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At least 973 records · Page 54Linked to original sources

PubMed2006

Removal of lead from aqueous solutions on palm shell activated carbon.

The performance of a commercially available palm shell based activated carbon to remove lead ions from aqueous solutions by adsorption was evaluated. The adsorption experiments were carried out at pH 3.0 and 5.0. The effect of malonic and boric acid presence on the adsorption of lead ions was also studied. Palm shell activated carbon showed high adsorption capacity for lead ions, especially at pH 5 with an ultimate uptake of 95.2mg/g. This high uptake showed palm shell activated carbon as amongst the best adsorbents for lead ions. Boric acid presence did not affect significantly lead uptake, whereas malonic acid decreased it. The diffuse layer surface complexation model was applied to predict the extent of adsorption. The model prediction was found to be in concordance with the experimental values.

Adsorption↗

PubMed2006

Ag/SiO2 core-shell nanoparticle-based surface-enhanced Raman probes for immunoassay of cancer marker using silica-coated magnetic nanoparticles as separation tools.

A simple, sensitive and highly specific immunoassay has been developed based on surface-enhanced Raman scattering for human alpha-fetoprotein (AFP), a tumor marker for the diagnosis of hepatocellular carcinoma. This strategy combines the Ag/SiO2 core-shell nanoparticles embedded with rhodamine B isothiocyanate dye molecules as Raman tags and the amino group modified silica-coated magnetic nanoparticle as immobilization matrix and separation tool. In the proposed system, a sandwich-type immunoassay was performed between polyclonal antibody functionalized Ag/SiO2 nanoparticle-based Raman tags and monoclonal antibody modified silica-coated magnetic nanoparticles. The presence of the analyte and the reaction between the antigen and antibody can be monitored by the Raman spectra of the Ag/SiO2 tags. Compared to the previous surface-enhanced Raman immunoassays, the main advantage of this strategy lies in two aspects. One is the high stability of Raman tags derived from the silica shell-coated silver core-shell nanostructure. The other is the use of silica-coated magnetic nanoparticles as immobilization matrix and separation tool, thus avoiding complicated pretreatment and washing steps. We have studied in detail the experimental parameters such as the effects of the antibody concentration modified on the Raman tags and on the magnetic particles, and the immunoreaction time. Using this strategy, concentration of human AFP up to 0.12 microg/ml was detected with a detection limit of 11.5 pg/ml.

Biomarkers, Tumor↗

PubMed2006

Shematrin: a family of glycine-rich structural proteins in the shell of the pearl oyster Pinctada fucata.

Random sequencing of molecules from a cDNA library constructed from mantle mRNA of the pearl oyster Pinctada fucata was used to obtain information on organic matrix proteins in the shell. In the determined sequences, we identified 7 distinct cDNAs encoding similar glycine-rich domains. Complete sequence analysis of these cDNAs showed that the predicted sequences of the proteins, which we named shematrins, possessed similar domains comprising repeat sequences of two or more glycines, followed by a hydrophobic amino acid. In addition, in shematrin-1, -2 and -3, a repeat domain designated as XGnX (where X is a hydrophobic amino acid) was conserved. It is of further note that all the shematrin proteins have RKKKY, RRKKY or RRRKY as their C-terminal sequence. According to northern blot analysis, all shematrins are exclusively expressed in the mantle, and particularly in the edge region of the mantle; furthermore, peptide fragments similar to shematrin-1 and -2 were detected in the prismatic layer of shells by MALDI-TOF/TOF MS analysis. These findings suggest that many of shematrins are synthesized in the mantle edge and secreted into the prismatic layer of the shell, where the protein family is thought to provide a framework for calcification.

Amino Acid Sequence↗

PubMed2006

Tyrosinase localization in mollusc shells.

