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Aldosterone interaction with epidermal growth factor receptor signaling in MDCK cells.

Epidermal growth factor (EGF) regulates cell proliferation, differentiation, and ion transport by using extracellular signal-regulated kinase (ERK)1/2 as a downstream signal. Furthermore, the EGF-receptor (EGF-R) is involved in signaling by G protein-coupled receptors, growth hormone, and cytokines by means of transactivation. It has been suggested that steroids interact with peptide hormones, in part, by rapid, potentially nongenomic, mechanisms. Previously, we have shown that aldosterone modulates Na(+)/H(+) exchange in Madin-Darby canine kidney (MDCK) cells by means of ERK1/2 in a way similar to growth factors. Here, we tested the hypothesis that aldosterone uses the EGF-R as a heterologous signal transducer in MDCK cells. Nanomolar concentrations of aldosterone induce a rapid increase in ERK1/2 phosphorylation, cellular Ca(2+) concentration, and Na(+)/H(+) exchange activity similar to increases induced by EGF. Furthermore, aldosterone induced a rapid increase in EGF-R-Tyr phosphorylation, and inhibition of EGF-R kinase abolished aldosterone-induced signaling. Inhibition of ERK1/2 phosphorylation reduced the Ca(2+) response, whereas prevention of Ca(2+) influx did not abolish ERK1/2 phosphorylation. Our data show that aldosterone uses the EGF-R-ERK1/2 signaling cascade to elicit its rapid effects in MDCK cells.

Aldosterone↗

Wingless-type frizzled protein receptor signaling and its putative role in human colon cancer.

We wish to identify new candidate genes involved in the pathogenesis of human colon cancer to better understand the diversity of phenotype presentation that varies from individual to individual. Our working hypothesis is that genetic polymorphism of genes in the Wingless-type (Wnt) frizzled protein receptor pathway is associated with the susceptibility to develop colon cancer. The putative role of the Wnt pathway in sporadic human malignancy of the colon suggests involvement in inherited cancer as well. beta-catenin is the crucial messenger in frizzled receptor signaling, transmitting Wnt-ligand signals such as signals from secreted apoptosis-related proteins to the nucleus. It functions as a genome denunciator by initiating amplification of oncogenes. The net effect of beta-catenin depends on the magnitude of its accumulation in the cytoplasm and, therefore, upon expression profiles of genes in the Wnt pathway. We propose that variations in allelic frequencies of genes involved in the beta-catenin cascade may either promote or impede malignant transformation of the colon. If certain polymorphisms in Wnt signaling through beta-catenin predispose to colon cancer, this might manifest as decreased binding affinity of proteins such as axin or the adenomatous polyposis coli protein to beta-catenin. Association studies are proposed to test the hypothesis, which could serve as an initial step toward understanding the complexity of tumor biology. The clinical rationale in unraveling the genetic susceptibility to cancer lies in identification of a subgroup of individuals who may benefit from beta-catenin targeting agents, which could potentially overcome this genetic instability.

Colorectal Neoplasms↗

Randomized antiarrhythmic drug therapy in survivors of cardiac arrest (the CASCADE Study). The CASCADE Investigators.

The Cardiac Arrest in Seattle: Conventional Versus Amiodarone Drug Evaluation (CASCADE) study evaluated antiarrhythmic drug treatment of survivors of out-of-hospital ventricular fibrillation (VF) not associated with a Q-wave myocardial infarction who were at especially high risk of recurrence of VF. Therapy was randomized to empiric treatment with amiodarone versus treatment with other antiarrhythmic drugs guided by electrophysiologic testing, Holter recording, or both (conventional therapy). The primary end points of the study were cardiac mortality, resuscitated cardiac arrest due to documented VF, or complete syncope followed by a shock from an implanted automatic defibrillator. Two hundred twenty-eight patients were enrolled in the study, and baseline characteristics were similar in the patients treated with amiodarone and with conventional therapy. Two hundred two patients (89%) were men with an average age of 62 years. Coronary artery disease was the most common underlying condition (188 of 228, 82%), and in coronary patients, 153 of 188 (81%) had experienced a prior myocardial infarction before the index VF event. Mean left ventricular ejection fraction was 0.35, and 102 patients (45%) had a prior history of congestive heart failure. Survival free of cardiac death, resuscitated VF, or syncopal defibrillator shock for the entire population was 75% at 2 years (amiodarone, 82%; conventional, 69%), 59% at 4 years (amiodarone, 66%; conventional, 52%), and 46% at 6 years (amiodarone, 53%; conventional, 40%); p = 0.007. The survival free of cardiac death and sustained ventricular arrhythmias was 65% at 2 years (amiodarone, 78%; conventional, 52%), 43% at 4 years (amiodarone, 52%; conventional, 36%), and 30% at 6 years (amiodarone, 41%; conventional, 20%); p < 0.001.

