Development Of Electrical Activity Research Articles

Beware of Cells Bearing Gifts

See related article, pages 159–167 Heart failure is a major worldwide health problem that is growing in prevalence despite recent treatment advances. Patients with heart failure ultimately die from either pump failure or cardiac arrhythmia, and there is a link between the degree of contractile dysfunction and arrhythmic risk. Since the 1960s, the definitive therapy for heart failure has been cardiac transplantation, but the limited supply of organs has restricted the impact of this therapy. Starting in the mid-1990s, a series of observations has led to the concept that cells might be used to repair myocardial damage. Subsequently, this therapy has shown promise in ischemic and nonischemic forms of myocardial injury. The increased availability of cells as compared with organs has driven an exuberant search for the right replacement cells. Nevertheless, after intense study, there is no obvious frontrunner.1 The concept driving the cell selection process has been the need for a sufficient number of immune compatible, contractile cells. Proposed cell sources have included skeletal myoblasts,2 bone marrow–derived progenitor cells,3 and embryonic stem cells.4 These 3 cell types have been shown to improve myocardial function in animal models, and the first 2 have shown promise in human clinical trials.5 Generally, the effects of these 2 cell types on myocardial function have been similar.6 If they are to fulfill their promise as replacement myocytes, it is important that the …

Development of electrical activity in cardiac myocyte aggregates derived from mouse embryonic stem cells.

Embryonic stem cells differentiate into cardiac myocytes, repeating in vitro the structural and molecular changes associated with cardiac development. Currently, it is not clear whether the electrophysiological properties of the multicellular cardiac structure follow cardiac maturation as well. In long-term recordings of extracellular field potentials with microelectrode arrays consisting of 60 substrate-integrated electrodes, we examined the electrophysiological properties during the ongoing differentiation process. The beating frequency of the growing preparations increased from 1 to 5 Hz concomitant to a decrease of the action potential duration and action potential rise time. A developmental increase of the conduction velocity could be attributed to an increased expression of connexin43 gap junction channels. Whereas isoprenalin elicited a positive chronotropic response from the first day of spontaneous beating onward, a concentration-dependent negative chronotropic effect of carbachol only developed after approximately 4 days. The in vitro development of the three-dimensional cardiac preparation thus closely follows the development described for the mouse embryonic heart, making it an ideal model to monitor the differentiation of electrical activity in embryonic cardiomyocytes.

Fetal human cortical neurons grown in culture: morphological differentiation, biochemical correlates and development of electrical activity

Cultured fetal human cortical neurons derived from second trimester human fetal cortex were analyzed with regard to their morphological differentiation and expression of cell-specific markers. The culture method was adapted from standardized protocols originally developed for the isolation and culture of rodent oligodendrocytes and astrocytes. This technique takes advantage of the different adhesive properties and stratification of central nervous system cells in vitro. Under these culture conditions fetal human cortical neurons underwent morphological differentiation, expressed neuron-specific markers and voltage- and ligand-gated ion channels. Highly enriched cultures of microglia and astrocytes generated from the same starting material also expressed cell-type specific markers. These cultures serve as a valuable tool for the establishment of normative data and as experimental models for neurodevelopmental and neurodegenerative studies.

Development of electrical activity in regenerating aggregates of hydra cells.

The development of electrical activity in aggregates of dissociated hydra cells was investigated. Both the number of events and the distribution of amplitude of electrical pulses during the process of regeneration were determined. Correlations between electrical pulses at two separate positions on an aggregate were also examined as regeneration progressed. The main results were as follows: From the measured frequency and amplitude of pulses, together with the correlations between pulses at two different sites, we could observe the way in which contraction pulses developed in regenerating aggregates. The percentage of the electrical pulses of large amplitude increased about 20 hr after the start of regeneration. The correlation between electrical pulses measured at two sites separated by 0.3 mm also increased at about 20 hr, reaching about 80% at 40 hr. The results suggest the possible details of the reorganization of the conduction system for contraction pulses among cells in a regenerating aggregate of hydra cells.

