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Use of a telemetered dispensing system for controlling nutrient additions to experimental patch reefs in the ENCORE study at One Tree Island, Great Barrier Reef, Australia.

A telemetrically controlled system was developed to add nutrients automatically to experimental patch reefs in a remote marine environment. The experiment, called ENCORE, was done in the lagoon of One Tree Island, a remote research station at the southern end of the Great Barrier Reef. Nutrient dispensing units (NDUs), moored adjacent to patch reefs in the lagoon, were telemetrically linked to a base station on the island. The base station, about 3 km away from the furthest NDU, consisted of a dedicated computer, controller and radio transmitter, which relayed coded signals to a radio receiver mounted on each NDU. This activated a solenoid valve to discharge a measured quantity of concentrated nutrient solution from a measuring chamber using compressed air from a SCUBA tank. The solution was discharged through 4-8 PVC outlets into the basins of the patch reefs to allow thorough mixing. The base station interrogated each NDU to find out if the operation had been successful and stored the information on disk to provide a daily log of operations. Nutrient samples taken within the patch reefs demonstrated that calculated initial mean concentrations of 2 micrograms-at PO4-P l-1 and 10 micrograms-at NH4-N l-1 were achieved. The system we have developed can be used in many situations where regular perturbations need to be introduced to aquatic ecosystems. It uses state-of-the-art technology, yet all components are commercially readily available and relatively inexpensive. Detailed specifications and drawings are available from the Great Barrier Reef Marine Park Authority.

Animals↗

Photocatalytic degradation of cyanobacterial microcystin toxins in water.

The microcystins are hepatotoxins produced by a number of cyanobacterial species (blue green algae) in fresh water systems. The increasing eutrophication of natural waters has led to an increase in the incidence of algal blooms and the consequent increased risk of microcystin contamination of water resources. The removal of microcystins LR, YR and YA from contaminated water was investigated using an experimental laboratory-scale photocatalytic 'falling film' reactor in which an oxygen purge, UV radiation and semiconductor titanium dioxide (TiO2) catalyst were used to oxidatively decompose the microcystin pollutants. Preliminary studies, using algal extracts spiked into distilled water, indicated that the microcystins were rapidly decomposed in this reactor. The decomposition followed first order reaction kinetics with half-lives of less than 5 min with the reactor operating in a closed-loop mode. Reaction rates were strongly dependent on the amount of TiO2 catalyst (O-5 g/l), but only marginally influenced by a change in gas purge from oxygen to compressed air. The use of lake water, rather than distilled water, showed that this process is feasible in natural waters, although increased levels of catalyst (up to 5 g/l) were required to achieve comparable decomposition rates.

Bacterial Toxins↗

Treatment of urinary calculi in a porcine and canine model using the Browne Pneumatic Impactor.

OBJECTIVES: To define the safety and efficacy of a pneumatically driven, mechanical lithotriptor using nitinol probes through semirigid and actively deflectable, flexible fiberoptic endoscopes. METHODS: The Browne Pneumatic Impactor (BPI) uses standard compressed air to drive a nitinol wire along its long axis onto a calculus, fragmenting it. Bench top and in vivo experiments were designed to explore variables, including the effects of various nitinol probe tip designs, outer diameters, excursion distances, and sheathing materials as well as the efficiency of fragmentation with active endoscope deflection. In vivo experiments in two animal models (porcine and canine) were performed using small diameter, fiberoptic semirigid, and actively deflectable, flexible ureteroscopes. Surgically placed calculi were fragmented with the BPI and representative tissue was obtained immediately and up to 2 weeks postoperatively to define histologic changes. A panel of human urinary calculi was chosen for their relative difficulty in fragmentation with other modalities. RESULTS: Calculi, including pure calcium oxalate monohydrate, brushite, cystine, and triamterene, were fragmented with the BPI used through both semirigid and actively deflectable, flexible endoscopes. A rounded tip design and excursions of 1 mm fragmented calculi most efficiently with minimal histologic reaction. Retrograde stone migration before fragmentation was noted in dilated upper urinary tracts. This was prevented by first entrapping the calculus within a standard basket. Ureteral calculi were fragmented with the nitinol probes deflected up to 45 degrees by the flexible endoscope. With increased active deflection, the efficiency of fragmentation decreased. CONCLUSIONS: The BPI represents a safe, thermal-free endoscopic lithotrite able to fragment the hardest calculi through semirigid and flexible ureteroscopes.

