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Biomedical subjects

M A Silva

Publications and source records attributed to M A Silva.

At least 37 records · Page 2Linked to original sources
PubMed1999

Expression and pharmacological characterization of alpha1-adrenoceptors in rat seminal vesicle.

In the present study, we investigated the alpha1-adrenoceptor subtypes mediating adrenaline-induced contractions of the rat seminal vesicle by using functional studies. The reverse transcription combined with polymerase chain reaction (RT-PCR) was also used to identify of alpha1-adrenoceptor mRNA subtypes. The rank order of potency of alpha1-adrenoceptor antagonists in blocking the contractile effects of adrenaline was: prazosin = WB 4101 >>> BMY 7378 > chloroethylclonidine, indicating the presence of alpha1A-adrenoceptors in the rat seminal vesicle. In the presence of nifedipine, there was a 76% reduction in the adrenaline-induced contractions. The nifedipine-insensitive component (24%) of the contractile response to adrenaline was unaffected by chloroethylclonidine. A small pool of spare alpha1-adrenoceptors for adrenaline (0.10%) was also detected. All three alpha1-adrenoceptor subtypes were amplified when RT-PCR was performed on total RNA isolated from rat seminal vesicle. In conclusion, these data indicate the presence of three alpha1-adrenoceptor mRNA subtypes, but only alpha1A-adrenoceptors are involved in the rat seminal vesicle contraction.

Adrenergic alpha-Agonists↗
PubMed1999

Preregistration study on the safety and contraceptive efficacy of a progesterone-releasing vaginal ring in Chilean nursing women.

The contraceptive efficacy and safety of a progesterone-releasing vaginal ring (PVR) manufactured in Chile were compared to that of the Copper T 380A IUD (T-Cu) in nursing women enrolled at three Chilean clinics. A total of 285 volunteers chose to use the PVR and 262 the T-Cu. Plasma progesterone levels attained with the ring decreased from 25 to 14 nmol/L from month 1 to month 3 of use. Ring replacement was scheduled every 3 months. Volunteers continued in the study until weaning or completing the continuous use of four PVRs. No pregnancies occurred in 2320 and 2183 woman-months of exposure with the PVR and the T-Cu, respectively. Lower continuation rates in the first 6 months because of problems with use and a longer lactational amenorrhea were observed in the PVR than in the T-Cu group. Breast-feeding performance and infant growth were similar in both groups. These results confirm the high efficacy and safety of the PVR for nursing women and have led to the registration of the PVR by Chilean health authorities.

Adult↗
PubMed1999

Right ventricular bifocal stimulation in the treatment of dilated cardiomyopathy with heart failure.

OBJECTIVE: To describe a new more efficient method of endocardial cardiac stimulation, which produces a narrower QRS without using the coronary sinus or cardiac veins. METHODS: We studied 5 patients with severe dilated cardiomyopathy, chronic atrial fibrillation and AV block, who underwent definitive endocardial pacemaker implantation, with 2 leads, in the RV, one in the apex and the other in the interventricular septum (sub pulmonary), connected, respectively, to ventricular and atrial bicameral pacemaker outputs. Using Doppler echocardiography, we compared, in the same patient, conventional (VVI), high septal ("AAI") and bifocal ("DDT" with AV interval approximately 0) stimulation. RESULTS: The RV bifocal stimulation had the best results with an increase in ejection fraction and cardiac output and reduction in QRS duration, mitral regurgitation and in the left atrium area (p </= 0.01). The conventional method of stimulation showed the worst result. CONCLUSION: These results suggest that, when left ventricular stimulation is not possible, right ventricular bifocal stimulation should be used in patients with severe cardiomyopathy where a pacemaker is indicated.

Adult↗
PubMed1998

Radiographic image of the hard palate and nasal fossa floor in panoramic radiography.

