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Biomedical subjects

A M Johnson

Publications and source records attributed to A M Johnson.

At least 127 records · Page 7Linked to original sources
PubMed1997

Surveillance of sexual behaviour among homosexual men in a central London health authority.

OBJECTIVE: To establish a surveillance mechanism of high risk sexual behaviour among homosexual and bisexual men living, socialising and using services in a central London health authority. DESIGN: Baseline survey for a system of repeatable behavioural surveillance using a self-completed questionnaire delivered by healthcare providers. SETTING: Genitourinary medicine clinics, gay bars, clubs, community groups and a cruising ground in the defined geographical area of a central London health authority. PARTICIPANTS: Five hundred and fifty three homosexual and bisexual men. MAIN OUTCOME MEASURES: Self-reported behaviours including unprotected anal intercourse (UAI), HIV status of unprotected anal intercourse partners, uptake of HIV testing and use of condoms at first time of anal intercourse. RESULTS: Five hundred and sixty questionnaires were returned (response rate 76%) from 553 men. A third (35%) of men surveyed had had UAI in the previous year. Nearly a fifth (19%) of the sample had had UAI with one or more partners of a discordant or unknown HIV status. A total of 343 (63%) men had had an HIV test. The proportion of men using condoms on the occasion of first anal intercourse has risen from 6% before 1980 to 88% after 1993. CONCLUSIONS: We have demonstrated that a surveillance programme to monitor high risk sexual behaviour among homosexual men can be easily established. The results can be employed to assess progress towards risk reduction targets and also inform future policy development. Our baseline data demonstrate that a large proportion of homosexual men are continuing to engage in high risk sexual behaviour, although there is some evidence of improvement in condom use at first anal intercourse over time. There is a need for continuing health promotion with evaluation among homosexual men.

Adolescent↗
PubMed1997

Direct estimates of prevalent HIV infection in adults in England and Wales for 1991 and 1993: an improved method.

OBJECTIVE: To estimate the number of prevalent HIV infections in England and Wales at the end of 1991 and 1993. METHOD: A direct method was used whereby population estimates derived from the National Survey of Sexual Attitudes and Lifestyle (NATSAL) and prevalence data from the Unlinked Anonymous HIV Prevalence Monitoring Programme (UAPMP) were combined to produce estimates of the number of adults infected and alive in the population. RESULTS: In the population of England and Wales the numbers of prevalent infections for defined transmission categories, at the end of 1993, were as follows: 12,600 through sex between men, 2500 through injecting drug use, and 6900 through heterosexual intercourse. The overall estimate was 22,800 HIV seropositive individuals. CONCLUSIONS: The direct method attempts to provide an estimate of the number of HIV infections using population based survey data. These estimates are consistent with other approaches using independent methods. Such methods are essential for inferring recent HIV incidence, projecting future AIDS cases, and for healthcare planning.

Adolescent↗
PubMed1997

Identification of patients with autosomal dominant polycystic kidney disease at highest risk for end-stage renal disease.

To identify those potential factors that, early in the course of disease, mark a population of patients with autosomal dominant polycystic kidney disease (ADPKD) who have worse renal survival, survival analysis and risk ratio calculation for 1215 ADPKD patients were performed. Survival times were calculated as time to dialysis, transplantation, or death. Risk ratios were calculated using the Cox proportional hazards model. Three hundred eighty-eight patients entered end-stage renal disease and 205 patients died. ADPKD2 subjects had longer renal survival than ADPKD1 subjects (median survival, 68 versus 53 yr; P < 0.0005; risk ratio, 2.5). Women had significantly better renal survival than men (56 versus 52 yr; P < 0.0001; risk ratio, 1.6). Subjects who were diagnosed before age 30 and those who developed hypertension before age 35 had worse renal survival than those subjects who were diagnosed after age 30 or those who remained normotensive after age 35, respectively (age of diagnosis: 49 versus 59 yr; P < 0.0001; risk ratio, 3.2; hypertension: 51 versus 65 yr; P < 0.0001; risk ratio, 4.4). Similarly, those who had an episode of gross hematuria before age 30 had a worse renal outcome than those who did not (49 versus 59 yr; P < 0.0001; risk ratio, 2.6). We have also calculated risk ratios for a combined model. When therapeutic interventions become available for this disease, these populations with high risk ratios should be considered for such interventions.

