Prevalence of food insecurity among students attending four Historically Black Colleges and Universities

Objective: This study examined the prevalence of food insecurity (FI) among students attending Historically Black Colleges and Universities (HBCUs) in the Southeastern United States. Participants: Students attending four HBCUs (N = 351) completed an anonymous Web-based survey. Methods: Food insecurity was assessed using the 2-item Hunger Vital Sign Tool. Summary statistics were used to quantify FI experiences. Logistic regression was conducted to determine if student demographic characteristics were significantly associated with FI outcomes. Results: Nearly 3 in 4 students (72.9%) reported some level of FI in the past year. Students representing all levels of postsecondary education reported FI. Meal plan participation did not prevent FI. Conclusions: Students attending HBCUs experience FI at levels that exceed estimates reported among students attending predominantly White institutions. More work is needed to understand the lived experience of food-insecure HBCU students as a means to ensure institution-level food policies support student academic success and wellbeing.

Using geographic information systems to characterize food environments around historically black colleges and universities: Implications for nutrition interventions

ObjectiveTo understand the distribution of healthy and unhealthy food stores near historically black colleges and universities (HBCUs). Participants and methods: Using ArcGIS Pro's network analysis tools and ReferenceUSA database, this study characterized the healthy (favorable) and unhealthy (unfavorable) retail food stores within a 5-mile radius, 15-min driving, and 15-min walking distance from each HBCU in North Carolina. Results: Most retail food stores within a 5-mile buffer radius of the 10 HBCUs in North Carolina were unfavorable. Within 15-min driving from each HBCU, 1082 stores (76.0%) were unfavorable food stores, while 332 (24.0%) were favorable. Additionally, there were four favorable and 35 unfavorable retail food stores within the 15-min walking distance of each HBCU. Conclusions: Favorable food retail stores around HBCUs in North Carolina are limited. Researchers, policy makers, and community stakeholders should work together to improve food environments surrounding HBCUs.

The toxicity of organic fractions from aged oil sands process-affected water to aquatic species

The process of surface mining and extracting bitumen from oil sand produces large quantities of tailings and oil sands process-affected water (OSPW). The industry is currently storing OSPW on-site while investigating strategies for their detoxification. One such strategy relies on the biodegradation of organic compounds by indigenous microbes, resulting in aged tailings waters with reduced toxicity. This study assessed the toxicity of OSPW aged statically for approximately 18 years. Dissolved organics in aged OSPW were fractionated using a preparative solid-phase extraction method that generated three organic fractions (F1-F3) of increasing polarity. Eight aquatic species from different trophic levels were exposed to whole OSPW (WW) and the derived OSPW organic fractions to assess toxicity: Pimephales promelas, Oryzias latipes, Vibrio fischeri, Daphnia magna, Lampsilis cardium, Hyalella azteca, Ceriodaphnia dubia, and Hexagenia spp. Broad comparisons revealed that P. promelas and H. azteca were most sensitive to dissolved organics within aged OSPW, while WW was most toxic to L. cardium and H. azteca. Three cases of possible contaminant interactions occurred within whole OSPW treatments, as toxicity was higher than organic fractions for H. azteca and L. cardium, and lower for P. promelas. As such, the drivers of toxicity appeared to be dependent on the species exposed. Of the organic fractions assessed, F3 (most polar) was the most toxic overall while F2 (intermediate polarity) displayed little toxicity to all species evaluated. This presents strong evidence that classical mono-carboxylic naphthenic acids, mostly present in F1 (least polar), are not primarily responsible for the toxicity in aged tailings. The current study indicates that although the aged tailings source (≥18 years) did not display acute toxicity to the majority of organisms assessed, inorganic components and polyoxygenated organics may pose a persistent concern to some aquatic organisms.

Campus climate comparisons in academic pursuits: How race still matters for African American college students

Perceptions of social estrangement felt by African American college students can account for group-based inequalities evident in a wide range of educational outcomes. Moreover, racial incidents, occurring on and off college campuses, make race more salient for African American students and influence emerging identity development. By recruiting African American students enrolled at predominantly White institutions (PWIs) as well as at historically Black college and universities (HBCUs), this study examined how individual differences in sensitivity to racial status related to self-reported scores of students’ academic success and satisfaction. African American participants ( N = 352) contributed to a longitudinal study surveying the daily life experiences of African American college students. We predicted that across the participant groups, assessed outcomes would be similar, but not identical due to varying campus climates. Results indicated that at both HBCU and PWI institutions, race matters at the individual level and campus climate impacts groups differently.

"Ready, set, go": checkpoint regulation by Cdk1 inhibitory phosphorylation

ABSTRACT Cell cycle checkpoints prevent mitosis from occurring before DNA replication and repair are completed during S and G2 phases. The checkpoint mechanism involves inhibitory phosphorylation of Cdk1, a conserved kinase that regulates the onset of mitosis. Metazoans have two distinct Cdk1 inhibitory kinases with specialized developmental functions: Wee1 and Myt1. Ayeni et al used transgenic Cdk1 phospho-acceptor mutants to analyze how the distinct biochemical properties of these kinases affected their functions. They concluded from their results that phosphorylation of Cdk1 on Y15 was necessary and sufficient for G2/M checkpoint arrest in imaginal wing discs, whereas phosphorylation on T14 promoted chromosome stability by a different mechanism. A curious relationship was also noted between Y15 inhibitory phosphorylation and T161 activating phosphorylation. These unexpected complexities in Cdk1 inhibitory phosphorylation demonstrate that the checkpoint mechanism is not a simple binary "off/on" switch, but has at least three distinct states: "Ready", to prevent chromosome damage and apoptosis, "Set", for developmentally regulated G2 phase arrest, and "Go", when Cdc25 phosphatases remove inhibitory phosphates to trigger Cdk1 activation at the G2/M transition.

