Application of electrolyzed acid water to sterilization of denture base part 1. Examination of sterilization effects on resin plate.

Bactericidal activities of electrolyzed strong and weak acid waters for acrylic denture base resin were evaluated in order to discuss the applicability of these waters for sterilization of denture base. Only 1-minute immersion in the electrolyzed strong or weak acid water could completely eliminate the attached bacteria, Staphylococcus aureus 209P, on the resin plate. When the resin was relined with tissue conditioner, 5-minute immersion or 1- to 2-minute ultrasonic cleaning reduced the number of the bacteria from 10(5)/cm2 level to 10(1)/cm2 and no surviving bacteria could be detected after 10-minute treatment. These findings suggest that both the electrolyzed strong and weak acid waters are well applicable to the disinfectant for acrylic denture base showing excellent bactericidal activities in a significantly shorter treatment as compared with the conventional denture cleaning.

A pivotal role for DNase I-sensitive regions 3b and/or 4 in the induction of somatic hypermutation of IgH genes.

Chimeric mice were prepared from embryonic stem cells transfected with IgH genes as transgenes and RAG-2-deficient blastocysts for the purpose of identifying the cis-acting elements responsible for the induction of somatic hypermutation. Among the three transgene constructs used, the V(H) promoter, the rearranged V(H)-D-J(H), an intron enhancer/matrix attachment region, and human Cmu were common to all, but the 3'-untranslated region in each construct was different. After immunization of mice with a T cell-dependent Ag, the distribution and frequency of hypermutation in transgenes were analyzed. The transgene lacking the 3' untranslated region showed a marginal degree of hypermutation. Addition of the 3' enhancer resulted in a slight increase in the number of mutations. However, the transgene containing DNase I-sensitive regions 3b and 4 in addition to the 3' enhancer showed more than a 10-fold increase in hypermutation, reaching levels comparable to those observed in endogenous V(H)186.2 genes of C57BL/6 mice.

Wearing behaviors of a hybrid composite resin for crown and bridge.

The wearing behaviors of a hybrid composite resin for crown and bridge (ES) were examined using a two-body impacting-sliding wear test with a porcelain (PO), Au-Ag-Pd alloy (PD), direct restorative composite resin (CR) and tooth enamel (TO). Although PO was the hardest of all, it showed the largest wear together with ES in the combination of ES-PO, which was probably initiated from the superficial destruction by their impact. The wear in ES-PD was the second largest. It was noted in this combination that the surface of ES was partially contaminated by scraped thin layers of PD to a degree distinguished by the naked eye. The mutual wears of the components were relatively low in the combination of ES with CR, TO or ES itself. It is suggested from these findings that the hybrid composite resin may be useful as an alternative to porcelain for posterior crown and bridge unless it opposes porcelain or alloys.

Fracture aspects of resin-dentin bonding in non-trimming microtensile test.

Comparative studies on resin-dentin bond strength and failure mode were performed between the conventional tensile test and the microtensile test with non-trimming small specimens, 1 x 1 mm in cross-section, for two brands of dentin bonding systems. The fracture surface of the conventional large specimen showed a catastrophic cohesive failure in dentin at its center and a lesser adhesive failure, suggesting that the whole failure was due to the development of some major cracks. The non-trimming microtensile test showed significantly larger average bond strength with markedly larger standard deviation and significantly larger fraction of adhesive failure than the conventional test. Some small specimens were extremely strong and some were weak according to the heterogeneous distribution of tight bonding and defective or deficient bonding over the whole dentin surface. These results suggest that the non-trimming microtensile test may potentially provide more realistic aspects of resin-dentin bonding than the conventional bulk specimen.

Utility of Ni-Ti shape memory orthodontic wire.

The characteristic temperature dependence of recovery force was evaluated for a Cu-containing Ni-Ti shape memory wire with the nominal Af point being 40 degrees C. It exerted mild recovery force within the range of the proposed optimum force at the usual oral temperature. Larger forces were generated when it was heated to temperatures above Af: 40, 50 or 60 degrees C. By subsequently cooling to temperatures below Af, the force decreased again, and vice versa. The excellent reversibility, reproducibility and durability of the recovery force were also confirmed. These results indicate that the shape memory wire may be a reasonable material for a new concept of intermittent orthodontic treatment, in which mild force will be applied to the tooth for most of the daily hours and the tooth movement will be intermittently accelerated by larger forces generated only when the patient has hot foods or drinks.

