OBJECTIVETo characterize the isometric contractility of Bufo gastrocnemius ex vivo in light of the rest tension.

METHODSBufo gastrocnemius treated with SOD inhibitor and ascorbate was stimulated electrically (12 V DC, 2 ms duration with a 2 s interval) to record the tension within 10 min. Weighted fitting to the relaxation curve of the tension below 90% of the peak tension with a mono-exponential model yielded the rest tension and relaxation rate.

RESULTSThe control gastrocnemius showed monotonic decrease of the rest tension, but treatment with SOD inhibitor and ascorbate resulted in a decrease of the rest tension followed by a fast increase within a 1.0 min contraction. The increase of the rest tension at 7.0 min of contraction of the treated muscle was significantly greater than that of the control muscle. The control muscle showed a monotonic decrease of the relaxation rate in 10 min, whereas treatment with SOD inhibitor and ascorbate produced increased relaxation rate followed by monotonic decrease till a plateau was reached. In the course of the 10 min recording, the relaxation rate of the treated muscle was lower than that of the control after the same duration of contraction.

CONCLUSIONRest tension is a characteristic index to represent the skeletal muscle contractility.

Animals ; Bufonidae ; Electric Stimulation ; In Vitro Techniques ; Isometric Contraction ; physiology ; Muscle Tonus ; physiology ; Muscle, Skeletal ; physiology

This experimental study was designed to unravel the relationship between muscle tension and its electrophysiological property. The experiments on repetitive pulse stimulus in different current intensity to rabbit's motor nerve were performed in different pulse frequency by electromyography which applied electrical pulses and excited the tibial nerve, and by Instron 5544 machine which measured muscle tensions. The experimental data revealed that the tension force varied with the stimulus frequency in a quasi-parabolic relation, while it seemingly increased little with the stimulus intensity.
Animals ; Electric Stimulation ; methods ; Electromyography ; Muscle Tonus ; physiology ; Muscle, Skeletal ; physiology ; Rabbits ; Tibial Nerve ; physiology

Evaluation of limbs muscle function is one of the difficult tasks in forensic clinical medicine. Recently, there are more and more cases needed to be evaluated on the limbs muscle function in forensic clinical appraisal. Thus the assessment methods for muscle function have been concerned increasingly. This paper introduces the classification of muscle function and the type of muscle contraction, reviews the assessment methods for muscle function and their application value, such as manual muscle test, simple instrumental muscle test, isokinetic muscle test and electrophysiological test. It has also proposed to evaluate the muscle function with multiple methods comprehensively.
Biomechanical Phenomena ; Electromyography/methods* ; Exercise Test/methods* ; Extremities/physiology* ; Forensic Medicine ; Humans ; Isometric Contraction/physiology* ; Muscle Contraction/physiology* ; Muscle Strength/physiology* ; Muscle Tonus ; Muscle, Skeletal/physiology* ; Muscles/physiology*

Seven sinapine analogs (6a-6g) were synthesized using cinnamon acid or benzoic acid and their derivatives as starting materials, which obtained from substituted benzaldehyde and malonate. The structures of target compounds were characterized by IR, 1H NMR and elemental analysis. The effects of compounds 6a-6g on the smooth muscle of intestine isolated from rabbit were studied, and the experimental results showed that compounds 6a, 6d and 6g had diastolic action, while 6f had contractile action.
Animals ; Choline ; analogs & derivatives ; chemical synthesis ; chemistry ; pharmacology ; In Vitro Techniques ; Intestines ; physiology ; Molecular Structure ; Muscle Contraction ; drug effects ; Muscle Tonus ; drug effects ; Muscle, Smooth ; physiology ; Rabbits

AIMTo investigate the role of delayed rectifier K+ channel (Kv), Ca2+ -activated K+ channel (K(Ca)) and ATP-sensitive K+ channel (K(ATP)) in the regulation of the resting and contracting tone of human control and passively sensitized bronchial smooth muscle (BSM).

METHODSThe regulating effects of the three K+ channels on the tone of human BSM (HBSM) were observed by measuring the isometric tone of bronchial rings in vitro.

RESULTS(1) The contraction of passively sensitized bronchial ring was significantly increased by histamine. (2) Kv blocker 4-aminopyridine (4-AP) caused concentration dependent contraction in resting bronchial rings of two groups, and the contraction sensitivity of the sensitized group rings was significantly stronger than that of control, that is, the negative logarithm of the drug concentration causing 50% of maximal effect (pD2) of the sensitized group rings were significantly larger than that of control rings, but there was no difference in the maximal effect (Emax) of two groups; Kca blocker tetraethylammonium (TEA) and K(ATP) blocker glibenclamide (Glib) had no such effects as those of 4-AP. (3) After pretreatment with 4-AP, the contraction of the control rings could significantly increased by histamine. After 4-AP treatment the Emax was significantly larger than that before 4-AP treatment. But the sensitized group rings had no such change, there was no significant difference in Emax before and after 4-AP treatment.

