Search PubMed⌕ Search

Biomedical subjects

M Lutz

Publications and source records attributed to M Lutz.

At least 55 records · Page 3Linked to original sources
PubMed2000

Long-range sigma-pi interactions in tetrahydro-4H-thiopyran end-capped oligo(cyclohexylidenes). Photo-electron spectroscopy, ab initio SCF MO calculations, and natural bond orbital analyses

Long-range sigma-pi interactions in tetrahydro4H-thiopyran end-capped oligo(cyclohexylidenes) were identified by He(I) photoelectron spectroscopy (PES) and ab initio RHF/6-31G* calculations. The vertical ionization energies Ivj of the highest occupied molecular orbitals (MO's) were assigned using Koopmans' theorem (Iv,j = -epsilonj) and by correlation with the ionizations of related reference compounds. The experimental (PES) and theoretical (RHF/6-31G*) results are in good agreement. For tercyclohexylidene derivatives which contain two nonconjugated pi-bonds splittings deltaIv,j of the pi-bands in the range from approximately 0.5 to 0.7 eV (delta-epsilonj approximately 0.6 to 0.9 eV). For the bi- and tercyclohexylidene compounds containing two sulfur atoms at their alpha- and omega-end positions the pi-type sulfur lone pair bands [Lppi(S)] split significantly by deltaIvj approximately 0.3 to 0.4 eV (delta-epsilonj approximately 0.3 to 0.4 eV), i.e. sigma-pi interactions over distances of ca. 8 and 12 A, respectively, occur. The magnitude of the interactions and the observed splittings are independent of the anti and syn conformations of the oligo(cyclohexylidene) hydrocarbon skeletons. RHF/6-31G* Natural Bond Orbital analyses reveal that the Hax-C-C-Hax precanonical MO's (PCMO's) centered on the cyclohexyl-type rings are paramount for the relay of the through-bond sigma-pi interactions; no through-space sigma-pi interactions were identified.

Journal Article↗
PubMed2000

Transcriptional repression by the insulator protein CTCF involves histone deacetylases.

The highly conserved zinc-finger protein, CTCF, is a candidate tumor suppressor protein that binds to highly divergent DNA sequences. CTCF has been connected to multiple functions in chromatin organization and gene regulation including chromatin insulator activity and transcriptional enhancement and silencing. Here we show that CTCF harbors several autonomous repression domains. One of these domains, the zinc-finger cluster, silences transcription in all cell types tested and binds directly to the co-repressor SIN3A. Two distinct regions of SIN3A, the PAH3 domain and the extreme C-terminal region, bind independently to this zinc-finger cluster. Analysis of nuclear extract from HeLa cells revealed that CTCF is also capable of retaining functional histone deacetylase activity. Furthermore, the ability of regions of CTCF to retain deacetylase activity correlates with the ability to bind to SIN3A and to repress gene activity. We suggest that CTCF driven repression is mediated in part by the recruitment of histone deacetylase activity by SIN3A.

3T3 Cells↗
PubMed2000

Diagnostic organometallic and metallodendritic materials for SO2 gas detection: reversible binding of sulfur dioxide to arylplatinum(II) complexes

A series of square-planar platinum(II) complexes of the N,C,N'-terdentate-coordinating monoanionic "pincer" ligand, [PtX(4-E-2,6-[CH2NRR']2-C6H2](X=Cl, Br, I, tolyl; R, R'=Et, Me; E=H, OH, OSiMe2tBu) has been prepared. In the presence of sulfur dioxide, these complexes spontaneously adsorb this gas to form penta-coordinated adducts. Solid-state crystal-structure analyses of the SO2 adducts 8c (X=I, R=R=Me, E=OSiMe2tBu) and 11 (X=Cl, R=R'=Me, E=OH) show a square-pyramidal geometry around the metal center with SO2 in the apical position. Most interestingly. the adduct 11 forms similar Pt-Cl... H-O hydrogen-bonded alpha-type networks as the corresponding SO2-free complex 5. The conservation of the supramolecular information (hydrogen-bonded self-assembly) throughout a reaction (SO2 adsorption) is unprecedented in crystal engineering. Adduct formation in the solid state or in solution is fast and reversible and is indicated by a characteristic color change of the material from colorless to bright orange. Since facile methods have been developed to remove SO2 from the adducts and to regenerate the square-planar starting complexes, these complexes fulfill several essential prerequisites of sensor materials for repeated diagnostic SO2 detection. The platinum sensors have been found to be highly selective for sulfur dioxide and particularly sensitive for submilimolar to molar gas quantities. Their response capacity is tuneable by electronic and steric modifications of the ligand array by introduction of, for example, different substituents on the nitrogen donors. The periphery of dendrimers is shown to be an appropriate macromolecular support for anchoring the detection-active sites, thus allowing full recovery of the sensor materials for repeated use. By using this concept, metallo-dendrimers 3 and 15 have been prepared. Owing to the dendritic connectivity, these sensors are suitable for repetitive qualitative and quantitative detection of small amounts of SO2.

