Search PubMed⌕ Search

Biomedical subjects

M R Young

Publications and source records attributed to M R Young.

At least 163 records · Page 9Linked to original sources
PubMed1986

Movements and other distinguishing features of small vesicles identified by darkfield microscopy in living macrophages.

Perinuclear vesicles (estimated diameter less than 0.15 micron), too small to be seen in living mouse macrophages by direct phase-contrast microscopy, could be detected by darkfield microscopy thanks to their rapid non-saltatory movements at 37 degrees C, contrasting with the slower saltations of accompanying phase-visible larger vesicles (0.25-0.5 micron, presumed secondary lysosomes). The movements of these 'small visicles' also differed from those of the 'larger visicles' in their responses to changes in temperature, and to chemical agents known to inhibit both the saltations of secondary lysosomes and the latter's fusion with phagosomes. Thus the 'larger vesicles' stopped moving at 25 degrees C, the small ones did not; both stopped at 18 degrees C. The 'small vesicles' continued to move actively after cell uptake of the polyanion poly-D-glutamic acid, while the saltations of the 'larger vesicles' were markedly slowed; both sets of vesicles stopped after uptake of ammonium chloride. Degranulation of the small vesicles paralleled that of the larger, while simultaneously observed preformed pinosomes (labelled with fluorescent wheat germ agglutinin (WGA) appeared to be unaffected. On the basis also of refractivity, location and speed the 'small vesicles' are considered not to be pinosomes, but probably to be lysosomes. The question of whether they are a subgroup of small immature secondary lysosomes or primary lysosomes (0.05-0.08 micron) is discussed. The broad spectrum of movement inhibited by ammonia in macrophages raises the possibility that this weak base inhibits movements of all lysosomes. Further characterization of these 'small vesicles' requires their relation to be defined to the small particles in other cell types (especially in axoplasm) which have been detected by video-enhanced microscopy.

Ammonium Chloride↗
PubMed1986

Macrophage-mediated suppression of natural killer cell activity in mice bearing Lewis lung carcinoma.

The natural killer (NK) cell cytotoxic capacity of C57BL/6 mice with implantation of Lewis lung carcinoma (LLC) was quantitated during tumor growth. The NK activity became suppressed at 1 week of tumor growth and remained suppressed. The mechanisms for the suppression during the first 3 weeks of tumor growth included secretion of prostaglandin E2 (PGE2) by both the LLC tumor and host macrophages. With tumor growth, plasma PGE2 concentrations progressively increased. Oral administration of indomethacin to tumor-bearing mice prevented the rise in serum PGE2 concentrations and the suppression of NK activity. Cultured LLC cells and splenic macrophages isolated from mice during the first 3 weeks of tumor growth secreted increased amounts of PGE2. Macrophages from tumor-bearer spleen cells were shown to suppress NK activity. Depletion of these macrophages restored the NK activity, and addition of these macrophages to normal spleen cells resulted in an indomethacin-sensitive suppression of the NK response. The mechanisms of suppression in mice bearing large tumors were different than those observed with smaller tumors. With a large tumor burden, the plasma PGE2 concentrations declined. Indomethacin treatment did not prevent the suppression of NK activity, and depletion of splenic macrophages did not restore NK cytotoxicity.

Animals↗
PubMed1986

Stimulation of hematopoiesis in untreated and cyclophosphamide treated mice by the inhibition of prostaglandin synthesis.

Indomethacin (IN) was administered to untreated or to cyclophosphamide (CY) treated C57B1/6 mice to study the roles of prostaglandins in regulating hematopoiesis. The following hematopoietic parameters were quantitated: peripheral blood leukocyte (PBL) count; total nucleated cells per spleen; total nucleated cells per femur; and spleen weight. Assays were performed in vitro to measure the number of colony forming units (CFU) present in the bone marrow and spleen. Untreated mice administered IN had a transient rise in their PBL count. These animals also developed splenomegaly and had an increased number of nucleated cells in their spleen. All CY treated mice had a marked decrease in PBL count, spleen cellularity, bone marrow cellularity, and spleen size during the first 5 days after CY treatment. These observations were followed by hematopoietic recovery over the next 10 days. Cyclophosphamide treated mice exhibited a more rapid hematopoietic recovery when treated with IN than without IN treatment. Analysis of the CFU capacity of bone marrow and spleen cells in soft agar showed a larger number of CFU in the bone marrow and spleen of IN treated mice or of CY/IN treated mice than in animals not receiving IN. These results indicate that prostaglandins are involved in the regulation of hematopoiesis in untreated mice and that prostaglandins may limit the hematopoietic recovery of CY treated mice.