Durability of resin-dentin bonds.

PURPOSE: The purpose of this study was to determine if the durability of resin-dentin bonds could be evaluated more quickly if the bond specimen was divided into 1 x 1 x 8 mm beams incubated at 37 degrees C for a 90-day period. MATERIALS AND METHODS: Extracted human third molars were prepared for bonding by removing the occlusal surface near the dento-enamel junction (superficial dentin group) or near the pulp (deep dentin group). The teeth were bonded either with MacBond, One Step or Clearfil Liner Bond 2, and then builtup to form a flat resin composite crown. After 24 hours in water, each buildup was vertically divided into slabs 1 mm thick, the top half of which was resin, with the bottom half as dentin. Each slab was then vertically sectioned at 1-mm increments to create 1 x 1 x 8-mm beams of resin-bonded dentin. They were incubated for 1 day or 90 days at 37 degrees C, followed by measurement of the tensile bond strengths. The results were analyzed by the Least-Squares Means method at the 95% confidence level. RESULTS: MacBond gave the highest (p < 0.05) 1-day bond strengths to superficial dentin, but significantly lower bond strengths were measured in deep dentin. There were no significant differences in the bond strengths of either One Step or Clearfil Liner Bond 2 to superficial vs deep dentin at 1 day, but at 90 days their bond strengths to deep dentin had fallen significantly (p < 0.05). Prepolymerized cylinders of resin composite bonded together with One Step showed little variation in bond strength over the 90-day experiment. SEM examination of the failed bonds showed increased porosity in intertubular dentin over time. CONCLUSION: The results indicate that division of large specimens into many small beams accelerated the deterioration of bond strength in deep dentin in all three bonding systems and in both superficial and deep dentin in the MacBond treated specimens. This method seems promising for studying the durability of resin-dentin bonds.

Blockade of antibody-induced glomerulonephritis with Crry-Ig, a soluble murine complement inhibitor.

A recombinant soluble form of the mouse membrane complement inhibitor Crry (complement receptor-related gene y) fused to IgG1 hinge, CH2, and CH3 domains has been created and designated Crry-Ig. Crry has been used because, similar to human soluble CR1, it demonstrates decay-accelerating activity for both the classical and alternative pathways of complement as well as cofactor activity for factor I-mediated cleavage of C3b and C4b. The mouse IgG1 isotype was incorporated because it is a noncomplement-activating isotype and, when fused to Crry, results in a complement inhibitor that should not be recognized as foreign when used chronically in murine models. Crry-Ig demonstrated complement-inhibitory activity in both the fluid phase and on target surfaces. Following in vivo injection, Crry-Ig manifested a two-phase serum elimination profile, a rapid initial loss most likely reflecting tissue redistribution and a second more prolonged decline with a t1/2 of 40 h. Inhibition of complement activation in mice following injection of Crry-Ig was demonstrated by a marked decrease in the ability of serum from treated mice to be activated by zymosan particles in vitro. Finally, in vivo efficacy of Crry-Ig was demonstrated by its ability to substantially diminish renal injury induced by complement-fixing nephrotoxic Ab. The use of Crry-Ig in vivo in murine models of chronic inflammatory and autoimmune disease should allow further insight into the potential therapeutic effects and possible untoward complications of continuous blockade of complement using inhibitors that act on activation products of C4 and C3.

Cross-linking CD21/CD35 or CD19 increases both B7-1 and B7-2 expression on murine splenic B cells.

