Biomedical subjects

R E Austic

Publications and source records attributed to R E Austic.

At least 37 records · Page 2Linked to original sources

PubMed1992

Direct measurement of nitric oxide in headspace gas produced by a chicken macrophage cell line in a closed culture system.

A simple and rapid method was applied for direct measurement of nitric oxide (NO) gas produced by cultured macrophages using a modified chemiluminescence detector, the thermal energy analyzer (TEA). HD11 chicken macrophages (1-3 x 10(6)/ml) were cultured on microcarrier beads (100 mg/ml) in 140 ml air-tight glass jars (5 ml cell suspension per jar) containing 0.5 micrograms/ml of LPS and different concentrations of L-arginine. Headspace gas was sampled at 24 hours of culture via a rubber septum and directly injected into a TEA with a liquid nitrogen trap set at -130 to -140 degrees C. The concentration of NO in the gas sample was quantified using a standard gas mixture of NO (2 microliters/L) in nitrogen. Gas samples from L-arginine-supplemented cultures contained NO (0.028-0.066 pl/microliter), whereas NO was not detected in samples from controls. These results suggest that chicken macrophages synthesize NO gas in a dose-dependent manner relative to L-arginine concentration.

Animals↗

PubMed1992

Dietary arginine influences Rous sarcoma growth in a major histocompatibility B complex progressor genotype.

L-Arginine (L-Arg) can serve as a substrate for the production of reactive nitrogen intermediates. One of these metabolites, nitric oxide, has been shown to possess significant antitumor properties in vitro. To investigate the importance of this system in vivo, we have examined the dietary L-Arg host tumor interaction in the chicken. Since chickens are incapable of de novo L-Arg synthesis, concentration of this amino acid is readily controlled by diet. Line UNH 105 New Hampshire chickens having the major histocompatibility complex genotype, B24/B24, were used to study in vivo effects of dietary L-Arg on Rous sarcoma growth. After 5 weeks on a standard diet, 119 chicks were fed either a basal (0.92% L-Arg) diet or a high arginine (2.40% L-Arg) diet. One week later, chicks were wing-web inoculated with subgroup A Rous sarcoma virus. Tumor growth was monitored weekly for 12 weeks after inoculation. Plasma L-Arg levels and body weights from birds on each dietary treatment were analyzed. Neither body weight gains nor latent period for tumor development was affected by diet. However, plasma L-Arg levels were significantly different between dietary treatments (basal, 0.245 +/- 0.01 mumol/ml; high, 0.738 +/- 0.03 mumol/ml). In addition, mean tumor size scores were significantly (P less than 0.05) lower over time in chickens fed the high L-Arg diet. The results suggest that dietary L-Arg in excess of the amount required for growth reduces tumor load.

Animals↗

PubMed1991

L-arginine-dependent production of a reactive nitrogen intermediate by macrophages of a uricotelic species.

L-arginine-dependent production of reactive nitrogen intermediates (RNIs: nitric oxide, nitrite, and nitrate) by mammalian macrophages has been proposed to occur via an L-arginine oxidative deimination pathway and is known to be responsible for certain antineoplastic and antimicrobial effector functions. The present study represents the first examination of this pathway in a non-mammalian vertebrate. Because chickens, unlike mammals, lack a urea cycle and are incapable of de novo synthesis of L-arginine, the possible existence of an avian macrophage pathway for production of RNIs is questionable. We have defined conditions under which chicken macrophages are able to produce nitrite. Sephadex-elicited chicken peritoneal macrophages required a bacterial lipopolysaccharide (LPS from Escherichia coli) signal to produce nitrite during 24 hour cultures in the presence of L-arginine. As little as 5 ng/ml LPS resulted in significant nitrite production in culture. The relationship of nitrite production to both LPS and L-arginine levels was dose-dependent. D-arginine was unable to substitute for L-arginine but also produced no inhibitory effect. In contrast, L-NG-monomethyl arginine showed a significant inhibitory effect on nitrite production. A virus-transformed chicken macrophage cell line, HD11, also produced nitrite in a dose-dependent manner relative to both LPS and L-arginine concentration. Concentrations as low as 5 ng/ml LPS and 0.1 mM L-arginine resulted in significant nitrite production, while maximum levels of nitrite production were obtained using greater than or equal to 0.5 micrograms/ml LPS and greater than or equal to 0.4 mM L-arginine. These results indicate that chicken macrophages can produce RNIs. This production is dependent upon activation and is influenced by local L-arginine concentration. Moreover, because the chicken does not possess the ability to synthesize arginine and has an absolute nutritional requirement for this amino acid, the chicken represents a highly controllable system to examine the in vivo effects of L-arginine on macrophage-related immune functions.

