scholarly journals The heat production in isometric and isotonic twitches

1930 ◽  
Vol 107 (749) ◽  
pp. 115-131 ◽  
Keyword(s):  
Lactic Acid ◽  
Heat Production ◽  
Isometric Contraction ◽  
Room Temperature ◽  
Probable Error ◽  
Isotonic Contraction ◽  
Complete Relaxation ◽  
Initial Load ◽  
The Difference ◽  
Isotonic Contractions

In a recent paper from Meyerhof's laboratory P. Rothschild (1930) has shown that in a series of isometric twitches of a frog's gastrocnemius or semi-membranosus considerably more lactic acid may be liberated than in the same number of isotonic twitches with the same initial load: while with sartorius there may be little or no difference. 90 to 150 shocks were applied, at intervals of 5 to 10 seconds, at room temperature (11° C. to 17° C.), and either directly or to the nerve: the intervals were sufficient to allow complete relaxation between twitches and the number of twitches was not so great as to cause appreciable fatigue. With semi-membranosus, with an initial load of 10 or 20 g. the lactic acid in the isotonic averaged about 35 per cent. less than in the isometric twitches: with gastrocnemius stimulated through its nerve following six results were obtained at 15° to 17° C. in 92 to 102 twitches: Initial load: g. ............ 25 20 20 20 10 10 After-load (isotonic): g. ............. 13 50 50 50 140 140 Deficit due to shortening: p. c. ............. 70 49 64 76 34 25 Thus in an isotonic contraction with considerable shortening the lactic acid may be ½ to ⅓ of the amount in an isometric contraction with the same initial load: while when the shortening is smaller (greater after-load) the difference may be less (last two experiments). With sartorius, however, in 110 to 150 contractions at 12° C. to 17° C., there was a slight excess of lactic acid in the isotonic contractions, averaging about 8 per cent. The smallness of the difference was regarded by Rothschild as insignificant, in view of the probable error of his estimations: in this, as will be seen, he unduly depreciated the accuracy of his own observations: his difference was probably genuine.

Cyclic production of tension force in the plasmodial strand of Physarum polycephalum and its relation to microfilament morphology

1978 ◽  
Vol 33 (1) ◽  
pp. 205-225
Author(s):  
R. Nagai ◽  
R.N. Yoshimoto ◽  
N. Kamiya
Keyword(s):  
Isometric Contraction ◽  
Physarum Polycephalum ◽  
Isotonic Contraction ◽  
Cyclic Contraction ◽  
Aggregation Pattern ◽  
Cyclic Changes ◽  
Contraction And Relaxation ◽  
Elongation Phase ◽  
Contraction Cycle ◽  
Isotonic Contractions

Cyclic contraction and relaxation of plasmodial strands of Physarum polycephalum were measured under both isotonic and isometric conditions, and their relation to changes in microfilament (MF) morphology was investigated. The contraction-relaxation rhythm of a strand segment was insignificant and irregular immediately after isolation from the mother plasmodium. It became regular half an hour later when local minute rhythms were synchronized spontaneously. If a strand kept under isotonic conditions was loaded with a heavier weight or a strand kept under isometric conditions was stretched a few times, the amplitude of each contraction wave was enhanced. After a strand had been thus conditioned, it was fixed at a selected phase of the contraction-relaxation cycle under both isotonic and isometric conditions. The state of MFs changed strikingly according to the phase of the contraction cycle. In the shortening phase of the strand under isotonic contractions, MFs with a diameter of 6–7 nm were arranged parallel to each other to form large compact bundles in which adjacent filaments were bridged with cross linkages. Among these MFs, thicker filaments were sporadically scattered. At about the phase of minimal strand length, most of the MFs became kinky and formed networks. In the elongating phase, new loose bundles of MFs developed from the network. These loose bundles became compact again when the strand reached its maximal elongation phase. In the isometric contraction, MFs in the increasing tension phase were nearly the same as those in the shortening phase in isotonic contraction. Around the maximal tension phase, dense areas of MFs appeared along the bundles in place of the network formed in the isotonic contraction phase. These areas were closely packed, with MFs arranged parallel to each other. In the decreasing and minimal tension phases in isometric contraction, MFs were arranged similarly to those in the elongating and maximally elongated phases, respectively, in isotonic contraction. Alternation between the straight bundle and fine network configuration of the MFs observed in isotonic contraction was inconspicuous in isometric contraction. This was probably due to spatial restriction of shortening under isometric contraction. The results are interpreted in terms of cyclic changes of the aggregation pattern of the MFs in the form of F-actin, as opposed to the possibility that the contraction-relaxation cycles depend on cyclic G-F transformation of actin.

