Search PubMed⌕ Search

Biomedical subjects

M Wajner

Publications and source records attributed to M Wajner.

At least 91 records · Page 5Linked to original sources
PubMed1995

Inhibition of in-vitro lymphocyte transformation by the isoquinoline alkaloid berberine.

Berberine is an isoquinoline alkaloid with multiple pharmacological actions, including an anti-inflammatory activity. The effects of berberine on in-vitro cellular proliferation of human peripheral lymphocytes stimulated with phytohaemagglutinin, concanavalin A and pokeweed mitogen were studied. Mononuclear cells were cultured in flat-bottomed 96-well microplates at 37 degrees C for 96-144 h in the presence of one mitogen at different concentrations and the alkaloid at doses of 2.5 to 20 microg mL-1. The mitogen-induced response of lymphocytes was evaluated from the extent of the incorporation of [3H]thymidine into cells in-vitro. A consistent and progressive inhibitory influence of berberine with increasing concentrations in culture was identified with all mitogens and was more pronounced with pokeweed mitogen. The effect of berberine was observed in phytohaemagglutinin (PHA)-and concanavalin A-activated lymphocytes when the drug was added during the first 24 h of culture, whereas the same effect occurred throughout the incubation period in pokeweed mitogen-stimulated cells. The viability of lymphocytes following treatment with the drug, as assessed by the trypan blue exclusion test, revealed no change when compared with the same untreated lymphocytes, indicating no lymphocytotoxic activity. We conclude that some effects of berberine, especially its anti-inflammatory action, may arise in part from the inhibition of DNA-synthesis in activated lymphocytes.

Adult↗
PubMed1995

ATP diphosphohydrolase activity in synaptosomes from cerebral cortex of rats subjected to chemically induced phenylketonuria.

ATP diphosphohydrolase (apyrase) (EC 3.6.1.5) activity was measured in synaptosomes from cerebral cortex of Wistar rats of both sexes subjected to experimental phenylketonuria, i.e., chemical hyperphenylalaninemia induced by subcutaneous administration of 5.2 mumol phenylalanine/g body weight (twice a day) plus 0.9 mumol p-chlorophenylalanine/g body weight (once a day). ATP diphosphohydrolase specific activity (nmol Pi min-1 mg protein-1) of synaptosomes was significantly decreased compared to controls for both ATP (from 147.6 to 129.9) and ADP (from 70.2 to 63.1) hydrolysis one hour after single administration of the drugs to 35-day old rats. Chronic treatment was performed from the 6th to the 28th postpartum day. The enzyme specific activity of synaptosomes was measured one week after the last administration of the drugs and was significantly reduced compared to controls for both ATP (from 164.1 to 150.2) and ADP (from 76.3 to 62.1) hydrolysis. The in vitro effects of the drugs on the synaptosome enzyme specific activity were also investigated. Phenylalanine alone or associated with p-chlorophenylalanine significantly reduced enzyme specific activity for both ATP (from 150.2 to 136.0) and ADP (from 70.5 to 59.3) nucleotides as substrates. Since ADP diphosphohydrolase seems to play an important role in neurotransmission, these findings may be related to the neurological dysfunction characteristic of human phenylketonuria.

Animals↗
PubMed1994

Effect of phenylalanine and its metabolites on ATP diphosphohydrolase activity in synaptosomes from rat cerebral cortex.

The in vitro effects of phenylalanine and some of its metabolites on ATP diphosphohydrolase (apyrase, EC 3.6.1.5) activity in synaptosomes from rat cerebral cortex were investigated. The enzyme activity in synaptosomes from rats subjected to experimental hyperphenylalaninemia (alpha-methylphenylalanine plus phenylalanine) was also studied. In the in vitro studies, a biphasic effect of phenylalanine on both enzyme substrates (ATP and ADP) was observed, with maximal inhibition at 2.0 mM and maximal activation at 5.0 mM. Inhibition of the enzyme activity was not due to calcium chelation. Moreover, phenylpyruvate, when compared with phenylalanine showed opposite effects on the enzyme activity, suggesting that phenylalanine and phenylpyruvate bind to two different sites on the enzyme. The other tested phenylalanine metabolites phenyllactate, phenylacetate and phenylethylamine) had no effect on ATP diphosphohydrolase activity. In addition, we found that ATP diphosphohydrolase activity in synaptosomes from cerebral cortex of rats with chemically induced hyperphenylalaninemia was significantly enhanced by acute or chronic treatment. Since it is conceivable that ATPase-ADPase activities play an important role in neurotransmitter (ATP) metabolism, it is tempting to speculate that our results on the deleterious effects of phenylalanine and phenylpyruvate on ATP diphosphohydrolase activity may be related to the neurological dysfunction characteristics of naturally and chemically induced hyperphenylalaninemia.

