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Biomedical subjects

A M Johnson

Publications and source records attributed to A M Johnson.

At least 199 records · Page 11Linked to original sources
PubMed1993

Contributions to the phylogeny of Platyhelminthes based on partial sequencing of 18S ribosomal DNA.

Partial sequencing of the 18S ribosomal DNA gene of one nemertean and 13 free-living and parasitic Platyhelminthes (556 nucleotides), and of one nemertean and 20 Platyhelminthes (556 nucleotides) was used to test several hypotheses concerning the phylogenetic relationships of Platyhelminthes. The following conclusions were reached: the Neodermata is monophyletic; Trematoda (Aspidogastrea and Digenea) is monophyletic, although a sister group relationship of the Aspidogastrea and all other Neodermata cannot be definitely ruled out; the Cestoda comprising the Eucestoda, Amphilinidea and Gyrocotylidea is monophyletic; it is unresolved whether the Monogenea is paraphyletic; neither Gyrocotylidea and Monopisthocotylea nor Gyrocotylidea and Monogenea as a whole are sister groups; Anoplodiscus is a monopisthocotylean monogenean; none of Proseriata, Pterastericolidae/Umagillidae, Kalyptorhynchia, Rhabdocoela as a whole, Dalyelliida or the Temnocephalidae is the sister group of the Neodermata; there is some evidence that a larger taxon consisting of Proseriata, Tricladida and Rhabdocoela may be the sister group of the Neodermata but definitive evidence for a sister group relationship between the Neodermata and any turbellarian taxon is lacking; Rhabdocoela and Lecithoepitheliata are not closely related; it is unresolved whether the Rhabdocoela is monophyletic; Umagillidae, Pterastericolidae and Temnocephalidae belong to one monophylum; the Temnocephalidae are very close to the dalyelliids; Tricladida and Rhabdocoela are sister groups, the exact position of the Catenulida and Nemertini in relation to the Platyhelminthes has not been resolved, although Catenulida and Lecithoepitheliata may belong to one clade.

Animals↗
PubMed1993

Analysis of the 18S ribosomal RNA gene of Strongyloides stercoralis.

The entire 1766 bases of the 18S rRNA gene of Strongyloides stercoralis have been sequenced. The gene has a 38% G+C content. Although it is similar in length to the 18S rRNA gene of Caenorhabditis elegans, the only other completely sequenced nematode 18S rRNA gene, it is only 69% identical. Closely related helminths will need to be sequenced in order to delineate sequences specific for the diagnosis of strongyloidiasis.

Animals↗
PubMed1993

Detection and characterization of DNA polymerase activity in Toxoplasma gondii.

A DNA polymerase activity has been detected and characterized in crude extracts from tachyzoites of Toxoplasma gondii. The enzyme has a sedimentation coefficient of 6.4 S, corresponding to an approximate molecular weight of 150,000 assuming a globular shape. Like mammalian DNA polymerase alpha, the DNA polymerase of T. gondii was sensitive to N-ethylmaleimide and inhibited by high ionic strength. However, the enzyme activity was not inhibited by aphidicolin which is an inhibitor of mammalian DNA polymerases alpha, delta and epsilon and also cytosine-beta-D-arabinofuranoside-5'-triphosphate which is an inhibitor of alpha polymerase. The activity was inhibited by 2',3'-dideoxythymidine-5'-triphosphate which is an inhibitor of mammalian DNA polymerase beta and gamma. Magnesium ions (Mg2+) were absolutely required for activity and its optimal concentration was 6 mM. The optimum potassium (K+) concentration was 50 mM and a higher concentration of K+ markedly inhibited the activity. Activity was optimal at pH 8. Monoclonal antibodies against human DNA polymerase alpha did not bind to DNA polymerase of T. gondii. Thus the T. gondii enzyme differs from the human enzymes and may be a useful target for the design of toxoplasmacidal drugs.

