Influence of Etching Mode on Enamel Bond Durability of Universal Adhesive Systems

The purpose of this study was to determine the enamel bond durability of three universal adhesives in different etching modes through fatigue testing. The three universal adhesives used were Scotchbond Universal, Prime&Bond Elect universal dental adhesive, and All-Bond Universal light-cured dental adhesive. A single-step self-etch adhesive, Clearfil S³ Bond Plus was used as a control. The shear bond strength (SBS) and shear fatigue strength (SFS) to human enamel were evaluated in total-etch mode and self-etch mode. A stainless steel metal ring with an internal diameter of 2.4 mm was used to bond the resin composite to the flat-ground (4000-grit) tooth surfaces for determination of both SBS and SFS. For each enamel surface treatment, 15 specimens were prepared for SBS and 30 specimens for SFS. The staircase method for fatigue testing was then used to determine the SFS of the resin composite bonded to the enamel using 10-Hz frequencies for 50,000 cycles or until failure occurred. Scanning electron microscopy was used to observe representative debonded specimen surfaces and the resin-enamel interfaces. A two-way analysis of variance and the Tukey post hoc test were used for analysis of the SBS data, whereas a modified t-test with Bonferroni correction was used for the SFS data. All adhesives in total-etch mode showed significantly higher SBS and SFS values than those in self-etch mode. Although All-Bond Universal in self-etch mode showed a significantly lower SBS value than the other adhesives, there was no significant difference in SFS values among the adhesives in this mode. All adhesives showed higher SFS:SBS ratios in total-etch mode than in self-etch mode. With regard to the adhesive systems used in this study, universal adhesives showed higher enamel bond strengths in total-etch mode. Although the influence of different etching modes on the enamel-bonding performance of universal adhesives was found to be dependent on the adhesive material, total-etch mode effectively increased the enamel bond strength and durability, as measured by fatigue testing.

Analysis of Heritability and Shared Heritability Based on Genome-Wide Association Studies for Thirteen Cancer Types

BACKGROUND

Studies of related individuals have consistently demonstrated notable familial aggregation of cancer. We aim to estimate the heritability and genetic correlation attributable to the additive effects of common single-nucleotide polymorphisms (SNPs) for cancer at 13 anatomical sites.

METHODS

Between 2007 and 2014, the US National Cancer Institute has generated data from genome-wide association studies (GWAS) for 49 492 cancer case patients and 34 131 control patients. We apply novel mixed model methodology (GCTA) to this GWAS data to estimate the heritability of individual cancers, as well as the proportion of heritability attributable to cigarette smoking in smoking-related cancers, and the genetic correlation between pairs of cancers.

RESULTS

GWAS heritability was statistically significant at nearly all sites, with the estimates of array-based heritability, hl (2), on the liability threshold (LT) scale ranging from 0.05 to 0.38. Estimating the combined heritability of multiple smoking characteristics, we calculate that at least 24% (95% confidence interval [CI] = 14% to 37%) and 7% (95% CI = 4% to 11%) of the heritability for lung and bladder cancer, respectively, can be attributed to genetic determinants of smoking. Most pairs of cancers studied did not show evidence of strong genetic correlation. We found only four pairs of cancers with marginally statistically significant correlations, specifically kidney and testes (ρ = 0.73, SE = 0.28), diffuse large B-cell lymphoma (DLBCL) and pediatric osteosarcoma (ρ = 0.53, SE = 0.21), DLBCL and chronic lymphocytic leukemia (CLL) (ρ = 0.51, SE =0.18), and bladder and lung (ρ = 0.35, SE = 0.14). Correlation analysis also indicates that the genetic architecture of lung cancer differs between a smoking population of European ancestry and a nonsmoking Asian population, allowing for the possibility that the genetic etiology for the same disease can vary by population and environmental exposures.

CONCLUSION

Our results provide important insights into the genetic architecture of cancers and suggest new avenues for investigation.

Effect of Phosphoric Acid Pre-etching on Fatigue Limits of Self-etching Adhesives

The purpose of this study was to use shear bond strength (SBS) and shear fatigue limit (SFL) testing to determine the effect of phosphoric acid pre-etching of enamel and dentin prior to application of self-etch adhesives for bonding resin composite to these substrates. Three self-etch adhesives—1) G- ænial Bond (GC Corporation, Tokyo, Japan); 2) OptiBond XTR (Kerr Corp, Orange, CA, USA); and 3) Scotchbond Universal (3M ESPE Dental Products, St Paul, MN, USA)—were used to bond Z100 Restorative resin composite to enamel and dentin surfaces. A stainless-steel metal ring with an inner diameter of 2.4 mm was used to bond the resin composite to flat-ground (4000 grit) tooth surfaces for determination of both SBS and SFL. Fifteen specimens each were used to determine initial SBS to human enamel/dentin, with and without pre-etching with a 35% phosphoric acid (Ultra-Etch, Ultradent Products Inc, South Jordan, UT, USA) for 15 seconds prior to the application of the adhesives. A staircase method of fatigue testing (25 specimens for each test) was then used to determine the SFL of resin composite bonded to enamel/dentin using a frequency of 10 Hz for 50,000 cycles or until failure occurred. A two-way analysis of variance and Tukey post hoc test were used for analysis of SBS data, and a modified t-test with Bonferroni correction was used for the SFL data. Scanning electron microscopy was used to examine the area of the bonded restorative/tooth interface. For all three adhesive systems, phosphoric acid pre-etching of enamel demonstrated significantly higher (p<0.05) SBS and SFL with pre-etching than it did without pre-etching. The SBS and SFL of dentin bonds decreased with phosphoric acid pre-etching. The SBS and SFL of bonds using phosphoric acid prior to application of self-etching adhesives clearly demonstrated different tendencies between enamel and dentin. The effect of using phosphoric acid, prior to the application of the self-etching adhesives, on SBS and SFL was dependent on the adhesive material and tooth substrate and should be carefully considered in clinical situations.

Localized and Generalized Simulated Wear of Resin Composites

A laboratory study was conducted to examine the wear of resin composite materials using both a localized and generalized wear simulation model. Twenty specimens each of seven resin composites (Esthet•X HD [HD], Filtek Supreme Ultra [SU], Herculite Ultra [HU], SonicFill [SF], Tetric EvoCeram Bulk Fill [TB], Venus Diamond [VD], and Z100 Restorative [Z]) were subjected to a wear challenge of 400,000 cycles for both localized and generalized wear in a Leinfelder-Suzuki wear simulator (Alabama machine). The materials were placed in custom cylinder-shaped stainless steel fixtures. A stainless steel ball bearing (r=2.387 mm) was used as the antagonist for localized wear, and a stainless steel, cylindrical antagonist with a flat tip was used for generalized wear. A water slurry of polymethylmethacrylate (PMMA) beads was used as the abrasive media. A noncontact profilometer (Proscan 2100) with Proscan software was used to digitize the surface contours of the pretest and posttest specimens. AnSur 3D software was used for wear assessment. For localized testing, maximum facet depth (μm) and volume loss (mm3) were used to compare the materials. The mean depth of the facet surface (μm) and volume loss (mm3) were used for comparison of the generalized wear specimens. A one-way analysis of variance (ANOVA) and Tukey post hoc test were used for data analysis of volume loss for both localized and generalized wear, maximum facet depth for localized wear, and mean depth of the facet for generalized wear. The results for localized wear simulation were as follows [mean (standard deviation)]: maximum facet depth (μm)—Z, 59.5 (14.7); HU, 99.3 (16.3); SU, 102.8 (13.8); HD, 110.2 (13.3); VD, 114.0 (10.3); TB, 125.5 (12.1); SF, 195.9 (16.9); volume loss (mm3)— Z, 0.013 (0.002); SU, 0.026 (0.006); HU, 0.043 (0.008); VD, 0.057 (0.009); HD, 0.058 (0.014); TB, 0.061 (0.010); SF, 0.135 (0.024). Generalized wear simulation results were as follows: mean depth of facet (μm)—Z, 9.3 (3.4); SU, 12.8 (3.1); HU, 15.6 (3.2); TB, 19.2 (4.8); HD, 26.8 (6.5); VD, 29.1 (5.5); SF, 35.6 (8.4); volume loss (mm3)—Z, 0.132 (0.049); SU, 0.0179 (0.042); HU, 0.224 (0.044); TB, 0.274 (0.065); HD, 0.386 (0.101); VD, 0.417 (0.076); SF, 0.505 (0.105). The ANOVA showed a significant difference among materials (p<0.001) for facet depth and volume loss for both localized and generalized wear. The post hoc test revealed differences (p<0.05) in localized and generalized wear values among the seven resin composites examined in this study. The findings provide valuable information regarding the relative wear characteristics of the materials in this study.

