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At least 991 records · Page 55Linked to original sources
PubMed2003

Intracellular calcium: a prerequisite for aldosterone action.

Transport of salt and water in various tissues is under control of the mineralocorticoid hormone aldosterone. As a liphophilic hormone, aldosterone diffuses through the plasma membrane and, then, binds to cytosolic mineralocorticoid receptors in the target cells. After binding to nuclear pore complexes, the activated receptor is translocated to the nucleus where transcription processes are initiated. After a lag period of about 20 minutes hormone-specific early mRNA transcripts leave the nucleus through nuclear pores. Some of the steps in this cascade can be followed by electrophysiology in Xenopus laevis oocyte nuclei. In addition to the genomic pathway, aldosterone exerts a rapid pre-genomic response that involves an increase in intracellular calcium. In this study, we tested for the potential role of Ca(2+) in the genomic response of the hormone. We measured the electrical resistance across the nuclear envelope in response to aldosterone, in presence and absence of intracellular Ca(2+). Nuclear envelope electrical resistance reflects receptor binding to the nuclear pore complexes ("early" resistance peak, 2 minutes after aldosterone), ongoing transcription ("transient" resistance drop, 5-15 minutes after aldosterone) and mRNA export ("late" resistance peak, 20 minutes after aldosterone). Pre-injection of the Ca(2+) chelator EGTA eliminated all electrical responses evoked by aldosterone. The transient resistance drop and the late resistance peak, induced by the hormone, were prevented by the transcription inhibitor actinomycin D, coinjected with aldosterone, while the early resistance peak remained unaffected. We conclude that (i). the presence of intracellular Ca(2+) is a prerequisite for the genomic action of aldosterone. (ii). Intracellular calcium plays a role early in the signaling cascade, either in agonist-receptor interaction, or receptor transport/docking to the nuclear pore complexes.

Aldosterone↗
PubMed2002

Role of redox status on the activation of mitogen-activated protein kinase cascades by NSAIDs.

High concentrations of non steroidal antiinflammatory drugs (NSAIDs) exert preventive effects against carcinogenesis. Their molecular mechanism of action remains to be elucidated. Based on previous reports with salicylate, we have made the hypothesis that various NSAIDs can activate the mitogen-activated protein kinases (MAPK). Moreover, we tested the idea that NSAIDs act by increasing the effects of oxidative stress. We report that in human colorectal carcinoma cells NSAIDs stimulated the three families of MAPK, extracellular regulated kinases, c-Jun N-terminal kinases, p38 MAPK and that this stimulation is prevented by N-acetyl cysteine. In cultured astrocytes, a biological system less sensitive to oxidative stress, we show that a short treatment by NSAIDs strongly activated the three MAP kinases in the presence of H(2)O(2). A 25 microM H(2)O(2), unable to stimulate by itself the MAP kinases, promote an almost complete activation of MAP kinases in the presence of NSAIDs. The activation of MAP kinases by H(2)O(2) and NSAIDs was suppressed by quinone reductase inhibitors, suggesting that "redox cycling" was involved in the activation mechanisms of MAP kinases by H(2)O(2) and NSAIDs. The mobility on SDS-PAGE of the apoptosis signal-regulating kinase, which activates C-Jun N-terminal kinases and p38 MAPK cascades, was reduced by H(2)O(2) and NSAIDs, suggesting, that H(2)O(2) and NSAIDs activated apoptosis signal-regulating kinase by increasing its state of phosphorylation. In conclusion, we demonstrate that various NSAIDs can activate the three families of MAP kinases and that this activation depends on the presence of reactive oxygenated species. These results give a new insight into the mechanism of the action of NSAIDs.

Animals↗
PubMed1987

Operation Everest II: coagulation system during prolonged decompression to 282 Torr.