Molecular genetic characterization of Drosophila ATM conserved functional domains

ATM-related kinases promote repair of DNA double-strand breaks and maintenance of chromosome telomeres, functions that are essential for chromosome structural integrity in all eukaryotic organisms. In humans, loss of ATM function is associated with ataxia telangiectasia, a neurodegenerative disease characterized by extreme sensitivity to DNA damage. Drosophila melanogaster has recently emerged as a useful animal model for analyzing the molecular functions of specific domains of this large, multifunctional kinase. The gene encoding Drosophila ATM kinase (dATM) was originally designated tefu because of the telomere fusion defects observed in atm mutants. In this report, molecular characterization of eight atm (tefu) alleles identified nonsense mutations predicted to truncate conserved C-terminal domains of the dATM protein, as well as two interesting missense mutations. One of these missense mutations localized within a putative HEAT repeat in the poorly characterized N-terminal domain of dATM (atm4), whereas another associated with a temperature-sensitive allele (atm8) changed the last amino acid of the conserved FATC domain. Leveraging this molecular information with the powerful genetic tools available in Drosophila should facilitate future analysis of conserved ATM-mediated molecular mechanisms that are important for telomere maintenance, DNA repair, and neurodegeneration.

A novel strategy for identifying mutations that sensitize Drosophila eye development to caffeine and hydroxyurea

This report describes a novel strategy for isolating Drosophila mutants with conditional eye phenotypes that should be generally applicable for identifying genes required for cellular responses to specific drugs. To test the strategy, we screened 3 of the 5 major chromosome arms for hydroxyurea- and (or) caffeine-sensitive (huc) mutants, and isolated mutations affecting 5 different complementation groups. Most of these were represented by single alleles; however, we also isolated multiple alleles of huc(29DE) gene, an essential gene that is also associated with a nonconditional pupal lethal phenotype. We also identified huc(95E) mutants, which are extremely sensitive to caffeine. Although huc(95E) is a nonessential gene, mutant imaginal disc cells undergo caffeine-dependent apoptosis, and huc(95E) gene function is required for the viability of the organism when mutant larvae are exposed to levels of caffeine that controls can easily tolerate. We have mapped the cytological positions of huc(29D) and huc(95E) as a first step toward molecularly characterizing the relevant genes.

Impact of large-angle scattering on diffusively backscattered halos

We discuss the impact of large-angle scattering events in highly forward-scattering media on the spatial distribution of the diffusively reflected light. We show that, even for highly forward-scattering media, the reflected light near the incident beam axis is strongly dependent on the small number of large-angle scattering events. Reliable modeling of near-axis reflection thus requires accurate knowledge of the scattering phase function's behavior at large angles.

Light scattering regimes along the optical axis in turbid media

We inject an angularly collimated laser beam into a scattering medium of a nondairy creamer-water solution and examine the distribution of the scattered light along the optical axis as a function of the source-detector spacing. The experimental and simulated data obtained from a Monte Carlo simulation suggest four regimes characterizing the transition from unscattered to diffusive light. We compare the data also with theoretical predictions based on a first-order scattering theory for regions close to the source, and with diffusionlike theories for larger source-detector spacings. We demonstrate the impact of the measurement process and the effect of the unavoidable absorption of photons by the detection fiber on the light distribution inside the medium. We show that the range of validity of these theories can depend on the experimental parameters such as the diameter and acceptance angle of the detection fiber.

Minimal exposure to ethanol increases ethanol preference in Maudsley reactive male rats

Male Maudsley reactive (MR/Har) rats often exhibit marked ethanol or alcohol preference (AP) after forced (one-bottle) exposure to 10% [volume/volume (vol./vol.)] ethanol, but exhibit variable AP without this exposure. In this study, we examined manipulations of one-bottle exposure to ethanol (10% ethanol as the sole source of fluid) in three experiments. In Experiment 1, we recorded voluntary consumption of 10% ethanol during 5 weeks of two-bottle choice in male and female MR/Har rats after 0, 1, 2, 3, or 4 days of one-bottle ethanol exposure. The results showed that, in male rats, one day of one-bottle exposure was as effective as multiple days in increasing AP relative to findings for ethanol-naive (control) rats. Female rats were not affected by one-bottle exposure. They drank equal amounts of ethanol across all groups and in greater amounts than observed for male rats (relative to body weight). The results of Experiment 2 supported the suggestion that 18 h of exposure to ethanol was similar to 24 h of exposure for increasing subsequent ethanol consumption, and that 12 h of exposure increased AP relative to findings for ethanol-naive rats, but on a delayed basis and at a lower level than that observed for 24 h of exposure. In Experiment 3, we tested whether these increases in ethanol consumption, observed in male MR/Har rats after one-bottle exposure to ethanol, might be related to habituating to an unpalatable substance. Thus, rats had one-bottle tests with either a 10% ethanol solution (as in earlier studies) or a 0.01 mmol quinine solution, after which groups of rats were tested for voluntary consumption (two-bottle test) of one of these solutions and water. Results showed that although rats in the quinine-exposed group drank more fluid than that consumed by rats in the ethanol-exposed group during the one-bottle period, rats preferred ethanol to water and avoided quinine relative to water during the 5 weeks of two-bottle choice. The results seem to indicate that relatively small amounts of 10% ethanol can markedly increase subsequent AP in male MR/Har rats, and that this increase in AP does not seem to be attributable to a process of habituating to an unpalatable fluid.

Ethanol self-administration in Maudsley reactive and Maudsley nonreactive inbred rats

This study was performed to investigate ethanol self-administration in inbred Maudsley rats, which were selected for differences in stress susceptibility and which often differ in their home cage ethanol consumption. Adult, male, Maudsley reactive (MR/Har) and Maudsley nonreactive (MNRA/Har) rats were tested in a standard protocol for the sucrose-substitution procedure for the initiation of self-administration of ethanol in an operant setting. Before and after initiation for self-administration in the operant setting, rats were tested for home cage consumption of 10% (vol./vol.) ethanol in a two-bottle test for 14 consecutive days. During the sucrose-substitution procedure, MNRA/Har rats consumed more sucrose and ethanol than did MR/Har rats. In addition, MNRA/Har rats self-administered a greater amount of ethanol during a concentration manipulation with the use of a fixed ratio (FR) 4 response requirement. However, both strains self-administered low amounts of 10% ethanol (MNRA/Har, 0.15 g/kg/day; MR/Har, 0.08 g/kg/day) after concentration manipulation compared with those observed in outbred rats and alcohol-preferring rats tested under identical conditions in other studies. Both MR/Har and MNRA/Har rats markedly increased their ethanol intake in the home cage after the initiation protocol, but there was no difference between MR/Har and MNRA/Har on that measure. The failure of MR/Har rats to self-administer ethanol was inconsistent with their home cage drinking in other studies, and this is distinctly different from the self-administration pattern of high-alcohol-drinking rat lines tested in this paradigm.

