Biomedical subjects

A C Costa

Publications and source records attributed to A C Costa.

12 recordsLinked to original sources

PubMed2000

Simulated dynamics and control of an extractive alcoholic fermentation.

In this study, we investigated the dynamics of a computer simulation of a continuous alcoholic fermentation process combined with a flash column under vacuum. The alcohol was partially extracted in order to maintain its concentration at about 40 kg/m3 in the fermentor. The mathematical model of the fermentation was developed for industrial conditions and considers the effect of the temperature on the kinetic parameters. The performance of the dynamic matrix control algorithm, single input single output and multiple input multiple output, for the control of the extractive process was studied. The concepts of factorial design were used in a simulation study to determine the best control structures for the process.

Biomass↗

PubMed2000

Preoperative diagnosis of pancreatic leiomyosarcoma.

BACKGROUND: The low incidence of pancreatic leiomyosarcoma is responsible for the small number of cases correctly diagnosed preoperatively, the tumor being frequently confused with benign pancreatic lesions. RESULTS: We describe a symptom free 52-yr-old male bearing an abdominal mass incidentally found at physical examination. Imaging techniques revealed a nonhomogenous large mass at the head of the pancreas that dislodged the portal vein and the superior mesenteric vein. Increased metabolic activity in the tumor area demonstrated by 18F-fluorodeoxyglicose positron emission tomography scan allowed the diagnosis of a malignant lesion. The patient was operated on and a pylorus preserving pancreatoduodenectomy performed. The pathology diagnosis was a low grade leiomyosarcoma. Immunohistochemistry revealed positivity for vimentin and smooth muscle specific actin. The clinical course was uneventful after 2 yr follow-up. CONCLUSION: Pancreatic leiomyosarcoma may be preoperatively diagnosed by image techniques and differentiated from benign lesions by means of fluorodeoxyglicose positron emission tomography scanning (FDGPET).

Actins↗

PubMed1999

Inspiratory flow-volume curve in snoring patients with and without obstructive sleep apnea.

We analyzed the flow-volume curves of 50 patients with complaints of snoring and daytime sleepiness in treatment at the Pneumology Unit of the University Hospital of Brasília. The total group was divided into snorers without obstructive sleep apnea (OSA) (N = 19) and snorers with OSA (N = 31); the patients with OSA were subdivided into two groups according to the apnea/hypopnea index (AHI): AHI < 20/h (N = 14) and AHI > 20/h (N = 17). The control group (N = 10) consisted of nonsmoking subjects without complaints of snoring, daytime sleepiness or pulmonary diseases. The population studied (control and patients) consisted of males of similar age, height and body mass index (BMI); spirometric data were also similar in the four groups. There was no significative difference in the ratio of forced expiratory and inspiratory flows (FEF50%/FIF50%) in any group: control. 0.89; snorers, 1.11; snorers with OSA (AHI < 20/h), 1.42, and snorers with OSA (AHI > 20/h), 1.64. The FIF at 50% of vital capacity (FIF50%) of snoring patients with or without OSA was lower than the FIF50% of the control group (P < 0.05): snorers 4.30 l/s; snorers with OSA (AHI < 20/h) 3.69 l/s; snorers with OSA (AHI > 20/h) 3.17 l/s and control group 5.48 l/s. The FIF50% of patients with severe OSA (AHI > 20/h) was lower than the FIF50% of snorers without OSA (P < 0.05): 3.17 l/s and 4.30 l/s, respectively. We conclude that 1) the FEF50%/FIF50% ratio is not useful for predicting OSA, and 2) FIF50% is decreased in snoring patients with and without OSA, suggesting that these patients have increased upper airway resistance (UAR).

Humans↗

PubMed1997

Substance P facilitates memory in goldfish in an appetitively motivated learning task.

The aim of this study was to investigate if the neuropeptide substance P (SP) can improve learning and memory in goldfish (Carassius auratus). Four groups of fish were trained for seven days to find food in one out of two compartments until discrimination was achieved. On the last training day, they were injected (intra-abdominal) with haloperidol or vehicle before the training, and with SP or vehicle immediately after the training session. Each group of fish received either: (1) vehicle+vehicle (n = 18); (2) vehicle + SP, (n = 20, SP 50 mg/kg); (3) haloperidol+ vehicle (n = 15, haloperidol 2 mg/kg); or (4) haloperidol+ SP (n = 14, haloperidol 2 mg/kg, SP 50 mg/kg). Twenty-four hours later, the time spent to find the food was recorded. Reversal training was done for four consecutive days after this post-injection test and the time spent to find the food was recorded again. The results indicate that only the group treated with vehicle + SP needed more time to reach reversal training than control fish (Mann-Whitney U-test, P = 0.0009). It is suggested that SP can enhance memory in fish and that this effect may have a dopaminergic mediation in discrimination learning task.

Animals↗

PubMed1997

[Reference values for carboxyhemoglobin].

