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Biomedical subjects

R Miranda

Publications and source records attributed to R Miranda.

At least 55 records · Page 3Linked to original sources
PubMed1997

Paroxetine increases heart rate variability in panic disorder.

Panic patients have decreased heart rate variability, a risk factor for sudden cardiac death, and increased rates of cardiac death and stroke. Imipramine has been found to further reduce heart rate variability in panic. This study uses power spectral analysis to compare autonomic components of heart rate variability in 16 unmedicated control subjects and 17 panic patients before and after treatment with paroxetine at 20 mg/day for 4 weeks. Patients had higher predrug reclining and standing sympathetic activity than control subjects. After drug, patients' total sympathetic activity decreased. Predrug patients failed to increase sympathetic activity on orthostasis, lacking the normal baroreflex response found in control subjects. After drug, patients normalized this sympathetic component of the baroreflex response. Before drug, patients' parasympathetic reclining and standing activity did not differ from control subjects, and patients showed the normal orthostatic parasympathetic decrease. After drug, patients' total parasympathetic activity increased, whereas the baroreflex response was preserved. Nine medicated patients had more than a 50% reduction of panic attacks. In view of paroxetine's increase of heart rate variability, potential benefits of selective serotonin reuptake inhibitors in decreasing cardiac mortality in panic disorder are discussed.

Adult↗
PubMed1997

Increased synthesis of cholesterol stearate in flanking organ from gonadectomized female hamsters treated with progesterone and 5 alpha-dihydroprogesterone.

We demonstrated for the first time that progesterone and 5 alpha-dihydroprogesterone stimulate [U-14C]glucose incorporation into lipids in gonadectomized female hamster flanking organs. We also found that cholesterol stearate is the major lipid synthesized female hamster flanking organs under progesterone and 5 alpha-dihydroprogesterone stimulation. In this manner, progesterone and 5 alpha-dihydroprogesterone alter the consistency of sebum from gonadectomized female glands.

5-alpha-Dihydroprogesterone↗
PubMed1996

Identification and analysis of the u6 small nuclear RNA gene from Entamoeba histolytica.

Among the small nuclear RNAs (snRNAs) involved in the spliceosomal processing of pre-mRNA, U6 is the most conserved. As a first evidence for the presence of the splicing machinery in the amitochondrial protozoan Entamoeba histolytica (Eh), we have cloned the u6 snRNA gene. We find that in this organism u6 is a single copy gene that is transcribed as a poly(A)- RNA molecule of approximately 105 nucleotides. We have mapped the 5' end of the U6 snRNA transcript, and identified typical elements of a putative polymerase III promoter. This is the first snRNA gene reported in Eh. Sequence analysis indicates that this gene contains all the conserved nucleotides known to be important for U6 snRNA function. These results, in conjunction with the earlier finding of genes that contain pre-mRNA introns, suggest that Eh has a functional spliceosomal complex.

Animals↗
PubMed1996

Circular nodes in neural networks.

In the usual construction of a neural network, the individual nodes store and transmit real numbers that lie in an interval on the real line; the values are often envisioned as amplitudes. In this article we present a design for a circular node, which is capable of storing and transmitting angular information. We develop the forward and backward propagation formulas for a network containing circular nodes. We show how the use of circular nodes may facilitate the characterization and parameterization of periodic phenomena in general. We describe applications to constructing circular self-maps, periodic compression, and one-dimensional manifold decomposition. We show that a circular node may be used to construct a homeomorphism between a trefoil knot in R3 and a unit circle. We give an application with a network that encodes the dynamic system on the limit cycle of the Kuramoto-Sivashinsky equation. This is achieved by incorporating a circular node in the bottleneck layer of a three-hidden-layer bottleneck network architecture. Exploiting circular nodes systematically offers a neural network alternative to Fourier series decomposition in approximating periodic or almost periodic functions.

Neural Networks, Computer↗
PubMed1996

Nerve growth factor (NGF) regulation of estrogen receptors in explant cultures of the developing forebrain.