Patterns of electrical activity in comb plates of feeding Pleurobrachia (Ctenophora).

The electromotor behaviour of ciliary comb plates was studied during prey-stimulated and electrically stimulated feeding by intact Pleurobrachia pileus (Müller). Comb plate electrical activity was recorded by extracellular electrodes attached directly to the cilia; comb plate motility was recorded by high-speed video microscopy. Comb plate electrical activity fell into two distinct classes, identified by waveform and amplitude: (i) excitatory postsynaptic potentials (EPSPS) in the comb plate (polster) cells and (ii) regenerative potentials in the cilia, as described previously (Moss & Tamm 1987). Slow phasic bursts of regenerative potentials (reversal volleys) were observed in comb plates of rows undergoing reversed beating during capture of prey or by rhythmic electrical stimulation of the tentacles. All plates of a given comb row exhibited virtually identical electrical activity. Timing and development of electrical activity in comb plates of the subtentacular (ST) rows were nearly identical even though separated by several centimetres; onset of the reversal volleys of plates of subsagittal (ss) rows were delayed on average by about 0.5 s relative to the ST rows, although individual EPSPS displayed very similar timing. Microsurgery, combined with extracellular recording from comb plates and the tentacle and associated basal structures, revealed the presence of an integrative center in the tentacular bulb. This communicates with the comb plates by means of a diffuse pathway, presumably the nerve net, which itself is maximally sensitive to rhythmic input. The pathway underlying the reversal volley may innervate only the stimulated hemisphere. In addition to the rhythmic pathway, a through-conducting pathway runs from distal regions of the tentacle to the comb plate cells. Yet another excitatory pathway, possibly distinct from the tentacular through-conducting pathway, may mediate certain cases of global postsynaptic activity. The pathway that controls mouth movements during feeding is entirely independent of any comb plate pathway.

Postnatal development of electrical activity of rat nigrostriatal neurons

Postnatal development of electrical activity of rat nigrostriatal neurons

Postnatal development of electrical activity of rat nigrostriatal neurons

Postnatal development of electrical activity of rat nigrostriatal neurons

Development of electrical activity in embryonic hearts

Development of electrical activity in embryonic hearts

Early events in development of electrical activity and contraction in embryonic rat heart assessed by optical recording.

Spontaneous action potential and contraction in the early embryonic heart of the rat have been monitored optically using a voltage-sensitive merocyanine-rhodanine dye together with a multiple-element photodiode matrix array, and the onset of rhythmical action-potential activity in the early phases of rat cardiogenesis was conclusively determined for the first time. Spontaneous rhythmical action potentials were first generated in the central part of the embryonic heart at the middle period of the 3-somite stage of development, at 91/2 days after copulation. Subsequently, contractions coupled with the action potential also appeared at the end of the 3-somite stage. Usually, at the 3-somite stage, spontaneous action signals were synchronized among the different areas in the heart. From this result, it is evident that the paired right and left cardiac primordia are fused completely at the time of initiation of spontaneous electrical activity. In the 3-somite embryonic heart, excitatory waves were conducted radially over the heart, at a uniform rate (0.4-0.8 mm/s), from the pace-making area. However, the regional priority of pace-making activity is not rigid but is flexible.

Optical recording of development of electrical activity in embryonic chick heart during early phases of cardiogenesis.

