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The three novel clusters [Mn6O4(OMe)2(OAc)4(Mesalim)4] (3), [Mn8O2(OH)2(OMe)12(OAc)2(Mesalim)4] (4), and [Fe10O4(OMe)14Cl2(Mesalim)6] (5) have been synthesized from a simple bidentate ligand HMesalim (HMesalim = methyl salicylimidate). Starting from the mononuclear complex [Mn(Mesalim)2(OAc)(MeOH)].MeOH (1), either the hexanuclear complex 3 or the octanuclear complex 4 is obtained after recrystallization, depending upon the reaction conditions and solvents used. Similarly, starting from the purple-colored mononuclear complex [Fe(Mesalim)2Cl] (2), the orange-colored decanuclear iron(III) cluster 5 has been obtained upon recrystallization from methanol. Complex 3, which could also be prepared directly from manganese acetate and the ligand, has a face-sharing double-cubane [Mn6O6] core, unique in transition metal chemistry. Compounds 4 and 5 are composed of [M3O4] partial cubanes. All complexes belong to a class of oxo-bridged cubic close-packed molecular clusters resembling the metal oxide/hydroxide ores. Complex 4 exhibits intramolecular ferromagnetic interactions, as evidenced from dc magnetic susceptibility studies (1.8-300 K), resulting in a high-spin ground state, probably with S(T) = 8. Complex 4 displays single molecule magnet behavior as indicated by frequency and temperature dependences of its ac susceptibility. An Arrhenius plot gave relatively large experimental activation energy of 36.0 K. The magnetic properties of complexes 3 and 5 are dominated by antiferromagnetic interactions leading to zero-spin ground states.

Objectives: The pig is generally considered a suitable alternative donor for clinical islet transplantation. However, adult pig islets are difficult to isolate and culture, often behave variably in in vitro assays, and do not consistently cure diabetic nude mice. In this study, we compared the in vivo function of freshly isolated and cultured adult porcine islets by transplantation in diabetic nude mice., Methods: Freshly isolated and cultured islets were transplanted in different doses to diabetic nude mice (N = 48)., Results: Average islet yield was 1924 islet-equivalents per gram of pancreas, purity 96%, and the viability that was measured by acridine orange and propidium iodide was greater than 80% in all freshly isolated islet preparations. Grafts of freshly isolated islets failed to reduce hyperglycemia in 17 of 18 recipients. Although after 1 day of culture islet recovery was only 21%, grafts of these islets cured 12 of 17 mice. After 7 to 14 days of culture, the recovery had decreased to 11%; however, these islets reversed hyperglycemia in all mice (13/13) and showed shorter time-to-normoglycemia and more tightly regulated blood glucose., Conclusions: Although freshly isolated adult porcine islets survive culture and transplantation poorly, islets selected by prolonged culture are of high potential.

The synthesis and characterization of two new iron(II) complexes, [Fe(pca)2(py)2].py (1) and {[Fe(pca)2(H2O)].H2O}n (2) and one new iron(III) complex, Na2{[Fe(pca)()]2O}.2H2O.2CH3CN (3) (pca- stands for 2-pyrazinecarboxylate), are reported. Complex 1 is obtained from the reaction of iron powder with 2-pyrazinecarboxylic acid. The reaction of Fe(ClO4)3.10H2O with Hpca in the presence of 3 equiv. of Bu4NOH yields 2, whereas the presence of NaOH yields 3. The molecular structure of 1 contains an iron(II) ion with a pseudo-octahedral environment resulting from the coordination of two pca- ligands in a bidentate chelating fashion and two pyridine molecules; pi-pi stacking interactions between pyridine and pyrazine rings lead to a one-dimensional chain. Complex 2 is an iron(II) coordination polymer with an infinite zig-zag motif and an Fe...Fe separation of 7.1 A. In 2, the pi-pi stacking interactions involving the pyrazine rings and the strong hydrogen bonds between the coordinated water molecule and the carboxylate oxygens of two pca- ligands result in a three-dimensional network structure. Complex 3 consists of an anionic micro-oxo-bridged diiron(III) core with two crystallographically distinct iron(iii) ions; the negative charge is compensated by two sodium cations. Complex 3 is assembled in a three dimensional network structure through coordination of Na(I) and hydrogen bond interactions. Temperature dependent magnetic susceptibility and Mössbauer spectroscopic studies indicate that 1 and 2 have similar magnetic properties. Both complexes are paramagnetic above 12 K, whereas antiferromagnetic ordering is observed below 12 K. The magnetic properties of reveal strong intramolecular antiferromagnetic interactions between the two iron(III) ions with a J value of -221 cm(-1); no long range intermolecular magnetic coupling is observed between 295 and 4.2 K.

