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1.
Studies on drawing circles with both hands in the horizontal plane have shown that this task is easy to perform across a
wide range of movement frequencies under the symmetrical mode of coordination, whereas under the asymmetrical mode (both limbs
moving clockwise or counterclockwise) increases in movement frequency have a disruptive effect on trajectory control and hand
coordination. To account for these interference effects, we propose a simplified computer model for bimanual circle drawing
based on the assumptions that (1) circular trajectories are generated from two orthogonal oscillations coupled with a phase
delay, (2) the trajectories are organized on two levels, “intention” and “motor execution”, and (3) the motor systems controlling
each hand are prone to neural cross-talk. The neural cross-talk consists in dispatching some fraction of any force command
sent to one limb as a mirror image to the other limb. Assuming predominating coupling influences from the dominant to the
nondominant limb, the simulations successfully reproduced the main characteristics of performance during asymmetrical bimanual
circle drawing with increasing movement frequencies, including disruption of the circular form drawn with the nondominant
hand, increasing dephasing of the hand movements, increasing variability of the phase difference, and occasional reversals
of the movement direction in the nondominant limb. The implications of these results for current theories of bimanual coordination
are discussed.
Received: 23 June 1998 / Accepted in revised form: 20 April 1999 相似文献
2.
Shuo-Hsiu Chang Shauna Dudley-Javoroski Richard K. ShieldsAuthor vitae 《Journal of electromyography and kinesiology》2011,21(5):847-853
Mechanical oscillation (vibration) is an osteogenic stimulus for bone in animal models and may hold promise as an anti-osteoporosis measure in humans with spinal cord injury (SCI). However, the level of reflex induced muscle contractions associated with various loads (g force) during limb segment oscillation is uncertain. The purpose of this study was to determine whether certain gravitational loads (g forces) at a fixed oscillation frequency (30 Hz) increases muscle reflex activity in individuals with and without SCI. Nine healthy subjects and two individuals with SCI sat with their hip and knee joints at 90° and the foot secured on an oscillation platform. Vertical mechanical oscillations were introduced at 0.3, 0.6, 1.2, 3 and 5g force for 20 s at 30 Hz. Non-SCI subjects received the oscillation with and without a 5% MVC background contraction. Peak soleus and tibialis anterior (TA) EMG were normalized to M-max. Soleus and TA EMG were <2.5% of M-max in both SCI and non-SCI subjects. The greatest EMG occurred at the highest acceleration (5g). Low magnitude mechanical oscillation, shown to enhance bone anabolism in animal models, did not elicit high levels of reflex muscle activity in individuals with and without SCI. These findings support the g force modulated background muscle activity during fixed frequency vibration. The magnitude of muscle activity was low and likely does not influence the load during fixed frequency oscillation of the tibia. 相似文献
3.
The variability of coupled rhythmic limb movements is assumed to be a consequence of the strength of a movement’s attractor
dynamic and a constant stochastic noise process that continuously perturbs the movement system away from this dynamic. Recently,
it has been suggested that the nonlinear technique of recurrence analysis can be used to index the effects of noise and attractor
strength on movement variability. To test this, three experiments were conducted in which the attractor strength of bimanual
wrist-pendulum movements (using coordination mode, movement frequency and detuning), as well as the magnitude of stochastic
perturbations affecting the variability of these movements (using a temporally fluctuating visual metronome) was manipulated.
The results of these experiments demonstrate that recurrence analysis can index parametric changes in the attractor strength
of coupled rhythmic limb movements and the magnitude of metronome induced stochastic perturbations independently. The results
of Experiments 1 and 2 also support the claim that differences between the variability of inphase and antiphase coordination,
and between slow and fast movement frequencies are due to differences in attractor strength. In contrast to the standard assumption
that the noise that characterizes interlimb coordination remains constant for different magnitudes of detuning (Δ ω) the results
of Experiment 3 suggest that the magnitude of noise increases with increases in |Δ ω|. 相似文献
4.
