bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and Evaluation as Glycosidase Inhibitors of Carbasugar‐Derived Spirodiaziridines, Spirodiazirines, and Spiroaziridines
Authors: Kapferer Peter , Birault Véronique , Poisson Jean‐François , Vasella Andrea 
Published: July 2003

AbstractThe spirodiaziridines 6 and 9, potential inhibitors of α‐ and β‐glucosidases, were prepared from the validoxylamine A‐derived cyclohexanone 5. The trimethylsilyl protecting groups of 5 are crucial for the formation of 6 in good yields. Oxidation of 6 gave 7. The diaziridine 6 (pKHA=2.6) and the diazirine 7 did not inhibit the β‐glucosidases from almonds, the β‐glucosidase from Caldocellum saccharolyticum, and the α‐glucosidase from yeast. The N‐benzyl diaziridine 9 is a very weak inhibitor of the α‐glucosidase, but did not inhibit the β‐glucosidases. To see whether the weak inhibition is due to the low basicity of the diaziridines or to geometric factors, we prepared the spiro‐aziridines 21 and 25 and 1‐epivalidamine (32). The known cyclohexanone 10 was methylenated and epoxidised to 16 and 17. Azide opening of 16 and 17, mesylation, LiAlH4 reduction, and deprotection gave the aziridines 21 and 25 respectively. 1‐Epivalidamine (32) was prepared from the known carba‐glucose 29. The aziridine 25 (pKHA=6.8) is a weak irreversible inhibitor of the β‐glucosidase from Caldocellum saccharolyticum and a weak reversible inhibitor of the α‐glucosidase from yeast, but did not inhibit the β‐glucosidases from almonds. The poorly stable aziridine 21 weakly inhibited the three enzymes. Similarly, 1‐epivalidamine (pKHA=8.4) proved only a weak inhibitor. The known cyclopentylamine 34 (pKHA=7.9), however, is a micromolar inhibitor of these enzymes. The much stronger inhibition by 34 is related to the pseudoaxial orientation of its amino group.
Hydrogel Formation Using New L‐Lysine‐Based Low‐Molecular‐Weight Compounds with Positively Charged Pendant Chains
Authors: Suzuki Masahiro , Yumoto Mariko , Kimura Mutsumi , Shirai Hirofusa , Hanabusa Kenji 
Published: July 2003

AbstractLow‐molecular‐weight compounds based on L‐lysine with alkylpyridinium or ‐imidazolium groups have been synthesized and studied for their gelation behavior in H2O. Most compounds formed gels below a concentration of 2.5 weight‐%, the pyridinium bromide 2a and the 1‐methyl‐1H‐imidazolium bromide 3 even at 0.1 weight‐%. The minimum gel concentration (MGC) necessary for hydrogelation increased with increasing length of the Lys Nα‐alkanoyl chain, but the gelation ability concomitantly decreased. Electron‐microscopic images demonstrated that these hydrogelators create a three‐dimensional network in H2O by entanglement of self‐assembled nanofibers. A fluorescence study with 8‐anilinonaphthalene‐1‐sulfonic acid (ANS) proved that some hydrophobic aggregates are formed at hydrogelator concentrations below an MGC of less than 50 μM (0.004%). FT‐IR, 1H‐NMR, and Fluorescence studies indicated that the driving forces for the self‐assembly into nanofibers are mainly hydrophobic interactions and H‐bonding between amide groups.
Convenient Entry to α‐Amino‐β‐hydroxy‐γ‐methyl Carboxylic Acids. Diastereoselective Formation and Directed Homogeneous Hydrogenation of 3‐(3‐Aryl‐1‐hydroxy‐2‐methylprop‐2‐enyl)‐1,4‐benzodiazepin‐2‐ones
Authors: Hameršak Zdenko , Gašo Dajana , Kovač Spomenka , Hergold‐Brundić Antonija , Vicković Ivan , Šunjić Vitomir 
Published: July 2003

