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Biomedical subjects

H R Roberts

Publications and source records attributed to H R Roberts.

At least 145 records · Page 8Linked to original sources
PubMed1980

Fibrinogen Chapel Hill: hypodysfibrinogenemia with a tertiary polymerization defect.

A patient with a functionally defective fibrinogen (fibrinogen Chapel Hill) has been investigated. Fibrinogen Chapel Hill is characterized by hypofibrinogenemia, with a plasma concentration about one third of normal, as measured both functionally and immunochemically. Fibrinogen survival is normal; so also is fibrinopeptide release. A polymerization defect in this fibrinogen results in the delay of fibrin fibrils in solution to form a normal three-dimensional gel. This defect is not associated with end-to-end aggregation or with lateral associations in solution. Delayed gelation results from an abnormality in a tertiary contact site involved in network branching, which is associated with the hydrophilic, carboxy-terminal segment of the alpha chain. Fibrinogen Chapel Hill exhibits two additional abnormal responses, which are also associated with the same region. The early plasmin cleavages of fibrinogen and fragment X are delayed, and there is a concomitant delay in the appearance of fragments Y, D, and E. This fibrinogen also has an unusual sensitivity to Ancrod proteolysis, whereby Ancrod cleaves a large carboxy-terminal segment of the alpha chain more rapidly than in normal fibrinogen. The abnormalities in fibrinogen Chapel Hill can be explained by a structural abnormality which is functionally related to an alpha chain associated polymerization domain.

Adult↗
PubMed1980

Medical complications of hemophilia.

The modern, comprehensive care of patients with hemophilia requires an awareness that complications other than those caused by acute hemorrhage can occur. The use of newer, more potent plasma concentrates has been accompanied by an increased incidence of liver disease in transfusion-requiring hemophiliacs. The progression to chronic active hepatitis and cirrhosis are particularly ominous developments in these patients. There is also a high incidence of urinary tract abnormalities in hemophiliacs, though the long-term consequences of these abnormalities are unknown. Furthermore, it must be remembered that urinary tract disorders unrelated to hemorrhage, such as nephrolithiasis, tumors, and nephritis, can occur in patients with hemophilia and may be mistaken for hemorrhage. Finally, hypertension occurs more frequently in patients with hemophilia than in the general population and may in part contribute to the occurrence of bleeding within the central nervous system. Methods for evaluating and treating these various disorders are discussed. Greater awareness of these potentially treatable medical complications will improve further the quality of care in hemophilia.

Acute Disease↗
PubMed1980

An agarose plate method for detecting alloantisera to coagulant factor IX and factor IX antigen.

An agarose plate method for detecting human alloantibodies (inhibitors) to coagulant factor IX has been developed. The assay is based on the ability of such antisera to inhibit the coagulation of a mixture of haemophilia B plasma, normal plasma and platelet subsitute in an agarose matrix. The agarose plate method was also adopted to measure levels of FIX antigen (IX:Ag) in plasma. Using this technique, 12 of 17 obligate carriers of haemophilia B demonstrated reduced levels of IX:Ag. Three of the five carriers with normal IX:Ag levels were members of kindred in which affected individuals had normal or near normal levels of IX:Ag.

Antigens↗
PubMed1980

Characterization of a variant prothrombin in a patient congenitally deficient in factors II, VII, IX and X.

An 18-month-old child, who had no evidence of liver disease, malabsorption, or chronic ingestion of coumarin compounds, was found to have plasma deficiencies of factors II, VII, IX and X. Assays for factor II and X by immunological techniques (antibody neutralization and immunoelectrophoresis) revealed normal or elevated antigenic activity of these factors, suggesting the presence of abnormal protein variants in the patient's plasma. On two-dimensional immunoelectrophoresis of the patient's plasma in calcium, a normal and an abnormal population of prothrombin were seen. The abnormal prothrombin had a mobility more anodal than that of normal prothrombin, but less anodal than that of acarboxyprothrombin. The abnormal prothrombin, in contrast to acarboxyprothrombin, adsorbed readily to both aluminum hydroxide and barium citrate, and could be identified by two-dimensional immunoelectrophoresis of a barium citrate eluate. We suspect that the abnormal variant represents a partially carboxylated prothrombin.

