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Biomedical subjects

C A Hart

Publications and source records attributed to C A Hart.

At least 343 records · Page 19Linked to original sources
PubMed1989

Granulocyte-macrophage colony-stimulating factor (GM-CSF) primes the respiratory burst and stimulates protein biosynthesis in human neutrophils.

Pre-treatment of human neutrophils with rGM-CSF resulted in a 3-fold increase in the rate of fMet-Leu-Phe stimulated reactive oxidant generation, as assessed by luminol- and lucigenin-chemiluminescence and O2- secretion. When blood-stream neutrophils were incubated in RPMI 1640 medium supplemented with [35S]methionine, both fMet-Leu-Phe (0.1 microM) and gamma-interferon (100 U/ml) stimulated a 3-4-fold increased incorporation of label into TCA-precipitable material. Similarly, rGM-CSF (50 U/ml) also stimulated protein biosynthesis in bloodstream neutrophils, and newly labelled polypeptides were separated by two-dimensional polyacrylamide gel electrophoresis. Two classes of polypeptides were visualised on these gels: the relative rate of labelling of one class changed very little upon rGM-CSF treatment whereas the relative rate of labelling of a second group increased 3-12-fold.

Colony-Stimulating Factors↗
PubMed1989

Interaction of enteropathogenic Escherichia coli 0111 with rabbit intestinal mucosa in vitro.

A model system using rabbit intestinal mucosal explants has been developed to examine the characteristic ultrastructural damage to the brush border induced by enteropathogenic Escherichia coli 0111. In this model, as in others, bacterial adherence to the microvillous membranes occurred in two morphologically distinct stages. Initial attachment of enteropathogenic strains of E. coli to ileal mucosa appeared to be a goblet cells and the mucous layer covering the microvilli. The next stage involved binding of enteropathogenic strains of E. coli to the bases of the microvilli that became elongated and vesiculated. Eventually, large areas of brush border effacement occurred with close apposition between bacterial and enterocyte membranes, leading to cup and pedestal formation. With a relatively large inoculum of bacteria (10(8) cfu/ml) these changes occurred within 4 h, but even with much lower inocula (10(5) cfu/ml) localized areas of damage were seen within 8 h. Although the bacteriostatic antibiotic tetracycline (700 mg/L) inhibited bacterial replication, it did not prevent the characteristic damage produced by enteropathogenic strains of E. coli. Enteropathogenic strains of E. coli 0111 were able to produce attaching effacement to gastric, duodenal, jejunal, ileal, and colonic mucosa.

Animals↗
PubMed1989

Legionella pneumophila serogroup 12 pneumonia in a renal transplant recipient: case report and environmental observations.

We describe the first reported case of pneumonia due to Legionella pneumophila serogroup 12 in the UK. This hospital-associated infection occurred in an immuno-incompetent patient and coincided with a change in character of the local environmental strains of legionellas. The patient produced a serological response both to her own isolate and to L. pneumophila serogroups 1-6. Thus serodiagnosis was attainable using the usual screening antigens.

Adult↗
PubMed1989

Detection of Legionella pneumophila in environmental water samples using a fluorescein conjugated monoclonal antibody.

Sixty-three environmental water samples from various sources were examined for the presence of Legionella pneumophila with a commercially available direct fluorescent monoclonal antibody (GS), an indirect fluorescent antibody test (IFAT) and culture. GS detected L. pneumophila in 94% and 100% of environmental water samples which were culture and IFAT positive for L. pneumophila, respectively. IFAT detected 69% of L. pneumophila culture positive samples. Cultures of L. pneumophila serogroups 1 to 12, 14 and non-L. pneumophila bacteria which may be found in water, and bacteria containing non-specific binding proteins, were stained by GS and IFAT. GS identified all serogroups of L. pneumophila and did not cross react with any non-L. pneumophila bacteria. L. pneumophila in environmental samples was easy to detect against a clear dark background when stained with GS.

Antibodies, Bacterial↗
PubMed1989

Restriction endonuclease characterization of resistant plasmids in Enterobacteriaceae isolated from children in the Sudan.

The investigation of plasmid similarity is an important component in the surveillance of antimicrobial resistance and in the detection of epidemic plasmids. The use of restriction endonucleases in the classification of transferable, multiply-resistant plasmids from faecal Enterobacteriaceae isolated at the Children's Emergency Hospital, Khartoum was investigated. Twenty-four transconjugant plasmids, coding for 11 different resistance patterns, each of molecular weight 62 MDa, were studied using four restriction enzymes; Pst I, EcoR I, Hind III and Ava II. Fifteen different digest profiles were obtained. Restriction profiles discriminated between plasmids with differing resistance patterns and demonstrated homology of plasmids with common resistance patterns. Restriction endonuclease digest patterns provide a potentially rapid and reproducible method of plasmid classification, that could contribute towards surveillance systems in tropical countries with a high prevalence of antimicrobial resistance.

