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At least 613 records · Page 34Linked to original sources
PubMed2000

Akt-dependent antiapoptotic action of insulin is sensitive to farnesyltransferase inhibitor.

CHO cells expressing the human insulin receptors (IR) were used to evaluate the effect of the potent farnesyltransferase inhibitor, manumycin, on insulin antiapoptotic function. Cell treatment with manumycin blocked insulin's ability to suppress pro-apoptotic caspase-3 activity which led to time-dependent proteolytic cleavage of two nuclear target proteins. The Raf-1/MEK/ERK cascade and the serine/threonine protein kinase Akt are two survival pathways that may be activated in response to insulin. We tested the hypothesis that inhibition of farnesylated Ras was causally related to manumycin-induced apoptosis and showed that the response to manumycin was found to be independent of K-Ras function because membrane association and activation of endogenous K-Ras proteins in terms of GTP loading and ERK activation were unabated following treatment with manumycin. Moreover, blocking p21Ras/Raf-1/MEK/ERK cascade by the expression of a transdominant inhibitory mSOS1 mutant in CHO-IR cells kept cells sensitive to the antiapoptotic action of insulin. Insulin-dependent activation of Akt was blocked by 4 h treatment with manumycin (P < 0.01), a kinetic too rapid to be explained by Ras inhibition. This study suggests that the depletion of short-lived farnesylated proteins by manumycin suppresses the antiapoptotic action of insulin at least in part by disrupting Akt activation but not that of the K-Ras/Raf-1/ERK-dependent cascade.

Alkyl and Aryl Transferases↗
PubMed2007

Influenza virus host resistance model.

Host resistance (HR) models are used to evaluate the effect of a test article on clearance of an infectious microorganism in order to assess total immunocompetence. HR models serve as biomarkers of net immunological health or immunological well-being. Immunotoxicity can result either in an impaired clearance of an infectious agent, increased susceptibility to an opportunistic microorganism, prevention of immunization, or exacerbation of latent viral infections. The purpose of immunotoxicity testing is to obtain data that is meaningful for safety assessment, and for immunosuppression the major objective is to determine the significance with respect to increased susceptibility to infectious disease. Host resistance models provide the only sure method of examining the influence of test articles on the functional integrity of the immune system and its ability to eliminate pathogenic microorganisms and tumor cells. They provide the means to directly assess the functional reserve of the immune system. Clearance of influenza virus requires an intact and functional immune system that incorporates a cascade of immune responses. Mechanistic studies can be included in the influenza virus host resistance model by measuring the effect of a test article on innate immunity (cytokine and interferon production, macrophage function, and natural killer (NK) cell function) and acquired or adaptive immunity (cytotoxic T lymphocyte (CTL) activity as well as influenza-specific IgM and/or IgG antibody).

Animals↗
PubMedDate not supplied

Implantable defibrillators are preferable to pharmacologic therapy for patients with ventricular tachyarrhythmias: an antagonist's viewpoint.

Despite their intuitive appeal, implantable cardioverter defibrillator s (ICDs) will require testing in randomized studies to establish their relative value as compared with antiarrhythmic drugs in patients with life-threatening ventricular tachyarrhythmias (ventricular tachycardia/ventricular fibrillation [VT/VF]). In these studies, only total mortality is an acceptable primary end point. Lessons from recent drug studies (CAST, ESVEM, CASCADE) have shown that class-III/beta-receptor antagonist therapy is superior to class-I drugs selected by electrophysiologic or Holter monitor testing. Thus, sotalol or amiodarone should now be considered first-line drugs for VT/VF therapy. Advantages of contemporary drug therapy for VT/VF include wide experience among clinicians, progressively better drugs, lower cost, universal availability, greater flexibility in use (easy to start, titrate, and stop), ability to suppress (not just terminate) events, and favorable effect on disease progression (eg, beta-blockade effects in cardiomyopathy and ischemic heart disease). Recent matched observational studies and a small randomized experience (CASH) suggest near equivalence in total mortality in ICD and drug-treated groups. Until or unless modified by the results of large, ongoing, randomized trials (AVID, CIDS), contemporary antiarrhythmic drug therapy has much to be recommended as first-line, standard treatment for patients with VT/VF. Even in patients receiving ICDs, added drug therapy is frequently indicated.

