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Biomedical subjects

W G Kerrick

Publications and source records attributed to W G Kerrick.

At least 55 records · Page 3Linked to original sources
PubMed1980

Associated changes in Ca2+ and Sr2+ activation properties and fiber proteins in cross-reinnervated rabbit soleus.

Changes in the Ca2+ and Sr2+ activation properties of functionally skinned slow-twitch soleus fibers were measured and compared with those of normal fast-twitch extensor digitorum longus (EDL) following cross-reinnervation of soleus with the nerve to EDL. Most of the fibers showed either complete transformation of activtion properties (66%) or remained unchanged (34%). The change in sensitivity to divalent cations was correlated with changes in the proteins present in fibers pooled on the basis of their activation properties. The banding patterns of the 35,000- and 37,500-dalton proteins (tropomyosin and troponin T) in cross-reinnervated soleus were correspondingly transformed to those of normal EDL. Slow and fast myosin light chains were present in the pooled cross-reinnervated fibers. Fiber distributions based on activation properties were confirmed by histochemical features. For the first time it has been demonstrated that cross-reinnervation produced changes in the activation properties of soleus fibers and associated changes in the regulatory proteins measured.

Animals↗
PubMed1980

Ca2+ and Sr2+ activation: comparison of cardiac and skeletal muscle contraction models.

The mechanism of contraction in rabbit fast-twich, and bovine and rabbit cardiac muscle was examined using functionally skinned fibers, ATPase activity of myofibrils, and cardiac or skeletal troponin-tropomyosin regulated actin heavy meromyosin. The Ca2+ and Sr2+ activation properties for the different measures of contraction were evaluated. (1) Tension in rabbit and bovine cardiac skinned fibers and rabbit cardiac myofibrillar ATPase were activated equally well by either Ca2+ or Sr2+. By contrast, rabbit adductor magnus (fast-twich) skinned fibers required substantially higher [Sr2+] than [Ca2+] for activation, as did rabbit myofibrils from back muscle (fast-twitch). (2) Substantially more Sr2+ than Ca2+ was also required for activation of skeletal muscle actin heavy meromyosin ATPase, controlled by either the skeletal or cardiac troponin-tropomyosin complex, similar to the activation of fast-twitch muscle. (3) The absence of correlation between the divalent cation selectivity properties of actin heavy meromyosin ATPase controlled by cardiac troponin-tropomyosin and cardiac muscle tension or myofibrillar ATPase activation by Ca2+ and Sr2+ suggests that troponin, if primarily responsible for the activation of cardiac muscle, has very different in vivo and in vitro binding properties. (4) The close correlation between percentage of maximal Ca2+- and Sr2+-activated myofibrillar ATPase and tension in skinned fibers strongly justifies the use of myofibrillar ATPase, in contrast to a reconstituted troponin-tropomyosin actin heavy meromyosin ATPase system, as a biochemical measure of contraction.

Adenosine Triphosphatases↗
PubMed1980

Insulin and glucose 6-phosphate stimulation of Ca2+ uptake by skinned muscle fibers.

Calcium uptake by skinned muscle fibers is stimulated by physiological concentrations of insulin. These fibers, which lack a functional plasma membrane, are permeable to macromolecules but retain extensive portions of their sarcolemma in the form of transverse tubules intercalated between the myofibrils. They have an active sarcoplasmic reticulum that removes 45Ca2+ from solution at concentrations below the threshold that initiates contraction (less than 1 microM). The Ca2+ uptake activity is stimulated by insulin, presumably in response to its binding to those receptors located in the transverse tubules. Addition of glucose 6-phosphate, whose intracellular concentration increases in response to insulin, also stimulates Ca2+ uptake, a unique property of this preparation. These data indicate that insulin and glucose 6-phosphate act in concert to stimulate the sarcoplasmic reticulum. The resulting decrease in myoplasmic Ca2+ and the increase in glucose 6-phosphate would serve to mediate some of the anabolic effects of the hormone.