In molluscan shellfish, pigmentation is frequently observed in the calcified shell, but the molecular basis of this process is not understood. Here, we report two tyrosinase proteins (Pfty1 and Pfty2) found in the prismatic shell layer of the pearl oyster Pinctada fucata; this layer is recognized as the pigmented region in P. fucata. The protein sequences were deduced from the corresponding cDNAs and confirmed by MALDI-TOF/TOF analysis. The sequences suggest that both tyrosinases have two copper-binding sites in similar N-terminal domains that are homologous to tyrosinases of cephalopods and hemocyanins of gastropods. In turn, this suggests that bivalve tyrosinases are evolved from a common ancestral copper-binding protein in the mollusc. Pfty1 and Pfty2 were specifically expressed in the mantle, and their expression in the mantle is different from each other, suggesting that these tyrosinases have distinctive roles in melanogenesis in shells.

Amino Acid Sequence↗

PubMed2004

Preparation and characterization of core-shell nanoparticles hardened by gamma-ray.

Core-shell nanoparticles have been prepared by irradiation of gamma-ray on block copolymer micelles consisting of hydrophilic polyacrylic acid and hydrophobic polyisoprene with each 40 monomer units. The structure was determined by means of dynamic light scattering (DLS), small angle X-ray scattering (SAXS) and atomic force microscopy (AFM). The size distribution of the core-shell nanoparticles determined by DLS and AFM was very narrow. The average diameter of the particles decreased from 48 nm for the original micelles to 26 nm by the irradiation of 30 kGy. The core size determined by SAXS combined with DLS was roughly constant of 10 nm, irrespective of irradiation dose, whereas the shell thickness of the micelles was twice as large as the core size, and decreased with increasing irradiation dose.

Gamma Rays↗

PubMed2006

The chitin synthase involved in marine bivalve mollusk shell formation contains a myosin domain.

Chitin is a key component in mollusk nacre formation. However, the enzyme complex responsible for chitin deposition in the mollusk shell remained unknown. We cloned and characterized the chitin synthase of the marine bivalve mollusk Atrina rigida. We present here the first chitin synthase sequence from invertebrates containing an unconventional myosin motor head domain. We further show that a homologous gene for chitin synthase is expressed in the shell forming tissue of larval Mytilus galloprovincialis even in early embryonic stages. The new data presented here are the first clear-cut indication for a functional role of cytoskeletal forces in the precisely controlled mineral deposition process of mollusk shell biogenesis.

Animals↗

PubMed2005

In vitro degradation of polyanhydride/polyester core-shell double-wall microspheres.

Double-wall microspheres (DWMS), comprising distinct polymer core and shell phases, are useful and interesting for controlled-release drug delivery. In particular, the presence of a surface-eroding polymer core may be expected to limit water penetration and, therefore, delay degradation of the core phase and drug release. In this study, solid microspheres and DWMS were fabricated using a surface-eroding polymer (poly[1,6-bis(p-carboxyphenoxy)hexane]; PCPH) and a bulk-eroding polymer (poly(D,L-lactide-co-glycolide); PLG). Erosion of the particles was observed by optical and electron microscopy, while polymer degradation was followed by gel permeation chromatography, during incubation in buffer at 37 degrees C. Degradation and erosion were very different depending on which polymer formed the particle shell. Nevertheless, the relatively thin (approximately 5 microm) PCPH shells could not prevent water penetration, and the PLG cores completely eroded by 6 weeks of incubation.

Chromatography, Gel↗

PubMed2004

Synthesis and characterization of SiO2/Gd2O3:Eu core-shell luminescent materials.

Europium-doped Gd2O3 with an average size of approximately 15 nm was coated on the surface of preformed silica nanospheres by the wet chemical method. SEM and TEM photographs showed that SiO2/Gd2O3:Eu core-shell submicrospheres are obtained. XRD patterns indicated that the Gd2O3:Eu shell is crystalline after heat treatment. FTIR and XPS spectra showed that the Gd2O3:Eu shell is linked to the silica surface by forming a Si-O-Gd bond. Photoluminescence studies showed that the luminescent properties are still retained after coating on an inert silica core; additionally, we noted that the emitting peaks are broadened, which results from size effects and interface effects of nanocrystal.