Adult↗
PubMed1997

Utility of ultrasonography in the diagnosis of autosomal dominant polycystic kidney disease in children.

To determine the utility of ultrasonography (US) in diagnosing autosomal dominant polycystic kidney disease (ADPKD) in children, this study examined 106 children who were at 50% risk for the disease. The children underwent a history, physical examination, abdominal US, and gene linkage analysis (GLA) with tightly linked markers for ADPKD1 and ADPKD2 genes. Only ADPKD1 children were studied. A child was considered affected by US if any cysts were detected and affected by GLA if he or she shared the same haplotype as the affected parent. Forty-two children (40%) were considered to be unaffected by both GLA and US. Forty-eight children (45%) were considered affected by both modalities. Only two of these children had a single cyst. Fourteen children (13%) were considered affected by GLA with normal initial US. These children tended to have larger kidneys than children who were unaffected by GLA. Eight of these 14 children had subsequent positive ultrasonograms. Two children had a positive ultrasonogram with GLA showing them to be unaffected; in one of these children, a subsequent ultrasonogram was interpreted to be normal with a medullary pyramid. Thus, overall the false negative rate was 25%, and the false positive rate was 2%. The false negative rate was highest in the children who were 3 months to 5 years of age (38%). Clinicians must understand the utility of US in diagnosing ADPKD in at-risk children and must not interpret a normal study as absence of disease in this population.

Adolescent↗
PubMed1997

Left ventricular hypertrophy in autosomal dominant polycystic kidney disease.

Cardiovascular complications are the most common cause of morbidity and mortality in patients with autosomal dominant polycystic kidney disease (ADPKD). To understand this relationship, known cardiovascular risk factors were examined in ADPKD. Left ventricular hypertrophy (LVH) is a known, important risk factor for premature cardiovascular death in patients with essential hypertension. Hypertension is known to occur frequently and early in ADPKD patients. The frequency of LVH in ADPKD patients and its relation with hypertension and other risk factors, however, is not known. In this study, echocardiographic tests were performed in 116 consecutive adult ADPKD patients and 77 healthy control subjects. There was a significantly higher frequency of LVH in ADPKD men (46 versus 20%, P < 0.05) and women (37 versus 12%, P < 0.005) compared with control subjects. LVH in ADPKD patients was associated with higher systolic and diastolic arterial BP. There also was an association between LVH, diminished renal function, and increased renal volume. When comparing ADPKD patients with and without LVH, the former were older, weighed more, had a higher prevalence of hypertension, and had a lower hematocrit value and more renal impairment. LVH was also present in 23% of normotensive ADPKD patients and 16% of healthy control subjects (P = NS), but did not correlate with BP. The role of BP as a contributing factor to LVH in ADPKD patients may be due in part to earlier onset and inadequate treatment.

Adult↗
PubMed1997

Isolation, genetic diversity, and geographic distribution of Bayou virus (Bunyaviridae: hantavirus).

Bayou hantavirus, previously implicated in human hantavirus pulmonary syndrome in Louisiana, was isolated from a rice rat (Oryzomys palustris) captured in Georgia. The presence of antibody among rice rats captured throughout the southeastern United States and the extent of diversity among the genetic variants of Bayou viruses suggest that the rice rat is the most likely natural reservoir of the virus and that both virus and host have probably co-evolved for some years.

Animals↗
PubMed1997

Capacity planning for the future.

Managed care is changing the way health care organizations plan for their futures. Traditional planning takes into account history and geography, while the new approach factors in the impact of managed care of future utilization. The new approach also incorporates strategic planning into an organization's broader strategic plan and budgeting process. The result is a more comprehensive planning method that is critical for health care organization's success.

Academic Medical Centers↗
PubMed1996

Production of a recombinant fusion protein of Sarcocystis tenella and evaluation of its diagnostic potential in an ELISA.

