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Biomedical subjects

J M Bridges

Publications and source records attributed to J M Bridges.

At least 37 records · Page 2Linked to original sources
PubMed1988

Red cell pyrimidine 5' nucleotidase deficiency: determination of nucleotidase activity and nucleotide content using HPLC.

The hereditary deficiency of erythrocyte pyrimidine 5' nucleotidase has been investigated using an HPLC anion-exchange procedure designed to measure both red cell nucleotide content and enzymic activity. Red cell nucleotide profiles were determined using a low pH phosphate buffer salt-gradient system in 20 min, whereas a low pH buffer alone permitted the determination of enzymic activity with each of six different nucleotide substrates in less than 4 min. Both the red cell nucleotide profiles and the enzymic activity of haemolysates from two affected brothers and their children agreed well with previously published values. This unified approach should prove useful for detailed studies of deficiencies involving isoenzymes of pyrimidine nucleotidase.

5'-Nucleotidase↗
PubMed1988

Comparison of the mouse spleen cell assay and a radioimmunoassay for the measurement of serum erythropoietin.

The mouse spleen cell assay (MSCA) has been compared with a radioimmunoassay for the measurement of serum erythropoietin (Ep). In 20 normal subjects the serum values ranged from 15 to 73 mU/ml for the MSCA compared with 5-30 mU/ml for the RIA. For normal sera there was no correlation between the results of the two assays. In 37 patients with anaemias of differing aetiologies and at various stages of treatment values ranged from 10 to 3645 mU/ml for the MSCA and 13-10,000 mU/ml for the RIA. Although patient values from the two assays were highly correlated (r = 0.98, P less than 0.001), the MSCA results were generally lower. These discrepancies can be largely accounted for by two factors. Firstly the MSCA is sensitive to non-specific matrix effects. Secondly, heat inactivation of serum, a prerequisite for the MSCA, but not for the RIA, destroys a variable and unpredictable proportion of the Ep in the test sera leading to an underestimation of Ep in the MSCA. We conclude that the RIA is more reliable than the MSCA which, in its present form, cannot be recommended for the accurate measurement of serum erythropoietin.

Anemia↗
PubMed1988

Erythropoietic response to hypobaric hypoxia in rabbits.

Animals subjected to hypoxia become hypocapnic and after some hours show an increase in circulating erythropoietin. The steps involved in the increased production of erythropoietin in response to hypoxia are not fully understood, although it has been postulated that changes in coincident variables such as acid-base balance may contribute to the mechanism of increased erythropoietin production. A rabbit model has been used to determine the physiological changes which occur in short-term hypobaric hypoxia. After 1 h, no changes were found in pCO2, pH, P50, base excess, standard bicarbonate or serum erythropoietic activity (SEA). After 3 h the pCO2, pH, base excess and standard bicarbonate had decreased while the P50 and SEA had increased. After 6 h, although the pCO2 was still significantly reduced, the pH, base excess and standard bicarbonate had returned to the initial levels and maximal SEA values. 20-fold greater than the pre-hypoxia values were found. Overall the data are consistent with the view that the magnitude of the erythropoietic response to hypoxia is modified by changes in acid-base balance.

Animals↗
PubMed1986

Can food affect the bioavailability of chlorambucil in patients with haematological malignancies?

Pharmacokinetic studies in ten patients with haematological disorders were undertaken on the first and second days of one course of chemotherapy. Patients received chlorambucil under fasting and non-fasting conditions. Plasma concentrations of chlorambucil were determined by a reversed-phase high-performance liquid chromatography assay. Statistical analysis by the Wilcoxon signed rank test for non-parametric data indicated that food caused a significant reduction in peak plasma levels (P less than 0.01), elimination rate constants (P less than 0.01) and area under the plasma chlorambucil/time curve (P = 0.01). Food was also found to prolong the time taken to attain peak plasma levels (P less than 0.01). Regression analysis of renal function with elimination rate constants showed that chlorambucil elimination was independent of renal function (n = 8; r = -0.007; P = 0.72). In view of these results we suggest that chlorambucil is given on an empty stomach.

