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A 43-year-old female patient diagnosed with chronic progressive external ophthalmoplegia (CPEO) because of mitochondrial myopathy documented by muscle biopsy is presented. The chief complaints were represented by blepharoptosis and ophthalmoplegia. The muscle biopsy was evaluated by histology, using the appropriate histochemical and histoenzimological stains. Ragged red fibers with Gomori trichrome stain were seen, which showed cytochrome coxydase deficiency and abnormal succinate dehydrogenase staining in around 20 of muscle fibres. Electron microscopy was also performed which demonstrated abnormal, hyperplastic, pleomorphic, and hypertrophic mitochondria, characterized by paracrystalline inclusions arranged in parallel rows (“parking-lot” inclusions), consisting of rectangular arrays of mitochondrial membranes in a linear or grid-like pattern. In conclusion, mitochondrial myopathy was definitely diagnosed. Although molecular analysis, which was subsequently carried out, failed to reveal mutations in the mitochondrial DNA or in selected nuclear genes, the pathologic diagnosis was not changed. The differential diagnosis of CPEO with other forms of ocular myopathies as well as the possible association of CPEO with systemic syndromes is discussed. Ophtalmologists and medical internists should always suspect CPEO when dealing with patients affected by ocular myopathy, either in its pure form or in association with other myopathic or systemic signs.

For a comprehensive modeling of pedestrian dynamics in real-world scenarios the consideration of tactical level decisions in addition to operational ones is necessary. This paper presents a hybrid agent architecture employing a Floor Field approach at the operational level but granting agents an abstract representation of the simulated environment. The paper briefly presents the environmental model and hybrid agent architecture based on the floor field approach, then a sample practical application in a simple case study is also presented to show how it allows specifying abstract behavioural scriptsfor different groups of agents.

Bone marrow mesenchymal cells (MSCs) can protect leukemic cells from chemotherapy, thus increasing their survival rate. We studied the potential molecular mechanisms underlying this effect in acute lymphoblastic leukemia (ALL) cells. Coculture of ALL cells with MSCs induced on the lymphoblast plasma membrane the expression of a signaling complex formed by hERG1 (human ether-à-go-go-related gene 1) channels, the ß1-integrin subunit, and the chemokine receptor CXC chemokine receptor-4. The assembly of such a protein complex activated both the extracellular signal-related kinase 1/2 (ERK1/2) and the phosphoinositide 3-kinase (PI3K)/Akt prosurvival signaling pathways. At the same time, ALL cells became markedly resistant to chemotherapy-induced apoptosis. hERG1 channel function appeared to be important for both the initiation of prosurvival signals and the development of drug resistance, because specific channel blockers decreased the protective effect of MSCs. NOD/SCID mice engrafted with ALL cells and treated with channel blockers showed reduced leukemic infiltration and had higher survival rates. Moreover, hERG1 blockade enhanced the therapeutic effect produced by corticosteroids. Our findings provide a rationale for clinical testing of hERG1 blockers in the context of antileukemic therapy for patients with ALL.

Targeted therapy is considerably changing the treatment and prognosis of cancer. Progressive understanding of the molecular mechanisms that regulate the establishment and progression of different tumors is leading to ever more specific and efficacious pharmacological approaches. In this picture, ion channels represent an unexpected, but very promising, player. The expression and activity of different channel types mark and regulate specific stages of cancer progression. Their contribution to the neoplastic phenotype ranges from control of cell proliferation and apoptosis, to regulation of invasiveness and metastatic spread. As is being increasingly recognized, some of these roles can be attributed to signaling mechanisms independent of ion flow. Evidence is particularly extensive for K channels. Their expression is altered in many primary human cancers, especially in early stages, and they frequently exert pleiotropic effects on the neoplastic cell physiology. For instance, by regulating membrane potential they can control Ca2 fluxes and thus the cell cycle machinery. Their effects on mitosis can also depend on regulation of cell volume, usually in cooperation with chloride channels. However, ion channels are also implicated in late neoplastic stages, by stimulating angiogenesis, mediating the cell-matrix interaction and regulating cell motility. Not surprisingly, the mechanisms of these effects are manifold. For example, intracellular signaling cascades can be triggered when ion channels form protein complexes with other membrane proteins such as integrins or growth factor receptors. Altered channel expression can be exploited for diagnostic purposes or for addressing traceable or cytotoxic compounds to specific neoplastic tissue. What is more, recent evidence indicates that blocking channel activity impairs the growth of some tumors, both in vitro and in vivo. This opens a new field for medicinal chemistry studies, which can avail of the many available tools, such as blocking antibodies, antisense oligonucleotides, small interfering RNAs, peptide toxins and a large variety of small organic compounds. The major drawback of this approach is that some ion channel blockers produce serious side effects, such as cardiac arrhythmias. Therefore, drug developing efforts aimed at producing less harmful compounds are needed and we discuss possible approaches toward this goal. Finally, we propose that a novel therapeutic tactic could be developed by unlocking ion channels from multiprotein membrane signaling complexes.

