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Biomedical subjects

M A Silva

Publications and source records attributed to M A Silva.

At least 19 recordsLinked to original sources
PubMed2004

Treatment of hydatid disease of the liver. Evaluation of a UK experience.

BACKGROUND: Hydatid disease of the liver though endemic in many countries, is rare in the UK. We evaluated a 16-year experience of treating hydatidosis using a management protocol combining surgery with anti-scolicidals. PATIENTS AND METHODS: There were 30 patients. 14 (47%) males, median age 41 (range 25-72) years, of whom 21 (70%) were symptomatic. Diagnosis was by serological tests and imaging. All had disease confined to the liver and received peri-operative anti-scolicidal drug therapy. RESULTS: The initial 4 (13%) patients received praziquantel combined with albendazole for 2 weeks and the following 26 (87%) patients received two cycles of albendazole 400 mg twice daily for 28 days, with a 14-day break in between. However, 2 (7%) patients could not tolerate albendazole, one due to GI side effects and the other developed deranged liver functions. These 2 patients subsequently received praziquantel for 2 weeks. All patients underwent surgery. Subtotal cystectomy was carried out on 29 (96%) patients and 1 patient required a segmentectomy. Cystobiliary communications were identified in 15 (50%) of patients which were oversewn using fine absorbable sutures. Of these, 7 had the bile ducts decompressed using a T tube, with only 1 developing a post-operative bile leak. In comparison, 8 were not drained of which 6 leaked (p = 0.03). The median post-operative hospital stay was 8 days (range 5-24). Patients who developed post-operative bile leaks, however, needed prolonged abdominal drainage for a median of 21 days (range 18-24). Two (7%) patients developed histologically proven recurrent disease. The median follow-up was 56 months (range 3-87). CONCLUSION: Surgery combined with anti-scolicidal therapy proved effective. Cystobiliary communications are common and, when identified, should result in the biliary system being drained, to avoid post-operative bile leaks.

Adult↗
PubMed2002

The internal jugular vein valve may have a significant role in the prevention of venous reflux: evidence from live and cadaveric human subjects.

INTRODUCTION: The internal jugular vein valve (IJVV), which is situated just above the termination of the internal jugular vein, is the only valve between the heart and the brain. This means that it plays a role in the prevention of cephalad flow of venous blood. If the IJVV is damaged or becomes incompetent, increase in intrapleural pressure could result in raised intracranial pressure. Additionally, the jugular venous pulse (JVP) is used clinically to estimate right atrial pressure, a functional IJVV may prevent accurate estimation of the JVP. OBJECTIVES: To describe the presence and the competence of the IJVV in post-mortem and live human subjects. DESIGN - setting and methods: The anatomical appearance of the IJVV from 30 cadavers was studied. Competence was checked by measuring maximum hydrostatic pressure before reflux occurred through the valve. The function of the valve was evaluated in 25 live subjects using colour duplex scanning. RESULTS: The IJVV was present in all cadavers just before its termination (60 IJVVs from 30 subjects). The valve was bicuspid in most cases (93%). The competence of 41 IJVVs was checked of which only three (7%) were found to be incompetent. All IJVVs in live subjects were found to be competent. CONCLUSION: This study confirms that a functional IJVV is present just above the termination of the internal jugular vein. The IJVV may therefore prevent reflux of venous blood from the right atrium into the internal jugular vein.

Adult↗
PubMed2001

Theoretical evaluation of the origin of the regio- and stereoselectivity in the Diels-Alder reactions of dialkylvinylboranes: studies on the reactions of vinylborane, dimethylvinylborane, and vinyl-9-BBN with trans-piperylene and isoprene.

Ab initio and DFT calculations have been performed to study the origin of the regio- and stereoselectivity of the Diels-Alder reactions of dialkylvinylboranes with substituted dienes. B3LYP/6-31G energies of the transition structures for the reactions of dimethylvinylborane and vinyl-9-BBN with trans-piperylene and isoprene yielded calculated ratios which are in very good agreement with experimental values. Nonclassical carbon-boron [4+3] secondary orbital interactions seem to account for the high endo stereoselectivity of these reactions. However, C-B interactions become less important when the bulkiness of the alkyl groups attached to boron increases. Both endo and exo transition structures for the reactions of dimethylvinylborane and vinyl-9-BBN adopt classical [4+2] character. This study also extends Singleton's investigation on butadiene to regioselectivity. FMO theory has been used to rationalize the lack of regioselectivity in the reactions of dimethylvinylborane. The anomalous meta regioselectivity of the Diels-Alder reaction of vinyl-9-BBN with trans-piperylene is mainly caused by steric effects.

