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.     

Assembly of heterodimeric luciferase after de novo synthesis of subunits in rabbit reticulocyte lysate involves hsc70 and hsp40 at a post-translational stage.

Heterodimeric luciferase from Vibrio harveyi had been established as a unique model enzyme for direct measurements of the effects of molecular chaperones and folding catalysts on protein folding and subunit assembly after de novo synthesis of subunits in rabbit reticulocyte lysate. It was observed that luciferase assembly can be separated in time from synthesis of the two subunits and that under these post-translational conditions assembly was inhibited by either ATP depletion or inhibition of peptidylprolyl cis/trans isomerases, that is, by addition of cyclosporin A or FK506. Furthermore, it was observed that the inhibitory effect of FK506 on luciferase assembly can be suppressed by addition of purified cyclophilin, thereby providing the first direct evidence for the involvement of peptidylprolyl cis/trans isomerases in protein biogenesis in the eukaryotic cytosol. Here the ATP requirement in luciferase assembly has been characterized. Depletion of either Hsp90 or CCT from reticulocyte lysate did not interfere with luciferase assembly. However, addition of purified Hsc70 stimulated luciferase assembly. While addition of purified Hsp40 did not have any effect on luciferase assembly, the stimulatory effect of Hsc70 was further increased by Hsp40. Thus, after synthesis of the two subunits in reticulocyte lysate assembly of heterodimeric luciferase involves Hsc70 and its co-chaperone Hsp40. Therefore, Hsc70 aids protein biogenesis in the eukaryotic cytosol not only at the levels of nascent polypeptide chains and precursor proteins that have to be kept competent for transport into cell organelles, but also at the level of subunits that have to be kept competent for assembly.     

Differential effects of cAMP and cGMP on in vitro epidermal cell growth.

Primary keratinocyte cultures free of dermal fibroblasts were used to investigate the effect of varying cyclic AMP (cAMP) concentrations on epidermal cell function. Addition of 10^?3, 10^?4 or 10^?5 M dibutyryl cAMP to plated cells (day 1) results by day 5 in a dose dependent increase of [³H]TdR incorporation into DNA as determined by increases in both the labeling index and incorporation of ³H label into an isolated DNA fraction. 8-Bromo cAMP, another cAMP analogue, likewise induced keratinocyte proliferation. The proliferative response was dose and time dependent, and 5- to 6-fold increases in ³H label incorporated into DNA were seen at day 6, 8 and up until day 15 of culture. Moreover, elevation of cellular cAMP by addition of cholera toxin, an irreversible stimulator of adenylate cyclase, also demonstrated a time dependent stimulation of [³H]TdR uptake into DNA and increased the labeling index. Specific histochemical staining for keratinaceous protein (Kreyberg technique) demonstrated that elevated cAMP levels also enhance the production of specialized (differentiated) epidermal cells. Determination of the level of cAMP and cyclic GMP (cGMP) by RIA of partially purified fractions of the cultures revealed that addition of 8-bromo cAMP or cholera toxin to the cultures increased the levels of cAMP but not of cGMP. Addition of 8-bromo cGMP to the keratinocytes on day 1 at concentrations of 10^?6, 10^?7 or 10^?8 M had no effect on culture proliferation on days 4, 6 and 8, although qualitative changes in the electron microscopic pattern of the culture stratification and specialization were observed. The results indicate (1) both large and moderate increases in cellular cAMP levels induce keratinocyte culture proliferation and specialization in the absence of fibroblasts or dermal influences, (2) the quantitative enhancement of keratinocyte growth and specialization occurs without apparent participation of cGMP, (3) cGMP may be a qualitative effector of epidermal cell differentiation.     

Mouse erythrocyte carriers osmotically loaded with methotrexate

The mouse red blood cell (RBC) and red blood cell ghost (RBCG) have been studied as carriers of methotrexate (MTX). When incubated with high concentrations of MTX, RBCs take up significant quantities of it. However, when active loading techniques, such as the slow dialysis and preswell methods, are applied to those cells, up to 15 times more MTX can be entrapped. We have studied factors critical to the incorporation, leakage, and morphology of RBCGs during their loading with MTX by the slow dialysis and preswell methods. Compounds added to the buffers to maintain the ATP content of the cells and osmolarity play functional roles in this process. The fate of the material entrapped within the ghosts after in vivo administration was shown to be capture by the reticuloendothelial system. The pharmacological efficacy of MTX-loaded RBCGs in treating mice bearing hepatoma ascites tumors was demonstrated by increases in average survival time of 28.5-42.8%.     

Choricotyle anisotremi n. sp. (Monogenea: Diclidophoridae) parasitic on Anisotremus scapularis (Tschudi) from the northern Chilean coast

Choricotyle anisotremi n. sp. is described from the gills and on the inner surface of the operculum of Anisotremus scapularis (Pomadasyidae) from the Chilean coast. Distinct characteristics of the new species are: presence of an oval accessory sclerite on the inner quadrant of the clamp adjacent to the accessory sucker; 12 genital hooks; short and stout peduncles, the last pair of which are closely apposed; a lobed seminal receptacle; and a fan-like posthaptor without a terminal lappet.     

