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Biomedical subjects

J Coutinho-Netto

Publications and source records attributed to J Coutinho-Netto.

At least 19 recordsLinked to original sources
PubMed2003

Mutation in a calpain-like protease affects the posttranslational mannosylation of phosphatases in Aspergillus nidulans.

In this communication, we show that the palB7 mutation drastically reduced the mannose and N-acetylgalactosamine content of the pacA-encoded acid phosphatase secreted by the fungus Aspergillus nidulans at pH 5.0, compared to a control strain. By using mRNA differential display reverse transcription and polymerase chain reaction, we isolated two cDNAs from the control pabaA1 strain that were not detected in the palB7 mutant strain that encode a mannosyl transferase and a NADH-ubiquinone oxidoreductase. Thus, a defect in the posttranslational mannosylation of proteins could be the consequence of mutations in the palB gene, which encodes for a nuclear calpain-like protease that may have specific functions in the processing of transcription factor(s) similar to its homolog, RIM13, in Saccharomyces cereviseae.

Amino Acid Sequence↗
PubMed2000

Effects of the crude venom of the social wasp Agelaia vicina on gamma-aminobutyric acid and glutamate uptake in synaptosomes from rat cerebral cortex.

Glutamate (L-glu) is the most important excitatory neurotransmitter in the mammalian central nervous system. Its action is terminated by transporters located in the plasma membrane of neurons and glial cells, which have a critical role in preventing glutamate excitotoxicity under normal conditions. The neurotransmitter gamma-aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the mammalian central nervous system. Venoms of solitary wasps and orb-spiders are composed of large proteins, medium-size peptides, polyamine amides (PAs), and other neuroactive components that are highly selective to nervous tissues. The abnormal operation of uptake systems is involved in several failures. Several studies indicate alterations in extracellular GABA and glutamate concentrations in epilepsy conditions that may relate to transporter functions. The effects of the crude and boiled venom of the social wasp Agelaia vicina, "cassununga," on GABA and L-glu uptake in rat cerebral cortex synaptosomes are related. The venom uncompetitively inhibited high- and low-affinity GABA uptake by 91.2% and by 76%, respectively. This kind of inhibition was also found to affect high- (99.6%) and low-affinity (90%) uptake of L-glu. These results suggest that the effects observed in these experiments indicate the venom of A. vicina to be a useful tool to further characterize GABA- and L-glu-uptake systems.

Animals↗
PubMed2000

Indicators of oxidative injury and alterations of the cell membrane in the skeletal muscle of rats submitted to ischemia and reperfusion.

BACKGROUND: Oxygen free radicals are considered to be important components involved in the physiopathological tissue alterations observed during ischemia and reperfusion. The objective of the present study was to investigate oxidative stress based on indicators of oxygen free radical activity and on the changes in behavior of the lipoprotein membrane (O-phosphoserine) in the skeletal muscle of rats. MATERIAL AND METHODS: Twenty Wistar rats were divided into two groups of 10. One group was submitted to 3 h of total ischemia by applying a tourniquet to the hind limb and the contralateral hind limb was used as control. The second group was submitted to the same procedure and was reperfused for 45 min after 3 h of ischemia by removing the tourniquet, where the contralateral hind limb of the same animal was used as control. Muscle biopsies were taken after ischemia and reperfusion and the parameters indicating oxidative stress (reduced and oxidized glutathione, malondialdehyde, glutamine synthetase, protein carbonyl) and O-phosphoserine (OPS) alterations were analyzed. RESULTS: The following results display control versus experimental hindlimbs groups obtained from the same animal. The skeletal muscle of rats submitted to total ischemia of 3 h duration showed increased OPS release (2.69 +/- 4.52 vs 8.03 +/- 7.20; n = 10; P = 0.024) and no change in reduced and oxidized glutathione, glutamine synthetase, protein carbonyl, or malondialdehyde. After 45 min of reperfusion there was an increase in oxidized glutathione levels (0.30 +/- 0.06 vs 0.39 +/- 0.09; n = 8; P = 0.02) and malondialdehyde levels (154. 78 +/- 26.13 vs 206.30 +/- 47.30; n = 9; P = 0.008), a fall in glutamine synthetase (21.80 +/- 3.61 vs 13.52 +/- 6.78; n = 9; P = 0. 004), and a return of OPS to levels close to the initial ones. No changes in reduced glutathione or protein carbonyl were observed in the two groups studied. CONCLUSIONS: After a total ischemia duration of 3 h there were signs of damage to the phospholipid membrane of the rat skeletal muscle, as demonstrated by the elevation of OPS and the few or no oxidative changes in the cell. After 45 min of reperfusion, oxidative damage to the lipoprotein components of the cell membrane was observed, characterized by elevations of oxidized glutathione and malondialdehyde levels and a fall in glutamine synthetase levels.

