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At least 19 recordsLinked to original sources
PubMed2026

A correction factor for bridging compaction simulator and different roller compactors.

Roller compaction (RC) is an important dry granulation technique. Since pilot and commercial scale roller compactors, which operate continuously on a large scale, usually require kilograms of material per run, formulation and process development directly on such roller compactors is not practical. In contrast, a compaction simulator (CS) can produce ribblets, also known as "slugs", using only a few grams of material with sinusoidal displacement profile replicating the motion of a specific point on the roll surface. Thus, it is possible to develop RC formulation and process in laboratory using a CS-based material-sparing approach. However, because of the inherently different configurations for applying pressure between die compression and roll compression, translating uniaxial pressure from CS experiments to roll pressure during RC is often unreliable, leading to significant uncertainties in the critical quality attributes of ribbons, such as ribbon solid fraction (or porosity) and mechanical strength. The objective of this study was to identify a correction factor (Kp = uniaxial die compression pressure/roll pressure), by correlating the compressibility profiles from CS and a roller compactor of interest, to enable more reliable process translation from CS to roller compactor. In this study, a Kp value of 0.5 was determined for Alexanderwerk WP120 and validated for Gerteis Mini-Pactor and Bepex Pharmapactor. This value may serve as a starting point for translating the optimal compaction pressure identified based on CS investigation to common roller compactors, requiring only minor adjustments to attain optimal RC process parameters (i.e., roll force and roll gap) for a chosen roller compactor.

Drug Compounding↗
PubMed1989

Laser dentistry: root canal diagnostic technique based on ultraviolet-induced fluorescence spectroscopy.

A diagnostic technique to detect residual tissues at different levels of the root canal during an endodontic treatment is presented. The diagnostic system is based on ultraviolet-induced fluorescence spectroscopy and uses suitable optical fibers for local delivery of excitation light and to collect back fluorescence spectra. Spectra of root canal tissues have been obtained from split teeth by labeling with a fluorescent solution. Residual tissue can be discriminated in respect to healthy dentin because of their different spectral responses: the spectral shape of the first response shows a clear peak at 530 nm because of a selective absorption of the fluorescent dye, whereas for the second response, the spectral curve monotonically increases toward ultraviolet wave-lengths with no particular structure. This technique has been tested on unsplit teeth simulating operative conditions. A compact spectroscopic system has been devised that can be easily integrated in an excimer laser system to perform residual tissue detection during laser cleaning of the canals.

Fiber Optic Technology↗
PubMed1987

In vivo assessment of vascular dilatation during percutaneous transluminal coronary angioplasty.

Previous studies of the mechanism of percutaneous transluminal coronary angioplasty used either postmortem specimens or animal models. To characterize the process of vascular dilatation in vivo, a system was devised for recording the instantaneous pressure-volume changes in the angioplasty balloon during inflation within the stenosed artery. The pressure-volume patterns obtained were compared with those observed in vitro with the balloon inflated in materials whose properties simulate stretching (Silastic tubing), compaction (styrofoam) and cracking (dry macaroni). Of 48 narrowings in 46 patients, a pressure-volume pattern of stretching was observed in 56%, compaction in 27% and cracking in only 17%. Of lesions manifesting a stretching pattern, 85% were longer than 5 mm cr had visible calcium deposits, whereas those that compacted were shorter and lacked calcium deposits. Both of these pressure-volume patterns were associated with a successful clinical outcome. Of 8 lesions exhibiting a cracking pattern, 6 showed dissection angiographically; 3 of these resulted in vessel occlusion.

Angioplasty, Balloon↗
PubMed1992

Compact mock loops of the systemic and pulmonary circulation for blood pump testing.

Mock loops are an important tool for in vitro investigations of artificial blood pumps. The simple windkessel, throttle, and atrium principle was used for the mock loop design presented. The components of the systemic and the pulmonary mock loop were designed according to calculated numerical simulation parameters. The loops offer a compact design and simple handling. For simulating biventricular assist or total artificial heart (TAH), both loops can be coupled correspondingly. The numerical simulation and the first results with the loops show very good similarity to physiological data of systemic and pulmonary circulation. The measurements of pump characteristics are significant for quantitative comparison of different pump sizes and types, or driving systems.

Blood Circulation↗
PubMed1992

Neutron and X-ray solution-scattering studies of the ternary complex between proteoglycan-binding region, link protein and hyaluronan.