Animals↗
PubMed1993

Tumours of the brain and presence of antibodies to Toxoplasma gondii.

The possible association between prior infection with the protozoan Toxoplasma gondii and development of brain tumours was investigated as part of two Australian population-based case-control studies of adult brain tumours. One study, based in Adelaide, South Australia, collected blood from 73 subjects with glioma, 53 subjects with meningioma and 348 controls. The other study, based in Melbourne, Victoria, collected blood from 44 subjects with glioma and 67 controls. All tumours had been verified histologically. IgG antibodies to T. gondii were measured using Enzyme Linked Immunosorbent Assay (ELISA) techniques. In both the centre-specific and combined analyses, there was no difference between subjects with glioma and controls in the prevalence of antibody test-positivity (35% test-positive in glioma versus 33% in controls, age-, sex- and centre-adjusted odds ratio (OR) = 1.00, 95% confidence interval (CI): 0.64-1.56). In the Adelaide study, there was a statistically significant increased risk of meningioma associated with antibody test-positivity (47% test-positive in meningioma versus 31% in controls, P = 0.02, adjusted OR = 2.09, 95% CI: 1.14-3.83). Our results do not support the hypothesis that antibody positivity to T. gondii is a risk factor for glioma, but suggest that it might be associated with meningioma.

Adult↗
PubMed1993

Patterns of hospital care for patients with HIV infection and AIDS.

OBJECTIVE: The aims were to describe the use of inpatient resources by patients with HIV infection and patients with AIDS; to examine trends in service use over time; and to provide data for planners concerned with service provision for HIV infection. SETTING: An inner London health district reporting 9% of AIDS cases nationally. DESIGN: Data on survival times and inpatient and day care use of resources were derived from existing patient records or collected prospectively between 1983 (when the first case of AIDS was diagnosed in the district) and 31 March 1990. SUBJECTS: A total of 488 HIV positive patients of whom 396 had been diagnosed as having AIDS were studied. MEASUREMENTS AND MAIN RESULTS: Inpatient days consumed per annum; trends in the number of bed days per person year with AIDS; the lifetime inpatient use per AIDS patient; and the influence of survival on service use estimates were determined. Altogether 16.4% of a total 17,785 hospital inpatient days were attributable to HIV positive patients who did not fulfil the criteria for AIDS. For patients with AIDS, there was an initial increase in the intensity of inpatient use in 1987 when a dedicated HIV ward was opened. After 1988, however, inpatient use fell to 30.8 bed days per person year with AIDS. Patients diagnosed after April 1987 had noticeably longer survival times than those diagnosed earlier (a median of 17-18 months compared with a median of 10-11 months). From 214 lifetime service use records, it was estimated that patients with short survival (less than six months) would consume 36 days of inpatient care, while those expected to survive longer would consume approximately twice that number of days, irrespective of how much longer they survived. CONCLUSIONS: The data indicate less intensive use of inpatient care by AIDS patients over time, and hence the apparent ability to manage an increasing AIDS patient workload without a comparable increase in occupied bed days. Increases in the size of that workload and changes in the survival profile of patients, together with a relatively constant rate of service demand by longer survivors, however, will continue to place increasing strains on finite inpatient resources. Further research is needed to establish the extent to which the greater use of outpatient and community services can offset this.

Acquired Immunodeficiency Syndrome↗
PubMed1993

Characteristics of very early onset autosomal dominant polycystic kidney disease.