AbstractAldol reaction of 7‐chloro‐1,3‐dihydro‐1‐methyl‐5‐phenyl‐2H‐1,4‐benzodiazepin‐2‐one (1) with 4‐substituted α‐methylcinnamaldehydes 2–5 afforded a mixture of threo‐ and erythro‐3‐(3‐aryl‐1‐hydroxy‐2‐methylprop‐2‐enyl)‐7‐chloro‐1,3‐dihydro‐1‐methyl‐5‐phenyl‐2H‐1,4‐benzodiazepin‐2‐ones 6–13. The chromatographically separated threo diastereoisomers 6, 8, 10, and 12 and erythro diastereoisomers 7, 9, 11, and 13 were submitted to ‘directed' homogeneous hydrogenation catalyzed by [RhI(cod)(diphos‐4)]ClO4 (cod=cycloocta‐1,5‐diene, diphos‐4=butane‐1,4‐diylbis[diphenylphosphine]. From the erythro‐racemates 9, 11, and 13, the erythro,erythro/erythro,threo‐diastereoisomer mixtures 16/17, 20/21, and 24/25 were obtained in ratios of 20 : 80 to 28 : 72 (HPLC), which were separated by chromatography. From the threo racemates 8, 10, and 12, the threo,threo/threo,erythro‐diastereoisomer mixtures were obtained in a ratio of ca. 25 : 75 (1H‐NMR). The relative configurations were assigned by means of 1H‐NMR data and X‐ray crystal‐structure determination of 21. Hydrolysis of 21 afforded the diastereoisomerically pure N‐(benzyloxy)carbonyl derivative 27 of α‐amino‐β‐hydroxy‐γ‐methylpentanoic acid 26, representative of the novel group of polysubstituted α‐amino‐β‐hydroxycarboxylic acids.
Regio‐ and Stereoselectivity of the SiO2‐Catalyzed Reaction of Thiocamphor (=1,7,7‐Trimethylbicyclo[2.2.1]heptane‐2‐thione) with Optically Active Monosubstituted Oxiranes
Authors: Fu Changchun , Linden Anthony , Heimgartner Heinz 
Published: July 2003

AbstractThe reactions of the enolizable thioketone (1R,4R)‐thiocamphor (=(1R,4R)‐1,7,7‐trimethylbicyclo[2.2.1]heptane‐2‐thione; 1) with (S)‐2‐methyloxirane (2) in the presence of a Lewis acid such as SnCl4 or SiO2 in anhydrous CH2Cl2 led to two diastereoisomeric spirocyclic 1,3‐oxathiolanes 3 and 4 with the Me group at C(5′), as well as the isomeric β‐hydroxy thioether 5 (Scheme 2). The analogous reactions of 1 with (RS)‐, (R)‐, and (S)‐2‐phenyloxirane (7) yielded two isomeric spirocyclic 1,3‐oxathiolanes 8 and 9 with Ph at C(4′), an additional isomer 13 bearing the Ph group at C(5′), and three isomeric β‐hydroxy thioethers 10, 11, and 12 (Scheme 4). In the presence of HCl, the β‐hydroxy thioethers 5, 10, 11, and 12 isomerized to the corresponding 1,3‐oxathiolanes 3 and 4 (Scheme 3), and 8, 9, and 13, respectively (Scheme 5). Under similar conditions, an epimerization of 3, 8, and 9 occurred to yield the corresponding diastereoisomers 4, 14, and 15, respectively (Schemes 3 and 6). The structures of 9 and 15 were confirmed by X‐ray crystallography (Figs. 1 and 2). These results show that the Lewis acid‐catalyzed addition of oxiranes to enolizable thioketones proceeds with high regio‐ and stereoselectivity via an Sn2‐type mechanism.
Reactions of Stable α‐Chlorosulfanyl Chlorides with CS‐Functionalized Compounds
Authors: Majchrzak Agnieszka , Janczak Aleksandra , Mlostoń Grzegorz , Linden Anthony , Heimgartner Heinz 
Published: July 2003