Journal Article↗
PubMed2000

Cooperative reactivity of early-late heterodinuclear transition metal complexes with polar organic substrates

A comprehensive investigation into the cooperative reactivity of two chemically complementary metal-complex fragments in early-late heterodinuclear complexes has been carried out. Reaction of the partially fluorinated tripodal amidozirconium complexes [HC-(SiMe2NR)3Zr(mu-Cl)2Li(OEt2)2] (R = 2-FC6H4: 2a, 2,3,4-F3C6H4: 2b) with K[CpM(CO)2] (M=Fe, Ru) afforded the stable metal-metal bonded heterodinuclear complexes [HC[SiMe2NR]3-Zr-MCp(CO)2] (3-6). Reaction of the dinuclear complexes with methyl isonitrile as well as the heteroallenes CO2, CS2, RNCO and RNCS led to insertion into the polar metal-metal bond. Two of these complexes, [HC[SiMe2N(2-FC6-H4)]3Zr(S2C)Fe(CO)2Cp] (9a) and [HC-[SiMe2N(2-FC2H4)]3Zr-(SCNPh)Fe(CO)2-Cp] (12), have been structurally characterized by a single crystal X-ray structure analysis, proving the structural situation of the inserted substrate as a bridging ligand between the early and late transition metal centre. The reactivity towards organic carbonyl derivatives proved to be varied. Reaction of the heterobimetallic complexes with benzyl and ethylbenzoate led to the cleavage of the ester generating the respective alkoxozirconium complexes [HC[SiMe2N(2-FC6H4)]3ZrOR] (R = Ph-CH2: 13a, Et: 13b) along with [CpFe-[C(O)Ph](CO)2], whereas the analogous reaction with ethyl formate gave 13b along with [CpFeH(CO)2]; this latter complex results from the instability of the formyliron species initially formed. Aryl aldehydes were found to react with the Zr-M complexes according to a Cannizzaro disproportionation pattern yielding the aroyliron and ruthenium complexes along with the respective benzoxyzirconium species. The transfer of the aldehyde hydrogen atom in the course of the reaction was established in a deuteriation experiment. [HC[SiMe2-N(2-FC6H4)]3Zr-M(CO)2Cp] reacted with lactones to give the ring-opened species containing an alkoxozirconium and an acyliron or acylruthenium fragment; the latter binds to the early transition metal centre through the acyl oxygen atom, as evidenced from the unusuallly low-field shifted 13C NMR resonances of the RC(O)M units. Ketones containing a-CH units react with the Zr-Fe complexes cooperatively to yield the aldol coupling products coordinated to the zirconium complex fragment along with the hydridoiron compound [CpFeH(CO)2], whereas 1,2-diphenylcyclopropenone underwent an oxygen transfer from the keto group to a CO ligand to give a linking CO2 unit and a cyclopropenylidene ligand coordinated to the iron fragment in [HC-[Si(CH3)2N(2,3,4-F3C6H2)]3Zr(mu-O2C)-Fe(CO)[C3Ph2)Cp] (19). The atom transfer was established by 17O and 13C labelling studies. Similar oxygen-transfer processes were observed in the reactions with pyridine N-oxide, dimethylsulfoxide and methylphenylsulfoxide.

Journal Article↗
PubMed2000

The use of a graft from the second extensor compartment to reconstruct the A2 flexor pulley in the long finger.

