Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Samarium”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources
PubMed2003

Samarium(II)-mediated pinacol coupling in water: occurrence of unexpected disproportionation and action of low-valent samarium as an active species.

[reaction: see text] Mechanistic studies of one-electron reduction in water using samarium were carried out. Unexpected disproportionation in water was observed via UV-vis spectroscopic analysis. This fact indicates that low-valent samarium species can exist in water. Furthermore, the SmCl(3)-Sm and SmCl(3)-Mg systems were found to act as good one-electron reducing agents in water.

Journal Article↗
PubMedDate not supplied

Preparation and pharmacokinetics of samarium(III)-153-labeled DTPA-bis-biotin. Characterization and theoretical studies of the samarium(III)-152 conjugate.

The complex(153)Sm(III)DTPA-bis-biotin was prepared with a 99% radiochemical purity and a specific activity of 370 MBq/mg employing a molar ratio of DTPA-bis-biotin/Sm from 2 to 4 at pH 8.0. In vitro studies demonstrated that the complex is stable after dilution in saline and in human serum. Avidity of labeled biotin for avidin was not affected by the labeling procedure. Pharmacokinetic data of (153)Sm(III)DTPA-bis-biotin in normal mice showed that blood clearance is biexponential during the time interval from 0 to 24 h and that 3 h postinjection 92 +/- 4.32% of the dose is eliminated in the urine. To have further evidence which could sustain that (153)Sm(III)DTPA-bis-biotin is stable in solution as a real coordination complex, (152)Sm(III)DTPA-bis-biotin was obtained in macroscopic quantities and its characterization was done by IR, TGA, and conductivity measurements. The results indicated that the complex was chemically pure, where the Sm(3+) ion is neutralized by three carboxylate groups of the DTPA-bis-biotin ligand and coordinated to it. Using the Force Field method followed by ab initio calculations, the DTPA-bis-biotin and the Sm(III)DTPA-bis-biotin molecules were done. Accordingly, the coordination sphere of Sm(III) was totally satisfied with nitrogen and oxygen donors; the best coordination number was 9. The conformation geometry of both compounds is presented.

Analysis of Variance↗
PubMed2003

Bond valence sums in coordination chemistry. The calculation of the oxidation state of samarium in complexes containing samarium bonded only to oxygen.

A simple method is presented for calculating the oxidation state of Sm in complexes where Sm is bonded only to O ligands. A total of 88 SmO(n)() fragments with n = 4-12 were retrieved from the Cambridge Structural Database and were analyzed using the bond valence sum (BVS) method. New R(0) values for Sm(II)-O of 2.116(21) A and for Sm(III)-O of 2.055(13) A were derived. The average R(0) value of 2.086 A gives a good approximation of the oxidation state of the Sm ion, either +2 or +3, from the observed distances without any assumptions. The Sm-O distances for +2 and +3 complexes with coordination numbers of 4-11 are tabulated and reflect the requirement that the BVS must equal the oxidation state. The distances for CN = 12 were not included because of problems with the reported crystal structures. Several X-ray structure determinations where the BVS and the oxidation state did not agree are discussed.

Journal Article↗
PubMed1992

[A dynamic observation on the fate of samarium in mouse liver].

It is generally considered that the rare earth compounds are plasma membrane-impermeable, thus affecting the cells only on their surface. Recently, we found that after repeated injections to mice of large dose of samarium trichloride, a soluble compound of rare earth, samarium aggregates appeared in Kupffer cells and hepatocytes of liver. In this study, we aimed at observing the route by which samarium enters the liver cells and the process of the formation of samarium aggregates. Samarium trichloride was given to Swiss mice at one dose of 70 mg/kg intravenously. Thereafter, at different intervals from 15 min to 48 h after the injection, the samarium in liver was traced dynamically by electron microscopy and X ray microanalysis. From 15 min to 2 h both Kupffer cells and hepatocytes endocytosed samarium-containing particles and formed phagosomes, in which the ingested particles were progressively concentrated. Besides, the small phagosomes fused with each other. Phagocytosis was especially active in Kupffer cells. During the 4 h to 24 h many Kupffer cells were degenerated and broken. In hepatocytes the phagosomes gathered mostly around the bile canaliculi. Groups of highly electron-dense particles were found in the lumen of bile canaliculi, implying the excretion of samarium by bile. At the 48 h, the samarium-containing phagosomies were found still in both kinds of cells in the liver.

Animals↗
PubMed2000

[Rapid reduction of a variety of organic functionalities including a new selective reduction with samarium diiodide].

