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Biomedical subjects

A Sommer

Publications and source records attributed to A Sommer.

At least 325 records · Page 18Linked to original sources
PubMed1987

Corneal ulceration, measles, and childhood blindness in Tanzania.

One hundred and thirty Tanzanian children with corneal ulceration were clinically examined to determine the cause of the ulceration. 37% of the ulcers were associated with recent measles infection and 38% of the children had bilateral ulceration. Herpes simplex virus infection was the commonest cause of ulceration in the series, but vitamin A deficiency was the major cause of bilateral ulceration, subsequent blindness, and mortality in this series. Other significant causes of childhood corneal ulceration were the use of traditional eye medicines, confluent measles keratitis, and ophthalmia neonatorum. We discuss the various mechanisms by which measles causes corneal ulceration, and the priorities in prevention and management of corneal ulceration in African children.

Blindness↗
PubMed1986

Macular hemorrhages associated with posterior vitreous detachment.

We treated three patients with small, macular-area hemorrhages associated with posterior vitreous detachment. All patients were young and had no associated systemic illness or associated retinal vascular disease. Visual acuity returned to normal without treatment as the hemorrhages resolved.

Adult↗
PubMed1986

Two monoclonal antibodies against Escherichia coli ribosomal protein L2 distinguish different locations for their respective epitopes in intact ribosomes.

Two monoclonal antibodies raised against intact Escherichia coli ribosomal protein L2 were isolated, affinity-purified, and characterized. One of the antibodies (Ab 5-186) recognizes an epitope within residues 5-186, and the other (Ab 187-272) recognizes an epitope within residues 182-272. Both antibodies strongly inhibit in vitro polyphenylalanine synthesis when they are first allowed to bind to 50 S subunits prior addition of 30 S subunits. However, only Ab 187-272 is inhibitory when added to preformed 70 S ribosomes. Ab 5-186 binds to 50 S subunits but not to 70 S ribosomes. Ab 187-272 does not cause dissociation of 70 S ribosomes under the ionic conditions of the assay for polyphenylalanine synthesis (15 mM magnesium), although at 10 mM magnesium it does cause dissociation. Both antibodies inhibit the reassociation of 50 S with 30 S subunits. Both antibodies strongly inhibit peptidyltransferase activity. The two antibodies differ in their effects on interactions with elongation factors Tu (EF-Tu) and G (EF-G). Neither antibody significantly inhibits EF-G-dependent GTPase activity, nor the binding of EF-G when the antibodies are incubated with 50 S subunits; however, Ab 187-272 causes a decrease in the binding of EF-Tu X aminoacyl-tRNA X GTP ternary complex and of EF-Tu-dependent GTPase when it is incubated with 70 S ribosomes. The Fab fragments of both antibodies had effects similar to the intact antibodies. The results show that monoclonal antibodies can be used to discriminate different regions of L2 and that EF-Tu and EF-G do not have identical ribosomal binding sites.

Antibodies, Monoclonal↗
PubMed1986

Attack blindness!

Explore the source record for details and available documents.

Blindness↗
PubMed1986

The selective release of one of the two L7/L12 dimers from the Escherichia coli ribosome induced by a monoclonal antibody to the NH2-terminal region.

