Digital intraoral radiographic quality assurance and control in private practice.

At present, the American Dental Association and the American Academy of Oral Maxillofacial Radiology have guidelines for the dental environment that include quality assurance and control of film-based radiography. Approximately 19%-30% of US dental offices currently use some form of digital intraoral radiography, and growth is expected to continue. It is anticipated that new tools and guidelines will be needed to aid in the development of quality assurance (QA) and control of digital intraoral radiographic images. Working with a representative sample of private practice dental offices, this study examined and evaluated the entire digital intraoral radiographic system used in each operatory. The X-ray machine was tested for equipment performance and accuracy, and the computer monitor calibration was evaluated and adjusted as needed. The results confirm the continued need for updated QA procedures in the dental office that include digital X-ray imaging. By implementing these changes and practices, dentists should be able to improve the diagnostic quality of radiographs while reducing the radiation exposure of the patient.

Ocean acidification causes bleaching and productivity loss in coral reef builders.

Ocean acidification represents a key threat to coral reefs by reducing the calcification rate of framework builders. In addition, acidification is likely to affect the relationship between corals and their symbiotic dinoflagellates and the productivity of this association. However, little is known about how acidification impacts on the physiology of reef builders and how acidification interacts with warming. Here, we report on an 8-week study that compared bleaching, productivity, and calcification responses of crustose coralline algae (CCA) and branching (Acropora) and massive (Porites) coral species in response to acidification and warming. Using a 30-tank experimental system, we manipulated CO(2) levels to simulate doubling and three- to fourfold increases [Intergovernmental Panel on Climate Change (IPCC) projection categories IV and VI] relative to present-day levels under cool and warm scenarios. Results indicated that high CO(2) is a bleaching agent for corals and CCA under high irradiance, acting synergistically with warming to lower thermal bleaching thresholds. We propose that CO(2) induces bleaching via its impact on photoprotective mechanisms of the photosystems. Overall, acidification impacted more strongly on bleaching and productivity than on calcification. Interestingly, the intermediate, warm CO(2) scenario led to a 30% increase in productivity in Acropora, whereas high CO(2) lead to zero productivity in both corals. CCA were most sensitive to acidification, with high CO(2) leading to negative productivity and high rates of net dissolution. Our findings suggest that sensitive reef-building species such as CCA may be pushed beyond their thresholds for growth and survival within the next few decades whereas corals will show delayed and mixed responses.

Effect of JPEG2000 compression on landmark identification of lateral cephalometric digital radiographs.

INTRODUCTION: As digital imaging improves and digital cephalometric radiography becomes more prevalent, the need for digital storage space and transmission speed will increase. Compression of the image files is 1 method to overcome transmission overload. However, compression could compromise image quality. The purpose of this study was to determine the range of compression ratios, by using the JPEG2000 standard, within which the identification of landmarks on cephalometric radiographs is not compromised. METHODS: Ten lateral cephalometric digital images were used. Six raters identified 19 landmarks under controlled viewing conditions. The images included the original uncompressed TIFF image and the JPEG2000 format at 3:1, 12:1, 50:1, and 110:1 compression ratios. The images were randomized and displayed with image processing software. The x and y coordinates of each landmark were recorded. RESULTS: All compression ratios performed equally well compared with the original images with the exception of A-point and nasion at 110:1 and gonion at 3:1 compression ratios. All landmark identifications were precise with the exception of the maxillary incisal apex and edge at the 12:1 and 50:1 compression ratios, respectively. CONCLUSIONS: JPEG2000 is a reliable file format that can be implemented in orthodontic practice.

Cohesive molecular genetic data delineate species diversity in the dinoflagellate genus Symbiodinium.