CONCLUSION(1) Not K(Ca) and K(ATP) but Kv participated in regulation of the resting tone of HBSM. (2) The activity of Kv decreased in bronchial smooth muscle passively sensitized by asthmatic serum compared with that of nonsensitized group. This change might be involved in the mechanism of asthma.

Asthma ; metabolism ; physiopathology ; Bronchi ; physiology ; Delayed Rectifier Potassium Channels ; physiology ; Female ; Humans ; Immune Sera ; Immunization, Passive ; In Vitro Techniques ; Male ; Middle Aged ; Muscle Tonus ; Muscle, Smooth ; physiology

There was a slow-relaxing tail of skeletal muscles in vitro upon the inhibition of Ca(2+)-pump by cyclopiazonic acid (CPA). Herein, a new linearly-combined bi-exponential model to resolve this slow-relaxing tail from the fast-relaxing phase was investigated for kinetic analysis of the isometric relaxation process of Bufo gastrocnemius in vitro, in comparison to the single exponential model and the classical bi-exponential model. During repetitive stimulations at a 2-s interval by square pulses of a 2-ms duration at 12 V direct currency (DC), the isometric tension of Bufo gastrocnemius was recorded at 100 Hz. The relaxation curve with tensions falling from 90% of the peak to the 15th datum before next stimulation was analyzed by three exponential models using a program in MATLAB 6.5. Both the goodness of fit and the distribution of the residuals for the best fitting supported the comparable validity of this new bi-exponential model for kinetic analysis of the relaxation process of the control muscles. After CPA treatment, however, this new bi-exponential model showed an obvious statistical superiority for kinetic analysis of the muscle relaxation process, and it gave the estimated rest tension consistent to that by experimentation, whereas both the classical bi-exponential model and the single exponential model gave biased rest tensions. Moreover, after the treatment of muscles by CPA, both the single exponential model and the classical bi-exponential model yielded lowered relaxation rates, nevertheless, this new bi-exponential model had relaxation rates of negligible changes except much higher rest tensions. These results suggest that this novel linearly-combined bi-exponential model is desirable for kinetic analysis of the relaxation process of muscles with altered Ca(2+)-pumping activity.
Animals ; Bufonidae ; physiology ; Electric Stimulation ; Electrophysiology ; In Vitro Techniques ; Indoles ; pharmacology ; Kinetics ; Models, Animal ; Models, Biological ; Muscle Relaxation ; drug effects ; physiology ; Muscle Tonus ; drug effects

To investigate the time-course changes of myogenic tone in mesenteric small artery (MSA) of spontaneously hypertensive rat (SHR), thirty-two 7-week aged SHR rats were randomly divided into four groups (8, 16, 24, 32 weeks of age), and 32 sex- and age-matched Wistar-Kyoto (WKY) rats were assigned to control groups (CON). On the day of the study, segments of MSA were isolated and then cannulated to the two pipettes. Vascular diameters in response to the increased intraluminal pressure (from 0 mmHg to 150 mmHg, by 25 mmHg steps) of isolated MSA under no-flow conditions were recorded by a Pressure Myograph System both in physiologic salt solution (PSS) (active diameter, Da) and calcium-free PSS (passive diameter, Dp). The myogenic tone was calculated by (Dp - Da)/Dp × 100%. The tail artery pressure and vascular myogenic tone in SHR rats were significantly higher than those of the CON rats. Before 24 weeks, the vascular myogenic tone of MSA in SHR group increased monotonically, but at the end of 32 weeks, the vascular myogenic tone decreased in comparison with that in 24-week group, but was significantly higher than that in CON group. The tail artery pressure in SHR group slowly increased monotonically with increasing weeks of age, and the tail arterial pressure in 32-week group remained significantly higher than that in 24-week group. Vascular myogenic tone may participate in the whole process of hypertension. Early in the development of hypertension, because of the compensatory role of vascular tone, the vascular function has been partially compensated, thus guaranteeing adequate blood supply to organs. Late in the development of hypertension, because of the decompensation of myogenic tone, the vascular function is damaged, leading to the occurrence of severe vascular disease.
Animals ; Blood Pressure ; Hypertension ; physiopathology ; Male ; Mesenteric Arteries ; physiopathology ; Muscle Tonus ; Muscle, Smooth, Vascular ; physiopathology ; Random Allocation ; Rats ; Rats, Inbred SHR ; Rats, Inbred WKY ; Time Factors ; Vasoconstriction ; physiology

OBJECTIVETo determine the effect of tension relaxation by small needle knife on the muscle tension and morphology changes of nerve terminals when sustained pressure was applied to muscular tissue.

