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Biomedical subjects

J L Davidson

Publications and source records attributed to J L Davidson.

8 recordsLinked to original sources

The visual function of professional baseball players.

PURPOSE: To measure the visual acuity, stereoacuity, and contrast sensitivity of professional baseball players. METHODS: Three hundred eighty-seven professional baseball players underwent several tests of visual function including distance visual acuity. Stereoacuity was evaluated at near by the Randot test and at distance by both contour and random dot targets. Distance stereoacuity was also tested under timed and untimed conditions. Contrast sensitivity was evaluated by the Vision Contrast Test System, Contrast Sensitivity Viewer, and Binocular Visual Acuity Tester. RESULTS: Visual acuity (measured with players' regular distance correction) in 774 eyes ranged from 20/8.89 to 20/100. Near stereoacuity ranged from 23 to 37 seconds of arc, mean untimed distance contour stereoacuity from 55 to 35 seconds of arc, and mean untimed distance random dot stereoacuity from 98 to 76 seconds of arc. The results under timed conditions were 86 to 65 seconds of arc (timed distance contour stereoacuity) and 104 to 83 seconds of arc (timed distance random dot stereoacuity). Statistically significant differences were found between major and minor league players on tests of untimed distance contour and random dot stereopsis, and on contrast sensitivity testing with the 3.0- and 6.0-cpd gratings using the Contrast Sensitivity Viewer. CONCLUSIONS: Professional baseball players have excellent visual skills. Mean visual acuity, distance stereoacuity, and contrast sensitivity are significantly better than those of the general population.

Baseball↗

Changes of activation and inactivation gating of the transient potassium current of rat pituitary melanotrophs caused by micromolar Cd2+ and Zn2+.

We studied the effects of Zn2+ and Cd2+ on the behaviour of IK(f), a transient outward potassium current in acutely dissociated melanotrophs of the pars intermedia of the rat pituitary gland. Micromolar concentrations of external Cd2+ or Zn2+ caused parallel and nearly equal rightward shifts along the voltage axis of the activation and steady-state inactivation curves for IK(f). The KD for the half-maximal shift of the activation curve was 278 microM for Cd2+ and 93 microM for Zn2+; the maximal shifts of the activation curve were 32.5 and 34 mV, for Cd2+ and Zn2+, respectively. The times to half-activation and half-inactivation were shifted rightward by 30-60 mV in both 500 microM Cd2+ and 500 microM Zn2+. We suggest that Cd2+ and Zn2+ interact specifically with a binding site on or electrically close to the IK(f) channel and in so doing modify the electric field "seen" by the voltage sensors.

Animals↗

Cholecystokinin antagonists. Synthesis and biological evaluation of 3-substituted benzolactams.

A series of 1,3-substituted benzolactams are reported that are potent nonpeptidal antagonists of the peptide hormone cholecystokinin (CCK). Design considerations were based upon the natural product CCK antagonist asperlicin and the potent benzodiazepine antagonist series exemplified by L-364,718 (1). Compound 19, the most potent compound in the benzolactam series, had an IC50 = 3 nM for inhibition of binding of 125I-CCK-8 to CCK receptors in rat pancreatic tissue, and its racemic analogue 8 was found to be orally active in inhibiting CCK-induced gastric emptying in mice, with an ED50 = 2.6 mg/kg po. The effects of ring size, substitution at positions 1 and 3, and stereochemistry at position 3 are discussed. Conformational studies of compound 19 and L-364,718 have delineated similarities that these molecules share in their core conformations and substituent orientations.

Animals↗

Benzolactams. A new class of converting enzyme inhibitors.

A series of potent inhibitors of angiotensin-converting enzyme (dipeptidyl carboxypeptidase, E.C. 3.4.15.1) derived from benzofused 1-carboxyalkyl-3-(1-carboxy-3-phenyl-propylamino) lactams (III) is described. In the most effective inhibitors (I50 2-4 X 10(-9)M) the lactam is 7 or 8 membered and the N-1 side chain is carboxymethyl or carboxyethyl. Conformational and steric factors pertinent to binding to the enzyme are discussed.

Angiotensin-Converting Enzyme Inhibitors↗

Balancing required resources and neighborhood opposition in community-based treatment center neighborhoods.

This paper analyzes the compatibility of two characteristics of neighborhoods containing community-based treatment centers (CBTCs): the availability of resources that can be used in treatment and the likelihood of neighborhood opposition. Do CBTC neighborhoods having high levels of geographically based resources also have characteristics associated with low opposition to these centers? The findings suggest that among neighborhoods with centers serving adults, inner-city transitional neighborhoods where low opposition would be expected have significantly higher levels of treatment resources than do more affluent, suburban neighborhoods. The implications of these findings for selecting sites for community-based treatment centers are discussed.

Adolescent↗

Location of community-based treatment centers.

Neighborhood opposition to community-based treatment centers (CBTCs) has prompted fears that these centers will become concentrated in inner city, "transitional neighborhoods." These neighborhoods are thought to lack the willingness and/or resources to oppose CBTCs. This paper examines the distribution of CBTCs in a northern metropolitan county. The findings suggests that the fears of "ghettoization" may be real only for certain types of centers. Most centers were located in higher-status city and suburban neighborhoods. However, these centers were physically or visually isolated from the surrounding housing, making them less likely to attract attention and therefore less likely to arouse neighborhood opposition.

Attitude to Health↗

Strabismus surgery in patients with myasthenia.

The efficacy of eye muscle surgery for strabismus in patients with myasthenia is not well-documented in the literature. We reviewed the results of strabismus surgery in six patients with the confirmed diagnosis of myasthenia. Patients selected for surgery had angles of deviation that were stable for at least 5 months preoperatively. Patient age ranged from 4 to 62 years. All patients were exotropic. The four adults had moderate limitation of adduction. Surgery included horizontal rectus muscle recession and/or resection in all cases. Three cases involved additional surgery of the vertical rectus or superior oblique muscles. The mean postoperative follow up was 44 months with a minimum of 7 months. Three adults and one child achieved stable satisfactory alignment after one procedure. One child required three procedures to achieve satisfactory alignment. The results suggest that surgery is a viable option in the management of strabismus in selected patients with myasthenia.

Adult↗