AbstractThe smooth reaction of 3‐chloro‐3‐(chlorosulfanyl)‐2,2,4,4‐tetramethylcyclobutanone (3) with 3,4,5‐trisubstituted 2,3‐dihydro‐1H‐imidazole‐2‐thiones 8 and 2‐thiouracil (10) in CH2Cl2/Et3N at room temperature yielded the corresponding disulfanes 9 and 11 (Scheme 2), respectively, via a nucleophilic substitution of Cl− of the sulfanyl chloride by the S‐atom of the heterocyclic thione. The analogous reaction of 3‐cyclohexyl‐2,3‐dihydro‐4,5‐diphenyl‐1H‐imidazole‐2‐thione (8b) and 10 with the chlorodisulfanyl derivative 16 led to the corresponding trisulfanes 17 and 18 (Scheme 4), respectively. On the other hand, the reaction of 3 and 4,4‐dimethyl‐2‐phenyl‐1,3‐thiazole‐5(4H)‐thione (12) in CH2Cl2 gave only 4,4‐dimethyl‐2‐phenyl‐1,3‐thiazol‐5(4H)‐one (13) and the trithioorthoester derivative 14, a bis‐disulfane, in low yield (Scheme 3). At −78°, only bis(1‐chloro‐2,2,4,4‐tetramethyl‐3‐oxocyclobutyl)polysulfanes 15 were formed. Even at −78°, a 1 : 2 mixture of 12 and 16 in CH2Cl2 reacted to give 13 and the symmetrical pentasulfane 19 in good yield (Scheme 5). The structures of 11, 14, 17, and 18 have been established by X‐ray crystallography.
Habitat Structure and Trichoptera Diversity in Two Headwater Flood Plains, N.E. Italy
Authors: Arscott Dave B. , Keller Barbara , Tockner Klement , Ward J. V. 
Published: July 2003

AbstractTwo headwater flood plains in tributaries of the Tagliamento catchment (N.E. Italy) were investigated to compare and contrast floodplain morphology, aquatic habitat structure, physico‐chemical characteristics, and Trichoptera community relationships. The two flood plains (one stable and forested, the other dynamic and open) were similar with respect to position along the longitudinal continuum, elevation, stream order, and geological material. However, the two flood plains differed greatly in aquatic habitat structure, physico‐chemical character, and Trichoptera abundance, distribution, and richness. The forested reach had lower slope, finer sediment, more standing waterbodies, significantly higher benthic organic matter standing stocks, and a closed canopy of predominantly Alnus incana. Trichoptera abundance in the forested flood plain was higher, as was taxa richness (27 taxa), than in the open flood plain (16 taxa). Differences in Trichoptera composition and richness were due to the presence of several species of Limnephilidae, which were correlated with benthic organic matter. These findings are discussed in the context of species‐abundance relationships, environmental factors, and reach‐specific morphological characters. Results illustrate the dependence of habitat type and invertebrate community response to reach scale factors (i.e., geomorphology and hydrology) that may be uncoupled from position along the longitudinal continuum.
Processes of Surface‐Subsurface Water Exchange in a Low Energy Sand‐Bed Stream
Authors: Mutz Michael , Rohde Anja 
Published: July 2003

AbstractThe surface‐subsurface water exchange at base‐flow conditions was assessed in a natural sand‐bed stream. The aim was to examine the relative contribution of sediment turnover and vertical hyporheic flow in a natural environment. Sediment turnover was determined using coloured sand columns implanted into the stream bed. Direction and velocity of hyporheic flow was recorded with a fluid tracer injected into the stream bed. Large amounts of wood caused a heterogeneous stream bed relief. Grain size distribution of sediments was homogenous with a porosity of 37%. The hydraulic conductivity ranged from 3 · 10−6 m s−1 to 1 · 10−4 m s−1 with a mean of 7 · 10−5 m s−1. Groundwater upwelling was a major process (0.39 l m−2 h−1) and stream water was passing through the hyporheic zone at a rate of 0.12 l m−2 h−1. Since hyporheic velocity was high in comparison to flume studies, the transfer of stream water through bed sediments might have been induced by the wood in addition to local topography in the sand‐bed. Sediment displacement at base‐flow was found in 79% of the stream bed. Release and trapping of pore water by sediment turnover contributed greatly to the surface‐subsurface water exchange. Pumping and sediment turnover were significant processes of the vertical connectivity in the natural sand‐bed stream.
Dietary and Stable Isotope (δ 13C, δ 15N) Analyses in Alpine Stream Insects
Authors: Füreder Leopold , Welter Camille , Jackson John K. 
Published: July 2003

