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PubMed1996

Optimal CT evaluation for functional endoscopic sinus surgery.

PURPOSE: To evaluate the optimal parameters for the CT examination of patients who are having functional endoscopic sinus surgery. METHODS: CT scanning was performed on two fresh cadaveric heads in the direct coronal plane, varying the section thickness, intersection gap, scanner gantry angle, and amperage. The nasal cavity and paranasal sinuses were examined independently in a blinded fashion by four staff neuroradiologists and a staff otolaryngologist with special attention to 10 anatomic landmarks within the ostiomeatal unit that are considered important for preoperative planning. A score of 0 (nonvisualization/incomplete visualization) or 1 (clear/complete visualization) was assigned to each of these 10 landmarks. Analysis of variance was used in which reader, subject, and side were simultaneously controlled by "blocking." Multiple comparison methods (ie, Bonferroni) were used to compare the different protocols. RESULTS: We found a significant reduction in the delineation, and therefore the perception, of the ostiomeatal unit structures when the section thickness was greater than 5mm, any intersection gap was used, and the gantry angle was greater than 10 degrees from the plane perpendicular to the hard palate. However, a reduction in the radiation exposure from 200 mA to 80 mA did not affect the display of the anatomic landmarks. CONCLUSION: We found the optimal screening CT protocol for the paranasal sinuses to be a section thickness of 3 mm, no intersection gap, and a section angle within 10 degrees from the plane perpendicular to the palate. Also, owing to inherent contrast between air, soft tissue, and bone in the paranasal sinuses, a reduction in the radiation exposure parameter to 80 mA did not affect image quality.

Endoscopes↗

PubMed1996

Visualisation in the SPROUT molecular design program.

SPROUT is an interactive computer system for structure based molecular design. The system consists of several modules that address the different subproblems of structure based drug design. This paper describes the visualisation techniques applied in the program: the display of the novel (geometric region) representation of the interaction sites and the molecular surface display based on a 3D grid representation of the cavity. The hydrogen bonding regions are represented by set operations (subtraction and intersection) of simple spherical and conical 3D objects (with given radii and opening angle) Some complex hydrogen bonding regions are represented by intersections of six or more basic objects. A method for calculating a triangular mesh representation (with normal vectors) of the analytical surfaces of the objects, that have sharp edges and corners because of the intersections, is presented in the paper. The geometric parameters of the interaction regions can be changed interactively in which case the surface display is updated real-time. The volume of space that is available for ligand generation (the cavity of the receptor site) is represented on a 3D grid within SPROUT. The surface of the available space is visualised using an algorithm presented in the paper, that generates a polygonial mesh of the grid points. The grid is also used to cut out stericaly forbidden parts of the interaction site regions. The surface of the reduced object is also visualised using further sphere subtractions. The presented algorithms are fast, aplicable in interactive visualisation programs. Result images of the rendering of the surfaces, calculated by the algorithms, are demonstrated on examples taken from applications of SPROUT to practical ligand design problems.

Computer Simulation↗

PubMed1979

Clinical specular microscopy. II. Qualitative evaluation of corneal endothelial photomicrographs.

The clinical specular microscope shows the morphological appearance of the endothelium in normal and abnormal corneas. This instrument resolves the endothelial mosaic of the normal cornea into a quasiregular pattern of contiguous cells having well-defined cell boundaries. Cell size varies over a wide range in a number of disorders, and endothelial cells may assume shapes that are substantially different from their usual hexagonal appearance. Cell boundaries are dark and most commonly appear as a straight, narrow line. However, other types of cell boundaries, collectively referred to as doubled boundaries, have been encountered. Cell boundaries normally intersect in a manner that results in three angles of intersection, each approximately 60 degrees, but variations from this pattern are seen. A number of noncellular structures also can be seen in the endothelial zone.

Adolescent↗

PubMed2002

Crosswalk markings and the risk of pedestrian-motor vehicle collisions in older pedestrians.

