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Biomedical subjects

R Serio

Publications and source records attributed to R Serio.

At least 55 records · Page 3Linked to original sources
PubMed1988

Electrophysiological analysis of responses to intrinsic nerves in circular muscle of opossum esophageal muscle.

The nerve-mediated responses to electrical field stimulation (EFS) along the opossum esophageal circular smooth muscle were studied with the sucrose-gap recording technique. Strips from 1-2, 4-5, 7-8, and 10-11 cm above the lower esophageal sphincter were stimulated with short-train (300 ms) and long-train (3 s) durations at 29 degrees C. The response always consisted of a hyperpolarization [inhibitory junction potentials (IJP)] followed by an "off depolarization" often associated with spike potentials and mechanical contraction. Proximal to distal differences in the characteristics of the evoked responses were found, i.e., increasing amplitude, duration and time to peak hyperpolarization of the IJP, increasing latency, and amplitude of the off depolarization. Neither atropine, scopolamine, physostigmine, nor guanethidine altered these characteristics substantially. Circular strips of muscularis externa, studied in the organ bath at 37 degrees C using 10-s EFS trains at 5-40 pps, produced off contractions, enhanced by physostigmine and reduced by atropine. High-frequency stimulation occasionally initiated small persistent intrastimulus ("on") responses; some were sensitive to cholinergic agents, but there was no gradient in the delay in their onset. Atropine-insensitive and tetrodotoxin-potentiated transient on responses were occasionally detected. We conclude that only the noncholinergic, nonadrenergic innervation provides a functional intrinsic innervation directly to the opossum esophagus circular smooth muscle when nerves are activated by EFS.

Acetylcholine↗
PubMed1988

Thromboxane effects on canine trachealis neuromuscular function.

The objective of this study is to determine which inflammatory mediators had direct effects on canine trachealis muscle neuromuscular control to identify candidate mediators of the hyperresponsiveness observed in vitro after O3 exposure. Studies were carried out in the sucrose gap at 29 degrees C and in the muscle bath at 37 degrees C. Leukotriene (LT) B4, LTD4, and prostaglandin (PG) D2 had neither direct nor significant effects on the excitatory junction potentials (EJP's), the secondary membrane potential oscillations, or the associated contractions that followed field stimulation of cholinergic nerves. U 46619, a stable analogue of thromboxane (Tx) A2, enhanced (10(-10)-10(-7) M) the duration and the amplitude of secondary oscillations and associated contractions without affecting the EJP's. In the muscle bath, U 46619 enhanced field-stimulated contractions; this was antagonized competitively by SQ 29548. In both the sucrose gap and the muscle bath, higher concentrations (10(-9) M and higher) caused direct effects, small depolarizations, and contractions. These effects of U 46619 were unaffected by indomethacin or guanethidine but were abolished by SQ 29548, an antagonist selective at TxA2-PGH2 receptors. U 46619 at 10(-9) M did not affect electrical or mechanical responses to acetylcholine and at 10(-9) M did not increase the sensitivity to acetylcholine. Platelet-activating factor (PAF) was inactive in all muscle-bath and most sucrose-gap experiments. In 7 of 20 of the latter, it caused effects qualitatively like those of U 46619, but whether it acted through release of TxA2 could not be tested because of the rapid tachyphylaxis to PAF. We conclude that TxA2 may mediate the hyperresponsiveness found in vitro after O3 treatment.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1988

Airway smooth muscle responsiveness from dogs with airway hyperresponsiveness after O3 inhalation.