Journal Article↗

PubMed2005

Preparation and characterization of intelligent core-shell nanoparticles based on poly(D,L-lactide)-g-poly(N-isopropyl acrylamide-co-methacrylic acid).

New thermo-responsive, pH-responsive, and biodegradable nanoparticles comprised of poly(D,L-lactide)-graft-poly(N-isopropyl acrylamide-co-methacrylic acid) (PLA-g-P(NIPAm-co-MAA)) were developed by grafting biodegradable poly(D,L-lactide) onto N-isopropyl acrylamide and methacrylic acid. A core-shell type nano-structure was formed with a hydrophilic outer shell and a hydrophobic inner core, which exhibited a phase transition temperature above 37 degrees C suitable for biomedical application. Upon heating above the phase transition temperature, PLA-g-P(NIPAm-co-MAA) nanoparticle showed a polarity increase of pyrene in either buffer solution or intra-hepato-carcinoma cells as determined by fluorescence measurement, indicating that the structure of nanoparticles caused leakages from outer shell copolymers aggregation and collapsed. The drug loading level of 5-fluorouracil (5-FU) encapsulated in the PLA-g-P(NIPAm-co-MAA) nanoparticles can be as high as 20%. The release of 5-FU from nanoparticles was strongly controlled by the pH in the aqueous solution. Based on these results, PLA-g-P(NIPAm-co-MAA) nanoparticles can be used as a drug carrier for intracellular delivery of anti-cancer drug.

Acrylamides↗

PubMed2006

Novel composite core-shell nanoparticles as busulfan carriers.

This study presents a method for the design of novel composite core-shell nanoparticles able to encapsulate busulfan, a crystalline drug. They were obtained by co-precipitation of mixtures of poly(isobutylcyanoacrylate) (PIBCA) and of a diblock copolymer, poly(epsilon-caprolactone)-poly(ethylene glycol) (PCL-PEG), in different mass ratios. The nanoparticle size, morphology and surface charge were assessed. The chemical composition of the top layers was determined by X-ray photo-electron spectroscopy (XPS). (3)H-labelled busulfan was used in order to determine the drug loading efficiency and the in vitro drug release by liquid scintillation counting. Physico-chemical techniques such as Zeta potential determination and XPS analysis provided evidence about a preferential surface distribution of the PCL-PEG polymer. Therefore, composite nanoparticles have a "core-shell"-type structure, where the "core" is essentially formed by the PIBCA polymer and the "shell" by the PCL-PEG copolymer. The use of PIBCA to form the core of the nanoparticles leads to a 2-4 fold drug loading increase, in comparison to the single PCL-PEG nanoparticles. In addition, the complement activation results showed a significant difference between the composite nanoparticles and the single PIBCA nanoparticles, thus demonstrating that PEG at the surface of the nanoparticles reduced the complement consumption. The PIBCA:PCL-PEG composite nanoparticles prepared using the new co-precipitation method here described represent an original approach for busulfan administration.

Antineoplastic Agents, Alkylating↗

PubMed2006

Acid-cleavable polymeric core-shell particles for delivery of hydrophobic drugs.

Here we describe the combined use of acid-labile microgel approach and RAFT-mediated seeded dispersion polymerization technique to prepare an acid-cleavable core-shell like polymeric colloidal system for the delivery of hydrophobic drugs at slightly acidic sites. A new bisacrylate acetal crosslinker was copolymerized with n-butyl acrylate (BA) in the presence of a RAFT agent using a dispersion polymerization technique, which yielded crosslinked spherical particles with the size ranging between 150 and 500 nm. The particles were cleaved in a pH-dependent manner similar to the acid-labile hydrolysis behaviour of the crosslinker. In order to mask the hydrophobic surface of the particles, polyethylene glycol acrylate (PEG-A) was grafted onto poly(BA) seed particles via the RAFT agent groups on the particle surface. The acidic-site selective delivery potential of the poly(BA)-g-poly(PEG-A) particles was assessed in-vitro using a lipophilic fluorescent dye as a model hydrophobic drug. Ca. 73% and 34% of the total dye loaded in the particles was found to be released at pH 5.0 and 7.4 in 24 h, respectively. The growth of human neuroblastoma cells was not affected by the incubation with the core-shell particles and their cleavage by-products up to 3 mg/ml concentration. The physicochemical and the functional features support the potential value of the acid-cleavable poly(BA) core-poly(PEG-A) shell particles as carriers for the delivery of hydrophobic drugs at acidic sites.

