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Biomedical subjects

J C da Costa

Publications and source records attributed to J C da Costa.

At least 19 recordsLinked to original sources
PubMed2004

Permeation of binary gas mixtures in ultramicroporous membranes.

High-quality nanometer thick ultramicroporous membranes were prepared from silica sol-gel processes and tested for the permeation of binary gas mixtures of He, H2, CO2, and CH4 across different temperature and partial pressure regimens. Pore size distribution by molecular probing showed that the majority of pore sizes had dimensions below 2.9 A. In 50:50 binary mixtures, the fluxes of gases increased as a function of temperature, indicating an activated transport mechanism. The ultramicroporous membranes showed high selectivities at 150 degrees C for He/CO2 (30), He/CH4 (93), H2/CO2 (10), and H2/CH4 (9) with lower selectivities for CO2/CH4 (5). High activation energies (Ea) were observed for the permeance of 50:50 binary mixtures containing He and H2 of 22.1-27.5 and 17.6-23.1 kJ.mol-1, respectively. The Ea for the permeance of the total mixture approached the Ea for the permeance of the molecule with the smaller kinetic diameter (He or H2).

Carbon Dioxide↗
PubMed2004

A two-step sol-gel method for synthesis of nanoporous TiO2.

This article reports a study of the effects of synthesis parameters on the preparation and formation of mesoporous titania nanopowders by employing a two-step sol-gel method. These materials displayed crystalline domains characteristic of anatase. The first step of the process involved the hydrolysis of titanium isopropoxide in a basic aqueous solution mediated by neutral surfactant. The solid product obtained from step 1 was then treated in an acidified ethanol solution containing the same titanium precursor to thicken the pore walls. Low pH and higher loading of the Ti precursor in step 2 produced better mesoporosity and crystallinity of titanium dioxide polymorphs. The resultant powder exhibited a high surface area (73.8 m2/g) and large pore volume (0.17 cm3/g) with uniform mesopores. These materials are envisaged to be used as precursors for mesoporous titania films as a wide band gap semiconductor in dye-sensitized nanocrystalline TiO2 solar cells.

Crystallization↗
PubMed2001

Psychoneuroendocrine characteristics of common obesity clinical subtypes.

OBJECTIVE: To relate psychological profiles, cerebral asymmetry and the hypothalamus-pituitary-adrenal axis (HPA) reactivity to clinical characteristics of common obesity. METHODS: Sixty consecutive adult female overweight and obese patients attending the outpatient endocrine department were included in this study. Clinical evaluation specifically selected a priori the following indexes: obesity age of onset, parenthood obesity, carbohydrate craving, binge eating with purging, obesity degree (defined by the body mass index (BMI)--weight (kg)/height (m(2))), body fat distribution (defined by the abdominal--thigh ratio (A/T)) and initial weight loss after medical treatment. Psychological evaluation was performed with the Minnesota Multiphasic Personality Inventory (MMPI). In the last 30 patients, the Edinburgh Inventory of Manual Preference (EIMP) and the corticotrophin-releasing hormone (CRH) test were also performed. RESULTS: Clinical characteristics defined a priori were independent variables as evaluated by contingency table analysis. Factorial analysis of variance (ANOVA) revealed a significantly different MMPI profile, according to parental obesity, with post-hoc significantly higher scores on the hypochondriasis (Hs), paranoia (Pa), psychasthenia (Pt) and schizophrenia (Sc) scales in patients with obese parents. Obese patients presented significantly higher dichotomized manual preference indexes in relation to overweight patients. Parental obesity, binge eating behaviour with purging, body fat distribution and the dichotomized manual preference index were independent significant factors for the ACTH response in the CRH test, together explaining 41% of the response variability. Age of onset of obesity and the dichotomized manual preference index were independent and significant factors for the cortisol response, together explaining 37% of its variability. A non-normal distribution was found for the ACTH response: high- and low-responders presented significantly different MMPI profiles, with high-responders presenting higher scores on all clinical scales except masculinity/femininity (Mf). CONCLUSION: Overweight/obese subjects with parental obesity present a distinctive personality profile and a higher ACTH response in the CRH test. Cerebral asymmetry may be a relevant factor for obesity development and is associated with the HPA reactivity. HPA reactivity is a sensitive index integrating clinical, psychological and neural asymmetric factors. International Journal of Obesity (2001) 25, 24-32

Adipose Tissue↗
PubMed2001

Surgical resection for intractable epilepsy in "double cortex" syndrome yields inadequate results.

