Search PubMed⌕ Search

Biomedical subjects

R Boivin

Publications and source records attributed to R Boivin.

At least 55 records · Page 3Linked to original sources
PubMed1985

[Start of mastication by esophageal distension in sheep].

Oesophageal wall distension was performed on standing conscious sheep by inflating a rubber balloon at four different levels inside the cervical and thoracic oesophagus. Although no retrograde oesophageal peristalsis was ever recorded, these stimulations were always followed by a conspicuous increase of parotid saliva secretion. They frequently induced the onset of chewing movements, whatever the level of the oesophageal distension. The cyclical reticular activity does not bear any relationship to the occurrence of the chewing movements. The masticatory response could be either of the "ON" or "ON - OFF" type, but most often of the "OFF" type. The response to thoracic oesophageal distension was suppressed by mid-cervical anaesthetic blockage of vagal conduction. A possible involvement of any sort of stimulation of the oral cavity was thus ruled out. The masticatory response to oesophageal distension is a reflex mechanism whose afferent pathway from the distal part lies in the vagal trunk. Such a reflex may participate early in the initiation of chewing movements during rumination, prior to the arrival of the regurgitated bolus into the mouth.

Animals↗
PubMed1984

[Origin of the secondary peristalsis of the esophagus in sheep].

Manometric and electromyographic methods were used for investigating oesophageal motor activity in conscious sheep. A contraction wave, the so-called "secondary peristalsis", was readily evoked by means of the fast inflation of a rubber balloon distending the oesophagus. This peristaltic wave travels onto the cardia at the same speed as the primary deglutitive peristalsis (28 m X sec-1, approximately). In that particular species, whose oesophageal muscular coat is all along entirely made of striated fibers, secondary peristalsis is always initiated at the origin of the cervical oesophagus, whatever the site, cervical or thoracic, of the distension.

Animals↗
PubMed1983

[Autonomic effects of scaritoxin in the cat and guinea pig. Cardiac protection by an anti-arrhythmia agent].

A purified extract from the muscles of the fish Scarus gibbus (93% scaritoxin and 7% ciguatoxin) was tried on anesthetized cats and isolated guinea-pig atria. Intra-venous injection to cats (10, 20 and 40 mg/kg) induced deep respiratory depression, inhibition of duodenal contractions, increased salivary secretion, mydriasis and lacrymal secretion. Heart rate was slowed by 17 to 44 per cent. Impaired cardiac conduction led to different types of blocks. On the contrary, cardiac excitability was enhanced, as evidenced by the occurence of many auricular and mostly ventricular extra-systoles, often evolving into long periods of ventricular paroxysmal tachycardia. The rate of contraction of isolated guinea-pig atria was equally depressed and this effect was antagonized by atropine. The duration of the refractory period was shortened; an inotropic effect was observed and the action of acetylcholine was potentiated by the toxin. Cholinesterase inhibition by scaritoxin, previously mentioned in other papers, is thus evidenced. Mydriasis and duodenal inhibition may be tentatively explained by a nicotinic effect on the sympatheticoadrenal system. This mechanism may be responsible for cardiac inotropic action and increased excitability. Other mechanisms may be suggested, including a possible digitalis-like effect due to a cyclopentanone ring in the scaritoxin molecule. Interestingly, intra-venous injections of the antiarrythmic drug procainamide (20 to 30 mg/kg) could either prevent or reverse the signs of cardiac hyperexcitability in the anesthetized cat. However, death results usually from respiratory depression, the intimate mechanism of which is not yet known.

Animals↗
PubMed1982

[Demonstration of strains of Escherichia coli with septicemic characteristics in the feces of calves with mucoid enteritis].

During a field study on neonatal diarrhea of calves, we examined the bacteremic ability of 78 strains of Escherichia coli isolated from diarrheic and non-diarrheic newborn calves. The following tests were performed: growth in newborn calf serum, mortality in adult mice inoculated intraperitoneally with about 5 X 10(7) bacteria, mortality and effect on weight gain in baby mice inoculated by oral route with about 10(8) bacteria. In addition, we tested their ability to adhere in vitro to intestinal villi of newborn lamb. Among the 78 isolates, 58% were able to grow in newborn calf serum and 22% were non-adherent to lamb intestinal villi. Fifteen isolates were pathogenic for adult mice, 12 of them originating from calves with a syndrome that we called "mucoid enteritis" and which consisted of the following signs: very abundant feces, bright and viscous, containing mucus, and physical prostration. From the 15 strains displaying a lethal effect on adult mice, 12 were adherent and 7 provoked at least 20% mortality in baby mice. Our observations suggest that bacteriemic E. coli with adhesive properties could be responsible for mucoid enteritis in calves.

Animals↗
PubMed1981

[Prandial stimulation of reticular movements in sheep: cephalic phase and oral reflex (author's transl)].

