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Biomedical subjects

E D Smith

Publications and source records attributed to E D Smith.

At least 55 records · Page 3Linked to original sources
PubMed1987

The xerocytosis of Hb SC disease.

Patients with Hb SC disease were found to have microcytic and hyperchromic red cell indices despite mild reticulocytosis. Iron deficiency anemia was ruled out by the finding of normal serum ferritin levels. In order to determine whether the microcytosis was due to coexistent alpha-thalassemia, restriction endonuclease mapping was performed on genomic DNA extracted from peripheral blood leukocytes. Patients with Hb SC disease had microcytic indices despite the presence of a full complement of four alpha-genes (alpha alpha/alpha alpha), suggesting that the microcytosis may be due to cellular dehydration (or xerocytosis), since the mean corpuscular hemoglobin concentration in Hb SC disease patients was significantly higher than in controls. This possibility was investigated further by the determination of RBC cation content. RBC Na levels were similar in SC and normal red cells. Hb SC RBCs, however, had significantly reduced K levels. These findings show that RBC cation content, and thus cell water, is decreased in Hb SC disease. The decreased RBC K level in the presence of normal cellular Na concentration suggests selective K loss that is not due to inhibition of the Na K pump. Ouabain-insensitive K+ efflux was increased to four times normal in SC cells. Cell dehydration was confirmed by the demonstration of increased high-density RBCs on discontinuous Stractan density gradients and by osmotic gradient ektacytometry. Cellular dehydration and its sequelae were worse in CC erythrocytes and milder in AC cells than in Hb SC red cells. Taken together, these data indicate that in Hb SC disease the RBCs are severely dehydrated and typically microcytic and hyperchromic. Hb SC RBCs seem to be dehydrated due to selective K loss. These findings suggest a functional interrelationship between Hb SC, the red cell membrane, and cation regulation.

Adenosine Triphosphatases↗
PubMed1987

Expert systems for implanted pacemaker analysis.

A computer-based software system has been proposed that will assist clinicians in the often difficult task of analyzing multi-channel pacemaker modified ECGs. The system contains three integrated modules. First, digital signal processing indentifies cardiac events from two sources provided by the latest pacemaker technology, intracardiac atrial and ventricular signals, activity markers, and a surface ECG. Secondly, the pacemaker's functional status at each event is analyzed by a rule-based monitor model of the pacemaker. Thirdly, Expert System (ES) techniques were used to combine the digital signal processing metrics, the pacemaker's functional status at each event, and the programmed parameters stored in the pacemaker's memory with a clinical knowledge base relating known problems and their causes. The domain specific tasks, briefly described here, that were most useful in the implementation of the ES are: data reduction, knowledge acquisition methods, knowledge representation, inferencing, and presentation of results.

Electrocardiography↗
PubMed1985

Glyceraldehyde-3-phosphate dehydrogenase of rat erythrocytes has no membrane component.

In the course of studying mammalian erythrocytes we noted prominent differences in the red cells of the rat. Analysis of ghosts by sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis showed that membranes of rat red cells were devoid of band 6 or the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (D-glyceraldehyde-3-phosphate: NAD+ oxidoreductase (phosphorylating), EC 1.2.1.12). Direct measurements of this enzyme showed that glyceraldehyde-3-phosphate dehydrogenase activity in rat erythrocytes was about 25% of that in human cells; all of the glyceraldehyde-3-phosphate dehydrogenase activity in rat erythrocytes was within the cytoplasm and none was membrane bound; and in the human red cell, about 1/3 of the enzyme activity was within the cytoplasm and 2/3 membrane bound. The release of glyceraldehyde-3-phosphate dehydrogenase from fresh rat erythrocytes immediately following saponin lysis was also determined using the rapid filtration technique recently described. The extrapolated zero-time intercepts of these reactions confirmed that, in the rat erythrocyte, none of the cellular glyceraldehyde-3-phosphate dehydrogenase was membrane bound. Failure of rat glyceraldehyde-3-phosphate dehydrogenase to bind to the membranes of the intact rat erythrocyte seems to be due to cytoplasmic metabolites which interact with the enzyme and render it incapable of binding to the membrane.

