Influence of protein intake on S-adenosyl methionine decarboxylase activity in normal and chronically uremic rats

The activity of S-adenosyl methionine decarboxylase (SAM decarboxylase), an enzyme mediating polyamine biosynthesis, was measured in liver and kidney of chronically uremic rats and their pair-fed controls. Effects of protein intake were assessed in groups of rats fed either 8 or 18% casein or switched from 18 to 70% casein for 14 hours. In control rats, both hepatic and renal SAM decarboxylase activities increased with the higher levels of dietary casein. In uremic rats, SAM decarboxylase activity was not responsive to alterations in protein intake. Hepatic and renal SAM decarboxylase activity was significantly higher in control rats than in uremic rats, but this was due to increases in activity that occurred with diets containing higher amounts of protein (18 and 70% casein versus 8% casein).

The effect of copper and protein on iron metabolism in rats fed a cereal diet

Weanling male white rats were fed a diet containing a commercially available breakfast cereal. In 28 days they developed a mild anemia coupled with an increased amount of iron in the liver. In parallel work, this same diet was supplemented in a factorial fashion with casein, iron, copper and zinc. The zinc had no effect. Copper supplementation increased the hemoglobin level. Casein decreased liver iron. The copper and casein, when fed together, produced results approaching normal control levels. Supplementation of the diet with additional iron did not increase the hemoglobin or hematocrit but it did further increase iron storage in the liver. It is suggested that cereal enrichment programs might do well to consider copper and protein rather than focus total attention to additional iron and zinc.

Dietary aluminum and Alzheimer's disease--a review

Current evidence suggests that dietary aluminum is neither an essential nutrient nor a toxic element causing neurological damage. The phosphate and fluoride salts of aluminum are very insoluble. When fed in excess, aluminum increases the dietary needs for these anions. Aluminum hydroxide is used as an antacid that can prevent the phosphatemia seen in severe kidney damage. In Alzheimer's disease there is progressive decrease in brain mass with the accumulation of phospholipid-rich cell debris. These membrane tangles tend to accumulate aluminum and are easily stainable with silver.

Metabolism of 1-14C-ornithine and 1,4-14C-putrescine in chronically uremic and control rats

The metabolism of ornithine and putrescine was studied in vivo in chronically uremic and control rats. Rats were injected intraperitoneally with 1,4-14C-ornithine or 1,4-14C-putrescine and expired 14CO2 was collected for 4 hr. After injection of 1-14C-ornithine. 14CO2 expiration was decreased in uremic rats as compared to controls. Conversely, after 1,4-14C-putrescine injection, expiration of 14CO2 was increased in uremic rats as compared to controls. Four hours after the injection of 1-14C-ornithine, there was more radioactivity in liver and muscle and less radioactivity in kidney of uremic rats as compared to the respective sources in control rats. In uremic rats, 4 hr after 1,4-14C-putrescine injection, the radioactivity retained in the muscle and plasma was greater than in corresponding sources in control rats; whereas the radioactivity retained in uremic liver and kidney was similar to that of control rats. The greater putrescine-derived radioactivity retained in uremic tissues reflects either the retention of injection racer compounds, or retention or decreased catabolism of putrescine metabolites. From 14CO2 expiration data obtained, it appears that ornithine catabolism is reduced while putrescine catabolism is increased in uremia.

Formation of carcinogenic N-nitroso compounds in corn-bread inoculated with fungi

DMNA, DENA and MBNA are formed in corn-bread which has been inoculated with the most common species of fungi found in foodstuffs of Lin Xian County, Henan Province, such as F. moniliforme, A. flavus and others, and then, added with small amount of NaNO2 after a few days of incubation. These carcinogenic N-nitroso compounds can induce cancer of the liver or/and esophagus in experimental animals. Results of the present study show the capability of some fungi to produce chemical carcinogens as well as mycotoxins in contaminated food, and thus, open a new field of research in cancer etiology.

Diamine oxidase activity in plasma and urine in uremia

Diamine oxidase activity was measured in plasma or urine in 12 normal men, 4 men with chronic liver or heart disease, 13 men with chronic renal failure, and 12 men undergoing maintenance hemodialysis. Also in five studies in 4 patients, plasma diamine oxidase activity and total amine levels were measured at hourly intervals during a hemodialysis treatment. Plasma diamine oxidase activity was normal in patients with liver or heart disease and was at least three times normal in chronically uremic patients and in patients undergoing maintenance hemodialysis. Plasma diamine oxidase activities before and after a hemodialysis therapy were similar and did not change during dialysis until the 4th hour when they fell transiently; plasma total amine levels, which were elevated initially, tended to rise during the 4th hour of dialysis. Urinary diamine oxidase activity was reduced in the chronically uremic patients as compared to normal subjects. These observations are consistent with three alterations in diamine oxidase in patients with renal failure: activity (a) is increased in plasma of chronically uremic patients and those undergoing maintenance hemodialysis, (b) does not increase normally in response to heparin administration during dialysis therapy, and (c) is reduced in urine of chronically uremic patients.

