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Biomedical subjects

E E Daniel

Publications and source records attributed to E E Daniel.

At least 289 records · Page 16Linked to original sources
PubMed1985

Target size of 5'-nucleotidase in smooth muscle.

Target size of the 5'-nucleotidase in six different smooth muscles was determined by radiation inactivation. The enzyme in the soluble fraction of rat myometrium and vas deferens gave a target size of approximately 80,000 daltons. The plasma membrane bound 5'-nucleotidase however, gave target size of 80,000 to 110,000 daltons in rat gastric fundus and vas deferens and dog stomach and ileum, 135,000 daltons in rat mesenteric artery and 210,000 daltons in rat myometrium.

5'-Nucleotidase↗
PubMed1985

Agonists interaction with radiolabeled alpha-adrenoceptor antagonists binding sites in rat mesenteric artery.

The nature of the postsynaptic alpha-adrenoceptors in vasculature has been a matter of debate with the differences in the observations from in vivo and in vitro experiments. These studies were done on the basis of the selectivity of the alpha-adrenoceptor agonists. In the present study, we investigated the nature of these agonists interaction with the [3H]prazosin and [3H]yohimbine binding sites in the plasma membrane vesicles of rat mesenteric artery. Phenylephrine and methoxamine were used as the putative alpha 1-adrenoceptor agonists. Clonidine, naphazoline, B-HT 920, and UK-14,304 were used as the putative alpha 2-adrenoceptor agonists. All these agonists except B-HT 920 competed with similar affinity for the specific binding sites of [3H]prazosin and [3H]yohimbine. The order of the potency for the agonists in competing for [3H]prazosin binding sites was clonidine greater than naphazoline greater than UK-14,304 greater than phenylephrine much greater than B-HT 920 greater than or equal to methoxamine, and for the [3H]yohimbine binding sites, the order was clonidine greater than naphazoline greater than B-HT 920 greater than UK-14,304 greater than phenylephrine much greater than methoxamine. Similar pA2 values for prazosin and yohimbine were calculated regardless of whether alpha 1-selective agonist, methoxamine, or alpha 2-selective agonist, B-HT 920 were used. Putative alpha 2-adrenoceptor-selective agonists behave as partial agonists in functional studies inhibiting just maximal responses to alpha 1-adrenoceptor agonists and norepinephrine in a dose-dependent fashion. It is therefore concluded that in rat mesenteric artery, there are two distinct sites of interaction for the antagonists, prazosin and yohimbine, but the alpha-adrenoceptor agonists interact nonselectively with a single site in such a way that they are capable of affecting binding of either antagonist. A model for the postsynaptic alpha-adrenoceptor as a macromolecule has been proposed.

Adrenergic alpha-Agonists↗
PubMed1985

Unusual potassium channels mediate nonadrenergic noncholinergic nerve-mediated inhibition in opossum esophagus.

Field stimulation of the circular muscle of the opossum esophagus produces a transient hyperpolarization (inhibitory junction potential, IJP) followed by an "off" depolarization. A similar nonadrenergic, noncholinergic (NANC) response in guinea pig taenia caecum has been shown to be due to an increase in the potassium ion permeability of the smooth muscle cell membrane. Double sucrose gap studies showed a decrease in resistance during the IJP, and a reversal at an estimated membrane potential of about -90 mV (4 mM K+). The reversal potential was dependent on the extracellular potassium concentration, shifting to -75 mV when the potassium in the superfusion medium was increased to 10 mM. The IJP in the opossum esophageal circular smooth muscle is therefore like the IJP of the guinea pig taenia caecum in that it is probably due to a selective increase in potassium ion permeability. Potassium conductance blocking agents, tetraethylammonium chloride (TEA, 20 mM) and 4-aminopyridine (4-AP, 5 mM) both caused a depolarization of the smooth muscle cell membrane, but TEA increased the membrane resistance, whereas 4-AP did not affect the membrane conductance in a consistent way. A decrease in IJP amplitude owing to these agents was not apparent. Apamin (10 microM) did not affect the membrane potential, the membrane resistance, or the IJP. Quinine (0.1 mM) produced effects quantitatively similar to those of TEA. Quinine (1 mM) did abolish the IJP, however, this was likely due to a blockade of impulse transmission of the intramural nerves.(ABSTRACT TRUNCATED AT 250 WORDS)

4-Aminopyridine↗
PubMed1985

Electrical properties of smooth muscle cell membrane of opossum esophagus.