Mechanism-based inactivation of dopamine beta-hydroxylase by p-cresol and related alkylphenols

The mechanism-based inhibition of dopamine beta-hydroxylase (DBH; EC 1.14.17.1) by p-cresol (4-methylphenol) and other simple structural analogues of dopamine, which lack a basic side-chain nitrogen, is reported. p-Cresol binds DBH by a mechanism that is kinetically indistinguishable from normal dopamine substrate binding [DeWolf, W. E., Jr., & Kruse, L. I. (1985) Biochemistry 24, 3379]. Under conditions (pH 6.6) of random oxygen and phenethylamine substrate addition [Ahn, N., & Klinman, J. P. (1983) Biochemistry 22, 3096] p-cresol adds randomly, whereas at pH 4.5 or in the presence of fumarate "activator" addition of p-cresol precedes oxygen binding as is observed with phenethylamine substrate. p-Cresol is shown to be a rapid (kinact = 2.0 min-1, pH 5.0) mechanism-based inactivator of DBH. This inactivation exhibits pseudo-first-order kinetics, is irreversible, is prevented by tyramine substrate or competitive inhibitor, and is dependent upon oxygen and ascorbic acid cosubstrates. Inhibition occurs with partial covalent incorporation of p-cresol into DBH. A plot of -log kinact vs. pH shows maximal inactivation occurs at pH 5.0 with dependence upon enzymatic groups with apparent pK values of 4.51 +/- 0.06 and 5.12 +/- 0.06. p-Cresol and related alkylphenols, unlike other mechanism-based inhibitors of DBH, lack a latent electrophile. These inhibitors are postulated to covalently modify DBH by a direct insertion of an aberrant substrate-derived benzylic radical into an active site residue.     

An interstitial duplication of the X chromosome in a male allows physical fine mapping of probes from the Xq13-q22 region

Summary An insertional translocation into the proximal long arm of the X chromosome in a boy showing muscular hypotony, growth retardation, psychomotor retardation, cryptorchidism, and Pelizaeus-Merzbacher disease (PMD) was identified as a duplication of the Xq21–q22 segment by employing DNA probes. With densitometric scanning for quantitation of hybridization signals, 15 Xq probes were assigned to the duplicated region. Analysis of the duplication allowed us to dissect the X-Y homologous region physically at Xq21 and to refine the assignments of the loci for DXYS5, DXYS12, DXYS13, DXS94, DXS95, DXS96, DXS111, and DXS211. Furthermore, we demonstrated the presence of two different DXYS13, and DXS17 alleles in genomic DNA of our patient, suggesting that the duplication resulted from a meiotic recombination event involving the two maternal X chromosomes.     

Inactivation of dopamine beta-hydroxylase by beta-ethynyltyramine: kinetic characterization and covalent modification of an active site peptide

beta-Ethynyltyramine has been shown to be a potent, mechanism-based inhibitor of dopamine beta-hydroxylase (DBH). This is evidenced by pseudo-first-order, time-dependent inactivation of enzyme, a dependence of inactivation on the presence of ascorbate and oxygen cosubstrates, the ability of tyramine (substrate) and 1-(3,5-difluoro-4-hydroxybenzyl)imidazole-2-thione (competitive multisubstrate inhibitor) to protect against inactivation, and a high affinity of beta-ethynyltyramine for enzyme. Inactivation of DBH by beta-ethynyltyramine is accompanied by stoichiometric, covalent modification of the enzyme. Analysis of the tryptic map following inactivation by [3H]-beta-ethynyltyramine reveals that the radiolabel is associated with a single, 25 amino acid peptide. The sequence of the modified peptide is shown to be Cys-Thr-Gln-Leu-Ala-Leu-Pro-Ala-Ser-Gly-Ile-His-Ile-Phe-Ala-Ser-Gln-Leu- His*- Thr-His-Leu-Thr-Gly-Arg, where His* corresponds to a covalently modified histidine residue. In studies using the separated enantiomers of beta-ethynyltyramine, we have found the R enantiomer to be a reversible, competitive inhibitor versus tyramine substrate with a Ki of 7.9 +/- 0.3 microM. The S enantiomer, while also being a competitive inhibitor (Ki = 33.9 +/- 1.4 microM), is hydroxylated by DBH to give the expected beta-ethynyloctopamine product and also efficiently inactivates the enzyme [kinact(app) = 0.18 +/- 0.02 min-1; KI(app) = 57 +/- 8 microM]. The partition ratio for this process is very low and has been estimated to be about 2.5. This establishes an approximate value for kcat of 0.45 min(-1) and reveals that (S)-beta-ethynyltyramine undergoes a slow turnover relative to that of tyramine (kcat approximately 50 s(-1), despite the nearly 100-fold higher affinity of the inactivator for enzyme.(ABSTRACT TRUNCATED AT 250 WORDS)     

Hydrocortisone regulates arylsulfatase A (cerebroside-3-sulfate-3-sulfohydrolase) by decreasing the quantity of the enzyme in cultures of cells dissociated from embryonic mouse cerebra

Previous work from our laboratory (Biochem. J. 219:689–697 (1984) had shown that hydrocortisone stimulated the net accumulation of the myelin-specific sulfolipid in cultures of cells dissociated from embryonic mouse cerebra. This accumulation caused by hydrocortisone was shown to be due to a decrease of sulfolipid degradation by arylsulfatase A (ASA) and not due to a stimulation of its synthesis by a sulfotransferase. Both ASA activity and the turnover of sulfolipid were decreased by hydrocortisone to 60–62% of untreated cells. In current work the same decrease in enzyme activity was obtained and enzyme linked immunosorbent assays demonstrate that hydrocortisone decreased the number of ASA protein molecules to 61% of untreated cells [(-)hydrocorcortisone 0.31±0.06 ng ASA/g protein; (+)hydrocortisone: 0.18±0.04 ng ASA/g protein]. This decrease in the number of ASA molecules correlates well with the decrease in both the enzyme activity and the sulfolipid turnover, which suggests that the major mode of inhibition of ASA activity by hydrocortisone involves a decrease in the concentration of ASA in the cells rather than some other mechanism of inhibition.The material in this paper has been included in a dissertation submitted by A.J.M. in partial fulfillment of the requirements for the degree of Doctor of Philosophy. Temple University.