Leticia Biscaino Alves

Quinolinic acid stimulates synaptosomal glutamate release and inhibits glutamate uptake into astrocytes

Quinolinic acid (QA) is an endogenous neurotoxin involved in various neurological diseases, whose action seems to be exerted via glutamatergic receptors. However, the exact mechanism responsible for the neurotoxicity of QA is far from being understood. We have previously reported that QA inhibits vesicular glutamate uptake. In this work, investigating the effects of QA on the glutamatergic system from rat brain, we have demonstrated that QA (from 0.1 to 10mM) had no effect on synaptosomal L-[3H]glutamate uptake. The effect of QA on glutamate release in basal (physiological K+ concentration) or depolarized (40 mM KCl) conditions was evaluated. QA did not alter K+-stimulated glutamate release, but 5 and 10mM QA significantly increased basal glutamate release. The effect of dizolcipine (MK-801), a noncompetitive antagonist of N-methyl-D-aspartate (NMDA) receptor on glutamate release was investigated. MK-801 (5 microM) did not alter glutamate release per se, but completely abolished the QA-induced glutamate release. NMDA (50 microM) also stimulated glutamate release, without altering QA-induced glutamate release, suggesting that QA effects were exerted via NMDA receptors. QA (5 and 10mM) decreased glutamate uptake into astrocyte cell cultures. Enhanced synaptosomal glutamate release, associated with inhibition of glutamate uptake into astrocytes induced by QA could contribute to increase extracellular glutamate concentrations which ultimately lead to overstimulation of the glutamatergic system. These data provide additional evidence that neurotoxicity of QA may be also related to disturbances on the glutamatergic transport system, which could result in the neurological manifestations observed when this organic acid accumulates in the brain.

Inhibition of adenylate cyclase activity by 5-aminolevulinic acid in rat and human brain.

The effect of the haem precursor 5-aminolevulinic acid (ALA) on the production of cyclic adenosine-monophosphate (cAMP) by rat cerebellar membranes was investigated. It was found that ALA dose-dependently decreased cAMP levels (maximal inhibition of 38%, at 1 mM), due to an inhibition of basal adenylate cyclase activity. ALA also inhibited fluoride- and Gpp(NH)p-stimulated, but not the forskolin-stimulated adenylate cyclase activity. 5-Aminovaleric acid (an inhibitor of GABA(B) receptors) did not prevent the inhibition, indicating that it was not mediated by the activation of the G(i)-protein coupled GABA(B) receptor. In addition, the nucleotide binding site of G-protein appeared not to be affected by ALA since it did not inhibit [3H]Gpp(NH)p binding to our membrane preparation. Antioxidants (glutathione, ascorbate and trolox) completely prevented the inhibition indicating that ALA effect was mediated by an oxidative damage of adenylate cyclase. ALA also inhibited the activity of adenylate cyclase in membranes isolated from rat cortex and striatum and from human cortex. These results may be of value in understanding the neurochemical mechanisms underlying the neurotoxic effects of ALA.

Neurochemical characterization of traumatic brain injury in humans.

Trauma is the leading cause of death in individuals between the ages of 1 and 44 years. And, in the case of severe head injury mortality can reach as high as 35-70%. Despite this fact, there has been little progress in the development of effective pharmacological agents to protect brain injured patients. To date, there is little data on the mechanisms involved in neuronal cellular insult after severe head injury, especially in humans. Glutamate acts both as a primary excitatory neurotransmitter and a potential neurotoxin within the mammalian brain. Evidence indicates that hyperactivity of the glutamate system contributes to neuronal death in brain trauma. Also, in animal models of neurotrauma, this neural injury is followed by gliosis which has been linked to the severity of brain injury. To investigate the glutamate system in brain trauma, we carried out [3H]glutamate and [3H]MK801 (a noncompetitive NMDA-receptor antagonist) binding and [3H]glutamate uptake assays in human cerebral cortex preparations obtained from severely brain injured and control victims. Additionally, to investigate gliosis following brain injury, we performed GFAP immunohistochemistry. There were no significant differences in [3H]glutamate binding (affinity or density of sites) between the control and head injured groups. In contrast, cerebral cortical [3H]MK801 binding revealed both a significant increase in the density of sites (Bmax) and a decrease in the dissociation constant (Kd) in the head injured group when compared to controls. There were no significant differences in [3H]glutamate uptake between groups. The injured brains presented an increased number of GFAP-positive astrocytes and more intense GFAP reaction in comparison to control brains. In the context of traumatic brain injury, our results encourage further investigation into compounds capable of selective modulation of NMDA receptor subtype in humans while also therapeutically manipulating glial cell responses following brain trauma.

