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Biomedical subjects

M Denac

Publications and source records attributed to M Denac.

At least 19 recordsLinked to original sources
PubMed1993

Effect of various neurotransmitters and electrical field stimulation on smooth muscle preparations from the esophagus of horses.

The effects of various neurotransmitters and electrical field stimulation on muscle strips from the distal equine esophagus were studied. Acetylcholine (ACH) caused concentration dependent (1.1-55 x 10(-6) mol/l) contractions of the longitudinal and circular muscle strips from the distal esophagus as well as from the lower esophageal sphincter (LES). Atropine (10(-5) mol/l) blocked these contractions. Noradrenaline (NA) induced concentration related (1.1-55 x 10(-6) mol/l) contractions of the muscle strips from the LES. This excitatory effect of noradrenaline was antagonized by the alpha 1-receptor antagonist prazosin. Tetrodotoxin (5 x 10(-6) mol/l) did not affect the contractile response of the muscle strips to noradrenaline (55 x 10(-6) mol/l). Noradrenaline (1.1-55 x 10(-6) mol/l) had no excitatory effect on the circular and the longitudinal muscle strips from the esophagus. Furthermore, noradrenaline induced a concentration dependent (1.1-55 x 10(-6) mol/l) relaxation of the longitudinal muscle strips from the esophagus. The relaxing effect of NA was antagonized by the beta-receptor antagonist propranolol (10(-5) mol/l). Histamine (10(-7)-10(-6) mol/l) elicited a contraction in 4 out of 18 muscle preparations from the LES. The histamine induced contractions were partly antagonized by the H1-receptor antagonist clemastine (10(-4) mol/l) and fully abolished by the H2-receptor antagonist clemastine (10(-4) mol/l). Electrical field stimulation (EFS, 5 Hz, 2 ms; 500 mA; 10 Hz, 2 ms; 500 mA) produced tetrodotoxin sensitive contractions in all three types of muscle strips. Atropine (10(-5) mol/l) fully suppressed these contractions in most preparations.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Effects of adrenaline, dopamine, serotonin, and different cholinergic agents on smooth muscle preparations from the ansa proximalis coli in cattle: studies in vitro.

The effects of adrenaline, dopamine, serotonin, and different cholinergic agents on isolated muscle strips from the ansa proximalis coli in cattle were studied. Adrenaline (5 x 10(-5) mol/l) evoked a relaxing effect (p < 0.05) on longitudinal and circular muscle strips, mediated via beta- and alpha 1-receptors respectively. High concentration of dopamine (5 x 10(-4) mol/l) caused a non-significant inhibitory effect on longitudinal smooth muscles, which was probably mediated by beta- and not by dopamine-receptors. Serotonin (5 x 10(-5) mol/l) and cisapride (75 x 10(-6) mol/l) had no effect. Carbachol (2 or 10 x 10(-6) mol/l) and bethanechol (5 or 10 x 10(-5) mol/l) caused a dose-dependent (p < 0.05) contraction of both smooth muscle types. This excitatory effect was inhibited (p < 0.05) by metoclopramide (1 x 10(-4) mol/l), as well as the muscarinic agents RS-86 (5 x 10(-5) mol/l) and CGP-37,218 (37.5 or 75 x 10(-6) mol/l).

Animals↗
PubMed1991

Effect of noradrenaline on smooth muscle strips from the reticular groove of adult cattle.

