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At least 847 records · Page 47Linked to original sources
PubMed2000

Differential requirement for the stress-activated protein kinase/c-Jun NH(2)-terminal kinase in RNAdamage-induced apoptosis in primary and in immortalized fibroblasts.

Onconase, an anticancer ribonuclease, damages cellular tRNA and causes caspase-dependent apoptosis in targeted cells (M. S. Iordanov, O. P. Ryabinina, J. Wong, T. H. Dinh, D. L. Newton, S. M. Rybak, and B. E. Magun. Cancer Res. 60, 1983-1994, 2000). The proapoptotic action of onconase depends on its RNase activity, but the molecular mechanisms leading to RNA damage-induced caspase activation are completely unknown. In this study, we have investigated whether onconase activates two signal-transduction pathways commonly stimulated by conventional chemo- and radiotherapy, namely the stress-activated protein kinase (SAPK) cascade and the pathway leading to the activation of nuclear factor-kappa B (NF-kappaB). We found that, in all cell types tested, onconase is a potent activator of SAPK1 (JNK1 and JNK2) and SAPK2 (p38 MAP kinase), but that it is incapable of activating NF-kappaB. Inhibition of p38 MAP kinase activity with a pharmacological inhibitor, SB203580, demonstrated that p38 MAP kinase is not required for onconase cytotoxicity. Using explanted fibroblasts from mice that contain targeted disruption of both jnk1 and jnk2 alleles, we found that JNKs are important mediators of onconase-induced cytotoxicity. Surprisingly, following the immortalization of these same cells with human papilloma virus (HPV16) gene products E6 and E7, additional proapoptotic pathways (exclusive of JNK) were provoked by onconase. Our results demonstrate that onconase may activate proapoptotic pathways in tumor cells that are not able to be accessed in normal cells. These results present the possibility that the cytotoxic activity of onconase in normal cells may be reduced by blocking the activity of JNKs.

Apoptosis↗
PubMed1975

The metastatic spread of myeloma and leukemias in men.

This investigation was based on the analysis of 580 autopsy records of patients with plasma cell myeloma or any type of leukemia. The data were collected by the Department of Pathology at Roswell Park Memorial Institute between 1956 and 1965. The primary purpose of this paper was to elucidate the metastatic process in myelomas and different types of leukemia. Two mutually exclusive hypotheses were tested, i.e. whether the spread of a cancer from the primary tumor throughout the body was due to a simple diffusion or if a cascade process took place. The basic definition of the "cascade or multistep" diffusion of cancer is that it takes place in steps; that is, at least one intermediate step is usually required for the disease to progress from the primary tumor to generalized dissemination throughout the body. It appeared that either the liver or spleen are the two major diffusing sites; that is, no generalized metastasis occurs unless the spleen and/or liver are seeded first.

Autopsy↗
PubMed2005

Gemcitabine aerosol: in vitro antitumor activity and deposition imaging for preclinical safety assessment in baboons.

AIM: To characterize gemcitabine aerosol, its in vitro activity against lung cancer cells, its deposition, and tolerance in a non-human primate model. METHODS: In vitro cytotoxicity of nebulized gemcitabine against NCI-H460 and A549 lung cancer cells was tested using a growth inhibition assay and compared with non-nebulized gemcitabine. The (99m)Tc-DTPA-radiolabeled gemcitabine aerosol was characterized by cascade impaction and the gemcitabine mass/(99m)Tc activity relationship was established for further quantitative nuclear imaging. Nine weekly inhalations at a target dose of 1 mg/kg body weight of gemcitabine were performed in three baboons using dynamic scintigraphic acquisitions for continuous monitoring of gemcitabine delivery during inhalation. Gemcitabine plasma concentrations were measured during the first inhalation. RESULTS: Growth inhibition assays for both NCI-H460 and A549 cells did not differ between nebulized and non-nebulized gemcitabine. Aerosol characterization showed a particle mass median aerodynamic diameter of 3.7+/-0.8 microm and a linear relationship between gemcitabine mass (y) and (99m)Tc activity (x) (y=0.82x - 10(-5), R (2)=0.88). No toxicity was observed after nine weekly inhalations of a mean dose of gemcitabine of 11.1 mg (88% of the target dose) as assessed from scintigraphic data. A dose-dependent peak plasma concentration of gemcitabine (20-74 ng/ml) was observed by the tenth minute of inhalation. CONCLUSIONS: We have characterized a gemcitabine aerosol suitable for intrathoracic airway deposition and demonstrated that jet nebulization does not alter the cytotoxic properties of the drug. In a primate model, we have developed a scintigraphic procedure for the monitoring of aerosol deposition, and we have demonstrated the safety of nine weekly aerosol administrations of gemcitabine.

