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Biomedical subjects

A M Johnson

Publications and source records attributed to A M Johnson.

At least 55 records · Page 3Linked to original sources
PubMed2001

Familial clustering of ruptured intracranial aneurysms in autosomal dominant polycystic kidney disease.

Ruptured intracranial aneurysm (RICA) is a life-threatening complication of autosomal dominant polycystic kidney disease (ADPKD). A family history of RICA may be a risk factor for RICA. Six hundred eight adult members of 199 ADPKD families were interviewed, and family pedigrees were constructed. Individuals were classified as having definite, probable, or possible RICAs from evidence and history obtained in interviews. Central nervous system (CNS) events not consistent with RICA were classified as other CNS events. Seventy-seven CNS events occurred in 906 subjects with ADPKD (8.5%) versus 13 events in 823 subjects without ADPKD (1.6%; P < 0.0001). No event in subjects without ADPKD was consistent with an RICA. Twenty-seven other (non-RICA) CNS events occurred in subjects with ADPKD (3%) versus 13 events in subjects without ADPKD (1.6%; P = 0.05). The frequency of RICA was increased in subjects with ADPKD: 21 definite RICAs in subjects with ADPKD (2%) versus none in subjects without ADPKD (P < 0.001); 28 definite and probable RICAs in subjects with ADPKD (3%) versus none in subjects without ADPKD (P < 0.001); and 50 definite, probable, and possible RICAs in subjects with ADPKD (5.5%) versus none in subjects without ADPKD (P < 0.001). The null hypothesis that RICAs are randomly distributed among subjects with ADPKD was tested for definite RICAs (n = 21), definite and probable RICAs (n = 28), and definite, probable, and possible RICAs (n = 50). In the three categories, the null hypothesis was rejected at P less than 0.05, P less than 0.05, and P less than 0.005, respectively. Vascular CNS events occurred more frequently in ADPKD than non-ADPKD family members, and clustering of RICAs occurred in families with ADPKD.

Adult↗
PubMed2001

The acceptability of urinary LCR testing for Chlamydia trachomatis among participants in a probability sample survey of sexual attitudes and lifestyles.

OBJECTIVES: To examine the factors that influence respondents' willingness to participate in urinary testing for Chlamydia trachomatis in a general population feasibility survey of sexual attitudes and lifestyles. METHODS: 199 sexually experienced, 18-44 year old participants, recruited as part of a larger (n=901) methodological study of sexual attitudes and lifestyles, were invited to provide a urine sample for chlamydial infection testing using ligase chain reaction (LCR) techniques. Analysis of the survey data and in-depth qualitative interviews were undertaken to explore the factors that influenced participants' decisions to participate. RESULTS: 143/199 (72%) participants agreed to provide a urine sample. The likelihood of providing a urine sample was reduced if other individuals were present in the home at the time of interview (OR 0.42, 95% confidence interval 0.20-0.90, p=0.03). Trust and rapport with the interviewer, understanding the aims of the test, sense of obligation, and perceived importance of the test were identified as additional influencing factors in the in-depth interviews. CONCLUSIONS: Survey respondents' uncertainty or embarrassment at participating in urine testing can be overcome if they are well informed, motivated by the potential health gain, and briefed by trained and confident interviewers.

Adolescent↗
PubMed2001

Protein standardization IV: Value transfer procedure for the assignment of serum protein values from a reference preparation to a target material.

A new approach for the assignment of values to serum proteins in a target material using a reference preparation has been developed. The procedure describes the general as well as the practical principles involved in the value assignment (with examples). Two models have been developed: 1) The direct value transfer between serum matrices and 2) the indirect value transfer from a pure protein preparation to a serum protein material. The necessary mathematical equations are developed and explained. The data reduction and statistical evaluation are discussed. The practical procedure (the transfer protocol) is based on six dilutions of the reference preparation assayed together with six dilutions of the target material. In this way imprecision is reduced and the proportionality of the two materials (i.e. the presence or absence of matrix effects) can be assessed directly by evaluating a single regression plot. If no matrix effects are found, the regression line will pass through zero with a slope equal to the ratio of the concentrations of the two materials. The transfer protocol is based on a multiple point value assignment obtained by several measurements a day repeated on several days, an important prerequisite being that all reconstitutions and dilutions are controlled by weighing.