Thin films of HfO2are grown by metal‐organic (MO)CVD on Si(001) and fused quartz substrates in the temperature range 400–500 °C, using a new series of bis‐cyclopentadienyl bis‐amino‐alkoxide hafnium precursors, namely [(C5H5)2Hf{OC(CH3)2CH2N(CH3)2}2] and [(C5H5)2Hf{OCH(CH3)CH2N(CH3)2}2], stable in air because of their strong coordination to the metal center. The films obtained are investigated by X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), Rutherford backscattering spectroscopy (RBS), and atomic force microscopy (AFM). Monoclinic phase HfO2(baddeleyite) films, characterized by a correct stoichiometric ratio and a granular surface morphology with a roughness/thickness ratio that decreases with increasing deposition rate, are obtained.

The extent of metal–metal electronic coupling was quantified for a series of synand antistereoisomers of (FeCp)2‐, (RhL2)2‐ and (FeCp)(RhL2)‐ (L2=1,5‐cyclooctadiene (cod), L=CO) as‐indacenediide mixed‐valent ions by spectroelectrochemical and DFT studies. The effect of the syn/antiorientation of the metal units with respect to the planar aromatic ligand indicates that electron transfer occurs through the bridge rather than through space. The nature of the metal was found to be crucial: while homobimetallic diiron species are localised valence‐trapped ions (Class II), the dirhodium analogues are almost delocalised mixed‐valent ions (borderline and Class III). Finally, despite their redox asymmetry, even in the heterobimetallic iron–rhodium as‐indacenediide complexes, strong metal–metal coupling is present. In fact, oxidation of the iron centre is accompanied by electron transfer from rhodium to iron and formation of a reactive 17‐electron rhodium site. synand antiFe–Rh as‐indacenediide complexes are rare examples of heterobimetallic systems which can be classified as borderline Class II/Class III species.

Magnesium boride films are synthesized from Mg(BH4)2by CVD. A new synthesis of the precursor is developed. Deposition time of the samples is varied to study its influence on film composition. The films are analyzed by means of X‐ray diffraction (XRD) and X‐ray photoelectron spectroscopy (XPS). The contributions of various chemical species (boride and oxides) in the depth profiles, carried out using Ar ion sputtering combined with cyclic XPS measurements, are separated by peak‐fitting analysis of photoelectron B1s and Auger MgKLL spectra. The samples are composed of MgBxfilm covered by an overlayer of magnesium and boron oxides.

Thin films of MgO are grown by CVD, with a high growth rate, on Si(001) and quartz substrates in the temperature range 400–550 °C, using bis(methylcyclopentadienyl)magnesium [Mg(CH3‐C5H4)2] as the precursor. The films obtained are investigated by X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and optical absorption, in order to investigate the interrelations between film properties and processing conditions. Cubic phase MgO (periclase) films, characterized by a low carbon contamination and a granular surface morphology, are obtained.

A series of heterobimetallic complexes of general structure [RhL2{η5‐(2‐ferrocenyl)indenyl}] (L2=cod, nbd, L=CO; cod=cyclooctadiene; nbd=norbornadiene) has been synthesised with the aim of tuning the metal–metal interaction in their mixed‐valence ions generated both by chemical and electrochemical oxidation, and the results are compared with those obtained for [RhL2{η5‐(1‐ferrocenyl)indenyl}] isomers. Crystallographic studies and DFT calculations provide a detailed description of the structural and electronic features of these complexes evidencing a significant difference in the extent of planarity of the flexible bridging ligand between the 1‐ and 2‐ferrocenyl isomers. Independent experimental probes, in particular the potential splitting in the cyclic voltammograms and the IT bands in the near‐IR spectra, are rationalised in the framework of Marcus–Hush theory and at quantum chemistry level by DFT and TD‐DFT methods. These methods allow us to establish a trend based on the magnitude of iron–rhodium electronic coupling Habranging from valence trapped to almost delocalised ions. The quasi planar bridge and the olefin ancillary ligands make [Rh(nbd){η5‐(2‐ferrocenyl)indenyl}]+and [Rh(cod){η5‐(2‐ferrocenyl)indenyl}]+rare examples of heterobimetallic systems which can be classified as borderline Class II/Class III species.

The complexes [Pd(η2-dmfu)(P–N)] [P–N = 2-(PPh2)C6H4-1-CHNR, R = C6H4OMe-4; CHMe2; C6H3Me2-2,6; C6H3(CHMe2)-2,6] react with an excess of BrC6H4R1-4 (R1= CF3; Me) yielding the oxidative addition products [PdBr(C6H4R1-4)(P–N)] at different rates depending on R [C6H4OMe-4 > C6H3(CHMe2)-2,6 > CHMe2 C6H3Me2-2,6] and R1(CF3 Me). In the presence of K2CO3and activated olefins (ol = dmfu, fn), the latter compounds react with an excess of 4-R2C6H4B(OH)2(R2= H, Me, OMe, Cl) to give [Pd(η2-ol)(P–N)] and the corresponding biaryl through transmetallation and fast reductive elimination. The transmetallation proceeds viaa palladium(ii) intermediate with an O-bonded boron anion, the formation of which is markedly retarded by increasing the bulkiness of R. The intermediate was isolated for R = CHMe2, R1= CF3and R2= H. The boron anion is formulated as a diphenylborinate anion associated with phenylboronic acid and/or as a phenylboronate anion associated with diphenylborinic acid. In general, the oxidative addition proceeds at a lower rate than transmetallation and represents the rate-determining-step in the coupling reaction of aryl bromides with arylboronic acids catalyzed by [Pd(η2-dmfu)(P–N)].

