Considerable attention has recently centered on the possible role of oxygen-derived free radicals in protein damage and degradation. In the present study, we investigated the reactivity of amino acids with superoxide and hydroxyl radical by an electron spin resonance assay using 5, 5-dimethyl-1-pyrroline-N-oxide (DMPO) as a spin trap. The intensity of the DMPO-OOH spin adduct generated from the hypoxanthine-xanthine oxidase system decreased in the presence of some amino acids such as cysteine and methionine at a final concentration of 1-10mM. However it was not influenced by the presence of other amino acids at the same final concentrations. The relative intensity of the DMPO-OH spin adduct generated from the Fenton reaction significantly decreased in the presence of various amino acids, especially aromatic amino acids, sulfur-containing amino acids, and histidine. The inhibition of DMPO-OH signal was not due to the inhibition of the Fenton reaction, but due to the competition of the amino acid with DMPO. In the early step of protein damage by active oxygen species, such amino acids residues are attacked.
It was found that the products of lipid peroxidation in liver homogenates, isolated from paracetamol-treated rats and incubated in presence of Fe2+, are significantly lower than those in homogenates from the control rats. The Fe2+-induced chemiluminescence in these homogenates was also inhibited. The capacity of liver homogenates isolated from phenobarbital+paracetamol-treated rats to undergo Fe2+-catalyzed lipid peroxidation with light emission was decreased with respect to both rats treated with phenobarbital and control rats. Using a phospholipid liposome suspension in which was initiated lipid peroxidation by Fe2+, we found that paracetamol possesses concentration-dependent antioxidant action. Paracetamol inhibited also the luminol and lucigenin-dependent chemiluminescence in the xanthine-xanthine oxidase system. In such system for generation of superoxide radicals, paracetamol suppressed the reduction of nitro blue tetrazolium to formazan. The results obtained showed that paracetamol has antioxidant activity, which may be due to its ability to scavenge lipid and superoxide radicals.
Incorporation of [3H]proline into collagenous proteins by cultured smooth muscle cells from rabbit aorta was found to be increased in the presence of linoleic acid hydroperoxide at its concentrations of 6-60nmol/ml, indicating that the net synthesis of collagen by these cells is increased by these concentrations of lipid peroxides. Although linoleic acid slightly increased the collagen synthesis, the effect seems to be mostly ascribable to its action to increase the proliferation of the cells.
Treatment of male guinea pigs with the potent chemical carcinogen N-nitrosodiethylamine (NDEA) at an intraperitoneal dose of 40mg/kg body weight for three consecutive days resulted in a significant decrease in the levels of ascorbic acid in liver, lungs, kidneys, and adrenal glands. The decrease in the brain and plasma was, however, not significant. Radiorespirometric, distribution, and urinary excretion studies conducted with the use of L-[carboxyl-14C] ascorbic acid revealed that a possible mechanism responsible for depletion of the body ascorbate store by NDEA might be the enhanced metabolic degradation of ascorbic acid into CO2, and other metabolites that are excreted through urine.
In rats with hypothyroidism caused by partial thyroidectomy, a significant decrease in mitochondrial electron-transport activity was found 6 weeks after the thyroidectomy. The level of acetylcholine in heart muscle cells of the left ventricle was found to be increased at the same time after the operation. Norepinephrine in the same cells increased even earlier; significant increase was found 3 weeks after the operation. Supplementation with triiodothyronine lessened these impairments. The relationship among these changes was discussed in relation to hypothyroid cardiomyopathy.
To investigate the cause of hyperoxaluria in vitamin A deficiency, we studied the specific activities of the major oxalate-synthesizing enzymes in the liver, viz., glycolic acid oxidase (GAO), glycolic acid dehydrogenase (GAD), and lactate dehydrogenase (LDH). Pair-fed control and experimental (vitamin A deficient) groups of rats were fed a high-calcium (9g/kg diet), calculogenic diet for 12 weeks. Vitamin A deficiency resulted in increased specific activities of GAO, GAD (p<0.001), and LDH (p<0.05) compared with those of pair-fed controls. Correction of vitamin A deficiency returned the enzyme activities to the levels observed in control animals. The possible biochemical mechanism of hyperoxaluria in vitamin A deficiency is discussed.
Light in the near-infrared range (700-1, 200nm) penetrates living tissues including the skull. Oxy- and deoxy-hemoglobin contents in living tissue can be measured from the absorbance in this range. Myoglobin and cytochrome oxidase also have their absorbance in this range. Therefore, we carried out near-infrared computed tomography by a modification of the method for X-ray CT for humans. Three semiconductor lasers were used as light sources with a laser beam scanner. The transmitted light was measured with a linear detector equipped with 25 photomultipliers. With this device, we constructed images of the heads of anesthetized rats from the differences between the absorbance data at 780 and 805nm. The brightness of the head images increased in rats with ischemia induced by occlusion of four vessels (carotid). The ischemic area in the central part of the head was shown on exchange transfusion of the blood with perfluorochemical emulsion.
The level of mRNA specific for myosin heavy chain in percutaneous biopsy specimens of skeletal muscle was analyzed in 6 healthy volunteers before and following 3 days of total starvation. Total RNA was isolated and hybridized to a radioactively labeled cDNA probe specific for myosin heavy chain of the beta type. Increasing concentrations of total RNA were applied to the membrane filters used in the hybridization analysis. Slopes of the linear function of radioactivity versus RNA concentration were calculated by linear regression. Following starvation the amount of hybridizable mRNA specific for myosin heavy chain decreased in relation to the total RNA. The decrease was individually specific, the mean value of the slopes after starvation being 91.6±2.8% that of the control (prestarvation) level (p<0.01). The low serum concentrations of insulin and C-peptide and the rise in glucagon together with the increase in urinary nitrogen excretion characterized the fasting condition of the 6 healthy volunteers. The analysis of mRNA specific for a single myofibrillar protein gave information on the physiological state of protein synthesis in muscle and indicated a fall in synthetic capacity due to the diminished availability of mRNA. The diminished level of myosin heavy chain mRNA in relation to total RNA confirmed previous findings of a decrease in muscle protein synthesis during short-term starvation. The decrease in mRNA added to the known decrease in ribosomal RNA.