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Biomedical subjects

F R Bell

Publications and source records attributed to F R Bell.

At least 37 records · Page 2Linked to original sources
PubMed1979

A study of olfaction and gustatory senses in sheep after olfactory bulbectomy.

The importance of taste and smell in discrimination of sodium salts was examined in normal and anosmic sheep. To test for anosmia, faeces of pig, calf and sheep were used as noxious odours. Intact sheep, and sheep with one olfactory bulb removed avoided the aversive stimulus whereas following total bulbectomy, the faecal odour was no longer a deterrent. Olfactory bulbectomy did not affect food intake but changes in fluid intake, urinary loss and electrolyte excretion were apparent. In two-choice preference tests, normal sheep showed a marked aversion for 0.48 M NaHCO3 and 0.51 M NaCl when compared to water. Following either unilateral or bilateral olfactory bulbectomy the aversion for sodium salts persisted but was less extreme. This suggests that in the final discrimination of sodium salts the sense of taste is dominant but olfaction or the olfactory bulb may have a minor role.

Animals↗
PubMed1979

Gastric emptying and secretion in the calf on duodenal infusion of tryptophan, tryptamine and 5-hydroxytryptamine.

1. Gastric emptying, gastric acid and pepsinogen secretion were assessed simultaneously in the conscious calf using the test meal and duodenal perfusion technique (Bell & Mostaghni, 1975).2. When 60 mM-HCl was infused into the duodenum, gastric emptying was arrested but both acid and pepsinogen secretion continued at a low level. Duodenal infusion with isotonic NaHCO(3) caused rapid exponential emptying of the test meal and acid and pepsinogen output was more than doubled.3. Duodenal infusion of amino acids in isotonic NaHCO(3) did not affect the rapid emptying, except infusion with tryptophan, which caused a measureable degree of inhibition of emptying, with concomitant effects on acid and pepsinogen secretion4. Tryptamine and 5-hydroxytryptamine (5-HT) incorporated in low concentration into isotonic NaHCO(3) also produced depression of gastric emptying, acid and pepsinogen levels comparable to the response initiated by acid infusate. Tryptophan was effective only in non-physiological amounts while 5-HT and tryptamine were active in smaller doses.5. Our results suggest that the inhibition of gastric emptying following duodenal infusion of tryptophan noted by Stephens, Woolson & Cooke (1975) may be due to the duodenal synthesis of its biogenic amine derivatives tryptamine and 5-HT.6. The level of activity of the three gastric functions, emptying, acid secretion and pepsinogen secretion appears to be linked. A single stimulus, therefore, could evoke a duodenal receptor or receptors to mediate or suppress activity of the gastric smooth muscle and secretory cells through interrelated mechanisms. The effect of some duodenal infusates, however, produces some variability in response which suggests differential activation of different receptors with consequent variable motor activity on effector cells.

Amino Acids↗
PubMed1979

The metabolic effects of sodium depletion in calves on salt appetite assessed by operant methods.

1. Sodium deficiency was induced in calves by unilateral exteriorization of the parotid duct, the continual loss of alkaline saliva from the body to the environment causing negative sodium balance. 2. The metabolic effect of negative sodium balance was seen in statistically significant reduction in plasma sodium and blood bicarbonate, together with marked acidosis and reduced plasma osmolality. 3. The homoeostatic response to sodium depletion was associated with a reversal of sodium/potassium ratio in parotid saliva and a reduction of the rate of secretion. Appetite diminished. The extracellular fluid was halved as marked diuresis developed with considerable weight loss. Urinary and faecal sodium was reduced to zero. 4. On restoration of sodium balance by allowing the calves to drink sodium bicarbonate solutions the metabolic deviations were eliminated. 5. During sodium depletion the parotid gland was able to respond to transient reflex stimulation by increasing flow rate and the sodium concentration of the saliva. 6. When sodium depleted, the calves became restless and agitated and would run from the home pen to the operant procedure stand. The sodium depleted animals readily pressed a panel for sodium bicarbonate rewards in direct proportion to the degree of sodium imbalance. When the balance was restored the motivation to work for sodium bicarbonate disappeared. 7. The motivation which developed during sodium depletion was directed specifically towards the sodium ion. Lithium was an exception to this rule and sodium carbonate was aversive. 8. It is possible that in sodium depletion the glottal sodium taste receptors develop an enhanced threshold for sodium ions because of the reduced sodium content of the saliva. This effect would be abolished when the content of sodium was restored in saliva. 9. The correlation of operant reactions and sodium depletion suggests that the consequential metabolic effects activate changes in the central nervous system. 10. The metabolic changes which develop in parallel with the severity of the sodium deficit appear to be able to evoke behavioural changes with increase in salt appetite directed towards restoration of sodium balance.

