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PubMed1980

Effect of shape on pressure-volume relationships of ellipsoidal shells.

Previous theoretical procedures for determining the slope and intercept of the stiffness-stress relationship of the passive myocardium from diastolic pressure-volume (P-V) data assume that the eccentricity of the left ventricle (LV) is invariant. In this study a mathematical model for an ellipsoidal membrane was developed that does not contain that constraint. The model predicts a small (less than 10%) but significant decrease in eccentricity as transmural pressure increases. This result was confirmed by the use of a thick-wall finite element model. The implications of this result are as follows. 1) The slope and intercept of the stiffness-stress relationship of unconstrained ellipsodial shells can be determined by fitting a spherical model to the P-V relationships exhibited by the shells. 2) An ellipsoidal model that assumes that the eccentricity of such shells is invariant for all pressures would predict erroneous intercepts. 3) If the eccentricity of the diastolic LV initially decreases relative to its value at zero transmural pressure, then a thick-wall spherical model may be adequate for determining the slope and intercept of the myocardial stiffness-stress relationship.

Compliance↗

PubMed1992

Presynaptic dopamine D1 receptors attenuate excitatory and inhibitory limbic inputs to the shell region of the rat nucleus accumbens studied in vitro.

1. Intracellular recordings were made from the shell region of the nucleus accumbens in an in vitro slice preparation. The mean resting membrane potential, input resistance, and action potential amplitude of these neurons were -76 +/- 1 mV, 87 +/- 5 M omega and 94 +/- 2 mV (N = 108), respectively. A sample of these neurons (N = 18) was identified as medium spiny neurons with the use of the biocytin-avidin labeling technique. 2. Electrical stimulation of the fornix, subcortical fibers, or neuropil within the nucleus accumbens shell itself elicited a depolarizing postsynaptic potential (PSP). Dopamine (10-100 microM) attenuated PSPs elicited by stimulation of all of these sites. In a paired-pulse stimulation protocol, dopamine was observed to enhance the facilitation of the test response with respect to the conditioning response. 3. The suppressive effect of dopamine was mimicked by the D1 receptor agonist SKF 82958 (10-30 microM), whereas the D2 receptor agonist quinpirole (10-30 microM) was ineffective. The action of dopamine was antagonized by the D1 receptor antagonist Sch 23390 (10-30 microM), but not by the D2 receptor antagonist sulpiride (10-50 microM) or various adrenergic receptor antagonists. 4. The PSP was usually composed of an excitatory postsynaptic potential (EPSP)-inhibitory postsynaptic potential (IPSP) sequence. Dopamine equally attenuated the excitatory and inhibitory component of the synaptic response. The attenuation of both EPSP and IPSP did not depend on membrane potential. 5. Dopamine effects on the resting membrane potential and input resistance were variable and did not correlate with changes in the PSP. Two further indications were found in favor of a presynaptic locus of dopaminergic modulation. First, the time course of the PSP was not altered during dopamine application. Second, dopamine did not attenuate depolarizations induced by bath-applied L-glutamate. In extracellular recordings, it was found that dopamine reduced the population spike but not the presynaptic fiber volley. 6. These findings strongly indicate that dopaminergic modulation of synaptic responses in neurons located in the accumbens shell region is mediated by presynaptic D1 receptors. Notably, dopamine does not exert a purely inhibitory effect on synaptic excitability in the nucleus accumbens, because it suppresses both the excitatory and inhibitory component of the synaptic response.

Afferent Pathways↗

PubMed2000

How a Turtle's Shell Helps It Survive Prolonged Anoxic Acidosis.

Anoxic turtles accumulate high levels of lactate in blood. To avoid fatal acidosis, turtles exploit buffer reserves in their large mineralized shell. The shell acts by releasing calcium and magnesium carbonates and by storing and buffering lactic acid. Together with profound metabolic depression, shell buffering permits survival without oxygen for several months at 3 degrees C.

Journal Article↗

PubMed2002

Active immunization against nicotine suppresses nicotine-induced dopamine release in the rat nucleus accumbens shell.