The diversity of symbiotic dinoflagellates (Symbiodinium) in pocilloporid corals originating from various reef habitats surrounding Heron Island, southern Great Barrier Reef, was examined by targeting ribosomal, mitochondrial, and chloroplast genes using six methods that analyse for sequence differences. The ability of each of 13 genetic analyses to characterize eight ecologically distinct Symbiodinium spp. was dependent on the level of conservation of the gene region targeted and the technique used. Other than differences in resolution, phylogenetic reconstructions using nuclear and organelle gene sequences were complementary and when combined produced a well-resolved phylogeny. Analysis of the ribosomal internal transcribed spacers using denaturing gradient gel electrophoresis fingerprinting in combination with sequencing of dominant bands provided a precise method for rapidly resolving and characterizing symbionts into ecologically and evolutionarily distinct units of diversity. Single-stranded conformation polymorphisms of the nuclear ribosomal large subunit (D1/D2 domain) identified the same number of ecologically distinct Symbiodinium spp., but profiles were less distinctive. The repetitive sequencing of bacterially cloned ITS2 polymerase chain reaction amplifications generated numerous sequence variants that clustered together according to the symbiont under analysis. The phylogenetic relationships between these clusters show how intragenomic variation in the ribosomal array diverges among closely related eukaryotic genomes. The strong correlation between phylogenetically independent lineages with different ecological and physiological attributes establishes a clear basis for assigning species designations to members of the genus Symbiodinium.

Gene expression of a green fluorescent protein homolog as a host-specific biomarker of heat stress within a reef-building coral.

Recent incidences of mass coral bleaching indicate that major reef building corals are increasingly suffering thermal stress associated with climate-related temperature increases. The development of pulse amplitude modulated (PAM) fluorometry has enabled rapid detection of the onset of thermal stress within coral algal symbionts, but sensitive biomarkers of thermal stress specific to the host coral have been slower to emerge. Differential display reverse transcription polymerase chain reaction (DDRT-PCR) was used to produce fingerprints of gene expression for the reef-building coral Acropora millepora exposed to 33 degrees C. Changes in the expression of 23 out of 399 putative genes occurred within 144 h. Down-regulation of one host-specific gene (AmA1a) occurred within just 6 h. Full-length sequencing revealed the product of this gene to be an all-protein chromatophore (green fluorescent protein [GFP]-homolog). RT-PCR revealed consistent down-regulation of this GFP-homolog for three replicate colonies within 6 h at both 32 degrees C and 33 degrees C but not at lower temperatures. Down-regulation of this host gene preceded significant decreases in the photosynthetic activity of photosystem II (dark-adapted F (v)/F (m)) of algal symbionts as measured by PAM fluorometry. Gene expression of host-specific genes such as GFP-homologs may therefore prove to be highly sensitive indicators for the onset of thermal stress within host coral cells.

Characterization of MTMR3. an inositol lipid 3-phosphatase with novel substrate specificity.

Inositol lipids play key roles in many fundamental cellular processes that include growth, cell survival, motility, and membrane trafficking. Recent studies on the PTEN and Myotubularin proteins have underscored the importance of inositol lipid 3-phosphatases in cell function. Inactivating mutations in the genes encoding PTEN and Myotubularin are key steps in the progression of some cancers and in the onset of X-linked myotubular myopathy, respectively. Myotubularin-related protein 3 (MTMR3) shows extensive homology to Myotubularin, including the catalytic domain, but additionally possesses a C-terminal extension that includes a FYVE domain. We show that MTMR3 is an inositol lipid 3-phosphatase, with a so-far-unique substrate specificity. It is able to hydrolyze PtdIns3P and PtdIns3,5P2, both in vitro and when heterologously expressed in S. cerevisiae, and to thereby provide the first clearly defined route for the cellular production of PtdIns5P. Overexpression of a catalytically dead MTMR3 (C413S) in mammalian cells induces a striking formation of vacuolar compartments that enclose membranous structures that are highly concentrated in mutant proteins.

The stress-activated phosphatidylinositol 3-phosphate 5-kinase Fab1p is essential for vacuole function in S. cerevisiae.

