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PubMed2004

BNCT dose distribution in liver with epithermal D-D and D-T fusion-based neutron beams.

Recently, a new application of boron neutron capture therapy (BNCT) treatment has been introduced. Results have indicated that liver tumors can be treated by BNCT after removal of the liver from the body. At Lawrence Berkeley National Laboratory, compact neutron generators based on (2)H(d,n)(3)He (D-D) or (3)H(t,n)(4)He (D-T) fusion reactions are being developed. Preliminary simulations of the applicability of 2.45 MeV D-D fusion and 14.1 MeV D-T fusion neutrons for in vivo liver tumor BNCT, without removing the liver from the body, have been carried out. MCNP simulations were performed in order to find a moderator configuration for creating a neutron beam of optimal neutron energy and to create a source model for dose calculations with the simulation environment for radiotherapy applications (SERA) treatment planning program. SERA dose calculations were performed in a patient model based on CT scans of the body. The BNCT dose distribution in liver and surrounding healthy organs was calculated with rectangular beam aperture sizes of 20 cm x 20 cm and 25 cm x 25 cm. Collimator thicknesses of 10 and 15 cm were used. The beam strength to obtain a practical treatment time was studied. In this paper, the beam shaping assemblies for D-D and D-T neutron generators and dose calculation results are presented.

Boron Neutron Capture Therapy↗

PubMed2004

QSAR modeling of globulin binding affinity of corticosteroids using AM1 calculations.

A quantitative structure-activity analysis of binding affinity of a series of 30 steroids for corticosteroid-binding globulin was performed using Wang-Ford charges of the non-hydrogen common atoms obtained from molecular electrostatic potential surface of AM1 optimized energy-minimized geometries of the compounds. Attempts were made to include lipophilicity (logP) and molar refractivity (MR) values of the whole molecules in the multivariate relations. The final relations were subjected to 'leave-one-out' cross-validation to check their predictive potential. It was found from the study that the charges of different atoms of the steroid nucleus [atoms 3, 4, 5 (ring A), 8, 9 (fusion points of rings B and C) and 16 (ring D)] contribute significantly to the binding affinity. This suggests the importance of these atoms/sites for the globulin binding affinity, which is also supported by previous reports on structure-activity relations of corticosteroids. Further, molar refractivity shows parabolic relation with the binding affinity, which indicates the possibility of dispersion interactions. The statistical qualities of the final equations generated in the present study (predicted variance 77-82%; explained variance 83-87%) are better than those of some of the previously reported models.

Adrenal Cortex Hormones↗

PubMed2004

The effects of biphasic waveform design on post-resuscitation myocardial function.

OBJECTIVES: This study examined the effects of biphasic truncated exponential waveform design on survival and post-resuscitation myocardial function after prolonged ventricular fibrillation (VF). BACKGROUND: Biphasic waveforms are more effective than monophasic waveforms for successful defibrillation, but optimization of energy and current levels to minimize post-resuscitation myocardial dysfunction has been largely unexplored. We examined a low-capacitance waveform typical of low-energy application (low-energy biphasic truncated exponential [BTEL]; 100 microF, < or =200 J) and a high-capacitance waveform typical of high-energy application (high-energy biphasic truncated exponential [BTEH]; 200 microF, > or =200 J). METHODS: Four groups of anesthetized 40- to 45-kg pigs were investigated. After 7 min of electrically induced VF, a 15-min resuscitation attempt was made using sequences of up to three defibrillation shocks followed by 1 min of cardiopulmonary resuscitation. Animals were randomized to BTEL at 150 J or 200 J or to BTEH at 200 J or 360 J. RESULTS: Resuscitation was unsuccessful in three of the five animals treated with BTEH at 200 J. All other attempts were successful. Significant therapy effects were observed for survival (p = 0.035), left ventricular ejection fraction (p < 0.001), stroke volume (p < 0.001), fractional area change (p < 0.001), cardiac output (p = 0.044), and mean aortic pressure (p < 0.001). Hemodynamic outcomes were negatively associated with energy and average current but positively associated with peak current. Peak current was the only significant predictor of survival (p < 0.001). CONCLUSIONS: Maximum survival and minimum myocardial dysfunction were observed with the low-capacitance 150-J waveform, which delivered higher peak current while minimizing energy and average current.

Animals↗

PubMed2005

Statistical evaluation of electrospray tandem mass spectra for optimized peptide fragmentation.

