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Biomedical subjects

R Moncada

Publications and source records attributed to R Moncada.

79 records · Page 5Linked to original sources
PubMedDate not supplied

Subcellular localization and properties of adenosine diphosphatase in human placenta.

It was found that mitochondria from human placenta exhibited an ADPase activity with the following characteristics. The enzyme responsible for this activity was associated with the inner mitochondrial membrane. It was not released by treatment of the submitochondrial particles with solutions of high ionic strength. Maximal ADP hydrolysis was reached at pH 8. Specific inhibitors for alkaline phosphatase (L-phenylalanine), myokinase (P1,P5-di(adenosine-5')pentaphosphate), or 5'-nucleotidase (concanavalin A) did not decrease ADP hydrolysis. ATP synthesis from ADP by myokinase was about 13 nmol/mg/min, whereas ADP hydrolysis reached values around 500 to 550 nmol/mg/min, indicating that a myokinase-H+ATPase combination could not account for the observed rates of ADP hydrolysis. The activity was stimulated by Mg2+, but high concentrations of this cation produced inhibition. High ADP concentrations did not inhibit ADPase activity. Kinetic measurements of the activity in the submitochondrial particles showed that the true substrate was ADP-Mg. The kinetic studies showed V(app) values of 476 and 270 nmol/mg/min, and Kmapp values of 416 and 8.7 microM.

Adenine Nucleotides↗
PubMedDate not supplied

Effects of nonionic contrast media (CM) on the components of coagulation and complement systems.

Several nonionic experimental contrast media (CM) were evaluated for their effects on coagulation cascade, platelet aggregation, and the activation of complement pathways. In an in vitro system, most of the contrast media tested showed a mild anticoagulant property by prolonging the clotting times, such as partial thromboplastin time and the thrombin time of pooled normal human plasma. However, aggregation of normal human platelets by adenosine-diphosphate (ADP), collagen, epinephrine, ristocetin, and thrombin was not blocked when the platelet-rich plasma was incubated with these agents. No quantitative or qualitative changes in the complement components C3 or C4 were detected when a mixture of CM and pooled normal human serum was analyzed by radial immunodiffusion, immuno- or crossed-immunoelectrophoresis techniques. These results indicate that nonionic contrast media produce certain transient hematologic changes and should be further tested for their immunologic properties in order to establish their absolute safety in diagnostic procedures.

Blood Coagulation↗
PubMedDate not supplied

CT diagnosis of congenital intrapericardial masses.

Prior to the development of CT, cardiac and pericardiac masses were evaluated by chest roentgenography, angiocardiography, and echocardiography. In most cases preoperative diagnosis of a specific entity was impossible. Preoperative CT diagnosis of an intrapericardial developmental mass becomes possible because of the presence of fat, fat/fluid level, thick walled cysts, as well as globular calcifications, bones, teeth, water density fluid, and soft tissue. A report of a young woman with a ruptured and infected intrapericardial teratoma and an infant with an intrapericardial bronchial cyst is presented.

Adult↗
PubMedDate not supplied

Computed tomography-guided fine needle aspiration biopsy of deep-seated lesions. A four-year experience.

With the increased sophistication of radiologic imaging techniques, the sensitivity of detecting nonpalpable, deep-seated lesions has greatly improved. Coupling these techniques with fine needle aspiration biopsy (FNAB) provides a cost-effective, minimum-risk, highly sensitive and specific method of diagnostically evaluating the lesions. Over a four-year period (1985-1989) a total of 2,229 FNABs were performed at Loyola University Medical Center, Chicago; 539 of these biopsies were computed tomographically guided. The geographic computed tomographic biopsy sites were: thorax, 267 (49.54%); abdomen, 175 (32.47%); and retroperitoneum, 97 (18%). Four hundred eighty FNAB cases were diagnostic, with subsequent histologic follow-up in 284 (58%) cases. Fifty-nine (10.9%) FNABs were unsatisfactory; of them, 31 had subsequent diagnostic histology, and 9 remained unsatisfactory. A good correlation between FNAB and histology was observed, with an overall sensitivity of 93.2%, specificity of 98.8%, false-negative rate of 6.8% and false-positive rate of 1.2%. Diagnostic pitfalls and biopsy adequacy in computed tomographically guided FNABs are discussed.

Abdominal Neoplasms↗
PubMedDate not supplied

Antiplatelet action of intravascular contrast media. Implications in diagnostic procedures.

The antiplatelet action of intravascular contrast media (CM) Renografin-76 (diatrizoate meglumine and diatrizoate sodium) was studied in vitro and in 21 patients undergoing radiodiagnostic procedures. In vitro studies suggested that in Renografin-76, meglumine was the chief constituent responsible for its antiplatelet action. In post-CM plasma from patients, clotting times were prolonged and platelet aggregation greatly impaired, albeit normal aggregation restored within 3 hours. Although changes in global clotting times and platelet aggregation were mostly transient, it is possible that CM usage in patients with thrombocytopenia, sickle cell phenomenon, and on anticoagulant-antiplatelet drugs may present a serious risk to their hemostatic integrity.

Adult↗