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Biomedical subjects

M Lutz

Publications and source records attributed to M Lutz.

At least 37 records · Page 2Linked to original sources
PubMed2002

Stage 3 Kienböck's disease: reconstruction of the fractured lunate using a free vascularized iliac bone graft and external fixation.

Eighteen patients with stage 3 Kienböck's disease were treated by débridement of the necrotic core of the lunate and implantation of a free vascularized corticocancellous iliac bone. The wrist was stabilized with an external fixator during healing. The efficiency of the procedure for restoring the structure of the fractured lunate, preventing carpal collapse and improving the clinical outcome was assessed at a mean follow-up of 5 years. The graft became incorporated in the lunate in 16 of the 18 patients and no fracture of the reconstructed lunate or carpal collapse occurred in these cases. The graft did not integrate and was resorbed in the other two patients.

Adolescent↗
PubMed2002

[Distal radius fractures and concomitant lesions. Experimental studies concerning the pathomechanism].

Since Colles (1814) first described a distal radius fracture and the publication by Dupuytren (1834), the frequency of and problems surrounding these fractures were increasingly recognised. Not only the treatment but also the formation and type of fracture were repeatedly analysed. The various theories concerning the pathomechanism led to names such as: "tear fracture", "bend fracture", "thrust fracture", "compression fracture", "snap fracture" and others. In our experimental studies we attempted to simulate the pathomechanism of distal radius fractures and present them pictorially. With the help of a materials testing machine, 63 prepared cadaver arms were hyperextended in the wrist joint until a radius fracture occurred. The concomitant lesions were registered radiologically and by dissection. Moreover, additional cadaver arms were deep-frozen and examined by means of computer tomography and cryosection according to Kathrein. Through experimental hyperextension it was possible to generate dorsal, central, and palmar types of fractures. We produced 42 dorsal, 14 central and 7 palmar fractures. Fundamentally, it seems that the fracture depends on the extent in which the carpal bones of the proximal row are pressed against the dorsal, central or palmar part of the articular surface of the distal radius. The subsequent dissection showed in 40 cases (63 %) mostly multiple concomitant lesions and in 23 cases (37 %) none of these. The reason for concomitant lesions may be the proportion of bone stability to the strength of ligaments. Most frequently (27 cases, i.e. 43 %), we found a destabilisation of the articular disk with or without a bony avulsion fragment (fracture of the ulnar styloid). We also commonly found ruptures of the interosseous ligaments between scaphoid and lunate (20 cases, i.e. 32 %) and lunate and triquetrum (11 cases, i.e. 18 %). It is difficult to apply knowledge gained from experimental studies on preserved cadaver arms clinically. There are of course no physiological reflexes and the slow fracture process must be taken into consideration. This holds true not only for concomitant lesions but also for the type of fracture. On the other hand, in these experimental studies it was possible to generate many realistic types of fractures with their concomitant lesions.

Biomechanical Phenomena↗
PubMed2001

Chemistry of porphyrin-appended cellulose strands with a helical structure: spectroscopy, electrochemistry, and in situ circular dichroism spectroelectrochemistry.

Around 100 porphyrin units have been selectively linked at C(6)-O to a cellulose (Avicel). The properties of the metal-free and zincated porphyrin-celluloses 2 and Zn-2 have been determined by optical and electrochemical methods. Circular dichroism indicates a helical arrangement of the porphyrin units and reveals intra-chain coupling reminiscent, in the broadest sense, of strands of nucleic acids. Cyclic voltammetry and spectroelectrochemistry have been used to characterize the radical ions and dianions. The electrochromism of the oxidation of cellulose 2 to porphyrin radical cations of 2 has been employed for both molecular switching and the transduction of an electrochemical input into chiroptical signal expression.

Journal Article↗
PubMed2001

Reaction of a complexed phosphinidene with 2,4,6-tri-tert-butyl-1,3,5-triphosphabenzene.

The terminal phosphinidene complex PhPW(CO)5 reacts with 2,4,6-tri-tert-butyl-1,3,5-triphosphabenzene to give two unexpected multicyclic organophosphorus compounds. One of them results from an initial 1,2-addition, followed by an intramolecular rearrangement. B3LYP/6-31G* calculations on simplified parent systems suggest that the reaction follows a unique concerted reaction pathway. The second, and major, product is a tetraphosphaquadricyclane derivative, which presumably results from an intramolecular [2+2] cycloaddition of an intermediate tetraphosphanorbornadiene complex. Single-crystal X-ray structures are presented for both products.