The heterobinuclear isomers [η⁶-(2-ferrocenyl)indene]-Cr(CO)3 (1) and [η⁶-(3-ferrocenyl)indene-Cr(CO)3 (2) have been prepared and the crystal structure determination showed that the Fe(C5H5) and Cr(CO)3 groups in the two molecules are disposed in different conformations with respect to the Cp-indene bridging ligand, cisoid in 1 and transoid in 2. Preliminary electrochemical (CV) and spectroscopic (IR and near-IR) results obtained for the corresponding monooxidized 1⁺ and 2⁺ demonstrate the existence of stronger electronic coupling in 1⁺ than in 2⁺.

Adhesive receptors of the integrin family are primarily involved in cell–extracellular matrix adhesion. Additionally, integrins trigger multiple signaling pathways that are involved in cell migration, proliferation, survival, and differentiation. We previously demonstrated that the activation of integrins containing the β1subunit leads to a selective increase in potassium currents carried by the human ether-a-go-go-related gene (hERG) channels in neuroblastoma and leukemia cells; this current activation modulates adhesion-dependent differentiation in these cells. We hypothesized that the cross-talk between integrins and hERG channels could be traced back to the assembly of a macromolecular signaling complex comprising the two proteins. We tested this hypothesis in both SH-SY5Y neuroblastoma cells and in human embryonic kidney 293 cells stably transfected with hERG1and, therefore, expressing only the full-length hERG1 protein on the plasma membrane. The β1integrin and hERG1 coprecipitate in these cells and colocalize in both intracellular and surface membrane compartments. The two proteins also coprecipitate with caveolin-1, suggesting the localization of the complex in lipid rafts/caveolae. hERG1-transfected cells undergo an activation of hERG currents after β1integrin-mediated adhesion to fibronectin; concomitant with this activation, the focal adhesion kinase associates with the hERG1 protein and becomes tyrosine phosphorylated. Using hERG1-specific inhibitors, we show that the tyrosine phosphorylation of focal adhesion kinase is strictly dependent on hERG channel activity. Similarly, the activity of the small GTPase Rac1 turned out to be dependent on hERG currents. On the whole, these data indicate that the hERG1 protein associates with β1integrins and modulates adhesion receptor signaling.

The complexes [Pd(η²-dmfu)(P−N)] {dmfu = dimethyl fumarate; P−N = 2-(PPh2)C6H4−1-CH=NR, R = C6H4OMe-4 (1a), CHMe2 (2a), C6H3Me2-2,6 (3a), C6H3(CHMe2)2-2,6 (4a)} undergo dynamic processes in solution which consist of a P−N ligand site exchange through initial rupture of the Pd−N bond at lower energy and an olefin dissociation-association at higher energy. According to equilibrium constant values for olefin replacement, the complex [Pd(η²-fn)(P−N)] (fn = fumaronitrile, 1b) has a greater thermodynamic stability than its dmfu analogue 1a. The kinetics of the oxidative addition of ArI (Ar = C6H4CF3-4) to 1a and 2a lead to the products [PdI(Ar)(P−N)] (1c, 2c) and obey the rate law, kobs = k1A + k2A[ArI]. The k1A step involves oxidative addition to a reactive species [Pd(solvent)(P−N)] formed from dmfu dissociation. The k2A step is better interpreted in terms of oxidative addition to a species [Pd(η²-dmfu)(solvent)(κ¹-P−N)] formed in a pre-equilibrium step from Pd−N bond breaking. The complexes 1c and 2c react with PhC≡CSnBu3 in the presence of an activated olefin (ol = dmfu, fn) to yield the palladium(0) derivatives [Pd(η²-ol)(P−N)] along with ISnBu3 and PhC≡CAr. The kinetics of the transmetallation step, which is rate-determining for the overall reaction, obey the rate law: kobs = k2T[PhC≡CSnBu3]. The k2T values are markedly enhanced in more polar solvents such as CH3CN and DMF. The solvent effect and the activation parameters suggest an associative SE2 mechanism with substantial charge separation in the transition state. The kinetic data of the above reactions in various solvents indicate that, for the cross-coupling of PhC≡CSnBu3 with ArI catalysed by 1a or 2a, the rate-determining step is represented by the oxidative addition and that CH3CN is the solvent in which the highest rates are observed. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

The new η²-formamidinyl Zr complex Zr(NMeCyc)2[C(NAr)NMeCyc]2 (1) (Ar = 2,6-dimethylphenyl, Cyc = cyclohexyl) was prepared upon double insertion of 2,6-dimethyl phenyl isocyanide in the Zr−N bond of Zr(NMeCyc)4. 1 was then converted into Zr(OC6F5)2[C(NAr)NMeCyc]2 (2) and ZrCl2[C(NAr)NMeCyc]2 (3) by reacting it with C6F5OH and [NHMe3]Cl, respectively. The crystal structure of 1 was established by X-ray analysis. All the complexes have been tested as catalysts for the polymerization of ethylene and 1-hexene in the presence of [NHMe2Ph][B(C6F5)4] as cocatalyst.

