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At least 217 records · Page 12Linked to original sources
PubMed1984

Evidence for the re-establishment of a heterogeneity in radiosensitivity among spermatogonial stem cells repopulating the mouse testis following depletion by X-rays.

Earlier studies have shown that the spermatogonial stem cells of the mouse testis recovering from previous radiation or chemical mutagen exposure give subnormal yields of genetic damage with subsequent X-irradiation. This response has been investigated further: (a) with a high, 9-Gy X-ray dose given 4, 12 or 21 days after a 1-Gy conditioning dose (Expt. 1), and (b) with a 1 + 7-Gy, 24-h fractionation regime given 4 or 14 days after a 1-Gy conditioning dose (Expt. 2). In Expt. 1 the 1 + 9-Gy, 4-day interval regime gave a very low response, lower than obtained previously with an equivalent 1 + 5-Gy treatment. This suggests that a heterogeneity in radiosensitivity, such as exists in unirradiated stem cell populations and absent 24-48 h after radiation depletion, is quickly re-established among the stem cells repopulating the testis. By contrast, the 1 + 7-Gy, 24-h fractionation when given 4 days after the 1-Gy conditioning dose (Expt. 2) gave a very high yield of genetic damage, almost as high as that given by the fractionated (1 + 7 Gy) dose applied to previously unirradiated stem cells. This suggests that the newly established heterogeneity is removed by the second 1-Gy conditioning dose. With longer intervals between treatments, genetic yields consistent with additivity were obtained in Expt. 1; less clear results were obtained Expt. 2. Comparison with earlier data generally suggested that the duration of the repopulating period is dose-dependent. In a third experiment evidence was obtained that genetic damage induced by X-irradiation can be reduced by a subsequent treatment with triethylenemelamine (TEM) during the repopulating phase. This confirmed an earlier finding. Such an interaction could not be demonstrated with two X-ray treatments. An explanation for the X-ray/TEM interaction is offered.

Animals↗
PubMed2003

Synthesis and structural characterization of novel Re(i) tricarbonyl complexes anchored on a phosphinoarylbenzylamine and a phosphinoaryloxazoline generated in situ.

Reduction of the amide or replacement of the hydroxyl by a bromide in 2-(diphenylphosphanyl)-N-(2-hydroxyethyl)benzamide (H2PNO) yielded the compounds 2-(diphenylphosphanyl)-N-(2-hydroxyethyl)benzylamine (H2CH2PNO, 1) and N-(2-bromoethyl)-2-(diphenylphosphanyl)benzamide (HPNBr, 2), respectively. Compound 2 is obtained in low yield and, depending on the reaction conditions, is mixed with starting material or with a product which has been identified as 2-(2-diphenylphosphinophenyl)oxazoline (PPh3oxaz, 3). Compounds 1 and 2 react with (NEt(4))(2)[ReBr(3)(CO)(3)], leading to the complexes [Re(CO)(3)(kappa(2)-H(2)CH(2)PNO)Br] (4) and [Re(CO)(3)(kappa(2)-PPh(3)oxazBr)] (5), fully characterized by (1)H and (31)P NMR spectroscopy and X-ray crystallographic analysis. Complex 5 is the first example of a Re(I) tricarbonyl anchored on a phosphorus-oxazoline ligand, which has been generated during the course of complex formation. In the unexpected and unusual complex 5, the Re atom is stabilized by a bidentate 2-(2-diphenylphosphinophenyl)oxazoline, by a bromide, and by three facially arranged carbonyl groups. In complex 4, the carbonyl groups are also facially coordinated to the metal center and the other three remaining coordination positions are occupied by a bromide and by the bidentate (P, N) ligand 2-(diphenylphosphanyl)-N-(2-hydroxyethyl)benzylamine.

Journal Article↗
PubMed2001

Robust, alkali-stable, triscarbonyl metal derivatives of hexametalate anions, [M6O19[M'(CO)3]n](8-n)- (M = Nb, Ta; M' =Mn, Re; n = 1, 2).