Mechanical Properties and Simulated Wear of Provisional Resin Materials

The purpose of this study was to determine flexural properties and erosive wear behavior of provisional resin materials. Three bis-acryl base provisional resins-1) Protemp Plus (PP), 2) Integrity (IG), 3) Luxatemp Automix Plus (LX)-and a conventional poly(methylmethacrylate) (PMMA) resin, UniFast III (UF), were evaluated. A resin composite, Z100 Restorative (Z1), was included as a benchmark material. Six specimens for each of the four materials were used to determine flexural strength and elastic modulus according to ISO Standard 4049. Twelve specimens for each material were used to examine wear using a generalized wear simulation model. The test materials were each subjected to wear challenges of 25,000, 50,000, 100,000, and 200,000 cycles in a Leinfelder-Suzuki (Alabama) wear simulator. The materials were placed in custom cylinder-shaped stainless-steel fixtures, and wear was generated using a cylindrical-shaped flat-ended stainless-steel antagonist in a slurry of nonplasticized PMMA beads. Wear (mean facet depth [μm] and volume loss [mm(3)]) was determined using a noncontact profilometer (Proscan 2100) with Proscan and AnSur 3D software. The laboratory data were evaluated using two-way analysis of variance (ANOVA; factors: 1) material and 2) cycles) followed by Tukey HSD post hoc test (α=0.05). The flexural strength ranged from 68.2 to 150.6 MPa, and the elastic modulus ranged from 2.0 to 15.9 GPa. All of the bis-acryl provisional resins (PP, IG, and LX) demonstrated significantly higher values than the PMMA resin (UF) in flexural strength and elastic modulus (p<0.05). However, there was no significant difference (p>0.05) in flexural properties among three bis-acryl base provisional resins (PP, IG, and LX). Z1 demonstrated significantly (p<0.05) higher flexural strength and elastic modulus than the other materials tested. The results for mean facet wear depth (μm) and standard deviations (SD) for 200,000 cycles were as follows: PP, 22.4 (5.0); IG, 51.0 (6.5); LX, 63.7 (4.5); UF, 70.5 (8.0); and Z1, 7.6 (1.2). Volume loss (mm(3)) and SDs for 200,000 cycles were as follows: PP, 0.311 (0.049); IG, 0.737 (0.074); LX, 0.919 (0.053); UF, 1.046 (0.127); and Z1, 0.111 (0.017). The two-way ANOVA showed a significant difference among materials (p<0.001) and number of cycles for both facet depth and volume loss. The post hoc test revealed differences (p<0.05) in wear values among the tested materials examined in this study. The findings provide valuable information regarding the flexural properties and the relative wear behavior of the provisional resins examined in this study.

Sexual functioning among testicular cancer survivors: a case-control study in the U.S

OBJECTIVE

Sexual function among testicular cancer survivors is a concern because affected men are of reproductive age when diagnosed. We conducted a case-control study among United States military men to examine whether testicular cancer survivors experienced impaired sexual function.

METHODS

A total of 246 testicular cancer cases and 236 ethnicity and age matched controls were enrolled in the study in 2008-2009. The Brief Male Sexual Function Inventory (BMSFI) was used to assess sexual function.

RESULTS

Compared to controls, cases scored significantly lower on sex drive (5.77 vs. 5.18), erection (9.40 vs. 8.63), ejaculation (10.83 vs. 9.90), and problem assessment (10.55 vs. 9.54). Cases were significantly more likely to have impaired erection (OR 1.72; 95% CI 1.11-2.64), ejaculation (OR 2.27; 95% CI 1.32-3.91), and problem assessment (OR 2.36; 95% CI 1.43-3.90). In histology and treatment analysis, nonseminoma, chemotherapy and radiation treated cases risk of erectile dysfunction, delayed ejaculation, and/or problem assessment were greater when compared to controls.

CONCLUSION

This study provides evidence that testicular cancer survivors are more likely to have impaired sexual functioning compared to demographically matched controls. The observed impaired sexual functioning appeared to vary by treatment regimen and histologic subtype.

Detectable clonal mosaicism and its relationship to aging and cancer

In an analysis of 31,717 cancer cases and 26,136 cancer-free controls from 13 genome-wide association studies, we observed large chromosomal abnormalities in a subset of clones in DNA obtained from blood or buccal samples. We observed mosaic abnormalities, either aneuploidy or copy-neutral loss of heterozygosity, of >2 Mb in size in autosomes of 517 individuals (0.89%), with abnormal cell proportions of between 7% and 95%. In cancer-free individuals, frequency increased with age, from 0.23% under 50 years to 1.91% between 75 and 79 years (P = 4.8 × 10(-8)). Mosaic abnormalities were more frequent in individuals with solid tumors (0.97% versus 0.74% in cancer-free individuals; odds ratio (OR) = 1.25; P = 0.016), with stronger association with cases who had DNA collected before diagnosis or treatment (OR = 1.45; P = 0.0005). Detectable mosaicism was also more common in individuals for whom DNA was collected at least 1 year before diagnosis with leukemia compared to cancer-free individuals (OR = 35.4; P = 3.8 × 10(-11)). These findings underscore the time-dependent nature of somatic events in the etiology of cancer and potentially other late-onset diseases.

Abstract 4468: Pre-diagnostic steroid hormone levels and risk of testicular germ cell tumors

