Expression of the mdr-1/P-170 gene in patients with acute lymphoblastic leukemia

Increased expression of the multidrug resistance gene (mdr-1/P-170) and the dihydrofolate reductase (DHFR) gene have been implicated in the development of in vitro drug resistance. Overexpression, with or without gene amplification, is seen in the development of drug resistance in culture and it has been postulated that genetic modulation of mdr-1/P-170 and DHFR may also be involved in the development of clinical drug resistance. We screened lymphoblasts from 28 patients with acute lymphoblastic leukemia (ALL) for evidence of overexpression of mdr-1/P-170 using RNAse protection, RNA in situ hybridization and immunohistochemistry. Overexpression of mdr-1/P-170 without gene amplification was detected in samples from four patients (three after multiple relapses, one at presentation). Overexpression of mdr-1/P-170 was heterogeneous within the population of malignant lymphoblasts as demonstrated by RNA in situ hybridization, immunohistochemistry, and drug uptake using daunomycin autofluorescence analysis. There was no evidence of overexpression of DHFR in any of the eight patient samples tested by RNAse protection nor was there any evidence of gene amplification in 11 patient samples on Southern blot analysis. From these observations it appears that overexpression without gene amplification of mdr-1/P-170 may be one mechanism of clinical drug resistance in ALL.     

Interleukin-8-stimulated polyphosphoinositide hydrolysis in human peripheral blood lymphocytes

We have attempted to provide evidence for the production of inositol phosphate (IP) metabolites as an indication of specific receptor- mediated signal transduction in human peripheral blood lymphocytes (PBL) in response to interleukin-8 (IL-8). IP metabolites were measured, after loading of PBL with [3H]-D-myo-inositol, by anion exchange high-performance liquid chromatography (HPLC) and liquid scintillation counting of collected fractions. In addition, inositol- 1,4,5-trisphosphate (IP3), in extracts from unlabeled cells, was measured using a specific radioligand binding assay. Compared with phytohemagglutinin (PHA), which stimulated an increase in IP metabolites and, specifically, IP3 by greater than threefold, human recombinant (hr) IL-8 (1 nmol/L) also stimulated an increase in IP metabolites, as measured by HPLC, and a greater than threefold increase in IP3. The increase in IP3 was observed as early as 15 seconds after stimulation with hrIL-8, reaching maximal levels by 30 seconds. To further assess the signal transduction mechanism involved, the protein tyrosine kinase inhibitor genistein was added to the cells 10 minutes before stimulation with hrIL-8. After preincubation of PBL with this inhibitor, the generation of IP3 in response to PHA (5 micrograms/mL) and hrIL-8 (1 nmol/L) was inhibited by 42% and 51% of control values, respectively. In contrast to the production of IP metabolites, there were only small increases in intracellular calcium in response to hrIL- 8 when compared with PHA.     

Isolated thrombocytopenia after allogeneic bone marrow transplantation: existence of transient and chronic thrombocytopenic syndromes

Isolated thrombocytopenia after bone marrow transplantation was investigated in 65 fully engrafted patients surviving at least 60 days posttransplant. Twenty-four patients (37%) developed this complication, which occurred most frequently in patients receiving pretransplant preparation with total body irradiation or busulfan. Two distinct thrombocytopenic syndromes were identified: (1) transient thrombocytopenia (nine patients), in which a normal platelet count (greater than 100,000/microL) was initially established by day +40 but then diminished to less than 10,000 to 45,000/microL on day +40 to +70, with subsequent resolution of the thrombocytopenia by day +90; (2) chronic thrombocytopenia (15 patients), in which a platelet count greater than 100,000/microL was not achieved at any time during the first four months posttransplant, despite the simultaneous presence of normal granulocyte and reticulocyte counts. Although the transient syndrome did not adversely affect prognosis, the chronic syndrome carried a high mortality (21% actuarial survival at 1,000 days posttransplant compared with 67% survival for all patients, P less than .01) and had a high association with both severe (grades 3 to 4) acute graft-versus-host disease (GVHD) and chronic GVHD. In three of nine patients with transient thrombocytopenia, a temporal association with trimethoprim-sulfamethoxazole administration was observed, whereas in all other patients, no drug association could be found. Bone marrow biopsies in those patients with drug-associated thrombocytopenia showed decreased numbers of megakaryocytes, whereas biopsies in the remainder of the transiently thrombocytopenic patients demonstrated adequate numbers of platelet precursors, suggesting peripheral platelet destruction or ineffective thrombopoiesis. Biopsies in the chronic thrombocytopenic patients included those with and without adequate numbers of platelet precursors, although the association with chronic GVHD was strongest in patients demonstrating normal numbers of megakaryocytes. We conclude that isolated thrombocytopenia represents a significant complication of bone marrow transplantation, particularly in patients receiving hematopoietic ablative preparatory regimens, and that it is the chronic, not the transient, thrombocytopenic syndrome that is associated with an adverse patient prognosis.     

