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At least 19 recordsLinked to original sources
PubMed1975

DNA polymerases in polyoma virus-infected mouse kidney cells.

Infection of arrested mouse kidney cells by polyoma virus results in the induction of the cellular 6-8S DNA polymerase activity. Levels of this enzyme increase two- to threefold in the cytoplasm but seven- to tenfold in nuclei and nuclear extract, suggesting an accumulation of the enzyme in the nucleus. Experiments using the inhibitor of DNA synthesis, fluordeoxyuridine, indicate that this accumulation is linked to active DNA synthesis. The activity and cellular distribution of the small 3.4S DNA polymerase remains unchanged.

Cell Fractionation↗
PubMed1979

Protective immune response in mice immunized with antigens from Trypanosoma gambiense-infected mouse blood.

Immunogenicity and property of antigens obtained from Trypanosoma gambiense-infected mouse blood (IMP) were examined. A strong vaccine effect against intravenous challenges with 3 x10(3) parasites given on study day 3, 5, or 14 (day 0 = immunization) was observed in mice immunized with a combination of IMP (2 mg protein/mouse) and Freund's complete adjuvant (FCA). But when the challenge was given on day 21 or 30, per cent survival in mice dropped to the 20- and 40-per cent level, respectively. Among fractioned components of IMP, IMP-1, IMP-2, and imp-3, by gel filtration with Sephadex G-200, all of the mice immunized with IMP-1 antigen alone or together with FCA and challenged on day 5 were able to conquer intraperitoneal challenges with 1 x10(2) parasites. Mice immunized with IMP-2 or IMP-3 died within 6 days after challenge. Moreover, protection efficacy shown by IMP-1p (144,000 xg sediment of IMP-1) antigen in mice was similar to that by IMP and IMP-1 antigens. IMP-3 yielded a single precipitin line against mouse anti-IMP serum by Ouchterlony double diffusion method but this response was eliminated when the antiserum was absorbed by IMP-1p. No precipitin line was identified between mouse anti-IMP serum and IMP-1 or IMP-2. From electron microscopic observations, elements of IMP-1 and IMP-1p are possibly corresponded to the fragments of filopodia of the parasites.

Agglutination Tests↗
PubMed1976

Natural immunity in the oncornavirus-infected mouse.

BALB/cfC3H females neonatally infected with mammary tumor virus (MTV) possess spleen cells capable of significant cytotoxic activity against target MTV-induced mammary tumor cells in microcytotoxicity assay. Spleen cells from supposedly MTV-free BALB/c females are also specifically reactive, as a result of horizontal transmission of MTV antigens. No quantitative differences in reactivity exist between females not susceptible to the development of mammary tumors (BALB/c) and those that may develop or already have tumors (multiparous BALB/cfC3H). However, there are qualitative differences in response between those at risk and those not at risk.

Age Factors↗
PubMed1977

Altered enzyme release by virus infected mouse salivary glands.

The rates of release of salivary amylase and esterase from normal and polyoma virus infected mouse submandibular glands were measured in a continuous flow perifusion system. Following stimulation by epinephrine, the rate of release of esterase by the infected glands was significantly greater than that from control glands. The rate of amylase release, while greater from infected glands, was not significantly different. The total enzyme contents from infected and control tissues were similar. Cyclic GMP was found to be higher in the infected glands than the control glands, suggesting one possible mechanism for the higher rates of enzyme release by infected tissues.

Amylases↗
PubMed2026

Population heterogeneity in Helicobacter pylori PMSS1 shapes variable mouse infectivity: derivation of the homogeneous reference strain PMSS2.

UNLABELLED: Experimental infection models are widely used to investigate host-microbe interactions, often under the assumption that bacterial populations are genetically uniform. Here, we examined population heterogeneity in the widely used Helicobacter pylori strain PMSS1 and its relationship to variation in mouse infectivity. Single-colony isolates derived from PMSS1 displayed substantial differences in colonization efficiency, indicating that pre-existing variation within the population contributes to infection outcomes. To distinguish the effects of initial population heterogeneity from changes arising during infection, we analyzed PMSS2, a genetically homogeneous reference strain derived from PMSS1 that exhibited consistent infection phenotypes across independently isolated clones. Comparative genomic analysis of isolates recovered from infected mice revealed differences in the extent and patterns of genomic variation between PMSS1- and PMSS2-derived populations. These results demonstrate that variability in infection outcomes can arise from pre-existing heterogeneity within bacterial populations and highlight the importance of considering population composition when interpreting experimental infection studies. IMPORTANCE: Animal infection models are widely used to study how bacterial pathogens cause disease and change during infection. These studies often assume that the bacteria used for infection are genetically uniform. Our study shows that this assumption may not always hold. We found that a commonly used Helicobacter pylori strain contains hidden genetic diversity that leads to large differences in how well bacteria infect mice. By comparing this strain with a genetically uniform derivative, we show how differences present before infection can shape infection outcomes and influence the genetic changes observed during infection. Our findings highlight the importance of considering starting population diversity when interpreting experimental infection studies and are broadly relevant to research on microbial pathogenesis.