INTRODUCTION: The reference values (RV) of biological indicators are used in the interpretation of the results of such indicators in individuals occupationally exposed to chemical agents. The Brazilian Group for the Establishment of Reference Values has worked on these definitions for the purpose of establishing RVs for several bioindicators in various regions of the country. In the present study, the RV for carboxyhemoglobin (COHb) was determined for the South of Minas Gerais. MATERIAL AND METHOD: The COHb was analyzed by the Beutler and West (1984) spectrophotometric method, optimized in our laboratory. In all the samples, analyses of some biochemical and hematological parameters were made to evaluate the health condition of a population of 200 volunteer non-smokers occupationally not exposed to CO. Each individual answered a questionnaire to obtain data pertinent to the interpretation of the results. The reference values were expressed as mean values +/- standard deviation, with a 95% confidence interval, and an upper reference value. The statistical distribution of the results was made so as to enable comparisons between the results of groups of workers, rather than individual evaluations, to be made. RESULTS AND CONCLUSIONS: The mean value +/- standard deviation was 1.0% +/- 0.75; the 95% confidence interval was 0.9-1.1% and the upper reference value was 2.5%. By the t Student test (p < or = 0.05), no difference was detected between the values related to sex, age or ingestion of alcoholic beverages. The reference values obtained were close to those reported for others countries.

Adolescent↗

PubMed1994

Improved technique for studying ion channels expressed in Xenopus oocytes, including fast superfusion.

The study of whole-cell currents from ion channels expressed in Xenopus oocytes with conventional two-electrode voltage clamp has two major limitations. First, the large diameter and spherical geometry of oocytes prevent extremely fast solution changes. Second, the internal medium is not controlled, which limits the experimental versatility of the oocyte expression system. For example, because the internal medium is not controlled, endogenous calcium-activated chloride conductances can contaminate currents measured with channels that are permeable to calcium. We describe a new technique that combines vaseline-gap voltage clamp for oocytes with a fast superfusion system. The vaseline-gap procedure is simplified by having the micropipette that monitors voltage serve a dual role as a perfusion micropipette that controls the internal solution. In addition, the technique provides fast external solution changes that are complete in 30-50 ms. We applied the approach to measure the calcium permeability of a muscle and a neuronal nicotinic acetylcholine receptor. Very fast agonist induced currents were measured without contamination by the secondary activation of calcium-dependent chloride channels.

Acetylcholine↗

PubMed1994

Dynamics of the actions of tetrahydro-9-aminoacridine and 9-aminoacridine on glutamatergic currents: concentration-jump studies in cultured rat hippocampal neurons.

The actions of 1,2,3,4-tetrahydro-9-aminoacridine (THA) and 9-aminoacridine (9-AA) on glutamatergic receptors were studied using the whole-cell and outside-out variants of the patch-clamp technique. Typically, either N-methyl-D-aspartate (NMDA) or kainate alone or combined with various concentrations of THA or 9-AA was applied via a U tube to activate whole-cell currents. Other superfusion techniques were also used. THA (25-50 microM) and 9-AA (10-25 microM) reduced the peak and steady-state amplitudes of NMDA-activated whole-cell inward currents and had no significant effect on outward currents. At higher concentrations, these agents produced a delayed current peak in addition to a further depression of the current size. A delayed current peak was a high-amplitude current peak delayed in relation to the time course of control currents. THA and 9-AA were much less potent in blocking kainate-activated currents. Also, the blockade of kainate currents was voltage independent, and no delayed current peak was generated. With the same superfusion method, the antagonists APV (DL-2-amino-5-phosphonovaleric acid) and Mg++ were tested independently of THA or 9-AA and were found not to produce delayed current peaks or NMDA-activated whole-cell currents. Bath perfusion of THA (250 microM) abolished the delayed current peaks produced by pulse application of NMDA and THA, whereas bath perfusion of the competitive blocker APV did not have this effect. High concentrations of glycine (10 microM) did not alter THA's blocking effects or the production of delayed current peaks.(ABSTRACT TRUNCATED AT 250 WORDS)

Aminacrine↗

PubMed1993

Barium permeability of neuronal nicotinic receptor alpha 7 expressed in Xenopus oocytes.

The rat alpha 7 neuronal nicotinic acetylcholine receptor was expressed and studied in Xenopus oocytes. The magnitude and reversal potential of instantaneous whole cell currents were examined in solutions containing varying concentrations of either calcium or barium, and in the presence or absence of the intracellular calcium chelator BAPTA. In external barium, application of nicotine elicits an inwardly rectifying response; in calcium the response is larger and has a linear IV relation. Pretreatment of oocytes with BAPTA-AM could not prevent activation of calcium-dependent chloride channels in external Ringer containing calcium. Using an extended GHK equation, the permeability ratio PBa/PNa of the alpha 7 receptor was determined to be about 17. Our results suggest that alpha 7 nicotinic receptors are highly permeable to divalent cations.

Animals↗

PubMed1991

Functional properties of the nicotinic and glutamatergic receptors.

