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Biomedical subjects

M Calderón

Publications and source records attributed to M Calderón.

At least 19 recordsLinked to original sources
PubMed2006

Specific immunotherapy with high dose SO standardized grass allergen tablets was safe and well tolerated.

BACKGROUND: Sublingual immunotherapy with grass allergen tablets may be the future treatment for grass pollen allergy because it reduces symptoms and medication use, improves quality of life and is easy to use. Rhinoconjunctivitis and asthma co-exist and we aimed to find a safe dose range of a self-administered grass allergen tablet (ALK Abello A/S) in patients suffering from rhinoconjunctivitis and asthma. METHODS: Four doses were investigated in a randomised, double-blind, placebo-controlled, dose escalation trial. Outside the pollen season 4 groups of 12 patients commenced treatment in a staggered manner, at intervals of 1 week. For 28 days doses of 75000 (approximately 15microg Phleum pratense protein 5), 150,000, 300,000, 500,000 standardised quality tablet (SQ-T) units or placebo were given once daily as sublingual tablets. RESULTS: Fourty three patients were randomised to receive either active treatment or placebo (3:1). Each dose group consisted of 12 patients except the 500000 SQ-T group (5 active, 2 placebo). No asthma exacerbations were seen and no serious or severe adverse events were reported. The majority of adverse events were local reactions. The number of adverse events was dose related. No patients withdrew from the study. CONCLUSIONS: Treatment with grass allergen tablets in doses up to 500000 SQ-T in patients with asthma and rhinoconjunctivitis was safe and well tolerated.

Administration, Sublingual↗
PubMed2001

[Problem based learning in the teaching of physics to medical students. Comparison with traditional teaching].

BACKGROUND: Problem based learning, integrating basic science with clinical problems, is one of the most recommended forms of teaching for medical schools. AIM: To compare a problem based learning program for physics with traditional teaching methods. MATERIAL AND METHODS: In the physics course, first year medical students were separated in groups with traditional learning and problem based teaching. Both groups were subjected to the same knowledge and qualitative evaluations. RESULTS: At the end of the course, cognitive performance in both groups was similar (60.8 and 61.3% among traditional teaching and problem based learning groups respectively). However, students assigned to the problem based learning group evaluated significantly better the teaching methodology and process. CONCLUSIONS: Physics education, using problem based learning, obtains the same cognitive results but a higher degree of satisfaction than traditional teaching among students.

Curriculum↗
PubMed1999

Low flow veno-venous ECMO via subclavian dialysis catheter for severe respiratory failure.

BACKGROUND: We present the case of a 12-year-old female with severe postoperative bacterial pneumonia unresponsive to conventional treatment following a failed renal transplant. CASE REPORT: The patient was placed on low flow veno-venous extracorporeal membrane oxygenation (ECMO) as an adjuvant treatment to antibiotic therapy and maximal ventilatory support. Venous ECMO resulted in rapid improvement and the patient was successfully weaned after 48 hours of circulatory assistance. Two days later, the patient was extubated and safely discharged from the intensive care unit. Eighteen months later, she remains stable on peritoneal dialysis and is awaiting a new donor kidney. CONCLUSIONS: Low flow veno-venous ECMO represents a new therapeutic alternative for critically ill patients whose condition does not meet the conventional ECMO criteria. Further clinical experience is still needed.

Catheters, Indwelling↗
PubMed1998

Late development of aortic pseudoaneurysm after coarctation repair with fistulization to the bronchial tree. A case report.

BACKGROUND: Fistulous communication between the aorta and the tracheobronchial tree is an uncommon and serious cause of hemoptysis secondary to complications of a previous operation performed on the aorta. In cases in which an appropriate surgical intervention is carried out, the survival rate approaches 76%. This surgery is considered one of the most risky operations on the aorta, challenging the surgeon's ability to resolve the problem. METHODS: We present the case report of a 43-year-old female with massive hemoptysis. Her medical history disclosed repair of coarctation of the aorta (15 years before). She underwent emergency left thoracotomy; surgical exploration revealed a false aneurysm from the previous aortic patch repair which communicated to a subsegmental bronchus of the left upper lobe. RESULTS: The thoracic aorta was isolated and clamped, and the previous patch was removed. The bronchial side of the fistula was managed with left superior lobectomy and the aorta was repaired with the placement of a coated woven dacron graft onto healthy aortic tissue. CONCLUSIONS: The patient had an uneventful recovery and remains asymptomatic six months after discharge.

Adult↗
PubMed1997

Mechanisms of pollution-induced airway disease: in vitro studies in the upper and lower airways.