Journal Article↗
PubMed2001

Addition of a phosphinidene complex to C=N bonds: P-ylides, azaphosphiridines, and 1,3-dipolar cycloadditions.

The terminal phosphinidene complex PhPW(CO)5 adds to the imine bond of PhHC=N-Ph to give 3-membered ring azaphosphiridines, which undergo ring-expansion with an additional imine to yield a set of four isomeric five-membered ring diazaphospholanes. Treatment with the diimines PhHC=N-(CH2)n-N=CHPh (n=2,3,4) results instead-in all three cases-in only a single isomer of the (CH2)n bridged diazaphospholane. For n=2 or 3, this aminal group is easily hydrolyzed to afford new 6- and 7-membered ring heterocycles. No intermediate azaphosphiridine complex is observed during the addition reaction to the diimines. B3LYP/6-31G* calculations on an unsubstituted, uncomplexed system suggest that the initially formed P,N-ylide of the H2C=N-(CH)2-N=CH2 diimine both kinetically and thermodynamically favors an intramolecular 1,3-dipolar cycloaddition over an imine insertion into the CPN ring of an intermediate azaphosphiridine. Single-crystal X-ray structures for the (CH2)2-bridged azaphospholane complex and the HCl adduct of the 7-membered hydrolysis product are presented.

Journal Article↗
PubMed2001

Novel ruthenium(II)2 carboxylates as catalysts for alkene metathesis.

The reactions of [Ru-(=CHR)Cl2(PCy3)2] (1: R = Ph; 1a: R = -CH=CPh2) with silver salts of carboxylic acids afforded new dimeric complexes of the general formula [Ru2(=CHR)2-(R'CO2)2(mu-R'CO2)2(PCy3)2(mu-H2O)] (2: R = Ph, R' = CF3; 3: R = Ph, R' = C2F5; 4: R = -CH=CPh2, R' = CF3; 5: R = Ph, R' = C6F5; 6: R = -CH=CPh2, R' = C6F5; 7: R = -CH=CPh2, R'=CCl3) in good yields. With R' = CF3, C2F5 or CCl3 these complexes are active catalysts for metathesis of acyclic alkenes, including unsaturated fatty acid esters, as well as for ring closing metathesis. The reactivity of these complexes with bases and weak donor solvents has been studied and their half-life times in several media were determined.

Journal Article↗
PubMed2001

Autoionization of homogeneous nickel(II) diphosphane hydrogenation catalysts. An NMR study and crystal structures of [Ni(o-MeO-dppe)I2] and [Ni(o-MeO-dppe)I2](PF6)2.

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.

Journal Article↗
PubMed2001

Steric and electronic ligand perturbations in catalysis: asymmetric allylic substitution reactions using C2-symmetrical phosphorus-chiral (bi)ferrocenyl donors.

Three series of P-chiral diphosphines based on ferrocene (1a-f, 2a-c) and biferrocenyl skeletons (3a-c), including novel ligands 1f and 3c, were employed in palladium-catalyzed allylic substitution reactions. Steric effects imposed by the phosphine residues were studied using C2-symmetrical donors 1 (1 = 1,1'-bis(arylphenylphosphino)ferrocene with aryl groups a = 1-naphthyl, b = 2-naphthyl, c = 2-anisyl, d = 2-biphenylyl, e = 9-phenanthryl, and f = ferrocenyl), whereas para-methoxy- and/or para-trifluoromethyl substitution of the phenyl moieties in 1a enabled investigation of ligand electronic effects applying ferrocenyl diphosphines 2a-c. Ligands 3 (3 = 2,2'-bis- (arylphenylphosphino)-1,1'-biferrocenyls with aryl substituents a,c = 1-naphthyl (diastereomers) and b = 2-biphenylyl) allowed for comparison of backbone structure effects (bite angle variation) in catalysis. Linear and cyclic allylic acetates served as substrates in typical test reactions; upon attack of soft carbon and nitrogen nucleophiles on (E)-1,3-diphenylprop-2-ene-1-yl acetate the respective malonate, amine, or imide products were obtained in enantioselectivities of up to 99% ee. A crystal structure analysis of a palladium 1,3-diphenyl-eta 3-allyl complex incorporating ligand (S,S)-1a revealed a marked distortion of the allyl fragment, herewith defining the regioselectivity of nucleophile addition.