Manganese complexes of the ligand HphoxCOOR (R=H or Me) have been synthesized and characterized by X-ray analysis, ESI-MS, ligand-field spectroscopy, electrochemistry, and paramagnetic 1H NMR. The ligands, chirally pure or racemic, influence the structures of the complexes formed. Manganese(III) complexes of the ligand HphoxCOOMe are square-pyramidal or octahedral with two ligands bound in a trans fashion in the solid state. The racemic ligand (RS-HphoxCOOMe) as well as the enantiopure ligand (R-HphoxCOOMe) forms manganese complexes with similar solid-state structures. Ligand-exchange reactions occur in solution giving rise to meso complexes as confirmed by ESI-MS and deuteration studies. The manganese(III) complex of R-HphoxCOOH is octahedral, with two dianionic ligands bound in a fac-cct fashion in a tridentate manner. The manganese(III) complex of RS-HphoxCOOH is also octahedral with two dianionic ligands now bound in a trans fashion in a didentate manner and with two water molecules occupying axial sites. The paramagnetic 1H NMR spectra of the complexes have been interpreted on the basis of the relaxation times with the help of the inversion-recovery pulse technique. The binding of imidazole with the metal center depends on the chirality of the ligands in the metal complexes of HphoxCOOMe. Imidazole coordination was found to occur with the metal complex that contains two ligands with the same chirality (R and R) (R-1), while no imidazole coordination was found upon reaction with the metal complex that contains two ligands with opposite chirality (R and S) (RS-1). Epoxidation reactions of various alkenes with H2O2 as the oxidant reveal that the complexes give turnover numbers in the range of 10-35, the epoxide being the major product. The catalytic activity depends on the additives used, and a clear base effect is observed. The turnover numbers have been found to be higher in the complexes where no binding of N-Meim is observed. The latter fact unambiguously shows that imidazole binding is not a prerequisite for higher turnover numbers, in contrast to the Mn-Schiff base catalysts.

The reaction of Cu(ClO(4))(2).6H(2)O with the new tripodal ligand HNpy(2)pz (N-bis[(pyridin-2-yl)methyl][1H-pyrazol-3-yl)methyl]amine) in the presence of 1 equiv of triethylamine results in the formation of a doubly pyrazolato-bridged dicopper(II) complex, [Cu(Npy(2)pz)](2)(ClO(4))(2).2CH(3)CN (1). The crystal structure of 1 was determined by X-ray crystallography and was found to consist of two nearly identical discrete dinuclear molecules with bis(pyrazolato) bridges. The copper(II) ion has a trigonal bipyramid geometry achieved by the coordination of an aliphatic nitrogen, two pyridine moieties, and two pyrazolato nitrogens. Variable temperature-dependent magnetic data show that antiferromagnetic interactions operate in 1 as a result of the binding angle of the pyrazolato bridge. In solution, the stability of the dinuclear cation, [Cu(py(2)pz)](2)(2+), is highly dependent on the concentration, as indicated by ESI-MS, ligand field, cyclic voltammetry, EPR, and (1)H NMR studies.

The novel octanuclear cluster [Mn8O2(OH)2(OMe)12(OAc)2(Mesalim)4] (1) presents SMM behaviour with a relatively high experimental energy barrier (eff/kB= 36.0 K) as shown by its dc and ac magnetic properties.

Reaction of Mn(ClO4)2.6H2O with 3(5)-methyl-5(3)-(2-hydroxyphenyl)pyrazole (H2phpz) affords a highly asymmetric octanuclear manganese(III) cluster resulting from the different bridging coordination modes of the ligand H2phpz.

Since 1921 and until recently, insulin by injection has been the only treatment for patients with diabetes mellitus type 1. After pancreas transplantation, which became possible in 1977, the next logical step to cure patients with diabetes mellitus type 1 is the transplantation of the islets of Langerhans. In the last few years, the results of islet transplantation are markedly improved thanks to developments in the isolation technique and better immunosuppressive protocols. Ongoing problems in islet transplantation are allo-immunity, auto-immunity and the growing shortage of donor pancreases. Alternatives to pancreas donation, be it post-mortem or from a living donor, could be: sources for islets are xenotransplantation with the aid of pig islets and beta-cell neogenesis from embryonic stem cells or pancreatic duct cells.

