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Biomedical subjects

E E Daniel

Publications and source records attributed to E E Daniel.

At least 325 records · Page 18Linked to original sources
PubMed1983

An analytical approach to the preparation and characterization of subcellular membranes from canine mesenteric arteries.

Subcellular membrane fractions were isolated from dog mesenteric arteries by differential and isopynic sucrose density gradient centrifugations. Isolated membrane fractions were characterized by marker enzyme activities, morphological features and sodium dodecyl sulfate-polyacrylamide gel electrophoretic patterns. Our results show that the microsomal fraction isolated by conventional differential centrifugation was highly heterogenous and contained substantial amount of plasma membranes which could be further enriched as a light density membrane fraction on a discontinuous sucrose density gradient. The microsomal fraction and its subfractions were vesicular in appearance under electron microscope and were capable of binding and actively transporting Ca2+. The binding of Ca2+ and ATP-supported Ca2+-transport in the presence or absence of oxalate paralleled the distribution of plasma membrane marker enzyme activities suggesting that plasma membranes in vascular smooth muscle may play a major role in handling Ca2+ and thus the control of contractile function.

Adenosine Triphosphate↗
PubMed1983

Neither a purine nor VIP is the mediator of inhibitory nerves of opossum oesophageal smooth muscle.

Effects of stimulation of intramural nerves in the circular smooth muscle layer of the body of the oesophagus of the opossum (Didelphis marsupialis) were studied, simultaneously measuring the membrane potential of muscle cells using the sucrose-gap technique and contractions of the muscle. Electrical field stimulation of the preparation, superfused with Krebs solution at 27 degrees C, induced a transient hyperpolarization of the smooth muscle cell membrane (i.j.p.) followed by a transient depolarization on which muscle action potentials were often superimposed. The muscle did not develop active tension spontaneously; it therefore did not relax during the i.j.p., but often contracted during the 'off' depolarization. The i.j.p. and the responses following it were characterized as mediated by intramural, non-adrenergic, non-cholinergic (n.a.n.c.) nerves. The i.j.p. amplitude was reduced by raising the external K concentration. When Cl was replaced by isethionate, a small hyperpolarization of the smooth muscle cell membrane ensued along with a comparable small reduction of the i.j.p. amplitude. The 'off' activity following the i.j.p. disappeared completely in Cl-free medium. Apamin (10(-7)-10(-5) M) did not influence this preparation nor the i.j.p. Adenosine and its related adenine nucleotides in concentrations up to 10(-3) M hardly affected the preparation. Prolonged superfusion with adenosine and 6-chloroadenosine revealed a gradually increasing attenuation of the i.j.p. Exogenously applied vasoactive intestinal polypeptide (VIP) induced rhythmic depolarizations of the smooth muscle cell membrane and spontaneous contractions, which were insensitive to neurotoxins but absent in Cl-free media. Field stimulation in the presence of VIP caused an i.j.p. which transiently interrupted the VIP-induced contractile responses. It is concluded that the inhibitory mediator of the intramural n.a.n.c. nerves present in the circular smooth muscle layer of the opossum oesophagus is neither a purine nor VIP. The i.j.p. may result from a selective increase in K permeability of the smooth muscle cell membrane, the 'off' depolarization may involve an increase in the Cl ion conductance. The suggestion is made that the release of neurotransmitter from intramural n.a.n.c. nerves is modulated presynaptically via P1-purinoceptors and that VIP is a likely candidate for an excitatory transmitter, released simultaneously with the inhibitory transmitter.

Action Potentials↗
PubMed1983

Uptake and release of calcium by canine gastric corpus smooth muscle plasma membrane enriched fraction.

