Evaluation of a reproduction technique for the study of the enamel composite/bracket base area.
The objective of the study was to evaluate a reproduction method that would enable the study of the enamel/ bracket/composite interface in vivo, and consisted of in vitro assessment of two different impression materials to compare reproduction of brackets bonded to extracted teeth followed by in vivo assessment of the superior material. In vitro standard edgewise brackets were bonded to two extracted teeth and impressions were taken using two different types of low viscosity silicone-based impression materials. A medium viscosity silicone impression material was used to support the original impression. Three impressions of both the gingival and occlusal aspect of the bracket base region were obtained using each of the impression materials. Replicas were then prepared for SEM viewing and these compared to SEMs of the real teeth for reproduction of detail. A 3-point Reproducibility Index was used to compare the SEM photographs of the comparable replicas. One impression material was clearly superior to the other and produced an acceptably accurate representation of the true clinical situation in three out of four samples. This material also performed well in the in vivo situation. The technique described is satisfactory for the production and analysis of SEM pictures of the enamel/composite/ bracket base interface in vivo. (+info
A requirement for cytoplasmic dynein and dynactin in intermediate filament network assembly and organization.
We present evidence that vimentin intermediate filament (IF) motility in vivo is associated with cytoplasmic dynein. Immunofluorescence reveals that subunits of dynein and dynactin are associated with all structural forms of vimentin in baby hamster kidney-21 cells. This relationship is also supported by the presence of numerous components of dynein and dynactin in IF-enriched cytoskeletal preparations. Overexpression of dynamitin biases IF motility toward the cell surface, leading to a perinuclear clearance of IFs and their redistribution to the cell surface. IF-enriched cytoskeletal preparations from dynamitin-overexpressing cells contain decreased amounts of dynein, actin-related protein-1, and p150Glued relative to controls. In contrast, the amount of dynamitin is unaltered in these preparations, indicating that it is involved in linking vimentin cargo to dynactin. The results demonstrate that dynein and dynactin are required for the normal organization of vimentin IF networks in vivo. These results together with those of previous studies also suggest that a balance among the microtubule (MT) minus and plus end-directed motors, cytoplasmic dynein, and kinesin are required for the assembly and maintenance of type III IF networks in interphase cells. Furthermore, these motors are to a large extent responsible for the long recognized relationships between vimentin IFs and MTs. (+info
Accuracy of real-time three-dimensional echocardiography for quantifying right ventricular volume: static and pulsatile flow studies in an anatomic in vitro model.
OBJECTIVE: The complex structural geometry of the right ventricle hinders accurate assessment of right ventricular volume and function on conventional two-dimensional echocardiography. We sought to evaluate the accuracy of real-time three-dimensional echocardiography for quantifying the volume of the right ventricle in an in vitro experimental study. METHODS: We developed 39 anatomically accurate latex phantoms of human and porcine right ventricles (range, 24-108 mL) for 39 static and 10 pulsatile models. Real-time three-dimensional scanning was performed with the models placed in a water bath and with a 3.5-MHz probe. In the dynamic models a pulsatile flow pump generated 2 different stroke volumes (29 and 64 mL/beat). Static chamber volumes and stroke volumes were verified by water displacement, which served as a reference standard. Three-dimensional echo right ventricle volumes were determined by tracing derived B- and C-scans, using the Simpson rule. RESULTS: Multiple regression analyses showed an excellent correlation between real-time three-dimensional echocardiographic determinations and the static volumes (B-scan, r = 0.99; C-scan, r = 0.98; P < .001), as well as stroke volumes in the dynamic model (B-scan, r = 0.90; C-scan, r = 0.86; P < .001). However, the C-scans tended to underestimate cavity and stroke volumes more than the B-scans (mean difference for static volume: B-scan, 1.4% +/- 9.8%; C-scan, -7.4% +/- 8.0%; P < .001; mean difference for stroke volumes: B-scan, 3.0% +/- 19.1%; C-scan, -2.5% +/- 20.9%; P < .001). CONCLUSIONS: Real-time three-dimensional echocardiography can accurately quantify right ventricle cavity volumes and stroke volumes without geometric assumptions. (+info
Use of casts in the necropsy diagnosis of fetal congenital heart disease.
OBJECTIVE: To evaluate a casting technique in the interpretation of fetal cardiac anatomy. DESIGN: In 32 fetuses, the echocardiographic and cast features were compared and correlated. PATIENTS: Three normal fetal heart specimens from spontaneous abortuses and 32 specimens from spontaneous or induced abortions with congenital heart malformation. RESULTS: There was close correlation between the echocardiographic and anatomical features in 32 abnormal fetuses studied. In some, additional features of diagnosis could be displayed on the cast and the relative sizes of the cardiac structures could be appreciated and defined. CONCLUSIONS: With increasing echocardiographic detection of congenital heart disease in early prenatal life, an increasing number of fetal heart specimens of small size are dissected for pathological confirmation. The use of silicone rubber casts to reproduce the internal anatomy proved a useful addition to dissection, providing a three dimensional model of the cardiac defect. (+info
Lipids partition caveolin-1 from ER membranes into lipid droplets: updating the model of lipid droplet biogenesis.