Alloys↗

Generation of stable test atmospheres of cocaine base and its pyrolyzate, methylecgonidine, and demonstration of their biological activity.

Generating controlled test atmospheres of known chemical identity and airborne concentration upon demand is a significant technical obstacle that limits the scope and repeatability of studies of inhaled substances. We addressed this problem as applied to the generation of atmospheres that result from heating crack cocaine, which include both cocaine and its pyrolyzate methylecgonidine (MEG). A condensation aerosol generator was used to generate atmospheres comprised of monodisperse particles of cocaine, MEG, or mixtures of both that are of submicron size suitable for deposition in the alveolar region of primates. Compressed air seeded with nanometer-size sodium chloride particles was passed through a constant depth of molten cocaine or MEG in a bead bed, reheated, and condensed to an aerosol within an annulus of cold air. To achieve control of a mixture of both compounds, MEG was condensed onto cocaine particles in a separate coating step. On-line analytical instruments provided verification of airborne concentration, estimates of particle size, and dispersion as well as chemical identity. Specific airway conductance (SGaw), heart rate, and rectal and skin temperatures were measured in squirrel monkeys breathing atmospheres containing condensation aerosols of cocaine or MEG free base. SGaw was reduced after inhalation of either base, and both induced temperature and cardiovascular changes, demonstrating that the aerosols so generated had biological activity.

Administration, Inhalation↗

Effect of water leaching the adhesion of composite resin to bleached and unbleached bovine enamel.

Standardized cylinders of light-cured composite resin were bonded to the ground labial enamel surface of bovine incisor teeth that had been immersed in double-distilled water for 7 days after having been (a) immersed in hydrogen peroxide for 5, 30, or 60 min, then etched for 60 s with 37% phosphoric acid; (b) immersed in saline for 5, 30, or 60 min, then etched for 60 s with 37% phosphoric acid; (c) etched with 37% phosphoric acid for 60 s, then immersed in hydrogen peroxide for 5, 30, or 60 min; or (d) etched with 37% phosphoric acid for 60 s, then immersed in saline for 5, 30, or 60 min. The enamel surface was washed with water for 1 min and dried with compressed air for 30 s prior to applying the resin. The tooth and applied resin were stored in water at 37 degrees C for 1 day prior to shear and tensile testing. A total of 192 specimens was used, 8 for each enamel preparation mode, for each time period, and for each test. Test values were tabulated and statistically analyzed. Analysis of variance revealed significantly higher bond strength values (p less than 0.005) for hydrogen peroxide-treated as compared with saline-treated specimens. A significant interaction was also noted between test solution and etching order. Scanning electron microscopic examination of failed shear- and tensile-tested specimens revealed no significant solution-related differences in the fracture pattern or the resin quality.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗

Effect of Phenyl-P/HEMA acetone primer on wet bonding to EDTA-conditioned dentin.

OBJECTIVES: The purpose of this study was to examine the effect of 2-methacryloyloxyethyl phenyl phosphoric acid (Phenyl-P)/2-hydroxyethyl methacrylate (HEMA) acetone-based primer on moist dentin surfaces that were preconditioned with ethylenediaminetetraacetate (EDTA) to remove the smear layer. METHODS: Bovine dentin were prepared with 180-grit paper, conditioned with 0.5M EDTA (pH 7.4) for 60s followed by water rinsing and then blot drying. Each surface was then primed with Phenyl-P/30 wt% HEMA in acetone for 10s followed by blot drying. A light-cured bonding agent was then applied, cured and trimmed to give dumbbell-shaped specimens. The Phenyl-P concentration ranged from 1 to 20 wt%. During the bonding procedure, no compressed air was used. After storage in water at 37 degrees C for one day, tensile bond strengths were measured and analyzed using one-way ANOVA. Dentin discs treated under the same conditions were observed under a scanning electron microscope (SEM). RESULTS: When the concentration of Phenyl-P was 12 wt%, the highest mean tensile bond strength was obtained (27 MPa). It was significantly higher than that of the 3, 5, 15 or 20 wt% groups (9-11 MPa) (p<0.05). The samples of 1 wt% group were all broken during trimming the dumbbell-shaped specimens. SEM observations showed a 1 microm-thick layer of hybridized dentin after polished cross-sections were chemically challenged with 6N HCl for 30s and then 1% NaOCl for 60 min. SIGNIFICANCE: The experimental Phenyl-P/HEMA acetone primer is effective in bonding resin to EDTA-conditioned dentin. Acetone as a solvent for Phenyl-P/HEMA primer has the clinical advantage of not requiring an air-stream to evaporate the solvent. The experimental bonding procedure can minimize the skin irritation by HEMA.

