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Biomedical subjects

M J Manco-Johnson

Publications and source records attributed to M J Manco-Johnson.

At least 37 records · Page 2Linked to original sources
PubMed2000

Heparin neutralization is essential for accurate measurement of factor VIII activity and inhibitor assays in blood samples drawn from implanted venous access devices.

The purpose of this study was to determine the prevalence and effect of heparin contamination in samples drawn from implanted venous access devices (VADs, ports) on factor VIII activity and Bethesda inhibitor assay (BU) and the efficacy of heparinase to neutralize heparin. Plasma samples containing 85, 45, and 2 U/dL factor VIII were spiked in vitro with heparin from 0 to 3 U/mL. Factor VIII activity was assayed with a one-stage clotting assay on paired samples before and after heparinase, 25 mg/mL plasma. Paired patient samples drawn from VADs were assayed for heparin concentration, factor VIII, and BU before and after heparinase. At all three concentrations of factor VIII in vitro, the addition of heparin at 0.12 to 0.25 U/mL decreased assayed factor VIII activity. Heparinase neutralized up to 2 U/mL heparin and resulted in accurate factor VIII determination. Of 105 VAD samples, 47 (45%) had heparin contamination >0.05 U/mL. Of 47 heparin-contaminated samples, 42 showed decreased factor VIII activity in before/after comparisons. False-positive BU results were detected in 6 of 47 heparin-contaminated samples. Heparin contamination occurs frequently in samples drawn from VADs and could increase costs through excessive factor concentrate use. We recommend that all VAD samples be pretreated with heparinase before the assay of factor VIII activity or Bethesda inhibitor titers.

Antibodies↗
PubMed1999

Hereditary deficiency of vitamin-K-dependent coagulation factors in Rambouillet sheep.

A flock of Rambouillet sheep experienced unexpected lamb mortality associated with excessive bleeding at the time of parturition. Most lambs died of blood loss through the umbilicus or into subcutaneous tissues. Subsequently, nine ewes which had previously delivered lambs that bled to death were bred to the suspected sire of the previous bleeding lambs. Fifteen lambs were born alive the following Spring, and three males and one female bled clinically. These lambs had markedly decreased factor IX (< 16%) and factor X (< 4%) activities, with variably decreased factor II (11-36%) and factor VII (20-37%) activities. Protein C chromogenic activity was also markedly decreased (< 1%) in these lambs. The results from crossed immunoelectrophoresis and 'protein-induced-in-vitamin-K-absence' determination of the plasma of affected lambs, with antiserum directed against coagulation factor X, protein C or proteins S, suggested that these proteins were not carboxylated normally. Examination of liver from one lamb in the first batch and the four subsequent lambs did not reveal a known vitamin K antagonist. The breeding data suggested that the coagulopathy in these sheep was inherited as an autosomal recessive trait. The genetic or molecular defect that exists in these lambs is unknown, but possibilities include abnormal gamma-glutamyl carboxylase activity or abnormal metabolism of vitamin K.

Animals↗
PubMed1998

Antiphospholipid antibodies in children.

Lupus anticoagulant (LA) is made up of heterogeneous IgG and IgM antibodies that prolong clotting times in vitro and is associated with an increased rate of both thrombosis and hemorrhage in vivo, although thrombosis is far more common. Many mechanisms of action have been explored, but none explains the coagulation abnormality of every sample tested. Binding of these antibodies to protein phospholipid complexes provides a unifying model. Antiphospholipid antibodies (APAs) are found in adult patients with a variety of disorders or as an isolated finding. The association of LA and anticardiolipin antibodies (ACAs) with thrombosis in adults has been established, although there is no test as yet to predict thrombotic risk for an asymptomatic affected individual. The presentation of thrombosis with postinfectious APA is uncommon in adults. Children who present with thrombosis and LA are found to have underlying disorders similar to those of adults. Although the presentation of thrombosis in children with postinfectious LA is rare, the association is established. LA-positive children with thrombosis have manifested a severe acquired deficiency of protein S; LA-positive children with hemorrhage have manifested an acquired deficiency of prothrombin. The association of thrombosis with ACA-positive children has been reported. Further work to determine the epidemiology, mechanism of action, and thrombotic potential of APA in children is warranted to better understand, prevent, and treat thrombotic and hemorrhagic complications.

Adolescent↗
PubMed1997

The factor V Leiden mutation in children with cancer and thrombosis.

