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Biomedical subjects

B M Palmer

Publications and source records attributed to B M Palmer.

24 records · Page 2Linked to original sources
PubMed1995

An automated [15Q]H2O production and injection system for PET imaging.

A computer controlled [15O]H2O injection system has been designed for multiple bolus injections during PET cerebral blood flow studies. The system is housed in a lead safe, and radiation exposure to nearby personnel is low; we have measured rates of approx. 100 microSv/h (10 mR/h) during 2 min of [15O]H2O production and < 50 microSv/h (< 5 mR/h) after 3.7 GBq (100 mCi) has been produced. Reproducibility studies show that the injected activity varies with a coefficient of variation of 2-3%.

Automation↗
PubMed1990

Determination of regional myocardial perfusion by x-ray fluorescence.

Validation studies were performed to demonstrate the effectiveness of an x-ray induced fluorescence system in quantitating regional myocardial perfusion in vivo. In a series of 13 open-chested canines, x-ray induced fluorescence was used to simultaneously monitor iodine concentration transients which arose in the left ventricular lumen and in the myocardium after the intravenous injection of an iodinated flow tracer. Deconvolution of the recorded transients produced a transfer function from which the mean transit time for the tracer to travel between the left ventricular lumen and the myocardium was calculated. Measurements of regional myocardial perfusion (Q) made by radioactive microspheres were compared with the reciprocals of the mean transit times (MTT-1) and gave a linear correlation (n = 38): MTT-1 = 0.033 + 0.069 Q, r = 0.71. Comparison of the percent change in perfusion (dQ) relative to a control study for each dog with the percent change in the respective reciprocals of the mean transit times (dMTT-1) produced a linear correlation coefficient of r = 0.88 for the regression line dMTT-1 = 0.46 dQ - 10.7. The x-ray induced fluorescence system may provide a minimally invasive means for monitoring iodine concentration transients and determining relative, if not absolute, measures of regional myocardial perfusion.

Animals↗
PubMed1990

Effect of temperature on myosin phosphorylation in mouse skeletal muscle.

The effect of muscle contraction on phosphorylatable myosin light chain (P-light chain) phosphate content and isometric twitch tension was examined at 25, 30, and 35 degrees C in intact mouse extensor digitorum longus muscle. Peak tetanic tension was unaffected by temperature, whereas peak unpotentiated isometric twitch tension was inversely proportional to muscle incubation temperature. The extent of phosphate incorporation into P-light chain elicited by a 20-s train of twitches (5/s) was inversely proportional to muscle incubation temperature, whereas the fractional increase in twitch tension (twitch potentiation) elicited by repetitive stimulation was directly proportional to muscle incubation temperature. After the twitch train, the rate of decline of potentiated twitch tension and of P-light chain dephosphorylation was directly proportional to muscle incubation temperature. The net result was that a significant and unique relationship between P-light chain phosphate content and contraction-induced tension potentiation existed at each temperature examined. The slope of the P-light chain phosphate vs. isometric twitch potentiation relationship varied directly as a function of muscle incubation temperature. The observations that the slope of this relationship increases and that unpotentiated twitch tension decreases when muscle incubation temperature is increased support the hypothesis that contraction-induced tension potentiation in intact mammalian skeletal muscle is the result of a sensitization of the contractile element to activation by Ca2+ that is brought about by P-light chain phosphorylation.

Animals↗
PubMed1989

Myosin light chain phosphorylation and tension potentiation in mouse skeletal muscle.

In intact mammalian fast-twitch skeletal muscle, a quantitative relationship exists between the phosphate content of myosin P-light chain (PLC) and the extent of isometric twitch tension potentiation. It has been proposed that PLC phosphorylation causes twitch potentiation in intact muscle by rendering the contractile element more sensitive to activation by Ca2+. If this hypothesis is correct, then an obligatory experimental outcome is that the slope of the "PLC phosphate vs. isometric tension potentiation (ITP)" relationship should increase when the amount of Ca2+ available to activate the contractile element is decreased. Intact mouse extensor digitorum longus muscles were studied in the absence and presence of sodium dantrolene, an agent that partially inhibits Ca2+ release from the sarcoplasmic reticulum (SR). Treatment of muscles with dantrolene produced a 73% reduction in isometric twitch tension and an approximately threefold increase in the slope of the PLC phosphate vs. ITP relationship. Under experimental conditions that produced fused, tetanic contractions equal to 0.52, 0.72, 0.94, and 1.0 force production, contraction-induced changes in PLC phosphate content were directly proportional to the extent of contractile element activation, whereas the extent of ITP was inversely proportional to the extent of contractile element activation. These data indicate that the slope of the PLC phosphate vs. ITP relationship varies inversely as a function of the amount of Ca2+ that is released from the SR to activate the contractile element during both twitch and fused, submaximal tetanic contractions. Furthermore, these findings support the hypothesis that ITP in intact skeletal muscle is due to a PLC phosphorylation-induced sensitization of the contractile element to activation by Ca2+.

Animals↗
PubMedDate not supplied

Convective-dispersive characteristics of tracer transport calculated from transfer function analysis of biological indicator-dilution curves.

A solution to the convection-dispersion model of tracer transport in biological systems is presented. This solution provides for the characterization of tracer transport through a network of blood vessels based on the tracer transients recorded at the inlet and outlet points of the circulation under investigation. Fourier transformations of the transients are used to produce a transfer function from which the mean transit time as well as other transport characteristics can be calculated. The practical aspects of applying transfer function analysis to retrieve transport characteristics under experimental conditions are also presented. The application demonstrates the efficacy of the transfer function analysis method independent of tracer recirculation effects and a priori knowledge of actual tracer concentrations.

Biological Transport↗