Journal Article↗
PubMed2001

Stereological determination of the volume of the rat hemimandible tissues.

Rodent incisors are useful models to study the development and behavior of dental and periodontal tissues. Some studies require three-dimensional reconstructions of the tooth but none of the described methods yield actual volumetric data. Unlike the rat lower incisors the hemimandible can be easily isolated and its volume was determined by Cavalieri's geometrical principle. This method associated with point-counting volumetry was used to calculate the volume of the structures found in that bone mainly those related to the lower incisor. For 172 g male rats the mean volume of the hemimandible was 182.7 mm(3), statistically not different from 184.9 mm(3) the mean volume of the same hemimandibles determined by Archimedes' principle. The coefficients of error (CE) of Cavalieri's estimates for the hemimandible, incisor as a whole (the tooth itself, odontogenic region and periodontium) and bone tissue were less than 0.04. For the incisor individual tissues the CEs were usually above 0.05, however their calculated volumes are probably not different from the actual ones. The data for incisors and their periodontal tissues and for bone, because of continuous growth of these structures, are meaningful only for rats of the same gender, strain and weight range.

Animals↗
PubMed2001

Ventricular endocardial right bifocal stimulation in the treatment of severe dilated cardiomyopathy heart failure with wide QRS.

The QRS widening by ventricular conventional pacing impairs the systolic and diastolic functions and increases mitral regurgitation. The aim of this study was to compare conventional pacing to an alternative stimulation mode with a narrower QRS using two leads in the RV. Thirty-nine (25 men, 14 women; mean age 60.1 +/- 15.1 years) dilated cardiomyopathy patients (Chagas' disease [n = 17], coronariopathy [n = 9], AV ablation for tachycardiomyopathy [n = 3], and other [n = 10]) with cardiac failure (NYHA 3.1 +/- 0.8), pacemaker indication, and chronic AV block (22 AF) had endocardial pacemaker implantations (27 Biotronik, 12 Guidant). Two RV leads (one septal, one conventional [RV apex] were connected, respectively, to the atrial and ventricular pacemaker plugs. After clinical stabilization they were studied under three stimulation modes in the same session: AAI (septal), VVI (conventional), and ventricular endocardial right bifocal stimulation (VERBS) (DDT/DVI/DDD = AV interval = 15/10 ms). In comparison to conventional pacing, VERBS increased ejection fraction (0.124), cardiac output (19.5%), and peak filling rate (31.0%), and decreased QRS duration (24.7%), left atrium area (11.9%), mitral regurgitation area (32.3%), the diastolic transmitral flow (E/A relation) (19.3%), and the propagation flow time (18.0%) from the mitral valve to the left ventricular apex (tE_col), (P < 0.05). The quality-of-life showed an impressive score reduction of 50.4%. The septal stimulation alone showed a less expressive benefit. In severe dilated cardiomyopathy with classic pacemaker indication, VERBS showed significantly better performance than the septal or the conventional stimulation alone. There was a good systolic and a remarkable diastolic improvement causing an important reduction in the quality-of-life score.

Adult↗
PubMed2001

Gastroesophageal reflux disease: New oral findings.

OBJECTIVE: The objective of this study was to investigate the effects of gastroesophageal reflux disease (GERD) on dentition, salivary function, and oral mucosa. STUDY DESIGN: Thirty-one patients with esophagitis underwent medical evaluation, which included taking their medical history, performing both an esophagogastroduodenoscopy and esophagus biopsy, and conducting a stomatologic examination. The latter consisted of an extraoral and intraoral physical examination, saliva tests (flow, buffer capacity, and pH), and biopsy and morphometry of the palatal mucosa, as well as taking a history of the patients' habits. Fourteen healthy volunteers from the same population were used as a control group. RESULTS: No relationship between GERD and changes in the oral cavity was shown by saliva tests, oral clinical examination, or histopathologic examination of the palatal mucosa. However, morphometric analysis of the palatal epithelium showed a statistically significant difference between the patients with GERD and the control group. CONCLUSIONS: GERD is associated with microscopic alterations in the palatal mucosa (epithelial atrophy and increased fibroblast number), which are only detected by morphometry.

