Biomedical subjects

M J Weidemann

Publications and source records attributed to M J Weidemann.

At least 37 records · Page 2Linked to original sources

PubMed1992

Anaerobic exercise causes transient changes in leukocyte subsets and IL-2R expression.

There is evidence that the stress of intense athletic competition and training depresses cellular immunity and predisposes athletes to increased infection. This paper reports changes in circulating leukocyte subsets of trained (group I: VO2max = 67.2 +/- 5.4 ml.kg-1min-1; age = 22.0 +/- 6.2 yr) and untrained (group II: VO2max = 55.0 +/- 4.9 ml.kg-1min-1; age = 21.4 +/- 2.0 yr) males following 1 min of bicycle ergometry at maximum effort. Significant post-exercise increases in concentrations of total leukocytes, monocytes, lymphocytes, CD3+, CD4+, CD8+ lymphocytes were observed in both groups (all P < 0.01). The CD4/CD8 ratio decreased significantly (P < 0.01) but the granulocyte concentration was not altered (P > 0.05). Despite groups I and II not differing in either peak power or total work performed during the exercise test (P > 0.05), group II had a significantly greater concentration and percentage of CD8+ lymphocytes immediately after exercise (P < 0.01). All of the early changes were transient, with normalization occurring within 1 h. Only trained subjects showed a significant decrease in the percentage of CD25+ lymphocytes following PHA stimulation of whole blood obtained 6 h post-exercise. Alterations in leukocyte subpopulations found in response to predominantly anaerobic exercise appear to be associated with a significant, but possibly transient, alteration in the mitogenic responsiveness of lymphocytes that is restricted to aerobically trained subjects.

Adolescent↗

PubMed1991

Interactions among granulocyte-macrophage colony-stimulating factor, macrophage colony-stimulating factor, and IFN-gamma lead to enhanced proliferation of murine macrophage progenitor cells.

This report examines the actions of IFN-gamma on monocytopoiesis in murine liquid and semisolid bone marrow cultures. The proliferative response of bone marrow cells to macrophage CSF and granulocyte-macrophage CSF was assayed by measuring [3H]TdR uptake in a range of mouse strains. No interstrain difference in kinetics was observed for CSF-1 action, but GM-CSF acted significantly more rapidly on C57B1/6, Swiss, and to a lesser extent A/J mice than on BALB/c or CBA. IFN-gamma inhibited [3H]TdR incorporation elicited by CSF-1, and to a much lesser extent, GM-CSF. When the two CSF were added together, the effects were not additive; in fact, the response was the same as that seen with GM-CSF alone. When IFN-gamma was also added, the response was restored to the level seen with CSF-1 alone. In essence, the inhibitory actions of GM-CSF and IFN-gamma were mutually exclusive. The mechanism of these actions was investigated using colony assays. As expected, CSF-1 caused the formation of pure macrophage colonies, whereas GM-CSF stimulated production of macrophage, granulocyte, and mixed granulocyte macrophage colonies. When the two CSF were added in combination, the total colony count was greater than with either alone, but less than additive. The number of pure macrophage colonies was reduced to the number seen with GM-CSF alone. IFN-gamma reduced the number of colonies in the presence of CSF-1, but slightly increased the number with GM-CSF. In the presence of both CSF, IFN-gamma increased the colony count by around 25 to 40%, so that the numbers were greater than the combined total of CSF-1 plus GM-CSF added separately. Similar results were obtained in all mouse strains tested. The results suggest that the thymidine uptake data reflect changes in the number of progenitor cells responding rather than changes in cell cycle time. The results are discussed in terms of the possibility that coadministration of GM-CSF and CSF-1 could ameliorate the myelosuppressive actions of IFN-gamma in vivo, leading to more effective use of this agent as a biologic response modifier.

Animals↗

PubMed1991

The human promyelocytic HL60 cell line: a model of myeloid cell differentiation using dimethylsulphoxide, phorbol ester and butyrate.

