S ummary : The elucidation of the mechanism of ethanol production in the stomachs of newborn animals is described. The condition was reproduced in lambs and piglets by feeding glucose in fat‐free milk, and shown to arise from fermentation by the naturally occurring yeast Torulopsis glabrata , which can reach population densities of 10 6 viable cells/ml of stomach contents. These yeasts ferment glucose, producing up to 500 mg of ethanol/100 ml of contents in the stomach, but do not ferment sucrose or lactose. High levels of ethanol in plasma of lambs are accompanied by obvious symptoms of intoxication. The characteristics of a constantly occurring coliform type bacterium, found at densities up to 10 8 viable cells/ml in association with the Torulopsis yeasts were examined. Its precise role is not clear.
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A technique is described for perfusing in isolation the livers of Soay sheep. Thirty‐two livers were perfused for 3–8·5 hr and their normality assessed by histology and by measuring blood and bile flow, Bromsulphthalein (B.S.P.) clearance, the uptake of O 2 and infused NH 3 and propionate, the production of CO 2 , urea and glucose and changes in tissue glycogen and weight. With portal pressure set below 10 mm Hg and arterial pressure set at l10 mm Hg, blood flow was 90–400 ml./100 g/min, 3–35 per cent of which came from the hepatic artery. Stimulation of nerves around the hepatic artery caused vasoconstriction in hepatic and portal vascular beds. Maximum bile flow during perfusion was similar to pre‐perfusion values, but generally declined to 20–75 per cent. The extraction of B.S.P. from the blood was inversely related to total blood flow, but directly to the hepatic artery flow. The percentage of injected B.S.P. appearing in the bile was related to bile flow. Perfused livers appeared normal histologically but small amounts of GOT (aspartate amino transferase) were released into the perfusate continually. O 2 consumption averaged 1·8 ± 0·21 ml./min/100 g liver with no substrate added to the perfusate and 3·28 ± 0·28 when ammonium propionate was added. Liver glycogen generally (but not invariably), fell during perfusion. Glucose and urea outputs were greatly stimulated by the addition of ammonium propionate to the perfusate, and carbon from 14 C propionate was transferred to glucose and CO 2 . The maximum rate of glucose production from propionate was comparable to that attained in the intact animal, but urea production from ammonia was less than values for the entry rate of urea into the circulation, from all sources, reported in the intact animal. The sheep liver, even when taken from a shot animal, appears to perfuse as well as rat or dog liver, and should be a useful preparation for studying gluconeogenesis and liver function in ruminants.
The preceding paper has detailed our current understanding of the processes of N digestion in the ruminant animal as they relate to the events occurring within the reticulo-rumen. It is the purpose of this paper to consider the processes of digestion occurring principally within the small intestine and to comment on the significance of events occurring within the caecum and colon in so far as they relate to nitrogen digestion. The fate of amino acids subsequent to their absorption from the gastro-intestinal tract will also be discussed, in particular the way they are catabolized and whether this limits their availability for the synthesis of protein. Reference will also be made to purine and pyrimidine nitrogen; these products arise from the considerable content of nucleic acids in the microbial mass which leaves the reticulo-rumen and undergoes digestion in the small intestine.
1. The over-all and regional metabolism of non-esterified fatty acids (NEFA) was studied using a combination of isotopic and arteriovenous-difference techniques. 2. There was a common linear relationship, whether stearic, palmitic or oleic acids were used as tracer, between the arterial NEFA concentration and the rates of entry and oxidation. 3. Assuming that the tracer used reflected the metabolism of all the NEFA, the total entry rate in fed and fasted pregnant ewes was (mean +/- SE) 0.44 +/- 0.02 and 0.55 +/- 0.07 mmol/h per kg body-weight respectively. Oxidation of NEFA contributed (mean +/- SE) 34 +/- 5 and 58 +/- 7% to the respiratory carbon dioxide in fed and fasted animals, this accounting for (mean +/- SE) 46 +/- 6 and 59 +/- 3% of the respective entry rates. 4. Hind-limb muscle both utilized and produced NEFA. The mean gross fractional extraction (calculated from isotopic uptake) was (mean +/- SE) 9 +/- 1%. Gross utilization of any NEFA and appearance of 14CO2 across the muscle were linearly related to the arterial concentration of tracer fatty acid, irrespective of whether this was oleate or stearate. The amount of 14CO2 appearing was consistent with (mean +/- SE) 54 +/- 8% of the CO2 produced by the hind-limb being derived from NEFA oxidation. 5. Infused NEFA were partly converted to ketone bodies. Uptake and oxidation in the hind-limb of ketones formed in the liver could account for approximately 20% of the 14CO2 apparently produced in muscle from NEFA. Correction for this reduces the proportion of CO2 derived from NEFA to 43%. There was some indication that ketones were also produced from NEFA in the hind-limb. 6. NEFA were not a significant energy source for the gravid uterus. 7. An over-all view of energy sources for the whole animal and for hind-limb muscle in normal and fasted pregnant sheep was presented.
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