Aged↗

Deployment of short-term assays for the detection of carcinogens; genetic and molecular considerations.

The deployment of short-term assays for the detection of carcinogens inevitably has to be based on the genetic alterations actually involved in carcinogenesis. This paper gives an overview of oncogene activation and other mutagenic events connected with cancer induction. It is emphasized that there are indications of DNA alterations in carcinogenicity, which are not in accordance with "conventional" mutations and mutation frequencies, as measured by short-term assays of point mutations, chromosome aberrations and numerical chromosome changes. This discrepancy between DNA alterations in carcinogenicity and the endpoints of short-term assays in current use include transpositions, insertion mutations, polygene mutations, gene amplifications and DNA methylations. Furthermore, tumourigenicity may imply an induction of a genetic instability, followed by a cascade of genetic alterations. The evaluation of short-term assays for carcinogenesis mostly involves two correlations that is, between mutation and animal cancer data on the one hand and between animal cancer data and human carcinogenicity on the other. It should be stressed that animal bioassays for cancer in general imply tests specifically for the property of chemicals to function as complete carcinogens, which may be a rather poor reflection of the actual situation in human populations. The primary aim of short-term mutagenicity assays is to provide evidence as to whether a compound can be expected to cause mutations in humans, and such evidence has to be considered seriously even against a background of negative cancer data. For the evaluation of data from short-term assays the massive amount of empirical data from different assays should be used and new computer systems in that direction can be expected to provide improved predictions of carcinogenicity.

Carcinogens↗

Interleukin-1B: a clinically relevant urinary marker.

Urinary cytokines as markers for the intravesical inflammatory response have become an active area of research. Interleukin-1b, a well studied and early produced cytokine in the immune recognition cascade, was evaluated. After extensive analysis of 56 control and study group urine samples, a simplified and reliable protocol for the preparation of urine before cytokine analysis was devised. The application of an available serum interleukin-1b enzyme-linked immunosorbent assay kit for urinary interleukin-1b analysis was then tested. Finally, a reference value for interleukin-1b in normal human urine was established and urinary interleukin-1b was measured in various bladder diseases. The normal and interstitial cystitis groups showed no interleukin-1b elevation. Significant elevation of urinary interleukin-1b was found in patients with bacterial cystitis compared to the interstitial cystitis and control groups (p < 0.001). Of the patients with bladder tumors 58% showed elevation of urinary interleukin-1b (p < 0.001). Urinary interleukin-1b may be used as a marker to distinguish between bacterial and interstitial cystitis. The absence of urinary interleukin-1b in interstitial cystitis argues against an immunological or autoimmune etiology of the disorder. This study represents an important methodological approach to cytokine subtyping of bladder diseases.

Adolescent↗

Activation of muscarinic receptors in PC12 cells. Correlation between cytosolic Ca2+ rise and phosphoinositide hydrolysis.