Animals↗
PubMed1980

Effects of enflurane on functionally skinned myocardial fibers from rabbits.

Enflurance, at clinical concentrations, decreases the contractility of isolated intact cardiac muscle. The authors investigated the intracellular mechanism(s) of this depression by examining the Ca2+ activation of the contractile proteins and Ca2+ uptake and release from the sarcoplasmic reticulum (SR) using functionally skinned fibers from right ventricular papillary muscle of rabbits. This preparation permits control of intracellular ionic composition (pH 7.0, 20 C). The [Ca2+]--tension relationship and caffeine-induced tension transient (as a measure of the amount of Ca2+ release) were analyzed. Enflurane significantly but only slightly depressed the maximum Ca2+-activated tension (10 per cent decrease at 5 per cent enflurane) and did not change the [Ca2+] required for half-maximal activation of the fibers. In contrast, enflurane markedly inhibited the Ca2+ uptake by the SR (30-85 per cent decrease at 2.5-7.5 per cent enflurane). The inhibition was dose-dependent. Ca2+ release from the SR with 25 mM caffeine was not changed at low concentrations of enflurane (1-5 per cent), but was decreased at high concentration (25 per cent decrease at 7.5 per cent enflurane). Enflurane (1-7.5 per cent), however, increased (13-44 per cent) the submaximum caffeine (2 mM)-induced Ca2+ release from the SR, and the effect was not dose-dependent. The aforementioned effects were reversible. These results are similar to those previously reported for halothane. It is concluded that enflurane may induce myocardial depression mainly by inhibiting Ca2+ uptake by the SR.

Animals↗
PubMed1980

Calcium-activated tension: the role of myosin light chain phosphorylation.

Small strips of intestinal or arterial smooth muscle composed of many functionally skinned muscle cells (nonfunctional sarcolemma), skinned skeletal single fibers, or bundles of skinned cardiac fibers were used to test the hypothesis that a myosin light chain kinase/phosphatase system is responsible for the activation of contraction. The results showed that in smooth muscle: 1) there is a close correlation between the degree of phosphorylation of the myosin light chains and tension development: 2) irreversible thiophosphorylation of myosin light chain results in irreversible activation of tension; and 3) inhibition of the light chain kinase by phenthiazines results in dephosphorylation of the myosin light chains and inactivation of tension in the presence of Ca2+. In contrast, in skinned striated muscle fibers 1) there is no correlation between phosphorylation and tension, 2) light chains could not be thiophosphorylated, and 3) phenothiazines did not affect Ca2+-activated tension. These findings indicate a Ca2+-sensitive light chain kinase/phosphatase system is responsible for the activation of smooth muscle, but no similar evidence was found for such a system in striated muscle.

Animals↗
PubMed1979

Irreversible thiophosphorylation and activation of tension in functionally skinned rabbit ileum strips by [35S]ATP gamma S.

Rabbit ileum strips were functionally skinned by exposure to staphylococcal alpha-toxin. Incubation of the strips in the ATP analog ATP gamma S or [35S]ATP gamma S in the presence of Ca2+ (but not in the absence of Ca2+) resulted in a maximal Ca2+-insensitive activated tension that persisted following removal of Ca2+. Correlated with this tension was 35S-labeling of the 20,000-dalton myosin light chain, LC20, that persisted even after removal of Ca2+. Tension in these strips partially relaxed when exposed to ATP (alpha,beta-methylene). In contrast, alpha-toxin-treated strips exposed to ATP or [gamma-32P]ATP showed Ca2+-sensitive, reversible activated tension and reversible 32P-labeling of the LC20. These results are consistent with a currently proposed model of Ca2+ control of smooth muscle contraction involving a myosin light chain kinase-phosphatase system.

Actins↗
PubMed1979

Effects of halothane on caffeine-induced tension transients in functionally skinned myocardial fibers.

