Biomedical subjects
Publications and source records attributed to L Thulin.
Circulatory effects of gastrointestinal hormones and related peptides are surveyed. Only experiments using low peptide dosages, non-extensive surgery and intravenous infusions give relevant data in this field. Glucagon, secretin, vasoactive intestinal peptide, gastrin, cholecystokinin, Substance P and Somatostatin are vasoactive within the splanchnic area, each fraction in a specific pattern.
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The chemistry, localisation, release and effects of gastrointestinal hormones and some related peptides are surveyed. Their main presumed physiologic actions are: gastric acid and pepsin secretion are stimulated by gastrin and to a less degree by secretin. Acid secretion is inhibited by bulbo-enterogastrone and GIP. Biliary water and electrolytes are augmented by gastrin, CCK-PZ, secretin and VIP and inhibited by Substance P. Pancreatic bicarbonate and enzyme secretions are stimulated by secretin and CCK-PZ, especially in combination. Lower oesophageal and antral motility and tonus are elevated following gastrin and motilin; the gallbladder and small intestine empty following CCK. Gastrin regulates gastrointestinal, and CCK pancreatic, tissue growth. Somatostatin inhibits all gut hormones. All peptides are vasoactive within the splanchnic area, each one in a specific manner.
The acute response of the hepatic circulation to thrombinaemia and endotoxinaemia were investigated in the anaesthetized dog. Small amounts of thrombin were infused into the hepatic artery and portal vein. The effects of thrombin were compared to those of minor amounts of portally infused endotoxin. Portal pressure increased significantly following portal infusion of thrombin and endotoxin. Both substances decreased the blood flow markedly in the hepatic artery, while that in the superior mesenteric artery and portal vein decreased only slightly. Heparin and polyphlorethin phosphate (PPP) abolished all effects of thrombin. Bradykinin infused simultaneously inhibited only the effect on the hepatic artery. Vasoactive intestinal peptide, which has the same vasodilatory effect in the liver, did not. It is believed that thrombin and perhaps endotoxin exert a vasoconstrictive effect mediated by products released from platelets.
Vasoactive intestinal peptide, VIP, was administered intravenously as 10-minute infusions, dosage 0.05 and 0.5 mug/kg/min, to anaesthetized dogs provided with common duct fistulas. When VIP was given to fasting animals, the output of bile, sodium and amylase increased significantly, the bile output by approximately 200% of the control. The biliary concentration of sodium was constant, while that of amylase decreased. When VIP was given to animals, which were fed before the experiment, the bile output was essentially unaffected. The two doses used gave equal peak responses, but the duration of the effect was doubled or trebled following the highest dosage.
Effects of halothane anaesthesia on aplanchnic blood flow and cardiac output were studied in six dogs. Blood flows in the hepatic artery, the superior mesenteric artery and the portal vein were measured electromagnetically. Cardiac output was measured by thermodilution. Depth of anaesthesia, ventilation, acid-base state and body temperature were controlled. Cardiac output and blood flows in the hepatic artery, the superior mesenteric artery and the portal vein decreased significantly to 73%, 54%, 59% and 60% of control values, respectively. Total peripheral vascular resistance decreased significantly, while mesenteric and portal resistance remained essentially unchanged and hepatic arterial resistance showed a significant increase. It is suggested that the difference between the various vascular responses may be caused by a differentiated release from baroreceptor inhibition in various parts of the bulbar vasomotor center.
The influence of halothane ansesthesia on splanchnic oxygen flow and oxygen uptake was studied in seven dogs. Mean oxygen supply to the liver and the portally-drained tissues decreased significantly to 44% and 53% of control values, respectively, while mena oxygen consumption diminished insignificantly to 68% and 82% of control values, respectively. There was a fall in the oxygen flow/oxygen consumption ratio in all animals following halothane. The relatively unimpaired oxygen uptake, in spite of a diminished oxygen supply, led to an increased extraction of oxygen by the tissues. Some factors affecting oxygen utilisation during halothane anaesthesia are discussed.
The semen from 20 men with varicocele was studied before and after surgical correction of the varicocele. The effect on sperm quality was only marginal and could not explain the fairly high conception rate (20%) after operation. The recommendation that varicocele in men with long-term infertility should be eliminated by ligation of the internal spermatic veins is still justified despite the absence of positive effects on sperm quality.
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