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Biomedical subjects

J D Ross

Publications and source records attributed to J D Ross.

At least 19 recordsLinked to original sources
PubMed2001

Demographic and behavioural profile of adults infected with chlamydia: a case-control study.

OBJECTIVES: To determine which demographic and behavioural parameters are independently associated with chlamydial infection in adults. METHODS: Subjects were recruited prospectively from male and female attendees at a large clinic for sexually transmitted infections (STI). All subjects were tested for chlamydia and gonorrhoea and asked to complete a questionnaire addressing demography, sexual and non-sexual (including drug taking) behaviour, and history of STI. Cases were those attending with a new clinical episode and found to be infected with chlamydia, but who did not have gonorrhoea. A control group was selected randomly from those found to be negative on screening for both infections. RESULTS: 986 cases and 1212 controls were recruited over one calendar year. The following were found to be independent risk factors for chlamydial infection on multivariate analysis (odds ratios with 95% confidence intervals in parentheses): being unmarried (1.8; 1.1-3.1); black Caribbean ethnicity (2; 1.5-2.7). Increasing age, fewer partners, and higher reported use of condoms were associated with a lower risk of infection. CONCLUSION: Black Caribbeans are at increased risk from chlamydia after controlling for sexual behaviour and socioeconomic status. Future research should seek an explanation elsewhere-for example, in terms of differences in sexual mixing or effectiveness of healthcare interventions.

Adolescent↗
PubMed2001

Protease inhibitor related type III hyperlipoproteinaemia is common and not associated with apolipoprotein-E E2/E2 phenotype.

OBJECTIVE: To determine the prevalence of type III hyperlipoproteinaemia in a cohort of HIV infected patients taking protease inhibitors and its correlation with the apolipoprotein-E2 isoform. DESIGN: Cross sectional study of 57 consecutive HIV infected subjects taking protease inhibitor therapy for a median of 12.5 (1-29) months, seen in an outpatient HIV clinic. Controls were 17 patients on non-nucleoside reverse transcriptor inhibitor therapy (NNRTI) for 9 (1-19) months and 50 antiviral naive patients. METHODS: Fasting cholesterol, triglyceride, HDL cholesterol, lipoprotein (a), and glucose were measured. Lipoprotein electrophoresis was performed on patients with a cholesterol >6.5 mmol/l and a triglyceride concentration of >4.5 mmol/l. Apolipoprotein-E phenotype was determined in serum. RESULTS: Dyslipidaemia was found in 43 (75%) PI treated patients-37 with triglyceride >2.3 mmol/l, 30 with cholesterol >6.5 mmol/l, and nine with HDL cholesterol <0.9 mmol/l. 38% had a lipoprotein (a) >300 mg/l. 11 patients (19.3%) had a type III hyperlipoproteinaemia pattern. Only one was homozygous for the E2 phenotype and none had clinical diabetes. An additional patient had a serum lipid profile compatible with type III hyperlipoproteinaemia and an E3/E2 phenotype in whom electrophoresis was not carried out before treatment. Six (35%) of the NNRTI and 16 (32%) of the antiviral naive patients had dyslipidaemia. 18 (31.6%) of the PI and none of the control patients had a cholesterol and/or triglyceride >8 mmol/l. CONCLUSION: Type III hyperlipoproteinaemia is common in this group of patients and need not be associated with the apolipoprotein-E2/E2 isoform. HIV protease inhibitors may interfere with lipoprotein receptor related protein.

Adult↗
PubMed2000

Suppression of a DnaX temperature-sensitive polymerization defect by mutation in the initiation gene, dnaA, requires functional oriC.

Temperature sensitivity of DNA polymerization and growth, resulting from mutation of the tau and gamma subunits of Escherichia coli DNA polymerase III, are suppressed by Cs,Sx mutations of the initiator gene, dnaA. These mutations simultaneously cause defective initiation at 20 degrees C. Efficient suppression, defined as restoration of normal growth rate at 39 degrees C to essentially all the cells, depends on functional oriC. Increasing DnaA activity in a strain capable of suppression, by introducing a copy of the wild-type allele, increasing the suppressor gene dosage or introducing a seqA mutation, reversed the suppression. This suggests that the suppression mechanism depends on reduced activity of DnaACs, Sx. Models that assume that suppression results from an initiation defect or from DnaACs,Sx interaction with polymerization proteins during nascent strand synthesis are proposed.

Bacterial Proteins↗
PubMed2000

Escherichia coli DNA polymerase III tau- and gamma-subunit conserved residues required for activity in vivo and in vitro.

The Escherichia coli DNA polymerase III tau and gamma subunits are single-strand DNA-dependent ATPases (the latter requires the delta and delta' subunits for significant ATPase activity) involved in loading processivity clamp beta. They are homologous to clamp-loading proteins of many organisms from phages to humans. Alignment of 27 prokaryotic tau/gamma homologs and 1 eukaryotic tau/gamma homolog has refined the sequences of nine previously defined identity and functional motifs. Mutational analysis has defined highly conserved residues required for activity in vivo and in vitro. Specifically, mutations introduced into highly conserved residues within three of those motifs, the P loop, the DExx region, and the SRC region, inactivated complementing activity in vivo and clamp loading in vitro and reduced ATPase catalytic efficiency in vitro. Mutation of a highly conserved residue within a fourth motif, VIc, inactivated clamp-loading activity and reduced ATPase activity in vitro, but the mutant gene, on a multicopy plasmid, retained complementing activity in vivo and the mutant gene also supported apparently normal replication and growth as a haploid, chromosomal allele.

