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Biomedical subjects

J Abels

Publications and source records attributed to J Abels.

At least 55 records · Page 3Linked to original sources
PubMed1986

Enhanced therapeutic effect of methotrexate in experimental rat leukemia after inactivation of cobalamin (vitamin B12) by nitrous oxide.

Exposure to nitrous oxide interferes selectively with the coenzyme function of vitamin B12 and causes inactivation of methionine synthetase, with subsequent impairment of folate metabolism and reduction of cellular proliferation. In a rat leukemia model (BNML) we investigated the combined administration of nitrous oxide, inactivating vitamin B12, and methotrexate (MTX), a folate antagonist inhibiting the enzyme dihydrofolate reductase. Through different mechanisms, both agents decrease the availability of tetrahydrofolate, and subsequently of other reduced folates, with increased impairment of folate-dependent synthesis of thymidylate. Effects on leukemic growth and on hematological values in rats demonstrated enhancement of the therapeutic effect of MTX by exposure to nitrous oxide. With several treatment schedules, the results of combined treatment were seen to be better than additive when compared with the effects of single agents. In particular, pretreatment of leukemic rats with nitrous oxide for 3 days before administration of MTX appeared effective. With higher doses of MTX, concomitant exposure to nitrous oxide even resulted in toxic effects. These findings were in accordance with the results of some metabolic studies performed in leukemic rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Pseudothrombocytopenia: a cold autoantibody against platelet glycoprotein GP IIb.

Increased binding of IgM to donor platelets was detected in serum of a patient demonstrating the phenomenon of pseudothrombocytopenia. The elevated IgM binding was dependent on EDTA concentration and temperature, and could not be demonstrated when platelets of patients with Glanzmann's disease were used. Immunoblotting and crossed immunoelectrophoresis showed that the IgM antibody reacted with platelet glycoprotein GP IIb. Evidence is presented that the antigenic binding site on GP IIb is made accessible to the antibody by means of the effect of EDTA on the Ca2+ dependent GP IIb/IIIa complex.

Agglutinins↗
PubMed1986

Uptake of transcobalamin II-bound cobalamin by isolated rat kidney tubule cells.

The uptake and intracellular processing of transcobalamin II-bound cobalamin by isolated rat kidney tubule cells were studied. The cells absorbed the complex in a temperature-and calcium-dependent process, which could be inhibited by monensin, an inhibitor of endocytosis. Cells, loaded with a mixture of 125I- and 57Co-labelled transcobalamin II-vitamin B12, released 125I-labelled protein-degradation products, while keeping the 57Co-labelled vitamin. Protein degradation was inhibited by chloroquine and monensin, which is further evidence for a process of endocytosis, followed by intralysosomal hydrolysis of the transport protein. Transcobalamin II-vitamin B12 uptake was not fully saturable and other proteins, for example, haemoglobin, inhibited the uptake in a concentration-dependent way. Apparently the uptake proceeds through relatively unspecific protein-binding sites, probably involved in the reabsorption of filtrated proteins, although the affinity for transcobalamin II seems relatively high. Consequently, elevated urinary excretion of cobalamin is expected in patients with overflow proteinuria, and was indeed found in a patient with paroxysmal nocturnal haemoglobinuria.

Animals↗
PubMed1985

Detection of the blastic crisis cell clone in chronic myeloid leukaemia.

Three patients with Ph1 positive chronic myeloid leukaemia (CML) were followed until the occurrence of blastic transformation by means of cytogenetic analysis of whole marrow or blood cells, of blast cell enriched fractions from marrow or blood and of colonies grown from these cell fractions in two culture systems. Karyotypic evolution was used to indicate the development of new clones from pre-existing cell lines either as transient phenomena during the chronic phase or as the ultimate indicators of a blastic crisis (BC). The clones which were to lead to a BC were detected some months before the clinical diagnosis of the BC. At a time before overt BC had become clinically manifest, the BC clone outgrew the other ones in culture and thus also in vitro showed specific proliferative advantages over the cell lines characteristic of the chronic phase of CML.

Adult↗
PubMed1985

Erythromelalgia caused by platelet-mediated arteriolar inflammation and thrombosis in thrombocythemia.