The effects of halothane on caffeine-induced tension transients in functionally skinned myocardial fibers were investigated. Fiber bundles from mechanically disrupted rabbit right ventricular papillary muscles were mounted on a tension transducer. The fiber preparation was loaded with Ca2+; Ca2+ was then released by the use of caffeine (25 mM); and the area of the resulting tension transient was measured. Each preparation was sequentially transferred from control to test to control solution. The control solutions were equilibrated with 100% N2, and the test solutions with a mixture of N2 and various halothane concentrations. The preparation was exposed to halothane during the Ca2+ uptake or the release phase only, or during both Ca2+ uptake and release phases. The areas of the test tension transients were compared with those of the two control tension transients. It was found that halothane depressed the caffeine-induced tension transient either during the uptake phase or the combined-uptake-and-release phase but not during the release phase. The halothane-induced depression was dose-dependent, reversible, and comparable to the depression observed in intact isolated papillary muscles. We conclude that halothane could induce myocardial depression by inhibiting Ca2+ uptake by the sarcoplasmic reticulum.

Animals↗
PubMed1979

The effects of pH on Ca2+-activated force in frog skeletal muscle fibers.

Ca2+-activated isometric force was recorded is skinned (sarcolemma mechanically removed) segments of frog skeletal muscle fibers immersed in bathing solution of different pH (5.0--10.5) and Ca2+ concentrations. Force in maximally activated fibers was near zero at pH 5.5, increased as pH increased to 7.5, remained relatively constant until pH 9.0 and then rapidly declined to zero by pH 10.5. The Ca2+ concentration at which 50% of maximum force was developed decreased 25-fold as pH increased from 5.5--7.5. The data also indicate that, while the fibers remains viable with acidosis, they deteriorate rapidly with alkalosis. These observations may be relevant clinically, since they parallel known effects of acidosis on cardiac contractility. The possible sites of action of H+ on the Ca2+-activated force generating mechanisms are discussed.

Animals↗
PubMed1979

Chicken gizzard: relation between calcium-activated phosphorylation and contraction.

Of the proteins in mechanically disrupted chicken gizzard fibers (no functional sarcolemma) only the 20,000-dalton light chains of myosin underwent large Ca2+-and Sr2+-dependent changes in phosphorylation. Phosphorylation closely corresponded with the Ca2+- and Sr2+-activated tensions. Adenosine 5'-O (3'-thiotriphosphate) only in the presence of Ca2+ induced irreversible Ca2+-insensitive activation of tension and thiophosphorylation of the 20,000-dalton light chains, and blocked incorporation of 32P from [gamma-32P]adenosine triphosphate into the myosin light chains.

Animals↗
PubMed1979

Characterization of Ca2+- and Sr2+-activated tension in functionally skinned chicken fibers of normal and dystrophic skeletal and normal cardiac muscle.

The Ca2+ and Sr2+ activation of tension in functionally skinned chicken fibers of normal and dystrophic skeletal and normal cardiac muscle were studied. The muscles studied can be separated into two groups based upon their Ca2+ and Sr2+ sensitivities: those which are significantly more sensitive to Ca2+ than to Sr2+, pectoralis and posterior latissimus dorsi (PLD), and those which show no Ca2+/Sr2+ sensitivity difference, cardiac and anterior latissimus dorsi (ALD). This suggests that there is more than one type of Ca2+ site involved in Ca2+ control of muscle contraction in different muscle types and suggests that ALD and cardiac muscle may be controlled by a different type of binding site than PLD and pectoralis muscle. Dystrophic ALD and PLD muscles showed little change in their Ca2+ and Sr2+ sensitivities from those of normal muscles in contrast to the pectoralis which showed a decrease in both Ca2+ and Sr2+ sensitivity (approaching that of PLD) with the onset of dystrophy. Similarly, upon SDS polyacrylamide gel electrophoresis, dystrophic ALD and PLD muscles showed no difference in contractile proteins from those of normal muscles, in contrast to pectoralis muscle where the appearance of a 36,000 dalton protein band correlated with the onset of dystrophy and the changes in the Ca2+/Sr2+ activation properties of this muscle. The contractile protein band pattern of normal and dystrophic PLD and dystrophic pectoralis muscle were similar including the presence of the 36,000 dalton protein.

