The effect of exposure to irrigant solutions on apical dentin biofilms in vitro

This study assessed the effectiveness of different concentrations of sodium hypochlorite (NaOCl), 2% chlorhexidine (CHX) (Vista Dental Products, Racine, WI), and BioPure MTAD (Dentsply Endodontics-Tulsa Dental, Tulsa, OK). Intracanal contents were collected from 10 patients diagnosed with chronic apical periodontitis. The samples were cultured on hemisections of root apices to generate a polymicrobial biofilm. Each biofilm was separately immersed in 6% NaOCl, 3% NaOCl, 1% NaOCl, 2% CHX, 1% NaOCl followed by BioPure MTAD, and sterile phosphate buffered solution (PBS). SEM analysis showed 6% NaOCl and 3% NaOCl were capable of disrupting and removing the biofilm; 1% NaOCl and 1% NaOCl followed by MTAD were capable of disrupting the biofilm, but not eliminating bacteria; 2% CHX was not capable of disrupting the biofilm. Viable bacteria could not be cultured from specimens exposed to 6% NaOCl, 2 % CHX, or 1% NaOCl followed by BioPure MTAD. These results indicate that 6% NaOCl was the only irrigant capable of both rendering bacteria nonviable and physically removing the biofilm.

Some health physics aspects of working with 203Hg in university research

The radioisotope 203Hg is used in university toxicology research experiments. When our commercial vendor ceased the production of the high specific activity 203Hg we required, an alternative source was sought. Other commercial sources were investigated without success leaving the synthesis of this radioisotope to us. This paper outlines the method we used to synthesize 203Hg and provides a summary of our results to date and a discussion of our experiences.

Expression, purification, and biochemical characterization of WbpP, a new UDP-GlcNAc C4 epimerase from Pseudomonas aeruginosa serotype O6

B-band lipopolysaccharide is an important virulence factor of the opportunistic pathogen Pseudomonas aeruginosa. WbpP is an enzyme essential for B-band lipopolysaccharide production in serotype O6. Sequence analysis suggests that it is involved in the formation of N-acetylgalacturonic acid. To test this hypothesis, overexpression and biochemical characterization of WbpP were performed. By using spectrophotometric assays and capillary electrophoresis, we show that WbpP is a UDP-GlcNAc C4 epimerase. The K(m) for UDP-GlcNAc and UDP-GalNAc are 197 and 224 micrometer, respectively. At equilibrium, 70% of UDP-GalNAc is converted to UDP-GlcNAc, whereas the yield of the reverse reaction is only 30%. The enzyme can also catalyze the inter-conversion of non-acetylated substrates, although the efficiency of catalysis is significantly lower. Only 15 and 40% of UDP-Glc and UDP-Gal, respectively, are converted at equilibrium. WbpP contains tightly bound NAD(H) and does not require additional cofactors for activity. It exists as a dimer in its native state. This paper is the first report of expression and characterization of a C4 UDP-GlcNAc epimerase at the biochemical level. Moreover, the characterization of the enzymatic function of WbpP will help clarify ambiguous surface carbohydrate biosynthetic pathways in P. aeruginosa and other organisms where homologues of WbpP exist.

Tyzzer's disease in an 11-day-old foal

An 11-day-old pony became depressed, anorectic, and pyrexic 2 days after the topsoil of its paddock had been turned over. Rapid progression to colic and head pressing occurred, despite intensive therapy for Tyzzer's disease, and the foal died within 7 h of the appearance of central nervous system signs.

Compartment syndrome of the leg after arthroscopic examination of a tibial plateau fracture. Case report and review of the literature

Increasing attention has been given to the role of arthroscopy in the treatment of tibial plateau fractures. Complications of arthroscopy are infrequent but are potentially severe. We present a case of acute compartment syndrome related to arthroscopic treatment of a tibial plateau fracture in an adolescent.

Potential damaging effects of blue light on the eye

Are we really well protected from light reflected on the enamel of the teeth during photopolymerisation?

Optimal stimulation of paralyzed muscle after human spinal cord injury

Muscle properties change profoundly as a result of disuse after spinal cord injury. To study the extent to which these changes can be reversed by electrical stimulation, tibialis anterior muscles in complete spinal cord-injured subjects were stimulated for progressively longer times (15 min, 45 min, 2 h, and 8 h/day) in 6-wk intervals. An index of muscle endurance to repetitive stimulation doubled (from 0.4 to 0.8), contraction and half-relaxation times increased markedly (from 70 to approximately 100 ms), but little or no change was measured in twitch or tetanic tension with increasing amounts of stimulation. The changes observed with 2 h/day of stimulation brought the physiological values close to those for normal (control) subjects. A decrease in the stimulation period produced a reversal of the changes. No effects were observed in the contralateral (unstimulated) muscle at any time, nor was there evidence of decreased numbers of motor units in these subjects secondary to spinal cord injury. Motor unit properties changed in parallel with those of the whole muscle. The occasional spasms occurring in these subjects are not sufficient to maintain normal muscle properties, but these properties can largely be restored by 1-2 h/day of electrical stimulation.

