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Biomedical subjects

G Crawford

Publications and source records attributed to G Crawford.

At least 73 records · Page 4Linked to original sources
PubMed1990

Pathogenesis of pulmonary edema associated with intracisternal endotoxin in dogs.

To examine the role of central nervous system injury in the pathogenesis of pulmonary edema, we injected Escherichia coli endotoxin (5 mg/kg) into the cisterna magna of six dogs (group E) and compared, over 4 h, both the pulmonary edema and cerebrospinal fluid (CSF) abnormalities with those in six control dogs (group C). In group E, intracisternal endotoxin raised intracranial pressure from 21 +/- 6 to 38 +/- 8 cmH2O (P less than 0.001), CSF total protein from 18 +/- 6 to 54 +/- 19 mg/dl (P less than 0.001), and CSF malondialdehyde from 0.12 +/- 0.11 to 0.61 +/- 0.35 nmol/ml (P less than 0.05); all were unchanged in group C. When the pulmonary wedge pressure was maintained at 10 mmHg by fluid infusion, extravascular thermal volume in group E increased from 7.2 +/- 1.2 to 12.0 +/- 2.7 ml/kg (P less than 0.005) at 4 h when the excised lungs weighed 13.6 +/- 1.5 g/kg; in group C, extravascular thermal volume did not increase, and the excised lungs weighed less (10.8 +/- 1.3 g/kg, P less than 0.05) than those in group E. The dry weights of the lungs were not different between groups, and the alveolar lining fluid-to-plasma albumin ratio in both groups remained low, 0.1-0.2. Fluid infusion in group E (9.2 +/- 2.9 liters) caused colloid oncotic pressure to decrease 4.5 +/- 2.8 mmHg; colloid oncotic pressure fell less (0.8 +/- 1.9 mmHg, P less than 0.001) in group C as less fluid (2.2 +/- 1.5 liters, P less than 0.001) was required to maintain pulmonary wedge pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

The effect of hypopnea on low-pressure pulmonary edema.

The effects of the mechanical factors involved in ventilation on pulmonary edema are only partially understood. To clarify the effect of ventilation on the adult respiratory distress syndrome (ARDS), we examined the effect of reducing rate and tidal volume on oleic acid-induced low-pressure pulmonary edema in dogs, hypothesizing that hypopnea would reduce lung edema. We placed the experimental animals on venous-venous extracorporeal membrane oxygenation (ECMO) for CO2 clearance and oxygenation 1 h after the injury. This allowed reduction of the ventilatory rate from 17.2 +/- 4.8 to 3.3 +/- 0.8 breaths/min and tidal volume from 20 to 16 ml/kg, effectively resting the injured lung. After 5 h of hypopnea there was no reduction in edema by gravimetric or extravascular thermal volume measurements. The ECMO-facilitated hypopnea reduced airway pressure and pulmonary artery pressure while improving arterial oxygen saturation but increased venous admixture. These results suggest that there may be a supportive role for ECMO-assisted hypopnea, but there was no direct beneficial effect of hypopnea on edema.

Animals↗
PubMed1989

Parathyroid subtraction imaging--pitfalls in diagnosis.

Since 1985 when parathyroid subtraction scintigraphy was presented in atlas form in this journal, the T1-201-Tc-99m computer subtraction studies have become more and more popular. Although the study has been quite accurate in localizing abnormal parathyroid pathology, the rate of false positive studies has been somewhat excessive, usually due to thyroid pathology. This atlas is an update of that previous work with the goal of presenting a scheme of interpretation that lessens the incidence of false positive studies as well as presenting many of the pitfalls in diagnosis of parathyroid disease.

False Positive Reactions↗
PubMed1989

Purification and characterization of a central cholinergic enhancing factor from rat brain: its identity as phosphoethanolamine.

A compound that can enhance the apparent synthesis of acetylcholine in cultured explants of the medial septal nucleus has been purified from rat brain and identified as phosphoethanolamine. Acetylcholine synthesis is stimulated two- to threefold in cultures grown for 5 days in the presence of phosphoethanolamine, ethanolamine, or cytidine 5'-diphosphoethanolamine at concentrations above 100 microM. This effect appears to result from an increase in the accumulation of choline via the high-affinity, sodium-dependent uptake mechanism. The development of choline acetyltransferase activity is not affected. Phosphoethanolamine and ethanolamine seem to enhance the ability of developing cholinergic neurons to utilize choline accumulated via the sodium-dependent high-affinity choline uptake mechanism for the preferential production of acetylcholine without increasing the general metabolism of the cultures. Choline itself and its related derivatives are not stimulatory for these effects.

Acetylcholine↗
PubMed1989

Alveolar pressure inhomogeneity and gas exchange during constant-flow ventilation in dogs.

Analysis of momentum transfer between inflow jets and resident gas during constant-flow ventilation (CFV) predicts inhomogeneity of alveolar pressures (PA) and volume, which might account for specific ventilation-variance in the lung. Using alveolar needles to measure pressures (PA) during CFV in eight anesthetized dogs with wide thoracotomy, we observed random dispersion of PA among lobes of up to 12.5 cmH2O. Within each lobe, the PA dispersion was up to 10 cmH2O at CFV of 90 l/min; when flow decreased, PA at all sites decreased, as did the intralobar dispersion. These pressure differences were not observed during conventional mechanical ventilation (CMV). During CFV with room air, dogs were hypoxemic [arterial PO2 (Pao2) 54 +/- 15 Torr] and the venous admixture (Qva/QT) was 50 +/- 15%. When inspiratory O2 fraction was increased to 0.4, Pao2 increased to 172 +/- 35 Torr and Qva/QT dropped to 13.5 +/- 8.4%, confirming considerable ventilation-perfusion (VA/Q) variance not observed during CMV. We conclude that momentum transfer between the inflow stream and resident gas caused inhomogeneities of alveolar pressures, volumes, and ventilation responsible for VA/Q variance and hypoxemia during CFV. Conceivably, the abnormal ventilation distribution is minimized by collateral ventilation and forces of interdependence between regions of high and low alveolar pressures. Momentum transfer also predicted the mucosal damage observed on histological evaluation of the bronchial walls near the site of inflow jet impact.

Animals↗