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A biochemical approach to the study of the transmission of mouse mammary tumor viruses in mouse strains RIII and C3H.

Mouse mammary tumor virus (MMTV) proviral sequences were detected in the cellular DNA of mammary tumors and livers of RIII and C3H mice by molecular hybridization with radioactively labelled MMTV 60-70S RNA or tritiated MMTV complementary DNA (cDNA). By means of DNA:DNA reassociation kinetics, the DNA of the mammary tumor cells of these two mouse strains were found to contain more MMTV proviral sequences than the DNA of liver cells of these same tumor-bearing mice. Evidence is also presented that the DNA of the liver cells lacks a part (approximately 25%) of the MMTV proviral sequences found in the mammary tumor cells of these mouse strains. The relationship of the extra MMTV proviral sequences found in mammary tumor cells to the early mammary tumor-igenesis seen in these mouse strains is discussed.

Animals

[Serological examinations on natural infections with mouse pathogens in inbred mouse strains: difference in antibody detection among the strains (author's transl)].

Serological surveys on several infections were performed on the inbred mouse strains maintained at the Central Institute for Experimental Animals. In the first survey, 11 strains of mouse, which were 8 weeks of age or older and were kept in separate cages in the same animal room, were tested for antibodies to Salmonella enteritidis, Corynebacterium kutscheri, Tyzzer's organisms, Mycoplasma pulmonis, mouse hepatitis virus (MHV), Sendai virus (HVJ), pneumonia virus of mice (PVM) and minute virus of mice (MVM). Positive results were obtained in MHV, HVJ, PVM and MVM. Positive rates for these viruses except for MVM were different among mouse strains. In the second survey, 5 strains of mouse kept together in the same cage for 4 weeks after weaning were examined for MHV and HVJ antibodies. Positive rates to MHV were different among mouse strains as observed in the first survey. For HVJ antibody, no difference was demonstrated in positive rates unlike in the first survey, but the titers varied between the strains. These results suggest the difference in antibody response to natural infections dependent on mouse strains.

Animals

Correlation between DNA repair of embryonic fibroblasts and different life span of 3 inbred mouse strains.

Primary mouse fibroblast cultures were established from 10 day old embryos of 3 inbred strains with a genetically determined different life expectancy. The capacity for unscheduled DNA synthesis following u.v. irradiation was studied in these cells at various passage levels. The mouse fibroblasts show considerable repair synthesis corresponding to the duration of exposure time. The capacity for induction of unscheduled DNA synthesis was different in the cells of each strain and correlated to the natural life span of the animal; in each case, however, the ability to perform repair synthesis was subjected to an age-associated decline.

Animals

Correlation between DNA repair of embryonic fibroblasts and different life span of 3 inbred mouse strains.

Primary mouse fibroblast cultures were established from 10 day old embryos of 3 inbred strains with a genetically determined different life expectancy. The capacity for unscheduled DNA synthesis following u.v. irradiation was studied in these cells at various passage levels of the in vitro ageing process. The mouse fibroblasts show considerable repair synthesis corresponding to the duration of exposure time. The capacity for induction of unscheduled DNA synthesis was different in the cells of each strain and correlated to the natural life span of the animal. In each case, however, the ability to perform repair synthesis was subjected to an age-associated decline, although semiconservative DNA synthesis and proliferative potential of the cells was not changed until the cultures entered phase III passages.

Aging

Mouse mammary tumor virus genome expression in chemical carcinogen-induced mammary tumors in low- and high-tumor-incidence mouse strains.

Involvement of mouse mammary tumor virus (MMTV) in 7,12-dimethylbenz[a]anthracene (DMBA)-induced mammary tumorigenesis was investigated in low- (BALB/c) and high- (BALB/cfC3H) mammary-tumor-incidence mouse strains. Both strains contain endogenous MMTV integrated into the cellular genome. Additionally, BALB/cfC3H mice are infected with exogenous MMTV-S which is responsible for a higher incidence of mammary tumors in breeding females. Administration of DMBA to virgin mice of both strains resulted in a moderate frequency of mammary tumors within 40 wk after treatment. No differences were found in DMBA-induced tumor incidences at 18 wk (6% and 7%) or at 38 wk (29% and 36%) after treatment of BALB/c and BALB/cfC3H mice, respectively. Expression of MMTV in these tumors was examined by assaying for the presence of MMTV RNA by hybridization using MMTV-specific cDNA and by immunohistochemical staining utilizing antibodies against MMTV 52,000-dalton glycoprotein, gp52, and 28,000-dalton internal protein, p28. Of 16 BALB/c tumors assayed, 11 did not contain detectable levels of MMTV RNA and the remaining 5 tumors contained only low levels (0.0005-0.0010%) of viral RNA. Importantly, MMTV RNA was not detected in 5 of 27 BALB/cfC3H tumors. The other BALB/cfC3H tumors contained quantities of MMTV RNA ranging from 0.0006 to 0.4170%. Most BALB/cfC3H tumors with detectable levels of MMTV RNA also synthesized viral proteins gp52 and p28. Thus, expression of the complete MMTV genome is not requisite for maintenance of the tumor phenotype in DMBA-induced mammary tumors in either BALB/c or BALB/cfC3H virgin mice under 1 year of age.