Calcium movements across plasma membrane enriched vesicles isolated from canine gastric corpus smooth muscle were investigated. The ATP-dependent Ca2+ uptake increased with time up to 10 min. The uptake for the initial 2-min period was approximately linear with time. The apparent initial velocity of the ATP-dependent Ca2+ uptake increased monotonically with free Ca2+ concentration from 0.1 to 2 microM, and further increases in free Ca2+ concentration did not increase the Ca2+ uptake. The free Ca2+ dependence curve could be described with a Hill coefficient of approximately 1.0 and Km of 0.85 +/- 0.01 microM for free Ca2+ concentration. Passive Ca2+ uptake (reaction time = 1 h) also increased with increasing free Ca2+ concentrations from 0.02 to 4.0 mM. Dilution of loaded vesicles in isotonic media containing EGTA led to initial rapid loss (less than 1 min) followed by a slower release which showed simple exponential decay. The t 1/2 values of the slower Ca2+ loss from these vesicles were 16.1 +/- 0.9 min (actively loaded n = 5) and 18.4 +/- 0.9 min (passively loaded n = 3), respectively. Dilution in isotonic medium containing both EGTA and A23187 released all the sequestered Ca2+ from these loaded vesicles.

Adenosine Triphosphate↗
PubMed1983

Studies of the mechanism of passive anaphylaxis in human airway smooth muscle.

This investigation was carried out to study allergic contraction of passively sensitized human airway smooth muscle in response to specific antigen challenge. We attempted to determine the role played by histamine, slow reaction substances (SRSs), and cyclooxygenase products in the mediation of this response in tracheal smooth muscle. Tissues were passively sensitized with serum from ragweed-sensitive patients (15 h, 4 degrees C). Subsequent challenge with ragweed antigen produced a slowly developing contraction. The peak contraction to a dose producing a maximal response was 37 +/- 6% of the carbachol maximum. Mepyramine (5 X 10(-6) M) did not alter the contraction. Methylprednisolone (2 X 10(-5) M) attenuated the response to antigen but had no significant effect on the contractile response to arachidonic acid. Indomethacin (5.6-28 X 10(-6) M) enhanced the peak antigen-induced contractions by 25 +/- 11% whereas 5,8,11,14-eicosatetraynoic acid (6.4 X 10(-5) M) selectively attenuated the antigen-induced contraction by 86 +/- 12%. Nordihydroguarietic acid (6-12 X 10(-6) M) attenuated both the antigen plus arachidonate induced responses. FPL-55712 (1-2 X 10(-6) M) antagonized the contractions to antigen. Compound 48/80 and goat antihuman immunoglobulin E produced similar slowly developing contractions in sensitized and in some nonsensitized tissues. These responses, except for an early component of the response to 48/80, were independent of histamine and were reversed by FPL-55712. These findings suggest that arachidonic acid metabolites mediate (slow reacting substances) and modulate (prostaglandins) allergic contraction of human airway smooth muscle while any histamine released contributes little or nothing to the contraction in the larger airways.

Anaphylaxis↗
PubMed1983

Cholinergic control mechanisms for immunoreactive motilin release and motility in the canine duodenum.

The relationship of immunoreactive (IR) motilin release from the duodenum to duodenal motility changes was investigated in anaesthetized dogs. Stimulation of one or both vagi at 5 or 15 Hz or field stimulation of intrinsic duodenal nerves produced significant increases in duodenal vein IR motilin concentrations and accompanying increases in duodenal motility. However, only stimulation of both vagi at 15 Hz produced significant changes in peripheral venous concentrations of IR motilin. These occurred after a delay at a time when both the duodenum and the antrum were quiescent. Either hexamethonium or atropine blocked IR motilin release induced by stimulation of intrinsic or extrinsic nerves while only atropine inhibited the release induced by intraarterial carbachol. The response stimulated by carbachol and blocked by atropine was tetrodotoxin insensitive and the muscarinic receptor involved was presumably located on a nonneural structure. The site sensitive to hexamethonium was presumably the neural pathway which terminated at the muscarinic receptor. Concomitant studies of duodenal motility responses to vagal and field stimulation suggested a conventional neural pathway with preganglionic cholinergic nerves in the vagus, postganglionic cholinergic nerves in the duodenum (activated by field stimulation) and a smooth muscle muscarinic receptor. Activation of antral motility by stimulation of the abdominal vagus or intraarterial carbachol injections to the antrum increased duodenal IR motilin release in the absence of duodenal motility. Thus activation of the intrinsic nerves which cross the pylorus initiated IR motilin release as well as inhibited duodenal motility.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

Human female bladder and its noncholinergic contractile function.