The effect of noradrenaline (NA) on smooth muscle strips from the reticular groove of adult cattle was studied. The mechanical activity of the muscle strips was recorded isometrically. Noradrenaline caused concentration dependent (1.1 x 10(-6)-55 x 10(-6) mol/l) contractions of both the transversal muscle strips from the floor and the longitudinal muscle strips from the lips of the reticular groove. This excitatory effect of noradrenaline was antagonized by the alpha 1-receptor antagonist prazosin (10(-8) mol/l) and by higher concentrations of the alpha 2-receptor antagonist yohimbine (10(-6) mol/l) and atropine (10(-5) mol/l). Tetrodotoxin (5 x 10(-6) mol/l) and latrotoxin did not affect the contractile response of the muscle strips to noradrenaline (55 x 10(-6) mol/l). Furthermore, strips stored for 24 hours in Tyrode's solution at 4 degrees C without oxygen supply maintained their full sensitivity to noradrenaline. Propranolol (10(-4) mol/l), a beta-receptor antagonist, led to a significant increase of the contractions induced by noradrenaline (55 x 10(-6) mol/l). These results suggest that noradrenaline increases the tone of the smooth muscle of the reticular groove via alpha-adrenergic receptors and decreases its tone via beta-adrenergic receptors. Both receptor types are located on the smooth muscle cells. The alpha 1-receptor mediated effect appears to be predominant.

Animals↗
PubMed1990

Relaxation of muscle strips from the reticular groove and reticulo-omasal orifice by vasoactive intestinal peptide (VIP).

The effect of Vasoactive Intestinal Peptide (VIP) on muscle strips from the reticular groove, the reticulo-omasal orifice (ROO) and the omasal canal was studied. VIP caused a concentration-dependent (10(-8)-5 x 10(-7) mol/l) reduction of the acetylcholine-induced (55 x 10(-6) mol/l) contraction of the reticular groove muscle preparations from calves and adult cattle. VIP was more effective in the muscle strips from calves than in those from adult cattle. Moreover, the circular muscle strips from the reticular groove were more sensitive to VIP than the longitudinal muscle strips. VIP also induced a concentration-related (10(-8)-5 x 10(-7) mol/l) relaxation of muscle strips from the calf ROO. Furthermore, both circular and longitudinal muscle strips from the omasal canal of the calf were relaxed by VIP (10(-7)-5 x 10(-7) mol/l). The relaxing effect of VIP on the circular muscle strips from the reticular groove of the calf was not significantly affected during incubation with 5 x 10(-6) mol/l tetrodotoxin. The relaxing effect of VIP therefore seems to be mediated by VIP receptors of smooth muscle cells. These properties of VIP in conjunction with its presence in nerve fibres located in the wall of the reticular groove and ROO are consistent with a role of VIP as inhibitory transmitter in this region of the bovine stomach.

Animals↗
PubMed1990

Effect of electrical field stimulation on muscle strips from chicken crop.

The effect of electrical field stimulation (EFS) on smooth muscle strips from the chicken crop was investigated. The EFS (5 Hz, 2 ms, 400 mA; 10 Hz, 2 ms, 400 mA; 5 Hz, 2 ms, 500 mA; 10 Hz, 2 ms, 500 mA) produced contractions in all preparations. Atropine (10(-5) mol l-1) diminished muscle contraction in response to EFS. Tetrodotoxin (5 X 10(-6) mol l-1) fully suppressed the contractile responses to EFS. A serotonin antagonist (methysergide, 10(-4) mol l-1) did not alter contractions elicited by EFS. Propranolol (10(-5) mol l-1) led to an increase of contractions induced by EFS. Noradrenaline (10(-6)-10(-4) mol l-1) reduced acetylcholine-induced (1.1 X 10(-6) mol l-1) contraction of the crop smooth muscle strips. Propranolol (10(-5) mol l-1) abolished noradrenaline-induced relaxation almost fully. Tetrodotoxin (5 X 10(-6) mol l-1) did not change the relaxing effect of noradrenaline. These results suggested that the responses of crop smooth muscle to EFS involve excitatory cholinergic and non-cholinergic (probably peptidergic) as well as inhibitory adrenergic nerves.

Animals↗
PubMed1990

[Effect of catecholamines on the smooth muscles of the esophageal groove of calves].

