Lymphomas and high-level expression of murine leukemia viruses in CFW mice

Historically, Swiss Webster mice of the CFW subline, both inbred and random-bred stocks, have been considered to have a low spontaneous occurrence of hematopoietic system tumors, and previous reports of infectious expression of murine leukemia viruses (MuLVs) have been rare and unremarkable. In marked contrast, in the present study of CFW mice from one source observed by two laboratories over a 2-year period, nearly 60% developed tumors, 85% of which were lymphomas, the majority of B-cell origin. All tumors tested expressed ecotropic MuLVs, and most expressed mink cell focus-inducing (MCF) MuLVs. Among normal mice of weanling to advanced age, over one-half were positive for ecotropic virus in tail or lymphoid tissues, and MCF virus was frequently present in lymphoid tissue, less often in tail. Patterns of ecotropic proviral integration indicated that natural infection occurred by both genetic and exogenous routes. Lymphomas were induced in NIH Swiss mice infected as neonates with tissue culture-propagated MuLVs isolated from normal and tumor tissue of CFW mice.     

Effect of Diet and Strain Difference on the Virulence of Staphylococcus aureus for Mice

Years of intensive investigations in our laboratories on staphylococcal infections in mice have indicated a gradual decrease in the virulence of Staphylococcus aureus for this animal, particularly the strain we were using, the random-bred BT mouse. The present investigations, based on changes in diet and strain differences in mice, were undertaken in an attempt to improve susceptibility of our stock strain, on the one hand, and to determine whether susceptibility was influenced by genetic strain differences, on the other. In the first series of experiments, littermate mice of the BT strain were placed on different diets: one group received a commercial diet; the other, a basic diet previously established in our laboratories as adequate for growth requirements of the animals. An increase in the susceptibility of the animals to staphylococcal infection was noted in the mice receiving the basic diet. In the second series of investigations, three other strains of mice (the Swiss albino, the C3H/HeJ, and the C57B1) previously not used by our laboratories in staphylococcal experiments were studied for staphylococcal susceptibility. These experiments revealed that all of these strains of mice were highly susceptible to the infection, even though they were maintained on a commercial diet.     

Failure to detect platelet-activating factor using the splenectomized mouse bioassay

The ability of purified preparations of platelet-activating factor (PAF), from three different suppliers, to induce thrombocytopaenia in mice after splenectomy and to activate mouse platelets in vitro was examined. Although the PAF preparations were potent activators of horse and cow platelets in vitro, injections of up to 1 microgram PAF failed to elicit thrombocytopaenia responses in either CD1 or Swiss Webster random-bred mice. However, when thrombin was injected into Swiss Webster mice, a dose-dependent decrease in the concentration of platelets was observed. Furthermore, isolated platelets from these strains and from 3 inbred lines (C3H/He, BALB/c, C57BL/6) of mice, were not aggregated by PAF in vitro but were sensitive to adenosine diphosphate and thrombin. No change in circulating platelet concentrations was observed over the initial 7 days of gestation in intact Swiss Webster and C57BL/6 or splenectomized C57BL/6 mice, suggesting either an absence of PAF production during early pregnancy in these strains or insensitivity of their platelets to PAF. These results suggest that many mouse strains are unsuitable for the bioassay of PAF.     

Hypoxanthine causes a 2-cell block in random-bred mouse embryos

Ham's F-10, a chemically defined, complex culture medium, commonly used for in vitro fertilization of human as well as animal oocytes, blocked development at the 2-cell stage of greater than 92% of embryos from random-bred Swiss mice (CD-1), but did not block development of embryos from hybrid-inbred mice (BDF1). In contrast, BWW, a simple, modified Kreb's-Ringer bicarbonate medium, supported development to blastocysts of 85% and 100% of 2-cell embryos from CD1 and BDF1 females, respectively. As little as 15% (v/v) Ham's F-10 added to the BWW blocked the development of the random-bred embryos. Supplementing the BWW with Ham's F-10 components revealed that hypoxanthine (6-30 microM) was responsible for the developmental block to the random-bred embryos. The hypoxanthine block was partially (40%) reversed by adding the chelating agent, ethylenediaminetetraacetic acid. Breeding experiments showed that the hypoxanthine sensitivity of embryos from CD-1 mothers was not affected by the paternal genome.     