The response of human female detrusor muscle to field stimulation at varying voltages, durations, and frequencies was studied in vitro. In addition, the effects of adrenergic and cholinergic agonists and antagonists, and various nerve toxins were studied. Beta-adrenergic receptors were found in detrusor muscle but no significant adrenergic innervation was seen; no alpha-adrenergic receptors were seen. Atropine, scorpion venom, tetrodotoxin, beta bungarotoxin and hemicholinium were found to inhibit bladder contraction at short-pulse durations and low frequencies by approximately 50%. Black widow spider venom was seen to abolish bladder contractions entirely. It is concluded that acetylcholine is the neurotransmitter responsible for approximately 50% of bladder contraction. The remaining 50% would seem to be noncholinergic and not dependent on fast sodium channels for transmission of excitation, but would seem to be due to a structure with a short-membrane time constant, such as nerve, and is sensitive to black widow spider venom.

Atropine↗
PubMed1983

Structural bases for neural and myogenic control of human detrusor muscle.

The ultrastructure of normal and neurotoxin-treated human detrusor muscle was studied to define the bases for myogenic and neurogenic control and to determine the extent and selectivity of effects of the toxins. No gap junctions were observed in the 30 strips studied but there were other cell-to-cell junctions which may allow cell-to-cell coupling. Nerve varicosities in the muscle bundles were present in high frequency (9 to 15 profiles per 100 muscle cell profiles); they sometimes formed close contacts with muscle and most were bare or partly bare of glial covering. They were often present as single axons or in bundles of only a few nerves. No myelinated nerves or nerve cell bodies were seen in or near muscle bundles. This muscle seemed to be designed primarily for neural control of contractile function with single nerves innervating discrete muscle regions. Most of the nerve varicosities contained a large majority of small agranular vesicles along with some large granular vesicles, but about 20% contained a few small granular vesicles as well. The proportion of the small granular vesicles was not increased but the percentage of varicosities containing them increased slightly after treatment with 5- or 6-hydroxydopamine. Scorpion venom seriously damaged 80% of nerve varicosities, sparing no particular class, but spared axons from structural damage. Beta-bungarotoxin had similar effects. 4-Aminopyridine did not induce gap junction formation but had neurotoxic effects. These data suggest that scorpion venom is a useful tool to eliminate selectively physiological functions dependent on synaptic vesicles, that all nerve types contain scorpion venom binding Na channels and that the persistent atropine- and tetrodotoxin-insensitive responses of this muscle involve mechanisms independent of synaptic vesicles observable by electron microscopy. The common occurrence of multilamellar membranous structures in bladder muscle cells was reported and their origin suggested.

Axons↗
PubMed1983

High-affinity pH-dependent passive Ca binding by myometrial plasma membrane vesicles.

Rat myometrium plasma membrane-(PM) enriched fraction N1 binds calcium passively in a pH-dependent manner at a Ca2+ concentration of 1 microM. The Ca binding increases with increasing pH from 6.27 to 7.47 with a half maximum near 6.8. The difference between binding at 6.27 and 7.07 (the pH-dependent Ca binding) depends on the pH of the reaction medium rather than the pH of the medium in which the membranes had previously been suspended. The pH-dependent Ca binding is not an artifact due to EGTA, the pH buffer used, or soluble protein trapped inside the membrane vesicles. The pH-dependent Ca binding occurs with a dissociation constant value of 0.28 microM and Hill coefficient of 2.37 for Ca2+. The high affinity pH-dependent Ca uptake and the release of Ca2+ from the membranes is virtually complete in 10 s in the presence of 1 microM A23187 but not in its absence. The distribution of the pH-dependent Ca binding in the various rat myometrium subcellular fractions parallels the activity of 5'-nucleotidase in these fractions and not the activities of NADPH-dependent or succinate-dependent cytochrome c reductases. The high affinity and rapid binding and release of Ca at the pH-dependent Ca binding sites in the PM-enriched fraction suggests that the binding and release from these sites may play a key role in excitation-contraction coupling of the smooth muscle.