Polyphosphoinositides have many roles in cell signalling and vesicle trafficking [1-3]. Phosphatidylinositol 3,5-bisphosphate (PI(3,5)P2), a recently discovered PIP2 isomer, is ubiquitous in eukaryotic cells and rapidly accumulates in hyperosmotically stressed yeast. PI(3,5)P2 is synthesised from PI(3)P in both yeast and mammalian cells [4,5]. A search of the Saccharomyces cerevisiae genome database identified FAB1, a gene encoding a PIP kinase homologue and potential PI(3)P 5-kinase. Fab1p shows PI(3)P 5-kinase activity both in vivo and in vitro. A yeast strain in which FAB1 had been deleted was unable to synthesise PI(3,5)P2, either in the presence or absence of osmotic shock. A loss of PI(3,5)P2 was observed also in a temperature-sensitive FAB1 strain at the non-permissive temperature. A recombinant glutathione-S-transferase (GST)-Fab1p fusion protein was shown to have selective PI(3)P 5-kinase activity in vitro. Thus, we have demonstrated that Fab1p is a PI(3)P-specific 5-kinase and represents a third class of PIP kinase activity, which we have termed type III. Deletion of the FAB1 gene produces a loss of vacuolar morphology [6]; it is therefore concluded that PI(3,5)P2, the lipid product of Fab1p, is required for normal vacuolar function.

Magnitude of the CREB-dependent transcriptional response is determined by the strength of the interaction between the kinase-inducible domain of CREB and the KIX domain of CREB-binding protein.

The activity of the transcription factor CREB is regulated by extracellular stimuli that result in its phosphorylation at a critical serine residue, Ser133. Phosphorylation of Ser133 is believed to promote CREB-dependent transcription by allowing CREB to interact with the transcriptional coactivator CREB-binding protein (CBP). Previous studies have established that the domain encompassing Ser133 on CREB, known as the kinase-inducible domain (KID), interacts specifically with a short domain in CBP termed the KIX domain and that this interaction depends on the phosphorylation of Ser133. In this study, we adapted a recently described Escherichia coli-based two-hybrid system for the examination of phosphorylation-dependent protein-protein interactions, and we used this system to study the kinase-induced interaction between the KID and the KIX domain. We identified residues of the KID and the KIX domain that are critical for their interaction as well as two pairs of oppositely charged residues that apparently interact at the KID-KIX interface. We then isolated a mutant form of the KIX domain that interacts more tightly with wild-type and mutant forms of the KID than does the wild-type KIX domain. We show that in the context of full-length CBP, the corresponding amino acid substitution resulted in an enhanced ability of CBP to stimulate CREB-dependent transcription in mammalian cells. Conversely, an amino acid substitution in the KIX domain that weakens its interaction with the KID resulted in a decreased ability of full-length CBP to stimulate CREB-dependent transcription. These findings demonstrate that the magnitude of CREB-dependent transcription in mammalian cells depends on the strength of the KID-KIX interaction and suggest that the level of transcription induced by coactivator-dependent transcriptional activators can be specified by the strength of the activator-coactivator interaction.

Phosphatidylinositol 4,5-bisphosphate regulates two steps of homotypic vacuole fusion.

Yeast vacuoles undergo cycles of fragmentation and fusion as part of their transmission to the daughter cell and in response to changes of nutrients and the environment. Vacuole fusion can be reconstituted in a cell free system. We now show that the vacuoles synthesize phosphoinositides during in vitro fusion. Of these phosphoinositides, phosphatidylinositol 4-phosphate and phosphatidylinositol 4,5-bisphosphate (PI(4,5)P(2)) are important for fusion. Monoclonal antibodies to PI(4,5)P(2), neomycin (a phosphoinositide ligand), and phosphatidylinositol-specific phospholipase C interfere with the reaction. Readdition of PI(4, 5)P(2) restores fusion in each case. Phosphatidylinositol 3-phosphate and PI(3,5)P(2) synthesis are not required. PI(4,5)P(2) is necessary for priming, i.e., for the Sec18p (NSF)-driven release of Sec17p (alpha-SNAP), which activates the vacuoles for subsequent tethering and docking. Therefore, it represents the kinetically earliest requirement identified for vacuole fusion so far. Furthermore, PI(4,5)P(2) is required at a step that can only occur after docking but before the BAPTA sensitive step in the latest stage of the reaction. We hence propose that PI(4,5)P(2) controls two steps of vacuole fusion.

Molecular determinants for the high constitutive activity of the human histamine H4 receptor: functional studies on orthologues and mutants.

