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PubMed1996

Totally implantable intrathoracic ventricular assist device.

BACKGROUND: A totally implantable, intrathoracic electrohydraulic ventricular assist device (EVAD) is being developed for permanent use or as a bridge to transplantation. METHODS: The blood pump with 70-mL nominal stroke volume, volume displacement chamber, reversible turbine, internal electronics and infrared diaphragm position sensor are combined in one compact unit (unified system). The size and geometry are based on human anatomic measurements and fluid dynamic studies. A transcutaneous energy transfer powers the system and recharges the implantable nickel-cadmium battery pack. Autotuning circuitry optimizes energy transfer efficiency over a range of transcutaneous energy transfer coil spacings and misalignments. An infrared diaphragm position sensor detects end-systole and diastole points. RESULTS: In vitro and acute in vivo tests have demonstrated flow rates greater than 6 L/min. The transcutaneous energy transfer system demonstrated power transfer efficiencies of 60% to 80% for power demands from 5 to 60 W. Thirteen systems are currently undergoing durability testing; one has run for more than 750 days failure-free. The system recently sustained circulation in an acute calf implantation for 96 hours. CONCLUSIONS: Results of the in vitro and in vivo testing to date have demonstrated that the developed system can function effectively as a totally implantable ventricular assist device. Chronic in vivo evaluation is planned.

Animals↗

PubMedDate not supplied

[Possible DNA conformations].

The complete analysis of possible DNA structures has been undertaken in the space of dihedral angles. The structural sets obtained join energetically and geometrically possible conformations. Thus, the necessary condtions of existence are fulfilled for these structural forms. The half of our structural families includes all structures and structural sets proposed by other authors [10, 24]. Other six families have not been presented elsewhere. The results of the energy optimization suggest the left handed forms are unfavourable energetically, because main chain torsional term and the energy of nucleotide moiety. At the same time there is a great number of various lefthanded forms.

DNA↗

PubMed2006

The vibrational spectra, assignments and ab initio/DFT analysis for 3-chloro, 4-chloro and 5-chloro-2-methylphenyl isocyanates.

The Raman (3500-50 cm(-1)) and infrared (4000-200 cm(-1)) spectra of 3-chloro, 4-chloro and 5-chloro-2-methylphenyl isocyanates have been measured. Ab initio and density functional theory calculations, at the levels of RHF/6-311G* and B3LYP/6-311G*, have been performed: energies, optimized geometrical parameters, vibrational frequencies, infrared intensities, Raman activities, depolarization ratios and nuclear displacements are obtained. Potential energy distributions (PEDs) and normal modes, for the spectral data computed at B3LYP/6-311G*, have also been obtained from a force-field calculations. A complete vibrational assignments of the observed spectra have been proposed. The force-field calculations have shown that, several of the normal modes are coupled, as is the case with large molecular systems possessing very low or no symmetry, such as investigated in the present study. Further, the investigation of the internal rotation of the isocyanate, NCO, by B3LYP/6-31G* level of theory has shown that the moiety maintains nearly the same orientation in all the three compounds (approximately 140-145 degrees tilt to the para-position) as in phenyl isocyanate. Two conformers, cis and trans forms, with respect to the substituents, NCO and CH(3), have been determined: the cis form lies above trans form by less than a kilocalorie per mole for each compound.

Calorimetry↗

PubMed2000

The corticotropin-releasing hormone system in the regulation of energy balance in obesity.