The release of the reactive oxygen species that accompanies the oxidative burst was studied in HL60 cells differentiated with either dimethylsulphoxide, butyrate or phorbol myristate acetate in order to establish the extent to which differentiated cells are phenotypically similar to human neutrophils, monocytes and macrophages. When phorbol myristate acetate was used as a stimulus, the rates of superoxide production by dimethylsulphoxide and butyrate differentiated HL60 cells was not significantly different from those observed in neutrophils and monocytes isolated from normal peripheral blood. Similar results were obtained when luminol-dependent chemiluminescence was measured in the presence of horseradish peroxidase using phorbol myristate acetate as the stimulus. However, in the absence of horseradish peroxidase, the luminol-dependent chemiluminescence in the dimethylsulphoxide and butyrate-differentiated HL60 cells was significantly lower than that of the control cells isolated from human blood, reflecting the absence of myeloperoxidase in the differentiated cells. In contrast, HL60 cells differentiated by phorbol myristate acetate failed to show any increased generation of superoxide or luminol-dependent chemiluminescence upon stimulation. Impaired release of lysosomal enzymes by the chemically differentiated cells suggests impairments in the extent of differentiation resulting in cells with defective azurophilic degranulation processes. It is concluded that HL60 cells differentiated by the above agents are somewhat controversial models of promyelocyte differentiation into typical neutrophilic, monocytic and macrophage-like cells.

Butyrates↗

PubMed1990

Exercise, training and neutrophil microbicidal activity.

The concentration in human plasma of putative neutrophil-"priming" cytokines like endogenous pyrogens is known to increase significantly in response to moderate exercise (11). This is characteristic of an acute-phase response. The ability of blood neutrophils isolated from both trained and untrained human subjects (n = 11, 9) to produce microbicidal reactive oxygen species was determined using luminol-enhanced chemiluminescence both before and after one hour of aerobic exercise at 60% VO2max. Irrespective of training and stimulus concentration, exercise nearly always caused significant "priming" of the capacity of neutrophils to produce H2O2 and HOCl upon stimulation with opsonized zymosan (P less than 0.01); however, compared to their untrained counterparts, the activity of cells isolated from trained individuals was depressed about 50% at unit stimulus concentration, both before and after exercise (P less than 0.075), whilst remaining unaltered at saturating concentrations. Although neutrophil oxygenation activity is only one parameter that contributes to immunological status, regular episodes of moderate exercise may increase resistance to infection by priming the "killing capacity" of neutrophils. In contrast, prolonged periods of intensive training may lead to increased susceptibility to common infections by diminishing this activity.

Acute-Phase Reaction↗

PubMed1990

The effects of interleukin 3 (IL-3) on cells responsive to macrophage colony-stimulating factor (CSF-1) in liquid murine bone marrow culture.

We have examined variation between inbred mouse strains in the proliferative response of bone marrow cells in liquid culture to macrophage colony-stimulating factor (CSF-1) and interleukin 3 (IL-3). In all mouse strains, thymidine incorporation was stimulated by CSF-1 and, after an initial lag period, it reached a peak on day 5. In contrast, two mouse strains, A/J and Balb c, had much lower proliferative responses to IL-3 than did the other strains. In A/J there was no increase in thymidine incorporation above the initial baseline, although the fall in incorporation seen in the absence of any added growth factor was prevented. IL-3 also prevented the loss of CSF-1 responsiveness observed when A/J bone marrow cells were incubated in medium alone. The lag phase in the response to CSF-1 was progressively abolished following IL-3 pre-treatment. Thus, the data with A/J mice separate two distinct activities of IL-3 and show that proliferation is not required for the synergistic effect exerted by IL-3 on CSF-1-stimulated macrophage generation from bone marrow. In strains in which IL-3 alone was able to stimulate proliferation, its action was not additive with that of CSF-1, and addition of both factors together did not overcome the lag phase. This suggests that the two factors act on the same cell population, and that the known synergistic effect of IL-3 on macrophage colony formation in soft agar does not result from an increase in the initial rate of proliferation. The possibility that the combination of factors might alter the duration of the growth response in vivo is discussed.

Animals↗

PubMed1990

Cyclic-AMP inhibits neither A23187-stimulated [14C]-arachidonic acid release from prelabelled lipids nor phospholipase A2 activity in resident rat peritoneal macrophages.