Erythromelalgia was the presenting symptom in 26 of 40 patients with thrombocythemia in its primary form or when associated with polycythemia vera. The localized painful burning, redness, and warm congestion in the extremities could be accurately documented with thermography. Skin punch biopsy samples taken from the affected areas showed typical arteriolar inflammation, fibromuscular intima proliferation, and thrombotic occlusions. Erythromelalgia often progressed to ischemic acrocyanosis or necrosis in toes or fingers. Complete relief of pain and restoration of microvascular circulation disturbances was obtained with the cyclo-oxygenase inhibitors aspirin and indomethacin, but not with sodium-salicylate or the platelet inhibitors dipyridamole, sulfinpyrazone, ticlopidine, and dazoxiben. The erythromelalgia was alleviated during busulfan-induced remissions of thrombocythemia and its recurrence coincided with relapsing thrombocythemia. These observations suggest a causal relationship between erythromelalgia and thrombocythemia, in which platelet-mediated inflammatory and occlusive arteriolar changes play a part in the etiology of erythromelalgia.

Adult↗
PubMed1985

Human bone marrow cells positive for terminal deoxynucleotidyl transferase (TdT), HLA-DR, and a T cell marker may represent prothymocytes.

Recent evidence suggests that prothymocytes, which occur in a low frequency in murine bone marrow (BM), are already committed to thymocyte differentiation and discrete from precursor B cells as well as pluripotent hematopoietic stem cells. Furthermore, it was suggested that, in rodents, prothymocytes are positive for the nuclear enzyme terminal deoxynucleotidyl transferase (TdT) and a T cell surface antigen. The human prothymocyte has not been identified as yet. We analyzed human BM cells by double immunofluorescence staining for TdT and the T cell surface markers Tp41 (recognized by the monoclonal antibodies WT1 and 3A1), T11, T1, and T6. In the BM samples tested, neither T1+/TdT+ nor T6+/TdT+ cells were detected, but Tp41+/TdT+ and T11+/TdT+ cells were present in low frequencies. In childhood BM, the frequency was about two to five in 10,000, whereas in adult BM and regenerating BM, these cells were not always detectable, but if detected, their frequency was five- to 10-fold lower. In a triple staining, using fluorescein, rhodamine, and colloidal gold particles as labels, it appeared that all Tp41+/TdT+ cells were also positive for HLA-DR. These Tp41+/HLA-DR+/TdT+ cells were also detectable in low frequencies in the thymus, and occasionally Tp41+/TdT+ and T11+/TdT+ cells were detected in the peripheral blood (PB), suggesting a migration from the BM to the thymus via the PB. The malignant counterpart of the Tp41+/HLA-DR+/TdT+ cell was detected in a patient with acute lymphoblastic leukemia with the Tp41+/T11+/HLA-DR+/TdT+/T1-/T6- phenotype and germ-line immunoglobulin heavy chain genes. We postulate that the Tp41+/T11+/HLA-DR+/TdT+/T1-/T6- cell represents a human prothymocyte.

Adult↗
PubMed1984

Transplantation of non-purified autologous bone marrow in patients with AML in first remission.

Four patients with acute myeloid leukemia (AML) were treated with high-dose cyclophosphamide and total body irradiation followed by reinfusion of a portion of their own bone marrow collected during remission. This procedure was applied when the patients were in complete remission. They did not receive further maintenance chemotherapy after grafting. The use of bone marrow for grafting that had been pre-exposed to high-dose chemotherapy for remission induction did not preclude good hematologic regeneration. All patients showed stable remissions that lasted for 64+, 21, 40+, and 19+ months, respectively. Death in the second patient was due to a medullary relapse of the leukemia. Autologous bone marrow transplantation in patients with AML in remission may permit lasting remissions, even when applied without additional chemotherapy and attempts to purify the marrow of neoplastic cells.

Adolescent↗
PubMed1984

Nitrous oxide reduces growth of experimental rat leukemia.