Liquid chromatography-tandem mass spectrometry (LC-MS/MS) has become the method of choice for the analysis of complex peptide mixtures. It combines the separation power of nanoflow LC with highly specific sequence analysis, allowing automated peptide sequencing with high resolution and throughput. For peptide fragmentation, the current experimental setup uses predefined parameters based on the mass-to-charge ratio of the individual precursor. Suitable parameters are typically established by empirical evaluation of fragment spectra of individual peptides used as standards. As a result, nonoptimal fragment spectra are obtained if peptides show fragmentation behavior different from these standards, which often result in the loss of sequence-specific fragment ion information. Here we describe a statistical approach for the systematic evaluation of the quality of individual peptide fragment spectra based on the calculation of their arithmetic mean and standard deviation. The method utilizes the dependence of these parameters on the difference in electric potential across the collision cell to determine the value that results in maximum information content. We show that the method is applicable to fragment spectra generated from a variety of multiply-charged tryptic peptides, over a wide concentration range, and on different types of mass analyzers. We also show how this novel approach can be used to define optimized collision energy settings over a wide mass-to-charge range.

Animals↗

PubMed2006

Molecular modeling of purinergic receptor P2Y12 and interaction with its antagonists.

Purinergic receptors are a class of cell surface receptors for purines that prefer ATP or ADP over adenosine. The surface receptors for extracellular nucleotides are called P2 receptors. They are activated by both pyrimidine and purine nucleotides. ADP initiates platelet aggregation by 'simultaneous activation of two G protein-coupled receptors, P2Y1 and P2Y12. P2Y12 has been shown to be the target of the thienopyridine drugs, ticlopidine and clopidogrel. Here, the active sites of P2Y12 for ATP as well as ADP are predicted by bioinformatics and molecular modeling. First, the three-dimensional (3D) structure of P2Y12 was constructed by InsightII/Homology module using the corresponding bovine rhodopsin (PDB code: 1HZX) as the template. Then the primary structures were optimized by energy minimization that has been successfully accepted by the Protein Data Bank (PDB code: 1VZ1). Second, a simple scoring matrix was built up based on the analysis of 13 known ATP-binding proteins. And the most probable active sites of P2Y12 were predicted using the scoring matrix, which include three distant areas: "head area" (LGTGPLRTFV, 87-96), "middle area" (VGLITNGLAM, 38-47, and LGAKILSVVI, 139-148), and "bottom area" (RTRGVGKVPR, 222-231). Subsequently the structural model of P2Y12 was docked with ATP/ADP in comparison with P2Y1 (PDB code 1ddd). As a comparison, we docked its antagonists, such as ticlopidine and clopidogrel, to the most probable sites and calculated their intermolecular energy. Our results imply that P2Y12 has the potential to be inhibited by ADP/ATP analogs, and it suggests that P2Y12 acts as a target of new drugs that inhibit platelet aggregation.

Adenosine Diphosphate↗

PubMed2005

Rapid and reliable determination of illegal adulterant in herbal medicines and dietary supplements by LC/MS/MS.

In recent years, dietary supplements and herbal medicines are increasing in popularity all over the world. However, it is problematic that some manufacturers illegally included synthetic drugs in their products. Due to the extremely complex matrices of those products, most existing methods for screening illegal adulterations are time-consuming and liable to false positive. In this paper, a robust LC/MS/MS method for the high-throughput, sensitive and reliable determination of illegal adulterations from herbal medicines and dietary supplements was established. Minimal LC separation was employed and MRM was used to simultaneously monitor the three transitions under their respective optimal collision energy for each compound. Positive results were determined only if well-defined peaks appeared at all of the three transitions and the ratios among the peak areas were within given threshold. In this study, the method had been applied for the screening of nine most commonly adulterated therapeutic substances, such as sildenafil (Viagra) and famotidine, and the lower limits of detection of these compounds ranged from 0.05 to 1.5 ng/ml. Little sample preparation was needed for this method and the analysis time was less than 5 min/sample. The reliability has been demonstrated by the test with blank matrix. Over 200 products that were under suspicion by SDA of China had been assayed and till now no false negative or positive result was found. This method is rapid, simple, reliable and capable of screening multiple adulterants in one run.

Capsules↗

PubMed2006

Neuronal macroautophagy: from development to degeneration.

