Arginase activity and lecithin/sphingomyelin (l/s) ratio in the amniotic fluid of pregnant women.

Arginase activity is important in polyamines and nitric oxide production which are required for the normal growth of placenta and embryo. A considerable arginase activity is observed in amniotic fluid in women at the end of pregnancy. Lecithin to sphingomyelin (L/S) ratio is widely used in order to assess fetal lung immaturity and prevention of neonatal respiratory distress syndrome, the major cause of neonatal morbidity and mortality. The purpose of our study was to determine if there is a relationship between arginase activity and L/S ratio in amniotic fluid. The study included 170 pregnant women, 18-43 years old, with normal and pathological pregnancy. The arginase activity was measured on the basis of the determination of the amount of liberated ornithine from arginine as substrate. The L/S ratio was done by using a thin layer chromatography. Increased level of arginase activity correlates with the fetal lung maturity. Arginase activity and L/S values may be useful biochemical data, for intrauterine baby maturity.

Dexamethasone decreases the spermidine and spermine concentrations and polyamine oxidase activity in rat thymus.

BACKGROUND: Glucocorticoids (GCs) exert a wide range of anti-inflammatory, immunosuppressive, and antineoplastic activities. The aim of our investigation was to elucidate the effect of dexamethasone, a synthetic GC, on polyamine metabolism in the rat thymus. METHODS: Male albino Wistar rats, weighing 180-230 g, were divided into two groups: control and experimental. The experimental group received dexamethasone intraperitoneally for 3 days, in a daily dose of 4 mg/animal. The last dose of the hormone was applied on the 3rd day, 1 h before killing. The control group received 0.9% NaCl instead of the hormone. The animals were killed by decapitation. The thymus was removed quickly and rinsed with ice-cold saline. Polyamines were extracted using butanol. The amount of polyamines was investigated by electrophoresis. For the estimation of polyamine oxidase (PAO) activity, 10% water homogenate was prepared. RESULTS: Our results suggested that dexamethasone supplementation of experimental animals for 3 days significantly decreased the spermine (Sp) and spermidine (Spd) levels in rat thymus tissue (Sp Control, 362.56±25.33 nmol/g wet weight; Sp Exp. Group, 313.01±21.16 nmol/g wet weight; Spd Control, 673.81±30.95 nmol/g wet weight; Spd Exp. Group, 410.21±17.26 nmol/g wet weight). PAO activity significantly decreased under hormone influence in comparison with the control group (PAO Control, 0.449±0.121 U/mg prot.; PAO Exp. Group, 0.312±0.096 U/mg prot.). CONCLUSIONS: The decrease in polyamine amounts in the rat thymus is not due to the change in PAO activity.

Effect of L-arginine on metabolism of polyamines in rat's brain with extrahepatic cholestasis.

Cholestatic encephalopathy results from accumulation of unconjugated bilirubin and hydrophobic bile acids in the brain. The aim of this study was to determine disturbances of polyamine metabolism in the brains of rats with experimental extrahepatic cholestasis and the effects of L-arginine administration. Wister rats were divided into groups: I: sham-operated, II: rats treated with L-arginine, III: animals with bile-duct ligation (BDL), and IV: cholestatic-BDL rats treated with L-arginine. Increased plasma gamma-glutamyltransferase and alkaline phosphatase activity and increased bile-acids and bilirubin levels in BDL rats were reduced by administration of L-arginine (P < 0.001). Cholestasis increased the brain's putrescine (P < 0.001) and decreased spermidine and spermine concentration (P < 0.05). The activity of polyamine oxidase was increased (P < 0.001) and diamine oxidase was decreased (P < 0.001) in the brains of BDL rats. Cholestasis increased the activity of arginase (P < 0.05) and decreased the level of citrulline (P < 0.001). Administration of L-arginine in BDL rats prevents metabolic disorders of polyamines and establishes a neuroprotective role in the brain during cholestasis.

Arginase activity in human milk during the first month of lactation.

Arginase (L-arginine amidinohydrolase, EC 3.5.3.1) is the key enzyme in urea synthesis, hydrolyzing L-arginine into L-ornithine and urea. Arginase modulates levels of nitric oxide, creatine, and creatinine, likely by regulating intracellular L-arginine availability. The objective of the present study was to determine the arginase activity and concentration of urea and creatinine in colostrum and mature human milk obtained from nursing mothers. Our longitudinal biochemical analyses show that arginase activities and urea concentrations were the highest at the first day of lactation (colostrum). The decreasing enzyme activity and urea start at the second day, remaining at this level until the end of the first month of lactation (30th day). The concentration of creatinine in human colostrum and mature milk did not significantly change. The alteration of arginase activity between colostrum and mature milk may be a consequence of the transfer of arginase from the blood of the breast mother mammary glands into the colostrum and mature milk. The concentration of nutrients in colostrum and mature milk undergo alterations, probably to satisfy the requirements of the nursing infant for arginine, essential amino acids for human body growth, and normal physiology.

Thymus as a target tissue of glucocorticoid action: what are the consequences of glucocorticoids thymectomy?

