scholarly journals Studies on the in Vitro Interaction of Electrical Stimulation and Ca++ Movement in Sarcoplasmic Reticulum

1966 ◽  
Vol 49 (4) ◽  
pp. 689-715 ◽  
Author(s):  
Kwang S. Lee ◽  
Herbert Ladinsky ◽  
Sin J. Choi ◽  
Y. Kasuya
Keyword(s):  
Electrical Stimulation ◽  
Sarcoplasmic Reticulum ◽  
Inorganic Phosphate ◽  
Muscle Model ◽  
Ca Uptake ◽  
In Vitro Interaction ◽  
Frequency Of Stimulation ◽  
Stimulation Of

Sarcoplasmic reticulum fragments (S.R.F.) were isolated from skeletal and heart muscles. These fragments were found to take up Ca++ very actively from media. When monophasic square waves were passed through the S.R.F. suspension, the Ca++ uptake by S.R.F. was decreased. When the suspension was stimulated electrically after the Ca++ was taken up by S.R.F., the initiation and the cessation of the stimulation were followed by the release and re-uptake of Ca++ by S.R.F., respectively. The degree of inhibition of the Ca++ uptake as well as of the Ca++ release by electrical stimulation was dependent on the voltage and the frequency of stimulation. The presence of inorganic phosphate or oxalate modified the influence of electrical stimulation on the release and the uptake of Ca++ by S.R.F. Attempts were made to observe the release of Ca++ by electrical stimulation from unfractionated sarcoplasmic reticulum remaining in myofibers, and the interaction of the released Ca++ with myofibrils in vitro. For this purpose, the glycerol-extracted fiber was selected as a muscle model, since it contains both sarcoplasmic reticulum and myofibrils. It was found that electrical stimulation of skeletal and heart glycerol-extracted fibers resulted in the contraction of fibers. It appeared that the contraction of glycerol fibers by electrical stimulation was caused by the Ca++ release from sarcoplasmic reticulum by stimulation.

scholarly journals Reexamination of Electrical Stimulation on Sarcoplasmic Reticulum Fragments In Vitro

1973 ◽  
Vol 62 (6) ◽  
pp. 773-786 ◽  
Author(s):  
H. Miyamoto ◽  
M. Kasai
Keyword(s):  
Electrical Stimulation ◽  
Sarcoplasmic Reticulum ◽  
Silver Chloride ◽  
Electrical Response ◽  
Platinum Electrodes ◽  
Irreversible Denaturation ◽  
Ca Uptake ◽  
Silver Silver ◽  
Silver Silver Chloride

The effect of direct electrical stimulation on suspensions of sarcoplasmic reticulum membrane fragments (SRF) was carefully re-examined using the method of Lee et al. (1966) J. Gen. Physiol. 49:689. Inhibition of Ca++ uptake or release by electrical stimulation was observed. When platinum electrodes were used as stimulating electrodes, the effect was dependent on the total current passed through the suspension. On the contrary, when silver-silver chloride electrodes were used, no effect was observed even if voltage and current were the same as in the case of the platinum electrodes. In addition, apparent re-uptake of Ca++ after cessation of electrical stimulation using platinum electrodes was shown to be due to a binding of Ca++ to denatured SRF which did not require an energy supply such as ATP, although such re-uptake had been taken as strong evidence of electrical response of SRF in Lee's paper. Finally, it was concluded that the effect of electrical stimulation on SRF was attributable to the irreversible denaturation of SRF due to the oxidation caused by the chlorine generated at the platinum electrode.

scholarly journals Establishment of a New Device for Electrical Stimulation of Non-Degenerative Cartilage Cells In Vitro

2021 ◽  
Vol 22 (1) ◽  
pp. 394
Author(s):  
Simone Krueger ◽  
Alexander Riess ◽  
Anika Jonitz-Heincke ◽  
Alina Weizel ◽  
Anika Seyfarth ◽  
...  
Keyword(s):  
Electrical Stimulation ◽  
Electric Fields ◽  
Cartilage Tissue ◽  
Type I ◽  
Dependent Manner ◽  
New Device ◽  
Alternating Electric Fields ◽  
Cartilage Cells ◽  
Stimulation Of

