Electronic structure of Q-A in reaction centers from Rhodobacter sphaeroides. I. Electron paramagnetic resonance in single crystals.

The magnitude and orientation of the electronic g-tensor of the primary electron acceptor quinone radical anion, Q-A, has been determined in single crystals of zinc-substituted reaction centers of Rhodobacter sphaeroides R-26 at 275 K and at 80 K. To obtain high spectral resolution, EPR experiments were performed at 35 GHz and the native ubiquinone-10 (UQ10) in the reaction center was replaced by fully deuterated UQ10. The principal values and the direction cosines of the g-tensor axes with respect to the crystal axes a, b, c were determined.

Condylar movement and mandibular rotation during jaw opening.

Inaccurate description of mandibular rotation can have profound effects on orthognathic surgical treatment planning and surgical outcome, as well as affect the precision of appliances fabricated on articulators. Disagreement exists concerning movements of the condyle during jaw opening. Although mandibular function is often described as rotation around an instantaneous center located outside of the condyle, many believe that jaw opening occurs around an axis of rotation that remains fixed at the center of the condylar head.

Creative arch wires and clinical conclusion.

When two successive couples are present, the absolute value of the moment at each bracket cannot be clinically determined. The larger moment can be identified, however, and this will show the direction of the associated equilibrium forces. If the couples at two adjacent brackets produce moments in opposite directions, the associated equilibrium forces are also in opposite directions.

Two-couple orthodontic appliance systems: torquing arches.

Twists placed in an arch wire between incisor brackets are often used in an attempt to obtain root torque. This is only partially effective because of the equal and opposite reciprocals acting on the adjacent teeth. Alternatively, a V-bend in a torquing arch, inserted at only the molar and incisor brackets, may use the bending properties of the arch wire to create dissimilar moments in a two-bracket system.

One-couple orthodontic appliance systems.

One-couple orthodontic appliances are capable of applying well-defined forces and couples to effect controlled tooth movement during treatment. There are two sites of attachment: one in which the appliance is inserted into a bracket or tube where both a couple and force is generated, and one at which the appliance is tied as a point contact where only a force is produced. Using relatively simple designs, powerful biomechanical force systems that are easy to discern clinically can be applied to move teeth according to a prescribed plan.

The ground rules for arch wire design.

All force systems applied to a tooth are composed of either single forces and/or couples. The application of a force through the center of resistance of a tooth will result in translation of the tooth. The application of a force to act at points other than through the center of resistance of a tooth will produce different tendencies for rotation.

Chin, nose, and lips. Normal ratios in young men and women.

Existing soft tissue analyses reference profile characteristics to lines determined by surface landmarks. This study uses surface landmarks only to define an area, and soft tissue profiles are analyzed in terms of the surface area of each component part present within this area. The profiles of 66 young adults were measured, and the mean total profile area and all of the component parts except the nose were statistically larger in the men than in the women.

Ceramic bracket fracture resistance to second order arch wire activations.

The fracture resistance of ceramic brackets to orthodontic activations has been incorrectly estimated by previous investigations that have reported second order loads in terms of force magnitudes rather than moments. Because force magnitudes alone do not reflect the influence of distance from the site of force application on total load, it is impossible to apply previous results to actual clinical situations. The purpose of this study was to determine the average moments (in gram-millimeters) necessary to fracture various ceramic brackets subjected to second order tipping activations and compare them with actual clinical loads.

Analysis of a naturally occurring K99+ enterotoxigenic Escherichia coli strain that fails to produce K99.

A spontaneously occurring field isolate of enterotoxigenic Escherichia coli that was genotypically K99+ but phenotypically K99- was analyzed for the reason that it did not express K99. The defect, which was cis active, was located within an area 5' to the first gene required for K99 biogenesis and was the result of the deletion of a single base pair.

Transmission of Salmonella typhimurium to swine.

These studies were designed to determine the rate of transmission and the colonization pattern of Salmonella typhimurium in swine. Two experiments were conducted. In experiment 1, swine challenged per os with either S.

Behavioral and neuroanatomical consequences of a unilateral intraventricular infusion of AF64A and limitations on the neuroprotective effects of nimodipine.

The monoethylcholine aziridinium ion, AF64A, (3 nmol in 1 microliter) or artificial CSF (1 microliter) was infused unilaterally into the right dorsal lateral ventricle of male adult rats. Treatment with the L-type calcium channel antagonist, nimodipine (70 micrograms/kg b.wt.