Macroautophagy, a lysosomal pathway responsible for the turnover of organelles and long-lived proteins, has been regarded mainly as an inducible process in neurons, which is mobilized in states of stress and injury. New studies show, however, that macroautophagy is also constitutively active in healthy neurons and is vital to cell survival. Neurons in the brain, unlike cells in the periphery, are protected from large-scale autophagy induction because they can use several different energy sources optimally, receive additional nutrients and neurotrophin support from glial cells, and benefit from hypothalamic regulation of peripheral nutrient supplies. Due to its exceptional efficiency, constitutive autophagy in healthy neurons proceeds in the absence of easily detectable autophagic vacuole intermediates. These intermediates can accumulate rapidly, however, when late steps in the autophagic process are blocked. Autophagic vacuoles also accumulate abnormally in affected neurons of several major neurodegenerative diseases, including Alzheimer's disease and Parkinson's disease, where they have been linked to various aspects of disease pathogenesis including neuronal cell death. The build-up of autophagic vacuoles in these neurological disorders and others may reflect either heightened autophagy induction, impairment in later digestive steps in the autophagy pathway, or both. Determining the basis for AV accumulation is critical for understanding the pathogenic significance of autophagy in a given pathologic state and for designing possible therapies based on modulating autophagy. In this review, we discuss the special features of autophagy regulation in the brain, its suspected roles in neurodevelopment and plasticity, and recent progress toward understanding how dysfunctional autophagy contributes to neurodegenerative disease.

Animals↗

PubMed2006

Cobalt(II) complexes of biologically active glutathione: spectroscopic and molecular modeling studies.

Cobalt(II) complexes of reduced glutathione (GSH) of general composition Na[Co(L)(X)].nH2O (where H2L = GSH; X = Cl-, NO3-, NCS-, CH3CO2-, HCO2-, ClO4- and n = 0-4) have been synthesized and characterised by elemental analyses, vibrational spectra, electronic spectra, magnetic susceptibility measurements, thermal studies and molecular modeling studies. Electronic spectra indicate planar geometry for all the complexes. Infrared spectra indicate the presence of H2O molecules (except perchlorate complex) in the complexes that has been supported by TG/DTA. The room temperature magnetic moment values for all complexes lie in the range of 2.60-2.80 BM range indicating departure from spin only values due to second order Zeeman effect. Thermal decomposition of all the complexes proceeds via first order kinetics. The Na[Co(L)(Cl)].2H2O complex has the minimum activation energy and Na[Co(L)(CH3CO2)].3H2O has the maximum activation energy. The molecular modeling calculation for energy minimization optimizes geometry of the metal complexes.

Cobalt↗

PubMed2004

Investigation of isolation and immobilization of a microbial consortium for decoloring of azo dye 4BS.

Eight high-effective decolorization strains were isolated by enrichment using Direct Fast Scarlet 4BS as sole source of carbon and energy. The optimal microbial consortium consisting of fungus 8-4(*) and bacterium 1-10 was selected by optimizing combination decolorization experiments with these eight freely suspended strains, whose decolorization activity was higher than individual strains due to synergistic reaction with each other. The optimal microbial consortium was also immobilized using polyvinyl alcohol (PVA) as the carrier. This paper optimized the immobilization and operational conditions, investigated the effect of the environmental factors (temperature, pH and dissolved oxygen (DO)) and initial dye concentration on the rate of decolorization by immobilized microbial consortium. The results showed that the optimal decolorization activity was observed in pH range (5-8), temperature range (25-40 degrees C) under shaking culture of high DO level. Decolorization with the optimal microbial consortium gave a relatively high maximum decolorization activity (ca. 81.25 mgl(-1)h(-1)), which occurred at a dye concentration of 1000 mgl(-1), suggesting the applicability of the strains in remediation of wastewater containing high azo dye concentrations. The immobilized beads could be reused for more than 30 cycles, without losing any degradation capacity. The changes of UV-visible spectra and the change curve of COD of 4BS solution before and after decolorization cultivation and the proliferation and distribution of microbial consortium in gel beads were also microscopically observed, which could be used for conferring the decolorization mechanisms of dye 4BS.

Azo Compounds↗

PubMed2006

Effect of ultrasound pretreatment in mesophilic and thermophilic anaerobic digestion with emphasis on naphthalene and pyrene removal.