The reactions of [Pd(η2-dmfu)(P–N)] [dmfu = dimethyl fumarate; P–N = 2-(PPh₂)C₆H₄-1-CH&z.dbd;NR, R = C₆H₄OMe-4 (1a), CHMe₂ (2a)] and [Pd(η2-dmfu)(P–N)₂] with IC₆H₄CF₃-4, ISnBu₃ and PhC&z.tbd;CSnBu₃ have been studied under pseudo-first-order conditions. The oxidative addition of IC₆H₄CF₃-4 yields [PdI(C₆H₄CF₃-4)(P–N)] (1b or 2b). No reaction takes place with PhC&z.tbd;CSnBu₃ and also with ISnBu₃ in the presence of an excess of PhC&z.tbd;CSnBu₃. In the presence of fumaronitrile (fn), 1b and 2b undergo transmetalation by PhC&z.tbd;CSnBu₃ followed by fast reductive elimination to yield [Pd(η2-fn)(P–N)]. The same reaction sequence occurs for the system [PdI(C₆H₄CF₃-4)(P–N)]/P–N (1 ∶ 1 molar ratio) to give [Pd(η2-fn)(P–N)₂]. The palladium(0) complexes are active catalysts in the cross-coupling of PhC&z.tbd;CSnBu₃ with aryl iodides ArI (Ar = C₆H₄CF₃-4, Ph). The catalytic efficiency depends on the complex: [Pd(η2-dmfu)(P–N)₂] > [Pd(η2-dmfu)(P–N)], and on the substituent R: C₆H₄OMe-4 > CHMe₂. The reactivity and spectroscopic data suggest a catalytic cycle involving initial oxidative addition of ArI to a palladium(0) species, followed by transmetalation of the product and by fast reductive elimination to regenerate the starting palladium(0) compound. For [Pd(η2-dmfu)(P–N)] as catalyst, the oxidative addition is the rate-determining step, while for [Pd(η2-dmfu)(P–N)₂] the oxidative addition and the transmetalation steps occur at comparable rate.

The role of K(+) channel activity during cell cycle progression has become a research topic of considerable interest. Blocking of K(+) channels inhibits the proliferation of many cell types, although the mechanism of this inhibition is unclear. There is speculation that K(+) channels differentially regulate the electrical potential of the plasma membrane (V(m)) during proliferation. We have demonstrated that in tumor cells the value of V(m) is clamped to rather depolarized values by K(+) channels belonging to the HERG family. We report here that tumor cell lines preferentially express the herg1 gene and a truncated, N-deleted form that corresponds to herg1b. This alternative transcript is also expressed in human primary acute myeloid leukemias. Both HERG1 and HERG1B proteins are expressed on the plasma membrane of tumor cells and can form heterotetramers. The expression of HERG protein isoforms is strongly cell cycle-dependent, accounting for variations in HERG currents along the mitotic cycle. Moreover, the blocking of HERG channels dramatically impairs cell growth of HERG-bearing tumor cells. These results suggest that modulated expression of different K(+) channels is the molecular basis of a novel mechanism regulating neoplastic cell proliferation.

The reactions of Pdη2-dmfuP–N dmfu dimethyl fumarate; P–N 2-PPh2C6H4-1-CHNR, R C6H4OMe-4 1a, CHMe22a and Pdη2-dmfuP–N2 with IC6H4CF3-4, ISnBu3and PhCCSnBu3have been studied under pseudo-first-order conditions. The oxidative addition of IC6H4CF3-4 yields PdIC6H4CF3-4P–N 1bor 2b. No reaction takes place with PhCCSnBu3and also with ISnBu3in the presence of an excess of PhCCSnBu3. In the presence of fumaronitrile fn, 1band 2bundergo transmetalation by PhCCSnBu3followed by fast reductive elimination to yield Pdη2-fnP–N. The same reaction sequence occurs for the system PdIC6H4CF3-4P–NP–N 1 1 molar ratio to give Pdη2-fnP–N2. The palladium0 complexes are active catalysts in the cross-coupling of PhCCSnBu3with aryl iodides ArI Ar C6H4CF3-4, Ph. The catalytic efficiency depends on the complex: Pdη2-dmfuP–N2 > Pdη2-dmfuP–N, and on the substituent R: C6H4OMe-4 > CHMe2. The reactivity and spectroscopic data suggest a catalytic cycle involving initial oxidative addition of ArI to a palladium0 species, followed by transmetalation of the product and by fast reductive elimination to regenerate the starting palladium0 compound. For Pdη2-dmfuP–N as catalyst, the oxidative addition is the rate-determining step, while for Pdη2-dmfuP–N2 the oxidative addition and the transmetalation steps occur at comparable rate.