During walking cutaneous stimulation of the foot yields neural and mechanical reflexes that serve a functional purpose to correct or assist the ongoing movement. Concurrently, while cutaneous stimulation of the hand during rhythmic arm movement parallel the neural responses observed in the legs, studies of rhythmic arm movement have only limited mechanical measurements. Therefore it is difficult to determine whether reflex responses in the arms during rhythmic arm movement serve a functional purpose similar to those seen in the lower limbs. The purpose of this study was to explore the mechanical outcomes of stimulating a cutaneous nerve innervating the hand during arm cycling. We hypothesized that there would be measurable mechanical effects to cutaneous stimulation during arm cycling that function to correct or assist the task of arm cycling. Specifically, kinetic responses measured at the handle would be considered assistive if they were tangential to the arm cycling path in the direction of forward progression. Also, limb kinematic responses would be considered corrective if they allowed limb movement that would result in removal of the limb from stimulus while not altering the kinetic profile at the handle necessary for arm cycling progression. Participants performed seated arm cycling while EMG was recorded from the arm and trunk muscles, kinematic data was recorded from the right arm, and kinetic data was recorded from the handle. Cutaneous reflexes were evoked by stimulating the superficial radial nerve. The results show that there are observable mechanical responses to cutaneous stimulation of the hand during arm cycling. Subjects responded to cutaneous stimulation of the hand during arm cycling with significant changes in backward and lateral forces at the handle as well as wrist abduction/adduction and wrist flexion/extension kinematics. These responses, related to the task and phase of movement, are consistent with the anatomical location of the stimulus and are correlated to the neural responses. Therefore, these responses are comparable to functionally relevant responses in the legs during rhythmic movement. However, while there is a single observation of a kinematic corrective strategy, the kinetics measured at the handle are not tangential to the arm cycling path and therefore not considered an assistive response. Therefore, unlike the observations in the lower limbs, the mechanical responses during arm cycling are not clearly related to the functional context of the ongoing task. 相似文献
5.
In electromyographic studies on healthy subjects, we recorded the H reflex from the right m. soleus and measured changes in the magnitude of this reflex response related to voluntary movements of the contralateral lower limb
performed according to a visual signal. The effects of back and plantar flexions of the contralateral foot of the tested subject
in the lying and standing positions were examined. Changes in the H reflex magnitude began to be recorded 60 to 90 msec prior
to voluntary movements of the contralateral limb. When the subject was in the lying position, these changes looked like facilitation
of the H reflex at both types of movement of the contralateral foot. When the subject stood, facilitation preceded back flexion
of the foot of this extremity, while plantar flexion was preceded by inhibition of the tested H reflex. Our results show that
the pattern of preliminary changes in the muscle tone of one of the lower limbs is determined by the type of future movement
of another limb and peculiarities of the support function realized by this limb. 相似文献
6.
Daniel A. Duprez Marc De Buyzere Johan M. De Sutter Sophie A. Deman Nicole Y. De Pue Denis L. Clement 《European journal of applied physiology and occupational physiology》1992,65(1):94-98
Ten normal healthy subjects performed a rhythmic handgrip at 30% MVC (maximal voluntary contraction) with and without arterial occlusion of the same limb. Contralateral forearm and calf venous capacitance were simultaneously measured by venous occlusion plethysmography. During rhythmic handgrip at 30% MVC contralateral venous capacitance decreased by -7.17% in the forearm and by -5.14% in the calf. With arterial occlusion the decreases in venous capacitance were even more pronounced: contralateral forearm -14.4% and calf -13.1%. In a second set of experiments (n = 5) rhythmic handgrip at 30% MVC with arrest of the forearm circulation 5 s prior to the cessation of contraction was applied to examine the influence of chemically sensitive metaboreceptors per se on the evoked limb venoconstriction. During the postexercise arterial occlusion forearm venous volume decreased further to -30.6% whereas calf venous volume increased slightly but remained below the control value. After the cessation of the arterial occlusion both forearm and calf capacitance returned to baseline values. Thus, this study provided evidence that as well as a chemically generated reflex arising from the working muscle, central command was found to be involved in the increase in venomotor tone in the nonexercising limbs during rhythmic handgrip at 30% MVC. 相似文献
7.
