Biomedical subjects

B Sawyer

Publications and source records attributed to B Sawyer.

32 records · Page 2Linked to original sources

PubMed1983

Measurement of K cell activity: use of human OR1R1 red cells and anti-D to study the role of different leucocytes as effector cells.

A method for quantitative assay of K cell activity (KCA) with an allogenic combination of human OR1R1 red cells and anti-D (IgG, incomplete antibody) as target cells is described. Lymphocytes alone have been shown to cause lysis of these target cells. Fc receptor-bearing lymphocytes appear to be the chief mediators of KCA. This sub-population is a heterogeneous mixture of sub-sets of other sub-populations defined on the basis of different surface markers and likely to show variable expression of Fc receptors by the EA gamma rosette method. Monocytes and neutrophils (and possibly eosinophils), most of which bear Fc receptors, are ineffective as effector cells. Monocytes may in some instances have an inhibitory effect on the expression of KCA of lymphocytes. The method described has the advantage of simplicity (easy availability of OR1R1 cells and anti-D) and a high degree of sensitivity (marked lysis at low L/T ratio) and appears suitable for routine use in clinical practice.

ABO Blood-Group System↗

PubMed1983

Erythropoietic activity in primary proliferative polycythaemia.

Explore the source record for details and available documents.

Colony-Forming Units Assay↗

PubMed1983

Erythroid colony formation in primary proliferative polycythaemia, idiopathic erythrocytosis and secondary polycythaemia: sensitivity to erythropoietic stimulating factors.

This is a study of in vitro production of erythropoietic colonies from peripheral blood and bone marrow of normal subjects and patients with different polycythaemic conditions. Proliferative stimuli included: 1. Fetal calf serum (FCS) only. 2. FCS plus a source of erythropoietic-stimulating activity (ESA). 3. FCS + ESA + erythropoietin (Ep). It was found that normal subjects and patients with secondary polycythaemia (SP) exhibited full colony growth only in the presence of both ESA and Ep, while patients with primary proliferative polycythaemia (PPP) showed colony production with FCS alone, further enhanced in the presence of ESA and Ep. A group of patients with idiopathic erythrocytosis (IE), namely with an increase of red cell mass not accompanied by other signs of myeloproliferative disorder, and without underlying cause, showed a heterogeneous response to ESA which in some patients was significantly greater than in normal subjects or in SP patients. It appears therefore that sensitivity of erythropoietic colony formation to Ep and ESA may be helpful in differentiating among various forms of polycythaemia; this study also establishes the heterogenicity of the IE group.

Bloodletting↗

PubMed1983

Haemopoietic patterns of acute leukaemia in remission: CFU-E and CFU-GM colony formation.

Colony formation in vitro from bone marrow haemopoietic progenitors was studied in a group of patients with acute myeloblastic leukaemia and acute lymphoblastic leukaemia at presentation of the disease and, in a few cases, during complete remission. Both granulocytic-macrophagic (CFU-GM) and erythropoietic (CFU-E) colonies were studied. A sharp contrast was observed between CFU-GM and CFU-E formation at presentation of the disease: while the former was markedly depressed, with considerable increase of the cluster colony ratio, CFU-E production was not significantly affected, with only a reduced sensitivity to low-dose erythropoietin. CFU-GM formation returned to normal in the early stages of complete remission, but showed a progressive decline in the course of time; the process of cell differentiation was not significantly impaired, although minor changes were observed. It appears that the leukaemic process has much greater impact altogether on CFU-GM than on CFU-E colony formation, the latter being only marginally affected, even in the presence of a high proportion of blast cells.

Antineoplastic Agents↗

PubMed1981

Exaggerated cyclic AMP accumulation and glial cell reaction in the cerebellum during Purkinje cell degeneration in pcd mutant mice.