Aerosols↗
PubMed2006

Nicotinic receptor agonists as neuroprotective/neurotrophic drugs. Progress in molecular mechanisms.

In the present work we reviewed recent advances concerning neuroprotective/neurotrophic effects of acute or chronic nicotine exposure, and the signalling pathways mediating these effects, including mechanisms implicated in nicotine addiction and nAChR desensitization. Experimental and clinical data largely indicate long-lasting effects of nicotine and nicotinic agonists that imply a neuroprotective/neurotrophic role of nAChR activation, involving mainly alpha7 and alpha4beta2 nAChR subtypes, as evidenced using selective nAChR agonists. Compounds interacting with neuronal nAChRs have the potential to be neuroprotective and treatment with nAChR agonists elicits long-lasting neurotrophic effects, e.g. improvement of cognitive performance in a variety of behavioural tests in rats, monkeys and humans. Nicotine addiction, which is mediated by interaction with nACh receptors, is believed to involve the modification of signalling cascades that modulate synaptic plasticity and gene expression. Desensitization, in addition to protecting cells from uncontrolled excitation, is recently considered as a form of signal plasticity. nAChR can generate these longe-lasting effects by elaboration of complex intracellular signals that mediate medium to long-term events crucial for neuronal maintenance, survival and regeneration. Although a comprehensive survey of the gene-based molecular mechanisms that underlie nicotine effects has yet not been performed a growing amount of data is beginning to improve our understanding of signalling mechanisms that lead to neurotrophic/neuroprotective responses. Evidence for an involvement of the fibroblast growth factor-2 gene in nAChR mechanisms mediating neuronal survival, trophism and plasticity has been obtained. However, more work is needed to establish the mechanisms involved in the effects of nicotinic receptor subtype activation from cognition-enhancing and neurotrophic effects to smoking behaviour and to determine more precisely the therapeutic objectives in potential nicotinic drug treatments of neurodegenerative diseases.

Animals↗
PubMed1994

Drug-metabolizing enzymes in ligand-modulated transcription.

Genes encoding many of the so-called drug-metabolizing enzymes (DMEs) are present in both prokaryotes and eukaryotes, suggesting that these genes arose on this planet more than 3.5 billion years ago--long before animal-plant divergence (estimated to be about 1.2 billion years ago) and long before the use and commercial development of drugs. What, therefore, are the real functions of DMEs? Several years ago I proposed that DMEs are upstream in the regulatory cascade of numerous signal transduction pathways, i.e. necessary for maintaining physiologically "safe", or "acceptable", steady-state levels of all small non-protein endogenous ligands (M(r) = 250 +/- 200) in each cell. Innumerable foreign chemicals and drugs mimic these small endogenous ligands, thus binding to a particular receptor and acting either as an agonist or antagonist in activating or inhibiting genes effecting growth, differentiation, apoptosis, homeostasis and neuroendocrine functions. Discussed in this review are additional examples consistent with this theory and not described in previous reviews, including: (i) insect-plant symbiosis; (ii) "cross-talk" amongst genes in the aromatic hydrocarbon-responsive [Ah] battery; (iii) signal transduction pathways involving the arachidonic acid cascade; and (iv) the explanation in carcinogen-screening studies as to why a maximum, or half maximum, tolerated dose (MTD, MTD50) of many test compounds might cause cell division and tumorigenesis in experimental animals.