A 10 mm wide ring graft from the second extensor compartment with periosteum from the floor of the sheath was used to correct bowstringing in six patients who sustained an isolated rupture of the A2 pulley. It was attached to the lateral rims of the sheath. Periosteum was used for additional graft fixation. Bowstringing was assessed by magnetic resonance imaging and ultrasound preoperatively and 19.5 months after surgery. It was corrected in five patients and improved in one. Pain was reduced from 35 to 7 points on a visual analogue scale. Digital circumference decreased from 76 to 71 mm. Flexion at the PIP joint increased from 88 degrees to 116 degrees. Pinch grip improved from 28 to 56 N.

Adult↗
PubMed2000

[Monteggia injuries in childhood].

The Monteggia-fracture dislocation is a characteristic combined injury of the forearm with fracture of the ulna and dislocation of the head of the radius. Monteggia- and equivalent injuries are rare. In the present study, we attempt to clarify the concept of therapy and observe the influence of this injury on the growth of the forearm bones. Between 1977 and 1996, 27 patients (three to thirteen years) with a Monteggia or a Monteggia-equivalent injury were treated. We present clinical and radiological long-term results of 20 patients, two to 21 years following the injury. Group I includes 12 patients with a classic Monteggia injury, five patients were treated conservatively, seven patients surgically. Ten patients were free of pain and had no loss of motion. In one patient there was a loss of pronation following an accompanying injury of the distal radius. Primary paresis of the radial nerve has a good prognosis. One patient presents a persisting dislocation of the radius head with a loss of flexion in the elbow joint, and a secondary persisting paraesthesia of the median nerve. Group II includes eight patients with a Monteggia-equivalent injury; all of them were treated surgically. The results in this group showed more loss of motion in elbow function, forearm rotation, and dislocation of the axis in the elbow joint. Monteggia and Monteggia-equivalent injuries in childhood have good functional results if correct reduction of the fracture of the ulna and the head of the radius is performed. If this is not possible conservatively, patients need open reduction and internal fixation.

Adolescent↗
PubMed2000

[Late sequelae of fractures of the distal third of the forearm during the growth period].

Fractures to the distal third of the forearm are the most common fractures of the upper extremity, with the majority occurring between the age of ten and 14 years. With the exception of the rare epiphyseal fractures, they have a favourable prognosis. The present study investigates the frequency and extent of potential clinical and radiological late sequelae of fractures in the distal third of the forearm during growth. Of the patients treated at the Innsbruck University Department of Traumatology from 1980 to 1992, 220 patients of a growing age with 232 closed fractures in the distal third of the forearm were followed up. The radius alone was affected in 60% of these cases; the radius and the ulna in 40%. Fractures of the ulna alone were not present. The mean age of the patients at the time of injury was nine years (range one to 16 years) and the mean time of follow-up ten years (range five to 16 years). In addition to the patient's subjective assessment, the right and left sides were compared with regard to mobility of the wrist and rotational movement of the forearm. Based on standard X-rays, the frontal (radio-ulnar) and lateral (dorso-palmar) radial joint angle as well as the difference in the radio-ulnar plane were compared with the contralateral side. Clinical and radiological findings were summarised into an overall result. 19% of the patients reported pain in the injured wrist. Mobility of the wrist in the sagittal and/or frontal plane was limited in 5% of patients and rotation of the forearm was limited in 16% of patients. A statistically significant accumulation of limited rotation was seen after physeal fractures of the ulna ("one-way" ANOVA-test, p = 0.0033). A difference between the left and right side in regard to the frontal radial joint angle was seen in 6% of patients and a difference in the lateral radial joint angle was registered in 2% of patients. A difference in the radio-ulnar plane was observed in 37% of patients. In the presence of relative ulna-plus variance, 75% of patients complained of pain in the ulnocarpal compartment of the wrist. In these patients, dynamic magnetic resonance tomography revealed a compression of the ulnocarpal disk between the proximal carpal bones and the head of the ulna, as well as degeneration in the central portion of the disk. The overall outcome was very good in 72%, good in 19%, moderate in 6% and poor in 3% of patients. The younger the children had been at the time of injury, the more favourable were the results (chi-square test, p = 0.009). Children older than ten years of age with an angulatory deformity of more than 20 degrees and/or fragment dislocation over half of the breadth of the shaft at fracture consolidation showed the poorest results. Further factors having a negative influence on the outcome were repeated reduction manoeuvres and an additional fracture of the ulna.

Adolescent↗
PubMed2000

Modulation of thyroid hormone receptor silencing function by co-repressors and a synergizing transcription factor.