Estrogen profoundly affects the organization of the nervous system. Its receptor, a nuclear transcription factor, is widely expressed in the developing forebrain. Earlier work established that forebrain estrogen target neurons coexpress nerve growth factor (NGF) receptors and receptor mRNA. The present study examined the regulation of forebrain estrogen receptors by NGF, using organotypic cultures of the developing cerebral cortex and basal forebrain. NGF significantly increased nuclear estrogen binding in cortical but not basal forebrain explants. Both cortical and basal forebrain explant cultures express the NGF receptor, TrkA. However, our earlier observation that developing cortical neurons, unlike basal forebrain neurons, widely coexpress mRNAs for NGF and its cognate receptors, suggests that in the present study cortical neuronal responses to exogenous NGF may have been primed by autocrine mechanisms. Alterations in nuclear estrogen binding but not estrogen receptor mRNA levels suggests that NGF may regulate cortical estrogen receptors posttranscriptionally.

Animals↗
PubMed1996

Delayed primary repair of intrathoracic esophageal perforation: is it safe?

The management of intrathoracic esophageal perforation with delayed diagnosis is a subject of controversy. Because of the obvious advantages of primary repair as a simple single-stage operation, this technique was preferentially used to treat 18 of 22 consecutive patients with esophageal perforation. These patients were stratified into three groups according to the time interval between perforation and repair: group A, less than 6 hours, five patients (28%); group B, 6 to 24 hours, six patients (33%); and group C, more than 24 hours, seven patients (39%). Group A patients were older (p < 0.05) and group B had fewer iatrogenic perforations (B, 17%; A, 80%; C, 57%, p < 0.1). Additional tissue was used to buttress the repair site in all three groups (A, 3/5 patients, 60%; B, 4/6 patients, 67%; C, 6/7 patients, 86%; p = not significant). In seven patients (39%), a fundic wrap was used to reinforce the site of primary repair. The outcomes of the three groups were analyzed. Group A had the lowest proportion of postoperative leaks (A, 0/4 patients, 0%; B, 4/6 patients, 67%; C, 5/6 patients, 83%; p < 0.05) and postoperative morbidity (A, 2/5 patients, 40%; B, 6/6 patients, 100%; C, 6/7 patients, 86%; p < 0.1). However the increased incidence of leak and morbidity did not lead to an increase in mortality. One death occurred in each group, with an overall mortality of 17% (A, 1/5 patients, 20%; B, 1/6 patients, 17%; C, 1/7 patients, 14%; p = not significant). We conclude that in the era of advanced intensive care capabilities, primary repair of intrathoracic esophageal perforation can be safely accomplished in most patients regardless of the time interval between perforation and operation. Leakage at the suture site is common unless primary repair is carried out without delay. Postoperative leakage, however, is usually inconsequential and does not necessarily result in an adverse outcome.

Aged↗
PubMed1996

Immunohistochemical detection of parathyroid hormone-related protein in a rare variant of hepatic neoplasm (sclerosing hepatic carcinoma).

Sclerosing hepatic carcinoma represents an uncommon subtype of hepatic malignancy, frequently associated with hypercalcemia. We applied immunohistochemistry using the avidin-biotin-complex technique to examine the presence of parathyroid hormone-related protein (PTHrP) in formalin-fixed and paraffin-embedded sections of tissue from a case of sclerosing hepatic carcinoma obtained at autopsy. Two polyclonal antibodies against the regions 24 to 35 and 107 to 111 of human PTHrP, and a monoclonal antibody that recognizes the human sequence 38 to 64 of this protein, were used. Preabsortion tests using the corresponding synthetic peptide as antigen were done with these antibodies. The neoplastic tissue displayed cytoplasmic immunostaining, diffuse with the antibodies against the amino- or carboxy-terminal regions of PTHrP, and with a predominant peripheral pattern when using the antibody to the midregion of the molecule. Tumor cells positive for PTHrP were also positive for hepatocellular markers cytokeratins 10, 17, and 18, but negative for chromogranin A. Our findings provide the first evidence for PTHrP production in the sclerosing subtype of hepatic carcinoma.

Antibodies, Monoclonal↗
PubMed1996

Burkitt's lymphoma in Brazil: strong association with Epstein-Barr virus.

The incidence of Burkitt's lymphoma (BL) in Brazil is intermediate between the endemic form of equatorial Africa and the sporadic form in the United States. To characterize these lymphomas, we evaluated the clinical, morphologic, and immunohistochemical features of 24 Brazilian cases of BL. We also analyzed the cases for the presence of Epstein-Barr virus (EBV)-RNA using a highly sensitive and specific method of in situ hybridization. Most cases presented with involvement of intraabdominal organs, similar to the sporadic form of BL. EBV-RNA was detected in 17 of 24 cases (71%) in all or virtually all the tumor cells. This prevalence of EBV-positivity in our cases is intermediate between the endemic form of BL in equatorial Africa (100%) and the sporadic form in the United States (30%). These findings suggest that EBV plays an important role in the pathogenesis of BL in Brazil. This intermediate incidence of EBV infection may explain in part the differences of incidence of BL in different geographic regions.