Influence of core buildup material on the fatigue strength of an all-ceramic crown

STATEMENT OF PROBLEM

Clinically relevant variables and testing methods have not been used to investigate the effects of core buildup materials on the strength of all-ceramic restorations.

PURPOSE

The aim of this study was to evaluate the compressive strength of Optimal Pressable Ceramic (OPC) all-ceramic crowns supported by 1 of 3 different core materials and subjected to static or cyclic loading in air or water.

MATERIAL AND METHODS

A total of 135 human extracted third molar teeth were divided into 3 equal groups, and cores of amalgam, composite, and dentin (control) were fabricated. Complete crown preparations with a circumferential 90 degrees shoulder margin 1 mm deep were prepared to support complete crown restorations. Testing in compression was performed at a loading rate of 2.0 mm/min. Sixty teeth (20 with each type of core) were subjected to static loading, with equal numbers tested in air and water. The remaining 75 teeth (25 with each type of core) were subjected to cyclic loading in water. The compressive and diametral tensile strengths of 6 x 12-mm OPC cylinders also were tested in both air and water. The data were analyzed with 1-way analysis of variance followed by the Tukey multiple means comparison test (P<.05).

RESULTS

Analysis of the static fracture stress of OPC crowns indicated no significant differences among the core materials (values from testing in air and water, respectively: dentin core 22.7 +/- 4.5 MPa and 19.7 +/- 4.7 MPa; amalgam core 25.2 +/- 5.2 MPa and 21.6 +/- 6.3 MPa; and composite core 20.9 +/- 4.1 MPa and 18.7 +/- 4.9 MPa). Under wet conditions, static versus cyclic loading produced significantly different results for each of the core materials (dentin core 19.7 +/- 4.7 MPa vs. 9.5 +/- 1.5 MPa; amalgam core 21.6 +/- 6.3 MPa vs. 10.3 +/- 1.6 MPa; composite core 18.7 +/- 4.9 MPa vs. 13.3 +/- 3.2 MPa). A significant difference was observed for the solid compressive cylinders tested in water (793.8 +/- 280.1 MPa) versus in air (1473.6 +/- 527.4 MPa).

CONCLUSION

Within the limitations of this study, the mean compressive strength of OPC crowns tested in water was significantly different under cyclic versus static loading. No significant difference among the 3 core materials was found with respect to crown compressive strength.

Effect of pH on endotoxin affinity for metal-ceramic alloys

STATEMENT OF PROBLEM

Crevicular pH may modify bacterial endotoxin affinity for high-noble metal-ceramic alloys.

PURPOSE

Porphyromonas gingivalis lipopolysaccharide (LPS) affinity for 3 metal-ceramic alloys at 3 different pH levels was compared in vitro by measuring adsorption to and release from the alloy surface.

MATERIAL AND METHODS

Metallographically polished disks were fabricated from Pd-Ag-Sn, Au-Pd-Ag-Sn-In, and Au-Pd-In-Ga alloys. Clean disks were placed individually into 1 mL at pH 6.5, 7.0, or 7.5 phosphate-buffered saline solution containing 0.9 endotoxin units per square millimeter tritiated LPS (n = 3 disks per alloy-pH group). The disks were incubated for 24 hours at 37 degrees C before being transferred to LPS-free buffer and incubated, again for 24 hours at 37 degrees C, to evaluate elution. This transfer continued at 24-hour intervals up to 96 hours total elution incubation. Lipopolysaccharide adsorption to and elution from disks was determined through liquid scintillation spectrometry. Adsorption data were evaluated with a 2-way analysis of variance (alpha=.05) and the post hoc Tukey honestly significant difference test.

RESULTS

Lipopolysaccharide adsorption values ranged from 0.48 +/- 0.04 EU/mm(2) for the Au-Pd-Ag-Sn-In alloy at pH 7.5 to 0.75 +/- 0.04 EU/mm(2) for the Pd-Ag-Sn alloy at pH 6.5. Alloy type (P=.0001) and environmental pH (P=.0001) significantly influenced adsorption. Adsorption to the Pd-Ag-Sn and Au-Pd-In-Ga alloys at pH 6.5, 7.0, and 7.5 were similar and decreased with increasing pH. In contrast, adsorption to the Au-Pd-Ag-Sn-In alloy was significantly less than to other alloys at pH 6.5 but did not differ at other pH levels. Lipopolysaccharide release from the alloy surface could not be detected.

CONCLUSION

P. gingivalis LPS affinity for metal-ceramic alloys was modified by environmental pH. The degree of LPS adsorption depended on the composition and surface chemistry of each alloy.

Surgeons and injury prevention: what you don't know can hurt you!

BACKGROUND

The most effective treatment for traumatic injuries is to prevent them from occurring. Currently, few surgeons receive any formal training in injury' control and prevention. This study was designed to test the knowledge of injury prevention principles among practicing surgeons, in order to identify areas in need of intensified educational efforts.

STUDY DESIGN

Survey questions designed by members of the American College of Surgeons Committee on Trauma were programmed into a specialized touch-screen computer, which was displayed at four different surgery and trauma meetings, including the ACS Clinical Congress in 1999 and 2000. Participants were questioned about their knowledge of trauma epidemiology, bicycle helmet effectiveness, child safety seat usage, suicide, and domestic violence.

RESULTS

Seventy-nine surveys were completed by surgeons, including 33 specializing in trauma care, and by 106 nurses attending trauma courses. Overall, the percentage of correct answers was 50%. There were no significant differences in survey scores between trauma surgeons and general surgeons, although both scored higher than trauma nurses. Areas where knowledge deficits were the most apparent included proper use of child safety seats, the effectiveness of airbags, the prevalence of suicide, and the annual cost of injury in America.