It has been found that [Mn(acac)(3)], by functioning both as a radical initiator and a hydroperoxide decomposition catalyst, has a very high activity in the autoxidation of ethyl linoleate (EL), a model compound for the binder molecule in household alkyd paint. Adding 1 equiv of bipyridine (bpy) to a reaction mixture of EL and [Mn(acac)(3)] significantly enhances the autoxidation rate. The redox properties of [Mn(acac)(3)] and [Mn(acac)(2)(bpy)] have been compared with cyclic voltammetry; the observed peak potentials show that addition of bpy facilitates reduction of Mn(III) to Mn(II), which may explain the increase in autoxidation activity.

Background: Transplantation of islets of Langerhans can restore insulin production in diabetic patients. Because of the shortage of human donor organs, transplantation of porcine islets may be an alternative solution. The present study was aimed at the characterization of rejection mechanisms of porcine islets transplanted into eight nondiabetic monkeys under the kidney capsule., Methods: Cultured adult pig islets were used, which showed no expression of the galactose(alpha1,3)galactose epitope, major histocompatibility complex class II, or CD45, and no binding of antibodies or complement after exposure to monkey serum. Immunosuppression consisted of cyclophosphamide, cyclosporine A (CsA), and steroids (group 1); or antithymocyte globulin, anti-interleukin-2 receptor antibody, CsA, and steroids (group 2). In three animals of group 2, islets were also transplanted in the portal vein., Results: Although all monkeys had preformed anti-pig antibodies, no correlation was found between antibody titers and rejection and no deposition of antibodies or complement was observed in the grafts. Group 1 showed islets up to day 11, followed by T-cell infiltration and rejection at approximately day 14. In group 2, two monkeys showed infiltrates consisting predominantly of T cells starting at approximately day 29, whereas two monkeys showed well-preserved islets without infiltration up to day 53. In the livers of the three monkeys that also received islets intraportally and were resectioned on days 21, 33, and 49, no islets could be detected., Conclusions: This study demonstrates that cultured adult pig islets can survive in the monkey for more than 53 days without signs of rejection under standard immunosuppression.

The title compound, tris[2-(4,5-dihydrooxazol-2-yl-kappa N)phenolato-kappa O]iron(III), [Fe(C(9)H(8)NO(2))(3)], is disordered over a non-crystallographic twofold rotation axis perpendicular to the crystallographic threefold rotation axis. The disorder can be a pure rotational disorder of an iron complex in the facial configuration, or the consequence of a mixture of facial and meridional configurations. In the latter case, at least 25% of the iron complexes must adopt the facial configuration in order to obtain the disorder ratio observed in the crystal.

Complex 1 [(N,N'-dimethyl-N,N'-bis(2-sulfanylethyl)ethylenediamine)nickel(II)], previously shown to react with H(2)O(2) to produce the fully oxygenated disulfonate 5 [diaqua(N,N'-dimethyl-N,N'-bis(2-sulfonatoethyl)ethylenediamine)nickel(II)], has been explored in detail to explain the observed reactivity of this compound and to discern intermediates in the oxygenation reaction. Reaction of 1 with 1 equiv of methyl iodide results in the monomethylated square-planar nickel complex 2 [[(N,N'-dimethyl-N-(2-sulfanylethyl)-N'-(2-methylthioethyl)(ethylenediamine)nickel(II)] iodide], while a slight excess of methyl iodide results in the dimethylated complex 3 [diiodo(N,N'-dimethyl-N,N'-bis(2-methylthioethyl)ethylenediamine)nickel(II)], an X-ray structure of which has shown that the nickel ion is in an octahedral N(2)S(2)I(2) environment. Crystal data of 3: monoclinic, a = 8.865(3) A, b = 14.419(4) A, c = 14.389(6) A, beta = 100.19(3) degrees, V = 1810.2(12) A(3), space group P2(1)/n, Z = 4. The equatorial positions are occupied by the two cis-amine N-atoms and the coordinated iodides, while the axial positions are occupied by the thioether sulfur atoms. In organic solvents, the dithiolate complex 1 reacts with molecular oxygen or H(2)O(2) to produce the mixed sulfinato/thiolato complex 4 [(N,N'-dimethyl-N-(2-sulfanylethyl)-N'-(2-sulfinatoethyl)(ethylenediamine)nickel(II)], and the fully oxidized product 5. X-ray analysis of complex 4 reveals a square-planar geometry in which the nickel ion is coordinated by two cis-amine nitrogens, one thiolate sulfur donor, and one sulfinato sulfur donor. Crystal data of 4: orthorhombic, a = 11.659(2) A, b = 13.119(3) A, c = 16.869(3) A, V = 2580.2(9) A(3), space group Pbca, Z = 8. This complex is the only intermediate in the oxygenation reaction that could be isolated, and it is shown to be further reactive toward O(2) to yield the fully oxidized product 5. For a better understanding of the reactivity observed for 4, DFT calculations have been undertaken, which show a possible reaction path toward the fully oxidized product 5.

