Biomedical subjects

C Reyes

Publications and source records attributed to C Reyes.

At least 19 recordsLinked to original sources

PubMed1997

A directional clustering technique for random data classification.

This paper introduces a new clustering technique for random data classification based on an enhanced version of the Voronoi diagram. This technique is optimized to deal in the best way possible with data distributions which in their spatial representations experience overlap. A mathematical framework is given in view of this enhanced analysis and provides insight to key issues involving (a) the use of a correction process to complement the traditional Voronoi diagram and (b) the introduction of directional vectors in Gaussian and elliptical data distributions for enhanced data clustering. The computational requirements of the proposed approach are provided, and the computer results involving both randomly generated and real-world data prove the soundness of this clustering technique.

Data Interpretation, Statistical↗

PubMed1997

Cytomegalovirus enteritis in a premature infant.

BACKGROUND/PURPOSE: Up to 2.5% of newborn infants are cytomegalovirus (CMV) positive at birth. Five percent will be symptomatic at birth, including cytomegalic inclusion disease. Symptoms such as hearing loss and mental retardation will ultimately develop in 15%. METHODS: The authors describe a case of CMV enteritis in a 2.2-kg newborn that presented as necrotizing enterocolitis (NEC) and subsequently developed a colonic stricture. RESULTS: There are four reports of neonatal CMV enteritis in the nonEnglish-language literature. Cytomegalovirus enteritis has become prevalent among the immunosuppressed pediatric and adult patient population. CONCLUSIONS: We propose the addition of CMV to the list of pathogens responsible for NEC. A review of neonatal CMV infection is provided.

Cytomegalovirus Infections↗

PubMed1997

Fetal lung maturation. Comparison of biochemical indices in gestational diabetic and nondiabetic pregnancies.

OBJECTIVE: To compare the biochemical maturation of the components of the lung profile according to gestational age between reliably dated gestational diabetic and nondiabetic pregnancies. STUDY DESIGN: Lung maturation was compared in reliably dated pregnancies in 501 gestational diabetic women and 561 nondiabetic women. Lecithin/sphingomyelin ratio (L/S) and phosphatidylglycerol (PG) were evaluated by analysis of variance according to the presence or absence of diabetes and weeks of gestational age. The effect of gestational diabetes on fetal lung maturation was determined by analysis of variance. RESULTS: The gestational diabetic group had no clinical or statistical differences in L/S ratios as compared to the nondiabetic patients at any gestational age. There were no differences in mean percent PG between the diabetic and nondiabetic groups at any gestational age. By 37 completed weeks, 86% of the L/S ratios and 78% of the PG values were mature in the diabetic group as compared to 80% of the L/S ratios and 78% of the PG values in the control group (P = .33 and .43, respectively). CONCLUSION: In reliably dated gestational diabetic pregnancies, biochemical maturation of the fetal lung strongly correlates with gestational age and does not appear to be significantly delayed when compared to a nondiabetic control group.

Adult↗

PubMed1996

A complete genomic screen for multiple sclerosis underscores a role for the major histocompatability complex. The Multiple Sclerosis Genetics Group.

Multiple sclerosis (MS), an inflammatory autoimmune demyelinating disorder of the central nervous system, is the most common cause of acquired neurological dysfunction arising in the second to fourth decades of life. A genetic component to MS is indicated by an increased relative risk of 20-40 to siblings compared to the general population (lambda s), and an increased concordance rate in monozygotic compared to dizygotic twins. Association and/or linkage studies to candidate genes have produced many reports of significant genetic effects including those for the major histocompatability complex (MHC; particularly the HLA-DR2 allele), immunoglobulin heavy chain (IgH), T-cell receptor (TCR) and myelin basic protein (MBP) loci. With the exception of the MHC, however, these results have been difficult to replicate and/or apply beyond isolated populations. We have therefore conducted a two-stage, multi-analytical genomic screen to identify genomic regions potentially harbouring MS susceptibility genes. We genotyped 443 markers and 19 such regions were identified. These included the MHC region on 6p, the only region with a consistently reported genetic effect. However, no single locus generated overwhelming evidence of linkage. Our results suggest that a multifactorial aetiology, including both environmental and multiple genetic factors of moderate effect, is more likely than an aetiology consisting of simple mendelian disease gene(s).

