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Biomedical subjects

E Yeh

Publications and source records attributed to E Yeh.

45 records · Page 3Linked to original sources
PubMed1983

Phorbol ester receptors and the in vitro effects of tumor promoters.

The evidence for the multistage nature of tumor promotion in vivo and for multiple subclasses of phorbol ester receptors in vitro argues that multiple mechanisms of tumor promotion exist. The existence of multiple mechanisms suggests that brute force assay for tumor promoters in vivo may be inadequate and that understanding of mechanisms may be essential. The interest in the phorbol esters is not primarily that they are environmental hazards for man, but rather that they provide a probe for phorbol ester receptors. These receptors are found in people, and modulation of their activity may play a role in tumor promotion in man.

Animals↗
PubMed1983

Metabolism of acetylcholine receptors on embryonic amphibian muscle.

The functional properties of acetylcholine receptors are altered during the development of Xenopus myotomal muscle. A similar change also occurs in dissociated cell cultures of embryonic myotomal muscle. Metabolism of acetylcholine receptors was examined in order to ascertain whether the turnover rate changed at a time when the functional changes were detected. Incorporation of newly synthesized receptors occurred at a constant rate over a 24-hr period. The degradation of receptors followed first order kinetics with a half-life of 52 hr. Incorporation and degradation occurred at approximately equal rates such that 1 to 1.5% of the total receptor number was replaced every hour at equilibrium. Addition of neural tube cells to muscle cell culture, which altered the functional properties of channels, had no effect on either the incorporation or the degradation rate. We conclude that the changes in the functional properties of receptors occur independent of changes in the turnover rate of receptors.

Acetylcholine↗
PubMed1982

Initial synaptic transmission at the growth cone in Xenopus nerve-muscle cultures.

The excellent visibility of cultured cells allows the early events during formation of the neuromuscular junction to be suitably studied. It has been shown in various culture systems that synaptic transmission occurs early after nerve-muscle contact. Early synaptic potentials are small in amplitude and slow in time course reflecting a low acetylcholine receptor density at the site of nerve contact. Acetylcholine receptors accumulate later at the contact region. We have examined initial synaptic transmission at the growth cone-muscle contact in Xenopus nerve-muscle cultures. The approaching growth cone was observed under a phase-contrast microscope while the membrane potential of its target muscle cell was continuously monitored by using an intracellular microelectrode. The innervating neuron was stimulated extracellularly at the cell body. No synaptic potential was evoked when the growth cone was contacting the muscle only at the tip of filopodia. However, as soon as the main portion of the growth cone contacted the muscle membrane, nerve-evoked synaptic potentials were detected after stimulation of the nerve. This immediate appearance of synaptic potentials raises the possibility that acetylcholine could be released at the growth cone even prior to contact with muscle cells. As the area of contact enlarged during the observation period the amplitude of end-plate potentials also increased. Spontaneous synaptic potentials (miniature end-plate potentials) were rarely observed in these early growth cone-muscle contacts. Although there were several inherent difficulties, quantal analysis of the end-plate potentials was attempted by using binomial statistics. This analysis suggests that nerve-evoked transmitter release at the growth cone occurs in a quantal fashion.

Acetylcholine↗
PubMed1978

Bruising in cattle transported over long distances.

The relative susceptibility of cattle of different sexes to bruising was examined in five trials. In each trial there were three groups of cattle--bullocks, cows and mixed (bullocks and cows). The weight of bruised tissue trimmed from the carcases of the cows was significantly greater than that trimmed from the carcases of bullocks. The amount of bruising in cows, but not in bullocks, increased with increase in duration of journey. There was no evidence to suggest that differences in carcase weight or temperament, or "riding" of cows in oestrus were major contributing factors to the different levels of bruising.

Animals↗
PubMed1975

A removable ultrasonic collimator for improving resolution.

A removable ultrasonic collimator is described. It could be easily attached to a general purpose transducer to improve resolution on ultrasound study of superficial small organs. The collimator is made of a small central focusing lens, 6 mm in diameter, surrounded by air. The air insulates the peripheral portion of the transducer surface. ONLY THE CENTRAL ULTRASONIC BEAM WOULD BE TRANSMITTED THROUGH THE LENS. As a result, the ultrasonic beam is narrowed and the resolution is improved. Draw-back of the collimator is a reduction in the ultrasound intensity. However, it can be compensated for by increasing either the transducer output or system gain.

Thyroid Gland↗
PubMedDate not supplied

Multicenter study of photorefractive keratectomy for myopia of 6.00 to 8.00 diopters. VISX Moderate Myopia Study Group.

PURPOSE: To summarize the initial results of excimer laser photorefractive keratectomy (PRK) on 89 eyes of 80 patients with moderate myopia (myopia of -6.00 to -8.00 diopters [D]; mean -6.98 +/- 0.90 D) at nine investigational sites. METHODS: All treatments used an argon fluoride excimer laser (VISX, Inc, Santa Clara, Calif) using standard settings. Sixty eyes received single-zone 6.0-millimeter ablations and 29 eyes received two-zone ablations. Follow up ranged from 1 month (n = 89) to 6 months (n = 46). RESULTS: At 3 months, uncorrected visual acuity measured 20/40 or better in 75% and 20/20 or better in 18%; 78% were within +/- 1.00 D of intended correction, 38% were within +/- 0.50 D, and 9% lost two or more lines of spectacle-corrected visual acuity. At 6 months, uncorrected visual acuity measured 20/40 or better in 74% and 20/20 or better in 17%; 67% were within 1.00 D of intended correction, 38% within 0.50 D, and 2% (1/46) lost two lines of spectacle-corrected visual acuity. CONCLUSIONS: PRK for moderate myopia with large diameter ablation zones appears safe and more predictable than that done using smaller ablation zone diameters. Longer follow up is needed to better define stability, the effects of postoperative corticosteroids, and the use of single-versus double-zone ablations.

Adult↗