PubMed Health⌕ Search

Biomedical subjects

N A Smith

Publications and source records attributed to N A Smith.

At least 19 recordsLinked to original sources
PubMed2003

Used leucodepletion filters as a source of large quantities of DNA suitable for the study of genetic variations in human populations.

UNLABELLED: A simple technique for developing large control panels with large quantities of DNA suitable for studies in population genetics was established. BACKGROUND AND OBJECTIVES: Both a lack of suitable controls and insufficient quantities of DNA for repeated analysis of the same control group often hamper the investigation of genetic markers for disease. MATERIALS AND METHODS: Using a waste product from routine blood donation, we describe a simple method that allows the investigator to extract large amounts of DNA. RESULTS: A mean of 1520 microg of DNA per sample was obtained. The DNA obtained remains suitable for polymerase chain reaction and sequencing techniques after 2 years of storage at both 4 degrees C and -40 degrees C. CONCLUSION: This technique allows the development of a large panel of controls with sufficient quantities of genomic DNA for thousands of tests.

Blood Donors↗
PubMed2002

Chlamydial co-infection among patients with gonorrhoea.

The objective was to determine how often gonococcal (GC) infection is accompanied by chlamydial co-infection and to determine risk factors for dual infection. All GC-positive cultures were identified between 24 April and 9 September 1998, among patients seen at the three genitourinary medicine (GUM) clinics across the Chelsea and Westminster Directorate. Chlamydia trachomatis was diagnosed using an enzyme-linked immunosorbent assay (ELISA) (Dade-Behring). One hundred and fifty-three episodes of gonorrhoea were identified. Information on chlamydial infection was available for 149 cases of GC of whom 16 (10.7%) were found to be co-infected with C. trachomatis. In univariate analysis, chlamydial co-infection was exclusively diagnosed in heterosexuals, and was more likely to be diagnosed among females, in younger individuals and in individuals of black Caribbean ethnic group. In multivariable analyses, however, only the sex and age of the individual were independently associated with chlamydial co-infection. The rate of co-infection was 10.7%. Independent risk factors were being less than 20 years old and being female.

Adolescent↗
PubMed2001

Replicating satellite RNA induces sequence-specific DNA methylation and truncated transcripts in plants.

Tobacco plants were transformed with a chimeric transgene comprising sequences encoding beta-glucuronidase (GUS) and the satellite RNA (satRNA) of cereal yellow dwarf luteovirus. When transgenic plants were infected with potato leafroll luteovirus (PLRV), which replicated the transgene-derived satRNA to a high level, the satellite sequence of the GUS:Sat transgene became densely methylated. Within the satellite region, all 86 cytosines in the upper strand and 73 of the 75 cytosines in the lower strand were either partially or fully methylated. In contrast, very low levels of DNA methylation were detected in the satellite sequence of the transgene in uninfected plants and in the flanking nonsatellite sequences in both infected and uninfected plants. Substantial amounts of truncated GUS:Sat RNA accumulated in the satRNA-replicating plants, and most of the molecules terminated at nucleotides within the first 60 bp of the satellite sequence. Whereas this RNA truncation was associated with high levels of satRNA replication, it appeared to be independent of the levels of DNA methylation in the satellite sequence, suggesting that it is not caused by methylation. All the sequenced GUS:Sat DNA molecules were hypermethylated in plants with replicating satRNA despite the phloem restriction of the helper PLRV. Also, small, sense and antisense approximately 22 nt RNAs, derived from the satRNA, were associated with the replicating satellite. These results suggest that the sequence-specific DNA methylation spread into cells in which no satRNA replication occurred and that this was mediated by the spread of unamplified satRNA and/or its associated 22 nt RNA molecules.

Base Sequence↗
PubMed2001

Construct design for efficient, effective and high-throughput gene silencing in plants.