Animals↗
PubMed1983

Na-Ca exchange in a smooth muscle plasma membrane-enriched fraction.

Na-Ca exchange in the plasma membrane-enriched fraction N1 isolated from rat myometrium has been demonstrated as Ca gain or loss depending on the direction of the [Na+] gradient [Grover et al., Am. J. Physiol. 240 (Cell Physiol. 9): C175-C182, 1981]. In this study, the [Na+]gradient-dependent Ca uptake by this membrane fraction was demonstrated to occur optimally at pH 6.67; and 7.0 +/- 2.2 microMs Ca2+ was required for the half-maximal uptake. Such Ca uptake occurred in vesicles previously loaded with a [Ca] that was the same as or higher than the one present in the Ca-uptake medium, i.e., as an uphill Ca-transport process. The Na-Ca exchange-dependent Ca uptake was abolished by the Ca ionophore A23187 or by the monovalent cation (Na+) ionophore monensin. It was not influenced by the presence of KC1, KC1 plus valinomycin, or the proton uncouplers carbonyl cyanine p-trifluoromethoxyphenyl hydrazone or 5'-chloro-3-t-butyl-2'-chloronitrosalicylanilide in the Ca-uptake medium. The properties of the Na-Ca exchange are compared with those of passive and ATP-dependent Ca uptake by this membrane fraction, and physiological implications of this process are discussed.

Animals↗
PubMed1983

Does substance P comediate with acetylcholine in nerves of opossum esophageal muscularis mucosa?

In opossum esophagus the highest density of varicose substance P-like immunoreactive deposits was in the muscularis mucosa, and this muscle layer, which is thick and prominent, was the most sensitive in contracting to exogenous substance P. On field stimulation, a tetrodotoxin-sensitive biphasic contraction was produced; an initial phasic component was followed after cessation of stimulation by a prolonged tonic component. This contractile response was unaffected by guanethidine or antagonists to several nerve mediators and to histamine and serotonin antagonists. Each component showed a different frequency dependence. The phasic component was abolished by atropine and potentiated by physostigmine; the tonic component was reduced or abolished after carbachol or physostigmine and potentiated by atropine. The tonic component was inhibited after substance P tachyphylaxis or by the substance P antagonist [D-Pro2, D-Trp7,9]substance P. On electron microscopic examination, the majority of nerve varicosities contained a mixture of small agranular and large granular vesicles. We postulate that acetylcholine and substance P may coexist in and be coreleased from nerves of this muscle and that the acetylcholine release occurs first, causing an initial phasic response and delaying and diminishing the release of substance P. The two mediators cause muscle contraction by actions on independent receptors.

Acetylcholine↗
PubMed1983

Morphometric study of structural changes in the mesenteric blood vessels of spontaneously hypertensive rats.

Structural changes of three categories of mesenteric arteries (representing elastic, muscular and arteriolar vessels) from 10- to 12-week-old and 28-week-old spontaneously hypertensive rats (SHR) were studied morphometrically at the light microscope level, and the results compared with age-matched Wistar-Kyoto normotensive rats. In 10- to 12-week-old SHR, hypertrophy of the vessel wall occurred only in the muscular and arteriolar vessels. At 28 weeks, further thickening of the vessel wall occurred in the muscular and arteriolar vessels, and the superior mesenteric artery (elastic vessel) was also thickened in the SHR. There was no evidence that the wall of the relaxed hypertrophied vessels encroached upon the lumen of the vessel. The structural basis for the increase in the vessel wall thickness varied with vessel type. In the superior mesenteric artery, increase in the media at 28 weeks of age would be consistent with hypertrophy of the smooth muscle cells. In the large muscular arteries, at 10-12 weeks of age, increase in medial mass occurred with increase in the number of the smooth muscle cell layers whereas at 28 weeks further increase in media could be due to hypertrophy of the smooth muscle cells. In the small arteriolar vessels, medial enlargement was due at all ages to an increase in the number of smooth muscle layers. Our results show that in the SHR hypertrophy of the media occurs not only in the small arteriolar vessels, but also in large elastic and muscular arteries.

