Oxygen tolerance in mice following exposure to butylated hydroxytoluene.

Adult BALB/c mice, which are sensitive to hyperoxia (LT50 = 4.5 days 100% O2), were made tolerant to 100% O2 after treatment with butylated hydroxytoluene (BHT). Following a single ip dose of 400 mg/kg, mice survived longer periods in O2 when exposed to O2 at 7, 14, and 21, but not 2 days, following BHT injection. The tolerance was most pronounced on Day 7 (LT50 = 9.6 days) and decreased with time (LT50 7.7 days on Day 14 and 7.3 days on Day 21). Glucose-6-phosphate dehydrogenase levels of whole lung homogenates following BHT exposure were elevated on Day 7 when expressed as per milligram of protein or DNA. Other antioxidant defenses were generally increased only when expressed on a per lung basis. Histopathology of lungs from BHT-treated mice revealed typical BHT-induced lung lesions. BHT treatment followed by long-term hyperoxic exposure produced additional damage to the lung manifested by the exudative phase of diffuse alveolar damage with 1 week of exposure. This was followed by the proliferative phase, then chronic interstitial pneumonitis and fibrosis with 2 and 6 weeks of exposure, respectively. Mice continued to survive in 100% O2 despite this damage. We conclude that pretreatment with BHT enhances O2 tolerance in mice, which may be mediated by induction of antioxidant defenses and also by cell renewal induced by BHT damage.

Effects of hyperoxia on B16-F10 cells in vivo.

The in vivo effects of hyperoxia were studied in lung colonies formed by B16-F10 melanoma cells in C57BL/6 mice. Several antioxidant defenses were found to change with in vivo exposure: glutathione reductase and glucose-6-phosphate dehydrogenase activities decreased as compared with levels in the cultured cells, glutathione peroxidase activity dramatically increased, and Mn-superoxide dismutase activity and levels of total glutathione were similar in vivo and in vitro. Exposure of tumor-bearing animals to 70%, O2 for 3 weeks did not alter the antioxidant defenses measured in the tumors. One hundred percent O2 exposure did not affect either initial arrest or subsequent retention of radiolabeled B16-F10 cells in the lung. Likewise, hyperoxia did not appear to alter cell division in B16-F10 cells growing in the lung. These results are consistent with our previous studies indicating that the B16-F10 cell line is resistant to levels of O2 in vivo that adversely affect other tumor cell lines.

Effects of hyperoxia on growth characteristics of metastatic murine tumors in the lung.

Suspensions of an oxygen-sensitive (MT-7) and of an oxygen-insensitive(M109) tumor cell line were injected i.v. into BALB/c mice. Exposure to 100% O2 after injection of the cells did not modify the initial arrest of either cell line in the lung. Exposure of animals given injections of MT-7 cells for 60 h to 100% oxygen decreased the number of lung colonies formed even when onset of oxygen exposure was delayed up to 10 days after injection of the cell suspension. Cell cycle time and growth fraction in lung colonies growing in vivo were estimated from an analysis of the percentage of mitoses labeled. In lung colonies formed by MT-7 cells, hyperoxia produced a mitotic delay and a 30 to 40% reduction in the growth fraction. In M109-derived colonies, oxygen did not change cell cycle times or reduce growth fraction. In earlier experiments done in vitro and reported by others it had been found that, in tumor cell lines other than the ones used in the present study, a prolongation of the early prophase was the most oxygen-sensitive event. The present data show that in vivo oxygen inhibits lung colony formation in MT-7 cells by a similar mechanism.

Effects of hyperoxia on growth of experimental lung metastasis.

Mice were given i.v. injections of various tumor cell lines and, beginning 24 h later exposed for 3 weeks to 70% oxygen. Hyperoxia reduced the number of lung colonies derived from MT-7 cells (originally a mammary carcinoma) and of the lung-tumor derived cell lines 498 and Line-1 early passage. Lung colonies derived from Line-1 late passage, lines M109, B16-F10 and Lewis lung carcinoma were oxygen resistant. Lung metastases following i.m. injection of MT-7 cells were oxygen-sensitive and metastases derived from B16-F10 cells or Lewis lung carcinoma were oxygen resistant. Pre-exposure of mice for 48 h to 100% oxygen enhanced colony formation for all cell lines examined whereas exposure to 100% oxygen after i.v. injection only curtailed the growth of the cell lines previously shown to be sensitive to 70% oxygen. There was no correlation between oxygen sensitivity or resistance and the levels of total glutathione or activities of superoxide dismutase (SOD), glutathione reductase or peroxidase or glucose 6-phosphate dehydrogenase in the cell lines. However, upon injection in mice a resistant cell line increased its anti-oxidant defense mechanisms while growing in vivo whereas a sensitive cell line failed to show such adaptation.

Inhibition of N-diethylnitrosamine metabolism by human lung cancer cell lines with features of well differentiated pulmonary endocrine cells.

