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PubMed2007

Amine-containing core-shell nanoparticles as potential drug carriers for intracellular delivery.

The present study aimed at exploring the use of amine-containing core-shell nanoparticles as potential drug carriers for intracellular delivery. Stable nanoparticles (100-200 nm in diameter) that consisted of poly(methyl methacrylate) (PMMA) cores with hydrophilic poly(ethyleneimine) (PEI) shells were synthesized and used to study their complexation with model drug, ibuprofen (IB), and release it under various electrolyte concentrations. The complexed IB/PEI-PMMA nanoparticles were characterized with FTIR, photon correlation spectroscopy, zeta-potential, and transmission electron microscopy (TEM). Results suggested that the PEI-PMMA nanoparticles could effectively complex with the IB via electrostatic interaction. The thick PEI shells ( approximately 30 nm) significantly enhanced the drug loading capacity up to 23% (w/w) of the complexed nanopartricle. In vitro release of the drug from the complexed nanoparticles was sensitive to the ionic strength of the media. Study of cellular entry of fluorescently labeled IB/nanoparticle complexes using a confocal laser scanning microscopy demonstrated that the entry of the complexed nanoparticles strongly depended on the complexing ratio between IB and PEI-PMMA nanoparticles.

Aziridines↗

PubMed1976

Ultrastructural investigation of the mechanism of muscle attachment to the gastropod shell.

The ultrastructure of the muscle-shell attachment was investigated in the land pulmonate snails Helix aspersa, Anguispira alternata, in the freshwater pulmonate Laevipex sp., and in the freshwater prosobranch Pomacea paludosa. In all cases, a collagenous intercellular matrix and a specialized epithelium (tendon cells) intervene between the columellar muscle and the shell. These tendon cells are characterized by hemidesmosomes at both apical and basal ends, connected by thick bundles of microfilaments. The tendon cells do not insert into the shell directly by microvilli, as formerly thought, but by an extensive network of extracellular organic fibers.

Animals↗

PubMed1992

Improved detection of cytomegalovirus viremia in AIDS patients using shell vial and indirect immunoperoxidase methodologies.

One hundred twelve peripheral blood specimens were tested for the presence of cytomegalovirus (CMV) by the tube culture indirect immunoperoxidase (TC-IPA) procedure, the shell vial assay [shell vials were pre- and postinoculation treated with medium containing 2 of 10% fetal bovine serum (FBS) or 100 micrograms% cortisol] (SV-IFA), and conventional (MRC-5) tube cultures (TC-CPE). CMV was detected in 25 (22%) of the 112 specimens tested by at least one of these methods. The detection/isolation of CMV among the 25 positive specimens in shell vials maintained with 2% FBS, 100 micrograms% cortisol + 2% FBS, and 10% FBS was 36, 44, and 52%, respectively. Detection/isolation of the virus from blood by TC-IPA and TC-CPE was 52% and 76%, respectively. A significantly greater CMV detection rate occurred using TC-CPE compared to SV-IFA treated with medium supplemented with an FBS concentration of 2% (P = .0132), but not medium containing the higher serum supplement or the glucocorticoid (P greater than .05). Differences in the identification of a CMV viremia were observed by IPA, SV-IFA, and TC-CPE methodologies on a patient-to-patient basis, denoting the necessity of incorporating each methodology into the CMV screening panel. Demographic analysis of 82 AIDS patients showed a CMV viremia prevalence of 9% (2/28) in intravenous drug users, 57% (27/47) in homosexual patients, and 22% (2/9) in heterosexual and transfusion patients. Overnight (24 hr) storage of whole blood at 4 or 24 degrees C, respectively, reduced CMV recovery by 40% and 65%, when tested by TC-CPE.(ABSTRACT TRUNCATED AT 250 WORDS)

AIDS-Related Opportunistic Infections↗

PubMed1985

Stress analysis of a condylar knee tibial component: influence of metaphyseal shell properties and cement injection depth.