Animals↗
PubMed1986

Inhibition of spleen cell cytotoxic capacity toward tumor by elevated prostaglandin E2 levels in mice bearing Lewis lung carcinoma.

The capacity to generate cytotoxic cells toward Lewis lung carcinoma (LLC) in mixed cultures of stimulator LLC and responder spleen cells of LLC-bearing C57BL/6 mice was monitored during the course of tumor growth. The cytotoxic response of mice bearing tumors that were not yet palpable was enhanced. However, as palpable tumors developed and tumor growth progressed, their cytotoxic capacity became suppressed. Concurrent with this decline in cytotoxic capacity, there was an increase in systemic immunoreactive prostaglandin E2 (PGE2) concentrations in tumor-bearing mice. Administration of indomethacin, a prostaglandin synthesis inhibitor, to LLC-bearing mice prevented the rise in PGE2 concentrations and the suppression in cytotoxic capacity toward LLC. A relationship between the elevated immunoreactive PGE2 levels, suppression in cytotoxic capacity, and progressive tumor growth was indicated when administration of indomethacin to tumor-bearing mice also reduced the rate of tumor development.

Animals↗
PubMed1986

Enhancement of Lewis lung carcinoma cell migration by prostaglandin E2 produced by macrophages.

The role of macrophages in tumor metastasis was examined by using migration of a cloned metastatic Lewis lung carcinoma (LLC) variant, LLC-C4, out of glass capillary tubes as an in vitro model for dissemination of tumor cells from a primary tumor mass. Macrophages, derived from LLC tumors of C57BL/6 mice or from peritoneal exudates of mice given injections of complete Freund's adjuvant, enhanced tumor cell migration through an indomethacin-sensitive mechanism. Resident peritoneal macrophages did not produce a tumor migration-enhancing activity but could be induced to do so by preincubation with LLC-C4 cells or their culture supernatants. The capacity of macrophages to enhance LLC-C4 migration corresponded to their secretion of prostaglandin E2. Addition of similar concentrations of prostaglandin E2 to the migration medium of LLC-C4 cells enhanced their migration out of the capillary tubes. These results suggest that macrophages, following exposure to tumor cells or their products or following stimulation with complete Freund's adjuvant, secrete elevated amounts of prostaglandin E2 which in turn may enhance tumor dissemination.

Animals↗
PubMed1986

Differential induction of suppressor macrophages by cloned Lewis lung carcinoma variants in mice.

The splenic T-lymphocyte blastogenic and natural killer cell (NK) activities of C57BL/6 mice bearing cloned metastatic C3 or nonmetastatic C8 variants of the Lewis lung carcinoma were suppressed. The suppression was greater in mice bearing the metastatic C3 tumors than the nonmetastatic C8 tumors, although primary tumor sizes were similar. Macrophages were shown to cause this differential in immune responsiveness, while depletion of splenic macrophages by adherence restored the T-cell and NK responses. Also, splenic macrophages from C3 tumor bearers were more suppressive to normal spleen cell activities than were splenic macrophages from C8 tumor bearers. The suppression by the macrophages of C3 bearers was indomethacin sensitive and was associated with an increased secretion of prostaglandin E2 (PGE2). Normal macrophages incubated with C3 culture supernatants were more suppressive to NK and T-cell activities and secreted more PGE2 than did macrophages incubated with the C8 supernatants or with medium. This finding suggested that the immune suppression in mice bearing C3 tumors was initiated by a soluble tumor factor(s) that stimulated the development of prostaglandin-dependent suppressor macrophages. An in vivo study examined if treating C3-bearing mice with indomethacin to prevent the prostaglandin-dependent macrophage suppressor activity would influence host survival. The survival time of C3-bearing mice treated with indomethacin was prolonged. These results suggest that the macrophage-mediated immune suppression induced by tumor cells may facilitate tumor growth and metastasis.

Animals↗
PubMed1985

Prostaglandin E2 production by EL 4 leukemia cells from C57BL/6 mice: mechanism for tumor dissemination.

