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Biomedical subjects

E E Daniel

Publications and source records attributed to E E Daniel.

At least 307 records · Page 17Linked to original sources
PubMed1984

Effects of scorpion venom on structure and function of esophageal lower sphincter (LES) and body circular muscle (BCM) from opossum.

In the lower esophageal sphincter (LES) and body circular muscle (BCM) from opossum, nerves appeared to innervate the interstitial cells of Cajal more closely than they innervated smooth muscle cells, and it was postulated that these cells might mediate nonadrenergic, noncholinergic ( NANC ) nerve effects. Tissues were treated with a toxin, selective for structures with Na channels, the venom of the scorpion, Leiurus quinquestriatus, to determine its morphological effects on nerves and other structures and its effect on responses of LES and BCM to NANC nerve stimulation by field stimulation with 0.5- and 5-ms pulses. Relaxations to 5-ms pulses are tetrodotoxin-insensitive and might result from the release of mediators from nerve terminals by a different, Na channel independent mechanism or from activation of a nonneural structure with a longer time constant than nerve. Scorpion venom relaxes the LES temporarily and, like tetrodotoxin, abolished responses of LES and BCM to 0.5-ms pulses of field stimulation, but not responses to 5-ms pulses of field stimulation. When responses to 0.5 ms of field stimulation were first inhibited, some nerve varicosities were damaged. Later nearly all were depleted markedly of synaptic vesicles. Venom did not structurally damage other cells. The venom effects to relax LES and to damage nerves were prevented by tetrodotoxin pretreatment, suggesting that venom released an inhibitory mediator and destroyed synaptic vesicles by acting on Na channels. The finding that interstitial cells of Cajal, which often had gap junction contacts to smooth muscle and close associations with nerves, were resistant to scorpion venom while the nerves that innervate them were not, is consistent with the hypothesis that interstitial cells are intercalated between the nerves and muscles and may mediate tetrodotoxin-insensitive responses to field stimulation.

Animals↗
PubMed1984

Neurotensin inhibition of canine intestinal motility in vivo via alpha-adrenoceptors.

Neurotensin given intra-arterially in bolus doses to the canine small intestine inhibited field-stimulated, atropine-sensitive contractile responses in the duodenum (mean effective dose (ED50) = 3.2 X 10(-11) mol) and in the ileum (mean ED50 = 2.1 X 10(-11) mol). Norepinephrine (ED50 = 3 X 10(-9) mol) also inhibited these contractile responses. Phenylephrine (ED50 = 1.3 X 10(-8) mol) was one-fourth as potent as norepinephrine and clonidine (ED50 = 8 X 10(-10) mol) was at least as potent as norepinephrine, while isoproterenol (up to 8 X 10(-8) mol) failed to show any inhibitory effects. Phentolamine (2 mg/kg) increased significantly the ED50 of neurotensin and norepinephrine. Prazosin (2 mg/kg) increased significantly the ED50 of norepinephrine in the duodenum but had no effect on the ED50 of neurotensin. Yohimbine (2 mg/kg) increased the ED50 values of neurotensin and adrenergic agonists. Both neurotensin and norepinephrine in doses causing maximal inhibition of field-stimulated responses decreased (by 40 to 60%) contractile responses to 9 X 10(-10) mol (approximately the intra-arterial ED50 dose) of acetylcholine. Reserpine pretreatment markedly diminished the inhibition of spontaneous or field-stimulated phasic contractions by distention or field stimulation of a distal site. Reserpine also diminished the ED50 for neurotensin from 1 X 10(-11) to 2 X 10(-11) mol (p less than 0.02), but did not abolish neurotensin's inhibitory effect. Tetrodotoxin (10-15 micrograms, intra-arterially) increased the dose of neurotensin required to inhibit spontaneous activity in the ileum but after this toxin, as after adrenergic antagonists or reserpine, maximal inhibition could still be obtained. These results suggested that neurotensin inhibited contractile activity of canine intestine by acting on neural receptors to release norepinephrine. Norepinephrine activated primarily alpha 2-adrenoceptors and ultimately inhibited acetylcholine release. Neurotensin also inhibited contractions by activating a second, less sensitive receptor on smooth muscle.