Genetic marker patterns and endogenous mammary tumor virus genes in inbred mouse strains of Japan

In order to establish the genetic relatedness of the inbred mouse strains kept in Nara, genetic marker patterns were determined in conjunction with a study on endogenous mammary tumor viral genes in these strains. Isoenzyme patterns combined with patterns of other genetic markers, show that the unrelatedness between various inbred strains of the dd stock is as high or even higher as between strains of known different origin and geneology. Based on endogenous viral gene patterns the dd stock derived mice can be subdivided into three group, DDD, DDN, DDO, KF and DD/Tbr. The DD/Tbr and its foster-nursed substrain (DD/Tbrf) have the lowest number of endogenous viral genes, i.e. two, while the other strains carry 4-6 such genes. The SLN and SHN strains, derived from a Swiss stock, have a similar pattern of viral genes different that of all other strains studied, also strains of Swiss origin from other sources, such as the NFS and the GR.     

Investigation of the histocompatibility of the NYA:NYLAR mouse colony by skin grafting.

The histocompatibility status of the Nya:NYLAR mouse colony was studied by exchange of skin grafts between female mice. The colony had been divided into two portions since 1962, a larger, outbred stock (Nya:NYLAR), and a smaller, inbred strain (NYLR/Nya). The results of skin graft exchanges between mice of the inbred strain indicated that they were skin-compatible. There was weak skin-incompatibility within the outbred stock and between this stock and the inbred strain, and strong skin-incompatibility between the outbred stock and outbred Webster Swiss mice.     

Chromosome damage and non-disjunction measured at the first cleavage division in normal and chromosomally mutant female mice irradiated at the diakinesis stage of female meiosis

We have irradiated primary murine oocytes at the diakinesis stage of the first meiotic division with 0.6 Gy X-rays. Fertilized oocytes were cultured overnight to arrest the first cleavage division and display pronuclear chromosomes. All preparations were preferentially stained for centric constitutive heterochromatin and analyzed for structural and numerical radiation effects. Females of 3 different karyotypes were irradiated (all on a Swiss random-bred genetic background): +/+ (221 female pronuclei analyzed), Rb(11.13)4Bnr T(1;13)70H/Rb(1.13)4Bnr T(1;13)70H with 11.13(1) and 1(13) large and small marker bivalents (RbT/RbT, 242 zygotes analyzed) and the same karyotype but with a 1(13)H;1(13) Wa heteromorphic bivalent (RbT/RbT*, 126 zygotes analyzed). Hyperploid chromosome counts were encountered with frequencies of 11.8% (+/+), 11.9% (RbT/RbT) and 16.6% (RbT/RbT*). In this order of karyotypes, the frequencies of dicentrics per zygote were 0.07, 0.16 and 0.11 and the frequencies of fragments 0.13, 0.18 and 0.31. In about half of the supernumerary chromosome spreads, a dicentric chromosome was included. The long marker bivalent 11.13(1) had a non-disjunction frequency of 2.5 times its control value, partially because it was involved in dicentric formation as well. For the RbT/RbT karyotype, the spontaneous maternal non-disjunction level was 5.4%. For the RbT/RbT* karyotype, it can be assumed to be the same or slightly higher because of the 1(13)H;1(13) Wa heteromorphic bivalent. This increased intrinsic sensitivity for non-disjunction was not expressed as an increased sensitivity for aneuploidy after irradiation. This fact and the numerical association between hyperploidy and dicentric formation, both for normal bivalents and for the 11.13(1) marker bivalent, lead us to suppose that in the female mouse, irradiation-caused aneuploidy is effectuated via chromatid exchange. The data presented do not rule out the existence of another mechanism.     

Spontaneous ophthalmic lesions in young Swiss mice.

