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Biomedical subjects

R D Barr

Publications and source records attributed to R D Barr.

At least 109 records · Page 6Linked to original sources
PubMed1984

Detection of circulating 'terminal transferase-positive' cells does not predict relapse in acute lymphoblastic leukemia.

Serial samples of peripheral blood were obtained from 35 children with ALL over a period of 18 months. The mononuclear cells were examined for TdT by indirect immunofluorescence using an unpurified anti-calf thymus TdT as the primary antibody. This analysis failed to distinguish those children who were destined to relapse (n = 9) from those who remained in continuous complete remission. Rather, the exhibition of fluorescence was linked to the co-existence of infection, with a negative predictive value of 0.91. Putative 'TdT-positive' cells were concentrated in the T-lymphocyte fraction and the very process of E-rosette formation seemed to contribute to this phenomenon. It appears as if the anti-TdT reagent recognizes not only TdT but also a variety of antigens which are expressed on or in immature and activated lymphocytes.

Adolescent↗
PubMed1984

Early relapse of acute lymphoblastic leukemia is not predictable by serial biochemical assays of terminal transferase activity in cells from peripheral blood.

Serial samples of peripheral blood were collected from 37 children with acute lymphoblastic leukemia (ALL) in remission. Activity of terminal transferase (TdT) was assayed by a biochemical technique. False positive results were obtained infrequently (approx. 1%), in contrast to experience with bone marrow analyses. However, early relapse of disease was not predictable in ALL by repeated measurement of TdT in circulating mononuclear cells during remission.

Bone Marrow↗
PubMed1984

The intracellular location of terminal transferase does not vary with cell cycle stage.

The biochemical activity of terminal transferase (TdT) in the thymocytes of leukemic AKR mice has no relationship to cell cycle stage, unlike the activity of replicative DNA polymerase which increases during the period of DNA synthesis. Moreover, such assays of DNA polymerase alpha reveal a shift in enzyme activity from cytoplasm to nucleus during S phase. In the present study, the role of TdT in DNA metabolism was explored further by examining the intracellular location of the enzyme during cytokinesis. Single cell suspensions of thymocytes from leukemic AKR mice were partially synchronized by velocity sedimentation in a sucrose gradient at unit gravity and harvested according to cell cycle stage. The content and location of TdT in individual cells was determined by indirect immunofluorescence using a rabbit antiserum to calf thymus TdT as the primary antibody. There was no relationship of fluorescence intensity or of the proportion of TdT-positive cells to cell cycle stage. In all samples examined (n = 6) the enzyme was located almost entirely in the nucleus throughout cytokinesis. These results do not support the hypothesis that the intracellular location of TdT may vary with cell cycle stage and a role for the enzyme in DNA synthesis remains to be defined.

Animals↗
PubMed1984

Demonstration of terminal deoxynucleotidyl transferase in single cells by indirect immunofluorescence. II. An examination of specificity.

Advantages in the use of indirect immunofluorescence for the identification of terminal transferase (TdT) in single cells may be offset by lack of specificity, as compared to the biochemical assay of the enzyme, especially in analyses of lymphocyte populations. False positive results were obtained in 15/15 tonsillectomy samples and in 9/27 specimens from children with acute lymphoblastic leukemia in remission, perhaps due to antihuman lymphocyte activity in the rabbit heteroantisera which are used in the indirect immunofluorescence technique. This phenomenon may be more pronounced in 'activated' normal lymphocytes. Such reactions are not due to antibodies directed against adenovirus, papovavirus or EB virus antigens, although these are common constitutents of human tonsillar cells. Additional problems with TdT heteroantisera may result from immunization with non-TdT determinants in calf thymus extracts, as was manifest in human non-lymphoid (KB) cells cultured in fetal bovine serum. These difficulties will be overcome only by production of a monoclonal antibody using human TdT as the antigen.

Adult↗
PubMed1984

Storage and transportation of samples for analysis of terminal transferase by indirect immunofluorescence.