The synthesis of a number of nickel(II) complexes containing the didentate phosphane ligand 1,2-bis(di(o-methoxyphenyl)phosphino)ethane (o-MeO-dppe) is reported. Two types of complexes have been synthesized, i.e., the mono(chelate) complex (1) of the general formula [Ni(o-MeO-dppe)X2] (where X = Cl, Br or I) and the bis(chelate) complex (2) of the general formula [Ni(o-MeO-dppe)2]Y2 (where Y = PF6 or trifluoroacetate (TFA)). These complexes have been characterized using electronic absorption and NMR spectroscopy. The structures of the mono(chelate) complex [Ni(o-MeO-dppe)I2] (1c) and of the bis(chelate) complex [Ni(o-MeO-dppe)2](PF6)2 (2e) have been determined by X-ray crystallography. [Ni(o-MeO-dppe)I2] crystallizes in the monoclinic space group P2(1)/c with Z = 4, a = 12.1309(1) A, b = 16.5759(3) A, c = 17.6474(2) A, beta = 119.3250(10) degrees. [Ni(o-MeO-dppe)2](PF6)2 crystallizes in the monoclinic space group C2/c with Z = 4, a = 22.5326(3) A, b = 13.6794(2) A, c = 21.7134(3) A, beta = 107.1745(7) degrees. In both structures the nickel ion is in a square-planar geometry with a NiP2I2 and NiP4 chromophore, respectively. Using 1H and 31P[1H] NMR spectroscopy the behavior of the complexes in various solvents has been studied. It appears that in solution these nickel complexes are involved in an autoionization equilibrium: 2[Ni(o-MeO-dppe)X2] <==>[Ni(o-MeO-dppe)2](2+) + ["NiX(4)"](2-). The ionized complex (3) consists of a cationic unit in which a nickel atom is surrounded by two didentate phosphane ligands, and an anionic unit that stoichiometrically consists of a nickel atom and four anions. The position of the autoionization equilibrium is highly dependent on the anion and the solvent used. In a polar solvent in combination with weakly coordinating anions only the ionized complex is observed, whereas in an apolar solvent in combination with coordinating anions only the mono(chelate) complex occurs. A comparison of the behavior of o-MeO-dppe with its unsubstituted analogue dppe in combination with nickel(II) acetate using 31P[1H] NMR spectroscopy shows that the latter is more readily oxidized.

Primary nonfunction (PNF) is seen very frequently after xenogeneic transplantation of islets of Langerhans. In a pig-to-rat model we recently observed that no PNF occurs when the islets are kept in culture at 37 degrees C for 1-2 weeks prior to transplantation. In order to investigate the rejection mechanisms in a preclinical model, we transplanted cultured porcine islets under the capsule of both kidneys in four cynomolgous monkeys. Islets were isolated from adult sows by means of digestion with Liberase in University of Wisconsin solution (UWS). The digest was purified by a density gradient of OptiPrep in UWS. Highly purified (>95%) islets were cultured 1-2 weeks in RPMI. All monkeys showed significant titers of preformed anti-pig antibodies. The immunosuppression of the monkeys consisted of cyclophosphamide (Cy) (2 days), cyclosporin A (CsA), and prednisolone. Anticipating a fast rejection we carried out nephrectomies at different time points within 2 weeks after transplantation. Following unilateral nephrectomy, well-preserved islets with no signs of rejection were observed between 3 and 7 days posttransplant. Later, between days 11 and 15 posttransplant, histology in the first three animals demonstrated no islets. In the fourth monkey histology on day 11 showed islets with excellent morphology and some small focal infiltrates. The highest CsA blood levels (around 1000 ng/ml) were found in animals with the best graft survival. We conclude that cultured porcine islets can be grafted without hyperacute rejection in monkeys with preformed anti-pig antibodies. In the presence of high levels of CsA only marginal signs of a cellular immune response were observed 11 days after transplantation.

