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PubMed1988

Symposium overview. The Shell Conference on Computer-Aided Molecular Modelling.

The 'Shell Conference on ...' series began in 1985 and meetings are held approximately twice a year. The idea behind the conferences is to bring together invited scientists from both universities and industry, and representatives from different Shell Research laboratories, to create a forum to discuss the future directions of the chosen research area. These meetings have embraced a wide range of topics of interest to Shell Research as a whole. This particular conference, organized by the Analytical Department of the Koninklijke/shell-Laboratorium, Amsterdam (KSLA), was held on 4-6 October, 1987 at Hoenderloo in the Netherlands. The aim was to review the state-of-the-art and to discuss the future of molecular modeling and design. The programme itself consisted of a series of presentations on prescribed topics, panel discussions, and software and hardware demonstrations. Many of the presentations given consisted of overviews, experiences, advice and predictions for the future. The panel sessions, which involved the speakers within that session and a discussion leader who summarised some of the points made in an introduction, encouraged even further discussion and speculation. This overview attempts to catch the flavour of the meeting and convey some personal views that were expressed and conclusions drawn.

Computer Simulation↗

PubMed1993

Evaluation of a monoclonal antibody for detection of varicella-zoster virus infections using a shell vial technique.

Standard cell culture and a shell vial technique using a monoclonal antibody were compared for the detection of varicella-zoster virus in 167 mucocutaneous specimens. Of 75 specimens from patients clinically diagnosed with varicella or zoster, a total of 40 (53.3%) were positive by either method (4 positive only by conventional culture and 4 only by shell vial). No false-positive results were obtained with shell vials stained after 48 h of incubation. This technique is rapid, 100% specific, and should be a good alternative to cell culture. Both techniques are equally influenced by antiviral treatment or by the time of evolution of disease.

Antibodies, Monoclonal↗

PubMed1995

Reward shifts and motor responses following microinjections of opiate-specific agonists into either the core or shell of the nucleus accumbens.

Differences in pharmacology, anatomical connections, and receptor densities between the "core" and "shell" of the nucleus accumbens suggest that behavioral activity normally modulated by the accumbens, such as reward and motor functions, may be differentially regulated across the mediolateral axis. This study investigated the effects of opiate receptor-specific agonists on reward and motor functions in either the accumbens core or shell, using the intracranial self-stimulation (ICSS) rate-frequency curve-shift method. Microinjections of the mu opiate receptor-specific agonist, DAMGO (vehicle, 0.03 nmol, and 0.3 nmol), or the delta opiate receptor-specific agonist DPDPE (vehicle, 0.3 nmol, 3.0 nmol), were administered bilaterally in a random dose order with a minimum of 3 days between injections. Rats were tested over three consecutive 20-min rate-frequency curves immediately following a microinjection to investigate the time course of drug effects. Both opiate agonists decreased the ICSS frequency necessary to maintain half-maximal response rates when injected into the medial and ventral shell region of the accumbens. However, DAMGO microinjections into the lateral accumbens core or the control site of the caudate increased the frequency necessary to elicit half-maximal response rates, while DPDPE microinjections into these regions had no effect. Evaluation of motor effects show that administration of DAMGO resulted in a suppression of activity in all locations. In contrast, DPDPE microinjections resulted in little or no effect on lever pressing activity at any location.

Analgesics↗

PubMed1996

Strukturdifferenzierungen in Y-chromosom von Drosophila hydei: the unique morphology of the Y chromosomal lampbrush loops Threads results from 'coaxial shells' formed by different satellite-specific subregions within megabase-sized transcripts.