Adult↗
PubMed2001

Relation between birth weight and placenta weight.

With the goal to establish a model that relates birth weight to placenta weight, adjusted for the most documented predictors of birth weight, 300 live newborns were studied, all were products of single gestation. Inclusion criteria were newborns with gestational age of 37 weeks or older according to the date of last menstruation, whose mothers did not have diabetes mellitus, high blood pressure, pre-eclampsia, or eclampsia. The weight of the newborn was identified from the anthropometry data collected by previously trained nursing personnel in each of the participating hospitals. Immediately after delivery, the placenta was weighed. Multiple linear regression was used to see the effect of placenta weight and each variable on birth weight. The mean of birth weight was 3,369 g with a standard deviation (SD) of 445 g. Placenta weight had a mean of 537 g (SD: 96 g). The relation between the weight of the placenta and the birth weight was significant, and we found that for each gram increase in placenta weight, birth weight is increased by 1.98 g (SE = 0.25, p < 0.01) and this relation is not linear, since the quadratic term is significant. Placenta weight has a nonlinear relation to the birth weight and is an important predictor of birth weight. Together with the gestational age and the maternal age and size, it explains 32% of the variability of birth weight. Placenta weight can be a 'sentinel' indicator of nutritional and/or environmental problems.

Adult↗
PubMed2001

CT-guided percutaneous punctate midline myelotomy for the treatment of intractable visceral pain: a technical note.

Surgical treatment of intractable visceral pain has always been a challenge. The relatively recent discovery of a specific visceral pain pathway brought a new insight to this matter. The authors describe a new technique to interrupt this pathway, the CT-guided percutaneous punctate midline myelotomy, successfully applied in two patients with intractable pelvic visceral pain. Due to its simplicity, safety and high effectiveness, it may become the treatment of choice for intractable visceral pain.

Cordotomy↗
PubMed2001

[Diagnosis of hepatitis C in clinical practice: review of the literature].

The objective of this study was to review the literature concerning laboratory tests to detect hepatitis C virus infection, which have been available since 1989. The diagnosis of hepatitis C is mainly based on serological techniques and on molecular techniques. Serological techniques to detect hepatitis C virus antibodies are the method of choice to identify past or present infection. There are two types of serological assays: highly sensitive enzyme-linked immunosorbent screening assays; and more specific immunoblot techniques, which are used as supplemental or confirmatory tests. With respect to molecular diagnostic techniques, there are several types of assays. One such assay detects viral RNA. It is useful for diagnosis in such situations as the early stages of infection, with immunosuppressed patients, and with persons who have a low probability of infection. Molecular assays are also recommended before treatment with interferon and ribavirin, in order to monitor response to treatment. Other assays allow determination of viral load by either target amplification (as in polymerase chain reaction) or signal amplification (as in branched-DNA). Determining the hepatitis C virus genotype is possible using either molecular techniques or serotyping. Determining viral load and genotype is useful for planning the duration of interferon and ribavirin treatment. There have been major advances in the diagnosis of hepatitis C in the past decade Improvements in the sensitivity and specificity of antibody tests have provided faster, less expensive diagnoses. However, more accurate assays are still needed for such groups as immunosuppressed persons and acute hepatitis patients.

Enzyme-Linked Immunosorbent Assay↗
PubMed2000

Superior water maze performance and increase in fear-related behavior in the endothelial nitric oxide synthase-deficient mouse together with monoamine changes in cerebellum and ventral striatum.

