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Biomedical subjects

D Meyer

Publications and source records attributed to D Meyer.

At least 487 records · Page 27Linked to original sources
PubMed1981

Ocular anomalies simulating double optic discs.

Three lesions simulating duplication of the optic disc are described. In case 1 the lesion was thought to be an ectatic peripapillary coloboma. Computer-assisted tomography demonstrated a single optic nerve in each orbit. In case 2 two optic disc with separate vascular systems were observed in photographs; blood vessels arising from the upper disc appeared to supply the superior portion of the retina, including the fovea. In case 3 a colobomatous defect with vascular anastomosis to the optic disc was observed in photographs. The resemblance of duplication of the optic disc to congenital disc anomalies, ectatic peripapillary colobomas and other simulating lesions is discussed. True duplication of the optic disc with associated duplication of the optic nerve is rare.

Coloboma↗
PubMed1980

Stage-related combined modality treatment of retinoblastoma. Results of a prospective study.

Forty-two consecutive patients with retinoblastoma were evaluated by a new staging system and combined modality therapy instituted according to stage. Nineteen patients had bilateral tumors and 23 had unilateral tumors. The staging system was effective in identifying subpopulations of patients and successfully predicted those at greater risk of recurrence or death. Thirty-nine of 42 patients survive (Median survival time, 42 months). Two of 4 children with tumor extension beyond the eye died while 37 of 38 children with tumor presumed confined to the eye survive. Toxicity of the chemotherapy was mild. Radiation therapy of intraocular tumor was associated with cataract formation but most children had satisfactory vision after extraction and the use of corrective lenses. Ophthalmologic findings did not always correlate with histologic extent of tumor and both should be used in planning and evaluating treatment. Recommendations are made on the role of chemotherapy and the need to reduce the morbidity of treatment.

Child↗
PubMed1980

Shear rate dependent inhibition of platelet adhesion and aggregation on collagenous surfaces by antibodies to human factor VIII/von Willebrand factor.

The effect of heterologous and homologous antibodies to factor VIII/von Willebrand factor (F.VIII/VWF) and purified VWF on the interaction of human platelets with subendothelium and with a surface consisting of collagen fibrils was investigated using annular flow chambers. Wall shear rates of 200--5200 s-1 were produced by varying the flow rate of the citrated blood which was circulated through these chambers by a pump. Surface coverage with platelets and with platelet aggregates was measured morphometrically. The antibodies had no effect on platelet adhesion at low shear rates. However, an increasing inhibition of adhesion was observed with increasing shear rates. The antibodies to F.VIII/VWF and to purified VWF virtually abolished adhesion at shear rates which are present in the microvascular (1300--5200 s-1). By contrast, antibodies to factor VIII:C which were isolated from two patients with haemophilia A had no effect on adhesion. In addition antibodies to F.VIII/VWF and to purified VWF inhibited adhesion-induced aggregation. We conclude that F.VIII/VWF plays an essential role as shear rates, i.e. when the time available for the establishment of a stable bond between platelets and collagenous surfaces is short.

Animals↗
PubMed1980

Effects of denervation and simple disuse on rates of oxidation and on activities of four mitochondrial enzymes in type I muscle.

To differentiate the effect of muscle contractile activity from that of motor nerve on oxidative processes in type I muscle, oxidative processes were studied in muscle after immobilization and after denervation. The two processes led to similar atrophy of muscle weight and of the mean diameter of muscle fibers. Disuse of soleus muscle (type I) did not affect rates of oxidation of 14C-labeled substrates although these were reduced by disuse of the vastus lateralis (type II). Disuse of the soleus did not affect activities of several mitochondrial enzymes assayed by histochemical or biochemical methods. However, denervation of the soleus did lead to a fall in metabolic rates and enzyme activities. The activity of 3-hydroxybutyrate dehydrogenase fell more than did the activities of succinic dehydrogenase, lipoamide dehydrogenase, or cytochrome-c oxidase in both homogenates and in mitochondrial fractions. These results suggest nerve may regulate mitochondrial enzymes in type I muscle. The mechanism appears to be different from that which regulates oxidative processes in type II muscle.

