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Biomedical subjects

J D Huizinga

Publications and source records attributed to J D Huizinga.

At least 109 records · Page 6Linked to original sources
PubMed1988

Immunoglobulin E mediated membrane conductance changes in rat basophilic leukemia cells.

Electrophysiological effects of anaphylactic stimulation of rat basophilic leukemia cells (RBL-2H3) were studied using conventional microelectrodes. Stimulation of passively sensitized cells by anti-immunoglobulin E resulted in hyperpolarization followed by depolarization. These changes in membrane polarization were associated with a decrease in input membrane resistance. No effect of anaphylactic stimulation was seen in Ca2+-free solution or when Ca2+ influx was blocked by Co2+, but it was mimicked by the Ca2+ ionophore A-23187. This suggests that the changes in ionic conductances were associated with calcium influx. These results support the hypothesis that membrane conductance changes are involved in the stimulus-secretion process of the RBL-2H3 cells.

Action Potentials↗
PubMed1988

Relationship between transmural potential difference and smooth muscle slow waves and contractility in the rabbit small intestine in vitro.

The relationship between transmural potential difference (PD) and smooth muscle electrical and mechanical activity was investigated in the rabbit ileum in vitro. Transmural PD was monitored using agar salt bridge electrodes connected via calomel half cells to an electrometer. Force displacement transducers recorded predominantly longitudinal smooth muscle activity. Concurrently, predominantly circular muscle activity was recorded at three sites using intraluminal pressure probes. At the same sites, suction electrodes monitored electrical activity of the smooth muscle. In all experiments, fluctuations in transmural PD were temporally linked to smooth muscle mechanical and electrical activity. The frequency of PD oscillations, electrical slow waves, and cyclic pressure changes were identical within each segment. Adrenaline abolished smooth muscle electrical spiking, all mechanical activity, and transmural fluctuations in PD. However, the slow waves were not abolished, though their frequency was increased. Phentolamine but not propranolol reversed the effects of adrenaline, thus slow wave frequency is influenced by alpha-adrenergic stimulation in the rabbit ileum. In conclusion, oscillations in transmural PD are unrelated to the ionic processes associated with the slow wave. However, they are in some way linked to smooth muscle contractile activity, possibly via an intrinsic neural mechanism as observed in the guinea pig.

Animals↗
PubMed1988

Electrical coupling and pacemaker activity in colonic smooth muscle.

The effect of heptanol on electrical coupling between submucosal circular muscle cells of the dog colon and consequences for slow-wave activity were investigated. Electrotonic potentials showed exponential decay giving a length constant of 2.6 +/- 0.5 mm and a time constant of 157 +/- 48 ms. Heptanol reversibly abolished electrotonic current spread, and subsequently no slow-wave activity was recorded. The length constant decreased to less than 0.2 mm. The input resistance increased from 3 to 36 M omega, suggesting a change from tissue syncytium to electrically isolated cells. D600 (5 X 10(-6) M) also abolished slow wave activity but had opposite effects on electrotonic current spread. The data are consistent with the hypothesis that heptanol reversibly inhibits intercellular coupling, resulting in loss of spread of extracellularly applied current, uncoupling of cells, and loss of pacemaker activity. Regulation of intercellular communication may be important in the control of intestinal motility.

Alcohols↗
PubMed1988

Electrotonic current spread in colonic smooth muscle.

Current-induced changes in the membrane potential (electrotonic potentials) were measured intracellularly. The electrotonic potentials were seen to decay exponentially over many cells, suggesting electrotonic current spread. The characteristics of the electrotonic current spread were used to determine passive membrane properties of both circular and longitudinal muscle cells of human and dog colon. Electrotonic current spread was first determined along the long axes of the cells. The space constant of the circular muscle of human colon was 2.14 mm and that of the longitudinal muscle was 1.63 mm. The space constants for the dog colon were similar. The value for the time constant of dog colon circular muscle was 160 ms, whereas much higher time constants, averaging between 500 and 800 ms, were recorded from dog longitudinal muscle and both human colon muscle layers. These data suggest good electrotonic coupling in all tissues studied, along the long axes of the cells. They further suggest a relatively high membrane resistance and junctional resistance in the longitudinal muscle. Electrotonic coupling along the short axes of circular muscle cells, along the long axis of the colon, was studied in the dog. The space constant was 0.43 mm, suggesting a relatively high resistance to current flow along the short axes of the cells. In addition, along the short axes of the cells from the submucosa to the myenteric plexus side (i.e., in radial direction) a gradient was observed in resting membrane potential, slow-wave amplitude, and rate of rise of the slow-wave upstroke.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Myogenic electrical control activity in longitudinal muscle of human and dog colon.