Acetates↗

PubMed2004

Efficacy of the soft-shell technique using Viscoat and Hyal-2000.

PURPOSE: To evaluate whether the soft-shell technique using Viscoat (sodium hyaluronate 3%-chondroitin sulfate 4%) and Hyal-2000 (sodium hyaluronate 1%) reduces corneal endothelial cell damage during cataract surgery. SETTING: Department of Ophthalmology, Kangnam St. Mary's Hospital, Seoul, Korea. METHODS: The nuclear opacity in 252 eyes of 230 cataract patients was classified as grade 1, 2, 3, or > or =4 using the Lens Opacities Classification System III. In each classification, the patients were divided into 4 groups before phacoemulsification based on the type of ophthalmic viscosurgical device (OVD) used during surgery: Viscoat and Hyal-2000 (soft-shell technique), Viscoat alone, Hyal-2000 alone, or Provisc (sodium hyaluronate 1%) alone. All patients were operated on using the same technique except for the OVD. The visual acuity, corneal endothelial cell density, corneal thickness, and intraocular pressure (IOP) were evaluated postoperatively. RESULTS: The rate of endothelial cell loss 2 months after surgery in eyes with a nuclear opacity grade of > or =4 was significantly different between the 4 OVD groups. The rate in eyes with a nuclear opacity grade of < or =3 was not significantly different between the groups. There were no statistically significant differences between the 4 groups in visual acuity, corneal thickness, or IOP throughout the follow-up period. CONCLUSION: The soft-shell technique using Viscoat and Hyal-2000 protected corneal endothelial cells during cataract surgery in patients with a nuclear opacity grade of > or =4.

Aged↗

PubMed2004

Removal of nickel(II) ions from aqueous solution using crab shell particles in a packed bed up-flow column.

This paper investigates the ability of crab shell to remove nickel(II) ions from aqueous solution in a packed bed up-flow column with an internal diameter of 2 cm. The experiments were performed with different bed heights (15-25 cm) and using different flow rates (5-20 ml/min) in order to obtain experimental breakthrough curves. The bed depth service time (BDST) model was used to analyze the experimental data and the model parameters were evaluated. The column regeneration studies were carried out for seven sorption-desorption cycles. The elutant used for the regeneration of the sorbent was 0.01 M EDTA (disodium) solution at pH 9.8 adjusted using NH4OH. Due to continuous usage of crab shell, a performance loss was observed as the breakthrough curves become more flattened also indicated by the broadened mass transfer zone. The breakthrough time decreased uniformly from 28.1 to 9.5 h as the cycles progressed from one to seven, whereas nickel uptake remained approximately constant throughout the seven cycles. The life-factors for crab shell in terms of critical bed length and breakthrough time were found to be 1.1 cm/cycle and 0.17 per cycle, respectively. The elution efficiency was greater than 99.1% in all the seven cycles. The pH profiles during both sorption and desorption process were also reported. In sorption cycles, there was a sudden raise in pH in the early part of the process and then the pH decreased as the time progressed. In desorption cycles, pH decreased in initial stages and followed by gradual increase in pH, which eventually reached the pH of the inlet elutant.

Adsorption↗

PubMed2006

Dye removal by low cost adsorbents: hazelnut shells in comparison with wood sawdust.