Journal Article↗
PubMed2001

Type III TGF-beta receptor-independent signalling of TGF-beta2 via TbetaRII-B, an alternatively spliced TGF-beta type II receptor.

Transforming growth factor-beta (TGF-beta) signals through membrane-bound serine/threonine kinase receptors, which upon stimulation phosphorylate Smad proteins and thereby trigger their nuclear translocation and transcriptional activity. Although the three mammalian isoforms of TGF-beta are highly homologous at the level of sequence, analysis of their in vivo function by gene knockouts revealed striking differences, suggesting no significant functional redundancy between TGF-beta1, -2 and -3. While signal transduction by TGF-beta1 has been well characterized, receptor binding and activation by the TGF-beta2 isoform is less well understood. Here, we show that TbetaRII-B, an alternatively spliced variant of the TGF-beta type II receptor, is a TGF-beta2 binding receptor, which mediates signalling via the Smad pathway in the absence of any TGF-beta type III receptor (TbetaRIII). L6 cells lacking endogenous TbetaRIII as well as TbetaRII-B do not respond to TGF-beta2. Transfection of these cells with TbetaRII-B restores TGF-beta2 sensitivity. The expression of TbetaRII-B is restricted to cells originating from tissues such as bone where the isoform TGF-beta2 has a predominant role. This reflects the importance of this receptor in TGF-beta isoform-specific signalling.

Activin Receptors, Type I↗
PubMed2001

[Dorsal dislocation of the proximal interphalangeal joints of the finger. Results after static and functional treatment].

In a follow-up examination of 30 patients who had sustained dorsal dislocations of the PIP joint, the results of two conservative therapy regimens, either immobilisation or early motion were investigated. In Group A, 15 patients were treated by closed reduction and immobilisation with a forearm cast for four weeks. Nine patients showed normal range of motion, whereas a limitation of extension of ten degrees and more was seen in six cases. All PIP joints were stable. Nine patients were satisfied. Three patients complained of a limitation of extension, two of a limitation of extension and pain and one of swelling. In Group B, 15 patients were treated by dorsal block splinting of the PIP joint following reposition. The finger was released in extension with daily active exercise of the PIP joint. Only two of 15 patients showed limitation of extension, whereas 13 cases showed normal range of motion. Instability of one collateral ligament was seen in two cases. Palmar instability did not occur. Eleven patients were satisfied. One patient complained of instability, pain and lack of extension, one of pain in combination with instability, one of pain and one of swelling of the joint.

Adult↗
PubMed2000

The revision of the air quality legislation in the european union related to ground-level ozone.

Complying with the obligation in the current ozone directive, the European Commission came forward in 1999 with a strategy to combat tropospheric ozone together with a proposed revision of the air quality legislation for this pollutant. As a daughter legislation under the 1996 Framework Directive on Air Quality, the proposed ozone daughter directive defines for the first time (interim) air quality targets for ozone to be attained by 2010, complemented by long-term objectives for ozone based on the guideline values of the World Health Organisation. It also sets out enhanced requirements for monitoring and assessment of ozone concentrations, as well as minimum criteria for appropriate information of the public about the measured air pollution. In the past, abatement strategies against air pollution consisted of concrete obligations for controlling emissions derived solely on the basis of technical and economic aspects, covering specific types of installations or activities, thus with no direct quantitative relationship to the level of air pollution let alone to its effects. In compensating this deficit, the Commission presented, as a complement to the existing sectoral legislation, a proposal for a directive on national emission ceilings (NEC) which quantifies emission targets for every Member State to bring its total precursor emissions by 2010 down to levels being considered as necessary to achieve everywhere on a regional scale the air quality targets set in the ozone daughter directive. As the core element of the ozone abatement strategy, the national ceilings for emissions of sulfur dioxide (SO(2)), nitrogen oxides (NO(x)), ammonia (NH(3)) and volatile organic compounds (VOC) were derived from a cost-effectiveness analysis integrating information on economic, technical, physical and biological aspects of ozone pollution and abatement. This integrated assessment considers the potential and costs for further emission control in the various economic sectors in the Member States and combines this with information on ozone formation and transport processes in the atmosphere and with indicators for the impact of ozone on human health and environmental. Reflecting the discussions with Member States and stakeholders, a number of decisive steps in the process of deriving the national emission ceilings are presented here: the way of framing interim objectives, how to choose an appropriate ambition level, aspects of how to cope with uncertainties in the model and the input data and how to treat extreme meteorological situations and resolve problems in the spatial distribution of the interim objectives given the different size of countries. Finally, the paper explains the scenario underpinning the proposed national emission ceilings, its environmental gains and the distribution of cost incurring for emission control measures in Member States.

