Blood
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Previous studies performed in vitro have indicated that platelets from patients with platelet-type von Willebrand's disease (vWD) have receptors for von Willebrand factor (vWF) already exposed on their surfaces and that the addition of purified vWF or cryoprecipitate to patient platelet-rich plasma under stirring conditions is capable of inducing platelet aggregation and secretion. The present work reports the results of the transfusion of cryoprecipitate in a patient with platelet-type vWD. ⋯ Shortening of the bleeding time occurs only very transiently. The results of this study provide direct evidence that, in patients with platelet-type vWD, an abnormal interaction of their platelets with plasma vWF occurs in vivo, resulting in the absence of high molecular weight vWF multimers, low platelet counts, and impaired hemostasis that are characteristic of this disease.
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We have determined the frequency of deletional alpha-thalassemia in black populations in the USA and Africa that harbor sickle cell anemia. In normals, the frequency of the chromosome bearing a deletion of one of the two normal alpha gene loci, designated (-alpha), ranged from 0.12 to 0.16, and in sickle trait subjects, the frequency ranged from 0.18 to 0.20. ⋯ In addition, the frequency of the (-alpha) chromosome was found to increase progressively with age, supporting the hypothesis that alpha-thalassemia is favorable to the survival of subjects with sickle cell anemia. Thus, individuals who inherit alpha-thalassemia and sickle cell anemia may represent a subgroup of patients with a longer life expectancy.
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A four-drug regimen, based on cell kinetic principles, induced complete remissions in 68 of 95 children (72%) with acute nonlymphocytic leukemia (ANLL). Patients entered remission after 2-5 weekly cycles of vincristine-daunorubicin (day 1) followed by sequential cytosine arabinoside and 6-azauridine (days 4-7). With continuation therapy of monthly vincristine-doxorubicin-cyclophosphamide, weekly cytosine arabinoside, and daily 6-mercaptopurine, the median duration of complete remission was 10 mo and the median survival time 21 mo. ⋯ Patients without central nervous system (CNS) leukemia at diagnosis, all treated prophylactically with intrathecal methotrexate, had a low frequency of initial CNS relapse (3/56, 5%). The 2-yr disease-free survival rate is 29% (20 of 68 patients attaining complete remission). fifteen patients have completed 2.5 yr of therapy, and each remains in continuous complete remission, off treatment, for 1+ -36+ mo. This induction chemotherapy was as effective as more intensive regimens, with the advantage of less toxicity and shorter periods of hospitalization.
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We have studied the modifications in the multimeric composition of plasma factor VIII/von Willebrand factor and the bleeding time response following administration of 1-Deamino-[8-D-arginine]-Vasopressin (DDAVP) to patients with different subtypes of von Willebrand's disease. In type I, all multimers were present in plasma in the resting state, though they were decreased in concentration. Administration of DDAVP resulted in an increased concentration of these forms as well as the appearance of larger forms than were previously present. ⋯ The characteristic multimeric composition of platelet factor VIII/von Willebrand factor in given subtypes predicted the alteration in plasma factor VIII/von Willebrand factor induced by DDAVP. These studies provide evidence that the different subtypes of von Willebrand's disease represent distinct abnormalities of factor VIII/von Willebrand factor. They also suggest that complete hemostatic correction following DDAVP can be routinely expected only in type I von Willebrand's disease, and only if factor VIII/von Willebrand factor can be raised to normal levels.
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The role of vitamin B12 in the folate dependent biosynthesis of thymidine nucleotides is controversial. In an attempt to clarify this, three methods have been used to assess the relative efficacy of vitamin B12 (hydroxocobalamin) and various folate analogues in titrated concentrations at correcting 'de novo' thymidylate synthesis by megaloblastic human marrow cells: (1) The deoxyuridine (dU) suppression test which analyses the reduction in (3H)-thymidine labeling of DNA by unlabeled dU. Marrow cells were also labeled with (6-3H)-dU with assessment of (2) its incorporation into DNA and (3) the accumulation of (6-3H)-deoxyuridine monophosphate (3H-dUMP). ⋯ Methyl-FH4 was effective in folate deficiency but not in vitamin B12 deficiency. These results confirm the failure of methyl-FH4 utilisation in vitamin B12 deficiency. They suggest that if vitamin B12 is needed in the formylation of FH4, this is a minor role in provision of the correct coenzyme for thymidylate synthesis compared with its major role of provision of FH4 from methyl-FH4.