CONTEXT: Motor vehicles struck and killed 4739 pedestrians in the United States in the year 2000. Older pedestrians are at especially high risk. OBJECTIVE: To determine whether crosswalk markings at urban intersections influence the risk of injury to older pedestrians. DESIGN: Case-control study in which the units of study were crossing locations. SETTING: Six cities in Washington and California, with case accrual from February 1995 through January 1999. PARTICIPANTS: A total of 282 case sites were street-crossing locations at an intersection where a pedestrian aged 65 years or older had been struck by a motor vehicle while crossing the street; 564 control sites were other nearby crossings that were matched to case sites based on street classification. Trained observers recorded environmental characteristics, vehicular traffic flow and speed, and pedestrian use at each site on the same day of the week and time of day as when the case event had occurred. MAIN OUTCOME MEASURE: Risk of pedestrian-motor vehicle collision involving an older pedestrian. RESULTS: After adjusting for pedestrian flow, vehicle flow, crossing length, and signalization, risk of a pedestrian-motor vehicle collision was 2.1-fold greater (95% confidence interval, 1.1-4.0) at sites with a marked crosswalk. Almost all of the excess risk was due to 3.6-fold (95% confidence interval, 1.7-7.9) higher risk associated with marked crosswalks at sites with no traffic signal or stop sign. CONCLUSIONS: Crosswalk markings appear associated with increased risk of pedestrian-motor vehicle collision to older pedestrians at sites where no signal or stop sign is present to halt traffic.

Accidents, Traffic↗

PubMed1996

Reduced surface: an efficient way to compute molecular surfaces.

Because of their wide use in molecular modeling, methods to compute molecular surfaces have received a lot of interest in recent years. However, most of the proposed algorithms compute the analytical representation of only the solvent-accessible surface. There are a few programs that compute the analytical representation of the solvent-excluded surface, but they often have problems handling singular cases of self-intersecting surfaces and tend to fail on large molecules (more than 10,000 atoms). We describe here a program called MSMS, which is shown to be fast and reliable in computing molecular surfaces. It relies on the use of the reduced surface that is briefly defined here and from which the solvent-accessible and solvent-excluded surfaces are computed. The four algorithms composing MSMS are described and their complexity is analyzed. Special attention is given to the handling of self-intersecting parts of the solvent-excluded surface called singularities. The program has been compared with Connolly's program PQMS [M.L. Connolly (1993) Journal of Molecular Graphics, Vol. 11, pp. 139-141] on a set of 709 molecules taken from the Brookhaven Data Base. MSMS was able to compute topologically correct surfaces for each molecule in the set. Moreover, the actual time spent to compute surfaces is in agreement with the theoretical complexity of the program, which is shown to be O[n log(n)] for n atoms. On a Hewlett-Packard 9000/735 workstation, MSMS takes 0.73 s to produce a triangulated solvent-excluded surface for crambin (1 crn, 46 residues, 327 atoms, 4772 triangles), 4.6 s for thermolysin (3tln, 316 residues, 2437 atoms, 26462 triangles), and 104.53 s for glutamine synthetase (2gls, 5676 residues, 43632 atoms, 476665 triangles).

Chemistry, Physical↗

PubMed1999

Effects of injector geometry and sample matrix on injection and sample loading in integrated capillary electrophoresis devices.

The double-T injector design employed in many microchip capillary electrophoresis devices allows for the formation of very small (50-500 pL) sample plugs for subsequent analysis on-chip. In this study, we show that sample plugs formed at the channel junction can be geometrically defined. The channel width and injector symmetry prove to be of great importance to good performance. A unique pushback of solvent into the side channels can be induced when the side channels have a very low resistance to flow, and this helps to better define the injected sample plug. Samples and running buffers of differing ionic strength (e.g., 10 mM KCl buffer and 20 mM KCl sample) can yield widely variable results in terms of plug shape and amount injected (variations of 1.5 to 10x). Applying bias voltages to all the intersecting channels aids in controlling the plug shape. However, when the ionic strengths of buffer and sample are not matched, the actual amount injected (up to 10x variations) can be inconsistent with the appearance of the plug formed in the injector (up to only 30 % variations). Operating at constant pH and ionic strength produced the most consistent results. This report examines the effects of altering the injector geometry and solution ionic strengths, and presents the results of using bias voltages to control plug formation. The observed results should provide a benchmark for modeling of the fluid dynamics in channel intersections.

