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Biomedical subjects

B R Bacon

Publications and source records attributed to B R Bacon.

At least 127 records · Page 7Linked to original sources
PubMed1990

A prospective, multi-center clinical trial of the Taylor intragastric balloon for the treatment of morbid obesity.

This report describes the result of a prospective, multicenter clinical trial of the Taylor intragastric balloon for the treatment of morbid obesity. Sixty patients, who had failed sustained weight loss on prior dietary restriction and behavior modification programs, were enrolled in four clinical centers. The Taylor intragastric balloon, a 550-ml, pear-shaped, liquid-filled, silicone device, was inserted in all patients for a period of 16 wk, and patients were maintained on a dietary restriction and behavior modification program. During the study period, patients experienced a 11.6% decrease in mean weight and an 11.4% decrease in body mass index. Seven balloons deflated spontaneously. Examination of these balloons revealed a manufacturing defect that was subsequently corrected. No further deflations occurred. Effects of the balloons on gastric mucosa were minimal with no gastric erosions or ulcerations noted.

Adult↗
PubMed1990

Esophageal perforation due to nasogastric intubation.

Esophageal perforation is a rare but catastrophic complication of nasogastric intubation. Diagnosis is frequently delayed, resulting in high mortality. We report a case of perforation due to nasogastric intubation in an otherwise normal esophagus. Patients at high risk of this complication can be identified, and special techniques can be used to avoid perforation. Percutaneous endoscopic gastrostomy is an alternative to nasogastric intubation for long-term enteral feeding. When nasogastric intubation is performed, clinical tests of tube position are not sufficient to guarantee proper tube position. The tip of the tube must be visualized radiographically in the stomach prior to initiation of tube feeding. When perforation does occur, proper management is often controversial. Therapy must be tailored to each individual case for the best possible outcome.

Aged↗
PubMed1989

Effects of vitamin E deficiency on hepatic mitochondrial lipid peroxidation and oxidative metabolism in rats with chronic dietary iron overload.

Peroxidative decomposition of organelle membrane phospholipids with subsequent organelle dysfunction is a postulated mechanism of liver cell injury in parenchymal iron overload. We studied the effects of different alpha-tocopherol concentrations on hepatic mitochondrial lipid peroxidation and oxidative metabolism in rats with chronic dietary iron overload. There was no evidence of mitochondrial lipid peroxidation (conjugated dienes) or alteration in mitochondrial oxidative metabolism in alpha-tocopherol-deficient rats with normal hepatic iron levels. Significant reductions in mitochondrial respiratory control ratios and oxidative phosphorylation ratios were seen in association with increased conjugated dienes in all three groups of iron-loaded rats regardless of the alpha-tocopherol status (deficient, normal or excess); thus, the alpha-tocopherol deficiency associated with dietary iron overload in this experimental model is not responsible for the mitochondrial abnormalities observed. In addition, chronic parenteral administration of alpha-tocopherol to iron-loaded animals, which increased hepatic levels of this substance 3-fold, did not ameliorate the hepatic mitochondrial lipid peroxidation or the defects in mitochondrial oxidative metabolism resulting from iron overload.

Animals↗
PubMed1989

Hepatic mitochondrial oxidative metabolism and lipid peroxidation in experimental hexachlorobenzene-induced porphyria with dietary carbonyl iron overload.

Both human porphyria cutanea tarda and experimental hexachlorobenzene-induced porphyria are associated with hepatic injury and are potentiated by excess hepatic iron. The mechanisms whereby cellular injury occurs and the synergistic role of iron overload are unknown. In the present experiments, we studied hepatic mitochondrial function and lipid peroxidation in rats with hexachlorobenzene-induced porphyria in which iron loading was achieved by dietary carbonyl iron supplementation. Female rats were treated for 8 weeks, receiving a chow diet supplemented with hexachlorobenzene (0.2%, w/w), carbonyl iron (1.0%, w/w) or hexachlorobenzene + iron. Hepatic total porphyrins were increased 100-fold in rats receiving hexachlorobenzene (hexachlorobenzene alone and hexachlorobenzene + Fe), and total hepatic iron was increased approximately 10-fold in rats receiving iron supplementation (Fe alone and hexachlorobenzene + Fe). There was a significant increase in mitochondrial lipid peroxidation in rats treated with hexachlorobenzene alone and hexachlorobenzene + Fe. A significant reduction in mitochondrial respiratory control ratios and in oxidative phosphorylation (ADP/O ratios) using glutamate and succinate as substrates was demonstrated when rats were treated with hexachlorobenzene + iron. The reductions in respiratory control ratios were due to a combination of an inhibitory defect in electron transport as evidenced by an irreversible decrease in State 3 respiration and an uncoupling effect as evidenced by an increase in State 4 respiration. These findings suggest that lipid peroxidation and mitochondrial dysfunction may contribute to the hepatotoxicity seen in hexachlorobenzene-induced porphyria.