BACKGROUND AND PURPOSE: Some histamine H4 receptor ligands act as inverse agonists at the human H4 receptor (hH4 R), a receptor with exceptionally high constitutive activity, but as neutral antagonists or partial agonists at the constitutively inactive mouse H4 receptor (mH4 R) and rat H4 receptor (rH4 R). To study molecular determinants of constitutive activity, H4 receptor reciprocal mutants were constructed: single mutants: hH4 R-F169V, mH4 R-V171F, hH4 R-S179A, hH4 R-S179M; double mutants: hH4 R-F169V+S179A, hH4 R-F169V+S179M and mH4 R-V171F+M181S. EXPERIMENTAL APPROACH: Site-directed mutagenesis with pVL1392 plasmids containing hH4 or mH4 receptors were performed. Wild-type or mutant receptors were co-expressed with Gαi2 and Gß1 γ2 in Sf9 cells. Membranes were studied in saturation and competition binding assays ([(3) H]-histamine), and in functional [(35) S]-GTPγS assays with inverse, partial and full agonists of the hH4 receptor. KEY RESULTS: Constitutive activity decreased from the hH4 receptor via the hH4 R-F169V mutant to the hH4 R-F169V+S179A and hH4 R-F169V+S179M double mutants. F169 alone or in concert with S179 plays a major role in stabilizing a ligand-free active state of the hH4 receptor. Partial inverse hH4 receptor agonists like JNJ7777120 behaved as neutral antagonists or partial agonists at species orthologues with lower or no constitutive activity. Some partial and full hH4 receptor agonists showed decreased maximal effects and potencies at hH4 R-F169V and double mutants. However, the mutation of S179 in the hH4 receptor to M as in mH4 receptor or A as in rH4 receptor did not significantly reduce constitutive activity. CONCLUSIONS AND IMPLICATIONS: F169 and S179 are key amino acids for the high constitutive activity of hH4 receptors and may also be of relevance for other constitutively active GPCRs. LINKED ARTICLES: This article is part of a themed issue on Histamine Pharmacology Update published in volume 170 issue 1. To view the other articles in this issue visit http://onlinelibrary.wiley.com/doi/10.1111/bph.2013.170.issue-1/issuetoc.

7-substituted-4-hydroxyquinoline-3-carboxylic acids as inhibitors of dehydrogenase enzymes and of the respiration of Ehrlich ascites tumor cells: multivariate analysis and quantitative structure-activity relationship for polar substituents.

The inhibitory activities of a set of nine 7-substituted-4-hydroxyquinoline-3-carboxylic acids against three dehydrogenase enzymes and one whole cell system (Ehrlich ascites tumor cells) have been subjected to principal component analysis. The results clearly indicate that activity against the whole cell test system cannot directly be attributed to inhibition of the enzymes evaluated. The enzyme systems are reflected by the first component that can be identified with polar and steric parameters while hydrophobic effects are absent. The second component is entirely due to the inhibition of ascites cell respiration that depends primarily on hydrophobicity.

On the rational selection of test series. 1. Principal component method combined with multidimensional mapping.

A method for the rational selection of optimal test series with high data variance and low collinearities is presented (PCMM method). The method combines the technique of multidimensional mapping originally introduced by Wootton and colleagues with the principal component method, and it is superior to other selection methods with respect to its collinearity decreasing power. Two examples of the application of PCMM are given, and the results are compared with corresponding results from other selection techniques.

On the rational selection of test series. 2. Two-dimensional mapping of intraclass correlation matrices.

A rational design of optimal test series can be performed by two-dimensional mapping of intraclass correlation matrices (TMIC method). The method results in a two-dimensional map from which substituents can be selected by simple inspection. Different test series can be obtained from the same map so that synthetic feasibility can easily be taken into account. The approach closely corresponds to the usual way of thinking of organic chemists, and the test series evaluated for an example show high data variance and low collinearities.

Discriminant--analytical investigation on the structural dependence of hyperglycemic and hypoglycemic activity in a series of substituted o-toluenesulfonylthioureas and o-toluenesulfonylureas.