Thromboembolic phenomena, frequently observed in children with cancer who are undergoing chemotherapy, can cause significant morbidity and, less frequently, mortality. Many contributory factors have been identified. Whether the recently identified and most common coagulation defect predisposing to thrombosis, factor V Leiden, is associated with thrombosis in this setting, has not been explored. The current study was undertaken to determine the prevalence of the factor V Leiden mutation in children with cancer who developed thromboembolic phenomena as compared to those with cancer who did not. Genomic DNA was amplified using the polymerase chain reaction (PCR), followed by digestion of the amplification product with the restriction enzyme MnlI. The digested PCR products were then size-fractionated to classify samples as heterozygous, homozygous or normal for the factor V Leiden mutation. 67 children with cancer were evaluated for the factor V Leiden mutation. One of 32 children with cancer and thrombosis, and none of 35 who had not experienced thrombotic problems, was found heterozygous for this mutation. We conclude that the factor V Leiden mutation does not play a significant role in the overall incidence of thromboses that occur in children with cancer.

Adolescent↗
PubMed1997

Correlation between the functional assay for activated protein C resistance and factor V Leiden in the neonate.

A factor V506 Arg-Gln mutation is the most common inherited cause of thrombophilia in adults. To date, there are no data regarding the detection of this mutation in neonatal blood or the relationship of this dysfunctional factor V to neonatal thrombosis. This study compared a modified activated protein C resistance functional assay with the PCR-based DNA assay for the factor V mutation in 115 prospectively collected umbilical cord blood samples. The incidence of activated protein C resistance in cord blood was 6%. The sensitivity and specificity of the modified assay for the factor V Leiden mutation was 100%.

Amino Acid Substitution↗
PubMed1997

Disorders of hemostasis in childhood: risk factors for venous thromboembolism.

In both children and neonates with venous thrombosis, one or more predisposing risk factors can generally be identified. Underlying prothrombotic medical conditions are common in these patients. In addition, a "trigger factor" such as a catheter, surgery or trauma is usually present. However genetic and acquired coagulation abnormalities are also identified in children with venous thrombosis who are appropriately studied. A careful family history and assays for the LA, AT-III, protein C, protein S and the factor V Leiden mutation should be part of the evaluation of infants and children with venous thrombosis.

Adolescent↗
PubMed1996

Lupus anticoagulant and protein S deficiency in children with postvaricella purpura fulminans or thrombosis.

OBJECTIVE: The objective of this study was to determine the cause of purpura fulminans, disseminated intravascular coagulation, or thrombosis in seven children with varicella. All children were found to have a lupus anticoagulant and acquired protein S deficiency. Thrombosis in five children was associated with presumed or documented infection with streptococcus. STUDY DESIGN: Coagulation tests included determinations of the activated partial thromboplastin time, the prothrombin time, the dilute Russell viper venom time, the prothrombin F 1 + 2 fragment, the C4b-binding protein (C4b), total and free protein S antigen, and clotting activities of factors II, V, VII, and X and of protein C and protein S. Autoantibodies to phospholipids, cardiolipin, and protein S were determined in enzyme-linked immunosorbent assays. RESULTS: All children had a lupus anticoagulant and acquired protein S deficiency. Thrombosis in five children was associated with presumed or documented infection with streptococcus. All children transiently expressed free protein S deficiency, elevated levels of IgG, IgM, or both binding to protein S, the lupus anticoagulant, and increased concentration of the F 1+2 fragment. Four children also had antiphospholipid or anticardiolipin antibodies. In one child a purified IgG fraction cross-reacted with both protein S and a specific varicella antigen. CONCLUSIONS: A subset of children with varicella infection, some of whom are coinfected with streptococcus, are prone to development of a lupus anticoagulant and an autoantibody to protein S, which results in acquired free protein S deficiency. Such children are at risk of having life-threatening thrombotic events.

Antibodies, Antiphospholipid↗
PubMed1996

Thrombosis in otherwise well children with the factor V Leiden mutation.

OBJECTIVE: To determine whether resistance to activated protein C caused by the factor V Leiden mutation (Arg506 to Gln) is associated with thrombosis occurring during childhood. STUDY DESIGN: Children with thrombosis were screened for activated protein C resistance. Children found resistant to activated protein C had DNA analysis for the factor V Leiden mutation. Family members of the children with activated protein C resistance were similarly studied. RESULTS: Three of fourteen children examined had abnormal normalized activated protein C sensitivity ratios. One child had protein S deficiency. The children had hyperlipidemia. Molecular confirmation of the factor V Leiden mutation was obtained for all three children. Family members of each of the three children were affected. CONCLUSIONS: Children have thromboses in association with the factor V Leiden mutation, as do adults. This mutation may be identified as an isolated risk factor or in association with other risk factors for thrombosis.