Acetylcholine↗
PubMed1984

Multiple responses to electrical field stimulation in circular muscle of canine gastric corpus.

Innervation of circular muscle of the canine stomach studied in vitro was investigated by subjecting muscle strips to electrical field stimulation. Strips were cut from the lesser curvature of the gastric corpus and stimulated with 10-s trains of 0.5-ms pulses at 0.5-20 Hz, 40 V. Most responses were classified into one of three types. In general, field stimulation tended to elicit sequences of varying magnitudes of transient on-contraction, on-relaxation, off-relaxation, off-contraction. Responses were abolished by tetrodotoxin. On-contraction was almost abolished by atropine plus desensitization by 5-hydroxytryptamine (5-HT) or substance P. On-relaxation and off-relaxation were not affected by adrenergic blockade, methysergide, apamin, or 4-aminopyridine. ATP usually caused contraction and slightly diminished relaxation to field stimulation. Vasoactive intestinal polypeptide (VIP) had little effect on tone and response to field stimulation. Relaxation disappeared after scorpion venom treatment. This probably resulted from depletion of the transmitter which mediates relaxation. Off-contraction was reduced by atropine, desensitization by 5-HT or substance P, cromoglycate, indomethacin or ATP, but was not affected by adrenergic blockade, hexamethonium, methysergide, mepyramine, or VIP. The findings suggest that innervation of gastric corpus circular muscle included excitatory cholinergic and both excitatory and inhibitory noncholinergic, nonadrenergic innervation. However, the responses of circular muscle to field stimulation in vitro were drastically different from those obtained previously in vivo, suggesting damage or altered inputs to circular muscle when strips of circular muscle are studied.

Adenosine Triphosphate↗
PubMed1984

Binding and degradation studies on angiotensin II.

125I-labelled angiotensin II (AII) and [3H]AII showed specific binding to rat mesenteric artery microsomes. The binding in either instance was inhibited by the AII analog saralasin. [3H]AII was not degraded by the microsomes but 125I-labelled AII was degraded. Autoradiography of thin layer chromatograms of 125I-labelled AII treated with microsomes showed the parent peak (Rf = 0.4-0.45) and a single major degradation product peak (Rf = 0.25-0.30), and [125I]NaI had an Rf value higher than both 125I-labelled AII and its degradation product. Chromatography of unlabelled AII or [3H]AII gave the same Rf value as 125I-labelled AII, but unlabelled AIII moved with Rf = 0.55-0.60. The formation of the degradation product was time and membrane concentration dependent. The degradation occurred at pH 6 and 7 but not at pH 8. However, specific binding of 125I-labelled AII was also lower at pH 8. The degradation could not be completely inhibited by the use of crude particulate fractions instead of microsomes, by preparing membranes in presence of protease inhibitors, or by including protease inhibitors and sulfhydryl agents in the assay medium. However, the degradation product neither showed specific binding to the microsomes nor interfered with the specific binding of 125I-labelled AII. Furthermore, the tightly bound material eluted from the microsomes in presence of 0.05 M acetic acid at 0 degree C consisted predominantly of the parent compound. The implications of these findings are discussed both in terms of validity of the binding experiments and possible relationship between the degradation and the receptor binding sites in the membrane.

Angiotensin II↗
PubMed1984

Effect of disulphonic stilbenes on Ca2+ transport in smooth muscle plasma membranes.

We studied the effects of two disulphonic stilbenes, 4',4'-diisothiocyano-2,2'-stilbene disulphonic acid (DIDS) and 4-acetamido-4'-isothiocyano-2,2'-stilbene disulphonic acid (SITS), on Ca2+ transport by plasma membrane vesicles from the circular muscle of the dog stomach. Both compounds inhibited ATP-dependent Ca2+ uptake and reduce the leak from loaded vesicles. The inhibition produced could not be significantly reduced by either permeant anions or by increasing the level of free Ca2+. The effects of DIDS could be rendered irreversible by incubating the membranes with this agent at 37 degrees C.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1984

Structural basis for function of circular muscle of canine corpus.

