scholarly journals The onset of contraction

1949 ◽  
Vol 136 (883) ◽  
pp. 242-254 ◽  
Keyword(s):  
Heat Production ◽  
Maximum Rate ◽  
Direct Evidence ◽  
Mechanical Response ◽  
Muscle Twitch ◽  
Chemical Methods ◽  
Physical Methods ◽  
Critical Comparison ◽  
Sequence Of Events ◽  
Activation Heat

The early heat production during the onset of a muscle twitch has been determined with the greatest precision possible for comparison with the mechanical response. When allowance is made for the time taken in propagation the heat is found to start off at its maximum rate. Its rate falls gradually to a constant value, while the muscle continues to shorten uniformly then decreases to zero as shortening draws to an end. The heat occurs in two separate processes, those of activation and shortening respectively. The heat of activation has well started before shortening is detected by ordinary methods. The heat of shortening runs parallel to the shortening. There is no sign of negative heat production at any stage of contraction. If endothermic processes occur they are exactly masked by exothermic ones. The latent period of the activation heat is about 10 msec. at 0°C in frog’s muscle, about 25 msec. in toad’s muscle. These, with an ordinary value of Q10, would correspond at 20°C to about 2 and 5 msec. respectively. Various physical methods are discussed of examining the rapid processes that occur during contraction. Chemical methods are inadequate in speed and sensitivity to give direct evidence of the nature and sequence of events occurring in a twitch. Theoretical con­clusions from experiments on muscle extracts, without critical comparison with the behaviour of living muscle, may lead to confusing results.

The priority of the heat production in a muscle twitch

1958 ◽  
Vol 148 (932) ◽  
pp. 397-402 ◽  
Keyword(s):  
Chemical Reactions ◽  
Heat Production ◽  
Mechanical Response ◽  
Substantial Part ◽  
Hypertonic Solution ◽  
Isotonic Solution ◽  
Muscle Twitch ◽  
Previous Conclusion

When a muscle has been soaked in a moderately hypertonic solution its mechanical response to a shock is delayed, but its heat production is almost normal and starts considerably earlier than its shortening. After a more hypertonic solution the mechanical response is abolished, but a substantial part of the heat production remains. These effects are rapidly reversed by soaking in a normal isotonic solution. They strengthen the previous conclusion that chemical reactions triggered by a stimulus precede the mechanical response.

Does heat production precede mechanical response in muscular contraction?

1950 ◽  
Vol 137 (887) ◽  
pp. 268-273 ◽  
Keyword(s):  
Skeletal Muscle ◽  
Heat Production ◽  
Maximum Rate ◽  
Mechanical Response ◽  
Muscular Contraction ◽  
Contraction And Relaxation

A decision between two current theories of muscular contraction is provided by the proof that the heat production in a twitch begins before the mechanical response. In the skeletal muscle of the tortoise at 0°C the heat production starts off at its maximum rate about 60 msec, after stimulation, while the tension cannot be detected before 90 to 100 msec. The heat of activation clearly precedes the mechanical response. The processes of contraction and relaxation in a tortoise’s muscle occur at about one-tenth of the speed found in a frog’s muscle at the same temperature. This should allow much greater accuracy in various investigations which are limited at present by the time taken in manipulation or recording.

scholarly journals Visco-Hyperelastic Characterization of the Equine Immature Zona Pellucida

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1223
Author(s):  
Elisa Ficarella ◽  
Mohammad Minooei ◽  
Lorenzo Santoro ◽  
Elisabetta Toma ◽  
Bartolomeo Trentadue ◽  
...  
Keyword(s):  
Zona Pellucida ◽  
Soft Matter ◽  
Mechanical Response ◽  
Mechanical Characterization ◽  
Nonlinear Material ◽  
Prony Series ◽  
Critical Comparison ◽  
Highly Nonlinear ◽  
Good Agreement

This article presents a very detailed study on the mechanical characterization of a highly nonlinear material, the immature equine zona pellucida (ZP) membrane. The ZP is modeled as a visco-hyperelastic soft matter. The Arruda–Boyce constitutive equation and the two-term Prony series are identified as the most suitable models for describing the hyperelastic and viscous components, respectively, of the ZP’s mechanical response. Material properties are identified via inverse analysis based on nonlinear optimization which fits nanoindentation curves recorded at different rates. The suitability of the proposed approach is fully demonstrated by the very good agreement between AFM data and numerically reconstructed force–indentation curves. A critical comparison of mechanical behavior of two immature ZP membranes (i.e., equine and porcine ZPs) is also carried out considering the information on the structure of these materials available from electron microscopy investigations documented in the literature.