PURPOSE: To analyze the results of surgical treatment of intractable epilepsy in patients with subcortical band heterotopia, or double cortex syndrome, a diffuse neuronal migration disorder. METHODS: We studied eight patients (five women) with double cortex syndrome and intractable epilepsy. All had a comprehensive presurgical evaluation including prolonged video-EEG recordings and magnetic resonance imaging (MRI). RESULTS: All patients had partial seizures, with secondary generalization in six of them. Neurologic examination was normal in all. Three were of normal intelligence, and five were mildly retarded. Six patients underwent invasive EEG recordings, three of them with subdural grids and three with stereotactic implanted depth electrodes (SEEG). Although EEG recordings showed multilobar epileptic abnormalities in most patients, regional or focal seizure onset was recorded in all. MRI showed bilateral subcortical band heterotopia, asymmetric in thickness in three. An additional area of cortical thickening in the left frontal lobe was found in one patient. Surgical procedures included multiple subpial transections in two patients, frontal lesionectomy in one, temporal lobectomy with amygdalohippocampectomy in five, and an additional anterior callosotomy in one. Five patients had no significant improvement, two had some improvement, and one was greatly improved. CONCLUSION: Our results do not support focal surgical removal of epileptogenic tissue in patients with double cortex syndrome, even in the presence of a relatively localized epileptogenic area.

Adolescent↗
PubMed2001

Hydrophobicity of templated silica xerogels for molecular sieving applications.

Silica xerogels were prepared by a sol-gel process catalyzed by acid with tetraethylorthosilicate, and using an organic covalent ligand template (methyltriethoxysilane) or a noncovalent template C6 surfactant (triethylhexylammonium bromide). The influence of hydrotreatment on the structure of templated xerogels is examined in terms of surface area, micropore volume, average pore size, and pore size distribution, and compared against a blank xerogel (nontemplated). The role of surface functional groups was evaluated using 29Si nuclear magnetic resonance. The structural integrity of the xerogel was maintained to a large extent in samples that had a high contribution of Q4 species (siloxane groups). Xerogel matrix densification occurred when there was a large concentration of Q3 and Q2 species (silanol groups), which also were responsible for increased hydrophilicity. The templated xerogels resulted in up to a 25% concentration of methyl functional groups (T3 and T2 species), leading to hydrophobic xerogels. The best results in terms of structural integrity and hydrophobicity were obtained with templated xerogels prepared with the C6 surfactant. The results in this study suggest that surfactant-enhanced condensation reactions lead to structures with a high contribution of Q4 groups, which are not susceptible to water attack, but are strong enough to oppose matrix densification during rehydration.

Adsorption↗
PubMed2000

Duration of rhythmic EEG patterns in neonates: new evidence for clinical and prognostic significance of brief rhythmic discharges.

OBJECTIVE: This study aimed at identifying the characteristics - especially the duration - of rhythmic discharges in neonatal EEG, and their association with clinical neonatal problems. Specifically, we aimed at testing the diagnostic and prognostic validity of using 10 s as minimal duration for defining electroencephalographic seizures. DESIGN AND METHODS: The polysomnographies of 340 neonates were reviewed, and episodes of rhythmic discharges were identified, analyzed, and quantified. The study sample was divided into 3 groups: one in which the maximal duration of rhythmic discharges was shorter than 10 s (brief rhythmic discharges, BRD), a second one in which there were rhythmic discharges longer than 10 s (long rhythmic discharges, LRD), and finally a group in which no rhythmic discharge was found (No-RD). These 3 groups of subjects were compared for the baseline and outcome clinical data. RESULTS: From the 340 neonates studied, 210 did not present any form of rhythmic discharge, 67 (19. 7%) had only BRD episodes, and 63 (18.5%) had at least one LRD episode. Prevalence of rhythmic discharges was low among healthy full term newborns, and was significantly higher among preterm and high-risk newborns. Electrophysiological characteristics of rhythmic discharges did not differ between healthy neonates and high-risk ones. Accompanying clinical manifestations were present in 26.3% of the LRD group, but also in 15.9% of the BRD group. The presence of BRD was significantly associated with leukomalacia and with hypoglycemia in the cross-sectional analysis of baseline data, and with an increased risk for abnormal neurodevelopmental outcome after a mean follow-up period of 47 months (adjusted relative risk=4.90, P<0.01). CONCLUSIONS: The present data demonstrate an association between BRD and clinical history of hypoxic-ischemic encephalopathy, especially when complicated by leukomalacia, and also with a prognosis of increased risk for abnormal neurodevelopmental outcome. The clinical and prognostic significance of isolated BRD justifies the need to include these brief episodes in future studies of neonatal seizures.

