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222Rn measurements have been made in over 10,000 ground-contact rooms in 908 federal buildings. These data were examined statistically to compare parametric distributions that might be useful in the design and execution of future surveys of indoor 222Rn in large buildings. In 152 of the 365 buildings with the most measurements per building, the log-normal distribution was acceptable. Many other distributions were observed in the other 213 buildings, including bi- and tri-modal distributions. In contrast, when data from entire facilities were examined, the data were usually described by a lognormal distribution. Because of the above observations, we propose that any future surveys of indoor 222Rn in large buildings be done in two phases, screening and assessment. During the screening phase, all facilities may be surveyed with a comparatively low sampling density, perhaps, one measurement per 465 m2 (5,000 ft2) of floor space. Based on the results presented here, it is expected that statistical analysis of the screening data will reveal any facilities with substantial evidence of a high incidence of rooms with elevated indoor 222Rn concentrations (e.g., above 150 Bq m-3). In the assessment phase, the identified facilities will be surveyed with a sampling density of one measurement for every ground-contact room or about one per 84 m2 (900 ft2). Using numerical simulation techniques, we have tested the proposed screening phase protocol against data from sixteen facilities. The results of the simulated screenings support the feasibility of a two-phased approach to the task of identifying facilities having rooms with elevated 222Rn concentrations.

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Small plastic chambers containing alpha track detectors are often used for measuring indoor concentrations of 222Rn. This paper reports an experimental assessment of sources of error in measurements made with alpha track detector-containing chambers. The results demonstrate the feasibility of a nondestructive test for the identification of alpha track detector-containing chambers that are packaged in a way that does not effectively prevent ambient 222Rn from inducing tracks prior to field exposure. Results also indicate that there is statistically significant variation among manufacturing lots and among chemical processing batches. Error from these sources can be avoided or compensated if appropriate control measures are implemented as part of a quality assurance program during any survey using alpha track detector-containing chambers.

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The congenic pair of mice, C57BL/10 (B10) and C57BL/10.F (B10.F), differ at the H-2 locus and have mean ages at death of 706 and 456 days, respectively. B10.F also has reduced basal serum IgA levels compared with B10, 63 and 256 mg/dl, respectively. Controlled matings between the two strains of mice were used to identify genetic factors that govern longevity. F2 and backcross progeny from reciprocal F1 hybrids were classified for H-2 genotype and serum IgA levels and allowed to live out their lifespan. F2 and backcross progeny homozygous for the H-2 allele of B10.F had a mean age at death (602 days) significantly reduced from that of progeny homozygous for the H-2 allele of B10 (689 days). However, the greatest reduction of lifespan occurred among progeny of the (B10.F X B10)F1 mothers, 693 compared with 540 days. The strain of the maternal parent also has been shown to affect the segregation of IgA phenotypes. An increased incidence of low IgA phenotype associated with H-2 genotype was observed among progeny of (B10.F X B10)F1 mothers. Survival curves demonstrated a relationship between low serum IgA levels and shortened lifespan and no maternal effect was observed. The basis of the shortened lifespan among progeny of F1 hybrids in which the maternal parent was B10.F was the increased incidence of offspring with low IgA phenotypes. The apparent association of H-2 and shortened lifespan also was because the low IgA phenotype was more frequent among progeny that carried the H-2 allele of the B10.F strain. The B10.F mice spontaneously shed an endogenous ecotropic retrovirus which may be responsible for the maternal effect on immunoglobulin levels and lifespan.

