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Biomedical subjects

R Powell

Publications and source records attributed to R Powell.

At least 91 records · Page 5Linked to original sources
PubMed1990

Electrotransfection of Escherichia coli with lambda gt10 DNA.

We have used electroporation to introduce lambda gt10 DNA into E. coli C600 (Electrotransfection). We obtained approximately 10(7) pfu (plaque forming units) per micrograms of lambda gt10 DNA. This frequency is 100-fold higher than the maximum reported for classical calcium chloride-induced transfection. We have also compared electrotransfection with in vitro packaging in cloning experiments using relatively small amounts (less than or equal to 10 ng) of DNA. Our results slow that electrotransfection can generate approximately 1000-fold more plaques than in vitro packaging at these concentrations.

Bacteriophage lambda↗
PubMed1990

A general method to generate DNA probes for microorganisms.

We present a method that permits the rapid generation of DNA probes for eubacteria. In the procedure the variable regions for the 16s rRNA genes are amplified using polymerase chain reaction (PCR) technology and primers based on the conserved regions of these genes. Following sequencing of the variable regions, a choice is possible for a probe specific for that organism. No knowledge of the molecular biology of the microorganism is required prior to the application of this approach. The generality of the method is shown using Salmonella typhimurium, Staphylococcus aureus, Clostridium perfringens, Klebsiella pneumoniae, Pseudomonas fluorescens, Aeromonas salmonicida and Mycobacterium bovis. A. salmonicida was examined in detail and a DNA probe was prepared that distinguishes it from other Aeromonas species.

Aeromonas↗
PubMed1990

Birthweight ratio and outcome in preterm infants.

The association between birthweight ratio and outcome was investigated in 429 infants born before 31 weeks' gestation. Birthweight ratio was calculated in each case as birth weight divided by mean birth weight for gestation (from reference data). It was shown that a given ratio corresponded to the same birth centile across the gestational age range studied; a ratio of 0.8 corresponding to the 10th centile. There was a linear relationship between birthweight ratio and requirement for mechanical ventilation and postneonatal mortality. Birthweight ratio was also strongly and linearly related to body weight, length, and head circumference at 18 months' corrected age. Overall, there was no association between this ratio and neurodevelopmental outcome to 18 months. However, the subgroup with the largest weights for gestation (birthweight ratio greater than or equal to 1.1), had significantly higher language subscores than all the other children. Our data show that conventional dichotomous categorisation of preterm infants into small or appropriate for gestation is inadequate when exploring the association between size for gestation and outcome.

Birth Weight↗
PubMed1989

Regression of left ventricular hypertrophy in treated hypertensive patients with dilevalol and metoprolol--a double blind randomized study.

This study was designed to evaluate the effects of a new beta-adrenergic blocking agent with beta 2 agonist activity (dilevalol, an R-R' isomer of labetalol) on left ventricular hypertrophy regression as seen by M-mode echocardiography. The study design was a 2:1 double blind randomization of dilevalol versus metoprolol. There was an equal blood pressure reduction in the two groups (supine diastolic blood pressure fell from 101 +/- 4.5 mm Hg to 87 +/- 13.7 mm Hg, P less than .001 in the dilevalol group, and 101 +/- 4.3 mm Hg to 87 +/- 8.6 mm Hg, P less than .01, in the metoprolol group). At the end of 2 months, there was an overall 7.5% decrease in left ventricular mass index in the 16 dilevalol treated patients (this was due to a 4.4% decrease in posterior wall thickness, end diastolic dimension increased by only 1%). Of the seven patients with an increased left ventricular mass index, all demonstrated hypertrophy regression (mean 17.14%). In contrast, no significant change in left ventricular mass was seen in the metoprolol treated group. Echocardiographic left ventricular mass index and electrocardiographic evidence of left ventricular hypertrophy (using the Sokolow-Lyons criteria and Romhilt-Estes point score) had poor correlation (r = .30 and r = .38, respectively). Resting ejection fraction increased by 5% and velocity of circumferential fiber shortening by 14% in the dilevalol treatment group (not significant).(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Antagonists↗
PubMed1989

Growth and development in premature twins.

A total of 476 infants (386 singletons and 90 twins) born before 32 weeks' gestation were studied to compare long term growth and development in twins and singletons. At 18 months, after adjusting for confounding social, obstetric, and neonatal factors, twins were not disadvantaged in their neurodevelopmental status, but were 1.6 cm shorter than singletons and had thicker triceps and subscapular skinfolds. No significant differences were found between first and second born twins in later growth or development at 18 months post-term. While preterm twins may have an inherent disadvantage in linear growth it is suggested that in other respects twinning is not a risk factor in preterm infants.