Adolescent↗
PubMed1995

Chelation therapy.

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Chelation Therapy↗
PubMed1995

Inorganic-ion resistance by bacteria isolated from a Mexico City freeway.

Bacteria were isolated from soil samples, containing high exchangeable lead concentrations, obtained from a busy freeway in the México City metropolitan area. Forty-five selected strains (86.7% Gram-positive) had a single MIC distribution pattern for lead (800-1600 micrograms/ml lead nitrate) and were considered lead-resistant. The isolates showed variable levels of resistance to arsenate (86.7%), chromate (66.7%), cadmium (57.6%), and mercury (31.1%) ions. Multiple inorganic-ion resistance was shown by all strains.

Arsenates↗
PubMed1995

One-stage primary repair of distal esophageal perforation using fundic wrap.

Esophageal leak following primary repair of esophageal perforation is a serious complication that can lead to severe mediastinitis and sepsis. Complete diversion with esophageal exclusion or resection is designed to minimize further mediastinal contamination. However, this approach is not necessarily associated with less morbidity or mortality. Furthermore, a second stage operation is required to restore esophageal continuity. From 1986 to 1994, we performed a one-stage primary repair of the distal esophagus in seven patients with either iatrogenic (n = 5) or spontaneous (n = 2) perforations and reinforced the repair by a fundic wrap. One patient underwent an additional modified Heller myotomy for achalasia. Delay between perforation and operation was less than 6 hours in 3 patients, 6 to 24 hours in 2 patients, and greater than 24 hours in 2 patients. Only one patient (14%) developed a small esophageal leak that spontaneously resolved with adequate mediastinal drainage, intravenous antibiotics, and aggressive nutritional support. One patient (14%), whose repair was delayed by 12 hours, died postoperatively of profound sepsis. This patient was moribund from sepsis preoperatively, and postmortem examination of the esophagus revealed no evidence of esophageal leak. Esophageal continuity was maintained in all patients. The median length of stay was 21 days (range, 15-58 days). We conclude that primary reinforced repair of esophageal perforation using a fundic wrap is an effective method of treatment for distal esophageal perforation, even when the repair is delayed by more than 24 hours.

Adult↗
PubMed1995

Patients with TSH-secreting pituitary tumor possess different TSH molecular isoforms.

The objective of the study was to demonstrate if TSH secreted by a pituitary tumor correlates with particular molecular forms of TSH. Aliquots of sera from two hyperthyroid patients with TSH-secreting pituitary tumor were subjected to gel filtration chromatography to be assayed for TSH. The assay was repeated in one case after transsphenoidal adenomectomy. Sera from two additional patients with long-lasting primary hypothyroidism, and from two subjects with normal thyroid function were also chromatographed. Molecular weight (mol wt) of isoforms was calculated on a calibration curve obtained with molecular markers. The molecular variants were characterized on the basis of elution volume, mol wt, and partition coefficient. Chromatographic profile of the two cases with TSH-secreting pituitary tumor exhibited mainly two peaks of TSH immunoreactivity. The major component of immunoreactivity eluted as a peak corresponding with the alpha-subunit of the glycoprotein. This pattern was different from that obtained in sera from two women with hypothyroidism, which was heterogeneous and presented a predominance of molecular variants corresponding with mol wt of 22 and 29 kD, and no alpha-subunit was present. In cases of normal thyroid function the chromatographic profile showed that the major proportion of TSH eluted simultaneously with the labeled standard and 22 kD marker. These results demonstrate that TSH secreted by pituitary tumors is composed of various molecular forms and the alpha-subunit is the major component. This chromatographic profile is different from that observed in other cases with elevated concentrations of TSH as it occurs in primary hypothyroidism.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Giant cell fibroblastoma of the scrotum. A case report.

A case of giant cell fibroblastoma occurring in the scrotum of a 21-year-old male is described. It may have been a recurrence of a previous lesion in the same region, which was only clinically diagnosed as fibrolipoma when excised 10 years before. Giant cell fibroblastoma is a benign, locally recurrent tumor of youth and childhood which arises from superficial soft tissue. To our knowledge, only 2 other cases of scrotal involvement by this neoplasm have been reported.

Adult↗