Batch adsorption of Methylene Blue, up to 1000 mg L(-1), and Acid Blue 25, up to 500 mg L(-1), onto ground hazelnut shells was studied in comparison with sawdust of various species of wood, in order to explore the potential use of this material as low cost adsorbent for dye removal in dyehouse effluents. The adsorption kinetics was investigated according to Lagergren's model, but the best fit was achieved by a second order equation. The equilibrium data were processed according to Langmuir's model and higher adsorption capacity values towards both dyes were shown by hazelnut shells than wood sawdust. Moreover, fixed bed adsorption of Methylene Blue was performed on hazelnut shell columns and the breakthrough curves were determined by varying bed depth, flow rate and influent concentration. The data were processed according to Bohart-Adams model and the column performances could be predicted by the bed depth service time (BDST) approach.

Adsorption↗

PubMed2003

Effect of amphetamine, cocaine and depolarization by high potassium on extracellular dopamine in the nucleus accumbens shell of SHR rats. An in vivo microdyalisis study.

Spontaneously hypertensive rats (SHR) exhibit behavioural abnormalities (hyperactivity and hyper reactivity to stress) that resemble the behavioural abnormalities of human attention-deficit with hyperactivity disorder (ADHD). Because dopamine has been implicated in ADHD we studied by in vivo microdialysis the dopamine output in the nucleus accumbens (NAc) shell of 6 week-old (pre-hypertensive stage) SHR rats and in their normotensive age matched Wistar Kyoto controls (WKY). We observed that SHR rats had significant higher basal dialysate dopamine concentrations (about 20%) than WKY. Systemic administration of amphetamine (0.25 and 0.5 mg/kg s.c.), and methylphenidate (1 and 2 mg/kg i.p.) produced an higher increase in dialysate dopamine in the NAc shell of SHR rats as compared with WKY rats, although only after the administration of the lowest dose of amphetamine and methylphenidate this difference was found to be significant. In contrast when the microdialysis fiber was perfused by 30 or 60 mM K(+), a lower increase of dialysate dopamine was observed in SHR rats as compared with WKY rats. These apparently contradictory results can be explained by postulating that SHR rats have a higher tone of NAc shell dopamine transmission and synthesis associated with a lower storage capacity of vesicles in dopamine terminals of the same area.

Amphetamine↗

PubMed2005

Daily bingeing on sugar repeatedly releases dopamine in the accumbens shell.

Most drugs of abuse increase dopamine (DA) in the nucleus accumbens (NAc), and do so every time as a pharmacological response. Palatable food also releases accumbens-shell DA, but in naïve rats the effect can wane during a long meal and disappears with repetition. Under select dietary circumstances, sugar can have effects similar to a drug of abuse. Rats show signs of DA sensitization and opioid dependence when given intermittent access to sucrose, such as alterations in DA and mu-opioid receptors, cross-sensitization with amphetamine and alcohol, and behavioral and neurochemical signs of naloxone-precipitated withdrawal. The present experiment asks whether sucrose-dependent rats release DA each time they binge. We also predict that acetylcholine (ACh), which rises as the end of a meal, will be delayed in rats with intermittent access to sucrose. To create dependency, the experimental group (Daily Intermittent Sucrose) was maintained on a diet of 12-h food deprivation that extended 4 h into the dark, followed by 12-h access to a 10% sucrose solution and chow, daily, for 21 days. As the main result, these rats gradually increased their sucrose intake from 37 to 112 ml per day (from 13 to 20 ml in the first hour of access), and repeatedly increased extracellular DA to 130% of baseline as measured in the NAc shell by microdialysis during the first hour of sucrose access on day 1, day 2 and day 21. Three control groups failed to show a significant increase in extracellular DA on day 21: Sucrose only for 1 h on days 1 and 21 (Sucrose Twice), ad libitum access to sucrose and chow (Daily Ad libitum Sucrose), and intermittent chow instead of sucrose (Daily Intermittent Chow). Acetylcholine measured at the same time as DA, increased significantly toward the end and after each test meal in all groups. In the Daily Intermittent Sucrose group, the highest ACh levels (133%) occurred during the first sample after the sucrose meal ended. In summary, sucrose-dependent animals have a delayed ACh satiation response, drink more sucrose, and release more DA than sucrose- or binge-experienced, but non-dependent animals. These results suggest another neurochemical similarity between intermittent bingeing on sucrose and drugs of abuse: both can repeatedly increase extracellular DA in the NAc shell.