Background: Testicular germ cell tumors (TGCT), the most commonly occurring cancer among young men in the U.S., are thought to be endocrine-related tumors. The relationship between steroid hormone levels and development of TGCT, however, has been difficult to study given the rarity of the tumor in the general population and the paucity of pre-diagnostic serum from young men. The U.S. Servicemen's Testicular Tumor Environmental and Endocrine Determinants (STEED) study, however, was able to overcome these obstacles by enrolling military servicemen who had previously donated serum specimens to the Department of Defense Serum Repository. Methods: STEED participants were enrolled between 2002 and 2005. The associations between TGCT risk and log-transformed serum concentrations of testosterone, free testosterone, estradiol, free estradiol, 3α-androstanediol glucuronide (3α-diol-G), an indicator of peripheral androgen action, and sex hormone-binding globulin (SHBG) were examined in 517 case and 790 control participants. Odds ratios (OR) and 95% confidence intervals (CI) were estimated using logistic regression models, adjusting for date of serum donation, age, race/ethnicity, family history of testicular cancer, history of cryptorchidism, height, and body mass index. Results: The analysis found that while testosterone was not significantly associated with TGCT risk, there was an inverse association between 3α-diol-G and risk (OR=0.80, 95%CI=0.63-0.99). In addition, there was a significant inverse association with TGCT and the ratio of 3α-diol-G to testosterone (OR=0.76, 95%CI=0.61-0.93). There was also a significant direct association between estradiol and TGCT risk (OR=1.41, 95%CI=1.06-1.87). The relationships between the free forms of testosterone and estradiol and risk were the same as the relationships between the total forms of each hormone and risk. There was no association between TGCT and SHBG. Conclusion: These results suggest that the hormone metabolism of men who subsequently develop TGCT may vary from that of other men. In men who develop TGCT, more testosterone may be converted to estradiol and less to dihydrotestosterone, the most potent form of androgen, than in men who do not develop TGCT. Further examination of metabolites, both upstream and downstream in the steroid hormone pathway, may help elucidate the mechanism by which these exposures are related to development of TGCT.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4468. doi:1538-7445.AM2012-4468

Abstract 4470: Pre-diagnostic gonadotropin levels and development of testicular germ cell tumors

INTRODUCTION: Testicular germ cell tumors (TGCT) are the most common cancer among young men (20-45 years of age). The pathogenesis of TGCT remains largely unknown; however, there is evidence that TGCT is related to other male reproductive disorders namely infertility and genitourinary malformations (cryptorchidism and hypospadias). It is generally assumed that the development of TGCT is under endocrine control and it has been hypothesized that gonadotropin dysregulation may be one potential cause of TGCT, as the testes are primary target organs for the gonadotropins, follicle-stimulating hormone (FSH) and luteinzing hormone (LH). FSH stimulates spermatogenesis via binding to receptors in Sertoli cells, while LH stimulates the Leydig cells to produce testosterone. Data support the role of primary LH deficiency in cryptorchidism, and also support the role of gonadotropin deficiency in infertility. It is currently not known whether FSH and LH levels are associated with TGCT risk. Thus, we assessed associations of pre-diagnostic serum FSH and LH concentrations and risk of TGCT among participants in the U.S. Servicemen's Testicular Tumor Environmental and Endocrine Determinants (STEED) Study. METHODS: TGCT cases diagnosed between 2002 and 2005 (n=517) were matched on age, race and serum draw date to at least one control (n=790). Associations between pre-diagnostic serum FSH and LH levels and TGCT were estimated using conditional logistic regression with further adjustment for prior cryptorchidism, family history of testicular cancer, height, body mass index and serum testosterone. Associations stratified on histology (seminoma, nonseminoma) were also examined. RESULTS: Overall, TGCT was associated with increased levels of FSH and decreased levels of LH. Men had an increased risk of TGCT if they were in the highest quartile of FSH [Q4 vs. Q1: OR 2.17, 95% CI 1.35-3.48] and in the lowest quartile of LH [Q1 vs. Q4: OR 1.99, 95% CI 1.25-3.16]. These associations were independent of one another and independent of serum testosterone concentration. In analyses stratified by histologic subtype the increased risk of TGCT with high FSH [Q4 vs. Q1: OR 2.86, 95% CI 1.33-6.18] and low LH [Q1 vs. Q4: OR 2.55, 95% CI 1.18, 5.49] was consistent for seminomas. Among nonseminomas, the ORs were indicative of elevated TGCT risk with high FSH [Q4 vs. Q1: OR 1.81, 95% CI 0.96-3.43] and low LH [Q1 vs. Q4: OR 1.80, 95% CI 0.97-3.36], albeit the results did not attain statisitical significance. DISCUSSION: Our findings of associations of TGCT with FSH and LH suggest that gonadotropin disruption may be a critical event in development of TGCT. LH deficiency has previously been associated with risk factors for TGCT, cryptorchidism and infertility, while high levels of FSH may indicate a defect in Sertoli cell production of inhibin B, a negative feedback regulator of FSH.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4470. doi:1538-7445.AM2012-4470

Childhood infections, orchitis and testicular germ cell tumours: a report from the STEED study and a meta-analysis of existing data

Background:

Similarities between the age-specific incidence pattern of testicular germ cell tumours (TGCTs) and the age-specific incidence pattern of cancers of viral origin prompted us to evaluate the relationship between common infections occurring during childhood or young adult life and TGCT using existing data from the US Servicemen's Testicular Tumor Environmental and Endocrine Determinants (STEED) case–control study.

Methods:

TGCT cases diagnosed between 2002 and 2005 (n=767) were matched on age, race and serum draw date to at least one control (n=929).

Results:

None of the infections evaluated were associated with TGCT risk. Further, a meta-analysis of mumps and mumps orchitis or orchitis infection did not support an association with TGCT (mumps pooled odds ratio (OR): 1.03, 95% confidence interval (CI): 0.89–1.20; mumps orchitis or orchitis pooled OR: 1.80, 95% CI: 0.74–4.42).

Conclusion:

Based on our evaluation of childhood and early life infections and meta-analyses of mumps and mumps orchitis and/or orchitis, TGCT does not appear to be associated with common childhood infections.

Trends in testicular germ cell tumors among U.S. military servicemen, 1990-2003

OBJECTIVE

To determine the incidence of testicular germ cell tumors among active duty males and compare it with the incidence in the general U.S. population.

METHODS

The Automated Cancer Tumor Registry and the Surveillance, Epidemiology, and End Results Program data from 1990 to 2003 were analyzed for men aged between 20 and 59 years by histology and stage at diagnosis. Rates were age adjusted using the male active duty military population as the standard.

RESULTS

Nonseminoma incidence was significantly lower in the military than in the general population (incidence rate ratio = 0.90, 95% confidence interval = 0.82-0.98). Trends in incidence tended to be similar in both the populations. Increases were observed for both histologic types but were only significant for seminoma (Automated Cancer Tumor Registry: 21% and Surveillance, Epidemiology, and End Results program: 16%; p < 0.05). Increases in incidence were only observed for localized tumors of both histologic types.

CONCLUSIONS

The lower incidence of nonseminoma in the military and the increased incidence of localized tumors in both populations remain unexplained.

Genetic contributions to the association between adult height and testicular germ cell tumors

BACKGROUND

Previously, we have shown that increasing adult height is associated with increased risk of testicular germ-cell tumor (TGCT). Recently, a number of single nucleotide polymorphisms (SNPs) have been found to be related to height. We examined whether these SNPs were associated with TGCT and whether they explained the relationship between height and TGCT.

METHODS

We genotyped 15 height-related SNPs in the US Servicemen's Testicular Tumor Environmental and Endocrine Determinants (STEED) case-control study. DNA was extracted from buccal cell samples and Taqman assays were used to type the selected SNPs. We used logistic regression models to estimate odds ratios (ORs) and 95% confidence intervals (95%CIs).

RESULTS

There were 561 cases and 676 controls for analysis. Two SNPs were found to be associated with risk of TGCT, rs6060373 (CC vs TT, OR = 1.51, 95% CI: 1.06-2.15) and rs143384 (CC vs TT, OR = 1.53, 95% CI: 1.09-2.15). rs6060373 is an intronic polymorphism of ubiquinol-cytochrome c reductase complex chaperone (UQCC), and rs143384 is a 5'UTR polymorphism of growth differentiation factor 5 (GDF5). No individual SNP attenuated the association between height and TGCT. Adjustment for all SNPs previously associated with adult height reduced the associations between adult height and TGCT by ~8.5%, although the P-value indicated only weak evidence that this difference was important (P = 0.26).