Adolescent↗
PubMed1996

Family issues in continuous infusion therapy with factor VIII.

Two recent advances in hemophilia therapy have led to clinical trials that incorporate more aggressive approaches to prevent bleeding complications. The production of factor VIII using recombinant DNA technology diminishes the risk of viral transmission in factor concentrate and thus increases safety. The administration of factor VIII by continuous infusion optimizes pharmacokinetics to achieve a sustained factor VIII level using the least number of units, and thus decreases cost. Providing factor concentrate by continuous infusion at home is very challenging to parents and children. Compliance can be supported by addressing issues that affect the family and its functioning. These issues include acceptance of the diagnosis, perception of the problem, parenting style, communication, social supports, disclosure issues, financial concerns, and perceived benefits and toxicities of the therapy plan. Health care providers must recognize and address these issues in order to provide adequate support for the family. Critical interventions include adequate time and optimal conditions for family education, support groups, determination of family expectations, understanding of parenting style, assistance with communication, disclosure, financial issues and clarification of the risks and benefits of various treatment plans.

Factor VIII↗
PubMed1995

Lupus anticoagulant in children with thrombosis.

Nineteen children who presented with thromboses over a 7-year period were found to have a lupus anticoagulant (LA). The initial thrombosis was proximal deep vein thrombosis (DVT) in six children, central nervous system (CNS) in five, primary pulmonary in four, distal DVT in two, central venous in one, and proximal arterial in one. Five children were diagnosed with systemic lupus erythematosus (SLE), including two children for whom thrombosis was the presenting sign of SLE. The remaining 14 children were diagnosed with the antiphospholipid antibody (APA) syndrome. The APA syndrome was manifest by venous or arterial thrombosis in association with a positive LA; positive anticardiolipin antibodies and a fine, speckled antinuclear antibody (ANA) pattern were additionally found in the majority of children. Approximately one-half of the children with SLE or the APA syndrome had a pulmonary embolus, and one-half developed recurrent thrombosis. Oral anticoagulation with coumadin to achieve an INR of > 2.0 prevented thrombosis recurrence. The recognition of a LA in children with thrombosis necessitates evaluation for SLE, APA, and other autoantibodies.

Adolescent↗
PubMed1995

Identification of a unique form of protein C in the ovine fetus: developmentally linked transition to the adult form.

To investigate fetal development of protein C, a pregnant ovine model was used. Protein C was isolated from ovine plasma, and a polyclonal antibody was raised. Citrated plasma was obtained from undisturbed chronically catheterized fetal lambs. On Western blot, nonreduced adult ovine protein C had a molecular mass of 70 kD. Fetal ovine protein C was determined to have a molecular mass of 4 to 6 kD larger than the adult molecule. Crossed immunoelectrophoresis demonstrated slightly increased anodal migration of the fetal form. Isoelectric focusing demonstrated a decreased pI of the fetal molecule (4.45 versus 4.6). The ovine protein C molecules were deglycosylated with N-glycanase. Deglycosylated fetal protein C migrated more similarly to the adult form, although a portion of the fetal form persisted. These experiments demonstrate the first example of a unique fetal form of a vitamin K-dependent protein and are compatible with increased glycosylation of fetal ovine protein C. It is speculated that altered posttranslational processing may exist as a general process by which certain coagulation proteins are modified during fetal development. mRNA was isolated from maternal and fetal hepatic tissue and analyzed by Northern hybridization. Fetal plasma concentration and hepatic mRNA for protein C were both 40% of normal maternal values from midgestation onward. At term, protein C mRNA increased to adult range (p < 0.025), although plasma protein C concentration decreased slightly (p < 0.001). A transition from fetal to adult protein C form was found beginning 6 d before term birth, with a doubling time of 24 h. These data are compatible with a gestationally determined maturation of ovine protein C.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1994

Results of secondary prophylaxis in children with severe hemophilia.

