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T Merlin

Publications and source records attributed to T Merlin.

10 recordsLinked to original sources
PubMed2001

A point mutation in the IL-12R beta 2 gene underlies the IL-12 unresponsiveness of Lps-defective C57BL/10ScCr mice.

Lps-defective C57BL/10ScCr (Cr) mice are homozygous for a deletion encompassing Toll-like receptor 4 that makes them refractory to the biological activity of LPS. In addition, these mice exhibit an inherited IL-12 unresponsiveness resulting in impaired IFN-gamma responses to different microorganisms. By positional cloning methods, we show here that this second defect of Cr mice is due to a mutation in a single gene located on mouse chromosome 6, in close proximity to the Igkappa locus. The gene is IL-12Rbeta2. Cr mice carry a point mutation creating a stop codon that is predicted to cause premature termination of the translated IL-12Rbeta2 after a lysine residue at position 777. The truncated beta2 chain can still form a heterodimeric IL-12R that allows phosphorylation of Janus kinase 2, but, unlike the wild-type IL-12R, can no longer mediate phosphorylation of STAT4. Because the phosphorylation of STAT4 is a prerequisite for the IL-12-mediated induction of IFN-gamma, its absence in Cr mice is responsible for their defective IFN-gamma response to microorganisms.

Animals↗
PubMed2001

Inherited IL-12 unresponsiveness contributes to the high LPS resistance of the Lps(d) C57BL/10ScCr mouse.

LPS(d) mouse strains are characterized by the presence of a defective LPS/tlr4 gene that make them refractory to the biological activity of LPS. One of the mouse strains commonly used to study LPS defects is the C57BL/10ScCr (Cr) strain. However, unlike other LPS(d) strains, the Cr strain also has a heavily impaired IFN-gamma response to micro-organisms. As a consequence, unlike other LPS(d) mouse strains, they do not acquire a partial LPS susceptibility when treated with sensitizing bacteria. Because IL-12 is important for the microbial induction of IFN-gamma, we investigated whether the production or function of IL-12 might be defective in Cr mice. IL-12 mRNA (p35 and p40) was present in the spleen of untreated Cr mice, IL-12p40 mRNA was inducible in mice injected with live or killed Salmonella typhimurium, and IL-12 (p70) was inducible in macrophages by bacteria. Thus, Cr mice exhibit normal IL-12 responses. In functional tests, splenocytes of untreated or of S. typhimurium-infected mice failed to produce IFN-gamma when stimulated with murine rIL-12 or with a combination of IL-12 and murine rIL-18 or Con A. Furthermore, Cr mice were identical with IL-12p35/p40 and IL-12 receptor beta(1) knockout mice in their impaired in vivo and in vitro IFN-gamma responses to bacteria. Thus, Cr mice carry a second genetic defect unrelated to the Lps/tlr4 mutation that underlies the IL-12 unresponsiveness and contributes to the LPS resistance and impaired innate immune response in this strain.

Animals↗
PubMed2001

TNF-alpha hyper-responses to Gram-negative and Gram-positive bacteria in Propionibacterium acnes primed or Salmonella typhimurium infected mice.

IFN-gamma-dependent hypersensitivity to LPS is inducible in mice by infection or pre-treatment with killed bacteria. Hypersensitive mice exhibit enhanced inflammatory responses to LPS, including the overproduction of TNF-alpha. Using Lps(n) BALB/c and Lps(d) BALB/c/l mice, primed with Propionibacterium acnes or infected with Salmonella typhimurium, we show that concurrently to hypersensitivity to LPS, a hypersensitivity to other constituents of killed Gram-negative or Gram-positive bacteria and to staphylococcal enterotoxin B (SEB) develops. The TNF-alpha hyper-responses in sensitized mice induced by different Gram-positive bacteria, are generally weaker than those by Gram-negative bacteria and vary significantly, due to the absence of a common, LPS-equivalent component. Using IFN-gamma R(-/-) and the respective wild-type mice, we demonstrate that although sensitization to LPS and killed Listeria monocytogenes is exclusively IFN-gamma-dependent, an IFN-gamma-independent, moderate sensitization to certain TNF-alpha-inducing constituents in bacteria may develop in parallel.

Animals↗
PubMed2000

Bacterial induction of beta interferon in mice is a function of the lipopolysaccharide component.

We investigated the reason for the inability of lipopolysaccharide (LPS)-resistant (Lps-defective [Lps(d)]) C57BL/10ScCr mice to produce beta interferon (IFN-beta) when stimulated with bacteria. For this purpose, the IFN-beta and other macrophage cytokine responses induced by LPS and several killed gram-negative and gram-positive bacteria in LPS-sensitive (Lps-normal [Lps(n)]; C57BL/10ScSn and BALB/c) and Lps(d) (C57BL/10ScCr and BALB/c/l) mice in vitro and in vivo were investigated on the mRNA and protein levels. In addition, double-stranded RNA (dsRNA) was used as a nonbacterial stimulus. LPS and all gram-negative bacteria employed induced IFN-beta in the Lps(n) mice but not in the Lps(d) mice. All gram-positive bacteria tested failed to induce significant amounts of IFN-beta in all four of the mouse strains used. As expected, all other cytokines tested (tumor necrosis factor alpha, interleukin 1alpha [IL-1alpha], IL-6, and IL-10) were differentially induced by gram-negative and gram-positive bacteria. Stimulation with dsRNA induced IFN-beta and all other cytokines mentioned above in all mouse strains, regardless of their LPS sensitivities. The results suggest strongly that LPS is the only bacterial component capable of inducing IFN-beta in significant amounts that are readily detectable under the conditions used in this study. Consequently, in mice, IFN-beta is inducible only by gram-negative bacteria, but not in C57BL/10ScCr or other LPS-resistant mice.