Animals↗
PubMed1989

Hepatic injury in chronic iron overload. Role of lipid peroxidation.

In both hereditary hemochromatosis and in the various forms of secondary hemochromatosis, there is a pathologic expansion of body iron stores due mainly to an increase in absorption of dietary iron. Excess deposition of iron in the parenchymal tissues of several organs (e.g. liver, heart, pancreas, joints, endocrine glands) results in cell injury and functional insufficiency. In the liver, the major pathological manifestations of chronic iron overload are fibrosis and ultimately cirrhosis. Evidence for hepatotoxicity due to iron has been provided by several clinical studies, however the specific pathophysiologic mechanisms for hepatocellular injury and hepatic fibrosis in chronic iron overload are poorly understood. The postulated mechanisms of liver injury in chronic iron overload include (a) increased lysosomal membrane fragility, perhaps mediated by iron-induced lipid peroxidation, (b) peroxidative damage to mitochondria and microsomes resulting in organelle dysfunction, (c) a direct effect of iron on collagen biosynthesis and (d) a combination of all of the above.

Animals↗
PubMed1989

Xanthine oxidase-induced injury to endothelium: role of intracellular iron and hydroxyl radical.

The major objective of the present study was to characterize the sequence of events leading to endothelial cytotoxicity induced by oxidants generated extracellularly by xanthine oxidase. 51Cr-labeled monolayers of calf pulmonary artery endothelial cells were exposed to a reaction mixture containing hypoxanthine, xanthine oxidase, and chelated iron (HX/XO) and endothelial cell injury was quantitated as 51Cr release into the media. Catalase, but not mannitol or superoxide dismutase, prevented endothelial cell injury induced by HX/XO, indicating that H2O2 was the mediator of the cytotoxicity. Pretreatment of the cells with free deferoxamine (an iron chelator), but not with deferoxamine bound to dextran (mol wt 40,000), prevented endothelial cell injury induced by HX/XO or H2O2. Of the membrane-permeant hydroxyl radical scavengers dimethylsulfoxide and dimethylthiourea, only dimethylthiourea prevented 1) HX/XO or H2O2-induced endothelial cytotoxicity and 2) deoxyribose degradation by hydroxyl radicals (.OH) generated by an iron-catalyzed reaction on the sugar (site-specific reaction). The concentration of ferritin required to produce significant quantities of .OH was much greater than that present in endothelial cells, and ferritin-catalyzed .OH formation was not affected by deferoxamine, indicating that ferritin-bound iron is most likely not the physiologically active catalyst. We conclude that extracellularly generated H2O2 can enter the cell and interact with nonferritin iron to produce the cytotoxic .OH via a site-specific reaction.

Animals↗
PubMed1989

Superparamagnetic iron oxide: pharmacokinetics and toxicity.

The pharmacokinetics (distribution, metabolism, bioavailability, excretion) and toxicity (acute and subacute toxicity, mutagenicity) of a superparamagnetic iron oxide preparation (AMI-25), currently used in clinical trials, were evaluated by 59Fe radiotracer studies, measurements of relaxation times, the ability to reverse iron deficiency anemia, histologic examination, and laboratory parameters. One hour after administration of AMI-25 to rats (18 mumol Fe/kg; 1 mg Fe/kg), 82.6 +/- 0.3% of the administered dose was sequestered in the liver and 6.2 +/- 7.6% in the spleen. Peak concentrations of 59Fe were found in liver after 2 hr and in the spleen after 4 hr. 59Fe slowly cleared from liver (half-life, 3 days) and spleen (half-life, 4 days) and was incorporated into hemoglobin of erythrocytes in a time-dependent fashion. The half-time of the T2 effect on liver and spleen (24-48 hr) was shorter than the 59Fe clearance, indicating metabolism of AMI-25 into other forms of iron. IV administration of AMI-25 (30 mg Fe/kg) corrected iron-deficiency anemia and showed bioavailability similar to that of commercially available IV iron preparations within 7 days. No acute or subacute toxic effects were detected by histologic or serologic studies in rats or beagle dogs who received a total of 3000 mumol Fe/kg, 150 times the dose proposed for MR imaging of the liver. Our results indicate that AMI-25 is a fully biocompatible potential contrast agent for MR.

Animals↗
PubMed1989

Hereditary hemochromatosis: pathogenesis and clinical features of a common disease.