Initiation of rapid discrete flexion movements is significantly altered when a secondary rhythmic movement is performed simultaneously
with the same limb; the onset of a stimulus-evoked discrete movement tends to occur time-locked to the oscillation: i.e.,
the rhythmic movement entrains the discrete response. This nonlinear interaction may reflect a specific principle of coordination
of motor tasks which are simultaneously executed with the same effector. This part II of a tripartite research report on such
single-muscle multiple-task coordination investigates the contribution of the dynamic properties of the muscle and its reflex
circuitry to phase entrainment. Assuming a simple threshold-linear relationship between the control signals generated by the
central nervous system and the observable kinematic and electromyographic signals, a secondary rhythmic movement will cause
an additional phase-dependent delay between the central “go” command and the first observable change in actual kinematics
of the compound movement. Several indicators for such threshold-linear interaction are derived and tested on real data obtained
in psychophysical experiments. Four healthy subjects performed rapid lateral abductions of the index finger in response to
a visual “go” signal. During a portion of the experiments, subjects produced additional low-amplitude oscillatory movements
before stimulus presentation with either the same finger (one-handed task), or with the index finger of the other hand (two-handed
task). Results showed phase entrainment and modulation of reaction times when the cyclic and the discrete movements were simultaneously
executed by the same finger. But there was no entrainment in the bimanual execution of the tasks. The model was capable of
reproducing the observed effects. It is concluded that coordination of voluntary movements which are concurrently performed
by the same effector involves specific discontinuous operations, which represents an essential part of the mechanism of motor
coordination. Phase entrainment reflects this characteristic discontinuous behavior of the lower stages of motor execution
and does not necessarily require nonlinear interaction of motor commands at higher levels of motor processing.
Received: 5 September 2001 / Accepted in revised form: 19 December 2001 相似文献
8.
W. Van Laar 《Acta biotheoretica》1970,19(3-4):95-139
Summary In the first parts of this study on the concept of the biological clock it has been investigated how it is used in the field of biorhythmology. The analysis of the contents of the concept is preceded by a survey of the current research in this field.There are two general hypotheses with respect to the ultimate origin of rhythmic phenomena: the Endogenous Timer Hypothesis and the Exogenous Timer Hypothesis. Within the Endogenous Timer Hypothesis two contrasting viewpoints with respect to the structure of the biological clock can be distinguished, which have been called: the Discrete Entity view, and the Organizational view.It has been shown that in the application of the general clock-idea upon the organism a logical distortion is present. The organism is conceived tobe a clock and tohave a clock simultaneously.In anticipation of the analysis of the explanatory value of the concept of the biological clock in part II, it has been put forward that in a number of cases time-measurement can be considered as a superfluous (redundant) element in the explanation of the phenomena involved.Finally it has been demonstrated that in the case of the Exogenous Timer Hypothesis the concept of the biological clock is not relevant. The Exogenous Timer Hypothesis has been compared with the Endogenous Timer Hypothesis with respect to the criterion of the principle of parsimony, orOccam's razor.List of rhythmological terms autonomous system
not under the influence of a periodic source of energy,i.e. selfsustained and free oscillations
- non-autonomous system
under the influence of a periodic source of energy,i.e. forced oscillations whether in active or passive systems
- period
time after which a definite phase of the oscillation reoccurs
- frequency
reciprocal of period
- phase
instantaneous state of an oscillation within a period, represented by the value of the variable and all its time derivatives
- phase angle
value of the abscissa corresponding to a point of the curve (phase) given either in radians, in degrees or in other fractions of the whole period. It can be given in units of time, if the length of the period is stated
- synchronization
state in which two or more oscillations have the same frequency due to mutual or unilateral influences
- entrainment
coupling of a self-sustained oscillation to a Zeitgeber (forcing oscillation) with the result that either both oscillations have the same frequency (synchronization) or that the frequencies are integral multiples (frequency-demultiplication): possible only within limited ranges of frequencies
- Zeitgeber
that forcing oscillation which entrains a biological rhythm
- free-running rhythms
selfsustained oscillations under constant conditions
- response-curve
indicates, in biology, how the amount and the sign of a phase shift, induced by a single stimulus, depends on the phase in which the stimulus is applied 相似文献
9.