Animals↗
PubMed2000

Paralizing activity of the Parawixia bistriata crude venom in termites: a new bioassay.

Spider venoms have high specificity to neuronal elements. Therefore, the use of venom has been important in the characterisation of mammal and insect nervous systems. The evaluation of insect paralysis has been an important tool for distinguishing the biological effects of venom. In this study we describe the paralysing effect of a spider crude venom (Parawixia bistriata) in termites, utilising a new bioassay. The crude venom of P. bistriata caused an irreversible and dose-dependent paralysis in the animals in the following doses: 2.10(-5) U; 2.10(-4) U; 2.10(-3) U; 2.10(-2) U and 0.12 U (1 U = 1 gland). This bioassay will allow for easy and direct evaluation of biological effects from different venoms and purified fractions.

Animals↗
PubMed1997

TsTX-VII, a new toxin from Tityus serrulatus scorpion venom able to induce the release of neurotransmitters from rat brain synaptosomes not blocked by tetrodotoxin.

A procedure for the isolation of the toxin Tityustoxin VII (TsTX-VII) from Tityus serrulatus scorpion venom and its biochemical characterization is reported. This protein has a M(r) = 6,700-6,800, eight half-cystine residues accounting for four disulfide bridges and no His. Its N-terminal sequence GHZGYGS ... characterizes it as a new toxin, able to release glutamic acid and gamma aminobutyric acid from rat brain synaptosomes "in vitro". This release was also induced by the whole venom. Tetrodotoxin however blocked the effect of the whole venom but not that of TsTX-VII, thus suggesting that the releasing mechanism by TsTX-VII does not involve Na+ but perhaps K+ or Ca++ channels.

Animals↗
PubMed1996

Isolation of toxin TsTX-VI from Tityus serrulatus scorpion venom. Effects on the release of neurotransmitters from synaptosomes.

A detailed procedure for the purification of Tityustoxin-VI, TsTX-VI, from Tityus serrulatus scorpion venom is described. For comparative purposes, a second toxin, CM-VI, obtained from the same fractionation procedure, was analyzed in parallel. Typical biochemical parameters, such as electrophoretic migration, mol.weight, amino acid composition and N-terminal sequence (first 42 amino acid residues out of a total of approx. 60) were determined for both. Our data showed that CM-VI is identical or extremely homologous to gamma-toxin (TsTX-I), the highly toxic major toxin from T. serrulatus venom. TsTX-VI was less toxic, although still effective at inducing an allergic reaction, lacrymation and contraction of the hind legs of mice. Both toxins produced a dose dependent release of the neurotransmitters glutamic acid and gamma aminobutyric acid from rat brain synaptosomes, this effect being blocked by tetrodotoxin.

Animals↗
PubMed1995

Peripheral and coronary sinus catecholamine levels in patients with severe congestive heart failure due to Chagas' disease.