Ten 1:1 and 2:1 complexes of [Mn(CO)(3)](+) and [Re(CO)(3)](+) with [Nb(6)O(19)](8)(-) and [Ta(6)O(19)](8)(-) have been isolated as potassium salts in good yields and characterized by elemental analysis, (17)O NMR and infrared spectroscopy, and single-crystal X-ray structure determinations. Crystal data for 1 (t-Re(2)Ta(6)): empirical formula, K(4)Na(2)Re(2)C(6)Ta(6)O(35)H(20), monoclinic, space group, C2/m, a = 17.648(3) A, b = 10.056(1) A, c = 13.171(2) A, beta = 112.531(2) degrees, Z = 2. 2 (t-Re(2)Nb(6)): empirical formula, K(6)Re(2)C(6)Nb(6)O(38)H(26), monoclinic, space group, C2/m, a = 17.724(1) A, b = 10.0664(6) A, c = 13.1965(7) A, beta = 112.067(1) degrees, Z = 2. 3 (t-Mn(2)Nb(6)): empirical formula, K(6)Mn(2)C(6)Nb(6)O(37)H(24), monoclinic, space group, C2/m, a = 17.812(2) A, b = 10.098(1) A, c = 13.109(2) A, beta = 112.733(2) degrees, Z = 2. 4 (c-Mn(2)Nb(6)): empirical formula, K(6)Mn(2)C(6)Nb(6)O(50)H(50), triclinic, space group, P1, a = 10.2617(6) A, b = 13.4198(8) A, c = 21.411(1) A, alpha = 72.738(1) degrees, beta = 112.067(1) degrees, gamma = 83.501(1) degrees, Z = 2. 5 (c-Re(2)Nb(6)): empirical formula, K(6)Re(2)C(6)Nb(6)O(54)H(58), monoclinic, space group, P2(1)/c, a = 21.687(2) A, b = 10.3085(9) A, c = 26.780(2) A, beta = 108.787(1) degrees, Z = 4. The complexes contain M(CO)(3) groups attached to the surface bridging oxygen atoms of the hexametalate anions to yield structures of nominal C(3)(v)() (1:1), D(3)(d)() (trans 2:1), and C(2)(v)() (cis 2:1) symmetry. The syntheses are carried out in aqueous solution or by aqueous hydrothermal methods, and the complexes have remarkably high thermal, redox, and hydrolytic stabilities. The Re-containing compounds are stable to 400-450 degrees C, at which point CO loss occurs. The Mn compounds lose CO at temperatures above 200 degrees C. Cyclic voltammetry of all complexes in 0.1 M sodium acetate show no redox behavior, except an irreversible oxidation process at approximately 1.0 V vs. Ag/AgCl. In contrast to the parent hexametalate anions that are stable only in alkaline (pH >10) solution, the new complexes are stable, at least kinetically, between pH 4 and pEta approximately 12.

Journal Article↗
PubMed2006

Syntheses and structural properties of rare earth carbodiimides.

Crystalline samples of rare earth carbodiimides were synthesized by solid-state metathesis reactions of rare earth trichlorides with lithium cyanamide in sealed silica ampules. Two distinct structures were determined by single-crystal X-ray diffraction. The structure determined for Sm2(CN2)3 [C2/m, Z = 2, a = 14.534(2) A, b = 3.8880(8) A, c = 5.2691(9) A, beta = 95.96(2) degrees , R1 = 0.0267, and wR2 = 0.0667] was assigned for RE2(CN2)3 compounds with RE = Y, Pr, Nd, Sm, Gd, Tb, Dy, Ho, and Er, and the structure determined for Lu2(CN2)3 [R32, Z = 3, a = 6.2732(8) A, c = 14.681(2) A, R1 = 0.0208, and wR2 = 0.0526] was assigned for the smallest rare earth ions with RE = Tm, Yb, and Lu by powder X-ray diffraction. Both types of crystal structures are characterized by layers of [NCN](2-) ions whose arrangements can be derived from the motif of a closest packed layer of sticks. These layers alternate with layers of rare earth ions in a one-by-one sequence. Different tilting arrangements of the N-C-N-axes relative to the stacking directions (c) and different arrangements of RE3+ ions within metal atom layers account for the two distinct structures in which Sm3+ and Lu3+ ions adopt the coordination numbers 7 and 6, respectively.

