Placental Enterovirus Infection Is Not Evident in Chronic Histiocytic Intervillositis.
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Journal Article↗
Biomedical subjects
David J Williams
Publications and source records attributed to David J Williams.
Antivenom use, premedication and early adverse reactions in the management of snake bites in rural Papua New Guinea.
OBJECTIVE: To examine antivenom use, premedication, early adverse reactions and patient outcomes after snake bite in rural Papua New Guinea. DESIGN: Retrospective chart analysis of all admissions for snake bite with documented antivenom use at 11 rural health facilities from January 1994 to June 2004. No formal protocol was followed and there was no attempt at randomisation or blinding of prophylaxis. RESULTS: Antivenom use was documented in 136/1881 (7.2%) snake bite admissions and most (121/136: 88.9%) received a single vial. CSL Polyvalent antivenom was administered to 112/136 (82.4%). One hundred and eleven patients (81.6%) happened to have been given premedication with adrenaline and/or promethazine and/or hydrocortisone. Early adverse reactions were reported in 25 patients (18.4%) including 23 treated with polyvalent antivenom. Intravenous test doses of antivenom were given to 32 patients, none of whom had a positive test result. Subsequent adverse reactions occurred in 9 of these 32 (28.1%) patients. One death may have been attributable to anaphylaxis after polyvalent antivenom. Reaction rates were significantly (p < or = 0.005) lower in adrenaline premedicated patients (7.7%) compared to patients premedicated without adrenaline (28.3%) and unpremedicated patients (28.0%). Adrenaline premedication caused no detectable changes in vital signs. The case fatality rate was 9.6% (13/136 patients). CONCLUSIONS: Polyvalent antivenom is the main treatment for envenomation in rural health centres, and early adverse reactions are common. Adrenaline premedication appears to significantly reduce acute adverse reaction rates. Premedication with promethazine and/or hydrocortisone without adrenaline did not reduce early adverse reactions.
Adolescent↗
Group 4 catalysts for ethene polymerization containing tetradentate salicylaldiminato ligands.
The structural properties of three new classes of titanium and zirconium complex bearing tetradentate salicylaldiminato proligands are elucidated using X-ray diffraction and NMR spectroscopy. On activation with MAO co-catalyst, their behaviour in ethene polymerization depends strongly on the nature of the structure and the substitution pattern. One titanium complex based on a 2-aminobenzylamine (C3-chain) backbone has a trans arrangement of the co-ligand sites and, unsurprisingly, does not polymerize ethene. The 1,8-diaminonaphthalene (C3-chain) backbone gives a rather ring-strained cis complex, but was also unproductive. A range of cis complexes of zirconium with the 2,2'-diaminobibenzyl (C6-chain) backbone give low to moderate productivities of multimodal poly(ethene), while in contrast the structurally analogous titanium compounds provide highly active, single site catalysts. Thermal degradation of these catalysts is slowed significantly by a substitution pattern on the phenolate unit which sterically protects the imine donor unit; a phenomenon which has been previously observed in much lower activity catalysts based on 2,2'-diaminobiphenyl (C4-chain) but which does not improve the stability of the very highly active unbridged systems.
Journal Article↗
Synthetic, structural, mechanistic, and computational studies on single-site beta-diketiminate tin(II) initiators for the polymerization of rac-lactide.
A family of tin(II) complexes supported by beta-diketiminate ligands has been investigated as initiators for the polymerization of rac-lactide. Kinetic studies reveal a first-order dependence on [lactide], but with a significant induction period. Linear plots of M(n) versus conversion and [M](o)/[I](o) versus conversion, along with narrow molecular weight distributions (typically 1.07-1.10), are indicative of well-controlled, "living" polymerizations. Less sterically hindered derivatives promote faster propagation than their bulky analogues, in accord with a more accessible active site. Enhanced rates of polymerization are observed for ligands bearing halogenated N-aryl substituents, a consequence of the more Lewis acidic nature of the Sn(II) centers. All of the initiators exhibit a similar bias toward heterotactic polylactide, which is attributed to a chain-end control mechanism influenced predominantly by the presence of the Sn 5s(2) lone pair of electrons rather than the steric or electronic properties of the beta-diketiminate ligand. The tin(II) isopropyl-(S)-lactate complex, ((Me)BDI(DIPP))SnOCH(Me)COO(i)Pr (14), has been synthesized as a model compound for the propagating species by treatment of ((Me)BDI(DIPP))Sn(NMe(2)) with isopropyl-(S)-lactate. An X-ray structure determination showed that the lactate ligand forms a five-membered chelate ring with a weak donor bond from the carbonyl oxygen atom to the tin center. A B3LYP density functional computational study indicates that insertion of the first lactide monomer into the tin(II) alkoxide bond is facile, with the induction period arising from a slower insertion of the second (and possibly third and fourth) monomer units.