Evidence from both epidemiological and laboratory-based studies suggests that increased exposure to liquid petroleum and gas-derived air pollutants [nitrogen dioxide (NO2), ozone, and respirable particulate matter] may play a role in the clinical manifestation of both allergic and non-allergic airway disease. The mechanisms and cell types involved in pollutant-mediated effects in the airways, however, are not clear. In vitro studies have suggested that human fibroblasts, B-lymphocytes, alveolar macrophages, and epithelial cells/cell lines may be involved. Studies of fibroblasts and macrophages have demonstrated that exposure to ozone results in decreased cell viability and increased release of pro-inflammatory mediators from macrophages. Similarly, studies of B-lymphocytes have demonstrated that exposure to diesel exhaust particles (DEP) enhances the synthesis of immunoglobulin E by these cells. The airway epithelial cells have received the greatest attention in mechanistic studies of air pollution-induced airway disease and suggest that these cells are likely to play a pivotal role in the pathogenesis of airways disease. Various studies have demonstrated that exposure of nasal or bronchial epithelial cells to NO2, ozone, and DEP results in significant synthesis and release of pro-inflammatory mediators, including eicosanoids, cytokines, and adhesion molecules. Additionally, evidence suggests that epithelial cells of atopic individuals release significantly greater amounts of cytokines such as granulocyte-macrophage colony stimulating factor (GM-CSF), interleukin-6 (IL-6), IL-8, and regulated on activation, normal T-cell expressed and secreted (RANTES), on exposure to NO2 and ozone. Studies investigating the biological relevance of epithelial cell-derived pro-inflammatory mediators have shown that these enhance eosinophil chemotaxis and eosinophil adherence to endothelial cells, suggesting that pollution-induced inflammation of the airways is likely to be influenced by modulation of epithelial synthesis and release of these mediators.

Air Pollutants↗
PubMed1996

Rates of tetanus protection and transplacental tetanus antibody transfer in pregnant women from different socioeconomic groups in Peru.

In developing countries, neonatal tetanus causes significant mortality. Using a new competitive enzyme-linked immunosorbent assay to measure anti-tetanus toxin antibody levels, we compared rates of protection, total antibody levels, and maternal-to-fetal antibody ratios between different socioeconomic groups in Peru. Upper-middle-class women 25 years and older had significantly lower rates of protection and mean anti-tetanus toxin antibody levels than did lower-class women of the same age. Nevertheless, the former had higher fetal-to-maternal antibody ratios, independent of maternal age, total antibody levels, or parity. We conclude that future vaccination programs in Latin America must target upper-middle-class as well as lower-class women.

Adolescent↗
PubMed1996

Right ventricular bypass for palliation of cardiac sarcoma.

A 33-year-old woman with a nonresectable right ventricular sarcoma and pulmonary outflow tract obstruction underwent a right ventricular bypass operation for symptomatic relief. The patient had an uneventful recovery and was asymptomatic on discharge, without jugular plethora or hepatomegaly. We consider this procedure to be an excellent palliative treatment of malignant right ventricular obstructive symptoms for improving the patient's quality of life.

Adult↗
PubMed1994

Low flow veno-venous ECMO: an experimental study.

Clinical use of extracorporeal membrane oxygenation (ECMO) and carbon dioxide removal (ECCO 2R) have become well established techniques for the treatment of severe respiratory failure; however they require full cardiopulmonary bypass, representing major procedures with high morbidity. We theorized the possibility of an efficient low flow veno-venous extracorporeal membrane gas exchange method. Four mongrel 12 kg dogs were submitted to veno-venous extracorporeal membrane gas exchange via a jugular dialysis catheter using a low flow (10 ml/min) roller pump and a membrane oxygenator for a period of four hours. Respiratory rate was set at 4 breaths/min with a FiO 2 of 21% and ventilatory dead space was increased. Adequate gas exchange was obtained (pO 2139, pCO 224, Sat 99.4%), without major hemodynamic changes or hematuria. Our results demonstrate the feasibility of a low flow, less aggressive system. Further research should be considered.

Animals↗
PubMed1993

[Formulation and evaluation of a beverage based on whole milk and precooked rice flour].