The intracellular signals generated by carbachol activation of the muscarinic receptor [release of inositol phosphates as a consequence of phosphoinositide hydrolysis and rise of the cytosolic Ca2+ concentration ([Ca2+]i, measured by quin2)] were studied in intact PC12 pheochromocytoma cells that had been differentiated by treatment with nerve growth factor. When measured in parallel samples of the same cell preparation 30 s after receptor activation, the release of inositol trisphosphate and of its possible metabolites, inositol bis- and mono-phosphate, and the [Ca2+]i rise were found to occur with almost superimposable carbachol concentration curves. At the same time carbachol caused a decrease in the radioactivity of preloaded phosphatidylinositol 4,5-bisphosphate, the precursor of inositol trisphosphate. Neither the inositol phosphate nor the [Ca2+]i signal was modified by preincubation of the cells with either purified Bordetella pertussis toxin or forskolin, the direct activator of adenylate cyclase. Both signals were partially inhibited by dibutyryl cyclic AMP, especially when the nucleotide analogue was applied in combination with the phosphodiesterase inhibitors RO 201724 and theophylline. The latter drug alone profoundly inhibited the carbachol-induced [Ca2+]i rise, with only minimal effect on phosphoinositide hydrolysis. Because of the diverging results obtained with forskolin on the one hand, dibutyryl cyclic AMP and phosphodiesterase inhibitors on the other, the effects of the latter drugs are considered to be pharmacological, independent of the intracellular cyclic AMP concentration. Two further drugs tested, mepacrine and MY5445, inhibited phosphoinositide hydrolysis at the same time as the 45Ca2+ influx stimulated by carbachol. Taken together, our results concur with previous evidence obtained with permeabilized cells and cell fractions to indicate phosphatidylinositol 4,5-bisphosphate hydrolysis and [Ca2+]i rise as two successive events in the intracellular transduction cascade initiated by receptor activation. The strict correlation between the carbachol concentration curves for inositol trisphosphate generation and [Ca2+]i rise, and the inhibition by theophylline of the Ca2$ signal without major effects on inositol phosphate generation, satisfy important requirements of the abovementioned interpretation.

Adrenal Gland Neoplasms↗

A central regulator of morphological differentiation in the multicellular bacterium Streptomyces coelicolor.

In the multicellular bacterium Streptomyces coelicolor, functions of developmental (bald) genes are required for the biosynthesis of SapB, a hydrophobic peptidic morphogen that facilitates aerial hyphae formation. Here, we show that aerial hyphal growth and SapB biosynthesis could be activated independently from the normal developmental cascade by providing unprogrammed expression of functionally interactive genes within the ram cluster. ramC, ramS and ramR were essential for normal growth of aerial hyphae, and ramR, a response regulator gene, was a key activator of development. The ramR gene restored growth of aerial hyphae and SapB formation in all bald strains tested (albeit only weakly in the bldC mutant), many of which are characterized by physiological defects. Disruption of the ramR gene abolished SapB biosynthesis and severely delayed growth of aerial hyphae. Transcription of ramR was developmentally controlled, and RamR function in vivo depended on its putative phosphorylation site (D53). We identified and mapped RamR targets immediately upstream of the region encoding ramC and ramS, a putative operon. Overexpression of ramR in the wild-type strain increased SapB levels and caused a distinctive wrinkled surface topology. Based on these results, we propose that phenotypes of bald mutations reflect an early stage in the Streptomyces developmental programme similar to the spo0 mutations in the unicellular bacterium Bacillus subtilis, and that RamR has analogies to Spo0A, the Bacillus response regulator that integrates physiological signals before triggering endospore formation.

Bacterial Proteins↗

Papillomaviruses in human cancers.

Papillomaviruses have proved to be the most complex group of human pathogenic viruses. Eighty-five genotypes have been fully characterized; approximately 120 additional isolates represent only partially characterized putative novel genotypes. Specific types, most notably human papillomavirus (HPV) types 16, 18, and a few others, have been shown to cause the majority of cervical cancers and their high-grade precursor lesions. The viral oncogenes E6 and E7 are required for the initiation and maintenance of the malignant phenotype in HPV-positive cancers. Proteins coded by these genes are multifunctional and interfere with important cell cycle regulatory proteins. Expression of viral oncogenes is tightly controlled in nondifferentiated keratinocytes by at least two signaling cascades, one operative at the functional level, the other at the transcriptional level. The latter has been partially characterized. Papillomaviruses are also suspected of playing a role in a subset of oropharyngeal cancers, in squamous cell cancers of the skin, and possibly also in esophageal cancers. Clinical trials are being conducted to test the preventive and therapeutic efficacy of HPV vaccines, directed particularly against HPV 16 and 18. If proven to be effective, their global application should have a measurable effect on the worldwide incidence of cancer.

Anus Neoplasms↗

Innervation of ectopic endometrium in a rat model of endometriosis.