CONCLUSIONS

The majority of practicing surgeons and nurses, including those working at trauma centers, are unaware of the basic concepts of injury prevention. Advancements in the field of injury control will require efforts to educate medical professionals and the public.

Periodontal tissue responses after insertion of artificial crowns and fixed partial dentures

PURPOSE

The purpose of this review was, first, to critically evaluate published evidence on the effects of artificial crowns and fixed partial dentures (FPDs) on adjacent periodontal tissue health, and second to synthesize this evidence into meaningful summaries. Restoration qualities that contribute to inflammatory responses were identified based on strength of evidence, and variables that should be controlled in future investigations were outlined. Such information is necessary to accurately predict the prognosis of periodontal tissues adjacent to crowns or FPDs.

METHODS

Clinical trial and epidemiologic evidence published in English was collected. The effects of crowns or FPDs on gingival inflammation, probing depths, and bone loss were evaluated based on accuracy of measurement, reliability of measurement, and/or appropriateness of data analysis.

RESULTS

Crowns and FPDs increased the incidence of advanced gingival inflammation adjacent to restorations, particularly if restorations had intracrevicular finish line placement, poor marginal adaptation, or rough surfaces. However, because of the limitation in the accuracy and reliability of probing depth measurements, reports of greater mean probing depths of crowned teeth, which tended to be less than 1 mm greater than control teeth, should be questioned. Finally, crowns and FPDs in general did not accelerate the rate of adjacent bone loss.

CONCLUSION

Clinically deficient restorations, as well as clinically acceptable restorations, can contribute to gingival inflammation. However, with the limitations of the applied methods of measurement, current evidence has not shown an increased attachment loss adjacent to crowns or FPDs. Future trials should document periodontal health before therapy and periodically after restoration insertion so that each tooth serves as its own control. In future studies, the periodontal disease history of the patient, the influence of the restoration on plaque formation, and the composition of the crevicular microflora must be recorded.

Domestic violence and the trauma surgeon: results of a study on knowledge and education

BACKGROUND

Despite the frequency of domestic violence in trauma patients, little emphasis has been placed on this subject in the education of surgeons and emergency medicine physicians. The 1997 Advanced Trauma Life Support (ATLS) course included, for the first time, education about domestic violence. This study was done to test the hypothesis that baseline knowledge about domestic violence in trauma care providers is poor and is not improved by the 1997 ATLS course.

STUDY DESIGN

A study on domestic violence was designed using attending general surgeons, general surgery and emergency medicine residents, and medical students as test subjects. An educational lecture and pre- and post-tests were developed using the Eastern Association for the Surgery of Trauma position paper on domestic violence and other peer-reviewed literature as information sources. Data collected included level of training, date ATLS course was taken, and pre- and post-test scores. Statistical analysis was performed with ANOVA, with significance attributed to p < 0.05.

RESULTS

Ninety-two subjects attended the lecture and completed the pre- and post-tests. The overall mean pre-test score was 54 +/- 1. There was no difference in scores for the 1997 ATLS cohort (with domestic violence material) versus the group with earlier ATLS courses (52 +/- 2 versus 51 +/- 1). The group that had never taken ATLS scored significantly better on the pre-test than the other groups (58 +/- 2, p < 0.05). All groups had significantly increased scores on the post-test (mean 77 < 1, p < 0.001 versus pre-test).

CONCLUSIONS

Baseline knowledge about domestic violence among surgeons and emergency medicine physicians was poor and was not improved by participation in the 1997 ATLS course. This study strongly supports the need for expanded domestic violence education for trauma care providers.

Drosophila wee1 has an essential role in the nuclear divisions of early embryogenesis

In Drosophila, the maternally expressed mei-41 and grp genes are required for successful execution of the nuclear division cycles of early embryogenesis. In fission yeast, genes encoding similar kinases (rad3 and chk1, respectively) are components of a cell cycle checkpoint that delays mitosis by inhibitory phosphorylation of Cdk1. We have identified mutations in a gene encoding a Cdk1 inhibitory kinase, Drosophila wee1 (Dwee1). Like mei-41 and grp, Dwee1 is zygotically dispensable but is required maternally for completing the embryonic nuclear cycles. The arrest phenotype of Dwee1 mutants, as well as genetic interactions between Dwee1, grp, and mei-41 mutations, suggest that Dwee1 is functioning in the same regulatory pathway as these genes. These findings imply that inhibitory phosphorylation of Cdk1 by Dwee1 is required for proper regulation of the early syncytial cycles of embryogenesis.

The role of external loop regions in serotonin transport. Loop scanning mutagenesis of the serotonin transporter external domain

Chimeric transporters were constructed in which the predicted external loops of the serotonin transporter (SERT) were replaced one at a time with a corresponding sequence from the norepinephrine transporter (NET). All of the chimeric transporters were expressed at levels equal to or greater than those of wild type SERT, but the transport and binding activity of the mutants varied greatly. In particular, mutants in which the NET sequence replaced external loops 4 or 6 of SERT had transport activity 5% or less than that of wild type, and the loop 5 replacement was essentially inactive. In some of these mutants, binding of a high affinity cocaine analog was less affected than transport, suggesting that the mutation had less effect on the initial binding steps in transport than on subsequent conformational changes. The more severely affected mutants also displayed an altered response to Na(+). In contrast to the dramatic reduction in transport and binding, the specificity of ligand binding was essentially unchanged. Chimeric transporters did not gain affinity for dopamine, a NET substrate, or desipramine, an inhibitor, at the expense of affinity for serotonin or paroxetine, a selective SERT inhibitor. The results suggest that external loops are not the primary determinants of substrate and inhibitor binding sites. However, they are not merely passive structures connecting transmembrane segments but rather active elements responsible for maintaining the stability and conformational flexibility of the transporter.

