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Biomedical subjects

R Figueroa

Publications and source records attributed to R Figueroa.

At least 55 records · Page 3Linked to original sources
PubMed1995

Obesity in children: recent advances in energy metabolism and body composition.

In this paper we review recent advances in energy metabolism and body composition studies in prepubescent children and the relationship to childhood obesity. Our review on energy expenditure focusses on studies of total energy expenditure using doubly labeled water, the role of energy expenditure in the development of obesity, and the determinants of resting energy expenditure in children. The relatively few studies that have examined the regulation of energy and macronutrient intake in children are also reviewed. In terms of body composition, we focus on recent methodological studies that have developed existing techniques for application to the pediatric population, including dual energy X-ray absorptiometry and bioelectrical resistance. Lastly, we review existing information relating to measurement and alteration of body fat distribution in children.

Body Composition↗
PubMed1995

Absence of relaxation to lactate in human placental vessels of pregnancies with severe preeclampsia.

OBJECTIVE: Our objective was to determine whether the observed relaxation to lactate and other agents in placental vessels of normal pregnancies is altered in severe preeclampsia. STUDY DESIGN: Isolated placental arteries and veins from women with severe preeclampsia and uncomplicated term pregnancies were precontracted with prostaglandin F2 alpha under 5% oxygen and 5% carbon dioxide with the balance nitrogen (Po2 35 to 38 torr) and then exposed to lactate (1 to 10 mmol/L, pH 7.4, n = 8 to 15), arachidonic acid (0.01 to 10 mumol/L, n = 6 to 13), nitroglycerin (1 nmol to 1 mumol/L, n = 4 to 12), or forskolin (0.01 to 10 mumol/L, n = 6 to 9). The response to lactate was also examined in placental vessels from appropriate-for-gestational-age preterm deliveries (n = 8) for comparison with a similar group with severe preeclampsia (n = 8). The t test and analysis of variance statistics were used. RESULTS: Relaxation to lactate was markedly inhibited in both placental arteries and veins of women with severe preeclampsia compared with vessels from uncomplicated term or preterm pregnancies. Responses to the other relaxing agents were not altered in the severely preeclamptic vessels. CONCLUSIONS: In severe preeclampsia absence of lactate-induced dilatation of placental vessels may contribute to the fetal complications associated with impaired blood flow and vasospasm.

Adult↗
PubMed1995

Short bowel syndrome.

Improvements in parenteral nutrition and supportive therapy have led to a growing population of patients who survive for prolonged periods with short bowel syndrome. Definitive treatment for these patients requires innovative therapy based on a sound knowledge of small intestinal physiology and adaptation. Current understanding of short bowel pathophysiology and of intestinal adaptation are reviewed. Medical and surgical therapeutic options are described, highlighting the promotion of small bowel adaptation and methods to increase the small intestinal mucosal mass.

Adaptation, Physiological↗
PubMed1994

Chronic liver disease in Peru: role of viral hepatitis.

The prevalence of antibodies to hepatitis C virus (anti-HCV) was determined in 105 patients with biopsy-proven chronic liver disease and 128 comparison patients without any evidence of liver pathology living in Lima, Peru. Using a second-generation EIA screening and supplemental immunoblot assay, anti-HCV was detected in four of 13 patients with chronic hepatitis, in 11% of 85 patients with cirrhosis, and in none of seven patients with hepatocellular carcinoma. Only two (1.6%) comparison patients without liver disease had anti-HCV. Hepatitis B surface antigen (HBsAg) was found in 23% of patients with chronic hepatitis, 12% of patients with cirrhosis, and three of seven patients with hepatocellular carcinoma. There was no evidence of chronic viral hepatitis or alcohol abuse (reported by one-third of subjects) in 48% of chronic liver disease patients. These preliminary data suggest that among this South American population neither hepatitis B nor hepatitis C infection is the predominate cause of chronic liver disease and that other infectious or environmental factors may be important.

Adult↗
PubMed1994

Sequential intestinal lengthening procedures for refractory short bowel syndrome.