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RFM/Un mice express an endogenous type C retrovirus throughout their life span in many tissues; primary or established embryo fibroblast cell cultures do not express a virus but can be induced by exposure to 5-iodo-2'-deoxyuridine. All of our sources yielded a single ecotropic virus (RFV) which appeared to be related more closely to the endogenous N-tropic virus (WN1802N) of BALB/c mice than to Gross leukemia virus on the basis of two-dimensional gel electropherograms of virion proteins. No xenotropic or recombinant viruses were isolated by cocultivation techniques. RFV is N-tropic, and RFM/Un cells possess the Fv-1n allele, as indicated by restriction of B-tropic virus and susceptibility to Gross strain N-tropic virus. However, RFM cells are highly resistant to RFV and other endogenous N-tropic viruses. This resistance is expressed by two-hit titration kinetics and by inhibition of viral linear duplex DNA formation. This is similar to the effects of the Fv-1 locus, but preliminary work has shown no apparent genetic linkage between the two restrictions. The relative strength of the restriction, the presence of a single class of ecotropic virus, and the absence of recombinant viruses suggest that in RFM mice virus is expressed only in cells in which it is induced and not by cell-to-cell transmission.

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Cell cultures derived from a variety of mouse strains were compared for their relative capacity to be induced to express endogenous retrovirus proteins by exposure to 5-iododeoxyuridine under optimized experimental conditions. Induction frequencies varied between 6.0 x 10(-1) and 1.7 x 10(-2) with AKR cells showing the highest capacity and C57BL/6 x C3H F1 cells the lowest. Virus expression was induced in AKR cells with other chemical mutagens of the polyaromatic hydrocarbon [benzo(a)pyrene and phenol, diol, and epoxide metabolites] and nucleoside analog classes, but alkylating agents were inconsistent or failed to induce. Considerable differences in the efficiency of induction were seen between various halogenated nucleosides, while under these conditions the nucleoside 5-azacytidine induced greater than 90% of AKR cells at a concentration of 2 to 4 micrograms/ml. The high frequency of induction by 5-azacytidine, relative to other nucleoside analogs, and the absence of induction by other mutagens further indicate that endogenous virus induction occurs via nonmutagenic mechanisms and that some mutagens may also affect regulatory functions independent of their mutagenic action.

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The role of stromal-supportive cells in hematopoietic stem cell responses to irradiation is poorly understood. The effects of in vivo total body irradiation (TBI) and interval from TBI to explant of marrow on: stromal cell proliferation in vitro; stromal cell support of hematopoiesis in continuous bone marrow culture; and generation of WEHI-3 growth factor (GF)-dependent lines of hematopoietic progenitor cells were evaluated. Continuous marrow cultures from non-irradiated control RfM/UN, C57BL/6J, C3H/HeJ, and N:NIH (Swiss) mice generated pluripotential hematopoietic stem cells (CFUs) and committed granulocyte-macrophage progenitor cells (GM-CFUc) for over 20 weeks. Explant of marrow at 2, 4, 5, or 6 months after single fraction TBI (300-800 rad) was associated with decreased longevity of hemopoiesis (2-12 weeks), and a decrease in the proliferative capacity of fibroblastic adherent-stromal colony forming cells (CFUf) as measured by colony size at 14 days and number of colonies per 10(6) cells plated. In contrast, explant of marrow 8 to 24 months after TBI produced cultures with longevity that was indistinguishable from age-matched control cultures (19-24 weeks). Marrow from irradiated first and second generation recipients of serially transferred marrow demonstrated a similar 7-month in vivo recovery period; however, the plateau maximum duration of hemopoiesis did not return to control levels. Purified stromal cell cultures were prepared by corticosteroid-deprivation of explanted marrow for 28 days and were then engrafted in vitro with marrow from C57BL/6J or RfM/UN mice that had been irradiated 1 month previously. Hemopoiesis in these cultures was restored, and they produced GM-CFUc and granulocytes for 15-24 weeks. Thus, healthy stroma supported growth of recently irradiated hemopoietic cells in vitro. Nonadherent cells removed from the above continuous marrow cultures generated clonal non-leukemogenic WEHI-3 GF-dependent hemopoietic progenitor cell lines with a frequency concordant with radiation effects on culture longevity, and this was increased by the presence of purified healthy stromal cultures. Indirect effects of x-irradiation on hemopoietic stem cells through damage and repair in the stromal cell compartment can be effectively studied with the present bone marrow culture system.