The Purkinje cell degeneration mutant (pcd) is characterized by a complete loss of cerebellar Purkinje cells. Norepinephrine causes an accumulation of cyclic AMP in the cerebellum of pcd that is far greater than in normal mice. Experiments were conducted 1) to correlated changes in the cyclic-nucleotide response with a histologic examination of the cerebellum during neuronal loss and 2) to examine the role of cyclic AMP catabolism and adenosine receptor interactions in the phenomenon. The greatest elevation in cyclic AMP occurred between 30 and 128 days of age when a severe astrocytic response was demonstrated throughout the cerebellar cortex. Purkinje cells had degenerated by 45 days of age. Norepinephrine elicited a smaller increase in cyclic AMP from 155-day-old mice than at earlier ages, and the response continued to decrease with age; at 270 days, equal accumulation, and at 365 days. lower accumulation of cyclic AMP was detected in pcd cerebella. During this time, the Purkinje cell debris had been removed, the granule cell layer was depleted of granule cells, and the molecular layer was deprived of a large number of parallel fibers. However, although phagocytosis of neuronal debris was completed, large numbers of astrocytic processes were still seen in the neuropil. Biochemical experiments in vitro established that the exaggerated accumulation of cyclic AMP in the presence of norepinephrine was not due to lower catabolism of cyclic AMP, a synergistic interaction with adenosine, or a result of lower protein in the pcd cerebellum. The correlates of heightened norepinephrine-stimulated accumulation of cyclic AMP with neuronal loss and the glial cell reaction might indicate that cyclic nucleotides play a role in controlling some glial cell functions, ie, proliferation, migration, and phagocytosis.

Animals↗

PubMed1978

Cytochrome P-450 distribution in rat liver and the effect of sodium phenobarbitone administration.

A microspectrophotometric method for assaying cytochrome P-450 in fresh 24 micrometer unfixed cryostat sections of rat liver has been developed. When used to assay this cytochrome in sections of microsomal preparations it has yielded results equivalent to those obtained by the conventional spectrophotometric assay of the same preparations. Random measurements made throughout sections of liver have given mean values for cytochrome P-450 concentrations which are twice those measured in microsomes prepared from the livers of the same animals (not corrected for the yield in the homogenate). Measurements of the cytochrome P-450 content of liver cells by the microspectrophotometric method show that in liver from male Wistar rats, cells nearer to the central veins contain up to twice as much cytochrome P-450 as those nearer to the portal tract (mean cell concentrations of 26.4 (+/-4.4) mumol/l and 17.5 (+/-3.0) mumol/l respectively). In the livers from similar rats, killed at the same time, but which has received 1 mg/ml sodium phenobarbitone in their drinking water for one week, the cells near the central vein contained up to five times as much cytochrome P-450 as those near the portal tract (mean cell concentrations of 77.3 (+/-25.0) mumol/l and 28.3 (+/-9.6) mumol/l respectively). The results show a selective increase in cytochrome P-450 content by the cells in the centrilobular region after treatment with sodium phenobarbitone and a smaller increase by some of the cells in the periportal region.

Animals↗

PubMed1978

Cell studies in prolymphocytic leukaemia.

A case of prolymphocytic leukaemia, showing several features not yet reported in this disease, is reported. The majority of lymphocytes in the peripheral blood and bone marrow had markers of both B- and T-lymphocytes. The simultaneous presence of receptors for sheep RBC and surface immunoglobulins on individual cells was demonstrated and the endogenous origin of these markers was established. The lymphocytes had some of the functional characteristics seen in chronic lymphocytic leukaemia (CCL). In vitro cell death in the presence of colchicine (colchicine ultrasensitivity) and polystyrene bead column retention were of the same order as seen in CLL. In contrast with the findings in CLL, these cells were markedly radioresistant in vitro. The dominant clinical features--anaemia and constitutional symptoms--appeared to be related to hypersplenism associated with massive splenomegaly. The relevance of these findings is discussed.

Aged↗

PubMed1975

The melanocytotoxic action of 4-hydroxyanisole.

Cultured normal mammalian melanocytes exposed to a variety of antioxidants in the presence of millimolar concentrations of 4-hydroxyanisole exhibit dose-dependent modifications of cytotoxicity. While some antioxidants reduced the extent of damage produced by 4-hydroxyanisole, others appeared to increase it. Similar effects were found in a model system using lysis of human erythrocytes as an index of cell damage. Estimations on rat liver microsomes in the presence of tyrosinase and 4-hydroxyanisole showed increased peroxidation only at low substrate concentrations.

Aldehydes↗

PubMed1975