In many anaerobic digestion processes for the treatment of the sludge produced in wastewater treatment plants, the hydrolysis of the organic matter has been identified as the rate limiting step. This study is focused on the effect of ultrasonic pretreatment of raw sewage sludge before being fed to the mesophilic and the thermophilic anaerobic digestion. From particle size reduction, COD disintegration degree and biodegradability test, 11,000kJ/kg TS was estimated as the optimal specific energy in ultrasonic pretreatment. Moreover, the use of pretreated sludge improved significantly the COD removal efficiency and biogas production in lab-scale anaerobic digesters when compared with the performance without pretreatment, specially under mesophilic conditions. During ultrasonic pretreatment, the diffusion of polycyclic aromatic hydrocarbons (PAH) compounds to the aqueous phase was stated by a reduction in the pretreated sludge micropollutants content. With sonication, naphthalene was better removed than without this pretreatment, particularly in the mesophilic digester. However, pyrene removal remained at same efficiency level with and without ultrasonic pretreatment.

Anaerobiosis↗

PubMed1997

Lead system optimization for transvenous defibrillation.

Lead systems that include an active pectoral shell reduce defibrillation thresholds and permit transvenous defibrillation in nearly all patients. A further improvement in defibrillation efficacy is desirable to allow for smaller pulse generators with a reduced maximum output. Accordingly, the purpose of this study was to compare defibrillation thresholds with multiple transvenous lead systems including those with an active pectoral shell to determine which system would optimize defibrillation energy requirements. This prospective study was performed on 21 consecutive patients. Each subject was evaluated with 3 lead configurations with the order of testing randomized. The configurations were a dual coil transvenous lead (lead), the distal right ventricular coil and pectoral pulse generator shell (unipolar), and all 3 components (triad). The right ventricular coil was the cathode for the first phase of the biphasic defibrillation waveform. Delivered energy at defibrillation threshold was 11.2 +/- 3.4 J for the lead configuration, 10.1 +/- 5.2 J for the unipolar configuration, and 7.8 +/- 3.6 J for the triad configuration (p <0.01). Leading edge voltage (p <0.01) and shock impedance (p <0.001) were also decreased for the triad configuration compared with the lead or unipolar configurations, whereas peak current was minimized with the unipolar configuration (p <0.01). We conclude that the combination of a dual coil, transvenous lead and an active pectoral shell reduces defibrillation energy requirements compared with either the lead alone or unipolar configuration. Moreover, the defibrillation thresholds were < or =15 J in all patients using the triad lead system.

Defibrillators, Implantable↗

PubMed1996

Effects of dispersive electrode position and surface area on electrical parameters and temperature during radiofrequency catheter ablation.

Positioning of the dispersive electrode has no significant effect during radiofrequency ablation. Doubling the surface are of the dispersive electrode results in a lower impedance, higher current delivery, and increased tip temperatures, particularly if the baseline impedance is >100 ohms. These findings may have important implications for optimizing radiofrequency energy delivery using currently available radiofrequency generators.

Cardiac Catheterization↗

PubMed1969

Calculations of pulsatile flow across bifurcations in distensible tubes.

A simple method is given for extending across junctions the numerical methods previously used to study fluid flow in nonuniform, nonbranching, distensible tubes. Calculations with this method suggest that the ratio of downstream to upstream cross-sectional areas and the pressure wave velocity ratio in mammals are optimal for energy transfer across the junction.

Biophysical Phenomena↗

PubMed1991

The effect of malnutrition on vaccination against Dermatophilus congolensis infection in ruminants.

Vaccination against Dermatophilus congolensis was carried out in groups of lambs raised on optimal or energy deficient diets. The groups differed significantly in weight, body condition score and plasma total protein and albumin. All animals were then challenged with D. congolensis in a dose response infection model. The vaccine was effective in the well nourished animals, reducing the number of affected lambs in the vaccinated group and the severity of the lesions and increasing the minimum dose required to cause infection. In contrast, all of the vaccinated energy-deficient lambs developed lesions. There was some evidence of vaccine effect in these animals but this was not as marked as that seen in the well nourished lambs. The malnourished lambs, vaccinated and non-vaccinated, took longer to heal than the well nourished groups. Resistance to challenge was not associated with serum antibodies or skin test reactivity to D. congolensis antigens.

Actinomycetales↗

PubMed1999

Local motion detectors cannot account for the detectability of an extended trajectory in noise.