OBJECTIVE: The aim of this investigation was to report on the radiographic interpretation of the hard palate and nasal fossa floor in panoramic radiographs by studying different skulls, x-ray machines, and head positions in relationship to the Frankfort plane before and after ostectomy. STUDY DESIGN: Twenty dry human skulls were radiographed with three different panoramic x-ray machines in three different positions. Three of the skulls were submitted to different ostectomies. RESULTS: Multiple images of the hard palate and nasal fossa floor were present in 96.12% of the radiographs. Single images (3.88%) occurred only in the "chin up" position. CONCLUSIONS: The lower image represents the nasal fossa floor, especially its lateral and anterior limits. The upper images are double real images mainly formed by the junction of the nasal septum with the nasal fossa floor and possibly by posterior parts of the hard palate and nasal fossa floor. All images overlap in the "chin up" position becoming a single image. The most common shape of the anatomic landmark was wide angle "W" (58.33%). Other shapes present in positions "chin up" and "chin down" indicate patient positioning errors. The x-ray machines did not influence the results.

Cephalometry↗
PubMed1998

[Relationship between conduction persistence through the slow pathway after atrioventricular nodal reentry tachycardia radiofrequency ablation and its recurrence].

PURPOSE: The aim of this study is to verify whether the persistence of conduction over the slow pathway is related to an increased trend for recurrence. METHODS: Recurrence rate was retrospectively analyzed in 126 patients who underwent slow pathway radiofrequency (RF) catheter ablation during a follow-up of 20 +/- 12 months. The ablative procedure was interrupted when AVNRT was no longer induced by atrial stimulation after intravenous infusion of isoproterenol. Ninety-eight patients had no evidence of slow pathway whereas 28 patients persisted with AV node jump and atrial echo beat. RESULTS: There were 15 recurrences: 9% of those who had no evidence of slow pathway (9 of 98 patients) and 21% of those with AV node jump and/or atrial echo beat but this difference was not statistically significant. CONCLUSION: As long as AVNRT cannot be induced by atrial pacing and isoproterenol infusion after slow pathway RF catheter ablation, the presence of AV node jump and/or atrial echo beat does not increase the risk of recurrence of AVNRT.

Adolescent↗
PubMed1998

[Overall experience with percutaneous occlusion of patent ductus arteriosus].

PURPOSE: To evaluate the overall experience of our institution with percutaneous occlusion of the patent ductus arteriosus. METHODS: Since December/92, 150 patients underwent 178 procedures (85-Rashkind technique; 87-Gianturco coils; 6-Duct Occlud). Median age was 6.5 years (1 to 57). Mean minimum ductal diameter was 3.05 +/- 1.24 mm (1 to 8). Clinical and echocardiographic evaluations were performed periodically. RESULTS: Adequate implantation was achieved in 143 (95.3%) patients. Prevalence of immediate residual shunting was 52.1%, falling to 15.9% during follow-up. This figure decreased to 5.2% after new additional procedures. Umbrella and coil embolization occurred in 1 and 12 procedures, respectively. Hemolysis and mild stenosis of left pulmonary artery were observed in one patient each. There was no mortality. CONCLUSION: This therapeutic modality is safe and efficacious with good follow-up results.

Child, Preschool↗
PubMed1998

Morphological effect of the type, concentration and etching time of acid solutions on enamel and dentin surfaces.

Thirty-six noncarious human molars were extracted and stored in saline. The buccal surfaces were ground wet on 400-grit silicon carbide paper to create a flat surface. The enamel and dentin surfaces were treated with 35% phosphoric acid gel, 10% phosphoric acid gel and 10% maleic acid gel for 15 and 60 seconds. Scanning electron microscope analysis showed that all the acid etchants modified the micromorphological appearance of enamel and dentin surfaces independent of the type of acid, the etching time and the concentration. On the enamel surface, the 35% and 10% phosphoric acid gels and the 10% maleic acid gel applied for 15 or 60 seconds preferentially removed the prism core material. In the specimens treated for 15 seconds with 10% maleic acid the prism core material was partially removed. On the dentin surface, the phosphoric acid gels (35% and 10%) and the 10% maleic acid gel applied for 15 and 60 seconds removed the smear layer and opened the dentinal tubule orifices; however, the dentinal surface etched for 15 or 60 seconds with 10% maleic acid gel showed residues of the smear layer.

Acid Etching, Dental↗
PubMed1997

Increased neostriatal dopamine activity after intraperitoneal or intranasal administration of L-DOPA: on the role of benserazide pretreatment.