The electrical properties of the circular smooth muscle layer from the North American opossum esophagus (body) were studied in vitro by microelectrode recording techniques, both at rest and during stimulation of intramural inhibitory nerves. All observations were made at 37 degrees C in an Abe-Tomita partitioned bath on muscle strips dissected 2 cm orad of the lower esophageal sphincter. At rest, the potential of the smooth muscle cell membrane was -49 +/- 4 mV (mean +/- SE); the length constant and the time constant were 2.0 +/- 0.6 mm and 120 +/- 16 ms, respectively. The inhibitory junction potential (IJP) elicited by stimulation of intramural nerves was followed by a "rebound" or "off" response, characterized by a membrane depolarization on which spikes were superimposed and concomitant mechanical activity of the preparation that usually caused dislocation of the recording microelectrode. The maximal IJP amplitude was 35 mV, and the response reversed at a membrane polarization to -90 mV, suggesting that the IJP was due to an increase of the permeability toward potassium ions. The invariability of the IJP latency at different distances from the stimulating electrodes (1.25-4 mm) suggests that the latency is largely due to diffusion of transmitter from nerve varicosities to postsynaptic receptor sites. Depending on the rate, prolonged stimulation caused fusion of IJP or a continuous hyperpolarization of the membrane. The hyperpolarization faded with time, but off responses were only observed after terminating stimulation. The passive electrical properties of the membrane are comparable with those of other gastrointestinal smooth muscles.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Muscarinic inhibition of canine small intestinal motility in vivo.

The quiescent canine gastrointestinal tract responsed to close intraarterial acetylcholine with an atropine-sensitive, hexamethonium, and tetrodotoxin-insensitive contraction, thus suggesting acetylcholine interacts with a muscarinic receptor located on the muscle. When the gut is actively contracting (spontaneously, in response to field stimulation or to motilin), acetylcholine caused a contraction followed by prolonged inhibition of contractions. No such inhibition was apparent after tetrodotoxin; therefore, the receptor for acetylcholine-induced inhibition was apparently on nerves. Neither the acetylcholine-induced excitation nor the inhibition was altered by hexamethonium or reserpine treatment. Both inhibitory and excitatory responses were greatly reduced by atropine, suggesting that both receptors were muscarinic in nature. McNeil A343 produced inhibition but no excitation. Tetrodotoxin, hexamethonium, reserpine, and pirenzepine all increased the concentration of McNeil A343 required for production of 50% inhibition, suggesting it acts via multiple mechanisms. Furthermore, pirenzepine reduced both the inhibitory and excitatory response to acetylcholine, suggesting that it is nonselective in its action on the neural inhibitory or muscular excitatory receptors. We suggest that the presynaptic muscarinic receptor responsible for inhibitory effects of acetylcholine is on the postganglionic cholinergic neuron itself and constitutes an important negative-feedback loop to reduce excessive cholinergic output. Although such a mechanism has been found in vitro previously, this is the first report in vivo in canine small intestine.

(4-(m-Chlorophenylcarbamoyloxy)-2-butynyl)trimethy↗
PubMed1985

Capsaicin effects on muscularis mucosa of opossum esophagus: substance P release from afferent nerves?