Expression of the terminal transferase (TdT) antigen, as revealed by indirect immunofluorescence, was retained in samples of human acute lymphoblastic leukemia (ALL) cells, of various phenotypes, during storage at 4 degrees C for almost six months. Similar specimens of ALL cells, of common phenotype, were transported successfully by air without notable loss of TdT. The unsatisfactory outcome of earlier studies may be explained on the basis of methodologic differences alone.

Bone Marrow↗
PubMed1983

Lithium and hematopoiesis.

Some of lithium's effects on blood cell formation suggest that the element may be of value in treating hematologic disorders. Lithium enhances granulopoiesis and thereby induces neutrophilia. Two possible mechanisms of action are suggested: a direct action on the pluripotent stem cells, or an inhibition of the suppressor cells (thymus-dependent lymphocytes) that limit hematopoiesis. Lithium also inhibits erythropoiesis. Although most studies use concentrations at or above pharmacologic levels there is evidence that lithium plays a role in normal cell metabolism.

Animals↗
PubMed1983

Demonstration of terminal deoxynucleotidyl transferase in single cells by indirect immunofluorescence--a methodological reappraisal.

The optimal conditions for assaying terminal transferase by indirect immunofluorescence with commercially available reagents have been explored. Target tissues examined included fresh, stored and cultured human acute lymphoblastic leukemia cells; normal human peripheral blood and bone marrow; and calf thymus. Brief, cold fixation in glutaraldehyde/ethanol or omission of fixation proved to be satisfactory. The most suitable primary antibody was an unfractionated rabbit serum with specificity for anti-calf thymus TdT which cross-reacted with human material and was neutralized in high dilution by purified enzyme. Inferior reagents and techniques gave false negative results. Identification of TdT appears to be feasible even in tissue samples stored for several months and enumeration of cells is facilitated by ethidium bromide counterstaining.

Animals↗
PubMed1983

The effects of cisplatin on normal human erythrocytes in vitro.

Therapeutic administration of cisplatin is often followed by anaemia which may not be due entirely or even largely to myelosuppression but rather to drug-induced haemolysis. Similar experience with other cytotoxic agents prompted earlier investigations which yielded evidence of drug-induced changes in RBC shape in vitro. Current studies of cisplatin and bleomycin, which have been used together in clinical practice, revealed a significant alteration in the profile of RBC morphology; specifically a reduction in the number of 'bowl' shaped cells. However, this finding is in contrast to the increase in 'bowls' which was observed previously with other drugs. So it appears that direct erythrocytotoxicity cannot explain the occurrence of anaemia in patients who receive cisplatin. An alternative mechanism, similar to that of penicillin induced haemolysis, is suggested by immunoradiometric assays of surface IgG on red cells.

Bleomycin↗
PubMed1983

An apparent lack of HLA restriction in the stimulation of granulocyte-macrophage colony formation from normal human null cells by helper T lymphocytes.

Haemopoietic progenitor cells capable of producing granulocyte-macrophage (GM) colonies have been demonstrated in the 'null' lymphocyte population of normal peripheral blood. The helper and suppressor roles of different T cell subpopulations have been implicated in the regulation of granulopoiesis in disease as well as in normal individuals. However, it is not certain whether such interactions between T cells and progenitor cells are HLA-restricted. We undertook further investigation of the effect of T cell subpopulations (TG and TnonG) on GM colony formation in vitro. In particular, we studied the possibility of HLA restriction in this process. Our results demonstrate that the enhancement of GM colony growth by T lymphocytes is not restricted by HLA compatibility between T cells and null cells, that such stimulation is radio-sensitive and that it is provided by the TnonG cell subpopulation.

Adult↗
PubMed1983

Hydrocortisone--a possible physiological regulator of human granulopoiesis.