BACKGROUND AND PURPOSE: Outbred mice are frequently used in toxicity evaluation. Due to their small size, ophthalmologic examination of such animals is difficult with regard to restraint and use of instruments designed for human medicine. The clinical appearance and incidence of spontaneous ophthalmic lesions should be helpful in selecting mice for toxicity studies and allow distinction between intercurrent spontaneous ocular changes and those attributable to drugs or chemicals. METHODS: Pretest ophthalmologic examinations of about 3,000 4- to 5-week-old Swiss mice, Crl:CD1 (ICR)BR, conducted in 1995 and 1996, provided information about spontaneous ocular changes and their incidence. Eye evaluations were performed after pupil dilatation (0.5% tropicamide instillation), using indirect ophthalmoscopy, and when indicated, a portable slit lamp. RESULTS: Lenticular opacities and heterogeneity/prominence were the most common findings (up to 19%) in the anterior segment. Abnormalities of the cornea and iris were detected in up to 4% of mice. Hyaloid artery remnant, as well as isolated cases of floating bodies or hemorrhage, was observed in the vitreous of 12 to 17% of mice. Approximately 2 to 4% of mice had colobomatous fundus, retinal fold, or retinal atrophy. A few mice had chorioretinal atrophy, hemorrhage, or abnormal pattern of the retinal vasculature. Remaining findings consisted of incomplete palpebral fissure, microphthalmia, exophthalmia, ophthalmic hemorrhage, and scleral mass. CONCLUSIONS: Due to severity of the condition or interference with ocular examination, affected mice should be eliminated from experimental studies. Hence, pretest ocular examinations of mice are indicated in safety-assessment toxicity studies.     

On the origin of Robertsonian fusions in nature: evidence of telomere shortening in wild house mice

The role of telomere shortening to explain the occurrence of Robertsonian (Rb) fusions, as well as the importance of the average telomere length vs. the proportion of short telomeres, especially in nature populations, is largely unexplored. In this study, we have analysed telomere shortening in nine wild house mice from the Barcelona Rb system with diploid numbers ranging from 29 to 40 chromosomes. We also included two standard (2n = 40) laboratory mice for comparison. Our data showed that the average telomere length (considering all chromosomal arms) is influenced by both the diploid number and the origin of the mice (wild vs. laboratory). In detail, we detected that wild mice from the Rb Barcelona system (fused and standard) present shorter telomeres than standard laboratory mice. However, only wild mice with Rb fusions showed a high proportion of short telomeres (only in p‐arms), thus revealing the importance of telomere shortening in the origin of the Rb fusions in the Barcelona system. Overall, our study confirms that the number of critically short telomeres, and not a simple reduction in the average telomere length, is more likely to lead to the origin of Rb fusions in the Barcelona system and ultimately in nature.     

Involvement of nitric oxide (NO) and TNF-alpha in the oxidative stress associated with anemia in experimental Trypanosoma cruzi infection

Trypanosoma cruzi infection in mice is associated with severe hematological changes, including anemia, which may contribute to mortality. TNF-alpha and nitric oxide (NO) play a critical role in establishing host resistance to this pathogen. We hypothesized that phagocyte-derived NO damages erythrocytes and contributes to the anemia observed during T. cruzi infection. To test this hypothesis, two strains of mice that differed in susceptibility and NO response to T. cruzi infection were used in these studies. We also blocked endogenous NO production by aminoguanidine (AG) treatment or blocked TNF-alpha with a neutralizing antibody and used mice that cannot produce phagocyte-derived NO (C57BL/6 iNOS(-/-)). Following infection with T. cruzi, resistant (C57BL/6) and susceptible (Swiss) mice displayed a parasitemia that peaked at the same time (i.e., day 9), yet parasitemia was 3-fold higher in Swiss mice (P < 0.05). All Swiss mice were dead by day 23 post-infection, while no C57BL/6 mice died during the study. At 14 days post-infection anemia in C57BL/6 mice was more severe than in Swiss mice. Treatment of both strains with the NO inhibitor, AG (50 mg/kg), and the use of iNOS(-/-) mice, revealed that the anemia in T. cruzi-infected mice is not caused by NO. However, the reticulocytosis that occurs during infection was significantly reduced after treatment with AG in both Swiss and C57BL/6 mice (P < 0.05). In addition, we showed that neutralization of TNF-alpha in vivo induced a significant increase in circulating reticulocytes in T. cruzi-infected C57BL/6 mice (P < 0.05), but did not modify other hematologic parameters in these mice. The evaluation of the oxidative stress after induction by t-butyl hydroperoxide (t-BHT) revealed that the treatment with AG completely protected against NO-mediated haemoglobin oxidation. Further, treatment with AG, but not with anti-TNF-alpha, protected against the infection-induced reduction of antioxidant capacity of erythrocytes as assessed by oxygen uptake and induction time. In summary, this is the first report showing the participation of NO and TNF-alpha in the oxidative stress to erythrocytes in acute T. cruzi infection. Further, our data suggest that NO does not play a direct role in development of the anemia. However, NO may contribute to other hematological changes noted during T. cruzi infection, such as the elevation of circulating reticulocytes and the reduction in circulating leukocytes and neutrophils.     