Animals↗
PubMed1979

A comparison of duodenal osmolality and energy content as controlling factors of gastric emptying in the calf.

1. The relative importance of energy content and osmolality of the duodenal chyme in the feed-back control of gastric emptying was investigated in the milk-fed calf fitted with gastric (abomasal) and duodenal re-entrant cannulae. 2. Duodenal infusion of isosmolal solutions, containing glucose, fructose or galactose, with a range of combustible energy content (0--1.46 MJ/l.) resulted in the same high rate of emptying of test meals from the stomach (abomasum). Abomasal emptying was, therefore, not affected by the energy content of the duodenal infusate. 3. Gastric secretion of acid and pepsinogen, and the volume of gastric secretions produced were also unaffected by the energy content of isosomolal duodenal infusates. 4. The results of the study show that the combustible energy content of the intestinal chyme is not a direct determinant of gastric function and that total osmolality of the lumenal contents is the only parameter influencing duodenal receptors under the conditions of our experiments.

Abomasum↗
PubMed1979

The sites in the duodenum of receptor areas which affect abomasal emptying in the calf.

Calves were prepared with abomasal and duodenal cannulae to assess the effects on abomasal emptying of duodenal infusates at different rates and different sites. In two calves infusions of isotonic NaHCO3 or 60 mM HCl 30 cm distal to the pylorus were as effective in controlling abomasal emptying as infusions of the duodenum from 5 cm distal to the pylorus, and in three other calves they were as effective as perfusing the whole duodenum including the most proximal 5 cm. Reducing the rate of duodenal infusion of 60 mM HCl from 10 to 2.5 ml/min diminished its effect from total inhibition of gastric emptying to slight or negligible inhibition. The stimulation of gastric emptying by duodenal infusion of isotonic NaHCO3 solution was undiminished by reduced rates of infusion. It is proposed that in the calf receptors which activate and inhibit gastric emptying are present throughout the duodenum.

Abomasum↗
PubMed1978

The effect of duodenal infusion of milk, casein, lactose and fat on gastric emptying and acid secretion in the milk-fed calf.

1. The effect of infusion of the duodenum with milk, casein, lactose and fat on gastric acid secretion and abnormal emptying of a saline meal was studied in milk-fed calves. 2. Compared with sodium bicarbonate, infusion with casein or lactose, alone or together, caused a small but statistically significant slowing of gastric emptying but did not effect gastric acid secretion. 3. Infection of the duodenum with cows' milk replacer or bovine milk fat slowed gastric emptying markedly and reduced gastric acid secretion significantly below levels obtained with sodium bicarbonate infusion. 4. The experiments provide evidence for the existence of mechanisms which prevent the passage of substantial amounts of whole milk into the duodenum before it has been subjected to gastric digestion.

Animals↗
PubMed1977

A radiological study of gastric (abomasal) emptying in calves before and after vagotomy.

1. Gastric emptying has been studied in the conscious, standing calf by lateral radiography and fluoroscopy of radiopaque meals instilled into the abomasum before and after vagotomy. 2. Bilateral cervical vagotomy proved to be the only certain way of achieving total vagal transection. By instillation of milk into the abomasum through a cannula calves were maintained in normal, healthy condition for up to 36 days after vagotomy. 3. Motility of the antrum was not impaired by vagotomy so that some movement of gastric chyme to the duodenum occurred within minutes of instillation into the abomasum. Complete transference of the test meal was, however, delayed after vagotomy. 4. The greatest effect of vagotomy appeared to be on the abomasal body so that inadequate amounts of chyme were transferred to the antrum for pumping to the duodenum. 5. Delay in passage of contrast material through the intestine was related to delay in gastric emptying although vagotomy may have affected the intestine directly. 6. Following vagotomy the abomasum showed a resumption of normal motility and emptying after 7-29 days. This effect of vagotomy is similar to that seen in the simple stomach and is probably due to the establishment of intrinsic gastric control.

Abomasum↗
PubMed1976

The influence of gastric distension and the duodenal infusate on the pattern of stomach (abomasal) emptying in the preruminant calf.

