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Biomedical subjects

D Lewis

Publications and source records attributed to D Lewis.

At least 37 records · Page 2Linked to original sources
PubMed1995

PCR analysis of HIV-seronegative, heterosexual partners of HIV-infected individuals.

A cohort of human immunodeficiency virus (HIV)-discordant couples was established to evaluate risk factors associated with heterosexual viral transmission. Polymerase chain reaction (PCR) was utilized to document the HIV-uninfected status among members of discordant heterosexual couples and to rule out immunosilent infection. HIV DNA PCR specific for a gag gene region was performed on peripheral blood mononuclear cell samples from 203 HIV antibody-negative adults who have long-term heterosexual relationships with HIV-infected partners. The results were negative for 200 but consistently positive in three individuals. More extensive evaluation of these three individuals with an additional primer pair specific for the envelope gene, quantitative DNA PCR, multiple additional time points, and variable nucleotide tandem repeat analyses revealed specimen processing problems in two cases but an apparent true positive PCR assay in the third case. This subject remains antibody and PCR negative for a 32-month follow-up period. These results confirm previous studies that document a negligible incidence of occult HIV infection as delineated by PCR in antibody negative heterosexual partners of HIV-infected individuals. Specimen processing errors occur at a low rate (1% in this study) and require careful evaluation. The possibility of transient, aborted infection versus successful infection with a long immunosilent period was observed in a single individual. Definitive resolution of infection status will require long-term evaluation.

Adult↗
PubMed1995

Mutational analysis of the peptide segment linking phosphorylation and Ca(2+)-binding domains in the sarcoplasmic reticulum Ca(2+)-ATPase.

The sarcoplasmic reticulum ATPase segment extending from the phosphorylation site (Asp-351) to the preceding transmembrane helix M4 (which is involved in Ca2+ binding in conjunction with transmembrane helices M5, M6, and M8) retains a marked sequence homology to the corresponding segments of other cation ATPases. We made 26 point mutations in this segment and found that nonconservative mutations of residues that are homologous in various cation ATPases result in strong inhibition of catalytic and transport function. Mutations of nonhomologous residues to match the corresponding residues of other cation ATPases are not inhibitory and, in some cases, produce higher activity. The inhibitory mutations affect the phosphorylated intermediate turnover, which is associated with the vectorial translocation of bound Ca2+. The same mutations do not affect the kinetics of ATPase activation by Ca2+ following enzyme preincubation with EGTA. This suggests that activation of the phosphoryl transfer reaction by Ca2+ binding and vectorial displacement of bound Ca2+ by enzyme phosphorylation do not occur simply as the forward and reverse directions of the same process, but are linked to distinct structural features of the enzyme. The peptide segment extending from the phosphorylation site in the enzyme extramembranous headpiece through the M4 helix in the membrane-bound region sustains a prominent role in transmission of the phosphorylation signal for displacement of bound Ca2+. A critical structural role of this segment is also demonstrated by the interference of specific mutations with membrane assembly of the expressed protein.

Animals↗
PubMed1995

Detection and characterisation of bisegmented double-stranded RNA viruses (picobirnaviruses) in human faecal specimens.

The prevalence of picobirnaviruses (PBVs) in human stools was investigated by polyacrylamide gel electrophoresis (PAGE) analysis of 832 faecal specimens collected between 1982 and 1993 from patients in various clinical groups. Similar prevalences (9-13%) were detected in patients with or without gastroenteritis and throughout the age range of 3 to > 65 years. Two methods for the extraction of nucleic acid, a phenol/chloroform method and a guanidinium thiocynate (GTC)/silica method, were compared. Detection of PBVs by PAGE was three times more sensitive following RNA extraction by the GTC/silica method. Characterisation of three strains was carried out. Segment sizes ranged from 1.625 to 1.95 kilo base pairs (Kbp) and 2.2 to 2.5 Kbp for the fast and slow migrating bands, respectively. The nuclic acid was shown to be double-stranded RNA (dsRNA) by nuclease digestion. PBV-like particles were detected by electron microscopy in two PAGE-positive stools. Virion diameters ranged from 35 to 41 nm and a buoyant density of 1.38-1.4 g/ml in caesium chloride (CsCl) was demonstrated. These findings suggest that PBVs are widespread in humans in the United Kingdom. However, no disease association could be demonstrated.