AbstractAlpine stream systems are known to be affected by the prevailing water sources (glacial, non‐glacial), regional climate and the vegetation of the watershed. Especially at higher altitudes, these conditions influence and shape abiotic factors and the biology of stream reaches, there usually resulting in harsh environmental settings for the biota. Little is known about nutrients, food availability and food utilization in these systems. We investigated the physico‐chemical conditions, food resources (DOM, CPOM, FPOM, seston, Aufwuchs) and the bottom fauna in nine reaches of different stream types (glacial, non‐glacial systems) above and below the treeline in two seasons. Gut content and stable isotope (δ 15N, δ 13C) analysis were used to estimate food consumption and assimilation for dominant species. Although most of the taxa were detritivores, some species showed a preference for specific food items. Both, the principal dietary component as well as stable isotope analyses confirmed the placement of taxa into functional feeding guilds. In addition the results of stable isotope analysis suggested opportunistic feeding of several species. Autochthony appeared to play an important role even in glacial streams, where long snow cover, frequent flooding and high turbidity limit Aufwuchs development for most months of the year.
Structure and Functional Organization of Benthic Invertebrates in a Regulated Stream
Authors: Fleituch Tadeusz 
Published: July 2003

AbstractThis paper examines modifications of benthic structure and species/traits organization of macroinvertebrate communities affected by various hydro‐technical structures in the regulated mountain Trzemesnia stream (southern Poland). The samples of aquatic invertebrates were collected seasonally (6 times) at: (1) one control site with natural substrate and at (2) five sites altered by sills, weirs, and canals during 1999.The stream canals, covered by Cladophora glomerata, were clearly distinguished from the other sites by: highest fauna density (mean of 8.5 103 ind. m−2), lowest taxa richness (mean number of 4.7 taxa), and lowest diversity (H′ = 1.1). The benthic communities consisted mainly of collector‐gatherers with the highest contribution in the stream canals (range 87–96%). These results suggest that most types of stream regulations (i.e. stream bed formed by concrete bricks) negatively affect the functional organization of benthic invertebrates (collector‐gatherers, predators, and scrapers).
A Study of Biofilm in a Second Order Tropical Stream, Njoro River, Kenya: First Results
Authors: Muia Wairimu A. , Bretschko Gernot , Herndl Gerhard J. 
Published: July 2003

AbstractBetween January and December 1999 the extent of biofilm development has been studied at two sites (muddy sediment site [A] and sandy sediment site [B]) in Njoro River, Kenya. Grain size, organic matter and bacterial abundance were determined at different depth layers of the sediment. Particulate carbohydrate concentrations were measured as an indicator of biofilm development in the sediment. Additionally, the development of the biofilm was investigated by placing glass slides at rock and sediment surfaces and in different sediment depth layers. Our first results for sediment samples collected in January 1999 and growth on slides exposed for 28 days in March 1999 is presented. Grain size analysis revealed that sediment particles <1 mm contributed between 82 to 91% at site A and 45 to 67% at site B depending on the sediment layer. At site A, total organic matter (% weight loss on ignition) and total organic carbon (TOC) were more or less constant with depth while both parameters significantly decreased with depth at site B. Total organic nitrogen (TON) was detectable at all depth layers at site A but only in the top 40 mm layer at site B. Bacterial numbers were highest in the top 40 mm layer at both sites. Bacterial abundance of 3.95 ± 5.96 × 108 and 4.10 ± 3.88 × 108 cells g−1 dry sediment were recorded at site A and B, respectively. For both sites, highest concentrations of colloidal carbohydrates occurred in the top 40 mm layer, but concentrations were more or less constant below. Bacterial abundance on glass slides was higher on slides placed on rock surfaces than on fine sediment surfaces or within fine sediments.
Effect of sphered particles on the firing contraction of porcelain inlay processed by cold isostatic pressing
Authors: Konishi Junko , Watari Fumio , Kawamoto Chiharu , Sano Hidehiko 
Published: July 2003