9,10-Dimethyl-1,2-benzanthracene

Transmission of mammary tumor virus in mouse strain DD: further support for the uniqueness of strain GR.

Outcrosses between high tumor mouse strain DD and low-incidence strains BALB/c and C57BL to produce reciprocal F1 susceptible offspring of both types resulted in high incidences of mammary tumors in (DD female X BALB/c male)F1 and (DD female X C57BL male)F1 females but not in the reciprocal hybrids with DD as the male parent. The finding that transmission of murine mammary tumor virus (MuMTV) in DD was through the milk, as most often observed in mouse strains, further supported the uniqueness of strain GR in which MuMTV is transmitted by either parent.

Animals

Involvement of mouse mammary tumor virus in spontaneous and hormone-induced mammary tumors in low-mammary-tumor mouse strains.

The involvement of the mouse mammary tumor virus (MTV) in spontaneous and hormone-induced mammary tumors in low-mammary-tumor mouse strains was studied by comparing the amounts of MTV RNA and MTV DNA sequences in mammary tumors and other tissues of mice with an without hormonal treatments. The following results were obtained. (i) Mammary tumors which appeared in C3H mice as a result of an infection with MTV contained more MTV DNA compared with noninfected organs; these mammary tumors also contained more MTV RNA than was present in lactating mammary gland cells. (ii) Hormonal stimulation by administration of excessive amounts of prolactin via hypophyseal isografts in C3Hf and O20 mice resulted in an increased expression of MTV RNA in the mammary glands. This elevated level of MTV RNA expression was, however, not maintained in the hormone-induced mammary tumors. (iii) Spontaneous mammary tumors in BALB/c mice contained similar levels of MTV DNA and MTV RNA sequences as were found in other cells of these animals.

Animals

Giardiasis in mice. I. Prolonged infections in certain mouse strains and hypothymic (nude) mice.

The natural history of Giardia muris has been studied in inbred mouse strains and hypothymic (nude) mice derived from a specific pathogen-free facility. Although giardiasis was readily established in several mouse strains, marked variation was observed in the time course of spontaneous elimination of the parasite. During a 10-week study, fecal excretion of Giardia cysts remained relatively constant in C3H/He mice, but decreased at a variable rate in other mouse strains. Resistance to reinfection was greater in strains in which the duration of primary infection was relatively short. Hypothymic (nude) mice derived from a strain showing a relatively rapid elimination of Giardia (BALB/c) maintained a stable infection with high cyst counts. Nude mice reconstituted with lymphoid cells from syngeneic thymus-intact mice showed a progressive reduction in cyst excretion and reconstitution with limited numbers of lymphoid cells from thymus-intact mice previously exposed to Giardia accelerated resolution of infection. In nude mice, giardiasis was associated with a reduction in the villus-crypt ratio of jejunal mucosa, but the degree of change was greater in nude mice reconstituted with lymphoid cells. This Giardia model involving inbred strains and nude mice permits further dissection of the function of thymus-derived cells in intestinal immune responses and induction of changes in small bowel morphology.

Animals

Mouse strain resistant to N-, B-, and NB-tropic murine leukemia viruses.

Mouse strain G was studied for its susceptibility to various strains of murine leukemia and sarcoma viruses. Both N- and NB-tropic Friend leukemia viruses neither induced splenomegaly nor grew efficiently in strain G mice. Using the XC test, cultured embryo cells were found to be resistant, but not absolutely, to all the tested viruses, N-tropic AKR virus, N- and NB-tropic Friend leukemia viruses, NB-tropic Rauscher leukemia virus, B-tropic WN1802B virus, NB-tropic Moloney leukemia and sarcoma viruses, and N-tropic Kirsten sarcoma virus, although the resistance to Moloney leukemia and sarcoma viruses is sometimes not as strong as that for other viruses. Thus, the strain G mice are unique among mouse strains because they show resistance that is not related to the N-B tropism of murine leukemia viruses.

AKR murine leukemia virus

Natural resistance to Salmonella typhimurium in different inbred mouse strains.