Animals↗
PubMed1979

Rabbit diaphragm: two types of fibres determined by calcium strontium activation and protein content.

1. Submaximum Ca2+- and Sr2+-activated tensions were measured in functionally skinned fibres from the rabbit diaphragm. 2. The fibres could be classified into two types on the basis of activation by divalent cations. Type S fibres required a slightly higher [Ca2+] than [Sr2+] for half-maximal activation of tension. Type F fibres required 2 times higher [Ca2+] than type S and 8.5 times higher [Sr2+]. 3. Sodium dodecyl sulphate disc gels of type F fibres showed protein band patterns similar to those of fast-twitch muscle; those of type S fibres were identical to those of slow-twitch fibres. 4. Sodium dodecyl sulphate disk gels of mixed, non-classified diaphragm fibres and an actual count of randomly selected fibres classified by Ca2+/Sr2+ tension characteristics showed the diaphragm to be composed of 60% fast-twitch fibres and 40% slow-twitch fibres. 5. The protein stoichiometries of the two fibre types are consonant with the accepted stoichiometries for skeletal muscle. 6. The percentages of type F and type S fibres in the diaphragm suggest that high adenosine-triphosphatase activity shown by histochemical techniques (Davies & Gunn, 1972) is associated with the type F fibres, and low activity with the type S fibres.

Animals↗
PubMed1978

Effects of halothane on Ca2+-activated tension development in mechanically disrupted rabbit myocardial fibers.

The effect of halothane on maximal and submaximal Ca2+-activated tension in mechanically disrupted right ventricular papillary muscle from rabbits was studied. Steady-state isometric tension generation was measured in the muscle bundle. The relaxing solution contained (in mM) [Mg2+] = 1, [K+] = 70, [MgATP2-] = 2, [creatine phosphate2-] = 15, [EGTA total] = 7 and imidazole proprionate. The contracting solution contained in addition Ca2+ in various concentrations. In all solutions ionic strength was maintained at 0.15 and pH at 7.00 +/- 0.02 at 20 degrees C. Each fiber bundle was immersed in control solutions equilibrated with 100% N2 and test solutions equilibrated with various concentrations of halothane-N2 mixture. Increasing doses of halothane (1--4%) significantly shifted the relationship between Ca2+ and tension towards higher [Ca2+] and depressed the maximum Ca2+-activated tension. The maximum tension generated at pCa = 3.8 was depressed 5% per 1% increase in halothane concentration. The percentage of maximum tension at submaximum Ca2+ concentrations (pCa = 5.6--5.0) was not significantly decreased until halothane concentration was greater than 2%. It is concluded that halothane slightly but significantly depressed the interactions of contractile proteins and to a lesser degree Ca2+-activation of the regulatory proteins. The halothane-induced depression was completely reversible.

Adenosine Triphosphatases↗
PubMed1977

Tension in mechanically disrupted mammalian cardiac cells: effects of magnesium adenosine triphosphate.

1. Maximum and submaximum Ca-activated tension in mechanically disrupted rat ventricular fibres was examined in solutions containing 30 micron, 100 micron and 4 mM-MgATP and either 50 micron or 1 mM ionized Mg. 2. In the absence of added Ca, significant amounts of base-line tension (up to 50% of maximum) develop in solutions containing less than 30 micron-MgATP. This effect is Mg-dependent; more tension is produced with 50 micron-Mg than with 1 mM. 3. Increasing the MgATP concentration shifts the pCa-% maximum tension relationship in the direction of increasing Ca required for activation. At 50 micron-Mg the pCa which produces 50% maximum tension is 5-8, 5-3 and 5-5 for the 30 micron, 100 micron and 4 mM-MgATP solutions. The effect of MgATP on position is relatively independent of the Mg concentration. 4. The steepness of the pCa-% maximum tension curve increases as MgATP is elevated to the millimolar range. The Hill coefficients for the different MgATP curves at 50 micron-Mg are 1-1, 1-3 and 3-0. This change in steepness accounts for the slightly lower Ca concentration needed for half-maximum tension as the MgATP concentration is increased to millimolar levels. Raising the Mg concentration to 1 mM greatly diminishes the effect of MgATP on the slope of the pCa-tension relationship. 5. The maximum tnesion a fibre bundle can produce decreases as the amount of MgATP is raised from micromolar to millimolar levels. For 50 muM-Mg, maximum tension drops about 35% as MgATP is raised from 30 micronM to 4 mM. For any concentraiton of MgATP, maximum tension is higher at 1 mM-Mg than at 50 micron-Mg. 6. Existing theories of interaction between myosin heads and the thin filament are sufficient to account for the effects of MgATP on the position of the pCa-tension curves and on maximum tension. The effects on slope are less satisfactorily explained.

