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PubMed1998

Acoustic modeling of shell-encapsulated gas bubbles.

Existing theoretical models do not adequately describe the scatter and attenuation properties of the ultrasound contrast agents Quantison and Myomap. An adapted version of the Rayleigh-Plesset equation, in which the shell is described by a viscoelastic solid, is proposed and validated for these agents and Albunex. The acoustic transmission and scattering are measured in the frequency band from 1-10 MHz. The measured transmission is used to estimate two parameters, the effective bulk modulus, Keff, describing the elasticity, and the friction parameter, SF, describing the viscosity of the shell. For the scattering, the difference between measurements and calculations is < 3 dB. For Quantison, the effective bulk modulus is independent of the bubble diameter. For Albunex, it increases for decreasing bubble diameter. The nonlinear response of Quantison is minimal for acoustic pressures up to 200 kPa. For acoustic pressures above 200 kPa, the measured scattering abruptly increases. This increase reaches a level of 20 dB for an acoustic pressure of 1.8 MPa. This response cannot be predicted by the theoretical model developed in this article.

Albumins↗
PubMedDate not supplied

Dynamical assessment of the accretionary record in the shell of the mussel Semimytilus algosus from a rocky shore in Chile.

Patterns of tidal microgrowth bands present in acetate peels of shell sections of the Chilean mussel Semimytilus algosus from three tidal levels on a wave-exposed shore were analyzed for the presence of recurring periodicities using numerical tools derived from signal nonlinear analysis. Both chaotic and coherent structure were found within the microgrowth pattern record, with mussels from the middle and lower tidal zones displaying a coherent structure to the patterns, whilst those from the upper tidal level displayed a chaotic banding pattern with a strong tidal component. It is suggested that because mussels in the upper tidal zone are subject to a wider suite of environmental conditions they are influenced by the spring-neap lunar tidal cycle to a greater extent than those growing in the mid to low tidal zone and display deterministic chaotic growth. This allows the mussels to grow continuously in the highly variable conditions that prevail in the upper tidal zone without continuous interruptions to shell deposition.

Animals↗
PubMed2000

Calcium binding constituents of the organic shell matrix from the freshwater snail Biomphalaria glabrata.

The Ca2+ binding of an EDTA-free water-soluble (SM) and -insoluble (IM) organic matrix of the freshwater snail Biomphalaria glabrata was investigated, using a 45Ca2+ autoradiography after SDS-electrophoretical separation and a calcium binding assay. Electrophoresis of the SM showed a considerable amount of Alcian blue and Stains all positive material, regarded as glycosaminoglycans (GAGs) or proteoglycans (PGs). This part of the SM was slightly positive after 45Ca2+ autoradiography at pH 6.8. The Ca2+ binding increased, raising the pH to 7.4 and 8.0 and was especially strong when simulating the real conditions of the extrapallial space with a carbonate buffer of pH 7.4. The Ca2+ binding assay of the IM showed the same pH-dependency that was observed in the SM. The titration of the IM with Ca2+ at pH 8.0 lead to a dissociation constant of 7.5 x 10(-5) M. While Mg2+ displaced 45Ca2+ in the same way as nonradioactive Ca2+, an approximately 400-fold amount of Na+ was necessary to reduce the binding of 45Ca2+ to 50%. The Ca2+ binding of the organic matrix from the B. glabrata shell appears to be a process of low specificity, medium affinity and high pH-dependency. Apparently, acidic carbohydrate-rich PGs are the only calcium binding constituents of the organic shell matrix.

Animals↗
PubMed2001

Hippocampal and cortical sensory gating in rats: effects of quinpirole microinjections in nucleus accumbens core and shell.