Anti-Arrhythmia Agents↗
PubMed2006

Involvement of c-Met/hepatocyte growth factor pathway in cholangiocarcinoma cell invasion and its therapeutic inhibition with small interfering RNA specific for c-Met.

BACKGROUND: Hepatocyte growth factor receptor (c-Met) plays an important role in many functions of cancer cells. We examined the roles of c-Met and its downstream signaling molecules in cholangiocarcinoma cell lines RMCCA1 and HuCCA1. MATERIALS AND METHODS: The expression of c-Met and their signaling cascades were determined in RMCCA1 and HuCCA1 cholangiocarcinoma cell lines by Western blotting. Small interfering RNA (siRNA) specific for c-Met was used to suppress the expression of c-Met. The proliferation, migration and invasion assay were tested in these cholangiocarcinoma cells treated with hepatocyte growth factor (HGF). RESULTS: Activation of c-Met with HGF triggered the signaling via the ERK cascade mediated by sequential phosphorylation of MEK1/2 and MAPK and induction of cholangiocarcinoma cell invasion. The expression of c-Met in cholangiocarcinoma cells was suppressed by treatment with small interfering RNA (siRNA) specific for c-Met, and resulted in decrease in phosphorylation of MEK1/2. Furthermore, treatment with siRNA specific for c-Met or MEK inhibitor U0126 inhibited cholangiocarcinoma cell invasion induced by HGF. CONCLUSIONS: These results indicated that HGF and c-Met involved in the mechanism of cholangiocarcinoma cell invasion. It implies a potential role for the inhibition of c-Met in the treatment of cholangiocarcinoma.

Actin Cytoskeleton↗
PubMed2003

Blood test detecting autoantibodies to N-methyl-D-aspartate neuroreceptors for evaluation of patients with transient ischemic attack and stroke.

BACKGROUND: Stroke is a multisystemic disorder that includes mechanisms of thrombosis and neurotoxic coupling. Key metabolites of the molecular cascade following biochemical events appear simultaneously in brain tissue, the blood-brain barrier, and brain vessels, activating the immune system and generating autoantibodies (aAbs) to brain-specific antigens. We developed an ELISA blood test to measure aAbs to a subtype of N-methyl-D-aspartate (NMDA) receptors, which are the key markers of neurotoxicity underlying cerebral ischemia. We investigated the diagnostic accuracy of serum aAbs to NR2A/2B, a subtype of NMDA receptors, in assessing transient ischemic attack (TIA) and ischemic stroke (IS) and its ability to distinguish cerebral ischemia from intracerebral hemorrhage (ICH). METHODS: Autoantibodies to NR2A/2B were measured in 360 serum samples: 105 from TIA/stroke patients and 255 from controls, including patients with controlled hypertension/atherosclerosis and gender- and age-matched healthy individuals. RESULTS: Patients with TIA (n = 56) and acute IS (n = 31) had significantly higher NR2A/2B aAb concentrations than controls (P <0.0001). The test sensitivities for TIA and IS were 95% and 97%, respectively, and predictive values were 86% and 91% at a cutoff point of 2.0 micro g/L. The area under the ROC curve was 0.99. Monitoring NR2A/2B aAbs within 72 h differentiated IS and ICH (P <0.001) and was confirmed by magnetic resonance imaging and computed tomography. CONCLUSIONS: NR2A/2B aAbs are independent and sensitive serologic markers capable of detecting TIA with a high posttest probability and, in conjunction with neurologic observation and neuroimaging, ruling out ICH. The test may help assess risk of TIA in routine general practice and may potentially be useful in assisting diagnosis of acute IS in the emergency setting.

Acute Disease↗
PubMed1997

Experimental evidence for a behavior-mediated trophic cascade in a terrestrial food chain.

