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41.
Maximal dynamic expiratory pressures are higher when forced expiration is preceded by a fast inspiration to total lung capacity
(TLC) than when preceded by a slow inspiration and a few seconds pause at TLC. We hypothesized that these pressure differences
are due to the stretch-shorten cycle (SSC), which refers to enhancement of muscle force when a concentric muscle contraction
is immediately preceded by an eccentric contraction. Seven volunteers [36 (2) years; mean (SEM)] performed maximal forced
expirations against minimal resistance with fast (F) or slow (S) maneuvers. F maneuvers consisted of a fast inspiration to
TLC followed immediately by a fast expiration, whereas S consisted of a slow inspiration to TLC and a 4- to 5-s pause at TLC
prior to forced expiration. We measured esophageal pressure (P
es), peak expiratory flow rate (PEFR), and the EMG activity of the transversus abdominis (Tr) by means of intramuscular fine-wire
electrodes. The subjects performed several runs of each maneuver in a random order, and runs with the greatest expiratory
P
es were analyzed. In comparison with S, F yielded greater P
es [182 (15) versus 167 (15) cmH2O; P=0.003)] but similar PEFR [9.8 (0.7) versus 9.6 (0.7) l/s, P>0.05] and EMG activity of the Tr during forced expiration [221 (31) versus 208 (34) a.u., P>0.05]. Further analysis revealed significant EMG activity of Tr during end-inspiration (eccentric contraction) with F maneuvers
only [73 (22) versus 32 (17) a.u., P<0.05]. We conclude that the ability of expiratory muscles to generate greater P
es with F maneuvers is related to the sequence of an eccentric contraction, which is followed immediately by concentric contraction
in a manner analogous to SSC described in skeletal muscles.
Electronic Publication 相似文献
42.
本文通过对小鼠急性毒性实验,抗炎实验,对胸腺脾脏的影响及对豚鼠在体、离体气管平滑肌作用实验,观察了郃郎喘必消冲剂的药理学效应。结果表明,该制剂无明显毒性,最大耐受量为1000g/kg/d。它有明显的对抗二甲苯致小鼠耳炎及延长组胺诱发哮喘发作潜伏期的作用,对豚鼠离体气管平滑肌无松驰作用,对小鼠胸腺和脾脏有使其重量减小的趋势,但与对照组比较无显著性差异。 相似文献
43.
Cross education of muscular strength during unilateral resistance training and detraining 总被引:2,自引:0,他引:2
Shima N Ishida K Katayama K Morotome Y Sato Y Miyamura M 《European journal of applied physiology》2002,86(4):287-294
Abstract. The purpose of the present study was to examine the changes in maximum voluntary isometric contraction (MVC) in the contralateral
untrained limb during unilateral resistance training and detraining, and to examine the factors inducing these changes by
means of electrophysiological techniques. Nine healthy males trained their plantar flexor muscles unilaterally 4 days·week–1 for 6 weeks using 3 sets of 10–12 repetitions at 70–75% of one-repetition maximum a day, and detrained for 6 weeks. Progressive
unilateral resistance training significantly (P<0.05) increased MVC, integrated electromyogram (iEMG), and voluntary activation in the trained and contralateral untrained
limbs. The changes in MVC after training were significantly correlated with the changes in iEMG in both limbs. No significant
changes occurred in MVC, voluntary activation, and iEMG in the contralateral limb after detraining. The changes in MVC after
detraining did not correlate with the changes in voluntary activation or iEMG in either limb. Training and detraining did
not alter twitch and tetanic peak torques in either limb. These results suggest that the mechanisms underlying cross education
of muscular strength may be explained by central neural factors during training, but not solely so during detraining.
Electronic Publication 相似文献
44.
Kapilevich LV Nosarev AV Kovalev IV D'yakova EY Baskakov MB 《Bulletin of experimental biology and medicine》2003,135(6):610-612
The involvement of cAMP- and cGMP-dependent signal systems into the regulation of the contractile reaction of smooth muscles of the rabbit pulmonary arteries was studied using a mechanographic method. For modulation of intracellular level of cyclic nucleotides we used adenylate cyclase activators -adrenoceptor agonist isadrin, guanylate cyclase inhibitor methylene blue, penetrating analog dibutyryl-cAMP, and phosphodiesterase inhibitors. The mechanisms of cAMP- and cGMP-dependent regulation of smooth muscle contractile activity were realized in close interrelationship, and the key component of this was cyclic nucleotide phosphodiesterases. The ratio of activities of phosphodiesterase subtypes in smooth-muscle cells can essentially modulate the adrenergic effects in the pulmonary artery wall and even invert them. 相似文献
45.