The structural relationship of nerve, muscle, and interstitial cells of Cajal in circular muscle of the lesser curvature of the dog stomach (corpus) has been studied. This muscle has also been characterized functionally. Muscle cells are arranged in bundles and are interconnected by numerous gap junctions averaging 30 per 100 cross-sectioned muscle cells, and leading to an estimate that each cell has about 200 gap junctions. No other smooth muscle studied to date has such a high density of gap junctions. Nerve varicosities, mostly containing a predominance of small agranular vesicles with some containing a predominance of large granular vesicles, are located outside muscle bundles, usually in small- to medium-sized bundles. Very few nerves containing small granular vesicles, presumably adrenergic, were found in agreement with functional studies. A substantial number of damaged nerve profiles was also found, perhaps contributing to the loss of nerve-dependent responses present in vivo, but absent in vitro. Interstitial cells of Cajal were rare in this tissue, about 1 per 1000 cross-sectioned muscle cells. When present, they often made gap junction contact with smooth muscle and were closely innervated. The findings of a structural basis for very tight coupling between cells, the absence of a structural basis for direct neural control over motor function, and other findings have implications for the control of contractions in this muscle.

Animals↗
PubMed1984

Neuromuscular structures in opossum esophagus: role of interstitial cells of Cajal.

The structures of the lower esophageal sphincter (LES) and body circular muscle (BCM) from opossum were compared as to neural and muscular structures and the structural relations of interstitial cells of Cajal to nerves and muscle cells. Both LES and BCM were densely innervated by nerves with varicosities containing many small agranular vesicles and a few large granular vesicles. These nerves were more closely related structurally to the interstitial cells of Cajal than to smooth muscle cells. More gap junctions were observed between smooth muscle cells and between interstitial cells of Cajal and smooth muscle cells in BCM than in LES. Those between smooth muscle cells were larger in BCM. Complete relaxation of the LES strip by isoproterenol reduced these differences but did not eliminate them. The finding that interstitial cells of Cajal often had gap-junction contacts to smooth muscle and close associations with nerves is consistent with the hypothesis that interstitial cells are intercalated between the nerves and muscles and may mediate nerve responses. These findings also suggest that LES muscle cells may be less well coupled electrically than BCM muscle cells.

Animals↗
PubMed1984

Smooth muscle cell herniation in the contracted arterial wall of spontaneously hypertensive and normotensive rats.

Structural changes of blood vessels from hypertensive animals during contraction were studied using light and transmission microscopy. In the arteries, maximally contracted with norepinephrine, vacuoles were found in the media of three categories of mesenteric arteries from two age groups (10-12, 28-30 weeks) of spontaneously hypertensive (SHR) and age-matched normotensive Wistar-Kyoto (WKY) rats. These vacuoles were related to contraction of the smooth muscle cells involving shape change, as they were absent in relaxed vessel walls, and also in muscles that underwent isometric contraction. In the SHR, the number of vacuoles/1,000 microns 2 of media was positively correlated with the degree of contraction of the vessels. Electron microscopic examination of these vacuoles showed that they were the result of herniation (or evagination) of smooth muscle cells into the intercellular space as well as into the neighbouring cells. When the number of herniae per unit cross-sectional area of the contracted media was used as the basis for comparison between SHR and WKY, we found no difference between the two strains of rats at 10-12 weeks of age. At 28-30 weeks, however, the number of herniae was significantly lower in the SHR as compared with age-matched WKY and younger SHR, suggesting that functional changes, that functional changes, probably related to the physical property of the plasma membrane in the smooth muscle cells, have taken place in older SHR.

Animals↗
PubMed1984

Effects of an endogenous cyclic AMP-dependent protein kinase catalytic subunit on Ca-uptake by plasma membrane vesicles from rat mesenteric artery.