The objective of this research was to formulate and evaluate a beverage based on powdered whole milk and precooked rice flour, with good nutritional contribution, good acceptability and stability, which permits to be included in the nutritional Protection Programs carried out by the National Institute of Nutrition of Venezuela. Six different mixtures were prepared and evaluated organoleptically in liquid form. The preferred one was submitted to nutritional evaluation, acid determination and microbiological analysis during seven months, while samples were kept at temperatures of 5 degrees C, 27 degrees C and 37 degrees C. The nutritional composition of the selected mixture expressed by 100g was the following: kcal 423, proteins 11g, fat 9.1g, niacin 1 mg, thiamine 0.2 mg, riboflavin 0.6 mg, calcium 295.8 mg and phosphorous 287.5 mg. The protein quality was determined by the Protein Efficiency Ratio (PER) and Net Protein Ratio (NPR) was 3.01 +/- 0.2 and 3.74 +/- 0.3 respectively, compared with casein of 3.54 +/- 0.3. This data showed that the product developed represents from the nutritional point of view a good alternative to prevent undernutrition in the country. The stability study reported a useful life time of seven months at temperatures of 5 degrees and 27 degrees C and less than two months at 37 degrees C.

Animals↗
PubMed1990

Replacement of a labile aspartyl residue increases the stability of human epidermal growth factor.

Long-term storage of recombinant human epidermal growth factor (EGF), an important promoter of cell division, results in its conversion to a new species that elutes later than native EGF on a reverse-phase column. This new species, called EGF-X, has only 20% of the biological activity of native EGF. Peptide mapping indicated that the primary structure of EGF-X differs from that of native EGF solely within the first 13 residues. N-Terminal sequencing of EGF-X revealed that about 30% of the polypeptides have been cleaved at the Asp-3/Ser-4 bond. In addition, the yields after the His residue at position 10 were extremely low, indicating that a chemical modification occurs at residue 11 that is incompatible with Edman degradation. We hypothesized that aspartic acid 11 had been converted to an isoaspartyl residue, and this was confirmed with L-isoaspartyl/D-aspartyl methyltransferase, an enzyme that methylates the side-chain carboxyl group of L-isoaspartyl residues but does not recognize normal L-aspartyl residues. EGF-X, but not EGF, was found to be a substrate of this enzyme, and proteolytic digestion of EGF-X with thermolysin localized the site of methylation to a nine-residue peptide containing position 11. We did not observe formation of the isoaspartyl derivative in EGF that had been denatured by reduction of its disulfide bonds. In addition, replacement of the aspartyl residue at position 11 with glutamic acid resulted in a fully active EGF derivative that does not form detectable amounts of EGF-X. We propose that conversion of this aspartyl residue to isoaspartate is a significant nonenzymatic degradation reaction affecting this growth factor.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1989

Effect of temperature on an enzyme assay to detect fenitrothion resistance in Anopheles albimanus mosquitos.

A laboratory strain of Anopheles albimanus Wiedemann of known fenitrothion resistance was used in the field to compare the results of the WHO test for determining fenitrothion resistance in mosquitos with those of an enzyme microplate assay. The level of resistance obtained with the enzyme assay increased with the ambient temperature, and in order to compensate for this temperature effect, the incubation time was reduced. With the adjusted incubation times, the results for the microassay from 23 degrees C to 32 degrees C were the same as those found with the WHO test. The fenitrothion resistance of a field population of A. albimanus mosquitos determined between 27 degrees C and 31 degrees C using the adjusted enzyme microassay or the WHO test did not differ in a statistically significant way.

Animals↗
PubMed1982

[Colorimetric determination of tryptophan in foods].

A modification of the method of Spies and Chambers for the determination of tryptophan in food products is described. The results were compared with those obtained with the microbiological method and gave identical results. The results on tryptophan content of bean broth were consistently higher than expected. Apparently, bean broth contains certain factors, which interfere with both procedures. In summary, the modified method is simple and easy to perform in large numbers of samples.

Animals↗
PubMed1981

[Formulation of a rice-based beverage of high nutritive value].

The purpose of this work was the production of a beverage with a nutritive value similar to that of milk, but available at a lower cost. A traditional beverage in Venezuela, "Chicha de Arroz" (Rice Chicha), was chosen. The various formulas studied were based on rice, non-fat milk and different kinds of soy flour, in addition to sugar, vegetable oil, vitamins, ferrous sulfate and different flavors. A product with protein and caloric values similar to those of milk was obtained. Twenty formulas were prepared and submitted to physico-chemical, microbiological and sensorial evaluations with respect to flavor, color, viscosity and stability during period of refrigeration. The most adequate formula was prepared on a pilot-plant scale. Rat assays gave the same PER results as those of casein. Consumer acceptability was tested on 1,080 school children, and showed to be greater than 95%. The stability was superior to that of milk and the cost, approximately three-fourths that of the latter. In the school-snack program of the National Institute of Nutrition, milk is now being replaced by this Chicha.

Amino Acids↗