Animals↗
PubMed1998

Cell cycle arrest in ovarian cancer cell lines does not depend on p53 status upon treatment with cytostatic drugs.

Human ovarian cancer cell lines with different p53 status were investigated for p53-dependency of cell cycle arrest upon treatment with cytostatic drugs. For this purpose commonly used anti-cancer drugs and a novel anti-cancer drug, gemcitabine, were applied. Cell cycle arrest was dependent on the drug dose used, as observed for all anti-cancer drugs applied, but not related to functional p53. With the exception of the etoposide-effected G2/M arrest at high concentrations, which seems to depend on functional p53, since it did not occur in cells with inactive p53. Only in cells with wt p53 and quasi-wild-type, p53 accumulated in the nucleus upon drug treatment with all anti-cancer agents applied. The level of accumulation was drug dose-dependent for each drug tested. The accumulated p53 was biochemically active, as measured in a transient transfection assay upon treatment with gemcitabine, cisplatin, etoposide, and Taxol. Activity was dependent on the drug dose applied and proportional to the level of accumulated p53, except for Taxol-induced p53 accumulation which correlated inversely with p53 biochemical activity. Apoptosis was estimated by in situ end labeling by biotinylated dUTP with the terminal deoxyribonucleotidyl transferase assay. Apoptosis occured after arrest at the various phases of the cell cycle in all cell lines tested, depending on the drug and the drug dose used. Nevertheless, cells with wt p53 exhibited the highest fraction of apoptotic cells.

Antimetabolites, Antineoplastic↗
PubMed1992

CD5-negative cell mediated experimental hypersensitivity pneumonitis.

Experimental hypersensitivity pneumonitis (EHP) can be transferred to Strain 2 guinea pigs by peripheral lymph node (PLN) cells cultured in vitro with antigen. The phenotype of the active cells has not been delineated. In addition, it is not known if cultured lung-associated lymph node (LALN) cells can transfer EHP. PLN and LALN cells from donor animals were cultured with a soluble extract of Micropolyspora faeni (10 micrograms/ml), and blast cells were isolated by centrifugation over Percoll gradients. Cultured PLN cells were passed through nylon wool columns, and the adherent and nonadherent fractions were tested for their ability to transfer EHP. PLN blast cell populations were depleted of CD5+ cells by treatment with monoclonal anti CD5 antibody (8BE6) and complement. Syngeneic recipients received media or LALN or PLN blast cells treated with antibody plus complement, media, or complement intravenously. Recipients were challenged intratracheally with M. faeni 48 h after the cell transfer, and they were killed 4 days later. The nonadherent PLN cell population was enriched for CD5+ (T) cells and depleted of surface immunoglobulin-positive (SIg+) cells. Treatment of the PLN blast cell population with 8BE6 and complement decreased CD5+ cells from 25 to 4% and increased SIg+ cells from 62 to 80%. All animals were maintained in HEPA-filtered air. Randomly selected microscopic fields of the lung (250/animal) were judged to be normal or abnormal without knowledge of treatment. There was a low level of pulmonary response to an intratracheal challenge of M. faeni in media recipients. There was a substantial increase (p less than 0.01) of the extent of pulmonary abnormalities in the animals receiving cultured PLN cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Alveolitis, Extrinsic Allergic↗
PubMed1987

Inoculation of blood culture bottles with ascitic fluid. Improved detection of spontaneous bacterial peritonitis.

The observation that only 42% of the cases of suspected spontaneous bacterial peritonitis at the University of New Mexico, Albuquerque, had positive cultures prompted a change in ascitic fluid culture technique such that a large volume (10 mL in toto) of ascitic fluid was inoculated into blood culture bottles at the bedside. This new method of culture increased the percentage of cases with positive cultures to 91% and decreased the interval between inoculation of the culture and detection of bacterial growth. This is a more sensitive method of culture than the conventional method in detecting spontaneous bacterial peritonitis.

Ascitic Fluid↗
PubMedDate not supplied

Role of lipopolysaccharide susceptibility in the innate immune response to Salmonella typhimurium infection: LPS, a primary target for recognition of Gram-negative bacteria.

Lipopolysaccharide is an important recognition marker by virtue of which the innate immune system senses and reacts against Gram-negative bacteria invading the LPS susceptible host. This review deals with the factors affecting LPS susceptibility and with the role of the latter in the course and outcome of Salmonella typhimurium infection.

Animals↗
PubMedDate not supplied

Reduced susceptibility of methicillin-resistant Staphylococcus aureus to cetylpyridinium chloride and chlorhexidine.

Sensitivities of 120 strains of Staphylococcus aureus to methicillin, cetylpyridinium chloride (CPC) and chlorhexidine (CH) were measured by the agar dilution technique. The MICs for CPC and CH were < or = 2 micrograms/ml in 93 and 83% of methicillin-sensitive S. aureus, respectively, and > 2 micrograms/ml in 81 and 83% of methicillin-resistant S. aureus (MRSA), respectively. Overall, the MICs for CPC and CH were 5-10 times greater in the methicillin-resistant than in the methicillin-sensitive strains (p < 0.001). The MICs for CPC and CH also predicted the relative susceptibilities of S. aureus strains to the bactericidal action of these agents in growth and time-kill studies. The possibility that antiseptics and disinfectants contribute to the selection and maintenance of multiply resistant MRSA is considered.

Anti-Infective Agents, Local↗