Cyclic AMP stimulation of Na-K pump activity in quiescent swiss 3T3 cells

Recently, we have found that an increase in the intracellular level of cAMP acts as a mitogenic signal for Swiss 3T3 cells (Rozengurt et al., Proc. Natl. Acad, Sci. USA, 78:4392, 1981). The results presented in this paper demonstrate that addition of cAMP-elevating agents to confluent and quiescent cultures of Swiss 3T# causes a marked increase in the rate of 86Rb+ uptake but has no effect on the rate of cation efflux. The stimulation of ion uptake is mediated by the Na-K pump as shown by the ouabain sensitivity of the 86Rb+ fluxes. The increase in Na-K pump activity occurs whether cAMP is generated endogenously by stimulation of adenylate cyclase activity by cholera toxin, adenosine agonists, or PGE1 or added exogenously as 8BrcAMP. The stimulatory effect of these compounds on 86Rb+ uptake is potentiated by inhibitors of cyclic nucleotide phosphodiesterase activity. Cholera toxin stimulates the Na-K pump in a dose-dependent manner; half-maximal effect is achieved at 0.7 ng/ml. The stimulation of ouabain-sensitive 86Rb+ uptake by cAMP-elevating agents reaches a maximum after 2-3 h of incubation. This contrasts with the rapid (within minutes) stimulation of the Na-K pump caused by serum and other mitogenic agents. Further, cAMP-elevating agents fail to increase Na+ influx into 3T3 cells whereas serum causes a marked increase in Na+ influx, under identical experimental conditions. These findings suggest that the stimulation of Na-K pump activity caused by increased cAMP levels contrasts mechanistically with the rapid control of pump activity by serum which is primarily mediated by increased Na+ entry into the cells.     

Tinctorial behavior of the cell types in the adenohypophysis of Swiss albino mice.

The cytological features of the pituitary of normal male inbred Swiss albino mice were studied. On the basis of 4 staining methods (CW, MTS, PAS-OG-MB, AT-PAS-OG), 5 types of chromophil cells have been identified: 2 types of acidophils--red and orange--and 3 types of basophils--angular to polyhedral dark-staining large cells, dark-staining small round cells and oval light-staining large cells.     

Demonstration of the correlation of the degree of synthesis and 4-aminobutyric acid levels in the central nervous system; effect of repeated convulsive seizures

GABA turnover rates have been determined in 15 brain areas in five inbred strains of Mice or sublines (DBA/2J, C57/6J, Swiss Rb1, Swiss Rb2, Swiss Rb3). GABA turnover rates and levels are correlated (2 P less than 0.05). After repeated seizures (twice a day for 15 days), induced by an acoustic stimulus in Swiss Rb1 Mice selected for audiogenic seizures, this correlation is no longer observed.     

Haploinsufficiency of p18(INK4c) sensitizes mice to carcinogen-induced tumorigenesis

The INK4 family of cyclin-dependent kinase (CDK) inhibitors negatively regulates cyclin D-dependent CDK4 and CDK6 and thereby retains the growth-suppressive function of Rb family proteins. Mutations in the CDK4 gene conferring INK4 resistance are associated with familial and sporadic melanoma in humans and result in a wide spectrum of tumors in mice. Whereas loss of function of other INK4 genes in mice leads to little or no tumor development, targeted deletion of p18(INK4c) causes spontaneous pituitary tumors and lymphoma late in life. Here we show that treatment of p18 null and heterozygous mice with a chemical carcinogen resulted in tumor development at an accelerated rate. The remaining wild-type allele of p18 was neither mutated nor silenced in tumors derived from heterozygotes. Hence, p18 is a haploinsufficient tumor suppressor in mice.     