CONCLUSIONS

This novel analysis provides tentative evidence that SNPs which are associated with adult height may also share an association with risk of TGCT.

Effect modification of endocrine disruptors and testicular germ cell tumour risk by hormone-metabolizing genes

It has been hypothesized that the increased prevalence of testicular germ cell tumours (TGCT) may be attributable to endocrine disrupting chemicals, such as persistent organic pollutants (POPs); these may be modulated by hormone-metabolizing enzymes. Using data from 568 cases and 698 controls enrolled in the US Servicemen's Testicular Tumor Environmental and Endocrine Determinants Study, we examined associations between TGCT and POPs, including p,p'-dichlorodiphenyldichloroethylene, chlordane-related compounds and polychlorinated biphenyls (PCBs), modified by polymorphisms in five hormone-metabolizing genes (CYP17A1, CYP1A1, HSD17B1, HSD17B4 and AR). Odds ratios (OR) and 95% confidence intervals (CI) were estimated using logistic regression models that stratified associations of POP exposure and TGCT risk by genotype. Two polymorphisms in CYP1A1, rs1456432 and rs7495708, modified the association between trans-nonachlor and total chlordanes and TGCT risk. Among men with a minor allele for rs1456432, those with the highest quartiles had an increased risk of TGCT (OR = 1.90, 95% CI, 1.01-3.56) compared with those with the lowest; there was no increased risk among men with the homozygous major allele genotype (p-interactions = 0.024). Similar results were seen for rs7495708. HSD17B4 rs384346 modified the associations between TGCT risk and PCB-118 and PCB-138 concentrations: the 45-55% reductions in TGCT risk for men with the highest quartiles compared with the lowest quartiles were only present in those who had a major homozygous allele genotype (p-interactions < 0.04). Thus, there are suggestions that certain CYP1A1 and HSD17B4 polymorphisms may modify the associations between POPs and TGCT risk. With false discovery rate values >0.2, however, caution is advisable when interpreting the findings of this study.

Polychlorinated biphenyls and risk of testicular germ cell tumors

Exposure to endocrine-disrupting chemicals, such as polychlorinated biphenyls (PCB), may alter hormonal balance and thereby increase risk of testicular germ cell tumors (TGCT). To study the relationship of PCBs to TGCT, prediagnostic serum samples from 736 cases and 913 controls in the Servicemen's Testicular Tumor Environmental and Endocrine Determinants study were analyzed. Adjusted odds ratios and 95% confidence intervals were estimated using logistic regression. PCB levels were examined in association with all TGCT and, separately, with each histologic type (seminoma and nonseminoma). Risks associated with seven functional groupings of PCBs, as well as sum of PCBs, were also examined. There were significantly decreased risks of TGCT in association with eight PCBs (PCB-118, PCB-138, PCB-153, PCB-156, PCB-163, PCB-170, PCB-180, and PCB-187) and no association with the remaining three (PCB-99, PCB-101, and PCB-183). The same eight congeners were significantly associated with decreased risk of nonseminoma, whereas five (PCB-138, PCB-153, PCB-156, PCB-163, and PCB-170) were associated with decreased risk of seminoma. All functional groupings of PCBs were also associated with decreased risk of TGCT and of nonseminoma, whereas six of the seven functional groups were associated with decreased risk of seminoma. Sum of PCBs was significantly associated with decreased risk of TGCT (P(trend) = 0.006), nonseminoma (P(trend) = 0.007), and seminoma (P(trend) = 0.05). Overall, these data do not support the hypothesis that PCB exposure increases the risk of TGCT.

Risk of cancer in first- and second-degree relatives of testicular germ cell tumor cases and controls

Risk factors for testicular germ cell tumors (TGCT) have not been well identified; however, data suggest that risks of cancer in family members of men with TGCT is elevated. Using family history data from 738 cases and 904 controls enrolled in the U.S. Servicemen's Testicular Tumor Environmental and Endocrine Determinants (STEED) Study from 2002 to 2005, the risk of cancer in first- and second-degree family members of these men was examined. Relative risks (RRs) and 95% confidence intervals (CIs) were estimated using Cox proportional hazards models, adjusting for reference age of case or control, race/ethnicity of case or control, sex of family member and lineage (maternal vs. paternal). An increased risk of all cancer among first-degree relatives of cases compared to controls was observed (RR = 1.17, 95% CI: 1.01-1.35). There were suggestions of differences in risk when stratifying all relatives by lineage. For maternal relatives, there was a statistically significant increased risk of all cancer (RR = 1.16, 95% CI: 1.04-1.30), digestive tract (RR = 1.52, 95% CI: 1.15-2.00) and male genital organ cancer (RR = 1.70, 95% CI: 1.15-2.51); there was also a suggestion of increased risks of hematopoetic cancers, cancers in the female genital organs and nonmelanoma skin cancer. For paternal relatives, there was a statistically significant association only with decreased risk of lung cancer (RR = 0.69, 95% CI: 0.51-0.94). Thus, this study suggests that there may be aggregation of cancer among families of men diagnosed with TGCT.

Insulin-like growth factor 1, insulin-like growth factor-binding protein 3, and testicular germ-cell tumor risk

Studies have consistently shown that taller men are at increased risk of testicular germ-cell tumors. Thus, it is plausible that factors associated with height may also influence risk of these tumors. The authors examined associations between testicular germ-cell tumor risk and circulating concentrations of insulin-like growth factor 1 (IGF-1) and insulin-like growth factor-binding protein 3 (IGFBP-3) among 517 cases and 790 controls from the US Servicemen's Testicular Tumor Environmental and Endocrine Determinants (STEED) Study (2002-2005). Odds ratios and 95% confidence intervals were estimated using logistic regression models, adjusting for age, race/ethnicity, height, and body mass index. All tests of significance were two-sided. Overall, there were no associations between IGF-1 or IGFBP-3 concentrations and risk of testicular germ-cell tumors (p > 0.05). However, when cases were separated by histologic type, there was a suggestion of a reduction in seminoma risk associated with the highest concentrations of IGF-1 as compared with the lowest concentrations (odds ratio = 0.66, 95% confidence interval: 0.40, 1.09). Although there were no overall associations with insulin-like growth factor, contrary to expectation, there was a suggestion that IGF-1 concentrations may be inversely associated with risk of seminoma.

Genetic variation in the inhibin pathway and risk of testicular germ cell tumors

Gene-knockout studies in mice suggest that INHA, encoding a subunit of gonadotropin-regulating proteins known as inhibins, is a tumor suppressor for testicular stromal cell tumors. It is not known whether genetic variation in the inhibin pathway also influences susceptibility to testicular germ cell tumors (TGCT), the most common testicular cancer in young men. To address this question, we conducted a case-control analysis (577 cases; 707 controls) of single-nucleotide polymorphisms (SNP) in genes in the inhibin pathway among participants in the U.S. Servicemen's Testicular Tumor Environmental and Endocrine Determinants Study. Thirty-eight tagging SNPs in six genes (INHA, INHBA, INHBB, INHBC, INHBE, and SMAD4) were genotyped. Odds ratios (OR) and 95% confidence intervals (CI) relating variant genotypes to TGCT risk were calculated using unconditional logistic regression. Among White subjects, an elevated risk of TGCT was observed for carriers of the T allele of the INHA variant rs2059693 (CT genotype: OR, 1.33; 95% CI, 1.04-1.71; TT: OR, 1.60; 95% CI, 1.01-2.52; P(trend) = 0.008). The association with rs2059693 was stronger for nonseminomas, and for teratomas and teratocarcinomas in particular (N = 58; CT: OR, 1.63; 95% CI, 0.89-2.99; TT: OR, 4.54; 95% CI 2.00-10.3; P(trend) = 0.0008). We found no evidence of association with variants in the other investigated genes. These findings suggest that genetic variation in the INHA locus influences TGCT development.

