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Biomedical subjects

A Matias

Publications and source records attributed to A Matias.

At least 19 recordsLinked to original sources
PubMed2006

Renal tubular dysgenesis: report of two cases in a non-consanguineous couple and review of the literature.

Renal tubular dysgenesis is a rare congenital abnormality of renal development characterized by short and poorly developed proximal convoluted tubules. It is associated to late-appearing oligohydramnios, Potter's sequence, pulmonary hypoplasia and calvarial bone hypoplasia with enlarged fontanels. The onset of oligohydramnios is delayed and variable, normally later than 22 weeks of gestation, conditioning variation in the expression of the other deformities. We report 2 cases of renal tubular dysgenesis occurring in a non-consanguineous couple.

Adult↗
PubMed2003

Domiciliation process of Rhodnius stali (Hemiptera: Reduviidae) in Alto Beni, La Paz, Bolivia.

We report a systematic collection of Triatominae inside houses and in the peridomestic environment of Alto Beni, department of La Paz, Bolivia. This area is free of Triatoma infestans and although we detected previously seropositivity for Trypanosoma cruzi, the Alto Beni region is not officially considered as endemic for Chagas disease. From 11 houses of five localities, we collected adults, nymphs and eggs of a Rhodnius species, which was confirmed by morphological and morphometric analysis as Rhodnius stali. This little-known species has long been confused with R. pictipes, and was originally described from museum specimens labelled as R. pictipes. Our data show that R. stali is able to establish colonies in domestic and peridomestic habitats in Bolivia, and it is probably the vector responsible for Chagas disease seropositivity observed in the indigenous population of Alto Beni.

Animals↗
PubMed2001

Electric current generated by ultrasonically induced Lorentz force in biological media.

The ions of solutions exposed to the propagation of ultrasound in the presence of a magnetic field experience Lorentz force. Their movement gives rise to a local electric current density, which is proportional to the electric conductivity of the medium. In vitro assessment of this current is performed using simple models of biological media. A constant magnetic field of 0.35 T and 500 kHz pulsed ultrasound are used. The sensing electrodes are exposed to neither the pressure wave nor the magnetic field, thus ensuring that the signal is not due to any undesirable electrode effect. The experimental results confirm that the current is proportional to the electrical conductivity of the medium. The changes in the measured current against the width of the measurement chamber show that the electrodes only collect a fraction of the current created within the medium. The magnitude of the measured current is 50nA in a saline solution of 0.5 S/m conductivity. The technique enabled the determination of the conductivity of a porcine blood sample against haematocrit. It is concluded that this type of measurement has the potential to allow the electrical conductivity of a medium to be determined using ultrasound.

Electric Conductivity↗
PubMed2001

Ductus venosus blood flow in chromosomally abnormal fetuses at 11 to 14 weeks of gestation.

This article reviews the role of ductus venosus (DV) Doppler evaluation in the screening for aneuploidies at 11 to 14 weeks of gestation. Ductus venosus flow velocity waveforms were obtained immediately before fetal karyotyping in 515 consecutive singleton pregnancies at 11 to 14 weeks. We found 446 normal and 69 abnormal karyotypes. Abnormal flow in the DV was the only significant difference between both groups. Sensitivity of the test was 80% and false positive rate < 1%. Normal karyotype but abnormal flow in the DV was recorded in 17 of 446 cases, 7 presenting a cardiac defect. Increased nuchal translucency seems to be related, in most cases, to early cardiac dysfunction. Chromosomal abnormalities and/or cardiac defects were often found in cases with increased nuchal translucency and abnormal flow in the DV. We suggest that the evaluation of ductal flow between 11 to 14 weeks of gestation should be adopted as a second level screening test to reduce invasive test rate derived from the exclusive measurement of nuchal translucency.

Adolescent↗
PubMed2001

Scanning electric conductivity gradients with ultrasonically-induced Lorentz force.

The ions in a fluid element oscillating under the effect of a sound wave in the presence of a magnetic field are submitted to Lorentz force. This gives rise to a bulk current density proportional to the medium's electric conductivity. In the present study, the integrality of this interaction current was collected using a pair of plane electrodes located on opposite sides of the sample. A focused transducer produced ultrasound bursts of 10 micros duration, 500 kHz frequency and 1.5 MPa peak pressure. The magnetic field was created by a purpose-built 0.35 T permanent magnet. Wiener inverse filtering was used to retrieve the system response from the recorded waveforms. The final signal was shown to be proportional to the gradient of sigma/rho along ultrasound propagation axis. Electric conductivity, sigma, predominantly controls this parameter since mass density, rho, does not vary in great proportions in biological media. Rectangular blocks of Agar gel and a layered bacon sample were used as models of biological media. The signals obtained in gel blocks had a longitudinal spatial resolution better than 1 mm. The successive layers of the bacon sample were clearly resolved. The advantages of this new modality for tissue characterization include the permeability of body tissue to magnetic field and ultrasound, the harmlessness of the applied fields and the improved spatial resolution in the measurement of a tissue's electric conductivity distribution.