Animals↗
PubMed1980

Multimeric structure of factor VIII/von Willebrand factor in von Willebrand's disease.

Recent studies have provided substantial evidence that F. VIII/vWF exists not only as a polymer of approximately 1 x 10(6) MW composed of 230,000 MW subunits but is further organized into a multimeric series (1 to 20 x 10(6) MW). With an immunologic technique to isolate F.VIII/vWF directly from small volumes of plasma of patients with vWD, the relative distribution and concentration of individual multimeric sets was examined by agarose gel electrophoresis in the presence of SDS. In classical vWD (type I) with decreased VIIIR:RCo, the relative distribution of multimeric forms of FVIII/vWF was comparable to normal plasma but reduced in quantity. In "variants" of vWD (type II) with undetectable VIIIR:RCo, the larger multimer subsets were absent, and the smaller one present in relatively greater concentration. Large multimers as well as VIIIR:RCo were also lacking in F.VIII/vWF prepared from normal plasma cryosupernatant. These observations suggest the existence of different molecular abnormalities of F.VIII/vWF underlying the two major types of vWD: reduced synthesis in type I and polymerization defect with resultant lack of VIIIR:RCo in type II.

Blood Coagulation Factors↗
PubMed1979

The factor VIII abnormality in severe von Willebrand's disease.

We attempted to characterize the small amounts of factor VIII-related antigen detectable in the severe recessive form of von Willebrand's disease with newly developed radioimmunoprecipitin techniques and radiocrossed immunoelectrophoresis. Previous studies have failed to demonstrate factor VIII-related antigen in most patients tested even with the highly sensitive immunoradiometric assays. Using the newer techniques, we found antigen in the plasma of six of eight patients with severe von Willebrand's disease from different kindreds. Qualitative abnormalities of the trace quantities of factor VIII-related antigen were demonstrated in five of the patients, with absence or relative decrease of the larger, less anodal forms. In addition, five distinct patterns were observed, each suggesting a different molecular abnormality. Heterozygous parents had normal to moderately decreased factor VIII-related antigen, with normal crossed immunoelectrophoretic patterns. This study suggests that severe von Willebrand's disease is a heterogeneous syndrome with various underlying molecular defects.

Antigens↗
PubMed1979

Peripheral neuropathy after administration of tetanus toxoid.

A reversible paresis of several muscles of the right arm was observed in a 20-year-old female, 3 weeks after the intragluteal injection of tetanus toxoid and 6--7 weeks after multiple injuries. The EMG findings indicated a transitory conduction block of nerve fibers to the deltoid and pectoralis muscles and a more severe axonal-demyelinating lesion of fibers to the biceps muscle. The cause of the palsy was probably a reaction to the administration of tetanus toxoid; other possible causes are discussed.

Accidents, Traffic↗
PubMed1979

Clinical, serologic, and epidemiologic characteristics of ocular toxocariasis.

The clinical, serologic, and epidemiologic characteristics of 17 cases of ocular toxocariasis (OT) were studied and compared with those of a control group of 15 cases of other ocular diseases whose differential diagnosis included retinoblastoma. The prevalence and mean titers of Toxocara antibody detected by enzyme-linked immunosorbent assay were greater (P less than 0.005) for patients with OT than for the control group, but not all clinically diagnosed OT cases had detectable antibody. The prevalence of pica was significantly greater in cases than in controls (P less than 0.05). Almost all case and control patients had a history of exposure to pet dogs and cats, but recent exposure to puppies (less than 3 months old) was significantly associated with Toxocara infection in this study group.

Adolescent↗
PubMed1979

Familial incidence of precipitating antibodies in von Willebrand's disease: a study of four cases.