Crystallography, X-Ray↗
Highly active titanium-based olefin polymerization catalysts supported by bidentate phenoxyamide ligands.
Phenoxyamide complexes of Ti-containing 2,6-X2C6H3 (X = Cl, Br) substituents, when activated by methyl aluminoxane, afford catalysts with very high activities for the polymerization of ethylene and with good incorporation of 1-hexene.
Journal Article↗
Combining hard and soft donors in early-transition-metal olefin polymerization catalysts.
Bis(phosphanylphenoxide) complexes of the group 4 metals, upon activation by methylaluminoxane, are highly active for ethylene and propylene polymerization; a zirconium derivative possesses one of the highest propylene polymerization activities found to date for a nonmetallocene system.
Journal Article↗
Quantitative proteomics identifies Gemin5, a scaffolding protein involved in ribonucleoprotein assembly, as a novel partner for eukaryotic initiation factor 4E.
Protein complexes are dynamic entities; identification and quantitation of their components is critical in elucidating functional roles under specific cellular conditions. We report the first quantitative proteomic analysis of the human cap-binding protein complex. Components and proteins associated with the translation initiation eIF4F complex that may affect complex formation were identified and quantitated under distinct growth conditions. Site-specific phosphorylation of eIF4E and eIF4G and elevated levels of eIF4G:eIF4E complexes in phorbol ester treated HEK293 cells, and in serum-starved tumorigenic human mesenchymal stromal cells, attested to their activated translational states. The WD-repeat, scaffolding-protein Gemin5 was identified as a novel eIF4E binding partner, which interacted directly with eIF4E through a motif (YXXXXLPhi) present in a number of eIF4E-interacting partners. Elevated levels of Gemin5:eIF4E complexes were found in phorbol ester treated HEK293 cells. Gemin5 and eIF4E co-localized to cytoplasmic P-bodies in human osteosarcoma U2OS cells. Interaction between eIF4E and Gemin5 and their co-localization to the P-bodies, may serve to recruit capped mRNAs to these RNP complexes, for functions related to RNP assembly, remodeling and/or transition from active translation to mRNA degradation. Our results demonstrate that our quantitative proteomic strategy can be applied to the identification and quantitation of protein complex components in human cells grown under different conditions.
Amino Acid Sequence↗
Discovery and optimization of new chromium catalysts for ethylene oligomerization and polymerization aided by high-throughput screening.
High throughput screening (HTS) of a 205 member Schiff base salicylaldimine ligand library derived from salicylaldehydes bearing bulky ortho-substituents, i.e., 9-anthracenyl, 1,4,5,8-tetramethylanthracenyl or triptycenyl, reacted in-situ with (p-tolyl)CrCl2(thf)3, identified two new classes of highly active chromium based systems for the oligomerization and polymerization of ethylene, respectively. The polymerization system comprises bidentate ortho-substituted anthracenyl Schiff bases bearing small primary or secondary alkyl imine substituents. The oligomerization catalysts are based upon tridentate ortho-triptycenyl-substituted Schiff bases with pyridylmethyl or quinolyl substituents. Validation tests confirmed polymerization productivities of up to 3000 g x mmol(-1)h(-1)bar(-1) for the polymerization catalyst systems while the oligomerization catalysts gave productivities up to 10 000 g x mmol(-1)h(-1)bar(-1). Key catalyst precursors have been characterized by X-ray crystallography.
Journal Article↗
Synthesis, structural characterization, and magnetic studies of polynuclear iron complexes with a new disubstituted pyridine ligand.
A series of novel polyiron species have been prepared from the reaction of iron chloride with the 2,5-disubstituted pyridines H2L(n) (H2L1) = N,N'-bis(n-butylcarbamoyl)pyridine-2,6-dicarboxamide; H2L2 = N,N'-bis(n-ethylcarbamoyl)pyridine-2,6-dicarboxamide). By small modifications of the experimental conditions under which the reactions are carried out, it has been possible to prepare the quadruply stranded diiron(II) complex [Fe2(mu-H2L1)4(mu-Cl)2][FeCl4]2 (1), the metallamacrocycle [Fe2(mu-H2L1)2(THF)4Cl2][FeCl4]2 (2), the hexairon(III) compound [Fe6(L1)2(mu-OMe)6(mu4-O)2Cl4] (3), and the mixed-valence trinuclear iron complexes [Fe3(L(n))3(mu3-O)] (n = 1, 4; n = 2, 5). The X-ray crystal structures of 3 and 5 and magnetic studies for all the compounds are herein presented. Interestingly, the structural analysis of 5 at room temperature indicates that one of the iron centers is Fe(III) while the other two have an average valence state between Fe(II) and Fe(III). The five complexes herein presented demonstrate the great versatility that the new ligand has as a building block for the formation of supramolecular coordination assemblies.
