Effects of muscle blood flow on muscle energy metabolism and contractility

Energy metabolism and contractility of rat’s femoral triceps muscles were investigated by varying blood flow levels with ligation of the femoral artery. The triceps were stimulated electrically to produce equivalent conditions as exercise loading, and phosphorus nuclear magnetic resonance (³¹P-NMR) spectra and muscle tension levels were monitored. The ratio of inorganic phosphate (Pi) to ‘Pi+phosphocreatine (PCr)’, i.e. Pi/(Pi+PCr), was obtained from ³¹P-NMR spectra. This ratio was related to the reduction of blood flow ratio (BFR) during and after the stimulation period, whereas before starting the stimulation, there was no significant correlation. These findings indicate: (i) muscle energy metabolism during decreased blood flow is influenced by the stimulation (loading) given to the muscle; and (ii) changes of muscle energy metabolism due to decreased muscle blood flow during the loading is evaluable by measuring ³¹P-NMR spectra. Muscle tension reached the plateau 8 min after starting the stimulation, regardless of BFR, but muscle tension ratio decreased as BFR became lower. This indicates that decreased blood flow diminishes muscle contractility, and then lowers muscle function levels. Our findings indicate that muscle blood flow plays an important role in muscle function, and blood flow and muscle function levels are evaluable by measuring ³¹P-NMR spectra of the muscle.     

Depletion of calcitonin gene-related peptide from the caudal trigeminal nucleus of the rat after electrical stimulation of the Gasserian ganglion

Electrical stimulation of the Gasserian ganglion resulted in partial depletion of calcitonin gene-related peptide (CGRP) from ipsilateral central terminals of pseudounipolar primary sensory ganglion cells. Affected terminals exhibit decreased CGRP immunoreactivity as shown by cytophotometric densitomery of the caudal trigeminal nucleus. The decrease in CGRP immunoreactivity is statistically significant only in the medial one-third of the caudal trigeminal nucleus. Since earlier studies have shown that electrical stimulation of the Gasserian ganglion induces first accumulation then depletion of CGRP from perivascular sensory terminals in the dura mater, the present experiments suggest that CGRP is depleted also from central terminals of primary sensory trigeminal neurons, which might be of importance in the pathogenesis of migraine headache. Received: 18 December 1996 / Accepted: 26 June 1997     

基于敏感性定理的EIT重构算法仿真研究

为了研究性能更好的EIT图像重构算法，我们对基于敏感性定理的EIT图像重构算法进行了计算机仿真研究，并与几种常用图像重构算法进行比较，提出对基于敏感性定理的EIT图像重构算法的改进措施。     

Motor unit recruitment order during voluntary and electrically induced contractions in the tibialis anterior

 The recruitment order of motor units (MU) was compared during voluntary and electrically induced contractions. With the use of spike-triggered averaging, a total of 302 MUs with recruitment thresholds ranging from 1% to 88% of maximal voluntary contraction were recorded in the human tibialis anterior muscle in five subjects. The mean (±SD) MU force was 98.3±93.3 mN (mean torque 16.8±15.9 mNm) and the mean contraction time (CT) 46.2±12.7 ms. The correlation coefficients (r) between MU twitch force and CT versus the recruitment threshold in voluntary contractions were +0.68 and –0.38 (P<0.001), respectively. In voluntary contractions, MUs were recruited in order of increasing size except for only 6% of the cases; whereas, during transcutaneous electrical stimulation (ES) at the muscle motor point, MU pairs showed a reversal of recruitment order in 28% and 35% of the observations, respectively, when the pulse durations were 1.0 ms or 0.1 ms. This recruitment reversal during ES was not related to the magnitude of the difference in voluntary recruitment thresholds between MUs. It is concluded that if the reversal of MU recruitment observed during ES is biophysically controlled by differences in their nerve axon input impedance, in percutaneous stimulation at the motor point, other factors such as the size and the morphological organisation of the axonal branches can also influence the order of activation. Received: 24 May 1996 / Accepted: 30 September 1996     

