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R Downes

Publications and source records attributed to R Downes.

At least 19 recordsLinked to original sources
PubMed2001

Identification, cloning, and expression of a functional phenylalanyl-tRNA synthetase (pheRS) from Staphylococcus aureus.

Phenylalanyl-tRNA synthetase (pheRS) is unique among aminoacyl tRNA synthetases in that it is a heterotetrameric enzyme composed of two alpha-subunits and two larger beta-subunits. In prokaryotes, the alpha- and beta-subunits of pheRS are encoded by the genes pheS and pheT, respectively. In this report we describe the isolation of a DNA fragment (3.52 kb) containing the pheS and pheT genes from a Staphylococcus aureus (WCUH29) genomic DNA library. Both genes, found as a part of transcriptional operon, were predicted to encode polypeptides which showed strong primary and structural similarity to prokaryotic phenylalanyl-tRNA synthetase alpha- and beta- subunits. We describe the high-level overexpression and purification of recombinant S. aureus pheRS using pheS and pheT genes as part of an artificial operon in Escherichia coli. For comparative analysis we also report a procedure for the purification of native pheRS from S. aureus (Oxford Strain) and demonstrate that Michaelis-Menten parameters for both recombinant and native enzyme, at least for phenylalanine tRNA aminoacylation are comparable.

Amino Acid Sequence↗
PubMed1998

ENT pathology and diplopia.

ENT pathology causes diplopia in a minority of patients. Because the various ENT conditions that can produce diplopia are relatively unusual they often escape early detection. We describe the various ENT disorders that can produce diplopia and illustrate this with our experience between 1992 and 1998. We wish to emphasise the benefit which can be obtained from undertaking an ENT history and examination in arriving at the correct diagnosis.

Aspergillosis↗
PubMed1996

Tracker-assisted photorefractive keratectomy for myopia of -1 to -6 diopters.

BACKGROUND: The Autonomous Technologies T-PRK (Tracker-assisted Photorefractive Keratectomy) excimer laser system uses a small beam scanner that allows flexibility in the ablation pattern that is applied to the cornea and incorporates a sophisticated LADARVision eye tracker that is capable of following saccadic movements. This paper describes the first clinical results on sighted eyes for the correction of low myopia. METHODS: Forty-two normal sighted eyes of 42 patients were treated for spherical myopia between -1.00 diopters (D) and -6.00 D with 6 mm ablations. Visual acuity, refractive error, contrast sensitivity (with and without glare), corneal haze, endothelial cell density, and patient satisfaction were measured. RESULTS: Mean manifest refraction was -0.39 D +/- 0.68 D at 1 month with regression to -0.94 D at 3 months and -1.05 D at 6 months. At 6 months, 5 (20%) eyes were +/- 0.50 D and 14 (56%) eyes were +/- 1.00 D. Consistent with this undercorrection and regression, uncorrected visual acuity (UCVA) of 20/20 and 20/40 or better was achieved by 10 (40%) and 34 (85%) eyes at 3 months and 16 (40%) and 17 (68%) eyes at 6 months. None of the eyes lost 2 or more lines of spectacle corrected visual acuity. Corneal haze was graded as 1/2 trace or less in 89% to 100% of eyes at all intervals. There was no loss of endothelial cells (mean +/- SD cell density centrally: preop 3115 +/- 322 and 6 months 3220 +/- 333) and contrast sensitivity recovered to baseline levels at 3 months. CONCLUSIONS: The Autonomous Technologies T-PRK excimer laser system is safe and effective for the reduction or correction of myopia from -1.00 D or -6.00 D. The refractive results may be improved by adjusting the calibration to reduce the undercorrection and by instituting use of topical corticosteroids on an individual basis for those who regress.

Cell Count↗
PubMed1995

The geographical epidemiology of ocular diseases: some principles and methods.

With the increasing availability of geographically referenced data in health research the time is ripe to review the use of particular geographical and spatial analysis techniques in ophthalmic research. Analysis of the geographical distribution of ocular diseases, particularly in Britain, has not had a high profile, but there are certain diseases, such as congenital eye malformations in children, where such analysis methods are particularly appropriate. We review the data requirements and then a variety of analytical techniques, some of which partition geographical space into areal units (such as counties or electoral wards), others of which treat space as continuous. We conclude with some comments on software that is available for such analyses.

Data Collection↗
PubMed1992

Riboflavin deficiency and iron absorption in adult Gambian men.

Iron absorption from 3.38 mg 58Fe was measured in riboflavin-deficient Gambian men with haemoglobin (Hb) less than 11.5 g/dl before and after oral riboflavin therapy, and the results compared with a group not receiving riboflavin. Riboflavin status (as determined by erythrocyte glutathione reductase activation coefficient) and Hb increased in teh riboflavin-supplemented but not placebo group. Plasma ferritin levels were low and did not change in either group. There was very wide variation in percentage iron absorption between individuals and also within single individuals on two separate occasions but no measurable change with riboflavin supplementation. The results of the study indicate that the efficiency of iron utilization is impaired in riboflavin deficiency, but that iron absorption is unaffected.

Administration, Oral↗
PubMed1992

Hydrophilic expanders for the congenital anophthalmic socket.

The congenitally contracted socket often poses a challenging management problem; early surgery may be necessary in spite of the attendant difficulties. A series of patients is presented, with particular emphasis upon the use of a new hydrophilic expander in the severely contracted socket, to illustrate our current management protocol. Factors pertinent to orbital development and growth are discussed. Two types of contracted sockets are identified that appear to correlate with the presence or absence of an eye or ocular remnant. Use of a hydrophilic expander in the severely contracted anophthalmic socket with marked lid phimosis has enabled subsequent fitting and retention of a hard conformer in many of these cases, thus obviating early interventional surgery.