L-DOPA provides the most potent medication to treat Parkinson's disease, and such systemic treatment is usually combined with a peripheral amino acid decarboxylase inhibitor to amplify its central effectiveness. Since L-DOPA can lose its efficacy or can lead to adverse effects with prolonged application, current pharmacokinetic and dynamic research is aimed at improving the drug's applicability. In a previous study, performed with in vivo microdialysis in the anesthetized rat, we have shown that intranasal L-DOPA administration (without prior decarboxylase inhibition) can increase extracellular dopamine levels in the neostriatum. Using similar experimental conditions in the present experiment, we tested the neurochemical effects of L-DOPA treatment in combination with the peripheral amino acid decarboxylase inhibitor benserazide. In accordance with other data, it was found that the combination of i.p. benserazide and i.p. L-DOPA led to pronounced increases of extracellular levels of dopamine, dihydroxyplenylacetic acid and homovanillic acid in the neostriatum, whereas i.p. L-DOPA alone only moderately increased dopamine, but strongly increased the metabolite levels. Furthermore, increased dopamine levels, and weaker increases of dihydroxyplenylacetic acid and homovanillic acid were observed after i.p. benserazide followed by intranasal L-DOPA. Finally, we found that i.p. benserazide alone can lead to pronounced increases in neostriatal dopamine and moderate increases of dihydroxyplenylacetic acid levels, whereas it did not affect homovanillic acid. Thus, not only the combination of L-DOPA (i.p. or intranasal) with the presumed peripheral L-DOPA decarboxylase inhibitor benserazide, but also each component alone can affect dopamine activity in the brain. Especially the findings with benserazide treatment might be of relevance for understanding the mechanisms of current L-DOPA therapy, since they indicate that part of the treatment's actions may possibly be determined by central dopaminergic effects of the accompanying amino acid decarboxylase inhibitor.

Administration, Intranasal↗
PubMed1997

[Profile of future nurses' aides in Campinas, SP, in 1995: reasons, expectations and problems related to their education].

The present study aims to characterize the profile of people studying in auxiliary nurse courses at the city of Campinas. The predominantly characteristics were: ages between 18 and 30 years old, majority female, single and catholic. The major part of the studied population does not work in nursing area, being the mainly motivation to begin the course the possibility of helping other people. Their difficulties were returning to school, conciliating the study schedule with other activities and paying the course.

Adolescent↗
PubMed1997

Manifestations of insulin-dependent diabetes mellitus in the periodontium of young Brazilian patients. A 10-year follow-up study.

Eight female and 3 male patients from a group of 30 patients studied 10 years earlier and who had received no periodontal treatment during this period, in order to evaluate the progression of untreated periodontal disease in patients with insulin-dependent diabetes mellitus, were evaluated in terms of plaque accumulation, gingival inflammation, probing depth, and alveolar bone loss. The total number of dental surfaces that presented clinically detectable plaque deposits increased significantly (29% to 43%; P < 0.01; chi 2 = 46.36). Site-specific comparisons for plaque index between studies showed a significant variation (P < 0.01) in the upper arch only for palatal surfaces and in the lower arch for the buccal and lingual surfaces. The total dental surfaces with inflamed surrounding gingiva increased from 11% to 33% in this study (P < 0.01; chi 2 = 175.78). Site-specific comparison for gingival index showed a significant variation for all upper surfaces, while such difference for the lower arch was significant only for the buccal and lingual surfaces. The arithmetic means for the probing depth for the upper buccal, upper palatal, lower buccal, and lower lingual surfaces increased significantly (P < 0.01). The arithmetic means of alveolar bone loss also increased significantly for the upper posterior and lower regions (P < 0.01) and for the upper anterior and lower anterior regions (P < 0.05). The correlation between age and probing depth was significant only for the upper palatal region (P < 0.01). The correlation between age and bone loss was significant only for the upper posterior region (P < 0.05). The results of this follow-up study suggest that despite little variation in plaque accumulation, gingival inflammation, probing depth, and bone loss increased after a 10-year interval in patients who had received no periodontal treatment during this period.

Adolescent↗
PubMed1996

Effects of anxiety and memory of systemic and intra-amygdala injection of 5-HT3 receptor antagonist BRL 46470A.