Exit from mitosis in Drosophila syncytial embryos requires proteolysis and cyclin degradation, and is associated with localized dephosphorylation

The cyclin proteolysis that accompanies the exit from mitosis in diverse systems appears to be essential for restoration of interphase. The early syncytial divisions of Drosophila embryos, however, occur without detectable oscillations in the total cyclin level or Cdk1 activity. Nonetheless, we found that injection of an established inhibitor of cyclin proteolysis, a cyclin B amino-terminal peptide, prevents exit from mitosis in syncytial embryos. Similarly, injection of a version of Drosophila cyclin B that is refractory to proteolysis results in mitotic arrest. We infer that proteolysis of cyclins is required for exit from syncytial mitoses. This inference can be reconciled with the failure to observe oscillations in total cyclin levels if only a small pool of cyclins is destroyed in each cycle. We find that antibody detection of histone H3 phosphorylation (PH3) acts as a reporter for Cdk1 activity. A gradient of PH3 along anaphase chromosomes suggests local Cdk1 inactivation near the spindle poles in syncytial embryos. This pattern of Cdk1 inactivation would be consistent with local cyclin destruction at centrosomes or kinetochores. The local loss of PH3 during anaphase is specific to the syncytial divisions and is not observed after cellularization. We suggest that exit from mitosis in syncytial cycles is modified to allow nuclear autonomy within a common cytoplasm.

The cell cycle program in germ cells of the Drosophila embryo

The germ cells of metazoans follow a program of proliferation that is distinct from proliferation programs of somatic cells. Despite their developmental importance, the cell proliferation program in the metazoan primordial germ cells is not well characterized and the regulatory controls are not understood. In Drosophila melanogaster, germ cell precursors (called pole cells) proliferate early in embryogenesis and then enter a prolonged quiescence. We found that polar nuclear divisions are asynchronous and lag behind somatic nuclear divisions during syncytial cycles 9 and 10. Thus, the polar division program deviates from the somatic division program when pole nuclei and somatic nuclei still share a common cytoplasm, earlier than previously thought. The lag in polar nuclear divisions is independent of grapes, which is required for lengthening somatic cell cycles 10-13. Mapping of the last S phase in pole cells and measurement of their DNA content indicate that pole cells become quiescent in G2 phase of the cell cycle. We were able to drive quiescent pole cells into mitosis by induction of either an activator of Cdc2 (Cdc25string phosphatase) or a mutant form of Cdc2 that cannot be inhibited by phosphorylation. In contrast, induction of wild-type Cdc2 with a mitotic cyclin did not induce mitosis in pole cells. We propose that inhibition of Cdc2 by phosphorylation contributes to G2 arrest in pole cells during embryogenesis. Furthermore, pole cells enter G1 following induced mitoses, indicating that entry into both mitosis and S phase is blocked in quiescent pole cells. These studies represent the first molecular characterization of proliferation in embryonic germ cells of Drosophila.

A system for digital reconstruction of gypsum dental casts

A range scanner is developed that can scan a gypsum dental cast and reconstruct the cast digitally for display and storage purposes. The scanner is based on subtractive light and computes the range values using optical triangulation. A fiducial marker is introduced that, when attached to a dental cast at the time of image acquisition, makes it possible to integrate multiview range images of the cast without image registration. A method for calibrating the scanner is described and experimental results showing the accuracy of the scanner are presented.

The Drosophila grapes gene is related to checkpoint gene chk1/rad27 and is required for late syncytial division fidelity

BACKGROUND

Cell cycle checkpoints maintain the fidelity of the somatic cell cycle by ensuring that one step in the cell cycle is not initiated until a previous step has been completed. The extent to which cell cycle checkpoints play a role in the initial rapid embryonic divisions of higher eukaryotes is unclear. The initial syncytial divisions of Drosophila embryogenesis provide an excellent opportunity to address this issue as they are amenable to both genetic and cellular analysis. In order to study the relevance of cell cycle checkpoints in early Drosophila embryogenesis, we have characterized the maternal-effect grapes (grp) mutation, which may affect feedback control during early syncytial divisions.

RESULTS

The Drosophila grp gene encodes a predicted serine/threonine kinase and has significant homology to chk1/rad27, a gene required for a DNA damage checkpoint in Schizosaccharomyces pombe. Relative to normal embryos, embryos derived from grp-mutant mothers exhibit elevated levels of DNA damage. During nuclear cycles 12 and 13, alignment of the chromosomes on the metaphase plate was disrupted in grp-derived embryos, and the embryos underwent a progression of cytological events that were indistinguishable from those observed in normal syncytial embryos exposed to X-irradiation. The mutant embryos also failed to progress through a regulatory transition in Cdc2 activity that normally occurs during interphase of nuclear cycle 14.

CONCLUSION

We propose that the primary defect in grp-derived embryos is a failure to replicate or repair DNA completely before mitotic entry during the late syncytial divisions. This suggests that wild-type grp functions in a developmentally regulated DNA replication/damage checkpoint operating during the late syncytial divisions. These results are discussed with respect to the proposed function of the chk1/rad27 gene.

Ceramics in dentistry: historical roots and current perspectives

This article presents a brief history of dental ceramics and offers perspectives on recent research aimed at the further development of ceramics for clinical use, at their evaluation and selection, and very importantly, their clinical performance. Innovative ceramic materials and ceramics processing strategies that were introduced to restorative dentistry since the early 1980s are discussed. Notable research is highlighted regarding (1) wear of ceramics and opposing enamel, (2) polishability of porcelains, (3) influence of firing history on the thermal expansion of porcelains for metal ceramics, (4) machining and CAD/CAM as fabrication methods for clinical restorations, (5) fit of ceramic restorations, (6) clinical failure mechanisms of all-ceramic prostheses, (7) chemical and thermal strengthening of dental ceramics, (8) intraoral porcelain repair, and (9) criteria for selection of the various ceramics available. It is found that strong scientific and collaborative foundations exist for the continued understanding and improvement of dental ceramic systems.