Acceleration of reticular contractions when chewing feed (oral reflex of the reticulum, ORR) has been well documented for many years. The aim of the present investigation was to study the evolution of this reflex throughout the meal period. A possible triggering effect of drinking water was also investigated. Reticular contractions and chewing movements were simultaneously recorded from four sheep by means of permanent reticular wire electrodes and foam rubber balloons fastened below the lower jaw. Records were drawn before and during presentation of feed, then during the meal which followed. Similar records were drawn while sheep were drinking during intervals between feeding periods. In every case, intensity of mastication decreases from beginning up to the end of the feeding period. This decrease is paralleled by a slope of reticular frequency, which is very high at the beginning of the meal. The significant correlation between the two phenomena suggests that the decrease of the ORR results from a lesser stimulation of oral mechanoreceptors. Reticular movements are obviously accelerated during isolated drinking periods. Existence of a true cephalic phase of prandial reticular stimulation is evidenced by a moderate acceleration on the sole presentation of feed.

Animals↗
PubMed1980

[Effects of intracerebroventricular injections of nalorphine on feeding behaviour and rumination in sheep (author's transl)].

Two sheep were fitted with permanent cannulus in the first cerebral ventricule and permanent electrodes were stitched to the wall of the reticulum. They were housed in individual pens and fed lucern pellets twice a day (total duration 1.30 hour) at fixed hours. Food intake was weighed. Chewing movements were recorded permanently by means of a submandibular balloon. Reticular motility was recorded by electromyography during feeding periods. Feeding behaviour and rumination were previously recorded during two control periods. No treatment was applied during the first control period of 6 days (Ta). During the second one (Tb), daily intracerebroventricular (ICV) injections of saline (0.2 ml)) were given for 4 consecutive days. During the following 4 days (Na period), the sheep received isovolumic ICV injections of nalorphine (1 mg per day). Saline was injected again ICV for the last 4 days of the experimental period (Tc). During the period of nalorphine administration there was an important fall in the circadian percentage of rumination of one sheep and a total suppression in the other, discarding the possibility of a volumetric effect. There was also a significant decrease of food intake in the two sheep but nalorphine did not modify the frequency of reticular contractions in any case. Regarding to the general behaviour, the drug induced a general excitation with bleating and increased responsiveness to stimuli. Oral activity included compulsive and continuous chewing movement, creaking the teeth, gnawing, nipping and an apparent activity of searching food for up to 15 hours. In conclusion, nalorphine and morphine effects upon the sheep are compared. The effects of the two drugs are exactly the same regarding to the decrease of rumination and feeding intake and the modification of general behaviour, but morphine decreases markedly the reticular rhythm whereas nalorphine does not. Besides, it seems that the animals get tolerant more readily to morphine than to nalorphine.

Animal Feed↗
PubMed1979

[Vasomotor innervation of the maxillary canines of the dog].

Maxillary canine pulpar pressure was recorded on anesthetized dogs by means of a small bore cannula threaded into a hole drilled through the lateral surface of the tooth. Vasoconstriction was brought by the electrical stimulation of the cranial cervical ganglion. Vasodilation was induced by stilmulation of the pterygo-palatine ganglion. This vasodilation was inhibited by atropine. Most often, constrictor fibres follow the course of the pterygo-palatine nerve, when dilator fibres follow the infraorbital nerve. However, both sorts of fibres may be found in the infraorbital nerve.

Animals↗
PubMed1979

[The effects of non-protein-nitrogen additives on lipid and carbohydrate metabolisms in sheep (author's transl)].

The effects of NPN administration on lipid and carbohydrate metabolisms were investigated in 14 sheep. Blood non-esterified fatty acids (NEFA) are increased by intra-ruminal dosage with urea (10 g), 1 p. 1000 ammonia solution (1 l) or ammonium chloride (17.6 g). Peak values are recorded 3 to 4 hours after the injection. An early rise of NEFA and hyperglycemia are observed when ammonium chloride is injected intra-venously. The time-course of the variations of the different blood constituents (ammonia, glucose, NEFA, urea) as well as the lack of any action following intra-venous urea injections suggest that lipid mobilization is induced by the increased level of blood ammonia. The involvement of a strenghened activity of the sympathetic-adrenal system is evidenced by the increased elimination of urinary catecholamines.

Ammonia↗
PubMed1977

[Saliva ammonia and urea in the sheep. Effects of alimentary nitrogen additives (author's transl)].

The salivary elimination of ammonia and urea was studied in 4 permanently salivary duct fistulated sheep. Sheep were fed either a regular diet or the same diet with addition of non protein nitrogen (NPN). Individual saliva ammonia levels vary from 34 to 71 microgram N/100 ml. After intra-ruminal dosing with urea (10 g) or ammonia (2 g), the values may rise up to 1000 microgram N/100 ml. Saliva ammonia and blood ammonia changes follow the same direction. Daily saliva urea variations are correlated with feeding behaviour. NPN administration increases saliva urea and blood urea; both concentration curves are parallel.

Ammonia↗