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Fv-1 gene-specific resistance to ecotropic murine retroviruses can be transferred to permissive cells with RNA prepared from restrictive cells. The active RNA has a sedimentation coefficient of 20-22S at low ionic strength and multiple regions of activity (5-6S, 10-12S, 24-27S) at high ionic strength. The maximum level of resistance transfer cannot be enhanced with noninhibitory carrier RNA or facilitators of RNA uptake, and the maximum inhibition (40-60%) is independent of the MOI. The low efficiency of resistance transfer is, therefore, probably the result of a fraction of cells resistant to RNA uptake.

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A standardized bioassay for transfer of Fv-1 gene-specific resistance to N-tropic and B-tropic murine retroviruses was developed using X plaque reduction in SC-1 (Fv-1-) cells inoculated with virus. Testing of subcellular fractions of restrictive cells showed that the resistance transfer activity was present in the cytoplasmic (microsomal and cytosol) fractions. The activity of the cytoplasmic extract was destroyed by treatment with ribonuclease, but not with deoxyribonuclease or proteases. RNA prepared by phenol-chloroform extraction of mouse tissues, including embryos and livers of weanling mice, transferred Fv-1 locus-specific resistance into DEAE-dextran-treated SC-1 cells. The activity of isolated RNA preparations against virus of the appropriate host-range type has been demonstrated to correspond to the Fv-1 genotypes of the cell sources. The specific transfer of resistance with cellular RNA was effective within a 5- to 6-h period from 2 h before to 4 to 5 after virus infection. Sucrose gradient centrifugation of the RNA showed that the activity sedimented as a broad peak, with an apparent maximum in the 22S region. Affinity chromatography of whole-cell RNA on polyuridylic acid-Sepharose tended to separate more activity into the polyadenylic acid RNA fraction than the non-polyadenylic acid RNA fraction. Except for the reciprocal inhibitory activity for the two host-range virus types, the RNAs of Fv-1n and Fv-1b specificities showed similar properties in all aspects studied.

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Fv-1-specific host-range pseudotypes of murine sarcoma virus (MuSV) were developed by rescue from nonproducer cells with N- or B-tropic leukemia viruses. The MuSV(B) and MuSV(N) pseudotype viruses were tested in vitro and were restricted specifically by the Fv-1 gene locus. When the pseudo-type viruses were tested in vivo in mice of specific Fv-1 geno-types, tumor induction was completely restricted in nonpermissive animals, including athymic nude mice, whereas tumors grew progressively in permissive animals. All tumors regressed in adult heterozygous mice, but not in adult athymic nude mice.

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Extracts of mouse cells have been shown to transfer to N- or B-trophic host range types of mouse leukemia viruses. The genetic specificity of the inhibition was tested in two ways: (i) by correlating the Fv-1 genotype of a number of mouse strains with the restriction-transferring activity of extracts of the respective embryo cell cultures, and (ii) by correlating the Fv-1 genotype of BLC3F2 (C57BL/6 female [Fv-1bb] by C3H male [Fv-1nn] parental strains) mouse embryos, which segregate the Fv-1 alleles in a 12:1 ratio, with the inhibitor activity of extracts of the cells from each embryo. Five independent matings, totaling 45 individual embryos, were tested. Each embryo was cultured, and the Fv-1 genotype was determined independently by titration of N- and B-tropic viruses; the extracts of replicate secondary cultures were tested for their effect on infection of permissive cells by N- and B-tropic viruses. The specific-restriction-transferring activity of the embryos was found to segregate with the appropriate Fv-1 genotype. These res-lts confirm the suggestion that the inhibitor of the leukemia virus host range types in the cellular extracts is a product of the Fv-1 locus.

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A technique utilizing coliphage as the test material has been developed and employed to evaluate the effectiveness of a containment system for zonal centrifugation of hepatits viruses. An Andersen Viable Particle Sampler which had been loaded with plates containing a base layer of agar nutrient with an overlay of E. coli- agar suspension was used to sample the test air. The containment system, which includes a HEPA filter, was challenged with an aerosolized suspension of coliphage.

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