Thromboembolic phenomena may occur as humans ascend to high altitude. To investigate the role of the coagulation cascade and its inhibitors in these disorders, venous blood was obtained from eight subjects who participated in the Operation Everest II project. Samples were obtained before and 5 min after completion of a progressive incremental exercise test to exhaustion at sea level and atmospheric pressures of 380 (18,000 ft) and 282 Torr (25,000 ft). Plasma was analyzed for the activity or concentration of factors II, V, VII, VIII complex, IX-XIII, prekallikrein, high-molecular-weight kininogen, fibrinogen, antithrombin III, alpha 2-macroglobulin, alpha 2-antiplasmin, C1-esterase inhibitor, alpha 1-antitrypsin, and protein C. Prolonged exposure to simulated high altitude did not alter the concentration of any of the coagulation factors or inhibitors. Exercise increased the circulating concentrations of the factor VIII complex at sea level, 380, and 282 Torr. However, the increment was less at the simulated high altitudes. The increase in the factor VIII complex was inversely related to arterial O2 saturation and directly related to the work load achieved and blood pH and plasma lactate concentrations. These studies suggest that the gradual development of marked chronic hypoxia does not affect the coagulation cascade.

Adult↗
PubMed2006

Long-term memory deficits in Pavlovian fear conditioning in Ca2+/calmodulin kinase kinase alpha-deficient mice.

Signaling by the Ca(2+)/calmodulin kinase (CaMK) cascade has been implicated in neuronal gene transcription, synaptic plasticity, and long-term memory consolidation. The CaM kinase kinase alpha (CaMKKalpha) isoform is an upstream component of the CaMK cascade whose function in different behavioral and learning and memory paradigms was analyzed by targeted gene disruption in mice. CaMKKalpha mutants exhibited normal long-term spatial memory formation and cued fear conditioning but showed deficits in context fear during both conditioning and long-term follow-up testing. They also exhibited impaired activation of the downstream kinase CaMKIV/Gr and its substrate, the transcription factor cyclic AMP-responsive element binding protein (CREB) upon fear conditioning. Unlike CaMKIV/Gr-deficient mice, the CaMKKalpha mutants exhibited normal long-term potentiation and normal levels of anxiety-like behavior. These results demonstrate a selective role for CaMKKalpha in contextual fear memory and suggest that different combinations of upstream and downstream components of the CaMK cascade may serve distinct physiological functions.

Animals↗
PubMed1999

Effects of post-training infusions of a mitogen-activated protein kinase kinase inhibitor into the hippocampus or entorhinal cortex on short- and long-term retention of inhibitory avoidance.

We recently demonstrated the time-dependent impairment of long-term retention of a step-down inhibitory avoidance task in rats induced by post-training infusion of the specific MAPKK (mitogen-activated protein kinase kinase) inhibitor PD 098059 into the hippocampus (HIP), amygdala (AMY), entorhinal cortex (EC) and posterior parietal cortex (PPC). Here we investigate the role of the MAPK cascade in the HIP and the EC on both short- and long-term retention of inhibitory avoidance in rats, using three different doses of the MAPKK inhibitor PD 098059. Adult male Wistar rats were trained and tested in inhibitory avoidance and given an infusion of PD 098059 (0.5, 5.0 or 50.0 microM) at 0, 30, 90, 120, 180, 270 or 360 min after training. A retention test session was carried out at 90, 180 or 270 min after training (short-term memory, STM) and/ or 24 h after training (long-term memory, LTM). When infused into the HIP at 0 min, but not at 30, 90, 120 or 180 min after training, PD 098059 impaired STM. Intrahippocampal PD 098059 impaired LTM when infused at 180 min, but not at 0, 30, 90, 120 or 270 min after training. When infused into the EC, PD 098059 enhanced STM when given at 0 min after training and had no effect when given at 30, 90, 120 or 180 min after training. In this structure, PD 098059 impaired LTM when given at 180 or 270 min, but not at 30, 90, 120 or 360 min after training. All effects were dose-dependent. These findings indicate that the MAPK cascade in the HIP and EC is differentially involved in short- and long-term retention of inhibitory avoidance in rats.

Animals↗
PubMed1997

Signal transduction mechanisms underlying axonal growth responses stimulated by cell adhesion molecules.