8-Bromo cyclic AMP inhibited A23187-stimulated PGE2 production in adherent resident rat peritoneal macrophages by 50% when this was assessed by radioimmunoassay. In contrast, neither exogenous 8-bromo cyclic AMP nor elevation of endogenous cyclic AMP with cholera toxin inhibited 14C-arachidonic acid release or labelled prostaglandin formation by [1-14C]-arachidonic acid-prelabelled macrophages stimulated with either A23187 or melittin. Inhibition by cyclic AMP appears to be confined to PGE2 originating from a pool of endogenous phosphoglyceride that does not readily exchange with isotopically-labelled arachidonic acid. Phospholipase A2 activity, assessed as calcium-dependent [1-14C]-arachidonic acid release from exogenous 1-stearoyl, 2-[1-14C]-arachidonyl phosphatidyl choline at pH 8.6, was activated by melittin but not by A23187 in 1000 x g supernates from sonicated cells. Neither melittin nor calcium activation of phospholipase A2 was inhibited by preincubation of the cells prior to breakage with 8-bromo-cyclic AMP, nor by inclusion of either 8-bromo cyclic AMP or the catalytic subunit of cyclic AMP-dependent kinase in the assay. The results are inconsistent with the hypothesis that inhibition of A23187-stimulated PGE2 production by cyclic AMP in peritoneal macrophages is due to inhibition of a calcium-stimulated phospholipase A2.

8-Bromo Cyclic Adenosine Monophosphate↗

PubMed1987

Lipids from Plasmodium vinckei-infected erythrocytes and their susceptibility to oxidative damage.

The constituent lipids of plasma and red blood cells (RBC) from mice late in infection with the malarial parasite Plasmodium vinckei were analyzed and compared with those obtained from uninfected animals. On a dry weight basis, the total extractable lipids of RBC increased threefold during infection, while those of the plasma did not change significantly. In general, changes in individual plasma lipid constituents paralleled those found in RBC of infected mice but were of smaller magnitude. While the increase in the total lipids of parasitized RBC was largely attributable to an increase of more than fourfold in total phospholipids, a significant increase in neutral lipids was also observed. Phosphatidylcholine and phosphatidylethanolamine were the major phospholipids present within RBC, and their total and relative concentrations increased as a result of the infection. A parallel increase occurred in the ratio of unsaturated to saturated fatty acids in the parasitized RBC phospholipids. Infection was also associated with decreases in the relative amount of cholesterol present in RBC and in the ratio of cholesterol to phospholipid. Consistent with this, the fluorescence polarization of 1[4-(trimethylamino)phenyl]-6-phenylhexa-1,3,5-triene within parasitized RBC plasma membranes was decreased in comparison with its value in noninfected RBC, indicating that malarial infection decreases the "order" of membrane lipids. These modifications, in conjunction with the increased levels of vitamin E and malonyldialdehyde reported elsewhere, are important determinants of the susceptibility of the different membrane compartments within infected RBC to peroxidative damage.

Animals↗

PubMed1987

Regulation of proliferation of bone marrow-derived macrophages.

The rate of mobilisation of macrophages from marrow is an important determinant of the outcome of many pathological lesions. Studies of BMDM have provided insight into the complex feedback regulation that may control macrophage production. In addition BMDM possess several properties in common with transformed cells of other tissue origins and an understanding of their growth regulation may provide an insight into the mechanism of malignant transformation.

Animals↗

PubMed1986

Possible mechanisms responsible for the increased ascorbic acid content of Plasmodium vinckei-infected mouse erythrocytes.