Glucocorticoids represent the most powerful endogenous anti-inflammatory and immunosuppressive effectors, interfering with virtually every step of immunoinflammatory responses. Glucocorticoids are often the most effective therapy in the prevention or suppression of inflammation and other immunologically mediated processes, but their use is limited by systemic side effects induced by the over-production of reactive oxygen species, causing dysregulation of physiological processes. The thymus is an organ with both endocrine and immune functions. Glucocorticoids induce thymocyte apoptosis, causing a profound reduction in thymic mass and volume and inducing hormonal thymectomy. The clinical aspects of glucocorticoid thymectomy are not under enough investigation. These unwanted systemic side effects may be the consequence of prolonged therapeutic application of glucocorticoids and prolonged or chronic activation of the hypothalamic-pituitary adrenal axis, which may lead to increased and prolonged secretion of glucocorticoids. This review will discuss the metabolic effects of glucocorticoids in the context of thymic physiology asthe primary sex hormone-responsive organ.

Melatonin reduces oxidative stress induced by chronic exposure of microwave radiation from mobile phones in rat brain.

PURPOSE: The aim of the study was to evaluate the intensity of oxidative stress in the brain of animals chronically exposed to mobile phones and potential protective effects of melatonin in reducing oxidative stress and brain injury. MATERIALS AND METHODS: Experiments were performed on Wistar rats exposed to microwave radiation during 20, 40 and 60 days. Four groups were formed: I group (control)- animals treated by saline, intraperitoneally (i.p.) applied daily during follow up, II group (Mel)- rats treated daily with melatonin (2 mg kg(-1) body weight i.p.), III group (MWs)- microwave exposed rats, IV group (MWs + Mel)- MWs exposed rats treated with melatonin (2 mg kg(-1) body weight i.p.). The microwave radiation was produced by a mobile test phone (SAR = 0.043-0.135 W/kg). RESULTS: A significant increase in the brain tissue malondialdehyde (MDA) and carbonyl group concentration was registered during exposure. Decreased activity of catalase (CAT) and increased activity of xanthine oxidase (XO) remained after 40 and 60 days of exposure to mobile phones. Melatonin treatment significantly prevented the increase in the MDA content and XO activity in the brain tissue after 40 days of exposure while it was unable to prevent the decrease of CAT activity and increase of carbonyl group contents. CONCLUSION: We demonstrated two important findings; that mobile phones caused oxidative damage biochemically by increasing the levels of MDA, carbonyl groups, XO activity and decreasing CAT activity; and that treatment with the melatonin significantly prevented oxidative damage in the brain.

Polyamine oxidase activity in peripheral blood of newborn infants with neonatal hyperbilirubinemia: is bilirubin an antioxidant?

BACKGROUND: Neonatal hyperbilirubinemia can be physiological and pathological and most frequently is a consequence of faster erythrocytes (RBC) hemolysis. Free unconjugated bilirubin is a highly toxic compound, especially for the central nervous system. The most abundant polyamines circulating in blood are spermidine (Spd) and spermine (Sp), which are mainly localized in RBC, where they control membrane permeability. Polyamine oxidase (PAO) exerts an important activity in the plasma and erythrocytes of newborn infants with hyperbilirubinemia, catalyzing the oxidative deamination of Sp and Spd, producing potentially toxic agents that induce apoptosis of mammalian cells. The present study investigated polyamine metabolism by measuring PAO activity in the blood of newborn infants with hyperbilirubinemia and explored the possible antioxidant function of bilirubin through monitoring malondialdehyde (MDA) levels. METHODS: The study included 43 newborns, 10 in the control and 33 in the diseased group. Blood PAO activity and bilirubin and MDA levels were measured using spectrophotometric methods. RESULTS/DISCUSSION: Our results indicate that bilirubin, at physiologic concentrations, protects neonatal erythrocytes against oxidative stress. The positive correlation between PAO activity and MDA levels with high bilirubin concentrations (> 200 micromol/L) in newborn infants indicates that in pathological conditions, bilirubin cannot exert its antioxidant function. CONCLUSION: Investigating the function of polyamines in erythrocytes and the importance of PAO related to hemolysis and bilirubin synthesis is necessary to shed light on the functions of PAO and its metabolites on the permeability of the erythrocyte membrane.

Protective effect of interferon-alpha on the DNA- and RNA-degrading pathway in anti-Fas-antibody induced apoptosis.

