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Biomedical subjects

M Wajner

Publications and source records attributed to M Wajner.

At least 73 records · Page 4Linked to original sources
PubMed1998

Chronic administration of propionic acid reduces ganglioside N-acetylneuraminic acid concentration in cerebellum of young rats.

Elevated levels of propionate comparable to those of human propionic acidaemia were achieved in the blood of young rats by injecting subcutaneously buffered propionic acid (PPA) twice a day at 8-h intervals from the 6th to the 28th day of life. A matched group of animals (controls) was treated with the same volumes of saline. The animals were weighed and sacrificed by decapitation at 28, 35 or 60 days of age. Cerebellum and cerebrum were weighed and their protein and ganglioside N-acetylneuraminic acid (G-NeuAc) contents determined. Body, cerebral and cerebellar weights were similar in both groups, suggesting that PPA per se neither alters the appetite of the rats nor causes malnutrition. Brain protein concentration was also not affected by chronic administration of PPA, in contrast to G-NeuAc concentration which was significantly reduced in the cerebellum. Since ganglioside concentration is closely related to the dendritic surface and indirectly reflects synaptogenesis, our results of an important ganglioside deficit in the brain of PPA-treated animals may be related to the neurologic dysfunction characteristic of propionic acidaemic patients.

Animals↗
PubMed1998

Inhibition of Na+,K+-ATPase from rat brain cortex by propionic acid.

Buffered propionic acid was injected s.c. into rats twice a day at 8 h intervals from the 6 to 21 days of age. Control rats received saline in the same volumes. The animals were weighed and killed by decapitation at 23 days. Whole brain and cerebral cortex were weighed and synaptic plasma membranes were prepared from cortex for the determination of Na+,K+-ATPase and Mg2+-ATPase activities. Body, whole brain and cortical weights were similar in the two groups, suggesting that propionic acid does not cause malnutrition in rats. Na+,K+-ATPase activity was significantly reduced by 30% in membranes from the propionate-treated group, whereas Mg2+-ATPase activity was not. In another set of experiments, synaptic plasma membranes were prepared from cerebral cortex of 23-day-old rats and incubated with propionic acid at final concentrations ranging from 0.1 to 2.0 mM. Na+,K+-ATPase activity, but not Mg2+-ATPase activity, was inhibited by 22-32%. Since propionic acid concentrations in plasma of chronically treated rats and of propionic acidemic children are of the same order of magnitude as those tested in vitro, the results suggest that the inhibition of Na+,K+-ATPase activity may be related to the neurological dysfunction of patients affected by propionic acidaemia.

Animals↗
PubMed1998

Effects of acute and chronic administration of methylmalonic and propionic acids on the in vitro incorporation of 32P into cytoskeletal proteins from cerebral cortex of young rats.

We studied the effects of acute and chronic administration of methylmalonic (MMA) and propionic (PA) acids on the in vitro incorporation of 32P into neurofilament subunits (NF-M and NF-L), alpha and beta tubulins, from cerebral cortex of rats. In the chronic treatment, drugs were administered subcutaneously from day 6-17 post-partum (MMA 0.76-0.89 micromol/g body weight and PA 0.93 micromol/g body weight). In the acute treatment MMA and PA were injected (MMA 3.78 micromol/g body weight and PA 3.90 micromol/g body weight). Control animals received saline in the same volumes. The Triton-insoluble cytoskeletal fraction of control in treated animals was isolated and incubated with 32P-ATP. Our results demonstrate that both drugs were able to inhibit 32P in vitro incorporation into neurofilaments and tubulins. The acute administration of MMA decreased the in vitro 32P incorporation into NF-L and alpha-tubulin subunit, whereas PA administration decreased the 32P in vitro incorporation into NF-M, NF-L, and tubulins. On the other hand, chronic MMA administration induced a decreased 32P in vitro incorporation into NF-M, while chronic treatment with propionate decreased the in vitro phosphorylation of NF-M and alpha-tubulin. This study provides consistent evidence that a decreased phosphorylation of cytoskeletal proteins is induced by MMA and PA metabolites which accumulate in methylmalonic and propionic acidemias respectively. Therefore, it is possible that an altered brain cytoskeletal metabolism could be related with the structural alterations of CNS observed in these disorders.

Animals↗
PubMed1998

Propionic and methylmalonic acids inhibit the in vitro phosphorylation of a 85 kDa cytoskeletal protein from cerebral cortex of rats.