An order parameter equation for correlated limb movements was applied to rhythmic coordination between the limbs of two people.
The interlimb coordination was established and maintained through vision. Manipulations of frequency competition, coupled
frequency, and intended mode (in-phase or anti-phase) produced equilibria and fluctuations in relative phase predicted by
the order parameter equation and confirmed originally in within-person coordination. It was concluded that there is an elementary
coordination dynamics governing the rhythmic coordination between organisms as well as between components of a single organism.
Received: 6 June 1994 / Accepted in revised form: 11 November 1994 相似文献
10.
Rhythms, or patterns in time, play a vital role in both speech and music. Proficiency in a number of rhythm skills has been linked to language ability, suggesting that certain rhythmic processes in music and language rely on overlapping resources. However, a lack of understanding about how rhythm skills relate to each other has impeded progress in understanding how language relies on rhythm processing. In particular, it is unknown whether all rhythm skills are linked together, forming a single broad rhythmic competence, or whether there are multiple dissociable rhythm skills. We hypothesized that beat tapping and rhythm memory/sequencing form two separate clusters of rhythm skills. This hypothesis was tested with a battery of two beat tapping and two rhythm memory tests. Here we show that tapping to a metronome and the ability to adjust to a changing tempo while tapping to a metronome are related skills. The ability to remember rhythms and to drum along to repeating rhythmic sequences are also related. However, we found no relationship between beat tapping skills and rhythm memory skills. Thus, beat tapping and rhythm memory are dissociable rhythmic aptitudes. This discovery may inform future research disambiguating how distinct rhythm competencies track with specific language functions. 相似文献
11.
Temporal coding of spike-times using oscillatory mechanisms allied to spike-time dependent plasticity could represent a powerful mechanism for neuronal communication. However, it is unclear how temporal coding is constructed at the single neuronal level. Here we investigate a novel class of highly regular, metronome-like neurones in the rat brainstem which form a major source of cerebellar afferents. Stimulation of sensory inputs evoked brief periods of inhibition that interrupted the regular firing of these cells leading to phase-shifted spike-time advancements and delays. Alongside phase-shifting, metronome cells also behaved as band-pass filters during rhythmic sensory stimulation, with maximal spike-stimulus synchronisation at frequencies close to the idiosyncratic firing frequency of each neurone. Phase-shifting and band-pass filtering serve to temporally align ensembles of metronome cells, leading to sustained volleys of near-coincident spike-times, thereby transmitting synchronised sensory information to downstream targets in the cerebellar cortex. 相似文献
12.
13.