Adolescent↗
PubMed1995

Broadly reactive reverse transcriptase polymerase chain reaction for the diagnosis of SRSV-associated gastroenteritis.

A limitation to date of reverse transcriptase polymerase chain reactions (RT-PCRs) for the detection of small, round structured viruses (SRSVs) has been that they have detected only a narrow range of SRSVs due to the marked genomic diversity among strains. A total of 331 faecal samples collected from 136 separate incidents of gastroenteritis occurring in the UK between 1992 and 1994 were examined by RT-PCR employing a single primer pair (N1/E3). SRSV RNA was detected in samples from 93 of 101 (91%) incidents shown to be SRSV-associated by electron microscopy (EM) and in 5 of 35 (14%) SRSV-negative incidents. Amplification products were tested by Southern blot hybridisation with a pool of four digoxigenin (DIG)-labelled oligonucleotides derived from genomic sequence data of SRSV SPIEM types UK 1 to 4. Products from approximately 5% of amplified strains did not hybridise. The N1/E3 primer pair were shown to be SRSV-specific by their failure to amplify other faecal viruses including other human caliciviruses with typical calicivirus morphology. Hybridisation of PCR products with the individual oligonucleotides relating to SRSV SPIEM types UK 1-4 was investigated: 1 of 60 (1.7%) reacted with the UK1 probe, 2/60 (3.4%) reacted with the UK2 probe, 51/60 (85%) with the UK3 probe, and 27/60 (45%) reacted with the UK4 probe. All PCR products that hybridised with the UK4 probe hybridised with the UK3 probe; 6 (10%) failed to hybridise. Identification of this primer pair facilitates routine diagnosis of SRSV infection by RT-PCR and offers the potential for direct detection in food and environmental samples.

Animals↗
PubMed1995

Ca2+ binding and translocation by the sarcoplasmic reticulum ATPase: functional and structural considerations.

Three experimental systems are described including sarcoplasmic reticulum (SR) vesicles, reconstituted proteoliposomes, and recombinant protein obtained by gene transfer and expression in foreign cells. It is shown that the Ca(2+) ATPase of sarcoplasmic reticulum (SR) includes an extramembranous globular head which is connected through a stalk to a membrane bound region. Cooperative binding of two calcium ions occurs sequentially, within a channel formed by four clustered helices within the membrane bound region. Destabilization of the helical cluster is produced following enzyme phosphorylation by ATP at the catalytic site in the extramembranous region. The affinity and orientation of the Ca2+ binding site are thereby changed, permitting vectorial dissociation of bound Ca2+ against a concentration gradient. A long range linkage between phosphorylation and Ca2+ binding sites is provided by an intervening peptide segment that retains high homology in cation transport ATPases, and whose function is highly sensitive to mutational perturbations.

Animals↗
PubMed1995

Successful prenatal management of hydrops, caused by congenital cystic adenomatoid malformation, using serial aspirations.

Congenital cystic adenomatoid malformation (CCAM) is a lung lesion that is now commonly diagnosed in utero with fetal ultrasonography. The described treatment of this lesion includes observation with treatment delivery, a single aspiration, thoraco-amniotic shunts, and fetal resection. This patient had an in utero diagnosis of a Stocker type I CCAM associated with hydrops. Fetal resection was not an option because of patient refusal. The fetus was treated with multiple serial aspirations. There was marked improvement of the anasarca, and subsequently the baby was born without respiratory distress. On the second day of life the CCAM began to expand, and the right lower lobe was resected. The baby's postoperative course was uneventful. CCAM with hydrops is associated with a high mortality rate. Current recommended therapy for these lesions is fetal resection or thoracoamniotic shunt. The authors' patient was treated with serial fetal thoracocenteses, with an excellent outcome. This therapy may be an alternative to fetal surgery or an adjunct to fetal surgery in selected cases.