Activation of the complement cascade and ligation of complement C3 receptors on B cells represent an important bridge between innate and Ag-specific acquired immunity. We show here that cross-linking of mouse CD21 (complement receptor type 2, CR2, C3d receptor) and CD35 (complement receptor type 1, CR1, C3b/C4b receptor) or co-cross-linking of CD21/CD35 and surface IgM rapidly up-regulates both B7-1 and B7-2 expression on murine resting splenic B cells. CD21/CD35-mediated up-regulation of both B7-1 and B7-2 expression is observed within 14 h, while other stimuli up-regulate only B7-2 but not B7-1 at this early time point. Consistent with the increase in B7 levels, BALB/c B cells on which surface IgM and CD21/CD35 have been co-cross-linked stimulate C57BL/6 T cells more effectively than controls. This CD21/CD35-enhanced allogeneic MLR is blocked nearly completely by anti-B7-2 mAbs and partially by anti-B7-1 mAbs. In addition, cross-linking of CD19, which is physically associated with CD21/CD35, leads to increased B7-1 and B7-2 expression. These data suggest that CD21/CD35 ligation results in enhanced B cell Ag presentation using costimulatory mechanisms shared with other activators and thus works cooperatively in this process. Rapid up-regulation of B7-1 expression, a unique response to CD21/CD35 and CD19 cross-linking, may be a particularly important effect of C3-containing ligands. We propose that CD21/CD35- and CD19-mediated B7-1 and B7-2 up-regulation is an important mechanism by which complement activation links innate and acquired immunity.

Mouse complement receptors type 1 (CR1;CD35) and type 2 (CR2;CD21): expression on normal B cell subpopulations and decreased levels during the development of autoimmunity in MRL/lpr mice.

Human complement receptors type 1 (hCR1;CD35) and type 2 (hCR2;CD21) are expressed on B lymphocytes at specific stages during differentiation and activation. These receptors play critical roles in the immune response to T-dependent Ags in addition to germinal center formation. Expression of both hCR2 and hCR1 is decreased on B lymphocytes of patients with systemic lupus erythematosus (SLE). We have studied the expression of mouse CR2 and CR1 on normal populations of mouse B lymphocytes in BALB/c mice. Our results demonstrate that expression of these receptors in the normal state closely parallels that of hCR2. During bone marrow development, expression is first detected on low B220/high IgM cells, demonstrating that complement receptors appear after central tolerance mechanisms are completed. In the splenic microenvironment the highest levels of receptor expression are found on marginal zone B lymphocytes. Mouse CR2 and CR1 are also found on peritoneal B1a and B1b cells in addition to IgA+ Peyer's patch B cells. Activation of splenic B cells under Th2 conditions results in a marked decrease in receptor expression. To determine whether the patterns of receptor expression also parallel those found in human disease, we studied the MRL lpr/lpr (MRL/lpr) model of SLE. Interestingly, we found an early decrease in complement receptor expression that is progressive and first detectable before major clinical manifestations of nephritis. We hypothesize that the early decrease in complement receptor expression such as that demonstrated by MRL/lpr mice plays an important role in the pathogenesis of murine and perhaps human SLE.

Individual variation of acetohexamide reductase activities in liver microsomes and cytosol of rats.

We examined individual variations in acetohexamide reductase activities in liver microsomes and cytosol of rats. Large differences among individuals were observed for acetohexamide reductase activity in liver microsomes of male Fischer-344 (Fischer), Sprague-Dawley (SD) and Wistar rats at 9 weeks of age, except in the Wistar-Imamichi (Wistar-IM) strain. These four strains of female rats did not exhibit any microsomal enzyme activity. Although acetohexamide reductase activities were fully detectable in liver cytosols from all the strains of male and female rats, there was neither strain-related difference nor considerable individual variation in the cytosolic enzyme activity. In liver microsomes of male Fischer rats at 4 weeks of age, acetohexamide reductase activity was not detectable. The microsomal enzyme activity in male Fischer rats markedly increased at 6 weeks of age to approach the levels at 9 and 12 weeks of age, with large individual variations.

Resting B cells from New Zealand Black mice demonstrate a defect in apoptosis induction following surface IgM ligation.

