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J H Wilkins

Publications and source records attributed to J H Wilkins.

10 recordsLinked to original sources
PubMed2006

The Antioxidants in Prevention of Cataracts Study: effects of antioxidant supplements on cataract progression in South India.

AIM: To determine if antioxidant supplements (beta carotene and vitamins C and E) can decrease the progression of cataract in rural South India. METHODS: The Antioxidants in Prevention of Cataracts (APC) Study was a 5 year, randomised, triple masked, placebo controlled, field based clinical trial to assess the ability of interventional antioxidant supplements to slow cataract progression. The primary outcome variable was change in nuclear opalescence over time. Secondary outcome variables were cortical and posterior subcapsular opacities and nuclear colour changes; best corrected visual acuity change; myopic shift; and failure of treatment. Annual examinations were performed for each subject by three examiners, in a masked fashion. Multivariate modelling using a general estimating equation was used for analysis of results, correcting for multiple measurements over time. RESULTS: Initial enrolment was 798 subjects. Treatment groups were comparable at baseline. There was high compliance with follow up and study medications. There was progression in cataracts. There was no significant difference between placebo and active treatment groups for either the primary or secondary outcome variables. CONCLUSION: Antioxidant supplementation with beta carotene, vitamins C and E did not affect cataract progression in a population with a high prevalence of cataract whose diet is generally deficient in antioxidants.

Adult↗
PubMed2003

Ultrastructure of the external gill epithelium of the axolotl, Ambystoma mexicanum with reference to ionic transport.

The ultrastructure of the external gill epithelium of the axolotl, Ambystoma mexicanum, has been examined using conventional transmission electron microscopy to elucidate its role in ionic transport. Four cell types are identified in the gill filament and primary gill bar epithelium. These are granular, ciliated, Leydig and basal cells. A fifth cell type, the flat mitochondria-rich cell is only found in the gill bar epithelium. The predominant granular cells display microvilli at their surface and their cytoplasm contains abundant mitochondria, rough endoplasmic reticulum, Golgi complexes, vesicles and PAS+ secretory granules that are extruded at the surface, which along with secretions from the Leydig cells form a mucous coat. The granular cells are joined apically by junctional complexes consisting of zonulae occludens, zonulae adherens and desmosomes. The lateral membranes of granular cells enclose large intercellular spaces that are closed at the apical ends but remain open at the basal ends adjoining capillaries. In AgNO3-treated axolotl, the gills become darkly stained, the silver grains penetrate apical membranes and appear in the cytoplasm, accumulating near the lateral membranes and also enter the intercellular spaces. These findings are consistent with the dual role of the gill epithelium in mucus production and active ionic transport.

Ambystoma mexicanum↗
PubMed1997

Cataract progression in India.

AIMS: The study was undertaken to test the feasibility of using the LOCS III cataract grading scale in the field and to determine the rate of cataract progression over a 1 year period of time. METHODS: For 150 subjects between the ages of 33 and 55 who attended the refraction clinic at Aravind Eye Hospital in Madurai, India, lens abnormalities were graded at the slit lamp using the LOCS III scale. One year later, 99 of the subjects were re-evaluated by the same methodology to assess the amount of lens change. RESULTS: Interrater reliability was high. A change of 0.5 or more in lens colour, cortical, nuclear, or posterior subcapsular cataract was observed in at least one eye of 54% of the subjects. CONCLUSION: The LOCS III grading scale is a feasible method for measuring lens changes in the field with the slit lamp. Cataract progression in India is rapid enough to permit intervention studies to be performed with relatively small numbers of subjects over a short period of time (that is, 600 subjects for 2 years).

Adult↗
PubMed1977

Coordinate and non-coordinate accululation of aspartate transcarbamylase and dihydroorotase in synchronous Chlorella cells growing on different nitrogen sources.

Regulation of the levels of aspartate transcarbamylase (carbamoylphosphate:L-aspartate carbamoyltransferase, EC 2.1.3.2) and dihydroorotase (L-5,6-dihydro-orotate amidohydrolase, EC 3.5.2.3) was studied in synchronous cultures of the eucaryotic microorganism Chlorella. Analytical polyacrylamide gel electrophoresis and sucrose density-gradient centrifugation studies revealed that these cells contain a single aspartate transcarbamylase and a dihydroorotase with apparent molecular weights of 160 000 and 80 000, respectively. In synchronous cells cultured in nitrate medium, these two enzymes accumulated in single step-patterns over different periods of the cell cycle. In contrast, these enzymes accumulated in a coordinate manner throughout the cell cycle in ammonium medium. Experiments with inhibitors of protein and RNA synthesis indicated that dihydroorotase is stable in vivo and suggested that cell cycle changes in the turnover rate of aspartate transcarbamylase might determine whether or not these enzymes accumulate in a coordinate manner. Although uracil and uridine could be absorbed and metabolized by the cells, synthesis of these two enzymes could not be repressed by culturing synchronous cells in medium, containing high concentrations (29-40 mM) of uracil or uridine, for an entire cell cycle.

Amidohydrolases↗
PubMed1973

Cell-bound thiaminase I of Bacillus thiaminolyticus.

The distribution of the extracellular enzyme, thiaminase I, was determined for logarithmically growing cultures of Bacillus thiaminolyticus. About 60% of the enzyme is associated with the cells throughout the growth cycle. The remainder of the enzyme is in the culture medium. The release of the cell-bound thiaminase I is examined under a variety of conditions. The rate and extent of release is dependent on the pH and the nature of the incubation solution. The release process appears to be relatively independent of de novo protein synthesis, energy derived from oxidative phosphorylation, or divalent metal ions. The absence of carbon or nitrogen sources has little effect on the release of the enzyme. Cell-bound thiaminase I probably is the immediate precursor for extracellular thiaminase I found in the culture medium. Washed cells continue to release thiaminase I at the expense of cell-bound enzyme. In addition, purified cell-bound thiaminase I is indistinguishable from purified extracellular thiaminase I by a number of physical and kinetic criteria.

Bacillus↗
PubMedDate not supplied

Extraocular muscle surgery in early infancy--anatomical factors.

The dimensions and topographical anatomy of 26 eyes from 14 neonates and infants were measured and photographed with special attention to the insertional position of the extraocular muscles. Additional measurements were made in histologic preparations of 12 normal infant eyes. Although the diameters of the neonatal eyes were found to be about 70% of the adult eyes, the volumes of the globes were only about half, and the surface areas even less. The insertions of the rectus muscles were about 2 mm nearer to the cornea than in emmetropic adult eyes, but some were close to or at the equator. The posterior segments of the neonatal eyes were much less developed than the anterior, so that the oblique insertions, as compared to the adult eye, were closer to each other, to the horizontal meridian and to the posterior pole. In some neonatal specimens the inferior oblique insertion was so close to the optic nerve that tenotomy at that point would have jeopardized some of the posterior ciliary vessels and nerves. The dramatic postnatal growth of the eye occurs in the scleral segment; there is minimal corneal growth. About half of the total lifetime increase in the diameters, volume and total surface area of the human eye occurs in the first six months of life. In the six-month-old specimens the volume of the globe and the surface area of the sclera had almost doubled as compared to the neonatal eyes.(ABSTRACT TRUNCATED AT 250 WORDS)

Esotropia↗