Internal fixation of slipped femoral capital epiphyses

The problems related to internal fixation for the treatment of slipped femoral capital epiphyses were reviewed in 164 cases and by a questionnaire of 59 orthopedic surgeons. Significant problems were reported with all fixation devices. With Trifin nails, the main difficulty was getting them to stay in in place. With threaded pins, there was difficulty removing them. The best fixation was obtained with the cast Vitallium Knowles pin, but it requires additional modification and improvement.

Diamine oxidase in renal failure

The enzyme, diamine oxidase, is present in many tissues and plays a role in the metabolism of certain amines, some of which may be toxic. In renal failure, plasma diamine oxidase activity was found to be increased in chronically uremic patients and before and after dialysis therapy in patients undergoing maintenance hemodialysis. Diamine oxidase activity was decreased in urine of the chronically uremic patients as compared to normal subjects. In chronically uremic rats, diamine oxidase activity was observed to be increased in plasma and reduced in urine as compared to sham-operated, pair-fed control rats. In the uremic rats diamine oxidase activity was also decreased in kidney and unchanged in liver and muscle. Total amine levels were elevated in plasma and reduced in urine of patients and rats with chronic renal failure. Although the clinical significance of abnormal diamine oxidase activity in renal failure is not clear, it is possible that this enzyme may have a pathophysiologic role in uremia.

Factors affecting serum and urinary guanidinosuccinic acid levels in normal and uremic subjects

Guanidinosuccinic acid (GSA) was measured in serum and urine from six normal subjects, 26 chronically uremic patients, and 17 patients undergoing maintenance hemodialysis. All normal subjects and 22 chronically uremic patients were fed diets providing 21 gm of essential amino acids or 20, 40, or 60 gm/day of protein. Serum GSA was usually undetectable in normal subjects and was increased in uremic patients (0.99 +/- S.D. 044. mg/100 ml). Serum creatinine and urea nitrogen were each correlated with serum GSA in the normal and uremic subjects combined and in uremic patients alone. Serum GSA was greater in hemodialysis patients (1.43 +/- 0.56 mg/100 ml) than in uremic patients (p less than 0.02) and decreased by 39% +/- 21 during hemodialysis in five patients. Serum GSA and the serum GSA/creatinine ratio tended to decrease with low protein intake in the uremic patients. Urinary GSA was increased in uremic patients (30.5 +/- 12.9 mg/day) as compared to that in normal subjects (7.5 +/- 1.9 mg/day), was greater in uremic patients than in normal subjects at each level of protein intake, and was directly correlated with protein intake and urinary urea and total nitrogen in both normal and uremic subjects. In three uremic patients who developed intercurrent illnesses, urinary GSA rose transiently. These results indicate four factors which affect serum or urinary GSA levels: (1) renal function, (2) protein intake, (3) catabolic stress, and (4) hemodialysis therapy.

Brain serotonin turnover in chronically uremic rats

Brain serotonin turnover was investigated in chronically uremic and sham-operated pair-fed control rats. Animals were injected ip with 100 mg/kg body wt of pargyline HCl, a nonreversible monoamine oxidase inhibitor, and decapitated 0, 30 and 60 min later. The level of total tryptophan in plasma was decreased, and that of free tryptophan was increased in the uremic group. Uremic and control rats had similar concentrations of tryptophan and serotonin at 0 and 30 min after pargyline administration. However, the brain serotonin concentration was elevated in the uremic group 60 min after pargyline treatment. The brain serotonin turnover rate was higher and serotonin turnover time was lower in the uremic group. These results indicate that uremic stress, in addition to altering plasma tryptophan levels, also affects brain serotonin turnover.