1. The myogenic electrical activities of longitudinal muscle cells of the dog and human colon were investigated using intracellular microelectrodes. 2. The resting membrane potentials of dog and human longitudinal muscle cells at the serosal side of the muscle layer were -49.4 +/- 0.9 and -44.8 +/- 1.3 mV respectively. 3. Spontaneous electrical activity consisted of electrical oscillations of 13.7 +/- 1.1 mV and 8.6 +/- 2.1 mV amplitude, and 19.8 +/- 1.0 cycles/min and 26.1 +/- 1.6 cycles/min frequency for dog and human cells respectively. 4. Spiking activity only occurred superimposed on the electrical oscillations; the mean rate of rise of spikes was approximately 150 mV/s in the dog and approximately 260 mV/s in human cells and that of the oscillations was approximately 18 mV/s in the dog and approximately 16 mV in human cells. 5. Spiking activity was abolished by calcium influx blockers and 0.01 mM-calcium Krebs solution. The amplitude of the electrical oscillations was reduced to 0.2-1.0 mV 30 min after calcium influx blockade or 30 min in 0.01 mM-calcium Krebs solution. 6. Because of the high frequency of the oscillation-spike complexes, there was summation of associated contractile events in such a way that contraction frequency corresponded to frequency of bursts of oscillations and not to the frequency of the individual oscillations. 7. The resting membrane potential of the longitudinal muscle cells at the myenteric plexus side of the layer was -44.9 +/- 1.0 mV, significantly lower than at the serosal side. 8. A gradient in membrane potential and slow-wave amplitude exists in circular muscle of dog colon, with the highest value at the mucosal side (-68.4 and 28.1 mV respectively) and the lowest at the myenteric side (-62.5 and 8.6 mV) of the muscle layer. 9. Differences between resting membrane potential and electrical activity of longitudinal and circular muscle cells of the dog colon measured at the myenteric side of both muscle layers suggests absence of electrotonic coupling between the two types of cells. 10. Similarity of resting membrane potentials of longitudinal and circular muscle of the human colon suggests possible electronic coupling. 11. Since the electrical oscillations in longitudinal muscle control occurrence of spiking activity and type of contraction, they may be called 'electrical control activity'.

Action Potentials↗
PubMed1987

Generation of spiking activity in circular muscle cells of the canine colon.

Spontaneous and current-induced electrical activity was recorded intracellularly to resolve the controversy whether or not the circular muscle layer of the colon generates spiking activity. Particularly in the first hour after mounting the tissue in the organ bath, spikes were recorded at both the submucosal and the myenteric plexus side of the muscle layer. Spikes were seen as part of the slow wave upstroke in the submucosal surface cells, and spikes occurred both at the upstroke potential and superimposed on the plateau potential in myenteric plexus surface cells. Spikes increased the force of contraction. The study supports earlier claims using extracellular recording techniques that circular muscle cells generate spiking activity, particularly in the presence of depolarizing stimuli, and that spikes contribute to contractile activity.

Animals↗
PubMed1987

Coordination of electrical activities in muscle layers of the pig colon.

Simultaneous recording of electrical activities from the circular and longitudinal muscle layers of the pig colon was performed in vitro to study possible coordination of activities. The electrical activity of both muscle layers consisted of electrical oscillations with superimposed spikes. The frequency range of the electrical oscillations in the circular muscle was 0.5-3.5 cycles per minute (cpm) and in the longitudinal muscle 24-42 cpm. Coordination of the activities of both muscle layers occurred consistently only after stretch or cholinergic stimulation. Then it occurred in a unique fashion. Each oscillation in the circular muscle layer occurred at the same time as the onset of a burst of oscillations in the longitudinal muscle. In addition, multiple simultaneous recordings of the electrical activities from each muscle layer were obtained showing that within the circular muscle layer electrical oscillations were phase locked in the circumferential direction and along the long axis of the colon. They appeared to propagate in either the oral or aboral direction. In tetrodotoxin (with stretch as stimulus) and also in presence of carbachol, bursts of oscillations in the longitudinal muscle layer were phase locked circumferentially (in the different taeniae) and longitudinally. This study shows that the muscle layers in the colon, which have different myogenic electrical activities, can obtain a high level of coordination.