We have isolated a cDNA clone encoding an antigenic polypeptide of Sarcocystis tenella by screening a cystozoite-derived cDNA library in lambda gt11 with antibodies from sheep infected experimentally with S. tenella. This clone, termed STC29, was subcloned and expressed in the vector pGEX-3X as a soluble fusion protein with glutathione S-transferase having an apparent molecular mass of 46 kDa. Antibody raised against the recombinant fusion protein recognized a native polypeptide of 25 kDa in cystozoites of S. tenella. In an ELISA with sera from experimentally infected sheep, the recombinant STC29 antigen could differentiate infections with S. tenella from those with Sarcocystis arieticanis or Toxoplasma gondii. Hence, the research described here reports the identification of the first recombinant S. tenella antigen that may be useful for standardization of a serological test for the diagnosis of S.tenella infections in sheep.

Amino Acid Sequence↗
PubMed1996

Epidemiology of AIDS dementia complex in Europe. AIDS in Europe Study Group.

The aim of the study was to describe the epidemiology of AIDS dementia complex (ADC) in Europe and to assess the possible role of zidovudine therapy in preventing or delaying its occurrence. We used an inception cohort, with data collected retrospectively from patients' clinical records from 52 clinical centers in 17 countries across Europe. The subjects were 6,548 adult people with AIDS consecutively diagnosed from 1979 to 1989. The main outcome measures were codiagnosis of ADC at the time of AIDS diagnosis and ADC-free time after AIDS diagnosis. ADC was reported in 295 patients (4.5%) at the time of AIDS diagnosis and during follow-up in a further 402 of the 5,160 patients (7.8%) who were diagnosed with AIDS based on diseases other than ADC. Whether at the time of AIDS diagnosis or later, the occurrence of ADC was significantly associated with age, transmission category, and CD4+ cell counts. The risk was greater in older patients (14 and 19% greater, at AIDS diagnosis and after, respectively, for a 5-year difference in age), in i.v. drug users than in homosexual and bisexual men (89 and 60% greater, at AIDS diagnosis and after, respectively), and for people with lower CD4+ cell counts (14 and 30% greater for a reduction of 1 on the natural log scale). Risk was almost double for women than for men. A significant reduction, of approximately 40%, was found in the risk of developing ADC after AIDS diagnosis for patients receiving zidovudine therapy, but this effect was present only during the first 18 months of treatment, irrespective of whether treatment began before or after AIDS diagnosis. In conclusion, an increase in the risk of developing ADC either at the time of AIDS diagnosis or thereafter is associated with increasing age, i.v. drug use, and decreased CD4+ cell count. Women tend to have a higher risk of ADC at the time of AIDS diagnosis. Zidovudine therapy appears to have a definite, but time-limited, effect of protecting patients against ADC development after AIDS diagnosis.

AIDS Dementia Complex↗
PubMed1996

A RAPD-PCR derived marker can differentiate between pathogenic and non-pathogenic Sarcocystis species of sheep.

Random amplified polymorphic DNA (RAPD)-PCR was used to differentiate among four cyst-forming coccidia of sheep, Sarcocystis tenella, Sarcocystis gigantea, Sarcocystis arieticanis, and Toxoplasma gondii. Genomic DNA of the four parasite species was amplified using RAPD-PCR and the DNA fragments were separated on agarose gels. A RAPD-PCR band derived from S. tenella was isolated from the gel and subcloned into pUC18. The insert was sequenced and found to be 1278 nucleotides long. This sequence appeared to be cryptic in nature as it showed no significant sequence peculiarities or similarity with any other known sequences either at the nucleotide or derived amino acid levels. The recombinant plasmid was radiolabelled and used as a probe in Southern hybridization. This probe, termed pSTF10, hybridised to Mbo I restricted genomic DNA of S. tenella and S. arieticanis, but not to DNA of S. gigantea, T. gondii, mouse, or sheep. It is likely that STF10 will become a valuable diagnostic tool for Sarcocystis infections in sheep to differentiate between pathogenic species of this genus and S. gigantea or T. gondii.

Animals↗
PubMed1996

The growing importance of the plastid-like DNAs of the Apicomplexa.