Electrophoresis, Capillary↗

PubMed1999

Detection of DNA curvature by transverse pore gradient gel electrophoresis on PhastSystem gels.

It has been known since 1990 that DNA curvature can be recognized on transverse pore gradient gels by an intersection of "Ferguson curves" with those of DNA size standards. The miniaturized PhastSystem polyacrylamide gels allow one to detect DNA curvature effortlessly and fast and at great economy of sample relative to alternative methods of electrophoresis. Using the transverse gradient gel electrophoresis method, it was found that the 660 bp length subfragment of the matrix attachment region (MAR) sequence of the chicken lysosyme gene migrates as a fragment of 800-900 bp length. When subjected to digestion with the restriction enzyme HaeIII, the fragment gives rise to two species of 248 and 412 bp length, respectively. The Ferguson curves of both species intersect with those of DNA size standards, indicating that both exhibit curvature. Only the curvature of the 412 bp fragment conforms to prediction. Ethidium bromide abolishes the effect of curvature on the fragment, reducing its apparent size from 900 to 660, the value obtained by agarose gel electrophoresis.

Animals↗

PubMed2000

Electrokinetic control of fluid flow in native poly(dimethylsiloxane) capillary electrophoresis devices.

Capillary zone electrophoresis (CZE) devices fabricated in poly(dimethylsiloxane) (PDMS) require continuous voltage control of all intersecting channels in the fluidic network in order to avoid catastrophic leakage at the intersections. This contrasts with the behavior of similar flow channel designs fabricated in glass substrates. When the injection plugs are shaped by voltage control and leakage from side channels is controlled by the application of pushback voltages during separation, fluorescein samples give 64 200 theoretical plates (7000 V separation voltage, E = 1340 V/cm). Native PDMS devices exhibit stable retention times (+/- 8.6% RSD) over a period of five days when filled with water. Contact angles were unchanged (+/- 1.9% RSD) over a period of 16 weeks of dry storage, in contrast to the known behavior of plasma-oxidized PDMS surfaces. Electroosmotic flow (EOF) was observed in the direction of the cathode for the buffer systems studied (phosphate, pH 3-10.5), in the presence or absence of hydrophobic ions such as tetrabutylammonium or dodecyl sulfate. Electroosmotic mobilities of 1.49 x 10(-5) and 5.84 x 10(-4) cm2/Vs were observed on average at pH 3 and 10.5, respectively, the variation strongly suggesting that silica fillers in the polymer dominate the zeta potential of the material. Hydrophobic compounds such as dodecyl sulfate and BODIPY 493/503 adsorbed strongly to the PDMS, indicating the hydrophobicity of the channel walls is clearly problematic for CZE analysis of hydrophobic analytes. A method to stack multiple channel layers in PDMS is also described.

Animals↗

PubMed2000

Exercise, methacholine, and adenosine 5'-monophosphate challenges in children with asthma: relation to severity of the disease.