The mechanisms underlying nerve growth have been extensively studied, and it has been found that the three cell adhesion molecules (CAMs) L1, NCAM and N-cadherin play a key role in this process. All three CAMs are able to stimulate axonal growth from a variety of neuronal cells, and a range of agents which either mimic or inhibit CAM stimulated neurite outgrowth have been identified and has provided a basis for understanding the nature of the response. Results from these studies suggested that activation of a tyrosine kinase-phospholipase C gamma (PLC gamma) cascade was required for the CAM response. Following the identification of a CAM-homology domain (CHD) within the fibroblast growth factor receptor (FGFR) and a putative CHD-binding motif within each of the CAMs, it was suggested that this might be the tyrosine kinase implicated in the CAM pathway. This has been tested experimentally in a number of ways, including the use of transgenic mice expressing a dominant-negative FGFR, and several results have now demonstrated that a functional FGFR is required for CAM stimulated neurite outgrowth. More recently, treatment of neurons with the CAMs has been shown to stimulate FGFR autophosphorylation and PLC gamma activity which in turn leads to activation of a second messenger cascade involving diacylglycerol and arachidonic acid and results in calcium influx into the neurons. Pharmacological studies have confirmed that this cascade is responsible for the neurite outgrowth response.

Animals↗
PubMed2005

Prevalence of transmitted HIV-1 drug resistance and the role of resistance algorithms: data from seroconverters in the CASCADE collaboration from 1987 to 2003.

OBJECTIVES: To examine factors influencing the rate of transmitted drug resistance (TDR) among seroconverters, with particular emphasis on 3 widely used genotypic drug resistance algorithms. METHODS: The study used data from CASCADE (Concerted Action on Seroconversion to AIDS and Death in Europe), a collaboration of seroconverter cohorts in Europe and Canada. Genotypic resistance data were derived within 18 months of the last seronegative test or date of laboratory evidence of acute infection and before the initiation of antiretroviral therapy. The Stanford algorithm was used to analyze each individual's nucleotide sequence. A multivariate logistic model was used to assess independent relationships between the presence of TDR and exposure category, sex, age at seroconversion, and year of seroconversion. The paper also describes 3 alternative definitions of resistance: the Stanford algorithm, the key resistance mutations defined by the International AIDS Society, and the Agence Nationale de Recherches sur le Sida (ANRS) algorithm. RESULTS: Forty-five of 438 patients (10.3%) seroconverting between 1987 and 2003 were infected with a drug-resistant HIV-1 variant. Forty patients (9.1%) showed resistance mutations to only 1 class of antiretroviral drugs, 2 (0.5%) to 2 classes, and 3 (0.7%) to 3 classes of antiretroviral therapy. It was suggested that individuals seroconverting later in calendar time were more likely to have TDR (relative risk 3.89 and 95% CI: 0.84 to 18.02, and relative risk 4.69 and 95% CI: 1.03 to 21.31, for 1996-1999 and 2000-2003, respectively, compared with pre-1996; P trend = 0.08). This trend was apparent regardless of the definition of TDR used. The total estimated proportion of individuals with TDR varied between 10.3% and 15.5% according to which definition was used. CONCLUSIONS: Evidence was found for the rise of TDR over time. A specific definition of what constitutes TDR rather than a simple list of mutations is needed.

Adolescent↗
PubMed1991

Complement activation by anticardiolipin antibodies.

A haemolytic assay was used to test the complement fixation ability of 16 serum samples with high concentrations of anti-cardiolipin antibodies. Fourteen patients had clinical complications usually associated with these antibodies--namely, recurrent abortions, thrombosis, or thrombocytopenia. Complement fixation by anticardiolipin antibodies was shown in only four of these patients and was not directly related to the antibody concentration. Because anticardiolipin antibodies in most of these patients did not activate the complement pathway it is unlikely that the complement cascade has an important role in the clinical complications associated with these antibodies.

Abortion, Habitual↗
PubMed1999

Immunocytochemical detection and mapping of a cytokeratin 18 neo-epitope exposed during early apoptosis.