AbstractThe effect of the sphered particles on the contraction ratio of porcelain inlay processed by the cold isostatic pressure (CIP) method was investigated. The conventional lathe‐cut porcelain powder was crushed to finer particles and the secondary particles with spherical shape by adding binders of acrylic resin, wax, and polyvinyl alcohol, respectively. Porcelain powder was molded as a disc‐shaped green body in a refractory model and compressed at 200 MPa by CIP. From this green compact, the sintered porcelain was obtained by only one step of firing. The porcelain discs were then used for the measurements of contraction ratio, scanning microscopic observation, biaxial flexure strength, Vickers hardness, and density. Firing contraction was decreased to about 1% in the sphered particle groups, compared with 7% of the lathe‐cut porcelain powder. Although biaxial flexure strength was about 85 MPa, which is lower than the 120 MPa of the control group, and the density was significantly decreased by about 10% from the 2.4 g/cm3 of the control substance, Vickers hardness, which ranged from 531 to 537, showed no significant differences among all of the groups. The CIP method could save labor in the process of making porcelain inlays, and sphered powders could contribute significantly to a decrease in the contraction ratio in the sintering process. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 66B: 553–558, 2003
Long‐term study of high‐strength hydroxyapatite/poly(L‐lactide) composite rods for the internal fixation of bone fractures: A 2–4‐year follow‐up study in rabbits
Authors: Ishii Shinsuke , Tamura Jiro , Furukawa Taizo , Nakamura Takashi , Matsusue Yoshitaka , Shikinami Yasuo , Okuno Masaki 
Published: July 2003

AbstractBiodegradation of hydroxyapatite (HA)/poly(L‐lactide)(PLLA) composite bone implant rods was studied with the use of two types of HA particles as reinforcing fillers: uncalcined HA (u‐HA) or calcined HA (c‐HA). Composite rods of u‐HA/PLLA and c‐HA/PLLA containing 30 or 40% (w/w) HA were implanted in the distal femur of 21 rabbits, and specimens were examined by light microscopy, scanning‐electron microscopy (SEM), and transmission‐electron microscopy (TEM) 2–4 years later. For u‐HA/PLLA, trabecular bone bonding directly onto the rod was maintained for up to 2 years. By 3 years, surface collapse had begun, and the implants were shrinking. By 4 years, they had shrunk further, with complete bone encapsulation. The u‐HA particles were small and needle shaped in the peripheries, and TEM confirmed their resorption. The cross‐sectional area after 4 years decreased by 23.3 ± 8.4%. The mean ratio of bony ingrowth to the initial cross‐sectional area around the shrunken rods was 6.7 ± 1.3 %. The viscosity molecular weight of PLLA reduced from 2 × 105 to less than 1 × 103. Thus, most of the PLLA had released from the rods. The c‐HA/PLLA implants also showed good osteoconductivity, but shrinkage and infiltration of histiocytes were less. No osteolytic or osteoarthritic changes were found. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 66B: 539–547, 2003
Residual ethylene oxide in medical devices and device material
Authors: Lucas Anne D. , Merritt Katharine , Hitchins Victoria M. , Woods Terry O. , McNamee Scott G. , Lyle Dan B. , Brown Stanley A. 
Published: July 2003