Acetone↗

Assessment of jet nebulisers for lung aerosol therapy.

The effect on nebuliser output of varying the flow rate of compressed air driving the device and the volume of respirator solution used was investigated in four brands of jet nebuliser. Raising the airflow rate from 4 to 6 1/min reduced the duration of nebulisation by approximately 40%, and a rise from 6 to 8 1/min reduced the duration by a further 15%. However, this change had only a slight effect on the proportion of the solution released. The volume of respirator solution placed in the nebuliser directly influenced the volume released as aerosol. After a 2 ml fill, less than 1 ml was released (50%). With a volume fill of 4 mg 60-80% was released, and with 6 ml 70-85% was released. Nebuliser output fell during nebulisation as the temperature of the solution dropped by 8-12 degrees C. A minimum 4 ml fill and an air-flow rate of 6 l/min are advocated to optimise nebuliser output.

Aerosol Propellants↗

Refractive changes caused by hypoxia after laser in situ keratomileusis surgery.

OBJECTIVE: To determine whether hypoxia induces refractive changes in subjects who have had laser in situ keratomileusis (LASIK) refractive surgery. DESIGN: Prospective paired eye clinical trial. PARTICIPANTS: There were 20 LASIK subjects (40 eyes) and 20 myopic non-LASIK controls (40 eyes). INTERVENTION: Each subject had one eye exposed to ocular surface hypoxia (humidified nitrogen) by use of an airtight goggle system at sea level for 2 hours. The other eye was simultaneously exposed to humidified, compressed air (21% oxygen) with the same airtight goggle system. MAIN OUTCOME MEASURES: Keratometry, cycloplegic refraction, and pachymetry were compared before and after exposure by use of repeated measures analysis of variance. RESULTS: A significant myopic shift (P: < 0.01) occurred in LASIK corneas exposed to hypoxia compared with myopic control subjects. A significant increase in corneal thickening occurred symmetrically in both LASIK and control subjects exposed to hypoxia. There was a trend toward corneal steepening (keratometry) in LASIK subjects, but this was not statistically significant. CONCLUSIONS: These results suggest that ocular surface hypoxia induces a myopic shift in LASIK subjects.

Adult↗

Yawning: no effect of 3-5% CO2, 100% O2, and exercise.

Using human college-age subjects, the present study tested the commonly cited but previously untested hypothesis that yawning is facilitated by higher than normal levels of CO2 or lower than normal levels of O2 in the blood by comparing the effect on yawning of breathing 100% O2 and gas mixtures with higher than normal levels of CO2 (3 or 5%) with compressed air, the control condition. If yawning is a response to heightened blood CO2, the CO2 mixtures should increase yawning rate and/or duration. If low blood O2 produced yawning, breathing 100% O2 should inhibit yawning. The CO2/O2 hypothesis was rejected because breathing neither pure O2 nor gases high in CO2 had a significant effect on yawning although both increased breathing rate. A second study found that exercise sufficient to double breathing rate had no effect on yawning. The two studies suggest that yawning does not serve a primary respiratory function and that yawning and breathing are triggered by different internal states and are controlled by separate mechanisms.

Adolescent↗

The 35% CO2 challenge test in patients with social phobia.