A neo-epitope in cytokeratin 18 (CK18) that becomes available at an early caspase cleavage event during apoptosis and is not detectable in vital epithelial cells is characterized. The monoclonal antibody M30, specific for this site, can be utilized specifically to recognize apoptotic cells, which show cytoplasmic cytokeratin filaments and aggregates after immunohistochemistry with M30, while viable and necrotic cells are negative. The number of cells recognized by the antibody increases after induction of apoptosis in exponentially growing epithelial cell lines and immunoreactivity is independent of the phosphorylation state of the cytokeratins. The generation of the M30 neo-epitope occurs early in the apoptotic cascade, before annexin V reactivity or positive DNA nick end labelling. In a flow cytometric assay, the majority of the M30-positive cells appear in the 'apoptotic' subG1 peak. Tests with synthetic peptides define positions 387-396 of CK18, with a liberated C-terminus at the caspase cleavage site DALD-S, as the ten-residue epitope of M30. This epitope starts at the end of coil 2 of the predicted CK18 structure, at a probable hinge region, compatible with the sensitivity to proteolytic cleavage. The definition of a specific caspase cleavage site in CK18 as a neo-epitope can be used for quantification of apoptotic epithelial cells with immunocytochemical techniques and is applicable to both fresh and formalin-fixed material.

Animals↗
PubMed2006

Expression of genes involved in the regulation of p16 in psoriatic involved skin.

It has been suggested that the up-regulation of the tumour suppressor p16 gene and induction of senescence protect the phenotype of psoriatic involved skin from malignant transformation. On the other hand, Id1, which is inversely correlated with p16 has been shown to be up-regulated in psoriatic involved skin. To test the hypothesis that there may be an altered regulation of p16 in psoriatic involved skin, we have measured genes involved in the Igf-1 receptor signalling through the Ras/MAPK cascade. Igf-1R, IGFBP3, hRas, Ets2, JunB, Egr-1, Id1, MIDA1 and p16 gene expressions were measured using quantitative real-time PCR in total RNA isolated from punch biopsies from psoriatic involved (n = 9) and uninvolved skin (n = 9) and from cutaneous squamous cell cancer (SCC) involved (n = 8) and uninvolved skin (n = 8). The IGFBP3, hRas, JunB, Egr-1, Id1 and MIDA1 genes were up-regulated in psoriatic involved skin compared with uninvolved skin. The p16, JunB and MIDA1 genes were up-regulated in SCC involved skin compared with uninvolved skin. Our results indicate that there may be a balance between the proliferation and induction of senescence in psoriasis. This balance may vary and the psoriatic involved skin represented in this study appears to be in a proliferative state rather than senescence. Furthermore, we suggest that the noted up-regulation of JunB, which has been shown to up-regulate p16, in combination with the previously reported elevation of p16 expression in psoriatic involved skin, may indicate activation of a pathway by which JunB may protect the psoriatic plaque by inducing p16 in an event of malignant stress.

Biopsy↗
PubMed1998

Failure of testicular development associated with a rearrangement of 9p24.1 proximal to the SNF2 gene.

In 46,XY individuals, testes are determined by the activity of the SRY gene (sex-determining region Y), located on the short arm of the Y chromosome. The other genetic components of the cascade that leads to testis formation are unknown and may be located on the X chromosome or on the autosomes. Evidence for the existence of several loci associated with failure of male sexual development is indicated by reports of 46,XY gonadal dysgenesis associated with structural abnormalities of the X chromosome or of autosomes (chromosomes 9, 10, 11 and 17). In this report, we describe the investigation of a child presenting with multiple congenital abnormalities, mental retardation and partial testicular failure. The patient had a homogeneous de novo 46,XY,inv dup(9)(pter-->p24.1::p21.1-->p23.3::p24.1-->qter) chromosome complement. No deletion was found by either cytogenetic or molecular analysis. The SRY gene and DSS region showed no abnormalities. Southern blotting dosage analysis with 9p probes and fluorescent in situ hybridisation data indicated that the distal breakpoint of the duplicated fragment was located at 9p24.1, proximal to the SNF2 gene. We therefore suggest that a gene involved in normal testicular development and/or maintenance is present at this position on chromosome 9.

Adolescent↗
PubMed1982

Sensitivity and specificity of M mode echocardiographic signs of mitral valve prolapse.

To assess the sensitivity and specificity of previously described M mode echocardiographic signs of mitral valve prolapse, 100 subjects with a mobile mid systolic click and 100 matched normal control subjects were prospectively studied. Late systolic posterior motion and holosystolic hammocking of the mitral leaflets were common, highly specific signs of mitral valve prolapse. When these signs were combined as a single criterion, sensitivity was 85 percent and specificity was 99 percent. Other signs, including systolic echoes in the mid left atrium, systolic anterior motion, early diastolic anterior motion of the posterior mitral leaflet and shaggy or heavy cascading linear diastolic echoes posterior to the mitral valve, were highly specific but uncommon. They occurred only in combination with late systolic posterior motion or holosystolic hammocking. The remaining signs tested did not differentiate subjects with mitral valve prolapse from normal persons.