The influence of a series of substituted o-toluenesulfonylthioureas and o-toluenesulfonylureas on the level of blood sugar was investigated in rats. According to the observed response the compounds were divided into three classes corresponding to hypoglycemic, hyperglycemic, and no activity. The distribution of the compounds over these classes can be described by discriminant functions using substituent constants, RM values, and indicator variables. Most important for the separation of classes are hydrophobic and/or steric properties as well as the presence or absence of the thiomide group. The results indicate that two different mechanisms of action with opposite effect overlap in the case of the series studied.

Measurement and validation of benchmark-quality thick-target tungsten X-ray spectra below 150 kVp.

Pulse-height distributions of two constant potential X-ray tubes with fixed anode tungsten targets were measured and unfolded. The measurements employed quantitative alignment of the beam, the use of two different semiconductor detectors (high-purity germanium and cadmium-zinc-telluride), two different ion chamber systems with beam-specific calibration factors, and various filter and tube potential combinations. Monte Carlo response matrices were generated for each detector for unfolding the pulse-height distributions into spectra incident on the detectors. These response matrices were validated for the low error bars assigned to the data. A significant aspect of the validation of spectra, and a detailed characterization of the X-ray tubes, involved measuring filtered and unfiltered beams at multiple tube potentials (30-150 kVp). Full corrections to ion chamber readings were employed to convert normalized fluence spectra into absolute fluence spectra. The characterization of fixed anode pitting and its dominance over exit window plating and/or detector dead layer was determined. An Appendix of tabulated benchmark spectra with assigned error ranges was developed for future reference.

Computer modelling of estrogenic transcriptional activation can account for different types of dose-response curves of estrogens.

Estrogenic activity of diphenylethanes and -ethenes was determined by uterine growth in immature mice and analyzed by weighed regression of logit-transformed effect on log dose values. This resulted in a range of Hill coefficients nH from 0.3 to 2 corresponding to the molecular mechanism of estrogenic transcriptional activation. Binding of agonists (hormones, H) to estrogen receptors (ER) leads to receptor dimerization depending on the structure of the ligand. Three hormone-receptor complexes, H-ER, H-ER-ER, and H-ER-ER-H, which bind with different affinity to short palindromic DNA sequences (estrogen responsive elements), can be proposed. Transcriptional activating functions of the DNA-bound ER are subsequently induced. We have derived an equilibrium model including these steps. Computer simulations of Hill plots based on the model have completely reproduced the range of observed nH values. Hill coefficients are > 1.5 if the homodimer H-ER-ER-H and < 0.7 if the heterodimer H-ER-ER strongly predominates. If ER dimerization is disturbed (H-ER monomer predominant), nH is closer to 1. Hill coefficients and pD2 values (negative decadic logarithms of molar estrogen doses causing 50% of the maximal effects) are related to parameters of ER dimerization and the two steps of hormone-receptor dissociation. When a series of 1,2-bis(3'-or 4'-hydroxyphenyl)ethanes and -ethenes is studied, a rather simple dependence of nH and pD2 on the nature of alkyl groups symmetrically substituted at C-atoms 1 and 2 can be observed. In terms of the model this implies that ethyl and alpha-branched higher alkyl substituents (nH >> 1) appear to stabilize the homodimer, while methyl and CF3 groups (nH << 1) could lead to a rapid dissociation of the homodimer to the heterodimer. With longer n-alkyl and beta-branched alkyl substitution (nH from 0.66 to 1.3), dimerization itself can be limited or the ligand-homodimer dissociation is only moderately increased. Thus, a strong sterical constraint could exist with respect to the stabilization of the second ligand-receptor bond in the homodimer.

NPY Y1 antagonists: structure-activity relationships of arginine derivatives and hybrid compounds with arpromidine-like partial structures.