Helicobacter pylori↗
PubMed1976

Induction of DNA polymerase in polyoma virus-infected mouse cells requires transcription and translation.

The induction of DNA polymerase activity and of DNA synthesis in polyoma virus-infected mouse kidney cells is inhibited by actinomycin D and cycloheximide, even in cells that are already T-antigen positive. This indicates that the induction of the DNA-synthesizing apparatus requires transcription and translation. The increase in cellular DNA polymerase activity and in the DNA synthesizing capacity follows the appearance of T-antigen only after a characteristic lag period of several hours.

Animals↗
PubMed1977

Nuclear localisation of DNA polymerase alpha and DNA synthesis in polyoma virus infected mouse cells.

Studies using inhibitors of DNA synthesis have shown that DNA polymerase alpha is located in nuclei of polyoma virus infected mouse cells to the same degree as these nuclei are engaged in DNA replication. These results indicate that either the enzyme is actively transported into nuclei concomitant with the onset of DNA synthesis, or that it is bound much more strongly in nuclei during DNA replication. In any case, these observations support the hypothesis that DNA polymerase alpha is involved in the replication of cellular and viral DNA.

Animals↗
PubMed1978

Simultaneous production of mouse endogenous virus and Rous sarcoma virus by Schmidt-Ruppin virus infected mouse cells.

Schmidt-Ruppin Rous sarcoma virus infected chick cells injected into newborn C3H/f mice gave rise to tumours at the site of inoculation. These tumours were transplantable in adult C3H/f mice and were able to induce tumours in the wing of adult Leghorn chickens. Tumour cells from the 18th passage in mice were used to establish a cell line in tissue culture (C3HSR). These cells released C-type virus particles that produced foci and were able to propagate in chick cells. Cloning of the C3HSR cells demonstrated that the same cell expressed both avian and murine antigens. Mouse cells infected with virus released by C3HSR cells produced murine leukaemia virus-like particles as revealed by the reverse XC syncytial test and by immunofluorescence tests.

Animals↗
PubMed1979

Multiple integration sites for Moloney murine leukemia virus in productively infected mouse fibroblasts.

The integration sites for viral DNA in cells infected with Moloney murine leukemia virus (M-MuLV) were studied by restriction endonuclease cleavage of cellular DNA followed by electrophoresis in agarose gels, blot transfer to nitrocellulose, and detection by M-MuLV-related sequences by hybridization with high-specific-activity 32P-labeled M-MuLV complementary DNA. When EcoRI was used to cleave cellular DNA, numerous DNA fragments with sequence homology to M-MuLV were detected in uninfected mouse cell DNA. These endogenous sequences are mouse specific since they are not detectable in rat cell DNA, and are related to the 38S genomic RNA of M-MuLV. Infected cells contain additional M-MuLV-specific DNA fragments which are not detected in uninfected cells. Different patterns of M-MuLV-specific DNA fragments were detected in each cloned infected line examined. These data suggest the existence of multiple sites for integration of M-MuLV DNA in infected mouse fibroblasts. Cleavage of infected cell DNA with BamHI, which cleaves M-MuLV viral DNA at least twice, released the internal BamHI B fragment from each infected line, confirming the presence of integrated M-MuLV DNA sequences in each infected cell line which retain some features of the sequence organization of unintegrated M-MuLV DNA.

Animals↗
PubMed1979

[Morphometric study of the bronchopulmonary lymphoid system in the normal mouse and the mouse infected with influenza virus].

Morphometric study of mouse bronchus-associated lymphoid tissue (BALT) using an image analyser and histological sections at close and regular intervals was carried out in lungs of control and influenza infected mice two to three months old. The mean area of BALT did not reach 0,1 p. 100 of the whole mean area of examined lung sections in control mice; this percentage was significantly greater one month after primary exposure to influenza virus.

Animals↗
PubMed1978

DNA-binding proteins in the cytoplasm of vaccinia virus-infected mouse L-cells.

Mouse L cell fibroblasts were infected with vaccinia virus and labeled 2 to 3 h postinfection with [35S]methionine. Labeled proteins were fractionated on native and denatured DNA-cellulose columns and then analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Twenty-four 90,000 to 12,500, were detected. VDP-12A (molecular weight, 29,750) had affinity for denatured but not native DNA, and its synthesis was dependent on viral DNA replication. VDP-20 (molecular weight, 41,000) bound very tightly to native and denatured DNA and was displaced only after boiling the protein-DNA-cellulose matrix in 1% sodium dodecyl sulfate. VDP-8,-11,-12,-13, -and-14 behaved electrophoretically like the polypeptide species previously shown to be present in DNA-protein complexes prepared from infected cells. The molecular weights of VDP-10 (50,000), VDP-11 (36,000), and VDP-8 (67,000) were similar to the polypeptide subunits of polyadenylate polymerase and phosphohydrolase I, enzymes purified from virions which have also been shown to have affinity for DNA.

