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Biomedical subjects

S Aspinall

Publications and source records attributed to S Aspinall.

33 records · Page 2Linked to original sources
PubMed1994

Prevalence of hepatitis B in !Kung (San) children from Bushmanland, Namibia.

Serum samples from 248 predominantly !Kung children (aged 5-19 years) attending various bush schools and a clinic in Bushmanland, northern Namibia were examined for the presence of hepatitis B virus (HBV) markers by radioimmunoassay. HBsAg was detected in 18 (7.3%) children while 117 (47.6%) showed one or more markers of HBV infection. These prevalence rates are lower than those of the closely situated territory of Kavango to the north and East Caprivi to the north-east. No significant difference in HBs antigenaemia between !Kung boys and girls was found (p > 0.05). However, HBs antigenaemia was found to vary between children in different bush schools. A significantly higher number of children attending the Omatako bush school were positive for HBsAg than the number attending the Luhebu bush school (p < 0.0167). These local variations could assist in the initial targeting of HBV vaccine to high-risk areas. In situ investigations of hyperendemic foci in Bushmanland, Namibia should help to elucidate the variation in HBs antigenaemia and the factors responsible for transmission of HBV.

Adolescent↗
PubMed1994

Detection of beta lactamase in sputum.

AIMS: To develop a rapid, sensitive, and reproducible test for the detection of beta lactamase in sputum, and to relate these findings to bacteriological culture results. METHODS: One hundred and twenty sputum samples from inpatients were investigated for beta lactamase activity using the chromogenic cephalosporin nitrocefin. Sputum samples were sonicated and incubated aerobically at 37 degrees C with nitrocefin for up to two hours. Positive results (production of a red colour) were treated with blue sepharose beads to remove albumin (which can cause non-specific hydrolysis of nitrocefin) and retested. Samples were also cultured for both aerobic and anaerobic bacteria, with all isolates being tested for beta lactamase production using nitrocefin. All positive sputum samples and beta lactamase producing isolates were further examined by isoelectric focusing (IEF) to determine isoelectric point(s) (pIs). RESULTS: The process of sonication and albumin removal had no demonstrable effect on beta lactamase activity. Forty seven of the 120 sputum samples were positive on initial testing, and of these, 16 remained positive following removal of albumin. These 16 subsequently yielded 19 beta lactamase producing bacteria. All sputum samples yielding beta lactamase producing bacteria were also positive on direct nitrocefin testing. On no occasion were sputum samples positive in the absence of enzyme producing bacteria--that is, the test was both 100% specific and 100% sensitive. The presence of beta lactamase activity in the sputum samples was also confirmed using a microbiological method. In 11 sputum samples the beta lactamases detected had similar pI values to the beta lactamases obtained from their bacterial isolates. CONCLUSION: Detection of beta lactamase activity in sputum using nitrocefin, after treatment with blue sepharose beads, is a rapid, reproducible test with high specificity and sensitivity. Analytical isoelectric focusing showed that for 11 of the 16 positive sputa, the source of the beta lactamases could be traced to their concurrent bacterial isolates.

Bacteria↗
PubMed1994

Low prevalence of human T lymphotropic virus type I in !Kung San in Bushmanland, Namibia.

Antibodies to human immunodeficiency virus 1 (HIV-1) and human T lymphotropic virus type 1 (HTLV-I) have been identified in various population groups living in southern and central Africa. Sera from 291 !Kung Bushmen in Bushmanland, Namibia were examined for the presence of antibodies to HIV-1 and HIV-2 and to HTLV-I. Initial screening for HIV-1/2 by two enzyme-linked immunosorbent assays (ELISAs) revealed evidence of past exposure in four individuals. However, no HIV-1/2 infection could be confirmed by a particle agglutination assay, a recombinant ELISA, or by Western blot for HIV-1 and HIV-2. Indeterminate Western blot profiles (with a p55 for each and either a p25 or p18 band) existed for all four HIV-1-reactive sera. Eight sera were reactive in the HTLV-I ELISA, although only five were positive on a second ELISA. Only three of the five HTLV-I-reactive sera could be confirmed by Western blot.

Adolescent↗
PubMed1993

Electrophoretic typing of nosocomial rotavirus infection in a general paediatric unit showing the continual introduction of community strains.

During 1989 stool specimens from hospitalised children with gastroenteritis at Ga-Rankuwa Hospital in South Africa were examined for the presence of rotaviruses. Overall 16% of the children were positive for rotavirus. However, 43% of the rotavirus positive patients were infected in the hospital. Further characterisation of the rotavirus strains was performed by electrophoresis of the RNA genome and hybridisation analysis of the VP7 and VP4 genes present. The strains associated with nosocomial infection were similar to those strains acquired in the community. The majority of the strains, both community- or hospital-acquired, were associated with a serotype 1 strain with a long electrophoretype and bearing the Wa-like VP4 gene. Three minor rotavirus strains with a long electrophoretype were also observed to be circulating bearing serotype 1 or 4 VP7 genes and the Wa-like VP4 gene. Interestingly, a serotype 4 strain bearing the M37-like VP4 gene was identified to occur almost exclusively in neonates although the gene was associated with diarrhoea in these cases. Two strains with differing short RNA electrophoretypes were also observed, members of which hybridised to VP7 serotype 2 and VP4 DS-1 type probes.