Cell lines derived from a human pulmonary carcinoid tumor (NCI-H727) and from a human pulmonary large cell carcinoma (NCI-H460) were investigated by transmission electron microscopy. Both cell lines, at early in vitro passage, demonstrated ultrastructural features of well differentiated pulmonary endocrine cells. Line NCI-H727 had more endoplasmic reticulum than line NCI-H460 and demonstrated L-dopa decarboxylase activity as well as production of calcitonin and bombesin. Because of their ultrastructural resemblance with normal pulmonary endocrine cells, these cell lines were used to test the theory derived from experiments in hamsters that human pulmonary endocrine cells can metabolize N-nitrosodiethylamine (DEN). The cells were incubated in vitro with [14C]DEN. Metabolism was assessed by 14CO2 production. Both cell lines metabolized DEN to a much greater extent than previously investigated human lung cancer cell lines of Clara cell and alveolar type II cell morphology. In keeping with its abundant endoplasmic reticulum, line NCI-H727 yielded 14CO2 in the 300 nM range, whereas NCI-H460 was less active. Metabolism was time dependent. Preincubation with various enzyme inhibitors yielded a highly significant inhibition of DEN metabolism with the two inhibitors of the fatty acid cyclooxygenase component of prostaglandin endoperoxide synthetase, aspirin and indomethacin. Inhibitors of cytochrome P-450 (CO, piperoxylbutoxide) did not inhibit DEN metabolism. Preincubation with sinigrin yielded similar negative results as CO and piperonylbutoxide. Our data are in support of the theory that human pulmonary endocrine cells can metabolize nitrosamines. Moreover, the experiments with enzyme inhibitors suggest that in this cell type such metabolism is largely dependent on prostaglandin endoperoxide synthetase.

Effect of phenytoin on antibody production: use of a murine model.

An animal model was used to study the effects of phenytoin on immune function. Inbred NFS mice, injected with phenytoin, 10-40 mg/kg, and immunized with bovine serum albumin (BSA), demonstrated a dose-dependent decrease in production of IgG antibodies to BSA. Phenytoin at the dosages used in this study did not appear to be overtly toxic to immune organs and cells as judged by normal weights of thymus and spleen and normal WBC counts of mice injected with phenytoin. In addition, mice receiving phenytoin had normal body weights, liver weights, and hematocrits. The usefulness of an animal model to study immunomodulatory effects of antiepileptic drugs is discussed.

Effects of phenytoin and carbamazepine on human natural killer cell activity and genotoxicity in vitro.

Human peripheral blood mononuclear cells (PBMC) were isolated from healthy volunteers and exposed in vitro to phenytoin or carbamazepine, two widely used antiepileptic drugs (AED). This study investigated the effects of these drugs on natural killer (NK) cell activity and antibody-dependent cell-mediated cytotoxicity (ADCC), which are both thought to protect against developing neoplasms. Also, the genotoxicity of phenytoin on human PBMC was investigated by gravity-flow alkaline elution. Concentrations of phenytoin considered therapeutic (10 and 20 micrograms/ml) and a dose considered acutely toxic (40 micrograms/ml) were used while carbamazepine levels of 8 micrograms/ml (therapeutic) and 10 and 16 micrograms/ml (acutely toxic) were tested. Phenytoin at all three concentrations significantly suppressed NK cell activity in a dose-dependent manner. Carbamazepine had no significant effect on NK cell activity at the dose levels studied. Incubation in propylene glycol, the diluent for carbamazepine, significantly decreased NK cell activity compared to saline. Phenytoin also significantly depressed interferon augmentation of NK cell cytotoxicity in a dose dependent manner. ADCC activity was significantly depressed with 20 and 40 micrograms/ml phenytoin. Alkaline elution showed a slight but significant increase in DNA single-strand breaks of PBMC exposed to 40 micrograms/ml phenytoin for 18 or 72 hr. These results show phenytoin may induce pronounced immunosuppression of NK cell and ADCC activity in patients receiving antiepileptic therapy and that this agent has a potential for genotoxic side effects. Phenytoin may also increase the potential for neoplasm development by a direct interaction with cellular DNA and/or an indirect mechanism by immunosuppression.

Modification of lung tumor growth by hyperoxia.

The effects of hyperoxia on lung tumor development were examined in mice and rats. In mice, exposure to 70% O2 prevented the development of urethan- or 3-methylcholanthrene-induced lung tumors. Dietary antioxidants [butylated hydroxytoluene (BHT) and butylated hydroxyanisole (BHA)] were unable to prevent the inhibition of tumor development by oxygen, although BHT retained its capability to enhance tumor development in mouse lung. In visible-size tumors, oxygen did not depress DNA synthesis. Oxygen also reduced the number of pulmonary metastatic nodules after i.v. injection of mammary gland-derived carcinoma cells, but failed to inhibit growth of murine lung carcinoma or murine melanoma-derived cell lines. Rats treated with one single intratracheal instillation of 3-methylcholanthrene developed multiple lung lesions; their growth could be prevented by exposure of the animals to 40 or 70% O2. It is concluded that hyperoxia prevents development of transformed cells in vivo in the lung and may affect adversely the growth of selected cell lines metastatic to the lung.

