB is also capable of direct interaction with metals as evidenced by 65Zn binding to the SmtB protein as well as the inhibition of repressor-DNA complex formation in the presence of various metal ions. Methylation interference analysis of such complexes identifies four protein contact points within the smt operator/promoter DNA. The points of contact appear to represent two pairs of binding sites, one pair in each of two inverted repeats (nt 548-563, 589-602). The contact points within each pair lie on opposing DNA strands and are separated by 10 bp, placing the repressor binding sites on opposite sides of the DNA helix. Based on electrophoretic mobility shift assays, methylation interference and molecular size calculations we propose that recombinant SmtB binds to the smt operator/promoter in multimeric fashion.

Bacterial Proteins↗
PubMed1995

An approach to the identification of the pathogens of bacterial meningitis by the polymerase chain reaction.

A combination of universal and species-specific primers was used to detect and differentiate by nested polymerase chain reaction (PCR) the four species most commonly causing bacterial meningitis. Primers recognising conserved sequences in the 16S and 23S ribosomal RNA genes were employed to amplify the 16S-23S spacer region from Neisseria meningitidis, Haemophilus influenzae (type b), Streptococcus pneumoniae, and Streptococcus agalactiae (group B streptococcus). The sequence of the most abundant spacer product was determined in each case and used to deduce species-specific primers. A nested PCR using universal primers in the first round and a species-specific primer in the second were able to detect and distinguish between the four common pathogens, in the presence of human DNA. Streptococcus pneumoniae DNA was detected in the cerebrospinal fluid of a meningitis patient with negative culture and Gram-stain results.

Base Sequence↗
PubMed1995

Plasma androgens in autism.

Plasma levels of testosterone and the adrenal androgen dehydroepiandrosterone sulfate (DHEA-S) were measured in male autistic subjects (31 prepubertal, 8 postpubertal), mentally retarded/cognitively impaired subjects (MR, 12 prepubertal), and normal control subjects (NC, 10 prepubertal, 11 postpubertal). Mean levels of plasma testosterone were similar in the postpubertal autistic (4.54 +/- 1.12 ng/ml) and postpubertal NC (5.02 +/- 1.87 ng/ml) groups. Plasma DHEA-S levels in postpubertal autistic (2170 +/- 1020 ng/ml) and postpubertal NC (1850 +/- 777 ng/ml) groups also were not significantly different. Similarly, no significant group differences were seen for testosterone or DHEA-S in the prepubertal autistic, MR, or NC individuals, although prepubertal MR individuals with cerebral palsy did have increased plasma DHEA-S levels compared to age-matched MR or NC individuals. Significant negative correlations were found between testosterone and whole blood serotonin (5-HT) levels in the combined (all subjects, all ages) groups and in the autistic group, suggesting that the effect of puberty on whole blood 5-HT may deserve further study. Data indicate that altered secretion of the androgens is not a common feature of autism. However, abnormalities of adrenal androgen secretion may be present in individuals with cerebral palsy.

Adolescent↗
PubMed1995

Acute and chronic effects of fluoxetine and haloperidol on mouse brain serotonin and norepinephrine turnover.

Evidence from clinical studies suggests that the noradrenergic system may play a role in the pathophysiology of antidepressant- and neuroleptic-induced akathisia. In limited previous neurochemical research, acute treatment with selective serotonin reuptake inhibitors (SSRIs) has been reported to increase rat brain norepinephrine (NE) turnover or release. We have examined the neurochemical effects of 2 hr, 4 day, and 20 day treatment with the SSRI fluoxetine, and the neuroleptic haloperidol, on regional brain monoamine metabolism. Short and long-term fluoxetine treatment produced substantial decreases (to 65-79% of control) in serotonin (5HT) turnover. However no effects of fluoxetine on mouse brain NE turnover--as assessed by forebrain, hypothalamus, and hindbrain 3-methoxy-4-hydroxyphenylglycol (MHPG) levels or MHPG/NE ratios--were observed. Acute (2 hr) fluoxetine also did not alter regional NE turnover in rat brain. In contrast, haloperidol tended to increase MHPG levels and MHPG/NE ratios in the mouse brain regions studied. The persistence of decreased 5HT turnover during fluoxetine treatment, the lack of an effect of fluoxetine on NE turnover, and the increased NE turnover seen after haloperidol may have important implications regarding drug responsivity and the mechanism of akathisia induction.