Better understanding of the long-term delivery of parenteral nutrition (PN) in neonates and children has increased the survival for patients who have neonatal short bowel syndrome. Most infants with short bowel syndrome experience progressive enteral adaptation and are weaned from PN. This report describes the authors' clinical experience with nine infants and children who had refractory short bowel syndrome; single or sequential procedures were performed to lengthen the small bowel. Gut lengthening procedures used included a small bowel nipple valve constructed distally, to provide temporary partial obstruction and thereby induce dilatation and lengthening of the proximal small intestine (six patients). Bianchi's technique was used in three patients primarily and in six others after the bowel had been dilated and lengthened by the nipple valve. Kimura's gut lengthening technique was used in one patient after the small bowel had spontaneously become dilated subsequent to a Bianchi procedure. In all, 16 lengthening procedures were performed on the nine patients. Preoperatively, the nine patients tolerated less than 10% of their caloric intake enterally, with no evidence of improvement for a minimum of 6 months. Small bowel segments ranged from 6 to 92 cm originally and were increased an average of 2 1/2 times the original length. Two patients have been totally weaned from PN. For the patients whose lengthening procedure was performed more than 1 year ago, the percentage of enteral caloric intake averages 50%. One of the patients was profoundly impaired neurologically and was not resuscitated from an apneic episode. Another patient died in his sleep of unknown causes 1 year after intestinal lengthening.(ABSTRACT TRUNCATED AT 250 WORDS)

Enteral Nutrition↗
PubMed1993

Properties of a lactate-induced relaxation in human placental arteries and veins.

OBJECTIVE: Our purpose was to determine the vasoactive effects and mechanism of action of lactate in human placental vessels by means of isometric muscle bath studies. STUDY DESIGN: Isolated 1 to 2 mm human placental arteries and veins from normal term pregnancies, precontracted with prostaglandin F2 alpha and incubated under a PO2 of approximately 35 torr were exposed to lactate, 1 to 10 mmol/L, (pH 7.4), pyruvate, hydrogen peroxide, nitroglycerin, or forskolin. The effects of endothelium removal or inhibitors of cyclooxygenase (indomethacin 10 mumol/L) and L-arginine metabolism (nitro-L-arginine 30 mumol/L) on the response to lactate and the effects of an antagonist of guanylate cyclase activation (methylene blue 10 mumol/L), cyanide (1 mmol/L), and hypoxia (PO2 8-10 torr) on responses to all agents were determined by analysis of variance and t test statistics. RESULTS: Lactate-elicited dose-dependent relaxation was not inhibited by endothelium removal, indomethacin, or nitro-L-arginine but was attenuated by methylene blue, cyanide, and hypoxia. Relaxation to hydrogen peroxide was inhibited by methylene blue and cyanide but not hypoxia. Relaxation to nitroglycerin was inhibited only by methylene blue, and relaxation to forskolin was not inhibited by these probes. Pyruvate did not produce a significant relaxation. CONCLUSIONS: These findings suggest that lactate causes relaxation in the human placental vessels by an oxygen and cyclic guanosine-3':5'-monophosphate-dependent mechanism, which may involve the generation of hydrogen peroxide but not the metabolism of arginine. Lactate-induced dilatation may be of importance during labor and in situations of acute and chronic fetal hypoxia.

Analysis of Variance↗
PubMed1993

Gestational diabetes alters human placental vascular responses to changes in oxygen tension.

OBJECTIVE: Our objective was to study tone responses caused by hypoxia, reoxygenation, and hydrogen peroxide in human placental vessels from gestational diabetic and normal term pregnancies. STUDY DESIGN: Isolated placental arteries and veins from women with well-controlled gestational diabetic and uncomplicated term pregnancies were precontracted with U46619 under 5% oxygen/5% carbon dioxide/balance nitrogen (PO2 35 to 38 torr) and then exposed to hypoxia (95% nitrogen/5% carbon dioxide) atmosphere (PO2 8 to 10 torr) for 5 to 7 minutes followed by rapid reoxygenation. Cumulative doses of hydrogen peroxide (1 to 100 mumol/L) were added at 2-minute intervals. The studies were conducted in both the presence and the absence of endothelium. Prostaglandin involvement was examined by treatment with indomethacin. Analysis of variance and t test statistics were used. RESULTS: After incubation under 5% oxygen, hypoxia caused a larger prostaglandin-independent relaxation in arteries and veins of women with gestational diabetes than in normal vessels. Placental vessels of women with gestational diabetes were found to undergo a significantly larger contraction than normal vessels when exposed to posthypoxic reoxygenation or micromolar concentrations of hydrogen peroxide. Both responses were eliminated and reversed to a relaxation by pretreatment with 10 mumol/L indomethacin in both gestational diabetic and normal vessels, consistent with mediation through the formation of prostaglandins. Removal of the endothelium did not appear to alter any of the observed responses. CONCLUSIONS: Gestational diabetes produces an enhancement of the observed relaxation caused by hypoxia and the contraction produced by reoxygenation or hydrogen peroxide.

Adolescent↗
PubMed1993

[Hepatitis C during puerperium].