A Rift Valley fever risk surveillance system for Africa using remotely sensed data: potential for use on other continents

The authors developed a monitoring and risk mapping system using normalized difference vegetation index (NDVI) times series data derived from the advanced very high resolution radiometer (AVHRR) instrument on polar orbiting national oceanographic and atmospheric administration (NOAA) satellites to map areas with a potential for a Rift Valley fever (RVF) outbreaks in sub-Saharan Africa. This system is potentially an important tool for local, national and international organisations involved in the prevention and control of animal and human disease, permitting focused and timely implementation of disease control strategies several months before an outbreak. We are currently developing a geographic information system (GIS)-based remotely sensed early warning system for potential RVF vectors in the United States. Forecasts of the potential emergence of mosquito vectors will be disseminated throughout the United States, providing several months' warning in advance of potentially elevated mosquito populations. This would allow timely, targeted implementation of mosquito control, animal quarantine and vaccine strategies to reduce or prevent animal and human disease.

Body size, dairy consumption, puberty, and risk of testicular germ cell tumors

The etiology of testicular germ cell tumors (TGCTs) is poorly understood, with cryptorchidism and family history being the only well-established risk factors. Body size, age at puberty, and dairy consumption, however, have been suggested to be related to TGCTs. To clarify the relation of these variables to TGCT risk and to one another, the authors analyzed data from 767 cases and 928 controls enrolled in the Servicemen's Testicular Tumor Environmental and Endocrine Determinants Study (2002-2005). Overall, increased height was significantly related to risk (odds ratio (OR) = 1.83, 95% confidence interval (CI): 1.36, 2.45), though body mass index was not (OR = 1.06, 95% CI: 0.66, 1.69). There was no association with age at puberty, based on ages at first shaving (OR = 1.29, 95% CI: 0.96, 1.73), voice changing (OR = 0.97, 95% CI: 0.71, 1.32), and nocturnal emissions (OR = 1.00, 95% CI: 0.73, 1.37). Similarly, there was no relation with dairy consumption at any age between birth and 12th grade. These results suggest that height is a risk factor for TGCTs, but the relation is unlikely explained by childhood dairy consumption. As adult height is largely determined in the first 2 years of life, increased attention to events in this interval may help elucidate the etiology of TGCTs.

Maternal Smoking and Testicular Germ Cell Tumors

Testicular germ cell tumors (TGCT) are the most common cancer among men ages 15 to 35 years in the United States. The well-established TGCT risk factors cryptorchism, prior diagnosis of TGCT, and family history of testicular cancer indicate that exposures in early life and/or in the familial setting may be critical to determining risk. Previous reports of familial clustering of lung cancer in mothers and testicular cancers in sons suggest that passive smoking in childhood may be such an exposure. To clarify the relationship of passive smoking exposure to TGCT risk, data from 754 cases and 928 controls enrolled in the Servicemen's Testicular Tumor Environmental and Endocrine Determinants study were analyzed. Data from 1,086 mothers of the cases and controls were also examined. Overall, there was no relationship between maternal [odds ratio (OR), 1.1; 95% confidence interval (95% CI), 0.9-1.3] or paternal smoking (OR, 1.0; 95% CI, 0.8-1.3) and TGCT risk. Although living with a non-parent smoker was marginally related to risk (OR, 1.4; 95% CI, 1.0-2.1), there was no relationship with number of smokers, amount smoked, or duration of smoking. Responses from both case-control participants and mothers also revealed no relationship between either maternal smoking while pregnant or while breast-feeding. Results did not differ by TGCT histology (seminoma, non-seminoma). These results do not support the hypothesis that passive smoking, either in utero or in childhood, is related to risk of TGCT. Other early life exposures, however, may explain the familial clustering of lung cancer in mothers and TGCT in sons.

A clinical comparison of glass ionomer, resin-modified glass ionomer and resin composite restorations in the treatment of cervical caries in xerostomic head and neck radiation patients

Controversy exists as to whether there is less secondary caries at the margins of glass ionomer restorations compared with other materials that do not release fluoride. This study examined the incidence of secondary caries for three types of restorative materials in Class V restorations in xerostomic patients. The study group consisted of 45 high caries-risk adult patients who had undergone head and neck irradiation for the treatment of cancer. All were substantially xerostomic and in need of at least three restorations in the same arch. Every patient received a restoration with each of the test materials, a conventional glass ionomer (GI), a resin modified glass ionomer (RMGI) and a resin composite (C). Patients were instructed in the daily use of a neutral pH sodium fluoride gel in custom trays. Recall appointments were made at 6, 12, 18 and 24 months, and the restorations were examined for material loss, marginal integrity and recurrent caries at the restoration margin. Fluoride compliance was determined at each recall period and recorded as the percentage of recommended use during that interval. Patients were categorized at the end of the study as fluoride non-users if their average compliance was 50% or less. Those with greater than 50% compliance were categorized as fluoride users. In the latter group, no recurrent caries was found for any of the restorations, whereas a material-dependent incidence of recurrent caries was found in the fluoride non-user group. None of the GI, one RMGI and eight C restorations failed due to recurrent caries. For the fluoride non-user patients, Fishers exact test (p=0.05) showed no statistical difference between GI and RMGI but statistical differences were found among those materials and resin composite at each recall period. Recurrent caries reductions for GI and RMGI relative to C were greater than 80% in xerostomic patients not using topical fluoride supplementation.

Effect of enamel pretreatments on bond strength of compomer

OBJECTIVES

The objective of this study was to evaluate the effect of various enamel surface treatments on the bond strength of a compomer to enamel.

METHODS

Ground bovine enamel specimens were divided into four groups. A compomer (F2000, 3M) was bonded to the specimens using different enamel surface treatments. Two groups examined the effect of application of the F2000 self-etching primer/adhesive (3M) with respect to static or dynamic priming. A third examined use of the primer/adhesive after phosphoric acid etching, and the fourth (control) group provided bond strength of the compomer to phosphoric acid etched enamel with a resin bonding system (Single Bond, 3M). Shear bond strengths for the specimens were measured after 24h storage in water at 37 degrees C. Effects of the various surface treatments on enamel were examined by SEM.

RESULTS

Significant differences in bond strength of compomer to enamel were found that were related to the various surface pretreatments. Dynamic priming resulted in higher enamel bond strengths than static priming, and the best bond strengths were obtained when the enamel was etched with phosphoric acid. SEM analysis showed that depth of etch and resin penetration was also directly related to the bond strengths measured.

