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Biomedical subjects

R M Nelson

Publications and source records attributed to R M Nelson.

At least 163 records · Page 9Linked to original sources
PubMed1977

Solute permeability of the alveolar epithelium in acute hemodynamic pulmonary edema in dogs.

Ten anesthetized dogs, 48 h postintravenous 131I-albumin injection, had a segment of lung airspace isolated by a balloon-tipped catheter lodged in a bronchus. An isotonic saline solution containing trace amounts of Blue Dextran, 125I-albumin, and 57Co-cyanocobalamin was instilled into the lung segment. During control periods, lung saline was absorbed at a rate of 0.133% per minute as measured by indicator dilution of Blue Dextran. Only 57Co-cyanocobalamin crossed the epithelium. Acute hemodynamic pulmonary edema was produced by aortic constriction plus saline overload. In pulmonary edema the fluid volume in the airspace increased at the rate of 0.96% per minute, and there was a significant influx of 131I-albumin into the lung saline from the blood in all animals. However, neither 125I-albumin nor Blue Dextran diffused from the airspace into blood during edema; both were merely diluted by fluid influx. The rate of diffusion of 57Co-cyanocobalamin increased fivefold during edema. A small number of discrete breaks in the lung epithelium allowing bulk flow of interstitial fluid is proposed to account for the one-way movement of albumin in hemodynamic alveolar edema.

Animals↗
PubMed1977

Transient tricuspid insufficiency of the newborn: a form of myocardial dysfunction in stressed newborns.

Fourteen term newborn infants have been recognized as having transient tricuspid insufficiency associated with significant perinatal stress. Five of these infants underwent cardiac catheterization for presumed congenital heart disease, but had only massive tricuspid valve insufficiency. The other nine infants were diagnosed on the basis of a murmur characteristic of tricuspid valve insufficiency and on other clinical grounds. All had a history of significant perinatal stress in the form of asphyxia with or without hypoglycemia. Frequently, congestive heart failure, persistent cyanosis, and ECG evidence of myocardial ischemia were present. Twelve of the 14 survived, and in each of them all cardiac signs and symptoms, including the murmur, spontaneously resolved. The two patients who died had histopathologic evidence of necrosis in the anterior papillary muscle of the tricuspid valve. The constant features of perinatal stress, ST-T wave abnormalities on the ECG, and spontaneous resolution of the transient tricuspid insufficiency strongly suggest that this syndrome is secondary to a reversible form of myocardial dysfunction, perhaps by affecting papillary muscle specifically. We believe that hypoxia with or without hypoglycemia precipitates the events leading to this clinical syndrome which is distinguishable from other cardiac abnormalities in the newborn by the history, distinctive murmur, and the ECG abnormalities.

Asphyxia Neonatorum↗
PubMed1976

Lung inflation and alveolar permeability to non-electrolytes in the adult sheep in vivo.

1. Experiments were performed on adult sheep to determine the effect of lung distension on the passive permeability of alveoli to water soluble non-electrolytes. With the animal breathing oxygen spontaneously, a segment of one lung was isolated by passing a balloon-tipped catheter through a tracheostomy into a distal bronchus. This isolated atelectatic segment was filled with an isosomotic saline solution containing radio-labelled solutes of known molecular size: [125I]albumin, [14C]inulin, [14C]-sucrose, [3H]mannitol, and [14C]urea. The segment was inflated with oxygen either to a preselected pressure, or to a predetermined fraction of its capacity. Inflation was then maintained for several 10-15 min periods between which the oxygen supply was disconnected and the saline sampled, allowing the tracer concentrations to be measured. 2. At low inflating pressures (20-32 cmH2O) and at low volumes (24-54% of capacity), alveolar permeability to water soluble solutes was slight and could be characterized in terms of a membrane penetrated by cylindrical water filled pores of 0-5-1-6 nm radius. In all experiments showing restricted diffusion, absorption of saline occurred. 3. There was a positive correlation between the degree of lung inflation and pore radius in both the pressure controlled and volume controlled experiments. At high inflating pressures and at inflation volumes which were close to the total capacity of the isolated segment, restriction of solute diffusion was lost; in five out of six such experiments there was a net movement of liquid into the alveoli. 4. These results can be explained by postulating that as the lung epithelium is progressively stretched there is an opening up of water filled channels between alveolar cells. At peak inflation, restriction of diffusion of water soluble solutes is lost, and the alveolar epithelium ceases to function as a barrier between the circulation and air spaces.

Albumins↗