Chromosome Mapping↗

PubMed1996

Interactions among receptors, thyroid hormone response elements, and ligands in the regulation of the rat uncoupling protein gene expression by thyroid hormone.

Uncoupling protein (UCP) is essential to the thermogenic function of brown adipose tissue (BAT). Thyroid hormone stimulates the rat UCP gene through two thyroid hormone response elements (TRE) located upstream of -2,300 and separated by 27 bp. They are an everted repeat (upstream TRE or upTRE) and a direct repeat (down-stream TRE or dnTRE). The goal of the present studies was to investigate whether these TREs interact and how such an interaction could contribute to explain the UCP responsiveness to T3 in vivo. We therefore aimed to define: the heterodimeric partner of the T3 receptor (T3R); the role of T3 in the receptor-receptor and receptors-DNA interactions; how such in vitro interactions relate to the enhancer function of TREs; and how the two TREs interact. Studies included electrophoretic mobility shift assays, utilizing T3R and retinoid X receptors (RXR); DNA footprinting; and transient transfections of HIB-1B cells, a BAT-derived cell line. As in many previously described TREs, the partner of the T3R is RXR. The unliganded T3Rs bind to the TREs as homodimers, which act as repressors of transcription. T3 reduces the binding of T3R homodimers, hence relieving the repression, and stimulates the binding of heterodimers and transcription in proportion to the heterodimer binding to the elements. Although qualitatively similar in these regards, there were important quantitative differences between both TREs. The upTRE binds more T3R homodimers and less T3R-RXR heterodimers than the dnTRE, and T3 more readily facilitates heterodimer binding to the dn- than to the upTRE. These in vitro characteristics are reflected in a lower efficiency of T3 to relieve T3R homodimer-mediated repression and to stimulate transcription through up-than through dnTRE. There were also significant interactions between the two TREs both in the binding of the receptors, T3R and RXR, and in the responsiveness to T3. By itself, each TRE responded modestly to T3, upTRE with lower sensitivity and dnTRE with higher sensitivity than traditional TREs, whereas together, in the context of the gene sequence, they mediated a response greater than the sum of those mediated by each TRE separately, with an intermediate sensitivity to T3. Thus, two TREs that are inadequate to explain the responsiveness of the UCP gene to T3, together form a complex unit appropriate for the regulation of the gene by thyroid hormone. These interactions represent yet another way TREs can shape up the responsiveness of genes to thyroid hormone.

Adipocytes↗

PubMed1996

A complex retinoic acid response element in the uncoupling protein gene defines a novel role for retinoids in thermogenesis.

Retinoids have been implicated in the control of cell proliferation and differentiation, and in several developmental processes. We report here the molecular bases for a metabolic role of RA, by showing that the expression of the uncoupling protein (UCP), the key element in brown adipose tissue (BAT) thermogenesis, is stimulated by retinoic acid (RA). Both all-trans-RA and 9-cis-RA powerfully increase UCP messenger RNA levels in isolated rat brown adipocytes. Transient transfection experiments in HIB-1B cells, a BAT-derived cell line, identified the sequence -2399/-2490 (called R90) as the RA-responsive sequence in the rat UCP gene. R90 mediated a 20- to 70-fold stimulation of the chloramphenicol acetyl transferase reporter gene by maximal concentrations of all-trans-RA or 9-cis-RA. Non-BAT cells were significantly less responsive. RA effect was also less when chloramphenicol acetyl transferase gene was driven by a heterologous promoter instead of the UCP minimal promoter. By footprinting and site-directed mutagenesis, we identified three discrete sequences as being essential for the RA response within R90, thus defining the complex RA response element (RARE) of this gene. Critical bases in these sequences are arranged in pairs of putative half-sites. RAR gamma-RXR heterodimers can bind to the R90 as revealed by electrophoretic mobility shift assays using in vitro translated receptors, and HIB-1B nuclear extracts with anti-RAR gamma or anti-RXR antibodies. The participation of RAR gamma-RXR heterodimers in RA stimulation is further supported by transient transfection experiments overexpressing selected receptors and dose-response analyses of RA isomers and analogues. These results show that retinoids strongly stimulate the rat UCP gene expression through a complex RARE, composed of three pairs of half-sites, and define a novel role for retinoids in the regulation of facultative thermogenesis and energy expenditure.

