Frequency encoding in excitable systems with applications to calcium oscillations.

A number of excitable cell types respond to a constant hormonal stimulus with a periodic oscillation in intracellular calcium. The frequency of oscillation is often proportional to the hormonal stimulus, and one says that the stimulus is frequency encoded. Here we develop a theory of frequency encoding in excitable systems and apply it to intracellular calcium oscillations that results from increases in the intracellular level of inositol 1,4,5-triphosphate.

The role of group I metabotropic glutamate receptor's in neuronal excitotoxicity in Alzheimer's disease

Neurodegenerative diseases such as Huntington's disease, ischemia, and Alzheimer's disease (AD) are major causes of death. Recently, metabotropic glutamate receptors (mGluRs), a group of seven-transmembrane-domain proteins that couple to G-proteins, have become of interest for studies of pathogenesis. Group I mGluRs control the levels of second messengers such as inositol 1,4,5-triphosphate (IP3) Cal(2+) ions and cAMP. They elicit the release of arachidonic acid via intracellular Ca2+ mobilization from intracellular stores such as mitochondria and endoplasmic reticulum. This facilitates the release of glutamate and could trigger the formation of neurofibrillary tangles, a pathological hallmark of AD. mGluRs regulate neuronal injury and survival, possibly through a series of downstream protein kinase and cysteine protease signaling pathways that affect mitochondrially mediated programmed cell death. They may also play a role in glutamate-induced neuronal death by facilitating Cal(2+) mobilization. Hence, mGluRs have become a target for neuroprotective drug development. They represent a pharmacological path to a relatively subtle amelioration of neurotoxicity because they serve a modulatory rather than a direct role in excitatory glutamatergic transmission.

Role of Ca2+ in proteolysis-inducing factor (PIF)-induced atrophy of skeletal muscle

Proteolysis-inducing factor (PIF) induces muscle loss in cancer cachexia through a high affinity membrane bound receptor. This study investigates the mechanism by which the PIF receptor communicates to intracellular signalling pathways. C2C12 murine myoblasts were used as a model using PIF purified from MAC16 tumours. Calcium imaging was determined using fura-4-acetoxymethyl ester (Fura-4-AM). PIF induced a rapid rise in Ca2 +i, which was completely attenuated by a anti-receptor antibody, or peptides representing 20 mers of the N-terminus of the PIF receptor. Other agents catabolic for skeletal muscle including angiotensin II (AngII) tumour necrosis factor-a (TNF-a) and lipopolysaccharide (LPS) also induced a rise in Ca2 +i, but this was not attenuated by anti-PIF-receptor antibody. The rise in Ca2 +i induced by PIF and AngII was completely attenuated by the Zn2 + chelator D-myo-inositol-1,2,6-triphosphate, and this was reversed by administration of exogenous Zn2 +. The Ca2 +i rise induced by PIF was independent of the presence of extracellular Ca2 +, and attenuated by the Ca2 + pump inhibitor thapsigargin, suggesting that the Ca2 +i rise was due to release from intracellular stores. This rise in Ca2 +i induced by PIF was attenuated by both the phospholipase C inhibitor U73122 and 2-APB, an inhibitor of the inositol 1,4,5-triphosphate receptor, suggesting the involvement of a G-protein. Binding of the PIF to its receptor in skeletal muscle triggers a rise in Ca2 +i, which initiates a signalling cascade leading to a depression in protein synthesis, and an increase in protein degradation.