Adult↗
PubMed1986

Renal function in the elimination of oral melphalan in patients with multiple myeloma.

Pharmacokinetic studies in 11 patients with multiple myeloma were undertaken on the first and last days of one course of chemotherapy. The drug was administered PO in single doses of 6-14 mg daily. Melphalan concentrations were determined by high-performance liquid chromatography. The interpatient variability of pharmacokinetic parameters noted by other authors was observed. Regression analysis showed a significant positive correlation between the elimination rate constant for melphalan and renal function (P = 0.003). The form of the line which describes the overall elimination rate constant for melphalan is given by the equation: Kel = 5.67 X 10(-3) + [4.90 X 10(-5) X GFR]. There was also a significant negative correlation between renal function and the area under the plasma melphalan concentration/time curve (P = 0.006). In vitro stability studies of melphalan in plasma at 37 degrees C and pharmacokinetic data suggest that hydrolysis and renal clearance are the major mechanisms of melphalan elimination. This work shows quantitatively the relationship between renal function and drug elimination and how the data may be used in predicting melphalan half-life from creatinine clearance.

Adult↗
PubMed1986

Enumeration of absolute numbers of T lymphocyte subsets in B-chronic lymphocytic leukaemia using an immunoperoxidase technique: relation to clinical stage.

An immunoperoxidase technique has been used to identify and enumerate helper and suppressor T-cell subsets, as defined by reactivity with Coulter T4 and OKT8 monoclonal antibodies in 54 patients with B chronic lymphocytic leukaemia (B-CLL) and in the same number of matched controls. The ratio of T4+ to T8+ cells was significantly reduced in the B-CLL group as a whole (P less than 0.001) and in each stage of the three clinical staging systems. There was an increase in the median absolute level of T8+ cells in the whole CLL group (P less than 0.001). However, subdivision of the CLL group by clinical staging systems revealed a large group (28 patients) in which median T8+ cell levels were not raised and median T4+ cell levels were low (P less than 0.01). There was no significant decrease in T4+:T8+ ratio, increase in T8+ cells or decrease in T4+ cells with progression of clinical stage. Absolute numbers of E+ cells were significantly raised in all staging systems as were E+ T4- T8- cells (P less than 0.001). A significant alteration in either of these populations with progression of clinical stage was not present.

Adult↗
PubMed1986

Lymphocytes from patients receiving lithium do not inhibit CFU-C growth.

Lymphocyte subset levels and function were examined in 12 patients on lithium therapy and in 11 healthy hospital personnel. Co-culture of allogeneic human bone marrow cells with monocyte-depleted lymphocyte preparations revealed that CFU-C formation was significantly reduced (mean 43% inhibition) in the presence of normal lymphocytes but not with the patients' lymphocytes (less than 5% inhibition). This did not reflect numerical changes in lymphocyte subsets, since these were similar for control and lithium subjects. T colony formation was significantly depressed in the patient group (P less than 0.05), whereas B colony numbers were similar in both groups (P greater than 0.1). The possible role of HLA-incompatibility affecting CFU-C growth was investigated in co-culture experiments, using lymphocytes from HLA-identical twins, one of whom was receiving lithium. In four separate co-culture experiments, the inhibitory effect was shown with lymphocytes from the non-lithium twin but was not demonstrated by the lithium subject. Addition of lithium in vitro to co-cultures of normal marrow and lymphocytes was found to negate the inhibitory phenomenon in a dose-related manner. It is postulated that granulocytosis induced by the administration of lithium may be a manifestation of changes in a lymphocytic control system.

Adult↗
PubMed1986

Obtaining estimates of marginal cost by DRG.