A plasma membrane-enriched fraction of vesicles from rat mesenteric artery possessed ATP-dependent calcium properties similar to those which have been reported previously. The catalytic subunit from a soluble, cyclic AMP-dependent protein kinase was prepared from the same tissue, in partially purified form. Calcium uptake by membrane vesicles increased 30% in the presence of this kinase. This effect was proportional to the kinase concentration, and was blocked by either catalytic subunit inhibitor or by prior boiling of the subunit preparation. Stimulation of calcium uptake by the kinase occurred maximally between 1 and 10 microM free calcium. These findings suggest that cyclic AMP and its dependent protein kinase may participate in the regulation of smooth muscle tension at high free myoplasmic calcium concentrations.

Animals↗
PubMed1984

The effect of atropine on allergen-induced increases in bronchial responsiveness to histamine.

We examined the role of cholinergic mechanisms in causing the increase in histamine bronchial responsiveness that follows allergen exposure. Five stable adult atopic asthmatics received inhalation tests with histamine on 2 days after both placebo and a dose of atropine sulphate (18 mg nebulized during tidal breathing), which reduced saliva output. On a third day, an allergen inhalation test was carried out to stimulate a dual asthmatic response. When the FEV1 had returned to within 10% of baseline, the histamine test was repeated after placebo and atropine. Before allergen inhalation, atropine marginally increased the FEV1 (p = 0.12) and reduced bronchial responsiveness to histamine (p = 0.003). When allergen challenge had induced an increase in histamine responsiveness (p = 0.001), atropine again marginally increased FEV1 (p = 0.063) and reduced the responsiveness (p = 0.004) but did not return the responsiveness to the preallergen level (p = 0.023). There was no evidence that the magnitude of the atropine blockade of histamine responsiveness was different before and after allergen (p = 0.92). We conclude that cholinergic mechanisms are not likely to explain the increase in bronchial responsiveness that follows allergen-induced inflammation.

Adult↗
PubMed1984

On the abnormalities of contractile responses of rat vasa deferentia to norepinephrine in genetic hypertension.

Contractile responses to norepinephrine (NE) of strips of vasa deferentia from prostatic end isolated from rats with genetic hypertension and deoxycorticosterone (DOC)-salt induced hypertension were examined. Maximum responses to NE of vasa deferentia from all hypertensive and corresponding normotensive control rats were biphasic. Spontaneous rhythmic activities superimposed on the NE-induced contraction were observed in most of the SHR (spontaneously hypertensive rat) strips, some of the WKY (Wistar-Kyoto normotensive rat) strips and none of the NWR (regular normotensive Wistar rat) strips. Neither the fast- nor the slow-component of the maximum contractile response to NE was altered in the vasa deferentia from SHR compared to those from WKY and in vasa deferentia from DOC-salt hypertensive rats (DHR) compared to those from the corresponding DOC-salt treated but normotensive controls (DNR). However, the strips from NWR developed significantly greater tension than those from WKY and DNR. Our findings suggest that interpretation of studies on hypertension in rats should take into account differences between tissues related to the strain of the rats used as controls for genetic hypertension.

Animals↗
PubMed1984

On the ouabain-sensitive potassium activated p-nitrophenyl phosphatase activity of vascular muscle plasma membranes.

Sodium-pump ATPase is known to be a cell membrane enzyme being responsible for vectorial transport of Na+ against electrochemical gradient across the plasma membranes of most cell types. In smooth muscles, this Na+-pump ATPase activity is notoriously low and its measurement is complicated by remarkably high level of the basal ATPase activities. In this communication, the properties of ouabain-sensitive, potassium-activated p-nitrophenyl phosphatase (pNPPase) activity which is a partial reaction of the Na+-pump are reported and compared in plasma membrane enriched fractions of mesenteric arteries from hypertensive and normotensive rats. The pNPPase activity of isolated plasma membrane vesicles from this vascular muscle is optimally stimulated by low concentrations of KCl (5-25 mM) at pH 7.8. Ouabain at 1.0 mM inhibits up to 75% of the K+-activated pNPPase activity under the optimal assay condition. Osmotic shock of the plasma membrane vesicles resulted in about 30% enhancement of the ouabain-sensitive K+-pNPPase activity compared to the control values. Although apparent difference was observed in this enzyme activity using similar preparations obtained from rats of different strains, the relative enhancement of such ouabain-sensitive K+-pNPPase activities by osmotic shock was not significantly different between vascular membrane fractions from the spontaneously hypertensive rats and the Wistar-Kyoto normotensive rats. Our results suggest that the intrinsic Na+-pump activity of small blood vessels in genetic hypertension in rats is not altered and the isolation procedure does not have differential effect on the orientation of plasma membrane vesicles in fractions obtained from hypertensive and normotensive rats.