Effects of firing cycle and surface finishing on distortion of metal ceramic castings

The "as-cast" fit of metal ceramic restorations has been reported to deteriorate during the high-temperature firing cycles used for application of porcelain veneer. In this study, thermocycling and surface finishing or cold working were examined for their effects on marginal adaptation of metal ceramic castings. Methods for minimizing the loss of marginal adaptation were evaluated, and casting variables were eliminated by construction of acrylic resin measuring dies directly in the restorations. Thermocycling of metal ceramic restorations resulted in increased marginal openings, and all of the loss of marginal fit occurred during the first thermocycling of the alloy. The restorations that were cold worked and then oxidized by conventional manipulation had substantially more marginal opening than any other group. A fourfold, statistically significant improvement (p < 0.001) in the marginal adaptation of a metal ceramic restoration was observed when the initial thermal cycle was completed before the specimens were finished.

A survey of temporomandibular disorder conducted by the Greater New York Academy of Prosthodontics

The results of a temporomandibular joint survey sent to 167 members of the Greater New York Academy of Prosthodontics indicated a great variation in the diagnosis and treatment of patients with temporomandibular joint dysfunction. Although most indicated that their background in temporomandibular joint disorders was from clinical experience and/or textbooks and the dental literature, only 59% treated patients for these disorders. The most common diagnostic procedures were occlusal evaluation; joint evaluation for tenderness, crepitus, and click; evaluation of range of motion of the mandible; and a muscular evaluation. Only 35% used a formal temporomandibular joint dysfunction questionnaire. The percentage of complete denture patients with these symptoms was 5% or less. Thirty-three percent of clinicians sometimes treated asymptomatic patients who were without pain but had a click. Two thirds of the respondents believed that surgery was sometimes indicated for disk degeneration and displacement. More recent graduates are more likely to treat patients who have temporomandibular joint dysfunction than are older more experienced practitioners.

Drosophila Wee1 kinase rescues fission yeast from mitotic catastrophe and phosphorylates Drosophila Cdc2 in vitro

Cdc2 kinase activity is required for triggering entry into mitosis in all known eukaryotes. Elaborate mechanisms have evolved for regulating Cdc2 activity so that mitosis occurs in a timely manner, when preparations for its execution are complete. In Schizosaccharomyces pombe, Wee1 and a related Mik1 kinase are Cdc2-inhibitory kinases that are required for preventing premature activation of the mitotic program. To identify Cdc2-inhibitory kinases in Drosophila, we screened for cDNA clones that rescue S. pombe wee1- mik1- mutants from lethal mitotic catastrophe. One of the genes identified in this screen, Drosophila wee1 (Dwee1), encodes a new Wee1 homologue. Dwee1 kinase is closely related to human and Xenopus Wee1 homologues, and can inhibit Cdc2 activity by phosphorylating a critical tyrosine residue. Dwee1 mRNA is maternally provided to embryos, and is zygotically expressed during the postblastoderm divisions of embryogenesis. Expression remains high in the proliferating cells of the central nervous system well after cells in the rest of the embryo have ceased dividing. The loss of zygotically expressed Dwee1 does not lead to mitotic catastrophe during postblastoderm cycles 14 to 16. This result may indicate that maternally provided Dwee1 is sufficient for regulating Cdc2 during embryogenesis, or it may reflect the presence of a redundant Cdc2 inhibitory kinase, as in fission yeast.

Dimensional and formation analysis of a restorative ceramic and how it works

In-Ceram ceramic appears to use conventional powder/liquid processing techniques to form the coping substructure; however, the process results in a near net-shape restoration with minimal sintering shrinkage. Scanning electron microscopy, Brunauer-Emmett-Teller analysis, particle size classification, and linear dimensional changes during sintering were used to analyze In-Ceram ceramic. In-Ceram ceramic had a minimal linear shrinkage of 0.21% after the sintering of the alumina powder. This shrinkage can be readily compensated for by the expansion of conventional gypsum products and should result in acceptable clinical fits for In-Ceram ceramic restorations. Theories and explanations were described to account for the near net-shape and high strength of In-Ceram. Continuous interpenetrating phase composite technologies were used to create a substantial increase in strength. Future applications of this technology are encouraging.

Thermal cycling distortion of metal ceramics: Part II--Etiology

The three-dimensional geometry of conventional fixed prostheses complicates the study of the thermal cycling distortion in metal ceramic alloys. Any explanation of the etiology of thermal cycling distortion in metal ceramic restorations must account for the observed magnitude, timing, and direction of the deformation. The simplified experimental geometry developed in Part I was applied to elucidate the etiologic factors involved in metal ceramic deformation. Techniques to minimize the thermal cycling distortion were also studied. It was found that all of the significant distortion occurred during the first thermal cycling of the alloy (oxidation) and that no distortion resulted from the application of body porcelain. The specimens that were cold worked and then oxidized had significantly more distortion than any other group. A significant reduction in distortion was observed when the initial thermal cycling was completed before the specimens were cold worked. It was determined that the release of casting- and cold working-induced stresses had a synergistic effect.

Thermal cycling distortion of metal ceramics: Part I--Metal collar width

The complex three-dimensional geometry of conventional full crown restorations severely complicates the study of thermal cycling distortion in metal ceramic castings. A simplified experimental geometry was developed to (1) maximize the measuring sensitivity, (2) eliminate the casting variables, (3) allow the direct measurement of casting distortion, and (4) evaluate the thermal cycling distortion of a wide range of metal collar widths. It was found that all of the one-walled castings distorted during the initial thermal cycling (oxidation) of the alloy. There was no significant distortion associated with porcelain application or glazing. The castings with an 0.8 mm metal collar had significantly less distortion than those with 0.1 and 0.4 mm collars at 2 of the 10 sites measured (inferior or facial margins).

Comparison of condylar control settings using three methods: a bench study

Articulators that program eccentric condylar pathways minimize occlusal adjustments of dental prostheses. This bench study compared three groups of methods for recording the immediate Bennett shift and the protrusive condylar path of the mandible. The experimental design restricted the variable associated with these methods. The various methods for recording protrusive excursions from best to worst were: (1) electronic pantography (Denar); (2) mechanical pantography (Denar); and (3) simplified mandibular motion analyzers (Whip-Mix and Denar). The methods of recording immediate side shift from best to worst were: (1) electronic pantograph; (2) polyether interocclusal records; (3) mechanical pantography (Denar) and simplified mandibular motion analyzer (Panadent); (4) simplified mandibular motion analyzer (Whip-Mix and Denar); and (5) zinc oxide interocclusal records.