The aim of this study was to assess the peripheral and cardiac autonomic system by catecholamine measurements in patients with severe chagasic and nonchagasic heart failure. Fifteen chagasic and 16 nonchagasic patients were enrolled in the study. Plasma venous norepinephrine levels (pg/ml) were 397.26 +/- 250.11 for chagasic and 660.05 +/- 455.57 for nonchagasic patients (p > 0.05), plasma venous epinephrine levels 215.84 +/- 254.04 for chagasic and 106.17 +/- 65.90 for nonchagasic patients (p > 0.05), aortic root norepinephrine levels 435.46 +/- 306.60 for chagasic and 668.16 +/- 512.82 for nonchagasic patients (p > 0.05), aortic root epinephrine levels 300.33 +/- 302.69 for chagasic and 199.98 +/- 162.88 for nonchagasic patients (p > 0.05), coronary sinus norepinephrine levels 636.10 +/- 495.22 for chagasic and 552.17 +/- 535.54 for nonchagasic patients (p > 0.05) and coronary sinus epinephrine levels 226.66 +/- 277.47 for chagasic and 69.21 +/- 35.62 for nonchagasic patients (p = 0.02). Myocardial and peripheral norepinephrine and epinephrine extractions were similar for both groups. Taken together, these findings may suggest that chagasic patients with congestive heart failure have biochemical evidence of cardiac autonomic dysfunction with preservation of the peripheral sympathetic activity.

Adolescent↗
PubMed1992

Glutamate release in experimental ischaemia of the retina: an approach using microdialysis.

A rabbit eye model of neural ischaemia is described that uses an increased pressure in the anterior eye chamber to block the capillary supply to the retina. A microdialysis probe placed very close to the retinal surface was used to monitor release of amino acids during ischaemia. A large (two- to threefold) increase in the release of glutamate and O-phosphoserine (twofold), but not of six other amino acids monitored, occurred during initial ischaemia. During reperfusion after release of intraocular pressure, much larger (five- to 10-fold) increases in the release of these amino acids were observed. Parallel ischaemic retinal tissue damage was observed. This damage was prevented by ketamine applied locally via a superfusion needle, suggesting that glutamate released during ischaemia, and particularly during reperfusion, was responsible for cell death.

Amino Acids↗
PubMed1989

[3H]-acetylcholine release from rat atria in chronic chagasic cardiopathy.

Isolated superfused rat atria release [3H]-acetylcholine when depolarized with 57 mM potassium. The depolarization-induced [3H]-acetylcholine overflow was significantly reduced in atria from chronically T. cruzi-infected rats with electrocardiographically characterized cardiopathy. This fact suggests the occurrence of functional alterations of cardiac parasympathetic control in these animals, probably related to cardiac ganglion cell destruction.

Acetylcholine↗
PubMed1983

Prejunctional supersensitization of adrenergic transmission of the isolated guinea pig vas deferens produced by an atoxic fraction from scorpion venom (Tityus serrulatus).

The effects of four atoxic fractions prepared from Tityus serrulatus venom on the response of isolated guinea pig vas deferens to norepinephrine (NE) and acetylcholine (Ach) were studied. The fractions, prepared by gel filtration on Sephadex G-50, did not contain Tityustoxin (TsTX) and were used in the concentration range 20-40 micrograms/ml tissue bath. Fraction III decreased the ED50 of NE 7.1-fold (P less than 0.01) and of Ach 17.8-fold (P less than 0.01) but did not significantly modify the maximal response (MR) to either agonist. The other fractions had much less pronounced effects, if any, on the ED50 and/or MR of either Ach or NE. The effect of Fraction III on responsiveness to NE was not demonstrable on vas deferens of pharmacologically "denervated" animals (pretreated with reserpine and alpha-methyl-p-tyrosine) but was demonstrable in tissue from normal animals tested in the presence of atropine. The effect of Fraction III on responsiveness to Ach was abolished by the presence of phentolamine in the tissue bath. These data indicate that Fraction III induces a prejunctional type of supersensitivity by acting mainly on adrenergic transmission and suggest that it may be a useful tool for the investigation of the mechanism of action of drugs that act on nerve terminals.

