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Biomedical subjects

W H Johnson

Publications and source records attributed to W H Johnson.

137 records · Page 8Linked to original sources
PubMedDate not supplied

Progressive pulmonary venous obstruction and pulmonary interstitial fibrosis associated with tetralogy of Fallot.

Stenosis of individual pulmonary veins is a rare condition associated with a very high mortality. The present report is the first known case of progressive pulmonary venous obstruction associated with the tetralogy of Fallot. This clinical and anatomical study suggests that initial dynamic and possibly reversible occlusion occurs at the junction of the pulmonary vein and left atrium. Anatomical lesions in pulmonary veins then develop, possibly secondary to functional stenosis. The usually fatal outcome of these cases is due to the development of fixed pulmonary venous occlusion and possibly pulmonary interstitial fibrosis. The rapid progression of pulmonary venous stenosis strongly suggests that discrete veno-atrial stenosis should be surgically corrected as early as possible to prevent the irreversible diffuse pulmonary venous obstruction associated with an invariably fatal prognosis.

Angiography↗
PubMedDate not supplied

Iodixanol pharmacokinetics in children.

The objective of this report was to study the elimination pharmacokinetics of iodixanol in children. Iodixanol (Visipaque, Nycomed Inc., Wayne, PA, USA) is a new iso-osmolar iodinated radiocontrast agent. We hypothesized that elimination of this agent would be dependent on age-related differences in renal clearance. Seven centers enrolled 43 patients. Cardiac catheterization was performed in 41 patients and cranial computed tomography in 2. Patients were entered into 5 age groups: newborn to <2 months, 2 to <6 months, 6 months to <1 year, 1 to <3 years, and 3 to 6 months of age that is comparable to normal adults. Prolonged elimination in children <6 months of age is related to renal immaturity.

Age Factors↗
PubMedDate not supplied

Transient left ventricular dysfunction in childhood sickle cell disease.

For unclear reasons, myocardial infarction is rare in childhood sickle cell disease, whereas lung, bone, and brain infarcts are more common. During vasoocclusive crisis and infection, acute myocardial ischemia and chronic volume overload from anemia may result in myocardial dysfunction. We report a child who had reversible cardiac dysfunction that mimicked myocardial infarction.

Child↗
PubMedDate not supplied

Subgravity states: key to understanding the role of terrestrial gravity in human behaviour.

The early orbital flights, although undertaken with considerable confidence, involved some uncertainty because of the impossibility of simulating under terrestrial conditions all of the conditions encountered in space. However, space-flight achievements by both the American astronauts and Soviet cosmonauts have firmly established that man, if appropriately selected, trained, and protected by suitable life-support systems, can perform efficiently for long periods of time in the hostile environment of space. We know that the side effects of vestibular origin pose important problems in space exploration, and the neurophysiological effects of any extensive, rapid adaptation processes in subgravity states have enabled a better understanding of man's compensatory capabilities. With the successful establishment of orbiting research laboratories, an unparalleled opportunity exists that will undoubtedly enable better understanding of the role played by gravity in normal terrestrial activity, not only as it affects our vestibular physiology, but also as it may or may not concern other systems and at different organizational levels in the body.

Acceleration↗
PubMedDate not supplied

Prostaglandin E1-induced hyperostosis: clinicopathologic correlations and possible pathogenetic mechanisms.

Prostaglandin E1 (PGE1) causes skeletal hypertrophy, a phenomenon noted when it is administered for several weeks to maintain ductus arteriosus patency in neonates with congenital heart disease. This effect, a dose-dependent and reversible hyperostosis, was described radiologically as bone within bone, but skeletal histopathology was not studied. We compared postmortem gross, radiological, and histological bone findings for untreated controls and term gestation infants after 4, 27, and 56 days of continuous 0.1-0.2 microgram/kg/min PGE1. Bone was not significantly different from controls after 4 days of PGE1. Radiographs were negative after 27 days, but femoral cortex showed early periosteal osteoblast proliferation. At 56 days of PGE1, there was severe, radiologically apparent neocortex formation in tubular, rib, and scapular bones. Corresponding sections of femoral shaft revealed distinctive histopathology with thickened periosteum and fibrocartilage-like tissue covering an exuberant neocortex of closely aligned, gracile, woven bone trabeculae. Paratrabecular stroma contained ectatic capillaries orthogonally oriented to the periosteum, suggesting that a vascular reaction to PGE1 is important in the observed effect. The native cortex was partially resorbed; because it is stress shielded by the neocortex and no inflammation was present, this was interpreted as a secondary effect. We conclude that PGE1-associated paracortical bone hypertrophy is distinct from inflammatory processes and that its early stages may not be apparent radiologically. Moreover, the time course of PGE1-induced osteoblast proliferation and mineralization suggests that experimental use for 4-8 weeks may benefit conditions such as ununited fractures.

Alprostadil↗
PubMedDate not supplied

Visual, refractive, and patient satisfaction results following bilateral photorefractive keratectomy for myopia.

Reports of the visual, refractive, and patient satisfaction results after photorefractive keratectomy (PRK) are now becoming available. The visual, refractive, and patient satisfaction results of 52 patients after bilateral excimer laser photorefractive keratectomy for myopia were studied. Patient satisfaction was measured using a five-part questionnaire. Initial patients obtained an overcorrection which necessitated adjusting the programmed correction to 75% of targeted correction.

Adult↗