PubMed Health⌕ Search

Biomedical subjects

R McNew

Publications and source records attributed to R McNew.

12 recordsLinked to original sources
PubMed2004

Investigation of proton conductance in liver mitochondria of broilers with pulmonary hypertension syndrome.

We previously reported an impaired ability to regulate hepatic mitochondrial state 4 respiration rate in response to sequential additions of adenosine diphosphate in pulmonary hypertension syndrome (PHS). As proton conductance is a major contributor to State 4 respiration, the major goal of this study was to investigate the nature of proton conductance in hepatic mitochondria isolated from broilers with and without PHS. Broilers were placed on floor litter in environmental chambers and exposed to cold temperatures (15 degrees C) from 3 to 7 wk of age to induce PHS. Liver mitochondria were isolated from birds that exhibited PHS (cyanosis, right ventricular weight ratio > 0.30) or from birds that appeared healthy (no cyanosis, right ventricular weight ratio < 0.27). Isolated mitochondria were placed in a chamber equipped with the ability to measure oxygen content and mitochondrial membrane potential. The mitochondrial membrane potential was assessed by an ion sensitive electrode to measure the distribution of methyltriphenylphosphonium across the inner mitochondrial membrane. Proton conductance was assessed by simultaneously measuring State 4 oxygen consumption rate as respiration was progressively inhibited with increasing concentrations of malonate. The addition of cardiolipin, a lipid found in high concentrations in mitochondrial membranes that can alter proton conductance, had no affect on respiration or mitochondrial membrane potential in either group. The relationship of curves depicting State 4 respiration and mitochondrial membrane potential indicates that PHS mitochondria exhibit impaired substrate oxidation and reduced proton conductance relative to controls. These findings provide further characterization of the altered cellular oxygen utilization in broilers with PHS.

Animals↗
PubMed2001

The hepatic extraction of plasma free amino acids and response to hepatic portal venous infusion of methionine sources in anesthetized SCWL males (Gallus domesticus).

This study was conducted to investigate the hepatic extraction of plasma free amino acids in anesthetized Single Comb White Leghorn (SCWL) males (Gallus domesticus). SCWL males were anesthetized and implanted with cannulae in the carotid artery, hepatic vein, hepatic portal vein and the left hepatic duct. Free amino acids in plasma and bile were determined before, during and after 30-min infusions of Saline (control), DL-Methionine (DL-Met) or DL-2-hydroxy-4-methylthio-butanoic acid (DL-HMB) into the hepatic portal vein. Hepatic extraction rates (HER) of amino acids were calculated based on the concentration of amino acids in plasma multiplied by estimations of blood flow in the hepatic portal vein, hepatic artery and hepatic vein. For the non-essential amino acids, alanine had the highest HER (46%). The liver also removed more than 20% of hepatic inflow of tyrosine and asparagine with substantial extraction (14-18%) of serine, glycine and glutamine, also. In contrast, less than 5% of hepatic inflow of glutamate and cystine were removed by liver. For the essential amino acids, HER for methionine, histidine and phenylalanine were 30, 14 and 17%, respectively, with less than 5% for branched-chain amino acids, lysine, arginine and threonine. Biliary secretion of amino acids represented a small percentage (<0.2%) of total hepatic extraction turnover of the amino acids. Infusion of methionine sources, DL-Met and DL-HMB, had no effect on hepatic metabolism of amino acids other than methionine. The results demonstrated for the first time, the hepatic extraction of circulating free amino acids in avian species in vivo.

Amino Acids↗
PubMed1999

Evidence of mitochondrial dysfunction in broilers with pulmonary hypertension syndrome (Ascites): effect of t-butyl hydroperoxide on hepatic mitochondrial function, glutathione, and related thiols.

The purpose of this study was to assess mitochondrial function and glutathione (a mitochondrial antioxidant) in response to oxidative stress in mitochondria in vitro obtained from broilers with and without pulmonary hypertension syndrome (PHS). Liver mitochondria from Control and PHS broilers were incubated with 0, 1, and 5-mM tertiary-butyl hydroperoxide (tBH). Indices of mitochondrial function [the respiratory control ratio (RCR) and the adenosine diphosphate to oxygen ratio (ADP:O)], and levels of mitochondrial and extra-mitochondrial reduced (GSH) and oxidized (GSSG) glutathione, cysteine, cystine, glutamate and cysteinyl-glycine were determined following tBH treatment. Lower RCR and ADP:O values were observed in PHS mitochondria than in controls. Whereas control mitochondria remained coupled (RCR > 2.0), only 3 PHS preparations remained coupled after 60 min of incubation with 5 mM tBH, indicating a greater susceptibility to oxidative stress in PHS mitochondria. The lower RCR in PHS mitochondria was due to increased oxygen consumption during State IV respiration. Oxidative stress following tBH treatment (decreased GSH and increased GSSG) was observed, but there were no differences in GSH or GSSG between control and PHS mitochondria. The PHS mitochondria did exhibit elevated mitochondrial and extramitochondrial cystine than controls, however. The results indicate that PHS mitochondria do not lack antioxidant protection from GSH, but lower RCR and ADP:O ratios in PHS mitochondria indicate a dysfunction that may contribute to the pathophysiology of this metabolic disease in broilers.