Plasma tryptophan levels and brain serotonin metabolism in chronically uremic rats

Plasma tryptophan (Trp) levels and brain concentrations of Trp, serotonin, and 5-hydroxyindoleacetic acid (5-HIAA) were measured in chronically uremic rats fed either 11% or 18% casein diets for 8 to 12 weeks. Uremic rats had increased levels of plasma urea nitrogen and 5-HIAA when compared with sham-operated pair-fed controls. The level of plasma total Trp decreased in both uremic groups and the level of plasma free Trp increased only in those fed an 11% casein diet. Uremic rats fed 11% casein had a higher level of plasma free Trp than those fed 18% casein. The ratio of plasma total Trp to the sum of five amino acids competing for the blood-brain transport system was decreased in both uremic groups, and the ratio of plasma free Trp to the same amino acids was increased only in uremic rats fed 11% casein. The concentration of brain 5-HIAA increased in uremic rats fed 11% casein, and that of Trp and serotonin decreased in uremic rats fed 18% casein. These results indicate that uremic stress and changes in protein intake in chronic uremia alter plasma Trp levels and brain serotonin metabolism.

Effects of arginine-devoid diets in chronically uremic rats

There is evidence that the kidney has a major role in the formation of the arginine used for extrahepatic protein synthesis. The effects of arginine-free diets were studied, therefore, in female Sprague-Dawley rats made uremic by partial left-renal artery ligation and contralateral nephrectomy. Uremic and sham-operated control rats were fed diets with amino acids proportioned as in casein or similar isonitrogenous diets in which the arginine was replaced by glutamic acid and alanine. Weight gain and the food efficiency ratio were determined, and 6 weeks after nephrectomy, a pulse dose of 14C-guanido arginine was administered. The rats were killed 2 hours later, and the radioactivity of proteins in various tissues was determined. Free arginine levels in tissues were also measured. Control rats fed diets devoid of arginine had reduced growth and a low food efficiency ratio. Free arginine levels in tissues and 14C-arginine incorporation into tissue protein in these rats were not different from controls receiving arginine except that 14C-incorporation into brain protein was decreased. Uremic rats fed an arginine-containing diet had a reduced growth rate as compared to control rats, and 14C-incorporation into brain protein was less. In uremic rats, when arginine was removed from the diet, there was no further effect on weight gain but the plasma arginine level was decreased and the incorporation of 14C-guanido arginine into protein of muscle and of kidney was reduced. Hence, the effects of an arginine-free diet appears to be different in chronically uremic as compared to control rats.

Effect of protein intake on weight gain and plasma amino acid levels in uremic rats

Chronically uremic rats weighing approximately 180-200 g and sham-operated controls of similar weight were pair fed diets containing 5, 15 or 23% protein for 10-12 wk. At each level of protein intake, uremic animals gained less weight and had lower protein efficiency ratios than controls. In addition, certain plasma amino acid levels were altered in the uremic animals. These included tyrosine and the tyrosine/phenylalanine ratio, which were decreased, and citrulline, glycine, and the methylhistidines, which were increased. In both uremic and control rats, plasma concentrations of certain amino acids, primarily nonessential ones, varied inversely with protein intake; with the 5% protein diet, the ratio of essential to nonessential amino acids was significantly reduced. These observations indicate that both uremia and reduced protein intake may affect growth and amino acid metabolism in rats with chronic renal failure. The finding that uremic rats utilize protein less efficiently may indicate that marked reductions in protein intake may be particularly hazardous to the nutritional status of the uremic patient.

Amino acid metabolism in the chronically uremic rat

The chronically uremic rat has been used as a model to study amino acid metabolism in uremia. Uremic rats fed low protein diets (6% casein) survived longer than uremic rats receiving either higher levels of dietary protein or a low protein diet supplemented with a mixture of nonessential amino acids. Alterations in plasma amino acid levels were observed in the uremic rats and were similar to those found in patients with renal failure. Plasma concentrations of citrulline, free tryptophan, glycine and the methylhistidines were increased and levels of serine, ornithine, lysine, total tryptophan, tyrosine, and the tyrosine-phenylalanine ratio were reduced. The metabolic basis of the altered tyrosine-phenylalanine ratio in plasma was studied. Tyrosine aminotransferase (TAT) and phenylalanine hydroxylase (PHL) activity were normal in the liver, but renal PHL activity of was decreased as compared to control rats. Tissue concentrations of citrulline were also found to be raised in liver and muscle of uremic rats. The activity of ornithine transcarbamoylase, was reduced in the liver and arginine synthetase activity was decreased in the kidneys of uremic rats. Thus elevated citrulline levels in uremic tissue appear to be caused by a decrease conversion of citrulline to arginine in the kidney. Preliminary studies of tryptophan metabolism in uremic rats have shown elevated brain levels of 5-hydroxyindoleacetic acid and increased hepatic tryptophan oxygenase activity. Increased plasma amine levels were associated with altered activities of monoamine oxidase and diamine oxidase in kidney and other tissues.