Animals↗
PubMed1983

Ultrastructural changes in mesenteric arteries from spontaneously hypertensive rats. A morphometric study.

Morphometric measurements at the electron microscope level were carried out on three categories of mesenteric arteries representing elastic (superior mesenteric), muscular and arteriolar vessels, from 10- to 12-week-old spontaneously hypertensive rats (SHR) and age-matched Wistar-Kyoto normotensive rats (WKY). Changes were observed only in muscular and arteriolar vessels of SHR, mainly as thickening of the vessel wall due to hypertrophy of the media. In muscular arteries, hypertrophy of the endothelial cells, widening of the subendothelial space, increased volume of the internal elastic lamina (IEL), and both hyperplasia and hypertrophy of the smooth muscle cells (SMC) in the media contributed to the wall thickening. In arteriolar vessels, increase in the subendothelial space and IEL, and hyperplasia of the SMC in the media were involved in the increased thickness of the vessel wall. There was no difference in the collagen content in all vessels, but elastin was increased in the muscular and arteriolar vessels of SHR. Nerve density was also increased in arteriolar vessels of SHR. These changes, especially the increase of SMC in muscular and arteriolar vessels, may be related to the elevated blood pressure in SHR.

Animals↗
PubMed1983

Comparison of blood vessel wall dimensions in normotensive hypertensive rats by histometric and morphometric methods.

The histometric method is often used in hypertension studies in order to reconstruct, from cross-sectional profiles of vessels in the contracted state, a hypothetical relaxed state of the vessels based on the measured length of the internal elastic lamina (IEL). In this study, the accuracy of the histometric method was tested by comparing values obtained with the histometric method from contracted vessels versus values from morphometric measurements of vessels of the same calibre but maximally relaxed. Mesenteric arteries from spontaneously hypertensive and normotensive Wistar-Kyoto rats were used. We found that the lumen size of the vessels was dependent on the methods of measurement and preparation. Lumen size, determined with the histometric method from contracted vessels, tended to be underestimated mainly because the IEL became shortened during contraction of the vessels. When vessels were prepared by perfusion fixation, a high perfusion flow rate (7.6 ml/min) caused expansion of the lumen in muscular (lumen diameter 120--250 microns) and arteriolar vessels (40--100 microns), but not in the elastic arteries (400--700 microns). The cross-sectional area of the vessel wall, however, remained unchanged when the vessels were either contracted with norepinephrine or expanded with high transmural pressure, so morphometric measurements of the vessel wall and its components can be done on both contracted and relaxed vessels. Our results suggest that the use of the histometric method for the estimation of relaxed lumen size from the contracted vessels is of very limited value. We also suggest that, for an accurate comparison of vessel wall dimensions between hypertensive and normotensive animals, cross-sectional area should be used instead of wall thickness alone.

Animals↗
PubMed1983

The protective effect of inhaled chlorpheniramine and atropine on bronchoconstriction stimulated by airway cooling.

We examined the role of histamine release and reflex bronchoconstriction in the bronchoconstriction stimulated by airway cooling. In 8 asthmatic subjects, dose-response curves were determined to isocapnic hyperventilation of cold air 30 min after inhalation of chlorpheniramine maleate (18 mg nebulized during tidal breathing), 2 doses of atropine sulphate (3 mg and 18 mg nebulized), or placebo. Treatments were given on separate days, in random order and under double-blind conditions. The bronchial antihistamine and anticholinergic actions of chlorpheniramine were determined by the effect on histamine and methacholine dose-response curves on another 4 days. Chlorpheniramine was selective as an antagonist against histamine; it increased the mean provocation concentration of histamine to reduce the FEV1 by 20% (PC20) 14.2-fold but increased the mean PC20 methacholine only 1.85-fold. Atropine in the 3-mg dose, previously shown to increase the PC20 methacholine at least 100-fold, had no effect on heart rate or saliva output in contrast to 18 mg, which significantly reduced saliva output and increased heart rate. Chlorpheniramine caused no bronchodilation and a small 1.28-fold increase in the amount of respiratory heat exchange needed to reduce the FEV1 by 10% (PD10RHE). Atropine caused maximal bronchodilation after 3 mg and a dose-dependent increase in PD10RHE (1.16-fold increase after 3 mg and 1.32-fold increase after 18 mg atropine). The effect of chlorpheniramine and atropine 18 mg on PD10RHE was not significantly different.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1983

Effects of 4-aminopyridine and tetraethylammonium chloride on the electrical activity and cable properties of canine tracheal smooth muscle.