Child↗
PubMed1989

Latex particle agglutination tests as an adjunct to the diagnosis of bacterial meningitis: a study from Malawi.

A prospective study using a Latex particle agglutination test for the detection of bacterial antigens in CSF has been carried out in 91 patients in Kamuzu Central Hospital, Malawi. The antigens sought were those of Streptococcus pneumoniae, Haemophilus influenzae b, Neisseria meningitidis B/E. coli K1, and Neisseria meningitidis A,C,Y,W 135. Forty-one patients had proven bacterial meningitis, two had tuberculous meningitis, 39 had cerebral malaria, four had aseptic meningitis and five had convulsions. The sensitivity and specificity of the tests (Str. pneumoniae, 88% and 100%, H. influenzae b, 87% and 96%; N. meningitidis A,C,Y,W 135, 100% and 100%; and N. meningitidis B, 100% and 98%) were as good as those reported from developed countries. Unlike in some other parts of Africa, group B meningococci seem to predominate in cases of meningococcal meningitis in Malawi.

Adolescent↗
PubMed1989

The effects of 5-azacytidine, 12-O-tetradecanoylphorbol 13-acetate and sodium n-butyrate on reactivation of alphaherpesvirus saimiri from explant cultures of latently infected rabbit dorsal root ganglia.

The DNA hypomethylating agent 5-azacytidine greatly increased the reactivation of alphaherpesvirus saimiri-1 (alpha HVS) from latently infected rabbit dorsal root ganglia, although it inhibited the virus yield and plaque formation efficiency of alpha HVS in Vero cells. 12-O-Tetradecanoylphorbol 13-acetate (a protein kinase C activator) and sodium n-butyrate both had a stimulating action on replication in Vero cells but did not affect the release of alpha HVS from latently infected rabbit dorsal root ganglia.

Animals↗
PubMed1989

Identification of epitopes recognized by monoclonal antibodies SM1 and SM2 which react with all pili of Neisseria gonorrhoeae but which differentiate between two structural classes of pili expressed by Neisseria meningitidis and the distribution of their encoding sequences in the genomes of Neisseria spp.

The pili expressed by all isolates of Neisseria gonorrhoeae react with two monoclonal antibodies, SM1 and SM2. In contrast, although many isolates of Neisseria meningitidis also express pili (class I) which react with antibodies SM1 and SM2, a proportion express pili (class II) which fail to react. In order to define the epitopes recognized by these antibodies, a series of overlapping peptides corresponding to the amino acid sequence of conserved regions of gonococcal pili have been synthesized. The minimum epitope recognized by antibody SM1 was found to comprise a linear peptide EYYLN, corresponding to residues 49-53 of mature pilin. In contrast, antibody SM2 reacted with a number of peptides from around the cysteine residue (Cys 1) at position 120, suggesting that an extended region may contribute to a conformational epitope recognized by this antibody in the native protein. The identification of the two epitopes defines structural differences between the classes of pili expressed by meningococci. In order to determine the distribution of pilin gene sequences in Neisseria we used as hybridization probes an oligonucleotide (PS1) with the sequence 5'-GAGTATTACCTGAATCA-3' which spans the coding region for the SM1 epitope, and a fragment of the 3' end of the gonococcal pilE gene which contains conserved sequences flanking the two Cys codons and encodes the SM2 epitope. All strains of N. gonorrhoeae and N. meningitidis tested, regardless of piliation phenotype, harboured DNA sequences homologous to those encoding the carboxy-terminus of meningococcal class I pilin. Furthermore, all gonococci and all meningococci producing class I pili hybridized with oligonucleotide probe PS1. Non-reverting non-piliated derivatives of previously class I pilus-producing strains showed reduced hybridization signals with this probe, but nevertheless retained sequences homologous to the coding sequence for the SM1 epitope. However, meningococci producing class II pili could be divided into two groups on the basis of their reaction with the PS1 probe: half the strains tested failed to react, which is consistent with our previous analysis of silent class I pilin sequences; the remainder reacted (relatively weakly) with the probe, suggesting that the silent pil sequences in these strains extend further towards the 5' end of the pilin gene than in strains studied previously. Some strains of Neisseria lactamica reacted weakly with both types of probe but failed to produce SM1-reactive pili. In contrast, isolates of Neisseria flava, Neisseria pharyngis, Neisseria sicca and a series of unrelated bacteria failed to react with both SM1 antibody and the DNA probes. This confirms that possession of 'gonococcal' pilin sequences is limited to the pathogenic neisseriae.