Immune abnormalities in patients with autism.

We have begun an investigation on the immune systems of patients with autism in attempt to determine if immune mechanisms are involved in the development of this severe developmental disorder. A study of 31 autistic patients has revealed several immune-system abnormalities, including reduced responsiveness in the lymphocyte blastogenesis assay to phytohemagglutinin, concanavalin A, and pokeweed mitogen; decreased numbers of T lymphocytes; and an altered ratio of helper to suppressor T cells. Immune-system abnormalities may be directly related to underlying biologic processes of autism, or these changes may be an indirect reflection of the actual pathologic mechanism.

Reduced natural killer cell activity and OKT4/OKT8 ratio in epileptic patients.

A number of immune abnormalities have been found in epileptic patients. Several, but not all, of these defects appear to be related to the toxic effects of antiseizure medications. To study the basis of immune abnormalities in epilepsy, various populations and subsets of peripheral blood mononuclear cells (PBMC) from epileptic patients were enumerated and their functions examined. Reduced natural killer cell activity was found in the patients and their siblings. Enumeration of the PBMC showed a lower proportions of Leu 11+ cells in some of the patients which may account for the lower natural killer activity. A reduced ratio of OKT4+/OKT8+ cells was also found in the patients. Responses of patient PBMC to the T-cell mitogens phytohemagglutinin, concanavalin A and the B-cell mitogen pokeweed mitogen were unchanged as were the total number of rosette-forming cells in the patients. The results provide more evidence for a genetic basis for some of the immune abnormalities in epileptic patients.

Long-term oral cadmium produces bone marrow hypoplasia in mice.

Marrow hypoplasia is described in CBA/H mice that drank water containing 300 mg/liter cadmium chloride for 12 months. This was characterized by a significant reduction of the totipotent stem cells (CFU-s), granulocyte-monocyte progenitor cells (GM-CFUc), and erythroid progenitor cells (CFU-e). The bone marrow cellularity and the proliferative capacity of GM-CFUc in vitro were decreased. The animals reflected these marrow alterations by demonstrating an anemia with reticulocytopenia and neutropenia. They did not show increased mortality or increased susceptibility to infections; however, their body weight was significantly reduced. In addition, iron deficiency was demonstrated in the cadmium-treated mice. The animals had a hypochromia of the peripheral red cells and diminished marrow iron stores. Thus, the anemia of cadmium toxicity is probably the combined result of bone marrow hypoplasia and iron deficiency.

Thymic stroma in AKR mice: its function and virus production.

This study reports experiments with thymic stromal remnants in AKR mice, a strain with a high natural incidence of thymic lymphoma. A method has been developed in which thymic stromal cells which survive a 4-week culture period, 1 week at 24 degrees C and 3 weeks at 37 degrees C are suitable for grafting. Most thymic lymphocytes die under these conditions. Stromal remnants were studied by culturing and grafting under the kidney capsule of 2-month-old syngeneic mice. Their in vitro morphology and virus production, their ability to reconstitute a new thymus from host progenitors and their eventual lymphoma development was evaluated. The stromal remnants were from: 1- and 3-month-old normal mice; 6-10-month-old normal mice; 21-28-day-old animals treated with the lymphomagenic virus, SL3-3, at 3 days of age. Our data show that thymic stromal function as measured by lymphoid reconstitution of thymic stromal grafts of AKR mice is not impaired with age or by the presence of oncogenic virus. Oncogenic viruses are found in the thymic stroma of old mice and in thymic stroma of young virus-treated mice. Oncogenic viruses are not found in thymic stroma of young normal mice. Lymphoma can develop in the grafted stromal remnants expressing lymphomagenic virus.

Spontaneous leukemia viruses: lymphomagenic ecotropic viruses of AKR mice.

The spontaneous leukemia (SL) viruses are ecotropic lymphomagenic viruses isolated from AKR spontaneous lymphomas. These viruses are produced stably by continuous cell lines from spontaneous lymphomas and by a cell line derived from the bone marrow stroma of an AKR mouse neonatally inoculated with an SL virus. All cell lines cloned from the parent lymphoma cell lines consistently produce SL viruses. These viruses can be passaged in vivo and maintain their leukemogenic properties. Cloned isolates of SL viruses accelerate lymphoma in AKR mice and induce thymic lymphoma in mice of other strains. Thus their lymphomagenic properties are conclusively shown. In a study with the use of a sensitive host range assay, xenotropic and/or dual-host range viruses are consistently found in spontaneous lymphoma and cell lines derived from them. However, viruses able to replicate in mink lung cells are not expressed in SL virus-induced lymphomas or their derived cell lines.