Animals↗
PubMed1986

Clofazimine-mediated stimulation of prostaglandin synthesis and free radical production as novel mechanisms of drug-induced immunosuppression.

The effects of clofazamine (3-(p-chloroanilino)-10-(p-chlorophenyl)-2, 10-dihydro-2-(isopropylimino)-phenazine) at concentrations of 0.625-20 micrograms/ml on the mitogen-induced transformation, luminol-enhanced chemiluminescence, arachidonic acid metabolism and sulphydryl content of human mononuclear leucocytes (MNL) were investigated in vitro. The drug at all concentrations tested decreased MNL sulphydryl content and inhibited mitogen-induced transformation. Clofazimine increased the spontaneous luminol-enhanced chemiluminescence and activated the arachidonic acid cascade in MNL. The anti-oxidants ascorbic acid and cysteine and the prostaglandin (PG) synthesis inhibitor indomethacin were used individually and in combination to identify the primary mediators of the anti-proliferative effects of clofazimine on MNL. Combinations of an anti-oxidant with a PG synthesis inhibitor completely protected MNL from clofazimine mediated inhibition of mitogen-induced transformation. These results show that the anti-proliferative activity of clofazimine is related to both the pro-oxidative and PG synthesis enhancing effects of the drug on MNL.

Clofazimine↗
PubMed2004

Stability of plasma-treated silicone rubber and its influence on the interfacial aspects of blood compatibility.

Medical-grade polydimethylsiloxane elastomer was subjected to low-powered plasma treatment in the presence of four different gases: O(2), Ar, N(2) and NH(3). Changes to the surface chemistry immediately after processing and the stability of the treatments following ageing in phosphate buffered saline or air for up to 1 month were investigated using X-ray photoelectron spectroscopy and dynamic contact angle analysis. Changes in surface morphology were assessed using optical microscopy and atomic force microscopy. All treatments resulted in an increase in wettability, attributed to major changes in chemistry combined with modest etching. Furthermore, the primary site of attack of the plasma species appeared to be dependent upon the feed gas implemented. The two main chemical changes observed after ageing were due to reactions with the storage media and relaxation processes resulting in further changes in wettability. The influence of the surface modifications on the blood compatibility of the materials was investigated by assessing contact phase activation using a partial thromboplastin time assay. It was demonstrated that the O(2) and Ar plasma treatments reduced the performance of the silicone but the N(2) and NH(3) treatments had a significantly beneficial effect on the activation of the coagulation cascade.

Biocompatible Materials↗
PubMed2006

Multiple seropathotypes of verotoxin-producing Escherichia coli (VTEC) disrupt interferon-gamma-induced tyrosine phosphorylation of signal transducer and activator of transcription (Stat)-1.