The preparation of a new bioartificial material based on poly(2-hydroxyethyl methacrylate) and the enzyme α-amylase by means of template polymerisation is described. The kinetics of the polymerisation reaction was monitored by dilatometry and a template influence on the initial rate evidenced. The morphological analysis indicated that the presence of the enzyme induced a porous structure of the obtained material, in which improved interactions between the two components could be detected with respect to its analogous prepared by simple blending of the preformed polymers. The negligible release of the active component (α-amylase) from the polycomplex suggested its possible application as an enzyme immobilisation system, since the enzyme showed to remain active in the polycomplex as well. In order to improve the properties of the system poly(N-vinylpyrrolidone) was added as an additional component in the polymerisation of 2-hydroxyethyl methacrylate in the presence of α-amylase. Higher biological activity of the immobilised enzyme was obtained for polycomplexes containing PVP, confirming the expected stabilising effect. Scanning electron micrographs of an α-amylase / PHEMA complex 0.250 (weight ratio). The sample was dried and sputtered with gold; bar = 50 μm.

The heterobimetallic CpFe(μ-η⁵: η⁵-as-indacenediide)RhL2 complexes (L2 = COD (2), NBD (3), (ethylene)2 (4)) have been obtained from metalation of the mononuclear lithium CpFe(η⁵-as-indacenediide) with [Rh(μ-Cl)L2]2. Mixtures of syn and anti heterobimetallic complexes were formed and fully characterized by 2D NMR spectroscopy. The reactivity at the rhodium center is greatly influenced by the presence of the ferrocenyl moiety. The voltammetric behavior and the optical spectra are in favor of the existence of significant electronic interactions between the two metals.

The binuclear [η⁵-(1-ferrocenyl)indenyl]Rh(NBD) (1), [η⁵-(1-ferrocenyl)indenyl]Rh(COD) (1a), and [η⁵-(1-ferrocenyl)indenyl]Rh(CO)2 (2) complexes have been synthesized (NBD = norbornadiene; COD = cycloocta-1,5-diene). The crystal structure determination showed that the iron and rhodium nuclei are disposed in a transoid configuration in 1 probably to avoid steric repulsions. On the contrary, in 2 the metals are in a cisoid configuration due to the presence of stabilizing π-hydrogen bonds between the CO's and the hydrogens of the unsubstituted cyclopentadienyl ring. The results of the chemical and electrochemical oxidation of 2 are in favor of the existence of an effective interaction between the two metals.

The five-coordinate complexes [PtMe(cod)(N–N')]BF₄ [cod = η2,η2-cyclooctadiene, N–N' = (6-R2)C₅H₃N-2-CH&z.dbd;NR1 (R1 = C₆H₄OMe-4, R2 = H (1), Me (2); R1 = CMe₃, R2 = H (3), Me (4); R1 = (R)-bornyl, R2 = Me (5))] are readily obtained from the reaction of [PtClMe(cod)] with N–N' in the presence of NaBF₄. The preparation of [PtMe(cod)(6)]BF₄ (6 = 4-MeOC₆H₄N&z.dbd;CHCHN&z.dbd;C₆H₄OMe-4), [PdMe(cod)(N–N')]BF₄ and [PtCl(cod)(N–N')]BF₄ (N–N' = 2, 4) requires chloride abstraction by AgBF₄ from [PtClMe(cod)], [PdClMe(cod)] and [PtCl₂(cod)], respectively, followed by coordination of N–N'. The NMR spectral data suggest a trigonal-bipyramidal structure with chelating cod and N–N' ligands, where the α-diimine and one C&z.dbd;C bond are on the equatorial plane and the second C&z.dbd;C bond in an axial position. The complexes [PtMe(cod)(1)]BF₄ and [PtCl(cod)(2)]BF₄ undergo dynamic processes in solution which bring about N–N' ligand site exchange for the former, and exchange of all the olefinic protons for the latter. The X-ray diffraction analysis of [PtMe(cod)(2)]BF₄ indicates that in the solid state, the complex assumes a distorted trigonal-bipyramidal geometry, similar to that proposed to exist in solution. For the two independent molecules in the asymmetric unit cell, the differences in the structural parameters between the equatorial Pt–(CH&z.dbd;CH) bond [Pt–C 2.08(1), 2.09(2) Å, C&z.dbd;C 1.43(2) Å (molecule I); Pt–C 2.13(2), 2.10(2) Å, C&z.dbd;C 1.42(2) Å (molecule II)] and the axial Pt–(CH&z.dbd;CH) bond [Pt–C 2.35(1), 2.34(1) Å, C&z.dbd;C 1.39(2) Å (molecule I); Pt–C 2.37(2), 2.34(1) Å, C&z.dbd;C 1.38(2) Å (molecule II)] are related to the high trans influence of the methyl ligand and to greater d–π back-donation in the equatorial bond.

Using the patch-clamp technique, we analysed changes in the biophysical properties of HERG potassium channels in neuroblastoma cells long-term exposed to hypoxia. In this condition, HERG channels underwent a profound modulation that consisted of: (i) a slowing in open-close kinetics; (ii) a marked hyperpolarizing shift in voltage dependence of steady-state activation; and (iii) a slowing of the inactivation removal. The overall physiological impact of these changes in neuroblastoma cells is an increase in the HERG window current in the range of the resting potential ( V REST ), which varied between −40 and −30 mV. Such a current modulation is suitable to stabilise the resting potential ( V REST ) in hypoxic environments.