Koyanagi S Okazawa S Kuramoto Y Ushijima K Shimeno H Soeda S Okamura H Ohdo S 《Molecular endocrinology (Baltimore, Md.)》2006,20(3):573-583
Although altered homeostatic regulation, including disturbance of 24-h rhythms, is often observed in the patients undergoing glucocorticoid therapy, the mechanisms underlying the disturbance remains poorly understood. We report here that chronic treatment with a synthetic glucocorticoid, prednisolone (PSL), can cause alteration of circadian clock function at molecular level. Treatment of cultured hepatic cells (HepG2) with PSL induced expression of Period1 (Per1), and the PSL treatment also attenuated the serum-induced oscillations in the expression of Period2 (Per2), Rev-erbalpha, and Bmal1 mRNA in HepG2 cells. Because the attenuation of clock gene oscillations was blocked by pretreating the cells with a Per1 antisense phosphothioate oligodeoxynucleotide, the extensive expression of Per1 induced by PSL may have resulted in the reduced amplitude of other clock gene oscillations. Continuous administration of PSL into mice constitutively increased the Per1 mRNA levels in liver and skeletal muscle, which seems to attenuate the oscillation in the expressions of Per2, Rev-erbalpha, and Bmal1. However, a single daily administration of PSL at the time of day corresponding to acrophase of endogenous glucocorticoid levels had little effect on the rhythmic expression of clock genes. These results suggest a possible pharmacological action by PSL on the core circadian oscillation mechanism and indicate the possibility that the alteration of clock function induced by PSL can be avoided by optimizing the dosing schedule. 相似文献
14.
The degree of activation of the central stepping program during passive leg movement was studied in healthy subjects under
unloading conditions; the excitability of spinal motoneurons was studied during passive and voluntary stepping movements.
Passive stepping movements with characteristics maximally close to those during voluntary stepping were accomplished by the
experimenter. The bursts of muscular activity during voluntary and imposed stepping movements were compared. In addition,
the influence on the leg movement of artificially created loading onto the foot was studied. The excitability of spinal motoneurons
was estimated by the amplitude of modulation of the m. soleus H reflex. Changes in the H reflex (Hoffmann’s reflex) after fixation of the knee and hip joints were also studied. In most subjects, passive movements
were accompanied by bursts of electromyographic (EMG) activity in the hip muscles (sometimes in shank muscles); the timing
of the EMG burst during the step cycle coincided with the burst’s timing during voluntary stepping. In many cases, the bursts
in EMG activity exceeded the activity of homonymous muscles during voluntary stepping. Simulation of foot loading influenced
significantly the distal part of the moving extremity during both voluntary and passive movements, which was expressed in
the appearance of movements in the ankle joint and an increase in the phasic EMG activity of the shank muscles. The excitability
of motoneurons during passive movements was higher than during voluntary movements. Changes and modulation of the H reflex throughout the step cycle were similar without restriction of joint mobility and without hip joint mobility. Fixation
of the knee joint was of great importance. It is supposed that imposed movements activate the same mechanisms of rhythm generation
as supraspinal commands during voluntary movements. During passive movements, presynaptic inhibition depends mostly on the
afferent influences from the moving leg rather than on the central commands. Under the conditions of “air-stepping,” the afferent
influences from the foot pressure receptors are likely to interact actively with the central program of stepping and to determine
the final activity pattern irrespective of the movement type (voluntary or passive). 相似文献
15.
Tsuyoshi Nakajima Rinaldo A. Mezzarane Sandra R. Hundza Tomoyoshi Komiyama E. Paul Zehr 《PloS one》2014,9(8)
Neural output from the locomotor system for each arm and leg influences the spinal motoneuronal pools directly and indirectly through interneuronal (IN) reflex networks. While well documented in other species, less is known about the functions and features of convergence in common IN reflex system from cutaneous afferents innervating different foot regions during remote arm and leg movement in humans. The purpose of the present study was to use spatial facilitation to examine possible convergence in common reflex pathways during rhythmic locomotor limb movements. Cutaneous reflexes were evoked in ipsilateral tibialis anterior muscle by stimulating (in random order) the sural nerve (SUR), the distal tibial nerve (TIB), and combined simultaneous stimulation of both nerves (TIB&SUR). Reflexes were evoked while participants performed rhythmic stepping and arm swinging movement with both arms and the leg contralateral to stimulation (ARM&LEG), with just arm movement (ARM) and with just contralateral leg movement (LEG). Stimulation intensities were just below threshold for evoking early latency (<80 ms to peak) reflexes. For each stimulus condition, rectified EMG signals were averaged while participants held static contractions in the stationary (stimulated) leg. During ARM&LEG movement, amplitudes of cutaneous reflexes evoked by combined TIB&SUR stimulation were significantly larger than simple mathematical summation of the amplitudes evoked by SUR or TIB alone. Interestingly, this extra facilitation seen during combined nerve stimulation was significantly reduced when performing ARM or LEG compared to ARM&LEG. We conclude that locomotor rhythmic limb movement induces excitation of common IN reflex pathways from cutaneous afferents innervating different foot regions. Importantly, activity in this pathway is most facilitated during ARM&LEG movement. These results suggest that transmission in IN reflex pathways is weighted according to the number of limbs directly engaged in human locomotor activity and underscores the importance of arm swing to support neuronal excitability in leg muscles. 相似文献
16.