Brain↗
PubMed2000

Polysomnography in neonatal seizures.

Seizures are one of the most frequent problems in the neonatal period, and are frequently associated with high mortality and morbidity rates. On the other hand, neonatal seizures may represent a first or even the only sign of central nervous system dysfunction. However, establishing the diagnosis of neonatal seizures poses several problems, and clinical observation is not sufficient in many cases. Neonatal polysomnography is a valuable tool both in the diagnostic and in the prognostic assessment of neonatal seizures. The present text reviews some technical aspects related to neonatal polysomnographies, and its usefulness in the area of suspected neonatal seizures. Moreover, some questions are raised regarding rhythmic discharges and their significance as a possible ictal and interictal epileptic pattern in the neonate.

Brain↗
PubMed2000

Differences in the dynamics of frontal sharp transients in normal and hypoglycemic newborns.

OBJECTIVE: This study focuses on the characteristics of frontal sharp transients (FST), a normal variant of neonatal EEG, in newborns with hypoglycemia. METHODS: The EEG from 20 newborns with symptomatic hypoglycemia were compared with a control group of normal newborns matched by conceptional age. The dynamics of these transients were evaluated concerning sleep stages. The density, type and bilateral synchrony of FST were also calculated. The results were compared in the two groups by Student's t test. RESULTS: When compared with controls, hypoglycemic newborns have increased density of frontal sharp transients in all sleep stages but less bilateral synchrony (P<0.05). FST density was even higher in small for gestational age newborns. CONCLUSIONS: The data suggests that normal patterns of neonatal EEG as FST can be influenced by systemic disturbances.

Electroencephalography↗
PubMed1999

Localization of the epileptogenic zone by ictal and interictal SPECT with 99mTc-ethyl cysteinate dimer in patients with medically refractory epilepsy.

PURPOSE: To evaluate the accuracy, feasibility and clinical value of both ictal and interictal 99mTc-ethyl cysteinate dimer (ECD) single photon emission computed tomography (SPECT) in patients with medically refractory epilepsy. METHODS: The study included 75 consecutive patients, 48 with temporal lobe epilepsy (TLE group), and 27 with extratemporal epilepsy (ExT group). The accuracy of SPECT was analyzed considering the final diagnosis reached by convergence of clinical, electrophysiologic, structural, pathologic and outcome data. RESULTS: Ictal SPECT correctly identified the epileptogenic zone in 21 (91.3%) of 23 patients, whereas interictal SPECTs could correctly identify the epileptogenic zone in only 41 (62.1%) of 66 patients (chi2 = 5.56, df = 1, p < 0.05). Results were similar when the two study groups were analyzed separately. Moreover, ictal studies had significantly higher specificity (91.3 vs. 60.6%) and positive predictive value (91.3 vs. 66.2%) than interictal studies for the whole series of patients. Considering all tools used in the preoperative workup of these patients, ictal SPECT significantly contributed to the final topographic diagnosis in seven of 14 patients from TLE group and in six of nine patients from the ExT group. In these patients, ictal SPECT either obviated the need for invasive EEG or helped to define where to concentrate the efforts of invasive investigation. CONCLUSIONS: These data demonstrate that ictal SPECT can be easily achieved by using 99mTc-ECD and can accurately localize the epileptogenic zone in both temporal and extratemporal epilepsies. Ictal ECD SPECT proved to be significantly more sensitive and specific than interictal ECD SPECT, and clinically useful in the definition of the epileptogenic zone.

Algorithms↗
PubMed1998

Dyslipidaemia in female overweight and obese patients. Relation to anthropometric and endocrine factors.

