Biomedical subjects

H Pelletier

Publications and source records attributed to H Pelletier.

At least 19 recordsLinked to original sources

PubMed1992

Crystal structure of a complex between electron transfer partners, cytochrome c peroxidase and cytochrome c.

The crystal structure of a 1:1 complex between yeast cytochrome c peroxidase and yeast iso-1-cytochrome c was determined at 2.3 A resolution. This structure reveals a possible electron transfer pathway unlike any previously proposed for this extensively studied redox pair. The shortest straight line between the two hemes closely follows the peroxidase backbone chain of residues Ala194, Ala193, Gly192, and finally Trp191, the indole ring of which is perpendicular to, and in van der Waals contact with, the peroxidase heme. The crystal structure at 2.8 A of a complex between yeast cytochrome c peroxidase and horse heart cytochrome c was also determined. Although crystals of the two complexes (one with cytochrome c from yeast and the other with cytochrome c from horse) grew under very different conditions and belong to different space groups, the two complex structures are closely similar, suggesting that cytochrome c interacts with its redox partners in a highly specific manner.

Amino Acid Sequence↗

PubMed1992

Confluence-dependent resistance in human colon cancer cells: role of reduced drug accumulation and low intrinsic chemosensitivity of resting cells.

In vitro sensitivity of HT29 human colon cancer cells to doxorubicin (DXR), vincristine (VCR), etoposide (VP16), cisplatin (CDDP), melphalan (L-PAM) and 5-fluorouracil (5FU) was markedly reduced when cell-culture density increased. For some drugs, confluence-dependent resistance (CDR) was partly due to decreased intracellular drug accumulation; the ratio of mean intracellular drug content of non confluent to confluent cells (NC/C) was 2.5 for DXR, 4.1 for VCR and 7.4 for VP16. Altered drug penetration with confluence could be related to decrease of plasma membrane fluidity as measured by the fluorescence polarization method. Reduction of drug intracellular accumulation was nil or weak for L-PAM (NC/C = 1.0), CDDP (NC/C = 1.2) and 5 FU (NC/C = 1.8). Even if drug concentration was adjusted in culture medium to produce similar intracellular drug content in confluent and non confluent cells, higher intrinsic resistance of confluent cells was still evidenced for DXR and VP16 but not for VCR, the only agent without direct interaction with DNA. DXR- and VP16-induced DNA breakage was also less important in confluent than in non-confluent cells. CDR appeared closely related to an increased proportion of non-cycling cells at confluence, as demonstrated by flow cytometry, expression of nuclear antigen recognized by Ki67 MAb and expression of topoisomerase II. CDR is probably a major factor in the poor sensitivity of colorectal adenocarcinomas to chemotherapy.

Antineoplastic Agents↗

PubMed1991

Cytotoxic activity of lymphocytes infiltrating progressive and regressive tumor variants from a rat colonic cancer.

Two tumor cell variants (PROb and REGb) isolated from a single chemically-induced rat colon adenocarcinoma were previously shown to differ in their tumorigenicity. When injected into syngeneic BDIX rats, PROb cells induce progressive tumors whereas REGb cells give rise to tumors which always regress. PROb and REGb variants also differ in their capacity to induce an immune response in the syngeneic host. Regression of REGb tumors could have been mediated by cytotoxic effector cells acting at the tumor site. To test this hypothesis, the cytolytic activity of non-adherent lymphoid cells isolated from PROb and REGb tumors and from the spleen of the same animals were compared. The same number of infiltrating lymphocytes was recovered per gram of PROb or REGb tumor. The cytolytic activity of tumor infiltrating lymphocytes, as that of spleen lymphocytes, was predominantly non specific, as demonstrated by their ability to kill YAC-1 cells, an NK-sensitive cell line. PROb cells were relatively resistant to the cytotoxic activity of spleen or tumor infiltrating lymphocytes. In the regressing REGb tumors, the cytotoxic activity of tumor infiltrating lymphocytes to homologous cells or to YAC-1 cells was low and significantly inferior to that of the corresponding spleen lymphocytes. These results suggest that the cytotoxic activity of lymphocytes was impaired at the local, intratumoral level, even in spontaneously regressing tumors.

Adenocarcinoma↗

PubMed1991

[Parental knowledge about their asthmatic children].