Marginal cost is the additional cost incurred for an additional unit of output. The importance of healthcare organizations knowing marginal costs in a DRG environment will increase due to greater competition and falling occupancy and payment rates. A method for obtaining estimates of marginal cost by DRG has been developed. This method is relatively inexpensive to apply, requires information from general accounting records and Medicare logs, and uses linear regression analysis.

Accounting↗
PubMed1986

In vitro bioassay of erythropoietic activity in serum using mouse spleen cells. The effect of heat inactivation on serum erythropoietin.

Untreated human serum is known to be toxic to in vitro assays for erythropoietin, including the mouse spleen cell assay system (MSCA). This phenomenon had previously been shown to be mediated by complement-dependent IgM heteroantibodies and can be overcome by heating the serum at 56 degrees C for 30 minutes. Using the MSCA, we have found that the toxic effect of serum could also be removed by treatment with a precipitating antibody against the C3c component of complement. The effects of the two methods of complement inactivation on the measurement of stimulatory activity in serum have been compared. For normal serum, the results after heat inactivation and antibody treatment were similar. In contrast, serum from a patient with aplastic anemia gave a result equivalent to 327 mU erythropoietin/ml after heat treatment, but after antibody treatment equivalent to 1,520 mU erythropoietin/ml. Gel permeation chromatography of unheated, heated, and antibody-treated sera showed that heating markedly reduced the activity of the erythropoietin peak. Seventy percent of the activity of partially purified urinary erythropoietin was lost during heating in the presence of normal serum. In addition, heating caused the appearance of high molecular weight compounds that are stimulatory in the MSCA. The level of this activity appeared to be directly related to the stimulatory activity of the unheated serum.

Anemia, Aplastic↗
PubMed1985

Increased plasma glycosidase and protease activity in uraemia: possible role in the aetiology of the anaemia of chronic renal failure.

We have measured plasma N-acetyl-beta-D-glucosaminidase (EC 3.2.1.30) and neuraminidase (EC 3.2.1.18) activities as markers of glycosidase activity and immunoreactive trypsin (EC 3.4.21.4) levels as a marker of proteolytic potential in the plasma of normal and uraemic subjects. The levels of all of these enzymes are significantly elevated in the plasma of uraemic subjects when compared to normal. We have postulated that the combined attack of glycosidases and proteases on erythropoietin will lead to fragmentation of this glycoprotein hormone with loss of activity. This may be a major contributory cause to the anaemia of chronic renal failure.

Acetylglucosaminidase↗
PubMed1985

Acid hydrolase activities in B cell chronic lymphocytic leukaemia lymphocytes: correlation of cytochemical reactions with immunological phenotype.

The cytochemical reactions of 5 acid hydrolases, alpha-naphthyl acetate esterase (ANAE), acid phosphatase (AP), beta-glucuronidase, beta-glucosaminidase and dipeptidylaminopeptidase IV (DAP IV) were investigated in lymphocytes from 30 patients with B cell chronic lymphocytic leukaemia (B-CLL). Based on ANAE and AP reactivities, 4 cytochemically distinctive subgroups were identified: Group 1: AP and ANAE less than 50% positive lymphocytes (5 cases); Group 2: AP greater than 50%, ANAE less than 50% positive lymphocytes (11 cases); Group 3: AP less than 50%, ANAE greater than 50% positive lymphocytes (7 cases); Group 4: AP and ANAE greater than 50% positive lymphocytes (7 cases). beta-Glucuronidase displayed similar patterns of reactivity to AP. beta-Glucosaminidase activity was observed in the majority of lymphocytes in most patients, whereas DAP IV activity was present in less than 20% of lymphoid cells. The study failed to establish any relationship between cytochemical grouping and patients' clinical status, peripheral lymphocyte counts, E or mouse rosette values, light or heavy chain cellular immunoglobulin (Ig) class. Attempts to correlate acid hydrolase and Ig heavy chain isotype expression, putative markers of B cell maturation, were unsuccessful and indicate that within the narrow spectrum of B cell differentiation seen in B-CLL these characteristics are unrelated.