The view that energy balance is regulated has gained acceptance in recent years. An important role in this regulation is played by brain circuitries involved in the control of energy intake (food intake) and energy expenditure (thermogenesis) that are capable of integrating peripheral signals, produced by perturbations of adipose tissue mass, into messages to effectors of food intake and energy expenditure, so as to prevent substantial variations in the level of energy reserves. More than one neurosystem has been reported to genuinely participate in the regulation of energy balance. Among them is the corticotropin-releasing hormone (CRH) system. This system, with its numerous clusters of brain neurons, its closely related peptide urocortin, its two receptor types and its binding protein, all generally widely distributed throughout the brain, forms a network of neuronal pathways capable of interacting with the circuitries controlling food intake and energy expenditure. In addition, CRH and urocortin's anorectic and thermogenic actions appear to be coordinated to optimize energy losses. Finally, the CRH system seems to demonstrate a certain degree of plasticity in obesity and in response to food deprivation that is consistent with its action on food intake and thermogenesis. The observations have been made that food deprivation and obesity can blunt the expression of the CRH type 2alpha receptor in the ventromedial hypothalamic nucleus and can induce the expression of the CRH-binding protein (a CRH-inactivating protein) in brain areas involved in the anorectic and thermogenic actions of CRH.

Brain↗

PubMed2004

Data-based model and parameter evaluation in dynamic transcriptional regulatory networks.

Finding the causality and strength of connectivity in transcriptional regulatory networks from time-series data will provide a powerful tool for the analysis of cellular states. Presented here is the design of tools for the evaluation of the network's model structure and parameters. The most effective tools are found to be based on evolution strategies. We evaluate models of increasing complexity, from lumped, algebraic phenomenological models to Hill functions and thermodynamically derived functions. These last functions provide the free energies of binding of transcription factors to their operators, as well as cooperativity energies. Optimization results based on published experimental data from a synthetic network in Escherichia coli are presented. The free energies of binding and cooperativity found by our tools are in the same physiological ranges as those experimentally derived in the bacteriophage lambda system. We also use time-series data from high-density oligonucleotide microarrays of yeast meiotic expression patterns. The algorithm appropriately finds the parameters of pairs of regulated regulatory yeast genes, showing that for related genes an overall reasonable computation effort is sufficient to find the strength and causality of the connectivity of large numbers of them.

Algorithms↗

PubMed2000

Energy expenditure in the extremely low-birth weight infant.

Information about energy requirements of extremely low-birth weight infants is sparse, despite the rapidly improving survival rates of this population. Metabolizable energy intake can be estimated from energy balance studies and the percentage of caloric intake that is actually absorbed by these infants is approximately 87%. Data on energy expenditure in extremely premature infants is limited; however, energy expenditure has been shown to increase with postnatal age. Because both intake and expenditure are affected by multiple factors, there is significant variability in estimates of the energy requirements in extremely low-birth weight infants. At present, no valid recommendations can be made regarding optimal energy requirements for the extremely low-birth weight infant, except that their requirements probably exceed those of stable, growing very low-birth weight infants, currently estimated at 105 to 135 kcal.kg-1d-1.

Energy Intake↗

PubMedDate not supplied

Evaluation of computational chemistry methods: crystallographic and cheminformatics analysis of aminothiazole methoximes.

Cheminformatics is used to validate the capabilities of widely used quantum chemistry and molecular mechanics methods. Among the quantum methods examined are the semiempirical MNDO, AM1, and PM3 methods, Hartree-Fock (ab initio) at a range of basis set levels, density functional theory (DFT) at a range of basis sets, and a post-Hartree-Fock method, local Moller-Plesset second-order perturbation theory (LMP2). Among the force fields compared are AMBER, MMFF94, MMFF94s, OPLS/A, OPLS-AA, Sybyl, and Tripos. Programs used are Spartan, MacroModel, SYBYL, and Jaguar. The test molecule is (2-amino-5-thiazolyl)-alpha-(methoxyimino)-N-methylacetamide, a model of the aminothiazole methoxime (ATMO) side chain of third-generation cephalosporin antibacterial agents. The Ward hierarchical clustering technique yields an insightful comparison of experimental (X-ray) and calculated (energy optimized) bond lengths and bond angles. The computational chemistry methods are also compared in terms of the potential energy curves they predict for internal rotation. Clustering analysis and regression analysis are compared. The MMFF94 force field such as implemented in MacroModel is the best overall computational chemistry method at reproducing crystallographic data and conformational properties of the ATMO moiety. This work demonstrates that going to a higher level of quantum theory does not necessarily give better results and that quantum mechanical results are not necessarily better than molecular mechanics results.