Former premenarcheal gymnasts exhibit site‐specific skeletal benefits in adulthood after long‐term retirement

Young female gymnasts have greater bone strength compared to controls; although possibly due to selection into gymnastics, it is thought that their loading activity during growth increases their bone mass, influencing both bone geometry and architecture. If such bone mass and geometric adaptations are maintained, this may potentially decrease the risk of osteoporosis and risk of fracture later in life. However, there is limited evidence of the persisting benefit of gymnastic exercise during growth on adult bone geometric parameters. Therefore, the purpose of this study was to determine whether adult bone geometry, volumetric density, and estimated strength were greater in retired gymnasts compared to controls, 10 years after retirement from the sport. Bone geometric and densitometric parameters, measured by peripheral quantitative computed tomography (pQCT) at the radius and tibia, were compared between 25 retired female gymnasts and 22 controls, age range 22 to 30 years, by multivariate analysis of covariance (covariates: age, height, and muscle cross‐sectional area). Retired gymnasts had significantly greater adjusted total and trabecular area (16%), total and trabecular bone mineral content (BMC) (18% and 22%, respectively), and estimated strength (21%) at the distal radius (p < 0.05) than controls. Adjusted total and cortical area and BMC, medullary area, and estimated strength were also significantly greater (13% to 46%) in retired gymnasts at the 30% and 65% radial shaft sites (p < 0.05). At the distal tibia, retired gymnasts had 12% to 13% greater total and trabecular BMC and volumetric bone mineral density as well as 21% greater estimated strength; total and cortical BMC and estimated strength were also greater at the tibial shaft (8%, 11%, and 10%, respectively) (p < 0.05). Former female gymnasts have significantly better geometric and densitometric properties, as well as estimated strength, at the radius and tibia 10 years after retirement from gymnastics compared to females who did not participate in gymnastics in childhood and adolescence. © 2012 American Society for Bone and Mineral Research.     

Neurotoxicity, anticoagulant activity and evidence of rhabdomyolysis in patients bitten by death adders (Acanthophis sp.) in southern Papua New Guinea

Thirty-two patients with enzyme-immunoassay-proven death adder (Acanthophis sp.) bites were studied in Port Moresby, Papua New Guinea. Eighteen were envenomed; local signs were rare and none had incoagulable blood, but all except one had signs of neurotoxicity. Five (27.7%) envenomed patients required intubation and ventilation. One patient developed renal failure, previously undescribed following death adder bites. Laboratory investigations showed mild prolongation of prothrombin and partial thromboplastin times in some patients. In vitro studies showed that the venom contains anticoagulant activity, but does not cause fibrinogenolysis. In contrast to taipan envenoming, neurotoxicity did not progress after antivenom administration, and there was reversal of neurotoxicity, evident within 6 h, in three severely envenomed patients treated less than 12 h after the bite. One patient treated with antivenom and anticholinesterases had the most dramatic response to treatment; the optimum management of bites by this species may include prompt treatment with both antivenom and anticholinesterases in addition to effective first aid.