The effects of capsaicin on the function and structure of muscularis mucosa of opossum esophagus were studied. In this tissue there are numerous nerves containing a substance P-like immunoreactive substance (SPLS), and electrical field stimulation (EFS) leads to a phasic response that appears to be due to release of acetylcholine, followed by a tonic response at higher frequencies of stimulation that appears to be due to release of a SPLS. The acetylcholine released by EFS and exogenous muscarinic agonists inhibits release of this SPLS (8). In the present study capsaicin (5 X 10(-5) M) was shown to cause a tonic submaximal contraction in most cases. This was prevented by substance P tachyphylaxis and by pretreatment with the partial agonist [D-Pro2, D-Trp7,9]substance P, the antagonist [D-Arg1, D-Trp7, Leu11]substance P, and tetrodotoxin. This response to capsaicin could not be repeated even after 2 h. Capsaicin also abolished the tonic response to high-frequency EFS without affecting phasic responses and reduced markedly the enhanced tonic response after atropine had abolished the phasic response. This occurred with or without a preliminary contraction to capsaicin. This tonic response to high-frequency EFS recovered completely 1-2 h after washing out capsaicin. Then, a further administration of capsaicin had no direct effect but again abolished tonic responses to EFS. Capsaicin reduced responses to exogenous substance P or carbachol only partially. When tissues were fixed and studied after capsaicin had abolished tonic responses to EFS, specific damage to nerve varicosities or synaptic vesicles in nerve varicosities could not be demonstrated.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗
PubMed1985

Limited bronchoconstriction to methacholine using partial flow-volume curves in nonasthmatic subjects.

We investigated whether the plateau of the dose-response to nonsensitizing stimuli, such as methacholine, could be explained by the airway dilation that follows lung inflation in nonasthmatics. We used maximal expiratory partial flow-volume curves to measure the response of the airways to doubling doses of inhaled methacholine up to 256 mg/ml (a noncumulative dose of 340 mumol delivered to the mouth during tidal breathing) in 12 nonasthmatics on 2 days. Maximal expiratory complete flow-volume curves and FEV1 were also obtained along with the partial curves. Flows were measured at 40% of control vital capacity using the complete (V40c) and the partial (V40p) curves. A maximal response plateau of 2 or more doubling concentrations was demonstrated in all subjects based on V40p, and in 10 subjects based on FEV1. The level of the plateau was the highest for the V40p (mean +/- SD = 65 +/- 19% of baseline), intermediate for V40c (45 +/- 22%), and the lowest for FEV1 (16 +/- 11%). There was more than a 100-fold range in responsiveness expressed as the provocative concentration to cause a 40% fall of baseline in V40p (PC40); the lower the PC40, the higher the level of the plateau. All the results were reproducible between the 2 days. We also investigated whether the plateau may have been due to a tachyphylactic effect of cumulative doses of methacholine. The maximal response after increasing concentrations of methacholine up to 256 mg/ml was not different from the response obtained after a single dose of 256 mg/ml.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Limited maximal airway narrowing in nonasthmatic subjects. Role of neural control and prostaglandin release.

In nonasthmatic subjects with normal airway responsiveness to methacholine, maximal airway narrowing is limited to a mild or moderate degree. We investigated whether the maximal response plateau or the position of the dose-response curve is due to functional inhibition by neurogenic mechanisms or to prostaglandin release. Four nonasthmatics inhaled doubling concentrations of methacholine up to 256 mg/ml (67 mg delivered during tidal breathing), followed by 4-fold-increasing doses of salbutamol up to 80 mg/ml (24 mg during tidal breathing) on 5 separate days. On each day 30 min before the test, the subjects inhaled (using a dosimeter) saline, propranolol (11 mg), or hexamethonium (910 mg) or, 2 h before the test, ingested indomethacin (75 mg) or placebo. The response to methacholine was measured from volume history standardized partial and complete maximal expiratory flow-volume curves, as FEV1 and the flows at 40% of the control FVC (V40p and V40c). Compared with saline, on average, baseline V40p was 18% lower after propranolol and 18% higher after hexamethonium. Indomethacin did not affect baseline values. There was no systematic difference between the 5 days in the dose of methacholine to cause a 10% fall in FEV1 or a 40% fall in V40p, or in the maximal response with FEV1, V40p, and V40c, or in V40p/V40c at 256 mg/ml methacholine. We conclude that limited maximal airway narrowing to methacholine in nonasthmatics is not due to a change in adrenergic, cholinergic, or ganglion-transmitted-nonadrenergic inhibitory activity nor to the release of prostaglandins.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Two distinct populations of [3H]prazosin and [3H]yohimbine binding sites in the plasma membranes of rat mesenteric artery.