Proteoglycan aggregates of cartilage are stabilized by the formation of a ternary complex between the G1 domain at the N-terminus of the proteoglycan monomer (aggrecan), link protein and hyaluronan polysaccharide. Both the G1 domain and link protein contain similar three-domain structures formed from an immunoglobulin fold and two proteoglycan tandem repeats, the arrangement of which had been investigated by neutron and synchrotron X-ray scattering [Perkins, Nealis, Dunham, Hardingham & Muir (1991) Biochemistry 30, 10708-10716]. Here, solution scattering was used to investigate the ternary complexes formed between a proteolytic fragment of proteoglycan monomer containing G1 (termed binding region), link protein and hyaluronan oligosaccharides containing either 34 or 450 saccharide units (HA34 and HA450). The ternary complex with HA34 had a neutron radius of gyration, RG, at infinite contrast not exceeding 5.5 nm. The ternary complex with HA34 had an X-ray cross-sectional radius of gyration Rxs of 2.4 nm and a neutron Rxs at infinite contrast of 2.00 nm. Since both were similar or larger than the Rxs for binding region (X-rays, 2.04 nm; neutrons, 1.84 nm) and link protein (neutrons, 0.8 nm), analyses showed that the cross-sectional mean width of the ternary complex is greater than those in each of the free proteins, i.e. the two proteins associated side-by-side. Similar results were obtained with HA450 complexed with binding region and with both binding region and link protein. This structural model was verified by hydrodynamic simulations of the experimental sedimentation coefficient of 5.5 S, which showed that a compact ternary-complex structure was formed. Although scattering curve simulations using small spheres were limited for the ternary complex with HA34 because of its approximate RG value, the scattering data were compatible with the formation of a compact complex formed by side-by-side contacts between G1 and link protein.

Extracellular Matrix Proteins↗
PubMed1990

A new cardiac auscultation simulator.

We have successfully developed a new cardiac auscultation simulator by applying recently developed digital and computer technology, which digitally records, stores, modifies, and plays back heart sounds and murmurs characteristic of various heart diseases. The simulator is capable of playing back different heart sounds or murmurs at each auscultatory site (aortic, pulmonic, tricuspid, and mitral) of a human chest-sized mannequin (made of urethane foam), through four built-in speakers. We were able to listen to accurate reproductions of heart sounds and murmurs at the same timing as in real patients by any type of stethoscope used in routine medical practice. This compact and portable educational apparatus, which simulates realistic auscultatory sounds, will impact greatly on the medical training of cardiac auscultation for physicians, medical students, nurses, and paramedicals.

Computer Simulation↗
PubMed1991

Protein folding. Effect of packing density on chain conformation.

Recent lattice polymer simulations by Chan & Dill suggest that compactness may be a significant driving force in the formation of secondary structure. We have addressed the robustness of this conclusion for non-lattice polymers using a rotational isomeric model of proteins. Boundary conditions are used to enforce compactness and excluded volume effects are explicitly incorporated. As in the cubic lattice studies, compactness is seen to influence secondary structure content. This effect is modest for densities comparable to native proteins but dramatic for chains that are approximately 30% more dense than native proteins. alpha-Helical structure is common but beta-sheet structure is rare. It appears that lattices impart to compact chains an organizational bias that favors beta-sheet structure. The strengths and weakness of various simplified representations of polypeptide chains are also discussed.

Crystallography↗
PubMed1989

Bioadhesive dosage form for peroral administration of timolol base.

Timolol base was prepared from its maleate salt and checked for purity, pKa (9.03) and n-octanol/phosphate buffer pH 6.6 partition coefficient (1.72). The rate of swelling of sodium carboxymethylcellulose, Carbopol 934 (CP) and hydroxypropylcellulose (HPC) was examined prior to use in bioadhesive compacts with the model drug methylene blue to study their influence on device integrity and drug diffusion. A final compact containing a core of timolol base and Precirol, a bioadhesive layer of CP and HPC, and a cap of magnesium stearate gave sustained release of the drug in simulated saliva pH 6.6. After preliminary evaluation in dogs, the compact was evaluated in a panel of humans in whom it was shown that the flux of drug could be increased from 70 to 127 micrograms mm-2 h-1 by inclusion of the penetration enhancer sodium lauryl-sulphate into the core formulation.

Adhesiveness↗
PubMed1992

Solution structure of endothelin-3 determined using NMR spectroscopy.