SIGNIFICANCE

Bond strength of compomer to enamel is significantly affected by the method of pretreatment of the enamel.

p300 coactivates the adipogenic transcription factor CCAAT/enhancer-binding protein alpha

Despite the knowledge that CCAAT/enhancer-binding protein alpha (C/EBPalpha) plays an important role in preadipocyte differentiation, our understanding of how C/EBPalpha interacts with nuclear proteins to regulate transcription is limited. Based on the hypothesis that evolutionarily conserved regions are functionally important and likely to interact with coactivators, we compared the amino acid sequence of C/EBPalpha from different species (frog to human) and identified four highly conserved regions (CR1-CR4) within the transactivation domain. A series of amino-terminal truncations and internal deletion constructs were made creating forms of C/EBPalpha which lack single or multiple conserved regions. To determine which regions of the C/EBPalpha transactivation domain are important in its ability to induce spontaneous differentiation of 3T3-L1 preadipocytes, we infected preadipocytes with expression vectors encoding the C/EBPalpha conserved region mutants and observed their ability to induce differentiation. We found that CR2 fused to the DNA binding domain is able to induce spontaneous differentiation independent of the other conserved regions. However, CR2 was not necessary for the adipogenic action of C/EBPalpha because a combination of CR1 and CR3 can also induce adipogenesis. Because the transcriptional coactivator p300 participates in the signaling of many transcription factors to the basal transcriptional apparatus, we examined whether functional interaction exists between C/EBPalpha and p300. Cotransfection of p300 with p42C/EBPalpha results in a synergistic increase in leptin promoter activity, indicating that p300 acts as a transcriptional coactivator of C/EBPalpha. Analyses using C/EBPalpha conserved region mutants suggest that multiple regions (CR2 and CR3) of the C/EBPalpha transactivation domain functionally interact with p300.

A fluoride-releasing composite for dental applications

OBJECTIVES

The aim of this work was to attempt formulation of a dental composite, for investigational purposes, which will release fluoride at a rate comparable to glass ionomer materials, while retaining physical properties adequate for potential use in a number of dental applications.

METHODS

An organic fluoride material, tetrabutylammonium tetrafluoroborate (TBATFB), was incorporated into a hydrophilic monomer system made of 2,2-bis[4-(2-hydroxy-3-methacroyloxypropoxy)phenyl]-propane (BisGMA) and 2-hydroxyethyl methacrylate (HEMA). This fluoride-containing monomer system was filled with silane treated quartz to 81 wt%. The resultant material was tested for fluoride release, physical strength properties and bond strength to enamel, each in comparison to control materials.

RESULTS

Cumulative fluoride release from the experimental composite was approximately linear over time and comparable to glass ionomer materials. The long term rate of release exceeded several of the glass ionomer materials tested. Diametral tensile strength was comparable to resin-modified glass ionomer (RMGI) materials. Bond strength to etched enamel was statistically equivalent to a commercially available hybrid composite control.

SIGNIFICANCE

The experimental resin-based composite material could potentially be used as an alternative to glass ionomer materials in non-stress bearing restorative applications and for orthodontic bracket bonding, where high fluoride release is desirable.

Demineralization of enamel in relation to the fluoride release of materials

PURPOSE

To examine the reduction in enamel demineralization provided by fluoride release from a conventional glass-ionomer, a resin-modified glass-ionomer and an experimental fluoride-releasing resin-based composite compared to a conventional resin-based composite control, and to correlate the level of fluoride release with demineralization.

MATERIALS AND METHODS

Enamel surfaces of extracted human incisors had a 0.4 mm thick layer of the specified test material carefully placed in a band across the mid-facial enamel to simulate a cement layer beneath an orthodontic bracket. The top surface of the test material was covered with nail varnish, leaving only the edges of the material exposed to release fluoride. The teeth were additionally covered with nail varnish to within 1 mm of the test material. Each group of teeth was placed into separate volumes of unstirred demineralizing solution at a pH of 4.7 for 4 days. The specimens were sectioned and examined by polarized light microscopy. Lesion areas were measured at distances from 100-800 microm away from the test material. Fluoride release for the test materials was measured for periods up to 5 months.

RESULTS

All of the fluoride-releasing materials demonstrated a statistically significant (P< 0.05) degree of protection of enamel from demineralization compared to the non-fluoride control material. The degree of protection was greatest near the material, but lesion areas increased with distance in an inverse relationship to the amount of fluoride release. Lesions were displaced from the region near the materials and the mean displacement was directly related to amount of fluoride release. The mean lesion areas for each distance decreased with the logarithm of the cumulative fluoride release.

Inhibition of adipogenesis by Wnt signaling

Wnts are secreted signaling proteins that regulate developmental processes. Here we show that Wnt signaling, likely mediated by Wnt-10b, is a molecular switch that governs adipogenesis. Wnt signaling maintains preadipocytes in an undifferentiated state through inhibition of the adipogenic transcription factors CCAAT/enhancer binding protein alpha (C/EBPalpha) and peroxisome proliferator- activated receptor gamma (PPARgamma). When Wnt signaling in preadipocytes is prevented by overexpression of Axin or dominant-negative TCF4, these cells differentiate into adipocytes. Disruption of Wnt signaling also causes transdifferentiation of myoblasts into adipocytes in vitro, highlighting the importance of this pathway not only in adipocyte differentiation but also in mesodermal cell fate determination.

Induction of the peroxisomal glycerolipid-synthesizing enzymes during differentiation of 3T3-L1 adipocytes. Role in triacylglycerol synthesis

The glycerophosphate backbone for triglyceride synthesis is commonly believed to be created through the conversion of dihydroxyacetone phosphate (DHAP) by glycerophosphate dehydrogenase (GPD) to sn-glycerol 3-phosphate (GP), which is then converted by glycerophosphate acyltransferase (GPAT) to 1-acyl-GP. Consistent with this, GPD and GPAT are highly induced during differentiation of mouse 3T3-L1 preadipocytes. While the acyl dihydroxyacetone phosphate (acyl-DHAP) pathway for glycerolipid synthesis is commonly believed to be involved only in glycerol ether lipid synthesis, we report here that during conversion of 3T3-L1 preadipocytes to adipocytes, the specific activity of peroxisomal DHAP acyltransferase (DHAPAT) is increased by 9-fold in 6 days, while acyl-DHAP:NADPH reductase is induced by 5-fold. A parallel increase in the catalase (the peroxisomal marker enzyme) activity is also seen. In contrast, the specific activity of alkyl-DHAP synthase, the enzyme catalyzing the synthesis of the ether bond, is decreased by 60% during the same period. Unlike microsomal GPAT, the induced DHAPAT is found to have high activity at pH 5.5 and is resistant to inhibition by sulfhydryl agents, heat, and proteolysis. On subcellular fractionation, DHAPAT is found to be associated with microperoxisomes whereas GPAT activity is mainly present in microsomes. Northern blot analyses reveal that induction of DHAPAT can be largely explained through increases in DHAPAT mRNA. A comparison of microsomal and peroxisomal glycerolipid synthetic pathways, using D-[3-(3)H, U-(14)C]glucose as the precursor of the lipid glycerol backbone shows that about 40-50% of triglyceride is synthesized via the acyl-DHAP pathway. These results indicate that the acyl-DHAP pathway is important not only for the synthesis of ether lipids, but also for the synthesis of triacylglycerol and other non-ether glycerolipids.

Protective effects of resin impregnation on demineralization of enamel

PURPOSE

To determine if resin penetrated into the enamel etch pattern, in the absence of a polymerized outer surface film, could reduce the degree of demineralization of enamel subjected to a simulated caries challenge, and to evaluate whether the addition of fluoride to the resin would enhance reductions in demineralization.

MATERIALS AND METHODS

Enamel surfaces of extracted human incisors were acid-etched. One-half of the etched area was treated with an unfilled bonding resin, while the other one-half was left untreated as a control. In another group, this same procedure was followed except the unfilled bonding resin contained fluoride. The applied resin was aggressively air thinned to ensure oxygen inhibition throughout the external surface film thickness. The thinned film was visible light-cured and the area was wiped with an ethanol swab to remove the inhibited layer. The specimens were exposed to a buffer solution of pH = 4.7 for 4 days, and were sectioned and examined by polarized light microscopy and microradiography.