Air Pollution↗
PubMed2000

New antitumor-active azole-bridged dinuclear platinum(II) complexes: synthesis, characterization, crystal structures, and cytotoxic studies.

Three new derivatives of the cytotoxic azole-bridged dinuclear platinum(II) complex [(cis-Pt(NH3)2)2(mu-OH)(mu-pz)][NO3]2 (1) have been prepared and structurally characterized. Their formulas are [(cis-Pt(NH3)2)2(mu-OH)(mu-1,2,3-ta)][NO3]2 (2) (1,2,3-ta = 1,2,3-triazolate), [(Pt(R,R-dach))(mu-OH)(mu-pz)(Pt(S,S- dach))][NO3]2 (3) (dach = 1,2-diaminocyclohexane, pz = pyrazolate), and [(Pt(R,R-dach))(mu-1,2,3- ta)2(Pt(S,S-dach))][NO3]2 (4). The compounds were characterized by 1H, 13C, and 195Pt NMR spectroscopy, and elemental analysis, and their crystal structures were determined. Relevant data for 2: triclinic, space group P1, a = 8.5225(15) A, b = 9.1977(18) A, c = 9.9771(7) A, alpha = 66.988(10) degrees, beta = 75.423(9) degrees, gamma = 67.321(13) degrees, Z = 2. 3: orthorhombic, space group Pca2(1), a = 17.7653(3) A, b = 12.4076(3) A, c = 10.7091(3) A, Z = 4. 4: orthorhombic, space group Pbca, a = 13.8944(1) A, b = 17.8668(1) A, c = 20.7647(2) A, Z = 8. In the crystal structures of 2, and 3, the intramolecular distances between the two Pt atoms are 3.4411(6) and 3.4873(5) A, and the dihedral angles between the platinum coordination planes are 14.1(3) and 9.3(4) degrees, respectively. In 2, an intramolecular hydrogen bond is observed between N9 of the ammine ligand and the noncoordinated nitrogen atom (N3) of the triazole ring (N9...N3: 2.962(10) A). 4 has a boat-form structure, and the two coordination planes cross at 83.64(10) degrees. A cytotoxicity assay of these dinuclear platinum(II) compounds on human tumor cell lines was performed. In most of the cell lines, 1 and 2 showed much higher cytotoxicity than those of cisplatin. On the other hand, 3 was found to be moderately active, and 4 was found only marginally cytotoxic. Implications of these findings are discussed in the context of a structure-activity relationship.

Antineoplastic Agents↗
PubMed2000

Vanadium(IV) and -(V) complexes with O,N-chelating aminophenolate and pyridylalkoxide ligands.