Hereditary hemochromatosis (HHC) is a common inherited disorder of iron metabolism characterized by excessive iron absorption and the toxic accumulation of iron in parenchymal cells. Homozygous inheritance of an abnormality on chromosome 6 causes this disorder by increasing the intestinal absorption of iron, which is slowly deposited in parenchymal cells of the liver, heart, pancreas, and other endocrine organs. Symptoms develop only after the marked accumulation of iron stores develop, which causes functional insufficiency of these organs. The symptoms are often variable, nonspecific, and attributed to other diseases. Early diagnosis requires a high index of suspicion and an awareness of the clinical features of HHC. Serum iron, total iron-binding capacity (TIBC), and ferritin levels are useful screening studies, but liver biopsy with quantitative chemical determination of iron concentration is essential to evaluate histopathological changes and to help distinguish hereditary hemochromatosis from secondary iron overload. Treatment with weekly phlebotomy frequently results in some clinical improvement in patients with established disease, and if initiated early, organ damage can be prevented and a normal life-span can be expected. The hereditary nature of the disease mandates familial screening of index cases.

Hemochromatosis↗
PubMed1988

Randomized, prospective, double-blind clinical trial of butorphanol and diazepam in patients undergoing upper gastrointestinal endoscopy.

Premedication that provides sedation and analgesia is commonly used for patients undergoing endoscopic procedures. We studied the efficacy and safety of butorphanol and diazepam as preprocedure medications for patients having upper gastrointestinal endoscopy. To achieve an adequate level of sedation, patients receiving diazepam required a mean (+/- SEM) dose of 12.0 +/- 1.0 mg, whereas those receiving butorphanol required a mean dose of 4.8 +/- 0.4 mg. There were no differences between treatment groups in the overall assessment of sedation, the ease of performance of the endoscopic procedure, or vital signs during or following the procedure. Fifty-four percent of butorphanol patients and 48% of diazepam patients experienced at least one minor adverse event. Butorphanol in small doses can produce satisfactory sedation and analgesia for patients undergoing gastrointestinal endoscopic procedures.

Adolescent↗
PubMed1988

Guanyl nucleotide interactions with dopaminergic binding sites labeled by [3H]spiroperidol in human caudate and putamen: guanyl nucleotides enhance ascorbate-induced lipid peroxidation and cause an apparent loss of high affinity binding sites.

The human caudate and putamen contain two high affinity binding sites for [3H]spiroperidol. Both of these affinity states exhibit dopaminergic selectivity. Ascorbic acid, at 0.1 mM, induces a slow loss of the low affinity component of [3H]spiroperidol binding in these tissues. The addition of guanyl nucleotides to the ascorbate produces a more rapid loss of [3H]spiroperidol binding which includes a loss of the highest affinity state for [3H]spiroperidol. Ascorbate induces lipid peroxidation in human caudate and putamen, an effect that is further enhanced by guanyl and inosine nucleotides. In the absence of ascorbate, guanyl nucleotides have no effect on [3H]spiroperidol binding but do decrease the affinity of dopamine at each affinity state greater than 60-fold. In the absence of ascorbate, guanyl nucleotides apparently decrease agonist affinity at human brain dopamine2-binding sites without causing an interconversion of agonist affinity states.

Ascorbic Acid↗
PubMed1987

Ferrite particles: a new magnetic resonance imaging contrast agent. Lack of acute or chronic hepatotoxicity after intravenous administration.

Intravenous administration of ferrite particles may be useful as contrast agents for magnetic resonance (MR) imaging of the liver. We studied several sensitive biochemical parameters of hepatocellular function and toxicity in rats after intravenous ferrite injections to determine whether there was any evidence of iron-induced hepatotoxicity. Light microscopy and iron determinations were performed on the liver, spleen, lung, and kidney. Forty-eight hours after a massive (250 mg iron per kilogram) ferrite injection, liver, spleen, and lung nonheme iron concentrations were markedly increased. Microscopy showed this iron to be entirely in reticuloendothelial cells. Despite the large increase in hepatic iron concentration, we found no evidence of hepatic mitochondrial or microsomal lipid peroxidation or organelle dysfunction, sensitive biochemical indicators of iron-induced hepatocellular injury. At 10 to 11 weeks after administration of ferrite in smaller doses (30 mg iron per kilogram), results of all biochemical and morphologic studies were normal. Furthermore, quantitative iron determinations and microscopic studies suggest that ferrite particles may be partially degraded and that iron is cleared from the liver during a 3-month period. Because ferrite particles are taken up by reticuloendothelial cells, hepatocellular function is not impaired and iron-induced hepatocellular injury does not occur.

Animals↗
PubMed1987

Pathology of dietary carbonyl iron overload in rats.

