Effect of microwave treatment on the shear bond strength of different types of commercial teeth to acrylic resin

doi:10.1111/j.1741‐2358.2009.00333.x
Effect of microwave treatment on the shear bond strength of different types of commercial teeth to acrylic resin Objective: The purpose of this study was to verify the effect of microwave treatment on the shear bond strength of commercial types of teeth to acrylic resin, when the glossy ridge laps were unmodified (groups 1 and 5), bur abraded (groups 2 and 6), bur grooved (groups 3 and 7) or etched by monomer (groups 4 and 8). Background: Controversial findings have shown that mechanical or chemical changes in ridge‐lap surface of the tooth increase or decrease the bond strength between tooth and acrylic resin, and the microwave disinfection may cause different changes on this bond strength. Materials and methods: Eighty specimens (n = 10) were made with the acrylic resin bonded to tooth glossy ridge lap, polymerised in water at 74°C for 9 h, and deflasked after flask cooling. Specimens of the groups 5, 6, 7 and 8 were individually immersed in 150 ml of water and submitted to microwave treatment in an oven at 650 W for 3 min. Control specimens (groups 1, 2, 3 and 4) were not microwave treated. Shear bond strength test was performed in an Instron machine with a cross‐speed of 1 mm/min. Collected data were submitted to anova and Tukey’s test (α = 0.05). Results: Microwave treatment decreased the shear bond strength values of the tooth/resin bond. In the microwaved and non‐microwaved procedures, mechanical retention improved the shear bond strength when compared with the control and monomer treatments. Conclusion: Shear bond strength of the tooth/resin bond was influenced by the microwave treatment and different commercial teeth association, and was lower for the Biotone tooth.     

Expression of mosquitocidal crystal protein genes in non-insecticidal Bacillus thuringiensis subsp. israelensis

Bacillus thuringiensis NTB-1 isolated from soil samples in Korea produces ovoidal parasporal inclusions with proteins of approximately 24–40 kDa in size. Although serological study indicated that the isolate has a flagella (H) antigen identical with subsp. israelensis , it seemed to be non-insecticidal against Lepidoptera and Coleoptera as well as Diptera. To investigate the activity of non-insecticidal B. thuringiensis transformed with insecticidal crystal protein genes, cryIVD and cytA genes of B. thuringiensis subsp. morrisoni PG-14, highly toxic to mosquito larvae, were introduced into the isolate NTB-1. The expression of mosquitocidal crystal protein genes in NTB-1 was characterized by SDS–PAGE analysis and electron microscopy. The results showed that crystalline inclusions of host, CryIVD and CytA were stably expressed in the transformant. However, the mosquitocidal activity of transformant was similar to that of B. thuringiensis subsp. kurstaki Cry⁻ B harbouring cryIVD and cytA genes, demonstrating that a synergistic effect by an interaction of both introduced insecticidal and resident non-insecticidal crystal proteins was not observed.     

Fluid replacement following dehydration reduces oxidative stress during recovery

To investigate the effects of hydration status on oxidative DNA damage and exercise performance, 10 subjects ran on a treadmill until exhaustion at 80% VO_2max during four different trials [control (C), 3% dehydration (D), 3% dehydration + water (W) or 3% dehydration + sports drink (S)]. Dehydration significantly decreased exercise time to exhaustion (D < C and S). Plasma MDA levels were significantly higher at pre-exercise in D than C. Plasma TAS was significantly lower at pre-exercise in C and S than in D, and was significantly lower in S than D at 60 min of recovery. Dehydration significantly increased oxidative DNA damage during exercise, but fluid replacement with water or sports drink alleviated it equally. These results suggest that (1) dehydration impairs exercise performance and increases DNA damage during exercise to exhaustion; and (2) fluid replacement prolongs exercise endurance and attenuates DNA damage.     

Variation in the growth of the preweaning Syrian hamster (Cricetus auratus)

An assessment of the growth rate spectrum based on a longitudinal weight study of golden hamsters was undertaken over the preweaning period. The period covered 23 days with data probes at 24-hourly intervals and encompassed 16 litters providing a birth number of 120 young and a weaning survival number of 82. Subsequent analysis directed initially at the pooled or averaged data showed sex differences with males gaining weight faster than females. Further analysis showed the total period to have three definitive break-points and therefore four phases of growth activity. The segmented linear regression line calculations showed that the phasic duration of males in the second and third phases were two days later than the females. Following data-analysis adjustments and taken into account aberrations of the sample, final indications pointed to the preweaning hamster growth spectrum as quadrophasic, exhibiting a stable first phase, a second and third phase terminating earlier in females and a final weaning weight being heavier in males. The growth curves demonstrated a 'U' shaped outline and formed an integral part of hamster preweaning precocity.     

Nuclear envelope‐associated dynein drives prophase centrosome separation and enables Eg5‐independent bipolar spindle formation

The microtubule motor protein kinesin‐5 (Eg5) provides an outward force on centrosomes, which drives bipolar spindle assembly. Acute inhibition of Eg5 blocks centrosome separation and causes mitotic arrest in human cells, making Eg5 an attractive target for anti‐cancer therapy. Using in vitro directed evolution, we show that human cells treated with Eg5 inhibitors can rapidly acquire the ability to divide in the complete absence of Eg5 activity. We have used these Eg5‐independent cells to study alternative mechanisms of centrosome separation. We uncovered a pathway involving nuclear envelope (NE)‐associated dynein that drives centrosome separation in prophase. This NE‐dynein pathway is essential for bipolar spindle assembly in the absence of Eg5, but also functions in the presence of full Eg5 activity, where it pulls individual centrosomes along the NE and acts in concert with Eg5‐dependent outward pushing forces to coordinate prophase centrosome separation. Together, these results reveal how the forces are produced to drive prophase centrosome separation and identify a novel mechanism of resistance to kinesin‐5 inhibitors.