Biomedical subjects
G Silver
Publications and source records attributed to G Silver.
Regulation of myofibrillar accumulation in chick muscle cultures: evidence for the involvement of calcium and lysosomes in non-uniform turnover of contractile proteins.
The effect of calcium on myofibrillar turnover in primary chick leg skeletal muscle cultures was examined. Addition of the calcium ionophore A23187 at subcontraction threshold levels (0.38 microM) increased significantly rates of efflux of preloaded 45Ca+2 but had no effect on total protein accumulation. However, A23187 as well as ionomycin caused decreased accumulation of the myofibrillar proteins, myosin heavy chain (MHC), myosin light chain 1f (LC1f), 2f (LC2f), alpha-actin (Ac), and tropomyosin (TM). A23187 increased the degradation rate of LC1f, LC2f, and TM after 24 h. In contrast, the calcium ionophore caused decreased degradation of Ac and troponin-C and had no effect on the degradation of MHC, troponin-T, troponin-I, or alpha, beta-desmin (Dm). In addition, A23187 did not alter degradation of total myotube protein. The ionophore had little or no effect on the synthesis of total myotube proteins, but caused a marked decrease in the synthesis of MHC, LC1f, LC2f, Ac, TM, and Dm after 48 h. The mechanisms involved in calcium-stimulated degradation of the myofibrillar proteins were also investigated. Increased proteolysis appeared to involve a lysosomal pathway, since the effect of the Ca++ ionophore could be blocked by the protease inhibitor leupeptin and the lysosomotropic agents methylamine and chloroquine. The effects of A23187 occur in the presence of serum, a condition in which no lysosomal component of overall protein degradation is detected. The differential effect of A23187 on the degradative rates of the myofibrillar proteins suggests a dynamic structure for the contractile apparatus.
Pentobarbital anesthesia and the response of tumor and normal tissue in the C3Hf/sed mouse to radiation.
Studies of the effect of pentobarbital anesthesia on the radiation response have been performed using early generation isotransplants of three spontaneous tumors of the C3H mouse: a mammary carcinoma (MCaIV), a fibrosarcoma (FSaII), and a squamous cell carcinoma (SCCVII). The enhancement ratio of pentobarbital [ER(PB)] for TCD50 as the end point was greater than or equal to 1 for all conditions tested. The ER(PB) for O2 3 ATA conditions and two equal doses was 1.46, 1.72, and 2.21 for MCaIV, FSaII, and SCCVII, respectively. The ER(PB) using MCaIV was the same for O2 and carbogen at 1 or 3 ATA. Also, tumor size of MCaIV did not significantly affect the ER(PB) for O2 3 ATA conditions. Further, with the two-dose protocol the anesthesia and the hyperbaric oxygen needed to be used at the second dose; condition at the first dose was not critical. For fractionated irradiation of MCaIV (10 and 15 equal doses) the ER(PB) was smaller than for two-dose treatment; also the effect was less for intratumor temperature of 35 degrees C than 26-27 degrees C. There was no effect of the anesthesia on the acute response of normal skin of the leg. Lung damage by hyperbaric oxygen was not an important factor in these results. Additionally, ERs were computed for O2 at 3 ATA. This ER(O2 3 ATA) was larger for anesthesized than conscious mice. The ER(O2 3 ATA) for MCaIV was high (greater than 1.5) even for radiation given in 10 or 15 equal doses.
The doctor's image.
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Missing: a national health programme in the USA.
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Experimental condition and the acute reaction of mouse skin to ionizing radiation.
The acute reactions of skin of the thigh-leg of normal young adult C3Hf/Sed mice following five equal radiation doses (60Co) were studied in mice irradiated at various leg skin temperatures and while respiring various gas mixtures in control or anesthetized condition (sodium pentobarbital, 0.05 mg/g-1 body wt.) At 25 and 35 degrees C, anesthesia reduced the RD50 (2.5+ reaction) by 4-5%. An increase of temperature from 25 to 35 degrees C resulted in a decrease in RD50 by 10-12% for subjects respiring air or 5% for subjects respiring O2 at 1 or at 3 ATA. The major modifier of radiation response was to change from respiration of air to O2 at 1 or 3 ATA. Enhancement ratios for RD50 Air/O2 1 ATA were 1.4-1.5 for 25 and 35 degrees C. The ratios O2 1 ATA/3 ATA were 1-1.05.
Conduction system in a sponge.
The hexactinellid sponge Rhabdocalyptus dawsoni is capable of arresting its exhalant water current in response to mechanical and electrical stimuli. The arrest is coordinated by a conduction system with a precise threshold of excitability and a chronaxie of 38 milliseconds. The response is propagated throughout the sponge at a mean velocity of 0.22 centimeter per second, and conduction is unpolarized.
The health-care merry-go-round.
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New types of personnel and changing roles of health professionals.
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Rate-increasing action of methylguanidine upon the isolated mammalian heart.
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The dental problems of elderly people.
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[Could a contest encourage smokers from an unfavorable environment to abstain from smoking for at least six weeks?].
A contest to encourage smokers to quit and to remain nonsmokers for at least six weeks was held in a low income neighbourhood in Montreal. The contest was one of many activities for a multifactorial community-based heart health promotion program. The objective of this article is to describe the intervention and its evaluation and to reflect on its relative successes. Thirty-one persons registered for the contest, seven stopped smoking during the six-week contest, and six persons remained abstinent two weeks after the end of it. Concrete recommendations regarding the contest and implementation of a smoking cessation program are discussed.