Serial light microscopic and ultrastructural studies were performed in rats with experimental iron overload produced by dietary supplementation with carbonyl (elemental) iron over a 12-month period. Hepatic iron increased rapidly to concentrations approximately 40 to 90 times those of control rats by 3 months. Within the liver, iron deposition was initially confined to periportal (zone 1) hepatocytes but subsequently extended to midzonal (zone 2) and centrilobular (zone 3) hepatocytes. Reticuloendothelial cell deposits of iron increased gradually and became prominent after 3 months. At this time, morphologic evidence of hepatocellular injury was mild and subtle with occasional foci of spotty necrosis and ultrastructural subcellular organelle damage. By 8 months, iron deposition was massive. Portal areas were enlarged with collections of iron-loaded macrophages and increased collagenous tissue. This portal fibrous tissue extended between periportal (zone 1) hepatocytes at sites of maximal iron deposition and around iron-loaded Kupffer cells and macrophages. At 12 months, the periportal (zone 1) fibrosis was more pronounced. These serial morphologic studies are the first to demonstrate the production of hepatic fibrosis by chronic dietary iron overload. This experimental model may reproduce important components of the pathophysiologic sequence of chronic liver damage seen in iron overload states in humans.

Animals↗
PubMed1986

Hepatic microsomal function in rats with chronic dietary iron overload.

We determined whether alterations in hepatic microsomal function occur in association with iron-induced lipid peroxidation in vivo in rats with chronic dietary iron overload. In rats fed a 2.0% carbonyl iron diet for a period of 20 wk, there was no significant microsomal conjugated diene formation (evidence of microsomal lipid peroxidation) or difference in cytochrome P450 concentration found at mean (+/- SEM) hepatic iron concentrations of 1210 +/- 92 micrograms/g liver (wet wt) or 2730 +/- 100 micrograms/g. At a hepatic iron concentration of 4090 +/- 245 micrograms/g, however, there was significant conjugated diene formation (p less than 0.001) and a 56% decrease in the cytochrome P450 concentration (p less than 0.001). In rats fed a 2.5% carbonyl iron diet for 10 wk, achieving a liver iron concentration of 4820 +/- 420 micrograms/g, there was significant microsomal conjugated diene formation (p less than 0.001), a 35% reduction in cytochrome P450 (p less than 0.005), and a 16% reduction in aminopyrine demethylase activity (p less than 0.025), but only an 8% reduction in glucose-6-phosphatase activity (p = not significant). Finally, in rats fed a 3.0% iron-supplemented diet for 7 wk, achieving a liver iron concentration of 2730 +/- 205 micrograms/g, there was a 23% reduction in cytochrome P450 (p less than 0.025), a 28% reduction in cytochrome b5 (p less than 0.001), and a 47% increase in heme oxygenase activity (p less than 0.025) (heme oxygenase activity measured in this group only). We conclude that oral iron loading can produce microsomal lipid peroxidation in vivo that is associated with selective decreases in microsomal hemoprotein concentrations and cytochrome P450-dependent enzymes.

Aminopyrine N-Demethylase↗
PubMed1986

Immediate diagnostic criteria for bacterial infection of ascitic fluid. Evaluation of ascitic fluid polymorphonuclear leukocyte count, pH, and lactate concentration, alone and in combination.

We prospectively evaluated the ascitic fluid (AF) polymorphonuclear cell (PMN) count, pH, and lactate concentration in single ascitic fluids from 60 patients to determine their relative predictive values for the immediate diagnosis of ascitic fluid infection. Nine of the 60 ascitic fluids were malignant. Of the remaining 51 samples, nine from cirrhotic patients were infected. The mean AF pH, lactate concentration, and PMN count in the infected group were 7.20 +/- 0.19, 80 +/- 51 mg/dl, and 18,199 +/- 19,650 cells/mm3, respectively, and all were significantly different from the corresponding values in noninfected ascites. Mean arterial blood-ascitic fluid (B-AF) pH and lactate gradients in the infected group were 0.23 +/- 0.17 and -46 +/- 31 mg/dl, respectively, and were significantly different from the corresponding values in noninfected ascites (p less than 0.05). Significant differences were not found between infected and malignant ascites, except for the AF PMN count (p less than 0.001). In cirrhosis with ascites, an AF pH less than or equal to 7.34 was the most specific single test (100%) and had the highest diagnostic accuracy (98%). In the larger group of patients with ascites of diverse etiology, a B-AF pH gradient greater than or equal to 0.10 or an AF PMN count greater than or equal to 500 cells/mm3 were the single tests with the highest diagnostic accuracy (92%). Combining an AF PMN count greater than 500 cells/mm3 with any of the other diagnostic criteria increased the specificity and diagnostic accuracy (up to 98%) compared to the best single criterion. Although our data support the use of a number of different combinations of AF measurements for the immediate diagnosis of infection, the simplest and most readily obtainable measurements are the pH and PMN count. Therefore, in the clinical setting we recommend the use of either an AF pH less than or equal to 7.34 or a B-AF pH gradient greater than or equal to 0.10 in combination with an AF PMN count greater than 500 cells/mm3 to obtain the highest degree of accuracy in the immediate diagnosis of ascitic fluid infection.

Adult↗