In this study, 13 children with severe hemophilia were given routine replacement infusions of factor VIII or IX to treat arthropathy. The children who had a mean age of 6.9 years (range 2.0-12.5) at initiation of prophylaxis had experienced an average of 43 acute hemorrhages (range 8-127) in the year prior to prophylaxis, of which a mean of 24 (range 5-46) were into joints. Therapy was begun in five children, using factor VIII concentrate at 20 U/kg three times a week, and one boy received factor IX concentrate 40 U/kg twice a week. This dose schedule was inadequate for three factor VIII-deficient boys and for the one factor IX-deficient boy. Two of three factor VIII-deficient boys responded to an increase to 30 U/kg prior to the 3-day interval. The dose frequency was increased to three times a week for the factor IX-deficient boy, but he continued to bleed and was taken to synovectomy. One of the original five factor VIII-deficient boys plus seven other factor VIII-deficient boys were begun on factor VIII 20 U/kg every other day; 3 boys ceased bleeding. Trough factor VIII levels were measured 24 hr after an infusion in the five boys who continued to bleed. Factor VIII dosage was adjusted to achieve a trough level of > 1%; 4 responded to an increase in the dose of factor VIII; 1 had an adequate trough but, due to compliance issues, was taken to synovectomy. Serial clinical and radiographic assessments determined stabilization of joint disease in more than one-half of the boys. No child showed reversal of abnormal radiographic findings. Institution of aggressive factor VIII and IX concentrate in children with established hemophilic arthropathy does not reverse joint disease but may alter the clinical course of hemophilia. Future studies to compare this intervention with primary prophylaxis instituted prior to the onset of recurrent joint hemorrhage are warranted.

Child↗
PubMed1994

Hyperglycemia-induced hyperinsulinemia decreases maternal and fetal plasma protein C concentration during ovine gestation.

To determine effects of diabetic gestation on plasma concentration of the coagulation regulatory protein, protein C, pregnant ewes were given glucose infusions to raise plasma glucose to twice baseline concentration or insulin infusions to lower glucose concentration to half baseline value. Control animals received no infusions. Concentrations of protein S, factor X, and antithrombin III were determined for comparison. Concentrations of glucose, insulin, and those above were determined thrice weekly for 2-9 wk. Short-term (8-12 h) infusions of glucose or insulin were performed to isolate their effect on concentration of protein C. Results were analyzed using a two-tailed t test, and protein C concentrations were further analyzed using a full linear mixed-effects model. In long-term infusions, hyperglycemia-induced hyperinsulinemia (mean insulin concentration 141 microU/L) exerted negative effects on maternal concentrations of protein C [0.69 U/mL, n (number of samples) = 32, experimental versus 0.97 U/mL, n = 157, control], protein S (0.86 U/mL, n = 31, experimental versus 1.04 U/mL, n = 109, control), and factor X (0.89 U/mL, n = 31, experimental versus 1.04 U/mL, n = 109, control); it exerted no effects on antithrombin III (1.05 U/mL, n = 23, experimental versus 1.04 U/mL, n = 32, control). The fetal lamb did not respond to chronic moderate hyperglycemia (mean 33 mg/dL) with a consistent change in insulin concentration (mean 10 versus 9 microU/mL): no coagulation protein changed.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Severe neonatal protein C deficiency: prevalence and thrombotic risk.

Severe deficiencies of protein C, a pivotal coagulation-regulatory protein, have been reported in neonates as an apparently transient condition. In this prospective study, cord blood was collected at 193 deliveries and assays of protein C were correlated with clinical status, other coagulation results, and outcome. Protein C levels of less than 0.1 unit/ml were found most frequently in preterm infants with respiratory distress, infants of diabetic mothers, and infants of twin gestations. Levels of protein C correlated with levels of factor VIII activity but did not correlate with markers of consumptive coagulopathy. A protein C level less than 0.1 unit/ml was significantly correlated with the subsequent onset of thrombosis, even when the effects of gestational age and birth weight were excluded. Low cord blood levels of protein C may reflect delayed maturation or increased turnover in certain infants and appear to convey an independent risk of thrombosis, but the critical concentration of protein C necessary to maintain neonatal hemostasis is not known.

Antithrombin III↗
PubMed1990

Postpartum intracranial venous thrombosis associated with dysfunctional protein C and deficiency of protein S.

Development of intracranial dural sinus thrombosis in the postpartum period has been attributed to the hypercoagulable state of pregnancy. With increasing recognition of the role of the vitamin K-dependent proteins, protein C and protein S, in intracranial venous and arterial thrombotic events, our understanding of the cause of thrombotic events has improved. We report a patient who developed a superior sagittal sinus thrombosis in the second week postpartum, associated with a dysfunctional protein C and a decreased free protein S concentration.

Adolescent↗