In cell-based therapies for cartilage lesions, the main problem is still the formation of fibrous cartilage, caused by underlying de-differentiation processes ex vivo. Biophysical stimulation is a promising approach to optimize cell-based procedures and to adapt them more closely to physiological conditions. The occurrence of mechano-electrical transduction phenomena within cartilage tissue is physiological and based on streaming and diffusion potentials. The application of exogenous electric fields can be used to mimic endogenous fields and, thus, support the differentiation of chondrocytes in vitro. For this purpose, we have developed a new device for electrical stimulation of chondrocytes, which operates on the basis of capacitive coupling of alternating electric fields. The reusable and sterilizable stimulation device allows the simultaneous use of 12 cavities with independently applicable fields using only one main supply. The first parameter settings for the stimulation of human non-degenerative chondrocytes, seeded on collagen type I elastin-based scaffolds, were derived from numerical electric field simulations. Our first results suggest that applied alternating electric fields induce chondrogenic re-differentiation at the gene and especially at the protein level of human de-differentiated chondrocytes in a frequency-dependent manner. In future studies, further parameter optimizations will be performed to improve the differentiation capacity of human cartilage cells.

scholarly journals Properties and Interconnections of Trigeminal Interneurons of the Lateral Pontine Reticular Formation in the Rat

2001 ◽  
Vol 86 (5) ◽  
pp. 2583-2596 ◽  
Author(s):  
M.-J. Bourque ◽  
A. Kolta
Keyword(s):  
Electrical Stimulation ◽  
Reticular Formation ◽  
Motor Pattern ◽  
High Frequency Stimulation ◽  
Motor Nucleus ◽  
Trigeminal Motor Nucleus ◽  
Postsynaptic Potentials ◽  
Frequency Stimulation ◽  
Stimulation Of

Numerous evidence suggests that interneurons located in the lateral tegmentum at the level of the trigeminal motor nucleus contribute importantly to the circuitry involved in mastication. However, the question of whether these neurons participate actively to genesis of the rhythmic motor pattern or simply relay it to trigeminal motoneurons remains open. To answer this question, intracellular recordings were performed in an in vitro slice preparation comprising interneurons of the peritrigeminal area (PeriV) surrounding the trigeminal motor nucleus (NVmt) and the parvocellular reticular formation ventral and caudal to it (PCRt). Intracellular and extracellular injections of anterograde tracers were also used to examine the local connections established by these neurons. In 97% of recordings, electrical stimulation of adjacent areas evoked a postsynaptic potential (PSP). These PSPs were primarily excitatory, but inhibitory and biphasic responses were also induced. Most occurred at latencies longer than those required for monosynaptic transmission and were considered to involve oligosynaptic pathways. Both the anatomical and physiological findings show that all divisions of PeriV and PCRt are extensively interconnected. Most responses followed high-frequency stimulation (50 Hz) and showed little variability in latency indicating that the network reliably distributes inputs across all areas. In all neurons but one, excitatory postsynaptic potentials (EPSPs) or inhibitory postsynaptic potentials (IPSPs) were also elicited by stimulation of NVmt, suggesting the existence of excitatory and inhibitory interneurons within the motor nucleus. In a number of cases, these PSPs were reproduced by local injection of glutamate in lieu of the electrical stimulation. All EPSPs induced by stimulation of PeriV, PCRt, or NVmt were sensitive to ionotropic glutamate receptor antagonists 6-cyano-7-dinitroquinoxaline and d,l-2-amino-5-phosphonovaleric acid, while IPSPs were blocked by bicuculline and strychnine, antagonists of GABAA and glycine receptors. Examination of PeriV and PCRt intrinsic properties indicate that they form a fairly uniform network. Three types of neurons were identified on the basis of their firing adaptation properties. These types were not associated with particular regions. Only 5% of all neurons showed bursting behavior. Our results do not support the hypothesis that neurons of PeriV and PCRt participate actively to rhythm generation, but suggest instead that they are driven by rhythmical synaptic inputs. The organization of the network allows for rapid distribution of this rhythmic input across premotoneuron groups.

Effects of endogenous calcium transport inhibitor from heart muscle on the active calcium uptake and passive calcium release properties of sarcoplasmic reticulum

1989 ◽  
Vol 67 (9) ◽  
pp. 999-1006 ◽  
Author(s):  
Njanoor Narayanan ◽  
Philip Bedard ◽  
Trilochan S. Waraich
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Heart Muscle ◽  
Calcium Release ◽  
Membrane Vesicles ◽  
Transport Inhibitor ◽  
Low Concentrations ◽  
Active Calcium ◽  
High Concentrations ◽  
Stimulation Of