Endometriosis (ENDO) is a disorder in which vascularized growths of endometrial tissue occur outside the uterus. Its symptoms include reduced fertility and severe pelvic pain. Mechanisms that maintain the ectopic growths and evoke symptoms are poorly understood. One factor not yet considered is that the ectopic growths develop their own innervation. Here, we tested the hypothesis that the growths develop both an autonomic and a sensory innervation. We used a rat model of surgically induced ENDO whose growths mimic those in women. Furthermore, similar to women with ENDO, such rats exhibit reduced fertility and increased pelvic nociception. The ENDO was induced by autotransplanting, on mesenteric cascade arteries, small pieces of uterus that formed vascularized cysts. The cysts and healthy uterus were harvested from proestrous rats and immunostained using the pan-neuronal marker PGP9.5 and specific markers for calcitonin gene-related peptide (CGRP) (sensory C and A delta fibers), substance P (SP) (sensory C and A delta fibers) and vesicular monoamine transporter (sympathetic fibers). Cysts (like the uterus) were robustly innervated, with many PGP9.5-stained neurites accompanying blood vessels and extending into nearby luminal epithelial layers. CGRP-, SP-, and vesicular monoamine transporter-immunostained neurites also were observed, with CGRP and SP neurites extending the furthest into the cyst lining. These results demonstrate that ectopic endometrial growths develop an autonomic and sensory innervation. This innervation could contribute not only to symptoms associated with ENDO but also to maintenance of the ectopic growths.

Animals↗

Conserved biological function between Pax-2 and Pax-5 in midbrain and cerebellum development: evidence from targeted mutations.

The development of two major subdivisions of the vertebrate nervous system, the midbrain and the cerebellum, is controlled by signals emanating from a constriction in the neural primordium called the midbrain/hindbrain organizer (Joyner, A. L. (1996) Trends Genet. 12, 15-201). The closely related transcription factors Pax-2 and Pax-5 exhibit an overlapping expression pattern very early in the developing midbrain/hindbrain junction. Experiments carried out in fish (Krauss, S., Maden, M., Holder, N. & Wilson, S. W. (1992) Nature (London) 360, 87-89) with neutralizing antibodies against Pax-b, the orthologue of Pax-2 in mouse, placed this gene family in an regulatory cascade necessary for the development of the midbrain and the cerebellum. The targeted mutation of Pax-5 has been reported to have only slight effects in the development of structures derived from the isthmic constriction, whereas the Pax-2 null mutant mice show a background-dependent phenotype with varying penetrance. To test a possible redundant function between Pax-2 and Pax-5 we analyzed the brain phenotypes of mice expressing different dosages of both genes. Our results demonstrate a conserved biological function of both proteins in midbrain/hindbrain regionalization. Additionally, we show that one allele of Pax-2, but not Pax-5, is necessary and sufficient for midbrain and cerebellum development in C57BL/6 mice.

Animals↗

CPG16, a novel protein serine/threonine kinase downstream of cAMP-dependent protein kinase.

Gene expression is necessary for the formation and consolidation of long term memory in both invertebrates and vertebrates. Here, we describe the expression and characterization of candidate plasticity gene 16 (cpg16), a protein serine/threonine kinase that was previously isolated from rat hippocampus as a plasticity-related gene. CPG16, when expressed in and purified from bacteria and COS7 cells, was only capable of autophosphorylation and phosphorylation of myelin basic protein but failed to phosphorylate many other peptides and proteins in in vitro phosphorylation assays. Recombinant CPG16, when overexpressed and purified from COS7 cells, had a relatively low level of autophosphorylation activity. This activity was significantly stimulated when cAMP-elevating agents (forskolin, 8-bromo-cAMP) were added to the cells but not by any other extracellular stimuli tested, e.g. serum, phorbol esters, and a calcium ionophore. Although the stimulation of CPG16 activity was inhibited by the cAMP-dependent protein kinase inhibitor H-89, it did not serve as a direct substrate for this kinase. This suggests that CPG16 may be activated by a cAMP-stimulated protein kinase cascade. Immunolocalization studies in COS7 and NIH-3T3 cells showed mostly cytoplasmic localization of CPG16 that turned partially nuclear upon stimulation with 8-bromo-cAMP. Moreover, overexpression of CPG16 seems to partially inhibit cAMP-stimulated activity of the transcription factor CREB (cAMP response element-binding protein), suggesting its involvement in the down-regulation of cAMP-induced transcription. Thus, CPG16 is a protein serine/threonine kinase that may be involved in a novel signaling pathway downstream of cAMP-dependent protein kinase.