In this study we examine the action of methylmalonic (MMA) and propionic (PA) acids, metabolites which accumulate in methylmalonic and propionic acidemias respectively, on the endogenous phosphorylating system associated with the cytoskeletal fraction of cerebral cortex of young rats. Chronic treatment with PA and treatment of tissue slices with MMA or PA are effective in decreasing the in vitro phosphorylation into a 85 kDa cytoskeletal associated protein. We tested the effect of the acids on the endogenous kinase activities by using specific kinase activators and inhibitors. Results demonstrated that the acids interfere with the endogenous cAMP-dependent and Ca2+/calmodulin-dependent kinase activities. Furthermore, in vitro dephosphorylation of the 85 kDa protein was totally inhibited in brain slices treated with the acids. Considering the importance of protein phosphorylation to cellular function, we speculate that alteration in the phosphorylating level of cytoskeletal associated phosphoproteins induced by MMA and PA treatments may somehow be involved in steps leading to brain damage.

Animals↗
PubMed1997

Methylmalonic acid reduces the in vitro phosphorylation of cytoskeletal proteins in the cerebral cortex of rats.

The present work was undertaken to determine the action of methylmalonic acid (MMA), a metabolite, which accumulates in high amounts in methylmalonic acidemia, on the endogenous phosphorylating system associated with the cytoskeletal fraction proteins of cerebral cortex of young rats. We demonstrated that pre-treatment of cerebral cortex slices of young rats with 2.5 mM buffered methylmalonic acid (MMA) is effective in decreasing in vitro incorporation of [32P]ATP into neurofilament subunits (NF-M and NF-L) and alpha- and beta-tubulins. Based on the fact that this system contains cAMP-dependent protein kinase (PKA), Ca2+/calmodulin-dependent protein kinase II (CaMKII) and protein phosphatase 1 (PP1), we first tested the effect of MMA on the kinase activities by using the specific activators cAMP and Ca2+/calmodulin or the inhibitors PKAI or KN-93 for PKA and CaMKII, respectively. We observed that MMA totally inhibited the stimulatory effect of cAMP and interfered with the inhibitory effect of PKAI. In addition, the metabolite partially prevented the stimulatory effect of Ca2+/calmodulin and interfered with the effect of KN-93. Furthermore, in vitro dephosphorylation of neurofilament subunits and tubulins was totally inhibited in brain slices pre-treated with MMA. Taken together, these results suggest that MMA, at the same concentrations found in tissues of methylmalonic acidemic children, inhibits the in vitro activities of PKA, CaMKII and PP1 associated with the cytoskeletal fraction of the cerebral cortex of rats, a fact that may be involved with the pathogenesis of the neurological dysfunction characteristic of methylmalonic acidemia.

Adenosine Triphosphate↗
PubMed1997

In vitro phosphorylation of cytoskeletal proteins in the rat cerebral cortex is decreased by propionic acid.

In the present study we demonstrate that propionic acid (PA), a metabolite that accumulates in large amounts in propionic acidemia, is able to decrease in vitro incorporation of [32P]ATP into neurofilament subunits (NF-M and NF-L) and alpha- and beta-tubulin. Considering that the endogenous phosphorylating system associated with the cytoskeletal fraction contains cAMP-dependent protein kinase (PKA), Ca2+/calmodulin protein kinase II (CaMKII), and protein phosphatase 1 (PP1), we first assayed the effect of the acid on the kinase activities by using the specific activators cAMP and Ca2+/calmodulin or the inhibitors PKAI or KN-93 for PKA and CaMKII, respectively. Results demonstrated that the acid totally inhibited the stimulatory effect of cAMP and interfered with the inhibitory effect of PKAI. In addition, PA partially prevented the stimulatory effect of Ca2+/calmodulin and interfered with the effect of KN-93. In addition, we demonstrated that PA totally inhibited in vitro dephosphorylation of neurofilament subunits and tubulins mediated by PP1 in brain slices pretreated with the acid. Taken together, these results demonstrate that PA inhibits the in vitro activities of PKA, CaMKII, and PP1 associated with the cytoskeletal fraction of the cerebral cortex of rats. This study suggests that PA at the same concentrations found in tissues from propionic acidemic children may alter phosphorylation of cytoskeletal proteins, which may contribute to the neurological dysfunction characteristic of propionic acidemia.

Animals↗
PubMed1997

Selective screening of 10,000 high-risk Brazilian patients for the detection of inborn errors of metabolism.