This study deals with the effects of the 5-HT3 receptor antagonist, BRL 46470A, on memory and anxiety, using the elevated T-maze. This method is useful for investigating the effects of anxiolytic drugs on memory, and the relationships between neural subsystems involved in emotionally related behaviors and in processes underlying learning. After the drug was either injected peripherally or microinjected into the amygdala, the animals were tested on the elevated T-maze (30 or 15 min later, respectively). Two kinds of aversively motivated behaviors, inhibitory avoidance and one-way escape, were recorded. These behaviors may reflect different types of fear/anxiety, namely, anticipatory anxiety and innate fear. Three days later, memory for these tasks was assessed by reexposing the subjects to the maze. The compound had an anxiolytic effect on the inhibitory avoidance response when given systemically, but an anxiogenic effect when injected into the amygdala. It had an anxiolytic action on the escape response when given either systemically or into the amygdala. The compound had no adverse effects on memory for either task. These results suggest that this new 5-HT3 antagonist may be useful in the treatment of certain types of anxiety disorders, especially those related to unconditioned fear, e.g. phobic or panic disorders, with the likelihood of having no side effects on memory processes. The contrasting results obtained with different measures of anxiety may also account for the inconsistencies found in the experimental literature dealing with compounds of this nature.

Amygdala↗
PubMed1995

Prooxidant and antioxidant hepatic factors in rats chronically fed an ethanol regimen and treated with an acute dose of lindane.

While acute lindane treatment and chronic ethanol feeding to rats have been associated with hepatic oxidative stress, the possible roles of these stresses in the pathogenesis of hepatic lesions reported in acute lindane intoxication and in those observed in some models of chronic alcoholism have not been established. Our previous studies in rats chronically fed ethanol regimens and then treated with a single intraperitoneal (i.p.) dose of lindane (20 mg/kg) showed that while lindane per se was invariably associated with hepatic oxidative stress, chronic ethanol feeding only produced this stress when the dietary level of vitamin E was relatively low. Chronic ethanol pretreatment did not significantly affect the lindane-associated oxidative stress, and neither chronic ethanol feeding nor acute lindane, single or in combination, produced any histologic and biochemical evidence of liver damage. In the present experiment, the acute dose of lindane was increased to 40 mg/kg, and we have studied a larger number of prooxidant and antioxidant hepatic factors. Male Wistar rats (115.5 +/- 5.4 g) were fed ad lib for 11 weeks a calorically well-balanced and nutritionally adequate basal diet, or the same basal diet plus a 32% ethanol/25% sucrose solution, also ad lib, and were then injected i.p. with a single dose of lindane or with equivalent amounts of corn oil. The results indicated that acute lindane treatment to naive rats increased practically all the prooxidant hepatic factors examined (cytochromes P450 and b5, NADPH cytochrome c reductase, NADPH oxidase), as well as the generation of microsomal superoxide radical and thiobarbituric acid reactive substances of liver homogenates, but did not modify any of the antioxidant hepatic factors studied. Conversely, the chronic administration of ethanol alone did not significantly affect the prooxidant hepatic factors but reduced some of the antioxidants (i.e., the activities of GSH-Px and the contents of alpha-tocopherol and ubiquinols 9 and 10). Although chronic ethanol pretreatment further increased the superoxide generation induced by lindane per se, it did not increase but generally reduced the effects of lindane per se on the other prooxidant factors studied. Furthermore, although acute lindane administration to ethanol-pretreated rats was associated with decreases in GSH and catalase (not affected by ethanol or lindane treatment alone), it did not substantially modify the reducing effects of ethanol feeding per se on GSH-Px, alpha-tocopherol, and ubiquinols. Once again, neither chronic ethanol feeding nor lindane treatment, single or in combination, was associated with any evidence of liver damage.

Animals↗
PubMed1995

Effects of misoprostol on circulating HDL-cholesterol, total cholesterol, triglycerides and their relationship with hepatic microsomal function.

The effects of misoprostol (cytotec, SC29333) on circulating lipoproteins and liver microsomal enzyme activity were studied. Misoprostol increased serum levels of high density lipoprotein-cholesterol and decreased total cholesterol and triglycerides. The high density lipoprotein-cholesterol/total cholesterol ratio increased by 54.8%. In parallel, misoprostol significantly altered enzyme hepatic activity. Liver microsomal cytochromes P450 and b5 were significantly increased in correlation with enhanced liver aminopyrine N-demethylase and antipyrine hydroxylase activities, suggesting a liver induction effect of misoprostol. Other observations such as increased liver weight and glycogen and increased plasma albumin and glucose in rats receiving misoprostol support this evidence.