This review deals with the rapid reduction of a variety of organic functionalities, including a new selective reduction of carboxylic acid, with samarium diiodide in the presence of additives under mild conditions. The single electron donor ability of samarium diiodide can be enhanced with ligands around Sm2+ when sufficient electrons are supplied from the ligands. Mechanistic consideration of this enhancement led to our finding that carboxylic acid, ester, amide, nitrile, pyridine and other functionalities were rapidly reduced with samarium diiodide in the presence of a base, acid, water and methanol as ligands at room temperature in good yields. Particularly, these systems directly reduced carboxylic acid into alcohol and a samarium diiodide--85% phosphoric acid system immediately reduced an aromatic primary amide to aldehyde in good yield. Pyridines were reduced to piperidines with a samarium diiodide-base or water system in excellent yields; also, the aromatic nucleus of phenol derivatives was rapidly reduced with a samarium diiodide-base system. Furthermore, these organic functionalities were rapidly reduced with an Sm or Yb metal-hydrochloric acid system. Aliphatic and aromatic carboxylic acids with a coexisting aldehyde or that bearing a formyl group were selectively reduced to the corresponding alcohols with a new samarium diiodide-samarium triflate-methanol-base or water system within a few minutes at room temperature in good to almost quantitative yield.

Amides↗
PubMed2001

Mechanistic aspects of samarium-mediated sigma-bond activations of arene C-H and arylsilane Si-C bonds.

To investigate the potential role of Sm-Ph species as intermediates in the samarium-catalyzed redistribution of PhSiH3 to Ph2SiH2 and SiH4, the samarium phenyl complex [Cp*2SmPh]2 (1) was prepared by oxidation of Cp2*Sm (2) with HgPh2. Compound 1 thermally decomposes to yield benzene and the phenylene-bridged disamarium complex Cp*2Sm(mu-1,4-C6H4)SmCp*2 (3). This decomposition reaction appears to proceed through dissociation of 1 into monomeric Cp*2SmPh species which then react via unimolecular and bimolecular pathways, involving rate-limiting Cp* metalation and direct C-H activation, respectively. The observed rate law for this process is of the form: rate = k1[1] + k2[1]2. Complex 1 efficiently transfers its phenyl group to PhSiH3, with formation of Ph2SiH2 and [Cp*2Sm(mu-H)]2 (4). Quantitative Si-C bond cleavage of C6F5SiH3 is effected by the samarium hydride complex 4, yielding silane and [Cp*2Sm(mu-C6F5)]2 (5). In contrast, Si-H activation takes place upon reaction of 4 with o-MeOC6H4SiH3, affording the samarium silyl species [structure: see text] Cp*2SmSiH2(o-MeOC6H4) (7). Complex 7 rapidly decomposes to [Cp*2Sm(mu-o-MeOC6H4)]2 (6) and other samarium-containing products. Compounds 5 and 6 were prepared independently by oxidation of 2 with Hg(C6F5)2 and Hg(o-MeOC6H4)2, respectively. The mechanism of samarium-mediated redistribution at silicon, and chemoselectivity in sigma-bond metathesis reactions, are discussed.

Journal Article↗
PubMed1997

Samarium 153Sm lexidronam.

Samarium 153Sm lexidronam is a medium energy beta-emitting radioisotope chelated to the tetraphosphate, ethylenediaminetetramethylenephosphonic acid (EDTMP). 153Sm has a physical half-life of 1.9 days. Samarium 153Sm lexidronam concentrates in bone tissue and has a metastatic lesion: normal bone ratio of 4. Clearance of nonskeletal radioactivity after administration of samarium 153Sm lexidronam is rapid, and is almost complete from the blood and urine within 1 and 6 hours, respectively. Some degree of pain relief was achieved in 72% of patients with bone metastases after a single dose of samarium 153Sm lexidronam 1 mCi/kg (37 MBq/kg) compared with 44% of placebo recipients (p < 0.025). Relief was generally attained within 2 weeks and lasted for a median of 8 to 15 weeks. After recurrence of pain, a second dose of samarium 153Sm lexidronam may produce further pain relief in some patients. The dose-limiting toxicity of samarium 153Sm lexidronam is reversible myelosuppression.

Analgesics, Non-Narcotic↗
PubMed1994

Differentiation of cytotoxicity using target cells labelled with europium and samarium by electroporation.

