Search PubMed⌕ Search

Biomedical subjects

M Kohler

Publications and source records attributed to M Kohler.

At least 73 records · Page 4Linked to original sources
PubMed1989

Quantification of proliferative lesions in hamster lungs after chronic exposure to cadmium aerosols.

The development of proliferative areas in the lungs of Syrian golden hamsters was studied after chronic inhalation of cadmium oxide, cadmium sulfide, cadmium chloride or cadmium sulfate. Lung tissue from randomly selected animals in each group was evaluated by morphometric histopathologic techniques. Estimation of the volumetric ratio of proliferative areas within the lungs of exposed animals showed significantly different extents of these lesions in dependence on the respective cadmium compound administered. The most severe changes were observed after inhalation of cadmium oxide and cadmium sulfide. Lesions were mainly found in the peribronchial region of the lung. Electron microscopic analysis of these proliferative areas revealed that they were composed of ciliated and Clara cells. From its histophatologic appearance this of lesion was qualitatively comparable in all hamsters which had been treated with the different cadmium compounds.

Administration, Inhalation↗
PubMed1989

Impaired generation of anti-viral cytotoxicity against lymphocytic choriomeningitis and vaccinia virus in mice treated with CD4-specific monoclonal antibody.

The role of CD4+ helper T cells in induction of anti-viral cytotoxic T-cell response was investigated by treating normal and thymectomized C57B1/6 mice with CD4-specific monoclonal antibodies (MoAb). In CD4-specific MoAb-treated mice infected with Vaccinia or lymphocytic choriomeningitis virus (LCMV), cytotoxic T-cell activity was 5-15 times lower than in normal controls when measured in a 51Cr release assay and computed as lytic units 6 and 8 days respectively after virus inoculation. This difference in the levels of effector T-cell activities did not reflect slower kinetics of cytotoxic T-cell induction in antibody-treated versus control mice, since it was also obvious at 8 days after infection for Vaccinia virus and 10 and 12 days after inoculation with LCMV. CD4-specific MoAb-induced inhibition of cytotoxic T-cell responses in vivo was seen up to 150 days after treatment in thymectomized mice. However, no significant suppressive effect of the same antibody treatment on T-cell cytotoxicity could be observed in animals treated on day 3 or later after infection with Vaccinia virus. Injection of CD4-depleted mice with recombinant interleukin 2 (rIL-2) partially corrected the impaired virus-specific cytotoxic T-cell response, suggesting that IL-2 supply may be limiting in mice lacking T helper cells.

Animals↗
PubMed1989

Indications of plasmapheresis and selection of different substitution solutions.

Substitution solutions used for plasmapheresis (PH) may be human albumin, serum protein conserves or plasma. 746 plasmapheresis carried out on 88 patients with a variety of diseases were examined and the side effects due to the substitution solutions were investigated. Side effects occurred in less than 10% of the cases where the four substitution solutions were used. The least side effects were observed in treatments using human albumin as substitution. Side effects increased for serum protein conserves, followed lyophilised plasma and were highest for fresh frozen plasma. In view of these possible side effects the criteria for PH should be strictly observed and the substitution solution should meet clinical requirements.

Albumins↗
PubMed1988

Enhancement of the clinical activity of melphalan by the hypoxic cell sensitizer misonidazole.

One hundred patients with non-small cell lung cancer were entered by members of the Northern California Oncology Group into a randomized Phase II trial of i.v. melphalan versus i.v. melphalan with concomitant oral misonidazole. The patients had not received prior chemotherapy. Eighty-five patients were evaluable for assessment of response and 89 were evaluable for toxicity analysis. The melphalan/misonidazole group had a superior response rate (two complete and four partial responses among 42 patients or 14%) compared to the melphalan group in which there were no responses among 43 patients (p = 0.024, two-sided Fisher exact test). Since hematological toxicity was equivalent in the two groups, there was an improvement in therapeutic index. Data from 12 patients undergoing pharmacological studies demonstrated that the plasma concentration of melphalan was 25% higher in the misonidazole group, a difference that is not statistically significant. Although the mechanism of interaction has not been fully established, this randomized trial demonstrates that a chemosensitizer can enhance the clinical antitumor activity of an alkylating agent and suggests that chemosensitizers in combination with alkylating agents should be investigated in further clinical trials.

