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Biomedical subjects

C C Chou

Publications and source records attributed to C C Chou.

At least 145 records · Page 8Linked to original sources
PubMed1987

Effects of xylazine on equine intestinal vascular resistance, motility, compliance, and oxygen consumption.

Isolated jejunal segments were perfused at a constant blood flow rate to determine simultaneously the effects of xylazine on intestinal vascular resistance, motility, compliance, and oxygen consumption in 12 anesthetized ponies. Xylazine was infused into the artery perfusing the intestinal segment (group 1), or into the jugular vein as a single IV bolus (group 2), or 3 times as IV boluses repeated at 10-minute intervals (group 3). Dose-response curves in group 1 indicated a biphasic response to the drug with vasoconstriction, increased motility, and increased oxygen consumption at lower doses followed by a return toward base-line values at higher doses. Intestinal compliance decreased at lower doses, but increased at higher doses. A single IV bolus of xylazine (group 2) induced systemic hypotension for 30 minutes, and increased intestinal vascular resistance for 10 minutes accompanied by increased motility, and repeatedly administered IV boluses of xylazine (group 3) increased and prolonged these effects. The results indicated that xylazine, especially in repeated doses, may decrease bowel viability by simultaneously increasing intestinal vascular resistance, motility, and oxygen consumption.

Animals↗
PubMed1986

The effects of mefenamic acid on postprandial intestinal carbohydrate metabolism.

The effects of mefenamic acid on the food-induced changes in intestinal carbohydrate metabolism were determined in an attempt to elucidate the mechanism(s) by which inhibition of prostaglandin synthesis enhances the postprandial increases in intestinal blood flow and oxygen consumption. The data show that when the luminal perfusate was changed from saline to a nutrient/bile solution, there was an increase in carbohydrate utilization, which was offset by absorption of glucose from the lumen. Intravenous administration of mefenamic acid significantly increased both carbohydrate absorption and metabolism when food was placed in the lumen. Changes in carbohydrate absorption and metabolism have been shown to play and important role in determining the magnitude of glucose induced changes in intestinal blood flow and oxygen consumption. Therefore, it is possible that the ability of mefenamic acid to enhance significantly the food-induced increases in blood flow and oxygen consumption may be due in part to its effects on intestinal carbohydrate absorption and utilization.

Angiotensin II↗
PubMed1986

Structure and expression of ferritin genes in a human promyelocytic cell line that differentiates in vitro.

HL-60 is a human promyelocytic cell line with the capability of differentiating in vitro to give neutrophils, macrophages, or eosinophils. We screened libraries of HL-60 cDNA clones representing different time points during these differentiation processes to isolate clones corresponding to mRNAs whose expression is regulated during terminal differentiation. Upon sequencing this group of regulated clones, one clone encoding the heavy subunit and two clones encoding the light subunit of human ferritin were identified by reference to published amino acid sequences. Southern blot analyses showed that these clones are encoded by distinct multigene families. These clones identify two mRNAs whose ratios vary in a complex manner during both neutrophil and macrophage differentiation.

Amino Acid Sequence↗
PubMed1986

Thromboxane synthesis inhibition and postprandial intestinal hyperemia and oxygenation.

The effects of imidazole and U-63557A (Upjohn), inhibitors of thromboxane synthesis, on food-induced changes in intestinal blood flow and oxygen uptake were determined in the jejunum of anesthetized dogs. Intra-arterial (5.0 mg/min ia) infusions of imidazole had no effect on the postprandial intestinal hyperemia but significantly potentiated food-induced increases in oxygen uptake via enhanced oxygen extraction. Furthermore, imidazole had no effect on intestinal glucose absorption. The selective thromboxane synthesis inhibitor U-63557A (5 mg/kg iv) also enhanced oxygen uptake during nutrient absorption and had no effect on the hyperemia or glucose absorption. Our study indicates that inhibition of thromboxane synthesis has no effect on either resting intestinal blood flow or postprandial intestinal hyperemia but significantly enhances postprandial oxygen extraction and uptake. The potentiation of the food-induced increases in oxygen uptake by imidazole and U-63557A appears not to be related to glucose absorption. Endogenous thromboxane therefore appears to inhibit oxygen uptake more than blood flow, and yet does not affect glucose absorption during nutrient absorption.

Animals↗
PubMed1986

Comparison of the effect of asphyxia, hypoxia, and acidosis on intestinal blood flow and O2 uptake in newborn piglets.