Animals↗

PubMed1990

Effects of dietary minerals on acid-base balance and eggshell quality in chickens.

Three experiments were conducted in hens to determine the effects of high levels of dietary phosphorus (P, 1-1.5%), chloride (Cl, 0.8%) or both on acid-base balance and eggshell quality and to consider whether any adverse effects on eggshell quality can be attributed to alteration of blood acid-base balance. Eggshell quality and values for a blood indicator of acid-base balance were reduced by high levels of dietary P or Cl in all of the experiments. Eggshell quality and values for the blood acid-base indicator were further reduced by high dietary levels of the combination of minerals. The adverse effects associated with high levels of the combination were greater than the sum of adverse effects associated with high levels of each mineral. The effects of P and Cl on plasma levels of these minerals were inconsistent and varied among experiments. The use of pair-fed controls revealed that the adverse effects of combined P and Cl on eggshell quality and acid-base balance were independent of their effects on feed and calcium intake. Calcium excretion was increased by consumption of the high P, high Cl diet. The information obtained from these experiments suggests that the adverse effects of high levels of dietary P and/or Cl on eggshell quality may be due, at least in part, to increased Ca excretion. This, in turn, may be mediated by acidemia resulting from the dietary manipulations, although the present data were insufficient to provide a direct link between acidemia and Ca excretion.

Acid-Base Equilibrium↗

PubMed1989

Influence of dietary electrolytes on lysine and arginine absorption in chick intestine.

The intestinal absorption of lysine and arginine in the chick was characterized using an in situ-ligated intestinal segment technique, and the influence of dietary electrolytes on their absorption was examined. Each amino acid, labeled with 14C and provided at a concentration of .5 mM, was introduced into the lumen of the small intestine of young chicks. Absorption was defined as disappearance of label from the lumen after 4 min. Lysine absorption was greater than arginine absorption in the duodenum and in the middle and distal small intestine. The Jmax values for absorption of lysine and arginine were 315.0 nmol/min and 112.0 nmol/min, whereas the respective Kt values were 2.3 mM and 2.0 mM. Maximal transport of lysine and arginine occurred at pH 6.0. Lysine absorption was depressed (P less than .05) at pH 5.0 and pH 8.0, whereas arginine absorption was depressed (P less than .05) only at pH 8.0. High dietary chloride (.89%) produced higher (P less than .05) lysine absorption than a high dietary level of potassium (1.81%). No effect (P greater than .05) of dietary electrolytes on arginine absorption was detected. These results indicate that the dietary balance of monovalent electrolytes, and, hence, acid-base balance, may influence the intestinal absorption of lysine.

Analysis of Variance↗

PubMed1988

Interaction of dietary calcium and chloride and the influence of monovalent minerals on eggshell quality.

