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Query: UMLS:C0432222 (SEM)
 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Sixteen novel derivatives of 1,1,1-tris (salicylaldiminomethyl)ethane have been synthesized for the purpose of encapsulating 99mTc(IV) ions and generating new 99mTc radiopharmaceuticals. Two methods for the preparation of the 99gTc(IV) analog complexes are presented; one utilizes SnCl2 reduction on 99gTcO4- and the other a direct substitution route starting with [99gTcCl6]2-. Free ligands (H3L) are characterized by melting points, 1H NMR, 13C NMR, mass spectroscopy, TLC, and/or elemental analyses. [99gTcL]+ complexes are characterized by FAB-ms, UV-VIS, IR and/or CV. An X-ray structural analysis was performed on a crystal of [M(6,6'-[[2-[[((4-Methoxy-2-hydroxyphenyl) methylene)-amino]methyl]-2-methyl- 1,3-propanediyl]bis(nitrilomethylidyne)]-bis-3-methoxyphenol )] tetraphenylborate, where M represents a 1/3 isomorphous mixture of 99gTc/Sn as determined by SEM. The metal coordination site is 6-coordinate, composed of N3O3 donor atoms, and intermediate between octahedral and trigonal prismatic geometry. The [99mTcL]+ complexes were prepared in a stannous environment; equivalence of the 99mTc and 99gTc complexes is demonstrated by HPLC techniques. The [SnL]+ complex was prepared for comparison purposes. An unusual ligand oxidation occurs for one series of ligands in which in situ amine-->imine conversion is observed during the complexation reaction in reducing media. Guinea pig, rat, dog, and human metabolism studies are reported for selected [99mTcL]+ complexes, the myocardial uptake of which approaches 2% of the injected dose.
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PMID:Synthesis and characterization of novel N3O3-Schiff base complexes of 99gTc, and in vivo imaging studies with analogous 99mTc complexes. 890 21

Proton decoupled 31P NMR spectroscopy of the occipital brain of healthy volunteers was performed with a 1.5 T whole-body imager. By use of two-dimensional chemical-shift imaging in combination with slice-selective excitation well resolved localized spectra (38 ml) were obtained within 34 min from which the homonuclear 31P-31P J-coupling constants of ATP could be determined: J(gammabeta) = 16.1 Hz +/- 0.2 Hz and J(alphabeta) = 16.3 Hz +/- 0.1 Hz (mean +/- SEM, n = 14). Both, the J-coupling constants and the chemical-shift difference between alpha- and beta-ATP (delta(alphabeta) = 8.61 ppm +/- 0.01 ppm) were used to calculate the concentration of intracellular free magnesium. The concentrations are 0.39 mM +/- 0.09 mM by using the average of both coupling constants of each spectrum, which is in fair agreement with 0.32 mM +/- 0.01 mM obtained from the chemical shift of alpha and beta phosphate resonances, which is the more accurate result.
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PMID:Phosphorus J-coupling constants of ATP in human brain. 912 56

6-Oxoestradiol (2) was protected as its bis[(2-trimethylsilylethoxy)methyl] ether (4) and converted to the corresponding oxime (4). The oxime (4) on reduction with zinc in ethanol afforded the bis-SEM ether of 6-alpha-aminoestradiol (5) in 96% epimeric excess. Subsequently, 5 was hydrolyzed with HF to 6-alpha-aminoestradiol (6) in good yield. The absolute stereochemistry of the amino group in 6 was established by NMR and confirmed by X-ray crystallography on the corresponding 4-bromobenzamide derivative (9). Treatment of amine (6) with 6-(t-butoxycarbonylamino)hexanoic acid succinimidyl ester (10) followed by hydrolysis produced the amine (12) with a C-6 linker. The fluorescent probes (7 and 13) were prepared from 6 and 12 respectively, in 54-60% yield and > 99% purity.
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PMID:An efficient stereoselective synthesis of 6-alpha-aminoestradiol: preparation of estradiol fluorescent probes. 918 93