Verotoxin-producing Escherichia coli (VTEC) O157:H7 inhibits interferon-gamma-stimulated tyrosine phosphorylation of signal transducer and activator of transcription (Stat)-1 in epithelial cells, independent of Verotoxins and the locus of enterocyte effacement pathogenicity island. Although E. coli O157:H7 is the major cause of disease in humans, non-O157:H7 VTEC also cause human disease. However, the virulence properties of non-O157:H7 VTEC are less well characterized. The aims of this study were to define the ability of VTEC strains of differing seropathotypes (classified as A-E) to inhibit interferon-gamma stimulated Stat1-phosphorylation and to further characterize the bacterial-derived inhibitory factor. Confluent T84 and HEp-2 cells were infected with VTEC strains (MOI 100:1, 6h, 37 degrees C), and then stimulated with interferon-gamma (50 ng/mL) for 0.5h at 37 degrees C. Whole-cell protein extracts of infected cells were collected and prepared for immunoblotting to detect tyrosine phosphorylation of Stat1. The effects of E. coli O55 strains, the evolutionary precursors of VTEC, on Stat1-tyrosine phosphorylation were also determined. The effects of isogenic mutants of O-islands 47 and 122 were tested to determine the role of genes encoded on these putative pathogenicity islands in mediating VTEC inhibition of the interferon-gamma-Stat1 signaling cascade. To evaluate potential mechanism(s) of inhibition, VTEC O157:H7-infected cells were treated with pharmacological inhibitors, including, wortmannin and LY294002. Relative to uninfected cells, Stat1-tyrosine phosphorylation was significantly reduced after 6h infection of both T84 and HEp-2 cells by VTEC strains of all five seropathotypes. E. coli O55 strains, but not enteropathogenic E. coli (EPEC), also caused inhibition of Stat1-tyrosine phosphorylation, suggesting that this effect was acquired early in the evolution of VTEC. Stat1-activation did not recover in epithelial cells infected with isogenic mutants of O-islands 47 and 122, indicating that the inhibitory factor was not contained in these genomic regions. Stat1-phosphorylation remained intact when VTEC-infected cells were treated with wortmannin (0-100 nM), but not by treatment with the more specific PI3-kinase inhibitor, LY294002. Inhibition of interferon-gamma stimulated Stat1-tyrosine phosphorylation by VTEC of multiple seropathotypes indicates the presence of a common inhibitory factor that is independent of bacterial virulence in humans. The results of treatment with wortmannin suggest that the bacterial-derived inhibitory factor employs host cell signal transduction to mediate inhibition of Stat1-activation.

Androstadienes↗
PubMed1999

Human single-chain Fv immunoconjugates targeted to a melanoma-associated chondroitin sulfate proteoglycan mediate specific lysis of human melanoma cells by natural killer cells and complement.

Two antimelanoma immunoconjugates containing a human single-chain Fv (scFv) targeting domain conjugated to the Fc effector domain of human IgG1 were synthesized as secreted two-chain molecules in Chinese hamster ovary and Drosophila S2 cells, and purified by affinity chromatography on protein A. The scFv targeting domains originally were isolated as melanoma-specific clones from a scFv fusion-phage library, derived from the antibody repertoire of a vaccinated melanoma patient. The purified immunoconjugates showed similar binding specificity as did the fusion-phage clones. Binding occurred to human melanoma cells but not to human melanocytes or to several other types of normal cells and tumor cells. A 250-kDa melanoma protein was immunoprecipitated by the immunoconjugates and analyzed by mass spectrometry, using two independent procedures. A screen of protein sequence databases showed an exact match of several peptide masses between the immunoprecipitated protein and the core protein of a chondroitin sulfate proteoglycan, which is expressed on the surface of most human melanoma cells. The Fc effector domain of the immunoconjugates binds natural killer (NK) cells and also the C1q protein that initiates the complement cascade; both NK cells and complement can activate powerful cytolytic responses against the targeted tumor cells. An in vitro cytolysis assay was used to test for an immunoconjugate-dependent specific cytolytic response against cultured human melanoma cells by NK cells and complement. The melanoma cells, but not the human fibroblast cells used as the control, were efficiently lysed by both NK cells and complement in the presence of the immunoconjugates. The in vitro results suggest that the immunoconjugates also could activate a specific cytolytic immune response against melanoma tumors in vivo.

Animals↗
PubMed1996

The U.S. Pharmacopeia's role in establishing public standards for aerosols.

USP, a non-governmental and not-for-profit organization, establishes public standards for and information on articles used in the healing art through an elected body of Committee of Revision comprised of scientific experts in the fields of medicine, pharmacy, pharmaceutical chemistry, analytical chemistry, and others. To be consistent with latest developments in manufacturing and analytical technologies, USP has a continuous revision policy. Major revisions to the General Chapter on Aerosols officially adopted recently that include detailed descriptions of multi-stage cascade impactor apparatus, two different single-stage impaction devises used in particle size of determination, uniformity of assage units, minimum fill and other tests are discussed. Further revisions to the chapter on Aerosols under consideration such as test procedure for nebulizers, extractables and particulate matter are discussed.

Administration, Inhalation↗
PubMed2005

Effects of NH4Cl intake on renal growth in rats: role of MAPK signalling pathway.