Adenosine Diphosphate↗
PubMed1998

Hepatic export of glutathione and uptake of constituent amino acids, glutamate and cysteine, in broilers in vivo.

This study was conducted to document the glutathione (GSH) cycle (interorgan circulation of GSH) in broilers in vivo. Two experiments were conducted on 36 anesthetized male broilers (n = 6 per treatment) implanted with cannulae in the carotid artery, hepatic portal, and hepatic veins. Plasma GSH, glutamate, cysteine, cystine, and cysteinylglycine levels in each vessel were monitored following a bolus injection [Experiment (Exp.) 1] or 30 min continuous infusion (Exp. 2) of GSH, or a gamma-glutamyltranspeptidase inhibitor (AT125) into the hepatic portal vein. Controls received saline alone. The GSH and AT125 treatments were used to determine the effect of increasing the prehepatic GSH load and of inhibiting systemic GSH degradation, respectively, on the GSH cycle. Hepatic export of GSH was clearly evident in all three treatment groups in both experiments (Exp.). The GSH and AT125 treatments raised amino acid levels in some or all of the vessels, whereas cysteinylglycine was elevated by AT125 and depressed by the GSH treatment compared to Controls. Hepatic uptake of glutamate, cysteine, and/or cystine was observed in Controls and GSH-treated birds, but not in birds given AT125 (Exp. 2). Neither hepatic export nor uptake of cysteinylglycine was observed in any treatment group. The results clearly demonstrate the ability of the avian liver to export GSH into the general circulation despite alterations that might arise from changes in extra-hepatic ability to utilize GSH or its constituent amino acids.

Animals↗
PubMed1996

Readability of printed sources of diet and health information.

This study surveyed nutrition education materials which are low in cost, brief and the type most used in patient education to determine which might be useful with low literacy clients. Readability of 209 pamphlets from professional health organizations, commercial organizations, government agencies, and educational institutions was assessed using three different tests. Using the Flesch and Raygor tests, materials from educational institutions had significantly lower reading levels than materials from professional organizations and government agencies. No significant differences were seen among the sources using the Fry test. Sixty-eight percent (142) of the publications were written at ninth grade level or higher. Eleven percent (24) scored at sixth grade or below on either the Fry or Raygor scale. Only two publications were written at the third grade level. Many of the publications reviewed can be read and understood by many Americans, but there were few for the millions that have limited literacy skills.

Educational Status↗
PubMed1995

Problems encountered in meeting the Recommended Dietary Allowances for menus designed according to the Dietary Guidelines for Americans.

Forty-three menus that were to be used in a diet manual were designed to meet the requirements of a specific diet; provide 2,200 to 2,400 kcal, unless energy-restricted; meet the 1990 Dietary Guidelines for Americans; meet current recommendations for sodium (2g to 3 g/day), cholesterol (< or = 300 mg/day), and fiber (20g to 30 g/day); and meet or exceed the highest level for adults in the 1989 Recommended Dietary Allowances (RDAs). In addition, regular and low-fat, low-cholesterol menus for 1 week were collected from 11 hospitals throughout Arkansas. Menus were analyzed for energy, cholesterol, and 18 nutrients. Only 11% of the menus met the RDA for zinc. Half of the menus did not meet the RDA for vitamin B-6 and one third did not meet the RDA for iron. Zinc content of the menus was positively correlated (P < .001) with protein (r = .73) and with beef (r = .45). Vitamin B-6 was positively correlated with protein (r = .44, P < .001) and with all meat (r = .38, P < .01). Regular and low-fat, low-cholesterol hospital menus had the same nutrient inadequacies because they did not differ in total servings from any food group. These data indicate that the public may have difficulty choosing a diet that meets both the Dietary Guidelines and the RDAs.

Arkansas↗
PubMed1995

Effect of alpha-tocopherol on antioxidants, lipid peroxidation, and the incidence of pulmonary hypertension syndrome (ascites) in broilers.