Acetylcholine↗

PubMed2005

c-Fos and deltaFosB expression are differentially altered in distinct subregions of the nucleus accumbens shell in cocaine-sensitized rats.

Repeated cocaine administration in rats can lead to sensitization as evidenced by an increased locomotor response to a subsequent exposure (challenge) dose of cocaine even after a drug-free period. Expression of the immediate early gene product, c-Fos, differs among distinct subregions of the nucleus accumbens shell. This would suggest that these subregions may be differentially involved in sensitization. The present study quantified c-Fos- and deltaFosB-immunoreactive nuclei in subterritories of the nucleus accumbens in animals behaviorally sensitized to cocaine. Rats received a sensitization-inducing regimen of cocaine (twice-daily injections of 15 mg/kg i.p. for five consecutive days). Fourteen days following the last injection, rats were given a challenge injection of cocaine (15 mg/kg i.p.), and killed 2 h later. Sections through the nucleus accumbens were processed for tyrosine hydroxylase and either c-Fos or deltaFosB. The number of immunoreactive nuclei was quantified in five subregions of the nucleus accumbens shell: the vertex, arch, cone, intermediate zone and ventrolateral zone, which can be identified by differential histological staining for tyrosine hydroxylase. Repeated cocaine administration resulted in robust sensitization that was associated with more deltaFosB in the vertex, arch, and cone compared with saline-treated controls. As previously reported, c-Fos immunoreactivity was increased in the intermediate zone in cocaine-sensitized rats. deltaFosB was significantly elevated in rats that did not receive a cocaine challenge, attesting to the long half-life of this transcription factor. These results provide further evidence suggesting distinct anatomical neuroadaptations within the nucleus accumbens shell that may play a functional role in psychomotor-stimulant sensitization.

Animals↗

PubMed2004

Subregion-specific down-regulation of 5-HT3 immunoreactivity in the nucleus accumbens shell during the induction of cocaine sensitization.

Repeated exposure to psychostimulants such as cocaine and amphetamine can result in behavioral sensitization, which is believed to model the onset of drug addiction, as well as neural adaptations that occur after repeated drug abuse that lead to addictive behaviors. Dopamine (DA) in the nucleus accumbens (NAc) has been shown to play an integral role in this phenomenon. However, cocaine also acts on the serotonin (5-HT) system, which has been shown to modulate psychostimulant-induced increases in motor behavior and DA release in the NAc. Recently, it has been demonstrated that the shell portion of the NAc can no longer be considered a homogeneous structure and can be subdivided into at least five separate regions. The present study examines 5-HT(3) receptors in the subdivisions of the NAc in cocaine-sensitized rats. Rats received a sensitization-inducing regimen of cocaine (twice-daily injections of 15 mg/kg ip for five consecutive days). Two or 14 days following the last injection, rats were given a challenge injection of cocaine (15 mg/kg ip) and sacrificed 2 h later. Sections of the NAc were processed for 5-HT(3) immunoreactivity (5-HT(3)-IR), and the number of puncta was quantified in each of the subregions of the shell, as well as the core of the accumbens. Repeated cocaine administration resulted in robust sensitization that correlated with a transient decrease in the density of 5-HT(3) immunoreactive puncta in the intermediate zone of the accumbens shell. After a 2-week withdrawal period, sensitized animals no longer showed any differences in any of the areas examined. These data suggest a possible role for 5-HT(3) receptors in the intermediate zone during the induction of cocaine sensitization.

Animals↗