Airway hyperresponsiveness occurs after inhalation of O3 in dogs. The purpose of this study was to examine the responsiveness of trachealis smooth muscle in vitro to electrical field stimulation, exogenous acetylcholine, and potassium chloride from dogs with airway hyperresponsiveness after inhaled O3 in vivo and to compare this with the responsiveness of trachealis muscle from control dogs. In addition, excitatory junction potentials were measured with the use of single and double sucrose gap techniques in both groups of dogs to determine whether inhaled O3 affects the release of acetylcholine from parasympathetic nerves in trachealis muscle. Airway hyperresponsiveness developed in all dogs after inhaled O3 (3 ppm for 30 min). The acetylcholine provocative concentration decreased from 4.11 mg/ml before O3 inhalation to 0.66 mg/ml after O3 (P less than 0.0001). The acetylcholine provocative concentration increased slightly after control inhalation of dry room air. Airway smooth muscle showed increased responses to both electrical field stimulation and exogenous acetylcholine but not to potassium chloride in preparations from dogs with airway hyperresponsiveness in vivo. The increased response to electrical field stimulation was not associated with a change in excitatory junctional potentials. These results suggest that a postjunctional alteration in trachealis muscle function occurs after inhaled O3 in dogs, which may account for airway hyperresponsiveness after O3 in vivo.

Acetylcholine↗
PubMed1987

Inhibitory influences of vagal afferences on the oesophageal EMG peristaltic pattern.

The influence of vagal afferents on the EMG peristaltic pattern was studied in pigeon oesophagus. Bilateral vagotomy did not abolish the primary peristalsis, but induced significant modifications of the peristaltic pattern parameters. Vagal afferent stimulation induced an inhibitory effect consisting of a temporary break or definitive block of the EMG peristaltic activity already in progress. Vagal afferent stimulation also induced a reduction of the spontaneous EMG activity and this effect was abolished either by glossopharyngeal bilateral section or ganglionic block. Likewise vagal afferent stimulation, the crop distension caused inhibitory effects on EMG peristaltic pattern. This effect was abolished by bilateral vagotomy. These results indicate that vagal afferents, originating from the crop, could influence the central neurons responsible for the peristaltic motor programme.

Afferent Pathways↗
PubMed1987

Pigeon oesophageal EMG activity: analysis of intramural neural control.

The effects of agonist and antagonist cholinergic and adrenergic drugs on spontaneous electrical activity of transverse muscular strips of pigeon cervical oesophagus were examined. Tetrodotoxin failed to affect EMG activity. Cholinomimetics produced excitatory effects. The response to carbachol was enhanced by hexamethonium and reversed into an inhibitory effect by atropine. Noradrenaline evoked a concentration-dependent, biphasic effect (inhibition at low and excitation at high concentrations). Isoproterenol induced inhibitory response unaffected by tetrodotoxin. Phenylephrine induced excitatory response completely antagonized by tetrodotoxin and partially opposed by atropine. It is concluded that: i) the oesophageal spontaneous EMG activity is myogenic; ii) the intramural neurons have no tonic influence on the spontaneous EMG activity; iii) in the intramural plexuses there are cholinergic excitatory-, non-cholinergic excitatory- and inhibitory neurons, with unknown neurotransmitter; iv) excitatory alpha-adrenoceptors, located on the nervous elements and inhibitory beta-adrenoceptors, located on the smooth-muscle cells, are present.

Action Potentials↗
PubMed1987

5-Hydroxytryptamine involvement in the intrinsic control of oesophageal EMG activity.

The effects and the sites of action of 5-Hydroxytryptamine (5HT) were examined in transverse muscular strips of pigeon oesophagus. 5-Hydroxytryptamine (0.001 to 30 microM) induced a concentration-dependent excitatory effect on the EMG activity. This response was mainly characterized by an increase in burst frequency. The maximum 5-HT-induced excitatory effect was not altered by methysergide (10 microM), but was abolished by tetrodotoxin (3 microM). Excitatory response to 5-HT was partly opposed by atropine (1 microM), potentiated by 5-methoxy-N, N-dimethyltryptamine (1 microM) and was not altered by guanethidine (10 microM). These results indicate that 5-HT activates the pigeon oesophagus indirectly via neural elements and has no direct action on the smooth muscle cells. 5-HT is thought to stimulate three different intramural neuron types: excitatory cholinergic neurons, excitatory non-cholinergic neurons and inhibitory non-cholinergic non-adrenergic neurons. The action on these different neurons seems to be mediated via different receptors.

Action Potentials↗
PubMed1985

Evidence for extrinsic control of oesophageal primary peristalsis.