OBJECTIVE: To characterize serum lipid abnormalities in overweight and obese female patients and to quantify the relative importance of associated factors. METHODS: Cross sectional study at the first visit to the out-patient department. 237 consecutive overweight and obese female patients (age 31 +/- 14 y, body mass index (BMI) 34.2 +/- 6.0 kg/m2) were studied. Evaluation included a questionnaire-based assessment of dietary and physical activity habits, determination of anthropometric indexes (BMI, abdominal/thigh ratio (A/T) and conicity index (CI)) and endocrine evaluation. Statistical analysis by factorial ANOVA and multiple regression. RESULTS: Dyslipidaemia was present in 46% of the patients, with hypercholesterolaemia (35%) being more frequent than hypertriglyceridaemia (10%). Age but not dietary habits or physical activity patterns was significantly related to serum lipid concentrations, independently accounting for 6-10% of their variability. Pharmacological drug use resulted in increased serum triglyceride concentrations, explaining less than 5% of their variability. Serum cholesterol concentrations were not significantly related either to anthropometric or to endocrine indexes. For serum triglyceride concentrations, anthropometric indexes accounted for 6% of their variability and endocrine indexes-postprandial insulin, serum cortisol, testosterone and androstenedione together accounted for 32%. CONCLUSION: In mild to moderate female obesity of the peripheral type, dyslipidaemia is common. However the most common abnormality, hypercholesterolaemia is not significantly related to anthropometric or endocrine indexes, while these together account for more than one third of variability in serum triglyceride concentrations.

Adolescent↗
PubMed1997

Vigabatrin in refractory childhood epilepsy. The Brazilian Multicenter Study.

Children, 47, with various types of severe drug-resistant epilepsy were entered into a prospective, add-on, open trial with vigabatrin. Patients with West syndrome and idiopathic generalized epilepsies were excluded. Seven children had the drug withdrawn, five because of increase in seizure frequency and two because of adverse effects. Drug efficacy, measured according to seizure type, showed a 100% decrease in seizure frequency in 18.6% of partial seizures and 17.3% of the generalized seizures. There was a higher than 50% decrease in 39.5% of partial and 60.8% of generalized seizures, and less than 50% decrease or increase in seizure frequency in 41.8% and 21.8% of partial and generalized seizures, respectively. Vigabatrin mean dosage during phase 3 was 63.6 mg/kg per day (S.D. = 30.5), ranging from 19.3 to 110.5 mg/kg per day. Parametric statistical analysis (Student's t-test) of seizure frequency between phases 1 and 3 showed a significant decrease in seizure frequency for partial (P = 0.022), and generalized seizures (P < 0.0001). Drug-related adverse effects were observed in 18/47 cases (38.3%), consisting mainly of irritability, hyperactivity, dizziness, somnolence and gastrointestinal symptoms.

Adolescent↗
PubMed1995

Intrinsic epileptogenicity of human dysplastic cortex as suggested by corticography and surgical results.

Cortical dysplastic lesions (CDyLs) are often associated with severe partial epilepsies. We describe the electrographic counterpart of this high degree of epileptogenicity, manifested by continuous or frequent rhythmic epileptogenic discharges recorded directly from CDyLs during intraoperative electrocorticography (ECoG). These ictal or continuous epileptogenic discharges (I/CEDs) assumed one of the following three patterns: (1) repetitive electrographic seizures, (2) repetitive bursting discharges, or (3) continuous or quasicontinuous rhythmic spiking. One or more of these patterns were present in 23 of 34 patients (67%) with intractable partial epilepsy associated with CDyLs, and in only 1 of 40 patients (2.5%) with intractable partial epilepsy associated with other types of structural lesions. I/CEDs were usually spatially restricted, thus contrasting with the more widespread interictal ECoG epileptic activity, and tended to colocalize with the magnetic resonance imaging-defined lesion. Completeness of excision of cortical tissue displaying I/CEDs correlated positively with surgical outcome in patients with medically intractable seizures; i.e., three-fourths of the patients in whom it was entirely excised had favorable surgical outcome; in contrast, uniformly poor outcome was observed in those patients in whom areas containing I/CEDs remained in situ. We conclude that CDyLs are highly and intrinsically epileptogenic, and that intraoperative ECoG identification of this intrinsically epileptogenic dysplastic cortical tissue is crucial to decide the extent of excision for best seizure control.

Adolescent↗
PubMed1995

Early onset bilateral calcifications and epilepsy.

Bilateral occipital calcifications associated with epilepsy and sometimes with celiac disease have been described previously. A boy with bilateral frontal and occipital diffuse calcifications accompanied by failure to thrive, nephrogenic diabetes insipidus, developmental delay and seizures, but without celiac disease is presented. Follow-up at 3 years of age disclosed neurodevelopmental delay, height and weight less than expected for age, and seizures controlled with carbamazepine. The uncommon association of these features and the early onset of symptoms is discussed. Although bilateral occipital calcifications share some clinical features with bilateral fronto-occipital calcifications, it is arguable whether the two are on a spectrum of a single disease or represent separate entities.