An atypical presentation of upper respiratory tract cryptococcosis in a cat

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Theoretical and experimental investigation of an active three-branch Ti:LiNbO(3) optical waveguide switch

A theoretical and experimental investigation of an active three-branch multimoded Ti:LiNbO(3) waveguide switch is presented. The theoretical study covers the efficiency of the electrooptic index change in a multimoded waveguide, the mode conversion occurring in a tapered transition and, finally, the power division among the branches of the switch. For the experimental characterization, the optical measurements of a device fabricated in a Z-cut LiNbO(3) crystal are presented and discussed. Several improvements as well as applications are pointed out.

Task-Dependent Compensatory Responses to Perturbations Applied During Rhythmic Movements in Humans

Modulation of the responses to perturbation applied during different phases of three rhythmic movements in humans-running, cycling, and hopping-was studied. The perturbation was an electrical stimulus. The results showed gating and modulation of the responses in both ipsi- and contralateral limb muscles. The responses during running and cycling were only excitatory in nature, while during hopping an inhibitory response was observed. These responses were not correlated with the normal activity during the movement. The latency of the response in general was not altered for different stimulation phases. The alterations in the step cycle demonstrated overt behavioral changes due to the responses. There were differences between the responses observed during these movements and walking. In running, the major adaptation to perturbations appears to be in the contralateral side as seen in the changes in the step cycle. During cycling (except for one phase) and hopping, the same set of muscles was activated in response to perturbation. This represents a simplifying strategy in response organization. The dependency of the response on the task characteristics, postural stability requirement, and external constraints imposed on the subject is discussed. These studies provide insights into task-dependent strategies adopted by the nervous system to meet unexpected perturbation during rhythmic movements in humans.

Phase-Dependent Compensatory Responses to Perturbation Applied During Walking in Humans

The interaction between the peripheral and the central regulation of locomotion was studied by examining the dependency of the response to unexpected perturbation on the phase of the step cycle. The changes in the latency and magnitude of various muscle responses to electrical stimulation of the toe and applied unexpectedly at different phases of the locomotor cycle in humans are described. The results show that response to perturbation is gated and modulated in both ipsi- and contralateral limb muscles. These muscle responses, when present, were always excitatory in nature. They were not correlated with the normal locomotor activity, thus suggesting a more complex organization of the response. Except for one muscle in the contralateral limb, the latency of the other muscle responses did not vary across the step cycle. in response to the perturbation, the appropriate phase of the step cycle was shortened. The results from this study suggest that the perturbation applied elicits a phase-independent, normal ipsilateral flexor response in the tibialis anterior muscle, while the gating and modulation of other ipsi- and contralateral muscles provide appropriate phase-dependent adaptive response to maintain postural stability and continue with the ongoing task of locomotion.

GaAs directional coupler devices: design considerations

Symmetrical and asymmetrical directional couplers in GaAs are analyzed. The performance of these devices as wavelength filters and switches is examined. It is shown that asymmetrical couplers require shorter coupling length and smaller index change for switching of light between the two waveguides.

Corrective responses to perturbation applied during walking in humans

Modulation of the flexor reflex response during walking in humans following stimulation at 5 points in the step cycle was studied. At heel strike, an extensor response was observed at the ankle and the knee which would allow one to stabilize and plant the ipsilateral foot fast. Later on in the stance, there was a dorsiflexor and an extensor response at the ankle and the knee, respectively, which would result in the removal of the foot from the stimulus without collapsing at the knee. During mid-swing, a flexor reflex response was observed at the ankle and the hip joint. There was a tendency for the normal stride to be longer than the perturbed stride in mid swing and early stance while it was of shorter duration in late stance and early swing.

Passive planar multibranch optical power divider: some design considerations

Design analysis has been performed on a passive planar multibranch waveguide optical power divider in a z-cut LiNbO3 substrate. Specifically, 5- and 3-branch waveguide structures were investigated with the effective index and field matching methods, taking into account the phase changes in the branches at the branching interface. Conditions for equal power division were examined regarding the appropriate branching angle and the relative index distribution in the branches. Illustrative numerical examples are presented and discussed.

Experience with 37 infants with tyrosinemia

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