The rôle of both peripheral and central mechanism in the control of primary peristalsis was studied in pigeon cervical oesophagus. The results from the transection of oesophageal muscular wall and of extrinsic nerves suggest that: primary peristalsis is programmed centrally. extrinsic motor input is carried in glossopharyngeal nerves and distributed separately at each oesophageal level through intramural neurons. intramural neurons do not seem capable of propagating the peristaltic sequence irrespective of the central control.

Animals↗
PubMed1985

Electrical stimulation of glossopharyngeal nerve and oesophageal EMG response in the pigeon.

The effects of the efferent glossopharyngeal nerve stimulation, on EMG activity of the pigeon cervical oesophagus, were studied. In control animals, stimulation caused a biphasic response characterized by an intra-stimulus excitatory component followed by a post-stimulus inhibitory one. The EMG response to glossopharyngeal stimulation appeared simultaneously throughout the cervical oesophagus. A bell-shaped mechanical wave was detected relating to the electrical excitatory component. Atropine administration antagonized the excitatory component, while the inhibitory one persisted. It occurs intra-stimulus, and its duration is increased, compared to control ones. A reduction in the oesophageal resting pressure was observed relating to the electrical inhibitory component. Hexamethonium caused complete disappearance of any EMG response to glossopharyngeal stimulation, as well as suppression of mechanical responses. The comparison between the EMG responses to swallow and to efferent glossopharyngeal stimulation suggests that in pigeon cervical oesophagus: primary peristalsis is central in origin; a dual system of glossopharyngeal fibres, excitatory and inhibitory, carries the central control for oesophageal motility; these excitatory and inhibitory fibres supply the oesophageal muscle via intramural neurons; the synaptic arrangement of the inhibitory pathway is more complex than the excitatory one.

Animals↗
PubMed1984

Role of glossopharyngeal nerve on the control of pigeon cervical esophagus motility.

The effects of i) glossopharyngeal section on the occurrence of the primary peristalsis and ii) electrical efferent stimulation of glossopharyngeal nerve on the EMG activity were studied in the pigeon cervical esophagus. The results pointed out that glossopharyngeal nerve is an indispensable requirement for the primary peristalsis occurrence and that motor sequence is centrally programmed.

Animals↗
PubMed1984

Purification and properties of chicken growth hormone and the development of a homologous radioimmunoassay.

Highly purified growth hormone (GH) has been isolated from pituitary glands of chicken (Gallus domesticus), and a specific homologous radioimmunoassay (RIA) has also been developed. The purified chicken GH was active in the rat tibia bioassay and it gave a dose-dependent response which paralleled that of the bovine GH standard. High pressure liquid chromatography revealed that the purified chicken GH was homogenous. Chicken GH had an Rf value of 0.2 in disc electrophoresis, and a MW of 26,000 from sodium dodecyl sulfate-gel electrophoresis. The isoelectric point was estimated to be 7.6 by gel isoelectric focusing. The amino acid composition of chicken GH was found to be similar to that of mammalian GH, and the NH2-terminal amino acid was threonine. Partial sequencing (114 amino acids) of the chicken GH showed 79% homology with bovine GH. An antiserum was developed to the purified chicken GH in a rabbit, and it was used to develop a homologous RIA using 125I-labeled chicken GH as the ligand. The purified chicken GH was iodinated via the lactoperoxidase method to a specific activity of approximately 100 microCi/micrograms. Plasma from chickens, medium from incubation of pituitary glands, and homogenates of pituitary glands gave parallel dilution-response curves with the chicken GH standard. Mammalian GH, prolactin (PRL), follicle-stimulating hormone (FSH), and luteinizing hormone (LH) showed no cross-reaction with the 125I-labeled chicken GH. Purified turkey GH showed parallel dose response with the chicken GH, but purified turkey PRL did not cross-react. Chicken FSH and LH also showed no inhibition of binding. The minimum detectable concentration of the assay was 0.93 ng/tube, and the intraassay and interassay coefficients of variation were 9 and 16%, respectively. The specific binding of 125I-labeled chicken GH to a microsomal fraction isolated from chicken liver was identified, and the specific binding was generally low (1-4%). Turkey PRL, and chicken LH and FSH showed no inhibition of the 125I-labeled chicken GH hepatic binding and the ontogeny of the hepatic GH receptor binding sites in male and female chickens was examined.