Murine EL 4 leukemia cells contained and secreted prostaglandin E2 (PGE2). PGE2 was secreted into the culture media during in vitro growth, as well as into plasma during growth in the peritoneum of inbred C57BL/6 mice. For the study of the role of PGE2 in tumor dissemination, migration of EL 4 cells out of glass capillary tubes was used as an in vitro model for tumor spread in a host. PGE2 enhanced the in vitro migration of EL 4 cells while indomethacin, a prostaglandin synthesis inhibitor, reduced the extent of migration. When EL 4 cells were allowed to migrate into medium containing both indomethacin and PGE2, the cells exhibited an enhanced migration ability suggesting an extrinsic effect on cells by PGE2. The participation of tumor-derived PGE2 in promoting tumor spread in a host was supported by demonstration that EL 4 cells grown in indomethacin-treated mice secreted less PGE2 and had reduced in vivo dissemination ability. These results indicated that tumor spread was promoted by tumor-derived PGE2. The extent of migration and dissemination can be reduced by prostaglandin synthesis inhibitors such as indomethacin.

Animals↗
PubMed1985

Relationships between morphology, dissemination, migration, and prostaglandin E2 secretion by cloned variants of Lewis lung carcinoma.

Lewis lung carcinoma cells (LLC) were isolated and cloned from metastatic lung nodules of C57BL/6 mice or from a cultured parental LLC line. Their dissemination abilities were defined in vivo by their capacities to disseminate to the lungs following s.c. or i.v. injection into mice and in an in vitro model for tumor dissemination by their ability to migrate out of glass capillary tubes. Cloned LLC cells with an enhanced dissemination capacity exhibited a rounded morphology, were nonadherent during in vitro culture, and readily migrated out of capillary tubes. In contrast, clones not capable of dissemination were adherent and spread during in vitro culture and did not migrate out of capillary tubes. Production of prostaglandin E2 by these clones was measured by a radioimmunoassay. An inverse relationship was observed between the extent of migration and dissemination of clones and their ability to secrete prostaglandin E2 in vitro and in vivo. However, the prostaglandin E2 did not regulate the migration-dissemination capacities of LLC clones as inhibiting prostaglandin synthesis did not alter their capacity to migrate in vitro or to lodge in the lungs following i.v. inoculation into mice.

Animals↗
PubMed1984

Prostaglandin E production by Lewis lung carcinoma: mechanism for tumor establishment in vivo.

Prostaglandin E (PGE) concentrations in supernatants of in vitro cultured Lewis lung carcinoma (LLC) cells were measured by radioimmunoassay. Growth of cells correlated with an increase in PGE concentrations in the media. This elevation of PGE in the LLC supernatant could be prevented by the culturing of the cells with indomethacin, a prostaglandin synthesis inhibitor. Serum PGE levels of LLC-implanted mice were also measured. As the tumors developed in vivo, the systemic levels of PGE increased. For examination of the in vivo effect of PGE2 on tumor growth, LLC-implanted C57BL/6 mice were treated with exogenous PGE2, which resulted in an increase in the frequency of tumor establishment. In contrast, oral administration of indomethacin to LLC-implanted mice resulted in a reduced rate of tumor establishment, growth, and metastasis. A relationship between PGE2 production by tumor cells and their survival in a host was indicated.

Animals↗
PubMed1984

Prostaglandin E2 regulation of tumoristatic factor production by macrophage-like P388D1 cells.

Macrophage-like P388D1 cells, when stimulated with lipopolysaccharide (LPS), produced a factor(s) whose activity was inhibitory to growth of Lewis lung carcinoma cells. Indomethacin, a prostaglandin-synthesis inhibitor, augmented the production of tumoristatic activity by LPS-stimulated P388D1 cells, whereas exogenous prostaglandin E2 (PGE2) suppressed its secretion. These results suggest that P388D1 cells regulate their antitumor abilities by producing PGE2, which inhibits production of soluble factor(s) with tumoristatic activities.

Animals↗
PubMed1983

Chemical inhibitors of phagosome-lysosome fusion in cultured macrophages also inhibit saltatory lysosomal movements. A combined microscopic and computer study.