In the present study, the effects of the cytosolic Ca2+ transport inhibitor on ATP-dependent Ca2+ uptake by, and unidirectional passive Ca2+ release from, sarcoplassmic reticulum enriched membrane vesicles were examined in parallel experiments to determine whether inhibitor-mediated enhancement in Ca2+ efflux contributes to inhibition of net Ca2+ uptake. When assays were performed at pH 6.8 in the presence of oxalate, low concentrations (<100 μg/mL) of the inhibitor caused substantial inhibition of Ca2+ uptake by SR (28–50%). At this pH, low concentrations of the inhibitor did not cause enhancement of passive Ca2+ release from actively Ca2+-loaded sarcoplasmic reticulum. Under these conditions, high concentrations (>100 μg/mL) of the inhibitor caused stimulation of passive Ca2+ release but to a much lesser extent when compared with the extent of inhibition of active Ca2+ uptake (i.e., twofold greater inhibition of Ca2+ uptake than stimulation of Ca2+ release). When Ca2+ uptake and release assays were carried out at pH 7.4, the Ca2+ release promoting action of the inhibitor became more pronounced, such that the magnitude of enhancement in Ca2+ release at varying concentrations of the inhibitor (20–200 μg/mL) was not markedly different from the magnitude of inhibition of Ca2+ uptake. In the absence of oxalate in the assay medium, inhibition of Ca2+ uptake was observed at alkaline but not acidic pH. These findings imply that the inhibition of Ca2+ uptake observed at pH 6.8 is mainly due to decrease in the rate of active Ca2+ transport into the membrane vesicles rather than stimulation of passive Ca2+ efflux; at alkaline pH (pH 7.4), enhanced Ca2+ efflux contributes substantially, if not exclusively, to the decrease in Ca2+ uptake observed in the presence of the inhibitor. It is suggested that if the cytosolic inhibitor has actions similar to those observed in vitro in intact cardiac muscle, acid–base status of the intracellular fluid would be a major factor influencing the nature of its effects (inhibition of Ca2+ uptake or stimulation of Ca2+ release) on transmembrane Ca2+ fluxes across the sarcoplasmic reticulum.Key words: sarcoplasmic reticulum, Ca2+ uptake, Ca2+ release, endogenous inhibitor, heart muscle.

The release of catecholamines from the adrenal medulla and its modulation by α2-adrenoceptors in the anaesthetized dog

1987 ◽  
Vol 65 (4) ◽  
pp. 550-557 ◽  
Author(s):  
Sylvain Foucart ◽  
Réginald Nadeau ◽  
Jacques de Champlain
Keyword(s):  
Electrical Stimulation ◽  
Adrenal Medulla ◽  
Plasma Concentrations ◽  
Splanchnic Nerve ◽  
Feedback Mechanism ◽  
Adrenal Vein ◽  
Low Frequencies ◽  
Negative Feedback Mechanism ◽  
Frequency Of Stimulation ◽  
Stimulation Of

The adrenal nerve of anaesthetized and vagotomized dogs was electrically stimulated (10 V pulses of 2 ms duration for 10 min) at frequencies of 1, 3, 10, and 25 Hz. There was a correlation between the frequency of stimulation and the plasma concentrations of epinephrine, norepinephrine, and dopamine in the adrenal vein, mainly after the 1st min of stimulation and the maximal concentration was reached sooner with higher frequencies of stimulation. Moreover, the relative percentage of catecholamines released in response to the electrical stimulation was not changed by the frequency of stimulation. To test the hypothesis that a local negative feedback mechanism mediated by α2-adrenoceptors exists in the adrenal medulla, the effects of the systemic administration of clonidine (α2-agonist) and yohimbine (α2-antagonist) on the concentrations of catecholamines in the adrenal vein were evaluated during the electrical stimulation of the adrenal nerve (5 V pulses of 2 ms duration for 3 min) at 3 Hz. Moreover, the effects of the systemic injections of more specific α2-agonist and antagonist (oxymetazoline and idazoxan) were tested on the release of catecholamines in the adrenal vein in response to electrical stimulation of the splanchnic nerve at 1 and 3 Hz frequencies. The injection of 0.5 mg/kg of yohimbine caused a significant increase in the concentrations of epinephrine and norepinephrine in the adrenal vein induced by the electrical stimulation of the adrenal nerve and the injection of 15 μg/kg of clonidine had no effects. In the second series of experiments, the injection of 2 μg/kg of oxymetazoline caused a significant decrease in the release of epinephrine and norepinephrine at 1 Hz, but similarly to clonidine, there were no changes at 3 Hz. In contrast, the release of epinephrine and dopamine in response to electrical stimulation of the splanchnic nerve was increased at 3 Hz after the injection of idazoxan, but not at 1 Hz. It is concluded that the adrenal medulla catecholamines secretion appears to be partly modulated by a presynaptic inhibitory mechanism that involves α2-adrenoceptors. The observation that agonists appear to be more efficient at low frequencies of stimulation while antagonists appear to be more efficient at higher frequencies could be explained by the possibility that adrenal medullary α2-receptors would be saturated at higher frequencies of stimulation.