BACKGROUND: There is a surprising lack of experimental data on the mechanisms of NH4Cl-induced chronic metabolic acidosis which causes kidney hypertrophy. The NH4Cl treatment results in an absolute increase in kidney mass. Despite findings to indicate a close interaction between NH4Cl-induced chronic metabolic acidosis and renal enlargement, the role of the stimulated serine kinase cascade, mediated by the stepwise activation of extracellular signal-regulated kinase (ERK) signalling, on kidney hypertrophy has not yet been investigated. METHODS: To test this hypothesis, the present study was undertaken to further explore the possible involvement of mitogen-activated protein kinase (MAPK) signalling pathway in renal growth in chronic NH4Cl-treated rats by western blot analysis. RESULTS: Our major findings are as follows: (1) Urinary sodium excretion significantly increased during the early phases of NH4Cl-induced acidosis, (2) This occurrence is associated with sustained renal hypertrophy, and (3) sustained basal phosphorylation of IRS-1, Shc, and MAPK/ERKs in acidotic kidneys. CONCLUSIONS: The present study confirms that NH4Cl-induced acidosis causes disturbances in renal sodium handling. In addition, these findings demonstrate a sustained pre-stimuli activation of kidney MAPK/ERKs signalling pathways in the NH4Cl-treated rats that may correlate with an increased rate of kidney hypertrophy and a transient renal tubule inability to handle sodium. Thus, the altered renal electrolyte handling may result from a reciprocal relationship between the level of renal tubule metabolic activity and ion transport. In addition, the study shows that the appropriate regulation of tyrosine kinase protein phosphorylation, and its downstream signal transduction pathway, plays an important role on renal growth in the NH4Cl-treated rats.

Acidosis, Renal Tubular↗
PubMed1995

Construction and behavior of biologically contained bacteria for environmental applications in bioremediation.

The survival of microorganisms can be predicted through the use of active biological containment systems. We have constructed contained Pseudomonas putida strains that degrade alkylbenzoates. The modified strain carries a fusion of the Plac promoter to the gef gene, which encodes a killing protein. Expression from Plac is controlled through a regulatory cascade, so that Plac is switched on or off by the absence or presence of alkylbenzoates, respectively. Similar uncontained strains were also constructed and tested as a control. Contained and uncontained strains were genetically stable, and their survival and functionality in soil microcosms were as expected. Both contained and uncontained strains survived well in soils supplemented with alkylaromatics, whereas survival of the contained strain in soil microcosms without methylbenzoates was markedly reduced, in contrast to the control strain, which survived in these soils in the absence of alkylbenzoates. The TOL plasmid was transferred in soils between Pseudomonas strains but was not able to mobilize the elements of the containment system.

Bacteria↗
PubMed1990

IgG and IgA subclass distribution of total immunoglobulin and rheumatoid factors in rheumatoid tissue plasma cells.

The subclass distribution of IgG and IgA plasma cells, and in IgG and IgA rheumatoid factor (RF) producing cells was studied in sections of synovial tissue from seropositive RA and various types of seronegative arthritis, including ankylosing spondylitis, psoriatic arthritis, and Reiter's syndrome. The study was performed with immunofluorescence technique and monoclonal IgG and IgA subclass specific antibodies. IgG RF producing cells were identified by their ability to bind and activate factors both in the early (C3) and late (C5b-9) part of the complement cascade. IgA RF cells were identified by double staining experiments with heat-aggregated IgG and monoclonal antibodies to IgA subclasses. In 23 tissues tested for total IgG, IgG1 cells were usually predominant, while the frequency of IgG3 cells was usually higher than that of IgG2. In 19 tissues also tested for IgA, both IgA subclasses were present in all tissues. IgA1 plasma cells were always predominant, with a mean ratio of IgA1 to IgA2 cells of approximately 10. In the 13 tissues tested for RF-producing cells, the highest frequency of IgG RF cells was found among the IgG3 cells, followed by IgG1 and IgG2. IgA RF cells were found in only one case, all cells being IgA1.