A questionnaire was administered to parents of 171 asthmatic children, and their knowledge of asthma was evaluated using a quantitative score. The mean age of children was 5 yr and the mean duration of their asthma was 3 yr. Each sign of the classical triad "noisy breathing, cough, indrawing" was mentioned by two-thirds of parents. Inhaled agents perceived as triggers of asthma were: animal hair (73.7%), dust (69.6%), pollen (60.2%), tobacco (44.4%), molds (14.6%). Other triggering agents mentioned were: stress (51.5%), infections (38%), exercise (13.5%). Mothers with college or university education knew more clinical signs of an attack (P less than 0.01) and more triggering factors (P less than 0.005). Parents satisfied with previous teaching knew more threatening signs of an attack (P less than 0.01). About 80% of those that used theophylline and 49.4% of those that used inhaled beta-2-agonists knew the correct mode of administration. Parents satisfied with previous teaching had better knowledge of the side-effects of theophylline (P less than 0.005) and beta-2-agonists (P less than 0.02). 58.5% of those that used cromolyn sodium did not know the mean duration of a therapeutic trial and 15% did not use it as prophylaxis. 57.1% of those that used oral corticosteroids did not know any side-effects of the drug. About half of the parents indicated that they would like to receive more information about the causes and the appropriate treatment of asthma. It was concluded that parental teaching should focus more on environmental and therapeutic issues.

Asthma↗

PubMed1990

Mechanisms of resistance of confluent human and rat colon cancer cells to anthracyclines: alteration of drug passive diffusion.

Two colon cancer cell lines, HT-29 (human) and DHD/K12/TRb (rat), were grown as monolayer cultures to various confluence degrees. The cytotoxic efficacies of doxorubicin and 4'-deoxydoxorubicin, evaluated by a survival assay, and the nuclear drug concentrations, measured by microspectrofluorometry, were shown to progressively decrease with the augmentation of confluence. This confluence dependent resistance (CDR) to anthracyclines was demonstrated independent of the multidrug resistance drug efflux mechanism. The cellular uptake of three compounds (sodium [51Cr]chromate, D-[14C]alanine, L-[14C]glucose) known to passively diffuse across the cell membrane as anthracyclines do was also reduced in confluent cells. After trypsin cell detachment, the kinetics of reversion of the sodium [51Cr]chromate uptake decrease and that of CDR were similar. Therefore, CDR may be attributed to a reduction of anthracycline cell intake due to a general alteration of passive diffusion across the cell membrane. However, CDR is only partly explained by this phenomenon since a reduced sensitivity of confluent cells was observed compared with nonconfluent cells for a similar amount of drug in their nuclei. CDR could explain the high resistance to anthracyclines of some solid tumors, such as colon tumors, in which cancer cells are tightly aggregated.

Animals↗

PubMed1990

Potential usefulness of quinine to circumvent the anthracycline resistance in clinical practice.

Quinine, the widely used antimalaria agent, was found to increase the cytotoxicity of epideoxorubicin (epiDXR) in resistant DHD/K12 rat colon cancer cells in vitro. Quinine appeared as slightly less effective than quinidine or verapamil for anthracycline potentiation but its weaker cardiotoxicity could counterbalance this disadvantage in vivo. Serum from six patients treated by conventional doses of quinine (25-30 mg kg-1 day-1) was demonstrated to enhance the accumulation of epiDXR in DHD/K12 cells as judged by fluorescence microscopy and HPLC assay (1.6 to 6-fold compared with control serum). In this patients quinine concentrations in serum ranged from 4.4 to 10.1 micrograms ml-1. Our results suggest that quinine could be safely used as anthracycline resistance modifier in clinical practice.

Animals↗

PubMed1989

In vitro proliferative responses of spleen lymphocytes from rats bearing progressive or regressive tumors induced by cell variants of a syngeneic colon carcinoma.

From one colonic carcinoma chemically induced in the rat, 2 sublines of tumor cells have been cloned, one (PROb) inducing progressive tumors, the other (REGb) generating tumors that regress a few weeks after s.c. injection into syngeneic hosts. Our study was aimed at comparing cellular immunity between animals bearing PROb or REGb tumors. Spleen cells were first tested for in vitro proliferation in response to mitomycin-treated PROb or REGb cells. Only spleen cells from rats injected with REGb cells proliferated significantly when mixed with PROb or REGb cells. The proliferative response induced by REGb cells was considerably higher than the response to PROb cells. When spleen cells from rats bearing REGb tumors were cultured with a mixture of REGb and PROb cells at various PROb/REGb cell ratios, PROb cells significantly suppressed the strong proliferative response generated by the same number of REGb cells alone. REGb-immune spleen cells, after in vitro stimulation by PROb or REGb cells, were not cytotoxic for either cell variant. REGb-immune spleen cells did not differ in their content of T lymphocytes expressing CD4 or CD8 markers when they were stimulated by PROb or REGb cells in vitro, but REGb cells induced a larger number of activated lymphocytes expressing the IL-2 receptor. Our results indicate that, compared to REGb cells, PROb cells are poorer stimulators of proliferation of tumor-immune spleen cells, and that they are able to suppress the proliferative response induced by REGb cells.