R G Carson R Chua W D Byblow P Poon C J Smethurst 《Proceedings. Biological sciences / The Royal Society》1999,266(1421):853-857
Two simple experiments reveal that the ease with which an action is performed by the neuromuscular-skeletal system determines the attentional resources devoted to the movement. Participants were required to perform a primary task, consisting of rhythmic flexion and extension movements of the index finger, while being paced by an auditory metronome, in one of two modes of coordination: flex on the beat or extend on the beat. Using a classical dual-task methodology, we demonstrated that the time taken to react to an unpredictable visual probe stimulus (the secondary task) by means of a pedal response was greater when the extension phase of the finger movement sequence was made on the beat of the metronome than when the flexion phase was coordinated with the beat. In a second experiment, the posture of the wrist was manipulated in order to alter the operating lengths of muscles that flex and extend the index finger. The attentional demands of maintaining the extend-on-the-beat pattern of coordination were altered in a systematic fashion by changes in wrist posture, even though the effector used to respond to the visual probe stimulus was unaffected. 相似文献
17.
Weibo Yi Shuang Qiu Kun Wang Hongzhi Qi Lixin Zhang Peng Zhou Feng He Dong Ming 《PloS one》2014,9(12)
Motor imagery (MI), sharing similar neural representations to motor execution, is regarded as a window to investigate the cognitive motor processes. However, in comparison to simple limb motor imagery, significantly less work has been reported on brain oscillatory patterns induced by compound limb motor imagery which involves several parts of limbs. This study aims to investigate differences of the electroencephalogram (EEG) patterns as well as cognitive process between simple limb motor imagery and compound limb motor imagery. Ten subjects participated in the experiment involving three tasks of simple limb motor imagery (left hand, right hand, feet) and three tasks of compound limb motor imagery (both hands, left hand combined with right foot, right hand combined with left foot). Simultaneous imagination of different limbs contributes to the activation of larger cortical areas as well as two estimated sources located at corresponding motor areas within beta rhythm. Compared with simple limb motor imagery, compound limb motor imagery presents a network with more effective interactions overlying larger brain regions, additionally shows significantly larger causal flow over sensorimotor areas and larger causal density over both sensorimotor areas and neighboring regions. On the other hand, compound limb motor imagery also shows significantly larger 10–11 Hz alpha desynchronization at occipital areas and central theta synchronization. Furthermore, the phase-locking value (PLV) between central and occipital areas of left/right hand combined with contralateral foot imagery is significantly larger than that of simple limb motor imagery. All these findings imply that there exist apparent intrinsic distinctions of neural mechanism between simple and compound limb motor imagery, which presents a more complex effective connectivity network and may involve a more complex cognitive process during information processing. 相似文献
18.