BACKGROUND: Tobacco smoking is the largest preventable cause of morbidity and premature mortality in the world. Although its medical consequences are well documented, 20-50% of the population even in developed countries remain tobacco smokers. The drugs presently used in smoking cessation have limited efficiency and, therefore, there is a need for alternative and improved treatments. One novel approach in this regard may be provided by immunization against nicotine. OBJECTIVE: The present study in male Wistar rats investigated if active immunization with a novel nicotine immunogen, IP18-KLH, may generate nicotine-selective antibodies and, furthermore, whether this treatment might prevent nicotine from exerting its stimulating effect on the mesolimbic, dopaminergic reward system in the brain. METHODS: Enzyme-linked immunosorbent assay (ELISA) was used to determine the titer of nicotine antibodies in plasma after immunization with IP18-KLH in Freund's adjuvant. Competitive ELISA was used to assess the selectivity of the antibodies. Finally, we used in vivo voltammetry to investigate whether active immunization with IP18-KLH could prevent nicotine-induced dopamine release in the shell of nucleus accumbens (NAC(shell)). RESULTS: The present study shows that active immunization with IP18-KLH generates antibodies that are highly selective for nicotine. Furthermore, immunization with IP18-KLH prevented the nicotine-induced increase in dopamine release in the NAC(shell), a biochemical correlate to the rewarding properties of nicotine. CONCLUSIONS: Active immunization with IP18-KLH prevents a central effect of nicotine that is considered critical for the induction of nicotine dependence. Consequently, active immunization may provide long-term protection against initiation of tobacco dependence, an effect that may prove particularly advantageous in relapse prevention.

Animals↗

PubMed1980

Does rice ragged stunt virus lack the typical double shell of the Reoviridae?

In rice ragged stunt virus preparations negatively stained with uranyl acetate, particles corresponding to the B-spiked subviral particles (SPVs) but not the double-shelled virions of fijiviruses were seen. The B spikes were broader at the base than those of fijiviruses, but otherwise the particles were similar in size and shape to fijivirus SVPs. In thin sections of infected plants, large numbers of virus-like particles were seen; most resembled the SVPs of fijiviruses but some appeared intermediate between these and complete fijivirus particles. It seems likely that rice ragged stunt virus does not produce a regular outer shell as do the fijiviruses, although the broad-based B spikes may in some profiles have given the appearance of a continuous shell.

Oryza↗

PubMed1983

Separate examinations on core and shell of urinary calculi.

Separate core and shell examinations were made on 10,000 urinary stones using a combined crystal-optical X-ray diffractometric method of analysis. 29.5% of these concrements showed differences in qualitative phases between central and peripheral stone parts. All the more frequent stone components were found in core and shell to the same extent. Only weddellite and uric acid dihydrate show a clear preference of the shell. Our method of analysis showed cores to be mostly monomineralic and peripheral stone parts mostly bimineralic. Consequences of this topographic stone analysis for metaphylaxis of urolithiasis are pointed out.

Apatites↗

PubMed2005

Template guided self-assembling two-dimensional array of Au@SiO2 core-shell nanoparticles for room-temperature single electron transistors.

The composite nanoparticles of a gold core capped by a SiO2 shell with well-controlled thickness have been synthesized and fabricated into two-dimensional array on silicon surface by a simple self-assembly method combined with an AFM nanolithography technique. Current-voltage measurements of the Au@SiO2 composite nanoparticles (shell thickness of 6 nm) show a well-pronounced Coulomb staircase with a period of 300 mV at room temperature, demonstrating single electron transistor behavior. The step width of the Coulomb staircase can be tuned by controlling the thickness of SiO2 shell. The tunable single electron tunneling properties make the 2D array of Au@SiO2 composite nanoparticles an ideal candidate for planar single electron transistor devices.

Colloids↗

PubMed2005

Phase transfer identification of core-shell structures in Ag-Au bimetallic nanoparticles.

The difference between the transfer of poly(vinylpyrrolidone)-protected Au and Ag nanoparticles from an aqueous solution to toluene was used to develop a simple experimental procedure that can positively identify the formation of bimetallic Ag-Au nanoparticles with the core-shell structure. The method was validated by UV-visible spectroscopy, EDX, and TEM measurements. Using this technique, we have found that core-shell nanoparticles of Ag-Au were formed by the seed-mediated growth method using Ag nanoparticles as the seeds. The reversed order of using Au nanoparticles as the seeds, on the contrary, could only produce a physical mixture of Ag-Au core-shell nanoparticles and isolated Ag nanoparticles.

Gold↗

PubMed2006

Sol-gel fabrication and photoluminescence properties of SiO2 @ Gd2O3:Eu3+ core-shell particles.