Sensory processing disturbances, as measured in the P50/sensory gating paradigm, have been linked to aberrant auditory information processing and sensory overload in schizophrenic patients. In this paradigm, the response to the second of paired-click stimuli is attenuated by an inhibitory effect of the first stimulus. Sensory gating has been observed in most healthy human subjects and normal laboratory rats. Because mesolimbic dopamine has been implicated in other filtering disturbances such as prepulse inhibition of the acoustic startle response and given the fact that amphetamine and apomorphine have been shown to disrupt gating, this study was performed to investigate the role of mesolimbic dopamine in sensory gating. The dopamine D2 receptor agonist quinpirole (10 microg/0.5 microl) was injected bilaterally in nucleus accumbens core and shell and effects on cortical and hippocampal sensory gating were investigated. Also, effects of the dopamine D2 receptor antagonist haloperidol (0.1 mg/kg, subcutaneously) as pretreatment were studied. First, quinpirole significantly reduced both the amplitude to the first click and gating as measured in the cortex and in the hippocampus. There was a tendency for the quinpirole effects on hippocampal gating to be more pronounced in rats injected in the shell. Secondly, haloperidol did not antagonize effects of quinpirole on hippocampal parameters, whereas haloperidol pretreatment fully antagonized quinpirole effects on cortical parameters. In conclusion, gating can be significantly reduced when a dopamine agonist is specifically targeted at mesolimbic dopamine D2 receptors. However, an important consideration is that the dopaminergic effects in the present study on gating are predominantly mediated by the effects on the amplitude to the first click. This has also been suggested for systemic amphetamine injections in rats and schizophrenic patients. This casts doubt on whether dopamine receptor activation affects the putative inhibitory process between the first and the second stimulus.

Acoustic Stimulation↗
PubMed2003

Clinical significance of atomic inner shell ionization (ISI) and Auger cascade for radiosensitization using IUdR, BUdR, platinum salts, or gadolinium porphyrin compounds.

PURPOSE: Halogenated pyrimidines (iododeoxyuridine [IUdR] and bromodeoxyuridine [BUdR]), platinum salts, and gadolinium porphyrins are heavy atom compounds used as radiosensitizers. For IUdR, it has been hypothesized that iodine inner shell ionizations (ISI) and Auger cascades could be one of the primary radiosensitization mechanisms. The purpose of this paper is to estimate the number of ISI produced per tumor cell and per 2 Gy irradiation in clinically relevant modelings. MATERIALS AND METHODS: ISI were evaluated using a two-step method. Photon-induced ISI were calculated using the MCNP-4C Monte Carlo code, heavy atom concentrations from clinical data published in the literature, and at various depths in a water phantom irradiated with 6-MV, (60)Co, (137)Cs, or (192)Ir sources. Electron knock-on induced ISI on K, L, and M atomic shells were evaluated with an hybrid method, using simulated electron spectra and cross-sections derived from the Møller formalism. Using a biological dose equivalence of 0.05 Gy per cell ISI, relative biological effectiveness (RBE) values were calculated for each situation. RESULTS: For platinum and gadolinium, ISI occurs in far less than 0.1% of the cell, whichever is the configuration. For IUdR and BUdR, ISI occurs in between 45% to 483% of the cell. Due to spectrum degradation, about 3 times more photoelectric ISI are generated at greater than shallower depths, and 10 times more for (192)Ir compared with (60)Co or 6-MV X-rays. Photoelectric ISI are about 3 times more frequent for iodine than bromine, but electron knock-on ISI are more frequent on bromine, and at the end about the same number of ISI are generated for both elements. RBEs were found to be between 1.01 and 1.12 for clinically relevant irradiation settings. CONCLUSIONS: The mechanisms of radiosensitization for platinum and gadolinium are clearly not related to an Auger cascade. For halogenated pyrimidines, however, clinically relevant numbers of ISI are generated within each cell. For IUdR, ISI appears to be strongly tied to the photon spectra. Halogenated pyrimidines should be evaluated again clinically, but using lower energy photons like a (192)Ir implant.

Bromodeoxyuridine↗
PubMed2001

Lactate dehydrogenase genes of caiman and Chinese soft-shelled turtle, with emphasis on the molecular phylogenetics and evolution of reptiles.

L-Lactate dehydrogenase (LDH) cDNAs encoding for LDH-A(4) (muscle) and LDH-B(4) (heart) isozymes from caiman (Caiman crocodilus apaporiensis) belonging to the order Crocodilia and Chinese soft-shelled turtle (Pelodiscus sinensis) belonging to the order Chelonia were sequenced. The phylogenetic relationships of the newly determined cDNA and their deduced protein sequences, as well as the previously published sequences of vertebrate LDH isozymes, were analyzed by various phylogenetic tree construction methods. These results indicated that Chelonia is indeed more closely related to Crocodilia. The divergent times between caiman and alligator, turtle and soft-shelled turtle, and Chelonia and Crocodilia were estimated to be approximately 36, 100 and 177 million years, respectively.

Alligators and Crocodiles↗
PubMed2000

Clonazepam release from core-shell type nanoparticles of poly(epsilon-caprolactone)/poly(ethylene glycol)/poly(epsilon-caprolactone) triblock copolymers.