New Zealand Black (NZB) mice spontaneously develop autoimmune disease, usually characterized by an autoimmune hemolytic anemia, and NZB genes are essential for a severe systemic lupus-like disease in (NZB x NZW)F1 mice. We have found that resting B cells from NZB mice demonstrate a pronounced defect, compared with five normal strains, in apoptosis induction after cross-linking with anti-IgM Abs. In contrast, spontaneous apoptosis of NZB B cells in culture was similar to normal strains. B cells from young (NZB x SM/J)F1 and (NZB x NZW)F1 mice underwent apoptosis normally, indicating that the NZB defect in apoptosis is a recessive trait. However, older (8-32 wk) predisease (NZB x NZW)F1 mice manifested a similar defect in apoptosis induction. The analysis of NXSM recombinant inbred mice derived from NZB and SM/J, in addition to backcross mice, suggested that the NZB apoptosis defect is a multigenic trait. Interestingly, resting B cells form B6.lpr and B6gld mice underwent apoptosis following anti-IgM treatment at a level similar to that of the C57BL/6 parental strain. Thus, the induced apoptosis of resting B cells and the NZB defect are likely not related to either Fas or Fas ligand. We propose that this phenotypic defect in apoptosis induction, or the biochemical alteration that underlies the defect, may be casually related to autoimmune disease in NZB mice and its contribution to lupus-like disease in (NZB x NZW)F1 mice.

Co-ligation of mouse complement receptors 1 and 2 with surface IgM rescues splenic B cells and WEHI-231 cells from anti-surface IgM-induced apoptosis.

Recent studies have shown that complement receptors play important roles in both T-dependent and T-independent B lymphocyte responses to low doses of antigen (Ag) in vivo. Complement activation by either the classical or alternative pathway results in the covalent binding of C3 molecules to Ag in forms that ligate complement receptors type 1 (CR1) and 2 (CR2). We hypothesized that C3-bound Ag might cross-link CR2 and/or CR1 with surface (s)IgM and alter the signal that would be transduced through sIgM by Ag binding alone. One result of the altered signal could be the rescue of B lymphocytes from apoptosis that would otherwise be induced by the binding of certain types of Ag alone. We find that co-cross-linking of mouse CR2 and CR1 with sIgM rescues both resting B cells and WEHI-231.7 cells from apoptosis induced by sIgM ligation in a fashion similar to that found using soluble mouse CD40 ligand (mCD40L). Anti-CR2/CR1-mediated rescue requires co-cross-linking of the receptors with sIgM, and has an additive effect on mCD40L-mediated apoptosis rescue. Based on these results, it is likely that the CR2/CR1-derived signal is cooperative with T cell-derived signals such as CD40L and interleukin-4.

Strain- and sex-related differences of acetohexamide reductase activities in liver microsomes and cytosol of rats: the Wistar-Imamichi strain lacks the male-specific microsomal enzyme activity.

A marked strain-related difference was observed among acetohexamide reductase activities in liver microsomes of male rats. The microsomal enzyme activities in the Fischer-344 (Fischer), Sprague-Dawley (SD) and Wistar strains were 2.58 +/- 0.50, 1.60 +/- 0.44 and 0.79 +/- 0.41 nmol/min/mg protein, respectively. The microsomal enzyme activities in these rat strains were much higher in males than in females, indicating that the microsomal enzyme is a male-specific enzyme. The Wistar-Imamichi (Wistar-IM) strain was found to lack the male-specific microsomal enzyme activity. In Fischer, SD and Wistar strains of testectomized male rats, the microsomal enzyme activities were significantly increased by the treatment with testosterone. However, testosterone treatment was ineffective on the microsomal enzyme activity in the Wistar-IM strain. These results suggest that Wistar-IM rats has a genetic deficiency of the microsomal enzyme. There was no strain-related difference among the cytosolic enzyme activities in male rats. The cytosolic enzyme activities in Fischer and Wistar rats were higher in females than in males.

Efficacy of gas purging for titanium casting.

Oxygen density in the melting atmosphere, oxygen uptake, hardness and castability of pure titanium castings were examined to evaluate the efficacy of gas purging in reducing contamination from the melting atmosphere and mold, using a newly developed titanium casting machine in which the double purging process is systematized. The adoption of a double purging operation resulted in an extremely low oxygen density in the melting atmosphere, followed by extremely low oxygen uptake in the casting when compared with the conventional titanium casting machine. When the purging operation was used, the surface hardness was markedly reduced, although there was no difference in castability. From these results, it was suggested that the newly developed titanium casting machine with the double purging operation could produce better titanium castings with less contamination due to the mold and gas impurities in melting atmosphere.