A uniform nanolayer of europium-doped Gd2O3 was coated on the surface of preformed submicron silica spheres by a Pechini sol-gel process. The resulted SiO2 @ Gd2O3:Eu3+ core-shell structured phosphors were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), photoluminescence (PL) spectra as well as kinetic decays. The XRD results show that the Gd2O3:Eu3+ layers start to crystallize on the SiO2 spheres after annealing at 400 degrees C and the crystallinity increases with raising the annealing temperature. The core-shell phosphors possess perfect spherical shape with narrow size distribution (average size: 640 nm) and non-agglomeration. The thickness of the Gd2O3:Eu3+ shells on the SiO2 cores can be adjusted by changing the deposition cycles (70 nm for three deposition cycles). Under short UV excitation, the obtained SiO2@Gd2O3:Eu3+ particles show a strong red emission with 5D0-7F2 (610 nm) of Eu3+ as the most prominent group. The PL intensity of Eu3+ increases with increasing the annealing temperature and the number of coating cycles.

Crystallization↗

PubMed2006

Synthesis and characterization of stable iron-iron oxide core-shell nanoclusters for environmental applications.

Iron-iron oxide core-shell nanoclusters are of great interest due to their potential applications as a remedy for environmental contamination. We report the room-temperature synthesis of core-shell iron-iron oxide nanoclusters using our novel cluster deposition system. Various types of measurements such as Transmission Electron Microscopy, X-ray Diffraction, X-ray Photon Spectroscopy, and Electron Energy Loss Spectroscopy are conducted in characterizing nanoclusters. Stable, monodispersive iron-iron oxide core-shell nanocrystals are identified.

Ferric Compounds↗

PubMed2004

Challenges and recent developments in hearing aids. Part II. Feedback and occlusion effect reduction strategies, laser shell manufacturing processes, and other signal processing technologies.

This is the second part of a review on the challenges and recent developments in hearing aids. Feedback and the occlusion effect pose great challenges in hearing aid design and usage. Yet, conventional solutions to feedback and the occlusion effect often create a dilemma: the solution to one often leads to the other. This review discusses the advanced signal processing strategies to reduce feedback and some new approaches to reduce the occlusion effect. Specifically, the causes of three types of feedback (acoustic, mechanical, and electromagnetic) are discussed. The strategies currently used to reduce acoustic feedback (i.e., adaptive feedback reduction algorithms using adaptive gain reduction, notch filtering, and phase cancellation strategies) and the design of new receivers that are built to reduce mechanical and electromagnetic feedback are explained. In addition, various new strategies (i.e., redesigned sound delivery devices and receiver-in-the-ear-canal hearing aid configuration) to reduce the occlusion effect are reviewed. Many manufacturers have recently adopted laser shell-manufacturing technologies to overcome problems associated with manufacturing custom hearing aid shells. The mechanisms of selected laser sintering and stereo lithographic apparatus and the properties of custom shells produced by these two processes are reviewed. Further, various new developments in hearing aid transducers, telecoils, channel-free amplification, open-platform programming options, rechargeable hearing aids, ear-level frequency modulated (FM) receivers, wireless Bluetooth FM systems, and wireless programming options are briefly explained and discussed. Finally, the applications of advanced hearing aid technologies to enhance other devices such as cochlear implants, hearing protectors, and cellular phones are discussed.

Acoustics↗

PubMed2006

Shell Vial Culture assay for the rapid diagnosis of Japanese encephalitis, West Nile and Dengue-2 viral encephalitis.

BACKGROUND: Encephalitis caused by flaviviruses, Japanese encephalitis virus (JEV) and West Nile virus (WNV) is responsible for significant morbidity and mortality in many endemic countries. Dengue-2 (Den-2) virus is a recent addition to the list of encephalitogenic viruses, after its Central Nervous System (CNS) invasion capability has been established. There is a wide array of laboratory tools that have helped us not only in the diagnosis of these conditions but also in understanding their pathogenesis and pathology. However, there are no reports of Shell Vial Culture (SVC), a centrifuge enhanced tissue culture assay that has revolutionized viral culturing in terms of rapidity and sensitivity being optimized for these flaviviral encephalitic conditions. The present study is an attempt to standardize and evaluate the usefulness of SVC for the laboratory diagnosis of JE, WN and Den-2 encephalitis cases and to compare it with Indirect Immunofluorescence (IIF) technique that detects cell associated virus antigen. Analysis of the various clinical parameters with respect to viral etiology has also been carried out. RESULTS: Pediatric patients constituted the major group involved in the study (92%). Etiological diagnosis of viral encephalitis could be established in twenty nine (58%) patients. JE encephalitis was the commonest with 19 (39%) cases being positive followed by, WN (9 cases-18%) and Den-2 (one case). IIF test could detect antigens of JE, WN and Den-2 viruses in 16(32%), 7(14%) and 1 case respectively. Shell vial culture assay picked up all cases that were positive by IIF test. In addition, SVC assay could detect 3 and 2 more cases of JE and WN encephalitis respectively, that were negative by the IIF test. CONCLUSION: Shell vial culture is a rapid and efficient tool for the etiological diagnosis of JE, WN and Den-2 encephalitis cases. Early, prompt collection, transport and processing of the CSF samples, would make SVC a better method for the rapid diagnosis of these flaviviral infections.