We generated three-dimensional finite element models of the proximal tibia with an implanted tibial component. The component features a cobalt-chromium tray with four short vertical posts and a porous-coated surface for improved fixation to polymethylmethacrylate (PMMA). We examined the stresses after varying: the structural rigidity of the metaphyseal cortical shell; the surface area of the cobalt-chromium tray; and the depth of pressure-injected PMMA bone cement. Our results indicate that previous finite element models of prosthetic tibial components have overestimated the structural contribution of the metaphyseal cortical shell by a factor of approximately 6. A standard size tray, in contrast to a tray that extends to the cortical shell, does not significantly alter the axial load distribution but could result in bone resorption beyond the tray periphery. An important consequence of the component peg locations is that they direct the compressive stresses into dense regions of trabeculae that run from the subchondral articular surface to the metaphyseal-diaphyseal junction. The use of a modified von Mises failure criterion suggests that at excessive load levels the most likely location of material failure is at the bone cement-trabecular bone interface immediately distal to the fixation posts. Due to its added rigidity, injection of cement beyond the fixation posts results in slightly increased stresses in this region, but these stress increases are compensated for by an increased strength of the cement-bone composite.

Bone Cements↗

PubMed2005

Core/shell particles containing 3-(methacryloxypropyl)-trimethoxysilane in the shell: synthesis, characterization, and application.

In comparison to the corresponding single-component counterparts, core/shell particles are widely used due to their better physical and chemical properties. The surface properties of core/shell particles evidently play an important role in the process of application. It is easy to deduce that surface properties mostly depend on the properties of the component in the shell. Therefore, desirable materials of shell are very significant for the study of composite materials, especially in core/shell field. It is well known that polysiloxane has excellent properties, such as the water repellency, high flexibility, low surface energy, and biocompatibility. Its application, however, is limited due to poor cohesiveness and poor film-forming properties. Recently, much endeavor has been made to overcome such flaws. It is found that polyacrylate is commonly considered for its good cohesiveness and excellent film-forming property. The combination of polysiloxane and polyacrylate has been shown to be important in the composite material field, especially as core/shell particles. Unfortunately, their hydrophobicity is considerably different and thus, the core/shell particles consisting of polyacrylate (PA)/polysiloxane (PSi) are hard to prepare by general seeded emulsion polymerization, and are also scarcely available in the literature. In this study, the new core/shell PA/PSi particles with poly(butyl methacrylate) (PA) as the core and poly(3-(methacryloxypropyl)-trimethoxysilane) (PSi) as the shell were prepared by dispersion polymerization under the kinetically controlled conditions. The characterization of the particles by TEM, DSC, particle size analyzer as well as static contact angle confirmed the formation of core/shell structure. The application of core/shell (PA/PSi) particles also has been considered and discussed here.TEM micrographs of core/shell (PA/PSi) particles.

Capsules↗

PubMed2006

Core-shell iron-iron oxide nanoparticles synthesized by laser-induced pyrolysis.

Passivated iron nanoparticles (10-30 nm) have been synthesized by laser pyrolysis of a mixture of iron pentacarbonyl and ethylene vapors followed by controlled oxidation. The nanoparticles show a well-constructed iron-iron oxide core-shell structure, in which the thickness and nature (structure similar to maghemite, gamma-Fe2O3) of the shell is found to be independent of the initial conditions. On the other hand, the composition of the core is found to change with the particle size from the alpha-Fe structure to a highly disordered Fe phase (probably containing C atoms in its structure). The dependence of the magnetic properties on the particle size, iron oxide fraction, and temperature was also investigated. In the case of smaller particles, the magnetic data indicate the existence at low temperature of a large exchange anisotropy field, the magnitude of which increases with decreasing temperature in correspondence with the freezing of magnetic moments in the oxide shell.

Ferric Compounds↗

PubMed2004

Electron microscopic dual labeling of high-affinity neurotensin and dopamine D2 receptors in the rat nucleus accumbens shell.

The dopamine D2 receptor (D2R) in the nucleus accumbens (NAc) shell is implicated in schizophrenia and in psychostimulant-induced drug-seeking behavior, both of which are affected by activation of the functionally opposed high-affinity neurotensin receptor (NTS1). To determine the functionally relevant sites, we examined the dual electron microscopic immunocytochemical localization of D2R and NTS1 in the NAc shell of rat brain. Immunolabeling for each receptor was seen in association with cytoplasmic organelles, or more rarely, on the plasma membrane of both axonal and somatodendritic profiles. Some of the axonal and many of the dendritic processes colocalized the two receptors. The dually labeled axon terminals often formed symmetric synapses or appositional contacts with unlabeled dendritic profiles. The morphology of these terminals suggests that they contain either inhibitory amino acids or dopamine. Other axonal profiles expressing exclusively NTS1 or D2R were without synaptic specializations or formed asymmetric, excitatory-type synapses mainly on unlabeled dendritic spines. In addition, however, several D2R-immunoreactive terminals were observed presynaptic to dendrites containing NTS1. The somatodendritic profiles immunolabeled for NTS1 and/or D2R had morphological features typical of inhibitory spiny projection neurons in the NAc. These results suggest that activation of NTS1 and D2R can dually modulate transmitter release from the same or separate phenotypically distinct axon terminals in the NAc shell. These presynaptic receptors as well as the postsynaptic NTS1 distribution in neurons that also contain or receive input from terminals containing D2R may mediate the opposing actions of neurotensin and dopamine in the NAc.