The mechanics of active muscle

1953 ◽  
Vol 141 (902) ◽  
pp. 104-117 ◽  
Keyword(s):  
Heat Production ◽  
Isometric Contraction ◽  
Time Course ◽  
Contractile Element ◽  
Outer Side ◽  
Active Muscle ◽  
In Series ◽  
The Difference ◽  
Isometric Twitch ◽  
Work Done

When a frog’s or toad’s sartorius is rapidly released during a maintained isometric contraction its tension drops immediately and is redeveloped later. The extent of release required to reduce the tension to zero is 3 to 4 % of the length of the muscle. This is much less than the 10 to 15 % originally stated by Gasser & Hill: the difference is explained. The amount of work done during release by the passive elastic element in series with the contractile element is affected only very slightly by speed of release: the damping of this element is small. The redevelopment of tension after release has been compared with the original development of tension when the stimulus began. Minor and variable differences only have been observed, and these are probably due to redistribution of length, during isometric contraction, between different regions of the muscle. At greater initial extensions the rise of tension during an isometric tetanus is much slower than at smaller initial extensions. This also is attributed to redistribution of length, within the muscle. At an initial extension not greater than that at which the developed tension is a maximum the system is ‘stable’ and the tension reaches its full value sharply: at extensions on the outer side of the maximum the system is ‘unstable’ and a long slow creep of rising tension occurs. The apparent complexity of the time-course of the heat production in an isometric twitch is discussed.

scholarly journals Energy Production in Cardiac Isotonic Contractions

1970 ◽  
Vol 56 (6) ◽  
pp. 732-750 ◽  
Author(s):  
C. L. Gibbs ◽  
W. R. Gibson
Keyword(s):  
Energy Expenditure ◽  
Heat Production ◽  
Isometric Contraction ◽  
Heat Rate ◽  
Energy Output ◽  
Contractile Element ◽  
External Work ◽  
Additional Heat ◽  
Time Integral ◽  
Isotonic Contractions

The energy output of rabbit papillary muscle is examined and it is shown that there is more energy liberated in an afterloaded isotonic contraction than in an "equivalent" isometric contraction. This statement holds true regardless of whether equivalence is based on the proposition that tension or the time integral of tension is the best index of muscle energy expenditure. Besides the external work performed there is additional heat production in isotonic contractions and this heat increases as the afterload is decreased. The additional heat is more evident when tension rather than the time integral of tension is made the determinant of energy expenditure. It is shown in single contractions that the rate of isotonic heat production, regardless of afterload size, never exceeds the heat rate recorded in an isometric contraction at the same initial length. Experiments reveal no simple linear correlation between isotonic energy output and contractile element work. Problems associated with the compartmentalization of the energy output of a contraction are discussed.

scholarly journals Mechanical control of the time-course of contraction of the frog heart.

1975 ◽  
Vol 65 (3) ◽  
pp. 329-344 ◽  
Author(s):  
E Bozler
Keyword(s):  
Isometric Contraction ◽  
Positive Feedback ◽  
Time Course ◽  
Frog Heart ◽  
Isotonic Contraction ◽  
Mechanical Control ◽  
The Difference ◽  
Relaxing Effect ◽  
Turtle Heart

Changes in load during most phases of an isotonic contraction of the frog and turtle heart increased or decreased the duration of the twitch. It was abbreviated by a maintained increase or by a brief decrease in load. The relaxing effect of these procedures developed with a delay lasting more than a second under some conditions and will be called lengthening deactivation. The reverse procedures, a maintained diminution or a brief increase in load, increased the duration of the twitch. This effect will be called shortening activation. Although the termination of relaxation may be delayed or advanced by the mechanical interventions mentioned, the normal time-course of isotonic relaxation was always resumed later, regardless of the starting level of the load, making it possible to measure accurately changes in the duration of the twitch. The responses to changes in load produce positive feedback during the isotonic contraction and explain, at least in part, the difference in the time-course of isotonic and isometric contraction. The effects of changes in load were much smaller and briefer in the atrium than the ventricle.

scholarly journals Synthesis and Characterization of Polyphosphazenes Modified with Hydroxyethyl Methacrylate and Lactic Acid

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Evelyn Carolina Martínez Ceballos ◽  
Ricardo Vera Graziano ◽  
Gonzalo Martínez Barrera ◽  
Oscar Olea Mejía
Keyword(s):  
Lactic Acid ◽  
Ring Opening ◽  
Room Temperature ◽  
Block Structure ◽  
Ring Opening Polymerization ◽  
Synthesis And Characterization ◽  
Poly Lactic Acid ◽  
Hydroxyethyl Methacrylate ◽  
H Nmr

Poly(dichlorophosphazene) was prepared by melt ring-opening polymerization of the hexachlorocyclotriphosphazene. Poly[bis(2-hydroxyethyl-methacrylate)-phosphazene] and poly[(2-hydroxyethyl-methacrylate)-graft-poly(lactic-acid)-phosphazene] were obtained by nucleophilic condensation reactions at different concentrations of the substituents. The properties of the synthesized copolymers were assessed by FTIR,1H-NMR and31P-NMR, thermal analysis (DSC-TGA), and electron microscopy (SEM). The copolymers have a block structure and show twoTg's below room temperature. They are stable up to a temperature of 100°C. The type of the substituents attached to the PZ backbone determines the morphology of the polymers.

