F. A. Harrison

Bio: F. A. Harrison is an academic researcher. The author has contributed to research in topics: Jejunum & Duodenum. The author has an hindex of 1, co-authored 1 publications receiving 73 citations.

Rate of passage of digesta in sheep. 3. Differential rates of passage of water and dry matter from the reticulo-rumen, abomasum and caecum and proximal colon.

Abstract: 1. Three groups of sheep receiving 400, 800 and 1200 g lucerne chaff/d in equal hourly meals were killed. The large intestines were removed and divided into segments 15 cm long to provide information on the amounts and dry-matter contents of digesta and on the rates of passage of digesta and absorption of water along the large intestine.2. With increasing intakes of food, increases were observed along the entire large intestine in the amounts of wet digesta present, in the transit rates of digesta and in the rates of absorption of water. The mean retention time of digesta in the large intestine decreased with increasing food intake, being 1737, 1056 and 692 min respectively.3. Four patterns of sodium and potassium concentrations in digesta water along the large intestine were found.

Rate of flow of digesta and electrical activity of the small intestine in dogs and sheep.

Abstract: 1. Spiking activity of the small intestine in the conscious dog and sheep was recorded continuously from electrodes chronically implanted on the jejunum and summed at intervals of 20 sec. The activity was related to the transit time and flow rate of intestinal contents as estimated by phenol red and by dilution of continuous marker infusions respectively. Also in some sheep the flow of digesta was measured directly from a cannula in the proximal part of the jejunum, and also by use of an electromagnetic flow meter. 2. In the fasted dog and in sheep on a normal diet the intestinal activity was characterized by a migrating myo-electric complex comprising an irregular phase followed by a regular phase. These migrating myo-electric complexes occurred regularly after a period of inactivity at a frequency of 15-20/24 hr. In dogs after feeding, a continuous spiking activity appeared and persisted for periods of 7-8 hr. This was associated with much higher rates of flow and shorter transit times than were observed during fasting. In sheep, continuous spiking activity could be induced by intravenous injection of 5-hydroxytryptophan and this, similarly, was accompanied by a more rapid flow and a shorter transit time than recorded during the control period. 3. In both species the longest transit time occurred when a phenol red bolus was injected during the period of electrical inactivity. Relatively short transit times were observed when the bolus was administered just before the period of regular spiking activity. 4. When relaxation of the bowel was induced by intraperitoneal injection of hypertonic saline there was no spiking activity and the transit time for the infused solution was greatly lengthened, especially in the sheep. A noticeable flow of digestive contents persisted in the dog. 5. In the sheep the intestinal contents flowed intermittently during periods of 10-15 min and at the same frequency as the migrating myo-electric complex. Two thirds of this flow took place in the 4-6 min immediately preceding the periods of irregular spiking activity. 6. It is concluded that in the fasted dog and in the sheep the migrating myo-electric complex controls the pressure gradients on which the flow of intestinal contents depends. This is accomplished in the main by the prolonged phase of irregular spiking activity, and it is suggested that the regular spiking activity which follows it, though not in itself propulsive, serves as a barrier to prevent backflow of digesta into the quiescent part of the intestine. When continuous spiking activity is induced, by feeding in the dog and by injection of 5-hydroxytryptophan in the sheep, no part of the intestine is quiescent and the transit time is shortened by the incessant irregular spiking activity.

Studies on intestinal digestion in the sheep. 1. The use of chromic oxide as an indigestible marker.

Abstract: 1. The use of chromic oxide (Cr 2 O 3 ) as an indigestible marker for studies on intestinal digestion in sheep has been examined. The sheep used were equipped with a cannula into the rumen and a re-entrant cannula in the proximal duodenum; some also had a re-entrant cannula in the terminal ileum. The marker was administered twice daily in the form of Cr 2 O 3 -impregnated paper, through the rumen cannula. 2. Recovery of Cr 2 O 3 in the faeces, based on 7-day collection periods, was satisfactory, the mean recovery for all seven experiments being 99.6 ± 0.7%. In seventeen 24 h collections of digesta entering the proximal duodenum, the mean recovery of the daily dose of marker was 83.7% (range 63.6-148.4%); in eleven such collections at the terminal ileum the mean recovery was 77.3% (54.0-90.0%). 3. Detailed examination of the concentrations of Cr 2 O 3 in dry matter was made with individual samples taken during single 24 h periods for five duodenal and three ileal collection periods. There were always marked variations in these concentrations. It is concluded that use of short collection periods to give mean values for the flow of digesta throughout the 24 h, at particular points along the tract, may lead to large errors.

Studies on intestinal digestion in the sheep. 3. Net movement of certain inorganic elements in the digestive tract on rations containing different proportions of hay and rolled barley.

Abstract: 1. In each of three experiments, two sheep were given diets consisting of hay, or two parts hay to one part barley or one part hay to two parts barley. Each sheep was equipped with a cannula into the rumen and re-entrant cannulas into the proximal duodenum and the terminal ileum. The rations containing barley were supplemented to adjust the intake of calcium, phosphorus, magnesium, sodium and potassium to a level similar to that in the all-hay ration. Paper impregnated with chromic oxide (Cr2O3) was given twice daily by rumen fistula.2. Amounts of crude ash and the five minerals entering and leaving the small intestine and excreted in the faeces were measured. The amounts passing through the re-entrant cannulas were adjusted to give 100% recovery of chromic oxide. The values were used to calculate the direction and net movements of the elements through the walls of the three main parts of the alimentary tract.3. In all instances there was an extensive net secretion of Na and P between mouth and small intestine, net absorption of K and P from the small intestine and of Na from the large intestine.4. The net movements of Ca and Mg were small and rather variable. In five of the six observations there was a small net secretion of Ca and small net absorption of Mg during passage of the digesta through the reticulo-rurnen, omasurn and abomasurn. Net secretion of Ca and Mg apparently occurred in the small intestine and net absorption of Mg in the large intestine.5. The only between-diet differences were small differences in net movements of Na and K.