Two brothers with myopathic coenzyme Q10(CoQ10) deficiency responded dramatically to CoQ10supplementation. Muscle biopsies before therapy showed ragged-red fibers, lipid storage, and complex I III and II III deficiency. Approximately 30 of myofibers had multiple features of apoptosis. After 8 months of treatment, excessive lipid storage resolved, CoQ10level normalized, mitochondrial enzymes increased, and proportion of fibers with TUNEL-positive nuclei decreased to 10. The authors conclude that muscle CoQ10deficiency can be corrected by supplementation of CoQ10, which appears to stimulate mitochondrial proliferation and to prevent apoptosis.

In the presence of methanesulfonic acid, the palladium(0)-olefin complexes: [Pd(η2-ol)(PN)] [ol=dimethyl fumarate or fumaronitrile, PN=1-(Ph2P)C6H4-2-CHNR (R=CMe3or C6H4OMe-4)] catalyse the alkoxycarbonylation of terminal alkynes. Moderately good rates are obtained when the catalysts are promoted with two equivalents of the free PN ligand and a large excess of acid at 120°C. The catalytic data suggest that derivatives of the type [Pd(alkyne)(PN)n] (n=2–3) are the active catalytic species.

Integrin receptors have been demonstrated to mediate either “inside-to-out” and “outside-to-in” signals, and by this way are capable of regulating many cellular functions, such as cell growth and differentiation, cell migration, and activation. Among the various integrin-centered signaling pathways discovered so far, we demonstrated that the modulation of the electrical potential of the plasma membrane (VREST) is an early integrin-mediated signal, which is related to neurite emission in neuroblastoma cells. This modulation is sustained by the activation of HERG K+channels, encoded by the ether-à-go-go-relatedgene (herg). The involvement of integrin-mediated signaling is being discovered in the hemopoietic system: in particular, osteoclasts are generated as well as induced to differentiate by interaction of osteoclast progenitors with the stromal cells, through the involvement of integrin receptors. We studied the effects of cell interaction with the extracellular matrix protein fibronectin (FN) in a human leukemic preosteoclastic cell line (FLG 29.1 cells), which has been demonstrated to express HERG currents. We report here that FLG 29.1 cells indeed adhere to purified FN through integrin receptors, and that this adhesion induces an osteoclast phenotype in these cells, as evidenced by the appearance of tartrate-resistant acid phosphatase, as well as by the increased expression of CD51/αvβ3integrin and calcitonin receptor. An early activation of HERG current (IHERG), without any increase in hergRNA or modifications of HERG protein was also observed in FN-adhering cells. This activation is apparently sustained by the β1integrin subunit activation, through the involvement of a pertussis-toxin sensitive Giprotein, and appears to be a determinant signal for the up-regulation of αvβ3integrin, as well as for the increased expression of calcitonin receptor.

The human ether‐a‐go‐go‐relatedgenes (herg) are expressed in tissues other than heart and brain where the HERG K+channels are known to regulate the repolarization of the heart action potential and the neuronal spike‐frequency accommodation. We provide evidence that herg1transcripts are present in human pancreatic islets that were used to study both insulin secretion and electrical activity with radioimmunoassay and single cell perforated patch‐clamp techniques, respectively. Glucose‐ and arginine‐induced islets insulin secretion data suggested a net increase of release under perfusion with antiarrhythmic drugs known to selectively block HERG channels. Indeed we could routinely isolate a K+current that was recognized as biophysically and pharmacologically similar to the HERG current. An analysis of the glucose‐ and arginine‐induced electrical activity (several applications during 30 min) in terms of firing frequency and putative insulin release was done in control and in the presence of selective blockers of HERG channels: the firing frequency and the release increased by 32% and 77%, respectively. It is concluded that HERG channels have a crucial role in regulating insulin secretion and firing of human β‐cells. This raises the possibility that some genetically characterized hyperinsulinemic diseases of unknown origin might involve mutations in the HERG channels.—Rosati, B., Marchetti, P., Crociani, O., Lecchi, M., Lupi, R., Arcangeli, A., Olivotto, M., Wanke, E. Glucose‐ and arginine‐in‐duced insulin secretion by human pancreatic β‐cells: the role of HERG K+channels in firing and release. The FASEB J.14, 2601–2610 (2000)

The expression pattern of K+currents is the principal regulator of electrical activity during development of the nervous and muscular system. We report here a study showing the expression pattern of HERG K+currents-encoding (erg) genes in various nervous and muscular tissues at different stages of quail embryo development.

The modulation of herg gene and HERG currents (IHERG) was studied in SH-SY5Y neuroblastoma (NB) cells treated with all-trans-retinoic acid (RA) in the absence or presence of the neurotrophin brain-derived neurotrophic factor (BDNF). Both treatments produced a strong increase in the percentage of cells differentiated along the neuronal pathway, with an orientation to a cholinergic phenotype, while a minority of cells displayed a glial phenotype particularly evident after long-term exposure to the inducers. Differentiation of NB cells was accompanied by an increase in herg gene transcription, which attained its maximum after 6 days of treatment with RA and was not further increased by BDNF. This effect evidently reflected on HERG currents: In fact, RA produced an increase in HERG current density which was strongly potentiated by BDNF. Moreover, RA treatment affected the biophysical properties of IHERG, inducing an increase in the deactivation time constant and a left shift of the activation curve. These effects were not substantially affected by BDNF. This modulation of IHERG influenced the value of the resting potential (VREST), which resulted significantly hyperpolarized in (RA with or without BDNF)-treated cells. Interestingly, these effects were absent in the glial population, which prevailed in cultures after long-term exposure to the inducers. On the whole, we demonstrate that besides expressing IRK currents, NB cells display another strategy to hyperpolarize their VREST, based on the appropriate modulation of HERG currents. Different from what happens in normal neuroblast development, the latter are never lost by cancer cells despite the progression of these cells along the neuronal differentiative pathway, raising intriguing questions about the role of HERG currents in tumour behavior. © 1999 John Wiley & Sons, Inc. J Neurobiol 40: 214–225, 1999