Laparoscopic sleeve gastrectomy with NOTES visualization--a step toward NOTES procedures.

BACKGROUND To demonstrate that bariatric procedures can be done with natural orifice visualization (NOTES) at 2 institutions (Nucleo Universitario de Estudos de Notes Centro de Cirurgia Experimental Vila do Conde-Junqueira, Vila do Conde, Portugal and Pontificia Universidade Catolica do Rio Grande do Sul, Porto Alegre, RS, Brasil). NOTES is a new surgical approach that is being developed. It consists of the use of a minimally invasive technique in which the surgical procedure is performed through natural orifices, thereby circumventing incisions through the skin. METHODS We performed vertical gastrectomy or laparoscopic sleeve gastrectomy in a porcine model using vaginal route visualization. RESULTS A laparoscopic vertical sleeve gastrectomy with NOTES visualization in a porcine model was performed with safety. CONCLUSION Bariatric procedures can be done with NOTES with results as good as those using laparoscopic techniques.

5-Aminolevulinic acid inhibits [3H]muscimol binding to human and rat brain synaptic membranes.

The interaction of 5-aminolevulinic acid (ALA) with GABAA receptors has been proposed to underlie the neurological dysfunctions of ALA-accumulating disorders, such as acute intermittent porphyria. The effects of ALA on [3H]muscimol binding to human and rat cerebral cortical membranes were compared. ALA (0.1–10 mM) significantly inhibited the binding of [3H]muscimol (12 nM), with a similar potency in rat and human membranes (IC50 = 199 vs. 228 μM, respectively). Kinetical analysis revealed that ALA (1 mM) significantly increased the Kd and decreased the Bmax of [3H]muscimol to both rat (100 and 50%, respectively) and human (200 and 40%, respectively) membranes, indicating a mixed-type inhibition. The similarity in the potency and mechanism of the ALA-induced inhibition of muscimol binding in rat and human membranes indicate that rat studies are useful to evaluate the neurotoxic properties of ALA towards the human GABAergic system, and may help to understand the pathophysiology of porphyria.

Retrospective Study of the Survival of Patients who Underwent Cardiopulmonary Resuscitation in an Intensive Care Unit

OBJECTIVE To evaluate clinical and evolutive characteristics of patients admitted in an intensive care unit after cardiopulmonary resuscitation, identifying prognostic survival factors. METHODS A retrospective study of 136 patients admitted between 1995 and 1999 to an intensive care unit, evaluating clinical conditions, mechanisms and causes of cardiopulmonary arrest, and their relation to hospital mortality. RESULTS A 76% mortality rate independent of age and sex was observed. Asystole was the most frequent mechanism of death, and seen in isolation pulmonary arrest was the least frequent. Cardiac failure, need for mechanical ventilation, cirrhosis and previous stroke were clinically significant (p < 0.01) death factors. CONCLUSION Prognostic factors supplement the doctors decision as to whether or not a patient will benefit from cardiopulmonary resuscitation.

PROGNOSTIC VALUE OF CARCINOEMBRYONIC ANTIGEN LEVELS IN TRANSOPERATIVE PERITONEAL LAVAGE IN PATIENTS WITH GASTRIC CANCER

ABSTRACT Background: The carcinoembryonic antigen level in peritoneal lavage has been showing to be a reliable prognostic factor in gastric cancer. Aim: To identify any association between carcinoembryonic antigen level in peritoneal lavage, in gastric cancer patients, with mortality, peritoneal recurrence, tumor relapse or other prognostic factors. Methods: In total, 30 patients (22 men, 8 women; median age 66 years) with resectable gastric cancer (mainly stage III and IV) were studied. Carcinoembryonic antigen level in peritoneal lavage was detected at operation by immunocytochemical method and a level over 210 ng/g of protein was considered as positive. Results: There were detected 10 positive cases (33.3%) of plCEA levels. These levels were associated with mortality, RR: 2.1 (p=0.018); peritoneal recurrence, OR: 9.0 (p=0.015); and relapse or gastric cancer progression, OR: 27.0 (p=0.001). Conclusion: Increased levels of plCEA fairly predicts mortality, peritoneal recurrence tumor relapse or cancer progression.