Organisms in the phylum Apicomplexa possess, in addition to their mitochondrial genome, an extrachromosomal DNA that possesses significant similarities with the extrachromosomal genomes of plastids. To date, the majority of data on these plastid-like DNAs have been obtained from the human malarial organism, Plasmodium falciparum. In common with plastid DNAs, the plastid-like DNA of P. falciparum possesses genes for DNA-dependent RNA polymerase subunits beta and beta 1 and for organellar-like large- and small-subunits ribosomal RNAs. Both the polymerase subunit and ribosomal RNA gene sequences share a number of features with those from plastid DNAs. In addition, the ribosomal RNA genes are organised in an inverted repeat arrangement, reminiscent of plastid DNAs. Additional molecular features shared between the 2 genomes are discussed. Plastid-like DNAs have also been identified in other Plasmodium species as well as Toxoplasma gondii, Eimeria tenella, Babesia bovis and a number of Sarcocystis species. A cryptic organelle often observed in apicomplexans has been proposed as the organelle that harbours the plastid-like DNAs, but conclusive evidence for this has not yet been obtained. Although approximately 1/2 of the plastid-like DNA of P. falciparum has been sequenced to date, no function has yet been ascribed to this DNA or its putative organelle. Phylogenetic inferences based on sequence data from this DNA have indicated an evolutionary origin from photosynthetic organisms, but the true provenance of the plastid-like DNAs remains to be determined. Because of the specific nature of the plastid-like DNAs, they may prove useful as effective targets for chemotherapeutics.

Animals↗
PubMed1996

Insurance for autosomal dominant polycystic kidney disease patients prior to end-stage renal disease.

There recently has been substantial dialogue about access to health insurance for Americans. This discussion has highlighted the issues of pre-existing diseases and portability as barriers to adequate health insurance coverage. For these reasons we decided to investigate the issues relating to health insurance and life insurance coverage experienced by patients with autosomal dominant polycystic kidney disease (ADPKD). A questionnaire-based study was conducted. Two hundred thirty-eight of 354 subjects responded. There was no significant difference in gender, age, number of children, or level of renal function between responders and nonresponders. Twenty-eight of the 238 respondents had eight-stage renal disease and were eligible for Medicare; these patients were not used in the analyses relating to health insurance, but were used in the analyses relating to life insurance. Although 87% of the ADPKD patients were concerned about the availability of health insurance, 88% were currently insured. Eight-three percent of subjects with health insurance obtained it through their own or their spouse's employer. Of those individuals with employer-based health insurance who were aware of their ADPKD, only 25% informed their employer and 35% informed their insurer at the start of coverage. Fifty-seven percent of those with employer-based health insurance had this availability determine their job choice and 37% stayed in the job because of health insurance. Thirty percent of the subjects had previously been denied health insurance. Although subjects were less concerned about life insurance, many of the same types of issues and factors were present. Thus, the current lack of universal health care in this country creates anxiety and difficulties for patients with ADPKD. The effect of a pre-existing condition and the lack of portability resulted in denials, work choice limitation, and unwillingness to share health information for this patient population with a hereditary, systemic disease.

Adult↗
PubMed1996

Factors associated with the CD4+ lymphocyte count at diagnosis of acquired immunodeficiency syndrome. The AIDS IN EUROPE Study Group.

To assess which factors are associated with the CD4+ lymphocyte count at the time of AIDS diagnosis we studied 3046 patients in the AIDS IN EUROPE study who were diagnosed with AIDS in 1 of 17 European countries between 1979 and 1989 and for whom the CD4 count at AIDS diagnosis was known. Data were extracted retrospectively from patient case notes, using a standardized form. There was a wide range of average CD4+ lymphocyte counts at AID diagnosis, according to which diseases were present at diagnosis. The highest geometric mean CD4+ lymphocyte counts at AIDS diagnosis were associated with the diagnosis of extrapulmonary tuberculosis, Kaposi's sarcoma, and non-Hodgkin's lymphoma while the lowest counts were found when histoplasmosis and cytomegalovirus (CMV) retinitis were present. There were no appreciable differences between CD4+ lymphocyte counts at AIDS in patients according to the three major transmission route categories (sex, age, or region of diagnosis) but there was a marked trend (p < 0.005) toward lower CD4+ lymphocyte counts at AIDS diagnosis in more recent years. These associations remained largely unchanged after adjustment for other factors.

AIDS-Related Opportunistic Infections↗
PubMed1996

Behavioural risk factors for HIV infection amongst blood donors in London.