Cloning and characterization of the scalloped region of Drosophila melanogaster

Viable mutants of the scalloped gene (sd) of Drosophila melanogaster exhibit defects that can include gapping of the wing margin and ectopic bristle formation on the wing. Lethal sd alleles characterized in the present study now implicate this gene in a genetic function essential for normal development. In order to further characterize the developmental role of this gene, we have undertaken to clone and characterize the region where sd maps. A P[ry+] transposon insertion at 13F associated with sd[ry+2216] served as the starting point for a 42-kb chromosomal walk. Molecular lesions associated with viable and lethal sd alleles were characterized by genomic hybridization analysis as a means of defining the extent of the gene. DNA rearrangements associated with 11 viable sd alleles map to a 2-kb interval which appears to be a "hot spot" for P element activity. Four of five recessive lethal sd mutations were mapped by denaturing gradient gel electrophoresis to a region 12-14 kb away from the region of viable lesions. In a sd+ genotype, at least two structurally related and developmentally regulated transcripts hybridize to the genomic region where several sd lethal alleles have been localized. A viable mutation, sd58, used for comparison in the transcript analysis, makes at least two slightly smaller transcripts that also hybridize to this region. Preliminary analysis of cDNA clones has identified three structurally related transcripts that hybridize to this genomic region. The 5' end of these transcripts extends into the 2-kb genomic region wherein DNA rearrangements were seen in the P element rearrangements. We favor the view that the transcripts represented by these cDNA clones are products of the sd gene. If this is true, the sd gene would include genomic sequences extending over at least 14 kb of the described chromosomal walk, and would appear to be subject to alternative splicing.

Evaluation of the relationship between anterior and posterior functionally disclusive angles. Part II: Study of a population

The lateral and protrusive anterior and posterior disclusive angles were recorded and measured by using a newly developed method (part I) on a population of 50 subjects (mean age 27.2 years). All of the subjects had natural anterior teeth, 45 had a clinically acceptable anterior guidance, and the remaining five had a partial (unilateral) or total lack of anterior guidance. A statistically significant correlation between the anterior and posterior disclusive angles was not found either in the entire population (n = 50) or in the stratum of the population that consisted of subjects with a clinically acceptable anterior guidance (n = 45). The Angle class of occlusion or anterior deep bite malocclusion were not identified as possible confounders or effect modifiers. This study suggested that the intra-articular tissues of the temporomandibular joint played a significant role in the relationship of their osseous components. Practical guidelines to determine anterior guidance could be established by using population means.

Evaluation of the relationship between anterior and posterior functionally disclusive angles. Part I: Literature review, instrumentation, and reproducibility

Authors are not in agreement concerning the existence of an anatomofunctional interrelationship between condylar and anterior guidances of the mandible in humans. Current literature consists either of speculative statements or studies omitting the role of the meniscus. This article (part I) describes a unique method to correlate the condylar functional anatomy to the lingual inclines of the maxillary anterior teeth (anterior guidance) and acknowledges all components of the temporomandibular joint. The measurements obtained by means of this method were reproduced five different times on five different subjects, making possible a valid statistical analysis of the correlation between condylar and anterior guidances of the mandible (part II).

Esthetic modification of cast dental-ceramic restorations

The advantages and disadvantages of conventional opaque substructures (eg, metal ceramic restorations) used for creating esthetic complete crown restorations are reviewed, and the esthetic advantages of veneering a translucent crown (Dicor) are considered. An appropriate aluminous veneering porcelain was identified (Vitadur Veneer). This veneer porcelain was chosen to match the thermal coefficient of expansion of the cast glass-ceramic substructure. A flexural strength study was then completed and it showed no difference in the strength of the veneered and nonveneered translucent cast glass-ceramic specimens. Scanning electron microscopy revealed that the interface between the porcelain veneer and cast glass-ceramic substructure had no visible porosity and resulted in a continuous-appearing structure. Potential coping designs, as well as the clinical applications and ramifications of this modified crown, are discussed.

Comparison of conventional paint-on die spacers and those used with the all-ceramic restorations

The study compared the thickness of conventional (Tru-Fit and Belle de St. Claire) and all-ceramic (Dicor and Cerestore) die spacers. Three coats of Tru-Fit, two coats of Belle de St. Claire, and two coats of Cerestore die spacers provided a 25 microns thickness. A single coat of the Dicor spacer resulted in a 37 microns layer. A significantly thinner layer occurred at the convex occlusal line angles for all of the materials tested. This could impede the flow of the luting agent at the time of cementation.

Fracture-surface analysis of dental ceramics

This study demonstrated that quantitative fractography can be used to study failed aluminous and glass-ceramic central porcelains. Fracture surfaces of DICOR and Vitadur-N core porcelain modulous-of-rupture bars were studied to identify fracture mirror features useful in (1) locating the source of fracture and (2) calculating the stress at fracture in clinically failed restorations. The morphology of fracture surfaces results from events related to the initiation and propagation of the crack front during failure. Modulus-of-rupture testing was performed in four-point bending. Fracture surfaces were studied by scanning electron microscopy. The mean fracture stress for the Vitadur-N porcelain was 94.7 +/- 12.4 MPa (13,730 psi); for DICOR the fracture stress was 55.4 +/- 10.6 MPa (8,030 psi). The standard quantitative fractography relationship between in mirror radius and ln fracture stress was followed for both materials. This quantitative fractography relationship was used to calculate the in vivo stress at failure in a clinically fractured DICOR molar crown. Five clinically failed DICOR crowns were seen to fail from the internal surface.

A comparative strength study of metal ceramic and all-ceramic esthetic materials: modulus of rupture

The modulus of rupture for three metal ceramics and five all-ceramic substructures with and without veneer porcelain was compared. Support of the veneer porcelain was directly related to the modulus of elasticity and not to the strength of the substructure material. The higher the modulus of elasticity, the greater was the strength of the veneered restoration. For each 1 x 10(6) increase in the modulus there was a corresponding 1040 psi increase in strength. The veneered all-ceramics had 45% to 70% of the strength of the metal ceramic restorations. The veneered nonprecious and gold-palladium metal ceramic test bars were significantly stronger than any veneered all-ceramic material.