Aminopyrine N-Demethylase↗
PubMed1995

Amnesia after diazepam infusion into basolateral but not central amygdala of Rattus norvegicus.

Recent findings indicate that the memory-impairing effects of benzodiazepines may preferentially involve the basolateral nucleus of the amygdala. To test this hypothesis we examined the effects on pretrial injection of diazepam into the central as compared to the lateral/basolateral amygdaloid nuclei on memory for a conditioned avoidance response. Rats were implanted bilaterally with cannulae directed to either the central or lateral/basolateral amygdaloid nuclei. Five to 7 days later they were trained on a multitrial inhibitory avoidance (step-down) task to criterion and tested 48 h later. Fifteen minutes before training they were given an injection of either vehicle or diazepam (0.7 or 1.4 nmol) into the central or lateral/basolateral nuclei. Administration of diazepam into the lateral/basolateral nuclei but not the central nucleus induced anterograde amnesia. These results add to the body of data linking the GABA-benzodiazepine system of the lateral/basolateral nuclei to the amnestic effects induced by peripheral as well as central administration of benzodiazepines.

Amnesia↗
PubMed1994

Brain and liver lipid peroxidation levels following acute and short-term lindane administration in the rat.

Oxidative stress-related parameters in rat brain and liver were evaluated following acute (60 mg/kg i.p., 2 and 24 h after dosing) or short-term (1000 ppm in the diet for 90 days) lindane administration. Both treatments elicited a significant accumulation of lindane in brain and liver, with convulsions observed in short-term and 24-h lindane-treated rats. In these conditions, lindane exposure did not alter brain lipid peroxidation, assessed as thiobarbituric acid reactants formation and spontaneous chemiluminescence, parameters that were enhanced in the liver. The activities of antioxidant enzymes in the brain (superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase and glucose 6-phosphate dehydrogenase) were not modified by acute lindane treatment, while brain glutathione content was significantly reduced by 13%. It is concluded that lindane does not alter the oxidative stress status of the brain as occurs in liver, regardless of the time of exposure of rats to either acute or short-term administration of the insecticide.

Animals↗
PubMed1994

Influence of lindane and paraquat on oxidative stress-related parameters of erythrocytes in vitro.

1. The influence of lindane and paraquat on oxidative stress-related parameters of the red blood cell was studied in vitro. 2. Lindane addition did not modify either the t-butyl hydroperoxide-induced oxygen uptake of the erythrocytes and the induction time preceding it, or the activity of catalase, superoxide dismutase, glutathione peroxidase and glucose 6-phosphate dehydrogenase, in conditions of comparable levels of haemoglobin and methaemoglobin. 3. Red blood cells exposed to paraquat exhibited a concentration-dependent decrease in the t-butyl hydroperoxide-induced oxygen consumption and increments in either the induction period or in the activity of catalase and glucose 6-phosphate dehydrogenase, with no changes in superoxide dismutase activity and a small decrement in that of glutathione peroxidase. 4. These data indicate that lindane does not interfere with the oxidant status of the erythrocyte, while paraquat addition leads to an increment in the anti-oxidant capacity of the red blood cell.

Animals↗
PubMed1993

Taurine modulates chemical nociception in mice.

The effect of taurine on nociception was investigated in adult male Swiss mice using the formalin and acetic acid tests. Taurine (50-200 mg/kg) injected sc into the animals (N = 6 per group) 30 min before formalin injection into the right hind paw reduced formalin-induced early phase (0-5 min) licking activity by 30-42%, but had no effect on the late phase (20-25 min) response. Writhing responses induced by acetic acid injected ip were also significantly inhibited by 49% and 56% by doses of 100 and 200 mg/kg taurine, respectively. In both tests taurine demonstrated antinociception which was significantly blocked by naloxone (1 mg/kg, sc, administered simultaneously with taurine). The naloxone-sensitive antinociceptive action of taurine was probably mediated via modulation of endogenous pain-regulatory systems that involve opioid peptides, neuropeptides like substance P and amino acids such as glutamate and aspartate.

Acetates↗