Animals↗
PubMed1994

The influence of amino acids on mitogen-activated proliferation of human lymphocytes in vitro.

Recurrent infections are common features in patients affected by various aminoacidopathies. Since these disorders are biochemically characterized by tissue accumulation of amino acids, it is possible that these compounds may act as immunosuppressants. We therefore investigated the influence of 21 amino acids on in vitro cellular growth of lymphocytes stimulated with phytohaemagglutinin (PHA), concanavalin A (Con A) and pokeweed mitogen (PWM), a recognized test of cellular immunocompetence. Human peripheral lymphocytes were cultured in flat-bottomed 96-well microplates at 37 degrees C for 96 (PHA and Con A) or 144 h (PWM) in the presence of one mitogen at different concentrations and of one amino acid added at doses of 2, 4 or 8 mM. Cell reactivity was measured by the incorporation of tritiated thymidine into cellular DNA and compared to that of identical cultures with no amino acids added (controls). We found that among the 21 amino acids tested, cysteine stimulated lymphocyte growth, whereas glutamate, tryptophan, phenylalanine and glutamine caused significant inhibition. These results may reflect an immunomodulatory role for some amino acids.

Adult↗
PubMed1994

Effects of postnatal methylmalonate administration on neurobehavioral development of rats.

Administration of methylmalonic acid in rats has been used as a model for methylmalonicacidemia in humans. Nestling Wistar rats of both sexes received 5 injections daily at 3-h intervals (starting at 7:30 a.m.) of saline or methylmalonic acid (MMA, 10 mg/ml) in a volume of 9 microliters/g body weight per injection subcutaneously in the lumbar region from the 5th to the 9th day of life and 11 microliters/g from day 10 to 14. Growth and neuromotor development were assessed by monitoring the following parameters daily in 54 rats: body weight, ear unfolding, incisor eruption, eye opening, righting, palmar grasp, negative geotaxis, cliff avoidance, free-fall righting and startle reflex. The only statistically significant effects of MMA administration were on the day of appearance of the free-fall righting reflex: MMA, 12.44 +/- 1.55 vs 11.0 +/- 0.39 days for saline control (P < 0.05, by two-way ANOVA) and a significant decrease in weight (P < 0.05, by ANOVA with repeated measures). The results suggest that chronic MMA administration to rats has a selective effect on neuromotor development.

Animals↗
PubMed1993

Inhibition of succinate dehydrogenase and beta-hydroxybutyrate dehydrogenase activities by methylmalonate in brain and liver of developing rats.

The effects of methylmalonate (MMA) on succinate dehydrogenase (SDH) and beta-hydroxybutyrate dehydrogenase (HBDH) activities in brain and liver of 15-day-old rats were studied. The apparent Km of SDH for succinate was 0.45 mmol/L in brain and 0.34 mmol/L in liver. MMA inhibited the enzyme activity in both tissues with Ki values of 4.5 mmol/L and 2.3 mmol/L in brain and liver, respectively, and the inhibition was of the reversible competitive type. The calculated Km for HBDH with beta-hydroxybutyrate as substrate was 1.26 mmol/L in brain and 0.36 mmol/L in liver. MMA inhibited the enzyme with a Ki value of 0.015 mmol/L in brain and 0.275 mmol/L in liver. These results are probably relevant to our understanding of cerebral metabolism in methylmalonic acidaemic children, especially during ketoacidotic and hypoglycaemic crises, and may be related to the pathogenesis of cerebral dysfunction of methylmalonic acidaemia.