METHODSRat gracilis muscles were exposed to pressure in vivo at 70 kPa for 2 hours. Sixty rats were divided into three groups: normal, control and experiment group respectively. In all rats except the six normal ones, the lower legs were considered as the control group, and the right left as experiment group. At day 1, 2 and 3, 9 rats from the two groups were randomly selected and sacrificed in order to determine the muscle tension change. At the same time, muscle histology and morphology changes of nerve terminals were observed.

RESULTSAbnormal tension increased in muscles under compression of 70 kPa. At the 1st and 2nd days, there were no significant differences between the two groups. Compared with control group, the tension was lower in experiment group, and there was statistically significant difference (P < 0.01) between the two groups. Exposure of striated muscle tissue to intensive and prolonged compression may pathologically alter its microstructure. Histological evaluation showed that this stiffening accompanied extensive necrotic damage. The changes could not be found in the nerve terminals.

CONCLUSIONDeep muscle tissue that undergoes prolonged compression may significantly increase its stiffness during acute injury. Tension relaxation applied by small needle knife can effectively reduce the mechanical load which is harmful to the whole tissue.

Animals ; Biomechanical Phenomena ; Female ; Male ; Medicine, Chinese Traditional ; Muscle Tonus ; Muscle, Skeletal ; innervation ; pathology ; physiology ; Nerve Endings ; pathology ; Pain Management ; Rats ; Rats, Sprague-Dawley

OBJECTIVETo find more evidence for mechanism and treatment of pelvic floor dysfunction (PFD), we observed muscle tension and neuropeptide of pelvic floor muscle in rats after spinal cord injury (SCI).

METHODS30 SD adult female rats were randomly divided into suprasacral cord injury group (SS), spinal cord injury at or below the sacral level group (SC) and normal group; 4 weeks after transection of spinal cord, muscle tension including compliance and excitability, and neuropeptide were observed.

RESULTSCompliances in SC group, SS group and normal group were (16.23 +/- 4.46) g, (13.44 +/- 4.15) g and (14.46 +/- 5.61) g respectively, there were no difference among them (P > 0.05), but their excitability under best initial length were (0.35 +/- 0.19) g, (2.80 +/- 2.12) g and (7.75 +/- 2.98) g according to SC, SS and normal group, excitability under prolonged length were (2.61 +/- 0.73) g, (4.67 +/- 1.16) g, (14.86 +/- 3.79) g respectively. SC and SS group were both lower than normal group (P < 0.05), meanwhile SC group was much lower than SS group (P < 0.05); neuropeptide Y and vasoactive intestinal peptide in SS and SC group were significant lower than normal group, and these two neuropeptides in SC were much lower than SS group (P < 0.05).

CONCLUSIONSMuscular excitability and neuropeptide in pelvic floor muscle are decreased obviously at both below and above sacral cord injury, SCI below sacral cord makes much lower level excitability and neuropeptide. The abnormality in pelvic floor muscle after SCI should be emphasized.

Animals ; Disease Models, Animal ; Female ; Muscle Tonus ; physiology ; Neuropeptides ; metabolism ; Pelvic Floor ; physiopathology ; Random Allocation ; Rats ; Rats, Sprague-Dawley ; Spinal Cord Injuries ; metabolism ; physiopathology ; Vasoactive Intestinal Peptide ; metabolism

OBJECTIVE: To observe effects of restraint position on the changes of diaphragmatic mechanical characteristic in rats, and try to explore the role of nitric oxide (NO). METHODS: Rat model of restraint position was established. Rats were divided into control group, restraint position 12h and 24h groups. The markers of respiratory functions in vivo and the biomechanical markers of diaphragmatic characteristic ex vivo were evaluated. Serum NO levels were measured with spectrophotometry. The expressions of nNOS and iNOS mRNA in diaphragm were detected using RT-PCR. RESULTS: Compared with control group, respiratory rate, tidal volume and minute ventilation were significantly decreased in the restraint position 12h and 24h groups. Pt of diaphragm significantly decreased and force-generating capacity reduced at low frequency stimulation in 12h group. Force-generating capacity over the full range reduced at low and high frequency stimulation in 24h group. Pt of diaphragm in control and restraint position groups increased after L-NNA pre-incubation. Force-frequency relationship after L-NNA pre-incubation reduced in 24h group. NO level in serum increased significantly in the restraint position groups. Diaphragmatic nNOS mRNA expression was upregulated significantly in the restraint position groups. CONCLUSION Restraint position induces the decreasement of diaphragmatic contractility and the decreasement is mediated by NO from diaphragm or circulation blood.
Animals ; Biomechanical Phenomena ; Diaphragm/physiopathology* ; Male ; Muscle Contraction/physiology* ; Muscle Tonus/physiology* ; Nitric Oxide/metabolism* ; Nitric Oxide Synthase/metabolism* ; Posture ; RNA, Messenger/metabolism* ; Rats ; Rats, Sprague-Dawley ; Respiration Disorders/physiopathology* ; Restraint, Physical ; Reverse Transcriptase Polymerase Chain Reaction