Alleles↗
PubMed1993

Prevalence of markers for human immunodeficiency, hepatitis B and hepatitis C viruses in maxillofacial and oral surgery patients at Medunsa.

Information on the incidence of human immunodeficiency virus (HIV) and hepatitis B (HBV) and C (HCV) virus infections is needed for the planning of preventative measures against the spreading of these blood borne pathogens through treatment in the clinic. A survey was conducted to determine the incidence for 180 patients attending the maxillofacial and oral surgery clinic at the Medunsa Dental Hospital. Antibodies to HIV were found in 1.1 per cent. Hepatitis B surface antigen in 2.8 per cent and Hepatitis B core antibodies as the sole marker in three patients who tested positive for HBV-DNA. The prevalence of anti-HCV was 1.1 per cent. The presence of these infections indicates that there is a need for dental health care workers to comply with all recommended precautionary measures, including immunization against hepatitis B.

Adolescent↗
PubMed1992

Immunogenicity of recombinant hepatitis B vaccine in urban black children from Ga-Rankuwa, Bophuthatswana, South Africa.

Many areas in Southern Africa have a relatively high endemicity for hepatitis B for which the only effective medical measure is vaccination. The aim of this study was to evaluate the antibody response to a recombinant hepatitis B vaccine (Engerix B; Smith Kline-Beecham) in a black urban population, with the use of the recommended regimen and a low dose, short course. One hundred eleven children seronegative for hepatitis B virus (5 to 19 years old) were randomized to receive one of the two vaccination schedules (20 micrograms at zero, 1 and 6 months or 2 micrograms at zero, 1 and 2 months). Antibody to hepatitis B surface antigen was determined 6 to 8 weeks after the last dose by radioimmunoassay (Ausab; Abbott Laboratories). The recommended schedule gave a seroconversion rate of 100% with a geometric mean titer of 585.9 mIU/ml. The low dose, short course schedule produced a seroconversion rate of 63.8% and a geometric mean titer of 73.8 mIU/ml. In the 5- to 9-year-old individuals, however, 71.6% seroconverted (geometric mean titer 114.2 mIU/ml). For cost reasons further investigations on low dose regimens are indicated.

Adolescent↗
PubMed1991

Characterization of a beta-lactamase produced by Pseudomonas paucimobilis.

A novel beta-lactamase enzyme produced by a strain of Pseudomonas paucimobilis is described. The enzyme differs from other recorded beta-lactamases from Gram-negative aerobic bacteria. It was constitutive, and had the characteristics of a penicillinase. One single band of beta-lactamase activity at pI 4.6 was seen on iso-electric focusing. The enzyme had a molecular mass of 30 kDa. The beta-lactamase was strongly inhibited by tazobactam, sulbactam and clavulanic acid but not by the thiol residue inhibitors p-chloromercuribenzoate and p-chloromercuriphenylsulphonic acid, or by metallo-enzyme inhibitors. Plasmid DNA was not demonstrable, suggesting that the enzyme was chromosomally encoded.

Cephalosporins↗
PubMed1991

Varying antibody response in dental health care workers vaccinated with recombinant hepatitis B vaccine.

Significance of the antibody levels to hepatitis B surface antigen (anti-HBs) as an indicator of protective immunity has recently been stressed. The aim of this study was to quantitatively evaluate the immune response in dental personnel vaccinated with Engerix B recombinant DNA vaccine (SK&F). The vaccine was administered to staff at the MEDUNSA Dental Hospital with either no immunity to HBV or with anti-HBs levels below 10 mIU/ml (n = 43). Anti-HBs was determined by AUSAB (Abbott) one, six and seven months after the start of vaccination and expressed in mIU/ml by comparison with a WHO standard. Only 29 per cent of seronegative subjects developed anti-HBs titers of greater than or equal to 10 mIU/ml after the first dose, while 94 per cent reached this level after the third dose. Results indicated that individuals with naturally acquired low anti-HBs were not protected against HBV before vaccination. All subjects previously vaccinated, but with anti-HBs below 10 mIU/ml, reacted with an anamnestic response and were therefore still immune. The overall antibody response after the third inoculation was good, with 95 per cent (41/43) acquiring a protective anti-HBs titer. However 6/43 were low responders with peak anti-HBs levels between 10-100 mIU/ml. Post-vaccination testing and quantitation of the immune response seems strongly advisable, both to identify non- and low responders and to give each vaccine a guideline to further vaccination.