We report the simultaneous use of europium-DTPA (Eu-DTPA) and samarium-DTPA (Sm-DTPA) in cytotoxicity experiments to analyze simultaneously LAK and NK cell lysis and to differentiate between specific target lysis and bystander killing. The target cells were either labelled with Eu-DTPA or Sm-DTPA chelates by electroporation, which permits the use of target cell lines or primary leukemic B cells (B-CLL) that cannot be labelled by the conventional dextran-sulphate method. The release of europium and samarium reaches a maximum at comparable time intervals (2-3 h). Due to the shorter counting interval within the samarium window the labelling efficiency is about ten times less efficient compared to europium. Using europium as label for the LAK target Daudi and samarium as label for the NK sensitive cell line K562 the differentiation of LAK versus NK activity can be performed in a single culture assay. Also, the killing of B cells and bystander cells by cytotoxic T cells was analyzed in a system where T cells were redirected to B cells through CD3 x CD19 bispecific antibodies. In fact, no bystander killing was noted when bispecific antibodies were used to bridge cytotoxic T cells to the B cells. This approach provides a simple non-radioactive method for evaluating cytotoxicity against two different cells in a single culture well.

Cell Line↗
PubMed2001

Systemic metabolic radiotherapy with samarium-153 EDTMP for the treatment of painful bone metastasis.

Various radioisotopes conjugated to pyrophosphate analogues have been developed for systemic metabolic radiotherapy. Samarium-153-EDTMP is a 1:1 complex of radioactive Samarium-153 and a Tetraphosphonate [ethylenediamine-tetramethylene phosphonic acid (EDTMP)]. Samarium Sm-153-EDTMP has a high affinity for skeletal tissue and concentrates by chemiabsorption in areas of enhanced metabolic activity, where it associates with the hydroxyapatite crystal. Samarium-153 Lexidronam [Quadramet (R)] has been approved for routine use by the FDA. This agent offers several advantages over other agents used for palliating bone pain. Due to its half-life of 46 hours and its beta emissions, a high dose rate can be delivered to regions adjacent to enhanced osteoblastic activity over a short period of time with little residual long term activity being left in the bone marrow. This paper summarizes both animal studies and clinical studies performed with this agent. Special emphasis will be given to the pivotal Phase-III clinical studies and subsequent studies performed since its approval by the FDA. Special considerations regarding appropriate selection of patients, preparation, follow-up of patients and adjustments to the usual recommended dose [1 mCi/kg (35 Mbq/kg)] will be discussed. Current and future treatment options utilizing Sm-153-EDTMP with other pharmaceuticals appear promising and will substantially extend its use into new areas. In addition, because it also emits a 103 keV gamma ray which makes it suitable for imaging and assessment of biodistribution, dosimetric applications are possible in the future.

Analgesics, Non-Narcotic↗
PubMed1996

Heteroleptic Lanthanide Complexes with Aryloxide Ligands. Synthesis and Structural Characterization of Divalent and Trivalent Samarium Aryloxide/Halide and Aryloxide/Cyclopentadienide Complexes.

Synthesis of a new class of heteroleptic samarium aryloxide complexes has been achieved by the use of homoleptic samarium(II) bis(aryloxide) Sm(OAr)(2)(THF)(3) (1, Ar = C(6)H(2)Bu(t)(2)-2,6-Me-4) as a starting material, which is easily obtained by reaction of Sm(N(SiMe(3))(2))(2)(THF)(2) with 2 equiv of ArOH in THF. 1 reacts with 1 equiv of SmI(2) in THF to give Sm(II) mixed aryloxide/iodide [(ArO)Sm(&mgr;-I)(THF)(3)](2) (2), which adopts a dimeric structure via very weak Sm.I (3.534(2) Å) interactions. Reaction of 2 with C(5)Me(5)K in THF/HMPA affords the corresponding Sm(II) aryloxide/cyclopentadienide (C(5)Me(5))Sm(OAr)(HMPA)(2) (3). Oxidation of 1 with 0.5 equiv of I(2) in THF gives monomeric samarium(III) aryloxide/iodide (ArO)(2)SmI(THF)(2) (4), while the similar reaction of 1 with ClCH(2)CH(2)Cl or (t)BuCl in THF affords dimeric samarium(III) aryloxide/chloride [(ArO)(2)Sm(&mgr;-Cl)(THF)](2) (5). Crystal data for 1: monoclinic, space group P2(1), a = 9.903(3) Å, b = 16.718(5) Å, c = 13.267(2) Å, beta = 95.17(2) degrees, V = 2187(2) Å(3), Z = 2, D(c) = 1.223 g cm(-)(3), R = 0.0634. Crystal data for 2.2THF: monoclinic, space group P2(1)/a, a = 18.330(6) Å, b = 14.320(4) Å, c = 13.949(3) Å, beta = 103.16(2) degrees, V = 3563(2) Å(3), Z = 2, D(c) = 1.46 g cm(-)(3), R = 0.0606. Crystal data for 3: triclinic, space group P&onemacr;, a = 10.528(1) Å, b = 12.335(2) Å, c = 19.260(2) Å, alpha = 101.33(1) degrees, beta = 95.230(9) degrees, gamma = 108.54(1) degrees, V = 2293.1(5) Å(3), Z = 2, D(c) = 1.25 g cm(-)(3), R = 0.0358. Crystal data for 4: monoclinic, space group C2/c, a = 17.191(7) Å, b = 10.737(6) Å, c = 21.773(7) Å, beta = 98.80(3) degrees, V = 3971(3) Å(3), Z = 4, D(c) = 1.44 g cm(-)(3), R = 0.0467. Crystal data for 5: monoclinic, space group P2(1)/n, a = 13.750(3) Å, b = 17.231(3) Å, c = 14.973(6) Å, beta = 95.81(2) degrees, V = 3529(2) Å(3), Z = 2, D(c) = 1.31 g cm(-)(3), R = 0.0557.