RESULTS

In each of the two test groups, the demineralization of the resin-treated side was significantly lower than the control side (P < 0.015). Under the conditions of this study, the experimental fluoride resin did not produce statistically significant reductions in demineralization compared with the non-fluoride resin.

Glycogen synthase kinase 3 is an insulin-regulated C/EBPalpha kinase

CCAAT/enhancer binding protein alpha (C/EBPalpha) is a transcription factor involved in creating and maintaining the adipocyte phenotype. We have shown previously that insulin stimulates dephosphorylation of C/EBPalpha in 3T3-L1 adipocytes. Studies to identify the insulin-sensitive sites of phosphorylation reveal that a C/EBPalpha peptide (amino acids H215 to K250) is phosphorylated on T222, T226, and S230 in vivo. The context of these phosphoamino acids implicates glycogen synthase kinase 3 (GSK3), whose activity is known to be repressed in response to insulin, as a potential kinase for phosphorylation of T222 and T226. Accordingly, GSK3 phosphorylates the predicted region of C/EBPalpha on threonine in vitro, and GSK3 uses C/EBPalpha as a substrate in vivo. In addition, the effect of pharmacological agents on GSK3 activity correlates with regulation of C/EBPalpha phosphorylation. Treatment of 3T3-L1 adipocytes with the phosphatidylinositol 3-kinase inhibitor wortmannin results in phosphorylation of C/EBPalpha, whereas treatment with the GSK3 inhibitor lithium results in dephosphorylation of C/EBPalpha. Collectively, these data indicate that insulin stimulates dephosphorylation of C/EBPalpha on T222 and T226 through inactivation of GSK3. Since dephosphorylation of C/EBPalpha in response to lithium is blocked by okadaic acid, strong candidates for the T222 and T226 phosphatase are protein phosphatases 1 and 2a. Treatment of adipocytes with insulin alters the protease accessibility of widespread sites within the N terminus of C/EBPalpha, consistent with phosphorylation causing profound conformational changes. Finally, phosphorylation of C/EBPalpha and other substrates by GSK3 may be required for adipogenesis, since treatment of differentiating preadipocytes with lithium inhibits their conversion to adipocytes.

Clinical performance and caries inhibition of resin-modified glass ionomer cement and amalgam restorations

BACKGROUND

The authors clinically examined two restorative materials to evaluate their effectiveness in Class II restorations in primary molars and their ability to inhibit recurrent caries.

METHODS

Forty subjects, each in need of two Class II restorations in primary molars, took part in this study. Each patient received one Class II restoration of resin-modified glass ionomer cement and one of amalgam. The authors evaluated the restorations at six-month, one-year, two-year and three-year recall appointments. On exfoliation, teeth with experimental restorations were retrieved and microscopically examined for inhibition of demineralization at restoration margins.

RESULTS

The results of the clinical evaluation demonstrated no significant differences between the resin-modified glass ionomer cement restorations and the amalgam restorations (P < .05). Polarized light microscopic examination of the returned teeth that were restored as a part of this study indicated that the resin-modified glass ionomer cement had significantly less enamel demineralization at restoration margins than did amalgam (P < .0001).

CONCLUSIONS

The resin-modified glass ionomer cement functioned clinically as well as amalgam for Class II restorations in primary molars. However, the resin-modified glass ionomer exhibited significantly less enamel demineralization at restoration margins than did amalgam.

CLINICAL IMPLICATIONS

Resin-modified glass ionomer cement restorative material functions well for Class II restorations in primary molars and exhibits less recurrent caries at restoration margins than does amalgam.

New light curing options for composite resin restorations

The concerned practitioner needs to understand the chemistry of the materials, the dynamics of polymerization, the stress factors created, and the specific light energy requirements needed to attain maximum results. If a practitioner chooses to use one of the nontraditional curing systems, he or she needs to consult with the manufacturer to determine the spectral output of the system, and contact the manufacturer of the composite to ensure that the material used will cure properly with the chosen light source. The manufacturers have customer service representatives who are usually very knowledgeable about their products. Current claims about new technological developments based on laboratory experiments and anecdotal information are promising. However, multicenter prospective clinical studies are still needed to validate safety and efficacy. Then clinicians can make informed decisions that will enable them to provide the highest quality dentistry for their patients. We will revisit this topic as more information becomes available.

Regulation of CCAAT/enhancer binding protein alpha (C/EBP alpha) gene expression by thiazolidinediones in 3T3-L1 adipocytes

Thiazolidinediones are a class of antidiabetic drugs that induce preadipocyte differentiation by binding and activating peroxisome proliferator-activated receptor gamma 2. Although thiazolidinediones are commonly thought of as insulin-sensitizing agents, these drugs have opposing and antagonistic effects to that of insulin on CCAAT/enhancer binding protein alpha (C/EBP alpha) gene expression in fully differentiated 3T3-L1 adipocytes. Thiazolidinediones induce expression of C/EBP alpha mRNA and protein, while insulin stimulates a rapid decline in C/EBP alpha mRNA and protein. When added in combination, thiazolidinediones block the suppression of C/EBP alpha mRNA by insulin; however, thiazolidinediones do not block the insulin-induced decline in GLUT4 mRNA, indicating that repression of C/EBP alpha mRNA is not required for insulin to suppress expression of a C/EBP alpha-responsive gene such as GLUT4. Instead, insulin may regulate GLUT4 mRNA by inactivating C/EBP alpha through dephosphorylation as well as by inducing the expression of the dominant-negative form of C/EBP beta (liver inhibitory protein), since both of these processes occur in the presence of thiazolidinediones.

Signaling pathways through which insulin regulates CCAAT/enhancer binding protein alpha (C/EBPalpha) phosphorylation and gene expression in 3T3-L1 adipocytes. Correlation with GLUT4 gene expression

Treatment of 3T3-L1 adipocytes with insulin (IC50 approximately 200 pM insulin) or insulin-like growth factor-1 (IC50 approximately 200 pM IGF-1) stimulates dephosphorylation of CCAAT/enhancer binding protein alpha (C/EBPalpha), a transcription factor involved in preadipocyte differentiation. As assessed by immunoblot analysis of one- and two-dimensional PAGE, insulin appears to dephosphorylate one site within p30C/EBPalpha and an additional site within p42C/EBPalpha. Consistent with insulin causing dephosphorylation of C/EBPalpha through activation of phosphatidylinositol 3-kinase, addition of phosphatidylinositol 3-kinase inhibitors (e.g. wortmannin) blocks insulin-stimulated dephosphorylation of C/EBPalpha. In the absence of insulin, wortmannin or LY294002 enhance C/EBPalpha phosphorylation. Similarly, blocking the activity of FKBP-rapamycin-associated protein with rapamycin increases phosphorylation of C/EBPalpha in the absence of insulin. Dephosphorylation of C/EBPalpha by insulin is partially blocked by rapamycin, consistent with a model in which activation of FKBP-rapamycin-associated protein by phosphatidylinositol 3-kinase results in dephosphorylation of C/EBPalpha. The dephosphorylation of C/EBPalpha by insulin, in conjunction with the insulin-dependent decline in C/EBPalpha mRNA and protein, has been hypothesized to play a role in repression of GLUT4 transcription by insulin. Consistent with this hypothesis, the decline of GLUT4 mRNA following exposure of adipocytes to insulin correlates with dephosphorylation of C/EBPalpha. However, the repression of C/EBPalpha mRNA and protein levels by insulin is blocked with an inhibitor of the mitogen-activated protein kinase pathway without blocking the repression of GLUT4 mRNA, thus dissociating the regulation of C/EBPalpha and GLUT4 mRNAs by insulin. A decline in C/EBPalpha mRNA and protein may not be required to suppress GLUT4 transcription because insulin also induces expression of the dominant-negative form of C/EBPbeta (liver inhibitory protein), which blocks transactivation by C/EBP transcription factors.

