Captopril-enhanced binding of PlA1 (HPA-1a) antibodies in posttransfusion purpura

A case of posttransfusion purpura is reported in a 90-year-old patient whose PlA1 antibody (anti-HPA-1a) was found to bind better to HPA-1a in the presence of captopril, a drug the patient had taken. Initially, IgG antibodies were found in the serum that reacted with normal platelets, but the binding of the antibody was increased in vitro by captopril, which suggested that captopril was responsible for the thrombocytopenia. However, in vitro studies demonstrated that the patient's platelets were negative for HPA-1a and that anti-HPA-1a was present in the serum, both of which findings were consistent with the diagnosis of posttransfusion purpura. The binding of this antibody was enhanced 50 percent by captopril in vitro, and increased binding in the presence of captopril did not occur when the anti-HPA-1a was removed. Similar results were obtained with serum containing anti-HPA-1a from another patient with posttransfusion purpura. Thus, captopril may increase the binding of anti-HPA-1a and confuse the determination of the cause of acute thrombocytopenia.     

The origin of ABH antigens on human platelets

ABH antigens are present on platelets from individuals of the corresponding red cell phenotype, but the extent to which these antigens are intrinsic or adsorbed remains undefined. To evaluate platelets for intrinsic H substance, an IgM mouse monoclonal antibody against type 2H chain (the intrinsic H structure found on erythrocytes) was labeled with 125I and incubated with platelets from donors of different ABO type. The antibody showed dose-response saturation curves, and binding to platelets paralleled that of the red cell ABO type, with O greater than B greater than A1 greater than A1B greater Oh cells, giving a single factor variance F of 190 (P less than .0005). Passive adsorption of A antigens by platelets has been previously reported. To verify this phenomenon for A and B antigens and to quantitate the elution of A and B antigens from platelets, the following assay system was used. Platelets from group A1 and B donors were incubated in plasma from group O donors, and platelets from group O donors were incubated in plasma from different ABO, Lewis, and presumed secretor-type donors. Human IgG anti-A or anti-B was added to the platelets. The amount of antibody bound was determined with a 125I- labeled mouse monoclonal anti-human IgG. When incubated for 96 hours in group O plasma, group A1 platelets showed a 45% to 50% decrease in binding of anti-A. There was no significant change in the level of type 2H antigen on these platelets during the same incubation period. Group O platelets incubated in A or B plasmas rapidly acquired the antigens, but if returned to their original plasma, 95% of this passively adsorbed antigen eluted off within 18 hours. The maximum uptake of A and B substances was influenced by the Lewis and secretor type of donor plasma. Our present study demonstrates that ABH antigens on platelets consist of type 2H chains, which are presumably intrinsic as when found on red cells, and of passively adsorbed ABH structures, which are presumably type 1H chains.     

Gastrointestinal tract focal mass lesions: role of CT and barium evaluations

Fifty-eight patients with focal mass lesions involving the gastrointestinal tract were studied retrospectively. The diagnostic value of CT scans was seen by assessing the barium studies alone, then by combined review of radiographs and CT scans. Patient management decision making was similarly evaluated. CT scanning aided in diagnosis of the focal masses in 17 patients (29%), changing the differential diagnosis in eight (14%) and increasing diagnostic confidence significantly in nine (16%). In 21 (36%) additional cases, the diagnosis did not change, but CT scanning improved the understanding of disease extent. In the remaining 20 cases (34%), CT scanning did not help diagnostically. CT scanning altered patient management decisions in 19 of the 58 patients (33%). CT study was most helpful in cases of benign extrinsic cystic disease, lymphoma, and smooth-muscle tumors and less helpful for adenocarcinomas of the bowel. The value of the CT data increased as one moved from mucosal lesions to submucosal or extrinsic lesions.     