Previous work has shown that a single dot moving in a consistent direction is easily detected among noise dots in Brownian motion (Watamaniuk et al., Vis Res 1995;35:65-77). In this study we calculated the predictions of a commonly-used psychophysical motion model for a motion trajectory in noise. This model assumes local motion energy detectors optimally tuned to the signal, followed by a decision stage that implements the maximum rule. We first show that local motion detectors do indeed explain the detectability of brief trajectories (100 ms) that fall within a single unit, but that they severely underestimate the detectability of extended trajectories that span multiple units. For instance, a 200 ms trajectory is approximately three times more detectable than two isolated 100 ms trajectories presented together within an equivalent temporal interval. This result suggests a nonlinear interaction among local motion units. This interaction is not restricted to linear trajectories because circular trajectories with curvatures larger than 1 degree are almost as detectable as linear trajectories. Our data are consistent with a flexible network that feeds forward excitation among units tuned to similar directions of motion.

Humans↗

PubMedDate not supplied

Structural aspects of protein kinase control-role of conformational flexibility.

Protein kinases catalyze the phosphotransfer reaction fundamental to most signaling and regulatory processes in the eukaryotic cell. Absolute control of individual protein kinase activity is, therefore, of utmost importance to signaling fidelity in the cell. Mechanisms for activity modulation, including complete and reversible inactivation, have been shown by crystal structures of many active and inactive protein kinases. The structures of inactivated kinases, compared with those of active and catalytically competent kinases such as the protein kinase A catalytic subunit, highlight recurring structural alterations among a set of elements of the catalytic kinase core. These 'activity modulation sites' apparently comprise the principal evolved mechanisms for control of enzyme activity in the catalytic domain. In combination, they enable diverse physiological regulatory mechanisms operative for most protein kinases. Identification and characterization of these sites should impact strategies for discovery and design of target-specific therapeutic drugs as the range of structural variations for specific kinases becomes known. The principle site, the ATP-binding pocket, is the target of many physiological regulators and also most experimental or therapeutic inhibitors, which typically block it in a competitive or allosteric fashion. Co-crystallization studies with protein kinase A and other kinases have revealed binding features of several classes of protein kinase inhibitors. Ligand-induced structural changes are common and tend to optimize buried surface areas. The ability to optimize binding energies arising from the hydrophobic effect creates a logarithmic dependence of binding energy on buried surface areas. Exceptions to this rule arise for specific inhibitor classes, and possibly also as artifacts of structure determination.

Adenosine Triphosphate↗

PubMed2001

[Skeletal configurations of cervical column during rest to motion transition: generalization that underlie the motor repertoire in rodents].

During forward locomotion, guinea pigs adopted a posture which, although different, was as stereotyped as at rest. The whole extent of the vertebral column was extended, parallel to the earth-horizontal plane. This result supports the hypothesis that, in mammals, gaze and postural control by the central nervous system would be simplified by the adoption of a limited number of skeletal configurations. They would be optimized for energy saving, biomechanical efficacy and limitation of the number of degrees of freedom of the skeletal apparatus. Transition between rest and forward locomotion displayed two prominent characteristics: the head was stabilized versus space throughout the whole transition and the modifications of the skeletal geometry were confined to the median plane and to two major articular regions. Such an organization revealed a fourth characteristic of the guinea pig postural control: the skeletal configurations retained by evolution would ensure that smooth transitions take place between rest and the various activities of its motor repertoire. Finally, our purely descriptive data shed new light on the architecture of the neuronal network which underlies the vestibular control of gaze and posture.

Animals↗

PubMedDate not supplied

The use of computed microtomography to monitor morphological changes in small animals.

RATIONALE AND OBJECTIVES: We investigate the methodological aspects of computerised microtomography (Cm 1) for monitoring the development of osteoporosis in male Sprague-Dawley rats. METHODS: 120 Rats were gastrectomized or sham operated. Femurs were prepared and tomograms with spatial resolutions of 5-500 mm were made. Bone diameters, bone areas and moments of inertia were determined from the tomograms. Optimal slice position and the need for spatial resolution for future in vivo applications were investigated. In order to minimise the absorbed dose to the specimen, a theoretical model for determination of optimal irradiation conditions is developed. RESULTS: Gastrectomy caused dramatic changes in the bone architecture. The main features were vaccuolisation of the bone and reduced amounts of compact bone. While the outer diameters of tubular bones were largely unaffected, their inner diameters were greatly increased following gastrectomy. Relative bone area and moment of inertia were greatly reduced. Optimal photon energy was 12 keV. CONCLUSIONS: It is possible to monitor gastrectomy-evoked changes in bone morphology at various sites in rats with computerised microtomography. The changes are suggestive of osteoporosis.

Animals↗