1. Developmental changes in the spontaneous action potential were measured using optical signals from early embryonic chick heart stained with a potential sensitive merocyanine-rhodanine dye. 2. The wave-length dependence of the dye signal is triphasic in early embryonic chick heart with a decrease in absorption from 525 to 600 nm, an increase from 625 to 720 nm, and a decrease at 750 nm. The signal was largest at 700 nm. 3. The magnitude of the spontaneous absorption signal increased as the development of the embryonic heart proceeded. In addition, the magnitude of the absorption signal differed among the various regions of an early embryonic chick heart and the number of electrically active cells increased dramatically throughout the 7-9 somite developmental stages. 4. The number of the electrically active cells was largest in the right portion of the ventricle at the 7-9 somite developmental stages. 5. The shape of spontaneous absorption signals could be classified into four types in the developmental stages between 7 and 9 somites: Signals resembling the cardiac action potential and the pace-maker potential were not recorded until the 8-9 somite developmental stage.

Ionic basis of electrical activity in cardiac tissues

Cardiac electrical events are described in terms of membrane physiology. The concept that cardiac membranes possess specific ionic channels controlled by gates bearing electrical charges is discussed. When open, these channels permit ions to cross the membrane, giving rise to passive inward (depolarizing) and outward (repolarizing) currents. Two different inward and four or five different outward currents appear to be responsible for the development of cardiac electrical activity; both inward currents appear to be controlled by activation and inactivation variables, whereas outward currents are essentially controlled by activation variables and/or inward-going rectifiers. The potential range in which the different currents activate and inactivate (or are limited by inward-going rectification), and the kinetics of activation and inactivation processes explain the development of electrical activity in normal cardiac tissues and in partially depolarized fibers. In addition to passive ionic currents, electrogenic active transport participates in the development of electrical phenomena. The conductance of the membrane for potassium ions and the electrical coupling between cardiac cells depend on the intracellular concentration of calcium ions.

Neurological and Electroencephalographic Correlative Studies in Infancy

This volume presents the proceedings of a conference and symposium held in Houston in October, 1963. The theme is the immature brain, and there is a wide range of subject matter in the 20 papers presented. About half the papers are devoted to morphologic and physiological studies in young animals, with emphasis on the development of electrical activity of the brain, the maturation of evoked potentials, and the relationship of morphologic and physiological characteristics of the developing brain to seizure susceptibility. Electroclinical correlations in the child occupy the other half, with greatest attention being given to seizures and hypoxia. Some of the data have been published elsewhere, but there are significant new studies and the conference format has given the opportunity for integration and coherence not available in the usual journal publication. This volume is not for the general pediatrician, but will be of interest to workers in many fields,

Development of electrical activity in cerebral hemispheres of the chick embryo.

Summary and Conclusions1. A study of the beginning and development of the EEG in 73 chick embryos is made. 2. “Spontaneous” electrical activity and that produced by strychnine appear simultaneously on the 13th day. 3. “Spontaneous” activity undergoes changes during the course of embryonic development. The “early” rhythm appearing on the 13 th day gradually increases in frequency and voltage and becomes more constant. On the 16th day the high voltage “late” rhythm appears, becoming more constant on subsequent days. 4. Strychnine causes the appearance of spikes, which are generally biphasic, and increases the amplitude, frequency and constancy of the “spontaneous” activity in most experiments. 5. With development of the embryo, the strychnine spikes become of shorter duration and higher voltage, pointing to a better synchronization of the neurones. Frequency increases and spikes begin to appear earlier as the embryo grows. 6. From the 14th day spike discharges are to be seen in the embryonic brain, similar ...

Development of Electrical Activity in the Cerebral Cortex of the Albino Rat.

Summary and Conclusion1. Electrocortico-grams were recorded from albino rats immobilized with various drugs. 2. Spontaneous electrical activity was irregular, intermittent, and of relatively low amplitude during the first week after birth. 3. Local application of strychnine to the cortex resulted in large, slow, spike potentials in rats several days old. 4. The general trend in the spontaneous activity from birth to about 10 days of age was towards increasing rhythmicity, regularity, continuousness, and amplitude. The strychnine-induced spikes gradually decreased in duration, and increased in amplitude and frequency of occurrence. 5. The ECoG of the 10-day-old rat was already basically similar to that of the adult.