The mechanisms of natural resistance to intravenous challenge with Salmonella typhimurium C5 are complex. LD50 determinations showed inbred mouse strains of low, intermediate and high natural resistance, with BALB/c and B10 strains the most susceptible, A/J the most resistant. Delayed (footpad) hypersensitivity was not by itself a measure of natural resistance. Resistant mouse strains sensitized either s.c. or i.v. with an attenuated salmonella strain showed positive 48 h footpad reactions when tested 8 days later with a salmonella extract, but three very susceptible strains also showed positive reactions. Determinations of the in vivo net growth rate of salmonellae in the liver and spleen during the first phase of the infection (up to day 4) arrange the different mouse strains into two categories of fast and slow net growth rate. All fast net growth rate strains are susceptible, but not all slow net growth rate strains are resistant. Besides slow net growth rate, resistance requires the participation of other factors appearing in the second phase of the infection (towards the end of the first week) probably involving the cellular immune response, which halts further bacterial growth. Not all slow net growth rate strains are equally capable of suppressing bacterial growth in this second phase. The host mechanism determining slow net growth rate is inherited as a dominant trait, and appears to be operating before the main cellular immune response. The influence of this mechanism on net growth rate is reflected in the time to death following a given dose of salmonellae. The present results suggest that overall resistance to salmonellae is polygenic, but that the mechanism responsible for the differences in early net growth rate is less complex.

Animals

Experimental studies on vertical infection of mice with Japanese encephalitis virus. I. Effect of mouse strain on placental and fetal infection.

An experiment was carried out with mice to study the effect of the mouse strain on the establishment of experimental vertical infection with Japanese encephalitis virus. Mice of various inbred strains were inoculated with a field strain of virus on the 7th day of pregnancy. An attempt was made on them to recover the virus from the placenta and fetuses. As a result, there were differences in the rate of placental and fetal infection among the mouse strains used. It was clarified that vertical infection could be established experimentally in some selected mouse strains. There was not always a parallel relationship between the rate of placental and fetal infection and the severity of viremia or visceral infection in the dam.

Animals

Mouse strain identification by means of discriminant analysis using mandible measurements.

Mouse strains were identified by the aid of discriminant functions obtained from discriminant analysis of values measured at 13 sites of the mandible. They consisted of nine inbred strains of mice, AA, DDD, DDK, DDY, DSD, KK, NC, RR, and SS, and one mutant strain, NC-brp, maintained exactly in the National Institute of Animal Health, Minstry of Agriculture, Forestry and Fisheries. As a result, the probability of erroneous discrimination was 1 head/246 head, or 0.41%, for the males and 2 head/238 head, or 0.84%, for the females. Therefore, almost all the mouse strains were identified correctly. These results seemed to indicate that the strains of mice would be identified more correctly than before, if the present method by the aid of discriminant functions was applied in addition to the methods of identification based on the coat color, biochemical marker-genes, and histocompatibility genes.

Animals

Different hematological diseases induced by type C viruses chemically activated from embryo cells of different mouse strains.

Type C RNA viruses can be induced by certain chemicals from cells of many mouse strains. Both C58 and BALB/c cells have been shown to contain endogenous viruses that are designated N-tropic because they grow preferentially in cells of NIH Swiss mouse origin. While demonstrating many similar biological and immunological properties, the C58-induced virus is around 10-fold more infectious per physical particle than the N-tropic virus of BALB/c cells. In the present studies, inoculation of these viruses into newborn NIH Swiss mice led to the development of diseases associated with splenomegaly and lymphadenopathy at similar frequency in each group. The disease induced by C58-MuLV was histophathologically diagnosed as lymphoblastic leukemia and was highly malignant following transplantation into newborn mice. The histopathological appearance of spleens from BALB/c virus-affected animals was distinguishable, demonstrating instead myeloid metaplasia or myelogenous leukemia. These findings provide evidence that different endogenous mouse type C viruses can induce distinct diseases in the same mouse strain. Furthermore, they implicate the N-tropic virus endogenous to C58 cells as a major factor in the development of lymphoblastic leukemia that occurs at high frequency in that strain.

Animals

Isolation of the mouse mammary tumor virus sequences not transmitted as germinal provirus in the C3H and RIII mouse strains.