Aging↗
PubMed1984

The antifertility and antiadrenergic actions of thiocarbamate fungicides in laying hens.

The effects of the thiocarbamate fungicides, thiram, ziram, ferbam, maneb, and zineb, on norepinephrine synthesis by laying hens were investigated. Inhibition experiments with dopamine beta-hydroxylase purified from chicken adrenals indicated that thiram, ziram, and ferbam are potent competitive inhibitors with the substrate the substrate ascorbate. Maneb and zineb were without effect at comparable concentrations. Experiments investigating the interaction of thiram, ziram, and ferbam with cupric ions suggested that these compounds probably inhibit the enzyme by complexing the fully oxidized copper at its active site. Maneb and zineb also complexed cupric ions in solution and thus their failure to inhibit is not due to their inability to complex copper. When tested in vivo, thiram, ziram, and ferbam at po doses of 2.5 mg/kg or greater significantly reduced the conversion of radioactive dopa, given systemically, to brain norepinephrine. Since they did not affect the uptake of radioactive dopa by the brain or its subsequent decarboxylation within the brain to yield dopamine, these three compounds inhibit cerebral dopamine beta-hydroxylase in vivo. In contrast maneb and zineb at a po dose of 20 mg/kg had no significant effect on brain norepinephrine synthesis. Previously published results (Weppelman et al., Biol. Reprod. 23, 40-46, 1980) demonstrated that thiram, ziram, and ferbam (but not maneb or zineb) have antifertility action in laying hens. The correlation between this action and inhibition of dopamine beta-hydroxylase suggests that the antifertility effects of thiram, ziram, and ferbam might result from their antiadrenergic action. The observation that all doses of thiram in the diet which caused significant antigonadal action when fed to laying hens for 1 week also significantly decreased central and peripheral stores of norepinephrine supports this conclusion.

Administration, Oral↗
PubMed1984

Primary peristalsis in pigeon cervical oesophagus: two EMG patterns.

Swallowing elicits two propagated EMG peristaltic patterns in pigeon cervical oesophagus: i) "simple" peristaltic pattern and ii) "complex" peristaltic pattern. "Simple" peristaltic pattern is characterized by an intense, long-lasting burst of spikes, high in amplitude with an aboral increasing delay in onset. "Complex" peristaltic pattern presents an early short period of reduction in spontaneous electrical activity, followed by an excitatory period similar to that of "simple" pattern. The early inhibitory component has a very short delay in onset increasing aborally. Atropine abolishes the EMG excitatory component of both patterns, while the inhibitory period persists, showing increased duration and reduced propagation speed. "Simple" peristaltic pattern, mediated by cholinergic nerves, acting on muscular muscarinic receptors, is identifiable with an "on response". "Complex" peristaltic pattern shows a cholinergic muscarinic excitatory component and an atropine-resistant inhibitory component. This latter component is not a passive post-inhibitory rebound ("off response").

Animals↗
PubMed1982

EMG activity of pigeon oesophagus in vivo.

At rest, the pigeon cervical oesophagus, which is entirely smooth muscle, shows electric activity. This activity consists of bursts of spikes with frequency increasing in the oral-aboral direction. The bursts are un-phase locked, and there are no slow waves (E.C.A.). The surgical transection of the oesophageal muscular wall does not affect the electric activity even in a disconnected segment. After asphyxia electric activity persists, whereas the aboral gradient of frequency disappears. Therefore, the electric activity is thought to be myogenic in origin, and the frequency gradient nervous in origin. Atropine and neostigmine administration suggests that the cholinergic system modulates the electric activity, but it is not involved in the control of the frequency gradient. On the contrary, hexamethonium administration, by abolishing this gradient, lends support to the idea of a postganglionic atropine-resistant neuronal system responsible for the gradient.

Action Potentials↗