Animals↗
PubMed1985

Effect of polyamines on hemoglobin and globin chain synthesis.

Exposure of reticulocytes to 25 mM spermidine and spermine stimulates the incorporation of 14C leucine into hemoglobin and globin polypeptide chains. These two polyamines stimulate beta chain synthesis to a greater extent than they stimulate alpha chain synthesis, thus resulting in a decreased synthetic alpha/beta globin ratio. Because of the low permeability of the red cell membrane to these polycations, less than 1.0% of extracellular spermidine and spermine accumulate within the erythrocyte, thus these effects occur at intracellular polyamine levels that are physiological. Putrescine progressively decreases hemoglobin synthesis at extracellular concentrations greater than 10 mM without affecting the synthetic alpha/beta ratio. These findings suggest a role for polyamines in the fine tuning of the alpha/beta globin ratio at the translational level.

Globins↗
PubMed1985

Reduced transglutaminase-catalyzed cross-linking of exogenous amines to membrane proteins in sickle erythrocytes.

In order to determine the capacity of sickle cells to undergo transglutaminase-catalyzed cross-linking of membrane proteins, human normal and sickle erythrocytes were incubated with [ring-2-14C]histamine in the presence of Ca2+ and ionophore A23187. The [14C]histamine incorporation into membrane components was observed in freshly prepared erythrocytes. Incorporation of radioactivity into spectrin and Band 3 membrane components was significantly (P less than 0.001) less in sickle erythrocytes than in normal cells. Transglutaminase deficiency was excluded by the finding of increased activity of this enzyme in sickle cells from patients with reticulocytosis. The incorporation of [3H]spermine into red cell membranes was also less in sickle erythrocytes than in normal cells under the same conditions of incubation used for [ring-2-14C]histamine. Sickle erythrocytes were more permeable to these amines than normal cells. It is proposed that the gamma-glutamyl sites of membrane proteins in sickle erythrocytes are less accessible for transglutaminase-catalyzed cross-linking to histamine and polyamines in vitro, perhaps due to prior in vivo activation of this enzyme by the increased calcium in sickle cells and/or shielding secondary to altered membrane organization.

Acyltransferases↗
PubMed1982

A study of the sequelae of posterior urethral valves.

We discuss the drainage procedures prior to valve ablation and the long-term sequelae in the upper urinary tract of 135 boys with posterior urethral valves. Cutaneous ureterostomy in infants, which had been used previously, now has been replaced largely by lower tract drainage using stab cystotomy combined with irrigation. The former technique is reserved for those few patients who do not improve. Older patients require no preliminary drainage. The long-term sequelae were studied with respect to urinary control, the fate of ureteral reflux and the state of upper tract dilatation. Of our patients 14 per cent remain incontinent owing to too radical a transurethral resection, bladder neck surgery or a gross degree of urethral dilatation found in neonates. Only 32 per cent of the renal units were presented with ureteral reflux. After valve ablation moderate or gross reflux ceased spontaneously in 29 per cent of the patients, it persisted in 35 per cent and it required antireflux surgery or nephrectomy in 36 per cent. The upper urinary tracts were dilated in 90 per cent of the renal units and most had moderate or gross dilatation, especially in infants. Of 116 united with moderate or gross dilatation, or nonfunction 65 per cent remained unchanged after valve ablation but 35 per cent improved to normal or nearly normal. In 35 units with persistent dilatation in nonrefluxing systems the dilatation was associated with pelvioureteral or vesicoureteral obstruction in 10 units, although in 25 patients no obstruction could be identified. The dilatation was considered to be a manifestation of developmental dysplasia of the ureters.

Child↗
PubMed1982

Closed renal trauma in children.

Closed renal trauma in children often results in serious injury. In a series of 100 consecutive patients with closed renal trauma treated at the Royal Children's Hospital from 1967 to 1978, 32 children required surgery. Of these, eight children came to nephrectomy, whereas in 19 children viable renal tissue was conserved by the use of techniques such as renal suture or partial nephrectomy. The remaining five children had surgery, not for trauma, but rather for preexisting hydronephrosis discovered during investigation. There was a close relationship between the classification of renal injuries and the need for surgery. In this series there were two deaths and two late complications.

Accidents↗