Journal Article↗
PubMed2001

Cochlear structures after implantation of a perimodiolar electrode array.

OBJECTIVE: A perimodiolar prototype electrode array has been evaluated on 12 human temporal bone specimens. To achieve modiolar proximity, a fine Teflon positioner is attached to the tip and base of a conventional Nucleus 22 electrode array. METHODS: Intracochlear electrode position was examined by macroscopic preparation and confirmed by a cochlear view x-ray after insertion into human temporal bones. The temporal bones were examined with light microscopy for intracochlear trauma after insertion, explantation, and re-implantation of the perimodiolar array. RESULTS: Macroscopic preparation and x-ray confirmed close proximity of the intracochlear electrodes to the modiolar wall. In some bones, electrode insertion and positioning was performed without significant damage to intracochlear structures, but explantation caused varying degrees of trauma depending on the explantation technique used. Re-implantation and repeat explantation appeared to destroy most of the intracochlear architecture. CONCLUSIONS: The perimodiolar electrode array prototype with Teflon positioner cannot be recommended for clinical use, especially in children in whom the possibility for re-implantation is high.

Child↗
PubMedDate not supplied

A simple approach to lightening an overexposed film with a blue ray copier.

It is sometimes necessary to have lighter versions of radiographs. Rather than re-expose a patient, a lighter radiograph frequently can be obtained by copying. This article describes a simple way to circumvent major internal alteration to the Blue Ray copier to permit an easy and effective lightening process.

Photography↗
PubMed2000

Re-use of implant coverscrews changes their surface properties but not clinical outcome.

This study examined the effect of re-using coverscrews for dental implants (Brånemark) and the influence of re-use on clinical outcome. Nine patients, each receiving 3 implants in either the maxilla or the mandible, received 1 new coverscrew, 1 re-used coverscrew, and a third coverscrew that had been used multiple times. In all cases, the re-used coverscrews had been washed, mechanically cleaned, and steam-sterilized prior to re-implantation. Clinical outcome was assessed by X-ray analysis of the mandible/maxilla and light microscopy of histologically prepared sections of the overlying tissue. The surfaces of the coverscrews were characterized by profilometry, scanning electron microscopy (SEM), Auger electron spectroscopy (AES), and atomic force microscopy (AFM). There was no difference in clinical outcome whether the coverscrews were new or re-used multiple times. Histological evaluation showed no influence of re-use on the overlying epithelial and connective tissues at the time the coverscrew was removed. Surface topography and roughness changed with increasing number of uses, but surface chemistry was virtually unchanged. SEM and AFM analyses revealed the presence of machining marks, as well as deep scratches, across the surface of the re-used coverscrews. This study shows that coverscrews can be cleaned and re-used without any apparent adverse affect on clinical outcome. However, the cleaning procedures, as well as the surgical procedure, change the surface characteristics. If this approach were applied to the implant itself, it might affect osseointegration.

Adult↗
PubMed2004

Unusual reactivity of the [Re(V)O]3+ core: syntheses and characterization of novel rhenium halide complexes with n-methyl-o-diaminobenzene.

