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Biomedical subjects

R G Mason

Publications and source records attributed to R G Mason.

At least 19 recordsLinked to original sources
PubMed1992

Achalasia evolving from segmental aperistalsis.

A 17-year-old woman was evaluated for dysphagia. Radiologic study revealed a rigid segment 10 cm long in the midesophagus, which was found to be aperistaltic on manometric evaluation. The rest of the esophagus and the lower esophageal sphincter were manometrically normal. Four years later the patient was seen for evaluation of severe dysphagia and symptoms of esophageal overflow. Characteristic radiologic and manometric findings of classic achalasia were noted. The case is discussed as an atypical form of achalasia evolving from a segmental esophageal aperistalsis.

Adolescent↗
PubMed1979

Heparin neutralization of PGI2: effects upon platelets.

Heparin neutralizes the inhibitory effect of prostacyclin (PGI2) on platelet aggregation. The PGI2-induced enhancement of platelet cyclic adenosine monophosphate levels is also inhibited. The mechanism appears to involve a direct interaction in which heparin neutralizes the inhibitory effects of PGI2 on platelet aggregation but, at the same time, does not lose its own anticoagulant activity. These findings may explain instances in which heparin infusions have been reported to produce hyperaggregation of platelets, thrombotic episodes, and thrombocytopenia in patients.

Adenosine Diphosphate↗
PubMed1979

Sickle cell syndromes. III. Silent-carrier alpha-thalassemia in combination with hemoglobin S and hemoglobin C.

Silent carrier alpha-thalassemia was identified in two individuals, one with sickle-cell trait and the other hemoglobin (Hb) C trait. Both are parents of a child with characteristic hematologic features of the Hb SC-alpha thalassemia syndrome, including microcytosis and an unbalanced pattern of globin synthesis. In contrast to the typical findings that accompany heterozygous Hb S or Hb C with concomitant alpha-thalassemia trait, neither of the parents had microcytosis nor a percent of the abnormal hemoglobin in their erythrocytes that was below the normal range. In both, however, globin synthesis of peripheral blood reticulocytes was unbalanced, consistent with mild alpha-thalassemia. These findings suggest that the alpha-thalassemia silent carrier may be hematologically indistinguishable from the nonthalassemic individual, even when hemoglobin S or C are present.

Anemia, Sickle Cell↗
PubMed1978

Unbalanced globin chain synthesis by Hb Lincoln Park (anti-Lepore) reticulocytes.

Hemoglobin synthesis was studied in vitro in reticulocytes from a patient with the anti-Lepore variant Hb Lincoln Park. Incorporation of L-leucine-3H into the alpha and beta delta chains of Hb Lincoln Park was substantially less than the incorporation into the corresponding globin chains of Hb A, with the rate of synthesis of the beta delta chain being similar to that of the delta chain of Hb A2. Synthesis of the alpha and total non-alpha globin components was unbalanced, with a substantial excess of alpha chain synthesis. These findings help to explain the mild hemolytic disease present in individuals with this hemoglobin variant.

Globins↗
PubMed1978

Sickle cell syndromes. II. The sickle cell anemia-alpha-thalassemia syndrome.

Five American black patients, ages 1 to 16 years, with the sickle cell anemia-alpha-thalassemia syndrome are described. Each patient had persistent microcytosis not explained by iron deficiency, and in each family the presence of alpha-thalassemia in combination with sickle cell trait was demonstrated in one of the parents. In one patient, in whom the diagnosis of sickle cell anemia was established at birth, an elevated level of Barts (gamma4) hemoglobin was also found. In these patients levels of alkali-resistant hemoglobin and reticulocyte counts were similar to those of sickle cell anemia patients of comparable age; however, stained smears of their peripheral blood rarely showed the presence of irreversibly sickled cells. No major ameliorative effect of the alpha-thalassemia on the clinical expression of the sickle cell disease of these patients was evident.

Adolescent↗
PubMed1978

Hemoglobin Lincoln Park: a betadelta fusion (anti-Lepore) variant with an amino acid deletion in the delta chain-derived segment.

An electrophoretically slow-moving hemoglobin variant was identified in three members of a family originating from Southern Mexico. The variant, Hb Lincoln Park, made up approximately 14% of the total hemoglobin and appeared to have normal stability and functional properties. None of the individuals in whom the abnormal hemoglobin was present was anemic, but each had a mildly elevated reticulocyte count. Structural data suggest that the non-alpha chain of Hb Lincoln Park represents a betadelta gene-fusion product, with normal beta chain structure of the amino-terminal portion of the chain and delta sequences subsequently, the crossover point occurring between animo acid residues 22 and 50. An additional abnormality is the deletion of valine-137, a component of the delta gene-derived segment of the betadelta chain. To account for the development of this abnormal globin chain, a series of intergenic crossovers is proposed; the first, a nonhomologous crossover between the beta and delta genes, presumably gave rise to the betadelta fusion gene; two additional crossovers, one of them unequal, may then have occurred between the same beta and delta genes to produce the amino acid deletion.

