Airway mucus was collected from healthy and chronic bronchitic subjects. The chronic bronchitic sputum was separated into gel and sol phase by centrifugation and mucins were isolated using isopycnic density-gradient centrifugation in CsCl. The presence of the MUC5AC and MUC2 mucins was investigated with antisera raised against synthetic peptides with sequences from the respective apoproteins. The gel and sol phase of chronic bronchitic sputum as well as healthy respiratory secretions were shown to contain MUC5AC whereas the MUC2 mucin could not be detected. Rate-zonal centrifugation showed that the MUC5AC mucin was large, polydisperse in size and that reduction yielded subunits. Ion-exchange HPLC revealed the presence of two subunit populations in all secretions, the MUC5AC subunits always being the more acidic. MUC5AC is thus the first large, subunit-based, gel-forming respiratory mucin identified and this glycoprotein is biochemically distinct from at least one other population of large, gel-forming mucins also composed of subunits but lacking a genetic identity.

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Little is known about whether the properties of respiratory mucins are altered as a result of airway irritation, but histochemical studies of respiratory tract secretory cells show a more 'acidic' staining pattern after exposure to tobacco smoke. Furthermore it has been suggested that proteoglycans are the major glycoconjugates in 'normal' respiratory secretions, whereas mucins predominate in sputum. To investigate these observations further, mucins from secretions collected from the tracheal surface of healthy non-smoking 'normal' subjects and sputum from patients with chronic bronchitis were compared. All samples contained one major mucin population after density-gradient centrifugation, and a small amount of 'denser' mucin was present in some chronic bronchitic and one of the 'normal' samples. Proteoglycans were not a major component of 'normal' secretions. The major mucin population from chronic bronchitic samples had molecular masses between 10 and 30 MDa and behaved as random coils in solution. Whole mucins from 'normal' individuals and chronic bronchitic patients were excluded from Sepharose CL-2B, whereas reduced subunits were included. Proteolysis of subunits yielded two populations of high-molecular-mass glycopeptides differing in size, suggesting the presence of two different tandem repeat regions in the mucins. Finally, mucins from patients with chronic bronchitis are less, rather than more, acidic than those from 'normal' individuals. Mucins from bronchitic sputum and 'normal' secretions are thus similar in their macromolecular properties, but differ slightly in charge density.

In order to make electrolytic tumor destruction more effective new electrode materials were tested (Part I) as well as a combination of electrolysis and megavolt therapy (Part II). All tests were performed in experimental tumors implanted subcutaneously in rats. Altogether in 41 rats in 5 series (Part I) electrodes made of rhodium (Rh), copper (Cu), or brass (Zn-Cu alloy) were investigated but the effect was not found to be better than that of the previously tested platinum (Pt). Oxidation and corrosion made Rh and Cu electrodes less suitable for electrolysis compared to Pt, while brass electrodes became isolated through zinc-salt-formation and performed unsatisfactorily. The radiosensitizing properties of electrolysis were tested in 55 rats with experimental tumors (Part II). One control group had only Co-irradiation, while in 2 other groups Cu-or Pt-electrolysis of the tumors was carried out before irradiation. The combined treatment resulted in a significantly better effect on the tumors, registered as inhibition of tumor growth or disappearance of tumor. As the electrolyzed, necrotic tissue remained in the tumor the effect might not be mediated through diminished target volume. An inflammatory reaction around the electrolytic lesion with increased blood flow and higher oxygenation of the tumor could cause a more positive response to megavolt treatment.