Adult↗
PubMed1995

Enzyme inhibition during the conversion of squalene to cholesterol.

Two separate enzymatic assays were developed in order to test the selectivity of inhibitors in cholesterol biosynthesis. One assay detects inhibition of delta 5.7-sterol delta 7-reductase, the enzyme involved in the conversion of 7-dehydrocholesterol to cholesterol. Delta 5.7-Sterol delta 7-reductase was inhibited by both RPR 101821, a protonated cyclohexylamine, and BM 15.766, a piperazine derivative, with IC50 values of 1 microM. The second assay detects accumulation of any of five intermediates (squalene oxide, squalene dioxide, lanosterol, desmosterol, and 7-dehydrocholesterol) upon inhibition of enzymes catalyzing reactions in the conversion of squalene to cholesterol. In this assay, inhibition data were most accurate when control assays exhibited a conversion of squalene to cholesterol in the order of 50%. The time required to attain 50% conversion of squalene to cholesterol was 6 h. Given a high inhibitor to substrate concentration ratio and the possible values of Ki, kon, and koff for the reaction between enzymes and inhibitor to form enzyme-inhibitor complexes, it was predicted that in the presence of inhibitors, intermediate accumulation could still be observed after 6 h incubation. The experimental results were in agreement with this prediction.

Animals↗
PubMed1995

Frequent measurement of chronic pain: an electronic diary and empirical findings.

The PIPER (Prompting Intensity of Pain Electronic Recorder) is a compact data-logging device, easily worn by a subject. It emits audible beeps at pre-programmed times, prompting the subject to enter a pain rating by button press. Ratings are stored, for later down-loading. We report two studies suggesting that PIPER pain ratings have good reliability, and good validity assessed against the VAS. In a third study, the PIPER was found practical for use by elderly subjects, and for periods of more than 2 months. In addition, PIPER pain ratings taken 4 times per day were found to have different properties than 4 other measures of chronic pain, suggesting that very frequent measures should be taken if a full understanding of chronic pain is to be obtained.

Aged↗
PubMed1995

Viral measurement by polymerase chain reaction-based assays in human immunodeficiency virus-infected infants.

Serial samples from human immunodeficiency virus-infected infants in the first year of life were analyzed by quantitative human immunodeficiency virus polymerase chain reaction assays. Very high, persistent levels of plasma RNA and proviral DNA were detected throughout the study period, suggesting the absence of an effective immune response. Most patients had normal CD4 lymphocyte counts and were symptom free for the first 3 to 6 months despite high levels of viral replication. These findings support the evaluation of early intervention (before symptoms develop) and efforts to establish the predictive value of these assays.

CD4 Lymphocyte Count↗
PubMed1995

The detection of hydrocodone in meconium: two case studies.

The detection of hydrocodone in meconium samples is reported for the first time. Hydrocodone, a semisynthetic antitussive and analgesic, is often prescribed as a painkiller following minor surgery or dental work. It also cross-reacts in enzyme and fluorescence polarization immunoassay opiate systems. In two cases recently received by our laboratory, hydrocodone was detected following a positive opiate immunoassay screening result. The meconium samples were not hydrolyzed because previous work in our laboratory showed that greater than 70% of morphine in meconium is not glucuronide bound. The confirmatory procedures showed that, in case No. 1, codeine was also detected but at a much lower concentration than the hydrocodone. In case No. 2, morphine was detected but, again, at a much lower concentration than the hydrocodone. Even though in both samples another opiate was also detected, the possibility still remains that a positive opiate test result may be reported by screen-only laboratories based solely on the presence of hydrocodone. We present a novel extraction method and a gas chromatographic-mass spectrometric confirmatory procedure for the determination of hydrocodone and hydromorphone in meconium.