Antigen-Antibody Complex↗
PubMed2000

[Corticotherapy in severe infectious states].

Septic shock is one of the leading cause of death in modern countries. Scientists have made huge improvement in the understanding of mechanisms of inflammation, and the sequence of activation of the various pro and anti-inflammatory markers is now well known. By contrary, physicians have failed to improve survival from septic shock, in spite of the development of specific targets of the various points of the cytokine cascade sought to have a key role in host survival to sepsis. Corticosteroids were among the first anti-inflammatory drugs, which have been tested in high quality randomised controlled trials. These trials clearly showed that patients with septic shock are unlikely to benefit from a short course of a large dose of an anti-inflammatory steroid. More recent findings highlighting the role of the integrity of the hypothalamic-pituitary -adrenal axis to appropriately respond to a septic insult, have led to a reappraisal of the use of steroids in septic shock. Several high quality randomised controlled trials have evaluated the efficacy and safety of a prolonged treatment with low dose hydrocortisone in severe sepsis. These trials strongly suggested that this strategy of corticotherapy reduced the morbidity of septic shock and may favourably affect survival from septic shock.

Adrenal Cortex Hormones↗
PubMedDate not supplied

Susceptibility to mycobacterial infections due to interferon-gamma and interleukin-12 pathway defects.

A case of interferon-gamma (IFN-gamma)/interleukin-12 (IL-12) pathway defect is presented. Pathophysiology, clinical characteristics, diagnostic test, and case management are reviewed. Clinical Pearls and Pitfalls include: (1) A high probability of a defect in the IFN-gamma/IL-12 cascade exists in patients with disseminated or recurrent infection due to poorly pathogenic mycobacteria or systemic infections caused by non-typhi Salmonella species that are persistent and recurrent despite antibiotic therapy. (2) Although less frequent, patients with impaired IFN-gamma/IL-12 mediated immunity are more susceptible to cytomegalovirus, human herpesvirus 8, herpes simplex virus, Listeria monocytogenes, and Histoplasma capsulatum.

Child↗
PubMed1986

Hydrogen peroxide induced pulmonary vasoconstriction in isolated rat lungs is attenuated by U60,257, a leucotriene synthesis blocker.

Reactive oxygen metabolites cause pulmonary vasoconstriction and activate arachidonic acid metabolism. We proposed that hydrogen peroxide, generated enzymatically in an insolated rat lung model, would cause vasoconstriction which was independent of circulating cells, but dependent on activation of the arachidonic acid cascade. Although hydrogen peroxide caused an increase in lung effluent thromboxane B2 concentration, indomethacin did not inhibit hydrogen peroxide induced vasoconstriction. In order to test the hypothesis that hydrogen peroxide activates the 5-lipoxygenase pathway, lung effluents were analyzed for 5-hydroxy-eicosatetranoic acid (5-HETE) using a sensitive, highly specific mass spectrometer technique. Glucose oxidase increased the 5-HEFE effluent concentrations and this was prevented by U60,257. We therefore conclude that hydrogen peroxide stimulates the 5-lipoxygenase pathway and that substances derived from this pathway are at least in part responsible for the hydrogen peroxide induced vasoconstriction in isolated rat lungs.

Animals↗
PubMed1998

Protein kinase C and IP3 in photoresponses of functionally intact rod outer segments: constraints about their role.

Protein kinase C and polyphosphoinositide metabolism are reported to affect light-activated processes in cell free systems. To investigate their role in phototransduction under more physiological conditions the effects of nonhydrolyzable inositol trisphosphate (IP3) analogs as well as of protein kinase C and phospholipase C inhibitors on the characteristics of the electrical light response were studied. Rod outer segments were dialyzed in whole-cell voltage clamp and photoresponses in the presence and absence of the tested compounds were compared. None of the compounds influenced the light responses suggesting that neither IP3 nor protein kinase C participate in the phototransduction cascade. A number of different proposals about the participation of protein kinase C and inositol trisphosphate (IP3) in the phototransduction process based on a wide variety of in vitro experiments should therefore be reevaluated.

Animals↗