Six healthy men (21 to 38 years; 58 to 80 kg) consumed an adequate diet in a metabolism unit. At 4-day intervals they ingested test meals and venous blood was drawn before and after ingestion at intervals for 8 hours. Test meals were 100, 200, and 300 g of cooked lean meat and quantities of corn oil, sucrose, and whiskey isoenergetic with 200 g of meat. Plasma was analyzed for 20 amino acids. Mean totals of amino acids (micromoles per liter) were maximally elevated at 1 or 2 hours post cibum for all meals and remained above fasting values at 4 hours, with one exception (glucose meal). At 8 hours they were all below fasting values with one exception (whiskey meal). Individual responses varied so much that mean values are misleading. One subject responded well to ingestion of 100 or 200 g of meat but failed to respond to 300 g of meat, oil, or sucrose. Another subject responded well to oil and sucrose, but failed to respond to 100 or 200 g of meat. Mean total fasting amino acid values for all subjects were relatively constant but values for individual subjects ranged from 16% above to 18% below their own fasting means. Ingestion of whiskey invariably resulted in a significant decline in molar ratios for histidine and a significant increase for threonine.
Impulses from the peripheral cut end of mesenteric nerves to the intestinal loops of anesthetized cats were recorded oscilloscopically. Dogs with Thiry-Vella loops and with electrodes implanted in mesenteric nerves were used for chronic studies. The loops were perfused with different solutions at constant temperature and pressure. After glucose perfusion of the lumen the increase in frequency of firing was more marked in medium and larger fibers. After perfusion with single amino acids the increase was more conspicuous in smaller fibers. Amigen (amino acid mixture, dextrose, and salts) perfusion resulted in mixed patterns. No appreciable changes were observed with 0.9% NaCl, Tyrode's solution, and 0.025 n NaOH, but a slight increase was obtained with 0.025 n HCl. The possibility of some chemoreceptor mechanism in the small intestine is suggested. Its possible role in ingestion of food is discussed.
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