Adenosine Triphosphatases↗
PubMed2000

Comparison of a ligase chain reaction-based assay and cell culture for detection of pharyngeal carriage of Chlamydia trachomatis.

In 264 genitourinary medicine clinic attenders reporting recent fellatio, the prevalence of pharyngeal Chlamydia trachomatis determined by an expanded standard including cell culture and two in-house PCR tests was 1.5% in 194 women and zero in 70 men. The ligase chain reaction (Abbott LCx) had a specificity of 99.2% and a positive predictive value of 60%.

Adult↗
PubMed2000

Potential to prevent carbon dioxide rebreathing of commercial products marketed to reduce sudden infant death syndrome risk.

OBJECTIVE: Rebreathing of exhaled air is one proposed mechanism for the increased risk for sudden infant death syndrome among prone sleeping infants. We evaluated how carbon dioxide (CO(2)) dispersal was affected by a conventional crib mattress and 5 products recently marketed to prevent prone rebreathing. SETTING: Infant pulmonary laboratory. EQUIPMENT: An infant mannequin with its nares connected via tubing to an 100-mL reservoir filled with 5% CO(2). The sleep surfaces studied included: firm mattress covered by a sheet, Bumpa Bed, Breathe Easy, Kid Safe/Baby Air, Halo Sleep System, and Sleep Guardian. The mannequin was positioned prone face-down or near-face-down. The sleep surfaces were studied with the covering sheet taut, covering sheet wrinkled, and with the mannequin arm positioned up, near the face. MEASUREMENTS: . We measured the fall in percentage end-tidal CO(2) as the reservoir was ventilated with the piston pump. The half-time for CO(2) dispersal (t(1/2)) is an index of the ability to cause or prevent rebreathing. RESULTS: Compared with the face-to-side control, 5 of 6 surfaces allowed a significant increase in t(1/2) in all 3 prone scenarios. The firm mattress and 4 of the 5 surfaces designed to prevent rebreathing consistently allowed t(1/2) above thresholds for the onset of CO(2) retention and lethal rebreathing in an animal model (J Appl Physiol. 1995;78:740). CONCLUSIONS: With very few exceptions, infants should be placed supine for sleep. For infants placed prone or rolling to the prone position, significant rebreathing of exhaled air would be likely on all surfaces studied, except one.

Bedding and Linens↗
PubMed1999

Viral sexually transmitted infections: current management strategies.

Viral sexually transmitted infections are a major health problem associated with considerable morbidity. This article reviews the current strategies used in the management of infections such as genital warts, genital herpes and molluscum contagiosum. Pros and cons of different treatment regimens have been discussed with an emphasis on a selective approach to therapy. The importance of education, counselling and follow-up is highlighted and issues relating to the associated psychosexual morbidity have been addressed. Treatment of these infections in pregnancy and HIV has also been described.

AIDS-Related Opportunistic Infections↗
PubMed1999

Do the factors associated with successful contact tracing of patients with gonorrhoea and Chlamydia differ?

OBJECTIVE: To assess and compare factors which may be associated with successful contact tracing in patients with gonorrhoea and chlamydia. STUDY DESIGN: Prospective observational study of patients attending a genitourinary medicine clinic with a diagnosis of gonorrhoea or chlamydia. Multivariate analysis model including demographic, socioeconomic, and behavioural variables. RESULTS: The attendance of at least one sexual contact was associated with naming more contacts for patients with gonorrhoea (OR 1.44, 95% CI 1.04-2.01). A history of gonorrhoea was associated with successful contact tracing for patients with chlamydia (OR 1.46, 95% CI 1.12-1.9). Successful contact tracing, as defined by at least one confirmed contact attendance after the index case, was not associated with age, sex, sexual orientation, history of chlamydia, use of condoms, marital status, ethnicity, or socioeconomic status for either gonorrhoea or chlamydia. CONCLUSIONS: Differences in the composition of the core groups infected with gonorrhoea and chlamydia are not explained by differences in contact tracing success. In the clinic setting studied, the outcome of contact tracing was not associated with a variety of demographic, socioeconomic, and behaviour factors.

Adult↗
PubMed1999

Asymptomatic urethritis and detection of HIV-1 RNA in seminal plasma.