Eleven children from eight families with autosomal dominant polycystic kidney disease who were diagnosed in utero (6 children) or in the first year of life (5 children) are reported here. Four children were evaluated for symptoms and three because of a sibling with very early onset disease. In three children, abnormal kidneys were found incidentally on a pregnancy screening ultrasound, and in only one child, the diagnosis was made by an ultrasound specifically directed at detecting polycystic kidney disease. Females were disproportionately represented among both the affected parents and offspring. Eight of the children were girls, and all affected parents were mothers. In three families, the parent's diagnosis was established only after the birth of the affected child. In two of these and in one other family, the mother's disease appeared to be the result of a new mutation. The most consistent renal ultrasonographic findings in the children were enlargement and increased echogenicity. On follow-up over 3 to 15 yr (mean, 6.8 yr) two children had ESRD and eight children had normal or nearly normal renal function as assessed by creatinine clearance. Renal concentrating ability was reduced in four children in whom it was measured. All children had bilateral renal cysts on follow-up, and nine children were hypertensive. Possible risk factors for early-onset disease identified in this study were an affected mother, an affected sibling, and an apparent parental new mutation. Symptoms and complications occurred frequently, but outcome was better than reported previously.

Adolescent↗
PubMed1993

Methodology of the National Survey of Sexual Attitudes and Lifestyles.

"The preparation and fieldwork for the National Survey of Sexual Attitudes and Lifestyles was carried out between 1987-1991. The survey was a combination of a face-to-face interview and self-completion questionnaire and comprised 18,876 individuals aged 16-59 years in Great Britain. The response rate was similar to other sample surveys on less sensitive topics. Women were overrepresented but the distributions of other demographic characteristics were similar to other data sets. The external validity and internal consistency of the data were found to be adequate. The likely sources and effects of bias are discussed."

Attitude↗
PubMed1993

A new international reference preparation for proteins in human serum.

A new international reference preparation for proteins in human serum will be released jointly by the Bureau Communitaire de Réference of the European Economic Community, Brussels, Belgium, and the College of American Pathologists, Northfield, Ill, in 1992-1993. This material has been prepared by the Committee on Plasma Protein Standardization of the International Federation for Clinical Chemistry. It is intended for use as a matrix reference from which values are to be transferred to working calibrants and controls for the immunoassay of serum proteins. The methods of preparation and value assignment are presented, along with a brief comparison of the international reference preparation for proteins in human serum with Reference Preparation for Serum Proteins Lot 4 and previous reference materials from the College of American Pathologists.

Blood Proteins↗
PubMed1992

Sexual lifestyles and HIV risk.

Britain's first large, national survey of sexual attitudes and lifestyles will allow improved estimates of the magnitude of the HIV epidemic in Britain and should lead to better strategies for prevention.

Adolescent↗
PubMed1992

Intracranial aneurysms in autosomal dominant polycystic kidney disease.

BACKGROUND AND METHODS: Intracranial aneurysms are a feature of autosomal dominant polycystic kidney disease, but their prevalence is uncertain. We studied 92 subjects with autosomal dominant polycystic kidney disease who had no symptoms or signs of any neurologic disorder. To determine the prevalence of intracranial aneurysms, we performed high-resolution computed tomography (CT) in 60 subjects, four-vessel cerebral angiography in 21, and both procedures in 11. RESULTS: Four of the 88 subjects in whom the radiologic studies were successfully completed had intracranial aneurysms (4 percent; 95 percent confidence interval, 0.1 to 9 percent), as compared with the prevalence of 1 percent reported for an angiographic study of the general population. Three of the four subjects had multiple aneurysms. Seven subjects for whom the results of CT studies were suspicious underwent cerebral angiography: two had aneurysms, and five had normal vascular structures that accounted for the suspicious results of tomography. Four subjects who had normal CT imaging studies also had normal angiographic examinations. Eight of the 32 subjects who underwent angiography (25 percent) had transient complications, as compared with 22 of 220 control subjects (10 percent) who did not have polycystic kidney disease (P less than 0.05). We could not identify any risk factor in these subjects that was related to the occurrence of aneurysm. CONCLUSIONS: Asymptomatic intracranial aneurysms appear to be more frequent in people with polycystic kidney disease than in the general population, although our 95 percent confidence interval includes the possibility of no difference. Because cerebral angiography is associated with increased morbidity in people with polycystic kidney disease, we recommend high-resolution CT as a screening test.

Adolescent↗