The aim of our study was to compare the effects of asphyxia and the two components of asphyxia, i.e. hypoxia and acidosis, on intestinal blood flow and oxygen consumption in anesthetized newborn piglets less than 3 days old. The first series of experiments, consisting of four groups of piglets, showed that blood flow to the proximal and distal small intestine and colon (as determined by the microsphere technique) significantly decreased after piglets were subjected to a sustained hypoxic hypoxemia (PaO2 50% of control) or asphyxia (acidosis plus hypoxia) for 90 min. A sustained acidosis (arterial pH = 7.0-7.15 for 90 min), however, decreased blood flow only to the proximal small intestine, and sham operation did not significantly alter any intestinal blood flow. All animals subjected to asphyxia and two of five of the animals subjected to hypoxia alone in this series, produced gross and microscopic intestinal lesions similar to those seen in human newborn with necrotizing enterocolitis. Acidosis alone, however, did not produce any pathologic lesions. The second series of experiments showed that the 90-min hypoxic hypoxemia decreased blood flow to both the mucosa and muscularis layers of the small intestine. The third series of experiments, consisting of four groups of piglets, determined the effects of 60-min acidosis, hypoxic hypoxemia, asphyxia, or sham operation on venous outflow and oxygen consumption of the isolated in situ terminal ileum. Acidosis or sham operation altered neither ileal blood flow nor oxygen consumption. Hypoxia or asphyxia, however, decreased ileal oxygen consumption without significantly decreasing blood flow.(ABSTRACT TRUNCATED AT 250 WORDS)

Acidosis↗
PubMed1985

Possible mechanisms for the initiation and maintenance of postprandial intestinal hyperemia.

Postprandial intestinal hyperemia is a locally mediated vascular response to the presence of nutrients in the lumen. In this review we discuss the role of various constituents of chyme in the development of the hyperemia and possible mechanisms of action. The luminal contents that produce the hyperemia are digested products of food; undigested food or pancreatic enzymes have no effect. Micellar fatty acids are the most potent vasodilators, whereas amino acids at physiological concentrations have little effect on intestinal blood flow. However, by-products of protein digestion are as potent as those of carbohydrates in increasing the blood flow. Bile increases ileal but does not alter jejunal blood flow. In addition, bile enhances the glucose-induced hyperemia and renders fatty and amino acids vasoactive. The mechanisms by which bile exerts its effect on the vasoactivity of these nutrients are poorly understood. The intestinal hyperemic response to the presence of nutrients in the lumen is mediated by a variety of regulatory pathways that vary with the nutrient. Factors involved include tissue metabolic rate, metabolites, nutrient absorption, tissue osmolality, tissue oxygen tension, intestinal peptides such as neurotensin and vasoactive intestinal polypeptide, and paracrine substances such as prostaglandins and histamine. It is likely that the hyperemia results from the complex interplay of all these factors on the intestinal vascular smooth muscle. Extrinsic and intrinsic nerves play a minor role in nutrient-induced hyperemia.

Animals↗
PubMed1985

Effect of atropine on digested food-induced intestinal hyperemia.

The aim of our study was to determine whether the discrepancy in the data reported on the effect of atropine on food-induced intestinal hyperemia results from a difference in experimental materials and methods. In the first two series of experiments, atropine (0.5 mg/kg iv) was given before or during intraluminal perfusion of digested food plus bile through a long jejunal loop (62% of the total small intestine) at 4 ml/min for 60 min while measuring the portion of the blood flow through the superior mesenteric artery (SMA) that perfused the loop. Atropine per se had no effect on jejunal blood flow. Before atropine food increased flow 31.5 +/- 10.1% and after atropine flow increased 54.8 +/- 11.0 and 66.0 +/- 28.0% above controls in the first and second series, respectively. Atropine also increased net fluid volume absorption. In the third series, food alone and food plus bile were placed into the lumens of the two adjacent jejunal segments. Atropine had no effect on the increases in flow and oxygen uptake produced by food alone but enhanced the hyperemia produced by food plus bile without affecting the increase in oxygen uptake. Our results suggest that the previously reported inhibition of increased SMA flow by atropine is due to the inhibitory effect of atropine on gastrointestinal motility and inhibition of pancreatic blood flow. In conclusion, food-induced jejunal hyperemia does not result from a direct vasodilator action of the cholinergic nerves.

Animals↗
PubMed1985

Regulation of jejunal blood flow and oxygenation during glucose and oleic acid absorption.