This paper compares the prevalence of risk factors for sexual acquisition of human immunodeficiency virus infection (HIV-1) among blood donors with the risk in the general population. Sexual behaviour data collected as part of a cross-sectional survey of central London blood donors were compared, after indirect standardization for age and sex, with those collected among Greater London participants of the National Survey of Sexual Attitudes and Lifestyles (NATSSAL). Overall, male blood donors had lower risk sexual lifestyles than age-matched NATSSAL participants in that they had had fewer lifetime female sexual partners, were more likely to have had first sexual intercourse after 16 years and were less likely to have had a homosexual partner. Men who have had sex with men since 1977 were asked not to donate blood. Despite this, 3.6% of male donors had had some sexual experience with another man and 1.9% had had sexual intercourse with at least one male partner. In contrast, female donors had had more sexual partners, were more likely to have had first sexual intercourse before 16 years and had probable higher rates of sexually transmitted disease (STD) clinic attendance than NATSSAL participants, explained by the much higher proportion of single rather than married female blood donors at each age. In conclusion, male donors had lower risk sexual lifestyles than age-matched NATSSAL participants, although even low levels of homosexual contact give some cause for concern. Female donors appeared to have higher risk sexual lifestyles than the general population because a much higher proportion of the female blood donors were single. The results provide important insights for those defining blood donor referral criteria.

Acquired Immunodeficiency Syndrome↗
PubMed1996

Relationship between antibodies to herpes simplex virus (HSV) and symptoms of HSV infection.

To determine the relationship between antibodies to herpes simplex virus (HSV) types 1 and 2 and diagnosis of orolabial and genital herpes, a cross-sectional survey was done among 869 sexually transmitted disease clinic attendees and 1594 blood donors in London. Among clinic attenders, the prevalence of HSV-1 infection was 59.5% and that of HSV-2 infection was 22.7%, and among blood donors the prevalence was 44.6% and 7.6%, respectively. The sensitivity and specificity of a diagnosis of oral herpes for the presence of HSV-1 antibody was almost identical in the 2 groups (clinic attendees: sensitivity, 33.1%, and specificity, 91.4%; blood donors: sensitivity, 32.3%, and specificity, 94.3%). A diagnosis of genital herpes was less sensitive for antibody for HSV-2 among donors than among clinic attenders (P < .001); however, the specificity was similar in the 2 populations (clinic attendees: sensitivity, 32.1%, and specificity, 96.6%; blood donors: sensitivity, 17.5%, and specificity, 99.5%). False-positive clinical histories were also relatively common (clinic attenders, 12%; donors, 6%). The sensitivity of the diagnosis of genital herpes would be improved if accurate serologic assays for detection of HSV type-specific antibodies were more widely available.

Antibodies, Viral↗
PubMed1996

Geographic variation in sexual behaviour in Britain: implications for sexually transmitted disease epidemiology and sexual health promotion.

OBJECTIVES: To explore geographical variation in sexual behaviour in Great Britain with reference to the prevalence of HIV infection. DESIGN: The National Survey of Sexual Attitudes and Lifestyles comprises a randomly selected, representative sample of almost 19,000 men and women aged 16-59 years living in Great Britain. METHODS: The survey was carried out using a combination of face-to-face interview and self-completion questionnaires and a wide range of data was collected. In this study, data on numbers and sex of sexual partners, condom use, injecting drug use, perception of risk of AIDS and lifestyle change were analysed, and comparisons were made between the different geographical areas in Great Britain. RESULTS: In the last 5 years, men living in Inner London were more likely to have a male partner [odds ratio (OR), 5.6; 95% confidence interval (CI), 3.1-10.0] or to have had 10 or more female partners (OR, 2.4; 95% CI, 1.6-3.6) than men living in other parts of the country. Similar results were observed for women living in Inner London: OR for a female partner in the last 5 years was 4.1 (95% CI, 1.6-10.2) and for five or more male partners in the last 5 years was 2.1 (95% CI, 1.5-2.8). More complex, but less striking patterns of behaviour were seen in different parts of the country. Both men and women living in Inner London were more likely to recognize that they were at some risk of acquiring HIV and were also more likely to report a change in sexual lifestyle. CONCLUSIONS: These analyses highlight the difficulties inherent in extrapolating from sexual behaviour data gathered using purposive samples to the population as a whole. The results are consistent with the known epidemiology of HIV and sexually transmitted diseases in Britain. The data suggest that cases of HIV will continue to be concentrated in Inner London, but Londoners are particularly aware of their risk. Reported behaviour change in response to perception of risk of AIDS underlines the importance of effective health promotion.

Adolescent↗