Adipocytes↗

PubMed1994

Cytologic patterns of metastatic thymoma: diagnosis by fine-needle aspiration biopsy.

Thymomas are the most frequent primary tumors of the anterior mediastinum. These lesions are slow growing and can be locally invasive, but extrathoracic metastases are rare, occurring in less than 2% of cases. Fine-needle aspiration biopsy (FNAB) may be helpful in making the diagnosis of metastatic thymoma, with or without a clinical history of primary mediastinal thymoma. We report three cases of metastatic thymoma diagnosed by FNAB. Each case illustrates a distinctive cytologic pattern. While two of the patients had a history of histologically confirmed thymoma 11 and 13 years previously, a third patient presented with an enlarged supraclavicular lymph node and pulmonary nodules, and no prior diagnosis of thymoma. These cases demonstrate that based on distinctive cytologic patterns and features, a diagnosis of metastatic thymoma can be made with FNAB. Ancillary studies will often confirm the diagnosis.

Aged↗

PubMed1993

Hepatoid carcinoma of the stomach.

A patient with primary gastric carcinoma exhibiting hepatoid differentiation is described. The tumor itself was not associated with a high serum alpha-fetoprotein, but the cells stained positive for alpha-fetoprotein and alpha-1 antitrypsin. The patient underwent a total gastrectomy and wedge excision of the liver metastasis. The presence of metastatic hepatoid adenocarcinoma of the stomach should be considered in a patient who, during surgery for a primary gastric carcinoma, is found to have a liver metastasis that is diagnosed by frozen-section biopsy as a hepatoma. Because of lymph node and liver metastasis, prognosis appears to be poor for such patients.

Adenocarcinoma↗

PubMed1993

Simple technique for determination of the correct length of percutaneous tunnelled catheters in neonates and children.

A simple technique for determining the correct catheter length in percutaneous tunnelled catheters in infants and young children has been devised that virtually guarantees accurate catheter tip placement. Sixty-six patients, aged newborn to 5 years (mean, 1.6 years) have successfully undergone this technique. It is safe, simple, precise, quick, and cost effective. It requires only a hemostat, a suture, and the supplies provided in the prepackaged catheter kit. This technique should be used whenever a percutaneous technique for accessing the vein is used and fluoroscopy is available.

Anthropometry↗

PubMed1993

[Major adverse reactions to propylthiouracil in 586 cases of hyperthyroidism].

Aiming to know the incidence and evolution of major adverse reactions to propylthiouracil in patients with hyperthyroidism, we performed a retrospective analysis of 586 patients treated between 1982 and 1992. All known complications associated to the use of propylthiouracil were considered major adverse reactions, when other causes were discarded. Eight patients (1.4% of the sample) had major adverse reactions: three had agranulocytosis, 3 hepatitis, 1 cholestasis and 1 vasculitis. All had a good evolution after discontinuing the drug. The patients with agranulocytosis were treated with antibiotics and the patient with cholestasis received prednisone. We conclude that major adverse reactions to propylthiouracil are infrequent, that they occur preferentially during the first months of treatment, earlier after reexposure and that there was no associated mortality.

Adolescent↗

PubMed1992

Mycobacterium kansasii infection following primary pulmonary malignancy.

The purpose of this study was to determine whether any of the Mycobacterium kansasii cases were the consequences of primary lung malignancy. The records and chest x-ray films of 295 patients with M kansasii pulmonary infection were reviewed. The infection was found to complicate the primary lung neoplasm in four cases. Three patients had had treatment for malignancy: one patient with small cell carcinoma received chemotherapy, steroids and radiation; one with adenocarcinoma underwent a lobectomy and radiation; and the third patient had a lobectomy and radiation for malignant fibrohistiocytoma. The fourth patient developed the infection three years after lung malignancy manifested itself, which was only a few months before the clinical evidence of distant metastasis with adenocarcinoma was detected. We suggest that this infection be considered in patients from M kansasii endemic areas, especially after they have received radiation treatment for lung malignancy. This association has never been described before.

Humans↗

PubMed1991

[Catheterization of petrous sinus and selective determination of ACTH: usefulness in the management of Cushing's syndrome in 2 cases].

