Biomedical subjects

M T Padilla

Publications and source records attributed to M T Padilla.

4 recordsLinked to original sources

PubMed1999

Response to 45 degrees head-down tilt as measured by organ weight/body weight ratios and spiral computed tomography.

BACKGROUND: Exposure to microgravity or simulated microgravity causes significant shifts in body fluids which may initiate physiological adaptations to the microgravity stressor. It is imperative to understand the physiological adaptations to microgravity in order to develop appropriate countermeasures to the deleterious aspects (i.e., muscle and bone wasting) of long-term spaceflights. HYPOTHESIS: The significant shifts in body fluids by 45 degrees head-down tilt can be measured by changes in organ weight/body weight (OW/BW) ratios and non-invasively by spiral computed tomography. METHODS: In a previous study (14), rats were weighed and exposed to either 45 degrees head-down tilt (45HDT) or a prone control position for one of the following experimental times: 0.5 h, 1 h, 2 h, 4 h, 8 h, or 24 h. A radioactive tracer was injected intramuscularly immediately prior to the start of the experimental time periods. At the end of the experiment, the major organs were harvested, weighed, and measured for gamma radiation levels. We used the organ weights from this previous study to calculate OW/BW ratios for the present study. Additionally, in the present study, rats in the 14-d experimental groups were weighed, lightly anesthetized to facilitate placement in the 45HDT position, and placed in a specially designed 45HDT cage (45HDT group) or left unrestrained in the cages (control group). At the end of the 14-d experimental time period, the rats were anesthetized and their lung densities measured with spiral computed tomography. RESULTS: The OW/BW ratios for the liver, kidneys, and spleen of 24 h 45HDT rats were significantly lower (p<0.05) than control values while at 1 h the 45HDT rats had a higher kidney OW/BW ratio. Lung density from the 14-d 45HDT rats was 24.4% greater than control rats' values. CONCLUSIONS: The physiological change due to the 45HDT position to simulate microgravity begins as early as 1 h, and the kidney appears to be the first organ affected. Spiral computed tomography may offer a viable method of non-invasively measuring organ densities in the 45HDT model. The OW/BW data generated in the present study does not correlate with the changes in radioactive tracer distribution data from our previous study.

Adaptation, Physiological↗

PubMed1997

Changes in radioactive tracer distribution in rats after 24 hours of 45 degrees hind limb unweighting.

INTRODUCTION: Changes in radioactive tracer distribution were examined in rats after exposure to a simulated microgravity model of 45 degrees head down tilt (45HDT) or 45 degrees hind limb unweighting (45HU) for up to 24 h. METHODS: Rats were randomly assigned to either 45HDT (or 45HU) experimental groups or control groups for each time point of 0.5 h, 1 h, 2 h, 4 h, 8 h, or 24 h. The 0.5-h through 8-h experimental rats were anesthetized and placed head-down on a ramp at 45 degrees, while control rats were placed in a prone position. Non-anesthetized rats in the 24-h experimental group were tail-suspended at 45 degrees, while control rats were allowed unrestrained movement. Technetium-labeled diethylenetriamine pentaacetate (99mTcDTPA, physical half-life of 6.02 h, MW = 492 amu) and indium-labeled diethylenetriamine pentaacetate (111In DTPA, physical half-life of 3.5 d, MW = 545 amu) were used to measure body organ distributions of the radioactive tracers at the 0.5-h-8-h and 24-h time points, respectively. Major organs were harvested after each time period and measured for radioactive counts. Light and electron micrographs were examined. RESULTS: Mean 111InDTPA counts for the lungs, kidneys, and brains of the 24 h 45HU groups were significantly higher than control counts. Light and electron microscopy demonstrated the development of pulmonary edema in the alveolar septal areas after 2 h of 45HDT, and a shift in edema to the pulmonary airways and pulmonary arteries after 24 h of 45HU. CONCLUSIONS: Pulmonary edema development, accompanied by a significant increase in 111InDTPA lung, kidney, and brain counts in the 24-h 45HU groups, suggests vascular injury in the microcirculation of these organs.

Animals↗

PubMed1997

The swing-lock removable partial denture.

The swing-lock removable partial denture is a good treatment alternative for maxillofacial prosthodontics, periodontally compromised dentitions and where some conventional designs for removable partial dentures cannot be applied. This paper presents clinical applications of the SLRPD. Indications, contraindications, advantages and disadvantages are discussed.

Contraindications↗

PubMed1992

Margin configuration, die spacers, fitting of retainers/crowns, and soldering.

This article focuses on different margin configurations and the criteria they must meet to be considered clinically successful. In addition, the use of die spacers to lessen the cement film thickness to achieve a better marginal adaptation of cast restorations is presented. Also, the article presents a step by step method for fitting crowns or retainers in the laboratory and in a clinical setting to make this important procedure less time consuming, more precise, and easy to finalize. Finally, soldering in dentistry and the criteria required for its successful execution are discussed.

Crowns↗