Multi-Modal Digital Impressions For Palatal Defects.

INTRODUCTION: This in-vitro study investigated limitations of intra-oral scanners (IOS) in capturing palatal defects at decreased mouth openings. The trueness and precision of composite 3D-printed models from Cone-Beam Computed Tomography (CBCT) and IOS were measured. METHODS: A partially dentate palatal defect model was scanned with IOS (3M™TrueDefinition) at various simulated mouth openings. Five silicone impressions were poured in gypsum. Scans were taken using 3M™TrueDefinition; Planmeca Planscan®, n=5 each. Model was scanned on two CBCT (PlanmecaProFace®; Accuitomo170®CBCT, n=5 each). Geomagic®Control2014™ was used to create composite-models merging CBCT with IOS. Thirty composite-models were 3D-printed. Trueness and precision were measured. Pearson Correlation Coefficients measured correlation between mouth opening and data capture. Data analysed using Kruskal-Wallis, Wilcoxon rank-sum, and ANOVA. Statistical significance inferred when p⟨0.05. RESULTS: Mouth openings ⟨20mm, IOS didn't capture information of soft tissue. Increased mouth opening positively correlated with increased data capture(r=0.93, p=0.001). AccuitomoCBCT and TrueDefinition IOS composite-models had the highest (trueness) and [precision](median (IQR) 0.172 mm(0.062-0.426)); [mean [SD] 0.080 mm [0.008]]. Casts had the lowest results (median (IQR) 0.289 mm(0.119-1.565));[mean [SD] 0.338 mm [0.089]](p⟨0.001). CONCLUSION: Mouth opening ⟨20mm resulted in insufficient data capture by IOS for clinical applications. Composite digital models showed promising trueness and precision results.

Two-colour pump-probe experiments with a twin-pulse-seed extreme ultraviolet free-electron laser.

Exploring the dynamics of matter driven to extreme non-equilibrium states by an intense ultrashort X-ray pulse is becoming reality, thanks to the advent of free-electron laser technology that allows development of different schemes for probing the response at variable time delay with a second pulse. Here we report the generation of two-colour extreme ultraviolet pulses of controlled wavelengths, intensity and timing by seeding of high-gain harmonic generation free-electron laser with multiple independent laser pulses. The potential of this new scheme is demonstrated by the time evolution of a titanium-grating diffraction pattern, tuning the two coherent pulses to the titanium M-resonance and varying their intensities. This reveals that an intense pulse induces abrupt pattern changes on a time scale shorter than hydrodynamic expansion and ablation. This result exemplifies the essential capabilities of the jitter-free multiple-colour free-electron laser pulse sequences to study evolving states of matter with element sensitivity.

Cholinergic inhibition by botulinum toxin in a rat model of congenital glaucoma raises intraocular pressure.

BACKGROUND: Cholinergic receptors are crucially involved in the regulation of intraocular pressure (IOP). Muscarinic agonists in the trabecular meshwork tissue increase aqueous humour outflow facility by a direct stimulation of ciliary muscle contraction. We investigated the contribution of cholinergic state to IOP regulation. METHODS: Intracameral injections of botulinum toxin A (BTA) were applied in a group with four normotensive rats and a group with four glaucoma rats (genetic glaucoma model). BTA is a potent neurotoxin which inhibits presynaptic cholinergic transmission for 6-8 weeks. The same amount of saline was injected in a third group of four normotensive rats (sham condition). IOP measurements were performed preoperatively, as well as 1, 2 and 4 weeks postoperatively. Afterwards, the rat eyes were removed and subjected to immunhistochemistry and western blotting analysis using antibodies against choline acetyltransferase (CHAT). RESULTS: Mean IOP in both normotensive groups was unaltered compared with the preoperative status. The glaucoma group showed a significant increase in the mean IOP (Student test, p<0.05) and a signal reduction for CHAT by immunolabelling in the trabecular meshwork compared with the other two groups. Western blotting confirmed the decreased expression of CHAT. CONCLUSION: Our results suggest that modification of the cholinergic status in the normotensive eye does not significantly affect the IOP; cholinergic regulation of the ciliary trabecular meshwork may have differential levels of control, apart from the ciliary muscle contraction. Moreover, it seems that differential expression of the muscarinic receptors may be responsible for the decreased trabecular cholinergic state occurring in this rat model of glaucoma.