Micturition reflexes in the in vitro neonatal rat brain stem-spinal cord-bladder preparation

1994 ◽  
Vol 266 (3) ◽  
pp. R658-R667 ◽  
Author(s):  
K. Sugaya ◽  
W. C. De Groat
Keyword(s):  
Spinal Cord ◽  
Electrical Stimulation ◽  
Brain Stem ◽  
Rat Brain ◽  
Bladder Wall ◽  
Spinal Reflex ◽  
Neonatal Rat ◽  
Evoked Contractions ◽  
Stimulation Of

An in vitro neonatal (1-7 day) rat brain stem-spinal cord-bladder (BSB) preparation was used to examine the central control of micturition. Isovolumetric bladder contractions occurred spontaneously or were induced by electrical stimulation of the ventrolateral brain stem, spinal cord, bladder wall (ES-BW), or by perineal tactile stimulation (PS). Transection of the spinal cord at the L1 segment increased the amplitude of ES-BW- and PS-evoked contractions, and subsequent removal of the spinal cord further increased spontaneous and ES-BW-evoked contractions but abolished PS-evoked contractions. Hexamethonium (1 mM), a ganglionic blocking agent, mimicked the effect of cord extirpation. Tetrodotoxin (1 microM) blocked ES-BW- and PS-evoked contractions but enhanced spontaneous contractions. Bicuculline methiodide (10-50 microM), a gamma-aminobutyric acid A receptor antagonist, increased the amplitude of spontaneous, ES-BW- and PS-evoked contractions. These results indicate that PS-evoked contractions are mediated by spinal reflex pathways, whereas spontaneous and ES-BW-evoked contractions that are elicited by peripheral mechanisms are subject to a tonic inhibition dependent on an efferent outflow from the spinal cord. PS-evoked micturition is also subject to inhibitory modulation arising from sites rostral to the lumbosacral spinal cord. Although electrical stimulation of bulbospinal excitatory pathways can initiate bladder contractions in the neonatal rat, these pathways do not appear to have an important role in controlling micturition during the first postnatal week.

Excitation-induced Ca2+uptake in rat skeletal muscle

1999 ◽  
Vol 276 (2) ◽  
pp. R331-R339 ◽  
Author(s):  
H. Gissel ◽  
T. Clausen
Keyword(s):  
Skeletal Muscle ◽  
Electrical Stimulation ◽  
Initial Rate ◽  
Low Frequency ◽  
Channel Blockers ◽  
Ca Uptake ◽  
Edl Muscle ◽  
Isotonic Contractions ◽  
Progressive Accumulation ◽  
Stimulation Of

In isolated rat extensor digitorum longus (EDL) muscle mounted for isometric contractions, chronic low-frequency electrical stimulation was found to lead to an increased uptake of45Ca (154% above control after 240 min) and a progressive accumulation of Ca2+ (85% above control after 240 min). In soleus, however, this treatment led to a small, but significant, increase in 45Ca uptake (30% above control after 180 min) but no significant accumulation of Ca2+. In muscles mounted for isotonic contractions without any external load, electrical stimulation gave rise to a larger45Ca uptake and accumulation of Ca2+ in both EDL and soleus. These uptakes of Ca2+ coincided with an accumulation of Na+. During isometric or isotonic contractions, stimulation at 40 Hz increased the initial (60 s) rate of 45Ca uptake in soleus muscle 15- and 30-fold, respectively. The stimulation-induced increase in 45Ca uptake was only reduced by 17% by the Ca2+-channel blockers nifedipine and verapamil but was blocked by tetrodotoxin. The initial rate of stimulation-induced 22Na and45Ca uptake was correlated ( r = 0.80; P < 0.003). Stimulation of Na+ channels with veratridine increased 45Ca uptake by 93 and 139% in soleus and EDL, respectively ( P < 0.001), effects that were abolished by tetrodotoxin. The results indicate that in skeletal muscle, excitation induces a considerable influx of Ca2+, mediated by Na+ channels.

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