UNLABELLED: The number of diagnosed inborn errors of metabolism (IEM) is growing constantly due to the improvement and widespread availability of analytical techniques. In 1982, a laboratory for the detection of IEM was set up in Porto Alegre, Brazil, and became a national reference centre for the diagnosis of these disorders. Ten thousand patients with signs and symptoms suggestive of IEM were investigated in our laboratory from 1982 to 1995 using specific protocols which included tests for the detection of glucosaminoglycans (GAGS), amino acids, sugars, oligosaccharides, sialyloligosaccharides, organic acids, as well as various metabolite. The biochemical investigation was completed in 9,901 patients and an IEM was detected in 647 cases (6.5%). Groups of IEM of higher incidence in our sample were lysosomal storage disorders (59.8%) and aminoacidopathies (21.2%). The disorders most frequently diagnosed were classical phenylketonuria, GM1 gangliosidosis, mucopolysaccharidosis type I, mucopolysaccharidosis type VI and metachromatic leukodystrophy. CONCLUSION: This study shows that the establishment of reference centres for the investigation of rare genetic diseases is a suitable approach to the study of IEM in developing countries such as Brazil.

Brazil↗
PubMed1997

Neurological dysfunction in methylmalonic acidaemia is probably related to the inhibitory effect of methylmalonate on brain energy production.

Methylmalonic acidaemia is an inherited metabolic disorder caused by a severe deficiency of the activity of the enzyme L-methylmalonyl-CoA mutase or its cofactor 5'-deoxyadenosylcobalamin, resulting in tissue accumulation of large quantities of methylmalonic acid. Among the various clinical features, neurological symptoms are frequently observed. Patients may present cerebral atrophy and basal ganglia abnormalities are common. In the present report, we update the current knowledge on the influence of methylmalonic acid on brain metabolism in the hope of better understanding the neurological dysfunction characteristic of methylmalonic acidaemia. We present evidence showing that the metabolite inhibits brain energy production by various mechanisms and propose that a fall in cellular ATP generation leading to excitotoxicity is crucial for the occurrence of the neurological damage observed in these patients.

Adenosine Triphosphate↗
PubMed1997

Effects of methylmalonate and propionate on [3H]glutamate binding, adenylate cyclase activity and lipid synthesis in rat cerebral cortex.

The effects of methylmalonic (MMA) and propionic acid (PPA), metabolites that accumulate in methylmalonic and propionic acidemia respectively, on [3H]glutamate binding, adenylate cyclase activity and [U-14C]acetate incorporation into lipids were investigated in rat cerebral cortex. Neither acid effected [3H]glutamate binding, regardless of the presence of sodium in the incubation medium. Also, the acids had no effect on basal or GMP-PNP-stimulated adenylate cyclase activity. These results suggest that MMA and PPA do not interact with glutamate binding sites and have no effect on basal or guanine nucleotide-stimulated adenylate cyclase activity. In contrast, [U-14C]acetate incorporation into brain lipids was significantly blocked by both acids, the effects being more pronounced with PPA, indicating an inhibition of brain lipid biosynthesis caused by MMA and PPA. These results may explain at least in part the hypomyelinization and/or demyelinization characteristic of patients affected by methylmalonic acidemia and propionic acidemia.

Acetates↗
PubMed1997

Detection of metabolic disorders in high-risk patients. A pilot study in Salvador, Bahia.

The purpose of this pilot-study was to evaluate the applicability of a screening protocol for the detection of inborn errors of metabolism (IEM) in high-risk patients. The protocol was applied in 65 patients referred to the Medical Genetics Laboratory of the University Hospital Professor Edgard Santos due to the suspicion of an IEM. Eight of these patients (12.3%) displayed an abnormal result in the screening protocol. These patients, along with 22 who displayed normal results in the screening protocol but who presented clinical symptoms or signs suggestive of an IEM not detectable by the tests applied, were selected for a further diagnostic investigation. In 5 of these 30 patients (7.7% of the total sample) it was possible to establish the diagnosis of an specific IEM. The results indicate that the designed screening protocol was successfully applied, allowing the detection of affected patients in a frequency comparable to that observed in larger studies performed elsewhere. The continuation of this study and the enlargement of the sample will help to delineate the profile of IEM in northeast of Brazil and will allow the identification of a significative number of patients and families, who could benefit from the therapeutic and preventive measures available for these diseases.

Amino Acids↗
PubMed1996

Intrastriatal methylmalonic acid administration induces rotational behavior and convulsions through glutamatergic mechanisms.

The effect of intrastriatal administration of methylmalonic acid (MMA), a metabolite that accumulates in methylmalonic aciduria, on behavior of adult male Wistar rats was investigated. After cannula placing, rats received unilateral intrastriatal injections of MMA (buffered to pH 7.4 with NaOH) or NaCl. MMA induced rotational behavior toward the contralateral side of injection and clonic convulsions in a dose-dependent manner. Rotational behavior and convulsions were prevented by intrastriatal preadministration of MK-801 and attenuated by preadministration of succinate. This study provides evidence for a participation of NMDA receptors in the MMA-induced behavioral alterations, where succinate dehydrogenase inhibition seems to have a pivotal role.