Cytoplasm↗
PubMed1977

Amount and distribution of virus-specific sequences in giant RNA molecules isolated from polyoma-infected mouse kidney cells.

A two-step hybridization with polyoma DNA was used to study the composition of giant RNA molecules synthesized in mouse kidney cells late in productive infection by polyoma virus. Giant molecules longer than a complete transcript of the polyoma genome were purified from cells that had been pulse-labeled for 30 min with [3H]uridine and annealed, under mild conditions (50% formamide, 37 degrees C), with polyoma DNA loaded on nitrocellulose filters. Hybridized RNA (6 to 7% of the entire population of 3H-labeled molecules and up to 15% of the molecules containing polyadenylic acid [poly(A)]] was eluted and annealed a second time with polyoma DNA under more stringent conditions. In this second step, 75% of the 3H-labeled RNA formed an RNase-resistant hybrid. Under the same conditions, complementary RNA hybridized with polyoma DNA to a maximal extent of 80%. Since the difference between 75 and 80% is within the experimental error of the hybridization assay, it is inferred that the giant molecules selected by the first hybridization may consist entirely of virus-specific sequences or contain, at the most, a minor fraction of nonviral sequences. To examine the possibility that such nonviral sequences are clustered at the 3'-terminus of these molecules, poly(A)+ giant RNA, which had not been preselected by hybridization with polyoma DNA, was fragmented by a limited alkaline hydrolysis. Fragments linked to the poly(A) segment were separated from the rest of the cleavage products. A one-step hybridization with polyoma DNA revealed that both fractions contain 8 to 10% of virus-specific sequences. These results indicate that the 3'-termini of the poly(A)+ polyoma-specific giant RNA molecules consist of viral rather than nonviral sequences.

Animals↗
PubMed1978

Mechanism of action of Pseudomonas aeruginosa exotoxin A in experimental mouse infections: adenosine diphosphate ribosylation of elongation factor 2.

The data presented indicate that one of the primary actions of Pseudomonas aeruginosa exotoxin during experimental infection is the inactivation of elongation factor 2 (EF-2) in various mouse organs. Organs from mice infected with the toxigenic P. aeruginosa strain PA103 contained considerably less EF-2 activity than did organs from uninfected controls. Whereas EF-2 activity was reduced in all organs examined from PA103-infected animals, the largest decrease was observed in the liver, where the active EF-2 levels were reduced by 70 to 90%. In addition, consistent inhibition of protein synthesis in livers but not in other organs was observed in mice infected with the toxigenic PA103 strain. Treatment of mice with antitoxin before infection with strain PA103 prevented inactivation of EF-2. When mice were infected with lethal doses of the nontoxigenic P. aeruginosa WR5 strain, tissue EF-2 levels were not markedly reduced below those derived from uninfected control animals.

Adenosine Diphosphate↗
PubMed1976

[The coxsackievirus-infected mouse: an animal model for the study of virus myocarditis].

Basing on the experimental infection of adult mice with coxsackie virus A9 reported by Lerner in 1965 and the successful cultivation of the virus from the hearts of experimental animals, a model for studying virus myocarditis is proposed. By a combination of factors favouring the infection (age of the animals above 1 year, physical load prior to infection by repeated swimming) a high virus re-isolation rate was achieved. Cultivation of the virus from the mouse heart was possible on the 3rd day p.i. in 81%, on the 6th day in 71%, on the 9th day in 31%, and on the 12th day in 12% of the cases. In 66% of the animals towards the end of the period of observation a significant increase in few cases is the virus isolated on the 3rd and 6th day p.i. also from the skeletal muscles. The model can be used both for pathogenetic studies on myocardites elicited by cardiotropic viruses and for in vivo testing of antiviral substances.

Animals↗
PubMed1976

Attempts to produce Theileria parva-infected mouse cells using cell fusion techniques.

Ehrlich ascites tumour (EAT) cells were fused with Theileria parva-infected bovine lymphoid (C2) cells using inactivated Sendai virus. A variety of techniques were employed to try and increase fusion percentage and harvest of heterokaryons. There was no evidence that pre-exposure of C2 cells to Sendai virus or phytohaemagglutinin improved fusion percentage, but the percentage was higher when 10(8) C2 cells were fused with 10(7) EAT cells, as compared with a ratio of 10(7) C2: 10(6) EAT. An increased yield of multinucleate cells was obtained using a calf serum gradient to separate cells of different sizes. An attempt to fuse EAT cells with free macroschizonts was not sucessful. When cells were grown in hypoxanthine/aminopterin/thymidine medium (HAT), T parva appeared to be selectively killed by the aminopterin present; this finding would seem to militate against the use of a HAT selection system to clone parasitised hybrids. C2 cells could be selected out by passage of mixed cultures through mice, but no evidence of parasitosis was detected in EAT cells which became established.

Animals↗