Radioactive 60-70S RNA from the mouse mammary tumor virus (MMTV) produced by the C3H mouse mammary tumor cell line (Mm5mt) hybridized to a greater extent, and at a lower Cot1/2 value, to the DNA of C3H mammary tumor cells than to the DNA of C3H liver cells. The 125I-labeled MMTV (C3H) 60-40S RNA was annealed to a vast excess of DNA from C3H livers, and single-stranded RNA was eluted from hydroxylapatite and recovered. This "recycled RNA" did not hybridize to the DNA of the apparently normal organs tested from normal or from mammary tumor-bearing C3H mice, but hybridized extensively to both the DNA from the C3H mammary tumor cell line and the DNA from spontaneous C3H mammary tumors. This hybridization could be competed out by the addition of unlabeled MMTV 60-70S RNA but was unaffected by the addition of unlabeled 60-70S RNA of C3H type C virus. Similar experiments were conducted with the RIII mouse strain. We therefore report on the isolation of the sequences of the RNA genomes of the MMTVs from C3H and RIII mice that are transmitted by some mechanism other than via the germ line. These studies further define the differences, via molecular hybridization, between the MMTV-S and the MMTV-L in both C3H and RIII mice.

Animals

Studies on immune responses to larval cestodes in mice. Increased susceptibility of certain mouse strains and hypothymic mice to Taenia taeniaeformis and analysis of passive transfer of resistance with serum.

Various inbred strains of mice vary markedly in their susceptibility to the larvae of the cestode, Taenia taeniaeformis. Males are generally more susceptible than females and the most susceptible common inbred mouse strains are those which are deficient in C5 and/or C4 components of complement. However, no genetic evidence is yet available to implicate loci controlling complement levels in susceptibility/resistance, and multiple genetic factors appear to be operative. Hypothymic, nu/nu ("nude") mice of the relatively resistant mouse strain, BALB/c, are highly susceptible in that cystic larvae in the liver develop in large numbers and more rapidly than in intact BALB/c.nu/+litter-mates. Cyclophosphamide pretreatment also increases the susceptibility of relatively resistant strains of mice in terms of both the number and size of liver cysts. Hypothymic and intact mice can be protected, absolutely, by an injection of serum from infected intact mice, provided the serum is given to recipient mice close to the time of oral egg administration. The protective activity of immune serum is absorbed totally by staphylococcal protein A-Sepharose columns and can be abolished by treatment of recipients with cobra venom factor. Cyst fluid from established larvae facilitates the activity of subhaemolytic amounts of guinea pig complement in a standard direct PFC assay. The data suggest that complement-fixing antibodies are responsible for inhibition of establishing larvae in mice and that one method of protection for established cystic larvae involves the alteration of host complement activity within the cyst.

Age Factors

[The inbred mouse strain STU. Development and properties (author's transl)].

The highly inbred STU mouse strain (up to 100 inbred generations) was developed from a German white mouse colony. Its properties are described with special emphasis on the occurrence of tumors, occurrence of C-type oncornaviruses and on its immunological reactivity. The predominant tumor is a fibrosarcoma (approximately 23% incidence).

Animals

Presence of anti-Sm reactivity in autoimmune mouse strains.

The investigation of the fine specificities of antinuclear antibodies (ANAs) has been fruitful in terms of the nosology and immunopathogenesis of human autoimmune syndromes. Particular reactivities serve as "markers," in that patients with certain syndromes have a much higher incidence of such ANAs than do patients with other diseases. In this category is the almost exclusive against the nuclear acidic protein Sm. Reactivity to Sm can be detected by precipitation in agar, complement fixation, or passive hemagglutination (1,2). Autoimmune mouse strains have also provided a fertile field for the investigation of the basic phenomena of self-activity. In particular, the NZB strain and its hybrid NZB x NZW have been considered excellent models for human SLE and have therefore been studied in great detail (3,4). In addition, Murphy et al at The Jackson Laboratory, Bar Harbor, Maine, have developed several new inbred mouse strains that spontaneously develop SLE-like syndromes (5,6). These are the BXSB strain, which has a male dominant disease characterized by little antiative DNA antibody; the MRL/1, which develops massive, nonmalignant lymphadenopathy, associated with enormous increases in serum immunoglobulin levels and fulminant renal disease; and the MRL/n, which does not develop SLE-like disease until well into the 2nd yr of life, but like the MRL/1 develops high titers of ANA and fatal glomerulonephritis. The MRL/1 differs from MRL/n in only about 10 percent of its genome, including the gene responsible for the MRL/1's lymphoproliferation. In the current study, we have used the technique of double immunodiffusion (ID) in agarose with standard human reference sera (of known ANA specificity) to survey a large number of mice from the NZB x NZW, MRL/1, MRL/n, BXSB, and other strains. We report here the finding of the anti-Sm marker" antibody almost uniquely in MRL/1 and MRL/n animals. These two related strains may serve as experimental models to explore the mechanism stimulating the production of this unique autoantibody in SLE.

Animals