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R C Woledge

Publications and source records attributed to R C Woledge.

At least 73 records · Page 4Linked to original sources
PubMed1984

Simultaneous heat and tension measurements from single muscle cells.

Simultaneous force and heat measurements were made in single cells from skeletal muscle of the frog during isometric twitches and tetani at 10 and 0 degree C. A Hill- Downing type thermopile of low heat capacity was used. In twitches, peak force development was found to be well correlated with heat production at both temperatures, during posttetanic twitch potentiation (at 10 degrees C) and during posttetanic twitch depression (at 0 degree C). In a twitch at 0 degree C, heat production started less than 14 msec after the stimulus had begun, before force development. As in whole muscle, the heat during a tetanus could be separated into two components: an early component produced at an exponentially decreasing rate, labile heat, and a steady rate, stable maintenance heat rate. Increasing temperature from 0 to 10 degrees C doubled the stable maintenance heat rate. At the higher temperature the time constant of labile heat production was halved and the quantity of labile heat decreased. When two tetani were given at 10 degrees C, a 5 min rest interval was required before the second tetanus produced the same force and heat as the first. At 0 degree C this interval was at least 10 min. With shorter intervals, both heat and force were depressed. At 10 degrees C both were depressed equally but at 0 degree C the effect on heat was greater than on force. At both temperatures labile heat was depressed to a greater extent than the stable maintenance heat rate. Results are interpreted in terms of possible calcium-parvalbumin interaction during a tetanus.

Animals↗
PubMed1984

The sarcomere length dependence of the rate of heat production during isometric tetanic contraction of frog muscles.

Heat production and force have been measured as a function of sarcomere length between 1.6 and 3.0 microns during isometric tetani at 0 degree C for two types of frog muscle: sartorius and extensor longus digiti iv (e.l.d. iv). Stable heat rate declines linearly with increasing sarcomere length above 2.20 microns for both e.l.d. iv and sartorius muscles. In sartorius muscle stable heat rate remains at or near its maximum value between 1.75 and 2.20 microns while force decreases. In e.l.d. iv muscle, both stable heat rate and force decline linearly as sarcomere length decreases below 2.20 microns.

Animals↗
PubMed1983

Heat production by single fibres of frog muscle.

The heat produced during contractions of preparations consisting of one or a few muscle fibres was measured for the first time. Fibres were dissected from the anterior tibialis muscles of the frog, Rana temporaria. Measurements were made with thermopiles of a design based on that described by Howarth et al. (1975). Although the fibre preparations were small, measurable signals could be recorded because the heat capacity of the thermopiles was also small. The output of the thermopile was amplified by a galvanometer circuit. In all the experiments the ends of the preparation were held in a fixed position during stimulation ("isometric'). Observations were made of heat production during twitches and tetanic contractions. The heat produced in a twitch of a single fibre depended on the stimulus strength in an all-or-nothing way. The results show that the amount of heat produced in individual twitches is fairly constant at different temperatures in the range 3-15 degrees C. In contrast, the heat produced in tetanic contractions is considerably greater at higher temperatures. The time course of heat production in a tetanus was influenced by temperature such that the early rapid phase of heat production was less obvious at the higher temperature. The quantities of heat produced by fibre preparations were in reasonable agreement with those produced by whole muscles when the comparison was made on the basis of heat produced per g wet weight of tissue.

Animals↗
PubMed1981

Effect of muscle length on energy balance in frog skeletal muscle.

1. Measurements were made of the extents of ATP splitting and the creatine kinase reaction and the heat + work (h+w) produced during 5s isometric tetani of frog semitendinosus muscle at 0 degrees C. A comparison was made of tetani at two different muscle lengths. These lengths were l0 (sarcomere length 2.3 micrometers before stimulation), which is near the optimum for interaction of actin and myosin, and lmax (sarcomere length 3.8 micrometers) at which actin-myosin interaction is largely prevented. 2. As in earlier studies of muscle at l0, the observed h+w was significantly greater than the amount explained by the energy from ATP splitting and the creatine kinase reaction. Our main new finding is that a significant amount of unexplained energy is also produced at lmax where there is a negligible amount of actin-myosin interaction. This suggests that the unexplained energy cannot be due solely to actin-myosin interaction. 3. On average less unexplained energy is produced at lmax than at l0. Thus it seems likely that the process (or one of the processes) producing this energy is dependent on muscle length. 4. The observed h+w was divided on the basis of its time course into the two parts, labile and stable, which were defined by Aubert (1956). The labile part of the h+w has an exponentially declining rate, and the stable part has a constant rate. The production of labile h+w influenced by muscle length in two ways: the total amount and the rate of its production are significantly smaller at lmax than at l0. 5. At both lengths the labile h+w is equal, within experimental error, to the unexplained h+w.

Actins↗
PubMed1981

The energy liberation of frog skeletal muscle in tetanic contractions containing two periods of shortening.

