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Biomedical subjects

J V Davies

Publications and source records attributed to J V Davies.

At least 19 recordsLinked to original sources
PubMed1989

Normal intestinal motility.

Perhaps because of the inherent difficulty in using horses as experimental animals, only a relatively small amount of data is as yet available regarding normal equine gut motility. However, it is clear that the horse is fundamentally similar to other mammalian species studied. The neural and humoral control of gut activity requires much exploration; it is likely that, in the horse, some of this information will be derived during the investigation of the effects of various substances that might have clinical relevance. This is alluded to in the chapter that follows (The Effects of Pharmacological Agents on Gastrointestinal Motility). The clinical applications are likely to remain limited, though some light may be shed upon the derivation of certain disorders.

Animals↗
PubMed1986

Reactions of reducing radicals with ribonuclease.

Radiation-induced reactions of hydrated electrons, formate- and ethanol radicals with ribonuclease were studied by pulse radiolysis and by electrophoresis. Initially formate radicals react rapidly and very specifically with the disulphide bonds of ribonuclease. This reaction leads to aggregation by intermolecular S-S-interchange, the process being more effective at pH 4, since formation and decay of S-S-.-radical anions increases with decreasing pH. With high doses additional unreducible aggregates are formed. Radical formation at the positively charged histidine residues seems to be involved. Hydrated electrons do not react as selectively as the formate radicals, but with several sites in native ribonuclease. Thus with low doses unreducible aggregates are formed. Electrophoresis shows that reaction of the electrons causes fragmentation of the peptide chain, when OH-radicals are scavenged. Very weak transient spectra and very little degradation result on reaction of ethanol radicals with ribonuclease.

Electrophoresis, Polyacrylamide Gel↗
PubMed1985

Effect of experimental vascular occlusion on small intestinal motility in ponies.

Small intestinal ischaemia is a cause of pain in man and horses. Occlusion of the vascular supply to Thiry loops in experimental ponies caused severe discomfort and loss of motility within a few minutes but these effects could not be reproduced by a similar procedure in intact gut preparations. However, embolisation of the mural vascular network produced ischaemia of the small intestine of anaesthetised ponies which led to a cessation of motility in the affected segments, though unaffected segments became hypermotile with a characteristic motility pattern. These results suggest the need for reappraisal of the classical theory of parasite-induced damage to the cranial mesenteric artery as the cause of ischaemic bowel disease.

Animals↗
PubMed1983

Radiation-induced reduction reactions with bovine serum albumin.

The reduction of bovine serum albumin (BSA) by hydrated electrons, formate and ethanol radicals leads to the formation of S-S-radicals. The reaction of the hydrated electrons becomes faster, if BSA was preirradiated in the presence of formate or ethanol, but the rate does not change if radiolysis is done in the presence of t-butanol or without scavenger. The reduction of BSA by formate radicals is 10 times slower but gives a higher yield of S-S-radicals than by hydrated electrons. The rate and yield of the reduction by the formate radicals are increased by preirradiation of BSA. The reduction by ethanol radicals is five times slower than by formate radicals and gives lower yields of S-S-radicals which are increased by preirradiation. All rates and yields of the reduction reactions are decreased by changing the pH from 6.3 to 7.3.

Butanols↗
PubMed1983

The radiation inactivation of glutamate dehydrogenase.

Pulse radiolysis and 60Co gamma radiolysis were used to study the effects of ionizing radiations on the activity of glutamate dehydrogenase. Hydroxyl radicals are considerably more effective than hydrated electrons in causing loss of enzymatic activity. Evidence is also presented that the free radical anions (SCN)-.2, (Br)-.2, and (I)-.2 react with the enzyme and cause a loss of enzymatic activity. The results implicate the possible involvement of cysteine, tyrosine, and tryptophan residues in the activity of glutamate dehydrogenase.

Binding Sites↗
PubMed1983

Electromechanical activity of the equine small intestine and its correlation with transit of fluid through Thiry-Vella loops.

Motility patterns in the equine small intestine were investigated in eight ponies. Muscular activity was assessed by means of extramural strain gauge transducers, bi-polar electrodes and in three of the animals, fitted with Thiry-Vella loops, the transit of fluid. Circular muscle contractions were preceded by spiking superimposed on the slow wave and fluid transit in the loops correlated with both these events.

Animals↗
PubMed1983

Effect of spasmolytic analgesic drugs on the motility patterns of the equine small intestine.

The effect of acepromazine, Buscopan (Crown Chemicals), pethidine and methadone was evaluated in ponies prepared with Thiry-Vella (T-V) loops. Motility was assessed by electrophysiological means (bipolar electrodes and strain gauge transducers) and by the passage through the T-V loop of a fluid test meal. Results were obtained from 26 experiments in three ponies and compared with six control experiments, in which saline had been administered to the same ponies. Each pony acted as its own control in each experiment and pre and post treatment values for slow wave frequency, spiking activity, delivery rate and flow rate were compared. Acepromazine reduced electrical activity, but increased volume transport. Buscopan produced little change, while pethidine and methadone both decreased electrical activity, but increased volume transit. These effects may be due to a decrease in tone with resulting increase in luminal volume of the intestine.

Acepromazine↗