Panic disorder (PD) and social phobia (SP) share many clinical, demographic and biological characteristics. To investigate the relationships between the two disorders, the responses to inhalation of a 35% carbon-dioxide (CO2) and 65% oxygen (O2) gas mixture were assessed. Sixteen patients with PD, 16 patients with SP, 13 patients with both SP and PD, seven patients with SP who experienced sporadic unexpected panic attacks and 16 healthy control subjects inhaled one vital capacity of 35% CO2 or compressed air. A double-blind, randomized, crossover design was used. PD patients and SP patients showed similar anxiogenic reactions to 35% CO2, both stronger than seen in control subjects. Patients with both disorders and SP patients with sporadic unexpected panic attacks reacted similarly to subjects with PD or SP alone. These results suggest that PD and SP share a common hypersensitivity to CO2 and thus might belong to the same spectrum of vulnerability.

Adult↗

Development and assessment of mini projectiles as drug carriers.

This paper describes a novel technology for the delivery of drugs into the subcutaneous and intramuscular tissue of farmed animals. The technology comprises small, hollow mini projectiles into which drug formulations can be loaded and administered using compressed air from an administration device which is held a few millimeters (3-10 mm) from the surface of the animals' skin. The design of the mini projectiles and administration procedure allows administration without contacting the skin, thereby avoiding cross-contamination between handlings and ensuring safe injection practice in livestock. In vitro experiments are described which investigate the parameters that affect mini projectile penetration into excised porcine and bovine skin. These include shape and weight of the mini projectiles and species type and injection site of the animal. An in vitro skin model for assessing mini projectile administration is described which permits visualization of the penetration of the mini projectiles through excised bovine or porcine skin into an underlying tissue simulant made from gelatin. The quantities of energy necessary to inject mini projectiles through excised porcine and bovine skin into the tissue simulant of the in vitro skin model were determined. The paper also describes the processes that occur during the administration of mini projectiles. The results suggest that tissue damage caused during administration of mini projectiles is comparable to the tissue damage caused by conventional syringe-needle injections. Finally, three different formulations of the model vaccine BSA, without adjuvant, are loaded into mini projectiles and administered to pigs. A seroconversion was shown for all three formulations, thus demonstrating proof of concept for the miniprojectiles.

Animals↗

Characterisation of HTO diffusion properties by an in situ tracer experiment in Opalinus clay at Mont Terri.

A long-term single borehole diffusion experiment using tritiated water as tracer was carried out in Opalinus clay, an argillaceous rock formation that is accessible at the Mont Terri Underground Research Laboratory, situated in the Swiss Jura. The tracer was diluted in reconstituted formation water and introduced into a packed-off section of a borehole located in saturated rock. Pressure in this interval was maintained equal to the pore pressure of the surrounding rock in order to prevent any hydraulic gradient around the borehole and to avoid advective transport processes. The evolution of the tracer concentration in the injection system was monitored over time. After 1 year of diffusion, the claystone surrounding the interval was retrieved by overcoring the whole borehole and packer system, and by an adjacent oblique borehole. Compressed air was used as drilling fluid to reduce rock disturbances. The recovered overcore was sampled along profiles perpendicular to the borehole wall with a view to determining the tracer-concentration profiles in the rock. To avoid further evaporation of tritiated water, subsamples were immediately transferred into polyethylene bottles and disaggregated by adding a known amount of tracer-free water. Fifteen profiles were determined and showed a decreasing tracer concentration with distance into the rock. The pore-water contents were constant along those profiles, confirming that only very little water was lost during overcoring operations. The evolution of tritium-tracer concentration in the injection system over time and in situ profiles were interpreted with a 3-D numerical simulation of the experiment. That allowed for the identification of the transport parameters (orthotropic diffusion tensor and porosity) by minimising the relative quadratic error between the experimental and simulated data. The fitting is good and the results are consistent with data obtained on drill-core samples. The result of tritiated water is discussed regarding (1) the potential effect of mechanical and/or chemical disturbances around the injection borehole and (2) the specific behaviour of tritiated water.

Aluminum Silicates↗

Tobacco smoke exposure and bombesin-like peptides in guinea pigs.

Bombesin-like peptides (BLPs) are associated with tobacco smoke (TS)-induced diseases. We sought to determine if acute TS exposure releases BLPs into the pulmonary circulation. Sensitized and non-sensitized guinea pigs were chronically exposed to TS or compressed air. Thereafter, the lungs were acutely challenged with TS while perfused. Perfusates were analyzed for BLPs. TS increased BLPs in non-sensitized guinea pigs. A separate study determined daily bombesin exposure increased lung cell counts but not airway hyperresponsivensess. TS exposure releases BLPs into the pulmonary circulation but can be modified by host factors and bombesin itself does not induce airway hyperresponsiveness.