The effect of hydrocortisone (HC) on the formation of granulocyte-macrophage (GM) colonies was assessed in vitro in cultures of normal human bone marrow. Subphysiological concentrations (less than or equal to 10(-8) mol/l) of HC had no impact on GM colony formation, but at physiological and therapeutic levels (10(-7) mol/l-10(-5) mol/l) the hormone stimulated the production of an increased number of colonies. By contrast, physiological concentrations of progesterone (10(-9) mol/l-10(-7) mol/l) were without effect and even at 10(-6) mol/l there was no influence of progesterone alone on GM colony formation. However, progesterone at 10(-6) mol/l inhibited the stimulant effect of HC to a degree which was related inversely to the concentration of HC and the duration of the culture interval. The data from this study suggest that the neutrophilia which accompanies glucocorticosteroid therapy is matched by an increase in the production of granulocytes and that HC may play a rôle, which is mediated by steroid receptors, in the physiological regulation of human granulopoiesis.

Colony-Forming Units Assay↗
PubMed1983

Acetylesterase in lymphoblastic leukaemia associated with thymic enlargement.

Focal cytoplasmic acetylesterase activity was sought in the malignant cells of 91 consecutive children with acute lymphoblastic leukaemia, of whom 10 had an anterior mediatstinal mass at diagnosis. This subgroup with thymic disease (TD) was characterized by hyperleucocytosis, the total leucocyte count being greater than 200 X 10(9)/1 in 6 patients. Furthermore, there was a significant association (P less than 0.025) between TD and the presence of leukaemic blast cells expressing a thymic phenotype, in the form of rosette formation with sheep erythrocytes. Focal cytoplasmic acetylesterase activity identified TD with a sensitivity of 20%, a specificity of 91%, a positive predictive value of 25%, a negative predictive value of 88% and a diagnostic accuracy of 81%. The demonstration of this feature by a simple cytochemical technique can be a useful component of the profile of investigations which are employed in the classification of acute lymphoblastic leukaemia.

Acetylesterase↗
PubMed1983

"Helper" and "suppressor" T lymphocytes regulating blood cell formation in man.

Human hemopoietic progenitor cells have been characterized as null lymphocytes. These primitive precursors are subject to interaction with mature cells which are derived from the thymus. Such T lymphocytes exist in several subpopulations which can exhibit "helper" and "suppressor" activity in various immune responses. Evidence for the involvement of these cells in hematopathological disorders has been presented and the possibility of a physiological role for helper and suppressor T cells in hemopoiesis has been discussed. It is proposed that "steady state" blood cell formation is maintained, at least in part, by the preponderance of suppressors in the bone marrow, while the dominant helper population in peripheral blood can recirculate under the influence of corticosteroids with consequent stimulation of hemopoiesis. The influence of histocompatibility antigens on this process of cellular regulation remains to be determined.

Hematologic Diseases↗
PubMed1983

Detection of human fetal fibrinogen in umbilical cord plasma by parallel assays of immunoreactive and thrombin-clottable protein.

Putative fetal fibrinogen was detected in normal human umbilical cord plasma by parallel assays of immunoreactive and thrombin-clottable protein. The 'excess' of immunoassayable fibrinogen was not due to products of proteolysis and the apparent 'insensitivity' to thrombin was reflected in delayed fibrin polymerization. Fetal fibrinogen was partially separable from the adult protein by two-dimensional immunoelectrophoresis.

Adult↗
PubMed1982

The role of autologous helper and suppressor T cells in the regulation of human granulopoiesis.

Helper and suppressor T cells play a physiological role in immunoregulation and possibly in other biological systems. Previous studies have suggested that unfractionated T cells influence human blood cell formation in vitro. Subpopulations of such cells (TM and TG cells) were prepared by immune ox erythrocyte rosetting techniques. Co-cultures were established in semi-solid agar with autologous null lymphocytes as a source of granulocyte-macrophage progenitor cells (CFU-GM). TM(helper) cells produced an increase and TG (suppressor) cells a decrease in the expression of CFU-GM as reflected in the number of GM colonies generated by comparison with cultures of null lymphocytes alone. These data point to a contribution from T lymphocyte subpopulations to the physiological regulation of human granulopoiesis.

Cell Separation↗