Predators of herbivorous animals can affect plant populations by altering herbivore density, behavior, or both. To test whether the indirect effect of predators on plants arises from density or behavioral responses in a herbivore population, we experimentally examined the dynamics of terrestrial food chains comprised of old field plants, leaf-chewing grasshoppers, and spider predators in Northeast Connecticut. To separate the effects of predators on herbivore density from the effects on herbivore behavior, we created two classes of spiders: (i) risk spiders that had their feeding mouth parts glued to render them incapable of killing prey and (ii) predator spiders that remained unmanipulated. We found that the effect of predators on plants resulted from predator-induced changes in herbivore behavior (shifts in activity time and diet selection) rather than from predator-induced changes in grasshopper density. Neither predator nor risk spiders had a significant effect on grasshopper density relative to a control. This demonstrates that the behavioral response of prey to predators can have a strong impact on the dynamics of terrestrial food chains. The results make a compelling case to examine behavioral as well as density effects in theoretical and empirical research on food chain dynamics.

Journal Article↗
PubMed2005

Seasonal gonadal recrudescence in song sparrows: response to temperature cues.

Day length predicts changing of seasons at mid-latitudes, but additional environmental cues (e.g., temperature, rainfall) give more precise information about timing of food peaks critical for offspring survival. We tested the effects of temperature on seasonal reproductive development of male song sparrows (Melospiza melodia morphna) from two populations: the Western Washington coast (3 m) and Cascade Mountains (500-1220 m). Previous work has shown that the timing of gonadal recrudescence can differ between the two sites in the field by as much as two months. However, in the laboratory under identical controlled conditions, testes grow at the same rate. To test whether temperature alone could account for a portion of the variation we measured in the field, we captured birds from each site and held them in temperature controlled environmental chambers that mimicked temperatures experienced either in the mountains or on the coast. We increased day length on a natural schedule, and measured testis volume, levels of circulating androgens and prolactin, and song rates. Increasing day length stimulated gonadal growth in all groups. We found only modest effects of temperature on reproductive development. In the mountain birds colder, montane temperatures slowed rates of growth, delaying the onset of growth by one month. Since temperature changes more markedly during the early winter months in the mountains than on the coast, increasing temperature may be a more relevant cue in timing of reproduction in the mountain population. These data suggest that while temperature helps to explain some of the variation in reproductive timing of free living sparrows, another as yet untested cue in the field may play a more important role. Furthermore, our data suggest that individuals within the same species may rely on different proximate cues for reproductive timing depending on the specific habitat in which they live.

Analysis of Variance↗
PubMed1994

Deciphering the MAP kinase pathway.

MAP kinases (MAPK) are serine/threonine kinases which are activated by a dual phosphorylation on threonine and tyrosine residues. Their specific upstream activators, called MAP kinase kinases (MAPKK), constitute a new family of dual-specific threonine/tyrosine kinases, which in turn are activated by upstream MAP kinase kinase kinases (MAPKKK). These three kinase families are successively stimulated in a cascade of activation described in various species such as mammals, frog, fly, worm or yeast. In mammals, the MAP kinase module lies on the signaling pathway triggered by numerous agonists such as growth factors, hormones, lymphokines, tumor promoters, stress factors, etc. Targets of MAP kinase have been characterized in all subcellular compartments. In yeast, genetic epistasis helped to characterize the presence of several MAP kinase modules in the same system. By complementation tests, the relationships existing between phylogenetically distant members of each kinase family have been described. The roles of the MAP kinase cascade have been analyzed by engineering various mutations in the kinases of the module. The MAP kinase cascade has thus been implicated in higher eukaryotes in cell growth, cell fate and differentiation, and in low eukaryotes, in conjugation, osmotic stress, cell wall construct and mitosis.

Amino Acid Sequence↗
PubMedDate not supplied

2-[125I]iodomelatonin binding sites in the testis and ovary: putative melatonin receptors in the gonads.