Previously, omega-guanidino- and omega-aminoalkanamides, structurally derived from arpromidine-like histamine H2 receptor agonists, were reported as novel neuropeptide Y Y1 antagonists. Regardless of the backbone, they resemble BIBP 3226, an argininamide with high NPY Y1 receptor affinity and selectivity, with respect to nature and arrangement of the 'terminal' diaryl, guanidine, and hydroxyphenyl groups. Hybrid compounds were synthesized combining the argininamide backbone of BIBP 3226 or partial structures derived from the C-terminal dipeptide of NPY with characteristic substructures of arpromidine- or amide-type NPY antagonists. Additionally, some analogs of BIBP 3226 with reduced flexibility were prepared. Structure-activity relationships indicate that, in contrast to alkanamides, homologs and/or isomers of BIBP 3226 with vicinal arrangement of the phenyl rings have decreased Y1 antagonistic activity (Ca2+-assay in HEL cells). Replacement of the hydroxybenzyl group by an imidazole ring further decreases activity. It is concluded that the binding sites of NPY antagonists with one and with two basic groups are not identical. Analogs with a rigid tetrahydro-2-benzazepine or an indan group in place of the benzyl moiety in BIBP 3226 are active, indicating the role of the OH group and supporting the model proposed for the interaction of BIBP 3226 with the Y1 receptor.

Modification and benchmarking of MCNP for low-energy tungsten spectra.

The MCNP Monte Carlo radiation transport code was modified for diagnostic medical physics applications. In particular, the modified code was thoroughly benchmarked for the production of polychromatic tungsten x-ray spectra in the 30-150 kV range. Validating the modified code for coupled electron-photon transport with benchmark spectra was supplemented with independent electron-only and photon-only transport benchmarks. Major revisions to the code included the proper treatment of characteristic K x-ray production and scoring, new impact ionization cross sections, and new bremsstrahlung cross sections. Minor revisions included updated photon cross sections, electron-electron bremsstrahlung production, and K x-ray yield. The modified MCNP code is benchmarked to electron backscatter factors, x-ray spectra production, and primary and scatter photon transport.

CT reconstruction algorithm for a dental panoramic x-ray unit.

A variable Jacobian and weighted backprojection algorithm, used for medical CT, was adapted to perform CT reconstructions on data obtained with a dental panoramic x-ray unit. A detector array, fitted to the unit for the purpose of acquiring digital panoramic radiographs, was used to collect the data. Compensations were made for the incomplete (230 degrees) rotation of the panoramic x-ray unit, the non-fixed centre of rotation, the irregular rotation of the x-ray target and detector, and the resulting variances in magnification. The algorithm was tested on mathematically simulated phantoms and on acquired data. Reconstruction of simulated data proved the success of the algorithm. Real data reconstructions showed some defects as a result of inaccuracies in quantifying the experimental panoramic device.

Clinical validation of a new subtraction radiography technique for periodontal bone loss detection.

BACKGROUND: Diagnostic subtraction radiography (DSR) is a new digital radiographic image subtraction method designed to enhance detection of crestal or periapical bone density changes and to help evaluate caries progression in teeth. In this clinical study, the performance of the DSR method was evaluated for its ability to detect periodontal bone loss and was compared with that of conventional evaluation of radiographs and the standardized cephalostat-guided image acquisition and subtraction technique (LRA) which served as the "gold standard." METHODS: In each of 25 subjects with alveolar crestal bone loss created by periodontal surgery, one set of DSR radiographs and one set of LRA radiographs were obtained before and after the surgery. Subtraction images were then generated by both the proprietary DSR and the LRA techniques. Four viewers evaluated the paired film sets and both subtraction image sets using a 5 point confidence scale to determine the presence or absence of crestal bone loss. Receiver operating characteristics (ROC) statistical procedures were applied to analyze the diagnostic accuracy and statistical differences between the three imaging modalities. RESULTS: The DSR subtraction viewing generated an ROC area of 0.882. For 2 of the viewers this represented a statistically significant gain (P <0.05) over the conventional viewing of the radiographs which had an average ROC area of 0.730. In comparison, the LRA method achieved an area of 0.954. The differences between the LRA and the DSR subtraction methods were not statistically significant, but the statistical power for claiming equality was low ranging from 0.2 to 0.6. CONCLUSIONS: The use of the DSR technique in clinical radiographic image acquisition and subsequent subtraction analysis clearly enhanced the accuracy of alveolar crestal bone loss detection when compared to conventional film viewing. Because this methodology is less resource demanding than LRA and the film exposure techniques and computer-based image analysis skills may be acquired with only a few hours of training, the DSR has potential in clinical practice.