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PubMed2005

Method and apparatus for soft tissue material parameter estimation using tissue tagged Magnetic Resonance Imaging.

We describe an experimental method and apparatus for the estimation of constitutive parameters of soft tissue using Magnetic Resonance Imaging (MRI), in particular for the estimation of passive myocardial material properties. MRI tissue tagged images were acquired with simultaneous pressure recordings, while the tissue was cyclically deformed using a custom built reciprocating pump actuator A continuous three-dimensional (3D) displacement field was reconstructed from the imaged tag motion. Cavity volume changes and local tissue microstructure were determined from phase contrast velocity and diffusion tensor MR images, respectively. The Finite Element Method (FEM) was used to solve the finite elasticity problem and obtain the displacement field that satisfied the applied boundary conditions and a given set of material parameters. The material parameters which best fit the FEM predicted displacements to the displacements reconstructed from the tagged images were found by nonlinear optimization. The equipment and method were validated using inflation of a deformable silicon gel phantom in the shape of a cylindrical annulus. The silicon gel was well described by a neo-Hookian material law with a single material parameter C1=8.71+/-0.06kPa, estimated independently using a rotational shear apparatus. The MRI derived parameter was allowed to vary regionally and was estimated as C1 =8.80+/-0.86kPa across the model. Preliminary results from the passive inflation of an isolated arrested pig heart are also presented, demonstrating the feasibility of the apparatus and method for isolated heart preparations. FEM based models can therefore estimate constitutive parameters accurately and reliably from MRI tagging data.

Algorithms↗
PubMed1986

An apparatus to study the response of cultured endothelium to shear stress.

An apparatus which has been developed to study the response of cultured endothelial cells to a wide range of shear stress levels is described. Controlled laminar flow through a rectangular tube was used to generate fluid shear stress over a cell-lined coverslip comprising part of one wall of the tube. A finite element method was used to calculate shear stresses corresponding to cell position on the coverslip. Validity of the finite element analysis was demonstrated first by its ability to generate correctly velocity profiles and wall shear stresses for laminar flow in the entrance region between infinitely wide parallel plates (two-dimensional flow). The computer analysis also correctly predicted values for pressure difference between two points in the test region of the apparatus for the range of flow rates used in these experiments. These predictions thus supported the use of such an analysis for three-dimensional flow. This apparatus has been used in a series of experiments to confirm its utility for testing applications. In these studies, endothelial cells were exposed to shear stresses of 60 and 128 dynes/cm2. After 12 hr at 60 dynes/cm2, cells became aligned with their longitudinal axes parallel to the direction of flow. In contrast, cells exposed to 128 dynes/cm2 required 36 hr to achieve a similar reorientation. Interestingly, after 6 hr at 128 dynes/cm2, specimens passed through an intermediate phase in which cells were aligned perpendicular to flow direction. Because of its ease and use and the provided documentation of wall shear stress, this flow chamber should prove to be a valuable tool in endothelial research related to atherosclerosis.

Animals↗
PubMed2007

Circadian-dependent learning and memory enhancement in nociceptin receptor-deficient mice with a novel KUROBOX apparatus using stress-free positive cue task.

Using the novel apparatus KUROBOX, learning and memory behaviors, as well as various parameters of movement activity, were reevaluated in mice deficient for nociceptin/orphanin FQ receptor (NOP-/- mice) or mu-opioid receptor (MOP-/- mice). This method has the advantages that no handling procedures are required throughout the experiments performed over 3 days, positive cue paradigms are used without water or shock stress, and the method does not disturb the nocturnal habit of mice. NOP-/- mice displayed a significant enhancement of learning and memory under stress-free conditions, but there were no changes in the various physical and psychological parameters of movement activity (nest stay ratio, distance moved, speed and angle in the movement) and biological rhythm that were measured. Enhancement of nocturnal learning was observed during the first 12-h dark cycle, and enhancement of memory was observed at the beginning of the second dark cycle in NOP-/- mice. In contrast, MOP-/- mice showed no significant change in learning and memory behaviors or in physical and psychological parameters of movement activity, except for speed, MOP-/- mice showed a significant decrease in speed of movement. Thus, the KUROBOX apparatus provides a useful alternative method to evaluate learning and memory activity under the more physiological conditions. In addition, this apparatus has an advantage that various physical and psychological parameters of movement activity affecting learning and memory behavior are also evaluated at the same time.