Animals↗
PubMed1986

Control of human colonic motor function.

Human colonic motility is governed by control mechanisms involving the electrical activity of the smooth muscle cell membranes, the intrinsic and extrinsic nervous activity, and hormonal action. The structural bases for neural and myogenic control have not been demonstrated. However, gap junctions are lacking between muscle cells, and nerves are not close to smooth muscle cells. The myogenic control, as observed in vitro, is described and compared with results obtained from different in vivo techniques. In vitro and in vivo measurements are critically evaluated, and a reconciliation between them attempted. No appropriate animal model is available to help resolve different findings and interpretations. Neural control of colon motility is exerted probably through modulation of myogenic activity as well as directly. The activities of extrinsic nerves, intrinsic motor nerves and afferent nerves are integrated within the colon, at prevertebral ganglia and in the spinal cord in animals, but similar data are not available for the human. There is a lack of studies directly relating transit to motility and conventional beliefs need reexamination.

Animals↗
PubMed1986

Electrical basis of excitation and inhibition of human colonic smooth muscle.

Excitation and inhibition of electrical activities of the musculature of the human colon and the consequent changes in motor activities were studied in vitro. The mechanisms of excitation and inhibition were very different from those of the small intestine and colons from animal models. Carbachol increased spiking activity and the frequency of bursts of electrical oscillations in longitudinal muscle. Each longitudinal muscle contraction was related to a burst of electrical oscillations. Carbachol induced one of three patterns of activity in circular muscle: (a) continuous electrical oscillatory activity (14-24 cpm) with spikes, associated with tonic contraction; (b) bursts of such electrical activity, associated with broad phasic contractions; or (c) prolonged membrane potential depolarizations (frequency 1-3 cpm) with superimposed intense spiking activity, associated with phasic contractions. Isoproterenol inhibited all electrical and mechanical activities in both muscle layers. These results may provide a better understanding of (a) the origins of the variable patterns of electrical and motor activities and (b) the relationship between electrical and mechanical activities of the human colon musculature.

Action Potentials↗
PubMed1986

Electrophysiology of human colon motility in health and disease.

Recent years have seen a number of studies measuring electrical activities of the human colon muscle layers. In vitro studies have enhanced our understanding of myogenic control of colon motility. In vivo studies have suggested a relationship between patterns of electrical activities and the transport of colon contents. This chapter describes the patterns of electrical and motor activity that the human colon can perform depending on the nature and intensity of the stimulus, using recent in vitro and in vivo data. In vitro studies with human tissue have shown differences between the electrical activity of the longitudinal and circular muscles. They have also revealed the unique nature of the electrical control activity of the circular muscle of human colon. The electrical oscillatory activity of this layer is variable in frequency from 1 to 60 cpm, variable in amplitude, and not omnipresent. Furthermore, the activity is sensitive to stretch and markedly altered by excitatory and inhibitory substances. In vivo data, especially spike action potential recordings for 24 h, have revealed patterns of electrical activity related to intake of meals, sleep, and also constipation. The limitations of some intraluminal techniques to record electrical activity are discussed. Further studies are needed to accurately relate in vivo activities to cellular events recorded in vitro, and to relate these to altered patterns of activity in disease. The suggestion is made that a relevant in vivo assessment of the colonic motility of a patient can only be achieved by long-lasting (24-h) studies, because of the large variability in the hour-to-hour colonic activity. Timing of experimental drug intervention is important since colonic motility undergoes diurnal changes. Recent studies into profiles of electrical and motor activity in irritable bowel syndrome (IBS) suggest that there is not a typical IBS myogenic activity. Rather, patterns of electrical activity can be related to the symptoms of IBS: diarrhea and constipation. Recent electrophysiologic data on Hirschsprung's disease reveal absence of intrinsic inhibitory innervation in the aganglionic segment. In vitro studies on tissue from diverticular disease patients show abnormal myogenic activity.

Colon↗
PubMed1985

The Ehlers-Danlos syndrome and colonic perforation. Report of a case and physiologic assessment of underlying motility disorder.