Two different monoanionic O,N-chelating ligand systems, i.e., [OC6H2(CH2NMe2)-2-Me2-4,6]- (1) and [OCMe2([2]-Py)]- (2), have been applied in the synthesis of vanadium(V) complexes. The tertiary amine functionality in 1 caused reduction of the vanadium nucleus to the 4+ oxidation state with either [VOCl3], [V(=NR)Cl3], or [V(=NR)(NEt2)3] (R = Ph, (3a, 5a), R = p-Tol (3b, 5b)), and applying 1 as a reducing agent resulted in the synthesis of the vanadium(IV) complexes [VO(OC6H2(CH2NMe2)-2-Me2-4,6)2] (4) and [V(=NPh)(OC6H2(CH2NMe2)-2-Me2-4,6)2] (6). In the case of [V(=N-p-Tol)(NEt2)(OC6H2(CH2NMe2)-2-Me2-4,6)2] (7b), the reduction was sufficiently slow to allow its characterization by 1H NMR and variable-temperature studies showed it to be a five-coordinate species in solution. Although the reaction of 1 with [V(=N-p-Tol)(O-i-Pr)3] (9b) did not result in reduction of the vanadium nucleus, vanadium(V) compounds could not be isolated. Mixtures of the vanadium(V) (mono)phenolate, [V(=N-p-Tol)(O-i-Pr)2(OC6H2(CH2NMe2)-2-Me2-4,6)] (10), and the vanadium(V) (bis)phenolate, [V(=N-p-Tol)(O-i-Pr)(OC6H2(CH2NMe2)-2-Me2-4,6)2] (11), were obtained. With the pyridylalkoxide 2, no reduction was observed and the vanadium(V) compounds [VOCl2(OCMe2([2]-Py))] (12) and [V(=N-p-Tol)Cl2(OCMe2([2]-Py)] (13) were obtained. 51V NMR showed 7b and 12 to be five-coordinate in solution, whereas for 10, 11, and 13 a coordination number of 6 was found. Compounds 12 and 13 showed decreased activity compared to their nonchelated vanadium(V) analogues when applied as catalysts in ethene polymerization. Two polymorphic forms with a difference in the V-N-C angle of 12.5 degrees have been found for 6. Crystal data: 6.Et2O, triclinic, P1, a = 11.1557(6) A, b = 12.5744(12) A, c = 13.1051(14) A, alpha = 64.244(8) degrees, beta = 70.472(7) degrees, gamma = 87.950(6) degrees, V = 1547(3) A3, Z = 2; 6.C6H6, triclinic, P1, a = 8.6034(3) A, b = 13.3614(4) A, c = 15.1044(5) A, alpha = 98.182(3) degrees, beta = 105.618(2) degrees, gamma = 107.130(2) degrees, V = 1551.00(10) A3, Z = 2; 12, orthorhombic, Pbca, a = 11.8576(12) A, b = 12.6710(13) A, c = 14.722(2) A, V = 2211.9(4) A3, Z = 8.

Journal Article↗
PubMed2000

Organoplatinum crystals for gas-triggered switches

Considerable effort is being devoted to the fabrication of nanoscale devices. Molecular machines, motors and switches have been made, generally operating in solution, but for most device applications (such as electronics and opto-electronics), a maximal degree of order and regularity is required. Crystalline materials would be excellent systems for these purposes, as crystals comprise a vast number of self-assembled molecules, with a perfectly ordered three-dimensional structure. In non-porous crystals, however, the molecules are densely packed and any change in them (due, for example, to a reaction) is likely to destroy the crystal and its properties. Here we report the controlled and fully reversible crystalline-state reaction of gaseous SO2 with non-porous crystalline materials consisting of organoplatinum molecules. This process, including repetitive expansion-reduction sequences (on gas uptake and release) of the crystal lattice, modifies the structures of these molecules without affecting their crystallinity. The process is based on the incorporation of SO2 into the colourless crystals and its subsequent liberation from the orange adducts by reversible bond formation and cleavage. We therefore expect that these crystalline materials will find applications for gas storage devices and as opto-electronic switches.

Journal Article↗
PubMed2000

The insulator protein CTCF represses transcription on binding to the (gt)(22)(ga)(15) microsatellite in intron 2 of the HLA-DRB1(*)0401 gene.

The insulator and transcription factor CTCF is a highly conserved 11 zinc finger protein possessing multiple specifities in DNA sequence recognition. CTCF regulates transcription of several genes, like the human oncogene c-myc or the chicken lysozyme gene by binding extremely divergent DNA sequences with different sets of its 11 zinc fingers. Recently, an insulator function was demonstrated for several CTCF binding elements. Here we show that CTCF binds to the (gt)(22)(ga)(15) microsatellite repeat A9 in intron 2 of the HLA-DRB1(*)0401 gene. Reporter gene activity is repressed by the A9 element. This repression is dependent on coexpressed CTCF and is even stronger compared with the CTCF binding site F1 of the chicken lysozyme gene, for which a silencer activity has been shown. This is the first report suggesting a function for microsatellite sequences in regulating specific gene expression.

Animals↗