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J L Carvalho

Publications and source records attributed to J L Carvalho.

At least 19 recordsLinked to original sources
PubMed2003

Direct visualisation of homogeneous and heterogeneous crystallisation in an ensemble of confined domains of poly(ethylene oxide).

We present a study of homogeneous and heterogeneous nucleation in polymer crystallisation. In bulk samples the crystallization is typically dominated by nucleation from defects (heterogeneous nucleation), and consequently studies must rely on sample preparation to minimize this effect. We present a study of nucleation within discrete droplets of poly(ethylene oxide) that are formed by the dewetting of a thin film on an unfavourable substrate. The samples provide an ensemble of impurity-free droplets, with length scales that can easily be measured. We show that the data for heterogeneous and homogeneous nucleation is qualitatively different, and that the data mirrors the fundamental differences in the underlying mechanisms for the two nucleation processes. The experiments presented here provide a simple method that can be used to study heterogeneous and homogeneous nucleation in great detail.

Journal Article↗
PubMed2002

[Intestinal duplications. A survey of 18 cases].

OBJECTIVE: The present study analyses the experience of two centers in the management of intestinal duplications in children. MATERIAL AND METHODS: We retrospectively reviewed the medical records of a series of 18 children with intestinal duplication (January 1993 to December 1999). The median age was 11 months (range: 9 days to 12 years). The variables analysed were: clinical presentation, diagnosis, localization, anatomic type, treatment, and complications. The relationship between age and clinical presentation was also analysed. RESULTS: Most cases were located in the ileum (n 14; 78 %) and presented with rectal bleeding (36 %) or intussusception (36 %). Most symptomatic cases in the first year of life presented with intussusception (n 5/6). All duplications, except one located in the ascending colon, were cystic. 99mTc-pertechnate abdominal scan was positive in three out of five patients. One case was diagnosed by prenatal ultrasonography. Diagnosis was confirmed by laparoscopy in three patients and by laparotomy in the remaining patients. In one patient, cystic esophageal duplication presented in the neonatal period as respiratory distress. Diagnosis as well as excision was performed by thoracoscopy. Of the two gastric duplications, one was diagnosed by prenatal ultrasonography and the other by laparotomy. Treatment consisted of segmental enterectomy (n 14) or excision of the lesion without enterectomy (n 4). No complications were found during a mean follow-up of 3 years. CONCLUSIONS: The onset of intestinal duplication may be late. The lesions were most commonly located in the ileum and were cystic. Clinical presentation was related to age. Minimally invasive surgery plays an important role in the management of these lesions.

Child↗
PubMed2001

Histochemical and immunohistochemical study of the intrinsic innervation in colonic dysganglionosis.

Defective innervation of the neuromuscular junctions (NMJ) was recently described in intestinal neuronal dysplasia type B (IND B). The aim of the present study was to correlate the alterations in NMJs to other classically described parameters in dysganglionoses and to determine the relationship between NMJ abnormalities in IND B and clinical symptoms. The rectal biopsies and full-thickness colonic biopsy specimens of 17 patients were studied applying histochemical (acetylcholinesterase [AChE], lactic dehydrogenase [LDH], and succinic dehydrogenase [SDH] reactions) and immunohistochemical (neuronal-cell adhesion molecule [NCAM] and SY antibodies) methods. Thirteen patients had Hirschsprung's disease (HD). IND B was diagnosed in 11 (associated with HD in 8 cases, isolated in 2, and associated with hypoganglionosis in 1). In the aganglionic segment of HD there was very intense AChE activity; in contrast, NCAM- and SY-immunoreactive nerve fibers were markedly decreased. A spectrum of abnormalities was observed in IND B, usually more severe in the most distal segments: giant and immature ganglia in the submucous plexus were observed in all cases; heterotopic myenteric ganglia were frequent (72.7%); hyperganglionosis was observed in 6 (54.5%) and was not related to the patients' age; thick and tortuous NCAM- and SY-immunoreactive nerve fibers, irregularly distributed in the colonic wall, were observed in 81.8% of the cases. No relationship was observed between abnormalities of NCAM- and SY-immunoreactive nerve fibers and AChE activity, ganglion-cell maturity, heterotopy, or the clinical symptoms presented by the patients with IND B. In hypoganglionism, low AChE activity and a slight decrease in NCAM- and SY-immunoreactive nerves were observed. Thick and tortuous, irregularly-distributed intrinsic NCAM- and SY-immunoreactive nerves were observed in every colon layer in IND B. Our results do not support IND B as a NMJ disorder.

Child↗
PubMed2001

Laparoscopic colonic mapping of dysganglionosis.