The actions of 4-aminopyridine (4-AP) on passive membrane properties of canine tracheal smooth muscle were compared to those of tetraethylammonium chloride (TEA). Transmembrane potential was studied with intracellular electrodes in a partitioned bath by extracellular current injection. The cells were electrically quiescent and showed rectification to depolarizing pulses. TEA (30 mM) depolarized the muscle and increased membrane resistance, time constant (282-421 msec), space constant (2.16-2.67 mm), decreased rectification and generated action potentials. D600, with TEA, abolished the spikes but further increased the membrane resistance, time constant (690 msec) and space constant (3.79 mm). TEA apparently blocked potassium conductance and initiated Ca++-dependent spikes owing to depolarization. 4-AP (5 mM) depolarized the membrane, but caused slow oscillations, decreased membrane resistance and space constant (1.94 mm), without affecting the time constant (265 msec) or rectification. These membrane effects of 4-AP were reversed to a large extent by atropine (10(-7) to 10(-6) M). D600 blocked the 4-AP-induced oscillations but not the decreased membrane resistance or space constant. 4-AP produced characteristic electrical and mechanical responses in a sucrose gap chamber when the muscle was functionally denervated by tetrodotoxin or scorpion venom. 4-AP appeared to activate the muscarinic receptor of canine trachealis to increase conductance, possibly to Na+ and K+. An effect on potassium conductance blockade might have been masked by the muscarinic receptor gated conductance changes, but is unlikely as it was not evident after exposure to atropine. We conclude that 4-AP actions in canine trachealis reflect chiefly activation of muscarinic receptors and not interference with potassium conductance.

4-Aminopyridine↗
PubMed1983

On the oxalate stimulation of ATP-dependent calcium accumulation by smooth muscle subcellular membranes.

Subcellular distribution of azide-insensitive, ATP-dependent Ca -accumulation in the presence and absence of 5 mM oxalate by fractions isolated from several different types of smooth muscle were studied. Although oxalate stimulated the Ca -accumulation to various degrees depending upon the source of smooth muscle used, there was no clear association between the stimulatory effect of oxalate and the distribution of any of the enzyme activities used as markers for various membranes. The distribution of ATP-dependent Ca -accumulation in the absence of oxalate, on the other hand, correlates relatively well with that of the plasma membrane marker in spite of reduced total recovery of the Ca -accumulation compared to those of the protein content and membrane markers. However, a greater reduction in the total percent recovery of the ATP-dependent Ca accumulation by fraction from three different types of smooth muscle was consistently observed when carried out in the presence compared to the absence of oxalate. The discrepancy in the total percent recovery of the Ca -accumulation in the presence and absence of oxalate poses a major concern on the uses of oxalate stimulated, ATP-dependent Ca accumulations as a subcellular membrane marker.

Adenosine Triphosphate↗
PubMed1982

Arterial muscle membrane abnormalities of hydralazine-treated spontaneously hypertensive rats.

Alkaline phosphatase activity and Ca2+ accumulation were examined in the plasma membrane enriched fractions isolated from mesenteric arteries of spontaneously hypertensive (SHR) and Kyoto-Wistar normotensive (WKY) rats after a long-term antihypertensive treatment with hydralazine. The membrane biochemical abnormalities of arterial smooth muscle such as enhanced alkaline phosphatase activity and reduced ATP-dependent Ca2+ transport previously observed in untreated SHR were persistently observed in hydralazine treated SHR with normalized systolic blood pressure. Our results suggest that the antihypertensive effects of hydralazine do not involve the reversal or modification of the altered Ca2+ handling by vascular muscle membrane in hypertension.

Animals↗