Smooth muscle cells of the guinea pig ureter were studied by the double sucrose gap method. An increase in the calcium ion concentration in the Ringer-Locke solution to 22 mM led to hyperpolarization and to a slight increase in the resistance of the membrane. The amplitude of the first spike potential and the height of the plateau were lowered but the amplitude of the oscillations was increased. In sodium-free Ringer-Locke solution, when the action potential in the smooth muscle cells of the ureter was converted into a simple spike potential, a marked increase in amplitude of the action potential was observed with an increase in the calcium ion concentration.Department of Neuromuscular Physiology, A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. (Presented by Academician of the Academy of Medical Sciences of the USSR N. N. Gorev.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 83, No. 5, pp. 522–526, May, 1977. 相似文献
46.
Chronic pelvic pain (CPP) is a common condition in women that is difficult to diagnose. Although heritability estimates have been published for some conditions potentially underlying pelvic pain, the heritability of CPP itself has never been investigated. Using data from 623 MZ and 377 DZ female twin pairs aged 29–50 from an Australian twin cohort, we found an increased CPP concordance among MZs compared to DZs, with tetrachoric correlations of 0.43 (95% CI: 0.26–0.58) and 0.11 (95% CI: –0.16–0.38), respectively. This corresponded to a heritability of 0.41 (95% CI: 0.25–0.56). Lack of correlations with environmental indicators suggested that violation of the equal environments assumption was not responsible for this effect. Multivariate Cholesky decomposition models incorporating CPP and significantly correlated phenotypes showed that the entire CPP heritability could be explained by genetic variance underlying endometriosis (38%), dysmenorrhoea (23%), fibroids (24%), and somatic distress (15%), the latter a possible indicator of increased nociception. CPP itself is unlikely to be a useful independent phenotype to conduct genetic aetiological studies; contributing conditions such as endometriosis and variation in nociception are likely to provide more useful phenotypes. 相似文献
47.
J Kucera 《Neuroscience letters》1985,53(1):27-31
Distributions of 25 motor axons to 60 intrafusal muscle fibers of 10 poles of monkey spindle were reconstructed from serial 1 micron thick transverse sections of lumbrical muscles. About 44% of motor axons co-innervated two or more types of intrafusal fiber. The (dynamic) bag1 fiber shared motor innervation with the (static) bag2 or chain fibers in about 50% of spindle poles. Activation of single intrafusal fibers independent of the other fibers of the same intrafusal bundle occurs to a lesser degree in spindles of monkeys than in spindles of cats. Functional implications of this pattern of motor innervation are discussed. 相似文献
48.
Duranti R Sanna A Romagnoli I Nerini M Gigliotti F Ambrosino N Scano G 《Pflügers Archiv : European journal of physiology》2004,448(2):222-230
We hypothesized that walking at increased speed or increasing gradient might have different effects on chest wall kinematics and respiratory muscle power components, and contribute differently to respiratory effort sensation. We measured the volumes of chest wall compartments by optoelectronic plethysmography, esophageal, gastric and transdiaphragmatic (P
di) pressures, and the sensation of the respiratory effort by a Borg scale in five normal subjects walking both at ascending gradient with constant speed (AG) and at ascending speed with constant gradient (AS). Chest wall kinematics, evaluated by displacement of chest wall compartments, did not show any significant difference between AS and AG. Muscle power, calculated as the product of mean flow and mean pressure, increased similarly, but its partitioning into pressure and velocity of shortening differed in the two modes. A greater increase in the pressure developed by the abdominal muscles (P
abm) (4.06-fold), and in the velocity of shortening of both rib cage inspiratory muscles (v
rcm,i) (2.01-fold) and the diaphragm (v
di) (1.90-fold) was associated with a lower increase in the pressure developed by the rib cage inspiratory muscles (P
rcm,i) (1.24-fold) and P
di (0.99-fold) with AG. Instead, with AS, a lower increase in P
abm (2.12-fold), v
rcm,i (1.66-fold) and v
di (1.54-fold) was associated with a greater increase in P
rcm,i (1.56-fold) and P
di (1.97-fold). A combination of P
abm and v
di during AG (Wald 2=23.19, P<0.0000), with the addition of P
rcm,i during AS (Wald 2=29.46, P<0.0000), was the best predictor of Borg score. In conclusion, the general strategy adopted by respiratory centers during different walking modes does not differ in terms of ventilation, chest wall kinematics, and respiratory muscle power production, whereas it does in terms of partitioning of power into pressure and velocity of shortening, and respiratory muscle contribution to respiratory effort sensation. Combinations of different patterns of flow and pressure generation made the respiratory effort sensation similar during AS and AG modes. 相似文献
49.