Postsynaptic alpha adrenoceptor subtypes have been investigated by radioligand binding studies in plasma membrane vesicles prepared from rat mesenteric arteries using [3H]prazosin and [3H]yohimbine. Both the radioligands displayed monophasic saturation in binding with a single component on Scatchard analysis. In the estrogenized female rat mesenteric artery, the specific binding of [3H]prazosin was rapid, saturable, reversible and of high affinity (0.65 +/- 0.05 nM) with a maximum binding capacity (Bmax) of 177 +/- 14 fmol/mg of protein. The maximum number of [3H]yohimbine binding sites were 427 +/- 31 fmol/mg of protein with the Kd equal to 34.5 +/- 3.8 nM. There was no evidence of cooperativity in the binding of both the ligands. The Kd values of [3H]prazosin and [3H]yohimbine, calculated from their respective kinetic analyses of binding, were in good agreement with the Kd values estimated from Scatchard plots. Prazosin was 15,000 times more potent in competing at the [3H]prazosin binding sites than at the [3H]yohimbine sites. In contrast, unlabeled yohimbine was 100-fold more potent in competing at the [3H]yohimbine binding sites than at the [3H]prazosin sites. The affinity of BE 2254 was 10,500 times higher for the [3H]prazosin binding sites than its affinity for the [3H]yohimbine binding sites. Non-alpha adrenoceptor antagonists competed poorly for both the radioligand binding sites. The Kd and Bmax of [3H]prazosin and [3H]yohimbine binding in the membranes of male rat mesenteric arteries were not significantly different from the corresponding values in the membranes of estrogenized female rat mesenteric artery.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Subcellular distribution of dihydropyridine isothiocyanate binding in guinea-pig ileal smooth muscle.

The subcellular distribution of the 3H--2,6-dimethyl-3,5-dicarbomethoxy-4(2-isothiocyano) phenyl-1,4-dihydropyridine (DPSCN) binding to guinea-pig ileal smooth muscle was studied by subcellular fractionation. Initial experiments on subcellular fractionation of 3H-DPSCN-labelled tissues by differential centrifugation showed that there was an excellent correlation between the levels of the label present in a fraction and the plasma membrane marker phosphodiesterase I (r = 0.98) but not between the label and the putative endoplasmic reticulum marker NADPH: cytochrome-c-reductase (r = 0.56) or the inner mitochondrial marker cytochrome-c-oxidase (r = 0.36). Centrifugation of the microsomes on a continuous sucrose density gradient showed an excellent correlation of the migration of the label with phosphodiesterase I activity (r = 0.93) but not with the activities of NADPH: cytochrome-c-reductase (r = 0.66) or cytochrome-c-oxidase (r = 0.44). Treatment of microsomes with digitonin (1 mg/ml) followed by centrifugation on continuous sucrose density gradients increased the weighted mean densities of the phosphodiesterase activity (plasma membrane marker) and the labelling by similar magnitudes (0.04 to 0.06 g/ml). The weighted mean densities of NADPH: cytochrome-c-reductase and the cytochrome-c-oxidase were not altered significantly. It is concluded that in the guinea-pig ileal smooth muscle, DPSCN labels the plasma membrane specifically.

Animals↗
PubMed1984

The mechanism of motilin excitation of the canine small intestine.

Close intraarterial injections of motilin to the small intestine of the anaesthetized dog produce prolonged phasic contractions. Tetrodotoxin infused intraarterially blocked field stimulated contractions and abolished the response to motilin as did treatment with a combination of hexamethonium and atropine. Atropine alone increased the dose of motilin required to induce responses. Hexamethonium alone similarly increased the dose of motilin required in the jejunum, but not for the ileum. These results suggest that motilin acts to contract small intestine by stimulation of intrinsic excitatory nerves, some of which are post-ganglionic cholinergic and some of which are not, but are activated by a pathway with a nicotinic synapse. The ED50 for ileal contractions was greater than that for the jejunum and the time to reach maximum contractions longer suggesting a decreased responsiveness of the lower small intestine to motilin as compared to the upper gastrointestinal tract. These results and the lesser quantity of immunoreactive motilin in the ileum than in the jejunum may explain the lack of relationship of the activity front of the migrating motor complex in the lower small intestine to venous motilin concentrations.