3T3 Cells↗

Binding to cadherins antagonizes the signaling activity of beta-catenin during axis formation in Xenopus.

beta-Catenin, a cytoplasmic protein known for its association with cadherin cell adhesion molecules, is also part of a signaling cascade involved in embryonic patterning processes such as the determination of the dorsoventral axis in Xenopus and determination of segment polarity in Drosophila. Previous studies suggest that increased cytoplasmic levels of beta-catenin correlate with signaling, raising questions about the need for in- teraction with cadherins in this process. We have tested the role of the beta-catenin-cadherin interaction in axis formation. Using beta-catenin deletion mutants, we demonstrate that significant binding to cadherins can be eliminated without affecting the signaling activity. Also, depletion of the soluble, cytosolic pool of beta-catenin by binding to overexpressed C-cadherin completely inhibited beta-catenin-inducing activity. We conclude that binding to cadherins is not required for beta-catenin signaling, and therefore the signaling function of beta-catenin is independent of its role in cell adhesion. Moreover, because beta-catenin signaling is antagonized by binding to cadherins, we suggest that cadherins can act as regulators of the intracellular beta-catenin signaling pathway.

Amino Acid Sequence↗

Development of amphotropic murine retrovirus vectors resistant to inactivation by human serum.

Replication-deficient amphotropic retrovirus vectors (RV) or RV-producer cells are being developed for a variety of human gene therapy strategies. One of the hurdles to in vivo use of these agents is their inactivation by components of human serum. Murine leukemia viruses (MLV), from which most current RV are derived, are known to be inactivated by human serum via activation of the classical complement cascade. Other type C retroviruses, e.g., RD114 and BaEV, are resistant to inactivation by human serum when derived from infection of human and mink cells but not murine cells. We hypothesized that amphotropic RV could be made resistant to human serum inactivation if a more appropriate producer cell could be found. To test this hypothesis, RV were made using a variety of human (293, HOS, TE671) and murine (NIH-3T3) cell types as the producer cell. The parental cell lines, RV-producer cells, and RV themselves were evaluated for sensitivity to inactivation by human serum. Results showed that the murine NIH-3T3 cell line, the NIH-3T3-derived PA317 producer cell line, and RV derived from it were all sensitive to human serum inactivation. In contrast, all human cell lines tested were resistant to lysis. RV and RV-producer cells derived from 293 cells were also resistant; RV derived from HOS cells were resistant. Surprisingly, while TE671 cells were resistant, TE671-derived RV were sensitive to inactivation. To test whether expression of the amphotropic envelope protein was responsible for conferring this serum sensitivity to the RV, env was expressed in the absence of gag and pol in TE671 cells. However, TE671 cells expressing env were resistant to human serum inactivation. These observations have important implications for use of RV and RV-producer cells for human gene therapy.

3T3 Cells↗

A new measure of the robustness of biochemical networks.

MOTIVATION: The robustness of a biochemical network is defined as the tolerance of variations in kinetic parameters with respect to the maintenance of steady state. Robustness also plays an important role in the fail-safe mechanism in the evolutionary process of biochemical networks. The purposes of this paper are to use the synergism and saturation system (S-system) representation to describe a biochemical network and to develop a robustness measure of a biochemical network subject to variations in kinetic parameters. Since most biochemical networks in nature operate close to the steady state, we consider only the robustness measurement of a biochemical network at the steady state. RESULTS: We show that the upper bound of the tolerated parameter variations is related to the system matrix of a biochemical network at the steady state. Using this upper bound, we can calculate the tolerance (robustness) of a biochemical network without testing many parametric perturbations. We find that a biochemical network with a large tolerance can also better attenuate the effects of variations in rate parameters and environments. Compensatory parameter variations and network redundancy are found to be important mechanisms for the robustness of biochemical networks. Finally, four biochemical networks, such as a cascaded biochemical network, the glycolytic-glycogenolytic pathway in a perfused rat liver, the tricarboxylic acid cycle in Dictyostelium discoideum and the cAMP oscillation network in bacterial chemotaxis, are used to illustrate the usefulness of the proposed robustness measure.