Acid Phosphatase↗
PubMed1985

Separation of erythropoietic stimulators in severe anaemia using high performance gel permeation chromatography.

Patients with various types of anaemia, but with comparable haemoglobin levels, show a wide range of serum erythropoietic activity. We have developed a method for the fractionation of serum by HPLC followed by bioassay of the individual fractions, using the mouse spleen cell microassay. Up to three distinct peaks of erythropoietic activity corresponding to molecular weights (MW) greater than 300,000, 250,000-300,000 and 40,000 have been found in serum from both normal and anaemic subjects. The erythropoietic profiles of the sera examined differ markedly in anaemias of different aetiology. The chemical nature and the physiological significance of the stimulators remain to be investigated.

Adolescent↗
PubMed1985

The effect of transferrin saturation on the estimation of erythropoietin by the mouse spleen cell microassay.

The effect of transferrin from various sources and the degree of saturation with iron on the stimulation of DNA synthesis by erythropoietin (Epo) has been investigated. Mouse, human, and bovine transferrins saturated with iron caused an increase in thymidine incorporation both in the absence and presence of Epo. In contrast, exogenous human and bovine apotransferrin resulted in significantly decreased incorporation of the tracer. The iron saturation of serum alters its apparent erythropoietic activity. This transferrin saturation effect may be overcome by a simple modification involving the addition of iron to the culture medium.

Animals↗
PubMed1984

Depletion of T-lymphocyte subsets using monoclonal antibody and complement: effect on T-colony formation.

Using monoclonal antibody and fresh rabbit serum, mononuclear cells from 11 healthy individuals were depleted of either helper or suppressor T-lymphocytes by complement-mediated lysis. The effect on T-lymphocyte colony formation was studied to determine the nature of the T-colony-forming cell. While depletion of either subset of T-lymphocytes significantly reduced T-colony formation compared to controls (P less than 0.01), colony formation did not differ significantly between helper or suppressor T-cell-depleted cells. Thus T-colony formation appears to be a property of both helper and suppressor T-lymphocytes, and both subsets are necessary for optimal colony formation.

Antibodies, Monoclonal↗
PubMed1984

Dipeptidylaminopeptidase IV activity in normal and leukemic T-cell subpopulations.

Dipeptidylaminopeptidase IV (DAP IV) cytochemical reactivity was investigated in monoclonal antibody defined T-lymphocyte subpopulations from normal blood and in cells from a series of T-cell leukemias of defined immunologic phenotype. A combined monoclonal antibody/immunocolloidal gold technic, which enabled simultaneous visualisation of immunogold label and DAP IV reactivity, was used to study enzyme reactivity in normal T-cell subpopulations. Single or several discrete granules of DAP IV reaction product were observed in 72% of OKT3+ and OKT4+ cells, whereas a significantly (P less than 0.01) lower percentage of OKT8+ cells (41%) displayed positivity; B-cells were invariably DAP IV negative. In the T-cell leukemias, DAP IV reactivity was strongest in T-lymphoblastic lymphoma and T-prolymphocytic leukemia cells. In contrast, DAP IV activity was absent or expressed in a minority of cells of the more immature T-acute lymphoblastic leukemia. The enzyme reaction also was negative in lymphocytes from other mature T-cell leukemias: T-chronic lymphocytic leukemia (OKT8+), adult T-cell lymphoma-leukemia, and Sezary syndrome (both OKT4+). DAP IV expression did not parallel that of acid phosphatase or alpha-naphthyl acetate esterase in leukemic T-lymphoid cells except in T-lymphoblastic lymphoma and T-prolymphocytic leukemia, where a strong reaction with the three hydrolytic enzymes was observed.

Antibodies, Monoclonal↗