Effects of rapid burnout type gypsum-bonded investment on performance of castings. Part 1. Surface aspects and fit of crowns.

Rapid burnout type gypsum-bonded investment materials were developed to shorten the time required for dental casting procedures. With these materials, molds can be prepared by rapid heating at 700 degrees C for 30 min from 30 min after the start of mixing. When the investment block was rapidly heated at 700 degrees C, no fractures were observed in the rapid burnout type investments with one exception, while a conventional cristobalite investment broke into pieces shortly after being placed in the furnace. Casting fins were sometimes induced only for the material which showed fracturing on rapid heating. No practical problems were found in the surface roughness of the castings. The 30 min-setting expansion was significantly different among the materials although there were no differences in thermal expansion, and the material showing greater 30 min-setting expansion was efficient to obtain better fit of the crown as in the conventional casting procedures.

Combined testosterone treatment in pubertal and adult periods induces male-specific acetohexamide reductase activity in liver microsomes of female rats.

The influence of testosterone treatment on acetohexamide reductase activities in liver microsomes and cytosol of female rats was examined. Acetohexamide reductase activity in liver microsomes was much lower in female rats than in male rats. Combined testosterone treatment in pubertal and adult periods induced male-specific acetohexamide reductase activity in liver microsomes of female rats. However, testosterone treatment only during puberty or during adulthood was without effect. Testosterone secreted from the testes during puberty appeared to have a significant effect similar to neonatal imprinting in the induction of acetohexamide reductase activity in liver microsomes of female rats. The combined testosterone treatment, or testosterone treatment only during puberty or during adulthood had no effect on acetohexamide reductase activity in liver cytosol of female rats.

Influence of aging on acetohexamide reductase activities in liver microsomes and cytosol of male rats.

The influence of aging on the reductase activity of acetohexamide, an oral antidiabetic drug with a ketone group, was examined in liver microsomes and cytosol of male rats. Acetohexamide reductase activities in liver microsomes of male rats at 26 and 31 months of age were much lower than that in liver microsomes of male rats at 9 weeks of age. Testectomy markedly decreased acetohexamide reductase activity in liver microsomes of the 9-week old rats and the decreased enzyme activity was significantly increased by testosterone administration. These results indicate, at least in part, that aging decreases the enzyme activity by decreasing the secretion of testosterone from the testes. On the other hand, aging (26 months of age) did not affect acetohexamide reductase activity in liver cytosol of male rats, although the enzyme activity at 31 months of age was slightly but significantly lower than that in liver cytosol of male rats at 9 weeks of age. Testectomy or testosterone administration had no effect on the enzyme activity in liver cytosol of 9-week old male rats.

Bactericidal activity of C9-deficient human serum.

Escherichia coli B/SM, strain 1-1, was killed dose dependently by human hereditary C9-deficient serum (C9DHS), which was shown to contain no C9 Ag by an ELISA method. On the other hand, human hereditary C7-deficient serum did not kill the bacteria under similar conditions. The bactericidal activity of C9DHS was inhibited by rabbit anti-C5 antibody but not by murine anti-C9 mAb. The anti-C9 antibody decreased the bactericidal activity of normal human serum (NHS) to the level of that with C9DHS. Sheep anti-human lysozyme antibody did not affect the bactericidal activity of C9DHS or NHS even when added at more than twice the concentration required to block the serum lysozyme activity on Micrococcus luteus. After treatment with C9DHS and washing, surviving Escherichia coli were killed by C9, but not by lysozyme, transferrin, or both. Other strains of E. coli (K12 W3110, C600, and NIHJ) and Salmonella typhimurium (strain NCTC 74), all maintained in the laboratory, were also killed by C9DHS. However, pathogenic strains recently isolated from patients with traveler's diarrhea and some strains of S. typhimurium were resistant to both C9DHS and NHS, at least at the serum concentration tested. A concentration of 0.1 M Tris did not increase the susceptibility of serum-resistant strains of bacteria to C9DHS, but made one strain of S. typhimurium tested susceptible to NHS, but not to C9DHS. These results clearly showed that C9DHS kills bacteria that are sensitive to NHS through activation of C up to the step of C8 in the same way that C9-deficient C serum lyzed sensitized erythrocytes.