The possible mechanisms underlying the acquisition of an increased ascorbic acid content by mouse erythrocytes containing the malarial parasite Plasmodium vinckei were investigated. Ascorbic acid was taken up readily by parasitized red blood cells but not by controls, whilst its partly oxidized form, dehydroascorbic acid, entered both. The uptake of both ascorbic acid and dehydroascorbic acid into erythrocytes was increased as a result of malarial infection. Lysates prepared from parasitized red blood cells reduced exogenous dehydroascorbic acid to ascorbic acid at a higher rate than control red blood cell lysates; this difference was abolished following dialysis of the lysates, a process which removes endogenous reduced glutathione (GSH). The rates of chemical and enzymatic reduction of dehydroascorbic acid to ascorbic acid by GSH were of similar magnitude, thus calling into question the existence of a specific dehydroascorbate reductase in erythrocytes and parasites. These observations suggest that the increased uptake of dehydroascorbic acid into parasitized red blood cells may be a result of enhanced dehydroascorbate-reducing capacity, whilst the presence of the parasite induces a selective increase in the permeability of the erythrocyte plasma membrane to ascorbic acid. The endogenous ascorbic acid content of livers obtained from infected mice was 55% below the normal concentration and its relative rate of destruction during incubation in vitro was enhanced in comparison with that of control livers. Furthermore, the capacity of liver homogenates to synthesize ascorbic acid from glucuronic acid was greatly reduced in infected mice. Therefore it is unlikely that the increase in ascorbic acid content of parasitized red blood cells is a consequence of increased biosynthesis and release of ascorbic acid by the host liver. We have not been able to exclude the possibility that the malarial parasite itself may be capable of de novo synthesis of ascorbic acid.

Animals↗

PubMed1986

Protection of vitamin E from oxidation by increased ascorbic acid content within Plasmodium vinckei-infected erythrocytes.

Erythrocytes isolated from mice at a late stage of infection with the malarial parasite Plasmodium vinckei contained increased levels of vitamin E, but neither control nor infected erythrocytes contained detectable levels of alpha-tocopherolquinone, an oxidation product of vitamin E. Total levels of the antioxidant, vitamin C, were more than doubled in the same populations of highly parasitized erythrocytes. These observations, and the lower ratio of oxidized to reduced forms of ascorbic acid in parasitized compared to nonparasitized erythrocytes, raise the possibility that increased redox-cycling between the two vitamins may account for the failure to detect alpha-tocopherolquinone. Thus, late in infection of mice with the lethal parasite P. vinckei, the content and redox state of erythrocytic ascorbic acid is altered so that it protects vitamin E, and presumably the parasitized red cell and its contents, from oxidative damage.

Animals↗

PubMed1986

Antioxidants in plasma from mice infected with Plasmodium vinckei.

The late stage of infection of mice with the malarial parasite Plasmodium vinckei was accompanied by significant changes in the content of most antioxidants within plasma. The plasma concentrations of uric acid and vitamin C increased, in contrast to those of vitamin E and total plasma proteins, whilst the activity of superoxide dismutase did not change significantly. In contrast to the situation within erythrocytes, the ratio of partly oxidized forms of vitamin C (dehydroascorbate and diketogulonic acid) to reduced ascorbic acid failed to decrease as a result of malarial infection. These results are consistent with earlier findings and add to the idea that malarial infection may result in oxidative tissue damage.

Animals↗

PubMed1985

Reactive-oxygen formation and its relationship to prostaglandin and cyclic AMP production by zymosan-treated rat peritoneal macrophages.

Addition of zymosan (20 particles/cell) to suspensions of resident rat peritoneal macrophages caused an increase in the concns of prostaglandins and cyclic AMP. Preincubation of the cells with inhibitors of arachidonate metabolism led to inhibition of prostaglandin, but not of cyclic AMP, formation, which suggested that the two processes may occur independently of each other in phagocytosing cells. The luminol-dependent chemiluminescence associated with the addition of zymosan to the cells consisted of a minor, Ca2+-dependent, glucose-independent component and a major, glucose-dependent, Ca2+-independent component. Only the minor, Ca2+-dependent component appeared to be related to the lipoxygenation of arachidonic acid. Close examination of the production of prostaglandins and cyclic AMP and of chemiluminescence after zymosan addition, indicated that the expanded pool of endogenous cyclic AMP was probably not a negative modulator of the other two processes, although they remained susceptible to inhibition by exogenously-added cyclic AMP analogues or PGE2. The events induced by zymosan may be relevant to the physiological roles of prostaglandins during the inflammatory response.

Animals↗

PubMed1985

Oxidative stress and protective mechanisms in erythrocytes in relation to Plasmodium vinckei load.