Anthropometry↗
PubMed1989

Fatigue syndromes: a comparison of chronic "postviral" fatigue with neuromuscular and affective disorders.

Patients (n = 47) presenting to a neurological centre with unexplained chronic "postviral" fatigue (CFS) were studied prospectively. Controls were patients with peripheral fatiguing neuromuscular diseases and inpatients with major depression in a psychiatric hospital. Seventy-two percent of the CFS patients were cases of psychiatric disorder, using criteria that excluded fatigue as a symptom, compared with 36% of the neuromuscular group. There was no difference in subjective complaints of physical fatigue between all groups. Mental fatigue and fatigability was equally common in CFS and affective patients, but only occurred in those neuromuscular patients who were also cases of psychiatric disorder. Overall, the CFS patients more closely resembled the affective than the neuromuscular patients. Attribution of symptoms to physical rather than psychological causes was the principal difference between matched CFS and psychiatric controls. The symptoms of "postviral" fatigue had little ability to discriminate between CFS and affective disorder. The fatigue in CFS appeared central in origin, suggesting it is not primarily a neuromuscular illness. The implications for research and treatment of chronic fatigue are discussed.

Adult↗
PubMed1988

Mother's choice to provide breast milk and developmental outcome.

The association between a mother's choice to provide breast milk and her baby's developmental status at 18 months post term was investigated in 771 low birthweight infants from five centres. Babies whose mothers chose to provide milk had an 8 point advantage in mean Bayley mental developmental index over infants of mothers choosing not to do so. A 4.3 point advantage remained after adjusting for demographic and perinatal factors. A similar finding was derived using a fundamentally different and questionnaire based test (academic scale of Developmental Profile II). Whether this significant residual developmental advantage relates to parental factors or to a beneficial effect of human milk itself on brain development has important implications for the nutritional management of premature babies.

Breast Feeding↗
PubMed1988

Relation between synovial fluid C3 degradation products and local joint inflammation in rheumatoid arthritis, osteoarthritis, and crystal associated arthropathy.

C3 degradation products (C3dg/d) were estimated in 288 synovial fluid (SF) samples (rheumatoid arthritis (RA) 93, osteoarthritis (OA) 68, chronic pyrophosphate arthropathy 80, acute pseudogout 20, others 27) from knees of 138 patients (bilateral 67, serial sampling on two to six occasions 40). At each aspiration knees were defined as 'active' or 'inactive' by single observer global assessment using six clinical parameters of inflammation. Lack of correlation between paired SF and plasma C3dg/d implied local C3 activation within joints. Raised SF C3d levels were found in active compared with inactive RA joints (mean (range) 51 (15-105) and 6 (0-15) units/ml respectively). Low SF C3dg/d levels were found in OA (mean (range) 0.8 (0-7) units/ml) and chronic pyrophosphate arthropathy (mean (range) 4 (0-16) units/ml), irrespective of clinical activity. In contrast, very high levels (mean (range) 61 (16-126) units/ml) were present in all cases of pseudogout. These differences remained after correction for SF C3 or albumin. This study is the first to show a positive correlation between SF C3dg/d and local inflammation in RA joints. It further suggests that C3 activation is a constant feature of pseudogout but not an accompaniment of inflammation associated with chronic crystal associated synovitis or OA.

Adult↗
PubMed1986

Plaque dot assay.

Explore the source record for details and available documents.

Bacteriophage lambda↗
PubMed1984

Influence of ascites on tobramycin pharmacokinetics.

The influence of ascites on the disposition of tobramycin was examined in eight subjects with cirrhosis of the liver. Five of these subjects had resolution of ascites so they could be used as their own controls. While there was no significant effect of ascites on the clearance and half-life of tobramycin, the volume of distribution of tobramycin was significantly larger when ascites was present, 0.32 versus 0.26 liter/kg (P less than 0.01). There was a trend for the volume of distribution to be larger in those patients with larger ascitic fluid volume.

Adult↗
PubMed1983

Characterization of complement-fixing activity and cross-idiotypes of rheumatoid factors in idiopathic mixed cryoglobulinemia.

The complement-fixing activity, specificity for IgG, and cross-idiotypes of rheumatoid factors (RF) isolated from the mixed cryoglobulins of nine patients with idiopathic mixed cryoglobulinemia were determined. All were IgM kappa and fixed complement. The RF complement-fixing activity did not correlate with hypocomplementemia or disease manifestations. The majority of RF belonged to the same cross-idiotype group. The RF from two of three patients with predominantly neurologic manifestations did not have any of the known cross-idiotypes and reacted better with rabbit IgG than with human IgG. The patients with neurologic manifestations also differed in that their serum complement was normal.

Adult↗