Animals↗

PubMed2006

Anatomic distribution of reinforcer selective cell firing in the core and shell of the nucleus accumbens.

We have previously reported that distinct populations of nucleus accumbens (NAc) neurons differentially encode information about goal-directed behaviors for "natural" (food/water) vs. cocaine reinforcement [J Neurosci 20:4255-4266, (2000)]. Here, the anatomic distribution of reinforcer-selective cell firing was examined within the core and shell of the NAc. Rats (n=8) were trained on a multiple schedule for water reinforcement and cocaine (0.33 mg/infusion) self-administration. Next, microelectrode arrays (eight wires/array) were bilaterally positioned in the NAc core and shell, and cell firing was recorded during the multiple schedule. All electrode tip placements were then "marked," and histological reconstruction of each electrode position was completed. Of 93 NAc cells, 44 neurons (47%) exhibited 1 of 4 types of well-documented patterned discharges relative to the water- or cocaine-reinforced response. Of the 44 phasic cells, 39 neurons (89%) displayed differential, nonoverlapping neuronal firing patterns across the two reinforcer conditions (i.e., reinforcer-selective activity). Histological reconstruction of electrode placement revealed that NAc patterned discharges, specific to goal-directed behaviors for water or cocaine, were not limited to one NAc subregion but were evenly distributed and intermixed throughout the core and shell. These findings are discussed with respect to the functional organization of the NAc.

Animals↗

PubMed2006

Dopamine D1 receptors have subcellular distributions conducive to interactions with prodynorphin in the rat nucleus accumbens shell.

Activation of dopamine (DA) D1 receptors (D1Rs) in the nucleus accumbens (Acb) markedly affects the levels of prodynorphin, the precursor of aversion-associated dynorphin peptides. The location of prodynorphin, specifically as related to the dopaminergic inputs and D1Rs in the Acb, is fundamental for establishing the physiologically relevant sites. To determine these sites, we examined the electron microscopic dual-immunolabeling of prodynorphin and D1R or tyrosine hydroxylase (TH), a marker of catecholamine terminals in the rat Acb shell. This subregion is targeted by mesolimbic dopaminergic inputs affecting reward-aversion responses and locomotor activity. Prodynorphin was prominently localized to large (100-200 nm) granular aggregates in somatodendritic and axonal profiles, some of which expressed dynorphin A/B. In somata and dendrites, prodynorphin was often found in punctate clusters in the cytoplasm. Of the total prodynorphin-labeled dendrites, approximately 63% expressed D1Rs, which were largely located on the plasma membranes. In comparison with dendrites, many more axon terminals contained prodynorphin, although only 15% of these terminals contained D1R-labeling. Prodynorphin terminals formed symmetric synapses with D1R-labeled or unlabeled dendrites, and also apposed TH-containing axon terminals. Our results provide ultrastructural evidence that in the Acb shell, the prodynorphin is available for cleavage to physiologically active peptides in both dendrites and terminals of neurons that express D1Rs. They also indicate that dynorphin peptides have distributions that would enable their participation in modulation of DA release or D1R-mediated postsynaptic responses in Acb shell neurons.

Animals↗

PubMed2001

Hydrophobic Core/Hydrophilic Shell Amphiphilic Particles.

Amphiphilic colloidal particles with hydrophobic cores and hydrophilic shells were prepared via a two-step method. First, polystyrene cores were obtained through the concentrated emulsion polymerization. A mixture of styrene, ethyl benzene, divinyl benzene, azobisisobutyronitrile, and cumene hydroperoxide (CHPO) was partially polymerized at 80 degrees C for 40 min and subsequently used as the dispersed phase of a concentrated emulsion in water. The concentrated emulsion was subjected to complete polymerization at 60 degrees C for 12 h; colloidal particles of crosslinked polystyrene were thus obtained. In the second step, the polystyrene particles were dispersed in water, after which acrylamide, N,N'-methylenebisacrylamide, and ferrous sulfate (FS) were added. The system was heated (typically at 30 degrees C) to conduct the polymerization of the hydrophilic monomers. The CHPO present on the surface of the polystyrene particles and the FS present in the aqueous phase (both together constitute a redox initiator) ensured that the initiation occurred mostly on the surface of the particles and that the hydrophilic polymer obtained formed a shell encapsulating the particles. Under proper conditions, a porous outer shell could be generated, making the hydrophobic core accessible to the outside medium. Copyright 2001 Academic Press.