The triblock copolymer based on poly(epsilon-caprolactone) (PCL) as hydrophobic part and poly(ethylene glycol) (PEG) as hydrophilic one was synthesized and characterized. Core-shell type nanoparticles of poly(epsilon-caprolactone)/poly(ethylene glycol)/poly(epsilon-caprolactone) (CEC) block copolymer were prepared by a dialysis technique. According to the amphiphilic characters, CEC block copolymer can self-associate at certain concentration and their critical association concentration (CAC) was determined by fluorescence probe technique. CAC value of the CEC-2 block copolymer was evaluated as 0.0030 g/l. CAC values of CEC block copolymer decreased with the increase of PCL chain length, i.e. the shorter the PCL chain length, the higher the CAC values. From the observation of transmission electron microscopy (TEM), the morphologies of CEC-2 core-shell type nanoparticles were spherical shapes. Particle size of CEC-2 nanoparticles was 32.3+/-17.3 nm as a monomodal and narrow distribution. Particle size, drug loading, and drug release rate of CEC-2 nanoparticles were changed by the initial solvents and the molecular weight of CEC. The degradation behavior of CEC-2 nanoparticles was observed by 1H NMR spectroscopy. It was suggested that clonazepam (CNZ) release kinetics were dominantly governed by diffusion mechanism.

Clonazepam↗
PubMed1996

Evaluation of a direct immunofluorescence assay, dot-blot enzyme immunoassay, and shell vial culture in the diagnosis of lower respiratory tract infections caused by influenza A virus.

We prospectively evaluated the efficacy of two commercial rapid methods for antigenic detection, a dot-blot enzyme immunoassay (EIA-DB) (Directigen FluA, Becton-Dickinson, USA) and a direct immunofluorescence assay (DIF) (Monofluokit Influenza A, Diagnostics Pasteur, France), compared with the shell-vial culture in the MDCK line, incubated 2 to 3 days and stained with the monoclonal antibody clone IA-52, the diagnosis of lower respiratory tract caused by Influenza A virus (IA). In the study period the presence of IA virus was detected in 59 of the 377 samples analyzed (15.7%). Only the SVC method detected all positive samples (100% sensitivity), being used as a reference method for comparison with the other techniques). The EIA-DB technique detected 50 cases (84.7%) and the DIF only 35 (59.3%). In nine (15.2%) cases the diagnosis was obtained only with the SVC method. The results of the comparison of the EIA-DB technique with SVC were: sensitivity 84.7%, specificity 100%, positive predictive value 100%, and negative predictive value 97.2%. The DIF technique gave values of 59.3%, 100%, 100%, and 92.9%, respectively. A statistically significant difference was observed between the sensitivity of the EIA-DB and the DIF method (p = 0.0001). In view of the results we recommended the use of the EIA-DB as a screening method when infection by the IA is suspected. But to obtain the maximum diagnostic yield all samples would be inoculated in a shell vial culture with the MDCK cell line.

Bacteriological Techniques↗
PubMed2001

Effect of pyrolysis temperature on composition, surface properties and thermal degradation rates of Brazil Nut shells.

Changes in chemical and surface characteristics of Brazil Nut shells (Bertholletia excelsa) due to pyrolysis at different temperatures (350 degrees C, 600 degrees C, 850 degrees C) were examined. For this purpose, proximate and ultimate analyses, physical adsorption measurements of N2 (-196 degrees C) and CO, (25 degrees C) as well as samples visualisation by scanning electronic microscopy (SEM) were performed. Appreciable differences in the residue characteristics, depending markedly on the pyrolysis temperature, were observed. Release of volatile matter led to the development of pores of different sizes. Progressive increases in micropore development with increasing pyrolysis temperature took place, whereas a maximum development of larger pores occurred at 600 degrees C. Furthermore, kinetics measurements of Brazil Nut shells pyrolysis from ambient temperature up to 900 degrees C were performed by non-isothermal thermogravimetric analysis. A model taking into account the significant changes in the residue during pyrolysis, through an increase in the activation energy with temperature and solid conversion, were found to properly fit the kinetics data over the wide range of degradation investigated.

Kinetics↗
PubMed2003

Separation of cashew (Anacardium occidentale L.) nut shell liquid with supercritical carbon dioxide.