Adult↗
PubMed1978

Reaction of blood with artificial surfaces of hemodialyzers. Studies of human blood with platelet defects or coagulation factor deficiencies.

Heparinized human blood was exposed to the dialysis membranes of commercially available pediatric size hemodialyzers in an in vitro flow circuit. Bloods from normal subjects and from patients with various blood coagulation and platelet function deficiencies were tested in this model system. In most cases, there was a heavy linear deposit of leukocytes on the dialysis membrane overlying support structures. In other areas, the cellular deposit was less uniform and consisted of single platelets, platelet aggregates, leukocytes, and occasional fibrocellular microthrombi. The number of adherent platelets was smaller in tests with blood from patients with congenital afibrinogenemia, factor XII deficiency, severe von Willebrand's disease, and thrombasthenia then in tests with blood from normal subjects or hemophilic patients. Hence, fibrinogen, factor XII, the von Willebrand factor, and a normal platelet plasma membrane appear necessary for adhesion of platelets to dialysis membranes.

Afibrinogenemia↗
PubMed1978

Interaction of plasma proteins with artificial surfaces: protein adsorption isotherms.

A simple technique using a small disc which is dipped into a 125I-labeled protein solution has been devised to study the adsorption of human albumin, fibrinogen, and IgG onto Cuprophane or PVC. The purity of these human plasma proteins has been examined carefully with PAGE and immunochemical methods. The adsorption isotherms of albumin, fibrinogen, and IgG show a langmuir type adsorption. Delipidation of albumin did not alter the albumin affinity to Cuprophane and PVC. The surface saturation concentration (ng/cm2) for albumin, fibrinogen, or IgG were all found to be more on PVC (a hydrophobic surface) than on Cuprophane (a hydrophilic surface). The competitive adsorption of one protein species in a two- or three-protein mixture was also studied. Albumin and fibrinogen complete with each other for adsorption. The effects of IgG on the adsorption of albumin or fibrinogen were inconsistent and not predictable; the reason for this is unknown. The effect of laminar flow on albumin adsorption was studied with a specially designed Richardson flow chamber. In general caused an increase in albumin adsorption over that at static conditions. The increase of albumin adsorption was more pronounced also for PVC than for Cuprophane from 1 to 10 ml/min.

Adsorption↗
PubMed1978

Affinity chromatographic demonstration of a thrombin binding protein from the platelet plasma membrane.

Human platelet plasma membrane glycoprotein I with an apparent molecular weight of approximately 150,000 has been shown to be one of the proteins retained by thrombin immobilized on Sepharose 4B. The retained glycoprotein has been recovered by sodium dodecyl sulfate elution and characterized by SDS polyacrylamide gel electrophoresis in the presence of 2-mercaptoethanol.

Blood Platelets↗
PubMed1977

The endothelium: roles in thrombosis and hemostasis.

The renewed interest in endothelial function is based partly on success with tissue culture of endothelial cells. Endothelium functions primarily in the control of blood vessel wall permeability and in the provision of a blood-compatible lining surface. Recent findings indicate that endothelial cells are active metabolically in ways that may help prevent thrombosis. Endothelium actively degrades several different vasoactive compounds that circulate in blood and that can serve as platelet-aggregating agents. Endothelium also contains an inhibitor of platelet function and an activator of plasminogen, both of which can be released from the cell in response to appropriate stimuli. While intact endothelium functions primarily in prevention of thrombosis, damaged endothelium can contribute greatly to thrombus formation. Release of prostaglandins, adenine nucleotides, and other intracellular components from damaged endothelium can enhance platelet aggregation. Damaged endothelium may not function effectively in removal of vasoactive agents and may not release effective quantities of the inhibitor of platelet function or the activator of plasminogen. Altered endothelium exhibits tissue-factor activity, which can activate the extrinsic blood coagulation-system cascade. Finally, altered endothelial cells may contract and expose basement membrane to blood, thus enhancing thrombosis.

Blood Coagulation↗
PubMed1977

A concise method for study of the binding of thrombin to human platelets.

A rapid and sensitive technique is described for use in the study of the binding of 125I-thrombin to human platelets. The procedure involves the separation of free thrombin from platelet-bound thrombin by passage of this mixture through a discontinuous sucrose density gradient at low centrifugal force (1,500xg). Results obtained by this method are shown to be comparably to data obtained by two other conventional methods. This technique may facilitate further kinetic study of the binding of thrombin to human platelets.

Blood Platelets↗