Animals↗
PubMed1996

The influence of organic acids on the proliferation of human peripheral lymphocytes activated by concanavalin A and pokeweed mitogen.

The present study was undertaken to assess the influence of 25 organic acids, which appear in high concentrations in tissues of patients with various organic acidaemias, on the proliferation of human peripheral lymphocytes stimulated with concanavalin A (Con A) (a T-cell activator) and pokeweed mitogen (PWM) (predominantly a B-cell activator). Mononuclear cells were cultivated in flat-bottomed 96-well microplates at 37 degrees C for 96 (Con A) or 144 h (PWM) in the presence of one mitogen at different concentrations and of one acid at doses ranging from 1 to 5 mM. Control cultures did not contain any acid. Cell reactivity was measured by the incorporation of tritiated thymidine into cellular DNA. We observed that, among the 25 acids tested, aminoadipic (AAD), 2-hydroxy-3-methylvaleric (HMV), 2-ketoisocaproic (KIC), 2-methylbutyric (MBA), propionic (PPA) and tiglic (TIG) acids strongly suppressed lymphocyte DNA synthesis in Con A-supplemented cultures, whereas in cultures stimulated with PWM, 2-ketoisovaleric (KIV) and PPA acids presented the same effect. In contrast, lactic (LAC) and pyruvic (PYR) acids activated lymphocyte DNA synthesis in cultures treated with Con A, the same effect occurring with LAC acid for PWM-stimulated lymphocytes. The most inhibitory or stimulatory acids were added to cultures at different times after the beginning of the incubation period when mitogens were added. Except for HMV, KIC, PPA and LAC acids, whose actions persisted even after 24 h from the beginning of culture, the others only exerted their effects when added at time zero. The present study therefore demonstrated that some organic acids modulate DNA synthesis in Con A- and PWM-stimulated human lymphocytes.

2-Aminoadipic Acid↗
PubMed1995

Neurochemical effects of L-pyroglutamic acid.

The effect of L-pyroglutamic acid, a metabolite that accumulates in pyroglutamic aciduria, on different neurochemical parameters was investigated in adult male Wistar rats. Glutamate binding, adenylate cyclase activity and G protein coupling to adenylate cyclase were assayed in the presence of the acid. L-pyroglutamic acid decreased Na(+)-dependent and Na(+)-independent glutamate binding. Basal and GMP-PNP stimulated adenylate cyclase activity were not affected by the acid. Furthermore, rats received unilateral intrastriatal injections of 10-300 nmol of buffered L-pyroglutamic acid. Vehicle (0.25 M Tris-Cl, pH 7.35-7.4) was injected into the contralateral striatum. Neurotoxic damage was assessed seven days after the injection by histological examination and by weighing both cerebral hemispheres. No difference in histology or weight could be identified between hemispheres. These results suggest that, although capable of interfering with glutamate binding, pyroglutamate did not cause a major lesion in the present model of neurotoxicity.

Adenylyl Cyclases↗
PubMed1995

The effect of organic acids on phytohaemagglutinin-activated proliferation of human lymphocytes in vitro.

The present study assesses the effects of 25 organic acids on in vitro proliferation of human peripheral lymphocyte stimulated with phytohaemagglutinin (PHA). Lymphocytes were cultured in flat-bottomed 96-well microplates at 37 degrees C for 96 h in the presence of the mitogen and of one acid. The concentrations of organic acids tested in the cultures were from 1 to 5 mM, corresponding to those usually found in the blood of patients with organic acidaemias. Cellular growth was measured by the incorporation of 6[3H]-thymidine into cellular DNA. We observed that tiglic (2-methylcrotonic), alpha-keto-beta-methylvaleric, aminoadipic, sebacic and alpha-ketoisocaproic acids strongly inhibited lymphocyte DNA synthesis, whereas alpha-ketoisovaleric, propionic, alpha-hydroxy-beta-methylvaleric, alpha-methylbutyric and isobutyric acids moderately suppressed DNA synthesis. Lactic and ethylmalonic acids, however, stimulated DNA synthesis. The most inhibitory acids were added to cultures at different times after the beginning of the incubation period. Except for tiglic acid, whose action persisted even after 48 h from the onset of cultures, the others acted only when added during the first 24 h. The present study demonstrated that organic acids modulate DNA synthesis in mitogen-stimulated human lymphocytes.

Adjuvants, Immunologic↗