Biomedical subjects

Jaime Villalba-Caloca

Publications and source records attributed to Jaime Villalba-Caloca.

4 recordsLinked to original sources

PubMed2003

Spatial indoor radon distribution in Mexico City.

We present a spatial analysis of residential radon concentrations in the Mexico City Metropolitan Area, which we intend to use to assign radon exposure in an ongoing case-control study. As part of a probabilistic household survey, carried out between May and June 1999, 501 dwellings were selected for indoor placement of solid state nuclear track detectors (LR 115) in a cup array over a period of approximately 90 days. As part of the sampling design, the city was grid partitioned into nine zones and a sample of dwellings was selected in each zone. All zones were simultaneously surveyed. The stratified sampling design allowed us to obtain radon geometric means, adjusted for household characteristics, week of detector placement and number of days of measurement for these zones. Additionally, adjusted geometric means were estimated for the 100 census tracts surveyed and this information was used to obtain a more detailed spatial distribution of residential radon levels through kriging interpolation and surface contouring. Radon levels depended on the room of placement, the floor level and the ventilation habits but not on building materials. Regarding the city zone, the highest adjusted geometric mean was found in the southwest (136 Bqm(-3)), where 46% of the households had an estimated radon level in excess of 200 Bqm(-3). In the rest of the city, the geometric mean concentration ranged between 41 and 98 Bqm(-3). A more detailed spatial distribution showed that, in general, most of the eastern and middle zones of the city had estimated radon geometric means below 74 Bqm(-3), while the western ones had geometric means above this concentration. Very high geometric means, exceeding 111 Bqm(-3) and even reaching 288 Bqm(-3), are estimated for some areas located in the southern and western zones of Mexico City. The obtained spatial distribution shows that the areas with very high estimated residential radon concentrations are close to inactive volcanic mountains. We believe that the geo-statistical techniques, we have used, offer reasonably good estimates of the average spatial residential radon distribution in Mexico City under average ventilation in homes. The use of this indirect approach for radon exposure measurement in epidemiological studies is an inexpensive alternative to direct radon exposure measurement but may be subject to non-differential misclassification error. The effect of such error on the detection of a real increase in lung cancer risk from indoor radon remains to be determined.

Air Pollution, Indoor↗

PubMedDate not supplied

Cryopreserved tracheal grafts: a review of the literature.

Cryopreserved tracheal grafts have been used in several experimental models of long segment replacement. The clinical application of the procedure has been limited due to the fact that contradictory results have been reported. The purpose of this article is to present a review of the literature on tracheal cryopreservation. Despite the fact that most authors indicate that cryopreserved tracheal allografts retain viability and have a low immunological response, though they continue to function after transplantation with good epithelialization and patency, cryopreservation leads to significant damage to cartilage, the degree of which is based on the freezing-storage methods that affect the function and durability of a graft. The long-term storage of cartilage must therefore be investigated in more detail in basic research models of cartilage viability: the evaluation of chondrocyte apoptosis, and the use of different solutions for tracheal cryopreservation other than RPMI-1640, Dulbecco's modified Eagle's, Eurocollins, and TC-199. Furthermore, problems that involve improving the blood supply to the graft after extensive resection and immunosuppression must be resolved before tracheal cryopreservation can become a clinically established method for tracheal grafts.

Animals↗

PubMedDate not supplied

[Tuberculosis: a current problem].

Tuberculosis is a public health problem. If the current trends continue, is expected to arrive to 10.2 million of new cases in 2005. There are three studies accomplished in 1995 in Mexican patients. The results show important difficulty in the application and the follow-up of the program of control of the tuberculosis, what has caused accumulation of chronic cases, moderate rate of primary resistance and alarming levels of primary and secondary multiresistance (23%). Mechanism of protective immunity against mycobacterium tuberculosis (MTB) in humans have not been clarified. Different subpopulations of lymphocytes CD4, CD8 and other populations as well as macrophages, and monocytes, have an important role. In industrialized countries, the managing of the MDRTB is based on the use of individualized treatments with second line drugs according to susceptibility test, however the foregoing has not been possible to apply it middle or low income countries. WHO has launches the initiative "DOTS plus" that consist in the administration of a standarized regimen on the basis of epidemiology of resistance in the country or region.

Drug Resistance, Microbial↗

PubMedDate not supplied

[Lung transplantation].

Lung transplantation (LT) has evolved to become an important alternative in the management of patients with end-stage pulmonary disease and chronic respiratory failure. The beginnings of this technique can be traced back to the experiments of Carrel and Guthrie over a hundred years ago. However, it was not until 1963 when the first clinical experience was performed by Hardy. Clinical success did not arrive until the 1980's thanks to the works of the Toronto Lung Transplant Group. Well established criteria have been described in order to consider a patient as a potential candidate to receive a lung. Several diseases are capable of causing terminal lung damage and in general they can be classified according to their origin as obstructive (COPD, emphysema), restrictive (fibrosis), chronic infectious (cystic fibrosis, bronquiectasis), and vascular (primary pulmonary hypertension). The most frequent diagnosis is COPD. Clinically relevant modes of LT include the implant of one lung (single LT), or both lungs (bilateral sequential LT). Transplantation of the cardiopulmonary block is reserved for special situations and lobar transplantation is still considered experimental. Donor condition is essential to the success of LT. The potential donor patient frequently suffers deterioration in lung function due to edema formation or infection and both complications restrict lung's using for transplantation. Lung preservation is also limited to a short period of time which rarely exceeds 6 hours in spite of specially-designed preservative solutions such as the low potassium dextran. Outcome after LT shows current one-year survival between 65-70% with reduction to 40-45% after five years. Mortality within the first year is usually related to primary graft failure and infection. Long-term survival depends on controlling infectious problems due to immunosuppression as well as the development of bronchilitis obliterans as a manifestation of chronic rejection. LT is a therapeutic modality reserved for selected patients with chronic respiratory failure due to end-stage lung disease.

Actuarial Analysis↗