The reactions of 1 or 2 equiv of N-methyl-o-diaminobenzene with trans-[ReOX(3)(PPh(3))(2)] (X = Cl, Br) in refluxing chloroform gave oxo-free rhenium complexes [Re(VI)X(4)(NC(6)H(4)NHCH(3))(OPPh(3))] (X = Cl, 3; X = Br, 6), [Re(V)X(2)Y(NC(6)H(4)NHCH(3))(PPh(3))(2)] (X, Y = Cl, 4; X = Br, Y = Cl, 7), [Re(IV)Cl(2)(NHC(6)H(4)NCH(3))(2)] (5), and [Re(IV)Br(3)(NHC(6)H(4)NCH(3))(PPh(3))] (8). All complexes were characterized by elemental analysis, (1)H NMR and IR spectroscopy, cyclic voltammetry, EPR spectroscopy, and X-ray crystallography. The complexes all display distorted octahedral coordination geometry. For Re(IV) complexes 5 and 8, the ligands coordinate in the benzosemiquinone diimine form. In Re(VI) complexes 3 and 6 and the Re(V) complexes 4 and 7, the ligands coordinate in the dianionic monodentate imido form. The EPR spectra of Re(VI) species 3 and 6 in dichloromethane solution at room temperature exhibit the characteristic hyperfine pattern of six lines, with evidence of strong second-order effects. The IR spectra of the complexes are characterized by Re=N and Re-N stretching bands at ca. 1090 and 540 cm(-)(1), respectively. The Re(IV) and Re(V) complexes display well-resolved NMR spectra, while the Re(VI) complexes exhibit no observable spectra, due to paramagnetism. The cyclic voltammograms of complexes 3 and 6 display Re(VII)/ Re(VI) and Re(VI)/Re(V) processes, those of 4 and 7 exhibit Re(VI)/Re(V) and Re(V)/Re(IV) couples, and those of 5 and 8 are characterized by Re(V)/Re(IV) and Re(IV)/Re(III) processes.

Benzene Derivatives↗
PubMed2005

Water molecules in the antibody-antigen interface of the structure of the Fab HyHEL-5-lysozyme complex at 1.7 A resolution: comparison with results from isothermal titration calorimetry.

The structure of the complex between hen egg-white lysozyme and the Fab HyHEL-5 at 2.7 A resolution has previously been reported [Cohen et al. (1996), Acta Cryst. D52, 315-326]. With the availability of recombinant Fab, the X-ray structure of the complex has been re-evaluated at 1.7 A resolution. The refined structure has yielded a detailed picture of the Fab-lysozyme interface, showing the high complementarity of the protein surfaces as well as several water molecules within the interface that complete the good fit. The model of the full complex has improved significantly, yielding an R(work) of 19.5%. With this model, the structural results can be compared with the results of isothermal titration calorimetry. An attempt has been made to estimate the changes in bound waters that accompany complex formation and the difficulties inherent in using the crystal structures to provide the information necessary to make this calculation are discussed.

Antigen-Antibody Complex↗
PubMed2000

Influence of acetylsalicylic acid on development of radiation-induced nephropathy.

PURPOSE: Previous studies have demonstrated that long-term treatment with acetylsalicylic acid (ASA) can significantly reduce the renal functional impairment that develops after high doses of irradiation. The effect is hypothesized to be mediated by selective inhibition of thromboxane A2 synthesis and inhibition of platelet aggregation. The present study was undertaken to investigate this phenomenon further using more clinically relevant fractionated and re-irradiation schedules. METHODS AND MATERIALS: Groups of mice were given bilateral renal irradiation with a series of four or 20 daily fractions of X-rays, or 10 daily fractions with a single dose of re-irradiation (0-10 Gy) after 27 weeks. Half the mice received ASA in drinking water (2.4 g x l(-1)) from 1 week before the start of irradiation and continuously throughout the follow-up period. Renal function was assessed by clearance of [51Cr]EDTA, about every 4 weeks for up to 80 weeks after the start of treatment. Histological damage in representative groups of mice was also assessed. RESULTS: Oral administration of ASA caused inhibition of thromboxane A2 synthesis (to < 36% of controls) and a strong inhibition of platelet aggregation in whole mouse blood (ex vivo). Prolonged treatment with ASA also resulted in a small, non-significant reduction of radiation-induced renal functional damage. No reduction in histological damage was seen in the ASA treated mice. CONCLUSION: Long-term oral administration of ASA gave only a modest, non-significant reduction of renal radiation injury after clinically relevant fractionated irradiation schedules.

Animals↗
PubMed2001

[The Roseland prosthesis in the treatment of osteoarthritis. A five years experience with the same surgeon].