Animals↗
PubMed1984

Subcellular distribution of [3H]nitrendipine binding in smooth muscle.

Distribution of specific binding sites for [3H]nitrendipine was studied in subcellular fractions isolated from rat gastric fundus smooth muscle and from rat myometrium. There was an excellent correlation between the distribution of [3H]nitrendipine binding determined at the nitrendipine concentrations of 0.138 and 1.38 nM, and the distribution of the plasma membrane markers K+-activated ouabain-sensitive p-nitrophenylphosphatase, 5'-nucleotidase, phosphodiesterase I, and Mg-ATPase, but not between the mitochondrial markers cytochrome c, oxidase, succinate-dependent cytochrome c reductase, or rotenone-insensitive NADH-dependent cytochrome c reductase or the putative endoplasmic reticulum marker NADPH-dependent cytochrome c reductase. The binding occurred with high affinity and with a similar (0.097-0.146 nM) equilibrium dissociation constant to all the fractions, even though the density of binding sites varied and was highest in the plasma membrane marker-enriched fractions. The maximal binding in the plasma membrane-enriched fraction from the rat gastric fundus smooth muscle was 0.43 +/- 0.04 pmol/mg, and in that from rat myometrium was 0.72 +/- 0.09 pmol/mg. Thus in the two smooth muscles studied the plasma membrane is the locus of the high affinity nitrendipine binding.

Animals↗
PubMed1984

Dense-cored membranous structures in smooth muscle cells of the vas deferens of the rat.

Smooth muscle cells from rat vas deferens were studied by electron microscopy. Vesicular and tubular membranous structures containing an electron-opaque material were found in the smooth muscle cells. Similar structures were also found in a subfraction (F3) of microsomes of vas deferens smooth muscle which was shown to be rich in both plasma membrane and putative endoplasmic reticulum markers. Treatment of the tissues with calcium-free Krebs solution containing EGTA prior to fixation eliminated almost completely the presence of these dense-cored membranous structures (DMS), whereas incubation of the subcellular membrane fraction with EGTA solution had no effect on the appearance of the DMS. Plasma membrane infoldings were found in the smooth muscle cells extending well into their interior. Horseradish peroxidase penetrates vesicles in a location similar to that of DMS in smooth muscle cells, suggesting that some of the DMS may be connected to the extracellular space. We conclude that the dense-core material within the DMS is calcium dependent. We also suggest that some of the DMS represent infoldings of the plasma membrane extending into the cell's interior.

Animals↗
PubMed1984

Membrane fractionation of canine aortic smooth muscle: subcellular distribution of calcium transport activity.

Various subcellular membrane fractions were isolated from dog aortic smooth muscle by conventional differential centrifugation followed by isopycnic centrifugation on a sucrose density gradient. These subcellular fractions were characterized by membrane marker enzyme activities, morphological features and the electrophoretic patterns on a sodium dodecyl sulfate polyacrylamide gel. Our results showed that the microsomal membrane fraction isolated by differential centrifugation was very heterogeneous and contained substantial amount of plasma membranes which could be further enriched as a light density fraction on the sucrose density gradient. The subcellular distribution of Ca2+ binding in the absence of ATP and Ca2+ transport in the presence of ATP closely paralleled the distribution of plasma membrane markers. The ATP-supported Ca2+ transport was inhibited by several Ca2+ ionophores, enhanced by inorganic phosphate and oxalate ions and cosedimented toward higher density in a continuous source density gradient with plasma membrane marker enzyme activity in the presence of digitonin. Our present work strongly suggests that plasma membrane is the predominant component of microsomal fraction and responsible for most, if not all, of the azide-insensitive ATP-supported Ca2+ accumulation.

Adenosine Triphosphate↗
PubMed1984

Contractile responses of vasa deferentia from rats with genetic and experimental hypertension.