Administration, Inhalation↗

Visual system degeneration induced by blast overpressure.

The effect of blast overpressure on visual system pathology was studied in 14 male Sprague-Dawley rats weighing 360-432 g. Blast overpressure was simulated using a compressed-air driven shock tube, with the aim of studying a range of overpressures causing sublethal injury. Neither control (unexposed) rats nor rats exposed to 83 kiloPascals (kPa) overpressure showed evidence of visual system pathology. Neurological injury to brain visual pathways was observed in male rats surviving blast overpressure exposures of 104-110 kPa and 129-173 kPa. Optic nerve fiber degeneration was ipsilateral to the blast pressure wave. The optic chiasm contained small numbers of degenerated fibers. Optic tract fiber degeneration was present bilaterally, but was predominantly ipsilateral. Optic tract fiber degeneration was followed to nuclear groups at the level of the midbrain, midbrain-diencephalic junction, and the thalamus where degenerated fibers arborized among the neurons of: (i) the superior colliculus, (ii) pretectal region, and (iii) the lateral geniculate body. The superior colliculus contained fiber degeneration localized principally to two superficial layers (i) the stratum opticum (layer III) and (ii) stratum cinereum (layer II). The pretectal area contained degenerated fibers which were widespread in (i) the nucleus of the optic tract, (ii) olivary pretectal nucleus, (iii) anterior pretectal nucleus, and (iv) the posterior pretectal nucleus. Degenerated fibers in the lateral geniculate body were not universally distributed. They appeared to arborize among neurons of the dorsal and ventral nuclei: the ventral lateral geniculate nucleus (parvocellular and magnocellular parts); and the dorsal lateral geniculate nucleus. The axonopathy observed in the central visual pathways and nuclei of the rat brain are consistent with the presence of blast overpressure induced injury to the retina. The orbital cavities of the human skull contain frontally-directed eyeballs for binocular vision. Humans looking directly into an oncoming blast wave place both eyes at risk. With bilateral visual system injury, neurological deficits may include loss or impairments of ocular movements, and of the pupillary and accommodation reflexes, retinal hemorrhages, scotomas, and general blindness. These findings suggest that the retina should be investigated for the presence of traumatic or ischemic cellular injury, hemorrhages, scotomas, and retinal detachment.

Air Pressure↗

Effects of polyvalent alcohol solutions as dentine primers.

OBJECTIVES: The purpose of this study was to examine the bonding effect of polyvalent alcohols as dentine primers without a methacrylate group, which may cause contact dermatitis. METHODS: The efficacy of polyvalent alcohols as dentine primers was estimated by measuring the wall-to-wall polymerization contraction gap width of a light-activated resin composite filled in a cylindrical dentine cavity in an extracted human tooth. A dentine cavity was cleaned with ethylenediaminetetraacetic acid (EDTA) and primed with an aqueous solution of either ethylene glycol, glycerol, erythritol, xylitol or sorbitol at concentrations of between 25 and 75 wt%. A light-cured resin composite was filled after the application of a commercial dual-cured bonding agent. RESULTS: Contraction gap formation was completely prevented only in the group in which the dentine cavity had been primed with an aqueous solution of 62.5% wt% ethylene glycol. Furthermore, in the measurement of a tensile bond strength to a flat dentine surface, high tensile bond strength (17.5 +/- 4.4 MPa) was observed in the group that was primed with 62.5% ethylene glycol solution. CONCLUSION: These results suggest that it is not necessary to dissolve methacrylates in a dentine primer when the primer is dried with a blast of compressed air before application of a polymerizable, suitable bonding agent. It is concluded that a dentine primer composed of polyvalent alcohol solutions without a methacrylate group which may cause contact dermatitis, is effective as a dentine primer, affects the dentine surface, and promotes the efficacy of the dentine bonding system.

Acid Etching, Dental↗

Clinical complications of obesity.