Effect of titanium alloys elasticity modulus on warping of stamped blanks during cooling

2021 ◽  
pp. 221-227
Author(s):  
M.O. Smirnov ◽  
A.M. Zolotov ◽  
A.M. Tyukhtyaev
Keyword(s):  
Mathematical Modeling ◽  
Titanium Alloys ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Elasticity Modulus ◽  
Preliminary Deformation ◽  
Wide Spread ◽  
Temperature Dependences ◽  
Cumulative Deformation ◽  
The Difference

Wide spread in the values of the elasticity modulus of the titanium VT6 alloy and its analogs Ti—6Al—4V, Ti—6Al—4V ELI at room temperature and at elevated temperatures is revealed аs result of the literature sources analysis. The data are ambiguous, the available temperature dependences of the elasticity modulus have very different values starting from the temperature T l 500 °C. Mathematical modeling of the warping process is carried out on the example of figurine-shaped stamped blank of turbine blade using various dependences of the elasticity modulus on temperature. Cases of warping during cooling of stamped blank after cooling-down in stamp with and without cumulative deformation are considered. The difference in the course of thermal deformations during the cooling of the workpiece is obtained using different temperature dependences of the elasticity modulus. The presence of preliminary deformation increases the warping of the workpieces.

Mitigating the Antimicrobial Activities of Selected Organic Acids and Commercial Sanitizers with Various Neutralizing Agents

2011 ◽  
Vol 74 (5) ◽  
pp. 820-825 ◽  
Author(s):  
YOEN JU PARK ◽  
JINRU CHEN
Keyword(s):  
Escherichia Coli ◽  
Acetic Acid ◽  
Lactic Acid ◽  
Organic Acids ◽  
Shiga Toxin ◽  
Room Temperature ◽  
Sodium Thiosulfate ◽  
Antimicrobial Activities ◽  
Phosphate Buffered Saline ◽  
Lactic Acids

This study was conducted to evaluate the abilities of five neutralizing agents, Dey-Engley (DE) neutralizing broth (single or double strength), morpholinepropanesulfonic acid (MOPS) buffer, phosphate-buffered saline (PBS), and sodium thiosulfate buffer, in mitigating the activities of acetic or lactic acid (2%) and an alkaline or acidic sanitizer (a manufacturer-recommended concentration) againt the cells of Shiga toxin–producing Escherichia coli (STEC; n = 9). To evaluate the possible toxicity of the neutralizing agents to the STEC cells, each STEC strain was exposed to each of the neutralizing agents at room temperature for 10 min. Neutralizing efficacy was evaluated by placing each STEC strain in a mixture of sanitizer and neutralizer under the same conditions. The neutralizing agents had no detectable toxic effect on the STEC strains. PBS was least effective for neutralizing the activity of selected organic acids and sanitizers. Single-strength DE and sodium thiosulfate neutralized the activity of both acetic and lactic acids. MOPS buffer neutralized the activity of acetic acid and lactic acid against six and five STEC strains, respectively. All neutralizing agents, except double-strength DE broth, had a limited neutralizing effect on the activity of the commercial sanitizers used in the study. The double-strength DE broth effectively neutralized the activity of the two commercial sanitizers with no detectable toxic effects on STEC cells.

scholarly journals Storage and Condition of Biomass Influence to Biosorption of Lead (II) and Zinc(II) by Saccharomyces cerevisiae Biomass

2010 ◽  
Vol 1 (1) ◽  
pp. 11-15
Author(s):  
Jasmidi Jasmidi ◽  
Eko Sugiharto ◽  
Mudjiran Mudjiran
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Atomic Absorption ◽  
Room Temperature ◽  
Final Concentration ◽  
Biomass Storage ◽  
Lead And Zinc ◽  
The Difference ◽  
Biomass Influence ◽  
And Storage ◽  
Zinc Storage