The effect of noradrenaline and adrenaline on isolated smooth muscle from the reticular groove of calves was studied. Both catecholamines caused a concentration-dependent (1.1.10(-6) mol/l) contraction of the transversal muscle strips from the floor of the reticular groove. This excitatory effect was antagonized by prazosin (10(-7)) mol/l), and by high concentrations of yohimbine (10(-6) mol/l) and atropine (10(-5)) mol/l). Tetrodotoxin (3.10(-6) mol/l), an inhibitor of nerve conduction, did not change the contraction induced by catecholamines (55.10(-6)) mol/l). Catecholamines did not produce a contraction of the longitudinal muscle from the lips of the reticular groove. The beta-adrenergic agonist isoprenaline (55.10(-6) mol/l) even elicited a reduction of acetylcholine (55.10(-6)) mol/l) induced contraction of both the transversal and the longitudinal muscle from the reticular groove. The relaxing effect of isoprenaline was antagonized by propranolol (55.10(-6)) mol/l). According to these results the excitatory effect of catecholamines on the smooth muscle cells occurs through alpha-adrenergic receptors, whereas the relaxing effect is mediated by beta-adrenergic receptors of the muscle cell. The excitatory effect of catecholamines on the transversal muscle appears to be predominant. Atropine appears to be an unspecific blocking agent of alpha-adrenergic receptors.

Animals↗
PubMed1988

Effect of bombesin and substance P on the smooth muscle of the chicken crop.

The effect of bombesin and of substance P was investigated in smooth muscle strips of the chicken crop. Bombesin in picomolar concentration (0.1 x 10(-12) - 5 X 10(-12) mol/l) caused a concentration-related contraction of the muscle strips. Substance P in nanomolar concentration (0.1 x 10(-9) - 10 x 10(-9) mol/l) was effective in the same manner. Tetrodotoxin (2 x 10(-7) mol/l) did not influence the contraction responses to either bombesin or substance P. The excitatory effect of bombesin and of substance P did not follow activation of cholinergic receptors since their effect on the crop smooth muscle was not antagonized by atropine (10(-4) mol/l) or by hexamethonium (10(-4) mol/l). Strips stored for 24 hours in the Tyrode's solution at 4 degrees C without a supply of oxygen maintained their full sensitivity to bombesin and to substance P. These results are consistent with a direct action of bombesin and substance P on the crop smooth muscle.

Animals↗
PubMed1987

Effect of neurotensin on the smooth muscle of the chicken crop.

1. The effect of neurotensin was studied in the isolated smooth muscle of the chicken crop. 2. This peptide induced concentration-dependent (10(-10)-10(-8) mol/l) contractions of muscle strips. 3. The response to neurotensin was not modified after incubation of the preparation with atropine, indomethacin, naloxone and tetrodotoxin. The neurotensin-exerted contractions are therefore probably myogenic. 4. These properties of neurotensin indicate a possible role for this peptide in the control of crop motility.

Animals↗
PubMed1977

[The Göttinger minipig as a laboratory animal. 4. Communication: respiration parameters (author's transl)].

The following parameters were determined: Rate of breathing (f): 31.95 +/- 6.73/min. Minute volume (V): 5.11 +/- 6.73 liter/min. Tidal volume (VT): 0.166 +/- 0.053 liter. Ratio expiratory to inspiratory time Et/It : 1.04 +/- 0.18. Physiological dead space (VD): 0.061 +/- 0.024 liter. Dead space quotient (VD)/VT): 29.92 +/- 1.53%. Dynamic lung compliance (C dyn): 0.06 +/- 0.06 liter/cm H2O. Maximum interpleural negative pressure during inspiration (max. neg. Ppl. Insp.): 12.00 +/- 4.06 cm H2O. Minimum interpleural negative respectively maximum interpleural positive pressure during expiration (min. neg. or pos. Ppl. Exp.): +0.07 +/- 6.53 cm H2O. Maximum change of interpleural pressure (delta Ppl. max): 11.97 +/- 3.18 cm H2O.

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