The results of pulsed-field gel electrophoresis (PFGE) analysis and two-colour transcript fluorescence in situ hybridization (FISH) for the three Threads-specific DNA satellites YLII, YLI and rally are in support of long-range clustering of these sequence families within the subterminal region on the long arm of the Y chromosome of Drosophila hydei. On the basis of the linear arrangement of at least four extended clusters of satellite-specific sequences, the loop morphology of wild-type and several mutant Threads can be explained by assumption of a single Threads-specific transcription unit comprising about 5.1 Mb of repetitive DNA located between the Pseudonucleolus and the Nucleolus organizer. Transcription is unidirectional from the Pseudonucleolus towards the terminally located Nucleolus organizer. Transcripts most likely start in front of or within the 3.2 Mb region of YLII-related sequences, pass through subsequent blocks of 1.2 and 0.3 Mb of YLI- and rally-related sequences, respectively, and cease within the region of a smaller block of YLI-related repeats. The megabase-sized transcripts remain physically linked to the DNA axis and their extended satellite-specific regions form coaxial clouds or shells around the central DNA axis. In this way each cluster of earlier-transcribed sequences generates a cloud or shell on top of the later-transcribed ones. According to this model of 'satellite-specific coaxial shells' the tube-like morphology and other peculiarities of the Y chromosomal lampbrush loops Threads can be explained as a result of satellite-specific RNA superstructures and/or formation of extended ribonucleoprotein (RNP) complexes between clusters of satellite-specific transcripts and specific proteins. On the basis of this model the specific morphology of several Threads mutants can be interpreted as the result of large interstitial or terminal deletions that alter the total length of the Threads-specific transcription unit without exerting other major effects on principal features of the transcription process along the Threads.

Animals↗

PubMed1992

Zinc deficiency in the rat alters the lipid composition of the erythrocyte membrane Triton shell.

The effect of dietary zinc deficiency on the lipid composition of the erythrocyte membrane Triton shell was determined. Weanling male Wistar rats were fed an egg white-based diet containing < 1.0 mg Zn/kg diet ad libitum. Control rats were either pair-fed or ad libitum-fed the basal diet supplemented with 100 mg Zn/kg diet. A Zn refed group was fed the -Zn diet until day 18 and then pair-fed the +Zn diet until day 21. Dietary Zn deficiency caused an increased cholesterol/phospholipid ratio in Triton shells compared to those from pair-fed controls. Zn deficiency caused a decreased double bond index of fatty acids in phosphatidylinositol (PI) and phosphatidylcholine (PC); there was a decreased proportion of 18:2n-6 and 22:4n-6 in PC and 20:4n-6 in PI as compared to that found in pair-fed controls. All glycerophospholipids that were retained in the shell had a lower double bond index and increased content of 16:0 and/or 18:0 relative to the phospholipid in the intact membrane.

Animals↗

PubMed1991

Thermal decomposition of Lingula shell apatite.

Lingula shell is composed of apatite with a preferred orientation. The shell apatites of Lingula unguis(Lu) and Lingula shantoungensis(Ls) were characterized and compared with apatite of human tooth enamel. Insight into the Lingula apatite was studied by following the change of lattice parameter, transformation to beta-tricalcium phosphate (beta-TCP), and the loss and change of CO3, OH, and H2O after heating up to 1,000 degrees C in air and N2 for 24 hours. The OH stretching band was not observed in unheated apatites and in apatites heated in dried N2. Lu and Ls apatite produced 26 and 17 wt% of beta-TCP at 700 degrees C, respectively. Fifty to 60% of H2O was lost at 200 degrees C, being accompanied by a drastic contraction of the a- and c-axis and a drastic decrease in the crystallinity. These results indicate that (1) Lu and Ls shell apatite is CO3 containing F + Cl-apatite, and (2) the structural H2O of the Lingula apatite is loosely bounded such that they are lost at lower temperature than tooth enamel.

Animals↗

PubMed2006

Doxorubicin release from core-shell type nanoparticles of poly(DL-lactide-co-glycolide)-grafted dextran.

