Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Phosphorylation of myosin regulatory light chain (R-LC) increases the sensitivity of skinned skeletal muscle fibers to low Ca2+ activation. The purpose of this study was to determine whether phosphorylation of R-LC-mediated increases in Ca2+ sensitivity provides a molecular basis for potentiated twitch forces observed during fatigue of intact mammalian skeletal muscle. Tetanic stimulation for 120 s reduced peak tetanic force (Po) of mouse extensor digitorum longus (EDL) muscle by 74 +/- 2%. Despite high frequency fatigue (HFF), Pt was potentiated by 18 +/- 3% when R-LC phosphorylation (in moles phosphate per mole R-LC) was increased from 0.11 +/- 0.05 (rest) to 0.52 +/- 0.04 by 15 s of stimulation. Thereafter Pt declined below resting values despite high levels for R-LC phosphorylation (0.80 +/- 0.04 after 120 s of stimulation). In separate experiments, 10 min of stimulation, which reduced Po and Pt by 80 +/- 2 and 67 +/- 3%, respectively, was used to induce low frequency fatigue (LFF) in mouse EDL muscle. During LFF, long-lasting reductions in Pt were evident despite near-normal levels for Po (79 +/- 2 and 98 +/- 2% of controls, respectively). Application of conditioning stimuli (CS) increased R-LC phosphate content of fatigued muscles from 0.15 +/- 0.03 (rest) to 0.56 +/- 0.03 (stimulated) and potentiated Pt by 26 +/- 2% compared with LFF. Twitch potentiation during LFF was transient, lasting only as long as R-LC was phosphorylated above resting values for fatigued muscles. Overall, our data showing potentiated twitch forces concomitant with elevations in R-LC phosphate content during either HFF or LFF of mouse EDL muscle suggest that this molecular event counters reduced twitch forces during these forms of fatigue. Our results may be explained by R-LC phosphorylation induced increases in Ca2+ sensitivity for twitch force production in fatigued muscle.
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PMID:Phosphorylation of myosin and twitch potentiation in fatigued skeletal muscle. 904 41

There is mounting evidence that the endothelium may play an important role in traditional cryosurgical treatments by acting to locally foster thrombi in the microvasculature of various tissues after freezing. In addition, new catheter based cryosurgical probes are being designed for cardiovascular applications where endothelial and smooth muscle cell freezing is involved but not well understood. Therefore, this study was designed to investigate, at the cellular level in human microvascular endothelial cells (hMEC), the various biophysical changes that occur during freezing which can affect post-freeze viability. The hMECs were loaded on a cryomicroscope stage and freezing experiments at 5, 10, 15, 25, 100 and 130 degrees C/min were performed to experimentally evaluate dehydration (water transport) as well as intracellular ice formation (IIF) within this cell system. The dehydration kinetics at 5, 10 and 25 degrees C/min were found to be governed by a membrane permeability L(pg) and activation energy E(Lp) of 0.05 (microm/min.atm) and 14.8 (kcal/mole) respectively [R(2)=0.94]. These parameters were then tested for predictive ability against the experimentally measured behavior at 15 degrees C/min with a good agreement [R(2)=0.98]. Intracellular Ice Formation (IIF) was found to occur at lower temperatures than many cell types (i.e. TIIF 50% approximately -18 degrees C) and at cooling rates greater than or equal to 25 degrees C/min. At cooling rates above 50 degrees C/min, two types of IIF, cell darkening and twitching, were both observed and quantified and were assumed to be governed by Surface Catalyzed Nucleation (SCN). IIF parameters, omega(o) and kappa(o), which fit data from 50, 100 and 130 degrees C/min were found to be 6.8 x 10(-8) (m(2).s)(-1) and 8.3 x 10(-9) (K5) [R(2)=0.94] respectively. Preliminary results show that viability drops precipitously between -20 and -30 degrees C, however, further studies are warranted to address the role of cooling rate, end-temperature, hold time and thawing rate to establish the freeze sensitivity of this cell.
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PMID:Evaluation of freezing effects on human microvascular-endothelial cells (HMEC). 1178 77