Influence of synchronous and sequential stimulation on muscle fatigue

In acute experiments the sciatic nerve of the rat is electrically stimulated to induce fatigue in the medial Gastrocnemius muscle. Fatigue tests are carried out using intermittent stimulation of different compartments (sequential) or a single compartment (synchronous) of the sciatic nerve. The activation of different compartments is achieved by dividing nerve fibres into subbundles and placing them in separate grooves in a multigroove electrode. The aim of the investigation is to quantify the effect of sequential contra synchronised stimulation in reducing muscle fatigue, with no overlap between compartments. Overlap between two compartments is calculated using the combined and individual forces from both compartments. Sequential stimulation of two and three compartments is investigated. There is a significant decrease of fatigue in sequential stimulation compared to synchronous. After 2 min of intermittent stimulation the force time level is significantly increased in sequential stimulation, than in synchronous stimulation. The rate of force time decrease is significantly slower in sequential stimulation than in synchronous stimulation. With sequential stimulation it takes significantly longer before the maximal force time is reached than with synchronous stimulation.     

Clinical applications of characteristic frequency measurements: preliminaryin vivo study

In vivo electrical impedance tomography images have been available for some years, and most of them show variation in impedance amplitude between two different states, for example between inspiration and expiration of the lungs. A refinement of the tomography technique has made it possible to show images of the complex impedance of the body. If several frequencies are used, more information on the investigated tissues can be collected, and new areas made available for investigation. It has been shown that tissues exhibit a characteristic frequency that can be derived from the maximum magnitude of the (negative) reactance. The characteristic frequency-related images can be calculated from several imaginary part curves obtained using the back-projection technique. The paper shows in vivo impedance spectra from different parts of the body, determines the characteristic frequency of the different in vivo measurements and suggests different applications of characteristic frequency imaging. Several data sets are collected to show the reproducibility of the measurements.     

Brain stimulation-induced changes of phonation in the squirrel monkey

Summary In 11 squirrel monkeys (Saimiri sciureus), the brain stem was systematically explored with electrical brain stimulation for sites affecting the acoustic structure of ongoing vocalization. Vocalization was elicited by electrical stimulation of different brain structures. A severe deterioration of the acoustical structure of vocalization was obtained during stimulation of the caudoventral part of the periaqueductal grey, lateral parabrachial area, corticobulbar tract, nucl. ambiguus and surrounding reticular formation, facial nucleus, hypoglossal nucleus, solitary tract nucleus and along the fibres crossing the midline at the level of the hypoglossal nucleus. It is suggested that these structures are part of, or at least have direct access to, the motor coordination mechanism of phonation. Complete inhibition of phonation was obtained from the raphe and raphe-near reticular formation.Abbreviations Ab nucl ambiguus - APt area praetectalis - BC brachium conjunctivum - BP brachium pontis - Cb cerebellum - CC corpus callosum - Cd nucl. caudatus - Cf nucl. cuneiformis - Cel nucl. centralis lateralis - Cl claustrum - CM centrum medianum - Cn nucl. cuneatus - Co nucl. cochlearis - CoI colliculus inferior - CoS colliculus superior - CP commissura posterior - CPf cortex piriformis - CRf corpus restiforme - CSL nucl. centralis superior lateralis thalami - CT corpus trapezoideum - DBC decussatio brachii conjunctivi - DG nucl. dorsalis tegmenti (Gudden) - DLM decussatio lemnisci medialis - DPy decussatio pyramidum - DR nucl. dorsalis raphae - DV nucl. dorsalis n. vagi - DIV decussatio n. trochlearis - EP epiphysis - FC funiculus cuneatus - FL funiculus lateralis - FLM fasciculus longitudinalis medialis - FRM formatio reticularis myelencephali - FRP formatio reticularis pontis - FRPc formatio reticularis pontis caudalis - FRPo formatio reticularis pontis oralis - FRTM formatio reticularis mesencephali - FV funiculus ventralis - G nucl. gracilis - GC substantia grisea centralis (periaqueductal grey) - GL nucl. geniculatus lateralis - GM nucl. geniculatus medialis - GP globus pallidus - GPM griseum periventriculare mesencephali - GPo griseum pontis - Hip hippocampus - HL nucl. habenularis lateralis - H habenula - IP nucl. interpeduncularis - LC locus coeruleus - LD nucl. lateralis dorsalis thalami - Lim nucl. limitans - LLd nucl. lemnisci lateralis, pars dorsalis - LLv nucl. lemnisci lateralis, pars ventrali - LM lemniscus medialis - LP nucl. lateralis posterior thalami - MD nucl. medialis dorsalis thalami - MV nucl. motorius n. trigemini - NCS nucl. centralis superior - NCT nucl. trapezoidalis - NMV nucl. mesencephalicus n. trigemini - NR nucl. ruber - NSV nucl. spinalisn. trigemini - NTS nucl. tractus solitarii - NIII nucl. oculomotorius - NIV nucl. trochlearis - NVI nucl. abducens - NVII nucl. facialis - NXII nucl. hypoglossus - OI oliva inferior - OS oliva superior - P nucl. posterior thalami - PbL nucl. parabrachialis lateralis - PbM nucl. parabrachialis medialis - PC depedunculus cerebri - Pd nucl. peripeduncularis - Pg nucl. parabigeminalis - Pp nucl. praepositus - PuI nucl. pulvinaris inferior - PuL nucl. pulvinaris lateralis - PuM nucl. pulvinaris medialis - PuO nucl. pulvinaris oralis - Py tractus pyramidalis - Pv nucl. principalis n. trigemini - R Ab nucl. retroambiguus - RL nucl. reticularis lateralis - RTP nucl. reticularis tegmenti pontis - Sf nucl. subfascicularis - SGD substantia grisea dorsalis - SGV substantia grisea ventralis - SN substantia nigra - ST stria terminalis - St subthalamus - TRM tractus retroflexus (Meynert) - TSc tractus spinocerebellaris - Ves nucl. vestibularis - VL nucl. ventralis lateralis - VPI nucl. ventralis posterior inferior - VPL nucl. ventralis posterior lateralis - VPM nucl. ventralis posterior medialis - VR nucl. ventralis raphae - Zi zona incerta - II tractus opticus - VII n. facialis     