Two experiments were conducted to determine the influence of dietary sodium and chloride on eggshell quality of leghorn hens. In the first, hens were fed for 4 wk diets containing three levels of calcium (2.0, 2.8, and 3.5%) and two levels of chloride (.25 and .86%) in a factorial arrangement of treatments involving four replicates of five hens/treatment. Neither chloride nor calcium significantly affected hen-day egg production or egg weight (P greater than .05); however, chloride decreased feed consumption and calcium increased body weight gain (P less than .05). Interactions of calcium and chloride were significant for eggshell strength (P less than .06) and eggshell thickness (P less than .05). Chloride decreased these measures of eggshell quality only for hens receiving 2.0% calcium, and calcium improved both measures only for hens receiving .86% chloride. Chloride decreased blood bicarbonate concentration and base excess (P less than .05), but did not affect blood pH and pCO2 (P greater than .05). The effect of dietary sodium and chloride on eggshells of hens receiving 2.0% dietary calcium was determined in a second experiment. Seven diets ranging from .18% sodium and .94% chloride to .76% sodium and .24% chloride were provided for 4 wk to five replicates of five hens/treatment. Dietary sodium and chloride levels did not affect hen-day egg production or egg weight (P greater than .05). Increasing the proportions of sodium relative to chloride decreased food intake but increased eggshell strength and thickness (P less than .01) and increased blood pH (P less than .05), bicarbonate concentration (P less than .01), and base excess (P less than .01).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1987

Carrier-mediated transport of urate by chicken (Gallus domesticus) renal brush-border membrane vesicles.

1. Urate is transported by an anion exchange system in chicken renal brush-border membrane vesicles. An outward chloride gradient stimulates an overshoot in urate uptake. 2. The anion exchanger is similar to those described for the kidneys of rats and dogs except that the chicken exchanger has a higher specificity for urate. 3. p-Aminohippurate has only a weak affinity, if any, for the urate exchanger. 4. There were no apparent qualitative differences in urate transport between brush-border membrane vesicles from genetically normouricemic and hyperuricemic chickens.

Animals↗

PubMed1987

Urate and p-aminohippurate transport in isolated kidney tubules of normal and hyperuricemic chickens.

Urate and p-aminohippurate accumulations of kidney tubule fragments were studied in 5- to 6-week-old normal (LUA) and hyperuricemic (HUA) chickens. Tubules from LUA chicks consistently accumulated two to three-fold as much urate and p-aminohippurate as tubules from HUA chicks and thus confirmed the tubular origin of the urate transport defect in HUA chickens. A sodium gradient was required for optimal urate and p-aminohippurate accumulations and ouabain inhibited the accumulations of both compounds. Similar responses of urate and p-aminohippurate to treatments and reciprocal inhibitions between these compounds suggest that urate and p-aminohippurate are accumulated through a shared transport system.

Aminohippuric Acids↗

PubMed1987

Effect of dietary electrolyte balance on growth and acid-base status in swine.

The effect of dietary electrolyte balance on pigs fed lysine- or tryptophan-adequate or tryptophan-deficient diets was investigated in four experiments using 8- to 12-wk-old pigs. Electrolyte balance, expressed as Na+K-Cl in meq/kg of diet, was varied by altering dietary levels of Na and Cl while holding all other minerals constant. In two experiments in which the basal diet contained a balance of 135 meq/kg, simple lysine or tryptophan deficiences caused depressed growth, feed intake and efficiency of feed utilization, but none of these responses was altered by dietary supplementation with NaHCO3. In one experiment in which the electrolyte balance of the basal diet was 61 meq/kg and in which both lysine and tryptophan were limiting. NaHCO3 supplementation significantly increased growth and feed intake. This did not occur if the diet was also supplemented with tryptophan. A final experiment was conducted to determine the response of pigs to a range of electrolyte balance (-85 to 341 meq/kg) in a practical corn-soy diet containing adequate levels of all amino acids. Growth and feed intake appeared to be maximal for balances of 0 to 341 meq/kg Na+K-Cl, but were decreased at -85 meq/kg (P less than .05). Acid-base balance was adversely affected at 0 meq/kg. The results suggest that the response of lysine-deficient pigs to sodium bicarbonate is dependent upon the electrolyte balance of the diet, and also is influenced by other dietary amino acids.

Acid-Base Equilibrium↗

PubMed1987

Effect of dietary supplements of sodium or potassium bicarbonate on short-term macromineral balance in swine.