To differentiate the mechanisms whereby actively absorbed glucose and passively absorbed oleic acid increase blood flow and oxygen uptake during their absorption, the effects of these two nutrients on jejunal blood flow, arteriovenous oxygen difference [(a-v)O2], O2 uptake, absorption, rubidium extraction, and capillary permeability-surface area product (PS) were compared in anesthetized dogs. Oleic acid (37 mM) produced significantly greater hyperemia (+28.2%) than glucose (270 mM) did (+12.5%). As estimated by (a-v)O2, tissue oxygen extraction was decreased by oleic acid (-12%) but increased by glucose (+6.5%); the increases in O2 uptake by these two nutrients did not differ significantly. Glucose absorption was accompanied by an increase in rubidium extraction and capillary PS (+11.3%), whereas oleic acid absorption was not. Unlike glucose, intra-arterial infusion of oleic acid decreased vascular resistance and increased blood flow equally to the mucosa and muscularis layers. A significant relation existed between oleic acid absorption and blood flow but not between glucose absorption and blood flow. The enhancement of glucose-induced hyperemia by bile was not related to glucose absorption. Unmasking of oleic acid-induced hyperemia by bile is unrelated to oleic acid absorption but is related to solubility of oleic acid in aqueous solution. The above findings suggest that glucose absorption affects both resistance and exchange vessels, whereas oleic acid absorption affects primarily resistance vessels.

Animals↗
PubMed1984

Arachidonic acid and postprandial intestinal hyperemia.

The effects of prostaglandin synthesis on food-induced increases in intestinal blood flow and O2 uptake were examined in the jejunum of anesthetized dogs. Intravenous (40 micrograms X kg-1 X min-1) or intra-arterial (0.8-1.6 microgram X min-1) infusions and luminal placement (6.5 X 10(-4) M or 200 micrograms/ml) of arachidonic acid (AA) significantly attenuated the food-induced jejunal hyperemia. Furthermore, luminal placement of AA significantly attenuated the food-induced increase in jejunal O2 uptake. Changes in blood flow and O2 uptake were significantly correlated both before and after arachidonic acid administration. Although intravenous infusion of AA decreased blood flow, intra-arterial infusion and luminal placement of AA did not significantly alter resting blood flow under free-flow conditions. In another series of experiments, intravenous infusions of AA under constant-flow conditions produced a biphasic response: vascular resistance rose when local blood AA concentration was raised to the range between 1 and 6 micrograms/ml blood and fell when the concentration was raised between 8 and 12 micrograms/ml blood. This study indicates that prostaglandin synthesis has a marked effect on both resting intestinal blood flow and postprandial intestinal hyperemia. The attenuation of the hyperemia may be due to its attenuation of the food-induced increase in intestinal oxidative metabolism.

Animals↗
PubMed1984

Time course of jejunal blood flow, O2 uptake, and O2 extraction during nutrient absorption.

Experiments were performed on anesthetized dogs to determine whether responses of jejunal blood flow, arteriovenous O2 difference, O2 uptake (VO2), and glucose absorption to luminal placement of predigested food or glucose would change with time during 30- and 60-min placement periods and to determine whether bile alters the responses. During the initial 15 min, food, glucose, food plus bile, and glucose plus bile produced a 13, 10, 51, and 30% increase in flow, respectively. During the next 15 min, flow returned to control levels, while arteriovenous O2 difference significantly increased with food or glucose; with glucose plus bile, flow decreased to 28% above control. In the case of food plus bile, flow decreased to 26% above control at 30 min and returned to control 50 min after placement. Despite the fluctuation in flow, the increase in VO2, and glucose absorption stayed at a steady level throughout the entire placement period. Bile significantly enhanced the increases in both flow and VO2 produced by food or glucose, prolonged the hypermia, delayed the significant rise in arteriovenous O2 difference, and had no effect on glucose absorption. In conclusion, the relative contributions of blood flow and O2 extraction to the enhanced VO2 produced by luminal food and glucose change with time, and bile significantly alters the magnitude or time course of changes in the above three variables.

Absorption↗
PubMed1984

Effect of Piper betle L. and its extracts on the growth and aflatoxin production by Aspergillus parasiticus.

Ground powder of the leaf and fruit of Piper betle L., a tropical spice plant grown in Southeast Asia, was prepared and extracted by chloroform, ethanol and water with one solvent only or with 3 solvents in sequence. The betel powder and various extracts were added to YES broth to determine their effects on the growth and aflatoxin production by Aspergillus parasiticus. Results showed that betel leaf powder exhibited higher antimycotic activity than fruit. One half percent of ground leaf powder completely inhibited the growth and aflatoxin production by A. parasiticus. Among the solvent extracts, chloroform and ethanol extracts of betel leaf prepared from a single solvent extraction showed more antimycotic activity. The ethanol extract of betel leaf at the level of 450 micrograms/ml would eliminate A. parasiticus growth and aflatoxin production. The antimycotic activity of this ethanol extract was most pronounced at pH 4.