OBJECTIVE: To define risk factors for detection of HIV-1 RNA in semen in men attending the two largest HIV clinics in the West Midlands. METHODS: 94 HIV-1 seropositive men at any stage of infection donated matched semen and blood samples. 36 subjects (38%) were on no antiretroviral treatment, 12 (13%) were on dual therapy, and 46 (49%) were on three or more drugs. Median CD4 count was 291 cells x 10(6)/l. 87 subjects underwent a urethritis screen (Gram stained urethral smear and culture for gonococcus, and LCR for Chlamydia trachomatis on first pass urine). Quantitative cell free HIV-1 RNA was determined by commercial nucleic acid sequence based assay with a lower detection limit of 800 copies/ml for semen and 400 copies/ml for blood. Independent risk factors for seminal HIV RNA detection were defined by logistic regression. RESULTS: In univariate analysis, subjects not taking antiretrovirals were 11 times more likely to shed HIV RNA (21/36 (58%) v 6/58 (10%); p < 0.0001). Seven subjects (8%) had urethritis (including one C trachomatis infection). Urethritis was significantly associated with detection of seminal HIV RNA (adjusted OR, 80.2; p = 0.006), as was blood plasma viral load (adj OR, 19.3 per factor 10 increase; p < 0.001) and age (adj OR, 1.16 per 1 year older; p = 0.001). Antiviral treatment status, absolute CD4 and CD8 count, clinical stage, treatment centre, ethnicity, and risk factor were not independent predictors. No subject with undetectable blood viral load had detectable seminal HIV RNA. CONCLUSION: Asymptomatic urethritis is independently associated with seminal HIV RNA shedding.

Adult↗
PubMed1999

Referral patterns between primary care and genitourinary medicine.

Many patients attending genitourinary medicine (GUM) clinics are self referred, but some patients initially present to their general practitioner (GP). The aim of this study was to describe the referral pattern of GPs in the Lothian region of Scotland to the local GUM clinic. A questionnaire was completed by all patients referred by their GP and a case note review supplied further diagnostic and demographic information. Of 1140 (23%) patients, 965 were available for study and were referred by their GP. There was a wide variability in referral rates from different practices and from different partners within a practice. The median referral rate per 100,000 practice population was 22.4/year (range 0-586). A referral letter accompanied the patient in 797/965 (83%) cases. The detection of cases of chlamydia and gonorrhoea in patients in primary care subsequently referred to the GUM clinic was low and poor diagnostic acumen for herpes simplex virus (HSV) was notable. No consistent practice for investigation or treatment prior to referral was found and there was marked failure of the investigations initiated in primary care to achieve diagnosis. Despite this, 24% of patients were already on treatment at the time of their GUM consultation. Few STDs were diagnosed in primary care and subsequently referred to the GUM clinic suggesting either failure to diagnose infections or reluctance to refer on for confirmation, treatment, test of cure and health education.

Adult↗
PubMed1998

Microscopy and latex antigen negative cryptococcal meningitis.

A HIV-positive patient presented with cryptococcal meningitis that was not detected by cerebrospinal fluid (CSF) latex antigen and direct microscopy. The diagnosis was confirmed by culture of the CSF and subsequent urine culture, both of which yielded an apparently acapsular strain of Cryptococcus neoformans. After 19 months the patient relapsed and capsulated yeasts were observed on this occasion on direct microscopy of the CSF. The latex antigen test was strongly positive. Culture again yielded an apparently acapsular isolate. Retrospective culture of all isolates obtained from this patient in sterile CSF resulted in the formation of capsules. This was confirmed by the requirement of normal non heat inactivated serum for neutrophil-cryptococcus attachment to occur in vitro. Although antigen and direct microscopy are frequently relied upon to diagnose cryptococcal meningitis, a negative result does not exclude the condition.

AIDS-Related Opportunistic Infections↗
PubMed1998

Biomechanical considerations of mandibular lengthening and widening by gradual distraction using a computer model.

PURPOSE: Experience using distraction osteogenesis for limb lengthening has shown the importance of appliance orientation. Although successful results of mandibular lengthening using osteodistraction have been reported, optimal orientation of the distractors relative to the mandible has not been determined. The purpose of this study was to evaluate the biomechanical effects of linear distractors placed parallel to the body of the mandible or parallel to the axis of distraction. MATERIALS AND METHODS: A two-dimensional model of the human mandible was generated for computer simulation of mandibular osteodistraction. Linear distractors were then analyzed based on their orientation, either parallel to the body of the mandible or parallel to the axis of distraction. In addition, two types of distraction osteogenesis procedures for mandibular reconstruction were analyzed: 1) bilateral mandibular lengthening, and 2) bilateral mandibular lengthening in combination with midline mandibular widening. RESULTS: Distractors oriented parallel to the body of the mandible caused a lateral displacement of the posterior components of the distraction devices and a reduction of the midline distraction gap during mandibular lengthening. These effects were eliminated when the device was oriented parallel to the axis of distraction. Midline symphyseal widening created axial rotation of the mandibular condyles regardless of the orientation of the distractors. CONCLUSIONS: Distraction appliances must be oriented parallel to the axis of distraction to prevent adverse biomechanical effects during bilateral mandibular lengthening. Additional ramus osteotomies, using hinged devices for angular correction, may be necessary to compensate for rotational movements of the mandibular condyles secondary to midline osteodistraction.

Biomechanical Phenomena↗