The solution behavior of the cationic complexes [Pd(η³-allyl)(P−N)]⁺ (P−N = o-(PPh2)C6H4CH&dbd;NR (R = C6H4OMe-4, Me, CMe3, (R)-bornyl); allyl = propenyl (1a−4a) and 3-methyl-2-butenyl (1b−4b)) consists essentially of three dynamic processes:  (i) a very fast conformational change of the P−N chelate ring, which moves above and below the P−Pd−N coordination plane, (ii) a relatively fast η³−η¹−η³ interconversion which brings about a syn−anti exchange only for the allylic protons cis to phosphorus; (iii) a slower apparent rotation of the η³-allyl ligand around its bond axis. For 1b−3b, two geometrical isomers are observed, the predominant one having the allyl CMe2 group trans to phosphorus. The complexes 4a and 4b, containing the chiral (R)-bornyl group, are present in solution with two and four diastereomeric species, respectively. The X-ray structural analysis of 4b(ClO4) shows the presence of two diastereomeric molecules in the unit cell, both having distorted-square-planar coordination geometries, characterized by rather elongated Pd−CMe2 bonds trans to phosphorus and by a marked distortion of the allyl ligand, which is rotated away from the PPh2 group. The complexes [Pd(η³-allyl)(P−N)]⁺ react with secondary amines HY in the presence of fumaronitrile, yielding [Pd(η²-fn)(P−N)] and allylamines. Under pseudo-first-order conditions the amination rates obey the laws kobs = k2[HY] + k3[HY]² for 1a−4a and kobs = k2[HY] for 1b, 3b, and 4b. The k2 term is related to direct bimolecular attack on a terminal allyl carbon of the substrate, whereas the k3 term is ascribed to parallel attack by a further amine molecule on the intermediate [Pd(allyl)(P−N)(HY)]⁺. The k2 values increase with increasing basicity and decreasing steric hindrance of the amine, and with increasing electron-withdrawing ability and increasing bulkiness of the P−N nitrogen substituent. The higher amination rates for [Pd(η³-allyl)(P−N)]⁺, compared to [Pd(η³-allyl)(α-diimine)]⁺, are essentially due to lack of displacement equilibria of the P−N ligand by amines.

Quail neural crest cells were cultured in a differentiative medium to study the inward K+channel profile in neuronal precursors at various stages of maturation. Between 12 and 24 h of culture, neural crest‐derived neurons displayed, in addition to the previously described outward depolarization‐activated K+currents, an inward current enhanced in high K+medium. A biophysical and pharmacological analysis led us to conclude that this inward K+current is identical to that previously demonstrated in mouse and human neuroblastoma cell lines (IIR). This current (quail IIRor qllR), which is active at membrane potentials positive to ‐35 mV, was blocked by Cs+and by class Ill antiarrhythmic drugs, thus resembling the K+current encoded by the human ether‐a‐go‐go‐related gene (HERG). At later stages of incubation (>48 h), neural crest‐derived neurons underwent morphological and biochemical differentiation and expressed fast Na+currents. At this stage the cells lost qllR, displaying instead a classical inward rectifier K+(IRK) current (quail IIRK= qIIRK). This substitution was reflected in the resting potential (VREST), which became hyperpolarized by >20 mV compared with the 24 h cells. Neurons were also harvested from peripheral ganglia and other derivatives originating from the migration of neural crest cells, viz. ciliary ganglia, dorsal root ganglia, adrenal medulla and sympathetic chain ganglia. After brief culture following harvesting from young embryos, ganglionic neurons always expressed qilR. On the other hand, when ganglia were explanted from older embryos (7–12 days), briefly cultured neurons displayed the IRK‐like current. Again, in all the above derivatives the qllRsubstitution by qllRKwas accompanied by a 20 mV hyperpolarization of VREST. Together, these data indicate that the VRESTof normal neuronal precursors is sequentially regulated by HERG‐ and IRK‐like currents, suggesting that HERG‐like channels mark an immature and transient stage of neuronal differentiation, probably the same stage frozen in neuroblastomas by neoplastic transformation.