The development of important respiratory disorders and significant hypertension in association with increasing body weight is not widely recognized. Altered respiratory function results from a combination of mechanical impedance to breathing exerted by thoracic and abdominal fat and a ventilation-perfusion mismatch. Sleep-disordered breathing with periods of hypoventilation, with or without apnoeic episodes, may commonly occur in patients with extreme obesity. Nocturnal hypercapnia and hypoxia in such patients may lead to a decrease in ventilatory drive, abnormal central respiratory control and possibly, in time, the development of the obese-hypoventilation syndrome. Respiratory abnormalities should be suspected in obese patients with a history of restlessness at night, loud snoring and daytime somnolence. Treatment is substantial weight reduction, but short-term measures include the use of compressed air via nasal cannulae for obstructive apnoea, and drugs which alter sleep pattern or stimulate respiration. The alterations in endocrine function, which accompany weight gain, may contribute to an increase in blood pressure and there appears to be a relationship between plasma insulin and catecholamine concentrations, fat cell size and the development of hypertension. The confirmation of a raised blood pressure requires that readings be taken with an adequately sized arm-cuff. In many instances endocrine function becomes normal with weight loss, and there is a corresponding decrease in blood pressure. The ideal management for an obese hypertensive patient is the combination of a suitable calorie-restricted diet with a programme of physical exercise.

Female↗

Feasibility of mitral flow assessment by echo-contrast ultrasound, part II: experimental study on a mechanical model of the left heart.

The feasibility of assessing mitral flow by means of ultrasonic monitoring of backscattered power from an echo-contrast agent in the left atrium and left ventricle was studied. A mechanical model of the left heart was built in which two thin rubber balloons connected to each other in a feedback loop via two artificial heart valves mimicked the left atrium and left ventricle. The model was driven by compressed air. Its input and output flows were measured as the functions of a pacing rate, driving pressure and artificially introduced mitral regurgitation. These were compared with the corresponding data derived from the ultrasonic measurements that are based on the correlation between echo-contrast agent concentration in the volume of interest and the flow through it. Algorithms for quantitative estimations of forward stroke volume (cardiac output) and mitral regurgitation are given. This study shows, for the first time, both analytically and experimentally, that the pulsating modulation of contrast agent concentration vs. time curves in the ventricle and atrium volumes is closely related to the pulsating nature of the flow in the system. It also shows that the amplitude of the atrium concentration modulation is directly proportional to the maximum value of the incoming (to atrium) flow.

Albumins↗

Episodic neonatal hypoxia evokes executive dysfunction and regionally specific alterations in markers of dopamine signaling.

Perinatal ischemic-anoxic and prolonged anoxic insults lead to impaired dopaminergic signaling and are hypothesized to contribute, at least in part, to the pathogenesis of disorders of minimal brain dysfunction such as attention-deficit hyperactivity disorder. We hypothesized that subtle intermittent hypoxic insults, occurring during a period of critical brain development, are also pathogenic to dopaminergic signaling, thereby contributing to behavioral and executive dysfunction. Between postnatal days 7 and 11, rat pups were exposed to either 20-s bursts of isocapnic hypoxic gas, compressed air, or were left undisturbed with the dam. On postnatal days 23 pups were instrumented with electroencephalographic/electromyographic electrodes and sleep-wake architecture was characterized. Locomotor activity was assessed between postnatal days 35 and 38, learning, and working memory evaluated between postnatal days 53 and 64. Rats were killed on postnatal day 80 and tyrosine hydroxylase, vesicular monoamine transporter, dopamine transporter, and dopamine D1 receptors were quantified in the prefrontal cortex, primary sensorimotor cortex, and precommissural striatum by Western blot analyses. Post-hypoxic pups spent less time awake and more time in rapid-eye-movement sleep during the lights-on phase of the circadian cycle, were hyperlocomotive, and expressed impaired working memory. Striatal expression of vesicular monoamine transporter and D1 receptor proteins were increased in post-hypoxic rats, consistent with depressed dopaminergic signaling. These observations lead to the intriguing hypothesis that intermittent hypoxia occurring during a period of critical brain development evokes behavioral and neurochemical alterations that are long lasting, and consistent with disorders of minimal brain dysfunction.

Animals↗