Serotonergic and noradrenergic effects on respiratory neural discharge in the medullary slice preparation of neonatal rats

Rhythmically active medullary slice preparations isolated from neonatal rats (postnatal days 0-3, P0-P3) were used to study the modulation of respiraory rhythmogenesis and hypoglossal (XII) nerve discharge by serotonin (5-hydroxytryptamine, 5-HT) and noradrenaline (NA). 5-HT, NA and their respective receptor agonists and antagonists were applied either to the bathing medium or focally via pressure injection into regions encompassing the pre-Botzinger complex or XII motoneurons. The effects of endogenously released 5-HT were also studied by chemical stimulation of neurons within the raphe obscurus. The frequency of respiratory burst discharge was increased when 5-HT was applied: (1) to the bathing medium (37+/-16%; 30 "mu"M; P < 0.05); (2) via pressure injection into the region of the pre-Botzinger complex (22 +/- 14%; < 25 pmol; P < 0. 05); or (3) endogenously released in response to activation of neurons within the raphe obscurus via pressure injection of (R,S)- "alpha"-amino-3-hydroxy-5-methylisoxazole-4-propionic acid hydrobromide (AMPA, 34 +/- 15%; P < 0.05) or 5-HT (33 +/- 5%; P < 0. 05). All of these effects were antagonized by bath application of methysergide (30-40 "mu"M). NA caused a reduction of respiratory burst frequency when applied to the bathing medium (40 +/- 15%; 100 "mu"M; P < 0.05) or when pressure injected into the region of the pre-Botzinger complex (22 +/- 11%; < 25 pmol; P < 0.05). These effects were blocked by the bath application of the "alpha"2-receptor antagonist idazoxan (2 "mu"M). 5-HT and NA both caused an augmentation of tonic discharge of XII nerves when applied either to the bathing medium or via pressure injection into the XII motoneuron pool. The 5-HT-induced XII nerve tonic discharge was mimicked by the 5-HT2 receptor agonist R(-)2-(2, 5-dimethoxy-4-iodophenyl) (DOI.HCl, 5 "mu"M) and blocked by the 5-HT2 receptor antagonist ketanserine tartrate (30-40 "mu"M). The NA-induced XII nerve tonic discharge was mimicked by the "alpha"1-receptor agonist phenylephrine HCl (500 nM) and blocked by the "alpha"1-receptor antagonist prozasin HCl (1 "mu"M).

Model investigations of caries inhibition by fluoride-releasing dental materials

Fluoride-releasing dental materials are generally believed to reduce or prevent secondary caries. The evidence for this is largely anecdotal and centers on clinical experience with silicate cements and, more recently, with glass-ionomer cements. Unfortunately, corroborating evidence from controlled clinical trials is inadequate to establish precisely how effective these materials are or under what conditions they might be effective. Even less is known about the clinical effectiveness of newer materials that, often, release less fluoride. In vitro model systems have been used to study the effects of dental materials on de/remineralization of surrounding tooth structure. Fluoride-releasing materials have been shown in these models to reduce demineralization of both enamel and dentin compared with a material that does not release fluoride. This is useful from a mechanistic standpoint, but without clinical "standards" to guide model results, it is not possible to define an acceptable level of fluoride release or the length of time such release is required. A limited number of in situ model studies has been conducted, and some fluoride dose-response information has been obtained. These models are closer to the real situation and perhaps provide the best means to define required levels of fluoride release from materials in the absence of adequate clinical information.

Root surface treatment with glass ionomers and resin composites

Recommendations for restorative treatments of root surfaces are made difficult by a lack of information on the etiology of root conditions and on the clinical performance of available materials used to treat these conditions. Resin composite and glass ionomer materials are popular restorative materials because they are esthetic and can bond to tooth structure. However, the role each can play in restoration of root surface lesions is not well documented. This article presents a rationale for using these materials for a number of restorative situations.

Acoustic correlates of breathy vocal quality

The purpose of this study was to evaluate the effectiveness of several acoustic measures in predicting breathiness ratings. Recordings were made of eight normal men and seven normal women producing normally phonated, moderately breathy, and very breathy sustained vowels. Twenty listeners rated the degree of breathiness using a direct magnitude estimation procedure. Acoustic measures were made of: (a) signal periodicity, (b) first harmonic amplitude, and (c) spectral tilt. Periodicity measures provided the most accurate predictions of perceived breathiness, accounting for approximately 80% of the variance in breathiness ratings. The relative amplitude of the first harmonic correlated moderately with breathiness ratings, and two measures of spectral tilt correlated weakly with perceived breathiness.

Evidence for a recent decrease in measles susceptibility among young American adults

As part of an ongoing evaluation of US Army immunization policies, two serologic surveys were conducted at an army basic training center. Antibody status to measles, mumps, and rubella were determined by an ELISA in 969 soldiers in 1989 and 992 soldiers in 1990. Measles seronegativity rates, directly adjusted to the 15- to 24-year-old US population in 1980, decreased from 21.3% in 1989 to 12.5% in 1990 (P < .001). Decreases also were observed in mumps (16.2% to 14.7%) and rubella seronegativity rates (18.4% to 14.3%) from 1989 to 1990 but were not statistically significant. In subgroup analyses, significant decreases in measles seronegativity were observed in younger, white, male, and female cohorts. There is evidence that susceptibility among young adults had declined, although it remains unclear if this is due to increased immunization or exposure to natural disease.

Shear bond strength of composite to enamel and dentin using Scotchbond Multi-Purpose

A laboratory study was conducted to determine the shear bond strength to enamel and dentin using the Scotchbond Multi-Purpose dental adhesive system. High shear bond strengths of P50 composite to both human enamel (26.8 +/- 5.2 MPa) and bovine enamel (24.8 +/- 4.1 MPa) were found when the system was used according to manufacturer's directions. The mean bond strength for human dentin (25.5 +/- 7.5 MPa) was also similar to that found for bovine dentin (23.4 +/- 4.9 MPa). Variations in the recommended application technique were examined on bovine dentin. Extreme air drying of the primer slightly reduced the mean shear bond strength (19.7 +/- 6.4 MPa), while a significant reduction was observed when the adhesive resin was aggressively air-thinned (10.1 +/- 6.6 Mpa).

An in vitro study of mechanical heart valve sound loudness

The purpose of the study was to measure the valve sound loudness of eight 25 mm aortic mechanical heart valve prostheses under controlled laboratory conditions in an isolated acoustic environment. A specially designed single-chamber pulse duplicator was constructed within an anechoic box that isolated the sounds of the valve from external noise. The valves were closed with a stimulated aortic pressure waveform of three different amplitudes. Valve sound loudness was measured with ISO-532/B (Zwicker method), which is based on a model of loudness perception that is better than dB(A), the traditional A-weighted sound pressure level. The average loudness for each valve was St. Jude Medical, 0.97 sones; CarboMedics, 0.98 sones; Sorin Biomedica Bicarbon, 1.08 sones; Edwards Tekna, 1.92 sones; Edwards Duromedics, 2.36 sones; Monostrut, 2.48 sones; Sorin Biomedica Carbocast, 3.17 sones; and Medtronic Hall, 3.57 sones. There was a positive trend between valve sound loudness and aortic drive pressure for most valves in the study.