We have found that the thyroid hormone receptor (T3R) functionally synergizes with the CCCTC-binding factor (CTCF). CTCF is a highly conserved zinc-finger protein that has been connected with multiple functions in gene regulation including chromatin insulator activity, transcriptional enhancement and silencing as well as tumour suppression. A specific property of CTCF is that some of the binding sites are found in the vicinity of T3R-binding sites. Interestingly, both factors synergize in repression as well as in activation. T3R-mediated repression has been shown to involve co-repressors such as the silencing mediator for retinoic acid and thyroid hormone receptor (SMRT), N-CoR or Alien. These co-repressors in turn have been found to interact with Sin3A. Until now, the mechanisms by which CTCF synergizes with T3R in transcriptional repression has not been determined. Here we show that CTCF comprises autonomous silencing domains that mediate transcriptional repression when tethered to a promoter sequence. At least one of these domains, the zinc-finger region of CTCF, binds Sin3A without binding to SMRT or N-CoR and recruits histone deacetylation activity. For Sin3A we identified two different domains interacting independently with the CTCF zinc-finger cluster. The ability of regions of CTCF to retain deacetylase activity is correlated with the ability to bind to Sin3A and to repress transcription. Taking these results together, the synergy in repression mediated by T3R and CTCF might be achieved by the binding of multiple molecules of Sin3A to the T3R/CTCF-DNA complex, thus providing a large platform for the recruitment of histone deacetylases.

Animals↗
PubMed1999

A Robust, Environmentally Benign Catalyst for Highly Selective Hydroformylation.

By a sol-gel process a rhodium complex containing a diphosphane with a large natural P-Rh-P bite angle is covalently anchored in a silica matrix (see picture). The immobilized catalyst is a very selective hydroformylation catalyst that is completely and conveniently separated from the product and can be reused in numerous cycles.

Journal Article↗
PubMed1999

Negative transcriptional regulation mediated by thyroid hormone response element 144 requires binding of the multivalent factor CTCF to a novel target DNA sequence.

DNA target sites for a "multivalent" 11-zinc-finger CCTC-binding factor (CTCF) are unusually long ( approximately 50 base pairs) and remarkably different. In conjunction with the thyroid receptor (TR), CTCF binding to the lysozyme gene transcriptional silencer mediates the thyroid hormone response element (TRE)-dependent transcriptional repression. We tested whether other TREs, which in addition to the presence of a TR binding site require neighboring sequences for transcriptional function, might also contain a previously unrecognized binding site(s) for CTCF. One such candidate DNA region, previously isolated by Bigler and Eisenman (Bigler, J., and Eisenman, R. N. (1995) EMBO J. 14, 5710-5723), is the TRE-containing genomic element 144. We have identified a new CTCF target sequence that is adjacent to the TR binding site within the 144 fragment. Comparison of CTCF recognition nucleotides in the lysozyme silencer and in the 144 sequences revealed both similarities and differences. Several C-terminal CTCF zinc fingers contribute differently to binding each of these sequences. Mutations that eliminate CTCF binding impair 144-mediated negative transcriptional regulation. Thus, the 144 element provides an additional example of a functionally significant composite "TRE plus CTCF binding site" regulatory element suggesting an important role for CTCF in cooperation with the steroid/thyroid superfamily of nuclear receptors to mediate TRE-dependent transcriptional repression.

Animals↗
PubMed1999

Olefin Cycloadditions of the Electrophilic Phosphinidene Complex

Highly strained methylenephosphiranes are formed in the reaction of the new electrophilic phosphinidene complex [iPr(2)N-P=Fe(CO)(4)] with allenes. Remarkably, reaction with diallenes at 0 degrees C also leads to a phosphirane, which rearranges upon warming to room temperature to a bis-isopropylidenephospholene (see scheme).

Journal Article↗
PubMed1999

[Integration of porous hydroxyapatite ceramic prosthesis at the distal radius in elderly patients. Radiological examination].