Journal Article↗

PubMed2003

DNA deformation energetics and protein binding.

The formation of protein-DNA complexes often involves deformation of the DNA double helix. We have calculated the energy necessary to produce this deformation in 71 crystallographically determined complexes, using internal coordinate energy optimization with the JUMNA program and a generalized Born continuum solvent treatment. An analysis of the data allows deformation energy to be interpreted in terms of both local and global structural changes. We find that, in the majority of complexes, roughly 60% of the deformation energy corresponds to backbone distortion. It is also found that large changes in stacking and pairing energies are often compensated for by other, longer range, stabilizing factors. Some deformations, such as base opening, can be large, but only-produce local energetic effects. In terms of backbone distortions, the angle alpha, most often involved in alphagamma transitions, makes the most significant energetic contribution. This type of transition is twice as costly as those involving beta, or coupled epsilonzeta changes. Sugar amplitude changes are also energetically significant, in contrast to changes in phase angles.

Crystallography, X-Ray↗

PubMedDate not supplied

[Parallel DNA helices. Conformational analysis of regular poly(dG).poly(dC) helices with different variants of base binding].

We have performed a conformational analysis of DNA double helices with parallel directed backbone strands. The calculations were made for homopolymers poly(dG).poly(dC). All possible models of base binding were checked. By the potential energy optimization the dihedral angles and helices parameters of stable conformations of parallel double polynucleotides were calculated. The dependences of conformational energy on the base pair structure were studied. Possible structure of parallel helices with various nucleotide composition are discussed.

DNA↗

PubMedDate not supplied

[Parallel double DNA spiral. A conformational analysis of regular spirals of poly(dA).poly(dT) with different variations of joining bases].

We have performed a conformational analysis of DNA double helices poly(dA).poly(dT) with parallel directed backbone strands in heteronomic model frames. All possible models of base pairs and various mutual orientation of base pair and sugarphosphate backbones were checked. By the potential energy optimization the dihedral angles and helices parameters of stable conformations of parallel double polynucleotides were calculated. The dependences of conformational energy on the base pair structure were studied.

Base Composition↗

PubMedDate not supplied

[Four-stranded DNA. Conformational analysis of regular spirals of poly(dT).poly(dA).poly(dA).poly(dT) with different base binding variations].

Conformational analysis of four stranded DNA helices poly(dT).poly(dA).poly(dA).poly(dT) with parallel arrangement of the identical sugar-phosphate chains connected by twofold symmetry has been performed. All possible models of symmetrical base binding were checked. By the potential energy optimization the dihedral angles and helices parameters of stable conformations of four stranded polynucleotides were calculated. The dependences of conformational energy on the base complex structure and mutual orientation of the poly(dA).and poly(dT) chains were studied. Possible biological functions of four stranded helices are discussed.

Base Sequence↗

PubMed2004

Nutritional requirements of surgical and critically-ill patients: do we really know what they need?

Malnutrition remains a problem in surgical and critically-ill patients. In surgical patients the incidence of malnutrition ranges from 9 to 44%. Despite this variability there is a consensus that malnutrition worsens during hospital stay. In the intensive care unit (ICU), 43% of the patients are malnourished. Although poor nutrition during hospitalisation may be attributable to many factors, not least inadequacies in hospital catering services, there must also be the question of whether those patients who receive nutritional support are being fed appropriately. Indirect calorimetry is the 'gold standard' for determining an individual's energy requirements, but limited time and financial resources preclude the use of this method in everyday clinical practice. Studies in surgical and ICU patient populations have been reviewed to determine the 'optimal' energy and protein requirements of these patients. There are only a small number of studies that have attempted to measure energy requirements in the various surgical patient groups. Uncomplicated surgery has been associated with energy requirements of 1.0-1.15 x BMR whilst complicated surgery requires 1.25-1.4 x BMR in order to meet the patient's needs. Identifying the optimal requirements of ICU patients is far more difficult because of the heterogeneous nature of this population. In general, 5.6 kJ (25 kcal)/kg per d is an acceptable and achievable target intake, but patients with sepsis or trauma may require almost twice as much energy during the acute phase of their illness. The implications of failing to meet and exceeding the requirements of critically-ill patients are also reviewed.