Caveolin-1, a putative mediator of intracellular cholesterol transport, is generally assumed to be integrated into the cytoplasmic leaflets of all cellular membranes. Lipid droplets form by budding at the endoplasmic reticulum (ER), and caveolin-1 is thought to be transferred to the droplet surface along with the cytoplasmic leaflet of ER membranes and not to enter the droplet core. We explored how caveolin-1 accesses lipid droplets from the ER by localizing caveolin-1 in ER membranes and in lipid droplets in cultured smooth muscle cells using freeze-fracture immunocytochemistry. We detected caveolin-1 in endoplasmic leaflets of ER membranes but never in cytoplasmic leaflets. Caveolin-1 was also present in lipid droplet cores. These findings are incompatible with the current hypothesis of lipid droplet biogenesis. We suggest that the inherent high affinity of caveolin-1 for neutral lipids causes caveolin-1 molecules to be extracted from the endoplasmic leaflets of ER membranes and to be transferred into the droplet core by inundating lipids during droplet formation. (+info
Comparative SEM evaluation of penetration of adhesive systems in human dentin with a non-rinse conditioner and a self-etching primer.
The purpose of this study was to compare the effect of a self-etching primer and a non-rinse conditioner with the effect of a conventional adhesive system on the penetration depth in dentin of human teeth, using scanning electronic microscopy (SEM). Fifteen human third molar teeth were sectioned into 2 pieces. All pieces were flattened with grade 600 to 1200 silicon carbide paper and divided into 6 groups: group 1 - Prime & Bond NT (NT), negative control; group 2 - 37% phosphoric acid + Prime & Bond NT (PANT), positive control; group 3 - Non-rinse Conditioner (NRC) + Prime & Bond NT (NRCNT); group 4 - NRC + Prime & Bond 2.1 (NRCPB); group 5 - NRC + Scotchbond MP (NRCSB); group 6 - Prompt L-Pop (PLP). All teeth were covered with Dyract AP. The tooth fragments were decalcified, and its resin replicas were evaluated by SEM by three previously standardized examiners. The penetration was scored from 0 (no penetration) to 3 (maximum penetration). The Kruskal-Wallis and Mann-Whitney U tests (p<0.05) showed three statistically homogeneous groups: (NT, NRCPB, NRCSB and PLP), (NRCNT) and [PANT]. The authors concluded that the self-etching primer and the non-rinse conditioner provide a lower penetration depth in human tooth dentin than the conventional adhesive system. (+info
Comparison of self-reported lifetime sun exposure with two methods of cutaneous microtopography.
There is currently no "gold standard" for measuring lifetime sun exposure. Exploration of alternatives to self-reports is important for examining illnesses related to ultraviolet light exposure. Using skin replicas obtained from 184 controls in a breast cancer case-control study (Toronto, Ontario, Canada, 2004-2005), the authors compared self-reported indicators of lifetime sun exposure with two measures of cutaneous microtopography, the Beagley-Gibson system and skin line counts. With the Beagley-Gibson system, significantly increased odds ratios were found for age (odds ratio (OR) = 1.10, 95% confidence interval (CI): 1.05, 1.16), spending 7 days outside per week during the summer (OR = 3.33, 95% CI: 1.48, 7.50), and lifetime number of sunlamp sessions. Significantly decreased odds ratios were found for having darker skin, ever giving birth, and ever using sunlamps. With the skin line count approach, significant positive associations were found for age (OR = 2.31, 95% CI: 1.23, 4.35), age squared, duration of working in outdoor jobs (OR = 0.88, 95% CI: 0.79, 0.98), and average number of outdoor activities per week at ages 20-29 years (OR = 1.05, 95% CI: 1.00, 1.10). While the Beagley-Gibson method was associated with more variables than the skin line count method, both methods require further refinement before graded skin replicas can be recommended as a substitute for self-report measures. (+info
Fractographic ceramic failure analysis using the replica technique.
OBJECTIVES: To demonstrate the effectiveness of in vivo replicas of fractured ceramic surfaces for descriptive fractography as applied to the analysis of clinical failures. METHODS: The fracture surface topography of partially failed veneering ceramic of a Procera Alumina molar and an In-Ceram Zirconia premolar were examined utilizing gold-coated epoxy poured replicas viewed using scanning electron microscopy. The replicas were inspected for fractographic features such as hackle, wake hackle, twist hackle, compression curl and arrest lines for determination of the direction of crack propagation and location of the origin. RESULTS: For both veneering ceramics, replicas provided an excellent reproduction of the fractured surfaces. Fine details including all characteristic fracture features produced by the interaction of the advancing crack with the material's microstructure could be recognized. The observed features are indicators of the local direction of crack propagation and were used to trace the crack's progression back to its initial starting zone (the origin). Drawbacks of replicas such as artifacts (air bubbles) or imperfections resulting from inadequate epoxy pouring were noted but not critical for the overall analysis of the fractured surfaces. SIGNIFICANCE: The replica technique proved to be easy to use and allowed an excellent reproduction of failed ceramic surfaces. It should be applied before attempting to remove any failed part remaining in situ as the fracture surface may be damaged during this procedure. These two case studies are intended as an introduction for the clinical researcher in using qualitative (descriptive) fractography as a tool for understanding fracture processes in brittle restorative materials and, secondarily, to draw conclusions as to possible design inadequacies in failed restorations. (+info