The aqueous solution structure of the 21-residue vasoactive peptide hormone endothelin-3 has been determined using high-resolution NMR spectroscopy. A total of 177 proton-proton distance measurements and 5 chi 1 dihedral angle constraints derived from NMR spectra were used to calculate the structure using a combination of distance geometry and dynamical simulated annealing calculations. The calculations reveal a highly ordered, compact conformation in which a helical region extending from K9 to C15 lies in close apposition with the C-terminal hexapeptide; this interaction seems to be largely driven by hydrophobic interactions. Structure-activity studies are interpreted in terms of the conformational features of the calculated endothelin-3 structure.

Amino Acid Sequence↗
PubMed2026

Computational discovery of emodin-based anthraquinones as PARP-1 inhibitors with relevance to ovarian and prostate cancer.

Cancer is a disease characterized by genomic instability and aberrant DNA repair. Poly (ADP-ribose) polymerase-1 (PARP-1) represents a well-established therapeutic target, particularly in ovarian and prostate cancer. However, the currently approved PARP inhibitors face challenges such as resistance, toxicity, and reduced efficacy. The search for alternative scaffolds has therefore become increasingly urgent. In this study, we used an integrated approach combining computer-aided methods to search for potential lead compounds among emodin-based anthraquinone derivatives as PARP-1 inhibitors. Using a PASS-based QSAR approach, drug-likeness prediction, and in silico ADMET assessment, we pre-screened a large set of anthraquinones and identified several potential hits for interaction with PARP-1. These hits were studied using molecular docking with the PARP-1 catalytic domain (PDB ID: 7KK4). The most stable and compact complexes were further explored by 500 ns molecular dynamics (MD) simulations and various dynamic properties (RMSD, RMSF, Rg, SASA, MolSA, hydrogen bonds, PCA, DCCM). The key finding of this study is that several emodin-derived anthraquinones exhibited binding behavior and ADMET profiles comparable to, or better than, the reference PARP-1 inhibitor. Among them, CID-10425624 emerged as the most promising candidate, exhibiting stable binding, reduced conformational fluctuation, compact complex formation, persistent hydrogen-bond interactions, and enhanced dynamic residue correlations within the PARP-1 catalytic domain. These findings suggest that the anthraquinone scaffold can provide a valuable starting point for developing structurally distinct PARP-1 inhibitors. In summary, this study identified several emodin-derived anthraquinones, particularly CID-10425624, as computationally prioritized lead candidates for PARP-1 inhibition, providing a novel anthraquinone-based scaffold for further experimental validation and optimization.

Anthraquinones↗
PubMed1991

Molecular structure matching by simulated annealing. IV. Classification of atom correspondences in sets of dissimilar molecules.

A set of 6 molecules, active at the benzodiazepine GABAA site are matched pairwise with one member of the set in turn. Matchings are performed by simulated annealing using null correspondences to reject poorly matched atom positions. Cluster analysis is employed to identify molecular similarities after an optimal molecular superimposition has been discovered. A statistic for the compactness of clustered atom positions is suggested. The introduction of null correspondences causes the clusters of matched atoms to become more compact.

Benzodiazepines↗
PubMed1991

Structural dynamics of calmodulin and troponin C.

We present the results of computational simulation studies of the structures of calmodulin (CAM) and troponin C (TNC). Possible differences between the structures of these molecules in the crystal and in solution were suggested by results from some recent experimental studies, which implied that their conformations in solution may be more compacted than the characteristic dumbbell shape observed in the crystal. The molecular dynamics simulations were carried out with the CHARMM system of programs, and the environment was modeled with a distance-dependent dielectric permittivity and discrete water molecules surrounding the proteins at starting positions identified in the crystals of CAM and TNC. Methods of macromolecular structure analysis, including linear distance plots, distance matrices and a matrix representation of hydrogen bonding, were used to analyze the nature, the extent and the source of structural differences between the computed structures of the molecules and their conformations in the crystal. Following the longest simulation, in which intradomain structure was conserved, the crystallographically observed dumbbell structure of the molecule changed due to a kinking or bending in the region of the central tether helix connecting the two Ca(2+)-binding domains which moved into close proximity. The resulting structure correlates with experimental observations of complexes between CAM and peptides such as melittin and mastoparan. Analysis of the corresponding pair distance distribution functions in comparison to experimental results suggests the dynamic existence of a non-negligible fraction of the compacted structure in aqueous solutions of CAM. In this more nearly globular shape, CAM reveals to the environment two interior pockets that contain a number of hydrophobic residues, in agreement with NMR data suggesting involvement of such residues in the binding of inhibitors and proteins to CAM.