Adolescent↗
PubMed1991

Vaccination against hepatitis B and protection against chronic viral carriage in The Gambia.

358 children in the Gambian villages of Keneba and Manduar, where hepatitis B virus (HBV) infection is endemic, were vaccinated with plasma-derived vaccine against HBV according to one of four regimens and followed for up to 4 years. Two regimens by which vaccine was injected intradermally into children between 0 and 4 years old led to peak geometric mean (95% CI) concentrations of antibody against HBV surface antigen of 270 (202-358) and 555 (418-748) mlU/ml. The third regimen--intramuscular vaccination of children aged between 0 and 4 years--gave geometric mean peak antibody concentrations of 926 (765-1122) mlU/ml. A fourth regimen was intramuscular vaccination of children between 1 and 9 months old, which gave geometric mean antibody concentrations of 5431 (3903-75,456) mlU/ml. Despite these widely divergent responses and a 89% decay in antibody over the first 2 years, vaccination against HBV was 97% effective in preventing chronic infection. Vaccination was less effective in preventing uncomplicated infection: 5.3% of 264 vaccinees in Keneba and 19.1% of 94 vaccinees in Manduar tested positive for antibody to HBV core antigen. These "breakthrough infections" did not differ in frequency between regimens, and were associated with low initial antibody responses and chronic maternal carriage of HBV.

Adolescent↗
PubMed1991

Outcome of low birth weight infants in a West African village.

Low birthweight (LBW) infants are at risk of increased mortality, impaired growth, and increased morbidity. We studied the progress of all LBW infants (less than 2.5 kg) born in a West African village where there is a resident pediatrician and midwife. There were 426 live births during the 8 years studied of which 42 (10 per cent) were of LBW. There were 17 infant deaths (IMR = 40/1000). Mean birthweight and gestation of infants dying in the first year were significantly lower than those of all live birth (2.33 kg v. 2.99 kg, P less than 0.001; 36.9 w v. 38.9 w, P less than 0.05). The mean weights of the 32 surviving LBW infants (15 preterm, 17 full term, small for gestational age) were compared with those of 32 full term, appropriate for gestational age matched controls over the first year. Growth velocities of paired groups were identical. The significant differences in weight at 1 year (P less than 0.005) reflected those at birth (P less than 0.001). There were no significant differences in clinic attendance rate or incidence of diarrhoea and respiratory disease between the four groups. We conclude that LBW is a strong risk factor for infant mortality, but not for diarrhoeal and respiratory morbidity in a community with ready access to obstetric and pediatric care.

Africa, Western↗
PubMed1991

An investigation into the effect of different intakes of vitamin C on drug metabolism in Gambian men.

Hepatic mixed-function oxidase activity was measured in Gambian men during a period of low seasonal vitamin C intake and after vitamin C supplementation. Demethylation of methoxyphenylacetamide (methacetin) was followed using a breath test, in which the exhalation of 13C-enriched CO2 was measured following an oral dose of 13C-methacetin. Vitamin C supplementation, sufficient to increase plasma levels significantly, did not influence methacetin metabolism. However, methacetin metabolism in unsupplemented men appeared normal in the majority of cases. Hepatic tissue may not have been sufficiently depleted of vitamin C to impair the activity of the mixed function oxidase system.

Acetamides↗
PubMed1989

Riboflavin status of adolescent vs elderly Gambian subjects before and during supplementation.

Riboflavin status was measured by activation coefficient of erythrocyte glutathione reductase (EGRAC) in elderly and adolescent rural Gambians whose intakes were low. Fifty-one adolescents and 52 elderly subjects were each subdivided into six supplementation groups to receive 0.25, 0.5, 0.75, 1.0, 1.5, or 2.5 mg riboflavin/d on 5 consecutive days weekly for 5 wk. Before supplementation, EGRAC values were grossly abnormal and differed (p less than 0.005) between the two female groups [elderly subjects, 1.94 +/- 0.33 (means +/- SD); adolescents. 1.72 +/- 0.27] but not between the two male groups. With supplementation greater than 0.25 mg/d the values became nearly equal in the two age groups. Only at total intakes between 1.8 and 2.5 mg riboflavin/d did the subjects attain acceptable status, with a mean EGRAC of 1.3-1.4. Clearly there is a need for further study of the discrepancy between observed index values during supplementation and the accepted ranges of normality at intakes close to the recommended amounts.

Adolescent↗
PubMed1988

Running performance in Gambian children: effects of water-soluble vitamins or iron.

Sixty-nine boys and girls between 10 and 14 years, with evidence of subclinical vitamin deficiencies and poor iron status were enrolled into the study at the beginning of the rainy season. Children were allocated to three treatment groups to receive five times weekly either a placebo, 200 mg ferrous sulphate or 5 mg riboflavin and 150 mg ascorbic acid. Before receiving the supplement, and 9 weeks later, children performed an exercise regimen on a treadmill during which expired air was collected and heart rate measured. There was a general deterioration in the running performance of the children during the study period which was not affected by either the iron or the vitamin supplement.

Adolescent↗
PubMedDate not supplied

Trachoma and water use; a case control study in a Gambian village.

Trachoma is prevalent in many arid areas but data assessing the relationship between water use and trachoma are very scarce. This study compared 18 families having one or more active trachoma cases among the children with 16 trachoma-free families in the same village with respect to water use. Potential confounders such as family size, distance to water source, socio-economic indicators, and hygiene behaviour were assessed in the 2 groups. The families with trachoma were found to use significantly less water per person per day for washing children than did the control group (P = 0.033) with no evidence of confounding by the other measured variables. Low amounts of water for washing were also associated with unclean faces and impetigo in the children. If such a relationship can be substantiated it might provide the basis for effective and cheap interventions against trachoma.

Adolescent↗