Adult↗
PubMed1987

Chemotherapy as a substitute for surgery in the treatment advanced resectable head and neck cancer. A report from the Northern California Oncology Group.

This trial determines the feasibility for patients with resectable Stages III/IV head and neck cancer who achieved a complete response to induction chemotherapy of eliminating surgery from their treatment program. Thirty patients were treated with three cycles of cisplatin and 5-fluorouracil (5-FU), followed by reendoscopy and biopsy. Twelve patients achieved a complete pathologic response at the primary and received radiation (interstitial and/or external beam) only. The remainder underwent surgical resection and postoperative radiation. At 2 years, the relapse-free survival was 52%, and the survival was 53% for the entire group. For the 12 complete responders who had surgery eliminated, the relapse-free survival was 60%, and the survival was 70%. This pilot study suggests that for patients with resectable disease who achieve a complete pathologic response to induction chemotherapy at their primary, it is feasible to omit surgery and treat with primary radiation without compromise in survival. This approach warrants further study in a randomized trial.

Adult↗
PubMed1987

Combined radiotherapy and chemotherapy with bleomycin and methotrexate for advanced inoperable head and neck cancer: update of a Northern California Oncology Group randomized trial.

Between 1978 and 1984, the Northern California Oncology Group (NCOG) conducted a randomized trial to study the efficacy of combined radiotherapy (RT) and chemotherapy (CT) for stage III or IV inoperable head and neck cancer. One hundred four patients were randomized to receive: (1) RT alone, or (2) RT plus CT. RT consisted of 7,000 cGy to the involved areas and 5,000 cGy to uninvolved neck at 180 cGy/fraction, five fractions/wk. CT consisted of bleomycin, 5 U intravenously (IV), twice weekly during RT, followed by bleomycin, 15 U IV, and methotrexate, 25 mg/m2 IV weekly for 16 weeks after completion of RT. Fifty-one patients in the RT alone group and 45 in the combined treatment group were evaluable. The local-regional complete response (CR) rate was 45% v 67% (P = .056); the 2-year local-regional control rate, including salvage surgery, was 26% v 64% (P = .001); and the incidence of distant metastasis was 24% v 38% (P greater than .25), for the RT alone and RT plus CT groups, respectively. The relapse-free survival curves were significantly different (P = .041), favoring the combined treatment. However, the survival curves were not significantly different (P = .16). Patient compliance to maintenance CT was poor. Bleomycin significantly increased the acute radiation mucositis, although the difference in late normal tissue toxicity was not statistically significant. Thus, bleomycin and concurrent RT produced a more favorable CR rate, local-regional control rate, and relapse-free survival, but the difference in survival was not statistically significant.

Adult↗
PubMed1987

A Northern California Oncology Group randomized trial of leucovorin plus 5-fluorouracil versus sequential methotrexate, 5-fluorouracil, and leucovorin in patients with advanced colorectal cancer who failed treatment with 5-fluorouracil or 5-fluorodeoxyuridine alone.

The current study was initiated to confirm preliminary reports that 20% or more of patients with colorectal cancer who fail treatment with 5-fluorouracil (FUra) will respond to treatment with either leucovorin plus FUra or with sequential methotrexate, FUra, leucovorin. One hundred two patients with advanced, measureable colorectal cancer who failed treatment with FUra and/or 5-fluorodeoxyuridine (FUdR) were randomized to treatment with either high-dose leucovorin plus FUra (Arm B) or sequential methotrexate, FUra, leucovorin (Arm C). In this interim report, 92 patients were evaluable for toxicity and 89 patients were evaluable for response. Grade 3 or 4 nonhematologic toxicity which was primarily gastrointestinal was experienced by 25% of patients on both treatment arms during at least 1 treatment cycle. Hematologic toxicity was minimal. Among 43 evaluable patients on Arm B, there were 2 complete responses (5%) and 1 minor response (3%). Among 46 evaluable patients on Arm C, there was 1 complete response (2%), 1 partial response (2%), and 6 minor responses (14%). The median time to treatment failure was 2.2 months on Arm B and 3.5 months on Arm C. The median survival was 8.3 months on Arm B and 8.7 months on Arm C. Colorectal cancers that are resistant to FUra are cross-resistant to both experimental combinations.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1986