Cashew nut shell liquid (CNSL) represents the largest readily available bioresource of alkenyl phenolic compounds. In this work, separation of CNSL from the pericarp of the cashew nut with supercritical carbon dioxide was studied. In the initial extractions with CO(2) at 40-60 degrees C and at pressures from 14.7 to 29.4 MPa, low yields were obtained. However, when the extractions were performed with one or more intermediate depressurization steps, the yield of CNSL increased to as high as 94%. Most of the oil did not separate from the shell during the depressurization step, but was obtained during the subsequent repressurization. The CNSL extract had a clear light brownish pink color and exhibited no evidence of polymerization or degradation. The pressure profile extraction method proposed in this work increases the possible CNSL extraction yields and greatly reduces the amount of CO(2) required for CNSL separation.

Anacardium↗
PubMed2003

Characterization of aspartate transcarbamylase activity from gonads of the soft shell clam, Mya arenaria.

Aspartate transcarbamylase (ATCase, EC 2.1.3.2) has been shown to be a good index of the reproductive cycle in marine molluscs. However, this enzyme has never been studied in the soft shell clam Mya arenaria. The characteristics of gonadal ATCase of the soft shell clam, Mya arenaria were therefore determined since we need powerful tools to assess the degree of effects of endocrine disruptors in this species at risk. Enzyme kinetic values observed at pH 8.3 were significantly lower than those measured at pH 9.4. The optimal conditions for the enzyme assays were reached in the presence of a 10 mM of substrate concentration and at pH 9.2 for 60 min at 37 degrees C. We have found that the enzyme was heat sensitive, markedly activated by DMSO and DMF, but no effect was observed with ethanol, ATP or CTP. However, clam ATCase activity was partly inhibited by the addition of CuSO(4) and PHMB to the medium, an inhibition that could be attributed to the presence of SH sites in cysteine residues localized in the catalytic site of this enzyme. All these results will be very useful in the near future to study the gametogenetic process of Mya arenaria, since little is known about the factors that control the physiological process of reproduction in this bivalve of ecological and economic importance. Studies of variations of the activity of aspartate transcarbamylase will also be useful as a potential biomarker to evaluate the disruption of gametogenesis in clams exposed to endocrine disruptors in situ.

Animals↗
PubMed2000

Solvation of Cr3+ cation in water-acetonitrile mixture studied by IR spectroscopy: molecular penetration into the solvation shells.

Infrared spectra of mixtures of water and deuteroacetonitrile containing the Cr3+ cation have been studied as a function of concentration, time and temperature. The CN stretching vibration of CD3CN molecules has been used as a probe of the structural environments. The CN band in the spectra of the solutions is a superposition of four subbands, which may be attributed to CD3CN bound in the first, second, and third solvation shells of the cation and to non-bound CD3CN. The character of changes of the integral intensities of the subbands with time for various H2O:Cr3+ molar ratios are explained by suggesting mechanisms of molecular replacement within the solvation shells of Cr3+.

Acetonitriles↗
PubMed2001

Closed-shell polycyclic aromatic hydrocarbon cations: a new category of interstellar polycyclic aromatic hydrocarbons.

Density functional theory has been employed to calculate the harmonic frequencies and intensities of a range of polycyclic aromatic hydrocarbon (PAH) cations that explore both size and electronic structure effects on the infrared spectroscopic properties of these species. The sample extends the size range of PAH species considered to more than 50 carbon atoms and includes several representatives from each of two heretofore unexplored categories of PAH cations: (1) fully benzenoid PAH cations whose carbon skeleton is composed of an odd number of carbon atoms (C(odd) PAHs); and (2) protonated PAH cations (HPAH+). Unlike the radical electronic structures of the PAH cations that have been the subject of previous theoretical and experimental work, the species in these two classes have a 'closed'-shell electronic configuration. The calculated spectra of circumcoronene, C54H18, in both neutral and (radical) cationic form are also reported and compared with those of the other species. Overall, the C(odd) PAHs spectra are dominated by strong CC stretching modes near 1600 cm(-1) and display spectra that are remarkably insensitive to molecular size. The HPAH+ species evince a more complex spectrum consistent with the added contributions of aliphatic modes and their generally lower symmetry. Finally, for both classes of closed-shell cations, the intensity of the aromatic CH stretching modes is found to increase with molecular size far out of proportion with the number of CH groups, approaching a value more typical of neutral PAHs for the largest species studied.

Carbon Isotopes↗
PubMed2001

Electronic spectra and ionization potentials of a stable class of closed shell polycyclic aromatic hydrocarbon cations.

