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Biomedical subjects

C Hughes

Publications and source records attributed to C Hughes.

At least 181 records · Page 10Linked to original sources
PubMed1994

Regulation of neutrophil responses by phosphotyrosine phosphatase.

By using immunofluorescent flow cytometry, we observed a profound up-regulation of CD45 on the plasma membrane of neutrophils exposed to low levels of a culture supernatant of the Gram-negative pathogen, Fusobacterium nucleatum (FN). Plasma membranes of neutrophils freshly prepared form human blood possessed little enzymatically active phosphotyrosine phosphatase. The activity of this enzyme was markedly potentiated in plasma membranes prepared from cells preexposed to the FN culture supernatant. This activity was vanadate sensitive and could be immunoprecipitated with anti-CD45 Ab. Cells preexposed to the FN culture supernatant were inhibited in their ability to release superoxide when challenged with the bacterial chemotactic factor, FMLP, but not PMA. The tyrosine kinase inhibitor, genistein, likewise inhibited FMLP but not PMA-induced superoxide release. Pretreatment of neutrophils with vanadate reversed FN-mediated inhibition of FMLP-triggered superoxide release but had no effect on genistein-mediated inhibition of FMLP-induced superoxide release. Of several proteins tyrosine phosphorylated in response to treatment of neutrophils with FMLP, Western analysis revealed one (m.w. approximately 93,000) that was lost when FMLP-stimulated cells were exposed to FN. This effect was inhibited when the cells were preexposed to vanadate. These results are consistent with the hypothesis that plasma membrane tyrosine phosphatase modulates FMLP-induced superoxide release by reversing the effects of tyrosine kinases activated in the initial phases of cell stimulation.

Cell Membrane↗
PubMed1994

Pore formation in artificial membranes by the secreted hemolysins of Proteus vulgaris and Morganella morganii.

Lipid-bilayer experiments were performed with the related hemolysins from Proteus vulgaris and Morganella morganii (HlyA). The addition of the toxins to the aqueous phase bathing lipid-bilayer membranes composed of different lipids resulted in the formation of transient ion-permeable channels. Membranes formed of pure lipids were rather inactive targets for the hemolysins as compared with lipid mixtures such as asolectin. The channels had several different substrates. The major open state had single-channel conductances of 500 pS in 0.15 M KCl at small transmembrane voltages. Experiments with different salts suggested that the hemolysin-induced channels of P. vulgaris and M. morganii were exclusively cation selective at neutral pH, caused by negative charges localized at the channel mouth. The mobility sequence of the cations within the channels was similar if not identical to their mobility sequence in the aqueous phase. The single-channel data were consistent with wide, water-filled channels with estimated minimal diameters of about 1 nm since the large organic cation Tris+ can permeate the channels without any detectable interaction with its interior. Pore-forming properties of these hemolysins were compared with those of HlyA of Escherichia coli. All these toxins share common features, oligomerize probably to form pores in lipid-bilayer membranes and form channels with similar properties which suggests that their structures are more or less identical.

Bacterial Proteins↗
PubMed1994

Evidence for executive dysfunction in autism.

A group of young people with autism (ranging in ability from high functioning to moderately learning disabled), and ability-matched control groups of (i) non-autistic individuals with moderate learning disabilities, and (ii) normally developing children, were presented with two tests of executive function: the Intra-dimensional/Extra-dimensional set-shifting task and the Tower of London planning task. These tests were graded in difficulty and included internal control measures. On each task, the autistic group was differentially impaired with respect to both control groups. Moreover, this impairment was specific to the stages of each task which placed greatest demands upon executive control. This evidence for executive dysfunction in autism is discussed in the context of Norman and Shallice's (Centre for Human Information Processing Technical Report 99, 1980) "Supervisory Attentional System" model of frontal function.

Adolescent↗
PubMed1994

The role of swarm cell differentiation and multicellular migration in the uropathogenicity of Proteus mirabilis.