In this study, we prepared core-shell type nanoparticles of a poly(DL-lactide-co-glycolide) (PLGA) grafted-dextran (DexLG) copolymer with varying graft ratio of PLGA. The synthesis of the DexLG copolymer was confirmed by 1H nuclear magnetic resonance (NMR) spectroscopy. The DexLG copolymer was able to form nanoparticles in water by self-aggregating process, and their particle size was around 50 nm approximately 300 nm according to the graft ratio of PLGA. Morphological observations using a transmission electron microscope (TEM) showed that the nanoparticles of the DexLG copolymer have uniformly spherical shapes. From fluorescence probe study using pyrene as a hydrophobic probe, critical association concentration (CAC) values determined from the fluorescence excitation spectra were increased as increase of DS of PLGA. 1H-NMR spectroscopy using D2O and DMSO approved that DexLG nanoparticles have core-shell structure, i.e. hydrophobic block PLGA consisted inner-core as a drug-incorporating domain and dextran consisted as a hydrated outershell. Drug release rate from DexLG nano-particles became faster in the presence of dextranase in spite of the release rate not being significantly changed at high graft ratio of PLGA. Core-shell type nanoparticles of DexLG copolymer can be used as a colonic drug carrier. In conclusion, size, morphology, and molecular structure of DexLG nanoparticles are available to consider as an oral drug targeting nanoparticles.

Administration, Oral↗

PubMed2002

Effects of the chestnut inner shell extract on the expression of adhesion molecules, fibronectin and vitronectin, of skin fibroblasts in culture.

The inner shell of the chestnut (Castanea crenata S. et Z., Fagaceae) has been used as an anti-wrinkle/skin firming agent in East Asia, and preliminary experiments have found that a 70% ethanol extract from this plant material can prevent cell detachment of skin fibroblasts from culture plates. In order to examine the molecular mechanisms underlying this phenomenon, its effects on the expression of adhesion molecules, such as fibronectin and vitronectin, were investigated using the mouse skin fibroblast cell line, NIH/3T3. Using fixed-cell ELISA, Western blotting and immunofluorescence cell staining, it was clearly demonstrated that the chestnut inner shell extract enhanced the expression of the cell-associated fibronectin and vitronectin. Scoparone (6,7-dimethoxycoumarin), isolated from the extract, also possessed similar properties. These findings suggest that the enhanced expression of the adhesion molecules may be one of the molecular mechanisms for how the chestnut inner shell extract preventing cell detachment and may be also responsible for its anti-wrinkle/skin firming effect.

3T3 Cells↗

PubMed2002

Administration of the D1-like dopamine receptor antagonist SCH-23390 into the medial nucleus accumbens shell attenuates cocaine priming-induced reinstatement of drug-seeking behavior in rats.

RATIONALE: A growing literature indicates that increased dopamine transmission in the nucleus accumbens contributes to priming-induced reinstatement of cocaine-seeking behavior. OBJECTIVES: The present experiments were designed to assess the role of D(1)-like dopamine receptors in the nucleus accumbens core and shell subregions in cocaine priming-induced reinstatement of drug seeking. METHODS: Rats were trained to lever press for cocaine using a fixed ratio (FR) 5 schedule of reinforcement. Drug-seeking was measured by active lever presses during daily 2-h sessions. After approximately 30 days of cocaine self-administration, the animals underwent an extinction phase during which cocaine was replaced with saline. Daily extinction sessions were conducted until responding was consistently less than 10% of the response rate maintained by cocaine self-administration. After the extinction phase, priming-induced reinstatement of cocaine-seeking behavior was assessed. RESULTS: Cocaine dose-dependently reinstated cocaine seeking, with robust drug seeking at 10 mg/kg cocaine. Administration of the D(1)-like dopamine receptor antagonist, SCH-23390 (0.1-1.0 micro g), directly into the medial nucleus accumbens shell dose-dependently attenuated drug seeking induced by 10 mg/kg cocaine. Microinjection of 1.0 micro g SCH-23390 into either the nucleus accumbens core or lateral septum had no influence on cocaine-seeking behavior. CONCLUSIONS: These results indicate that stimulation of D(1)-like dopamine receptors in the medial nucleus accumbens shell contributes to drug-induced reinstatement of cocaine-seeking behavior.

Animals↗

PubMed2005

Effects of intra-nucleus accumbens shell administration of dopamine agonists and antagonists on cocaine-taking and cocaine-seeking behaviors in the rat.