Adenocarcinoma↗

PubMed1989

Comparative effect of rat and fetal calf serum on measurement of the natural tumoricidal activity of rat lymphocytes, macrophages and polymorphonuclear cells.

The effect of rat serum versus fetal calf serum on the in vitro natural cytolytic activity of rat lymphocytes, macrophages and polymorphonuclear cells against syngeneic tumour cells was compared. The cytolysis level mediated by the three varieties of effector cells was lower when rat serum was used instead of fetal calf serum to supplement the culture medium. This could explain in part the discrepancies found between in vitro and in vivo studies.

Animals↗

PubMed1989

Effects of cyclosporin A on progressive and regressive tumors induced by two cancer lines derived from a single colon carcinoma chemically induced in the rat.

The effects of cyclosporin-induced immunosuppression were assessed in a rat model of progressive and regressive colonic tumors. Two cloned cell variants, obtained from the same chemically induced colonic carcinoma, differ in their capacity to grow when injected into the syngeneic rat. PROb cells yield progressive tumors and often metastases; in contrast, REGb cells produce tumors which regress in 3 to 6 weeks. Cyclosporin A (CsA) administered daily, 20 mg/kg subcutaneously (s.c.) for 30 days after tumor cell inoculation, drastically enhanced the local growth of PROb tumors and increased the number of metastases. It increased the local growth and prevented the regression of REGb tumors which persisted even as long as 8 weeks after the termination of CsA administration and occasionally yielded metastases. CsA prevented the accumulation of inflammatory cells with the T lymphocyte phenotype at the periphery of both PROb and REGb tumors but did not alter the tumor infiltration by macrophages and NK cells. CsA did not modify the natural cytotoxicity of peripheral blood mononuclear cells against PROb and REGb target cells. These results suggest that CsA-induced suppression of T lymphocyte activity may enhance tumor progression and suppress tumor regression in this model.

Animals↗

PubMed1989

Histoimmunological characterization of the cellular reaction to liver metastases induced by colon cancer cells in syngeneic rats.

Artificial liver metastases were produced by injecting in vitro cultivated colonic cancer cells into the mesenteric vein of syngeneic rats. An immunohistologic study of the inflammatory host cells infiltrating the tumors was carried out from 1 to 46 days after tumor cell injection, using a set of monoclonal antibodies labelling tumor cells, macrophages or lymphoid cells subpopulations. In small metastases, 3-7 days after tumor cell injection, tumor cell foci were surrounded by a dense corona of inflammatory cells, predominantly T lymphocytes and NK cells. This inflammatory corona regressed when metastases grew larger and completely disappeared around the large metastases found more than 28 days after cell injection. Inside the metastases, the tumor cells were mixed with a small number of cells with the characteristic labelling of macrophages (KiM2R+, W3/25+); however, the inside macrophages are OX8+ in contrast to macrophages found in normal liver and in the peritumoral corona. The progressive disappearance of the coronal inflammatory cells suggests that cancer cells are able to produce or to induce other cells to produce anti-inflammatory agents inhibiting the accumulation of macrophages and lymphoid cells around the tumors.

Animals↗

PubMed1988

Specificity of the immune response leading to protection or enhancement by regressive and progressive variants of a rat colon carcinoma.

Two cell clones, K12/TRb (PROb) and K12/TSb (REGb), have been isolated from the same serially transplantable tumor, DHD, established from a colon carcinoma chemically induced in the rat. Inoculation of REGb cells gives a tumor which regresses within 4 to 8 weeks and generates immune protection against subsequent injection of the progressive tumor cells, PROb. Inoculation of PROb cells gives a progressive tumor and generates tolerance allowing progressive growth of contralaterally injected REGb cells. Inoculation of REGb cells fully protects the host against growth of a DHD tumor graft, the tumor from which REGb and PROb cells were originally obtained. On the other hand, inoculation of REGb cells does not confer any protection against growth of 4 other syngeneic tumor grafts, DHA, DHB, DHC and DHE. These tumors were obtained from other colonic tumors induced as DHD by 1.2 dimethylhydrazine (DMH). Progressive growth of the tumor induced by inoculation of REGb cells is observed in animals bearing a contralateral DHD tumor, but not in animals bearing tumor from other transplantable lines, DHA, DHB, DHC and DHE. Our results show that immune enhancement of a regressive tumor and the immune protection that it confers constitute specific responses to a tumor-specific transplantation antigen present on a single transplantable colon tumor.