Responses of sacral visceral afferents from the lower urinary tract,colon and anus to mechanical stimulation 总被引:6,自引:0,他引:6
E. Bahns Ulrike Halsband W. Jänig 《Pflügers Archiv : European journal of physiology》1987,410(3):296-303
The discharge characteristics of sacral visceral afferents supplying the urinary bladder, urethra, colon and anus to mechanical stimuli were analyzed in the anaesthetized cat. The stimuli used were passive distension (urinary bladder, colon), isovolumetric contraction (urinary bladder), movements of the urethral catheter and mechanical shearing stimuli (mucosal skin of the anal canal). (1) In total 245 afferent units which projected in the pelvic nerve were isolated from the sacral dorsal roots. From one of the following organs, urinary bladder, colon, urethra and anus 117 afferent units were activated. By these stimuli from the bladder, urethra and anus 122 afferent units could not be activated, and as far as tested also not from the colon; in 6 afferent units the classification was unclear. (2) Afferent units from the urinary bladder and the colon responded consistently to passive distension of the respective organ. The units from the urinary bladder showed graded responses at intraluminal pressures of about 10–70 mm Hg and responded also to isovolumetric contractions of the organ. The thresholds of the units from the bladder to passive distension and contraction varied from about 5 to 20 mm Hg intravesical pressure. (3) The afferent units from the urethra and the anus did not react or showed some weak phasic and irregular responses to distension and contraction applied to the urinary bladder or to distension of the colon. They were consistently excited by low threshold mechanical stimulation of the urethra and anus, respectively. (4) The axons from the bladder, urethra and anus were presumably myelinated (conduction velocity above 2 m/s) and conducted at 10.3±6.1 m/s (n=34, mean±SD), 26.3±9.3 m/s (n=13) and 9.5±5.1 m/s (n=37), respectively. The axons from the colon conducted at about 0.5 to 16 m/s (n=20), 13 of them conducting at less than 2 m/s. About 75% of the axons which could not be activated by mechanical stimulation of the visceral organs were presumably unmyelinated (conduction velocity below 2 m/s). (5) Some ongoing activity was found in 9 out of 26 afferent units from the anus but, with one exception, the afferent units from the bladder, urethra and colon were silent. (6) It is concluded that the pelvic afferent units from the urinary bladder, urethra, colon and anus consist of distinct populations with characteristic response patterns. There is no indication from this investigation that the urinary bladder is supplied by sacral afferents which are only recruited at high intravesical pressures during passive distension and isovolumetric contractions and which are possibly associated with pain.Supported by the Deutsche Forschungsgemeinschaft 相似文献
50.
目的:探讨腰大肌作用力带动脊柱伸展应力的生物力学关系。方法:取家兔12只,分3组,每组4只,解剖后保留枢椎以下完整之脊柱及骨盆、髋关节、上段股骨,不损伤脊柱前、后纵韧带、椎间盘及所附着之腰大肌,保留脊柱背侧的竖脊肌、棘上韧带,置于生物力学拉伸测试仪(日本岛津制作所产AGS-J系列)。上端十字头分别夹枢椎(颈胸腰段)、第1胸椎(胸腰段)和第12胸椎(腰段),下端十字头夹股骨上部;分别作有腰大肌状态下和切断腰大肌状态下,股髋自屈曲位到过伸带动脊柱自屈曲位到过伸位拉伸试验,测定两种不同状态下脊柱各节段的伸展应力(N/mm2)。结果:有腰大肌状态和切断腰大肌状态下,股-髋-脊柱拉伸后脊柱伸展应力分别为:颈胸腰全段平均为306.6675N/mm2:78.7167N/mm2;胸腰段为680.8417N/mm2:373.0375N/mm2;腰段为1990.7944N/mm2:523.0608N/mm2;经统计学分析,具显著性差异,P<0.01。结论:腰大肌作用力对脊柱伸展应力影响显著,颈胸腰段占74.33%、胸腰段占45.21%,腰段占73.73%的伸展应力源自腰大肌。脊柱在腰大肌作用下产生腰椎向腹部的弯曲。 相似文献