1. Heat and work production have been measured in pairs of frog sartorius muscles undergoing two periods of rapid isovelocity shortening at 0 degrees C. The first (conditioning) shortening occurred in the sarcomere length range 2.70--2.25 micrometer (as measured in resting muscles) and the second (test) shortening in the range 2.25--2.10 micrometer. The shortening heat associated with the test shortening was obtained as the difference in heat production between pairs of tetani which were identical except for the presence of the test shortening. 2. The shortening heat associated with the test shortening was reduced when it was preceded by the conditioning shortening; with no interval between shortenings its value was 52 +/- 3% (mean +/- S.E. of mean, n = 6) of that without the conditioning shortening. As the interval between shortenings was increased the shortening heat became larger; its recovery was more than half complete with an interval of 0.3 sec. 3. The work produced in the test shortening was also reduced in tetani which contained the conditioning shortening; its dependence on the interval between shortenings was similar to that of the shortening heat.

Animals↗
PubMed1981

The dependence on extent of shortening of the extra energy liberated by rapidly shortening frog skeletal muscle.

1. Pairs of frog sartorius muscles were stimulated for 2 sec at 0 degrees C, after 1 sec of isometric contraction, were released at a constant velocity. The total excess heat (shortening heat) and work associated with the release were determined by comparison with isometric control tetani. 2. Shortening heat and work production were non-linearly related to the distance shortened. There was proportionally more energy liberation for smaller releases. 3. The dependence of shortening heat on muscle length was investigated within the sarcomere length range 2.1--2.6 micrometer (as measured in resting muscle) and was found to be similar to that of isometric tension. 4. A simple model in which heat and work are produced in a two-state cycle can describe these and previous results concerning the energetics of rapidly shortening muscle.

Animals↗
PubMed1979

The heat produced by frog muscle in a series of contractions with shortening.

1. Heat production has been measured in muscles undergoing rapid shortening 1 sec after the start of stimulation in a 2 sec tetanus. In a series of three such tetani where the periods of shortening were separated by 5 sec the shortening heats in the second and third tetani were 111 (+/- 4)% and 116 (+/- 6)% respectively of that in the first tetanus (mean +/- S.E. of mean, nine experiments). 2. When a similar series was carried out after an interval of 3 min the shortening heat in the first tetanus of the second series was 127 (+/- 3)% of that in the first tetanus of the first series (mean +/- S.E. of mean, three experiments). 3. The results are not in agreement with those of Dickinson & Woledge (1974). The discrepancy is explained by an artifact which, with certain arrangements of the apparatus, affects the measurements of shortening heat in a series of contractions. We have measured this artifact by two independent methods; the shortening heat values quoted above have been corrected accordingly. 4. The increase in the shortening heat in repeated contractions is not a specific consequence of previous shortening; an increase of the same magnitude is observed following isometric tetani. 5. During the time when the muscle is shortening, the total rate of heat production, which is initially high, falls to a steady value. This value is not significantly different in the three tetani of the series.

Animals↗
PubMed1979

Chemical change, production of tension and energy following stretch of active muscle of frog.

1. Measurements were made of the tension and the heat + work produced during 6.5 s of tetanic stimulation at 0 degrees C. The muscle was stretched by 3 mm to 1.2 times rest length either 1 s before stimulation began of 1 s after it began. 2. The extent of ATP splitting during the period from 1.5 to 6.5 s after stimulation began was determined from observations of the levels of phosphocreatine, creatine and the sum of inorganic phosphate and glucose-6-phosphate and glucose-1-phosphate. (The creatine kinase reaction was taken to be in equilibrium.) 3. In agreement with earlier findings more active tension was produced following a stretch when the stretch occurred during stimulation than when it occurred before stimulation. This increase was large and statistically significant. 4. The mean splitting of ATP was greater following a stretch during stimulation, but this change was small and not statistically significant. 5. During the interval from 1.5 to 2.5 s after stimulation began, which is shortly after the stretch ended, the rate of heat production was significantly greater than in the isometric contraction. 6. From 2.5 s to the end of stimulation and during relaxation the heat + work was not significantly different in the two types of contraction.

Adenosine Triphosphate↗
PubMed1979

Chemical change and energy production during contraction of frog muscle: how are their time courses related?

1. The heat+work (h+w) and the changes in the levels of creatine, phosphocreatine and ATP were determined for 1, 2, 5, 10 and 15 sec isometric tetani at 0 degrees C under aerobic conditions. The change in the sum of inorganic phosphate and glucose-1-phosphate and glucose-6-phosphate was measured also. The changes in the levels of all these chemicals and of lactate were measured in muscles stimulated for 15 sec under anaerobic conditions. 2. The lactate measurements and a comparison of the results for aerobic and anaerobic conditions showed that during a 15 sec tetanus there was a negligible amount of resynthesis of ATP from reactions other than the creatine kinase reaction. 3. For all durations of stimulation, except 1 sec, a significant part of the h+w could not be explained by the energy from ATP splitting and the creatine kinase reaction. The existence of an unexplained part of the h+w confirms earlier findings. 4. On the basis of its time course, the h+w was divided into the stable part and the labile part. The energy from the observed chemical reactions was always sufficient to account for the stable part of the h+w. 5. Early in the tetanus the unexplained energy is less than the labile part of the h+w. At the end of a 15 sec tetanus the total amounts of unexplained energy and labile h+w are equal. For this reason and others which are discussed it is probable that there is a close relationship between them.