AIM: Fas membrane-associated polypeptide antigen is a receptor molecule responsible for apoptosis-mediated signals. In animal models of acute viral hepatitis, apoptosis of hepatocytes is mediated by Fas-death receptors; therefore, the aim of this study was to evaluate the effect of interferon (IFN)-alpha on apoptotic markers and nuclease activity against different coding and non-coding single and double stranded RNAs during Fas-induced liver apoptosis. METHODS: An in vivo experiment was performed with simultaneous administration of anti-Fas (CD95) antibodies and IFN-alpha, and an in vitro experiment was performed in hepatocyte cultures treated with anti-Fas antibodies and IFN-alpha. RESULTS: Detection of apoptosis using Annexin V-FITC/propidium iodide, Bcl-2 and Bax expression in hepatocyte cultures confirmed the appearance of early apoptotic events and progression toward late apoptosis after anti-Fas antibody treatment. IFN-alpha had a tendency to retard the apoptosis process in Fas-induced apoptosis by increasing the number of viable cells and decreasing the number of cells in late apoptosis, by increasing the percentage of Bcl-2 positive cells, by decreasing the percentage of Bax positive cells, and by decreasing the nuclease activity compared to the anti-Fas antibody treated group. Total DNA and RNA concentration was much reduced in the Fas group and DNA fragmentation assay provided evidence for increased DNA degradation. Enhanced nuclease activity against DNA, rRNA, poly(A), poly(C), poly(U), poly(I:C), and poly(A:U) was manifested in the anti-Fas antibody treated group, except for the inhibitory-bound alkaline RNase. CONCLUSIONS: The results demonstrate that the RNA-degrading pathway in Fas-induced apoptosis can accelerate the liberation of the latent enzyme from the inhibitor complex. IFN-alpha prevented enormous, Fas-ligand induced degradation of all the substrates used in this experimental study, most probably due to similarities in the signal transduction pathways. Investigations of death receptor-induced apoptosis may lead to novel treatment combinations for patients with acute or chronic liver diseases.

Possible impact of plasma RNase activity on immune dysfunction in juvenile diabetes mellitus.

AIM: The ribonuclease (RNase) family represents important enzymes used widely in biomedical and biotechnological applications, as well as for diagnostic and therapeutic purposes. This study was undertaken to test the possibility that plasma alkaline RNase (free or inhibitory bound) determination may be useful in studying the dysregulation of nucleic acid and oligonucleotide metabolism as a possible pathogenetic mechanism in development of immune dysfunction in juvenile diabetes mellitus. PATIENTS AND METHODS: Children with type 1 diabetes (n=32, age group of 5--14 yr), together with age-matched control subjects (n=35), were enrolled in the study. None had microvascular complications. According to the metabolic regulation of the disease and the hemoglobin A1c (HbA1c) level, all patients were divided into two groups (HbA1c<7.5% and HbA1c>7.5%). According to the duration of diabetes, diabetic children were divided into two groups: duration of diabetes less than 1 yr and duration of diabetes greater than 1 yr. The control group consisted of age-matched subjects (n=35; 15 girls and 20 boys) who were clinically healthy. The activity of free and inhibitory-bound RNase and the level of acid soluble nucleotides were measured in heparinized plasma. RESULTS: The inhibitory-bound enzyme activity was higher in diabetic children, followed by sharply decreased free enzyme, especially in the group with the level of HbA1c above 7.5%. Recent-onset diabetic patients had lower free RNase activity compared with those with longer duration of the disease. The amount of pre-existing acid-soluble oligonucleotides was significantly increased in diabetic children, especially in those with poor metabolic control. CONCLUSION: Our observed preliminary results may suggest a hypothesis that a persistent increase of oligonucleotide fragments, most probably due to insufficient RNase activity, may lead to T-cell hyperactivity in type 1 diabetes through the activation of toll-like receptors (TLRs). The measurement of RNase(s) activity (free, inhibitory-bound, or specific toward different substrates), together with the well-known immunobiochemical parameters of diabetes, may help further efforts in identifying a disease-specific early biological marker of immunity dysfunction in juvenile diabetes.

Effect of caffeine on metabolism of L-arginine in the brain.

Methylxanthines are widely consumed because of their stimulating effect primarily on the central nervous system. Their diuretic and respiratory stimulant action is used in clinical medicine. L-Arginine metabolism in the brain is very important for normal brain function. In addition to brain protein synthesis, arginine is a substrate for the production of urea, creatine, nitric oxide, agmatine, glutamic acid, ornithine, proline and polyamines. As known, many of these compounds are very important in brain function. There is no information relating to effects of caffeine on arginine metabolism in the brain, however, there is a lot of new information about arginine metabolism and caffeine action on the central nervous system. So, we have hypothesized the existence of a relationship that may be of interest in understanding mechanisms of caffeine effects on the central nervous system that may have utility in the clinical applications. In our experiment protocol we used male Wistar rats weighing about 200 g. Caffeine was added to the drinking water in gradually increasing amounts, from 2 g/l over the first 3 days, to 4 g/l over the last 7 days. A control group was given drinking water without caffeine. The level of lipid peroxidation, arginase and diamine oxidase (DAO) activity in the brain was measured. The results of our study show that arginase and diamine oxidase were decreased in animals treated with caffeine. The level of lipid peroxidation (MDA) was decreased also. The inhibitory effect of caffeine on arginase activity indicates that caffeine provides more arginine for consumption in other metabolic pathways. Considering the central stimulant effects of caffeine and the decreased lipid peroxidation level, it can be assumed that moderate short-term consumption of caffeine may be beneficial for brain function.