The influence of length and condition of Biomass Storage on the biosorption of lead and zinc that present together in a solution by Saccharomyces cerevisiae biomass were studied. In this experiment, variables of length and condition of biomass storage were examined. Concentration of lead and zinc were determined by atomic absorption spectrophotometric (AAS) using air-acetilene as atomizing flame. Loading of lead and zinc on the biomass were determined as the difference between the initial and the final concentration of lead and zinc in the solution. Biosorption of lead and zinc were influenced by condition and storage of the biomass. Storage of biomass in the room temperature for one week cause an increasing uptake. Storage for longer period result in decrease of lead and zinc uptake. Storage of biomass in a freezer up to 2 weeks increased the uptake of lead, but did not influence the uptake of zinc. Storage for longer period decreased the uptake of both of lead and zinc. For all condition the uptake of lead higher than the uptake of zinc by Saccharomyces cerevisiae.

scholarly journals Production of Nigerian Yoghurt Using Lactic Acid Bacteria as Starter Cultures

2020 ◽  
pp. 32-42
Author(s):  
S. Aforijiku ◽  
S. M. Wakil ◽  
A. A. Onilude
Keyword(s):  
Lactic Acid ◽  
Lactic Acid Bacteria ◽  
Proximate Composition ◽  
Room Temperature ◽  
Starter Cultures ◽  
Cow Milk ◽  
Spontaneous Fermentation ◽  
Overall Acceptability ◽  
Fermentation Control ◽  
Better Than

Aim: This work was carried out to investigate the influence of Lactic Acid Bacteria (LAB) on organoleptic quality and proximate composition of yoghurt, and viability of starter cultures in yoghurt. Methods: The LAB starter cultures were selected based on their ability to produce diacetyl and lactic acid. Results: Lactobacillus caseiN1 produced the highest quantity (2.72 g/L) of diacetyl at 48 hrs of incubation while Pediococcus acidilacticiG1 had the lowest amount (0.50 g/L). The pH of produced yoghurt ranged between 4.40 and 5.58 while the corresponding lactic acid contents ranged between 0.70 and 0.96 g/L. Yoghurt produced with cow milk inoculated with L. PlantarumN24 and L. BrevisN10 had the lowest pH (4.40) at significant level of P≤0.05. Yoghurt with mixed culture of L. PlantarumN24 and L. PlantarumN17 had the highest protein content (5.13%) while spontaneous fermentation (control) produced the least (0.48%). Yoghurt produced from cow milk inoculated with L. PlantarumN24 and L. PlantarumN17 was rated best with overall acceptability (9.0) during first day of storage while the commercial yoghurt (5.8) and spontaneous fermentation (6.8) had least overall acceptability at P≤0.05. Conclusion: Yoghurt samples stored in refrigerator had more viable LAB counts for a period of 21 days while the samples stored at room temperature had a day count except for yoghurt produced with cow milk inoculated with L. plantarumN24 which retained its viability at the second day. The yoghurt produced with selected LAB starters are better than commercial yoghurt in terms of sensory properties, proximate composition, pH and viability.

scholarly journals The principal magnetic susceptibilities of neodymium sulphate octahydrate at low temperatures

1939 ◽  
Vol 170 (941) ◽  
pp. 266-271 ◽  
Keyword(s):  
Low Temperatures ◽  
Room Temperature ◽  
Energy Levels ◽  
Constant Factor ◽  
The Other ◽  
Crystalline Field ◽  
Cubic Symmetry ◽  
The Subject ◽  
The Difference ◽  
The One

The magnetic and other related properties of neodymium sulphate have been the subject of numerous investigations in recent years, but there is still a remarkable conflict of evidence on all the essential points. The two available determinations of the susceptibility of the powdered salt at low temperatures, those of Gorter and de Haas (1931) from 290 to 14° K and of Selwood (1933) from 343 to 83° K both fit the expression X ( T + 45) = constant over the range of temperature common to both, but the constants are not the same and the susceptibilities at room temperature differ by 11%. The fact that the two sets of results can be converted the one into the other by multiplying throughout by a constant factor suggested that the difference in the observed susceptibilities was due to some error of calibration. It could, however, also be due to the different purity of the samples examined though the explanation of the occurrence of the constant factor is then by no means obvious. From their analysis of the absorption spectrum of crystals of neodymium sulphate octahydrate Spedding and others (1937) conclude that the crystalline field around the Nd+++ ion is predominantly cubic in character since they find three energy levels at 0, 77 and 260 cm. -1 .* Calculations of the susceptibility from these levels reproduce Selwood’s value at room temperature but give no agreement with the observations-at other temperatures. On the other hand, Penney and Schlapp (1932) have shown that Gorter and de Haas’s results fit well on the curve calculated for a crystalline field of cubic symmetry and such a strength that the resultant three levels lie at 0, 238 and 834 cm. -1 , an overall spacing almost three times as great as Spedding’s.

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