Animals↗
PubMed1992

Effect of methylmalonate on in vitro lactate release and carbon dioxide production by brain of suckling rats.

Methylmalonate (MMA) accumulates in the tissues of patients with methylmalonic acidaemia, who present severe neurological signs soon after birth and later mental retardation. Attempting to understand the pathophysiology of the disorder, we investigated the effects of MMA on brain glucose uptake, lactate release and CO2 production. Glucose uptake and lactate release were studied by incubating 40 microns wide brain prisms from 15-day-old rats in Krebs-Ringer bicarbonate buffer, pH 7.0, containing 5.0 mmol/L glucose and one of three concentrations of MMA (1.0, 2.5 and 5.0 mmol/L). Controls did not contain MMA in the incubation medium. MMA induced a significant increase of lactate production in a dose-dependent pattern that was proportional to glucose uptake by the brain prisms. We also studied the influence of MMA on brain CO2 production from [2-14C]glucose and [U-14C]acetate by incubating brain prisms in the same buffer in the presence of the substrates with (experimental groups) or without (controls) 5.0 mmol/L MMA. MMA significantly reduced CO2 formation from both substrates.

Animals↗
PubMed1992

Biochemical investigation of a Brazilian patient with a defect in mitochondrial acetoacetylcoenzyme-A thiolase.

A case report of 3-ketothiolase deficiency due to a defect of mitochondrial acetoacetyl-CoA thiolase protein in a Brazilian boy and its biochemical investigation is presented. The child had moderate generalized hypotonia, EEG alterations and crises of metabolic acidosis following infections. Hypotonia and EEG abnormalities disappeared with a low protein diet, and physical and mental development are normal. Urinary organic acid excretion was typical of 3-ketothiolase deficiency, showing consistently high levels of 2-methyl-3-hydroxybutyric acid and tiglylglycine. Activation of acetoacetyl-CoA thiolase activity by potassium (K) ion in cultured fibroblasts was not observed, demonstrating the lack of activity of mitochondrial acetoacetyl-CoA thiolase. In addition, the signal for the mitochondrial acetoacetyl-CoA thiolase protein was undetectable in the immunoblot analysis. In the pulse-chase experiments, the signal for mitochondrial acetoacetyl-CoA thiolase was detected after a 1-h pulse but not after a 24-h chase. These results indicate that the deficiency was caused by an unstable mitochondrial acetoacetyl-CoA thiolase protein.

Acetyl-CoA C-Acetyltransferase↗
PubMed1991

Effects of methylmalonate and propionate on uptake of glucose and ketone bodies in vitro by brain of developing rats.

Methylmalonate (MMA) and propionate effects on glucose and ketone body uptake in vitro by brain of fed and 30-hour-fasted 15-day-old rats were studied. In some experiments cerebrum prisms were incubated in the presence of glucose and either MMA or propionate in Krebs-Ringer bicarbonate buffer, pH 7.0. In others, the incubation medium contained beta-hydroxybutyrate (HBA) or acetoacetate (AcAc) instead of glucose. We verified that MMA increased glucose uptake by brain of fasting animals, whereas propionate had no effect. In addition, MMA diminished HBA but not AcAc incorporation into brain prisms, whereas propionate provoked a diminished utilization of both ketone bodies by brain. The in vitro effect of MMA and propionate on brain and liver beta-hydroxybutyrate dehydrogenase activity was also investigated. It was shown that MMA but not propionate significantly inhibited this activity. Rats were also injected subcutaneously three times with a MMA buffered solution, and the in vivo effects of MMA on the above-mentioned parameters assessed. Results from these experiments confirmed the previously found in vitro MMA effects. Methylmalonic acidemic patients accumulate primarily methylmalonate and secondarily propionate and other metabolites in their tissues at levels comparable to those we used in our assays. Most patients who survive early stages of the disease show a variable degree of neuromotor delay. Since glucose and sometimes ketones are the vital substrates for brain metabolism, it is possible that our findings may contribute to a certain extent to an understanding of the biochemical basis of mental retardation in these patients.