Codeine↗
PubMed1995

Predicting hypoxia in children with acute lower respiratory infection: a study in the highlands of Papua New Guinea.

Pneumonia accounts for nearly half of all admissions amongst children less than 5 years of age to health centres and hospitals in the highlands of Papua New Guinea. Until recently, the indications for the use of oxygen in the management of childhood pneumonia in Papua New Guinea had been confined to the detection of cyanosis and restlessness. Oxygen is, however, difficult to deliver to many parts of Papua New Guinea, leading to high transport costs and shortages. Health workers in rural areas are continually faced with decisions as to which children should be given oxygen when it is in short supply. This study related clinical signs to the oxygen saturation of the blood using a pulse oximeter, in order to offer rational criteria for the use of oxygen in health centres and hospitals in remote areas. Data were collected on 110 children who were admitted to Tari Hospital with a diagnosis of moderate or severe pneumonia. Following admission, assessments were repeated at 12-hourly intervals until the child was discharged from the intensive nursing ward. All clinical assessments and oximetry readings were taken by a registered nurse. A rule developed via quadratic discrimination analysis was able to correctly classify 80 per cent of children as having adequate/inadequate oxygen saturation, with 'inadequate oxygen saturation' defined as less than 85 per cent. This, however, involved a complicated equation which would not be suitable for general use in a developing country. The use of a 'clinical score' using a summation of the major clinical signs was not found to offer any advantage over the recognition of any one of four 'indicator' signs.(ABSTRACT TRUNCATED AT 250 WORDS)

Child, Preschool↗
PubMed1995

Use of CHROMagar Candida medium for isolation of yeasts from dental samples.

A new differential medium, CHROMagar Candida, for the isolation of clinically important yeasts was investigated to determine its usefulness in facilitating the study of oral yeasts. The recovery of yeasts on the medium was not significantly different from the recovery on Sabouraud dextrose agar. The identities of 450 green colonies on CHROMagar Candida, presumptively identified as Candida albicans on the basis of the manufacturer's instructions, were confirmed by testing for beta-N-acetylgalactosaminidase. Candida tropicalis also formed distinctive colonies, and other yeasts including Candida (Torulopsis) glabrata, Candida Parapsilosis, Candida Magnoliae, Candida lusitaniae, Candida Famata, Candida kefir, and Saccharomyces cerevisiae were readily distinguished from C. albicans and C. tropicalis isolates. CHROMagar Candida is a very useful medium, and its use will facilitate the study of yeasts associated with dental diseases.

Candida↗
PubMed1995

Use of solid-phase immune electron microscopy for classification of Norwalk-like viruses into six antigenic groups from 10 outbreaks of gastroenteritis in the United States.

Norwalk-like viruses observed in fecal specimens from 10 outbreaks of gastroenteritis investigated in the United States between 1987 and 1992 were analyzed by solid-phase immune electron microscopy. Outbreak virus strains were classified into six antigenic groups: the four types (UK1 to UK4) previously defined in the United Kingdom, Norwalk virus, and the Oklahoma agent that was newly defined in this study. The diversity of antigenic types demonstrated in these outbreaks was greater than previously recognized and will serve as a basis for characterization of these strains at the molecular level.

Antibodies, Viral↗
PubMed1995

Measurement of serum troponin T, creatine kinase MB isoenzyme, and total creatine kinase following arduous physical training.