The changes in hypertension of the characteristics of the contractile responses of the prostatic portion of the vasa deferentia to norepinephrine (NE), K+, Ca2+ and transmural field stimulation were investigated. Responses of strips from Wistar-Kyoto strain normotensive rats (WKY) were compared to those of strips from spontaneously hypertensive rats (SHR). Also strips from regular normotensive Wistar rats (NWR) which failed to develop hypertension after deoxycorticosterone (DOC)-salt treatment (DNR) were compared to those from NWR with DOC-salt induced hypertension (DHR). Cumulative dose-response curves to NE or KC1 were similar for strips from controls and hypertensive animals in both forms of hypertension. The relaxation of strips from NE contraction after drug washout followed a single exponential component and was slower for those from SHR than for the control but the relaxation rate of strips from DHR was not significantly different from that of the control strips. Relaxation of vasa deferentia from high K+-contraction displayed two exponential components. Significantly slower relaxation was found only in the second component in SHR compared to that in WKY. The relaxation rate was not different in either component of the relaxation response after washout of KC1 in vasa deferentia from DHR and DNR. The maximum contractile responses to NE, were unchanged in hypertension but differed between groups used to study genetic and experimental hypertension. The maximum contractile responses to NE were significantly higher in both DNR and DHR than in strips from either WKY or SHR. The contractile response of vasa deferentia to Ca2+ in potassium depolarized muscle was increased significantly at higher Ca2+ concentration in DHR compared to DNR.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Cellular calcium mobilization.

In vascular and other smooth muscles, occurrence of intracellular Ca stores which can be mobilized to support contraction may be a general phenomenon. The Ca stores are characterized by the requirement for release by high concentrations of agonists acting on plasma membrane receptors, by the failure of the released Ca2+ to recycle to the store, by the occurrence of rapid refilling of the store from the extracellular space, and by disappearance of the store when the plasma membrane is made leaky by saponin. In contrast to agonist-released Ca stores, those released by caffeine to support contraction in Ca2+-free solutions are more slowly lost and refilled, are not always emptied when the agonist-related store is emptied, and do not disappear after saponin treatment. Stores released by agonists have been suggested to be in the endoplasmic reticulum near the plasma membrane or at the inner aspect of the plasma membrane related to high affinity, pH-dependent Ca-binding sites. Caffeine-released stores are assumed to be in endoplasmic reticulum. Continued exposure of some tissues to Ca2+-free solutions unmasks what is considered to be a recycling Ca store releasable by agonists. Release of Ca2+ and its reaccumulation in this store appear to be slower than at the nonrecycling store. The contractions which persist for many hours in Ca2+-free solution are inhibited temporarily by Ca2+ restoration. Existence of a recycling store of releasable Ca2+ requires occurrence of mechanisms to abolish Ca2+ extrusion or leak-out of the cell and to ensure recycling to the same store.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Early structural changes in precapillary vessels in hypertension and their relationship to functional changes.

This presentation has reviewed evidence from our laboratory that both structural and functional changes participate in the initiation and maintenance of hypertension in spontaneously hypertensive rats (SHR). Structural changes are present in the muscular arteries of the mesenteric and renal vasculature at 3- to 5-week-old SHR as compared with WKY. The major structural change in SHR arteries was increased cross-section area with increased thickness of the media owing to hyperplasia of smooth muscle; lumen sizes were interchanged. Later, at 10-12, 21, and 28 weeks of age, there was further increase in medial thickness owing to hyperplasia, and some hypertrophy and changes in elastic arteries also became evident. Increases in medial thickness of elastic arteries included hypertrophy as well as hyperplasia. Changes in lumen diameter were never observed in arteries fixed in a relaxed state at physiological flow rates. In addition, a deficit in Ca handling (decreased ATP-dependent Ca2+ accumulation) was observed in plasma-membrane vesicles from mesenteric arteries of SHR prior to and after the development of hypertension. It persisted when hypertension was reversed by hydralazine in SHR. It was present in various forms of experimental hypertension. It was present whenever hypertension was present and disappeared with normalization of blood pressure by withdrawal of the stimulus. The Ca-handling deficit was found in several nonarterial tissues and may be a generalized genetic defect in SHR. It was always accompanied by increased alkaline phosphatase activity of plasma membranes, and this was suggested to reflect the smooth-muscle hyperplasia occurring simultaneously. A model of the initiation and maintenance of hypertension based on medial thickening and deficient Ca handling as primary, interacting causes of genetic hypertension is proposed.

Animals↗