Post-transcriptional silencing of plant genes using anti-sense or co-suppression constructs usually results in only a modest proportion of silenced individuals. Recent work has demonstrated the potential for constructs encoding self-complementary 'hairpin' RNA (hpRNA) to efficiently silence genes. In this study we examine design rules for efficient gene silencing, in terms of both the proportion of independent transgenic plants showing silencing, and the degree of silencing. Using hpRNA constructs containing sense/anti-sense arms ranging from 98 to 853 nt gave efficient silencing in a wide range of plant species, and inclusion of an intron in these constructs had a consistently enhancing effect. Intron-containing constructs (ihpRNA) generally gave 90-100% of independent transgenic plants showing silencing. The degree of silencing with these constructs was much greater than that obtained using either co-suppression or anti-sense constructs. We have made a generic vector, pHANNIBAL, that allows a simple, single PCR product from a gene of interest to be easily converted into a highly effective ihpRNA silencing construct. We have also created a high-throughput vector, pHELLSGATE, that should facilitate the cloning of gene libraries or large numbers of defined genes, such as those in EST collections, using an in vitro recombinase system. This system may facilitate the large-scale determination and discovery of plant gene functions in the same way as RNAi is being used to examine gene function in Caenorhabditis elegans.

Arabidopsis↗
PubMed2001

Antiretroviral therapy for HIV-2 infected patients.

OBJECTIVES: To evaluate clinical and RNA load response to antiretroviral therapy amongst patients infected with HIV-2 and to study the development of drug resistance. METHODS: Seven HIV-2 seropositive patients were monitored with clinical examination, CD4 cell count and HIV-2 viral RNA load. Viruses from four subjects were genotyped and in vitro recovery of virus by co-cultivation with PBMCs and HVS T-cells was attempted. Viruses isolated from two subjects were assayed for phenotypic antiviral resistance. The main outcome measures were the relationship between disease stage, viral load, CD4 cell count, viral subtype and the clinical course of HIV-2 infection and the effect of combination antiretroviral therapy on disease progression, CD4 cell count, HIV-2 RNA viral load and drug resistance. RESULTS: The median time of follow-up was 3 years (range 0-8 years). Three patients had AIDS, and one had symptomatic disease. Of the four patients genotyped, three were infected with HIV-2 subtype B and one with subtype A. Viraemia was detectable only at CD4 counts of less than 300 x 10(6)/ml. Two patients with high viral loads failed to respond to antiretroviral therapy although their treatment may not have been optimal. One developed in vitro phenotypic antiviral resistance. The genotype of this patient's viral reverse transcriptase is being analysed. CONCLUSIONS: In contrast to HIV-1, HIV-2 RNA levels were often undetectable despite advanced disease and low CD4 cell counts. However, HIV-2 was clearly capable of causing CD4 cell depletion resulting in symptomatic disease. The principles of highly active antiretroviral therapy seem to apply to HIV-2 and suboptimal therapy may lead to drug resistance. The timing of therapy initiation, monitoring of response and the measurement of resistance remain unresolved issues and conclusions cannot be extrapolated from HIV-1.

Acquired Immunodeficiency Syndrome↗
PubMed2001

Lateral epicondylitis in a hospital phlebotomist--an ergonomic solution.

This report outlines a case of lateral epicondylitis in a hospital phlebotomist thought to be due to the forceful gripping, and repetitive twisting, involved in breaking the seals on green vacutainer needles. An ergonomic solution in the form of a device to aid breaking of the vacutainer seals is presented. The importance of seeking ergonomic solutions with manufacturers is highlighted.

Blood Specimen Collection↗
PubMed2000

Anticoagulant-induced pseudothrombocytopenia in a patient presenting for coronary artery bypass grafting.

A 73-yr-old man with severe ischaemic heart disease presented for coronary artery bypass grafting. His preoperative platelet count, obtained from an ethylene diamine tetraacetic acid (EDTA) sampling bottle, was 61 x 10(9) litre-1, but he had no history of bleeding problems. Previous platelet counts demonstrated results ranging from 16 x 10(9) litre-1 to 254 x 10(9) litre-1 with variable degrees of in vitro platelet clumping. Preoperative thrombelastography reflected a normal coagulation profile. The laboratory findings and the absence of a history of haemorrhagic complications suggested a diagnosis of EDTA-dependent pseudothrombocytopenia. We present the perioperative implications of this in vitro phenomenon and methods of detecting the functional and numerical integrity of circulating platelets.