1. In the conscious calf it is possible to use duodenal re-entrant cannulae to measure the output of a gastric test meal directly from the proximal cannula placed near the pylorus. At the same time the duodenum can be isolated from the stomach and maintained under constant stimulus by a continual infusion at regulated pressure, volume and temperature into the distal cannula. 2. Under these experimental conditions the pattern of gastric emptying is exponential in form. Thus direct recording of gastric emptying validates indirect methods, such as the serial test meal, where volume markers are used. It appears likely that the exponential pattern of gastric emptying is common to man, dog, cat and calf. 3. When the isolated duodenum was infused with water, the exponential pattern of gastric emptying was maintained even when the volume of meal instilled was increased substantially from 1 to 41. 4. Distension of the stomach by larger test meals did not affect the relative rate of emptying so that the half-time of emptying of all meals was about the same. 5. When the isolated duodenum was infused with 0-06 M-HCl gastric emptying of the smaller meals was almost completely inhibited. The inhibition of gastric evacuation was accompanied by inhibition of the gastric e.m.g. 6. Infusion of the duodenum with acid also produced marked, but not complete, inhibition of emptying the larger test meals but the distension produced by the larger meals appeared to partially overcome the inhibitory effect of the acid duodenal infusate so that a small efflux occurred from the stomach. This small efflux was usually associated with some slight degree of gastric e.m.g. activity. 7. We are still investigating the mechanisms whereby the duodenum affects gastric emptying, but it is clearly demonstrable from our present results that the inhibitory effects of acid duodenal infusate are sufficiently powerful to overcome the forces, both physical and reflex, which normally aid gastric evacuation.

Abomasum↗
PubMed1975

Duodenal control of gastric emptying in the milk-fed calf.

1. It has been ascertained experimentally that an open duodenal cannula does not cause any marked variation in emptying of the abomasum when compared to the rate of emptying of the normal viscus or when the cannulae are closed. 2. Duodenal re-entrant cannulae provide a preparation whereby it is possible to infuse the duodenum via the distal cannula and to collect simultaneously the effluent fluid of the abomasum from the proximal arm of the cannula (Fig. 1). 3. With this preparation the duodenal infusate is not contaminated by the gastric effluent and thus the duodenal stimulus can be restricted to the single non-varying effect of the infusate. 4. In the milk-fed calf using this preparation the following facts have been established. (a) On infusion into the duodenum, hypotonic and isotonic solutions of sodium chloride and sodium bicarbonate increase abomasal emptying; bicarbonate being the more effective stimulus. (b) Potassium chloride, calcium chloride, glucose and hydrochloric acid inhibit gastric emptying when infused into the duodenum. (c) Ammonium chloride, urea, lactose and acetic acid have little effect. (d) Hypertonic solutions of all substances tested were inhibitory to gastric emptying when infused into the duodenum. 5. It has been demonstrated unequivocally that it is the effect of the infusate in the duodenum which controls gastric emptying for when the stomach is isolated from the duodenum, gastric emptying can be manipulated from the duodenum whatever the stomach contents may be. 6. Our results bring firm experimental confirmation of the views discussed by Hunt & Knox (1968) that gastric outflow is regulated by mechanisms initiated from receptors situated in the duodenum.

Abomasum↗
PubMed1975

The effect of duodenal infusion on the electromyogram of gastric muscle during activation and inhibition of gastric emptying.

1. When the abomasum of the conscious calf is partially distended, rhythmic motility can readily be recorded from the e.m.g. of the smooth muscle of the fundus (body) and antrum. 2. In gastric evacuation rhythmic contractions of the antrum are reinforced by both rhythmic and tonic fundic contractions. 3. The output volume of the stomach can be directly correlated with e.m.g. activity. 4. Intragastric fluid is usually emptied in gushes coinciding with a strong contraction of the antrum but fluid may be evacuated, when the antrum is inactive, through the force generated by persisting rhythmic fundic contractions. 5. Using re-entrant cannulae so that the duodenum can be infused separately from the gastric effluent, isotonic sodium bicarbonate produced almost 100% gastric evacuation with greatly enhanced e.m.g. activity of fundus and antrum. Infusion of the duodenum with a solution of HCl, 60 m-equiv/l., produced the opposite effect, the gastric muscle becoming quiescent and 100% of the gastric test meal being retained. 6. These results show that the activating or inhibitory effects of a duodenal infusate are produced through an activating or inhibitory effect on the smooth muscle of the stomach. 7. The mechanism of the interrelation between duodenal receptor and gastric effector has not yet been elucidated but the connexion is not intramural since it continues when the duodenum is transected near to the pylorus.

Abomasum↗