Screening of donor blood for hepatitis B led to recognition that most cases of post-transfusion hepatitis were due to an agent known as non-A, non-B. Until recently the causative agent for non-A, non-B hepatitis was identified, being denominated hepatitis C virus. It is estimated that one-half of patient with hepatitis C develop chronic liver disease, and 20% of this will develop cirrhosis. We describe a patient who due to obstetric complications received blood transfusion and during puerperium developed an icteric syndrome which was identified as C hepatitis. We review the diagnostic methodology, clinical characteristics, evolution and preventive measures of the C hepatitis.

Adult↗
PubMed1992

The use of transcranial ultrasonography to predict stroke in sickle cell disease.

BACKGROUND: Stroke, especially cerebral infarction, is a major cause of morbidity and mortality in children with sickle cell disease. Primary prevention of stroke by transfusion therapy may be feasible if there is a way to identify the patients at greatest risk. Transcranial Doppler ultrasonography can measure flow velocity in the large intracranial arteries. The narrowing of these arteries, which leads to cerebral infarction, is characterized by an increased velocity of flow. METHODS: Using transcranial Doppler ultrasonography, we prospectively measured the velocity of cerebral blood flow in children and young adults being followed because of sickle cell disease. The results were classified as either normal or abnormal on the basis of the highest velocity of flow in the middle cerebral artery. Abnormal velocity was defined as a flow greater than or equal to 170 cm per second, a definition determined by post hoc analysis to maximize the predictive success of the test. The end point was a clinically apparent first cerebral infarction. RESULTS: Two hundred eighty-three transcranial ultrasound examinations were performed in 190 patients with sickle cell disease (age at entry, 3 to 18 years). After an average follow-up of 29 months, cerebral infarction was diagnosed in seven patients. In 23 patients the results of the ultrasound examinations were abnormal, and in 167 patients they were normal. The clinical and hematologic characteristics of the two groups were similar, but six of the seven strokes occurred among the 23 patients with abnormal ultrasound results (P less than 0.00001 by Fisher's exact test). In this group, the relative risk of stroke was 44 (95 percent confidence interval, 5.5 to 346). CONCLUSIONS: Transcranial ultrasonography can identify the children with sickle cell disease who are at highest risk for cerebral infarction. Periodic ultrasound examinations and the selective use of transfusion therapy could make the primary prevention of stroke an achievable goal.

Adolescent↗
PubMed1992

Hydrogen peroxide and reoxygenation cause prostaglandin-mediated contraction of human placental arteries and veins.

OBJECTIVE: Because our previous studies in several vascular preparations suggest that posthypoxic reoxygenation elicits tone responses by generation of hydrogen peroxide we compared the actions of reoxygenation and hydrogen peroxide on isolated human placental arteries and veins. STUDY DESIGN: Endothelium-intact and denuded arteries and veins (1 to 2 mm diameter, from normal term deliveries), incubated under 95% oxygen/5% carbon dioxide or 5% oxygen/5% carbon dioxide (balance nitrogen) and precontracted with 1 to 10 nmol/L U46619, were exposed to hypoxia (95% nitrogen/5% carbon dioxide, PO2 8 to 10 torr) followed by reoxygenation and to 1 to 100 mumol/L hydrogen peroxide in the presence and absence of the inhibitor of prostaglandin biosynthesis, 10 mumol/L indomethacin. RESULTS: In both arteries and veins posthypoxic reoxygenation or exposure to hydrogen peroxide produced vascular contraction that was eliminated or reversed to a modest relaxation by indomethacin, consistent with mediation by prostaglandins. Hypoxia after incubation with 5% oxygen, but not 95% oxygen, caused a modest prostaglandin-independent relaxation. Removal of the endothelium did not alter any of these responses. CONCLUSION: Placental arteries and veins show a similar prostaglandin-mediated contraction to hydrogen peroxide and posthypoxic reoxygenation, consistent with a possible involvement of hydrogen peroxide in the response to reoxygenation.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1992

Properties of an endogenous arachidonic acid--elicited relaxing mechanism in human placental vessels.