Animals↗
PubMed1975

Flagellar coordination in Chlamydomonas reinhardtii: isolation and reactivation of the flagellar apparatus.

The flagellar apparatus (both flagella with basal bodies and accessory structures) of Chlamydomonas reinhardtii was isolated from a wall-less mutant and induced to swim in the presence of adenosine triphosphate. The movement of the flagella of the isolated apparatus was largely synchronous and indistinguishable from the movement of flagella on living cells. These observations suggest that the mechanism of flagellar coordination in this biflagellate alga is largely intrinsic to the structure of the flagellar apparatus itself.

Adenosine Triphosphate↗
PubMed2006

A virulence locus of Pseudomonas aeruginosa encodes a protein secretion apparatus.

Bacterial pathogens frequently use protein secretion to mediate interactions with their hosts. Here we found that a virulence locus (HSI-I) of Pseudomonas aeruginosa encodes a protein secretion apparatus. The apparatus assembled in discrete subcellular locations and exported Hcp1, a hexameric protein that forms rings with a 40 angstrom internal diameter. Regulatory patterns of HSI-I suggested that the apparatus functions during chronic infections. We detected Hcp1 in pulmonary secretions of cystic fibrosis (CF) patients and Hcp1-specific antibodies in their sera. Thus, HSI-I likely contributes to the pathogenesis of P. aeruginosa in CF patients. HSI-I-related loci are widely distributed among bacterial pathogens and may play a general role in mediating host interactions.

Animals↗
PubMed1979

Attached Growth of Sphaerotilus natans in Continuous-Flow Apparatus and Its Growth Inhibition by 9-beta-d-Arabinofuranosyladenine.

Sphaerotilus natans grew at the maximum specific growth rate (mu(max)) of 0.43/h when cultivated on PGY medium at 25 degrees C. The organism mainly grew attached to inside of the culture vessels when the culture medium was fed to the completely mixed continuous-flow apparatus at a dilution rate above mu(max) and the attached growth was directly related to the dilution rate. When a low concentration of the medium was supplied to the apparatus, almost all of the cells grown were filamentous and attached to the inside of the vessels. When a high concentration of the medium was fed, the organism grew as single cells or short chains and flowed out into the effluent. The attached growth of S. natans in the continuous-flow apparatus was inhibited by the minimal inhibitory concentration of 0.5 to 1.0 mug of 9-beta-d-arabinofuranosyladenine per ml. 9-beta-d-Arabinofuranosyladenine showed bacteriocidal activity against S. natans at a concentration of 50 to 100 mug/ml.

Journal Article↗
PubMed1970

Microbiological aspects of ethylene oxide sterization. I. Experimental apparatus and methods.

A specially built thermochemical death-rate apparatus is described which can be used to determine the resistance of microorganisms to ethylene oxide under controlled conditions. The apparatus was designed to provide instantaneous exposure of microorganisms to ethylene oxide and to eliminate variables that could result in errors when death kinetic reaction rates are calculated. The apparatus is used to obtain ethylene oxide resistance data which are useful in evaluating and developing sterilizing cycles for materials with known bacterial concentrations, as well as for calculating probability factors on which a given test condition can be expected to provide sterilization.

Bacillus subtilis↗
PubMed2003

Secretin of the enteropathogenic Escherichia coli type III secretion system requires components of the type III apparatus for assembly and localization.

At least 16 proteins are thought to be involved in forming the enteropathogenic Escherichia coli (EPEC) type III translocation apparatus which delivers virulence factors into host cells, yet their function and location have not been determined. A biochemical analysis was performed on three components: EscN, a predicted cytoplasmic ATPase; EscV, a predicted inner membrane protein; and EscC, a predicted outer membrane secretin. Wild-type EPEC and mutants constructed in these genes were fractionated by lysozyme treatment, ultracentrifugation, and selective detergent extraction. Fractionation revealed that the type III effectors Tir and EspB required a complete type III apparatus for any degree of export by EPEC, suggesting a continuous channel. Epitope-tagged EscC, EscV, and EscN were localized by fractionation, confirming computer modeling predictions for their location. Transcomplementation experiments revealed that localization of EscV and EscN was unaffected by mutations in other examined type III components. Remarkably, localization of EscC was altered in escV or escN mutants, where EscC accumulated in the periplasm. EscC was correctly localized in the escF needle component mutant, indicating that secretin localization is independent of needle formation. These data indicate that, contrary to previous indications, correct insertion and function of EscC secretin in the outer membrane depends not only on the sec-dependent secretion pathway but also on other type III apparatus components.