Body Temperature and Singing in the Bladder Cicada, Cystosoma Saundersii

1979 ◽  
Vol 80 (1) ◽  
pp. 69-81 ◽  
Author(s):  
R. K. JOSEPHSON ◽  
D. YOUNG
Keyword(s):  
Heat Production ◽  
Cell Biology ◽  
Sound Production ◽  
Marked Decrease ◽  
Cooling Curve ◽  
Muscle Twitch ◽  
Temperature Excess ◽  
Air Mixing ◽  
Artificial Heat ◽  
Sound Pulses

1. Body temperatures during singing were measured in the cicada, Cystosoma saundersii Westwood, both in the field and in tethered animals indoors. 2. The temperature of the sound-producing tymbal muscle rises rapidly during singing to reach a plateau approximately 12°C above ambient. This produces a temperature gradient in the abdominal air sac which surrounds the muscle. When singing stops, the tymbal muscle cools exponentially. 3. Heat production during singing, estimated from the cooling curve, is 4.82 cal min−1 g muscle−1. Generation of the same temperature excess in the air sac by an artificial heat source yields an estimated heat production of 54.4 cal min−1 g muscle−1. This discrepancy may be caused by air mixing in the air sac during singing. 4. As temperature rises, tymbal muscle twitch contractions become faster and stronger. This and heat transfer to the thorax cause changes in the song pattern: a marked decrease in the interval between the two sound pulses produced by a single tymbal buckling and a lesser decrease in the interval between bucklings. The fundamental sound period remains unaltered. These effects are consistent with earlier data on sound production. Note: Present address: Department of Developmental and Cell Biology, University of California, Irvine, California 92717, U.S.A.

scholarly journals Feasible Ways Promoting Nitrate Removal in Riparian Zone Downstream of a Regulated River

Water ◽  
2020 ◽  
Vol 12 (7) ◽  
pp. 2054
Author(s):  
Dongsheng Liu ◽  
Bei Zhu ◽  
Haoyu Zhu ◽  
Jian Zhao
Keyword(s):  
Ecological Restoration ◽  
Riparian Zone ◽  
Nitrate Removal ◽  
Reaction Model ◽  
Regulated River ◽  
Hyporheic Exchange ◽  
Fixed Degree ◽  
Chemical Methods ◽  
Physical Methods ◽  
Contaminated Area

Set in the downstream riparian zone of Xin’an River Dam, this paper established a 2D transversal coupling flow and solute transport and reaction model by verification within situ groundwater level and temperature. The denitrifying methods and principles in the riparian zone from the perspective of hyporheic exchange were explored, which provided a basis for the engineering techniques for river ecological restoration. Our studies have shown that under the condition of water level fluctuation, a biological method such as adding denitrifying bacteria biomass to a fixed degree (the same below) can greatly increase the denitrifying rate (1.52 g/d) in the riparian zone; chemical methods such as adding organic carbon into the surface water or groundwater can increase the total riparian nitrate removal (8.00–8.18 g) and its efficiency (19.5–20.0%) to a great extent; hydrogeological methods such as silt cleaning of the aquifer surface or local pumping around the contaminated area can increase the total riparian nitrate removal (1.06–14.8 g) to some extent, but correspondingly reduce the denitrifying efficiency (0.95–1.4%); physical methods such as designing the bank form into gentle slope or concave shape can slightly increase the total riparian nitrate removal (0.22–0.52 g) and correspondingly improve the denitrifying efficiency (0.25–0.85%). At the application level of river ecological restoration, integrated adopting the above methods can make the riparian denitrifying effect “fast and good”.