Blood Coagulation Disorders↗
PubMed1980

Detection of factor IX antibodies by radioimmunoassay: effect of calcium on antibody-factor IX interaction.

A radioimmunoassay for alloantibodies (inhibitors) and heteroantibodies to human factor IX has been developed using radioiodinated human factor IX and formalin-fixed, heat-killed Staphylococcus aureus cells (Staph A). Staph A was used as a solid-phase adsorbent for immune complexes. The assay is specific, shows excellent correlation with factor IX coagulant neutralization assays in detecting alloantibodies (r = 0.98), and is 60 times more sensitive. The Staph A method allows rapid separation of immune complexes (within 10 min of addition) and binds immunoglobulin with equivalent efficiency in the presence and absence of calcium. These characteristics have made the Staph A binding method useful for observing the Ca++ effect on the antigenicity of factor IX as detected by hetero- and alloantibodies. All antisera investigated showed some increase in antibody titer when measured in the presence of Ca++. One particular alloantibody showed the greatest increase in titer (> twofold). The reversibility of the calcium effect by excess EDTA indicates that it was not caused by Ca++-dependent proteolysis of the factor IX molecule. The Staph A procedure can also be used as a sensitive competitive radioimmunoassay for human factor IX using alloantibody. The assay could detect factor IX antigen to a dilution of 1:1280 of normal plasma and correctly classified hemophilia B plasmas as cross-reacting material positive or negative.

Antibodies↗
PubMed1980

Calcium, phosphorus, iron, iodine, and zinc in the "total diet".

Advances in food technology have changed the nutrient composition of foods, raising questions as to whether mineral intakes in the U.S. are now adequate or excessive. When the FDA assayed "market basket" samples collected at the retail level in twenty urban areas of the U.S. during 1974 and 1975, the following minerals and the daily intake as percentages of the U.S. RDAs were found: (a) For adults (based on a 2,800 kcal intake)--calcium, 114; phosphorus, 171; iron, 98; iodine, 428; and zinc, 89; (b) for six-month-old infants--calcium, 163; phosphorus, 173; iron, 47; iodine, 878; and zinc, 112; and (c) for two-year-olds--calcium, 114; phosphorus, 130; iron, 112; iodine, 526; and zinc, 106.

Adolescent↗
PubMed1979

Detection of an abnormal plasma clot structure by a simple rigidity assay.

We report here on a patient whose abnormal fibrin clot was detected via the measurement of clot rigidity with a simple buoyant inner cylinder elastometer. The patient's clinical coagulation studies were all within normal limits except for prolonged thrombin and reptilase clotting times and high level of fibrin split products. The measured rigidity of the patient's clot was approximately ten times lower than that of a clot formed from normal pooled plasma. Light scattering studies indicated that this modified structure was not caused by a gross change in gel fiber morphology. Antithrombin activity was eliminated as a possible cause of the altered clot structure; this suggests the possibility of a modified fibrinogen. Abnormalities in the reptilase time and fibrinogen levels in two siblings support the hypothesis that the modification is an inherited defect. We suggest that the simple measurement of rigidity can be used rountinely to detect abnormalities in plasma clot structure. The screening for such disorders should be of importance to clinician, patient, and biochemical researcher.

Aged↗
PubMed1979

Isolation and characterization of granulocyte lysosomal proteins and study of their effects on the clotting system.

Lysosomes (granules) of rabbit PMN leukocytes were extracted with either HCl or H2SO4, and the extracts were chromatographed over Sephadex to separate protein constituents. Some of the low molecular weight cationic proteins homogeneous on SDS PAGE (8% and 12.5% gels) were characterized by electrophoretic mobility in acid gels and by amino acid analysis. A 3,700 dalton polypeptide, rich in arginine and cysteine, prolonged the partial thromboplastin time of normal plasma. In low concentration, this protein shortened the clotting time of pure fibrinogen by thrombin. In high concentration this lysosomal cationic protein precipitated fibrinogen from solution; no fibrinopeptides were released to suggest cleavage of fibrinogen. Fibrinolytic protease activity was detected in crude H2SO4 extracts but not in crude HCl extracts. Two separate plasminogen activators, differing from kallikrein or prekallikrein, were isolated from the H2SO4 lysosomal extract and were partially characterized; neither exhibited proteolytic activity on fibrinogen free of plasminogen.