RATIONALE: Dopamine signaling in the nucleus accumbens (NAc) plays an important role in regulating drug-taking and drug-seeking behaviors, but the role of D(1)- and D(2)-like receptors in this regulation remains unclear. OBJECTIVES: Our objective was to study the role of NAc D(1)- and D(2)-like receptors in the reinstatement of cocaine-seeking behavior and the regulation of stabilized cocaine intake in rats. METHODS: Using a within-session reinstatement procedure, whereby animals self-administer cocaine (90 min) and extinguish responding (150 min) in a single session, we assessed the ability of NAc microinfusions of the D(1) agonist SKF 81297 and the D(2) agonist 7-OH-DPAT to reinstate extinguished cocaine seeking. The effects of the D(1) antagonist SCH 23390 and the D(2) antagonist eticlopride pretreatment on agonist- and cocaine-primed reinstatement were also measured. Similar agonist and antagonist treatments were tested for their ability to modulate stabilized cocaine and sucrose self-administration. RESULTS: Intra-NAc infusions of either SKF 81297 (0.3-3.0 microg) or 7-OH-DPAT (1.0-10.0 microg) dose-dependently reinstated cocaine seeking with greater efficacy in the medial core than in the shell subregion and at doses that also stimulated locomotor behavior. Intra-NAc shell infusions of SCH 23390 (1.0 microg) and eticlopride (3.0-10.0 microg) blocked cocaine-primed reinstatement (2.0 mg/kg, i.v.) and indiscriminately blocked reinstatement induced by either intra-NAc D(1) or D(2) agonists. Doses of agonists that triggered reinstatement failed to alter stabilized cocaine intake, whereas doses of antagonists that blocked reinstatement increased cocaine intake in the shell. CONCLUSIONS: Both D(1) and D(2) receptors in the NAc play a prominent, and perhaps cooperative, role in regulating cocaine-taking and cocaine-seeking behaviors.

Animals↗

PubMed2006

Facilitated extinction of appetitive instrumental conditioning following excitotoxic lesions of the core or the medial shell subregion of the nucleus accumbens in rats.

The nucleus accumbens has been implicated in the control of goal-directed behaviour, including instrumental conditioning. Here, we evaluated the effect of N-methyl-D: -aspartate (NMDA)-induced excitotoxic lesions restricted to either the core or the medial shell subregions of the nucleus accumbens (NAC) on extinction in rats using a trial discrete fixed ratio-5 (FR-5) appetitive operant procedure. Neither core nor shell lesions of the NAC affected the acquisition of instrumental responding. Both lesions facilitated the cessation of responding when the instrumental act no longer yielded reinforcement. Our results suggest that both the NAC core and medial shell contribute to the control of extinction learning of appetitively motivated instrumental behaviour.

Analysis of Variance↗

PubMed1997

Rock-shells (Thais clavigera) as an indicator of As, Cu, and Zn contamination on the Putai Coast of the black-foot disease area in Taiwan.

This study presents the distribution of arsenic (As), copper (Cu), and zinc (Zn) in various seafoods-oysters (Crassostrea gigas), false fusus (Hemifuscus tuba), venus clams (Cyclina sineasis), green mussels (Perna viridis), blood clams (Arca granosa), flounders (Psettodes erumei), and rock-shells (Thais clavigera) collected from the Putai coast of the black-foot disease (BFD) area in Taiwan. Special attention is paid to evaluate the relationships among As, Cu, and Zn and effect of body size on metal concentration in Thais clavigera. Maximum Zn and Cu geometric mean (GM) concentrations (GM = 615 and 376 microg/g, dry wt, respectively) are found in oysters (Crassostrea gigas), and the values are much higher than those of the other organisms by about 1.7-208 and 1.8-375 times, respectively. Similarly, Thais clavigera has a high capacity for accumulating Cu and Zn collected from the same location. One interesting point is that relatively high As concentrations (GM = 65.7 microg/g, dry wt) in Thais clavigera are found as compared with those in other organisms (range from GM = 2.37 to 40.2 microg/g, dry wt). The As concentrations are significantly higher in Thais clavigera (1.62-27.7 times) than those in other organisms (p < 0.05), except for the false fusus (Hamifuscus tuba). A linear regression analysis shows a significant increase in Zn concentration with increasing Cu concentration in Thais clavigera. On the other hand, the As concentration is correlated with Cu and Zn concentrations (r = 0.77 and 0.77, respectively; p < 0.05) in Thais clavigera. Double logarithmic plots of metal content and concentration against dry-body weight and shell length show linear relationships. The result indicates that large individuals have higher contents of Cu, Zn and As, and have slopes of 1.58, 1.38, and 1.34, respectively. In addition, metal concentrations against shell length for all animal sizes also indicate that Cu, Zn and As have slopes of 1.92, 1.18, and 1.11, respectively. In conclusion, Thais clavigera has a high capactiy for accumulating As, Cu, and Zn and is a potential bioindicator for monitoring As, Cu and Zn.