Nitric oxide (NO) has been implicated in the control of emotion, learning, and memory. We have examined endothelial NO synthase-deficient mice (eNOS-/-) in terms of habituation to an open field, elevated plus-maze behavior, Morris water maze performance, and changes in cerebral monoamines. In the open field, eNOS-/- animals were less active than wild-type controls but showed unimpaired habituation. In the plus-maze, an anxiogenic effect was observed. Proceeding from previous findings of deficits in hippocampal and neocortical long-term potentiation (LTP) in our eNOS-/- mice, we investigated whether these animals also express deficits in learning tasks that have been linked to hippocampal function and LTP. Unexpectedly, eNOS gene disruption led to accelerated place learning in the water maze. Furthermore, during long-term retention and reversal learning, eNOS-/- mice showed improved performance. In a cued version of the water maze task, eNOS-/- and control mice did not differ, implying that the superior performance of eNOS-/- animals on the former tasks cannot be attributed solely to differences in sensorimotor capacities. The neurochemical evaluation of the eNOS-/- mice revealed increases in the concentrations of the serotonin metabolite 5-HIAA in the cerebellum, together with an accelerated serotonin turnover in the frontal cortex. Furthermore, eNOS-/- mice had a higher dopamine turnover in the ventral striatum. These findings are discussed in terms of possible concomitant effects on physiological parameters, such as a decreased reactivity of GABAergic neurotransmission or changes in vascular functions, and effects on behavioral processes related to reinforcement, learning, and emotion.

3,4-Dihydroxyphenylacetic Acid↗
PubMed2000

Understanding diastereofacial selection in carbohydrate-based domino cycloadditions: semiempirical and DFT calculations.

The sequential cycloaddition of nitroalkenes with methyl vinyl ether was investigated by semiempirical (PM3) and density functional methods (B3LYP/6-31G*). The asymmetric version was also examined with a threoconfigured carbohydrate auxiliary. This produces a larger, more flexible system that complicates the calculation. Most transition structures were then fully optimized at the PM3 level and further refinement was done at ab initio levels. This study represents a model case that enables the rationalization of the high facial selectivity observed in carbohydrate-based nitrone- and nitronate-alkene cycloadditions. The selective endo orientation of the [4+2] pathway results from Coulombic attraction and secondary orbital interactions in the transition state. The stereochemical outcome is largely influenced by a combination of steric shielding from the bulky chiral substituent at C4 and the anomeric effect that places the nitronate C6-alkoxy group in a pseudoaxial arrangement. The resulting conformation favors the subsequent exo approach of methyl vinyl ether to the less hindered re face of the nitronate. It is also remarkable to note that solvation energies stabilize significantly a particular transition structure, thereby explaining the marked stereoselection observed in a polar medium.

Carbohydrates↗
PubMed2000

Role of kinins and nitric oxide on the rabbit arthritis induced by Bothrops jararaca venom.

The effects of the nitric oxide synthase inhibitor N(omega)Nitro-L-arginine-methyl ester (L-NAME) and of the bradykinin B(2) receptor antagonist HOE 140 were evaluated in the inflammatory reaction induced by Bothrops jararaca venom (BjV) in New Zealand White rabbits. Arthritis was induced by injecting 0.5 ml of a sterile solution of BjV (1-64 microg/ml) into the knee intraarticular cavity. The contralateral joint was injected with bovine serum albumin (BSA) diluted in sterile saline. At selected times thereafter (4, 24 and 48 h), the vascular permeability and the leukocyte influx in both the synovial fluid and synovium were evaluated. BjV caused a dose-dependent increase in both leukocyte influx and protein extravasation which reached a maximal response at 16 microg. Bothrops jararaca venom also induced the increase in the leukocyte accumulation in the synovium and in the concentration of both NO(2)/NO(3) in the synovial fluid. Chronic administration of L-NAME (20 mg/kg/day in the drinking water for 2 weeks) markedly reduced the leukocyte accumulation (90%), protein leakage (44%), and NO(2)/NO(3) (50%) levels in the synovial fluid, measured at the 4th h. Hoe 140, given i.v. (0.3 mg/kg, 30 min before) also reduced leukocyte accumulation (75%), protein leakage (48%), and NO(2)/NO(3) (79%) levels in the synovial fluid, measured at the 4th h. Similar results were obtained with acute administration of L-NAME (30 mg/kg, i.v., 30 min before). These results indicate that arthritis induced by BjV is triggered by kinin formation and that the increase in both vascular permeability and leukocyte accumulation is modulated by NO release.

Animals↗
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↗