Through the synthesis and secretion of the hormone, melatonin, the pineal has been assigned the role of synchronizing a reproductive response to appropriate environmental conditions. Theoretical melatonin target sites may occur at several levels of the hypothalamic-pituitary-gonadal hierarchy, including a direct action on the gonads. The availability of a biologically active radioligand, 2-[125I]iodomelatonin, has provided the opportunity to examine the possible direct melatonin action on the gonads. 2-[125I]Iodomelatonin binding sites were identified in the testes and ovaries of chickens, ducks and quail but were not measurable in mammalian gonads, with the exception of tree shrew testes. The avian gonadal 2-[125I]iodomelatonin binding sites were stable, saturable, reversible, specific and of high affinity. 2-[125I]Iodomelatonin appeared to label a single class of binding sites as evidenced by the linearity of Rosenthal analysis of the specific binding data, the Hill coefficients close to unity and the monophasic competition curves. The high affinity on the gonadal 2-[125I]iodomelatonin binding sites, characterized by apparent equilibrium dissociation constants in the low picomolar range, was in accordance with circulating levels of melatonin suggesting that they may be physiologically relevant. Autoradiography indicated that these 2-[125I]iodomelatonin binding sites were widely distributed throughout the testes but localized in ovarian follicles in the birds studied. Specific inhibition of testicular 2-[125I]iodomelatonin binding by a guanine nucleotide analog has provided evidence that the 2-[125I]iodomelatonin binding sites in chicken testes may be coupled to a guanine nucleotide binding protein-effector system, thus promoting the idea that testicular 2-[125I]iodomelatonin binding sites may mediate a cascade of intracellular events. Although no circadian rhythm in the density or affinity of 2-[125I]iodomelatonin binding in chicken ovaries was found, there was a decrease in 2-[125I]iodomelatonin binding affinity at middark in chicken testes with no change in the number of testicular 2-[125I]iodomelatonin binding sites. The present evidence is in line with the hypothesis of a direct melatonin action on the gonads and further investigations on the above problem will be rewarding.

Animals↗
PubMed2004

EGFR signaling attenuates Groucho-dependent repression to antagonize Notch transcriptional output.

Crosstalk between signaling pathways is crucial for the generation of complex and varied transcriptional networks. Antagonism between the EGF-receptor (EGFR) and Notch pathways in particular is well documented, although the underlying mechanism is poorly understood. The global corepressor Groucho (Gro) and its transducin-like Enhancer-of-split (TLE) mammalian homologs mediate repression by a myriad of repressors, including effectors of the Notch, Wnt (Wg) and TGF-beta (Dpp) signaling cascades. Given that there are genetic interactions between gro and components of the EGFR pathway (ref. 9 and P.H. et al., unpublished results), we tested whether Gro is at a crossroad between this and other pathways. Here we show that phosphorylation of Gro in response to MAPK activation weakens its repressor capacity, attenuating Gro-dependent transcriptional silencing by the Enhancer-of-split proteins, effectors of the Notch cascade. Thus, Gro is a new junction between signaling pathways, enabling EGFR signaling to antagonize transcriptional output by Notch and potentially other Gro-dependent pathways.

Animals↗
PubMedDate not supplied

[The centennial of blood coagulation doctrine].

For centuries, the mystery surrounding blood coagulation stimulated the curiosity of researchers. The knowledge about this function has increased notably in the last century and has permitted to understand numerous physiopatho logical phenomena in several hemorrhagic and thrombotic diseases, and has made it possible to develop diverse drugs of proved efficacy for prevention and therapy. All this was initiated in 1905, when Paul Morawitz published an extensive monograph on the four factors of blood coagulation known until then (fibrinogen, thrombin, thrombokinase, and calcium). In that work, he proposed a blood coagulation model in two stages: thrombin generation and fibrinogen coagulation. In the 1940s a true golden age in coagulation was started with the results of Quick's prothrombin time test, described in 1936, and since then the most employed coagulation test. Besides numerous factors involved in this function were discovered and classified. The discovery and introduction of heparin and coumarin in the anticoagulant therapeutics opened a measureless panorama for the arrival of new antithrombotic drugs. By the middle of the XX century, the mechanism of coagulation had been practically deciphered and diverse models based on sequential enzymatic function were proposed, called first chain reactions and in cascade reactions later. In the second half of the XX century, numerous regulatory mechanisms of coagulation were identified and diverse laboratory tests appeared that have allowed highly precise diagnoses of a variety of diseases. Blood separation techniques have permitted to produce factor concentrates for clinical use. With the identification of the genes that encode the synthesis of coagulation factors, it has been possible to produce them by means of molecular biology techniques, being the most significant the production of factors VIII, IX, and VII. The present model of coagulation is based on tissular factor activation and the participation of cells, concepts that were already implicit in the classical theory of Morawitz.