Adenosine Triphosphate↗
PubMed1977

Calorimetric studies of the ADP binding to myosin subfragment 1, heavy meromyosin, and to myosin filaments.

A calorimetric titration method was used to study the ADP binding to the chymotryptic subfragments of myosin, heavy meromyosin (HMM) and myosin subfragment 1 (S-1), and to myosin aggregated into filaments at low ionic strength. The binding constant (K) and heat of reaction (deltaH, kiloJoules (moles of ADP bound)-1) were determined. For HMM in 0.5 M KCl, 0.01 M MgCl2, 0.02 M Tris (pH 7.8) at 12 degrees, log K = 5.92 +/- 0.13 and deltaH = -70.9 +/- 3.6 kJ mol-1. These results agree with our previous findings for myosin in 0.5 M KCl at 12 degrees. When the KCl concentration was reduced to 0.1 M, the binding constant did not change significantly (log K = 6.09 +/- 0.06) but the binding was more exothermic (deltaH = -90.1 +/- 3.3 kJ mol-1). Similar results were obtained for myosin filaments in 0.1 M KCl and also for both the isoenzymes of S-1(S-1(A1) and S-1(A2) in 0.1 M KCl. In 0.5 M KCl, the binding curves suggest that about one ADP is bound per active site, but as 0.1 M KCl, the apparent stoichiometry drops from 0.7 to 0.75. The most probable explanation is that there is some site heterogeneity which is more evident at lower ionic strength.

Adenosine Diphosphate↗
PubMed1977

A comparison of the energy balance in two successive isometric tetani of frog muscle.

1. Measurements were made of the energy produced as heat and work (h + w) and the chemical changes which occurred between the beginning and end of each of two periods of stimulation. The muscles contracted tetanically under isometric conditions. Each period of stimulation (tetanus) lasted 5 sec and there was an interval of 3 sec between them. The tension developed in the second tetanus was 91% of that in the first.2. The observed (h + w) was greater in each tetanus than the quantity expected from the measured chemical changes. This excess was 230 +/- 43 mJ/g dry wt. (mean +/- S.E. of mean) in the first tetanus, but only 89 +/- 46 mJ/g in the second tetanus (mean +/- S.E. of mean). The result for the first tetanus agrees with previous findings.3. The observed (h + w) was divided into two parts, labile and stable, which were defined by Aubert (1956). This division was made on the basis of the time course of the (h + w) production, without reference to the chemical changes. The labile part of the (h + w) has an exponentially declining rate, and the stable part has a constant rate.4. The observed (h + w) was less in the second tetanus than in the first. This was due largely to the decrease in the labile part in the second tetanus; it was only ca. 0.35 of that in the first tetanus. However, the stable part remained relatively constant, 0.83 of that in the first tetanus. Aubert & Maréchal (1963) and Aubert (1968) have reported similar results.5. Having divided the (h + w) into the stable and labile parts, we found that the stable part could be accounted for by the chemical change, but the labile part could not. Thus, for both tetani, the stable part of the energy is about equal to the explained energy, and the labile part is about equal to the unexplained energy. The possible interpretations of these equalities are discussed.

Adenosine Diphosphate↗
PubMed1976

Calorimetric studies of the interaction of myosin with ADP.

A calorimetric titration method was used to study ADP binding to native myosin. Data were analyzed by assuming that the myosin molecule has n independent and identical sites for ADP binding. The enthalpy change (deltaH), the binding constant (K), and n were determined. In 0.5 M KCl, 0.01 M MgCl2, and 0.02 M Tris/HCl (pH 7.8), we found: at 0 degrees, deltaH = -57.1 +/- 3.2 kJ-mol-1, log K = 6.42 +/- 0.13, n = 1.49 +/- 0.07; at 12 degrees, deltaH = 73.1 +/- 3.2 kJ-mole-1, log K = 6.08 +/- 0.13, and n = 1.74 +/- 0.07. The average heat capacity change on ADP binding to myosin between 0 and 12 degrees is thus -1.4 +/- 0.4 kJ-mol-1-K-1. Reasonably consistent results were obtained at 25 degrees, suggesting ADP binding to myosin is as strongly exothermic as at lower temperatures, although further interpretation of this result seems unwarranted, mainly because of the instability of myosic at this temperature. The number of protons released on binding of ADP to myosin was determined in separate experiments. The value was 0.19 +/- 0.02 at both 0 and 12 degrees. The reaction of protons with Tris thus contributes about -9.5 kJ-mol-1 to the observed heat on ADP binding.

Adenosine Diphosphate↗