Amino Acid Sequence↗
PubMed1989

Role of myeloperoxidase in the killing of Staphylococcus aureus by human neutrophils: studies with the myeloperoxidase inhibitor salicylhydroxamic acid.

We have used salicylhydroxamic acid (SHAM) to inhibit intraphagosomal myeloperoxidase activity in order to evaluate the role of this enzyme in the killing of Staphylococcus aureus by human neutrophils. 50 microM-SHAM reduced the luminol-dependent chemiluminescence response stimulated during phagocytosis of unopsonized latex beads and opsonized S. aureus by over 80% and 60%, respectively. When opsonized S. aureus were incubated with neutrophils, 45% were killed within 15 min incubation and 60% by 1 h. However, in neutrophil suspensions incubated with 50 microM-SHAM, only 13% were killed by 15 min whilst 71% still remained viable after 1 h. This inhibitor had no effect upon the number of bacteria phagocytosed or upon degranulation. In a cell-free system, 2.5 microM-H2O2 alone killed 55% of the bacteria, whereas in the presence of myeloperoxidase (i.e. 10 mU myeloperoxidase and 2.5 microM-H2O2) virtually all of the bacteria were killed: the addition of 50 microM-SHAM abolished this myeloperoxidase-enhanced killing but did not affect the H2O2-dependent killing. We therefore conclude that in normal neutrophils whilst H2O2 is required for killing of this pathogen, both myeloperoxidase-dependent and -independent pathways exist.

Cell Degranulation↗
PubMed1989

Patterns of colonisation of Campylobacter pylori in the oesophagus, stomach and duodenum.

Thirty five subjects underwent upper gastrointestinal endoscopy and multiple biopsy (30 patients, five normal subjects). A total of 11 biopsies per subject from four sites (oesophagus (three), gastric body (two), antrum (three), duodenum (three] were examined for inflammation and the presence of Campylobacter pylori and using standard methods of culture and by light (LM) and electron microscopy (EM). The organism was cultured from oesophageal biopsies in eight of 30 (27%) patients but could not be identified at this site by LM or EM. There was evidence of oesophageal inflammation in 20 patients which was associated with the local finding of C pylori in five (25%) including two of seven (29%) with Barrett's mucosa. Antral C pylori was present in 22 of 23 (96%) patients with chronic active gastritis. The organism was found in the antrum and oesophagus in four of 22 patients (18%), in the antrum and duodenum in four of 22 patients (18%) and in all three sites in a further two of 22 patients (9%). Antral C pylori was found in five of six patients with peptic ulceration. C pylori was cultured from the duodenum in six patients with confirmation by LN and EM in three, but only on areas of gastric metaplasia. The organism was not found in the normal group. This study indicates that C pylori may be irregularly isolated from the oesophagus and duodenum in patients with antral C pylori and chronic active gastritis. The role of C pylori in the oesophagus is most likely that of a commensal or contaminant.

Adult↗
PubMed1989

Varicella in an immunocompromised patient an electron microscopic study.

We report the electron-microscopic appearances of tissues from an immunocompromised patient who died of chickenpox. We observed structures consistent with some of the reported appearances of Varicella-Zoster virus in cultured cells, and tubular structures that have not to our knowledge been previously described.

Adult↗
PubMed1988

In vitro activity of florphenicol.

Florphenicol was active at a lower concentration than chloramphenicol against over half of 234 recent clinical bacterial isolates. The majority (98%) of the isolates were inhibited by florphenicol at a concentration of 8 mg/l or less. Florphenicol was particularly effective against chloramphenicol resistant strains of Haemophilus influenzae. Klebsiella aerogenes and Bacteroides spp. Florphenicol was bacteristatic for salmonellae and Escherichia coli but bactericidal for Haemophilus influenzae. Florphenicol was slightly more active than chloramphenicol against Chlamydia trachomatis, Mycoplasma hominis and Mycoplasma pneumoniae but less active against Ureaplasma urealyticum.

Chloramphenicol↗
PubMed1988

Enterobius vermicularis infection in a children's ward.

Following the discovery that two patients on a children's orthopaedic ward were excreting Enterobius, all patients and staff on the ward were screened for the presence of pinworms. None of the staff was infected but 11 (55%) of 20 patients either had Enterobius ova on the anal margin or excreted worms following piperazine treatment. Epidemiological investigations indicated that this was unlikely to be a ward outbreak because four of the infected children had been on the ward for under 3 days, i.e., less than the prepatent period for Enterobius. Although none of the children was symptomatic, all children and staff on the ward were treated with piperazine. Faecal samples were collected from nine children and the majority of their worm load was shed within 32 h of starting therapy. Microscopic examination of the adult male worms showed that each patient was excreting both Enterobius vermicularis and E. gregorii.

Animals↗