Bronchial hyperreactivity is a characteristic feature of asthma and can be evaluated by different challenges. The aim of this study was to compare exercise, methacholine (MCH), and adenosine 5'-monophosphate (AMP) challenges in 135 children and young adults (mean age +/- SD, 12.4+/-3.9 years) with asthma, and to examine the utility of the different challenges in predicting those children with asthma likely to require prophylactic antiinflammatory treatment. The sensitivity of MCH challenge in detecting bronchial hyperreactivity (at or below 8 mg/mL) was 98%, that of AMP challenge (at or below 200 mg/mL) 95.5%, and that of exercise (more than 8.2% fall in FEV(1)) was 65%. There was a significant difference between mild asthmatic children (85 patients, intermittent asthma, step 1 of NIH guidelines) and moderate asthmatics (50 patients, steps 2 and 3 of guidelines) in relation to the logarithmic mean provocation concentration to elicit a 20% fall in FEV(1) (PC(20)) to MCH (0.49 mg/mL vs. 0.15 mg/mL, P<0.00001), that to AMP (7.67 mg/mL vs. 3.60 mg/mL, P = 0.001), and in relation to the mean percent fall in FEV(1) after exercise (13.9% vs. 22.0%, P = 0.001). Sensitivity and specificity curves between the two severity groups of asthma were constructed, and the intersection point of the two curves for each type of challenge was determined. When mild asthmatics were compared to moderate asthmatics, the intersection points for MCH, AMP, and exercise were 66%, 63%, and 61%, respectively. Logistic regression analysis and receiver operating characteristic (ROC) curves of the three challenges for the two severity groups of asthma showed that methacholine was a better discriminating challenge between the severity groups than the other two challenges. We conclude that the sensitivities of AMP and MCH challenges in the detection of bronchial hyperreactivity in children and young adults with asthma are very similar and higher than that of exercise. There is a significant difference between mild and moderate asthmatics within the three bronchial challenges, with MCH discriminating better than AMP or exercise between groups.

Adenosine Monophosphate↗

PubMed2002

Femtochemistry of Norrish type-I reactions: IV. Highly excited ketones--experimental.

Femtosecond dynamics of Norrish type-I reactions of cyclic and acyclic ketones have been investigated in real time for a series of 13 compounds using femtosecond-resolved time-of-flight mass spectrometry. A general physical description of the ultrafast processes of ketones excited into a high-lying Rydberg state is presented. It accounts not only for the results that are presented herein but also for the results of previously reported studies. For highly excited ketones, we show that the Norrish type-I reaction is nonconcerted, and that the first bond breakage occurs along the effectively repulsive S2 surface involving the C-C bond in a manner which is similar to that of ketones in the S1 state (E. W.-G. Diau et al. ChemPhysChem 2001, 2, 273-293). The experimental results show that the wave packet motion out of the initial Franck-Condon region and down to the S2 state can be resolved. This femtosecond (fs) internal conversion from the highly excited Rydberg state to the S2 state proceeds through conical intersections (Rydberg-valence) that are accessed through the C=O stretching motion. In one of these conical intersections, the internal energy is guided into an asymmetric stretching mode. This explains the previously reported pronounced nonstatistical nature of the reaction. The second bond breakage involves an excited-state acyl radical and occurs on a time scale that is up to one order of magnitude longer than the first. We discuss the details regarding the ion chemistry, which determines the appearance of the mass spectra that arise from ionization on the fs time scale. The experimental results presented here, aided by the theoretical work reported in paper III, provide a unified picture of Norrish reactions on excited states and on the ground-state potential energy surfaces.

Journal Article↗

PubMed2001

Investigation of the physicochemical basis of enantiomeric enrichment: The example of alpha-phenylethylamine with achiral dicarboxylic acids.

We investigated the enantiomeric enrichment of enantiomeric mixtures of alpha-phenylethylamine by achiral dicarboxylic acids. As achiral agents oxalic, malonic, fumaric, and phthalic acids were used. The results of the enantiomeric enrichment via partial salt formation followed by distillation were compared with enantiomer separation via crystallization of the neutral salt. Without the presence of a solid phase, enantiomeric separation is impossible. Our results show that the properties of the solid phase determine the separation. It is also confirmed by our observation that the eutectic points, which are observed on the 3-phase solubility diagrams of the solid neutral salts, can be found at the same initial enantiomeric composition as the point of intersection of distillate and residue of the distillation curves and the point of intersection of precipitated salt and mother liquor of the crystallization curves. Copyright 2000 Wiley-Liss, Inc.

Journal Article↗

PubMed1989

Human occlusofacial form commonality: race-related traits, ontogeny, paedomorphism, and functional correlates.