The protection of mouse erythrocytes (RBC) parasitized with Plasmodium vinckei vinckei against activated oxygen species was examined in relation to the intraerythrocytic parasite load. RBC from highly infected animals were separated by density gradient centrifugation into six bands with increasing parasite content and with parasitemias ranging from 17% to 100%. Increase in parasite load was accompanied by a decrease in the activities of the enzymes superoxide dismutase (EC 1.15.1.1), catalase (EC 1.11.1.6), glutathione peroxidase (EC 1.11.1.9), glutathione reductase [NAD(P)H] (EC 1.6.4.2), and NADH-methemoglobin reductase (EC 1.6.2.2; NADH:ferricytochrome b5 oxidoreductase) in the RBC lysates. In contrast, the total amount of reduced glutathione increased in the highly parasitized bands. Furthermore, the vitamin E content of all RBC bands, including the one that contained mainly nonparasitized erythrocytes, was 3- to 5-fold higher than that of control noninfected RBC. Increasing parasite load was accompanied by an increase in the production of malonyldialdehyde, indicating enhanced lipid peroxidation. Our results indicate that oxidative stress is experienced by all RBC during a malarial infection and is accompanied by a variety of changes in the antioxidant defense mechanisms of the host and the parasite. Furthermore, it appears that the plasma membrane of the host cell is better protected against oxidative injury than are the membranes surrounding the parasite.

Animals↗

PubMed1984

Oxygen uptake associated with Sendai-virus-stimulated chemiluminescence in rat thymocytes contains a significant non-mitochondrial component.

Sendai virus (150 haemagglutinating units/10(6) cells) stimulates rat thymocytes incubated in medium containing 5 mM-glucose at 37 degrees C to produce luminol-dependent chemiluminescence and a simultaneous increase in O2 consumption of 40%. Stimulation of thymocytes with Sendai virus is accompanied by reduction of exogenous acetylated ferricytochrome c, which is inhibited by superoxide dismutase, and the quantitative conversion of ferricyanide to ferrocyanide, which is not. Replacement of air in the gas space with N2 inhibits the chemiluminescent response by 97% but does not prevent the virus-stimulated reduction of ferricyanide. The non-permeant ferricyanide anion (2 mM) also inhibits the chemiluminescent response to Sendai virus, its accompanying 'extra' O2 uptake and the reduction of acetylated ferricytochrome c without affecting the basal respiration of the cells. Thymocytes in which the basal O2 consumption has been stimulated maximally with dinitrophenol (10 microM) or inhibited completely with antimycin A (0.1 microM) respond to Sendai virus with an additional increment of ferricyanide-inhibitable O2 consumption. The chemiluminescent response to virus is not inhibited by concentrations of antimycin A that block the basal respiration completely. We suggest that a portion of the increased O2 uptake induced by Sendai virus is involved in the non-mitochondrial reduction of O2 to O2- at the cell surface where the non-permeant ferricyanide anion inhibits O2-. formation by acting as an alternative high-affinity electron acceptor to O2.

Animals↗

PubMed1984

Glucose and glutamine metabolism in rat thymocytes.

The metabolism of glucose and glutamine in freshly prepared resting and concanavalin A-stimulated rat thymocytes was studied. Concanavalin A addition enhanced uptake of both glucose and glutamine and led to an increase in oxidative degradation of both substrates to CO2. With variously labelled [14C]glucose, it was shown that the pathways of glucose dissimilation were equally stimulated by the mitogen. A disproportionately large percentage of the extra glucose taken up was converted into lactate, but concanavalin A also caused an increase in the oxidation of pyruvate as judged by the enhanced release of 14CO2 from [2-14C]-, [3,4-14C]- and [6-14C]-glucose. Addition of glutamine did not affect glucose metabolism. The major end products of glutamine metabolism by resting and mitogen-stimulated rat thymocytes were glutamate, aspartate, CO2 and NH3. Virtually no lactate was formed from glutamine. Concanavalin A enhanced the formation of all end products except glutamate, indicating that more glutamine was metabolized beyond the stage of glutamate in the mitogen-activated cells. Addition of glucose caused a significant decrease in the rates of glutamine utilization and conversion into aspartate and CO2 in the absence and in the presence of concanavalin A. In the presence of glucose, almost all nitrogen of the metabolized glutamine was accounted for as NH3 released via the glutaminase and/or glutamate dehydrogenase reactions. In the absence of glucose, part (18%) of the glutamine nitrogen was metabolized by the resting and to a larger extent (38%) by the mitogen-stimulated thymocytes via a transaminase or amidotransferase reaction.