The ability of nitrous oxide to inhibit the in vivo growth of hematological neoplasms was investigated in a rat model for acute myeloid leukemia (BNML). Nitrous oxide, administered in a concentration of 67% with 33% oxygen, resulted in a reduction of spleen and liver weights of approx. 30%, as compared with leukemic rats kept in ambient air. Peripheral white cell counts were also considerably lower in the treated rats. Plasma levels of vitamin B12 were found to be elevated in untreated leukemia, but fell to about normal levels after nitrous oxide exposure. On the contrary, folic acid levels were low in untreated leukemic rats, and significantly higher in animals exposed to nitrous oxide. The observed effects of nitrous oxide appeared to be dose-dependent. The deoxyuridine suppression test performed with leukemic cells became abnormal after nitrous oxide inhalation, in accordance with the effect on normal bone marrow. These results indicate that the interference of nitrous oxide with vitamin B12-related metabolism, which leads to impairment of de novo thymidine synthesis, has the potency to reduce leukemic proliferation in vivo.

Animals↗
PubMed1984

Synergistic growth inhibiting effect of nitrous oxide and cycloleucine in experimental rat leukaemia.

Nitrous oxide (N2O) inactivates the vitamin B12-dependent enzyme methionine synthetase with subsequent impairment of folate metabolism and a reduction of cellular proliferation. Indications exist that this effect is antagonized by S-adenosylmethionine (SAM), and it was investigated whether combination with an inhibitor of SAM synthesis, cycloleucine, would result in increased inhibition of growth in rat leukaemia model (BNML). Leukaemic growth was compared in untreated rats, in rats treated with either nitrous oxide/oxygen (1:1) or cycloleucine (50 mg kg-1 i.p.), and in rats receiving both agents. Combined treatment resulted in the strongest reduction of leukaemic infiltration in spleen and liver, and this reduction often was more than the added effects of single treatments. Peripheral leukocyte counts were also lowest after combined treatment. The deoxyuridine suppression test, measuring folate-dependent de novo synthesis of thymidine, was more severely disturbed with combined treatment. Levels of vitamin B12 in plasma were reduced in rats receiving N2O, but an increase in plasma folate occurred in all treated rats. These results indicate that a reduction of SAM synthesis by cycloleucine can increase the disturbance of folate metabolism that is caused by nitrous oxide, with a potentiation of the effects on leukaemic growth.

Amino Acids↗
PubMed1984

Dutch beta 0-thalassaemia: a 10 kilobase DNA deletion associated with significant gamma-chain production.

A unique beta 0-thalassaemia in a Dutch family results in fetal haemoglobin expression comparable to that of delta 0 beta 0-thalassaemia. Haemoglobin analysis and restriction endonuclease mapping studies of DNA suggest that the beta-globin gene is entirely deleted, but that the delta-globin gene is intact. The 5' break point of the deletion is 3-4 kilobases 3' to the delta-globin gene, while the 3' break point is 6-7 kilobases 3' to the beta-globin gene (relative to the normal DNA restriction map). The result is a approximately 10 kilobase deletion of DNA whose 3' end point may lie very close to that for one delta 0 beta 0-thalassaemia, within a cluster of Kpn I-family repetitive sequences. The Dutch beta 0-thalassaemia deletion is thus the shortest one which, in the absence of additional chromosomal rearrangements, results in enhancement of gamma-chain synthesis above that seen for haemoglobin Lepore. These data support the hypothesis that the region of DNA 3' to the beta-globin gene may be important to the developmental regulation of fetal gamma versus adult beta chain production.

Chromosome Deletion↗
PubMed1984

Histopathology of erythromelalgia in thrombocythaemia.

Erythromelalgia always appears to be an expression of thrombocythaemia which may be provoked by intravascular platelet aggregation, because it is relieved by agents interfering with platelet prostaglandin synthesis. Biopsies were taken from affected areas 1-3 weeks after discontinuation of aspirin. At that time arteriolar changes were present: the endothelial cells were often swollen with large nuclei. Narrowing of the lumen occurred by proliferation of smooth muscle cells with vacuolisation and swelling of the cytoplasm and deposition of intercellular material. The internal elastic lamina appeared to be split between the proliferated cells. This gave rise to the appearances of fibromuscular intimal arteriolar proliferation which were often occluded by thrombi of differing age. Ultimately the arterioles become completely fibrosed. These vascular changes are restricted to arterioles, are partly reversible with aspirin treatment and seem to be a characteristic of erythromelalgia.

Adult↗
PubMed1984

Vitamin B12 absorption in cystic fibrosis.