Animals↗

PubMed2005

Effects of hypoxic and osmotic stress on the free D-aspartate level in the muscle of blood shell Scapharca broughtonii.

Blood shell, Scapharca broughtonii, contains large quantities of free D-aspartate comparable to free L-aspartate in its tissues. When the shell was reared in hypoxic seawater, D-aspartate as well as L-aspartate in the foot muscle decreased rapidly, and their total level became about one-fourth within 24 hr. None of the other amino acids examined showed a similar behavior, but many of them rather increased during the same period. The increase in L-alanine was especially remarkable and was almost equal to the sum of the decrease in aspartate enantiomers. When the shell that had been acclimated to hypoxic seawater for 96 hr was transferred to normoxic seawater, all the amino acid levels mostly returned to the control levels within 96 hr. In contrast to these effects of hypoxic stress, hyperosmotic stress of 150% seawater had no effect on the D- and L-aspartate levels in the same tissue. These results suggest that D-aspartate is involved in anaerobic energy metabolism of this bivalve as well as L-aspartate, whose vital role in anoxia-tolerant bivalves is well known.

Animals↗

PubMed2002

Isolation and characterization of 2-nitroimidazole produced by Streptomyces species as an inhibitor of both carbonic anhydrase and shell formation in the barnacle Balanus amphitrite.

Carbonic anhydrase is thought to be involved in the process of calcium carbonate deposition in calcified tissues of many organisms. Barnacles form hard calcified shells for protection against predation, and represent a class of marine-fouling animals. In order to inhibit barnacle growth by inhibiting shell formation, we searched for carbonic anhydrase inhibitors from microbial secondary metabolites. A simple assay for assessing carbonic-anhydrase-inhibiting activity was developed. Screening of many microorganisms isolated from soil with this assay resulted in a microbial strain that produced a carbonic anhydrase inhibitor. This strain was identified as Streptomyces eurocidicus mf294. The inhibitor was isolated through 4 purification steps and identified as 2-nitroimidazole on the basis of spectroscopic data. 2-Nitroimidazole inhibited barnacle carbonic anhydrase dose-dependently and complete inhibition was reached at the concentration of 1 x 10(-5) M. 2-Nitroimidazole did not affect settlement or metamorphosis of barnacle larvae, but inhibited shell formation at concentrations higher than 1 x 10(-4) M. These findings strongly support the idea that carbonic anhydrase is involved in calcification.

Journal Article↗

PubMed2006

Biphasic and dually coordinated expression of the genes encoding major shell matrix proteins in the pearl oyster Pinctada fucata.

Regional expression patterns of shell matrix protein genes of Pinctada fucata were investigated using real-time quantitative polymerase chain reaction (PCR) and in situ hybridization. Six shell matrix proteins examined in this study indicated a distinct biphasic pattern of expression, falling into one of the following three groups: (1) expressed only in the more dorsal region of the mantle (MSI60 and N16); (2) expressed only in the more ventral region (MSI31, Prismalin-14, and Aspein); and (3) expressed in both regions (nacrein). The ubiquity of the last protein probably reflects its general role as a carbonate-producing enzyme, while the other groups are interpreted as corresponding to the distinction between the two varieties of shell layers, the aragonitic nacreous layer and the calcitic prismatic layer. In addition, the constituent genes of each of these two groups indicated similar levels of relative expression among different sites even among different individuals, suggesting that the genes of each group share a single upstream regulatory factor, respectively, and that these genes are expressed in a dually coordinated fashion.