Aflatoxins↗
PubMed1983

Evidence against local neural mechanism for intestinal postprandial hyperemia.

The role of local intestinal nerves in the nutrient-induced intestinal hyperemia was investigated in jejunal segments of anesthetized dogs by comparing the hyperemic effect of intraluminal glucose and oleic acid solutions before and after mucosal anesthesia and infusions of methysergide, hexamethonium, and tetrodotoxin. Methysergide, hexamethonium, and tetrodotoxin all failed to alter either the vascular or metabolic responses to luminal placement of glucose or oleic acid. The increases in blood flow and oxygen uptake produced by glucose or oleic acid, however, were blocked or attenuated after exposing the mucosa to dibucaine. The effect was norepinephrine due to an altered vascular response to vasoactive substances as dibucaine did not alter vascular responses to isoproterenol or norepinephrine. Dibucaine, however, inhibited active transport and increased passive transport of glucose across rat intestinal sacs in vitro. Oxygen consumption of the canine jejunal mucosa was also inhibited by dibucaine in vitro. It seems that inhibition of the nutrient-induced intestinal hyperemia by dibucaine is due, at least in part, to its effect on oxygen consumption and glucose transport of the mucosal epithelial cells. Nutrient-induced hyperemia appears not to be neurally mediated but more closely related to metabolism.

Animals↗
PubMed1983

Release of cardiodepressants from the canine jejunum in irreversible hemorrhagic shock.

The possible release of cardioinhibitory factors from the small intestine during severe hemorrhagic shock was examined by testing arterial and intestinal venous plasma samples obtained at various stages during the experiment in two groups of anesthetized dogs. One group of dogs was subjected to arterial hypotension at 35 +/- 5 mmHg for 3 h followed by reinfusion of all shed blood, while the other group was treated alike except that there was no hemorrhagic hypotension. The plasma samples were assayed for cardioinhibitory activity by utilizing the Langendorff guinea pig heart preparation. None of the plasma samples obtained from the sham operated dogs significantly alter the performance of the guinea pig heart. The arterial sample taken during the compensation phase of hemorrhagic hypotension increased, while the arterial and intestinal venous plasma taken at the terminal stage decreased the dP/dt. Plasma Na+, K+, total Ca2+, and Mg2+ concentration of all samples were within normal limits. It is concluded that the small intestine releases cardioinhibitory factors in severe hemorrhagic shock.

Animals↗
PubMed1983

Equine esophageal pressure profile.

Esophageal motility was studied in 5 healthy adult horses, using a 4 side-hole catheter assembly continuously perfused with distilled water. Resting pressure and maximal pressures generated during swallowing were measured over the whole length of the esophagus (mean +/- S means = 132.7 +/- 2.31 cm). Four functionally distinct regions of the esophagus were demonstrated: cranial esophageal sphincter, caudal esophageal sphincter, and "fast" and "slow" regions in the body of the esophagus. The resting pressure of the cranial and caudal esophageal sphincters were 171.1 +/- 20.45 (x +/- S means) and 10.5 +/- 0.61 (x +/- S means) mm of Hg, respectively. The maximal pressure of the "fast" and the "slow" esophageal regions and caudal esophageal sphincter were 63.1 +/- 3.75 (x +/- S means), 71.9 +/- 3.65 (x +/- S means), and 63.1 +/- 2.60 (x +/- S means) mm of Hg, respectively. The length of each region and duration of pressure events were quantitated, establishing an equine esophageal pressure profile.

Animals↗
PubMed1983

Splanchnic and overall cardiovascular hemodynamics during eating and digestion.

The cardiovascular system responds to feeding in two distinctly different phases. During anticipation and ingestion of food, cardiac output, heart rate, aortic pressure, and vascular resistance in various vascular beds are altered in a pattern that mimics an increase in sympathetic neural activity. Myocardial oxygen consumption and adenosine concentration increase. Cardiovascular responses to exercise performed during this period are similar to those that occur during fasting except that the exercise-induced skeletal muscle hyperemia is smaller during the ingestion phase. Within 5-30 min after a meal, all cardiovascular responses to feeding subside except that blood flow to the digestive organs increases while that to skeletal muscle decreases in resting animals. The times of onset, duration, and localization of the hyperemia in the digestive organs appear to be related to the feeding-induced changes in tissue and organ activities. Exercise performed during the digestion phase does not affect intestinal hyperemia but severe excitement can actually decrease intestinal blood flow. Digestion is accompanied by an increase in total body, splanchnic, and intestinal oxygen consumption. The increase in oxygen consumption, however, is proportionally greater than the increases in splanchnic and intestinal blood flow.

Animals↗