Journal Article↗
Pyridine N-alkylation by lithium, magnesium, and zinc alkyl reagents: synthetic, structural, and mechanistic studies on the bis(imino)pyridine system.
The 2,6-bis(alpha-iminoalkyl)pyridines 2,6-[ArNC(CR(3))](2)C(5)H(3)N [R = H, D; Ar = 2,6-i-Pr(2)C(6)H(3) (DIPP), 2,6-Me(2)C(6)H(3) (DMP)] react with MeLi in Et(2)O to give a binary mixture of products: the pyridine N-methylated species 2,6-[ArNC(CR(3))](2)C(5)H(3)N(Me)Li(OEt(2)) and the deprotonated/dedeuterated species 2-[ArNC(CR(3))],6-[ArNC(=CR(2))]C(5)H(3)NLi(OEt(2)). For R = D, the product ratio is 2:1 in favor of the N-methylated product, while, for R = H, the deprotonated product is favored by 5:1, increasing to 8:1 in toluene solvent. Warming solutions of the N-methylated species leads to clean conversion to the thermodynamically preferred deprotonated species. Crossover experiments show that MeLi is re-formed and dissociates from the terdentate ligand before deprotonating the ketimine methyl unit. For MgR(2) (R = Et, i-Pr) and ZnR(2) (R = Et) reagents, N-alkylation products are formed exclusively, but derivatives containing bulky aryl substituents are found to undergo further rearrangement to 2-alkylated species, arising by migration of the alkyl group of the N-alkyl moiety to the adjacent ring carbon atom. The reversibility of the N-alkylation process has been probed using deuterio-labeled Mg alkyl reagents and mixed alkyl zinc species. A cationic zinc derivative is shown to undergo "reverse" alkyl migration, from the heterocycle nitrogen atom to the zinc center. EPR spectroscopy reveals a paramagnetic intermediate in which the unpaired electron is delocalized over the heterocycle and di-imine moieties of the ligand, indicating that the N-alkylation reactions proceed via single electron-transfer processes.
Journal Article↗
Synthesis and characterisation of tungsten(VI) oxo-salicylate complexes for use in the chemical vapour deposition of self-cleaning films.
Tungsten(VI) oxo-salicylate complexes were prepared in moderate yield (47 to 63%) by the reactions of WOCl4 and two equivalents of either 3-methylsalicylic acid (MesaliH2) or 3,5-di-isopropylsalicylic acid (di-i-PrsaliH2). Performing the reaction in refluxing toluene afforded the two analogous ditungsten complexes 1, [{WO(Mesali)(MesaliH)}2(mu-O)], and 2, [{WO(di-i-Prsali)(di-i-PrsaliH)}2(mu-O)], however in refluxing hexane the mononuclear tungsten complex , [WO(di-i-Prsali)(di-i-PrsaliH)Cl], was isolated. The single crystal X-ray study of revealed a pseudo-octahedral geometry around the tungsten centres. Aerosol assisted chemical vapour deposition of or afforded brown tungsten trioxide thin films. These films were converted to yellow fully oxidised WO3 on annealing in air at 550 degrees C for 30 minutes. The yellow WO3 films demonstrate preferred orientation on the substrate and show interesting functional properties-photo induced hydrophilicity and photocatalytic activity.
Journal Article↗
Synthesis of titanium(IV) guanidinate complexes and the formation of titanium carbonitride via low-pressure chemical vapor deposition.
The mono(guanidinato) complex [Ti(NMe2)2Cl{i-PrNC[N(SiMe3)2]N-i-Pr}] (1) was prepared by reaction of [Ti(NMe2)2Cl2] with 1 or 2 equiv of the lithium guanidinate salt [Li{i-PrNC[N(SiMe3)2]N-i-Pr}]. Compound 1 has been characterized by X-ray crystallography. Treatment of TiCl4 with 2 equiv of [Li{i-PrNC[N(SiMe3)2]N-i-Pr}] resulted in the formation of dark red crystals. X-ray crystallography showed that these crystals consist of a 70:30 mixture of two bis(guanidinato) complexes, namely, [TiCl2{i-PrNC[N(SiMe3)2]N-i-Pr}{i-PrNC(N=CMe2)N-i-Pr}] (2) and [TiCl2{i-PrNC[N(SiMe3)2]N-i-Pr}{i-PrNC[N(H)-i-Pr]N-i-Pr}] (3). Both compounds 2 and 3 possess a transformed guanidinate ligand. Low-pressure chemical vapor deposition of either compound 1 or [TiCl2{i-PrNC(NMe2)N-i-Pr}] (4) at 600 degrees C results in thin films of titanium carbonitride.
Journal Article↗
Synthesis of iron(II), manganese(II) cobalt(II) and ruthenium(II) complexes containing tridentate nitrogen ligands and their application in the catalytic oxidation of alkanes.