Blood Proteins↗
PubMed2001

Effect of certified reference material 470 (CRM 470) on national quality assurance programs for serum proteins in Europe.

The introduction of the international reference material for serum proteins, CRM 470, has resulted in significant reduction of the among-laboratory variance for most proteins assayed in European national quality assurance programs. In general, the CVs have decreased by 5 to 65%. However, both among- and within-manufacturer variances in many cases remain unacceptably high. In addition, concentration-dependent differences in variance and bias are present for some proteins. Although some variance will persist, reducing variance and bias to levels required for the institution of universal reference ranges will necessitate more accurate transfer of values to calibrants and controls and improved calibration curve fitting by manufacturers, as well as better quality control within laboratories.

Blood Proteins↗
PubMed2001

Commutability of serum protein values: persisting bias among manufacturers using values assigned from the certified reference material 470 (CRM 470) in the United States.

Significant among-manufacturer differences in values for serum proteins persist 7 years after the introduction of the international reference material (Certified Reference Material 470; Reference Preparation for Proteins in Human Serum). In some cases, such as transthyretin and C4, the biases actually continue to increase. Further efforts at standardization are needed in order to improve commutability of results among laboratories and are essential if universal reference intervals are to be developed.

Blood Proteins↗
PubMed2001

The existing interim consensus reference ranges and the future approach.

The release of the reference material for serum proteins, CRM 470/RPPHS, in 1993, has given rise to a great improvement in the between-laboratory variability of serum protein measurements worldwide. However, conversion to the new reference material has resulted in significant changes in reference values for some proteins. The establishment of new reference ranges is currently in progress; in the interim, several professional societies and diagnostic companies have agreed to use consensus reference ranges based on studies that were already undertaken.

Adult↗
PubMed2001

Strategy for determining racial and environmental similarities and differences for plasma proteins.

The aim of this protocol is to establish a common basis for the production of reference values and well-defined and documented reference intervals for plasma proteins, based on common standardization, using the IFCC/BCR/CAP Certified Reference Material CRM 470. The strategy is to search for racial and environmental/geographical similarities and sources of differences in order to describe the main causes for variability among smaller or larger groups in selected societies and to estimate the sizes of differences for the different proteins according to the investigated sources. For this purpose, groups of reference individuals are selected according to race and geographical/environmental location, e.g. African Americans and Caucasians from the US. The reference individuals are groups of approximately 160 healthy male blood donors, 20 to 60 years of age. Rule-out criteria are positivity for HIV, hepatitis B and C antibodies and blood hemoglobin below the lower reference limit. Exclusion in relation to different C-reactive protein (CRP) levels will be investigated. Coagulation, storage conditions, transport, and the procedure for thawing are specified. The laboratories undertaking the measurements must have adequate analytical performance, and calibration and quality of performance are defined and documented, together with recommended control materials and procedures. Statistical models for describing distributions and for comparing groups are described. It is recommended that the data be presented as reference limits with 90% confidence intervals of those limits.

Adult↗
PubMed2001

Preparing for the NSF: a clinical governance model for diabetic care.

The imminent introduction of a National Service Framework for diabetes has highlighted the need to develop an appropriate nursing model of care. With over 1.4 million people affected by diabetes in the UK, a multidisciplinary approach is required. This paper discusses the benefits and difficulties associated with this during the development of a clinical governance model.

Diabetes Mellitus↗
PubMed2000

AIDS across Europe, 1994-98: the EuroSIDA study.