Aged↗
PubMed1999

MRI of the brain in HIV-positive patients: what is the value of routine intravenous contrast medium?

Our purpose was to assess the value of routine administration of intravenous gadolinium-DTPA (Gd-DTPA) for cranial MR in a series of human immunodeficiency virus (HIV)-positive patients. Two radiologists retrospectively reviewed 150 consecutive examinations of 104 patients. All patients underwent unenhanced and contrast-enhanced images. Each radiologist independently assessed first the unenhanced images alone and then the pre- and postinjection images together. Then both reviewed the complete study and produced a consensus report. The history, investigations and management were collated separately and were unknown to the radiologists. Contrast-enhanced T1-weighted images showed new focal abnormalities, not seen on the T2-weighted or unenhanced images in 15 (14 %) patients, but almost always in the context of abnormal unenhanced images. In only 2 patients (2 %) did contrast medium reveal abnormalities when the unenhanced study had been considered normal. In only 1 of these (1 %) was the new finding, cytomegalovirus diffuse ependymal enhancement, of clinical importance, although the diagnosis of encephalitis was made on routine examination of cerebrospinal-fluid. The other revealed a toxoplasma lesion in a patient known to have resolving disease. Meningeal disease not suspected on the unenhanced images was shown in 2 patients (2 %). In these case the unenhanced images were abnormal in other respects. Intravenous Gd-DTPA was helpful to the radiologist in making a radiological diagnosis in 11 patients (11 %), usually by improving characterisation of a lesion seen on the unenhanced images. The contribution of intravenous Gd-DTPA in this series does not warrant recommending its use in every case.

AIDS Dementia Complex↗
PubMed1999

Red cell exchange in sickle cell disease.

Red cell exchange transfusion is frequently of use in the management of patients with sickle cell disease either electively or therapeutically. Modern cell separators allow this procedure to be performed rapidly, effectively and safely. These machines have a number of advantages over manual exchange procedures. The patient remains isovolaemic, there is little loss of plasma or platelets, the procedure is relatively short and in elective circumstances can be performed on an outpatient basis. In this series 66 exchanges were performed on 21 patients with an overall increase in HbA of 70%. The COBE Spectra gave a mean increase in HbA of 77%, with the majority of patients achieving an HbA of > 90% post exchange. Automated redcell exchange was well tolerated by most patients, and adverse effects were limited to symptoms of hypocalcaemia which were easily treated, and to transfusion reactions. Cell separators can therefore be recommended for exchange transfusion in patients with sickle cell disease, who require an increase in HbA levels either prophylactically or therapeutically. They are safe, effective, easy and quick to use.

Anemia, Sickle Cell↗
PubMed1999

Human herpesvirus 8: seroepidemiology among women and detection in the genital tract of seropositive women.

An indirect IFA to detect antibodies against latent nuclear antigens of human herpesvirus 8 (HHV-8) was used to determine the prevalence of HHV-8 antibodies in 169 women attending a sexually transmitted diseases clinic and a human immunodeficiency virus (HIV) clinic at a London hospital. Nested polymerase chain reaction was used to detect HHV-8 DNA in 93 blood samples and 89 cervical brush scrapes (CBS). Another 96 CBS from women attending a colposcopy clinic were also analyzed. The overall seroprevalence of HHV-8 was 18.3%. The seroprevalence was higher among women born in Africa (24.7%) than among women born elsewhere (11.5%; P=.06) and was independent of HIV serostatus. HHV-8 DNA was detected in 3 CBS and 6 peripheral blood samples from 11 HHV-8-seropositive women but not in CBS from 78 seronegative women, 96 women from the colposcopy clinic, or in blood samples from 82 seronegative women.