Two monoclonal antibodies against different epitopes in Escherichia coli ribosomal protein L7/L12 were prepared and characterized as reported previously (Sommer, A., Etchison, J.R., Gavino, G., Zecherle, N., Casiano, C., and Traud, R.R. (1985) J. Biol. Chem. 260, 6522-6527). Both antibodies strongly inhibited polyuridylic acid-directed polyphenylalanine synthesis, ribosome-dependent GTPase activity, and the binding of elongation factor G to the ribosome at mole ratios over ribosomes of 4:1 or less. One epitope was shown to be within residues 1-73 (Ab 1-73) and the other within 74-120 (Ab 74-120). Incubation of 50 S ribosomal subunits or 70 S ribosomes with Ab 1-73, but not with Ab 74-120, leads to a partial loss of L7/L12 from the particle with no loss of any other protein. The experiment was repeated with ribosomes reconstituted with pure radioactive L7/L12 of determined specific activity in order to quantify the L7/L12 in the antibody-treated particle. The protein-deficient core particles isolated by sucrose gradient centrifugation after incubation with Ab 1-73 were found to contain, on average, two copies of L7/L12 and one Ab 1-73. The constancy of this stoichiometry in many experiments and the demonstration of Ab 1-73 on all particles indicate the presence of a homogeneous population of ribosomes, each with only one of the two L7/L12 dimers originally present. The results show a difference in the interactions of the two dimers with the ribosome and present a means of preparing ribosomes with one dimer in a specific binding site. The accompanying paper (Olson, H.M., Sommer, A., Tewari, D. S., Traut, R.R., and Glitz, D.G. (1986) J. Biol. Chem. 261, 6924-6932) shows by immune electron microscopy the location of the two antibody-binding sites and the effect of Ab 1-73 on structure.

Antibodies, Monoclonal↗
PubMed1986

Localization of two epitopes of protein L7/L12 to both the body and stalk of the large ribosomal subunit. Immune electron microscopy using monoclonal antibodies.

Four molecules of ribosomal protein L7/L12 are found as two dimers on the Escherichia coli 50 S ribosomal subunit. Immune electron microscopy using monoclonal antibodies directed against two epitopes of protein L7/L12 has allowed placement of elements of each dimer. One monoclonal antibody, directed against a determinant in the COOH-terminal domain, allows localization of two identical determinants at or near the end of the subunit stalk. The same antibody was used to place two additional determinants at the periphery of stalkless subunits, in an area from which a stalk might be expected to project. A second antibody, directed against an epitope in the amino-terminal portion of L7/L12, caused loss of stalks from the 50 S subunits. The micrographs showed symmetrical oligometric complexes of the dissociated dimeric protein with bivalent antibody. Antibodies were also seen to bind to the body of stalkless subunits, in a region near the COOH-terminal sites. The results are explained by a model in which one dimer of protein L7/L12 exists in a folded conformation on the subunit body and the second dimer occurs in an extended conformation in the subunit stalk.

Antibodies, Monoclonal↗
PubMed1986

Impact of vitamin A supplementation on childhood mortality. A randomised controlled community trial.

450 villages in northern Sumatra were randomly assigned to either participate in a vitamin A supplementation scheme (n = 229) or serve for 1 year as a control (n = 221). 25 939 preschool children were examined at baseline and again 11 to 13 months later. Capsules containing 200 000 IU vitamin A were distributed to preschool children aged over 1 year by local volunteers 1 to 3 months after baseline enumeration and again 6 months later. Among children aged 12-71 months at baseline, mortality in control villages (75/10 231, 7.3 per 1000) was 49% greater than in those where supplements were given (53/10 919, 4.9 per 1000) (p less than 0.05). The impact of vitamin A supplementation seemed to be greater in boys than in girls. These results support earlier observations linking mild vitamin A deficiency to increased mortality and suggest that supplements given to vitamin A deficient populations may decrease mortality by as much as 34%.

Capsules↗
PubMed1986

Asymmetry and variation in the normal hill of vision.

This analysis describes the symmetry and variation in the shape and height of the "hill of vision" obtained from automated static visual field testing of 146 normal eyes of 81 people aged 20 to 78 years. Threshold values dropped from the center to the 30 degrees periphery, with the greatest decrease occurring in the superior quadrant. Variability also increased with distance from the center of fixation, with the greatest variability occurring in the superior quadrant. Threshold values were lower throughout the field in individuals over age 60 years compared with those who were younger, with the greatest decrease in thresholds occurring in the superior quadrant. This age effect was not explained by differences in pupil diameter or central acuity. Variability was higher in the older group, but only in the periphery (greater than 24 degrees from fixation).