The muscle intracellular (IC) free glucose concentration and the rate of muscle glycogen synthesis were measured by using in vivo 13C and 31P NMR spectroscopy in normal volunteers under hyperinsulinemic ( approximately 300 pM) clamp conditions at the following three plasma glucose levels: euglycemia ( approximately 6 mM), mild ( approximately 10 mM), and high ( approximately 16 mM) hyperglycemia. In keeping with biopsy studies, muscle IC free glucose concentration at euglycemia (-0.03 +/- 0.03 mmol/kg of muscle, mean +/- SEM, n = 10) was not statistically different from zero. A small but statistically significant amount of IC free glucose was observed during mild and high hyperglycemia: 0.15 +/- 0.08 (n = 5) and 0.43 +/- 0.20 mmol/kg of muscle (n = 5), respectively. Muscle glycogen synthesis rate, in mmol per kg of muscle per min, was 111 +/- 11 at euglycemia (n = 10), 263 +/- 29 during mild hyperglycemia (n = 5), and 338 +/- 42 during high hyperglycemia (n = 5), these three rates being significantly different from each other. As previous in vitro and in vivo studies, these rates suggest a Km (concentration at which unidirectional glucose transport reaches half-maximal rate) of the muscle glucose transport system in the 15-25 mM range under hyperinsulinemic conditions. The low concentrations of muscle IC free glucose observed under hyperinsulinemic conditions were interpreted, with this estimate and in the framework of metabolic control theory, as glucose transport being the predominant step controlling muscle glucose flux not only at euglycemia but also during hyperglycemia.
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PMID:13C/31P NMR studies of glucose transport in human skeletal muscle. 944 28

Amination of 3,17 beta-Bis[(2-trimethylsilylethoxy) methoxy]-1,3,5(10)-estratriene-6-one (2) using NaCNBH4 and NH4OAc afforded 3,17-bis(SEM)-6-aminoestradiol (3) as a mixture of alpha and beta-isomers in 60:40 ratio. Hydrolysis of the mixture of 3 using HF and separation by preparative high-performance liquid chromatography afforded pure 6 beta-aminoestradiol (4) in good yield. The relative stereochemistry of the amino group in 4 was established by NMR. The biotinylated estradiol probe (7), chemiluminescent probe (9), and fluorescent probe (11), were prepared from 6 beta-aminoestradiol (4) and the corresponding biotin, 10-(3-sulfopropyl)-N-tosyl-N-(3-carboxypropyl)acridinium-9-carboxamide, and 5-carboxyfluorescein N-succinimidyl esters in 43-63% yields and > 99% purity.
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PMID:Synthesis of 6 beta-aminoestradiol and its biotin, acridinium, and fluorescein conjugates. 955 12

The inclusion complexes of ursodeoxycholic acid (UDCA) with beta-cyclodextrin (betaCD) coprecipitated with choline dichloride (CDC) or beta-cyclodextrin were investigated to evaluate the effect of the presence of choline for UDCA inclusion in betaCD. The inclusion complexes were investigated in solution by phase solubility diagrams and 1H NMR spectrometry and in solid state (kneading, freeze-drying, sealed heating and spray-drying) by DSC, SEM, HSM, XRD and IR spectroscopy. Stability constants were determined at pH 5.5 and 7.0 to simulate the environmental pH of the first intestinal tract and at different temperatures (25, 30 and 37 degrees C) to obtain the thermodynamic parameters of inclusion. Both betaCD-CDC and betaCD increased the water solubility of UDCA particularly betaCD-CDC. All complexes showed a high dissolution rate particularly the spray-dried complexes obtained in the presence of betaCD-CDC.
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PMID:Complexation of ursodeoxycholic acid with beta-cyclodextrin-choline dichloride coprecipitate. 1054 54

We demonstrate that MRI imaging at sub-millimetre resolution can distinguish between periportal and perivenous zones of the rat liver lobule. This made it possible to measure the hepatic lobular radius in ex-vivo perfused fixed livers using MRI. Comparisons of histomorphometric and MRI measurements of lobular radius were in good agreement, although MRI measurements were significantly smaller (P< 0.001). Male rats whose mothers were fed 40% of the protein of controls during gestation and lactation, had a significantly larger hepatic lobular radius than that of controls [449+/-11 microm vs. 373+/-9 microm (mean +/- SEM), respectively, p<0.001, n = 12; histomorphometry data]. The proton T(2) in periportal and perivenous zones was mapped both before and after antegrade or retrograde perfusion of 10 ml of digitonin (4 mg ml(-1)). Only the T(2) of the hypointense regions increased significantly following antegrade perfusion of digitonin and conversely only that of the intense regions following retrograde perfusion. Digitonin causes permeabilization of cells in specific hepatic zones, determined by the direction of perfusion. The intense and hypointense regions of the hepatic MR images thus arise from the perivenous and periportal zones of the hepatic lobule, respectively.
NMR Biomed 2000 Apr
PMID:Fetal programming of hepatic lobular architecture in the rat demonstrated ex vivo with magnetic resonance imaging. 1079 36