OBJECTIVE: Our objective was to examine the action of arachidonic acid on tone in isolated human placental arteries and veins (1 to 2 mm diameter) for mechanisms involving endothelium-derived mediators, the stimulation of guanylate cyclase, and prostaglandin and cytochrome P450 metabolites. STUDY DESIGN: Pharmacologic probes and endothelium-removal were used to examine the mechanism of relaxation to arachidonic acid (10 nmol/L to 10 mumol/L) observed in placental arteries and veins obtained after delivery from uncomplicated term pregnancies and precontracted with prostaglandin F2 alpha. RESULTS: Neither removal of the endothelium nor inhibition of prostaglandin biosynthesis with 10 mumol/L indomethacin, arginine-derived nitric oxide formation with 30 mumol/L nitro-L-arginine, or guanylate cyclase stimulation with 10 mumol/L LY83583 altered the observed relaxation to arachidonic acid in either preparation. However, this relaxation was markedly attenuated by 30 mumol/L proadifen (SKF-525A), an inhibitor of cytochrome P450, suggestive of a role for arachidonic acid metabolism by an epoxygenase or monooxygenase pathway. CONCLUSION: Human placental arteries and veins possess an endogenous mechanism of relaxation to arachidonic acid, which seems to be mediated by metabolites formed by a cytochrome P450 enzyme. This endogenous relaxation mechanism could function as a suppressor of vasospasm in the placental circulation.

Arachidonic Acid↗
PubMed1992

Transcranial Doppler correlation with cerebral angiography in sickle cell disease.

BACKGROUND AND PURPOSE: Cerebral infarction in sickle cell disease is associated with arterial narrowing or occlusions of intracranial arteries. Primary stroke prevention would be feasible if a noninvasive screening test could be developed to detect intracranial disease in patients before symptoms develop. METHODS: To determine the sensitivity and specificity of transcranial Doppler in detecting significant (greater than or equal to 50% lumen diameter reduction) intracranial arterial lesions, we compared transcranial Doppler and cerebral angiography in a primarily young, symptomatic group of 33 patients (18 males and 15 females) with sickle cell disease. RESULTS: From a total of 34 examinations, transcranial Doppler detected significant abnormalities in 26 of 29 (sensitivity 90%, specificity 100%). Five were normal by both techniques. The transorbital examination detected abnormalities in two patients whose studies were otherwise unremarkable. CONCLUSIONS: Transcranial Doppler is sensitive and specific for the detection of arterial vasculopathy of sickle cell disease. Screening should include a transorbital examination of the distal internal carotid artery as well as examination using the transtemporal approach.

Adolescent↗
PubMed1990

Cerebral vessel stenosis in sickle cell disease: criteria for detection by transcranial Doppler.

Ischemic stroke is a common and disabling complication of sickle cell disease (Hb SS). Most infarctions occur in the presence of intracranial stenotic lesions of the large vessels of the circle of Willis. Transcranial Doppler (TCD), by measuring flow velocity in these arterial segments, can detect focal stenosis on the basis of elevated flow velocity. We report the preliminary results of a prospective study to develop criteria for detection of stenotic lesions based on TCD and identification of patients with Hb SS at risk for stroke. Comparing the TCD findings from six patients with lesions demonstrated by angiography to those from 115 Hb SS children without stroke, we conclude: (a) middle cerebral (MCA), anterior cerebral (ACA), or internal carotid (ICA) artery mean velocities greater than 190 cm/s strongly suggest focal stenosis; (b) MCA or ACA mean velocities of 150 to 190 cm/s suggest abnormality but at present cannot be considered diagnostic of stenosis; (c) mean velocities up to 150 cm/s are possibly due to the effects of low hematocrit and/or young age, and cannot as yet be distinguished from velocity elevations due to vessel stenosis.

Adolescent↗
PubMed1990

Comparative neuroimaging with pathologic correlates in Alexander's disease.

We describe a case of pathologically confirmed Alexander's disease in which serial cranial ultrasound studies demonstrated unique findings of enlarging subependymal cysts with evolving periventricular hyperechogenicity. Computed tomographic scan of the head showed low attenuation of the periventricular white matter and centrum semiovale. Magnetic resonance imaging (MRI) demonstrated diffuse, confluent high signal predominantly in frontal white matter. These imaging modalities, particularly cranial ultrasound and MRI, may be useful tools in the diagnostic evaluation of children with degenerative neurologic disease, megalencephaly, and suspected Alexander's disease.

Brain↗
PubMed1989

[Primary sclerosing cholangitis associated with Sjögren's syndrome, retroperitoneal fibrosis and chronic pancreatitis. Report of a case].

Primary Sclerosing Cholangitis (PSC) is an unusual chronic, cholestatic disease of unknown etiology, more frequently seen in young adults in close relationship with Chronic Ulcerative Colitis. We report the case of a 30 year old woman, coming from the peruvian amazon with PSC associated with Sjögren Syndrome, Chronic Pancreatitis and Retroperitoneal Fibrosis, without colonic involvement. She was treated with external biliary drainage and controlled for 12 months. In this paper, clinical, biochemical, radiological, histological and therapeutic features are reviewed as well as its possible immunologie autoimmune origin.

Adult↗