Influence of surface preparation on the strength and surface microstructure of a cast dental ceramic

The effect of three surface preparations on the flexural strength of a cast glass-ceramic (Dicor) was studied. The microstructure of the external and fracture surfaces was evaluated using electron microscopy. It was found that there was no difference in strength for the "as-cast/cerammed," acid-etched, or glazed shading porcelain specimens. A significant increase in strength (twofold) was observed when the "ceram layer" was mechanically removed from the surface of the ceramic. Scanning electron microscopy revealed that the "ceram layer" was 25 to 100 microns thick and consisted of crystal "whiskers" oriented perpendicular to the external surfaces. It was observed in both the laboratory and the clinically failed specimens that a zone of strength-limiting porosity was associated with this "ceram layer." Potential origins of the crystal "whiskers" and the porosity were discussed.

Use of an elastomeric material to improve the occlusal seat and marginal seal of cast restorations

A method to improve the fit of castings by the use of a light-bodied condensation silicone impression material was tested. Eighteen-full coverage castings were made on individual resin dies and divided into two groups. The experimental group was adjusted internally to a uniform precementation space by using the silicone impression material as a disclosing agent for binding of the castings on the axial or occlusal walls. Measurements of marginal fit were made with a light microscope using a filar eyepiece both externally and internally by sectioning after cementation with a zinc phosphate cement. Results demonstrated a significant improvement in marginal seal and occlusal seating in the experimental group compared with the control group. The condensation silicone material proved to be an appropriate research tool for nondestructive, three-dimensional evaluation of the postcementation space and offers a new method of evaluation of cement thickness because seating was found to be not significantly different from that with zinc phosphate cement.

Evaluation of surface roughness and polishing techniques for new ceramic materials

The surface roughness of crown and bridge materials should be minimized to obtain optimal biocompatability. This study used scanning electron microscopy to evaluate the effect of polishing procedures on two all-ceramic crown materials (Dicor and Cerestore). The "as formed," unpolished specimens of both Dicor and Cerestore materials presented a rough surface. It was found that any attempt to polish the Cerestore coping material resulted in an extremely rough surface. Finishing of the Dicor ceramic resulted in a smoother but pitted surface. Polishing of both ceramic materials resulted in a surface that was rougher than the glazed metal ceramic controls. The smoothest finish was obtained when the glazed veneer (Cerestore) and shading porcelain (Dicor) were applied to the all-ceramic materials.

Null mutation of copper/zinc superoxide dismutase in Drosophila confers hypersensitivity to paraquat and reduced longevity

The role of copper/zinc-containing superoxide dismutase (cSOD; superoxide:superoxide oxidoreductase, EC 1.15.1.1) in metabolic defense against O2 toxicity in Drosophila is examined through the properties of a mutant strain carrying a cSOD-null mutation, cSODn108. Homozygotes are viable as larvae, which indicates that cSOD is not essential for cell viability per se. cSODn108 confers recessive sensitivity to the superoxide anion (O2-)-generator paraquat and to the transition metal compound CuSO4, which indicates that the cSOD-null condition in fact leads to impaired O2- metabolism. The primary biological consequences of the reduced O2- dismutation capacity of cSODn108 Drosophila are realized in the adult as infertility and reduction in life-span. We conclude that the infertility and reduced life-span of cSODn108 adults arise as a consequence of the reduced capacity of embryos, larvae, and pupae to adequately protect developing preimaginal cells from O2- -initiated cytotoxic damage.

Nondestructive, three-dimensional internal fit mapping of fixed prostheses

Crown fit may be three-dimensionally mapped by using a nondestructive optical technique. Reflected light transmission through thicknesses of a colored impression material was shown to follow the Beer-Lambert relationship over a range of approximately 10 to 300 microns, a useful range of interest for study of cement layer thickness. Control thicknesses of impression material were first formed between the measuring platens of a micrometer, and light transmission values (relative reflections) were measured through these control thicknesses of impression material held against air-abraded, noncast gold alloy. Relative reflection values were similarly measured from impression material formed inside cast gold crowns seated on their respective dies and these values were plotted against direct thickness measurements by using the Beer-Lambert relationship. It was established that the micrometer-produced control specimens yielded a valid standard curve for use with the cast gold crowns. Precementation space measurements determined photometrically were found to correlate significantly (r = 0.72, p less than 0.001) with zinc phosphate cement thickness measured on subsequently cemented and cross-sectioned crowns. A three-dimensional representation of the precementation space inside one crown was developed after mapping of 45 points in less than 5 minutes.

Evaluation of the fit and strength of an all-ceramic fixed partial denture

A laboratory investigation of the fit and strength of three-unit all-ceramic FPDs was performed with a metal-ceramic FPD control. The conclusions were: 1. No difference was found between the marginal seal of the metal-ceramic and all-ceramic FPDs. 2. The all-ceramic FPDs had a more uniform cement space and their occlusal seat was significantly (99.9%) better than the metal-ceramic restorations. 3. The metal-ceramic FPDs were significantly stronger than the all-ceramic FPDs. 4. Load calculations suggest that short-span all-ceramic FPDs may be strong enough to resist normal masticatory forces for selected patients. However, generalized usage will probably result in an unacceptable failure rate.

Effects of butylated hydroxytoluene on membrane lipid fluidity and freeze-thaw survival in mammalian cells

Butylated hydroxytoluene (BHT) increases the fluidity of membrane lipids in the hydrocarbon but not the polar regions, as measured by electron spin resonance spin label probes. BHT also sensitizes nucleated mammalian cells to freeze-thaw damage as measured by colony formation survival assays. Furthermore, the membranes of BHT-exposed cells are more susceptible to physical stress, as reflected by the BHT-induced sensitization to hypotonic stress. Since others have shown that BHT induces hexagonal phase lipids in lipid bilayers, this phenomenon may also influence the above survival results.