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Biomedical subjects

C Porras

Publications and source records attributed to C Porras.

6 recordsLinked to original sources

[Large myxoma of the right atrium].

We describe the case of a patient in whom two-dimensional echocardiography, performed due to dissociated cholestasis and jugular ingurgitation, demonstrated a huge mass in the right atrium which prolapsed in the right ventricle. Intraoperative transesophageal echocardiography was performed to further assess the dimension and characteristics of the mass and to discard the involvement of associated structures. The patient underwent a cardiopulmonary bypass surgery and the mass (12 * 5 cm) was removed without complications. Histologic examination confirmed the diagnosis of myxoma. This case is of interest because of the size of the mass, and is centered in the diagnosis following clinical suspicion due to the pattern of dissociated cholestasis and jugular ingurgitation leading to surgery to prevent the potential embolic complications.

Heart Atria↗

Effects of hypoxia and glutathione depletion on hemoglobin- and myoglobin-mediated oxidative stress toward endothelium.

We investigated the toxicity of hemoglobin/myoglobin on endothelial cells under oxidative stress conditions that include cellular hypoxia and reduced antioxidant capacity. Bovine aorta endothelial cells (BAECs), grown on microcarrier beads, were subjected to cycles of hypoxia and reoxygenation in a small volume of medium, and endothelial cell monolayers were depleted of their intracellular glutathione (GSH) by treatment with buthionine sulfoximine. Incubation of diaspirin cross-linked hemoglobin (DBBF-Hb) or horse skeletal myoglobin (Mb) with BAECs subjected to 3 h of hypoxia caused transient oxidation of the hemoproteins to the ferryl form (Fe(4+)). Formation of the ferryl intermediate was decreased in a concentration-dependent manner by the addition of L-arginine, a substrate of NO synthase, after 3 h of hypoxia. Optimal inhibition of ferryl formation, possibly due to the antioxidant action of NO, was achieved with 900 microM L-arginine. Addition of hydrogen peroxide to GSH-depleted cells in the presence of DBBF-Hb or Mb significantly decreased cell viability. Ferryl Mb, but not ferryl DBBF-Hb, was observed in samples analyzed at the end of treatment, which may explain the greater toxicity observed with Mb as opposed to DBBF-Hb. This model may be utilized to identify causative agent(s) associated with hemoprotein cytotoxicity and in designing strategies to suppress or control heme-mediated injury under physiologically relevant conditions.

Animals↗

Left ventricular outflow tract obstruction with mitral mechanical prosthesis.

Left ventricular outflow tract obstruction after mitral valve replacement may occur when the native mitral apparatus is preserved intact. Although it has usually been reported using bioprostheses, we present one case using a low-profile mechanical prosthesis. The reduction of left ventricular dimensions and valvular redundancy contributed to this complication. We obtained definitive relief of left ventricular outflow tract obstruction by transaortic exposure and partial resection of the obstructing tissue with the help of video-assisted cardioscopy.

Female↗

Evaluating the Role of Plantations as Carbon Sinks: An Example of an Integrative Approach from the Humid Tropics

/ Despite their fast growth, tropical plantations are a small sink of atmospheric carbon because they occupy only a small area in relation to other land uses worldwide. Proper design and management of plantations can increase biomass accumulation rates, making them more effective C sinks. However, fast-growing plantations can extract large amounts of nutrients from the soil, and site fertility declines may limit sustained plantation forestry after a few rotations. We measured aboveground biomass accumulation, carbon sequestration, and soil chemistry in three young plantations of 12 indigenous tree species in pure and mixed designs in the humid lowlands of Costa Rica. Annual biomass increments for the three mixed plantations ranged from 10-13 Mg/ha. The mixtures of four species gave higher biomass per hectare than that obtained by the sum of one fourth hectare of each species in pure plots. At this early age of the plantations, estimated annual C sequestration values were comparable to other reports from young plantations of exotic species commonly grown in the tropics. Four years after planting, decreases in soil nutrients were apparent in pure plots of some of the fastest growing species, while beneficial effects on soils were noted under other species. The mixed plots showed intermediate values for the nutrients examined and, sometimes, improved soil conditions. A mixture of fast and slower growing species yields products at different times, with the slower growing species constituting a longer term sink for fixed carbon. Examination of the role of tropical plantations as C sinks necessitates integrative approaches that consider rates of C sequestration, potential deleterious effects on ecosystem nutrients, and economic, social, and environmental constraints.KEY WORDS: Native trees; Aboveground biomass; Stem increments; Rotation length; Soil nutrients; Economics

Journal Article↗

Recovery from rabies in man.

A 45-year-old woman from Mendoza, Argentina, was severely bitten by a dog that died 4 days later. Before death, the dog was nervous, aggressive, and had occasional seizures. Ten days after the woman had been bitten, rabies vaccine treatment was begun: 14 daily doses of suckling mouse brain vaccine followed by 2 booster doses. Twenty-one days after the biting episode, she developed a cerebellar striatal syndrome, which persisted throughout several months, and severe encephalitic symptoms, which persisted for 75 days. After 13 months, recovery was nearly complete. The patient's serum and cerebrospinal fluid contained rabies-neutralizing antibodies reaching maximum titers of 1:640 000 and 1:160 000, respectively. Titers of this magnitude have never been previusly recorded after suckling mouse brain vaccine treatment. This phenomenon, together with the epidemiologic, clinical, and laboratory data presented, supports the conclusion of a nonfatal case of rabies in man.

Adrenocorticotropic Hormone↗