The role of Ca2+ in the generation of spontaneous astrocytic Ca2+ oscillations

Astrocytes in the rat thalamus display spontaneous [Ca2+]i oscillations that are due to intracellular release, but are not dependent on neuronal activity. In this study we have investigated the mechanisms involved in these spontaneous [Ca2+]i oscillations using slices loaded with Fluo-4 AM (5 μM) and confocal microscopy. Bafilomycin A1 incubation had no effect on the number of spontaneous [Ca2+]i oscillations indicating that they were not dependent on vesicular neurotransmitter release. Oscillations were also unaffected by ryanodine. Phospholipase C (PLC) inhibition decreased the number of astrocytes responding to metabotropic glutamate receptor (mGluR) activation but did not reduce the number of spontaneously active astrocytes, indicating that [Ca2+]i increases are not due to membrane-coupled PLC activation. Spontaneous [Ca2+]i increases were abolished by an IP3 receptor antagonist, whilst the protein kinase C (PKC) inhibitor chelerythrine chloride prolonged their duration, indicating a role for PKC and inositol 1,4,5,-triphosphate receptor activation. BayK8644 increased the number of astrocytes exhibiting [Ca2+]i oscillations, and prolonged the responses to mGluR activation, indicating a possible effect on store-operated Ca2+ entry. Increasing [Ca2+]o increased the number of spontaneously active astrocytes and the number of transients exhibited by each astrocyte. Inhibition of the endoplasmic reticulum Ca2+ ATPase by cyclopiazonic acid also induced [Ca2+]i transients in astrocytes indicating a role for cytoplasmic Ca2+ in the induction of spontaneous oscillations. Incubation with 20 μM Fluo-4 reduced the number of astrocytes exhibiting spontaneous increases. This study indicates that Ca2+ has a role in triggering Ca2+ release from an inositol 1,4,5,-triphosphate sensitive store in astrocytes during the generation of spontaneous [Ca2+]i oscillations

Analysis of the signal transduction in the hawk moth Manduca sexta

Fliegende Insekten orientieren sich in ihrer Umwelt mit Hilfe ihres hoch entwickelten olfaktorischen Systems. Es ermöglicht ihnen das Auffinden geeigneter Futter- und Eiablageplätze und ist unverzichtbar bei der innerartlichen Kommunikation. Der Geruchssinn muss dabei gleichzeitig sehr schnell und sensitiv sein um selbst geringste Mengen, z.B. des arteigenen Sexualpheromons, wahrnehmen zu können. Spezifische olfaktorische Rezeptoren (ORs) zur Detektion dieser Duftstoffe werden zusammen mit einem hoch konservierten Co-Rezeptor (Orco) in olfaktorischen Rezeptorneuronen (ORNs) auf den Insektenantennen exprimiert. Sie gehören zu den 7 Transmembran Rezeptoren, zeigen jedoch eine invertierte Membrantopologie im Vergleich zu den ORs der Vertebraten. Darüber hinaus bildet der OR/Orco-Komplex einen spontanaktiven Kationenkanal, die Bindung an ein G Protein ist allerdings umstritten. Daher ist noch ungeklärt, ob die Duftstoffbindung zu einer ionotropen Aktivierung des OR/Orco Kanals führt oder ob metabotrope Mechanismen die Bildung von zyklischem Adenosinmonophosphat (cAMP) oder Inositol 1,4,5-trisphosphat (IP3) bewirken. Mit Hilfe von extrazellulären Ableitungen einzelner Trichoidsensillen (tip recordings) auf den Antennen männlicher Manduca sexta wurde die Rolle von Orco sowie die Beteiligung einer Phospholipase Cβ (PLCβ)-abhängigen Transduktionskaskade untersucht. Es konnte gezeigt werden, dass die durch VUAA1 induzierte Spontanaktivität der ORNs durch OLC15 inhibiert und Orco somit kompetitiv gehemmt wurde. Eine Inhibition von Orco sollte die Antwort auf kurze Pheromonpulse sofort reduzieren, sollte die Transduktion über die Aktivierung des OR/Orco Kanals erfolgen. Die Ergebnisse dieser Arbeit zeigten jedoch keine Beeinflussung der primären Pheromonantwort, vielmehr wurde die späte, langanhaltende Antwort reduziert. Die ebenfalls als Orco-Antagonisten charakterisierten Amiloride MIA und HMA beeinflussen offensichtlich weitere Ziele, da eine substanz- und zeitgeberzeitabhängige Reduzierung der primären Antwort auftrat. Zusätzlich wurde die primäre Pheromonantwort durch die Inhibierung der PLCβ und der Proteinkinase C (PKC), sowie durch die Verwendung zweier Diacylglycerol (DAG)- Derivate signifikant beeinflusst. Hierbei zeigte die Inhibierung von PLCβ und PKC zeitgeberzeitabhängige Unterschiede in der Stärke der Antwortreduktion. Auch die Applikation des DAG-Derivates DOG reduzierte die Pheromonantwort, während die Zugabe von OAG die ORN Aktivität steigern oder reduzieren konnte, abhängig von der verwendeten Derivatkonzentration und der Pheromonkonzentration. Die Ergebnisse dieser Arbeit deuten somit auf einen metabotropen, sehr wahrscheinlich PLCβ-abhängigen Mechanismus für die Pheromontransduktion bei Manduca sexta.