We have compared measurement of cardiac troponin T by enzyme linked immunosorbent assay with creatine kinase MB isoenzyme (CK-MB) concentration measurement in 219 Royal Marine commandos with no evidence of cardiovascular disease who have elevated creatine kinase (CK) produced by arduous physical training. CK was elevated up to 22.6 times and CK-MB mass up to 6.6 times the upper reference limit. Only two commandos had detectable cardiac troponin T, with neither exceeding the upper reference limit of 0.2 micrograms/L. At decision thresholds optimized for diagnosis of acute myocardial infarction in previous published work, 58.3% of the total CK activity, 13.8% of the CK-MB concentration/CK activity ratio and 1.6% of CK-MB concentration measurements showed elevated values but no elevations in cardiac troponin T occurred. Cardiac troponin T is currently the investigation of choice for the differential diagnosis of patients with an elevated CK due to skeletal muscle trauma to exclude myocardial damage.

Aspartate Aminotransferases↗
PubMed1995

Humoral response to Plasmodium falciparum ring-infected erythrocyte surface antigen in a highly endemic area of Papua New Guinea.

The prevalence and concentration of antibodies to ring-infected erythrocyte surface antigen (RESA) were measured in blood samples collected during a cross-sectional survey conducted in Papua New Guinea. Antibodies were measured by enzyme-linked immunosorbent assay to the recombinant RESA protein in 1,398 subjects and to RESA 8 and RESA 11 synthetic peptides in a subsample of 200 adults. Overall, the seropositivity rate to recombinant RESA was 66% and the geometric mean antibody concentration was 28 micrograms/ml. There was a slow increase in antibody prevalence and concentration with age that continued to occur even after 40 years of age. In children less than 10 years of age, there was a significant positive correlation between both RESA antibody prevalence and concentration and concurrent infection with Plasmodium falciparum. The opposite was true in adults more than 20 years of age, with those having a high antibody concentration to RESA being less likely to be parasitemic at the time of the survey. This observation was consistent with the finding of a weak but significant negative correlation between log antibody concentration and log P. falciparum density, which was mainly found in adults. No consistent correlation was found between humoral immune response to RESA and morbidity indicators.

Adolescent↗
PubMed1995

False-positive and false-negative rates in meconium drug testing.

To determine the number of false-negative results produced by inefficient extraction of drugs from meconium, three published procedures were compared by using previously confirmed positive and negative meconium specimens. The methods were not equivalent in their ability to extract drugs from the matrix. To determine the number of false positives reported by the use of screen-only (unconfirmed) results, 535 screen-positive meconium specimens were subjects to confirmation by gas chromatography-mass spectrometry. Fifty-seven percent of the samples were confirmed positive for one or more of the drugs under investigation, showing that a false-positive rate as high as 43% may exist when unconfirmed screening results are used.

Amphetamines↗
PubMed1995

Breast lymphoma. A clinical and pathological review and 10-year treatment results.

Sixteen patients presenting with lymphoma involving the breast are described. Seven fulfilled the criteria for primary breast lymphoma, while the other 9 had evidence (sometimes only detected after extensive staging procedures) of concurrent lymphomatous involvement outside the breast. Histological diagnoses of the so-called primary breast lymphomas included 1 case of Hodgkin's disease and 6 of non-Hodgkin's lymphoma (including 2 with T-cell phenotypes). The patients with so-called secondary breast involvement included 8 with non-Hodgkin's lymphoma and 1 with a plasmacytoma of the breast with concomitant myelomatous involvement of bone marrow. Among the non-Hodgkin's lymphomas involving the breast the whole range of histological subtypes from low-grade to high-grade lesions were seen. There was no subtype of lymphoma with a specific predilection for breast involvement. Expression of oestrogen receptor protein as determined by immunocytochemical investigation using specific monoclonal antibodies was uniformly negative in lymphoid cells of 11 patients studied. Most of the patients in this series were treated by chemotherapy with uniformly good local control of lymphomatous involvement of the breast and an outcome similar to that of lymphomas presenting at other body sites. It is concluded that the approach to lymphomas of the breast should be similar to that of the equivalent types presenting elsewhere.

Adult↗