AbstractEthylene oxide (EO) gas is commonly used to sterilize medical devices. The amount of residual EO remaining in a device depends partly on the type and size of polymeric material. A major concern is the amount of residue that may be available in the body. With the use of the method described by AAMI for headspace analysis of EO residues, different polymers and medical devices subjected to different numbers of sterilization cycles were examined. Next, the effect of various extraction conditions and extraction solutions on these polymers and medical devices was evaluated. The results showed different polymers desorb EO differently. One polyurethane (PU 75D) had much higher EO residue than a different polyurethane (PU 80A). Repeated extraction of the PU 75D was necessary to quantify total EO residue levels. Different extraction solutions influence the amount and reproducibility of EO detected, whereas multiple resterilizations showed no difference in amount of residual EO. Bioavailability of EO was estimated by extracting the devices and polymers in water. Comparison of total EO residues to EO that was bioavailable showed no difference for some polymers and devices, while others had an almost eightfold difference. Some standard biocompatibility tests were run on extracts and devices, but no significant effects were observed. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 66B: 548–552, 2003
In vivo efficacy of bone‐marrow‐coated polycaprolactone scaffolds for the reconstruction of orbital defects in the pig
Authors: Rohner Dennis , Hutmacher Dietmar W. , Cheng Tan Kim , Oberholzer Martin , Hammer Beat 
Published: July 2003

AbstractAlloplastic materials offer a number of advantages over bone autografts in the reconstruction of craniofacial defects. These include: lack of donor site morbidity, unlimited quantities of available material, and the possibility to conform exactly to the defect. An ideal bioresorbable material would degrade slowly, and have osteoconductive properties to allow replacement and remodeling by osseous tissue. This is seldom observed, the materials instead being replaced by fibrous tissue. Polycaprolactone (PCL), an FDA‐approved bioresorbable polymer, has several properties that might make it suitable for reconstruction of craniofacial defects. The technique of fused deposition modeling (FDM) allows for the fabrication of highly reproducible bioresorbable 3D scaffolds. The nature of the fully interconnected pore network might enhance vascular ingrowth and osteoconductive properties. It was hypothesized that coating the scaffolds in bone marrow might enhance bone formation due to the osteoinductive nature of the bone‐marrow mesenchymal cells. This study aimed to test these hypotheses in the pig model. Defects measuring 2 × 2 cm were surgically created in each orbit of eight Yorkshire pigs. The orbits were divided into three groups: Group 1 (n = 4), no reconstruction (control); Group 2 (n = 6), reconstruction with no coated PCL scaffolds; and Group 3 (n = 6) reconstruction with bone‐marrow‐coated PCL scaffolds. The results were evaluated at 3 months by histological and histomorphometric analyses. The defects in Group 1 were covered with fibrous scar tissue. The shape of the reconstructed area was insufficient. The defects in Groups 2 and 3 were reconstructed correctly. In Group 2 the noncoated scaffolds showed 4.5% of new bone formation compared with 14.1% in Group 3, which is statistically significant (p < 0.05). The entirely interconnected 3D polycaprolactone scaffold seems to be a promising material. It induces the bone ingrowth required for reconstructing craniofacial and orbital defects. Further long‐term evaluations of these PCL scaffolds must be made in order to confirm these conclusions. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 66B: 574–580, 2003
Evaluation of a new CPC‐to‐gauge bonding technique with the use of in vitro fluid flow
Authors: Fernandez Mark M. , Szivek John A. , Margolis David S. 
Published: July 2003

AbstractStrain gauging enables the measurement of bone deformation during physical activity, leading to a better understanding of the physiological effects of loading on bone growth and remodeling. Development of a technology that will withstand long‐term in vivo exposure and bond securely to bone is imperative for accurate, consistent measurement collection. Polysulfone is currently used to attach calcium‐phosphate ceramic (CPC) particles, which promote bone‐to‐gauge bonding, to polyimide‐backed strain gauges. This study evaluated the use of an implant‐grade epoxy as an alternative CPC–polyimide adhesive. Polyimide–epoxy–CPC interfaces were loaded to failure and shear strengths calculated. In vitro studies providing a constant flow of medium over test specimens were designed, and long‐term in vitro fluid exposure studies of the epoxy's shear strength were conducted. Average shear strength of polysulfone‐polyimide interfaces were reported to be 7 MPa.11 The average shear strength of the epoxy‐polyimide interface before long‐term in vitro exposure was 17 MPa, which is stronger than the shear strength of the bone–CPC interface.12 The strength of the epoxy–polyimide interface decreased to 6.8 MPa after 24 weeks in vitro and 3 MPa after 24 weeks in vivo. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 66B: 514–519, 2003