New neutral organometallic palladium(II) complexes, [PdPhI(PNMe2)] (1), [PdPhI(PC=NMe)] (2), [PdPhI(PC=NEt)] (3), and [PdMeCl(PNMe2)] (4), {PNMe2 means N,N-dimethyl-2-(diphenylphosphanyl)aniline; PC=NMe means N-[2-(diphenylphosphanyl)benzylidene]-N-methylamine; PC=NEt means N-[2-(diphenylphosphanyl)benzylidene]-N-ethylamine} have been synthesized by oxidative addition of PhI to [Pd(dba)2] in the presence of the P^∩N ligand (1–3), or by substitution reaction on [PdMeCl(COD)] with PNMe2 (4). Cationic σ-organometallic species [PdR(PPh3)(P^∩N)]⁺ are obtained upon treating complexes of the type [PdRX(P^∩N)] with PPh3 and AgCF3SO3 and consist predominantly of the trans-P,P isomer in CDCl3 solution, as shown by NMR spectroscopic studies. The cationic η³-allyl complex [Pd(η³-all)(PNMe2)]PF6 has also been prepared and characterized, both in solution and in the solid state. Compounds [PdPhI(PNMe2)] (P21/n), [PdPhI(PC=NMe)] (P1¯), [PdPhI(PC=NEt)] (P1¯), and [Pd(η³-all)(PNMe2)]PF6 (P1¯) have been authenticated by X-ray analysis

New neutral pentacoordinate nickel(II) complexes of the type [NiCl2(PR3)(P^∩N)] [PR3 = PMe3, PMe2Ph, PMePh2; P^∩N = 2-(diphenylphosphanyl)aniline (P^∩NH2), N-methyl-2-(diphenylphosphanyl)aniline (P^∩NHMe), N,N-dimethyl-2-(diphenylphosphanyl)aniline (P^∩NMe2)], as well as cationic tetracoordinate nickel(II) complexes of the type [NiCl(PR3)(P^∩N)]⁺ have been synthesized and characterized both in the solid state and in solution. Interesting X-ray structural data have been collected for each class of compounds, which show, inter alia, that the pentacoordinate neutral complexes can be isolated in two different molecular forms, namely square-pyramidal or bipyramidal-trigonal.

The complexes [Pd(η³-allyl)(N-N‘)]ClO4 [allyl = 2-butenyl or 3-methyl-2-butenyl, N-N‘ = C5H3(6-R)N-2-CH&dbd;NR‘ (R = H, R‘ = Me, CMe3, C6H4OMe-4; R = Me, R‘ = C6H4OMe-4) and C5H4N-2-CH2NMe2] are present in solution with different isomers, the structures of which may be assigned by an ¹H NMR criterion based on chemical shift changes of the pyridine H(6) and/or of the allylic methyl protons, as confirmed also by 2D ¹H NMR spectra. The isomer distribution depends mainly on the steric requirements of both the allyl and N-N‘ ligands:  for [Pd(η³-3-methyl-2-butenyl)(N-N‘)]ClO4 the predominant isomer (ca. 100%) has a structure with the allylic methyl groups cis to the coordinated pyridine nitrogen when N-N‘ = C5H4N-2-CH&dbd;NCMe3 and cis to the coordinated imino nitrogen when N-N‘ = C5H3(6-Me)N-2-CH&dbd;NC6H4OMe-4. In chlorinated solvents (dichloromethane-d2 or 1,1,2,2-tetrachloroethane-d2) the isomers undergo mutual interconversion through a mechanism involving an apparent rotation of the η³-allyl ligand around its bond axis to the metal. The interconversion rates depend on the nature of allyl and N-N‘ ligands and increase considerably when the compounds are dissolved in dimethyl-d6 sulfoxide. The apparent allyl rotation also occurs for the analogous (η³-2-methyl-2-propenyl)palladium(II) derivatives. For [Pd(η³-2-methyl-2-propenyl)(N-N‘)]ClO4 [N-N‘ = C5H3(6-Me)N-2-CH&dbd;NC6H4OMe-4] the allyl rotation rate increases with increasing concentration up to a limiting constant value. This behavior is interpreted on the basis of a mechanism involving a fast and reversible association of the cationic complex with the perchlorate anion to form a loose ion pair which undergoes a rate-determining molecular geometry rearrangement upon coordination of ClO4^-. For a solution of [Pd(η³-3-methyl-2-butenyl)(N-N‘)]ClO4 (N-N‘ = C5H4N-2-CH2NMe2) in 1,1,2,2-tetrachloroethane-d2, the 2-D ROESY spectrum suggests that the apparent allyl rotation at 28 °C does not involve Pd−NMe2 bond breaking. The rupture of this bond takes place when the temperature is raised to ca. 90 °C or when the complex is dissolved in dimethyl-d6 sulfoxide at ambient temperature.

The modulation of inward K+conductances was studied during neuronal differentiation of human SH-SY5Y neuroblastoma cells. Under standard culture conditions, these cells express theherggene, and the HERG current is the main inward K+current regulating their Vrest. After 10-20 days exposure to Retinoic Acid (RA), SH-SY5Y cells showed, in addition to HERG currents, a novel current characterized by inward rectification, dependence on the extracellular K+concentration, and blockade by Cs+and Ba2+, the main features of the IRK1 current. The appearance of this current is accompanied by a strong hyperpolarisation of Vrest. RT-PCR experiments confirmed that a transcript of the IRK1 (Kir 2.1) gene actually appears in SH-SY5Y cells treated for 10–20 days with RA. On the whole, data here presented demonstrate that RA-induced neuronal differentiation of neuroblastoma cells is accompanied by the switch from a HERG-driven to a IRK1-driven control of Vrest, similarly to what happens in normal differentiating neurons; however, in tumor cells, this switch does not imply the abolition of HERG channel expression.