INTRODUCTION: The results of the Roseland trapeziometacarpal prosthesis in the treatment of the TMP arthritis has been reviewed and the trapezial component fixation discussed. METHOD: The material has been collected between November 1995 and January 2000. The immobilisation lasted 15 days if the prosthesis was cemented and one month if not. The following criteria were studied: pain, opposition, first and the second metacarpal angle, patient satisfaction, X-rays data, surgeon opinion on the components position, complication and re-operation. RESULTS: The series is made of 45 cases (43 patients), eight males and 37 females. The average age was 59.7 years, with an average pre-operative duration of 3.5 years. X-rays data shows 43% with Dell II and 33% with Dell III aspect. 19 prosthesis were cemented, 22 not, 9 cases had a mixed fixation. The average follow up is 14 months. There was no or few post-operative pain (74% of cases). The opposition has been improved in most of the cases. 78% of the patients were satisfied. Post-operative X-rays were correct in 66% for the trapezial component and in 86.5% with the metacarpal one. There were 12 complications, with eight trapezial component failures. Eight patients were re-operated on. All cases were satisfying then. DISCUSSION: If some foreign causes occurred in some complication, six failures were due to a technical problem. We must point out the frequency of failure with the cemented trapezium. However, the Roseland prosthesis is a satisfying arthroplasty but the trapezial component implantation must be improved.

Aged↗
PubMed1988

Induction of sister-chromatid exchanges by d(42 MeV)-Be neutrons in unstimulated human-blood lymphocytes.

The ability of d(42 Mev)-Be neutrons and 250 kV X rays to produce sister-chromatid exchanges (SCE) has been re-examined using unstimulated (G0) human-blood lymphocytes. Contrary to a previous report, the neutrons produced a significant and dose-dependent increase in SCE. X rays, as previously, produced no measurable increase at any absorbed dose. The relative biological effectiveness (RBE) for this end-point is therefore undefined and effectively infinite. In contrast to the findings of many workers, the between-cell distributions of SCE were, in most cases, underdispersed. This could imply that the SCE burden of a cell was not selectively neutral in these experiments.

Dose-Response Relationship, Radiation↗
PubMed1976

X-ray-induced recombination during oogenesis in the silkworm (Bombyx mori l.).

The physical induction of recombinational events has been studied in the female silkworm (Bombyx mori), in which crossing-over does not normally occur. Female silkworms heterozygous in the trans type of two egg-color genes, pe (V-0.0) and re (V-31.7), received a single dose of X-rays (1000 R) at various developmental stages. Then they were crossed to marked males homozygous for both genes. The results indicated that X-rays increase the occurrence of recombinational events in silkworm females from first instar larvae to late stage pupae. The spontaneous frequency of exchange type recombinants in the control series was 2.5 X 10(-5), while after irradiation the frequency of these recombinants was up to 38.8 X 10(-5). The sensitive stage to X-ray-induced recombinational events was late stage larvae from fourth to fifth instar. Exchange (cross-over) type recombinants were about three times more frequent than interchange types among the 122 recombinants recovered. The biological significance of the present finding is discussed.

Animals↗
PubMed2003

A pi-basic rhenium center that effects cyclohexene isomerization to a beta-agostic carbene ligand.

The molecule (PNPR)Re(H)4 (PNPR = (R2PCH2SiMe2)2N, R = iPr or cyclohexyl) reacts at 20 degrees C with 2 mol of cyclohexene to form equimolar cyclohexane and (PNPR)Re(H)2[=C(CH2)5]. This product is characterized by 1H, 13C, and 31P NMR and by X-ray diffraction as having one CH2 hydrogen (from a carbon located beta to Re) donating to the metal ("agostic CH"). This interaction occurs in preference to PNPR amide nitrogen pi-donation. DFT calculations confirm this agostic interaction, and show that the (PNPR)Re(H)2 fragment indeed reverses the greater stability of free olefin vs free carbene.

Journal Article↗
PubMed2005

A phase II study of nilutamide in men with prostate cancer after the failure of flutamide or bicalutamide therapy.