Antioxidant and antimicrobial properties of 2-(4,5-dihydro-1H-pyrazol-1-yl)-pyrimidine and 1-carboxamidino-1H-pyrazole derivatives

Five previously synthesized 4-trifluoromethyl-2-(5-aryl-3-styryl-1H-pyrazol-1yl)-pyrimidines and six 5-aryl-3-styryl-1-carboxamidino-1H-pyrazole derivatives were screened for their antioxidant proprieties. The antioxidant activities were evaluated by using the DPPH and the HRP/luminol/H2O2 chemiluminescence assay systems and for their antimicrobial activity (MIC). The results were good for those series in some concentration in comparison with the standards.

1-Benzoyl-5-phenyl-2-(propan-2-yl)-1,2,3,4-tetrahydropyrimidin-4-one

The tetrahydropyrimidinone ring in the title compound, C(20)H(20)N(2)O(2), is in a half-boat conformation with the N-C-N C atom 0.580 (2) angstrom out of the plane defined by the remaining five atoms. In the crystal structure, molecules are connected into centrosymmetric dimers via N-H center dot center dot center dot O interactions. The dimeric aggregates are linked into supramolecular chains along the a axis via C-H center dot center dot center dot pi interactions.

Design of 1D and 2D molecule-based magnets with the ligand 4,5-dimethyl-1,2-phenylenebis(oxamato)

Three new bimetallic oxamato-based magnets with the proligand 4,5-dimethyl-1,2-phenylenebis-(oxamato) (dmopba) were synthesized using water or dimethylsulfoxide (DMSO) as solvents. Single crystal X-ray diffraction provided structures for two of them: [MnCu(dmopba)(H(2)O)(3)]n center dot 4nH(2)O (1) and [MnCu(dmopba)(DMSO)(3)](n center dot)nDMSO (2). The crystalline structures for both 1 and 2 consist of linearly ordered oxamato-bridged Mn(II)Cu(II) bimetallic chains. The magnetic characterization revealed a typical behaviour of ferrimagnetic chains for 1 and 2. Least-squares fits of the experimental magnetic data performed in the 300-20 K temperature range led to J(MnCu) = -27.9 cm(-1), g(Cu) = 2.09 and g(Mn) = 1.98 for 1 and J(MnCu) = -30.5 cm(-1), g(Cu) = 2.09 and g(Mn) = 2.02 for 2 (H = -J(MnCu)Sigma S(Mn, i)(S(Cu, i) + S(Cu, i-1))). The two-dimensional ferrimagnetic system [Me(4)N](2n){Co(2)[Cu(dmopba)](3)}center dot 4nDMSO center dot nH(2)O (3) was prepared by reaction of Co(II) ions and an excess of [Cu(dmopba)](2-) in DMSO. The study of the temperature dependence of the magnetic susceptibility as well as the temperature and field dependences of the magnetization revealed a cluster glass-like behaviour for 3.

Antioxidant Capacity of 2-(3,5-diaryl-4,5-dihydro-1H-pyrazol-1-yl)-4-phenylthiazoles

The antioxidant capacity of 2-(3,5-diaryl-4,5-dihydro-1H-pyrazol-1-yl)-4-phenylthiazoles was evaluated. The values of antioxidant capacities of compounds 2d and 2e were found to be, respectively, 2,700 +/- 150 and 3,135 +/- 230 TE by the ORAC method, corresponding to a significant antioxidant capacity.

New antitumoral agents I: In vitro anticancer activity and in vivo acute toxicity of synthetic 1,5-bis(4-hydroxy-3-methoxyphenyl)-1,4-pentadien-3-one and derivatives

This paper describes a new method for the preparation of 1,5-bis(4-hydroxy-3-methoxyphenyl)-1,4-pentadien-3-one 1 and its derivatives 2-5. This set of synthetic compounds exhibited high antitumoral activities regarding in vitro screening against several human tumor cell lines as lung carcinoma NCI-460, melanoma UACC-62, breast MCF-7, colon HT-29, renal 786-O, ovarian OVCAR-03 and ovarian expressing the resistance phenotype for adriamycin NCI-ADR/ RES, prostate PC-3, and leukemia K-562. Compounds were also tested against murine tumor cell line B16F10 melanoma and lymphocytic leukemia L1210 as well as to their effect toward normal macrophages. Specific activity against colon cancer cells HT-29 was observed for all tested compounds and suggests further studies with models of colon cancer. Compounds 1, 2, and 4 showed significant cytotoxic activity with IC(50) values <= 2.3 mu M for all human cancer cell lines. Intraperitoneal acute administration of compound 1 and 2 showed very low toxicity rate. (C) 2010 Elsevier Ltd. All rights reserved.