BACKGROUND: The clinical presentation of HIV-1 related diseases could have changed after the introduction of highly active antiretroviral treatment (HAART). We aimed to assess changes over time in the incidence of ADIs overall and within CD4 lymphocyte count strata, the relationship with treatment and degree of immunodeficiency at diagnosis of ADIs. METHODS: We did a prospective observational multicentre study of over 7300 patients in 52 European HIV-1 outpatient clinics. Incidence rates per 100 patient-years of observation were calculated. FINDINGS: In total, we recorded 1667 new ADIs; the incidence of ADIs declined from 30.7 per 100 patient-years of observation during 1994 (95% CI 28.0-33.4) to 2.5 per 100 patient-years of observation during 1998 (95% CI 2.0-3.0, p<0.0001, test for trend). Median CD4 lymphocyte count at diagnosis of a new ADI increased from 28 cells/microL to 125 cells/microL between 1994 and 1998 (p<0.0001), yet a steep decline in the rate of ADIs was seen after stratification by latest CD4 lymphocyte count within each year (< or = 50, 51-200, and > 200 cells/microL). Patients on HAART had a lower rate of ADIs than patients not on this treatment within each CD4 lymphocyte count strata. The proportion of ADIs attributable to cytomegalovirus retinitis and Mycobacterium avium complex declined over time (p=0.0058 and 0.0022, respectively), whereas the proportion of diagnoses attributable to non-Hodgkin lymphoma has increased (p<0.0001). In 1994, less than 4% of ADIs were non-Hodgkin lymphoma, in 1998 the proportion was almost 16%. This condition has become one of the most common ADIs in patients on HAART. INTERPRETATION: Our findings lend support to the idea that treatment regimens can lower the incidence of ADIs. The immediate risk of an ADI for a given CD4 lymphocyte count has declined over time and is lower among patients on HAART. Long-term follow-up of patients on combination treatment is essential to monitor the incidence of new and emerging diagnoses.

AIDS-Related Opportunistic Infections↗
PubMed2000

Nonweight-related body image concerns among female eating-disordered patients and nonclinical controls: some preliminary observations.

OBJECTIVE: Eating disorders(ED) have been classically associated with a concern about body shape and size that manifests mainly as an intense fear of weight gain (DSM-IV criteria). To further examine the nature of the body image disturbance in ED, we surveyed the prevalence of nonweight-related body image concerns among ED patients and nonclinical controls. METHOD: We examined 53 women (M +/- SD age: 28.1 +/- 6.8 years) with anorexia nervosa and/or bulimia nervosa (DSM-III-R criteria) and 73 randomly selected nonclinical women (M +/- SD age: 30.2 +/- 6.6 years) from the community. The participants rated (by checking a "Yes" or "No") whether they were satisfied with the appearance of the following body regions: their skin, teeth, jaw, nose, eyes, ears, hair, and height and completed the Drive for Thinness (DT) and Body Dissatisfaction (BD) subscales of the Eating Disorders Inventory (EDI). RESULTS: The frequencies of dissatisfaction with the appearance of various physical attributes among the ED patients versus the nonclinical controls were as follows: skin: 79.2% vs. 52.1%, p =.002; teeth: 62.3% vs. 39.7%, p =. 012; jaw: 24.5% vs. 9.7%, p =.026; nose: 45.3% vs. 24.7%, p =.015; eyes: 22.6% vs. 12.3%, p =.12; ears: 20.8% vs. 2.7%, p =.001; hair: 52.8% vs. 39.7%, p =.14; and height: 28.3% vs. 13.7%, p =.04. As expected, the M +/- SD DT (EDI): 14.0 +/- 6.1 vs.3.5 +/- 4.6, p <. 0001 and the M +/- SD BD (EDI): 19.7 +/- 5.8 vs. 10.1 +/- 7.3, p <. 0001, were both higher in the ED group. Furthermore, greater dissatisfaction with nonweight-related body image was associated with higher DT and BD scores. CONCLUSION: The higher prevalence of dissatisfaction with appearance of most of the nonweight-related physical attributes is probably an indication of the core ego deficits that are often present in ED and an index of the severity of the overall body image disturbance in these patients, and not indicative of another condition (e.g., body dysmorphic disorder) as the current nosology (DSM-IV) suggests.