Animals↗

Phytophthora parasitica elicitor-induced reactions in cells of Petroselinum crispum.

Cultured parsley (Petroselinum crispum) cells respond to treatment with elicitors derived from different species of the genus Phytophthora with transcript accumulation of defense-associated genes and the production of furanocoumarin phytoalexins. Pep-25, an oligopeptide fragment of a Phytophthora sojae 42-kDa cell wall protein, and a cell wall elicitor preparation derived from Phytophthora parasitica (Pp-elicitor) stimulate accumulation of the same gene transcripts and formation of the same pattern of furanocoumarins. Treatment of cultured cells and protoplasts with proteinase-digested Pp-elicitor identified proteinaceous constituents as active eliciting compounds in parsley. Similar to Pep- 25, Pp-elicitor induced effluxes of K+ and Cl- and influxes of protons and Ca2+. Concomitantly, as monitored in aequorin-transgenic parsley cell lines both elicitors induced an immediate increase in the cytoplasmic Ca2+ concentration up to sustained levels of 175 nM (Pp-elicitor) or 300 nM (Pep-25), respectively. The signature of the Ca2+ response differed greatly between the two elicitors tested. Extracellular Ca2+ proved essential for activation of an oxidative burst, MAP kinase activity and phytoalexin production by either elicitor. While Pp-elicitor induced a qualitatively similar spectrum of defense responses as did Pep-25, elicitor-specific quantitative differences in response intensity and kinetics suggest activation of a conserved signaling cascade through separate ligand binding sites.

Apiaceae↗

[The role of immunological mechanisms in the development of the late sequelae of nuclear disasters].

Effects, both specific and non-specific, were analysed of ionizing radiation in a comparative evaluation of medical sequels of the Chernobyl disaster and of the Semipalatinsk Range nuclear test. A hypothesis is advanced assuming that development of all major bodily morbid conditions is directly related to the dysfunction of certain complex of organs, the thyroid gland in the first place, the thymus gland known to be a central organ of systemic immunogenesis. A breach in the thymus link triggers harmful cascade reactions of neuroimmunoendocrinological regulation, appeared to be responsible for the pathogenesis of practically all pathologies disclosed.

Gene Expression Regulation↗

Venous thromboembolism. A review.

Venous thromboembolism (VTE) includes deep vein thrombosis (DVT) and pulmonary embolism (PE). A number of factors can increase VTE risk, including aging, smoking, immobility, pregnancy and a hereditary thrombophilia. Presenting symptoms are not definitive for DVT or PE, and objective testing is necessary for an accurate diagnosis. A number of antithrombolic agents are used in the prophylaxis and treatment of VTE. The current trend is toward using low-molecular-weight heparins instead of unfractionated heparin. There is increasing interest in new agents that can target a single factor in the coagulation cascade.

Age Factors↗

[Hydrogenase activity of the thermophilic hydrogen-oxidizing bacterium Pseudomonas thermophila].

The hydrogenase activity of the intact cells of a thermophilic hydrogen-oxidizing bacterium Pseudomonas thermophila K-2 was determined using methylene blue; it was several times higher than the rate of hydrogen uptake in the presence of oxygene and carbon dioxide. The activity of membrane-associated hydrogenase was assayed with the aid of phenazine methosulphate and 2,6-dichlorphenolindophenol as a cascade electron carrier. The enzyme is sufficiently stable in the air. The stability increases in the atmosphere of hydrogen. The membrane-bound enzyme was activated by Mn2+ ions. The pH-optimum of the enzyme activity in 0.1 M Tris-HCI buffer was 8,5-9,0. Natural electron acceptors tested, such as NAD, FMN, riboflavin, and cytochrome c, had no effect on the reaction rate. The enzyme is relatively thermostable: its activity was halved after heating at 78 degrees C for 10 min or at 80 degrees C for 8 min. Energy of activation was calculated. It was 14.5 kcal-mol-1 within the range of 23-40 degrees C and 10.3 kcal-mol-1 within the range of 40-60 degrees C.

Hot Temperature↗