Animal Structures↗

PubMed1984

Dielectric analysis of mitochondria isolated from rat liver. II. Intact mitochondria as simulated by a double-shell model.

The dielectric dispersion of isolated intact mitochondria in suspension has been measured between 10 kHz and 500 MHz. In isotonic KCl media at 4 degrees C, the mitochondria maintained their characteristic 'double membrane' structure as examined by electron microscopy, and the observed dispersion curves were successfully simulated in terms of a superposition of two sub-dispersions having different characteristic frequencies and different permittivity magnitudes. Taking these observations into account we analyzed the dispersion data on the basis of a 'double-shell' model in which two concentric shells are meant to represent the mitochondrial outer and inner membranes. The analyses by a computerized curve-fitting method revealed that: (i) electric capacities for the outer and the inner membrane are 1.7 and 0.5 microF/cm2, respectively, (ii) relative permittivity for the inner compartment (or the equivalent homogeneous matrical space) = 50-60, (iii) outer compartment-to-external conductivity ratio = 0.4-0.6, and (iv) inner compartment-to-external conductivity ratio = 0.14. The implications of these parameter values are discussed with due attention paid to the limitations inherent in our 'double-shell' model approach.

Animals↗

PubMed1987

Passive electrical properties of the membrane and cytoplasm of cultured rat basophil leukemia cells. I. Dielectric behavior of cell suspensions in 0.01-500 MHz and its simulation with a single-shell model.

Frequency dependence of relative permittivity (dielectric constant) and conductivity, or the 'dielectric dispersion', of cultured cells (RBL-1 line) in suspension was measured using a fast impedance analyzer system capable of scanning 92 frequency points over a 10 kHz-500 MHz range within 80 s. Examination of the resulting dispersion curves of an improved reliability revealed that the dispersions consisted of at least two separate components. The low-frequency component (dispersion 1) had a permittivity increment (delta epsilon) of 10(3)-10(4) and a characteristic frequency (fc) at several hundred kHz; for the high-frequency component (dispersion 2), delta epsilon was smaller by a factor of 10(2) and fc = 10-30 MHz. Increments delta epsilon for both components increased with the volume fraction of cell suspension, while fc did not change appreciably as long as the conductivity of suspending medium was fixed. By fitting a model for shelled spheres (the 'single-shell' model) to the data of dispersion 1, the dielectric capacity of the plasma membrane phase (Cm) was estimated to be approx. 1.4 microF/cm2 for the cells in an isotonic medium. However, simulation by this particular shell model failed to reproduce the entire dispersion profile leaving a sizable discrepancy between theory and experiment especially at frequencies above 1 MHz where dispersion 2 took place. This discrepancy could not be filled up even by taking into consideration either the effect of cell size distribution actually determined or that of possible heterogeneity in the intracellular conductivity. The present data strongly indicate the need for a more penetrating model that effectively accounts for the behavior of dispersion 2.

Animals↗

PubMed1987

A novel method for obtaining poliovirus 14 S pentamers from procapsids and their self-assembly into virus-like shells.

Poliovirus procapsids, isolated and partially purified from infected HeLa cells, were found to dissociate into 14 S pentamers following freezing at -20 degrees overnight. Unlike pentameric subunits isolated directly from virus-infected cells or those obtained by alkaline treatment of procapsids, the "freeze-dissociated" subunits self-assembled at room temperature into two kinds of empty capsids, one of which was similar to the shell of poliovirions as shown by its neutral pl, resistance to alkaline dissociation, and the presence of neutralization-related (N) epitopes. The other empty shell resembled that which was previously described as a self-assembled empty capsid (SAEC), as indicated by its acidic pl and absence of N antigenic determinants. At 37 degrees, the assembly reaction was significantly faster but only SAEC were formed. By following the assembly reaction by electron microscopy, intermediate structures were visualized; their relatively low amount at any given time was consistent with the previous hypothesis (J.R. Putnak and B.A. Phillips (1981), J. Virol. 40, 173-183) that initiation is the rate-limiting step in the morphogenesis of empty shells. The relevance of these findings to the morphogenesis of picornaviruses, and polioviruses in particular, is discussed.

Capsid↗