4-Nitrophenylphosphatase↗
PubMed1984

Increased density of (3H)-yohimbine binding sites in spontaneously hypertensive rat mesenteric artery.

Specific binding of (3H)-prazosin and (3H)-yohimbine to plasma membrane vesicles of mesenteric arteries from SHR and WKY rats at 16-18 weeks was compared. The radioligand binding was carried out in Mg-MOPS buffer at 25 degrees C for 25 min. There was no change in the density or the affinity of (3H)-prazosin binding in SHR vessels (Bmax 188 +/- 33 fM/mg protein, Kd 1.26 nM) compared with WKY (Bmax 211 +/- 28 fM/mg protein, kd 1.24 nM). However, the Bmax of (3H)-yohimbine binding was moderately, but significantly, increased in SHR arteries (Bmax 323 +/- 22 fM/mg protein) compared with WKY (Bmax 252 +/- 17 fM/mg protein) without any change in the sensitivity (Kd 26 nM versus 25.9 nM). These results suggest that postsynaptic alpha 2-adrenoceptors density is increased in hypertensive rat mesenteric arteries. The role of this increased number of receptors in the pathogenesis of hypertension is not known.

Animals↗
PubMed1984

Pharmacological characterization of the postsynaptic alpha adrenoceptors in vascular smooth muscle from canine and rat mesenteric vascular beds.

Postsynaptic alpha adrenoceptors have been characterized in rat superior mesenteric artery and branches of canine mesenteric artery. l-Phenylephrine, naphazoline and clonidine were used as agonists and prazosin and yohimbine were used as antagonists. The pA2 values for prazosin and yohimbine were determined against these agonists in canine and rat mesenteric arteries. The pA2 values for either prazosin or yohimbine were similar when l-phenylephrine and naphazoline were used as the agonists. The slope of the Schild plot was less than unity for prazosin and yohimbine acting as antagonists to l-phenylephrine in canine mesenteric artery whereas in the rat mesenteric artery, the slopes obtained for either phenylephrine or naphazoline against the antagonists were not significantly different from unity. In rat mesenteric artery, the pA2 value for yohimbine against clonidine was not statistically different from values obtained with the other agonists; however, in the presence of prazosin the dose-response curve to clonidine was biphasic, suggesting that the action of clonidine is mediated through two distinct sites to which prazosin has different affinities. However, these results do not provide definitive support for the concept of functionally independent subtypes of postsynaptic alpha adrenoceptors in rat and canine mesenteric artery.

Animals↗
PubMed1984

Tris inhibits binding and transport of calcium in microsomal fraction isolated from rat vas deferens.

The effect of Tris on Ca2+ accumulation by microsomal membrane fraction isolated from rat vas deferens was studied. Preincubation with Tris of isolated microsomal membranes caused a dose-dependent inhibition of Ca2+ binding in the absence of ATP at low Ca2+ concentration (20 microM). This inhibitory effect of Tris on Ca2+ binding was not observed at high Ca2+ concentration (1 mM). Preincubation of membranes with Tris also resulted in decreased Ca2+ accumulation in the presence of ATP. Both ionomycin-sensitive and -insensitive components of the ATP-supported Ca2+ accumulation were significantly lower in membrane fraction preincubated with Tris than these in the control membrane fraction not treated with Tris suggesting that both Ca2+ binding and active transport of Ca2+ were affected by Tris. This was further supported by the fact that oxalate-stimulated ATP-supported Ca2- accumulation by the membrane was potently inhibited by Tris. This inhibition was more prominent when the membranes were preincubated with Tris. Efflux of Ca2+ into EGTA containing medium from a preloaded membrane fraction was not significantly different whether or not the membrane fractions were preincubated with Tris indicating that the membrane permeability to Ca2+ may not be altered by Tris. Our results provided direct evidence that Tris altered the Ca2+ binding and transport at the subcellular membrane level and may provide a cellular basis for the alterations of contractile function of vas deferens in the physiological saline solution buffered with Tris.