Africa↗
PubMed1999

Serologic evidence of human herpesvirus 8 transmission by homosexual but not heterosexual sex.

Epidemiologic studies link Kaposi's sarcoma with a sexually transmitted agent. Human herpesvirus 8 (HHV-8) is likely to be that agent, but routes of transmission are poorly described. A seroepidemiologic study was conducted to determine whether HHV-8 is transmitted sexually between heterosexuals. Sera from 2718 patients attending a sexually transmitted disease (STD) clinic were tested for antibodies to HHV-8 and herpes simplex virus type 2 (HSV-2). Information on sex partners in the previous 12 months and past STDs were obtained by questionnaire. Relationships between possible risk factors and HHV-8 infection were assessed by logistic regression. Overall, seroprevalence of HHV-8 was 7.3%. Independent risk factors for HHV-8 in the whole group were homo/bisexuality and birth in Africa and, among homo/bisexual men, a history of syphilis and HSV-2 and human immunodeficiency virus seropositivity. Among heterosexuals there was no evidence for sexual transmission; the only independent risk factor for HHV-8 seropositivity was birth in Africa.

Adolescent↗
PubMed1999

Evidence for horizontal and not vertical transmission of human herpesvirus 8 in children born to human immunodeficiency virus-infected mothers.

A survey of antibody responses to human herpesvirus 8 (HHV-8) was undertaken to examine the mode of transmission of this virus to children born to mothers with HIV. Methods. Serum samples from a cohort of 92 mother-infant pairs and a cross-sectional cohort of 100 children (median age, 4 years) were tested. In the cohort of mother-infant pairs, 14 infants were HIV-infected, 72 were not and the HIV status was unknown for 6. In the cohort of children 70 were HIV-infected and 30 were vertically exposed but uninfected. Serologic responses to two HHV-8 antigens, latency-associated nuclear antigen and the structural antigen encoded by open reading frame 65 were detected by immunofluorescent antibody test and enzyme-linked immunoassay. Results were confirmed by Western blot. Results. All HHV-8-seropositive mothers were African (17 of 92, 18.5%). Six of their infants were HHV-8-seronegative and 11 had at least 1 HHV-8-seropositive sample. One of the 11 infants tested only at birth had a lower antibody titer than the mother; the remaining 10 infants had decreasing titers up to 7 months of age and 6 became seronegative. No infants born to HHV-8-seronegative mothers had antibodies to the virus. The seroprevalence to HHV-8 was 6% in the cohort of children. All had African mothers and their median age was greater than that of the cohort (8.4 vs. 4.0 years). Five were coinfected with HIV. Conclusions. HHV-8 was not vertically transmitted by any of the HIV-coinfected mothers. Acquisition of antibody to HHV-8 occurred in older children, implying a horizontal route of transmission.

Adult↗
PubMed1998

Efficacy of ramipril in therapy-resistant hypertension.

In an open, 48-week study the antihypertensive efficacy of ramipril when administered as add-on therapy to existing triple antihypertensive treatment (diuretics, beta-blockers, vasodilators) was investigated in 56 patients (24 females, 32 males) with therapy-resistant hypertension. The main variable (sitting diastolic blood pressure) decreased from 112 mmHg at baseline to 91 mmHg at week 8 (p < 0.01) and remained stable thereafter until the end of the trial. The systolic blood pressure in the sitting position decreased from 175 mmHg at baseline to 146 mmHg at week 8 (p < 0.01) and also remained stable thereafter until the end of the trial. Ramipril doses between week 8 and the end of the trial were not changed in 82% of patients. 45% of patients were treated with 5 mg ramipril/day, 33% with 10 mg/day and 22% with 20 mg/day at the end of the study. Addition of ramipril allowed a reduction in the doses of concurrrent therapy, especially in relation to beta-blockers (p < 0.02) and vasodilators (p < 0.01). The safety was good--no serious adverse events were observed. Ramipril is, therefore, a suitable drug for the patients with therapy-resistant hypertension allowing reduction of the doses of concomitant medication.

Adult↗