Journal Article↗
PubMed1999

Strontium and samarium therapy for bone metastases from prostate carcinoma.

A review was performed of all patients who received strontium-89 chloride or samarium-153 ethylenediamine-tetramethylenephosphonate for prostate cancer metastatic to bone at the Royal Brisbane Hospital between 1992 and 1997. There were 57 patients, 38 treated with strontium-89 and 19 with samarium-153. Forty patients had radionuclide therapy alone, and 28/40 (or 70%) responded in terms of experiencing a beneficial effect on pain. In the other 17 patients, the effect of the radionuclide on pain could not be assessed because they received external beam radiotherapy concomitant with a therapeutic radionuclide. There was no difference in response rates between the samarium and strontium groups as measured by the effect on pain or in the time to progression. The median time to progression for all patients was 2-3 months. The present study confirms that following administration of a therapeutic radionuclide, a high proportion of patients experienced improvement of pain, but the time to progression is not long, so that the overall degree of benefit is modest.

Aged↗
PubMed2003

[6-endo-trig mode cyclization to a hydrindanone using samarium (II) iodide].

Samarium (II) iodide has been employed to promote the vinylogous pinacol coupling reaction of aldehyde to alpha, beta-unsaturated ketones. The diastereoselectivity of 6-endo-trig mode products was changed by the addition of a proton source and/or HMPA and by the reaction temperature. The stereochemistry of the hydrindanone was controlled by the coordinated samarium species, resulting in the cis-orientation in respect of the hydroxyl group at C-4 and the juncture proton at C-3a under mild reaction conditions. Coronafacic acid has been synthesized from a hydrindanone prepared by the cyclization reaction of the enone-aldehyde with samarium (II) iodide.

Cyclization↗
PubMed1996

Clinical outcome after one year following samarium-153 particulate hydroxyapatite radiation synovectomy.

The clinical outcome and tolerability following treatment with samarium-153 particulate hydroxyapatite was evaluated in patients with persistent rheumatoid knee synovitis. The clinical review of 18 patients treated with intra-articular samarium-153 particulate hydroxyapatite combined with triamcinolone hexacetonide who had failed to obtain more than 4 weeks symptom relief from a prior intra-articular glucocorticoid injection was undertaken. No unwanted effects from the treatment were observed. Symptom relief was maintained in 56% patients at 6 months and in 44% of patients at 12 months following treatment. Median duration of symptom relief was 9 months. There was a significantly higher mean baseline Ritchie Articular Index in patients relapsing within 3 months and a trend towards earlier relapse in patients with higher indices of disease activity at the time of treatment. There was a trend towards earlier relapse in patients with a poor range of knee flexion at baseline and with worse indices of intra-articular radiopharmaceutical distribution. Samarium-153 particulate hydroxyapatite knee synovectomy is well tolerated and may be an effective treatment for carefully selected patients with persistent rheumatoid knee synovitis.

Adult↗
PubMed1995

The effects of samarium-cobalt magnets and pulsed electromagnetic fields on tooth movement.