Acetylcholine↗
PubMed1982

Morphine suppression of neurotransmitter release evoked by sensory stimulation in vivo.

The effects of morphine and naloxone on the release of acetylcholine and amino acid neurotransmitters from sensorimotor cortex were studied employing an in vivo superfusion cannula. Morphine (20 mg/kg) reduced the spontaneous release of acetylcholine but had no detectable effect on the spontaneous release of amino acids. It also suppressed the release of acetylcholine and amino acid neurotransmitters evoked by sensory stimulation of the contralateral sensorimotor cortex via the brachial plexus. Naloxone (5 mg/kg) prevented all of these inhibitory actions of morphine. Naloxone also caused a significant increase in spontaneous acetylcholine release.

Acetylcholine↗
PubMed1982

Dopamine inhibition of the release of endogenous acetylcholine from corpus striatum and cerebral cortex in tissue slices and synaptosomes: a presynaptic response?

The effect of dopamine on the release of endogenous acetylcholine from striatal slices and synaptosomes and from cerebral cortex synaptosomes was studied. K+ (56 mM) and veratrine (75 microM) increased the release of acetylcholine from striatal slices by 3.7 and 3.3 times the resting release, respectively. The effect of veratrine was completely abolished by tetrodotoxin (1 microM). Dopamine (10(-6) to 10(-3) M) reduced the K+-evoked release of acetylcholine from striatal slices in a dose-dependent manner. The resting release of acetylcholine was also significantly reduced by dopamine. Apomorphine (20 microM) significantly reduced the K+-evoked release of acetylcholine, and both this effect and the inhibition due to dopamine (1 mM) were significantly antagonised by chlorpromazine (20 microM). Dopamine had a similar effect on the release of acetylcholine from striatal synaptosome beds; the resting release was depressed 32% by the presence of dopamine (1 mM). A greater effect of dopamine was seen on the release of acetylcholine from cerebral cortex synaptosome beds, the resting release being reduced by 54% and the K+-evoked release by 29%. These results are discussed in terms of the possible role of presynaptic dopamine receptors in controlling the release of acetylcholine and the magnitude of their contribution compared with that of the postsynaptic dopamine receptor.

Acetylcholine↗
PubMed1982

Actions of Ptychodiscus brevis red tide toxin on metabolic and transmitter-releasing properties of synaptosomes.

A pure toxin isolated from Ptychodiscus brevis stimulated differential release of amino acid neurotransmitters from mammalian cortical synaptosomes together with loss of K+ content and respiratory stimulation at 40 ng/ml. The effect was blocked by tetrodotoxin and by verapamil, implicating Na+ channel activation and possibly Ca2+ influx as necessary for the response, although the response did not change upon omission of Ca2+. Verapamil was therefore likely to be acting as a Na+ channel blocker in this instance. The toxin at 40 ng/ml caused acetylcholine release from guinea pig ileum, which is consistent with the proposed depolarising action for the toxin.

Acetylcholine↗
PubMed1982

In vivo inhibition of incorporation of [U-14C]glucose into proteins in experimental focal epilepsy.

The in vivo incorporation of [14C] from [U-14C]-glucose into rat brain proteins from different cortical areas was examined in three different experimental focal epilepsies: cobalt, freeze-lesions, and tityustoxin. When [U-14C]-glucose was injected intraperitoneally into awake and unrestrained animals with marked signs of epileptic hyperactivity, the inhibition of incorporation of [14C]-amino acids into trichloracetic acid (TCA)-insoluble proteins was highest in the focal (sensorimotor) area when compared with distant regions (approx. 60%), but less when compared with the contralateral (sensorimotor) region (approx. 23%). Greatly decreased incorporation caused by both cobalt and freeze-lesion-induced epilepsies was also observed in the contralateral area when a comparison was made with distant regions (approx. 50%), but there were no significant differences in protein-specific radioactivity between the different distant areas.

Animals↗