Adult↗
PubMed2000

The production of a 70 kDa heat shock protein by Toxoplasma gondii RH strain in immunocompromised mice.

A 70 kDa heat shock protein (HSP70) has been reported previously to be strongly expressed in virulent Toxoplasma gondii strains taken from immunocompetent mice but it is poorly expressed by virulent parasites in mice immunocompromised by treatment with cortisone acetate or by virulent parasites cultured in vitro. Immune factors such as interferon-gamma, tumour necrosis factor and reactive nitrogen intermediates derived from nitric oxide are known to be important inducers of HSP70 production and are also known to be produced during the immune response to acute T. gondii infection. The ability of these immune factors to induce T. gondii HSP70 production was tested by analysing HSP70 production in tachyzoites of the virulent RH strain of T. gondii recovered from mice deficient in: (1) T cells (nude mice); (2) T and B cells (SCID mice); (3) interferon-gamma receptors (interferon-gamma receptor knockout mice); and (4) tumour necrosis factor receptors (tumour necrosis factor receptor knockout mice). Parasites from nude and SCID mice produced as much HSP70 as immunocompetent mice. Likewise, T. gondii tachyzoites from mice lacking receptors for interferon-gamma or tumour necrosis factor produced HSP70 in quantities similar to wild-type mice. The ability to produce reactive nitrogen intermediates in response to T. gondii infection, as detected by elevated levels of nitrate and nitrite in sera, was normal in tumour necrosis factor receptor knockout mice but was completely lacking in interferon-gamma receptor knockout mice, indicating that reactive nitrogen intermediates are also not responsible for induction of parasite HSP70. Thus, immune factors that induce HSP70 production in mammalian cells do not appear to play primary roles in inducing HSP70 production by T. gondii.

Animals↗
PubMed2000

Effect of antihypertensive therapy on renal function and urinary albumin excretion in hypertensive patients with autosomal dominant polycystic kidney disease.

Hypertensive patients with autosomal dominant polycystic kidney disease (ADPKD) have a faster progression to end-stage renal disease (ESRD) than their normotensive counterparts. The aim of this prospective, randomized study is to compare the effects of the calcium channel blocker amlodipine and the angiotensin-converting enzyme inhibitor enalapril as first-line therapy on blood pressure, renal function, and urinary albumin excretion in hypertensive patients with ADPKD. Twenty-four patients with ADPKD with hypertension with creatinine clearances (Ccrs) greater than 50 mL/min/1.73 m(2) were included in the study. Twelve patients received amlodipine (mean dose, 9 mg/d), and 12 patients received enalapril (mean dose, 17 mg/d). The patients were followed up for 5 years. Baseline mean arterial pressures, which were 109 +/- 3 mm Hg in the amlodipine group and 108 +/- 3 mm Hg in the enalapril group, decreased significantly after 1 year of follow-up (amlodipine, 96 +/- 3 mm Hg; P < 0.005; enalapril, 89 +/- 2 mm Hg; P < 0.0005) and remained stable at year 5 (amlodipine, 97 +/- 3 mm Hg; P < 0.0005 versus baseline; enalapril, 94 +/- 3 mm Hg; P < 0.005 versus baseline). Ccrs, which were 83 +/- 5 mL/min/1.73 m(2) in the amlodipine group and 77 +/- 6 mL/min/1.73 m(2) in the enalapril group, remained stable after 1 year of follow-up and decreased significantly at year 3 in both groups (amlodipine, 67 +/- 5 mL/min/1.73 m(2); P < 0.01 versus year 1 and baseline; enalapril, 58 +/- 4 mL/min/1.73 m(2); P < 0.05 versus year 1 and P < 0.0005 versus baseline) with no significant change thereafter. No change was observed in urinary albumin-creatinine ratio in the amlodipine group (baseline, 68 +/- 21 mg/g; year 1, 52 +/- 21 mg/g; year 5, 148 +/- 74 mg/g), whereas it decreased significantly in the enalapril group at year 1 (baseline, 23 +/- 4 mg/g; year 1, 13 +/- 3 mg/g; P < 0.05) and remained stable until the end of the study at year 5 (14 +/- 6 mg/g). The investigators concluded that blood pressure was similar in both groups but only enalapril had a significant effect to sustain decreased urinary albumin excretion for a 5-year follow-up. Although proteinuria has been considered a surrogate of renal disease progression, further studies will be necessary to confirm this hypothesis in ADPKD, because after 5 years, no differences in renal function were observed between the enalapril and amlodipine groups. In comparison with patients with ADPKD with uncontrolled hypertension, effective control of blood pressure, as undertaken in the present study, should delay the onset of ESRD by approximately 15 years.