Adenosine Triphosphate↗
PubMed1975

Characterization of the effects of Mg2+ on Ca2+- and Sr2+-activated tension generation of skinned skeletal muscle fibers.

Changes in [Mg2+] in a millimolar range have a significant inverse effect on the Ca2+- (or Sr2+)activated tension generation of skeletal muscle fibers. Single frog (Rana pipiens) semitendinosus muscle fibers were "skinned" (sarcolemma removed) and contracted isometrically in bathing solutions of varying [Ca2+] or [Sr2+] and [Mg2+] but a constant pH, [MgATP2-], [K+], [CP2-], [CPK], and ionic strength. Ca2+- (or Sr2+-)activated steady-state tensions were recorded for three [Mg2+]'s: 5 X 10(-5)M, 1 X 10(-3) M, and 2 X 10(-3) M; and these tensions were expressed as the percentages of maximum tension generation of the fibers for the same [Mg2+]. Maximum tension was not affected by [Mg2+] within Ca2+-activating or Sr2+-activating sets of solutions; however, the submaximum Ca2+-(or Sr2+)activated tension is strongly affected in an inverse fashion by increasing [Mg2+]. Mg2+ behaves as a competitive inhibitor of Ca2+ and also affects the degree of cooperativity in the system. At [Mg2+] = 5 X 10(-5)M the shape of tension versus [Ca2+] (or [Sr2+]) curve showed evidence of cooperativity of Ca2+ (or Sr2+) binding or activation of the contractile system. As [Mg2+] increased, the apparent affinity for Ca2+ or Sr2+ and cooperativity of the contractile system declined. The effect on cooperativity suggests that as [Mg2+] decreases a threshold for Ca2+ activation appears.

Animals↗
PubMed1975

Disruption of the sarcolemma of mammalian skeletal muscle fibers by homogenization.

A new method has been developed for mechanically disrupting the sarcolemma of mammalian sketletal muscle fibers (sarcolemma nonfunctional). Single fibers were produced from small pieces of the soleus muscle of the rabbit by gentle homogenization in a relaxing solution in a tissue homogenizer. These fibers were found to be longitudinally intact, with a sarcomere spacing of approximately 2.1 mum, permeable to large molecules of 10,000 MW, sensitive to the chemical stimuli that cause Ca2+ to be released from the sarcoplasmic reticulum, and responsive to Ca2+ in the same manner as frog fibers skinned in the traditional manner. The single fibers were mounted in a tension transducer and steady-state tensions were recorded in test solutions of different Ca2+ concentrations. The data did not differ statistically from data similarly obtained in identically prepared fibers that, in addition, we had longitudinally split in half to ensure disruption of the sarcolemmal barrier to the diffusion of ions.

Animals↗
PubMed1974

Calcium ion release in mechanically disrupted heart cells.

In cardiac muscle fibers which have had their sarcolemma disrupted intracellular stores of calcium ions can be released by the same chemical stimuli which cause their release from the sarcoplasmic reticulum of skinned skeletal muscle fibers. These stimuli are increases in calcium or caffeine concentrations and substitution of chloride for propionate or sodium for potassium in solutions bathing the fibers.

Animals↗