Journal Article↗

PubMed2000

Comparison of the soluble organic matrices of healthy and diseased shells of Pinctada margaritifera (L.) and Pecten maximus L. (Mollusca, Bivalvia).

Pinctada margaritifera and Pecten maximus are among the mollusks of commercial value. Both are known to show abnormal calcification processes that strongly increase the mortality rate. Several parameters of the soluble organic matrices extracted from the shells of P. margaritifera and P. maximus are analyzed: bulk composition, molecular weights, and acidity. The composition of the matrices of healthy and diseased shells were compared, showing that the protein and the sugar contents are variously modified. Differences between healthy and diseased shells are dissimilar in the two species. This is in accordance with the previously described macroscopic and microscopic alterations (red color, numerous brown membranes). This study does not allow identification the origin of the disease, but provides new insights on the role of sugars in biomineralization processes.

Acids↗

PubMed2001

The nature of siliceous mosaics forming the first shell of the brachiopod Discinisca.

The juvenile shell of the brachiopod Discinisca consists of a mosaic of micrometer-sized siliceous tablets embedded in a chitinous substrate. The first-formed tablets are secreted on glycocalyx by a newly differentiated collective of outer epithelial cells. They are mainly rhombic but may also be ellipsoidal, discoidal, or deformed and sporadically overlap one another. On the surrounding juvenile shell, secreted by an incipient outer mantle lobe, the tablets are nearly all perfect rhombic plates in rhombic arrays. Their constant size, arrangement, and centripetal crystallization suggest intracellular assembly. The tablets, which are normally bilamellar, consist of discrete aggregates of crystalline spherules of silica in rhombic arrays within an organic matrix of fibrous protein and, presumably, a soluble polysaccharide(s). Mosaic secretion ceases at about the time when juveniles settle on the sea bed, which more or less coincides with the secretion of a ring of lamellae around the mosaic, induced by rapid advances and retractions of the outer mantle lobe prior to deposition of the organophosphatic mature shell. Energy dispersion X-ray analyses of pelagic and newly settled juveniles show that phosphatic secretion, even in the site of the first-formed outer epithelial collective, does not begin until all siliceous secretion has ceased.

Animals↗

PubMed2001

Large-scale fractionation of molluscan shell matrix.

The numerous proteins occluded within the molluscan shell play a key role in the control of the mineralization process. Although extensively studied, these proteins are still poorly known, mainly because they are difficult to fractionate. In the present paper, we present, for the first time, a simple combined strategy for separating successfully large amounts of molluscan shell proteins. Since shell proteins do not absorb at 280 nm, our approach is based on the "blind" separation of these proteins by a preparative denaturing electrophoresis. They are subsequently detected on dot-blot with polyclonal antibodies raised against the unfractionated soluble matrix. In the present case, this approach allows one to collect enough purified proteins to obtain amino-acid composition as well as N-terminal sequences, and to perform in vitro tests and glycosylation studies. Furthermore, this method permits one to raise polyclonal antibodies against the isolated proteins.

Animals↗

PubMed1993

Rescue of infectivity by in vitro transcapsidation of rotavirus single-shelled particles.

We investigated the possibility of rescuing the infectivity of noninfectious single-shelled rotavirus particles by in vitro transcapsidation. The soluble outer capsid proteins VP4 and VP7 were prepared by EDTA treatment of double-shelled (ds) particles of SA11-4F (G serotype 3), followed by removal of single-shelled (ss) particles by three sequential rounds of centrifugation. Ss-particles of B223 (G serotype 10) were prepared by two cycles of EDTA treatment of ds-particles followed by iospycnic CsCl gradient purification. A trace of infectivity (< 1000 PFU/ml) was always detected in the preparations of ss-particles, while no detectable infectivity (< 5 PFU/ml) was present in the preparations of outer capsid proteins. By mixing soluble outer capsid proteins VP4 and VP7 purified from SA11-4F and ss-particles of B223 at acidic pH (5.4), ds-like, transcapsidated particles were obtained. The transcapsidated particles were indistinguishable from genuine ds-particles by negative stain electron microscopy. However, the particles had a density intermediate between that of ds- and ss-particles. Protease-resistance studies revealed that VP7 was assembled onto transcapsidated particles in a resistant (native) form, but VP4 associated with the particles was completely protease sensitive. Viral infectivity was rescued by in vitro transcapsidation as indicated by a 500- to 1000-fold increase over background. The increased infectivity was neutralized by antiserum against SA11 (outer capsid donor), but not by antiserum against B223 (ss-particle donor). The transcapsidated particles formed small plaques like the B223 parent, and all the infectious progeny viruses contained the B223 genome. These results strongly indicate that the observed increase of infectivity was the result of in vitro transcapsidation.