Adult↗
PubMed1986

Detection of early xerophthalmia by impression cytology.

Vitamin A deficiency causes blindness, increased systemic morbidity, and increased mortality among preschool children in many developing nations. Presently, there is no simple, reliable test to detect early, physiologically significant vitamin A deficiency. We used conjunctival impression cytology results to evaluate children with early xerophthalmia before treatment and again three to eight weeks later. Subsequently, we modified our technique. We then compared children with early xerophthalmia to normal children. Conjunctival impressions from children with xerophthalmia all showed complete loss of goblet cells and the appearance of enlarged, partially keratinized epithelial cells. Conjunctival impressions from treated and normal children showed normal goblet cells and sheets of small epithelial cells. These results suggest impression cytology may represent the first simple, objective, diagnostic test for the detection of early vitamin A deficiency.

Child, Preschool↗
PubMed1986

Duration of automated suprathreshold vs quantitative threshold field examination. Impact of age and ocular status.

We investigated the impact of age and ocular status on the duration of automated threshold and suprathreshold testing of the visual field in a study of 57 eyes with glaucomatous field loss, 58 eyes with ocular hypertension, and 190 eyes of normal controls. It was faster to run a three-zone threshold-related suprathreshold 120-point full-field screening test on younger subjects and normal controls than on older subjects or subjects with early glaucomatous field loss. In contrast, the time required for full quantitative thresholding of 76 points within the central 30 degrees was unaffected by either age or ocular status. Normal individuals required 40% more time to complete the quantitative threshold test than the "full-field" screening test.

Adult↗
PubMed1986

Similarities between the visual fields of ocular hypertensive and normal eyes.

We tested 136 well-documented ocular hypertensive eyes with no visual field abnormalities on detailed manual perimetry using the C-30-2 program of the Humphrey Visual Field Analyzer. The results were compared with those of 274 age-matched normal eyes. No significant differences in threshold sensitivity were found between ocular hypertensive and normal eyes at any of the 76 points tested in the central 30 degrees. In the ocular hypertensive eyes, the presence of nerve fiber layer defects, especially diffuse atrophy, was associated with depressed threshold values. Threshold values were not associated with the size of the cup-disc ratio, level of intraocular pressure, or time since diagnosis of ocular hypertension.

Humans↗
PubMed1986

A summertime peak of Down's syndrome in Franklin County, Ohio.

In June, July, and August of 1984, more infants than usual were born with Down's syndrome in Franklin County, Ohio. A direct physician survey was done, and chromosome reports were reviewed, resulting in the identification of 11 infants with Down's syndrome born during that period. Using a chi 2 analysis, the expected number of affected newborns was five, making the actual number of 11 significant. Although a summertime peak was observed, the yearly incidence of 1.09 per 1000 live births was within the expected range.

Adolescent↗
PubMed1986

Further delineation of Weaver syndrome.

Seven new cases of Weaver syndrome are described, including the first reported case in an adult. Overgrowth is usually but not always present. The combination of characteristic facies and developmental delay, with the peculiar radiographic findings of accelerated dysharmonic osseous maturation and splaying of the distal long bones, is diagnostic of Weaver syndrome.

Adult↗
PubMed1986

Screening with automated perimetry using a threshold-related three-level algorithm.

Eighty eyes were tested using the computer-driven, automated threshold-related, three-level screening strategy of the Humphrey Field Analyzer. Using Goldmann perimetry as the standard, different statistical algorithms were used in an attempt to differentiate eyes with glaucoma (n = 24) from normal controls (n = 56). Seventeen or more absolute and/or relative defects anywhere in the full field test area identified approximately 95% of the glaucoma eyes and screened out 80% of the control eyes. Retesting these criteria on a second group of 25 glaucomatous and 108 control eyes provided comparable results. The number of stimulus presentations can be substantially reduced, without deterioration in either sensitivity or specificity, by using a two-level strategy and limiting testing to the nasal field.

Algorithms↗