Adult↗
PubMed2005

Multiple signaling pathways regulate FGF-2-induced retinal ganglion cell neurite extension and growth cone guidance.

Growth cones use cues in their environment in order to grow in a directed fashion to their targets. In Xenopus laevis, fibroblast growth factors (FGFs) participate in retinal ganglion cell (RGC) axon guidance in vivo and in vitro. The main intracellular signaling cascades known to act downstream of the FGF receptor include the mitogen-activated protein kinase (MAPK), phospholipase Cgamma (PLCgamma) and phosphotidylinositol 3-kinase (PI3K) pathways. We used pharmacological inhibitors to identify the signaling cascade(s) responsible for FGF-2-stimulated RGC axon extension and chemorepulsion. The MAPK, PI3K and PLCgamma pathways were blocked by U0126, LY249002 and U73122, respectively. D609 was used to test a role for the phosphotidylcholine-PLC (PC-PLC) pathway. We determined that the MAPK and two PLC pathways are required for FGF-2 to stimulate RGC neurite extension in vitro, but the response of axons to FGF-2 applied asymmetrically to the growth cone depended only on the PLC pathways.

Animals↗
PubMed2004

Impairment of olfactory discrimination by blockade of nitric oxide activity in the terrestrial slug Limax valentianus.

The terrestrial slug Limax readily associates an innately preferred food odor with the aversive taste of quinidine. We investigated slugs' olfactory discrimination capability among structurally similar alcohols and the effects of inhibition of nitric oxide (NO) synthesis to the olfactory discrimination behavior, using an olfactory discriminatory learning task. Limax could discriminate among the odor of 1-octanol (OT), 3-methylcyclohexanol (MC) and 1-hexanol (HX). OT was perceptually more similar to HX than was MC for them. When NO synthesis was inhibited by injecting N-nitro-L-arginine methyl ester (l-NAME) shortly before the discrimination test, slugs could not discriminate between OT and HX whereas the retrieval of olfactory memory and the discrimination between OT and MC remained intact. These results indicate that the NO cascade plays a crucial role for fine olfactory discrimination in Limax.

Animals↗
PubMed2005

Evidence for the Stepwise Stress Model: Gambusia holbrooki and Daphnia magna under acid mine drainage and acidified reference water stress.

The Stepwise Stress Model (SSM) states that a cascade of regulative behavioral responses with different intrinsic sensitivities and threshold values offers increased behavioral plasticity and thus a wider range of tolerance for environmental changes or pollutant exposures. We tested the SSM with a widely introduced fish Gambusia holbrooki (Girard) (Pisces, Poeciliidae) and the standard laboratory test species Daphnia magna Straus (Crustacea, Daphniidae). The stress was simulated by short-term exposure to acid mine drainage (AMD) and to acidified reference water (ACID). Recording of behavioral responses with the multispecies freshwater biomonitor (MFB) generated continuous time-dependent dose-response data that were modeled in three-dimensional (3D) surface plots. Both the pH-dependent mortalities and the strong linear correlations between pH and aqueous metals confirmed the toxicity of the AMD and ACID gradients, respectively, for fish and Daphnia, the latter being more sensitive. AMD stress at pH < or = 5.5 amplified circadian rhythmicity in both species, while ACID stress did so only in G. holbrooki. A behavioral stepwise stress response was found in both species: D. magna decreased locomotion and ventilation (first step) (AMD, ACID), followed by increased ventilation (second step) (AMD). G. holbrooki decreased locomotion (first step) (AMD, ACID) and increased ventilation at intermediate pH levels (second step) (AMD). Both species, although from different taxonomic groups and feeding habits, followed the SSM, which might be expanded to a general concept for describing the behavioral responses of aquatic organims to pollution. Stepwise stress responses might be applied in online biomonitors to provide more sensitive and graduated alarm settings, hence optimizing the "early warning" detection of pollution waves.