Adenosine Triphosphate↗
PubMed1983

Effect of Tris buffer on the contractile responses of rat vas deferens.

The influences of Tris-(hydroxymethyl)aminomethane (Tris) on the contractile responses of rat vas deferens to norepinephrine (NE), potassium chloride (KCl) and field stimulation were investigated. Equilibration of rat vas deferens muscle strips in Tris containing Tyrode medium caused a significant increase in sensitivity to KCl, but had no effect on the maximum tension induced by NE or KCl. The biphasic responses to 10(-4) M NE and 100 mM KCl, characterized by an initial fast (F) component followed by a slow (S) component, were differentially affected by Tris. The F components of NE- or KCl-induced contractions were significantly potentiated by Tris, whereas the S components of NE- or KCl-induced contractions were depressed. When the muscle strips were washed after NE- or KCl-induced contraction, the rate of relaxation reflecting the rate of loss of the sustained S-component was significantly slower in Tris-Tyrode than in Tyrode medium. In Ca2+ free medium, the F component of NE-induced contraction but not the S component was markedly potentiated by Tris. Verapamil (10(-5) M) eliminated the potentiation by Tris of the F component and further reduced the S component of the NE-induced contraction in the Tris-Tyrode medium. Both F and S components of KCl-induced contractions of rat vas deferens were sensitive to verapamil and these depressant effects were further enhanced in the presence of Tris. The contraction elicited by field stimulation was also biphasic. However, only the S component was significantly depressed by Tris and this inhibitory effect was irreversible. We conclude that Tris can exert adverse effects on the contractile properties of rat vas deferens, probably via the disturbance of Ca2+-handling by the smooth muscle membrane and possibly by affecting release of norepinephrine.

Animals↗
PubMed1983

Sites and mechanisms of action of neuropeptides on canine gastric motility differ in vivo and in vitro.

Motilin, pentagastrin and substance P (SP), injected intra-arterially into the canine gastric corpus in vivo increased the amplitude of contractions by an action dependent on activation of cholinergic nerves; i.e. atropine or tetrodotoxin (TTX) completely blocked the responses to motilin and pentagastrin and increased the ED50 of SP. TTX and atropine were not equally effective in increasing the ED50 for SP in vivo and the effect of combining them depended on the order of their addition. Both were much more effective than the SP analog D-Pro2, D-Trp7,9 SP (DSP) which appeared to be a weak antagonist of actions dependent on neural activity. In strips from the same region in vitro no receptors dependent on cholinergic nerve activation could be demonstrated for any peptide; i.e., all were atropine- and TTX-insensitive. Motilin, as expected in the absence of such receptors caused no contractile response in vitro. SP, also as predicted, caused contractions suggesting that a smooth muscle receptor, independent of nerve activation was present. However contrary to expectation pentagastrin induced an atropine and TTX-insensitive increase in the amplitude and frequency of contractions. These results show that 1) the most sensitive sites of action of a number of excitatory peptides depend on cholinergic nerve function in vivo; 2) such sites or the nerve activity on which they depend cannot be demonstrated in vitro; 3) SP has an additional site of action on smooth muscle demonstrable in vivo and in vitro, but motilin does not; 4) pentagastrin has only an action dependent on nerve function in vivo, but manifests an action independent of nerve function in vitro. We conclude that sites and mechanisms of action of peptides cannot be assumed to be identical in vivo and in vitro. Actions dependent on nerves are often lost in vitro and not all smooth muscle actions can be demonstrated in vivo.

Animals↗