Summary A human malignant pleural mesothelioma was xenografted serially in athymic nude Rowett rats for 27 passages during 33 months. After the two initial passages (P), the take rate during P3-9 was 100% (192/192). The tumour grew progressively during P3-9 in 99% (190/192) and regressed totally in 1% (2/192). The take rate for the tumour xenografted to athymic BALB/c mice was also 100% (17/17) and no regressions were observed. During serial passaging in nude rats, the tumour-volume doubling time (TD) decreased from 6 days in P2 to 3 days in P8-9 (P<0.001) and then remained around 3 days during P10-25. A TD of 11 days in P1 (man-mouse) for tumours grown in mice decreased during 10 passages in rats to 4 days (P<0.005) when the tumour was transplanted to mice in P11. Light microscopic morphology of the tumour was retained in rats and mice. We believe that our experimental tumour model using the nude rat as a carrier of the xenograft will be useful for studies of human mesothelioma.Malignant human pleural mesothelioma (MHPM) is a rare tumour with a poor prognosis. The evaluation of chemoand radiotherapy is difficult in MHPM owing to difficulties in measuring the tumour volume, lack of a generally accepted staging system (Dimitrov et al., 1983) and different prognoses in the three main histologic subtypes of this tumour (Elmes & Simpson, 1976).Growth of human tumour xenografts in athymic nude mice or artificially immunosuppressed mice is regarded as the best currently available experimental model for studying the response of human tumours to drugs (Pihl, 1986). Most human malignant tumours, including pleural mesotheliomas (Chahinian et al., 1980;Linden et al., 1982), have been xenografted to athymic mice.Festing et al. (1978) described an athymic nude rat with an immunodeficiency state comparable to that of the athymic mouse, suggested to be more robust for certain experimental situations, e.g., for experiments requiring surgical manipulations and frequent blood sampling.Experience with the athymic rat is sparse compared to that with the athymic mouse, but many human malignant tumours, including one human malignant pleural mesothelioma (Linden et al., 1982), have been successfully xenografted to rats.In the present study we transplanted another MHPM to both athymic rats and mice and studied the long-term growth pattern of this tumour line in nude rats. We also compared the growth pattern of the tumour in athymic mice and rats. Materials and methods TumourA 66-year old man was found to have an epithelial pleural mesothelioma at thoracoscopic biopsy of the parietal pleura.The tumour was treated with irradiation to a total dose of 40 Gy. About 2 weeks after the completion of the radiotherapy against the diseased hemithorax, an implantation metastasis was noted in the former needle tracks. This tumour nodule was excised and used for establishing this (AKG) tumour cell line. The patient was treated further with 3 courses of combined chemotherapy consisting of doxorubicin and cyclophosphamide, but in spite of this trea...

Nude athymic rats of Rowett genetic background were injected subcutaneously with cells from a poorly differentiated human pulmonary adenocarcinoma, following propagation in nude mice. The tumour cells were obtained by thoracentesis and by pleural biopsy during thoracoscopy. So far, we have heterotransplanted 13 different malignant human tumours including malignant mesothelioma, pulmonary adenocarcinoma, malignant melanoma and malignant lymphoma. Subcutaneous tumour growth was seen in all inoculated animals, with an exponential tumour growth pattern and with tumour volume doubling times of approximately 8 days. After two initial passages in nude athymic mice of BALB/c genetic background, the human tumour so far has undergone 9 passages in athymic rats, i.e. collection of tumour material by biopsy from the preceding tumour-bearing rat generation, processing and inoculation of tumour brei with subsequent tumour growth have been repeated 8 times. Four-to-8-week-old rats of both sexes were used throughout and tumour growth was controlled by palpation twice a week. Routine histopathological sections were prepared from the tumour at various passages to assess similarity to the original tumour in the patient. The growth pattern of the xenografts remained similar at all passages just as the remarkable similarity of the heterotransplanted tumours to the original adenocarcinoma was retained at all passages. No spontaneous regressions of heterotransplanted tumours could be demonstrated. Electron microscopical analysis revealed numerous blunt microvilli and lumina partly filled with conglomerates of mucigen granules and small glycocalyceal bodies associated with external superficial microvilli. Scantiness of dark secretory granules together with free and membrane-bound polyribosomes were seen in the cytoplasm. We believe that the nude athymic rat is a valuable research tool and that the permanently transplantable human tumour reported here could be of value in delineating further the mechanisms for tumour take, growth and control.