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Biomedical subjects

T A Armstrong

Publications and source records attributed to T A Armstrong.

25 records · Page 2Linked to original sources
PubMed1992

Refractive effect of capsular bag lens placement with the capsulorhexis technique.

Fifty consecutive patients who had cataract extraction and intraocular lens implantation with a can-opener anterior capsulotomy were compared to 50 patients who had a continuous tear capsulotomy and confirmed capsular bag lens placement. The actual versus the predicted postoperative refraction was calculated with both the SRK II and the Holladay lens power formulas. With both formulas, the capsulorhexis patients required a spectacle correction 0.43 (or 0.44) diopter greater than the can-opener patients when the same A-constant or surgeon factor was used. The recalculated A-constant was 118.23 for the can-opener patients and 118.76 for the capsulorhexis patients; the manufacturer's recommended A-constant was 118.3. The results were statistically significant.

Cataract Extraction↗
PubMed1990

Evaluation of the Tono-Pen and the Pulsair tonometers.

A clinical evaluation of two new portable tonometers, the Oculab Tono-Pen and the Keeler Pulsair, was performed to determine their accuracy and efficacy. Measurements were obtained in 229 eyes of 130 normal patients and compared to measurements obtained with the Goldmann applanation tonometer. The average absolute deviation for the Tono-Pen and the Pulsair was a significant 2.70 mm Hg and 2.49 mm Hg, respectively. Thirteen of 188 (7%) Tono-Pen readings and 19 of 229 (8%) Pulsair readings differed from the Goldmann readings by more than 5 mm Hg. Both instruments were highly sensitive and specific for detecting intraocular pressures greater than 21 mm Hg.

Evaluation Studies as Topic↗
PubMed1990

Insect resistant cotton plants.

We have expressed truncated forms of the insect control protein genes of Bacillus thuringiensis var. kurstaki HD-1(cryIA(b) and HD-73 (cryIA(c) in cotton plants at levels that provided effective control of agronomically important lepidopteran insect pests. Total protection from insect damage of leaf tissue from these plants was observed in laboratory assays when tested with two lepidopteran insects, an insect relatively sensitive to the B.t.k. insect control protein, Trichoplusia ni (cabbage looper) and an insect that is 100 fold less sensitive, Spodoptera exigua (beet armyworm). Whole plants, assayed under conditions of high insect pressure with Heliothis zea (cotton bollworm) showed effective square and boll protection. Immunological analysis of the cotton plants indicated that the insect control protein represented 0.05% to 0.1% of the total soluble protein. We view these results as a major step towards the agricultural use of genetically modified plants with insect resistance in this valuable, high acreage crop.

Amino Acid Sequence↗
PubMed1990

Effects of supraphysiologic temperature and broth dilution on serum protein binding.

Pooled human serum, unheated (UU) and heated at 56 degrees C for 30 (HU-30) and 60 (HU-60) min, and these media diluted 1:1 with broth (UD, HD-30, and HD-60) were used to assess the effects of supraphysiologic temperature and broth dilution on the serum protein binding of ceftriaxone. Protein binding was determined by ultrafiltration and subsequent high-performance liquid chromatography analysis. Significant differences in protein binding between UU and HU-60 (P less than 0.05), UD and HD-60 (P less than 0.01), HD-30 and HD-60 (P less than 0.01), and all undiluted and diluted media (P less than 0.01) were found. These alterations in protein binding may influence the in vitro microbiologic testing of highly protein-bound antibiotics.

Adult↗
PubMed1984

Intraocular lenses in myopes.

A series of 40 consecutive myopic eyes with intraocular lens implants of 13.0 diopters or less was examined with regard to visual result, complications and accuracy of commonly used lens implant power formulas. Recommendations are given for the use of implants in myopic patients as well as the various approaches to visual rehabilitation of the anisometropia in the fellow eye following surgery.

Aged↗
PubMed1979

Polyamine Metabolism in Embryogenic Cells of Daucus carota: II. Changes in Arginine Decarboxylase Activity.

Embryogenic cultured cells of Daucus carota have been shown to synthesize putrescine from exogenously supplied [(14)C]arginine at twice the rate of control nonembryogenic cells. In the present paper, the activity of arginine decarboxylase (arginine carboxy-lyase, EC 4.1.1.19), an important enzyme in the synthesis of putrescine, was assayed and also found to be elevated by as much as 2-fold in embryogenic cells. This difference between embryogenic and nonembryogenic cells was observed as early as 6 hours after the induction of embryogenesis and appeared not to result from the presence of a diffusible inhibitor or activator. It seemed to be dependent upon concomitant RNA and protein synthesis, as judged using 6-methyl-purine and cycloheximide. After cycloheximide addition to the culture medium, arginine decarboxylase activity declined with a half-time of about 30 minutes in both embryogenic and nonembryogenic cells. It is suggested that elevated arginine decarboxylase activity is involved in the mechanism leading to elevated putrescine levels in these cells and hence may play a role in the embryogenic process.

Journal Article↗