For studies on the intrahepatic engraftment of transplanted hepatocytes, labeling of donor cells is necessary. Current labeling techniques enable only short-term monitoring of engraftment. In the present study, we describe the use of 5-bromo-2'-deoxyuridine (BrdU) for a more permanent hepatocyte labeling. BrdU is stably incorporated into replicating DNA; consequently, BrdU labeling was performed in regenerating livers. In 10 Lewis rats, a two-thirds partial hepatectomy was performed, followed by continuous, low-dose BrdU administration. This approach provided a fraction of 89+/-1.5% BrdU-labeled donor hepatocytes, without influencing the efficacy of the ensuing isolation of donor hepatocytes. Subsequently, +/-1 x 10(7) isolated hepatocytes were transplanted either intraportally or intrasplenically into syngeneic recipients, and the engraftment of transplanted cells was evaluated in liver lobes at successive time intervals after transplantation. BrdU-positive hepatocytes could be identified and quantitated in recipient livers up to 180 days after transplantation. Repetitive quantitative assessments over time revealed an initial, drastic loss of transplanted cells (<24 hr), followed by a stabilization at approximately 7% of the injected cells. Histological monitoring showed that during this period (<48 hr) the transplanted cells migrate from the portal venules to the liver parenchyma. In recipient livers a homogeneous lobe distribution of hepatocyte engraftment was found 30 days after both intraportal and intrasplenic transplantation. Moreover, no significant difference between the intrahepatic liver cell engraftment of the two transplantation routes was demonstrated. In conclusion, the BrdU-labeling technique of donor hepatocytes enables long-term histological monitoring and quantitative evaluation of the engraftment of transplanted liver cells in recipient livers.

In the near future, xenotransplantation of porcine islets of Langerhans might be an alternative in the treatment of patients with diabetes mellitus. However, xenotransplantation of islets of Langerhans in large animals has been shown to result in an exceedingly short graft survival, which suggests that a humoral immune response might play a major role in islet demise. This study was performed to assess binding human preformed antibodies to isolated porcine islet cells (PIC) and to determine the lysis of PIC using human sera in complement-mediated cytotoxicity (CMC) and antibody-dependent cell-mediated cytotoxicity (ADCC) assays. Ten Dutch Landrace pigs were used for the isolation of PIC. Sera from 30 healthy blood donors (1/10 diluted) were used in a 51Cr release assay to assess CMC. Heat-inactivated normal human sera and fresh sera from patients with agammaglobulinemia were used as controls. Binding of human IgM IgG, and IgA antibodies to PIC was tested in an ELISA using isotype-specific secondary monoclonal antibodies ADCC was tested in a 51Cr release assay using normal human sera and sera from newly diagnosed type I diabetics with peripheral blood mononuclear cells as effector cells and PIC as targets. It was found that PIC were recognized by human IgM and IgG preformed antibodies and that fresh human sera had strong CMC activity inducing a percentage-specific PIC lysis of 61 +/- 10% (mean +/- SD) within 60 min. Agammaglobulinemic sera killed 42 +/- 12% of PIC. No significant cytotoxic activity was found in ADCC assays using normal sera or sera from diabetic patients. These results show that all tested human sera lyse PIC via CMC, even in the absence of human antibodies, as concluded from the use of agammaglobulinemic sera. In pig-to-human transplantation, islets may be hyperacutely rejected by antibody-dependent and antibody-independent activation of complement and not by antibody-dependent cell-mediated mechanisms.

The effect of recombinant rat interferon-gamma (rRIFN-gamma) on allograft rejection was studied in two rat heart transplantation models. Recipients were treated with rRIFN-gamma by intraperitoneal or intravenous injection, either by bolus or continuous infusion. Treatment was started after transplantation and continued during a period ranging from 4 to 10 days; dosages varied from 2.5 x 10(2) U/kg/day to 3 x 10(6) U/kg/day. Controls were infused with PBS. Treatment with rRIFN-gamma had no effect on allograft survival, irrespective of the route of administration, the dosage used or the duration of treatment. Higher dosages of rRIFN-gamma induced serious morbidity and mortality. In conclusion, systemic treatment of cardiac allograft recipients with rRIFN-gamma has no effect on graft rejection and is associated with serious toxicity and mortality when high dosages are used.

Single-crystal ultraviolet spectroscopy, X-ray absorption spectroscopy and EPR measurements have been used to examine the oxidation and oxygenation state of the dinuclear copper site of several types of hemocyanin crystals. The crystals contain Panulirus interruptus hemocyanin which forms hexameric molecules with a molecular mass of approximately 470 kDa. Three types of crystals have been investigated. Type-I monoclinic crystals, which have been used for the X-ray structure determination, contain virtually only deoxyhemocyanin. Type-II monoclinic crystals, which are less well ordered than the type-I crystals, contain a mixture of deoxy, oxy and met forms. Older crystals contain relatively more methemocyanin. A third, hexagonal, crystal form is also partially oxygenated, and, like the type-II monoclinic form, subject to gradual conversion to methemocyanin.