Calcium↗
PubMed2023

A new horizon in the phosphorylated sites of AGA: the structural impact of C163S mutation in aspartylglucosaminuria through molecular dynamics simulation.

Aspartylglucosaminuria (AGU) is a lysosomal storage disorder caused by insufficient aspartylglucosaminidase (AGA) activity leading to chronic neurodegeneration. We utilized the PhosphoSitePlus tool to identify the AGA protein's phosphorylation sites. The phosphorylation was induced on the specific residue of the three-dimensional AGA protein, and the structural changes upon phosphorylation were studied via molecular dynamics simulation. Furthermore, the structural behaviour of C163S mutation and C163S mutation with adjacent phosphorylation was investigated. We have examined the structural impact of phosphorylated forms and C163S mutation in AGA. Molecular dynamics simulations (200 ns) exposed patterns of deviation, fluctuation, and change in compactness of Y178 phosphorylated AGA protein (Y178-p), T215 phosphorylated AGA protein (T215-p), T324 phosphorylated AGA protein (T324-p), C163S mutant AGA protein (C163S), and C163S mutation with Y178 phosphorylated AGA protein (C163S-Y178-p). Y178-p, T215-p, and C163S mutation demonstrated an increase in intramolecular hydrogen bonds, leading to greater compactness of the AGA forms. Principle component analysis (PCA) and Gibbs free energy of the phosphorylated/C163S mutation structures exhibit transition in motion/orientation than Wild type (WT). T215-p may be more dominant among these than the other studied phosphorylated forms. It might contribute to hydrolyzing L-asparagine functioning as an asparaginase, thereby regulating neurotransmitter activity. This study revealed structural insights into the phosphorylation of Y178, T215, and T324 in AGA protein. Additionally, it exposed the structural changes of the C163S mutation and C163S-Y178-p of AGA protein. This research will shed light on a better understanding of AGA's phosphorylated mechanism.Communicated by Ramaswamy H. Sarma.

Molecular Dynamics Simulation↗
PubMed1990

Bioadhesive lozenge for the improved delivery of cetylpyridinium chloride.

Conventional lozenges produce a high initial release of drug in the oral cavity, which rapidly declines to subtherapeutic levels, and requires multiple daily administration with associated problems of systemic toxicity and compliance. Various multilayer compacts containing cetylpyridinium chloride were evaluated in vitro using release into simulated saliva (buffer pH 6.6). The drug loading, the wax content of the active layer, and the composition of the bioadhesive layer were important variables affecting product performance. Following preliminary in vivo studies, the release of a three-layered device containing drug in a nonadhesive and flavored waxy exposed layer was studied in six humans using HPLC and was shown not to be affected by location within the mouth. In comparison with a proprietary lozenge formulation, the device produced more uniform and effective levels of drug (approximately 20 micrograms.mL-1), with adequate comfort, taste, and irritancy over a period of 3 h.

Adhesiveness↗
PubMed1976

Quantification of bone mineralization using computed tomography.

Computed tomography was used to find a sensitive parameter for bone mineralization. A precision scanning instrument was constructed for determination of the mineral distribution in sections of the forearm. The quality of the reconstructed images allows separate quantification of compact and spongy bone even when gamma rays are used. Computer simulation and measured of models and macerated human bones showed that under clinical conditions it is possible to quantify spongy bone density within an accuracy of +/-2%.

Adolescent↗
PubMed1991

The development of a test system for investigating the performances of personal aerosol samplers under actual workplace conditions.

The performances of new "total" aerosol samplers for use in workplaces are required to match the inhalability criteria as contained in the latest recommendations of the International Standards Organization (ISO) and the American Conference of Governmental Industrial Hygienists (ACGIH). In the past, practical evaluations have been carried out under idealized conditions in wind tunnels, and there is now the need to extend these to more realistic workplace conditions. This paper describes a new test system that was designed and built for this purpose. It consisted of a life-size mannequin mounted on a trolley so that it can be taken to and wheeled around in workplaces. The mannequin itself incorporated a robotic arm so that, under joystick control, it can be made to simulate a range of worker movements, orientations, and attitudes. An electronically controlled, compact breathing machine provided a range of typical breathing parameters for the mannequin. The pump also provided air movement for a number of personal samplers that were mounted on the torso of the mannequin and tested in that position. Sampler performance should be assessed by comparing directly the aerosol collected by the sampler with that inhaled by the mannequin (and collected on filters inside the head).

Aerosols↗