Adolescent↗

PubMed1976

Control of shell settling in the swimming sea anemone Stomphia coccinea.

1. Electrical activity has been recorded from Stomphia coccinea during the behavioural sequence in which the detached anemone settles on to a Modiolus shell. 2. When a responsive tentacle contacts the shell, a short, complex burst of pulses is elicited. These remain confined to the region of contact. The endodermal slow-conduction system (SS2) then begins to fire repetitively (a typical example is 16 SS2 pulses at a mean interpulse interval of 5 s) until the pedal disc begins to inflate. Shell-tentacle contact is essential for stimulation of SS2 activity. 3. The complete response, apart from local bending of the column, may be reproduced by electrical stimulation of the SS2 alone. As few as 10 stimuli at frequencies between 1 shock/s and 1 shock/10 s are required to elicit the response.

Action Potentials↗

PubMed2002

[Preparation and evaluation of press-coated aminophylline tablet using crystalline cellulose and polyethylene glycol in the outer shell for timed-release dosage forms].

In an attempt to achieve chronopharmacotherapy for asthma, press-coated tablets (250 mg), which contained aminophylline in the core tablet in the form of low-substituted hydroxypropylcellulose (L-HPC) and coated with crystalline cellulose (PH-102) and polyethylene glycol (PEG) at various molecular weights and mixing ratios in the amounts of PH-102 and PEG as the outer shell (press-coating material), were prepared (chronopharmaceutics). Their applicability as timed-release (delayed-release) tablets with a lag time of disintegration and a subsequent rapid drug release phase was investigated. Various types of press-coated tablets were prepared using a tableting machine, and their aminophylline dissolution profiles were evaluated by the JP paddle method. Tablets with the timed-release characteristics could be prepared, and the lag time of disintegration was prolonged as the molecular weight and the amount of PEG, for example PEG 500,000, in the outer shell were increased. The lag time of disintegration could be controlled by the above-mentioned method, however, the pH of the medium had no effect on disintegration of the tablet and dissolution behavior of theophylline. The press-coated tablet (core tablet:aminophylline 50 mg, L-HPC and PEG 6000; outer shell:PH-102:PEG = 8:2 200 mg) with the timed-release characteristics was administered orally to rabbits for an in vivo test. Theophylline was first detected in plasma more than 2 h after administration; thus, this tablet showed a timed-release characteristics in the gastrointestinal tract. The time (tmax) required to reach the maximum plasma theophylline concentration (Cmax) observed after administration of the press-coated tablet was significantly (p < 0.05) delayed compared with that observed after administration of aminophylline solution in the control experiment. However, there was no difference in Cmax and area under the plasma theophylline concentration-time curve (AUC0-->24) between the press-coated tablet and aminophylline solution. These results suggest that the press-coated aminophylline tablet (with the timed-release characteristic) offers a promising forms of theophylline chronotherapy for asthma.

Aminophylline↗

PubMed2006

Identification of polyoma BK virus in kidney transplant recipients by shell vial cell culture assay and urine cytology.

Urine cytology often is used to identify BK virus in kidney transplant recipients in the cytology laboratory. To assess the usefulness of the shell vial cell culture assay to identify BK virus, urine samples from 42 kidney transplant recipients were tested by the urine cytology and shell vial cell culture assays. The shell vial cell culture assay is just as sensitive and specific as urine cytology for the identification of BK virus in kidney transplant recipients.

Antigens, Viral, Tumor↗

PubMed2003

Expression profiles of PER2 immunoreactivity within the shell and core regions of the rat suprachiasmatic nucleus: lack of effect of photic entrainment and disruption by constant light.