Two patients with Cushing's syndrome are reported. The syndrome was the consequence of relapse after transphenoidal resection of a pituitary tumor in one and due to occult ACTH secretion in the other. Determination of ACTH after bilateral petrosal sampling in both cases and after systemic venous sampling at different sites in one, allowed localization of the source of hormone secretion which was confined to one side of the hypophysis in one case and to the thorax in the other. Hypophyseal resection in the first case and bilateral adrenal resection in the other were performed successfully. The value of this diagnostic test is analyzed.

ACTH Syndrome, Ectopic↗

PubMed1990

Anatomic and functional abnormalities of the esophagus in infants surviving congenital diaphragmatic hernia.

As more infants with congenital diaphragmatic hernia (CDH) survive by means of extracorporeal membrane oxygenation (ECMO), new clinical observations are being made. We report anatomic and functional abnormalities of the esophagus in these infants. Twenty-two of 30 infants with CDH survived. Three of 7 non-ECMO-treated infants and 14 of 17 ECMO-treated infants had an air- or fluid-filled mediastinal mass that was confirmed by an upper gastrointestinal series as ectatic esophagus. Contrast studies demonstrated severe gastroesophageal reflux. Intra-esophageal pH monitoring confirmed significant reflux (Euler scores greater than 50) in 69% of tested patients. Prolonged acid clearance in most patients implied abnormal peristalsis. Hydramnios was correlated to the observed esophageal abnormalities, being present in 13 of 16 infants with an available amniotic history. All patients had symptomatic gastroesophageal reflux managed without antireflux surgery and were discharged 36 +/- 2 days after initiation of feeding. Follow-up (range: 7 to 56 months; mean: 32 months) showed that weight gain in affected children was slower than in those not affected. All but one are asymptomatic. Repeat upper gastrointestinal series shows persistent ectasia but less gastro-esophageal reflux. Gastroesophageal reflux/ectasia is a new observation with CDH. The associated hydramnios may result from proximal foregut obstruction by kinking the gastroesophageal junction with CDH. The radiographic appearance can be quite unusual. Clinical manifestations of gastro-esophageal reflux are manageable without surgery but may account for the observed compromised growth.

Dilatation, Pathologic↗

PubMed1989

[Primary hyperparathyroidism: usefulness of high resolution echography in local diagnosis].

Recent reports show a better surgical outcome in primary hyperparathyroidism when an accurate preoperative localization of the lesion in available. We performed high resolution sonography in 23 consecutive patients (20 women) with biochemically proven hyperparathyroidism. Twenty two of them were operated on and their sonographic reports were compared to the surgical and pathological findings (20 adenomas, 1 carcinoma and 1 hyperplasia). One patient did not have surgery but the sonogram was compared to a Tl 201-Tc99 scintigram that suggested an adenoma. Sonography showed a single parathyroid tumor in 17 patients and failed to demonstrate a lesion in six. There were two false positives and 6 false negatives. The sensitivity was 71.5% and the positive predictive value was 88%. Three out of 6 patients with a negative sonography had an adenoma located out of reach for the method. Our results show that the high resolution sonography is a useful, non invasive method to localize abnormally enlarged parathyroid glands in hyperparathyroidism and we think it should be performed in every patient with a biochemical diagnosis of this disease.

Adult↗

PubMed1988

[Quantitative morphologic studies of so-called dynamic, eccentric coronary stenoses in cases of acute coronary death].

The residual normal wall segment of an eccentric stenosis of the coronary artery can reduce the residual lumen by spastic contraction of the media. Such dynamic coronary artery stenoses may consequently cause or intensify myocardial ischemia or may lead to sudden coronary death due to dysrhythmia. In 39 cases of sudden coronary death, the histological cross section of extramural coronary arteries were measured by planimetry after postmortem coronary angiography. Of a total of 382 stenoses wit more than 45% narrowing, 178 (48.6%) were of the eccentric kind. These eccentric stenoses of the coronary artery were localized in the RIVA in 48%. On average, 4.5 eccentric stenoses were found in each case of coronary death. Eccentric stenoses with round (49.4) or elliptically situated (35,3%) restenoses was on average 30.5% of the residual lumen wall. The quantitative findings show that the high percentage of eccentric stenoses with a larger normal wall segment is of functional significance with regard to acute coronary deficiency. The morphological description and evaluation of the coronary sclerosis should also take into consideration the kind of stenosis.