Material and Energy Flows and Environmental Impacts of the Internet in Switzerland

The Internet leads to material and energy consumption as well as various environmental impacts on both the regional and global scale. Yet, assessments of the Internet's energy consumption and resulting greenhouse gas emissions are still rare, and assessments of material flows and further environmental impacts are virtually non‐existent. This article investigates material flows, the direct energy consumption during the use phase, as well as environmental impacts linked to the service, “Internet in Switzerland.” In our model, the service, Internet in Switzerland, is divided into various Internet participant categories. All devices used to access or provide Internet services are merged in a limited number of equipment families and, as such, included in an inventory of the existing infrastructure (stock). Based on this inventory, a material flow analysis (MFA) is performed, which includes the current stock as well as flows resulting from growth and disposal. The direct energy consumption for the operation of the infrastructure is quantified. Environmental impacts are calculated with a life cycle assessment approach, using the ecoinvent database and the software, SimaPro, applying four different methods. The MFA results in a 2009 stock of 98,100 tonnes. Approximately 4,130 gigawatt hours per year, or 7% of the total Swiss electricity consumption, were used in 2009 to operate the Swiss infrastructure. The environmental impacts caused during the production and use phases vary significantly depending on the assessment method chosen. The disposal phase had mainly positive impacts as a result of material recovery.     

Mortality in Swiss albino mice after i.p. injection of oxazepam in dimethyl sulphoxide.

Twenty percent of the Swiss albino mice administered with a single dose (60 mg/kg) of oxazepam dissolved in dimethyl sulphoxide (DMSO) died within 7 days. Similarly high mortality rate (37%) was observed in diazepam sensitive mice derived from a Swiss albino stock. In contrast, zero mortality was observed in Swiss albino mice administered with DMSO or diazepam (35 mg/kg). Mortality at 60 mg/kg diazepam was only 10%. The high mortality caused by oxazepam in Swiss albino mice seemed to be strain-related as only 7% mortality was observed with identically treated BALB/c mice. Since DMSO is the only convenient vehicle for the administration of oxazepam by injection, it is suggested that a suitable strain must be selected for experimentation in order to avoid unnecessary loss of animals.     

Normal murine and porcine embryos recruit NK cells to the uterus

Decidual NK cells, indistinguishable from those found in lymphoid tissues, are present in cell suspensions prepared from maternal decidua of random-bred mice between Days 6.5 and 10.5 of first gestation. The stringency of the correlation between NK cells and normal embryos during successful pregnancy is unknown. Our previous finding that active NK cells were unable to mediate lysis of fresh embryonic tissues at any stage during gestation suggests that if NK cells play a functional role in normal pregnancy it would be a noncytolytic role. Before studies on the function of uterine NK cells were undertaken, evidence that the association of NK cells with normal embryos is widespread was sought by assessing NK cell activity in cell suspensions from decidua of syngeneically mated mice, from decidua of multiparous, random-bred mice, and from the endometrium of pigs during first pregnancy. Neither parity nor maternal-fetal compatibility changed the pattern of high levels of decidual NK cell activity early in pregnancy followed by decline. Porcine NK cell activity was not detected in uterine cells isolated from cycling pigs but in pregnant animals it gradually increased during the preattachment period and reached levels greater than those in blood, postattachment (Day 28). Some of this activity was hormone dependent but sustained increases in NK cell activity required the presence of an embryo. These studies demonstrate that the association of functional NK cells with normal embryos is widespread during early pregnancy.     

A comparison of muscle precursor replication in crush-injured skeletal muscle of Swiss and BALBc mice

Summary Muscle precursor replication in Swiss mice, in which muscle regeneration is exceptionally vigorous, was compared with previous data for regeneration in BALBc mice. The tibialis anterior muscles of 23 male and 15 female inbred Swiss SJL/J mice were crush injured, and tritiated thymidine injected into mice at various times after injury to label replicating muscle precursors. Lesion samples were taken 10 days after injury, processed for autoradiography, and grain counts of myotube nuclei analysed. Muscle regeneration was more vigorous in male compared with female Swiss mice, and in both was strikingly greater than that in BALBc mice in which there was extensive fibrous connective tissue throughout the lesions. Autoradiographic analysis showed that muscle precursor replication started at 24 hours in Swiss mice, 6 hours earlier than the onset at 30 hours in BALBc mice. Muscle precursor replication appeared to be more active 96 hours after injury in female Swiss compared with male BALBc and male Swiss mice respectively, although numbers of precursor cells replicating at other times were similar. It is not known whether the slight difference in onset of muscle precursor replication can alone account for the more complete muscle regeneration seen in Swiss mice. Similar studies were carried out in 11 male and 10 female F₁ hybrid (SJL/J x BALBc) mice. Analysis of labelled myotube nuclei showed that muscle precursors did not synthesise DNA prior to 30 hours after injury, and regeneration resembled that of the parental BALBc strain.