Critical Illness↗

PubMed1997

Fat gram target to achieve high energy intake in cystic fibrosis.

OBJECTIVE: Higher fat and energy intakes confer a survival advantage in cystic fibrosis (CF). There is a need to develop effective nutrition programmes that ensure optimal energy intake in CF. METHODOLOGY: A cross-sectional measurement of clinical characteristics and energy and fat intakes in patients attending the CF outpatients clinic of the John Hunter Hospital, Newcastle was undertaken. Twenty-nine subjects, mean age 12 years (range 4.3-20.2), completed weighed food records to determine the contribution of fat to the percentage of the recommended energy intake obtained and to document use of pancreatic enzyme replacement therapy. RESULTS: Diets with a high percentage of energy derived from fat did not guarantee that individuals with CF met their energy requirements. Subjects with total fat intakes of 100 g per day or greater, however, achieved in excess of 110% recommended daily intake (RDI) for energy. Up to 47% of subjects consumed more pancreatic enzyme replacement capsules than shown to give maximum effectiveness. CONCLUSION: Setting a 100 g daily fat target is a realistic way of ensuring high energy intakes in CF. Fat ready reckoners would identify the fat content of food and prescribe specific numbers of pancreatic enzyme replacement capsules to be consumed with each meal or food item.

Adolescent↗

PubMed2001

Sclerostomy with an Erbium YAG Laser. The Relationship with Pulse Energy.

Purpose: To investigate the optimal pulse energy to do sclerostomy with an erbium YAG laser.Materials and Methods: The experiments were performed in enucleated porcine eyes. We changed pulse energy and examined the effects on surrounding tissue.Results: With the increase of pulse energy, the effects of the laser extended to the area surrounding the laser probe. At the threshold energy for doing full-thickness sclerostomy, the total energy was significantly higher than with higher pulse energy. And with pulse energy higher than 2 mJ, the total energy did not show any significant change. Histopathologically, the damaged area around sclerostomy became larger with the increase of pulse energy.Conclusion: The optimal energy to do full-thickness sclerostomy with this system seemed to be 2 mJ.

Journal Article↗

PubMed1991

Diets of yearling female primates (Papio cynocephalus) predict lifetime fitness.

The foraging of yearling baboons (Papio cynocephalus) was studied in Amboseli National Park, Kenya. The nutrient content of the diets of individual females was compared with the composition of energy-maximizing optimal diets. Energy in the diets of all individuals fell appreciably short of their respective optima. Nonetheless, linear combinations of just two variables, protein intakes in excess of requirements and proximity of energy intakes to those specified in the optimal diets, were sufficient to provide good predictions of reproductive lifespans, numbers of infants and juveniles produced, and probability of surviving to adulthood.

Animals↗

PubMed2005

Monochromatic x-rays in digital mammography.