Vitamin B12 absorption was measured in 30 patients with cystic fibrosis by means of the urinary excretion method and found to be impaired, i.e. less than 10%, in 25. The mean urinary excretion amounted to 4.7 +/- 0.8%. In all patients vitamin B12 absorption improved by the addition of trypsin (18.9 +/- 2.1%). Addition of the vitamin B12 analogue cobinamide, which prevents vitamin B12-binding by R-binders, raised the vitamin B12 absorption to 15.0 +/- 2.2%. A further improvement was obtained by the simultaneous addition of cobinamide and trypsin, 18.2 +/- 2.6%, the same value as with trypsin alone. Assuming that cobinamide addition was effective in suppressing all R-binder activity, the additional effect of trypsin suggests a second, stimulatory function of trypsin on vitamin B12 absorption, separate from R-binder-inactivation. In 5 patients only marginal improvement of vitamin B12 absorption was gained by the addition of either trypsin or cobinamide. The deficient serum vitamin B12 (110 pmol/l) in one of them indicates that the normal pancreas-substitution therapy not always implies sufficient restoration of vitamin B12 absorption.

Adolescent↗
PubMed1984

Elevated serum vitamin B12 in cystic fibrosis.

In 62 patients with cystic fibrosis the serum vitamin B12 concentration ranged from 160-2600 pmol/l with a mean of 1 105 pmol/l. Both vitamin B12-binding proteins in the serum, transcobalamin II and R-binders, carried increased amounts of vitamin B12, but showed relatively normal levels of unsaturated vitamin B12-binding capacity. This combination is rather typical for hepatic dysfunction, although the recurrent pulmonary infections might exert an upward effect on plasma R-binder concentration through increased turnover of myeloid cells. A significant positive correlation between transcobalamin II-vitamin B12 and serum alkaline phosphatase suggests that transcobalamin II-bound vitamin B12 might be an early indicator of focal biliary cirrhosis, which is known to occur in these patients.

Adolescent↗
PubMed1984

Richter's syndrome with different immunoglobulin light chains and different heavy chain gene rearrangements.

In a patient with Richter's syndrome, the chronic lymphocytic leukemia (CLL) expressed lambda, mu, and delta immunoglobulin (lg) chains and the non-Hodgkin lymphoma (NHL) kappa, mu, and delta lg chains. The difference in lg light chain expression suggests that the CLL and NHL are independent malignancies, or that the oncogenic event occurred in a B cell differentiation stage after the heavy chain gene rearrangements but before the selection of the light chain. Analysis of DNA by Southern blotting revealed that the lg heavy chain genes of the two malignancies were rearranged in a different way. We therefore conclude that in this patient the NHL cannot be regarded as a progression of the CLL but should most likely be considered as an independent B cell malignancy, which arose in a susceptible host.

Aged↗
PubMed1983

Improved distribution analysis of cobalamins and cobalamin analogues in human plasma in which the use of thiol-blocking agents is a prerequisite.

In this paper the quantitative analysis of cobalamins and cobalamin analogues in human plasma by means of high performance liquid chromatography (HPLC) and radioisotope dilution assay (RIDA) is described. Current methods for the extraction of cobalamins from plasma proved impracticable due to the selective loss of hydroxo- and sulphitocobalamin, caused by concomitant reduction to the Co2+ form and tight binding to thiol groups of denatured plasma proteins. Although this process can be prevented by exchange of the hydroxyl group with sulphite, azide or nitrite ions, further separation of the respective cobalamin forms from the other endogenous cobalamins by HPLC proved to be impossible. Efficient extraction of hydroxo- and sulphitocobalamin has been obtained in the presence of the thiol-blocking agent N-ethylmaleimide, which does not interfere with the subsequent chromatographic separation of any of the plasma cobalamin forms. The use of R-binder free Intrinsic Factor and salivary R-binder separately as binding substances in RIDA made it possible to analyse the distribution of biologically active cobalamins as well as cobalamin analogues over the various HPLC fractions. Analyses are reported of 15 normal human plasma samples, in which the major components were found to be methylcobalamin (46.9 +/- 4.5%, mean +/- SD) and hydroxocobalamin (40.4 +/- 7.1%, mean +/- SD). Analyses of plasma extracts in the absence of N-ethylmaleimide showed a gross relative overestimation of the amount of methylcobalamin, due to loss of hydroxocobalamin during the extraction procedure. Cobalamin analogues appeared to be evenly distributed over the cobalamin fractions in a pattern almost similar to that of the biologically active forms.

Blood Proteins↗