Bilateral deficit (BLD) describes the phenomenon of a reduction in performance during synchronous bilateral (BL) movements when compared to the sum of identical unilateral (UL) movements. Despite a large body of research investigating BLD of maximal voluntary force (MVF) there exist a paucity of research examining the BLD for explosive strength. Therefore, this study investigated the BLD in voluntary and electrically-evoked explosive isometric contractions of the knee extensors and assessed agonist and antagonist neuromuscular activation and measurement artefacts as potential mechanisms. Thirteen healthy untrained males performed a series of maximum and explosive voluntary contractions bilaterally (BL) and unilaterally (UL). UL and BL evoked twitch and octet contractions were also elicited. Two separate load cells were used to measure MVF and explosive force at 50, 100 and 150 ms after force onset. Surface EMG amplitude was measured from three superficial agonists and an antagonist. Rate of force development (RFD) and EMG were reported over consecutive 50 ms periods (0–50, 50–100 and 100–150 ms). Performance during UL contractions was compared to combined BL performance to measure BLD. Single limb performance during the BL contractions was assessed and potential measurement artefacts, including synchronisation of force onset from the two limbs, controlled for. MVF showed no BLD (P = 0.551), but there was a BLD for explosive force at 100 ms (11.2%, P = 0.007). There was a BLD in RFD 50–100 ms (14.9%, P = 0.004), but not for the other periods. Interestingly, there was a BLD in evoked force measures (6.3–9.0%, P<0.001). There was no difference in agonist or antagonist EMG for any condition (P≥0.233). Measurement artefacts contributed minimally to the observed BLD. The BLD in volitional explosive force found here could not be explained by measurement issues, or agonist and antagonist neuromuscular activation. The BLD in voluntary and evoked explosive force might indicate insufficient stabiliser muscle activation during BL explosive contractions. 相似文献
19.
Oishi H Schuster A Lamboley M Stergiopulos N Meister JJ Bény JL 《Life sciences》2002,71(19):2239-2248
Vasomotion, the phenomenon of vessel diameter oscillation, regulates blood flow and resistance. The main parameters implicated in vasomotion are particularly the membrane potential and the cytosolic free calcium in smooth muscle cells. In this study, these parameters were measured in rat perfused-pressurized mesenteric artery segments. The application of norepinephrine (NE) caused rhythmic diameter contractions and membrane potential oscillations (amplitude; 5.3 +/- 0.3 mV, frequency; 0.09 +/- 0.01 Hz). Verapamil (1 microM) abolished this vasomotion. During vasomotion, 10(-5) M ouabain (Na(+)-K(+) ATPase inhibitor) decreased the amplitude of the electrical oscillations but not their frequency (amplitude; 3.7 +/- 0.3 mV, frequency; 0.08 +/- 0.002 Hz). Although a high concentration of ouabain (10(-3) M) (which exhibits non-specific effects) abolished both electrical membrane potential oscillations and vasomotion, we conclude that the Na+-K+ ATPase could not be implicated in the generation of the membrane potential oscillations. We conclude that in rat perfused-pressurized mesenteric artery, the slow wave membrane type of potential oscillation by rhythmically gating voltage-dependent calcium channels, is responsible for the oscillation of intracellular calcium and thus vasomotion. 相似文献
20.
Lloyd D 《Mitochondrion》2003,3(3):139-146
Protonophores have several different perturbative effects on dissolved O2 concentrations in continuous cultures of Saccharomyces cerevisiae. As well as uncoupling energy conservation from mitochondrial electron transport in vivo, they reset ultradian clock-driven respiratory oscillations and produce cell cycle effects. Thus, additions at low concentration (1.25 microM) of either m-chlorocarbonyl-cyanide phenylhydrazone (CCCP) or 5-chloro-3-t-butyl-2-chloro-4(1)-nitrosalicylanilide (S13) led to phase resetting of the 48 min ultradian clock-driven respiratory oscillations. At 2.5 microM CCCP or 4 microM S13, transient inhibition of oscillatory respiration (for 5 h) preceded synchronisation of the cell division cycle seen as a slow (9 h period) wave that enveloped the 48 min oscillation. At still higher concentrations of CCCP (5 microM), the cell division cycle was prolonged by about 7 h, and during this phase, the respiratory oscillation became undetectable. The significance of these observations with respect to the time-keeping functions of the ultradian clock is discussed. 相似文献