The Ehlers-Danlos syndrome is a genetically determined disorder of connective tissue which is generally known for its features of fragile, hyperextensible skin, hypermobile joints, and tissue fragility. Less commonly, colorectal complications can occur, including bleeding, prolapse, and diverticulitis. A rare case of colonic perforation associated with Ehlers-Danlos syndrome is presented. Additionally, in vitro electromyographic studies of the colonic tissue were performed which suggested a possible link between abnormal myogenic activity and the colonic perforations. The authors recommend that treatment be either a permanent colostomy or a subtotal colectomy with anastomosis to the rectum for similar cases.

Adult↗
PubMed1985

Electrophysiologic control of motility in the human colon.

Characteristics of electrical activities, and the relationship between electrical and motor activities, were studied in circular and longitudinal (taenia) muscle of the human colon that was obtained from 21 individuals. Recordings were obtained with suction electrodes, the sucrose-gap method, and microelectrodes. The circular muscle electrical activity consisted of oscillatory activity of relatively low amplitude, with a frequency range from 4.5 to 60 cycle/min. Spiking activity was present on most oscillations. Contractile activity was associated with individual oscillations at frequencies below 12 cycle/min. Contractions related to periods of oscillations at frequencies above 12 cycle/min showed summation resulting in prolonged contractions. In these periods, oscillations were either of relatively high amplitude, or had superimposed spiking activity. Longitudinal muscle activity consisted of slow electrical oscillations at frequencies between 24 and 36 cycle/min with spiking activity superimposed on most oscillations. Contractions were related to bursts of such activity. These findings provide the electrophysiologic basis for short and prolonged phasic contractions and for sustained contractions of the human colon muscle layers. Activities in both muscle layers were myogenic in nature, were very sensitive to stretch, and could be initiated or modulated by nervous activity.

Colon↗
PubMed1984

The effects of cholecystokinin-octapeptide and pentagastrin on electrical and motor activities of canine colonic circular muscle.

The effects of cholecystokinin-octapeptide (CCK-OP) and pentagastrin on electrical and motor activities of circular muscle of the canine colon were studied with the sucrose gap technique. Additional organ bath experiments were performed to further characterize the motor response to the peptides and to elucidate their site of action. The electrical activity consisted of slow waves having an initial potential followed by a plateau potential, at a regular frequency of 4.5 cycles/min. Both peptides prolonged the duration and increased the amplitude of the plateau phase of the slow waves. Concomitantly, the slow wave frequency was reduced. In addition, CCK-OP increased spiking activity. Both spiking activity and the prolonged plateau potential generated contractile activity, prolonged phasic contraction occurring with slow waves with a prolonged plateau. In organ bath experiments, both CCK-OP and pentagastrin increased the basal tone of the muscle strips and prolonged the duration of the phasic contractions. The prolongation of the duration of the contractions was not antagonized by tetrodotoxin (TTX) and atropine. CCK-OP but not pentagastrin increased the force of contractions, this action was not affected by atropine but was reduced in the presence of TTX, suggesting that the increase in force may be partially mediated by noncholinergic excitatory nerves. The increase in basal tension by the peptides was enhanced in the presence of TTX indicating that myenteric inhibitory neurones were tonically active under our experimental conditions. The results provide the electrophysiological basis for CCK-OP and pentagastrin induced changes in colonic motility.

Animals↗
PubMed1984

Electrophysiological basis of excitation of canine colonic circular muscle by cholinergic agents and substance P.

The circular muscle layer of the canine colon exhibits omnipresent rhythmic periodic waves of depolarization (slow waves), acting as pacemaker activity. The electrophysiological and motor responses of this layer to the muscarinic agonists acetylcholine and carbachol, and to the excitatory peptide substance P, were studied using the sucrose-gap technique. In addition, changes in the contractile activity were examined in organ bath experiments. The slow waves consisted of an initial potential followed by a plateau potential. All substances depolarized the membrane and increased dramatically the duration of the plateau potential resulting in a decrease of the slow wave frequency. In addition, the amplitude of the plateau potential was often increased significantly. Carbachol and substance P readily evoked spiking activity whereas acetylcholine did not. Both spiking activity and the plateau potential generated contractile activity. The prolongation of the slow wave duration caused a profound alteration of the pattern of contractions. Long-lasting tachyphylaxis to the effect of substance P, but not to acetylcholine or carbachol, occurred. The electrophysiological and motor effects of the drugs were due to a direct action on the smooth muscle cell membrane. This study provides an electrophysiological basis for prolonged circular muscle contractions of the colon, and it emphasizes the pacemaker activity of gastrointestinal smooth muscle as an important site of drug action.