Animals↗

PubMed2002

Loss of activities for mRNA synthesis accompanies loss of lambda2 spikes from reovirus cores: an effect of lambda2 on lambda1 shell structure.

The 144-kDa lambda2 protein, a component of the transcriptionally active reovirus core particle, catalyzes the last three enzymatic activities for formation of the 5' cap 1 structure on the viral plus-strand transcripts. Limited evidence suggests it may also play a role in transcription per se. Particle-associated lambda2 forms pentameric turrets ("spikes") around the fivefold axes of the icosahedral core. To address the requirements for lambda2 in core functions other than the known functions in RNA capping, particles depleted of lambda2 were generated from cores in vitro by a series of treatments involving heat, protease, and ionic detergent. The resulting particles contained less than 5% of pretreatment levels of lambda2 but showed negligible loss of the other four core proteins or the 10 double-stranded RNA genome segments. Transmission cryo-electron microscopy (cryo-TEM) and scanning cryo-electron microscopy demonstrated loss of the lambda2 spikes from these otherwise intact particles. In functional analyses, the "spikeless cores" showed greatly reduced activities not only for RNA capping but also for transcription and nucleoside triphosphate hydrolysis, suggesting enzymatic or structural roles for lambda2 in all these activities. Comparison of the core and spikeless core structures obtained by cryo-TEM and three-dimensional image reconstruction revealed changes in the lambda1 core shell that accompany lambda2 loss, most notably the elimination of small pores that span the shell near the icosahedral fivefold axes. Changes in the shell may explain the reductions in transcriptase-related activities by spikeless cores.

Cryoelectron Microscopy↗

PubMed1976

Manganese in the shell of Centropyxis (Rhizopodea: Protozoa).

The proteinaceous shells of Centropyxis hirsuta contain a relatively high concentration of manganese in an amorphous state. The concentrations of manganese fill the alveoli which are characteristic of the shell structure. Observations based on cultured animals and subsequently examined by X-ray diffraction, a solid state energy dispersive X-ray analyser, and an analytical electron microscope, lead to the conclusions that manganese is selectively absorbed by Centropyxis hirsuta and deposited in the shell.

Amoeba↗

PubMed1979

In vitro recalcification of the demineralized shell-repair membrane of the snail, Helix pomatia L.

The role of the amoebocytes in the calcification process of the shell-repair membrane of the snail, Helix pomatia, was investigated in vitro. The shell-repair membranes were demineralized with 0.5 M EDTA at pH 7.4. For the recalcification of the demineralized membranes two substrates were chosen: (i) Tris-buffered Helix pomatia-saline, pH 7.4, and (ii) Helix pomatia-saline supplemented with 5 mM CaCl2 and 5mM NaHCO3. The membranes were incubated in 2 ml substrate at 37 degrees C and examined after 2 h, 24 h, and 3, 5 and 7 days. Calcium deposition and crystal formation were observed within the membranes incubated in the salt-supplemented substrate. The control membranes were either heat-inactivated or deprived of lipids. No calcium precipitation was observed in control membranes. The experiments show that the recalcification of the shell-repair membrane is under strict cellular control and that the granules released from the amoebocytes serve as sites for calcium deposition. The role of phospholipids in the calcification process is discussed.

Animals↗

PubMed1987

Ultrastructure of Brugia malayi egg shell and its comparison with microfilarial sheath.

Ultrastructure of Brugia malayi egg shell and microfilarial sheath have been compared. They are identical in appearance, thus confirming that the microfilarial sheath is derived from the egg shell. The surface of the egg shell and the microfilarial sheath have distinct electron-dense projections which may have a protective role for the parasite.

Animals↗