Research has demonstrated a compromised antioxidant capacity in broilers with pulmonary hypertension syndrome (PHS). Thus, the objective of the present study was to assess the effects of vitamin E on PHS-induced mortality, tissue antioxidants, and plasma lipid peroxides in male broilers. Control broilers were provided normal ventilation but others, maintained under low ventilation conditions to induce PHS, were randomly assigned to nonimplanted (NI), placebo (PL), or vitamin E (VE) implanted groups. The VE implant released a total of 15 mg of alpha-tocopherol from 0 to 3 wk of age. Tissues and blood samples were obtained at 3 and 5 wk of age from birds with (PHS+) and without (PHS-) PHS. Five-week PHS cumulative mortality was lowered by alpha-tocopherol with mortality rates of 3.6, 4.2, 11.9, and 11.8%, for Controls, VE, NI, and PL groups, respectively. The PHS+ birds exhibited lower body weights, higher hematocrit, right ventricular hypertrophy, lower alpha-tocopherol and glutathione (GSH) concentrations in liver and lung, as well as indicators of oxidative stress, including elevated plasma lipid peroxides and lower oxidized GSH in liver and erythrocytes, at 5 wk of age. All birds exhibited lower erythrocyte catalase activity at 5 than at 3 wk of age. An improved antioxidant capacity was observed in VE birds, including higher liver and lung alpha-tocopherol at 3 and 5 wk, higher liver GSH at 3 wk, and lower plasma lipid peroxide values at 5 wk of age. Direct correlations observed between body weight and plasma lipid peroxides at 3 wk (r = .45) and between right ventricular hypertrophy and plasma lipid peroxides at 5 wk (r = .48), suggests that lipid peroxidation plays a role in the etiology of PHS. The results indicate that the VE implant was effective in lowering PHS-induced mortality in broilers apparently by attenuating processes leading to lipid peroxidation.

Analysis of Variance↗
PubMed1994

Patterns of food choices among Arkansans with less than a high school education.

This study surveyed students in Adult Basic Education (ABE) Programs in Arkansas to determine their pattern of food choices. The results indicated that entire food groups, e.g. vegetables, fruits, or milk were not included in the diets of many participants. This population more frequently chose high fat than low fat foods. Regression analyses indicated that the choice of low fat products increased with age and family income level. The most dramatic trends were in changes in consumption of dairy products, fruits, and vegetables. These data support the need for nutrition education in Arkansans with less than a high school education.

Adolescent↗
PubMed1991

Altered developmental toxicity caused by three carrier solvents.

Many aquatic bioassays rely on chemical solvents to solubilize water-insoluble test materials. Interactions between solvents and test materials can lead to false positive or negative results. For this reason, tests for interactions between solvents and test materials were performed. The Frog Embryo Teratogenesis Assay--Xenopus (FETAX) was chosen because of its capacity to assess three different endpoints; mortality, malformation and embryo growth. Three solvents--dimethylsulfoxide (DMSO), acetone and triethylene glycol (TG)--were tested with two teratogens--methylmercury chloride (MMC) and trichloroethylene (TCE). DMSO potentiated the lethal effect of both teratogens but did not alter significantly the rate of malformation. Acetone increased the mortality for both teratogens, but only increased the MMC malformation greater than the additive effects. TG only increased the mortality and malformation with TCE. There were additive effects for growth for all solvents with the teratogens. The carrier solvents caused interactions even at their no-observable-effect concentration (NOEC). Therefore, the choice of carrier solvent should be made with caution. This study shows that different results can occur depending on the solvent used, and that a difference in one endpoint does not necessarily change the other endpoints.

Acetone↗
PubMed1989

Effects of allopurinol in experimental endotoxin shock in horses.

The effect of allopurinol pretreatment 12 hours before an intraperitoneal challenge with a sublethal dose of Escherichia coli endotoxin (50 micrograms kg-1) was evaluated in 18 horses. The horses were divided among three equal groups: 1-endotoxin alone; 2-5 mg allopurinol kg-1 bodyweight plus endotoxin; and 3-50 mg allopurinol kg-1 bodyweight plus endotoxin. A variety of evaluation parameters were used. No differences among the groups were noted in rectal temperature, heart rate, respiration rate, haematological values, blood PaO2, blood PaCO2, blood pH or blood bicarbonate. Significant (P less than 0.05) differences between the groups were noted as regards the changes in capillary refill time, base excess, blood glucose, blood lactate, blood beta-glucuronidase and recumbency time. The protection afforded by 5 mg allopurinol kg-1 appeared to be superior to that with 50 mg allopurinol kg-1.

Allopurinol↗