Amino Acids↗
PubMed1979

Congenital deficiency of blood clotting factors II, VII, IX, and X.

A patient congenitally deficient in factors II, VII, IX, and X has been further investigated after a follow-up of 15 yr. At birth, these factors, when determined by clotting assays, were undetectable. Following therapy with vitamin K1, the clotting activity of these factors rose but never exceeded 18% of normal. Immunologic assays revealed much higher levels of these factors than did clotting assays, thus suggesting that the vitamin-K-dependent factors were present in abnormal forms. Two-dimensional crossed immunoelectrophoresis showed that at least two forms of prothrombin were present in the patient's plasma. One form was similar to normal prothrombin; the other had the same mobility as acarboxyprothrombin. In addition, the majority of this fast-migrating peak was not adsorbable onto insoluble barium salts. These observations suggested that some molecules of the patient's prothrombin lacked the normal complement of gamma-carboxyglutamic acid residues. This observation was confirmed by a specific assay for gamma-carboxyglutamate. Since malabsorption of vitamin K, warfarin intoxication, and hepatic dysfunction were excluded as causes of this patient's syndrome, this rare congenital abnormality could represent either a defective gamma-carboxylation mechanism within the hepatocyte or faulty vitamin K transport.

Adolescent↗
PubMed1978

Purification and characterization of an abnormal factor IX (Christmas factor) molecule. Factor IX Chapel Hill.

Human Factor IX (Christmas factor) was isolated from the plasma of a patient with mild hemophilia B. The patient's plasma contained 5% Factor IX clotting activity but 100% Factor IX antigenic activity as determined by immunological assays, which included inhibitor neutralization and a radioimmunoassay for Factor IX. This abnormal Factor IX is called Factor IX Chapel Hill (Factor IXCH). Both normal Factor IX and Factor IXCH have tyrosine as the NH2-terminal amino acid. The two proteins have a similar molecular weight, a similar amino acid analysis, the same number of gamma-carboxyglutamic acid residues (10 gamma-carboxyglutamic acid residues), and a similar carbohydrate content. Both exist as a single-chain glycoprotein in plasma. The major difference between normal Factor IX and Factor IXCH is that the latter exhibits delayed activation to Factor IXa in the presence of Factor XIa and Ca2+. Thus, Factor IXCH differs from other previously described abnormal Factor IX molecules.

Adult↗
PubMed1977

Treatment of anti-factor VIII antibodies.

Bleeding episodes in patients with hemophilia A with anti-factor VII antibodies are frequently difficult to treat. Factor VIII concentrates administered by continuous infusion or prothrombin complex concentrates (PCC) have been used for treatment. Hemophilia A patients with inhibitors who respond to factor VIII concentrates generally have low to moderate inhibitor titers (generally less than 20 Bethesda units). Those patients who receive PCC are quite difficult to evaluate but promising clinical responses have clearly been observed. This paper describes our experience with both modalities of therapy and will offer specific guidelines for such therapy.

Adult↗
PubMed1977

Isolation and characterization of factor IX Chapel Hill: comparison to normal human factor IX.

A classification scheme for patients with hemophilia B has been devised. Assessment of factor IX antigen and factor IX coagulant activity has confirmed the genetic heterogeneity of hemophilia B and has shown that some affected patients have normal amounts of factor IX-like protein. An abnormal factor IX, factor IX Chapel Hill, has been isolated from one of these variants and compared structurally and functionally to the purified normal human factor IX molecule. The major difference between factor IX Chapel Hill and normal human factor IX appears to be defective activation of the abnormal molecule by factor XIa and calcium.

Factor IX↗
PubMed1977

Liver biopsy in hemophilia A.

Hepatitis is a significant complication of the treatment of hemophilia A with factor VIII concentrates. Chronic liver disease in these patients is infrequently documented in the literature. The results of percutaneous liver biopsy, under the coverage of glycine-precipitated factor VIII, in six patients with hemophilia A who had the persistence of abnormal liver-function tests for at least 6 months, are described. Three patients had chronic active hepatitis, and three had chronic persistent hepatitis. No complications were encountered as a result of the biopsy procedure. These results suggest that percutaneous liver biopsy should be considered in patients with hemophilia A with continuously abnormal liver-function tests to establish a histologic diagnosis and to guide further therapy.

Acute Disease↗