Between April 1994 and December 1995 14 patients (average age 56 (41-71) years, 13 women, one man) suffering from a fracture of the distal radius (Extensionsfracture, type 1B by Pechlaner, AO-classification A2 and A3) were treated by minimal invasiv procedure. The bone defect was substituted with hydroxylapatit ceramic. In a prospective study the osteointegration of the alloplastic bone graft was evaluated radiographically and on MRI. Up to week 12 X-ray revealed a radiolucenty around the allograft in all patients. After 6 months trabecular structure reached the alloplastic bone graft in 57% of the patients. After one year the surface of the hydroxylapatit ceramic was remodelled in 36% of the patients. At this time MRI examination with contrast agent demonstrated marginal integration of the alloplastic bone craft in 71%. X-ray follow up showed stageable integration of the porous hydroxylapatit ceramic. MRI examination demonstrated partial osteointegration. Hydroxylapatit ceramic was incorporated in radial metaphyse of elder patients without any complications.

Adult↗
PubMed1999

Vascularized bone graft from the iliac crest for the treatment of nonunion of the proximal part of the scaphoid with an avascular fragment.

BACKGROUND: It was hypothesized that nonunion of the proximal third of the scaphoid associated with avascular necrosis could be treated successfully with a free vascularized bone graft obtained from the iliac crest. METHODS: Fifteen patients who had a nonunion of the proximal part of the scaphoid that had been present for an average of two years and three months (range, nine months to seven years) were managed with use of a free vascularized bone graft obtained from the iliac crest. Avascularity of the scaphoid, as assessed on preoperative radiographs, was characterized by loss of trabecular structure, collapse of subchondral bone, and formation of bone cysts. The results of the procedure were assessed in terms of osseous union, pain, active motion of the wrist, and osteoarthritis. Postoperatively, vascularity of the scaphoid was evaluated with use of magnetic resonance imaging and color Doppler ultrasonography. The average duration of follow-up was six years and one month (range, two years and one month to eight years and one month). RESULTS: Preoperatively, one patient had had pain with any movement of the wrist and fourteen had had pain after strenuous manual labor or sports activity. The average pain score, derived with use of a 10-point visual analog scale, was 2.4 points (range, 1.0 to 6.7 points). Postoperatively, union was achieved in twelve patients; six were pain-free, and six had occasional pain during strenuous manual labor or sports activity, or both. The average pain score for these twelve patients was 1.1 points (range, 0.0 to 4.2 points) on the visual analog scale. Preoperatively, osteoarthritis was limited to the region between the radial styloid process and the distal part of the scaphoid in fourteen patients and to the radioscaphoid region in one patient. Postoperatively, the degree of osteoarthritis remained unchanged in seven of the twelve patients who had union and progressed to the radioscaphoid region in five. Vascularity, as seen on the imaging studies, was restored in all twelve patients who had union. The nonunion persisted in three patients, all of whom had progressive osteoarthritis leading to carpal collapse. CONCLUSIONS: The index procedure was successful in twelve of the fifteen patients who had a symptomatic nonunion of the proximal part of the scaphoid associated with avascular necrosis and osteoarthritis that was limited to the radioscaphoid joint.

Adult↗
PubMed1999

Sonographic detection of radial nerve entrapment within a humerus fracture.

Radial neuropathy is frequently associated with fracture of the middle third of the humerus owing to the course of the nerve adjacent to the humeral shaft. The prevalence varies from 2 to 18% of humeral fractures. The therapeutic management is still controversial. Some authors recommend initial surgical exploration, whereas others prefer observation and intervention only if the injured nerve failed to recover after a period of more than 4 months. According to the literature, verification of an entrapped radial nerve in a fracture gap requires surgical exploration, but diagnostic tools to verify the existence of a pathologic condition are limited. We describe the sonographic findings of an entrapped radial nerve and review the literature regarding diagnosis and treatment of entrapped radial nerve in cases of humeral fracture.

Adult↗
PubMed1999

Design of Novel Hexametallic Cartwheel Molecules from Persubstituted Benzene Compounds.

The cartwheel complexes A are novel, nano-sized hexametallic species available from persubstituted benzenes C(6)[3,5-(CH(2)Y)(2)C(6)H(3)] (Y=NMe(2), P(O)Ph(2), PPh(2), SPh). The molecular structure of A (Y=SPh, ML(n)=PdCl) shows C(3) symmetry with adjacent radial Pd-Pd separations of 7.339(2) and 8.006(2) Å and a diametrically opposed Pd-Pd separation of 15.340(2) Å. Because of their size hexametallic species such as A are potential homogeneous catalysts in organic reactions which can be recovered by nanomembrane filtration techniques.

Journal Article↗