Reduced expression of the gap junction protein Connexin 43 in keratoconus.

PURPOSE: The purpose of the present study was to examine whether keratoconus, which is a bilateral noninflammatory corneal ectasia with multifactorial aetiology, shows altered expression of Connexin (Cx43). Cx43 is an important gap junction protein that contributes crucially to epithelial and stromal integrity of cornea. METHODS: Eight keratoconic human corneal buttons were examined with immunohistochemistry and Western blotting and compared with eight normal human corneal buttons, to unravel changes in Cx43 expression. RESULTS: All normal corneas exhibited similar epithelial Cx43 expression patterns, with the protein located in the basal epithelial layer. In contrast, some keratoconic corneas showed an altered pattern of immunostaining and Western blotting confirmed a decreased expression of Cx43 in keratoconic corneas. CONCLUSIONS: Our results indicate that a decrease in Cx43 amount together with functional alteration of the protein is associated with keratoconus pathophysiology However, these changes apply only to some of the corneas examined and may not generally account for the development of keratoconus.

Combined microscope for scanning X-ray transmission and surface topography.

A brief description is given of a scanning transmission X-ray microscope (STXM) for use with synchrotron radiation allowing simultaneous X-ray imaging and imaging of surface topography. Surface topography, appropriate to both conducting and non-conducting samples, is sensed by successive "specimen hopping" i.e. planting of the specimen at and withdrawal from a fixed sharp tip, or stylus, formed by the scanning tip of an atomic force microscope (AFM). First experiments are described with 3 keV photons with zone plate resolution of about 100 nm. Preliminary work is also mentioned to add a collimator to improve spatial resolution (in principle to < 20 nm for 300-500 eV photons), by installing a pierced AFM tip at the zone plate focus. The topographic measurement, currently with specimen thickness resolution of about 10 nm, but potential for approximately 1 nm, and feature-dependent in-specimen plane resolution of about 100 nm as limited by the stylus geometry, is an adjunct to the STXM results, to provide information helpful in the interpretation of the X-ray image. Examples are given for simple specimens of the gains in specimen understanding from simultaneous STXM and hopping contact topographic images. Typical applications areas are radiation damage, and dynamic processes like specimen corrosion.

Incoherent imaging with the soft X-ray microscope

The imaging characteristics for X-ray wavelengths in the "water window" under incoherent imaging conditions (large detector aperture) are examined for the King's College London scanning transmission X-ray microscope with zone-plate objective installed at the Daresbury (UK) synchrotron. The principal consideration was to express image theory, incorporating wave aberrations and apodised zone plates, and to apply the theory to experimental data. Comparisons are made, showing reasonable agreement, for a range of defocus values and two wavelengths. Due to problems in fabrication it was necessary to determine the effective, or operational, zone-plate parameters (radius of outermost active zone rN, width of outermost active zone drN); this was accomplished by through-focus series. Calculated point spread functions were used to deblurr images, in through-focus series of two-dimensional scanned X-ray images of specimen holes and test grating patterns. Significant contrast enhancement is achieved after deconvolution with a best point-to-point resolution of about 35 nm.

Preneoplastic significance of hepatic iron-free foci in genetic hemochromatosis: a study of 185 patients.

Sublobular nodules of hepatocytes free of iron or exhibiting much less iron than the surrounding parenchyma, referred to in this study as iron-free-foci, are frequently found in the livers of patients with genetic hemochromatosis complicated by hepatocellular carcinoma. To test the hypothesis that such nodules are preneoplastic lesions, iron-free foci were sought in the initial liver biopsy specimens of 185 patients with untreated and uncomplicated genetic hemochromatosis. Iron-free foci were found in 14 (7.6%) patients, all men, aged from 38 to 76 yr, with heavy iron overload and with fibrosis or cirrhosis. Twelve patients with iron-free foci were followed for 0.9 to 15 yr (7 +/- 6 yr). In six (50%), HCC developed, compared with 2 (8%) from a control group consisting of 24 patients without IFF matched according to age, sex, degree of fibrosis, liver iron amount and follow-up duration. The mean number of iron-free foci per iron-free foci-positive specimen was 3.2 +/- 2.1. Ten patients had dysplastic aspects in their iron-free foci, and four had intrahepatocytic iron-positive inclusions at the periphery of iron-free foci. Proliferative cell nuclear antigen was positive in 75% of iron-free foci and in 24% +/- 21% of hepatocyte nuclei in iron-free foci. This study clearly demonstrates that iron-free foci are proliferative lesions and strongly suggests that such nodules are preneoplastic foci. Therefore the finding of IFF in the initial liver biopsy specimen from a patient with genetic hemochromatosis should lead to regular screening for hepatocellular carcinoma.

