Biomedical subjects
Publications and source records attributed to V Chen.
A 66-year-old man underwent extracapsular cataract extraction and posterior chamber intraocular lens implantation, which was complicated by accidental intravitreal bethamethasone injection. This case was characterized by a benign course and good recovery of vision. Appropriate management of such accident is discussed.
A 32-year-old man with central retinal vein occlusion followed by severe and rapidly progressing neo-vascular glaucoma is presented. This case was characterized by a severe ischemic process, in which the rubeosis iridis was followed by almost total atrophy of the iris within a short period of time. The onset of the central retinal vein occlusion was associated with mild dehydration and stress polycythemia following strenuous physical activity.
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Adult heartworms were surgically removed from 4 infected dogs by use of intracardiac techniques during cardiopulmonary bypass. The number of worms removed ranged from 12 to 14 per dog. Observation for 9 months after surgery gave no clinical evidence of active adult heartworm infection, in spite of the consistent finding of circulating microfilariae during the follow-up period. There were no significant early or late postoperative complications. Results of postoperative hematologic and biochemical studies were unremarkable. At necropsy (following euthanasia, 9 months after surgery) the heart and pulmonary arteries of all dogs were free of adult heartworms; pathologic changes attributable to residual infection were not found.
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The secondary structural compositions of the human erythrocyte glucose transporter in proteoliposome vesicles were assessed on the basis of circular dichroism (CD) spectra measured in the absence and in the presence of D-glucose or an inhibitor, cytochalasin B. We designed and used a scattered-light-collecting device, which corrects CD spectra for optical artifacts originating from light scattering. Relative contents of eight types of secondary structure were estimated by using basis spectra generated by the eigenvector method based on CD spectra of 15 proteins of known structure. Results indicate that the glucose transporter is composed of approximately 82% alpha-helices, 10% beta-turns, and 8% other random structure, with no beta-strands. In the presence of an excess of D-glucose, the alpha-helical content is reduced by more than 10% and there is a significant increase in the random structure content. Cytochalasin B does not appear to affect the secondary structural composition of the transporter to any significant degree.
Three cases are described of acute glaucoma following vitrectomy and silicone oil injection in proliferative vitreous retinopathy. The first case developed silicone-induced pupillary block in a phakic eye. Cases 2 and 3 developed elevated pressure in aphakic eyes with deep anterior chambers. Cases 1 and 3 were treated by laser iridectomy. Case 2 was treated by removal of silicone. The pathogenesis and treatment of these problems are discussed.
Effect of a chronic excess or deficit of thyroid hormone on intrinsic myocardial performance in rats was assessed. Animals were thyroidectomized or treated with thyroid hormone or vehicle 6-7 wk before the study. Body weight and heart weight were decreased in the hypothyroid group, and heart weight was elevated in the hyperthyroid group. Hearts were removed from thyroidectomized, euthyroid or thyroid-treated animals and studied as isolated, perfused working heart preparations. Ventricular function curves were generated by increasing left atrial filling pressure, whereas outflow resistance was not varied. Coronary flow, aortic outflow (and thus cardiac output), heart rate, and peak aortic systolic pressure were measured as a function of preload. These studies showed that performance of hearts from hyperthyroid animals was similar to that of euthyroid controls. Hearts from hypothyroid rats had decreased rate, pressure, and cardiac output but normal stroke volume. Since heart weight was 55% lower than control, normalization of volume work to dry heart weight reversed the difference in cardiac output. Comparison of hearts from hypothyroid animals to control rats of similar weight showed minimal differences in pump function. Thus hyperthyroidism did not result in altered in vitro cardiac output or peak systolic pressure as a function of changing preload when compared with age-matched euthyroid controls, hypothyroidism resulted in a decreased in vitro heart rate but greater cardiac output normalized to heart weight when compared with age-matched controls and hyperthyroid animals; external pacing of hypothyroid hearts yielded myocardial work parameters that were comparable to euthyroid control rats of similar body weight; and cardiac efficiency was significantly greater in hypothyroid hearts than in hyperthyroid hearts.(ABSTRACT TRUNCATED AT 250 WORDS)
We exposed 128- to 130-day-gestation fetal lambs by cesarean section leaving the umbilical cord and placenta undisturbed, and we then treated the lungs with pulmonary conditioning (i.e., repeated prolonged inflations to 35 cm H2O, followed by a continuous positive airway pressure of 15 cm H2O). To investigate the added effect of pulmonary vasodilation upon the increase of total compliance and pulmonary oxygen uptake, we also administered acetylcholine intravenously at a rate of 80 micrograms min-1. Eleven of 13 lambs met the endpoint criteria of either compliance (0.5 ml [cm H2O]-1 kg-1; 1 animal), or pulmonary oxygen uptake (6 ml kg-1 min-1; 6 animals), or both (4 animals), and were delivered within 0.6 +/- 0.3 h. This time was significantly (p less than 0.05) shorter than previously seen in similar studies without the infusion of a vasodilator; all animals so delivered survived 24 h of mechanical ventilation in excellent health. We suggest that pharmacologic pulmonary vasodilation, in addition to deep sustained pulmonary insufflation and distension, is an effective and rapid means of transforming stiff immature lungs into lungs that can sustain normal ventilation and gas exchange.