Adenosine Triphosphatases↗
PubMed2004

Secretion of virulence proteins from Campylobacter jejuni is dependent on a functional flagellar export apparatus.

Campylobacter jejuni, a gram-negative motile bacterium, secretes a set of proteins termed the Campylobacter invasion antigens (Cia proteins). The purpose of this study was to determine whether the flagellar apparatus serves as the export apparatus for the Cia proteins. Mutations were generated in five genes encoding three structural components of the flagella, the flagellar basal body (flgB and flgC), hook (flgE2), and filament (flaA and flaB) genes, as well as in genes whose products are essential for flagellar protein export (flhB and fliI). While mutations that affected filament assembly were found to be nonmotile (Mot-) and did not secrete Cia proteins (S-), a flaA (flaB+) filament mutant was found to be nonmotile but Cia protein secretion competent (Mot-, S+). Complementation of a flaA flaB double mutant with a shuttle plasmid harboring either the flaA or flaB gene restored Cia protein secretion, suggesting that Cia export requires at least one of the two filament proteins. Infection of INT 407 human intestinal cells with the C. jejuni mutants revealed that maximal invasion of the epithelial cells required motile bacteria that are secretion competent. Collectively, these data suggest that the C. jejuni Cia proteins are secreted from the flagellar export apparatus.

Antigens, Bacterial↗
PubMed1984

Reverse-flow apparatus for enhanced colorimetric detection of bacteriuria.

The reverse-flow apparatus is a new device for enhancing the detection of bacteria in urine. Bacteria are trapped onto a customized filter, and the pigments, crystals, and other interfering substances in the urine pass through the filter and are discarded. The bacteria are backflushed and are recovered as a concentrate, and the concentrate is then processed through the previously described colorimetric bacteriuria detection device. A total of 1,000 urine samples were obtained from randomly selected patients and were cultured on agar. Upon enumeration of the colonies, 160 urine samples were shown to contain more than 10(5) CFU/ml. In the bacteriuria detection device, 150 urine samples could not be processed (pigmenters and cloggers), and of the 850 urine samples processed, 127 were culture positive for 10(5) CFU/ml or greater, and 150 urine samples contained between 10(4) and 10(5) CFU/ml. At 10(5) CFU/ml, there were 140 false-positives and 14 false-negatives. When duplicate urine samples were processed through and concentrated by our new reverse-flow apparatus, all samples, including the above pigmenters and cloggers, could be tested in the bacteriuria detection device. The 150 unprocessable samples described above yielded 33 additional bacteria-positive urines, 23 at the 10(5)-CFU/ml cutoff and 10 at the 10(4)-to-10(5)-CFU/ml cutoff. There were 105 false-positives at 10(5) CFU/ml and only 2 false-negatives at the same level of bacteria. At 10(4) to 10(5) CFU/ml there was only 1% false-positive and 4% false-negative. The reverse-flow apparatus allows greater specificity and sensitivity in the rapid bacteriuria test. Urine containing 10(4) CFU/ml or more can now be detected with a 96% sensitivity in a total processing time of less than 2 min.

Bacteriological Techniques↗
PubMed1976

Small inexpensive anesthetic apparatus for rats.

An anesthetic apparatus is described that is capable of delivering easily controlled, constant ether-air mixtures to rats and other small laboratory animals. The apparatus is readily calibrated and is stable for extended periods of time under laboratory conditions. In addition, the apparatus can be constructed of commonly available components.

Anesthesiology↗
PubMed1977

A new apparatus for the accurate measurement of airway resistance in infancy.

A new heated rebreathing system has been developed for the measurement of thoracic gas volume (TGV) and airway resistance (Raw) in infants by the plethysmographic technique. The apparatus has a linear response to flow rates between 0-160 ml-s-1, a dead space of 12 ml and a resistance of 5 cmH2O-1-1-S-1 at a flow rate of 60 ml-s-1. The inclusion of pneumatically operated valves in the apparatus is a major improvement over previous methods of occlusion for TGV measurements. The infant is allowed to rebreathe saturated gas at body temperature through the heated system, thus overcoming a potential source of error when measuring Raw in infants. Using this apparatus, the average coefficient of variation was 3.7% for TGV and 5.9% for Raw.