Four crossbred barrows, weighing an average of 26 kg each, were fitted with simple T-cannulas in the terminal ileum and placed in metabolism cages to evaluate the effect of dietary supplements of NaHCO3 or KHCO3 on the short-term metabolism of sodium (Na), potassium (K), calcium (Ca), magnesium (Mg) and chloride (Cl). A control diet containing 2.8 g/kg Na and 4.1 g/kg K was compared with similar diets supplemented with either 13 g/kg or 26 g/kg NaHCO3 or 30 g/kg KHCO3. All diets contained 4 g/kg Cr2O3 as an external marker and were offered twice daily (1,100 g X pig-1 X d-1) in a 4 X 4 Latin square arrangement. Feces and total urine output were collected for 24 h on the fifth day after introducing a new diet; digesta was collected for 12-h periods on d 6 and 7. Sodium and K concentrations at the terminal ileum were unaffected by dietary treatment. Apparent ileal digestibility of Na was increased by NaHCO3 supplements. Over the total gastrointestinal tract, diet had no affect on apparent Na digestibility. Urinary Na clearance was increased by NaHCO3 in the diet in a dose-dependent manner. Net Na retention (g/d) was increased by NaHCO3. Apparent ileal digestibility of K was increased by KHCO3. Apparent fecal digestibility of K was increased by KHCO3 and NaHCO3. Urinary K clearance was elevated by KHCO3, but not enough to overcome the increased K intake; net K balance (g/d) rose in response to dietary KHCO3 supplements. Sodium bicarbonate or KHCO3 had no effect on short-term digestibility or balance of Mg, Ca or Cl.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1986

Urea cycle activity and arginine formation in rainbow trout (Salmo gairdneri)

Studies were conducted to determine whether rainbow trout fingerlings possess the ability to synthesize arginine via the urea cycle. Several urea cycle enzymes were detected in trout tissues. An experiment was conducted to determine whether the enzymes increase in response to starvation or in response to dietary protein level (0, 30, 40, 50% protein). Although some effects were observed, they did not appear to be consistent with the function of the urea cycle as a mechanism of detoxifying ammonia in the fish. The activities of kidney arginase and liver and muscle carbamoyl phosphate synthetase (CPS) were higher (P less than 0.05) when protein was omitted from the diet (P less than 0.05) than when it was present but were unaffected by protein level otherwise. The activities of liver arginase and kidney and muscle CPS and ornithine transcarbamoylase (OTC) were higher (P less than 0.05) in starved fish than in fish that received adequate levels of protein. Liver CPS and OTC were lower in starved fish than in fish fed 30% protein. L-[l-14C]ornithine hydrochloride and L-[carbamoyl-14C]citrulline, injected intraperitoneally, were incorporated into tissue arginine, a finding consistent with arginine biosynthesis via the urea cycle. When one-half of dietary arginine was replaced by equimolar amounts of glutamic acid, ornithine or citrulline, glutamic acid markedly reduced growth (P less than 0.05), whereas growth was depressed only slightly by ornithine (P less than 0.05) and not depressed by citrulline (P greater than 0.05). We conclude that trout have a urea cycle that provides for potential arginine biosynthesis.

Animals↗

PubMed1986

Intestinal absorption of glucose and amino acids in chickens administered monensin.

Effects of the ionophoric anticoccidial agent monensin on glucose and amino acid absorption were investigated in young broiler chickens. Chicks housed in cages with wire floors were fed a practical diet containing 0 or 121 ppm monensin for 2 to 3 weeks prior to measurement of nutrient absorption. Chicks were anesthetized with halothane, and the intestine was accessed through an incision in the abdominal wall. A 10-cm segment of the intestine immediately anterior to Meckel's diverticulum was rinsed free of digesta and used for measurement of absorption in situ. One milliliter of saline solution containing 2 mM of glucose or a mixture of amino acids was injected into the lumen of the ligated segment, and recovery of glucose and amino acids in the lumen was determined after 4- and 5-min intervals, respectively. In one glucose study, the solution contained 0, 1, 10, or 80 micrograms/ml of monensin. In one amino acid study, the solution contained 0, 5, or 80 micrograms/ml of monensin; in subsequent studies, monensin was not included in the solution. Results show that neither dietary monensin nor monensin in the saline solution affected glucose absorption. Dietary monensin tended to depress lysine absorption but increased the absorption of tryptophan and arginine, the latter amino acid being markedly affected by monensin. Dietary monensin alone had no effect on absorption of cystine, isoleucine, methionine, or threonine. Inclusion of monensin in the saline solution depressed methionine absorption but only when birds also had been fed the diet containing monensin. Monensin in the saline solution depressed isoleucine absorption irrespective of dietary treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗

PubMed1985

Development and adaptation of protein digestion.

