PubMed Health⌕ Search

Biomedical subjects

D Neuman

Publications and source records attributed to D Neuman.

11 recordsLinked to original sources
PubMed2000

Structural and functional characteristics of rhenium clusters derived from redox chemistry of the triangular [ReIII3(mu-Cl)3] core unit.

The present study investigates structural and functional aspects of the redox chemistry of rhenium(III) chloride [Re3Cl9] (1) in aqueous and organic solvents, with emphasis on the dioxygen-activating capabilities of reduced rhenium clusters bearing the Re3(8+) core. Dissolution of 1 in HCl (6 M) generates [Re3(mu-Cl)3Cl9]3- (2a), which can be isolated as the tetraphenylphosphonium salt (2b). Anaerobic one-electron reduction of 1 by Hg in HCl (6-12 M) produces [(C6H5)4P]2[Re3(mu-Cl)3Cl7(H2O)2].H2O (3), the structure of which features a planar [Re3(mu-Cl)3Cl3] framework (Re3(8+) core), involving two water ligands that occupy out-of-plane positions in a trans arrangement. Compound 3 dissociates in the presence of CO, yielding [(C6H5)4P]2[ReIII2Cl8] (4) and an unidentified red carbonyl species. In situ oxidation (O2) of the reduced Re3(8+)-containing cluster in HCl (6 M) produces quantitatively 2a, whereas oxidation of 3 in organic media results in the formation of [(C6H5)4P]4[(Re3(mu-Cl)3Cl7(mu-OH))2].2CH2Cl2 (5). The structure of 5 reveals that two oxygen ligands (hydroxo units) bridge asymmetrically two Re3(9+) triangular clusters. The origin of these hydroxo units derives from the aquo ligands, rather than O2, as shown by 18O2 labeling studies. The hydroxo bridges of 5 can be replaced by chlorides upon treatment with Me3SiCl to afford the analogous [(C6H5)4P]4[(Re3(mu-Cl)3Cl7(mu-Cl))2].10CH2Cl2 (6). The reaction of 5 with Hg in HCl (6 M)/tetrahydrofuran regenerates compound 3. Complexes 1-3 exhibit nitrile hydratase type activity, inducing hydrolysis of CH3CN to acetamide. The reaction of 3 with CH3CN yields [(C6H5)4P]2[Re3(mu-Cl)3Cl6.5(CH3CN)1.5(CH3C(O)NH)0.5] (7), the structure of which is composed of [Re3(mu-Cl)3Cl7(CH3CN)2]2- (7a) and [Re3(mu-Cl)3Cl6(CH3CN)(CH3C(O)NH)]2- (7b) (Re3(8+) cores) as a disordered mixture (1:1). Oxidation of 7 with O2 in CH3CN affords [(C6H5)4P]2[Re3(mu-Cl)3Cl7(CH3C(O)NH)].CH3CN (8) and small amounts of [(C6H5)4P][ReO4] (9). Compound 8 is also independently isolated from the reaction of 2b with wet CH3CN, or by dissolving 5 in CH3CN. In MeOH, 5 dissociates to afford [(C6H5)4P]2[Re3(mu-Cl)3Cl8(MeOH)].MeOH (10).

Journal Article↗
PubMed1998

Operative treatment of hip fractures in patients with renal failure.

The conditions of a hip fracture and renal failure cause particularly high mortality. Eight patients (average age, 63 years) who had operative treatment for nine hip fractures were studied retrospectively. Three had intertrochanteric fractures fixed with sliding compression screws, and five had femoral neck fractures (bilateral in one patient): two nondisplaced femoral neck fractures were fixed with percutaneous screws, and four displaced femoral neck fractures were treated with arthroplasties in three and percutaneous screws in one. Operative treatment was done when the patient was in medically stable condition (average, 8 days). Full weightbearing was allowed on the injured limb after surgery. Early morbidity analysis showed no wound infections, thromboembolic events, or hemorrhagic complications. The first year mortality was three (38%). Late morbidity included one nonunion and one sliding screw penetration. Total mortality at 6 years was seven (88%) patients, with an average postoperative survival time of 28 months. Preoperative ambulation was preserved in five of seven (71%) patients. One the basis of this study, it appears that a team approach to operative management including nephrologist and surgeon helps to reduce short term complications and mortality and allows such patients to be mobilized and regain ambulation.

Aged↗
PubMed1991

Lens anatomical principles and their technical implications in cataract surgery. Part II: The lens nucleus.

Preservation of the intact ("true") capsular bag, with no tears to the periphery, is essential to assure permanent in-the-bag fixation of the intraocular lens. Removal of a large nucleus using the open-system planned extracapsular cataract extraction (ECCE) technique is often associated with tearing of the capsulectomy or serious complications such as zonular rupture, vitreous loss, unintended intracapsular cataract extraction, or posterior lens prolapse. A closed-system planned ECCE technique which allows a safe removal of the lens while maintaining the integrity of the capsular bag is presented. Hydrodissection of the lens nucleus to an epinucleus and a central hard nucleus allows hydroextraction of the small hard core while pushing the posterior capsule backward. The positive pressure in the anterior chamber, provided by the anterior chamber maintainer, keeps the position of the lens steady in its natural location, and minimizes the stress on the zonular apparatus during nucleus delivery. The remaining epinucleus can be either hydroexpressed or aspirated. Fracturing the central core, when possible, enables removal of the lens material through a small limbal incision. Viscoelastic material can be combined with a low-flow, anterior chamber maintainer in a closed-system and provides a useful surgical tool.

Cataract Extraction↗
PubMed1983

Inhibition of non-neuronal cell proliferation in the goldfish visual pathway affects the regenerative capacity of the retina.

Proliferating cells associated with the visual pathway were found in the present study to affect the regenerative capacity of the goldfish retina following optic nerve injury. The contribution of these cells to the process of regeneration was investigated in the goldfish visual system by reducing their proliferation in the optic tract and tecta, using X-irradiation. The regenerative ability of the retina was then evaluated by the following parameters: sprouting from retinal explants, protein synthesis in the retina and accumulation of radiolabeled transported components in the tectum. X-irradiation of the visual system at an early stage of the regeneration process had a promoting effect whereas irradiation at a later stage resulted in a reduced capacity to regenerate. The results are discussed with respect to the possibility that proliferating cells, possibly glia, exert two contradictory contributions: an inhibitory effect at the site of injury, whereas distal to it, a supportive, perhaps trophic effect.

Animals↗