A series of Fe(II), Mn(II), Co(II) and Ru(II) complexes containing bis(imino)pyridine or bis(amino)pyridine ligands and weakly coordinating triflate (OTf-) or non-coordinating SbF6- anions have been prepared. The complexes have been fully characterized including several solid-state structure analyses. Two unusual mono-chelate six-coordinate bis(imino)pyridine Fe(II) and Mn(II) complexes have been observed. The catalytic properties of the complexes for the oxidation of cyclohexane with H2O2 have been evaluated. Only the Fe(II) complexes have shown catalytic activity, which is mainly due to Fenton-type free radical auto-oxidation.
Journal Article↗
Snakes across the Strait: trans-Torresian phylogeographic relationships in three genera of Australasian snakes (Serpentes: Elapidae: Acanthophis, Oxyuranus, and Pseudechis).
We analyze the phylogeny of three genera of Australasian elapid snakes (Acanthophis-death adders; Oxyuranus-taipans; Pseudechis-blacksnakes), using parsimony, maximum likelihood, and Bayesian analysis of sequences of the mitochondrial cytochrome b and ND4 genes. In Acanthophis and Pseudechis, we find evidence of multiple trans-Torresian sister-group relationships. Analyses of the timing of cladogenic events suggest crossings of the Torres Strait on several occasions between the late Miocene and the Pleistocene. These results support a hypothesis of repeated land connections between Australia and New Guinea in the late Cenozoic. Additionally, our results reveal undocumented genetic diversity in Acanthophis and Pseudechis, supporting the existence of more species than previously believed, and provide a phylogenetic framework for a reinterpretation of the systematics of these genera. In contrast, our Oxyuranus scutellatus samples from Queensland and two localities in New Guinea share a single haplotype, suggesting very recent (late Pleistocene) genetic exchange between New Guinean and Australian populations.
Animals↗
Why tissue engineering needs process engineering.
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Animals↗
The dual-specificity protein phosphatase DUSP9/MKP-4 is essential for placental function but is not required for normal embryonic development.
To elucidate the physiological role(s) of DUSP9 (dual-specificity phosphatase 9), also known as MKP-4 (mitogen-activated protein kinase [MAPK] phosphatase 4), the gene was deleted in mice. Crossing male chimeras with wild-type females resulted in heterozygous (DUSP9(+/-)) females. However, when these animals were crossed with wild-type (DUSP9(+/y)) males none of the progeny carried the targeted DUSP9 allele, indicating that both female heterozygous and male null (DUSP9(-/y)) animals die in utero. The DUSP9 gene is on the X chromosome, and this pattern of embryonic lethality is consistent with the selective inactivation of the paternal X chromosome in the extraembryonic tissues of the mouse, suggesting that DUSP9/MKP4 performs an essential function during placental development. Examination of embryos between 8 and 10.5 days postcoitum confirmed that lethality was due to a failure of labyrinth development, and this correlates exactly with the normal expression pattern of DUSP9/MKP-4 in the trophoblast giant cells and labyrinth of the placenta. Finally, when the placental defect was rescued, male null (DUSP9(-/y)) embryos developed to term, appeared normal, and were fertile. Our results indicate that DUSP9/MKP-4 is essential for placental organogenesis but is otherwise dispensable for mammalian embryonic development and highlights the critical role of dual-specificity MAPK phosphatases in the regulation of developmental outcomes in vertebrates.
Alleles↗
Anion-templated synthesis of metallacages as a means for the colorimetric detection of chlorides.
In the presence of chloride or bromide in the appropriate mixture of solvents, 6 equiv of nickel(II) and 8 equiv of Hatu [Hatu=H2NC(=NH)NHC(=S)NH2] assemble to yield the metallacages [Ni6(atu)8X][ClO4]3 (atu=deprotonated form of Hatu; X=Cl, 5; Br, 6) where four "units" of the square-planar complex Ni(atu)2 are coordinated to two further nickel centers, forming an octahedral cage around an encapsulated chloride or bromide anion. Synthesis of the cages is highly dependent on the nature of the anions and the solvents used. In methanol, the cage only forms if chloride is present; in a mixture of acetone/methanol, the cage forms in the presence of either chloride or bromide. An interesting feature of the templation process is that there is a dramatic color change associated with assembly of the building blocks in the presence of the appropriate anion to yield the cages. This color change has been used as the basis for the colorimetric detection of chloride anions in methanol. The reaction of 4 equiv of nickel(II), 8 equiv of Hatu, and 2 equiv of platinum(II) has also been carried out, yielding the mixed-metal cage [Pt2Ni4(atu)8Cl][ClO4]3 (7a); the X-ray crystal structure of this compound is reported herein.
Journal Article↗