Several important physiological processes such as plasticity, memory, cell death, and rhythmic firing involve the N-methyl-D-aspartate (NMDA)-type of glutamatergic receptor. Nicotinic acetylcholine receptors (AChR), recently demonstrated in the central nervous system (CNS), are also of great interest. We have used several ligands to study the physiology and pharmacology of the agonist recognition sites of these receptors and kinetic properties of associated ion channels using whole-cell, cell-attached or outside-out variants of the patch-clamp technique. Enzymatically dissociated frog interosseal muscles were used to study peripheral AChRs, and tissue cultured or acutely dissociated hippocampal neurons and retinal ganglion cells (RGCs) for CNS receptors. For reproducible and fast solution changes when recording in the whole-cell configuration, we modified the "U"-shaped tube system to obtain different outputs from the same outflow port. We used fluorescent rhodamine-labeled latex microspheres to identify RGCs. Our studies provide important information regarding the molecular mechanisms of several clinically used agents. Additionally, similar actions of noncompetitive agents on the ion channels of the nicotinic ACh and NMDA receptors support the concept of a receptor ion channel superfamily.

Animals↗

PubMed1990

Selective blockade of NMDA-activated channel currents may be implicated in learning deficits caused by lead.

The effect of Pb2+ on glutamate receptor activity in rat hippocampal neurons was investigated with a view of explaining the cognitive and learning deficits produced by this heavy metal. Pb2+ (2.5-50 microM) selectively inhibited N-methyl-D-aspartate (NMDA)-induced whole-cell and single-channel currents in a concentration-dependent but voltage-independent manner, without significantly altering currents induced by either quisqualate or kainate. The frequency of NMDA-induced channel activation was decreased by Pb2+. Neither glycine (10-100 microM), nor Ca2+ (10 mM) reversed the effect of Pb2+. Pb2+ also inhibited the [3H]MK-801 binding to rat hippocampal membranes in vitro. The elucidation of the actions of Pb2+ on the NMDA receptor ion channel complex provides important insights into the clinical and toxic effects of this cation.

Animals↗

PubMed1990

Molecular effects of dimethylanatoxin on the peripheral nicotinic acetylcholine receptor.

N,N-dimethylanatoxin (DMAnTX), the quaternary derivative of the potent nicotinic agonist (+)-anatoxin-a (AnTX), has been evaluated for potency and efficacy at nicotinic acetylcholine receptors of frog motor endplates and Torpedo electric organs. DMAnTX was only weakly effective in eliciting contracture of the frog rectus abdominis and was orders of magnitude less potent than AnTX. Biochemical assay showed that DMAnTX was a weak inhibitor of [125I]alpha-bungarotoxin binding to the receptors in frog muscle and Torpedo electroplaque membranes: the IC50 values were 60 and 14 microM, respectively. A low frequency of single channel currents recorded from isolated interosseal fibers at concentrations from 20 to 100 microM of DMAnTX and the stimulation of [3H]perhydrohistrionicotoxin [( 3H]H12-HTX) binding (half-maximal at 0.3 microM) confirmed the weak activation of the receptor. DMAnTX also exhibited antagonist effects. In muscle twitch assays, 100 microM of DMAnTX effectively decreased the tension induced by nerve stimulation, although DMAnTX did not affect muscle membrane action potentials. The binding of [3H] perhydrohistrionicotoxin was also inhibited at high micromolar concentrations of DMAnTX. Combination of DMAnTX with acetylcholine in single channel current experiments demonstrated that DMAnTX possesses ion channel blocking properties, which become apparent at low micromolar concentrations, and DMAnTX enhances the desensitization induced by acetylcholine above 10 microM AnTX. The difference in agonist potency between AnTX and DMAnTX may be attributed to a change in conformation of the molecular skeleton induced by the N-methyl groups.

Acetylcholine↗

PubMedDate not supplied

Motor dysfunction in a mouse model for Down syndrome.

Motor deficits are among the most frequently occurring features of Down syndrome (DS). Individuals with DS exhibit disturbances in the dynamics of movement production and postural control that are thought to have a significant impact in delaying their acquisition of motor skills. The origin of these deficits has been hypothesized to be cerebellar. The Ts65Dn mouse is the most robust and genetically sound animal model for DS currently available. Ts65Dn mice show many DS-like features, including significant learning deficits in different behavioral tasks and neurodegeneration of cholinergic neurons. In the present study, we investigate the motor function of these animals. We have analyzed hind paw print patterns during walking, running speeds, rotarod performance, grip force production, swim paths, and swimming speeds. Our results indicate that Ts65Dn mice present mild to severe dysfunction according to all of the above assessments. The most evident impairments presented by these mice were related to equilibrium and motor coordination, which agrees with reported clinical observations made on individuals with DS. Because none of these findings were readily apparent by simple inspection of these animals, these findings reiterate the need for a careful evaluation of any mutant mouse strain for which there is reason to suspect motor deficits. The identification of motor dysfunction in Ts65Dn mice may have important consequences for the interpretation of some previous assessments of learning and memory of these animals that assumed intact motor function, and further strengthens the use of this aneuploid mouse strain as a model for DS.

Animals↗