The uropathogenic bacterium Proteus mirabilis displays a form of multicellular behavior called swarming, in which typical vegetative rods differentiate into long hyperflagellate swarm cells that undergo rapid and coordinated population migration across surfaces. Such behavior might inherently assist ascending colonization of the urinary tract, and it has also been shown that swarming differentiation in vitro is central to the expression of conventional virulence factors. This study provides support for a role of swarming in vivo. Mortality rates of mice inoculated intravenously with 2.5 x 10(8) vegetative cells were lower than rates for those inoculated with wild type strains in the case of motile transposon mutants either completely unable to swarm (< 1%) or able to undergo only aberrant swarming migration (< 40%, P < .001). Histologic analysis of renal tissues from mice infected by wild type Proteus strains showed that long differentiated cells were the major cell type, whereas the extracellular inflammatory exudate contained primarily short vegetative cells. Following intravesical (bladder) inoculation with 2.0 x 10(7) vegetative cells, kidney infection was not established by any of the three motile swarm-defective mutants; indeed, the nonswarming mutant was not retained in the bladder. In contrast, the wild type strain and a normally swarming but nonhemolytic mutant achieved a high incidence of ascending infection to the kidney.

Animals↗
PubMed1994

Pain after subcutaneous injection of recombinant human erythropoietin: does Emla cream help?

Recombinant human erythropoietin (rHuEpo) is used to correct anaemia in dialysis patients. Subcutaneous administration of rHuEpo may be associated with pain at the injection site. This study assessed the pain of subcutaneous infiltration of two different preparations of rHuEpo, alpha and beta, and the value of a local anaesthetic (Emla) cream, in reducing the pain of infiltration. Forty-eight haemodialysis patients were enrolled into a double-blind, placebo-controlled, paired-comparison study. Pain was assessed using a visual analogue scale, a verbal descriptive scale and a direct comparison between paired treatments. Subcutaneous injection of rHuEpo alpha was more painful than rHuEpo beta (P < 0.001); using placebo cream 42% of patients described the pain of rHuEpo alpha as severe or very severe, whereas none of the patients found rHuEpo beta so painful. Application of Emla for at least 2 h prior to injection resulted in a significant reduction in the pain of both preparations, but was unable to reduce the pain of rHuEpo alpha to that of rHuEpo beta. Subcutaneous injection of rHuEpo alpha is more painful than rHuEpo beta, even after application of Emla. Although the discomfort of rHuEpo beta is graded as very mild by most adult patients the use of Emla is associated with a significant reduction in discomfort, which may be of benefit to paediatric patients.

Adult↗
PubMed1994

Matched-pairs analysis of co-worker interactions in relation to opportunity, type of job, and placement approach.

Workers with and without disabilities (n = 85) were studied in an effort to determine whether co-worker relations differed between these employees. Few differences were found. Interactions of co-workers without disabilities with their supported co-workers who had disabilities were remarkably similar to their interactions with other co-workers without disabilities in eight of the nine interaction categories investigated. In the ninth category (befriending off the job), co-workers without disabilities interacted more among themselves. Considering only workers with disabilities, those employed individually in light industry occupations experienced less physical integration than did those employed either in groups or in any other occupation. These findings were discussed in relation to available research.

Employment↗
PubMed1994

The Waianae Diet Program: a culturally sensitive, community-based obesity and clinical intervention program for the Native Hawaiian population.

The Waianae Diet Program (WDP) is a community-based program designed at the Waianae Coast Comprehensive Health Center in response to the high rates of obesity and chronic disease among Native Hawaiians. Its foundation is a 3-week program of traditional Hawaiian diet and cultural teachings. It employs 8 innovations in clinical nutrition and health promotion theory: 1. Non-calorie restricted weight loss protocol, 2. Dietary clinical intervention, 3. Cultural sensitivity, 4. Transition diet, 5. Whole-person approach, 6. Group ohana (family) support, 7. Community intervention, and 8. Role modeling. It has demonstrated significant weight loss with no calorie restriction, improvement in blood pressure, serum glucose, and serum lipids. It appears to have wide acceptance in the Hawaiian community. More studies are warranted to determine the long-term effect of this program.

Community Health Services↗
PubMed1993

Bacterial signal peptide-independent protein export: HlyB-directed secretion of hemolysin.

Bacterial ABC transporter proteins are associated with a great number of cellular processes. While many of the best characterised examples are involved in the import of small molecules into the cell, others mediate export of substrates, especially hydrophilic proteins. This article focuses on these bacterial ABC exporters, in particular the HlyB protein which is central to secretion of the 110 kDa hemolysin across both the cytoplasmic and outer membranes. This is an example of non-conventional protein export which does not require an N-terminal signal sequence or the cellular SecA-dependent machinery.

Adenosine Triphosphatases↗
PubMed1993

Loss of activity in the secreted form of Escherichia coli haemolysin caused by an rfaP lesion in core lipopolysaccharide assembly.