Animals↗
PubMed1995

Cytogenetic and molecular localization of tipE: a gene affecting sodium channels in Drosophila melanogaster.

Voltage-sensitive sodium channels play a key role in nerve cells where they are responsible for the increase in sodium permeability during the rising phase of action potentials. In Drosophila melanogaster a subset of temperature-sensitive paralytic mutations affect sodium channel function. One such mutation is temperature-induced paralysis locus E (tipE), which has been shown by electrophysiology and ligand binding studies to reduce sodium channel numbers. Three new gamma-ray-induced tipE alleles associated with either visible deletions in 64AB or a translocation breakpoint within 64B2 provide landmarks for positional cloning of tipE. Beginning with the flanking cloned gene Ras2, a 140-kb walk across the translocation breakpoint was completed. Germline transformation using a 42-kb cosmid clone and successively smaller subclones localized the tipE gene within a 7.4-kb genomic DNA segment. Although this chromosome region is rich in transcripts, only three overlapping mRNAs (5.4, 4.4, and 1.7 kb) lie completely within the smallest rescuing construct. The small sizes of the rescuing construct and transcripts suggest that tipE does not encode a standard sodium channel alpha-subunit with four homologous repeats. Sequencing these transcripts will elucidate the role of the tipE gene product in sodium channel functional regulation.

Alleles↗
PubMed1995

Transferable production of PER-1 beta-lactamase in Pseudomonas aeruginosa.

PER-1, an extended-spectrum class A beta-lactamase, has been described only from Pseudomonas aeruginosa RNL-1, which was obtained in France in 1991. During studies on ceftazidime-resistant P. aeruginosa collected from December 1991 to July 1993 in Ankara, Turkey, we found 14 further isolates with PER-1 enzyme, as recognised by isoelectric point (pI 5.4), hydrolytic activity, gene hybridization and DNA sequence. Five of these isolates also had OXA-10 (PSE-2)-related enzymes and one hyper-produced ampC beta-lactamase, whereas eight had PER-1 enzyme alone. The last group, from four wards, appeared to be identical, giving the same DNA restriction patterns and carrying the PER-1 gene on an 8.5 kb HincII fragment. Two more producers were related but the other four were unique. In several representatives of the group of eight replicates, the PER-1 gene was shown to be encoded on a plasmid, larger than 154 kb in size, which transferred to P. aeruginosa PU21. A further isolate had the gene on an even larger conjugative plasmid. By contrast, the PER-1 gene reportedly was chromosomally-inserted in strain RNL-1. The PER-1 producers and their transconjugants were highly resistant to ceftazidime and aztreonam (MIC > or = 128 mg/L) but not to carbapenems or latamoxet. Piperacillin insusceptibility was marginal (MIC 8 mg/L). Clavulanate 4 mg/L, but not tazobactam 4 mg/L, reversed resistance to ceftazidime and carbenicillin. Purification of the enzyme to homogeneity was achieved by three ion exchanges and one gel filtration. We found much lower Vmax rates for aminothiazolyl cephalosporins than reported previously for PER-1 enzyme. This reflected the present assays being in 0.1 M phosphate buffer pH 7.0, whereas the previous were pH-stat-regulated; concentrated phosphate reduced enzyme activity against ceftazidime, but not against cephaloridine.

Base Sequence↗
PubMed1995

Resistance to extended-spectrum cephalosporins, caused by PER-1 beta-lactamase, in Salmonella typhimurium from Istanbul, Turkey.