Electric Conductivity↗
PubMed2001

Adult and nymphs of Microtriatoma trinidadensis (Lent, 1951) (Hemiptera: Reduviidae) caught from peridomestic environment in Bolivia.

This is the first report of adult and nymphs (20 nymphs of all stages and 4 adults) of Microtriatoma trinidadensis (Lent 1951) (Hemiptera: Reduviidae: Triatominae) collected in peridomestic environment, in the department of La Paz, Bolivia. These specimens were associated to Rhodnius stali Lent, Jurberg & Galvão 1993. The exceptional finding of M. trinidadensis in peridomestic environment, illustrates the general tendency of triatominae to adapt to human dwellings and dependences.

Animals↗
PubMed2001

Rhodnius robustus in Bolivia identified by its wings.

Wings of a Rhodnius specimen from Alto Beni (Bolivia) was examined for identification and compared with R. stali, R. robustus, (certified Bolivian species), R. pictipes and R. prolixus (suspected Bolivian species). A projection of the unidentified wings as supplementary data into a discriminant analysis of shape revealed clear cut differences with R. stali and R. pictipes, less differences with R. prolixus, and none with R. robustus. Combining global size and shape of the wings, the unknown specimen was identified as R. robustus. Thus, this study confirmed the presence of R. robustus in Bolivia. It also highlighted the possibility of morphometrics to taxonomically interpret one individual, or even one piece of an individual, when related species data are available for comparison.

Animals↗
PubMed2001

Wing geometry as a tool for studying the Lutzomyia longipalpis (Diptera: Psychodidae) complex.

Toro Toro (T) and Yungas (Y) have been described as genetically well differentiated populations of the Lutzomyia longipalpis (Lutz & Neiva, 1912) complex in Bolivia. Here we use geometric morphometrics to compare samples from these populations and new populations (Bolivia and Nicaragua), representing distant geographical origins, qualitative morphological variation ("one-spot" or "two-spots" phenotypes), ecologically distinct traits (peridomestic and silvatic populations), and possibly different epidemiological roles (transmitting or nor transmitting Leishmania chagasi). The Nicaragua (N) (Somotillo) sample was "one-spot" phenotype and a possible peridomestic vector. The Bolivian sample of the Y was also "one-spot" phenotype and a demonstrated peridomestic vector of visceral leishmaniasis (VL). The three remaining samples were silvatic, "two-spots" phenotypes. Two of them (Uyuni and T) were collected in the highlands of Bolivian where VL never has been reported. The last one (Robore, R) came from the lowlands of Bolivia, where human cases of VL are sporadically reported. The decomposition of metric variation into size and shape by geometric morphometric techniques suggests the existence of two groups (N/Y/R, and U/T). Several arguments indicate that such subdivision of Lu. longipalpis could correspond to different evolutionary units.

Animals↗
PubMed2000

False-high blood salicylate levels in neonates with hyperbilirubinemia.

Drug assays may yield false-positive results caused by cross-reacting compounds. After finding a serum salicylate concentration of 81 microg/mL by using Trinder's colorimetric method, in a comatose child admitted to the authors' pediatric intensive care unit, in the absence of reported salicylate intake, the authors aimed to compare this situation with the phenomenon involving endogenous digoxin-like substances, which cross-react with the routine assay of digoxin. None of the participants in the study had been exposed to salicylate. Salicylate concentration was measured in all patients using Trinder's colorimetric method and in the second stage of the study also by AxSYM salicylate assay. Salicylate concentration using Trinder's method was 18 +/- 25 (4-81) microg/mL among nine seriously ill children in the pediatric intensive care unit, of whom two children with extensive burns had salicylate levels of 30 and 81 microg/mL, respectively. Salicylate concentrations were 107 +/- 24 (45-143) microg/mL and 60 +/- 25 (28-92) microg/mL, among 18 premature newborns and 18 term newborns, with hyperbilirubinemia, respectively. In the second stage, which involved 22 jaundiced term newborns and cord blood from 21 pregnant women, Trinder's method yielded elevated salicylate blood levels among the hyperbilirubinemic infants: 82 +/- 5 (73-89) microg/mL; however, the AxSYM assay yielded significantly lower blood levels: 2.5 +/- 3.4 (0-10.9) microg/mL (P < 0.0001). Among the pregnant women, salicylate cord blood levels were found to be low-within the limit error of the assay with both assay methods. In conclusion, when salicylate intoxication is suspected, particularly during the neonatal period, it is advisable to measure salicylate levels by immunoassay technology.

