The role of cardiopulmonary exercise testing in lung and heart-lung transplantation.

Cardiopulmonary exercise testing in recipients of lung and heart-lung transplants demonstrates significant restoration of exercise tolerance to individuals severely disabled by their underlying cardiopulmonary disease. Recipients can perform moderate levels of activity compatible with a normal lifestyle. Considerable exercise limitation, however, remains in most recipients as measured by maximum oxygen uptake and work rate, despite substantial improvement and often normalization in resting cardiopulmonary function. The amount of exercise limitation observed in recipients of single-lung, bilateral-lung, and heart-lung transplants is interestingly similar, and the pattern of limitation is somewhat stereotyped. Ventilatory abnormalities are never limiting. Gas exchange abnormalities are sometimes seen (especially in single-lung transplant recipients) but generally are not limiting. Cardiac dysfunction is sometimes seen (particularly in heart-lung transplant recipients) but also does not appear to be limiting. Peripheral factors limiting exercise (which may include abnormalities in the peripheral circulation and peripheral neuromuscular structure and function) are almost universally seen and are probably the primary determinant of exercise limitation in these patients. At present, the relative contributions of various peripheral factors to exercise limitation are unclear. Further study may help elucidate these issues.

The effect of positive end-expiratory pressure on regional pulmonary perfusion during acute lung injury.

PURPOSE: To determine whether positive end-expiratory pressure (PEEP) would change the altered regional pulmonary perfusion pattern caused by oleic acid (OA)-induced acute lung injury was the aim of this study. Our hypothesis was that fixed intravascular obstruction would not be affected by PEEP, leaving the perfusion pattern unchanged if this was the principal cause of perfusion redistribution after lung injury. METHODS: Regional measurements of pulmonary perfusion and lung water concentration (LWC) were obtained both before and after lung injury and before and after PEEP (10 cm H2O) with the nuclear medicine imaging technique of positron emission tomography after injections of H2 15O in 7 supine anesthetized dogs. Four animals were also treated with meclofenamate to enhance perfusion redistribution after acute lung injury. RESULTS: The application of PEEP before lung injury did not significantly affect the regional perfusion pattern. After administration of OA, LWC increased and fractional flow (without PEEP) decreased to the most edematous lung regions, consistent with perfusion redistribution. With the reapplication of PEEP, the perfusion pattern reverted toward the baseline pattern. The magnitude of this effect was roughly proportional to the effect of PEEP on regional inflation (r = .53), as evidenced by changes in LWC. CONCLUSIONS: The reversibility with PEEP of the perfusion pattern caused by acute lung injury suggests that fixed intravascular obstruction is not the principal determinant of perfusion redistribution after OA-induced injury.

Chemical carcinogen-mouse mammary tumor virus interactions in cell transformation.

We have studied the process of mammary cell transformation in vitro using a single cell clone (Clone 18) from a presumptive epithelial cell line, C57MG, derived from a normal mammary gland; a mouse mammary tumor virus (MMTV) host-range variant (RIII)vp4; and the potent initiating carcinogen 7,12-dimethylbenz(a)anthracene (DMBA). After several serial subcultures, cells treated with virus and then with carcinogen exhibited an altered (transformed) morphology, a dramatic increase in anchorage independence, an increase in multinucleation after exposure to cytochalasin B, an enhanced ability to proliferate in low Ca2+ (0.01 mM) medium, and tumorigenicity when inoculated subcutaneously into athymic (nude) mice. Although some of these phenotypic alterations were observed also in cultures treated singly with MMTV or DMBA and in cultures exposed to DMBA before infection with MMTV, enhanced cytochalasin B multinucleation and tumorigenicity were properties observed only in mass cultures of cloned cells first infected with MMTV and then exposed to DMBA. This demonstrates for the first time that exposure of presumptive mammary epithelial cells to MMTV followed by DMBA, but not to either agent alone or to DMBA followed by MMTV, results in malignant transformation of these cells.

Isolation of a series of novel variants of murine mammary tumor viruses with broadened host ranges.