A series of tri-component copolymers was synthesized by ring opening copolymerization of cyclic lactones, i.e. glycolide, L-lactide, and caprolactone, using stannous octoate as a catalyst. Various techniques, including FT-IR, 1H NMR, DSC, X-ray diffraction, tensile strength, and contact angle measurements, were used to elucidate structural characteristics, thermal behavior, mechanical properties, and hydrophilicity of the resulting copolymers. Data showed that the properties of these copolymers could be modulated by adjusting the composition of the copolymers. The DSC and X-ray analysis demonstrated amorphous structures for most of the PGLC copolyesters. The degradation behavior of these PGLC copolymers had been studied in vitro, i.e. in 0.10 M pH 7.4 phosphate buffer solution (PBS). The degradation was monitored by intrinsic viscosity and weight loss measurements. SEM and GPC were also used to monitor the morphology and molecular weight change during degradation. The PGLC copolymers were shown to have variable degradation rates, and most of them could disappear within a few months due to their amorphous structure and low glass transition temperature.
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PMID:Synthesis and degradation of a tri-component copolymer derived from glycolide, L-lactide, and epsilon-caprolactone. 1084 Dec 79

A novel class of multiblock poly(epsilon-caprolactone)-based polymers containing hydrophilic trioxyethylene segments and potentially relevant to the delivery of drugs is described in this work. L-phenylalanine residues may also be inserted into the hydrophilic blocks to generate peptide bonds susceptible to enzymatic attack. The investigated polymers were poly(ether-ester-amide)s (PEEAs) obtained by a two-step polymerization procedure from OH-end capped low molecular weight poly(epsilon-caprolactone), sebacoyl chloride and either 4,7,10-trioxa-1,13-tridecanediamine (PEEA1) or 1,13-di(L-phenylalaninamido)-4,7,10-trioxatridecane (PEEA2). PEEAs were characterized by 1H-NMR spectroscopy, differential scanning calorimetry, gel permeation chromatography and were tested for their suitability in producing microspheres. Particles obtained by the single emulsion-solvent evaporation technique were regular and smooth (SEM analysis) showing a monomodal distribution of dimensions. To assess the potentiality of PEEAs in the oral delivery of drugs, three model compounds with different pKa and solubilities--diclofenac, nicardipine and dicumarol--were encapsulated within PEEA microspheres. For the sake of comparison, microspheres prepared from poly(epsilon-caprolactone) (PCL) with a molecular weight similar to PEEAs were also prepared and tested. The release of diclofenac from all the microspheres was very rapid (100% released within 2 h) whereas nicardipine release was slower and biphasic. The initial phase approximated a near zero-order release, being the fraction of nicardipine released after 8 h from PEEA microspheres higher with respect to PCL particles (about 70 vs. 30%). This result was ascribed to the lower crystallinity of PEEAs with respect to PCL which results in a facilitated access of water molecules through the polymer matrix. The lipophilic-unionizable dicumarol was released from PEEA microspheres at a very slow rate. Therefore, dicumarol-loaded PEEA2 microspheres allowed the study of the influence on the release rate of the insertion into the polymer chain of enzymatically degradable bonds. PEEA2 microspheres released dicumarol at the same rate in a medium with or without the proteolitic enzyme alpha-chymotrypsin. Although the insertion of an isolated amino acid was not sufficient to confer enzyme susceptibility to the polymer, the distinctive properties of PEEAs make their use very attractive in the field of controlled release.
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PMID:Biodegradable microspheres of novel segmented poly(ether-ester-amide)s based on poly(epsilon-caprolactone) for the delivery of bioactive compounds. 1133 10

Type I collagen-PEO fibers and non-woven fiber networks were produced by the electrospinning of a weak acid solution of purified collagen at ambient temperature and pressure. As determined by high-resolution SEM and TEM. fiber morphology was influenced by solution viscosity, conductivity, and flow rate. Uniform fibers with a diameter range of 100-150 nm were produced from a 2-wt% solution of collagen-PEO at a flow rate of 100 microl min(-1). Ultimate tensile strength and elastic modulus of the resulting non-woven fabrics was dependent upon the chosen weight ratio of the collagen-PEO blend. 1H NMR dipolar magnetization transfer analysis suggested that the superior mechanical properties, observed for collagen-PEO blends of weight ratio 1:1, were due to the maximization of intermolecular interactions between the PEO and collagen components. The process outlined herein provides a convenient, non-toxic, non-denaturing approach for the generation collagen-containing nanofibers and non-woven fabrics that have potential application in wound healing, tissue engineering, and as hemostatic agents.
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PMID:Engineered collagen-PEO nanofibers and fabrics. 1178 24


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