Retention of a proximal aganglionic segment or the unrecognized coexistence of other dysganglionoses may jeopardize the definitive surgical treatment of Hirschsprung's disease (HD). To assess the extent of the disease and/or the presence of other dysganglionoses without an additional laparotomy, we developed a laparoscopic-assisted technique to perform colonic full-thickness biopsies. After creation of a pneumoperitoneum, a 5-mm laparoscope is inserted in the supraumbilical area and a working 10/12-mm port is placed in the left iliac fossa. The sigmoid/descending colon is grasped and pulled through the abdominal wall and a full-thickness biopsy done. The same procedure is applied to the transverse and ascending colon. Rectal and colonic biopsy specimens were studied using enzyme histochemical methods. Over the last year, five children aged 7 months to 12 years with dysganglionosis underwent laparoscopic-assisted mapping of the colon. Previous rectal suction biopsies were diagnostic of HD in three patients and suspicious of hypoganglionosis in two. Proximal full-thickness biopsies revealed: normal colon in two cases of HD; coexistent type B intestinal neuronal dysplasia up to the descending colon in the other case of HD; and hypoganglionosis up to the ascending colon in the two patients with suspected hypoganglionosis. The procedures were performed easily, the patients being discharged after 36 to 48 h with no complications. Four children have already undergone pull-through procedures with resection of the affected colon in adhesion-free abdominal cavities and did not develop constipation or enterocolitis. Laparoscopic-assisted mapping of the entire colon is a simple, safe, and effective procedure that may contribute to improving the outcome of intestinal dysganglionosis by better characterization of the disease.

Child↗
PubMed2001

Neonatal perforation of a Y-shaped sigmoid duplication.

Tubular colonic duplications are exceedingly rare; the "Y"-shaped forms are exceptional. In the absence of associated low vertebral or urogenital malformations (often fistulas), the tubular colonic malformations frequently stay hidden for several years until a complication develops. The authors report a case of a spontaneous perforation of a Y-shaped tubular colonic duplication during the neonatal period.

Anastomosis, Surgical↗
PubMed2001

Delayed gastric emptying and gastroesophageal reflux: a pathophysiologic relationship.

BACKGROUND: Delayed gastric emptying (DGE) is frequent in patients with gastroesophageal reflux (GER), but its pathophysiologic role has not yet been established. To identify a relationship between DGE and GER, we assessed whether DGE increases esophageal acid exposure and the related importance of possible mechanisms. METHODS: Thirty pediatric patients with pathological GER were divided according to gastric emptying scintigraphy into a DGE group (n = 14) and normal-emptying group (n = 16). The esophageal pH-monitoring parameters of the two groups were compared with respect to the individual variation between postprandial and fasting periods. RESULTS: Patients with DGE had less total acid exposure than did those with normal emptying, but patients in both groups had a pathological fraction of time when pH was below 4 in both the postprandial (median: 18 vs. 27.6; P = 0.49) and fasting (8.5 vs. 23.9; P = 0.01) periods. Patients in the normal-emptying group had similar fraction of time when pH was below 4 in the postprandial and fasting periods. However, patients in the group with DGE had a fraction of time when pH was below 4 in the postprandial period that was almost double that presented in fasting period (postprandial to fasting ratio: 2.11:0.90; P = 0.002). The postprandial to fasting ratio for episodes per hour was similar in the two groups (1.81 vs. 1.79; P = 0.62). Patients with DGE had a significantly higher frequency of long episodes in the postprandial period than did those with normal emptying (62.5% vs. 38.2%; P = 0.04). The occurrence of the longest episode in the postprandial period was also significantly higher for patients with DGE (57.1% vs. 6.2%; P = 0.003). CONCLUSIONS: DGE seems to accentuate postprandial reflux by increasing the volume of refluxate per episode of reflux through an underlying incompetent lower esophageal sphincter.

Case-Control Studies↗
PubMed2001

[Prognostic indexes derived from ventricular morphology in congenital diaphragmatic hernia induced by nitrofen].

BACKGROUND: Some indices derived from cardiac morphology have been proposed as prognostic factors in fetuses and newborns with congenital diaphragmatic hernia (CDH). These would be of interest in evaluating the risk of pulmonary hypoplasia and the need for surgery in the fetus. The aim of this study was to evaluate the heart-related indices in the nitrofen-induced CDH rat model. METHODS: At day 9 1/2 of gestation dated pregnant female Wistar rats received 100 mg of nitrofen. Fetuses were harvested at day 21 1/2 by laparotomy. The fetuses exposed to nitrofen without CDH were defined as the control group (n = 38) while the fetuses exposed to nitrofen with CDH were defined as the CDH group (n = 30). The hearts from both groups were weighed, processed for paraffin embedding and fragmented in serial 7 microns thick transverse sections. In the hearts without cardiac morphological defects the right and the left ventricular cavity volumes were estimated. These allowed calculation of cardioventricular and left-ventricular mass indices. RESULTS: In the fetuses without cardiac malformations, no significant difference was found regarding heart-to-body weight ratio, cardioventricular index or left ventricular mass between the study groups. CONCLUSION: In this model the presence of CDH was not associated with any alteration in cardiac dimension, in the absence of structural malformations. These results suggest that the indices derived from ventricular morphology should not be used to evaluate the prognosis in fetuses and newborns with CDH.