Effects of 2-n-butyl-methylenedioxyindene on skeletal muscle mechanics and energetics

1982 ◽  
Vol 242 (5) ◽  
pp. C347-C352 ◽  
Author(s):  
D. M. Burchfield ◽  
J. A. Rall ◽  
R. G. Rahwan
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Heat Production ◽  
Muscle Mechanics ◽  
Stimulus Frequency ◽  
Energy Liberation ◽  
Force Development ◽  
Unit Energy ◽  
Kinetics Of ◽  
Activation Heat

Mechanical and energetic effects of 2-n-butyl-3-dimethylamino-5,6-methylenedioxyindene (2-butyl-MDI) were investigated in isolated frog semitendinosus muscles at 0 degrees C. Previous research on various tissues suggested that this compound functions as an intracellular Ca2+ antagonist. The effects of 2-butyl-MDI (2 X 10(-4) M) with respect to time were progressive and reversible with exposures of 30 min or less. A 30-min exposure to the agent significantly decreased twitch and tetanus force and energy liberation, increased the twitch-to-tetanus ratio, prolonged kinetics of force development, induced a stimulus frequency-dependent tetanic fatigue, and decreased contractile economy (measured as force per unit energy liberation). Energy associated with Ca2+ cycling, activation heat, was depressed by 31 +/- 4%. The significant reduction of activation heat production by 2-butyl-MDI suggests that the quantity of Ca2+ released by the sarcoplasmic reticulum upon stimulation is reduced. However, the complexity of the results summarized above suggests multiple sites and/or modes of action for the agent.

scholarly journals Study on Transformation of Ginsenosides in Different Methods

2017 ◽  
Vol 2017 ◽  
pp. 1-10 ◽  
Author(s):  
Meng-meng Zheng ◽  
Fang-xue Xu ◽  
Yu-juan Li ◽  
Xiao-zhi Xi ◽  
Xiao-wei Cui ◽  
...  
Keyword(s):  
Biological Activity ◽  
Chinese Medicine ◽  
Traditional Chinese Medicine ◽  
Pharmacological Activity ◽  
Theoretical Foundation ◽  
Major Constituent ◽  
Chemical Methods ◽  
Physical Methods ◽  
Medicinal Value

Ginseng is a traditional Chinese medicine and has the extensive pharmacological activity. Ginsenosides are the major constituent in ginseng and have the unique biological activity and medicinal value. Ginsenosides have the good effects on antitumor, anti-inflammatory, antioxidative and inhibition of the cell apoptosis. Studies have showed that the major ginsenosides could be converted into rare ginsenosides, which played a significant role in exerting pharmacological activity. However, the contents of some rare ginsenosides are very little. So it is very important to find the effective way to translate the main ginsenosides to rare ginsenosides. In order to provide the theoretical foundation for the transformation of ginsenoside in vitro, in this paper, many methods of the transformation of ginsenoside were summarized, mainly including physical methods, chemical methods, and biotransformation methods.

scholarly journals Visualization research on the influence of an ultrasonic degassing system on the operation of a hydraulic gear pump

2018 ◽  
Vol 211 ◽  
pp. 03005 ◽  
Author(s):  
Piotr Antoniak ◽  
Jarosław Stryczek ◽  
Michał Banaś ◽  
Oleksandr Lyhovskyi ◽  
Ihor Gryshko ◽  
...  
Keyword(s):  
High Speed ◽  
Theoretical Description ◽  
Working Fluid ◽  
Operating Parameters ◽  
Gear Pump ◽  
Hydraulic Systems ◽  
Chemical Methods ◽  
Physical Methods ◽  
Working Medium ◽  
Gear Pumps

Gear pumps make a group of the most popular hydraulic energy generators. Research and development works concerning those units have been going on for decades, and thanks to them gear pumps feature very good operating parameters. However, even well-designed gear pumps will not work properly if the physical properties of the working fluid are incorrect. One of such properties is compressibility of the fluid, which largely depends on the amount of gas dissolved in the medium. For this reason, the aim is to reduce the amount of gas dissolved in the working medium. It can be done using both chemical and physical methods. Because chemical methods can affect the chemical composition of the working fluid, it is the physical methods that are usually used in hydraulic systems. This paper presents preliminary visualization research into the influence of an ultrasonic degassing system on the operation of a hydraulic gear pump. Apart from that, operation of such a system and its theoretical impact on the work of the gear pump is discussed Experimental study, using a high-speed camera, was carried out in order to verify the theoretical description.

A note on the heat of activation in a muscle twitch

1950 ◽  
Vol 137 (888) ◽  
pp. 330-331 ◽  
Keyword(s):  
Heat Production ◽  
Mechanical Work ◽  
Muscle Twitch ◽  
Extreme Loads

Under extreme loads a stimulated muscle neither shortens nor develops tension. The heat production in a twitch is then rather less than one-half of its value with maximal shortening. Under such conditions the heat of shortening and the mechanical work are nil. The remaining heat, therefore, is heat of activation alone. It is about the same in magnitude and onset as the heat of activation at ordinary lengths.

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