Previous cephalometric studies of occlusofacial angular and metric data show small variability within and between population samples of Caucasian children and adults. Comparable results were obtained by use of standardized X-ray cephalometry and direct craniometric measurements of skulls of mature specimens of Alouatta caraya and Cebus capucinus. These data measure facial and occlusofacial form and form relationships. Identical measuring techniques are applied to compare data derived from headplates of 19 young adult American Caucasians and 19 articulated Hindu skulls of mature individuals. The data are expanded to include measurements that relate symphyseal form to occlusal and nasomaxillary structure. The facial plane and an "internal" facial plane (nasion to a point tangential to the superior genial tubercles) straddle the mandibular symphysis. The angles they form at nasion and at their intersections with the maxillary occlusal plane were derived and statistically analyzed. The occlusal plane intersect angles show small absolute variability and are not significantly different (P greater than .05) in the two groups. The nasion plane angles are significantly different (P less than .025), reflecting sample differences in facial height. Linear measurements confirm a considerably larger dentoalveolar prognathism in the Hindu group. Data derived from the geometrically averaged tracings of Bjork, Broadbent, Sassouni, and Solow provide further evidence of occlusofacial form commonality. These shared phyletically conservative traits are evidence of highly integrated morphological adaptations for the attainment, maintenance, and functioning of the species-wide pattern of precisely fitting complementary crowns and crown parts that constitute the dental occlusion.

Adolescent↗

PubMed1986

Dendritic atrophy in children with Down's syndrome.

Dendritic branching was evaluated in the visual cortex of 8 children with Down's syndrome and 10 controls, ranging in age from 4 months to 7 years and divided into infantile, late-infantile, and juvenile groups. Camera lucida drawings of Golgi-impregnated neurons were used for examining the following dendritic aspects: dendritic intersections as a function of distance from the cell body, point of maximum dendritic branching, number of branch orders, total number of branch segments, and total dendritic length. The number of intersections and the total dendritic length were above normal in the infantile period (6 months old or less) and dropped steadily to significantly below normal in the juvenile group (older than 2 years). These reductions contrasted with expanding dendritic arborization in normal children. The results suggest that the dendritic tree atrophies in early childhood in Down's syndrome.

Child, Preschool↗

PubMed1986

Determination of the lengths of nonisotropic linear features in micrographs.

The method described was devised to facilitate rapid and reasonably accurate estimations of the length of a nonisotropic linear feature in a micrograph. It arose from studies in which we were determining the length of the Purkinje cell layer in each of a set of serial sections through the rat cerebellum. The Purkinje cell layer appears as a linear feature in such sections and the simplest and most rapid method of estimating the length of this type of feature is to count the number of intersections that it makes with a series of equally spaced parallel test lines (see, e.g., Weibel, E.R., 1979: Stereological Methods Vol. 1, Practical Methods for Biological Morphometry). In many sections, the Purkinje cell layer was markedly nonisotropic, and the length obtained by this method varied very considerably depending on the orientation of the section relative to the test lines. The present method employs two orthogonal sets of parallel test lines, and the length of the feature is estimated from the square root of the sum of the squares of the counts of the number of intersections with each of the two sets of lines. The result obtained varies very little with the relative orientations of the feature and the test grid and a good estimate of the length can be obtained from the counts from a single random placement of the grid on the section. It has been found that the technique can be carried out efficiently and reliably by relatively inexperienced personnel, and the results are obtained more rapidly than when alternative methods for estimating dimensions of nonisotropic features are used.

Animals↗

PubMed1989

In vitro reconstruction of a cartilage matrix granule network.