A 15-year-old pupil was injured by an explosive mixture of red phosphorus powder and potassium chlorate causing seeding of multiple foreign bodies upon superficial and deep corneal layers. Unlike the few fulminant cases reported in the English literature our case had a benign course and outcome, without any late complications.
Cardiac mechanical function and coronary flow (CF) were measured in isovolumically beating hearts from neonatal piglets 0.5 to 12 days of age. The hearts were perfused retrogradely at 70 cm H2O with a recirculating modified Krebs-Henseleit solution containing washed adult pig red cells (hematocrit, 25%). They were electrically paced (180 beats/min), and left ventricular developed pressure (delta P), maximum rate of rise of pressure (dP/dt), CF, and myocardial oxygen consumption were measured. These parameters were found to remain stable for at least 60 minutes. In one group, a single dose of amrinone was added to the perfusate to yield a concentration of 50 micrograms/ml. Within 5 minutes delta P decreased from 104.0 +/- 7.1 to 65.3 +/- 8.6 mm Hg (p less than 0.001), and dP/dt fell from 1,160 +/- 96 to 658 +/- 78 mm Hg/sec (p less than 0.001). In a second group, successive doses of amrinone were added to yield concentrations ranging from 5 to 50 micrograms/ml. There was a progressive decrease in delta P and dP/dt to 66.5 +/- 4.2% and 57.6 +/- 4.8% of initial values, respectively. CF increased progressively from 3.2 +/- 0.2 to 6.8 +/- 0.5 ml/min/g. In 3 experiments, amrinone was washed out after achieving the maximum concentration. Depressed mechanical function reversed and delta P and dP/dt returned to control values in each heart. Additionally, CF decreased from 7.6 +/- 0.3 to 5.0 +/- 0.2 ml/min/g. It is concluded that amrinone has concentration-dependent negative inotropic actions in the neonatal piglet heart. Hence, the drug may not be useful in treating heart failure in the human neonate.
We explored the pulmonary effects of continuous mechanical ventilation (MV) at a peak inspiratory pressure of 50 cm H2O in healthy, paralyzed, and anesthetized adult sheep during a period of 48 h. The 9 control sheep (Group A) were ventilated with 40% oxygen at a tidal volume of about 10 ml/kg and a peak inspiratory pressure of 15 to 20 cm H2O. All these animals remained stable throughout the 48 h of MV with no change in lung function. The 7 sheep in Group B were ventilated with 40% oxygen using a pressure-controlled ventilator at 50 cm H2O peak inspiratory pressure, at a VT of 50 to 70 ml/kg. All sheep in Group B developed severe respiratory failure and died or were killed within 2 to 35 h, and showed parenchymal consolidation at autopsy. The 9 sheep in Group C were ventilated as in Group B, except that 3.8% CO2 was added to the inspired gases: the Group C animals deteriorated more slowly, with little change in PaO2 but with a severely reduced FRC, VT, total static lung compliance, and grossly abnormal lungs at autopsy. We conclude that in this model, mechanical ventilation at peak airway pressure of 50 cm H2O will lead to progressive impairment in pulmonary mechanics, lung function, acute respiratory failure, and alveolar cellular dysfunction, as demonstrated by highly abnormal minimal surface tension values of saline lung lavage fluid in both study groups.
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