OBJECTIVE: To determine the prostate-specific antigen (PSA) response and time to PSA or radiographic progression in men with prostate cancer refractory to bicalutamide and/or flutamide therapy. PATIENTS AND METHODS: Men with histologically confirmed prostate cancer not amenable to curative surgery or radiation therapy were eligible for the study if they had radiographic or PSA progression on at least one antiandrogen (not nilutamide) despite continued androgen suppression and standard antiandrogen withdrawal periods. All men received nilutamide 150 mg/day orally for > or = 8 weeks unless there was unacceptable toxicity or disease progression. All men were evaluated for response, safety and toxicity. Baseline PSA levels, chest X-ray, bone scan and abdominopelvic computed tomography studies were obtained; the re-evaluation included PSA levels every 4 weeks and repeated imaging every 8 weeks in those with baseline abnormalities. The chest X-ray was repeated if there were pulmonary symptoms. Nineteen men were consented and 16 were evaluable for response. RESULTS: The median (range) Gleason score was 7 (6-9) and the median number of previous second-line therapies was 2 (1-4). Bicalutamide therapy had failed in all patients. At baseline, 13 (of 16 men) had radiographically evident disease, nine with diffuse osseous and four with radiographically measurable metastases. There was no grade 3/4 toxicity; the commonest grade 1/2 toxicities were constipation (three), sensory neuropathy (four), fatigue (six), and visual changes (two) involving transiently altered colour vision and sensitivity to light, respectively. Responses included three partial and 13 with progressive disease. CONCLUSIONS: The study was discontinued after a planned interim analysis because nilutamide had no apparent activity. Although well tolerated, nilutamide offers benefit to few men with prostate cancer in whom bicalutamide has failed.

Adult↗
PubMed2002

Relative effectiveness of polyacrylamide gel dosimeters applied to proton beams: Fourier transform Raman observations and track structure calculations.

The feasibility of using polyacrylamide gel (PAG) to characterize a clinically relevant 74 MeV proton beam has been considered. Fourier transform Raman spectroscopy has been used to measure the response (i.e., consumption of monomer) of PAG exposed to the central and end portions of a spread out Bragg peak (SOBP), i.e., in two regions with measurable difference in proton linear energy transfer (LET). The response curve in each region was compared with a typical 6 MV x-ray irradiated gel response curve, thus arriving at a gel "relative effectiveness" (RE) in each of the two regions. In addition, the theory of track structure, which is typically used to calculate a detector RE, is shown to give reasonable agreement when compared with the experimental results. Both experimental and track structure results indicate a decrease in gel response when irradiated with protons, as compared with the x-ray response. In addition, both sets of results indicate a variation in gel response between the mid and end SOBP regions, thus illuminating the dependence of gel response to proton LET. The physical phenomenon causing a lower proton versus x-ray gel response may be understood by considering the track structure calculations, which indicate that gel radiosensitive elements close to the track of a proton (i.e., within 1.5 x 10(-6) cm) are saturated. This saturation is due to the high delta-ray doses deposited in these regions. The track calculations are extended to other situations (e.g., raw BP, different gel compositions) where experimental determination of RE is difficult or time consuming. Results again indicate a gel response dependent on position in the depth dose curve (i.e., LET). Overall, this study illuminates the difficulty in using polyacrylamide gel to extract quantitative dose maps when exposed to proton radiation.

Acrylic Resins↗
PubMed1990

An alternative approach to nonpalpable breast biopsies.

Traditionally, when a negative specimen radiograph is obtained during biopsy of a nonpalpable breast lesion, immediate re-excision is performed in an attempt to successfully remove the lesion. Based on a retrospective study of the biopsy results of 792 nonpalpable breast lesions, the authors suggest delaying the re-excision, despite a negative specimen x-ray, until postoperative mammography confirms the persistence of the lesion. Utilization of this approach was associated with a comparably low incidence of missed lesions (3%) and had the added advantages of preserving breast tissue and decreasing operative time.

Biopsy↗