Noninvasive method for measuring the electrical properties of deep tissues using an open-ended coaxial probe

A new noninvasive method of measuring the structure and the electrical properties of bilayered biological tissues was evaluated as a potentially useful diagnostic means for detecting changes in subcutaneous tissues. First, the input impedance of an open-ended coaxial probe radiating into a bilayered model was calculated using a full-wave method, the results showed that the evanescen higher order modes do not have a significant influence on the reflection coefficient of muscle layer surface. Then, it was clearly proven that the phase shift and the modulus of the reflection coefficient of muscle layer surface depending on the frequency are useful to estimate the thickness of fat layer and the electrical properties of muscle respectively. The experimental results showed an excellent agreement with the theoretical relationship between the phase shift and the thickness. The sensitivity of estimation of the electrical properties of muscle was shown to be not enough for differentiating between normal and diseased deep tissue because of noises from the experimental systems.     

Control of the rat's circadian self-stimulation rhythm by light-dark cycles.

Rats with hypothalamic and septal electrodes were maintained in continuous test environments where bar-press responses produced brief reinforcing electrical stimulations. Long-term trends in response emission were measured under continuous exposure to light, dark and 12 hr light-dark alternations. In addition, transient behavioral adjustment to sudden 180 degrees phase shifts in the light-dark schedule was studied. The ambient light condition was found to control the period and phase of the circadian rhythm of brain self-stimulation behavior, as quantified by Fourier analysis. The circadian period was greatest under constant light (up to 24.90 hr under dim illumination), and approximated 24.00 hr under constant dark. Successful nocturnal entrainment to 12 hr light-dark alternations was obtained, with the peak of the 24 hr Fourier fundamental occurring in the middle-to-late dark segments. Three to 11 days were required for re-entrainment to 180 degrees light-dark phase shifts, during which the behavioral oscillation period increased to values comparable to periods under constant light. The rate of re-entrainment appeared to be proportional to illumination intensity during light segments.