Animals↗

PubMed1984

Activation of cyclic AMP-dependent protein kinase in macrophages.

The activity of cyclic AMP-dependent protein kinase (cyclic AMP-PK) was significantly higher (P less than 0.001) in thioglycollate-elicited than in resident rat peritoneal macrophages. The activity ratio of the enzyme (its activity in the absence of added cyclic AMP divided by that in the presence of 5 microM cyclic AMP) was similar in the two cell types. The divalent ion ionophore A23187 induced a rapid increase in the activity ratio of cyclic AMP-PK in both macrophage types. This effect was blocked by pretreating the cells with indomethacin or aspirin (inhibitors of cyclo-oxygenase) and bromo-phenacyl bromide (an inhibitor of phospholipase A2), implicating the synthesis of a prostanoid as an intermediary step. Prostaglandin (PG) E2, 8-bromo cyclic AMP and cholera toxin, all of which inhibit chemiluminescence and/or PG formation in macrophages, increased the activity ratio of cyclic AMP-PK in these cells. We propose that the activation of cyclic AMP-PK plays a central role in the response of macrophages to both endogenously-generated and exogenously added PGE.

Acetophenones↗

PubMed1984

Production of luminol-reactive oxygen radicals during Plasmodium vinckei infection.

We tested the ability of whole blood and enriched fractions of peripheral blood polymorphonuclear leukocytes obtained from mice during the course of infection with Plasmodium vinckei to produce luminol-mediated chemiluminescence in response to phagocytic and nonphagocytic stimuli. The chemiluminescence response of whole blood to all stimuli increased dramatically and nonlinearly as the infection progressed, and there was a concomitant increase (80%) and decrease (70%) in the total numbers of leukocytes and erythrocytes, respectively. The proportion of polymorphonuclear leukocytes in the total leukocyte population increased threefold. On a per cell basis and at a constant hematocrit, the chemiluminescence response of peripheral leukocytes from infected animals to phorbol myristate acetate or opsonized zymosan was only slightly greater than that of cells from uninfected animals. Polymorphonuclear leukocytes isolated from the blood of infected animals also showed no large increase per cell in chemiluminescence responsiveness. Thus, although leukocyte numbers increase during a murine malarial infection, there appears to be no major change in the capacity of individual peripheral blood leukocytes to produce activated species of oxygen. However, the physiological reduction in the total concentration of hemoglobin at high parasitemia, due to hemolysis and hemoglobin digestion by the parasites, increases the possibility of oxygen radical-mediated damage to tissues and intraerythrocytic parasites as a result of decreased antioxidant protection.

Animals↗

PubMed1983

Reactive oxygen production, arachidonate metabolism and cyclic AMP in macrophages.

Chemiluminescence was used as an indicator of the production of reactive oxygen species by thioglycollate-elicited rat peritoneal macrophages stimulated by A23187. This action of the ionophore was inhibited by bromophenacyl bromide and nordihydroguaiaretic acid, inhibitors of the phospholipase A2 and lipoxygenase enzymes, respectively. The cyclo-oxygenase inhibitors, indomethacin and aspirin, did not diminish the light output. Preincubation of the cells with the 8-bromo- or dibutyryl analogues of cyclic AMP or with the cyclic AMP-phosphodiesterase inhibitors theophylline and RO-20-1724, or with PGE2, inhibited the A23187-evoked chemiluminescence. The results suggest that he lipoxygenase pathway of arachidonic acid metabolism may make a significant contribution to reactive oxygen production. This process may be modulated, and its duration limited, by cyclic AMP-mediated actions of prostaglandins, which are products of the cyclo-oxygenation of arachidonate.

8-Bromo Cyclic Adenosine Monophosphate↗