Chronic aluminum fluoride administration. I. Behavioral observations.

This study examined the behavioral effects of chronic ingestion of various monofluoroaluminum complexes (AlF3) in drinking water. Forty young adult male Long-Evans rats were divided into four groups of 10 rats each. The groups received different concentrations of AlF3 in the drinking water from three sample solutions having a total Al concentration of 0.

The effects of pregnenolone on acquisition and retention of a food search task.

Two experiments were undertaken in which the effects of semichronic administration of the precursor steroid, pregnenolone, were examined in a food search task. In both experiments male rats were required to find a food reward in a designated hole in an arena with 16 equally spaced holes. Hormone administration began 8 days before the onset of training.

Transcriptional organization of the Escherichia coli pilus adhesin K99.

The production of the Escherichia coli pilus adhesin K99 requires the expression of eight unique proteins: FanA-H. The transcriptional organization of the K99 operon was investigated by Northern blot analysis. Four RNAs of 0.

Nimodipine's functional benefits depend on lesion completeness in medial septal area.

The effects of a 4-day nimodipine treatment (70 micrograms/kg IP beginning on the day of surgery) given to rats with lesions directed at the medial septal area were monitored for 120 days. Body weight, water intake, open-field activity, rearing, hole-poking, and repetitive motor acts were periodically measured through 120 postsurgical days. Although no differences were found in water intake between any of the groups, the body weights of rats with any medial septal damage, whether treated with nimodipine or not, were lower than rats with control operations by postsurgery day 120.

Moments with the edgewise appliance: incisor torque control.

Traditional edgewise orthodontic mechanics are significantly limited in their ability to provide incisor torque control because of the limitations of bracket-to-bracket mechanics and the poorly defined reciprocal actions inherently produced. Attempts to address this issue clinically have been largely empirical. The science of mechanics dictates that all incisor torque control mechanisms must act through one of two basic principles: the moment of a couple or the moment of a force.

Extracellular calcium does not contribute to cryopreservation-induced cytotoxicity.

The possible role of extracellular calcium ([Ca+2]e) in cryopreservation-induced cytotoxicity was tested using Madin-Darby canine kidney (MDCK) cells and a fluorescent multiple endpoint assay. MDCK cells maintained in 2 mM [Ca+2]e and treated with the calcium ionophore, ionomycin, increased their intracellular calcium ([Ca+2]i) as revealed by the calcium indicator dye, Fluo3 and the bottom-reading spectrofluorometer, CytoFluor 2300. The addition of 10 mM [ethylene bis (oxyethylenenitrilo)]-tetraacetic acid (EGTA) to the extracellular medium before treatment with ionomycin blocked this ionomycin-dependent increase in [Ca+2]i.

Activating a 2 x 4 appliance.

When the long span of wire in a 2 x 4 orthodontic appliance enters a bracket in a nonparallel manner, it develops a couple and tendency for rotation called a moment. The moment of a couple creates inherent equal and opposite Newtonian equilibrium forces not readily sensed clinically. Moments at successive brackets, producing rotations in opposite directions, create equilibrium forces also in opposite directions which are subtractive from each other.

Case report: four permanent second molar extractions.

A patient who had earlier undergone four second molar extractions and who demonstrated Class II buccal segments and major incisor crowding was treated with the relatively unusual extraction pattern of maxillary lateral incisors. The treatment resolved the crowding and created Class II buccal segments with maxillary canines substituted for extracted lateral incisors. Favorable tooth anatomy produced an acceptable esthetic result accomplished with a predictable outcome over a reasonable duration of treatment.

Tantalum implants as markers for evaluating postoperative orthognathic surgical changes.

The stability of sagittal split osteotomy advancements is not always 100% predictable. Assessment of postsurgical changes has historically relied on clinical evaluation of dental changes and superimposition of serial cephalograms, both of which have been shown to have serious drawbacks. A technique that improves the analysis of postsurgical changes is described in this paper; tantalum pin implants are placed in the osteotomized segments of patients undergoing surgical advancements.

On tooth movement.

Current concepts of clinical orthodontic tooth movement are misleading. Traditionally, these have been described as dependent on force levels and being tipping/bodily in nature. The following is a reevaluation of the relationships between tooth movement and orthodontic mechanotherapy not usually considered when analyzing tooth movement clinically.