Airway Resistance↗
PubMed1978

New apparatus for exercising a monkey seated in a primate chair.

A new apparatus and method for exercising a monkey seated in a primate chair are described. The apparatus consists of a set of hand and foot bars mounted at either end of a rocker arm that pivots in a vertical plane. This arm is connected by a steel cable to a wooden box that houses lead weights. By simultaneously pushing the foot bar and pulling the hand bar, the monkey lifts a weight and triggers a microswitch which releases a banana-flavored food pellet into a well close to the animal's mouth. The amount of work performed is varied by changing the a) amount of weight to be lifted, b) distance the weight must be lifted, or c) number of times that the animal lifts the weight for a single reward. During 30 min of exercise, the heart rate of a given monkey rose 120 beats/min, respiratory rate 24/min, and colonic temperature 1.2 degrees C above base-line values. Total work performed in 30 min varied from 250 to 360 kpm. Major advantages of this apparatus over a treadmill or bicycle ergometer are that the animal 1) is restrained sufficiently to permit the delicate experimental manipulations and physiological measurements, 2) can be exercised strenuously in a quantitative fashion, and 3) is readily trained to perform the task in a short time.

Animals↗
PubMed1992

An apparatus to measure in vivo biomechanical behavior of dorsi- and plantarflexors of mouse ankle.

We developed an apparatus to quantify the biomechanical behavior of the dorsi- and plantarflexor muscles of the ankle of an anesthetized mouse. When the dorsi- or plantarflexor muscle group is activated by electrical stimulation of either the peroneal or tibial nerve, the apparatus measures the moment developed about the ankle during isometric, isovelocity shortening, or isovelocity lengthening contractions. Displacements may be performed over the full 105 degrees range of ankle motion with an angular resolution of 0.09 degrees. Bidirectional isovelocity ramps in ankle angle up to 1,100 degrees/s are possible and are equivalent to maximum velocities of 2.3 fiber lengths/s (Lf/s) for the fibers in tibialis anterior muscle and 11.9 Lf/s for those in gastrocnemius muscle. During single contractions of the dorsi- and plantarflexor muscle groups at 37 degrees C and with both knee and ankle joint at 90 degrees neutral position, the isometric tetanic force developed was 1.4 and 3.3 N, power output at 2.2 Lf/s was 3.1 and 5.9 mW, and power absorption at 0.5 Lf/s was 4.9 and 9.0 mW, respectively. These values are in reasonable agreement with data from the same muscle groups tested in situ. We conclude that the apparatus provides valid measurements of force and power of the dorsi- and plantarflexor muscle groups.

Animals↗
PubMed1998

Functional aspects of skeletal muscle contractile apparatus and sarcoplasmic reticulum after fatigue.

This study examined the effects of fatigue on the functional aspects of the contractile apparatus and sarcoplasmic reticulum (SR). Frog semitendinosus muscles were stimulated to fatigue, and skinned fibers or a homogenate fraction was prepared from both fatigued and rested contralateral muscles. In fatigued fibers, maximal Ca2+-activated force of the contractile apparatus was unaltered, whereas maximal actomyosin-ATPase activity was depressed by 20%. The Ca2+ sensitivity of force was increased, whereas that of actomyosin-ATPase was not altered. Also, the rate constant for tension redevelopment was decreased at submaximal Ca2+ concentration. These latter findings suggest that fatigue slows the dissociation of force-generating myosin cross bridges. Ca2+ uptake and Ca2+-ATPase activity of the SR were depressed by 46 and 21%, respectively, in the fatigued muscles. Fatigue also reduced the rates of SR Ca2+ release evoked by AgNO3 and 4-chloro-m-cresol by 38 and 45%, respectively. During fatigue, the contractile apparatus and SR undergo intrinsic functional alterations. These changes likely result in altered force production and energy consumption by the intact muscle.

Animals↗
PubMed1986

Valvular-ventricular interaction: importance of the mitral apparatus in canine left ventricular systolic performance.