Complex formation of simian virus 40 large T antigen with cellular protein p53.

We investigated the formation of native complexes between simian virus 40 large T antigen and the cellular protein p53 (T-p53) by using simian virus 40 tsA58-transformed mouse fibroblasts (tsA58 F2b). We observed that newly synthesized p53 bound to all structural subclasses of large T antigen detectable on sucrose density gradients. This led to various intermediates of T-p53 complexes which converted within 2 h into typical mature aggregates. The final levels of stable T-p53 complexes seemed to be determined by p53 rather than by large T antigen.

Animals↗
PubMed1986

High-dose cisplatin in hypertonic saline: reduced toxicity of a modified dose schedule and correlation with plasma pharmacokinetics. A Northern California Oncology Group Pilot Study in non-small-cell lung cancer.

Although increased efficacy has been described with a five-day schedule of high-dose cisplatin (CDDP) in hypertonic saline, severe myelosuppression and cumulative neurotoxicity have limited the usefulness of this therapy. In order to evaluate a possible dose-response relationship in non-small-cell lung cancer (NSCLC), 17 patients with metastatic disease were treated with a modified dose schedule delivering the same total dose (200 mg/m2) in a divided day 1 and 8 schedule. During a pilot study, a total of 47 cycles of therapy were administered, with a median of three cycles per patient and a median total cumulative dose of 600 mg/m2. Nine of 17 patients received at least 600 mg/m2. While nephrotoxicity was similar to previous reports of the five-day schedule, the incidence and severity of myelosuppression and peripheral neuropathy were markedly reduced. Using this modified schedule, severe myelosuppression did not occur. Clinically severe peripheral neuropathy developed in only one patient (6%). The overall response rate was 47% (eight of 17 patients). Plasma platinum pharmacokinetics during five cycles of the modified day 1 and 8 schedule were compared with pharmacokinetics of the five-day schedule. Accumulation of plasma ultrafiltrate platinum occurred in the five-day schedule, but not in the day 1 and 8 schedule. This difference in pharmacokinetics is one possible explanation for the reduced toxicity of this modified schedule. Although the degree of activity seen in this pilot study is encouraging, the efficacy of high-dose CDDP in NSCLC remains to be defined. In view of reduced myelosuppression and neurotoxicity, further trials with this modified schedule are indicated.

Adult↗
PubMed1986

Prednimustine in refractory non-Hodgkin's lymphoma: a phase II study of the Northern California Oncology Group.

Fifty-six patients with advanced non-Hodgkin's lymphoma (NHL) were entered into a phase II study of prednimustine, an ester of chlorambucil and prednisolone. All patients were refractory to extensive prior combination chemotherapy. Therapy with prednimustine, 100 mg/m2/day orally, was given for three consecutive days every 2 weeks. The overall response rate in 43 evaluable patients was 30% (13/43), with 9% (4/43) achieving complete response (CR) and 21% (9/43) achieving partial response (PR). In the favorable histology subgroup (23 patients), the response rate was 39% (9/23), with 4% (1/23) achieving CR and 35% (8/23) achieving PR. In the unfavorable histology subgroup (20 patients), responses were seen in 20% (4/20) with 15% (3/20) achieving CR, all in heavily pretreated diffuse histiocytic lymphoma. Toxicity of this regimen was mild, with leukopenia below 3,000/mm3 in 22% and thrombocytopenia below 90,000/mm3 in 16% of patients. A positive correlation was observed between response and hematologic toxicity, indicating the potential for a dose-escalation schedule in future trials. These data confirm activity of prednimustine in NHL refractory to standard treatment. In view of its relatively mild toxicity, we conclude that prednimustine is an appropriate agent to test in combination chemotherapy regimens in this group of lymphomas.