Angina Pectoris↗

PubMed1988

Extracorporeal membrane oxygenation causes significant changes in intracranial pressure and carotid artery blood flow in newborn lambs.

The effects of ECMO on cerebral dynamics, particularly in the face of asphyxia, are largely unknown. We inquired as to whether carotid artery blood flow (CABF) and intracranial pressure (ICP) were affected by carotid artery/jugular vein ligation, asphyxia, ECMO, and ECMO with asphyxia. Lightly sedated newborn lambs (two to four days old, 3 to 4 kg) in four groups were monitored for mean ICP by an epidural sensor, mean CABF by a flow probe, and mean arterial pressure. Mean values were determined for the duration of each step of the experiment. ECMO was venoarterial at 100 to 120 mL/kg/min. CABF and ICP were measured in group 1 before and after CA/JV ligation; in group 2 during normoxia/normocapnia followed by hypoxia (30 to 40 torr)/hypercapnia (70 to 90 torr); in group 3 before, during, after ECMO while normoxic/normocapnic throughout; and in group 4 as ECMO was begun while hypoxic/hypercapnic. Vessel ligation alone caused no significant CABF/ICP changes. Asphyxia caused physiologic increases in CABF (P less than .03) and ICP (P less than .01). ECMO alone caused a significant decrease in ICP (P less than .003). ECMO with asphyxia caused an even more severe decrease in ICP (P less than .001) combined with augmented CABF (P less than .03). The ICP decrease was limited to the duration of ECMO. Possible explanations include loss of cerebral autoregulation induced by hypoxia/hypercarbia and alterations in cerebral venous drainage necessitated by this method of cardiopulmonary bypass.

Animals↗

PubMed1988

Right pneumonectomy syndrome: a lethal complication of lung resection in a newborn with cystic adenomatoid malformation.

A newborn girl underwent a right pneumonectomy for cystic adenomatoid malformation. She subsequently developed compression of the trachea and left mainstem bronchus by a combination of aortic arch, pulmonary artery, and ductus arteriosus. She died while planning aortic suspension, and the anatomic relationships were confirmed by autopsy. This problem is potentially treatable by a variety of means.

Coronary Angiography↗

PubMed1988

Selective use of extracorporeal membrane oxygenation in the management of congenital diaphragmatic hernia.

Extracorporeal membrane oxygenation (ECMO) provides lung rest for moribund infants with congenital diaphragmatic hernia (CDH) after deterioration from a "honeymoon" period. This suggests that unstable pulmonary hypertension determines demise more than pulmonary hypoplasia. We avoided treating overwhelming pulmonary hypoplasia by using ECMO only if the premoribund condition had been marked by evidence of adequate lung parenchyma as a best preductal PO2 greater than 100 torr and PCO2 less than 50 torr with maximal therapy. Twenty-six CDH infants with respiratory distress within 4 hours survived operation. Five were not ECMO candidates, with best PO2 33 +/- 9, PCO2 157 +/- 30 torr, and died. Seven honeymoon infants, with best PO2 325 +/- 80, PCO2 27 +/- 5, survived without ECMO. Fourteen additional infants had honeymoon 26 +/- 13 hours with PO2 256 +/- 48, PCO2 30 +/- 8 followed by a-AdO2 gradients 600 torr x 16 +/- 4.5 hours despite maximal therapy. All 14 were treated with ECMO for 48 to 210 hours. Arterial blood gas values at initiation were PO2 34 +/- 6, PCO2 59 +/- 19, and pH 7.22 +/- 0.2. Right-to-left shunting due to pulmonary hypertension was documented by oximetry and two-dimensional echo/Doppler examination. Twelve of 14 (86%) ECMO-treated infants survived with normal arterial blood gas values on room air, no right-to-left shunting, and no gross neurologic sequellae to date. Two of 14 died. Improvement on ECMO was marked by positive hyperoxia response and decreased right-to-left shunting.(ABSTRACT TRUNCATED AT 250 WORDS)

Carbon Dioxide↗