Adult↗
PubMed2000

Anatomic and metabolic risk factors for nephrolithiasis in patients with autosomal dominant polycystic kidney disease.

The prevalence of nephrolithiasis is considerably greater in patients with autosomal dominant polycystic kidney disease (ADPKD) than in the general population. We evaluated anatomic and metabolic factors that may be associated with an increased prevalence of nephrolithiasis in patients with ADPKD. We compared anatomic parameters among ADPKD patients with or without nephrolithiasis as diagnosed by ultrasonography, whereas metabolic factors were determined by 24-hour urinary chemical analysis. Patients with ADPKD and nephrolithiasis had more renal cysts (P < 0.05) and a larger predominant renal cyst size (P < 0.005) than patients without nephrolithiasis. Concurrently, individual stone-forming kidneys had a greater cyst number (P < 0.05) and a significantly larger predominant cyst size (P < 0.01) compared with kidneys without stones. Patients with ADPKD and nephrolithiasis had a significantly lower creatinine clearance than those without nephrolithiasis (68.7 +/- 8.6 versus 94.8 +/- 5.4 mL/min, respectively; P < 0.05). Twenty-four-hour urinary analysis showed that patients with ADPKD and nephrolithiasis had significantly lower urinary volumes (P < 0. 05), and levels of urinary phosphate (P < 0.05), magnesium (P < 0. 005), and potassium (P < 0.05). Although not statistically significant, patients with ADPKD with stones tended to have lower levels of urinary citrate, and both groups showed a high percentage (range, 49% to 60%) of patients with hypocitraturia. Our data are consistent with the hypothesis that patients with ADPKD who develop nephrolithiasis do so because of increased intrarenal anatomic obstruction, as well as lower levels of such urinary inhibitors of stones as magnesium and citrate.

Adult↗
PubMed2000

Progress in blood pressure control in autosomal dominant polycystic kidney disease.

Hypertension occurs commonly in autosomal dominant polycystic kidney disease (ADPKD) and is an important factor in the progression of the disease and cardiovascular mortality. The aim of this prospective 15-year study is to report the rate of blood pressure control and the potential effect of a 10-point education program developed by our center for ADPKD patients and their physicians. The patients' blood pressure treatment was managed by their primary care physicians. Three 5-year periods were analyzed in which similar rates of hypertension in patients with ADPKD were present (63% to 68%). In the first period (1985 to 1989), the rate of blood pressure control (<140/90 mm Hg) was 38% for 216 hypertensive patients with ADPKD. From 1990 to 1994, the percentage of blood pressure control increased to 55% in 194 hypertensive patients with ADPKD (P < 0.001 versus 1985 to 1989); and the level of blood pressure control increased to 64% in 181 hypertensive patients with ADPKD during 1995 to 1999 (P < 0.001 versus 1985 to 1989). Although this percentage of blood pressure control in patients with ADPKD remains suboptimal, it compares very favorably with the 27% estimated blood pressure control in patients with essential hypertension from 1991 to 1994 in the United States.

Adult↗
PubMed2000

Effects of sequence alignment and structural domains of ribosomal DNA on phylogeny reconstruction for the protozoan family sarcocystidae.