We have previously isolated mouse mammary tumor virus (MMTV) host range variants by serial virus passage in feline cells. These variants productively infect cells of a broad range of species but replicate most efficiently in feline cells. We report here the isolation of a series of novel MMTV host range variants that have the ability to replicate with high efficiency in murine, rat, canine and human cells, respectively; these variants were isolated by serial virus passage in cells of each respective species. These new variants, furthermore, all retained their ability to efficiently replicate in feline cells, and each exhibited unique host range properties. The novel MMTV variants obtained from murine, rat, feline, canine, and human cells showed no overt evidence of recombination with endogenous type-C viruses in that they retained their antigenic reactivities in group-specific radioimmunoassays for MMTV polypeptides, and were unreactive for type-C virus proteins when tested by radioimmunoassays and DNA polymerase assays. These novel MMTV host range variants now broaden the spectrum of studies that can be undertaken involving MMTV replication and the initiation and promotion of virus-mediated mammary cell transformation.

Differential host ranges for in vitro infectivity of mouse mammary tumour viruses.

Host-range variants of mouse mammary tumour viruses (MMTVs) have previously been shown to productively infect cells of several species in vitro (Howard & Schlom, 1978). We report here that cell lines have been identified which exhibit differential restriction for replication of different MMTV variants. In addition, a cell line has been identified that changes as a function of passage in culture from being permissive to being restrictive to infection with MMTVs. MMTVs propagated in both murine and non-murine cells retained their antigenic reactivities in a group-specific radioimmunoassay for MMTVs and demonstrated no evidence for the presence of type-C viruses as determined by a variety of techniques. These studies thus establish in vitro cell substrate tropisms that can be used to differentiate between MMTVs.

Characterization of a retrovirus isolated from normal mink cells co-cultivated with a dog mammary tumour.

A retrovirus antigenically distinct from known type C, B and D viruses was isolated from normal mink (Mustela vison) lung cells that had been co-cultivated with 5-iododeoxyuridine- and dexamethasone-treated dog mammary tumour cells. Cytogenetic studies of the virus-releasing co-culture showed mitotic figures identical to the normal mink cell line (MvlLu) with the exception of a low frequency of cells with extensive chromosomal breakage and uncoiling. The new virus bands at a buoyant density of 1.16 g/ml, contains 60S RNA and a reverse transcriptase which prefers Mn2+ over Mg2+ for the synthesis of DNA. This enzyme utilizes poly(rA).oligo(dT) more efficiently than poly(dA).oligo(dT) and is also able to synthesize DNA copies from the endogenous RNA. Morphologically, it is a typical type C virus. Filtered virus readily infects mink, dog and other mammalian cells indicating the amphotropic nature of its cell growth requirement. Hybridization studies showed that normal mink DNA contains multiple copies of proviral sequences of this newly isolated virus. Serological analyses indicate that the mink endogenous virus contains in its core protein, in addition to the interspecies type-C determinant, an antigenic component related to one of the determinants found in the feline leukaemia virus p30 protein. This determinant is not present in the Rauscher leukaemia virus, RD114 virus or simian sarcoma virus.

Isolation of host-range variants of mouse mammary tumor viruses that efficiently infect cells in vitro.

Host-range variants of mouse mammary tumor virus (MMTV) have been isolated that have the ability to productively infect cells in vitro with high efficiency (at multiplicities of infection

Characterization of mouse mammary tumor viruses propagated in heterologous cells.

Mouse mammary tumor viruses (MMTV) from three different strains of mice have been used to establish productive infections in feline and mink cell lines. The virions that are released by these cells compete completely in a radioimmunoassay for the major virion surface glycoprotein of MMTV (gp52), thus demonstrating that antigenic determinants of gp52 are viral coded. Competitive molecular hybridization studies have shown that the 60 to 70 S RNA's of MMTV's propagated in feline cells contain all the nucleic acid sequences found in 60 to 70 S RNA from MMTV synthesized by murine cells. The virion buoyant densities in sucrose and cesium chloride, virion sedimentation coefficient, divalent cation requirement of the virion DNA polymerase, and morphology of MMTV's synthesized in heterologous cells are similar to those of MMTV's grown in murine cells. Cultures of MMTV-infected feline cells have continuously released between 0.1 and 1.0 microgram of virus per 10(7) cells (75-sq cm flask) per day during the 60-week observation period. No detectable feline or murine type C viruses were produced by these cultures.