Protein digestion is a complex process in which most aspects have a developmental pattern of activity. Gastric pH and intestinal peptide and amino acid transport as well as the activities of pepsinogen, trypsin, chymotrypsin, enterokinase and intestinal dipeptidases vary during development. No one species has been assessed for all these aspects and it is not possible to present an integrated developmental view of protein digestion. The following developmental changes, however, have been observed. Gastric pH declines, and peptic and pancreatic proteases exhibit increasing activity in pigs and rats after birth. The increase in pigs is gradual over several weeks starting at birth, whereas the increases in the rat begin at 2 wk, just prior to the time of weaning. The activities of dipeptidases in the rat and pig, peptide transport systems in the guinea pig and rabbit and amino acid transport systems in the rat, rabbit, guinea pig and chicken, however, appear (with few exceptions) to be active in the small intestine at the time of birth. Frequently, these activities peak in the neonate and decline during the postnatal period. In the rat, dietary protein tends to increase the activities of pancreatic proteases and intestinal peptidases and to increase the rate of uptake of amino acids by the intestinal epithelium. Individual dietary amino acids also influence amino acid transport systems. The data indicate that most processes in protein digestion undergo marked changes during prenatal and postnatal development and are influenced by the level of feeding and composition of the diet.

Adolescent↗

PubMed1985

Effects of feed restriction on growth and metabolism of replacement pullets.

The effects of feed restriction on lipogenesis, carcass composition, and protein utilization were investigated. Two feed restriction programs were used: restricted duration of feeding (RDF) whereby pullets had access to feed for 7 or 9 hr/day and restricted access to feed (ADF) in which feed was available on alternate days. A control group received the same diet as the restricted groups but on an ad libitum basis. The feeding programs were applied to a white egg and brown egg strain of commercial laying hens from 1 until 5 weeks of age or from 3 days (RDF) or 10 weeks (ADF) until 19 weeks of age. The ADF restriction resulted in 12 to 25% decrease in body weights at 5 weeks and 5 to 11% decrease in body weights at 18 or 19 weeks. The RDF depressed body weights 24% at 5 weeks and 2% at 18 weeks. The RDF and ADF increased hepatic malic enzyme and glutamic oxaloacetic transaminase activities in both age groups. Plasma uric acid and hepatic glutamic pyruvic transaminase were affected, but not consistently, by ADF. It is hypothesized that ADF and RDF lead to increased lipogenesis and increased utilization of amino acids as sources of energy. Under conditions of mild restriction, this may result in increased carcass fat content.

Adipose Tissue↗

PubMed1984

Changes in plasma, tissue, and urinary nitrogen metabolites due to an inflammatory challenge.

Studies were undertaken to define the changes in protein metabolism that result from stimulation of the immune system by noninfectious inflammatory agents. Chicks were injected with inflammatory agents and metabolite concentrations were determined between 4 and 48 hr postchallenge. Inflammatory agents resulted in a generalized decrease in the concentration of plasma nitrogen metabolites, including ammonia, uric acid, urea, and several amino acids. Escherichia coli and sheep red blood cell (SRBC) injections induced changes in the concentrations of tissue-free amino acids at 16 hr postchallenge. After E. coli injections, free amino acid concentrations were increased by 175% in muscle and decreased by approximately 25% in liver, spleen, and bursa. A SRBC challenge resulted in similar decreases in free amino acid concentrations in the spleen and bursa as did E. coli; however, muscle and liver free amino acid concentrations were mostly unchanged. Urinary ammonia was increased, urinary uric acid was decreased, and urinary amino acids were not affected by E. coli injection. These findings indicate that stimulation of the immune system by noninfectious inflammatory agents induces tissue-specific changes in nitrogen metabolism. Changes in amino acid pool sizes in various tissues suggest alterations in rates of protein synthesis or degradation.