Finding correct species relationships using phylogeny reconstruction based on molecular data is dependent on several empirical and technical factors. These include the choice of DNA sequence from which phylogeny is to be inferred, the establishment of character homology within a sequence alignment, and the phylogeny algorithm used. Nevertheless, sequencing and phylogeny tools provide a way of testing certain hypotheses regarding the relationship among the organisms for which phenotypic characters demonstrate conflicting evolutionary information. The protozoan family Sarcocystidae is one such group for which molecular data have been applied phylogenetically to resolve questionable relationships. However, analyses carried out to date, particularly based on small-subunit ribosomal DNA, have not resolved all of the relationships within this family. Analysis of more than one gene is necessary in order to obtain a robust species signal, and some DNA sequences may not be appropriate in terms of their phylogenetic information content. With this in mind, we tested the informativeness of our chosen molecule, the large-subunit ribosomal DNA (lsu rDNA), by using subdivisions of the sequence in phylogenetic analysis through PAUP, fastDNAml, and neighbor joining. The segments of sequence applied correspond to areas of higher nucleotide variation in a secondary-structure alignment involving 21 taxa. We found that subdivision of the entire lsu rDNA is inappropriate for phylogenetic analysis of the Sarcocystidae. There are limited informative nucleotide sites in the lsu rDNA for certain clades, such as the one encompassing the subfamily Toxoplasmatinae. Consequently, the removal of any segment of the alignment compromises the final tree topology. We also tested the effect of using two different alignment procedures (CLUSTAL W and the structure alignment using DCSE) and three different tree-building methods on the final tree topology. This work shows that congruence between different methods in the formation of clades may be a feature of robust topology; however, a sequence alignment based on primary structure may not be comparing homologous nucleotides even though the expected topology is obtained. Our results support previous findings showing the paraphyly of the current genera Sarcocystis and Hammondia and again bring to question the relationships of Sarcocystis muris, Isospora felis, and Neospora caninum. In addition, results based on phylogenetic analysis of the structure alignment suggest that Sarcocystis zamani and Sarcocystis singaporensis, which have reptilian definitive hosts, are monophyletic with Sarcocystis species using mammalian definitive hosts if the genus Frenkelia is synonymized with Sarcocystis.

Animals↗
PubMed2000

HIV, sexually transmitted infections, and risk behaviours in male commercial sex workers in Sydney.

OBJECTIVES: To assess prevalence of HIV and sexually transmitted infections (STIs), risk behaviours, and demographics in male commercial sex workers (CSWs)/prostitutes in Sydney. METHODS: Retrospective, cross sectional study with two comparison groups. Demographic, behavioural, and morbidity data were analysed from standardised medical records of patients attending a public STI and HIV service in Sydney between January 1991 and March 1998. Two comparison groups were used: female CSWs and non-CSW working homosexual men who attended over the same time. RESULTS: 94 male CSWs, 1671 female CSWs, and 3541 non-CSW working homosexual men were included. The prevalence of HIV in male CSWs tested (6.5%) was significantly greater than in female CSWs (0.4%, p = 0.0001), but less than in non-CSW homosexual men (23.9%, p < 0.0001). Genital warts occurred significantly more frequently in male CSWs than in comparison groups. Prevalence of other STIs was similar in all groups. Male CSWs saw significantly fewer clients per week than female CSWs and male and female CSWs used condoms with almost all clients. Male CSWs reported significantly more non-work sexual partners than female CSWs and non-CSW homosexual men and were significantly more likely to have unprotected penetrative sex with their non-work partners than non-CSW homosexual men. Injecting drug use was significantly more frequent in male CSWs than in both comparison groups. CONCLUSIONS: Although male CSWs use condoms with clients, they are more likely to practise unsafe sex with non-work partners (especially women) and inject drugs than female CSWs and non-CSW homosexual men. Some men with HIV are working within the commercial sex industry. Targeted health education to encourage safer drug use and safer sex outside work is needed.

Adolescent↗