The purpose of this study was to determine whether the application of either samarium cobalt magnets or pulsed electromagnetic fields could increase the rate and amount of orthodontic tooth movement observed in guinea pigs. In addition, the objective was to evaluate the effect of a magnetic field on bony physiology and metabolism and to monitor for possible systemic side effects. Fifteen grams of laterally directed orthodontic force were applied to move the maxillary central incisors of a sample of 18 young male Hartley guinea pigs divided into three groups: group 1, an orthodontic coil spring was used to move the incisors; group 2, a pair of samarium-cobalt magnets provided the tooth moving force; and group 3, a coil spring was used in combination with a pulsed electromagnetic field. The results showed that both the static magnetic field produced by the samarium-cobalt magnets and the pulsed electromagnetic field used in combination with the coil spring were successful in increasing the rate of tooth movement over that produced by the coil springs alone. The mechanism producing this effect appears to have involved a reduction in the "lag" phase often seen in orthodontic tooth movement. Both magnetically stimulated groups also showed increases in both the organization and amount of new bone deposited in the area of tension between the orthodontically moved maxillary incisors.

Animals↗
PubMed2002

A mechanistic study of the samarium(II)-mediated reduction of aryl nitro compounds to the corresponding crylamines. The crystal structures of [Sm[N(SiMe(3))(2)](2)(thf)](2)(mu(2)-O) and [(Me(3)Si)(2)N](2)Sm(thf)(mu-PhNNPh)Sm[N(SiMe(3))(2)](2).

Treatment of nitrobenzene and other various nitroarenes with 6 equiv of samarium(II) under strictly anhydrous conditions allows for the isolation of aniline or the corresponding arylamine. Reducing the number of samarium(II) equivalents allows for the isolation of intermediate species, e.g., azoarenes or hydrazines. Use of Sm[N(SiMe(3))(2)](2), in place of the typically used SmI(2), has allowed for the detailed examination of the aqueous and nonaqueous species formed in this reduction and has been instrumental in delineation of the stepwise reaction mechanism. This is the first time that the reaction intermediates of an organic reaction mediated by samarium(II) have been isolated and analyzed by (1)H NMR and X-ray crystallography.

Journal Article↗
PubMed2001

Samarium(0) and 1,1'-dioctyl-4,4'-bipyridinium dibromide: a novel electron-transfer system for the chemoselective reduction of aromatic nitro groups.

A mild and efficient electron-transfer method was developed for the chemoselective reduction of aromatic nitro groups using samarium(0) metal in the presence of a catalytic amount of 1,1'-dioctyl-4,4'-bipyridinium dibromide. This method was found to give the product aromatic amine in 79-99% yield with selectivity over a number of other functional and protecting groups such as alkene, azide, benzyl ether, nitrile, amide, halide, p-toluenesulfonamide, t-Boc, tert-butyldiphenylsilyl ether, and aliphatic nitro groups. Our results also indicate that samarium(0) plays an important role in the reduction process and that 1,1'-dioctyl-4,4'-bipyridinium dibromide acts as an electron-transfer catalyst and is essential in the activation of samarium(0) metal. The major active reducing agent responsible for the reduction is believed to be the radical cation species formed from 1,1'-dioctyl-4,4'-bipyridinium dibromide.

Journal Article↗
PubMed1996

Reductions, Reductive Alkylations, and Intramolecular Cyclizations of Acyl Silanes with Samarium Diiodide or Tributyltin Hydride.

A series of acyl silanes including aliphatic-, aromatic-, and bis-acyl silanes, as well as the acyl silanes bearing other substituents such as a bromine atom and alkenyl, succinimide, and carbonyl groups, were prepared, and their reactions with samarium diiodide or tributylstannane were studied. The reactions of acyl silanes occurred in various manners such as reductions, reductive alkylations, intramolecular radical cyclizations, pinacol couplings, aldol reactions, and Tishchenko reactions, depending on the nature of substrates and reaction conditions. Acyl silanes were generally reduced to give the corresponding alpha-silyl alcohols without transfer of silyl groups. Intramolecular radical cyclizations of 5-hexenoyl silanes and 1-silyl-1,5-pentanedione were realized to give alpha-silyl cyclopentanols and 1,2-cyclopentanediol derivatives, respectively. On treatment with samarium diiodide in tetrahydrofuran, 1-(trimethylsilyl)-1,6-hexanedione underwent a pinacol coupling reaction in the presence of t-BuOH, whereas it underwent a Tishchenko reaction in the presence of MeOH. The Tishchenko reaction of 1-silyl-1,5-pentanedione gave a delta-silyl-delta-lactone. On treating with samarium diiodide, 1-(trimethylsilyl)-1,5-hexanedione and 1,5-bis(trimethylsilyl)-1,6-hexanedione, underwent, respectively, intramolecular aldol reactions.

Journal Article↗