Blood Coagulation↗
PubMed1996

The response regulator-like protein Pos9/Skn7 of Saccharomyces cerevisiae is involved in oxidative stress resistance.

We have isolated mutants of Saccharomyces cerevisiae with an increased sensitivity to oxidative stress. All pos9 mutants (pos for peroxide sensitivity) were hypersensitive to methylviologene, hyperbaric oxygen or hydrogen peroxide, but grew similarly to the wild-type under all other conditions tested. Isolation and sequencing of the respective POS9 gene revealed that it was identical to SKN7. The predicted Skn7/Pos9 protein possesses a domain with high homology to prokaryotic response regulators. These regulatory proteins are part of a simple signalling cascade termed a "two-component system", where a phosphorylation signal of a histidine kinase is transferred to a conserved aspartate residue of the response regulator. To test the functional role of the respective aspartate residue of Skn7/Pos9 protein in oxidative stress, we mutagenized this residue in vitro to alanine, arginine and glutamate. Only the glutamate allele (D427 to E) was able to rescue the hydrogen peroxide-sensitivity of pos9 mutants. By fusion experiments with the Gal4 DNA-binding domain we identified the isolated response regulator-like domain as a novel eukaryotic domain sufficient for gene activation. Whereas this hybrid protein activated transcription of a lacZ reporter gene under aerobic conditions, no activation was observed under anaerobic conditions, indicating that the response regulator domain is involved in a signalling reaction. Two-hybrid investigations also suggest an oligomerization of the Pos9 protein. Our results indicate that a two-component system is involved in the oxidative-stress response of yeast.

Anaerobiosis↗
PubMed1996

Some causes of genotypic and phenotypic discordance in monozygotic twin pairs.

The use of the adjective "identical" rather than monozygotic leads to misunderstandings about the biology of monozygotic twinning. Most monozygotic twin pairs are not identical; there may be major discordance for birth weight, genetic disease, and congenital anomalies. These indicate that postzygotic events may lead to the formation of two or more cell clones in the inner cell mass and early embryo that actually stimulate the monozygotic twinning event. There is also evidence that there may be unequal allocation of numbers of cells to the monozygotic twins; this may have widespread implications for the cascade of developmental events during embryogenesis, formation, and vascularization of the placenta. Large-scale zygosity testing at birth could be the template for analysis of twin outcomes and their biologic causes.

Chorion↗
PubMed1989

Morphogen gradients and the control of body pattern in insect embryos.

The basic body plan of insects is set up in response to determinants initially localized at the anterior and posterior poles of the egg. Early in development, these determinants give rise to a series of morphogen gradients which in turn trigger a cascade of molecular signals determining the body pattern. This signalling process is outlined and recent experiments testing the roles of these gradient systems in determining anterior and posterior pattern are described. The results of these experiments suggest that anterior pattern is controlled by a single instructive gradient, whereas posterior pattern depends on the overlap of several gradients, each providing only one or a few distinct responses.

Animals↗
PubMed1994

Soluble CD23 potentiates interleukin-1-induced secretion of interleukin-6 and interleukin-1 receptor antagonist by human monocytes.

The low-affinity receptor for IgE (CD23) is cleaved into biologically active soluble fragments (sCD23), some of which have been reported to exhibit pleiotropic activities. However, it is not known whether the sCD23 fragments contribute to the induction and/or regulation of pro-inflammatory cytokine production. In this study, this possibility was tested using interleukin (IL)-1-stimulated human whole blood as an ex vivo model of cytokine cascade production. We show that human recombinant 25-kDa sCD23 significantly enhanced the production of IL-6 in whole blood stimulated by IL-1, but had only little or no effect in the absence of IL-1. The potentiating effect of sCD23 was concentration dependent within the range of plasma levels occurring during various inflammatory processes in man. These results prompted us to study whether sCD23 and IL-1 together also enhance the production of regulating factors exhibiting anti-cytokine activities. Our data indicate that sCD23 augments the release of IL-1 receptor antagonist induced by IL-1. Finally, examining the effect of sCD23 on human peripheral monocytes stimulated by IL-1, we confirmed the capacity of sCD23 to potentiate cytokine production. We suggest that sCD23 can modulate monocyte functions, thereby contributing to the amplification and regulation of immune and inflammatory processes.