Effect of chronic iron overload on procollagen gene expression.

The pathogenesis of hepatic fibrosis and cirrhosis in genetic hemochromatosis may involve a direct effect of excess iron on collagen synthesis in the liver. To investigate this theory, we measured procollagen messenger RNA levels (types I, III and IV) in the livers of rats in which we produced chronic parenchymal iron overload by feeding them dietary carbonyl iron (2.5%, wt/wt) for up to 18 mo. This feeding resulted in predominantly parenchymal iron deposition in a periportal distribution similar to that seen in genetic hemochromatosis. Increased amounts of collagen fibrils were observed in iron-loaded livers on electron microscopy; all iron-loaded livers showed some periportal fibrosis. Although very high hepatic iron concentrations (range = 340 to 1,100 mumol/gm dry wt) were achieved in the carbonyl iron-loaded rats, we saw no consistent difference between steady-state messenger RNA levels for procollagens types I, III and IV in control and iron-loaded livers examined at five different time points up to 18 mo. Messenger RNA levels of the cytokine transforming growth factor-beta 1, which has been implicated as having a role in the production of extracellular matrix proteins, were also measured. No significant differences were observed between iron-loaded and control livers. These results suggest that excess parenchymal iron does not have a direct effect on the expression of the procollagens or transforming growth factor-beta 1 genes in iron-loaded livers and that factors other than, or in addition to, iron are necessary for fibrosis to occur.

Modification by pyrethroids and DDT of phosphorylation activities of rat brain sodium channel.

The effects of pyrethroids and DDT on the alpha-subunit protein of the rat brain sodium channel were studied by using both native and exogenously added cAMP-dependent protein kinases. For this purpose, the sodium channel was partially purified, using the method of Hartshorne and Catterall [J Biol Chem 259: 1667-1675, 1984], and 32P-phosphorylated using [gamma-32P]ATP and exogenously added catalytic subunit of cAMP-dependent protein kinase. By comparing the phosphorylation patterns of the isolated sodium channel to those of the partially purified or unpurified (i.e. intact synaptosomes) preparations, it was concluded that the alpha-subunit of the voltage-sensitive sodium channel protein is the only phosphorylatable protein present at the 260 kD molecular weight range on the sodium dodecyl sulfate-polyacrylamide gel electrophoretogram. Phosphorylation of the alpha-subunit was induced by depolarization, and this process was inhibited by 10(-6) to 10(-10) M 1R-deltamethrin, but not by 1S-deltamethrin, the latter being an inactive enantiomer of the former. DDT produced a similar effect, but only at a higher concentration range. By using lysed synaptosomal membranes, it was possible to study the direct effects of these compounds on the alpha-subunit, which were similar to those produced by depolarization of intact synaptosomes.

Multiple signals in STEM.

A brief description is given of the eight image signals that can be simultaneously recorded in digital form using an appropriate data recording system and high resolution STEM; this involves a set of detectors covering bright and dark field. Details are provided of the collection and manipulation of image data for STEM, including on-line estimation of off-focus distance, on-line assessment of astigmatism, on-line signal to noise ratio in any or all detectors; examples of all three procedures are given. The use of the data recording system is discussed together with some aspects of image display, including the use of colour. A method is introduced of providing, using the appropriate hardware, a prescribed colour map (image intensity converted to colour) using replaceable PROMS. Two off-line procedures are considered. One is the Karhunen-Loeve transform and its application to bringing together the information contained within the multiple signals, and the other is the discrete cosine transform by which the storage problem for digital image storage may be reduced, according to the image, by between 15 and 30 times.