Efficient sonochemical synthesis of novel 3,5-diaryl-4,5-dihydro-1H-pyrazole-1-carboximidamides

An Ultrasound-assisted preparation of a series of novel 3,5-diaryl-4,5-dihydro-1H-pyrazole-1-carboximidamides that proceeds via the efficient reaction of chalcones with aminoguanidine hydrochloride under clean conditions is described. (C) 2009 Elsevier B.V. All rights reserved.

Environmentally friendly sonocatalysis promoted preparation of 1-thiocarbamoyl-3,5-diaryl-4,5-dihydro-1H-pyrazoles

An efficient and green synthesis of thiocarbamoyl-3,5-diaryl-4,5-dihydro-1 H-pyrazoles via the condensation of chalcones with thiosemicarbazide in ethanol and KOH under ultrasound irradiation is reported. The products were isolated in good yields after short reaction times. (C) 2009 Elsevier B.V. All rights reserved.

Synthesis of 5-alkynyl-2,2,6-trimethyl-1,3-dioxin-4-ones and 1,4-disubstituted-1,2,3-triazoles

Herein we report an approach to the formation of 5-alkynyl-1,3-dioxin-4-ones using Suzuki-Miyaura cross-coupling reaction of potassium alkynyltrifluoroborate salts with 2,2,6-trimethy1-5-iodo-1,3-dioxin-4-one. The resulting 5-ethynyltrimethylsilyl-1,3-dioxin-4-ones obtained through the Sonogashira reaction were further reacted in a Cu(I)-catalyzed Huisgen azide-alkyne 1,3-dipolar cycloaddition to form functionalized 1,4-disubstituted-1,2,3-triazoles in good yields, using mild conditions and ultrasonic radiation to expedite the reaction. (C) 2011 Elsevier Ltd. All rights reserved.

mRNA differential display of 2-amino-1-methyl-6-phenylinlidazo[4,5-b]pyridine-induced rat mammary gland tumors

The mRNA differential display technique was used to compare mRNAs between normal mammary gland and turner-derived epithelial cells from female Sprague-Dawley rat mammary gland tumors induced by the heterocyclic amine 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) and promoted by a high-fat diet (23.5% corn oil). Two genes, beta-casein and transferrin, were identified as differentially expressed. The expression of these genes was examined across a bank of rat mammary gland tumors derived from animals on a low-fat diet (5% corn oil) or the high-fat diet. Carcinomas had over a 10- and 50-fold lower expression of beta-casein and transferrin, respectively than normal mammary gland. In addition, carcinomas from animals on the high-fat diet showed on average a 5-fold higher expression of beta-casein, and transferrin than carcinomas from animals on the low-fat diet. The results indicate the process of mammary gland tumorigenesis alters the expression of certain genes in the mammary gland, and that the level of dietary fat further modulates the expression of these genes.

Characterization of peroxisome proliferator-activated receptor alpha in normal rat mammary gland and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine-induced mammary gland tumors from rats fed high and low fat diets

Normal Sprague-Dau ley rat mammary gland epithelial cells and mammary gland carcinomas induced by 2-amino-1 -methyl-6-phenylimidazo[4,5-b]pyridine, a carcinogen found in the diet, were examined for the expression of peroxisome proliferator-activated receptor alpha (PPAR alpha). PPAR alpha mRNA and protein was detected in normal and tumor tissue by reverse transcriptase polymerase chain reaction (RT-PCR) and immunohistochemistry. By quantitative RT-PCR, carcinomas had a 12-fold higher expression than control mammary glands, a statistically significant difference. PPAR alpha expression was examined in carcinomas and normal tissues from rats on high fat (23.5/% corn oil) and low fat (5% corn oil) diets. Although neither carcinomas, nor control tissues showed statistically significant differences between the two diet groups, PPAR alpha expression was the highest in carcinomas from rats on the high fat diet. The expression of PPAR alpha in normal mammary gland and its significant elevation in mammary gland carcinomas raises the possibility of its involvement in mammary gland physiology and pathophysiology. (C) 2000 Published by Elsevier Science Ireland Ltd. All rights reserved.