The effects on lysosomal movements produced by the weak base ammonium chloride and by a representative polyanion poly-D-glutamic acid (PGA), previously reported to inhibit phagosome-lysosome (P-L) fusion, have been studied in cultured mouse macrophages using direct visual phase-contrast microscopy, a previously described (1, 3, 7) fluorescence assay of fusion, and computer analysis techniques. Treatment of the macrophages with 5-10 mM NH4Cl for 0.5-2 h or with 100 micrograms PGA/ml for 5 d caused a striking inhibition of saltatory lysosomal movements, as well as the expected inhibition of P-L fusion. Two other anionic fusion inhibitors tested, dextran sulphate and suramin, inhibited movements similarly. Removal of the NH4Cl from the cell medium reversed the lysosomal stasis and restored P-L fusion. Computer analyses of changes in lysosomal positions in treated and untreated macrophages during 2, 10, and 30-s intervals, using data from photomicrographs, computer graphics, and quantitative nearest-neighbour techniques developed for this purpose, supported the qualitative visual observation of the inhibition of lysosomal movements by the fusion inhibitors NH4Cl and PGA. Over the chosen intervals, from 80 to 96% of the lysosomes could be paired within 1 micron of each other in the NH4Cl- and PGA-treated cells in comparison with 50-70% in normal cells. The differences between the drug-treated and normal cells were highly significant. In an analogous system, the lysosomal stasis induced by hypertonic sucrose was examined and it was observed that P-L fusion too was inhibited. Both effects were reversible. We conclude that inhibition of P-L fusion and of lysosomal movement are associated. We suggest a causal relationship between these changes, namely, that the lysosomotropic inhibitors of fusion under study produce their effects largely, though perhaps not exclusively, by reducing saltatory lysosomal motion and consequently periphagosomal assembly, rather than directly and independently on P-L contact or on the fusion process itself. The possibility is raised that microtubules may be involved in the effector mechanism of these modulations.

Acridine Orange↗
PubMed1983

Enhancement of immune function and tumor growth inhibition by antibodies against prostaglandin E2.

Mice bearing a Lewis lung carcinoma (LLC) were passively immunized against prostaglandin E2 (PGE2) by administration of rabbit serum containing anti-PGE2 antibodies. The effect of PGE2-immune serum on the suppressed immunity of LLC-bearing mice was examined. Treatment of tumor-bearing mice with anti-PGE2 prevented the suppression of lymphocyte mitogenesis and the alterations in macrophage migration which typically occur in LLC-bearing mice. Furthermore, tumor growth was reduced in LLC-bearing mice which received antibodies directed against PGE2 rather than a placebo treatment.

Animals↗
PubMed1982

Purification and functional characterization of a low molecular weight immune modulating factor produced by Lewis lung carcinoma.

Previously, we reported that mouse tumors contain a low molecular weight factor which is capable of affecting in vitro properties of macrophages. We now describe the purification to homogeneity of the only factor with macrophage modulating activity from one of these tumors Lewis lung carcinoma. The purified tumor factor appears to be a carboxylic acid and it retains all of the macrophage modulating properties which are characteristic of the unfractionated crude tumor extracts. This factor therefore reverses the spreading of macrophages, enhances the migration of macrophages out of capillary tubes and inhibits their chemotactic and tumoricidal activities. The purified tumor factor also inhibits immune responses of spleen cells. Specifically, proliferation of normal lymphocytes in response to mitogens and to alloantigens, as well as the generation of cytotoxic T lymphocytes in a mixed leukocyte culture, are suppressed when these cells are cultured in the presence of the purified tumor factor. The mixed leukocyte reaction of lymphoid cells obtained from mice which had been treated with the tumor factor is reduced compared to the response of lymphocytes obtained from normal mice. It is possible that there is a relation between production of this factor by tumor cells and survival of the tumor in a host.

Animals↗
PubMed1982

Enhancement in immunity of tumor bearing mice by immunization against prostaglandin E2.

C57Bl/6 mice bearing a palpable Lewis lung carcinoma (LLC) were immunized against prostaglandin E2 (PGE2) in order to prevent the immune suppression typical of tumor bearers. Proliferation in response to concanavalin A (Con A) by normal spleen cells cultured in the presence of PGE2 or by spleen cells of LLC-bearing mice cultured with Con A alone was suppressed. However, the mitogenic response of spleen cells from PGE2 immunized LLC-bearing mice was only partially suppressed. The random migration of normal macrophages cultured in the presence of PGE2 or of macrophages from LLC-bearing mice cultured in medium alone was enhanced when compared to the random migration of normal macrophages cultured in the absence of PGE2. In contrast, the random migration of macrophages obtained from PGE2 immunized LLC-bearing mice was the same as that of normal macrophages cultured in the absence of PGE2.

Animals↗