Adult↗
PubMed1985

Oligomerization of simian virus 40 tumor antigen may be involved in viral DNA replication.

Biological implications of the oligomerization of simian virus 40 (SV40) large T antigen for viral DNA replication were studied by using two temperature-sensitive SV40 A-gene mutants, tsA 58 and tsA 1499. Both mutants are defective at elevated temperature for viral DNA replication whereas tsA 58 is like most other tsA mutants additionally heat sensitive for cell transformation. We found that in contrast to tsA 58 encoded T antigen, tsA 1499 T antigen is thermostable in the ability to bind specifically to the origin of replication of SV40 DNA. Detailed structural analysis of tsA 1499 T antigen by sucrose density gradient centrifugation revealed that it is strictly temperature sensitive for the formation of homologous oligomers but, as we reported previously (M. Montenarh, M. Kohler, and R. Henning, 1984, J. Virol, 49, 658-664), not for the association with the cellular phosphoprotein p53. These observations are compatible with the idea that, in addition to the specific origin-binding ability as well as other functional features, the oligomerization of T antigen may be essential for viral DNA replication.

Animals↗
PubMed1985

Structural prerequisites of simian virus 40 large T antigen for the maintenance of cell transformation.

We have investigated the functional roles of two structural subsets of simian virus 40 (SV40) large T antigen, namely homo-oligomers and complexes with the host cellular p53 protein, for the transformed phenotype. We examined T antigen produced in cells transformed by temperature-sensitive SV40 large T mutants: heat-sensitive or unrestricted SV40 tsA58-transformed rat cells and unrestricted tsA1499 transformants. In both unrestricted cell lines, T antigen was temperature-sensitive only for the formation of fast sedimenting homo-oligomers. Corresponding to our recent observations obtained with tsA1499-infected monkey cells, in tsA1499 transformants large T was competent to form stable T-p53 complexes independently of the temperature. However, T antigen coded for by tsA58, which is heat-sensitive for binding to p53, occurred in stable complexes with this protein in unrestricted tsA58 transformants under all conditions. Furthermore, in both unrestricted transformants T-p53 complexes arise in the absence of homo-oligomers of T antigen. In conclusion, T antigen homo-oligomers are not involved in cell transformation, whereas T-p53 complexes may be involved in the maintenance of this phenotype.

Animals↗
PubMed1984

Oligomerization of simian virus 40 large T antigen is not necessarily repressed by temperature-sensitive A gene lesions.

Simian virus 40 large T antigen is a multifunctional protein which exists in different molecular weight forms. According to several reports, T antigen encoded by temperature-sensitive simian virus 40 A locus mutants (tsA) is unable to oligomerize into high-molecular-weight species. To try to correlate structural and functional properties, we selected tsA58 and tsA1499, both of which are heat sensitive for lytic growth, but only tsA58 is heat sensitive for transformation. Here we report that at permissive and nonpermissive temperatures, T antigen from tsA1499-infected monkey cells retained the ability to oligomerize, whereas reported previously, tsA58 T antigen failed to oligomerize at the nonpermissive temperature. Furthermore, we studied the formation of complexes between T antigen and the cellular p53 protein (T-p53) late in infection. Corresponding to its heat-stable oligomerization properties, T antigen encoded by tsA1499 formed T-p53 complexes regardless of temperature. In contrast, tsA58 encoded T-p53 complexes, preformed at the permissive temperature, remained heat stable after shifting up to the nonpermissive temperature; but at this temperature no new T-p53 complexes arose. The mutants did not replicate viral DNA at the nonpermissive temperature, suggesting that neither the oligomerization of T antigen nor the formation of T-p53 complexes seems to be sufficient for viral DNA replication or for the expression of late viral proteins.

Animals↗