The circadian clock cells of the mammalian suprachiasmatic nucleus (SCN) generate oscillations in physiology and behavior that are synchronized (entrained) by the external light/dark (LD) cycle. The mechanisms that mediate the effect of light on the core molecular mechanism of the clock are not well understood, but evidence suggests that the Period2 gene, which encodes a key clock regulator (PER2), might be involved. We assessed the expression of PER2 immunoreactivity in the retinorecipient core and shell compartments of the SCN of rats entrained to cycles of discrete light pulses presented at the early subjective day (dawn) or night (dusk), or housed in constant light. We found that in animals entrained to a 0.5 h:23.5-h LD cycle (light falls near dawn), PER2 expression is rhythmic both in the shell and in the core regions of the SCN and indistinguishable from that seen in the SCN of control rats housed in complete darkness. Similarly, the pattern of PER2 expression in the SCN of rats entrained to a 0.5-h:25.5-h LD cycle (light falls near dusk) resembled that in dark-housed controls. We also found that presentation of a discrete light pulse in the early subjective night did not induce PER2 protein expression in the SCN, even 6 h after photic stimulation. Finally, in constant light-housed, behaviorally arrhythmic rats, PER2 expression in the SCN was low and nonrhythmic. These results show that rhythmic PER2 expression occurs both in the shell and core regions of the rat SCN. Furthermore, they show that the expression of PER2 in the SCN is not regulated by entraining light. Finally, constant light-induced behavioral arrhythmicity is associated with a disruption of rhythmic PER2 expression in the whole SCN. Together, the results are consistent with a proposed role for PER2 in the core mechanism of the circadian clock but argue against an important role for PER2 in the mechanism mediating photic entrainment.

Animals↗

PubMed2006

Decomposition of protein experimental compressibility into intrinsic and hydration shell contributions.

The experimental determination of protein compressibility reflects both the protein intrinsic compressibility and the difference between the compressibility of water in the protein hydration shell and bulk water. We use molecular dynamics simulations to explore the dependence of the isothermal compressibility of the hydration shell surrounding globular proteins on differential contributions from charged, polar, and apolar protein-water interfaces. The compressibility of water in the protein hydration shell is accounted for by a linear combination of contributions from charged, polar, and apolar solvent-accessible surfaces. The results provide a formula for the deconvolution of experimental data into intrinsic and hydration contributions when a protein of known structure is investigated. The physical basis for the model is the variation in water density shown by the surface-specific radial distribution functions of water molecules around globular proteins. The compressibility of water hydrating charged atoms is lower than bulk water compressibility, the compressibility of water hydrating apolar atoms is somewhat larger than bulk water compressibility, and the compressibility of water around polar atoms is about the same as the compressibility of bulk water. We also assess whether hydration water compressibility determined from small compound data can be used to estimate the compressibility of hydration water surrounding proteins. The results, based on an analysis from four dipeptide solutions, indicate that small compound data cannot be used directly to estimate the compressibility of hydration water surrounding proteins.

Algorithms↗

PubMed1998

Is the caudomedial shell of the nucleus accumbens part of the extended amygdala? A consideration of connections.

The conceptual origins of two forebrain functional-anatomical systems, the ventral striatopallidum and extended amygdala, are reviewed briefly, and reductionist and constructionist doctrines pertaining to descriptions of forebrain organization are generally discussed briefly. The cortical, subcortical, and intrinsic connectional relationships of the caudomedial shell of the nucleus accumbens, an anomalous component of the ventral striatopallidum, are compared with those of the extended amygdala, leading to an attempt to formulate an assessment as to the extent to which the caudomedial shell might actually be regarded as a part of extended amygdala, or a transitional structure with a capacity to bridge extended amygdaloid and striatal mechanisms. The relatively distinct intrinsic circuitries and different outputs of the two are noted. Extended amygdala projects most strongly to the posterior half of the lateral hypothalamus and brainstem autonomic effector sites. Caudomedial shell and ventromedial ventral pallidum project throughout the lateral preoptico-lateral hypothalamic continuum and are major components in a basal ganglia-thalamocortical pathway to the prefrontal cortex. It is concluded that connectional features distinguishing the caudomedial shell/ventromedial ventral pallidum and extended amygdala are of sufficient magnitude that the two should most usefully be regarded as separate, interacting functional-anatomical entities.

Afferent Pathways↗