A transposon mutant of Escherichia coli 5K was isolated which reduced 10- to 50-fold the secreted extracellular haemolytic activity of cells carrying the complete hlyCABD operon while leaving unaffected the intracellular haemolytic activity and the levels of intracellular and extracellular haemolysin protein, HlyA. The transposon insertion was identified within the rfaP gene (required for attachment of phosphate-containing substituents to the lipopolysaccharide inner core), and extracellular haemolytic activity was restored in trans by the intact rfaP gene. The loss in cytolytic activity of the secreted HlyA protein was not related to the HlyC-directed acylation of the protoxin. Activity of the secreted toxin was restored by chaotropic agents and during rate-zonal centrifugation the mutant-secreted HlyA migrated as a larger species than the wild type. The results indicate that the rfaP mutation affects the aggregation behaviour of the active toxin during or following the signal peptide-independent secretion process.

Bacterial Proteins↗
PubMed1993

Cell differentiation of Proteus mirabilis is initiated by glutamine, a specific chemoattractant for swarming cells.

Swarming by Proteus mirabilis involves differentiation of typical short vegetative rods into filamentous hyperflagellated swarm cells which undergo cycles of rapid and co-ordinated population migration across surfaces and exhibit high levels of virulence gene expression. By supplementing a minimal growth medium (MGM) unable to support swarming migration we identified a single amino acid, glutamine, as sufficient to signal initiation of cell differentiation and migration. Bacteria isolated from the migrating edge of colonies grown for 8 h with glutamine as the only amino acid were filamentous and synthesized the characteristic high levels of flagellin and haemolysin. In contrast, addition of the other 19 common amino acids (excluding glutamine) individually or in combination did not initiate differentiation even after 24 h, cells remaining typical vegetative rods with basal levels of haemolysin and flagellin. The glutamine analogue gamma-glutamyl hydroxamate (GH) inhibited swarming but not growth of P. mirabilis on glutamine MGM and transposon mutants defective in glutamine uptake retained their response to glutamine signalling and its inhibition by GH, suggesting that differentiation signalling by glutamine may be transduced independently of the cellular glutamine transport system. Levels of mRNA transcribed from the haemolysin (hpmA) and flagellin (fliC) genes were low in vegetative cells grown on MGM without glutamine or with glutamine and GH, but were specifically increased c. 40-fold during glutamine-dependent differentiation. In liquid glutamine-MGM cultures, differentiation to filamentous hyper-flagellated hyper-haemolytic swarm cells occurred early in the exponential phase of growth, and increased concomitantly with the concentration of glutamine from a 0.1 mM threshold up to 10 mM.(ABSTRACT TRUNCATED AT 250 WORDS)

Base Sequence↗
PubMed1993

ATPase activity and ATP/ADP-induced conformational change in the soluble domain of the bacterial protein translocator HlyB.

The haemolysin exporter HlyB and its homologues are central to the unconventional signal-peptide-independent secretion of toxins, proteases and nodulation proteins by bacteria. HlyB is a member of the ATP-binding cassette (ABC) or traffic ATPase superfamily, and resembles closely in structure and function mammalian exporters such as the multidrug-resistance P-glycoprotein, combining both integral membrane and cytosolic domains. Overproduction of the HlyB cytoplasmic domain as a C-terminal peptide fused to glutathione S-transferase allowed the direct affinity purification and concentration of 30-50 mg ml-1 of soluble protein (GST-Bctp) in an apparently dimeric form possessing both transferase and ATPase activity. GST-Bctp bound to ADP-agarose and was eluted specifically by ATP and ADP, affinity behaviour which was confirmed in both the full-length HlyB and the unfused HlyB cytoplasmic domain synthesized in vitro. The stoichiometry of binding to MgATP and MgADP was close to equimolar and both ligands induced substantial conformational change in the protein. Mg(2+)-dependent ATPase activity of GST-Bctp (Vmax 1 mumol min-1 mg-1, Km 0.2 mM) was comparable with the activity of the bacterial importer MalK and human P-glycoprotein reconstituted into proteoliposomes, and over an order of magnitude higher than in vitro measurements of disaggregated MalK purified from inclusion bodies. Activity was unaffected by inhibitors of F- and V-type ATPases, non-hydrolysable ATP analogues, or translocation substrate, but was severely inhibited by inhibitors of E1E2 (P-type) ATPases, and the acidic phospholipid phosphatidyl glycerol.

Adenosine Diphosphate↗