Acids↗
PubMed2004

The critical features and the mechanism of inhibition of a kinase interaction motif-based peptide inhibitor of JNK.

We previously reported that a small peptide based on amino acids 143-153 of the c-Jun N-terminal kinase (JNK)-binding domain of JIP-1 functioned as an in vitro inhibitor of JNK activity. This peptide (TI-JIP: RP-KRPTTLNLF) resembles the kinase-interaction motif (KIM = (K/R)(2-3)X(1-6)(L/I)X(L/I)), which is common to upstream activators, downstream substrates, phosphatases, and scaffold proteins present in MAPK cascades. In this study, we characterized the mechanism of JNK inhibition by this peptide and further investigated the biochemical features of this peptide resulting in potent JNK inhibition. We also tested various KIM-based peptides for their ability to inhibit JNK activity. TI-JIP was found to be competitive with respect to the phosphoacceptor substrate c-Jun (K(I) = 0.39 +/- 0.08 microm), and exhibit mixed (non-competitive) inhibition with respect to ATP. All seven substitutions of Pro-5 we tested significantly reduced the JNK inhibition, as did altering the Pro-5 to Leu-8 spacing. When we independently tested eight substitutions of either Thr-6 or Thr-7, only one substitution in each position was well tolerated. Furthermore, peptides based on the KIMs from other proteins were significantly less potent JNK inhibitors than TI-JIP, including a peptide from the JNK interactor Sab that contained all critical inhibitory residues present in TI-JIP. Therefore, despite having previously identified Arg-4, Pro-5, Leu-8, and Leu-10 in TI-JIP as independently critical for mediating JNK inhibition, we find their presence in other 11-mer peptides is not sufficient for JNK inhibition. TI-JIP is therefore a unique KIM-based inhibitor of JNK activity.

Adenosine Triphosphate↗
PubMed2005

Mitogen-activated protein kinases regulate platelet-activating factor-induced hyperpermeability.

OBJECTIVE: The authors tested the hypothesis that p42/44- (ERK-1/2) and/or p38-mitogen-activated protein kinases (MAPK) are in vivo regulatory elements in the platelet-activating factor (PAF) activated signaling cascade that stimulates microvascular hyperpermeability. METHODS: FITC-dextran 70 was used as the macromolecular tracer for microvascular permeability in the mouse mesenteric fat tissue. Interstitial integrated optical intensity (IOI) was used as an index of permeability. RESULTS: An application of 10(-7) M PAF increased IOI from 23.1 +/- 3.6 to 70.8 +/- 7.4 (mean +/- SEM). Inhibition of ERK-1/2 with 3 microM and 30 microM AG126 reduced IOI to 32.3 +/- 2.5. Similarly, inhibition of p38-MAPK with 6 nM, 60 nM and 600 nM SB203580 lowered IOI to 29.1 +/- 2.4. CONCLUSIONS: The results demonstrate that ERK-1/2 and p38MAPK participate in the signaling cascade that regulates PAF-induced microvascular hyperpermeability in vivo.

Animals↗
PubMed1999

Model-free functional MRI analysis using Kohonen clustering neural network and fuzzy C-means.

Conventional model-based or statistical analysis methods for functional MRI (fMRI) suffer from the limitation of the assumed paradigm and biased results. Temporal clustering methods, such as fuzzy clustering, can eliminate these problems but are difficult to find activation occupying a small area, sensitive to noise and initial values, and computationally demanding. To overcome these adversities, a cascade clustering method combining a Kohonen clustering network and fuzzy, means is developed. Receiver operating characteristic (ROC) analysis is used to compare this method with correlation coefficient analysis and t test on a series of testing phantoms. Results shown that this method can efficiently and stably identify the actual functional response with typical signal change to noise ratio, from a small activation area occupying only 0.2% of head size, with phase delay, and from other noise sources such as head motion. With the ability of finding activities of small sizes stably this method can not only identify the functional responses and the active regions more precisely, but also discriminate responses from different signal sources, such as large venous vessels or different types of activation patterns in human studies involving motor cortex activation. Even when the experimental paradigm is unknown in a blind test such that model-based methods are inapplicable, this method can identify the activation patterns and regions correctly.

Adult↗