Adult↗
PubMed2000

Anticipating twin-twin transfusion syndrome in monochorionic twin pregnancy. Is there a role for nuchal translucency and ductus venosus blood flow evaluation at 11-14 weeks?

Twin-twin transfusion syndrome is a major complication of monochorionic twin pregnancies. In foetuses from monochorionic twinning the presence of increased nuchal translucency thickness (NT) has been associated with an increased risk of developing this syndrome. One of the presumed mechanisms of increased NT is early cardiac failure, indirectly indicated by abnormal blood flow in the ductus venosus. We present eleven cases of monochorionic twin pregnancies in which nuchal translucency thickness and ductus venosus blood flow evaluation was performed at 11-14 weeks. In the two cases presenting with nuchal translucency discrepancy between the two foetuses along with anomalous ductus venosus blood flow in the foetus with increased nuchal translucency, twin-twin transfusion syndrome (TTTS) eventually developed. In none of the twins displaying no inter-twin difference in NT measurements and in those with discrepant NT but normal flow in both ductus venosus, was the progression to TTTS observed. In the two cases which developed TTTS, foetoscopic laser coagulation of the vascular anastomosis was successfully carried out at 18 weeks and normalisation of the venous return was registered. These findings suggest that the association of increased NT and abnormal flow in the ductus venosus in monochorionic twins may be an early manifestation of haemodynamic imbalance between the donor and the recipient eventually manifested as twin-twin transfusion syndrome. Further studies, however, are necessary to establish the potential role of the combination of NT and ductus venosus blood flow assessment as a screening method for TTTS.

Adult↗
PubMed2000

Prenatal diagnosis of congenital heart disease. Critical evaluation of a twelve-month experience.

INTRODUCTION: A retrospective study of fetal echocardiographies performed in the Ultrasound Unit of the Department of Obstetrics and Gynecology between January and December 1998 was carried out. MATERIAL AND METHODS: We performed 271 fetal echocardiographies (236 fetuses; 230 pregnant women). A triplex ultrasound machine was used with a 5 or 3.5 MHz transabdominal probe. RESULTS: The median maternal age was 31 years (17-44) and the median gestational age at the time of the first examination was 27 weeks (15-38). A hundred and thirty-two pregnant women (57.4%) were internal referrals and (98) 42.6% were referred by other hospitals. The most common indications for referral were maternal age > or = 35 years old (n = 48), gestational diabetes (n = 38), family history of congenital heart disease (n = 24) and insulin-dependent diabetes (n = 23). Accuracy of 32 echocardiographies was limited by technical difficulties. Out of 236 fetuses, 205 (86.9%) presented a normal scan, whereas 31 (13.1%) showed some abnormality: 22 structural cardiac defects; 5 rhythm anomalies and one with a mixed abnormality. In three cases a pericardial effusion was detected in the absence of any structural or rhythm anomaly and regressed spontaneously after birth. Three fetuses were referred prenatally for treatment to another center. Eight out of fifteen patients followed in the Pediatric Cardiology outpatient clinic were submitted to surgical treatment. In four cases the parents opted for termination of pregnancy and two neonatal deaths occurred. Four patients were lost for follow-up. DISCUSSION: Our study suggests that strict criteria for a referral of pregnant women to specialized fetal echocardiography are still missing. The median gestational age of 27 weeks at the time of the first examination was clearly out of the generally accepted recommended period (18-24 weeks). It is time to improve the collaboration between the different health professionals involved in the care of pregnant women in order to increase the sensitivity of screening for congenital heart disease.

Adult↗
PubMed1999

Prenatal diagnosis of left ventricular aneurysm: a report of three cases and a review.

