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Biomedical subjects

M Sanchez

Publications and source records attributed to M Sanchez.

At least 217 records · Page 12Linked to original sources
PubMed1977

Lack of correlation between thyroid size and body growth in an area of endemic goiter.

There is conflicting information in the literature about the relationship between thyroid size and body growth in endemic goiter. This study reports data from highland Bolivia where 408 children were examined for thyroid size, height, weight, head circumference, and academic performance, the latter as measured by teacher evaluation. The presence or size of goiter showed no consistent correlation with height, weight, or head circumference. School performance was significantly correlated with all other variables in boys and not in girls, but there are severe limitations involved in the use of school grades alone for assessment of intelligence. Height and weight were less than for normals in the United States at each age level, but did not differ from those of other Quechuan children in neighboring Peru who were reportedly nongoitrous. Our data support the conclusion that there is no clear relationship between thyroid size and body growth in areas of endemic goiter.

Adolescent↗
PubMed1977

Serial changes in arterial endothelium following ischemia and perfusion.

The acute and chronic changes produced in canine femoral arteries by ischemia and by perfusion with D10W were examined by light and by scanning electron microscopy. Mild changes of injury characterized by medial and adventitial inflammation and an increase in intimal lining cells occur following 30 minutes of perfusion with return to a normal microscopic appearance within one week. Perfusion for 6 hours produces significant injury to the entire arterial wall, as evidenced by depletion of cells and elastin from the media, replacement with collagen, and eventual fibrosis. The intimal surface is replaced by a layer of spindle cells which appear to originate in the media. The internal elastic membrane is flattened and thrombosis is prominent, particularly in areas where medial fibrosis is severe. Many of the vascular changes produced by perfusion injury may persist for 3 months and some may even by permanent. A period of 6 hours of ischemia also produces similar but less prominent alterations in vascular morphology which return to near-normal appearance within 8 weeks.

Animals↗
PubMed1977

Serial changes in arterial structure following radiation therapy.

Acute and chronic morphologic changes in the endothelium and the media of canine femoral arteries following 4,000 roentgen given over a ten day period were evaluated by light and scanning electron microscopy. The endothelium showed evidence of moderate to severe acute injury within 48 hours after the course of radiation was completed, as evidenced by marked nuclear disruption with sloughing of entire cells in some areas and widespread patchy intimal fibrin deposition. Repopulation of the luminal surface with new cells forming an irregular and thickened surface became apparent within three weeks but was still incomplete at four months. The internal elastic membrane appeared to be preserved following radiation. The media evidenced minimal alteration during the first week subsequent to radiation, after which a progressive increase in cellularity and later fibrosis with some focal areas of necrosis and round cell infiltration occurred. The adventitia showed progressive hemorrhage and chronic inflammation. The results of this study suggest that radiation injury to the endothelium may be independent from injury to the remainder of the wall of the vessel. The morphologic alterations in the media and adventitia may be long lasting and perhaps permanent in contrast to the more acute changes with gradual repair in the endothelium. Arterial thrombosis is uncommon following radiation.

Animals↗
PubMed1976

Evaluation of pulmonary function in the ischemic expanded canine lung.

Twenty-four dogs underwent in vivo left pulmonary hilar occlusion with the lung continuously expanded at 10 centimeters or 25 centimeters of water pressure to determine the period of pulmonary ischemia that may be tolerated before consistent pulmonary edema and congestion develop after lung revascularization. Consistent and prolonged pulmonary edema and congestion that caused death of the dog occurred in at least one-half of the dogs when the period of hilar occlusion was extended beyond six hours. Elevation of the left pulmonary artery pressure was only a rough measurement of the severity of the anoxic pulmonary injury. Expansion of the lung at 10 centimeters of water continuous pressure was more beneficial than was expansion at 25 centimeters of pressure. Cyclic ventilation with slight negative-expiratory pressure provided less support to the lung than did continuous expansion at either pressure tested. Intial decreases in both ventilation and perfusion isotope uptake and the percentage of the total volume of oxygen uptake per minute by the ischemic lung returned to near normal levels in three weeks in dogs that survived. Lung expansion during periods of ischemia appears to prevent alveolar collapse and to facilitate oxygenation.

Animals↗
PubMed1976

Arterial endothelial changes after ischemia and perfusion.

The effects of six hours of ischemia and six hours of perfusion with 10 per cent dextrose and water solution, Sacks' solution and Intralipid on the endothelium of common femoral arteries in dogs were examined by light and by scanning electron microscopy and compared with normal arteries. Arteries that were ischemic or perfused with 10 per cent dextrose and water solution or Sacks' solution showed a flattening of the normal linear convolutions and extensive crater formation, with fragmentation and even complete loss of endothelial cells in many areas. The more severe changes occurred in perfused vessels. Fibrin and platelets covered the luminal surface in many areas in which there was extensive injury to the endothelium. Light microscopy revealed thickening of the internal elastic membrane and intimal fibrosis. Results of biopsies performed two weeks after perfusion showed slight, although incomplete, improvement in the structure of the endothelium. Arteries perfused with Intralipid had thickening of the intima with a proliferation of plump cells orientd linearly over the surface but with an absence of craters. Results of present studies confirm the observations of other investigators that injury to endothelial cells may be produced by ischemia and that perfusion with various solutions may produce an even more severe alteration in structure of the endothelial cell which does not return to normal within two weeks. The origin of new endothelial cells is not demonstrated by this study.

Animals↗
PubMed1975

A comparative study of the effects of dry vs. humidified ventilation on canine lungs.

To compare the effects on canine ciliary and bronchial mucosal function of varying periods of ventilation with dry vs. humidified gas mixtures, 29 anesthetized dogs underwent 2, 4, and 6 hours of ventilation through a Carlen's double-lumen tube. Six dogs were evaluated by clearance studies, nine by differential bronchospirometry, six by surfactant studies, six by electron microscopy, and two by ventilation scanning. By means of two separate respiratory systems, dry gas (DG) was used to ventilate the right lung, and humidified gas (HG) ventilated the left lung in each dog. Serial chest roentgenograms showed more rapid clearance of inspired tantalum dust from the HG-ventilated lung in each of the six dogs, the disparity in clearance between the two lungs being more pronounced after longer periods of ventilation. The surface tension in DG-ventilated lungs increased fourfold, whereas in HG-ventilated lungs it increased only twofold as compared to preoperative values. Longer periods of ventilation did not change the surface tension appreciably in either DG- or HG-ventilated lungs. Scanning electron micrographs of bronchial mucosa from DG-ventilated lungs showed tangling and matting of cilia with a granular and stringy material attached to most cilia; these changes were much less pronounced in HG-ventilated lungs. Bronchospirometric studies showed an increase in ventilatory function in each of the lungs ventilated with the HG mixture (percent Vo2 on 100 percent oxygen increased 27.7 percent) to compensate for the decreased gas exchange provided by the contralateral DG-ventilated lung. Function in each of the lungs returned to normal within 24 hours. Ventilation scans with Xenon133 showed no apparent change in isotope uptake in the HG-ventilated lungs as compared to the DG lungs during the first 24 hours after ventilation. The observations from the present study suggest that ventilation of canine lungs with DG for 4 or more hours dries mucus and transiently retards mucociliary clearance and gas exchange. These changes may be minimized by ventilation with a humidified gas mixture. Application of these findings to patients undergoing prolonged general anesthesia and to lung preservation studies is suggested.

Animals↗