As the mitral valvular apparatus tenses during systole, forces transmitted along the chordae tendineae to the left ventricular chamber may influence left ventricular performance. To test this hypothesis, 10 dogs anesthetized with fentanyl were studied during cardiopulmonary bypass. The importance of the mitral apparatus in left ventricular systolic function was assessed independent of load by means of the slope of the contractile state-dependent left ventricular peak isovolumetric pressure-volume relationship (Emax), which was measured at constant heart rate and aortic pressure with a micromanometer inside a left ventricular intracavitary balloon before and immediately after all chordae tendineae were severed. Herniation of the balloon was prevented by a disk secured to the mitral anulus. Emax decreased from 11.97 +/- 3.35 (+/- SD) to 6.38 +/- 0.96 mm Hg/ml (p less than .001) with chordal severing. The volume intercept (Vo) was unchanged. Fluoroscopic studies of the balloon contour in eight additional dogs revealed dyskinesia in the area of the papillary muscle insertion and substantial alterations in chamber geometry during systole after the chordae were severed. Accordingly, we conclude that global left ventricular systolic performance is impaired when chordal attachments of the mitral valve are disrupted. Changes in left ventricular geometry or loss of inward force normally transmitted to the left ventricular wall as the valve tense may underlie these changes. These findings suggest that postoperative left ventricular dysfunction after mitral valve replacement may be attributable, in part, to excision of the native mitral apparatus at the time of surgery and support efforts to spare chordae during mitral valve surgery.

Animals↗
PubMed2002

Endothelin-1-induced vasospasms of spiral modiolar artery are mediated by rho-kinase-induced Ca(2+) sensitization of contractile apparatus and reversed by calcitonin gene-related Peptide.

BACKGROUND AND PURPOSE: Vasospasms of the spiral modiolar artery may cause an ischemic stroke of the inner ear that manifests itself by a sudden hearing loss. Previously we have shown that endothelin-1 (ET-1) induces vasospasms of the spiral modiolar artery. Here we tested the hypotheses that ET-1-induced vasospasms are (1) reversible by ET(A) receptor antagonists; (2) mediated by a Ca(2+) sensitization of the contractile apparatus via a Rho-kinase-induced inhibition of myosin light chain phosphatase; and (3) reversible by the vasodilator calcitonin gene-related peptide (CGRP). METHODS: The Ca(2+) sensitivity of the contractile apparatus was evaluated by correlation between the smooth muscle cell Ca(2+) concentration and the vascular diameter, which were measured by microfluorometry with the fluorescent dye fluo-4 and videomicroscopy, respectively. RESULTS: ET-1-induced vasospasms were prevented but not reversed by the ET(A) receptor antagonists BQ-123 and BMS-182874. The Ca(2+) sensitivity of the contractile apparatus was increased by ET-1 and by inhibition of myosin light chain phosphatase with calyculin A and was decreased by CGRP. ET-1-induced vasospasms and Ca(2+) sensitization were prevented and reversed by the Rho-kinase antagonist Y-27632 and by CGRP. CONCLUSIONS: ET-1 induces vasospasms of the spiral modiolar artery via ET(A) receptor-mediated activation of Rho-kinase, inhibition of myosin light chain phosphatase, and an increase in Ca(2+) sensitivity, which is reversed by CGRP. The observation that vasospasms were reversed by Y-27632 but not by BQ-123 or BMS-182874 suggests that Rho-kinase, rather than the ET(A) receptor, is the most promising pharmacological target for the treatment of ET-1-induced vasospasms, ischemic strokes, and sudden hearing loss.

Amides↗
PubMed1984

The nasal mucociliary apparatus. Correlation of structure and function in the rat.

Rats are used extensively in inhalation toxicologic studies, but little information is available on the rat nasal mucociliary apparatus. The function of the rat nasal mucociliary apparatus was studied in vitro by video analysis, and its structure was examined by light and electron microscopy. Video analysis permitted determination of mucus flow rate and ciliary beat frequency without disrupting mucociliary function. In different regions of the nose, there was a characteristic mucus flow rate, flow pattern, and ciliary beat frequency, with minimal interanimal variation. Analysis of data pairs revealed no evidence of a correlation between mucus flow rate and ciliary beat frequency, ciliary length, density of the ciliated cell population, or the products of these factors. Mucus was seen to flow over certain nonciliated areas, and it is proposed that the mucus is pulled over these areas. Mucus flow characteristics indicated that the hypophase was less viscous than, and moved in the same direction as, the epiphase. The nasal mucus was present as a continuous layer over the respiratory epithelium, and had an osmiophilic surface film, which was found to be made up of 2 separate membranous components. On the basis of these studies, it was concluded that the rat nasal mucociliary apparatus represents a useful and readily accessible model for in vitro studies of nasal mucociliary function.

Animals↗