Two Salmonella typhimurium isolates were studied, one as a representative from a series of neonatal meningitis cases treated at an Istanbul teaching hospital, the other from a gastro-enteritis case seen at a different Istanbul hospital. Both isolates were resistant to extended-spectrum cephalosporins, as well as penicillins, aminoglycosides and chloramphenicol. Cephalosporin resistance depended on production of PER-1 beta-lactamase, which is an extended-spectrum class A enzyme that is only distantly related to TEM and SHV enzymes, and which was previously known only from Pseudomonas aeruginosa isolates. The PER-1 gene was carried by an 81-MDa plasmid, which also determined resistance to aminoglycosides and chloramphenicol. Although it was not self-transmissible to Escherichia coli, this element did transfer if mobilised with plasmid pUZ8. The two S. typhimurium isolates gave indistinguishable DNA restriction patterns and, in addition to their 81-MDa plasmid, also contained 52- and 2.8-MDa plasmids, the last of these encoded TEM-1 enzyme. The two isolates were identical in serotype, antibiogram and plasmid-profile but nevertheless differed in phage type, and, therefore, represented distinct strains. The emergence of cefotaxime and ceftriaxone resistance in salmonellae is disturbing, since these agents are preferred therapy for neonatal meningitis caused by members of the genus.

Base Sequence↗
PubMed1995

OXA-14, another extended-spectrum variant of OXA-10 (PSE-2) beta-lactamase from Pseudomonas aeruginosa.

Pseudomonas aeruginosa 455, isolated in Ankara, Turkey, produced a pI 6.2 beta-lactamase determined by plasmid pMLH53 and resisted all beta-lactams except carbapenems. This beta-lactamase, named OXA-14, corresponded to OXA-10 (PSE-2) except that aspartate replaced glycine at position 157 and thus is intermediate between OXA-10 and OXA-11, which has aspartate at position 157 and a further substitution at position 143.

Anti-Bacterial Agents↗
PubMed1995

Cloning and characterization of a calcium channel alpha 1 subunit from Drosophila melanogaster with similarity to the rat brain type D isoform.

We report the complete sequence of a calcium channel alpha 1 subunit cDNA cloned from a Drosophila head cDNA library. This cDNA encodes a deduced protein containing 2516 amino acids with a predicted molecular weight of 276,493. The deduced protein shares many features with vertebrate homologs, including four repeat structures, each containing six transmembrane domains, a conserved ion selectivity filter region between transmembrane domains 5 and 6, and an EF hand in the carboxy tail. The Drosophila subunit has unusually long initial amino and terminal carboxy tails. The region corresponding to the last transmembrane domain (IVS6) and the adjacent cytoplasmic domain has been postulated to form a phenylalkylamine-binding site in vertebrate calcium channels. This region is conserved in the Drosophila sequence, while domains thought to be involved in dihydropyridine binding show numerous changes. The Drosophila subunit exhibits 78.3% sequence similarity to the rat brain type D calcium channel alpha 1 subunit, and so has been designated as a Drosophila melanogaster calcium channel alpha 1 type D subunit (Dmca1D). In situ hybridization shows that Dmca1D is highly expressed in the embryonic nervous system. Northern analysis shows that Dmca1D cDNA hybridizes to three size classes of mRNA (9.5, 10.2, and 12.5 kb) in heads, but only two classes (9.5 and 12.5 kb) in bodies and legs. PCR analysis suggests that the Dmca1D message undergoes alternative splicing with more heterogeneity appearing in head and embryonic extracts than in bodies and legs.

Amines↗
PubMed1994

Cloning and functional expression of a neuronal calcium channel beta subunit from house fly (Musca domestica).

The primary structure of a calcium channel beta subunit (beta M) from housefly (Musca domestica) has been deduced by cDNA cloning and sequence analysis. The open reading frame encodes a 441-amino acid polypeptide with a calculated molecular mass of 48,755 Da. Whole-mount in situ hybridization indicates that beta M mRNA is predominantly expressed in neuronal tissues. Transcription of beta M mRNA is evident from stage 13/14 of embryogenesis up to adulthood. Different expression patterns of splice variants were found in larvae and in adult fly heads. Amino acid identity between beta M and mammalian beta subunits is lower (66-68%) than within mammalian beta subunits (74-80%). Calculation of a phylogenetic tree indicates that beta M is an ancestral form of the four distinct beta subunit gene products identified in mammalian tissues so far. Despite these sequence differences, beta M is able to enhance endogenous calcium channel activity in Xenopus laevis oocytes as well as dihydropyridine binding to membranes from COS 7 cells transfected with rabbit heart alpha 1 cDNA in the same manner as was previously shown for mammalian beta subunits.