The cartilage extracellular matrix contains electron-dense granules and fine filaments when studied electron microscopically after staining with ruthenium red. The matrix granules contain proteoglycans, while the filaments are thought to represent hyaluronic acid. In the present study partial extraction of proteoglycans from the cartilage prior to staining reduced the density of matrix components to allow visualization of a well-developed network involving the matrix granules and hyaluronic acid filaments. The matrix granules frequently had multiple filamentous attachments and the network appeared to be formed by intersecting filaments with the matrix granules at points of intersection. A similar network was created in Sepharose CL-2B beads when proteoglycans, link proteins, and hyaluronic acid were concentrated in the beads. Elimination of any one of these components resulted in failure to form a complete network. Purified proteoglycan monomers alone were sufficient to create matrix granules in the beads. Filaments were seen only when hyaluronic acid was added to the beads. The nature of the network suggests that some type of association between separate aggregates is occurring both within cartilage and within the Sepharose CL-2B beads.

Animals↗

PubMed1992

Architectural design, fiber-type composition, and innervation of the rat rectus abdominis muscle.

The rectus abdominis muscle is architecturally compartmentalized by tendinous intersections and is supplied by multiple thoracic nerves. In this study, the rectus abdominis of the rat has been qualitatively and quantitatively examined with regard to muscle dimensions, fiber organization, fiber-type composition, and innervation. The muscle exhibits architectural heterogeneity and different patterns of innervation among its thoracic, epigastric, and hypogastric parts. The epigastric part, adherent to the rectus sheath via tendinous intersections, represents relatively simple design. It is formed by serially arranged compartments with shorter fibers, compared with the other parts. These compartments are segmentally supplied by thoracic nerves. The hypogastric part is more complex, forms an interdigitation of muscular slips, and has segmental distribution of thoracic nerves in mediolateral direction. The thoracic part much differs from the other parts. It has smaller cross-sectional areas, compartments composed of abundant nonspanning fibers with intrafascicular termination, and non-segmental distribution of thoracic nerves. In addition to these craniocaudal specializations among the three parts, the muscle exhibits mediolateral differences in fiber-type composition. Slow-twitch oxidative fibers are more densely distributed in the medial half region than the lateral, whereas fast-twitch glycolytic fibers follow an inverse pattern. The mediolateral differences in fiber-type composition as well as the craniocaudal specializations in architectural design and innervation imply regionally differentiated recruitments of the muscle in various behaviors.

Abdominal Muscles↗

PubMed1987

Temperature-specific inhibition of human red cell Na+/K+ ATPase by 2,450-MHz microwave radiation.

The ATPase activity in human red blood cell membranes was investigated in vitro as a function of temperature and exposure to 2,450-MHz continuous wave microwave radiation to confirm and extend a report of Na+ transport inhibition under certain conditions of temperature and exposure. Assays were conducted spectrophotometrically during microwave exposure with a custom-made spectrophotometer-waveguide apparatus. Temperature profiles of total ATPase and Ca+2 ATPase (ouabain-inhibited) activity between 17 and 31 degrees C were graphed as an Arrhenius plot. Each data set was fitted to two straight lines which intersect between 23 and 24 degrees C. The difference between the total and Ca+2 ATPase activities, which represented the Na+/K+ ATPase activity, was also plotted and treated similarly to yield an intersection near 25 degrees C. Exposure of membrane suspensions to electromagnetic radiation, at a dose rate of 6 W/kg and at five temperatures between 23 and 27 degrees C, resulted in an activity change only for the Na+/K+ ATPase at 25 degrees C. The activity decreased by approximately 35% compared to sham-irradiated samples. A possible explanation for the unusual temperature/microwave interaction is proposed.

Calcium-Transporting ATPases↗

PubMed2001

Merging sex and position.

The choice between male and female development arises from a simple binary decision made in early development. Studies in a few model organisms led to a detailed understanding of the regulatory mechanisms that convey male or female identity at the cellular level. We have learned little, however, of how this information translates into the actual sexual phenotype with regionally dimorphic characters. Where does positional information come from and how does it integrate with the sex-determining pathway? A recent report sheds light onto this enigma and reveals possible intersections between sex-determining and homeotic pathways in Drosophila. Such intersections may also play an important part in evolution, providing a basis for phenotypic diversity among related species. BioEssays 23:304-306, 2001.

Animals↗