Due to their stability, closed shell polycyclic aromatic hydrocarbon (PAH) cations are possible candidates as carriers for some of the diffuse interstellar bands (DIBs). The electronic absorption spectra and ionization potentials of several closed shell PAH cations are determined in this study. We use density functional theory (DFT) at the BLYP/6-31G* level to determine the ionization potentials and thus confirm the stability of the PAH cations of interest. We use time-dependent density functional theory (TDDFT), again at the BLYP/6-31G* level, to calculate the vertical excitation energies and oscillator strengths of the PAH cations. We observe dominant single absorptions within the DIB spectral region of interest in all of the PAH cation spectra except for the smallest member of the series.

Astronomical Phenomena↗
PubMed1983

The production and functional morphology of helminth egg-shells.

The high energy costs of egg-shell production in many helminths suggests that this structure plays an important role in their biology. The mechanical and chemical resistance of the egg-shell and the barrier it provides to the entry and loss of material are important in the survival of the free-living stages within the egg. The presence of egg filaments may increase the availability of infective stages and the operculum may be important in the infective process.

Acanthocephala↗
PubMed1979

The structure and formation of the egg-shell of Syphacia obvelata Rudolphi (Nematoda: Oxyurida).

The egg of Syphacia obvelata is a flattened elipsoid. The egg-shell consists of 5 layers: external uterine layer, internal uterine layer, vitelline layer, chitinous layer and lipid layer. An operculum is present at one pole of the egg. The opercular groove consists of a break in the uterine layers and the modification of the chitinous layer by the deposition of lipoprotein material. On the curved side of the egg the uterine layers are modified to form alternate ridges and depressions. Discrete spaces are present in the internal uterine layer between the ridges. These are open to the exterior via pores in the external uterine layer. The structure of the uterine layers is quite different on the flattened side of the egg. The morphology of the reproductive system and the formation of the egg-shell is described. It is suggested that the complex structure of the uterine layers of oxyurids forms by a self-assembly process.

Animals↗
PubMed1986

Permeability changes in the egg-shell of hookworms during development and eclosion.

The development and hatching of Ancylostoma ceylanicum and Ancylostoma tubaeforme eggs in a range of potentially inimical solutions has been examined using time-lapse video micro-recording techniques. In all compounds tested the larvae developed to the active pretzel stage. The inception of activity resulted in an increase in shell permeability to water and small molecules. In anthelmintics of molecular weight (Mr) 400 development continued normally until about the time that control eggs hatched, when there was a marked decrease in larval activity and eclosion did not occur. The addition of a low Mr surface-active agent potentiated the effect of the anthelmintic and caused larval activity to be lost earlier. The calcium inhibitor lanthanum chloride affected larval development rather than eclosion. Large Mr compounds did not affect either development or hatching and the results suggest that the egg-shell may act as a form of sieve, allowing the essential oxygen to reach the developing larva while excluding large potentially dangerous molecules. No appreciable differences were found between the two species of hookworm examined.

Acridine Orange↗
PubMed2006

Shell shock: an outcome study of a First World War 'PIE' unit.

BACKGROUND: 'Forward psychiatry' was introduced by the French Army in 1915 to stem the loss of troops to base hospitals. Also known by the acronym PIE (proximity to the battle, immediacy of treatment and expectancy of recovery, including return to duty), it was subsequently used by the British and Americans in both World Wars. The US Army used PIE techniques in Korea and Vietnam. Although widely accepted as an effective intervention, forward psychiatry is not amenable to random-controlled trials and only one controlled outcome study has been conducted. METHOD: All 3580 soldiers with shell shock admitted to 4 Stationary Hospital between January and November 1917 were recorded. Unit details, military experience, length of stay and outcomes were analysed. Soldiers were categorized into combat, combat-support and non-combatant groups. Admissions were correlated with military operations to compare the impact of defensive and offensive phases of warfare. RESULTS: Rates of admission for shell shock rose significantly during offensives when physical casualties escalated. Combat troops were disproportionately represented. Over 50% of admissions had less than 9 months service in France and 21% broke down within 3 months of going overseas. Less than 20% returned directly to combat units, most going to other hospitals, convalescent depots or base duties. CONCLUSIONS: Forward psychiatry was not effective in returning combat troops to fighting units but, by allocating soldiers to support roles, it prevented discharge from the armed forces. Uncertainties remain about relapses, including other routes that servicemen used to escape from a combat zone.

France↗