Adult↗
PubMed1988

Radioiodination of murine anti-alpha-foetoprotein E.9 monoclonal antibody and its F(ab')2 fragment for the diagnosis of hepatocellular carcinoma.

The high incidence of hepatocellular carcinoma amongst certain population groups of Southern Africa made feasible the investigation of a radiolabelled monoclonal anti-alpha-foetoprotein as a radioimmunodiagnostic agent for this disease. This paper reports the preclinical trials with monoclonal anti-alpha-foetoprotein E.9 (anti-AFP) and its F(ab')2 fragment after radiolabelling with 131I. Various radioiodinations were tried. The best results were obtained with the lodogen and Bolton-Hunter methods. 131I from only one of the sources tested gave an 131I-labelled anti-AFP with meaningful immunoreactivity. It was shown by means of gamma-camera scans and monitoring of radioactivity in individual organs that 131I-anti-AFP and the 131I-anti-AFP F(ab')2 fragments did not accumulate abnormally in any organ(s) in healthy animals. The correlation in healthy mice of the biodistribution of 125I human IgG to 131I-anti-AFP, and 125I human IgG to 131I-F(ab')2 was good. Human hepatoma xenografts in athymic mice showed uptake of 131I-anti-AFP and the 131I-F(ab')2 fragment. The uptake of 131I-F(ab')2 was improved by liver background subtraction. There was correlation between circulatory alpha-foetoprotein concentrations and tumour uptake of 131I-F(ab')2 in tumour-bearing athymic mice and a definite relationship was found between tumour size and radiolabelled antibody and the F(ab')2 fragment. After the biological action of the 131I-anti-AFP and the 131I-F(ab')2 fragment was known, sterile pyrogen-free consignments were supplied for clinical trials in humans on a regular basis.

Animals↗
PubMed1986

Part of the human ribosomal RNA locus stabilizes a plasmid in yeast.

Most yeast plasmids--particularly those containing chromosomal replicators (ARS)--are unstable and do not segregate equally to mother and daughter cells unless they contain centromeric sequences. We have screened a fraction of the human genome for sequences that stabilize YRp7, a plasmid containing ARS1. We selected a fraction which we hoped would be enriched in human centromeric sequences--the DNA attached to the nucleoskeleton. We obtained one human sequence that partially stabilized a yeast plasmid and, surprisingly, it contained sequences homologous to those coding for the 3' end of 18s rRNA, the transcribed spacer and 5' end of 28s rRNA. This sequence did not show any ARS activity nor did it increase the copy number of the plasmid and so probably improved partition of the plasmid between mother and daughter cells. It had no homology to yeast centromeres.

Cloning, Molecular↗
PubMed1986

Comparative expression of hepatitis B virus antigens in several cell model systems.

In this paper the kinetics of hepatitis B virus (HBV) gene expression were investigated in natural and experimentally transfected cell systems. These systems included four human hepatocellular carcinoma cell lines containing HBV DNA (TONG/PHC, HEp 3B2, PLC/PRF/5 and HA22T/VGH) as well as a mouse and a rat cell line both experimentally transfected with HBV DNA. Comparative results on the kinetics of hepatitis B surface antigen in these cell systems suggested that the S gene in the integrated state is expressed at different levels. No human cell line derived from HBV-associated hepatocellular carcinoma produced hepatitis B e antigen (HBeAg) when medium was concentrated by ultrafiltration. In distinct contrast, the two experimentally transfected cell systems produced e antigen at different levels. When all HBV-containing cell lines were grown as tumours in nude mice, no HBeAg was detected in the serum of these mice inoculated with human hepatocellular carcinoma cell lines, in the tumour homogenates, or in the tumour-derived lines, whereas e antigen was expressed both in vivo and in vitro in the experimentally transfected cell lines. These observations indicate that C gene expression is restricted to transfected cell cultures and this suggests a distinct difference in the mechanisms of HBV gene expression between the two types of in vitro model systems.

Animals↗
PubMed1985

Hepatitis B virus gene expression in two cell lines, one derived from a natural human infection, the other experimentally infected in vitro.

Hepatitis B virus (HBV) gene expression was investigated in the PLC/PRF/5 human hepatoma cell line and the mouse L-cell line transfected with HBV DNA by modulating the in vitro growth conditions. Both cell lines contain the viral genome integrated into cell chromosomes and both have been shown to produce hepatitis B surface antigen only. Treatment with 5-azacytidine (5-azaC) did not enhance hepatitis B core antigen (HBcAg) synthesis in experimentally transfected mouse L cells. Low levels of hepatitis B e antigen (HBeAg) were detected from the L cells regardless of 5-azaC treatment, and synthesis of HBeAg was dependent on the growth state of the cultures. No HBcAg or HBeAg was detected in PLC/PRF/5 cells with or without 5-azaC treatment. This observation suggests that there is a distinct difference between experimentally transfected cells with HBV and the naturally derived material.

Animals↗