Precipitating antibodies directed toward human F.VIII/WF were found in the plasma of four out of 17 multitransfused patients with severe, homozygous-like VWD. The familial incidence was illustrated by the development of these antibodies in three patients from the same kindred. Such antibodies, titrated with newly developed quantitative assays of anti-VIIIR:Ag and anti-VIIIR:RCo, were directed toward only these components of F.VIII/WF. VIII:C was neutralized in a time-independent manner in plasma and was not inactivated when separated from F.VIII/WF by solid-phase PE absorption. Plasma, serum, or immunoglobulin reacted in precipitation systems (immunodiffusion, EID, CIE) with human VIIIR:Ag, with some degree of cross-reactivity toward VIIIR:Ag from other mammalian plasmas. When used in IRMA, these antibodies demonstrated the same abnormalities as heterologous antisera in variant VWD: decreased binding affinity or nonparallelism of the dose-response curves. They are polyclonal IgG with both kappa and lambda light chains. It is suggested that in some patients with severe homozygous-like VWD, the synthesis of the component of F.VIII/WF carrying VIIIR:Ag and VIIIR:RCo is suppressed whereas VIII:C production is not completely abolished.

Antibody Formation↗
PubMed1979

Fluid-phase immunoradiometric assay for the detection of qualitative abnormalities of factor VIII/von Willebrand factor in variants of von Willebrand's disease.

Antigenic reactivity of F.VIII/WF in variants of von Willebrand's disease (vWd) was studied with both fluid-phase and solid-phase immunoradiometric assays. Two different (rabbit and goat) 125I-labeled specific antibodies against purified F.VIII/WF were used in both their divalent (IgG) and their monovalent (Fab fragment) forms. Dose-response curves obtained by reacting a constant amount of antibody with serial dilutions of plasmas from normal or homozygous vWd demonstrated the specificity of the test. The accuracy was significantly higher with 125I-Fab fragments of goat anti-F.VIII/WF antiserum that intact goat IgG or rabbit IgG or Fab fragments. The significant decrease of the slope of the dose-response curves obtained with plasma from variants of vWd has been interpreted as due to the presence of abnormal F.VIII/WF molecules with decreased antigenic reactivity. A similar anomaly was found in cryosupernatant prepared from normal plasma, paralleling similarities demonstrated between variants of vWd and cryosupernatant. Results of experiments performed by reacting constant plasma dilutions from control or variants of confirmed the decreased antigenic reactivity of variant F.VIII/WF.

Blood Coagulation Factors↗
PubMed1979

Selective absence of large forms of factor VIII/von Willebrand factor in acquired von Willebrand's syndrome. Response to transfusion.

A previously healthy elderly man with mucocutaneous bleeding was found to have a benign monoclonal IgG gammapathy associated with criteria for severe von Willebrand disease (Factor VIII procoagulant activity, Factor-VIII-related antigen, and ristocetin cofactor activity, less than 10% of normal). Associated qualitative abnormalities of factor VIII/von Willebrand factor were demonstrated by radiocrossed immunoelectrophoresis and immunoradiometric assay. The late clinical onset and negative family history are in favor of an acquired form of vWD. The monoclonal gammapathy and abnormalities of factor VIII/von Willebrand factor have been stable over a 10-yr period. No inhibitor to Factor VIII procoagulant activity, ristocetin cofactor activity, or Factor-VIII-related antigen could be demonstrated. Following transfusion of cryoprecipitate (with a normal cross immunoelectrophoretic pattern), there was a rapid removal of the large forms of Factor.-VIII-related antigen, paralleled by a decay of ristocetin cofactor activity. The transfusion study of this patient with acquired von Willebrand disease type II (variant of von Willebrand disease) serves to emphasize the relationship between polydispersity of Factor VIII/von Willebrand Factor and functional heterogeneity.

Adult↗