Brain Diseases↗
PubMed1995

Trihexyphenidyl and isoprinosine in the treatment of subacute sclerosing panencephalitis.

Six cases of subacute sclerosing panencephalitis (1 stage I, 3 stage II, 2 stage III) were diagnosed at our institution in the last 10 years. Five patients were treated with isoprinosine and the antiepileptic drug valproic acid. Three patients presented with myoclonic seizures refractory to valproic acid and the usual antiepileptic therapy. They received trihexyphenidyl with good results. We suggest the use of trihexyphenidyl in combination with isoprinosine in patients with subacute sclerosing panencephalitis with myoclonic seizures refractory to valproic acid.

Adjuvants, Immunologic↗
PubMed1995

[Value of EEG in the characterization and prognosis of neurological diseases in premature infants].

The importance of the EEG for the investigation of neurological diseases in the neonatal period has been largely discussed, since it is often the only way to approach cerebral function in newborns with severe pathologies or under drug effect. The present study was carried out with 85 newborns (NB) who presented perinatal dysfunctions and were submitted to neurological and electroencephalogram (EEG) or polysomnography (PS) evaluation. EEG/PS alterations, pathologies and prognosis were reported. The EEG were classified according to basal activity alterations, presence of paroxysmal activity and sleep stages organization and maturity. The most frequent pathology was perinatal asphyxia (40%) followed by intraventricular hemorrhage (HIV, 16%). The most frequent complaint for exam indication was apnea (71%) followed by convulsion (19%). Fifty-five percent of the exams exclusively required because apnea complaint were considered normal and out of all exams required because seizures only 31% were normal. The EEG alteration most frequently related to perinatal asphyxia, HIV and intrauterine growth delay was immaturity and in the NB with seizures immature EEG and abnormal paroxysms. Many different alterations were registered in the NB with nervous system infection. The EEG findings more correlated with unfavorable prognosis were isoelectricity and abnormal paroxysmal activity including positive sharp waves (100%).

Central Nervous System Diseases↗
PubMed1994

Quantification of immunoglobulin A in chorioamniotic membrane of patients with premature rupture of membranes.

OBJECTIVE: The proposal was to study the presence of immunoglobulin A (IgA) in the chorioamniotic membrane of healthy postpartum women with premature rupture of the chorioamniotic membrane (PROM). METHOD: A single radial immunodiffusion technique was used to quantify the IgA in the chorioamniotic membrane tissues. RESULTS: The level of IgA was approximately 10 times higher in patients whose membranes had been ruptured for > 10 h (24.58 mg/dl). These results were compared with those of a previously published study where the mean of amount of IgA was 2.52 mg/dl in membranes of patients with rupture < 10 h. Our results show that IgA began to rise after 10-15 h following rupture. CONCLUSION: Although more studies need to be performed our data indicate that the increasing IgA in our patients after 10 h of latency probably represents the beginning of an ascending colonization of bacteria which could be the source of future infection.

Adult↗
PubMed1994

Operative strategies for patients with cortical dysplastic lesions and intractable epilepsy.

Cortical dysplastic lesions (CDLs) are usually identified by magnetic resonance imaging (MRI). Clinical, electrographic and histologic findings suggest that focal CDLs (FCDLs) are highly epileptogenic, often involve the rolandic cortex, and can present variable degrees of histopathologic abnormalities. An ictal or "ictal-like" bursting pattern of electrographic activity was recorded over dysplastic cortex in 65% of our patients. Resective surgery can eliminate or significantly reduce seizure frequency in many medically intractable patients, depending on lesion location, degree, and extent of histopathologic abnormalities. Best results are achieved when complete or major excision of both the MRI-visible lesion and the cortical areas displaying ictal electrographic activity can be performed. This is more likely when the degree of histopathologic abnormality is mild to moderate or when the lesion is in a temporal lobe. More severe histopathologic abnormalities and central insular or multilobar lesions usually lead to less favorable results: either major excision of the visualized lesion is impractical or the lesion is microscopically more extensive than shown by MRI. Multilobar resection or hemispherectomy for patients with infantile spasms associated with CDLs and for patients with hemimegalencephaly are often associated with dramatic improvement in seizure control. Callosotomy can be performed in selected patients with diffuse CDLs who have intractable drop attacks.

Adolescent↗