3-Hydroxybutyric Acid↗
PubMed1991

Effect of postnatal methylmalonate administration on adult rat behavior.

1. Methylmalonate (MMA) levels (2.0-2.5 mM) comparable to those of human methylmalonic acidemia were achieved in blood of young rats from the 5th to the 25th day of life by injecting the drug subcutaneously twice a day with an interval of 8 h. MMA doses ranged from 0.76 to 1.69 mumol/g body weight as a function of animal age. MMA-treated rats had normal body and brain weights. 2. Behavioral studies using aversive and nonaversive tasks were performed at 60 days of life. Motor activity was similar in MMA-treated and saline-treated controls. No differences in performance between these groups were identified in the shuttle-avoidance responses and in the inhibitory avoidance tasks. However, MMA-injected rats escaped footshock faster than the controls (1.22 +/- 0.11 vs 1.76 +/- 0.14 (mean +/- SEM) for 24 rats in each group (P less than 0.01)) suggesting that they may be hyperreactive to this stimulus. 3. In the open field, a nonaversive behavior task, MMA-injected rats, in contrast to control rats, presented no habituation. 4. Our results suggest that MMA by itself may impair central nervous system function, causing minor disabilities which result in specific learning deficiencies.

Analysis of Variance↗
PubMed1990

High urinary excretion of N-(pyrrole-2-carboxyl) glycine in type II hyperprolinemia.

A case report of type II hyperprolinemia in a 5-year-old boy and its biochemical investigation is presented. The child has mild developmental delay, recurrent seizures of the grand mal type and EEG alterations. Although this disorder has been recently considered a benign condition, variants accompanied by characteristic symptomatology cannot be fully ruled out. The urinary excretion of high concentrations of N-(pyrrole-2-carboxylic acid)-glycine conjugate is stressed, since it appears that only one previous report in the literature described this compound in the urine of two patients affected by this disturbance.

Amino Acid Metabolism, Inborn Errors↗
PubMed1989

Distribution of xanthine dehydrogenase and oxidase activities in human and rabbit tissues.

The activity of xanthine dehydrogenase in human postmortem tissues is surprisingly high in brain and heart; activity was found in most tissue samples, whereas many samples contained little or no oxidase activity. We have confirmed the high level of oxidase activity in liver in which tissue conversion of dehydrogenase to oxidase appears complete. We have also confirmed the virtual absence of either activity in fresh human placenta. Fresh rabbit tissues similarly show considerable dehydrogenase activity in brain and heart. In view of the stability and generalised distribution of dehydrogenase activity, our results suggest that some modification of existing ideas on the physiological and pathological roles of the enzyme may be needed.

Animals↗
PubMed1989

Effect of proline administration on rat behavior in aversive and nonaversive tasks.

Sustained levels of proline comparable to those of human type II hyperprolinemia were achieved in blood and brain of rats subcutaneous proline administration twice a day from the 6th till the 28th day of life. Control rats were treated with saline in the same volumes. Behavioral studies using aversive and nonaversive tasks were performed one week or one month after treatment. Proline treatment did not affect rats' performance in the inhibitory avoidance task, but reduced significantly habituation in the open field. Our results seem to indicate that early postnatal administration of proline to rats affects habituation to a novel environment. If this happens to be so the present tendency to consider hyperprolinemia as a benign condition should be revised.

Age Factors↗
PubMed1989

Reduced locomotor activity of rats made histidinemic by injection of histidine.

Acute histidinemia was provoked in 30-d-old male Wistar rats by injecting intraperitoneally either histidine alone (0.5 mg/g body wt) or histidine (0.25 mg/g body wt) plus the histidase inhibitor nitromethane (0.73 mg/g body wt). Histidase activity was approximately 90% inhibited in rats receiving nitromethane. Serum histidine in both groups reached levels similar to those of histidinemic patients. Rats were subjected to the open field behavioral task, and the number of rearings and crossings were counted. A consistently lower locomotor activity was observed in the histidinemic rats. It is proposed that reduced locomotor activity and its relationship to psychomotor development should be investigated in histidinemic children.

Animals↗