Animals↗
PubMed2001

Field observations of dilution on the Ipanema Beach outfall.

Field observations of the Ipanema Beach, Rio de Janeiro, ocean sewage outfall are presented. Measurements of dilution and other wastefield characteristics were obtained by adding dye tracer to the effluent and measuring in-situ. Simultaneous measurements of oceanographic conditions were made by Acoustic Doppler Current Profilers, thermistor strings, and profiling instruments. Four experiments were performed, two during unstratified conditions when the plume was surfacing, and two during conditions of strong stratification when the plume was submerged. The minimum dilution varied from 30 to 130. The measurements reflect the worst case conditions as the campaigns were all made for weak currents.

Algorithms↗
PubMed2000

Acute gastric volvulus secondary to a Morgagni hernia.

Gastric volvulus (GV) is a rare surgical emergency in infancy and childhood. The first case of a child with an acute GV secondary to a Morgagni hernia (MH) is reported. The authors briefly discuss the etiology, clinical features, and management of acute GV and review the scattered reports of strangulated MHs in children.

Child, Preschool↗
PubMed2000

Heart-related indices in experimental diaphragmatic hernia.

BACKGROUND: Heart-related indices have been suggested as useful tools to evaluate left ventricular (LV) hypoplasia, which might predict the outcome of fetuses and infants with congenital diaphragmatic hernia (CDH). The current study analyzed the behavior of such indices in the nitrofen-induced CDH rat model. METHODS: Dated pregnant Wistar rats received at day 9.5 of gestation either a dose of 100 mg of nitrofen or just the vehicle. Body, lung, and heart weights were measured in 12 newborn rats not exposed to nitrofen (Ctrl group) and 68 animals exposed to nitrofen: 30 without CDH (non-CDH group) and 38 with left CDH (CDH group). Each heart was fragmented in 7-microm thick sections. Only hearts with no evidence of cardiac morphologic defects (CMD) were studied further to estimate right and left ventricular cavity volumes, septal, right, and left ventricular free wall masses. These parameters allowed the calculation of the cardio-ventricular (CVindex) and LV mass indices. The aorta-to-pulmonary artery ratio also was calculated. RESULTS: Excluding fetuses with CMD, the heart-to-body weight ratio was reduced significantly in animals exposed to nitrofen, whereas no significant differences were observed between non-CDH versus CDH groups. Although the left and right ventricular cavity volumes were both reduced significantly in nitrofen-treated rats, they were not changed significantly by the existence of CDH, and the calculated CVindex was similar in the 3 groups. Estimated septal and LV masses were reduced markedly in the nitrofen-treated animals and further reduced by the presence of CDH. However, when LV mass was normalized (LV mass index) the difference became restricted to the animals exposed to nitrofen but was not influenced by the presence of CDH. Finally, the aorta-to-pulmonary artery ratio was similar in all studied groups. CONCLUSIONS: The results of the current study suggest that, although nitrofen had been responsible by global heart hypoplasia, the presence of CDH was not associated with significant underdevelopment of the heart or of the LV in rat fetuses without CMD. Based on these results, we think that the evidence for prenatal counseling based on heart-related indices should be critically reconsidered.

Animals↗
PubMed1999

[Absence of cardiac hypoplasia in an experimental model of congenital diaphragmatic hernia].

INTRODUCTION: Congenital diaphragmatic hernia (CDH) is a rare malformation in newborns. Amongst the various prenatal prognostic criteria, it is suggested that heart weight could be useful in evaluating the severity of lung hypoplasia. In this work we studied heart development in a rat model with nitrofen-induced CDH. MATERIAL AND METHODS: Pregnant female Wistar rats were treated on day 9 1/2 of gestation with 100 mg of nitrofen dissolved in 1 ml of olive oil. The control group was only treated with 1 ml of olive oil. The foetuses were delivered by caesarean section on day 21 1/2 of gestation. The weight of the foetuses was recorded. Under microscopy, the foetuses were dissected and the diaphragm was inspected. The wet weight of the heart and lung were recorded. The results are presented as a mean +/- standard deviation. A statistical analysis was made with the one-way ANOVA test on Ranks, and the Dunn test for post-test analysis. The statistical significance was set at a p < 0.05. RESULTS: The foetuses with CDH (n = 16) were lighter and had a smaller left lung/body weight ratio when compared with animals exposed to nitrofen without CDH (n = 18) and with controls (n = 12) (p < 0.05). The heart/ body weight ratio was smaller in foetuses exposed to nitrofen (p < 0.05), but we could not find any differences between nitrofen-treated treated foetuses with vs without CDH (n.s.). CONCLUSIONS: In spite of the lung hypoplasia, we could not demonstrate the presence of heart hypoplasia in rats with CDH when compared to nitrofen-treated foetuses without CDH.

Animals↗