Enzyme-Linked Immunosorbent Assay↗
PubMed2005

Energy expenditure in Crocidurinae shrews (Insectivora): is metabolism a key component of the insular syndrome?

A cascade of morphological, ecological, demographical and behavioural changes operates within island communities compared to mainland. We tested whether metabolic rates change on islands. Using a closed circuit respirometer, we investigated resting metabolic rate (RMR) of three species of Crocidurinae shrews: Suncus etruscus, Crocidura russula, and C. suaveolens. For the latter, we compared energy expenditure of mainland and island populations. Our measurements agree with those previously reported for others Crocidurinae: the interspecific comparison (ANCOVA) demonstrated an allometric relation between energy requirements and body mass. Energy expenditure also scaled with temperature. Island populations (Corsica and Porquerolles) of C. suaveolens differed in size from mainland (gigantism). A GLM showed a significant relationship between energy expenditure, temperature, body mass and locality. Mass specific RMR allometrically scales body mass, but total RMR does not significantly differ between mainland and island, although island shrews are giant. Our results are consistent with other studies: that demonstrated that the evolution of mammalian metabolism on islands is partially independent of body mass. In relation to the insular syndrome, we discuss how island selective forces (changes in resource availability, decrease in competition and predation pressures) can operate in size and physiological adjustments.

Animals↗
PubMed2006

Sonic hedgehog, BMP4, and Hox genes in the development of anorectal malformations in Ethylenethiourea-exposed fetal rats.

BACKGROUND: shh signaling pathway has been shown to be involved in the morphogenesis of many organ systems. In this study, we investigated the expression of shh and its targets, BMP4 and Hox genes, in the development of anorectal malformations in Ethylenethiourea (ETU)-exposed embryos. METHODS: We used ETU murine model of the vertebral, anal, cardiac, tracheoesophageal, renal, and limb association. Ethylenethiourea 1% (125 mg/kg) was given to the pregnant females via gavage feeding on gestational day (gD) 10 and saline to control animals. Embryos were collected at gD12 to gD16 and gD21; hindguts were dissected and snap frozen. Highly purified RNA was isolated, and expression of shh, BMP4, Hoxa13, and Hoxd13 genes was confirmed with RT-PCR. Relative quantitative expression of shh and target genes at each time point was done with SYBR Green I qPCR. Normalized gene of interest expression was calculated by geNorm, and data analysis was done with 2-tail Student t test. RESULTS: shh, BMP4, Hoxa13, and Hoxd13 transcripts were detected in all samples, confirming that shh cascade is active during the process of hindgut development in fetal rats. Relative quantitation demonstrated that shh cascade expression shows time-dependent changes in the developing hindgut. CONCLUSION: This study shows that ETU disturbs the expression of shh signaling pathway during the development of hindgut. We provide evidence that shh plays a pivotal role in the hindgut morphogenesis, and its misexpression affect the expression of targets, BMP4 and Hox genes.

Anal Canal↗
PubMed2003

Nickel and cobalt activate complement factor C3 faster than magnesium.

We have found that incubation of heparin plasma with Ni(2+) or Co(2+) at concentrations below 100 microM can stimulate the conversion of complement factor C3 to C3b faster than magnesium, which is the natural cofactor in the alternative complement activation. This conversion was monitored by light absorbance measurement after separation by isotachophoresis, immunofixation and protein staining. The generation of C3b stimulated by these metals (<0.5 mM) proceeds up to about four times faster than the stimulation by Mg(2+). Half of total C3 in the incubation media was converted by Ni(2+) or Co(2+) at 0.5 mM after 20 min at 37 degrees C. Increasing Ni(2+) concentrations over 0.5 mM decreased the C3 conversion rate. Activation of C3 stimulated by Ni(2+), Co(2+) and Mg(2+) was concomitant with the conversion of complement factor B to Bb, but complement factor C4 was not affected by the activation. The conversion of B to Bb was monitored after separation by isotachophoresis and immunoblotting. Other divalent metal ions tested, namely Ca(2+), Ba(2+), Cu(2+) and Zn(2+), did not stimulate the complement cascade. We postulate that the increased rate of C3-fragment production induced by nickel or cobalt ions is central for the immunotoxicity of these metals.

Animals↗