Amino Acids↗

PubMed1984

Changes in protein synthesis due to an inflammatory challenge.

Rates of protein synthesis in various chick tissues were examined 16 hr after an inflammatory challenge. Protein synthetic rates were calculated from the rate at which [14C]leucine was incorporated into protein and the specific activity of [14C]leucine in the precursor pool. An injection of either Escherichia coli or sheep red blood cells (SRBC) decreased the rate of protein synthesis in the gastrocnemius muscle, and increased the rate in liver, bursa, spleen, and thymus. E. coli, but not SRBC, decreased protein synthesis in the pectoralis muscle. E. coli significantly decreased the aggregation of pectoralis muscle polysomes and increased the aggregation of polysomes in the thymus, bursa, and spleen. E. coli increased the aggregation of free, but not bound, polysomes in liver, suggesting an increase in synthesis of export proteins. SRBC significantly increased polysomal aggregation in bursa and spleen only. A crude preparation of leukocyte endogenous mediator, isolated from peritoneal macrophages, decreased muscle-polysomal aggregation. These studies indicate that tissue-specific changes in protein synthesis occur after a noninfectious inflammatory challenge. These changes may be part of a homeostatic mechanism which supports the immune response.

Animals↗

PubMed1984

Changes in protein degradation in chickens due to an inflammatory challenge.

Tissue-specific changes in protein catabolism were examined in chicks 16 hr following an inflammatory challenge. It was determined that tyrosine was not catabolized or converted to phenylalanine in muscle, thymus, bursa, or spleen. Therefore, rates of tyrosine release from protein were used to estimate rates of protein catabolism in these tissues. Arginine was not catabolized to urea by chick liver; consequently, arginine release from liver protein was used to measure protein catabolism in this tissue. An injection of sheep red blood cells (SRBC) or Escherichia coli did not change rates of protein catabolism in liver or bursa as compared to saline-injected controls. SRBC significantly increased protein catabolism in muscle and spleen by 29 and 15%, respectively. E. coli resulted in significant increases in muscle, spleen, and thymus of 43, 30, and 34%, respectively. These changes in protein catabolism, together with known changes in protein synthesis, suggest that an inflammatory response to SRBC and E. coli result in increased protein accretion in the bursa and liver, and net protein loss from muscle.

Animals↗

PubMed1984

Influence of dietary electrolytes on digestive tract pH and acid-base status of chicks.

The nutritional interaction of lysine and arginine is affected by the electrolyte balance of the diet. Because the ionization and, therefore, the transport and metabolism of these amino acids may be affected by the pH of fluids in which they are dissolved, the present study was conducted to determine the effect of dietary electrolytes on the pH of the digestive tract and the acid-base status of the chicken. A purified casein diet deficient in arginine was modified by addition of either KHCO3 or CaCl2 X 2H2O at levels sufficient either to alleviate or to exacerbate the lysine-arginine antagonism. Addition of KHCO3 led to a more alkaline diet than the arginine-deficient control while CaCl2 X 2H2O resulted in a more acidic diet. Varying the electrolyte balance had little effect on digestive tract pH. The pH of the crop was depressed (P less than .05) by dietary Cl-, but neither Cl- nor K+ had an effect on the pH of the proventriculus, duodenum, or middle and distal portions of the small intestine (P greater than .05). Dietary Cl- significantly depressed plasma bicarbonate, base excess, and PCO2 (P less than .05) but did not significantly decrease plasma pH (P greater than .05). These same acid-base parameters were unaffected by addition of K+ to the control diet. It is concluded that variations in dietary electrolytes affect the acid-base balance of the chicken and alter the pH of the crop. However, the pH of the digestive tract from the proventriculus to the distal small intestine is unaffected.(ABSTRACT TRUNCATED AT 250 WORDS)

Acid-Base Equilibrium↗