We report three cases of left ventricular aneurysm diagnosed prenatally and followed by fetal Doppler echocardiography. A review of the literature reveals a paucity of information about this rare cardiac malformation. Most of the described cases (6 out of 9) have remained asymptomatic during pregnancy and after birth. Our cases, in contrast, and three others in the literature, had an ominous prognosis presenting cardiac failure initially or during follow up and showing a dynamic evolution of the aneurysm. Cross-sectional echocardiography provides the diagnosis, revealing the thin-walled aneurysm, usually apical, to be connected by a broad neck to the left ventricle. Color and pulsed Doppler shows low velocity and to-and-fro flow in the aneurysm. Sequential fetal Doppler echocardiography detects the potential growth of the aneurysm relative to ventricular size, revealing any compromise of cardiac performance by a decreased mitral opening, reversed atrial shunting, a hypokinetic infero-posterior left ventricular wall, and a poor systolic thickening of the wall of the aneurysm. Compromise of cardiac function, and deleterious impact on development of the lungs during fetal life, may depend on the early onset, growth and location of the aneurysm,which may occupy most of the fetal chest. We discuss issues of prenatal diagnosis, sequential surveillance of the natural history, and factors of prognosis as well as myocardial histological data from one of our cases.

Adult↗
PubMed1999

Cardiac defects in chromosomally normal fetuses with abnormal ductus venosus blood flow at 10-14 weeks.

OBJECTIVE: To assess a possible relationship between ductus venosus blood flow abnormalities and cardiac defects in chromosomally normal fetuses with increased nuchal translucency thickness at 10-14 weeks of gestation. METHODS: Ductus venosus Doppler ultrasound blood flow velocity waveforms were obtained at 10-14 weeks' gestation immediately before fetal karyotyping in 200 consecutive singleton pregnancies with increased nuchal translucency. Fetal echocardiography was subsequently carried out in those with normal fetal karyotype. RESULTS: Reverse or absent flow during atrial contraction was observed in 11 of the 142 chromosomally normal fetuses with increased nuchal translucency. Major defects of the heart and/or great arteries were present in seven of the 11 with abnormal ductal flow and increased nuchal translucency, but in none of the 131 with normal flow. CONCLUSION: These preliminary results suggest that abnormal ductus venosus blood flow in chromosomally normal fetuses with increased nuchal translucency identifies those with an underlying major cardiac defect.

Blood Flow Velocity↗
PubMed1998

Outcome of 88 pregnancies with absent or reversed end-diastolic blood flow (ARED flow) in the umbilical arteries.

OBJECTIVES: To investigate both perinatal and postneonatal morbidity and mortality in fetuses with absent or reversed end-diastolic flow (ARED flow) in the umbilical artery. STUDY DESIGN: A 5 year prospective follow-up of 88 fetuses with ARED flow. RESULTS: Sixteen stillbirths, 16 neonatal deaths, six postneonatal deaths and one death at 2 years of age were noted. Out of the 42 fetuses born alive, 36 showed a normal neurological development whereas six were mentally handicapped. Adverse prognosis was more frequently found in the group with absent end-diastolic flow at first examination and then reversed flow until delivery, compared to the groups of always absent or always reversed end-diastolic flows. CONCLUSIONS: Prompt delivery is recommended in these high-risk pregnancies in order to prevent long-term sequelae, obviously depending on the local limits of viability. Further studies appropriately designed for assessing long-term neurodevelopment of fetuses with ARED flow, although demanding, are mandatory.

Female↗
PubMed1998

Anomalous fetal venous return associated with major chromosomopathies in the late first trimester of pregnancy.

We report three cases of increased nuchal translucency at 12-13 weeks of gestation in three fetuses with trisomies 13, 18 and 21. All three fetuses were associated with anomalous venous return evaluated by Doppler ultrasonography. Complete pathological examination was performed following termination in each case. We suggest that alterations in the venous compartment can be an early sign of poor outcome and should prompt a detailed search for cardiac defects early in gestation.

Adult↗
PubMed1998

Variation of embryonic/fetal heart rate at 6-13 weeks' gestation.

The aim of this study was to investigate changes in heart rate, namely the intraindividual variation, in normal embryos/fetuses between 6 and 13 weeks' gestation. A prospective study was performed of 41 singleton pregnancies undergoing routine ultrasound examination during the first trimester of pregnancy. For each case, the embryonic/fetal heart rate was measured on three consecutive occasions with a mean interval of 4 min. The difference in heart rate values between the serial measurements varied from 0 to 18 beats/min and was significantly associated with gestational age (Spearman r = 0.26, p < 0.01). In the group of 15 fetuses (examined before 10 weeks' gestation), the difference between measurements (median = 0 beats/min, range 0-8 beats/min) was significantly lower (z = 2.48, p < 0.05) than in fetuses assessed after 10 weeks of gestation (median = 3, range 0-18 beats/min). Reliable and reproducible information concerning embryonic/fetal heart rate may be obtained from a single measurement, especially when pregnancies are examined before 10 weeks of gestation.

Female↗