Adenocarcinoma↗

PubMed1988

Differential sensitivity to natural cell-mediated cytotoxicity of two rat colon adenocarcinoma variants differing in their tumorigenicity: identification of the effector cells as natural killer cells.

DHD/K12 TRb (PROb) and DHD/K12 TSb (REGb) are two cancer cell variants originating from the same rat colon adenocarcinoma. They differ in their tumorigenicity: when inoculated into syngeneic BDIX rats, PROb cells induce progressive tumors whereas REGb cells induce tumors which always regress. As previously described, there is an inverse relation between their tumorigenicity and their susceptibility to NCMC mediated by syngeneic spleen or peripheral blood lymphocytes: PROb cells are significantly less sensitive to NCMC than REGb cells. This suggests a role for NCMC in the regression of REGb tumors. In this work the BDIX NCMC effector cells active in vitro against REGb cells were identified as NK cells according to four criteria: (1) efficacy in a 4-h 51Cr release assay, (2) sensitivity to anti-asGM1 antibody plus complement, (3) LGL morphology, and (4) ability to bind with the same affinity REGb and YAC-1 cells. In spleen, these NK cells were heterogeneous with respect to their asGM1 surface density and their morphology. PROb cells were not lysed by these NK cells in a short-term cytotoxicity assay, but only in a 16-h assay. It was shown that PROb and REGb cells were bound with the same affinity by NK cells, thus they certainly differ in their ability to resist to NK lytic mechanisms. This difference could play a role in the different tumorigenicity of the two variants.

Adenocarcinoma↗

PubMed1988

Regression induced by lentinan, of peritoneal carcinomatoses in a model of colon cancer in rat.

Lentinan has been tested in a model of colon cancer in rats. Peritoneal carcinomatoses were induced in BDIX rats by i.p. injections of syngeneic cells isolated from a colon carcinoma, and established in a permanent cell line. The treatment consisted of five i.p. injections, 2 days apart, of 2 mg lentinan/kg at a concentration of 200 micrograms/ml. This was started on day 14 after tumor cell injection, when the rats bore numerous nodules of 1-5 mm. Lentinan significantly inhibited the growth of carcinomatoses. Eleven out of the 20 rats treated with the best lentinan therapy were tumor free at autopsy on day 42. Lentinan significantly increased the life span of carcinomatous rats. The half life following tumor cell injection was 42 days in the control and 70 days in the treated group. Four out of 10 treated rats were still alive on day 210. They were tumor free at autopsy, whereas all the controls died between the 40th and the 70th day. The effectiveness of lentinan was dependent on the number and frequency of the injections. A dose effect was obtained and a strong influence of the concentration was shown.

Animals↗

PubMed1987

Effects of a single injection of anti-asialo GM1 serum on natural cytotoxicity and the growth of a regressive colonic tumor in syngeneic rats.

The REGb tumor cell line is a cloned variant of the DHD-K12 cell line, established from a colon carcinoma chemically induced in the rat. Unlike the parent DHD-K12 cell line, or other clones, which give progressive tumors when inoculated to the syngeneic rat, REGb cells produce tumors which regress in 3 to 5 weeks and never cause metastasis. In order to explore the role of natural killer (NK) cells in REGb tumor regression, each rat was given one injection of anti-asialoGM1 (anti-asGM1) serum, a known inhibitor of NK activity. This injection was done 24 hr before REGb cell challenge. This injection significantly depressed the in vitro cytotoxicity of peripheral blood lymphocytes on REGb cells for 2 weeks. REGb tumors grew larger and regressed later in the treated animals than those in the controls. Furthermore, a progressive or recurrent tumor was observed in 4 out of 10 treated rats, giving lung and/or lymph-node metastases in 2 cases. Immuno-histological study of the cells infiltrating the REGb tumors in control and treated animals showed a decrease number of asGM1+ and OX8+ lymphocytes, presumably NK cells, after anti-asGM1 treatment. An increase in number of macrophages was demonstrated in the progressive tumors of treated animals. These results suggest that NK cells play an important role in the initial stage of the regression TSb tumors in untreated syngeneic rats.

Animals↗

PubMed1987

An immunohistological study of cells infiltrating progressive and regressive tumors induced by two variant subpopulations of a rat colon cancer cell line.