Acetylcholine↗
PubMed1983

Electrical basis of contractions in the muscle layers of the pig colon.

Simultaneous in vitro measurements of electrical and mechanical activities were performed, using suction electrodes and force transducers, respectively, on longitudinal and circular muscle layers of the pig proximal colon. In addition, circular muscle strips were studied with the sucrose gap technique. Spontaneous activity was present in both preparations. In the circular muscle, slow waves with superimposed spikes occurred at a variable frequency, accompanied by phasic contractions. Longitudinal muscle preparations showed a different behavior. Regular appearance of distinct slow waves as described for the circular muscle did not occur. Instead, periods of membrane potential oscillations at a frequency of 41 cycles/min and a duration of approximately 12 s were observed in this layer. Most oscillations had superimposed spikes, and each period of oscillations was associated with a contraction. Spontaneous activity in the circular layer was myogenic in nature but susceptible to innervation and stretch. In contrast, an excitatory stimulus (acetylcholine or stretch) was a prerequisite for activity in the longitudinal layer. Cholinomimetics increased and adrenergic agents decreased the frequency of the slow waves and spiking activity and frequency and force of contractions in the circular muscle. Cholinergic agents increased the activity in the longitudinal muscle into continuous electrical oscillations with spiking activity and concomitant tonic contractile activity, whereas adrenergic agents abolished electrical and mechanical activity. Spontaneous release of acetylcholine occurred, partly due to regenerative activity of myenteric cholinergic nerves. In addition, tonic activity in the noncholinergic nonadrenergic inhibitory neurons decreased circular muscle tone.

Animals↗
PubMed1981

Dual action of high energy adenine nucleotides in comparison with responses evoked by other adenine derivatives and intramural nerve stimulation on smooth muscle.

Fundic strips from stomach smooth muscle of the guinea-pig responded with a contraction preceded by a relatively small relaxation upon addition of the high energy adenine nucleotides ADP and ATP at 37 degree C. The contractile response was concentration-dependent in the range of 10(-8) - 10(-4) M, while the relaxation appeared at higher concentrations (10(-6) - 10(-4) M). The contractile phase observed in the presence of ADP or ATP was inhibited by the prostaglandin antagonist p-benzyl-4-(1-oxo-2-(4-chlorobenzyl)-3-phenylpropyl)phenyl phosphonate (N-0164; 5 X 10(-8) M) The low energy nucleotide AMP, adenosine and the ATP analogue beta, gamma-methyleneadenosine 5'-triphosphate caused relaxation of the stomach muscle. This relaxation was not affected by N-0164 (5 X 10(-8) M). Stimulation of the non-adrenergic inhibitory nerves caused relaxation of the muscle cells, in contrast to the effect of ATP. This seems to be in conflict with the purinergic nerve hypothesis. However, the relaxation evoked by field stimulation may have been due adenosine if it can be assumed that ATP is degraded after its possible release from nerve terminals. Furthermore, the limited availability of ATP if released from nerves for the short period of stimulation is presumably ineffective to stimulate prostaglandin biosynthesis. The results suggest that synthesis of prostaglandins is promoted by the high energy adenine nucleotides ADP and ATP which induce contraction of stomach smooth muscle in contrast with the low energy adenine derivatives and stimulation of the intramural non-adrenergic nerves which produce muscle relaxation.

Adenosine↗
PubMed1980

The effect of amino acids on intestinal smooth muscle related to their content in blood and tissue.

The concentration of amino acids in the blood of the guinea pig is about 0.1 mM, while the intracellular concentration in the gastrointestinal smooth muscle cells is about ten times higher. Most amino acids, applied exogenously to isolated smooth muscles, exert effects in concentrations resembling their intracellular concentration. The results show that the inhibiting amino acids do not function as a neurotransmitter in the non-adrenergic inhibitory nervous system. The effective amino acids may possess modifying properties with respect to the contractile state of the muscle.

Amino Acids↗