Alternative Splicing↗
PubMed1994

Characterization of class II and class III ADP-ribosylation factor genes and proteins in Drosophila melanogaster.

ADP-ribosylation factors (ARFs) are ubiquitous approximately 20-kDa guanine nucleotide-binding proteins that enhance the ADP-ribosyltransferase activity of cholera toxin and are involved in intracellular vesicular transport. Based on size, phylogenetic analysis, amino acid identity, and gene structure, mammalian ARFs fall into three classes (class I, ARF1, -2, and -3; class II, ARF4 and -5; class III, ARF6). A class I ARF had been identified in Drosophila melanogaster. To search for ARFs of other classes in Drosophila, polymerase chain reaction-based techniques were used, resulting in cloning of Drosophila ARF (dARF) II and dARF III with deduced amino acid sequences similar to those of class II and class III mammalian ARFs, respectively. The three Drosophila ARF genes map to different chromosomes and the coding regions have different splicing sites. dARF II mRNA, like ARF I mRNA, is fairly uniformly distributed throughout adult flies, whereas dARF III mRNA is significantly more abundant in heads than in legs or bodies. Recombinant dARF II and dARF III have biochemical and immunological properties similar to those of human ARF5 (hARF5) and hARF6, respectively. These observations are consistent with the conclusion that the three classes of ARFs are present in non-mammalian as well as mammalian species.

ADP-Ribosylation Factor 1↗
PubMed1994

Agonist-specific coupling of a cloned Drosophila octopamine/tyramine receptor to multiple second messenger systems.

A cloned seven transmembrane-spanning Drosophila octopamine/tyramine receptor, permanently expressed in a Chinese hamster ovary cell line, both inhibits adenylate cyclase activity and leads to the elevation of intracellular Ca2+ levels by separate G-protein-coupled pathways. Agonists of this receptor (octopamine and tyramine), differing by only a single hydroxyl group in their side chain, may be capable of differentially coupling it to different second messenger systems. Thus, a single receptor may have a different pharmacological profile depending on which second messenger system is used to assay its efficacy.

Animals↗
PubMed1994

Variation in plasma cholesterol concentration over time in the domestic fowl.

1. Variations in the concentration of plasma cholesterol available to the developing oocyte over a three week period in Gallus domesticus are described. 2. There are small changes in concentration between weeks for individual birds, but no changes between consecutive days within weeks or times within days. 3. It is recommended that future attempts to assess the relationship between variation in blood and yolk cholesterol concentrations estimate blood cholesterol concentration from two samples taken a week apart.

Analysis of Variance↗
PubMed1994

Are point mutations or DNA rearrangements responsible for the restriction fragment length polymorphisms that are used to type bacteria?

Restriction fragment length polymorphisms (RFLPs) detected in total DNA or in rRNA genes are widely used to differentiate strains of bacteria. The changes accounting for these polymorphisms and the extent of genomic difference that they reflect are generally unknown. In this report, several methods have been used to examine the DNA differences between nine Enterococcus faecalis isolates. Restriction fragments from total DNA and from rRNA genes were compared between isolates using four and five different restriction enzymes, respectively. The proportion of polymorphic fragments detected was greater with total DNA than with rRNA gene patterns, but depended considerably on the restriction enzyme used. DNA changes underlying nine RFLPs were investigated by using the polymorphic fragments as probes to test for alteration in the position of recognition sites of other enzymes. Two polymorphisms were deduced to result from point mutation in a restriction site. Six were judged to result from DNA rearrangements, five of which involved deletion/insertion of the entire probe fragment. The results demonstrate that DNA rearrangements may be responsible for a high proportion of RFLPs used to differentiate and type strains of bacteria. While this does not limit the utility of such methods, it does preclude calculation of overall DNA sequence conservation from similarities in restriction pattern between isolates. DNA sequence determination of the 16S-23S rRNA intergenic spacer of three isolates revealed minimal base substitutions (less than 1%), suggesting that overall sequence divergence between the isolates may be low.

Bacterial Typing Techniques↗