Molecular genetic analysis of porcine von Willebrand disease: tight linkage to the von Willebrand factor locus

von Willebrand disease (vWD), one of the most common bleeding disorders in humans, is manifested as a quantitative or qualitative defect in von Willebrand factor (vWF), an adhesive glycoprotein (GP) with critical hemostatic functions. Except for the rare severely affected patient with a gene deletion as etiology of the disease, the molecular basis for vWD is not known. We studied the molecular basis for vWD in a breeding colony of pigs with a disease closely resembling the human disorder. The porcine vWF gene is similar in size and complexity to its human counterpart, and no gross gene deletion or rearrangement was evident as the pathogenesis of porcine vWD. A restriction fragment- length polymorphism (RFLP) within the porcine vWF gene was identified with the restriction endonuclease HindIII, and 22/35 members of the pedigree were analyzed for the polymorphic site. Linkage between the vWF locus and the vWD phenotype was established with a calculated LOD score of 5.3 (1/200,000 probability by chance alone), with no crossovers identified. These findings indicate that porcine vWD is due to a molecular defect within (or near) the vWF locus, most likely representing a point mutation or small insertion/deletion within the vWF gene.     

The relationship among platelet-associated IgG, platelet lifespan, and reticuloendothelial cell function

Platelet-associated IgG (PAIgG) has been reported to be elevated in nonthrombocytopenic patients who have a normal platelet lifespan. This has been interpreted as indicating that PAIgG is a nonspecific finding in these patients and not a determinant of platelet survival. It is important to recognize that the reticuloendothelial (RE) system plays an important role in the clearance of antibody-sensitized cells. In this study, we related the level of PAIgG and the platelet lifespan to the RE function in patients with: (A) idiopathic thrombocytopenic purpura (ITP), and (B) five patients with elevated levels of PAIgG yet normal or near-normal platelet counts. RE function was assessed by measuring the clearance of autologous chromium-labeled red cells sensitized with a precise amount of alloantibody (2,000-3,600 molecules of IgG/cell). Eight patients with immune thrombocytopenia had significantly shortened platelet survivals (less than 2-113 hr). In contrast, the five patients with elevated PAIgG, yet normal or near- normal platelet counts, all had normal autologous platelet survivals (186-222 hr). These patients also had significantly impaired clearance of IgG-sensitized red cells, with an average of 85% of the infused red cells remaining in the circulation at 60 min (normal 42% +/- 14%, n = 10). In this study, every patient with elevated PAIgG and normal RE function had a shortened platelet lifespan. Those patients with elevated PAIgG and impaired RE function did not invariably have a shortened platelet lifespan. The observation that the PAIgG is elevated in some patients whose platelet survival is normal does not indicate that PAIgG is not biologically relevant. It indicates that these patients may have RE blockade and do not clear IgG-sensitized cells.     

Densitometric analysis of the paranasal sinuses

Summary The knowledge of weak points in the osseous structure of the skull is of great importance for endonasal operations. For this reason the anatomy of the skull is accurately described in serial sections. Serial sections of 1.5 mm thickness are evaluated by a computerized image analyzing system, which allows qualitative as well as quantitative statements on the structure of the paranasal sinuses and their neighbourhood. The bone density in the frontobasal area of the skull as well as of the ethmoid cells is presented separately. The anatomy of the sphenoid sinus is described by densitometric and gross techniques.

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Analyse densitométrique des sinus paranasaux

Résumé La connaissance des points forts dans la structure osseuse du crâne est d'une grande importance pour les interventions endonasales. Pour cette raison, l'anatomie du crâne est décrite avec précision sur des coupes sériées. Les coupes sériées de 1,5 mm d'épaisseur sont étudiées par un système d'analyse d'images computérisées, qui permet l'étude à la fois qualitative et quantitative de la structure des sinus paranasaux et de leur environnement. La densité osseuse dans l'aire fronto-basale du crâne et celle des cellules éthmoïdales sont présentées séparément. L'anatomie du sinus sphénoïdal est décrite à partir de la tomodensitométrie et de cette technique macroscopique.