In order to understand the mechanisms leading up to progression or regression, tumors resulting from the s.c. inoculation of progressive or regressive variants of a cell culture established from a chemically-induced rat colonic carcinoma were subjected to sequential histological study. As immunological factors have been previously described in this system of progressive or regressive tumors, special interest was given to inflammatory cells, T and B lymphocytes and macrophages, located inside and outside the tumor. Immunohistological methods using monoclonal or polyclonal antibodies and enzyme histology were performed to identify different populations of infiltrative cells. In both variants of tumors an accumulation of these cells were seen at the periphery of the tumor, surrounding the nodules. In contrast, very few inflammatory cells, macrophages or T lymphocytes were seen inside the clumps of tumor cells where cytolytic cells could have a contact-dependent tumoricidal effect. Only small differences were found between progressive and regressive tumors in the density of the various populations of T helper, T cytotoxic/suppressor, B lymphocytes or macrophages inside or around the tumor nodules. On the other hand, progressive and regressive tumors clearly differ in the relationship between tumor cells and the fibroblastic reaction they induce. Regressive tumors were rapidly encircled by a fibroblastic reaction isolating them from the peripheral tissues. The fibroblastic reaction was less dense around the progressive tumor cells which were able to migrate and invade the periphery. This suggests that immunological factors leading to tumor progression or regression could act indirectly through a control of the fibroblastic reaction, rather than through a direct cytotoxic effect on the tumor cells.

Animals↗

PubMed1987

In vitro natural killer activity against progressive and regressive variants of a rat colon adenocarcinoma. Effect of treatments with anti-asialo GM1 plus complement.

In a previous work, a cell line (DHD/K12) was established from a colon adenocarcinoma induced in a BDIX rat by 1,2-dimethylhydrazine. From this line, two cloned sublines, PROb and REGb, were then isolated. When subcutaneously inoculated into syngeneic rats, PROb cells yield progressive tumors, whereas REGb cells yield tumors which regress. In this study, in a 16-h 51Cr release assay, natural cytotoxicity mediated by BDIX splenic nonadherent lymphoid cells (NK cells) was shown to be much higher against REGb cells than against PROb cells. Whatever the target cells, NK cytotoxicity was always higher when the effector cells were obtained from males rather than from females. Treatment of BDIX splenic lymphocytes by anti-asGM1 serum plus complement revealed that both anti-asGM1 sensitive and non-sensitive NK cells exist. The activity of anti-asGM1 non-sensitive NK cells appeared to be minor and to be detected only when the level of cytotoxicity before treatment was sufficiently high. The difference between PROb and REGb tumor growth appears to be linked, at least in part, to a higher sensitivity of REGb cells to NK cells and especially to anti-asGM1-sensitive NK cells.

Adenocarcinoma↗

PubMed1987

Lack of effect of a high polyunsaturated fat diet on the growth of transplantable colon tumors and on the cytolytic activity of macrophages in rats.

The effect of a high dietary level of polyunsaturated fat was tested on the growth of three different colon cancer cell lines injected subcutaneously into syngeneic rats. This effect was also tested on the in vitro cytolytic activity of resident peritoneal macrophages, natural or endotoxin and/or indomethacin-modulated. A 12% corn oil dietary supplement had no effect in any of the cases tested.

Animals↗

PubMed1987

Treatment with endotoxins of peritoneal carcinomatosis induced by colon tumor cells in the rat.

Peritoneal carcinomatosis, a common spreading of human colon carcinoma, can be obtained by intraperitoneal injection of colon tumor cells in rats. When BDIX rats are injected with 10(6) syngeneic tumor cells, isolated and cloned from a chemically induced colon carcinoma, they die within 2-3 months with solid peritoneal tumors and hemorrhagic ascites. Repeated intraperitoneal injections of 20 micrograms endotoxins (Escherichia coli W0128:B12) from day 3 after tumor cell challenge inhibited tumor growth. This effect was long-lasting since 7 out of 10 treated rats were still alive and tumor-free 6 months after tumor cell challenge. When the endotoxins were administered from day 15 after the tumor cell challenge, in rats with established tumors visible with the naked eye, the survival times were significantly increased, and 6 out of 30 treated rats were still alive and tumor-free 6 months after tumor cell challenge. The optimum effect was obtained with 5 repeated injections. The different frequencies of injection tested, i.e. 1, 3 or 5 days apart were equally effective. Endotoxins were ineffective when administered intravenously. No side effect was observed.

1,2-Dimethylhydrazine↗