RATIONALE AND BACKGROUND: The emission spectrum of an x-ray tube is determined by the anode and filter materials as well as by the high voltage being used. For mammography, typical anode materials are molybdenum (Mo), rhodium (Rh), and tungsten (W); molybdenum, rhodium, and aluminum are favored for filters. Mammography is a soft tissue imaging modality demanding a high spatial resolution as well as a high detector sensitivity. Low-energy photons are only absorbed in tissue and have no contribution to the image; nevertheless, they increase the dose. High-energy photons mostly penetrate soft tissue and generate a background noise as a result of strong scattering that deteriorates the image quality. For mammography, the optimal energy window is in a range from 17 and 25 keV. From a theoretical perspective, one would favor monoenergetic x-rays (eg, the Mo-emission line at 17.5 keV). This article presents the realization of imaging with monochromatic x-rays using a diagnostic mammography unit. METHODS: Basically, a monochromatic module was added to a conventional mammographic system. The monochromatic module can be mounted at the end of the x-ray tube and it consists of a curved HOPG (highly oriented pyrolytic graphite) crystal and a slit collimator. For image generation, the object is moved through the fan-shaped monochromatic radiation field. In addition to the conventional polychromatic 2-dimensional case, the polychromatic irradiation was also able to be performed under similar conditions. For image acquisition, image plates or a linear array detector were used. Exposure doses were measured for both poly- and monochromatic radiation. The initial evaluation of the system performance was carried out by imaging a contrast-detail phantom and biologic specimens. RESULTS: The monochromatic x-ray beam has a size of approximately 35 mm x 200 mm in the object plane. The photon flux of the monochromatic x-rays is considerably lower than the photon flux of the polychromatic x-rays but adequate for initial studies of phantoms, biologic tissue, or small animals. The comparison of the results obtained with the monochromatic and polychromatic imaging modalities reveal a conspicuous increase of image contrast in the monochromatic case. CONCLUSION: The results suggest that the experimental setup for monochromatic excitation shows clear potentials for improvements of the image in comparison to the conventional polychromatic case.

Equipment Design↗

PubMed1981

Conformational calculations on gastrin C-terminal tetrapeptide.

Energy optimizations were performed on some typical conformations of the gastrin C-terminal peptide amide NAc-Trp-Met-Asp-Phe-NH2. Two families of lowest energy conformations were found corresponding to: (a) alpha-helical structures; (b) conformations having beta-structure at the level of Trp residue, and C7-structure at the level of Asp residue. The two aromatic rings were folded on the peptide backbone and ca. 5 A distant from each other (centre to centre). The last family, favoured by energy and population probability, can better account for conformational experimental results and biological activity observations.

Amino Acid Sequence↗

PubMed2003

Higher energy monophasic DC cardioversion for persistent atrial fibrillation: is it time to start at 360 joules?

BACKGROUND: Electrical direct-current cardioversion (DCCV) has become a routine therapy for atrial fibrillation (AF), although some uncertainty remains regarding the optimal energy settings. AIMS: This study examines whether the use of a higher initial energy monophasic shock of 360 joules (J) for external DCCV, in patients with persistent AF would prove more effective, yet as safe, as the use of a lower initial energy 200 J shock. METHODS: A cohort of 107 patients with persistent AF was prospectively randomized to an initial synchronized DCCV shock of 360 J versus 200 J (n = 50 vs 57), followed by a similar shock sequence thereafter of four further shocks of 360 J for the two groups. In all patients the levels of troponin I (cTnI) were measured precardioversion and 18-20 hours later, the following day. In a subgroup of 36 patients in each group, the levels of creatine kinase (CK) and aspartate transaminase (AST) were measured pre- and 18-20 hours postcardioversion. RESULTS: The success rate for DCCV was significantly higher in the 360 J group compared to the 200 J group (96.0% vs 75.4%, P = 0.003). The mean CK IU/L levels (1137.5.0 vs 2411.8, P = 0.014) and AST levels (39.83 vs 52.86, P = 0.010) were significantly lower in the 360 J group compared to the 200 J group. There was no statistical rise in cTnI (microg/L) in either group (P = 1.00). The average number of shocks delivered (1.84 vs 2.56, P = 0.006) was significantly less in the 360 J group than in the 200 J group, although total energy requirements for DCCV were similar for the two groups (662.4 J vs 762.4 J, P = 0.67). CONCLUSION: For patients with persistent AF the use of a higher initial-energy monophasic shock of 360 J achieves a significantly greater success rate, with less skeletal muscle damage (and no cardiac muscle damage) as compared with the traditional starting energy of a 200 J DC shock.

Adult↗