Physiological evidence that periodontal collagen in the rat exists as fibres prior to histological fixation.

The hypothesis that the collagen in the periodontal membrane forms a thixotropic gel in life and that the arrangement seen in histological preparations is a fixation artifact was tested by comparing the effects of various agents on the position of teeth in isolated unfixed mandibles and on the length of bundles of rat tail tendon collagen. Changing from Ringer solution to deionized water produced a reversible shortening of fibres and extrusion of teeth. Sucrose solutions produced irreversible lengthening and intrusion. Glutaraldehyde generally produced no length changes in the fibres or movements of the teeth but made both the fibres and teeth unresponsive to further changes of solution. Six mandibles in Ringer solution were heated in 5 degrees C increments to 70 degrees C. Between 60 and 65 degrees C (denaturation temperature of soft tissue collagens) the incisor extruded by 60 +/- 15 (SD) micron. This extrusion did not occur in mandibles that had been stored in formalin. These results are consistent with at least part of the periodontal collagen existing as obliquely oriented fibres before fixation. This orientation is such that contraction of the fibres could produce an eruptive force.

Amalgam bonding: visualization and clinical implications of adhesive displacement during amalgam condensation.

Resin adhesive was visualized in this in vitro study of amalgam bonding using methylene blue dye incorporated into the resin or by scanning electron microscopy. Class II amalgam cavities were prepared in extracted teeth previously stored in buffered formalin. The preparations were then restored following manufacturers' instructions, but included methylene blue dissolved in ethanol into the adhesive resin mixture. This procedure had little effect on the setting time of the resin. Following condensation and carving, excess resin was incorporated into the body of the restorations as well as onto all adjacent coronal surfaces with significant occlusal and proximal accumulations. Resin also accumulated in significant amounts on the gingival floor of the proximal box and at line angles and retentive grooves within the preparation. In conclusion, radiological studies demonstrated that artifacts produced by resin accumulation at the gingival floor of the box could be mistaken for an open margin or recurrent caries. Other potential clinical consequences of resin residue on tooth surfaces are discussed, including the problem of interproximal ledges and occlusal discrepancies. The incorporation of a radiopaque material in the resin systems should be a universal requirement.

Localization of renal kallikrein in the dog.

Renal kallikrein was estimated in glomerular, tubular and medullary fractions of dog kidneys. It was found primarily in the cortex, the highest level of activity being detected in glomeruli-rich fraction. These results support previous observation that kallikrein may be associated with the juxta-glomerular complex.

Demilune cells of the cat submandibular gland; an unlikely source of kallikrein.

The functional significance of kallikrein in the salivary gland remains unclear partially because of uncertainty over its precise cellular localization. Kallikrein was thought to originate in acinar cells, until recent evidence from cat and rat localized it primarily to the ducts. The possibility that salivary kallikrein may also be located in demilune cells was investigated in this study. - The total kallikrein content of cat submandibular glands was found to be substantially reduced by sampathetic nerve stimulation; whereas parasympathetic stimulation had no significant effect. These biochemical findings did not correlate with morphological studies that revealed almost complete depletion of the demilune cells secretory granules after stimulation of either division of the autonomic nerve supply. This lack of correlation makes it unlikely that kallikrein is present in the demilune cell secretory granules.

The localization of kallikrein in the dog and guinea-pig submandibular glands.

In the dog and guinea-pig submandibular glands kallikrein seems to be present in the striated duct cells. Following sympathetic nerve and in vivo isoproterenol stimulation of the dog and guinea-pig submandibular gland respectively, there is a reduction of kallikrein concentration. Ultrastructurally this reduction corresponds to the decrease of straited duct secretory granules in both species. Parasympathetic stimulation also causes some release of kallikrein from both species.

Spectrometer slit-power-coupling calculations for natural and laser guide-star adaptive optics.

We use numerical calculations to examine the relation between adaptive optics (AO) turbulence compensation and power coupled through a spectrometer slit for both laser and natural guide-star AO systems. The AO system and observing parameters used are relevant to the Gemini-North 8-m telescope. For this study, we separate residual tilt from residual higher-order aberrations to isolate their relative effects under a variety of operating conditions. Our results demonstrate that slit-coupled intensity is not uniquely determined by system Strehl alone; we show that this is due to the differing effects of higher-order and tilt aberrations on the shape of the compensated point-spread function. For the Gemini spectrometer and AO system, the wider point-spread function halo associated with an added residual higher-order aberration reduces slit-coupled intensity more rapidly than a broad point-spread function core induced by residual tilt.

Model-based image reconstruction by means of a constrained least-squares solution.

The problem of the optimal use of object model information in image reconstruction is addressed. A closed-form solution for the estimated object spectrum is derived with the Lagrange multiplier technique, which assumes a measured image, knowledge of the optical transfer function, statistical information about the measurement noise, and a model of the object. This reconstruction algorithm is iterative in nature because the optimal Lagrange multiplier is not generally known at the start of the problem. We derive the estimator, describe one technique for determining the optimal Lagrange multiplier, demonstrate a stopping criterion based on the mean-square error between a noise-free image and the photon-limited version of the image, and show representative results for both filled- and sparse-aperture imaging applications.

Modeling the combined effect of static and varying phase distortions on the performance of adaptive optical systems.

The end-to-end performance achieved by an adaptive optical (AO) imaging system is determined by a combination of the residual time-varying phase distortions associated with atmospheric turbulence and the quasi-static unsensed and uncorrectable aberrations in the optical system itself. Although the effects of these two errors on the time-averaged Strehl ratio and the time-averaged optical transfer function (OTF) of the AO system are not formally separable, such an approximation is found to be accurate to within a few percent for a range of representative residual wave-front errors. In these calculations, we combined static optical system aberrations and time-varying residual phase distortion characteristics of a deformable mirror fitting error, wave-front sensor noise, and anisoplanatism. The static aberrations consist of focus errors of varying magnitudes as well as a combination of unsensed and uncorrectable mirror figure errors derived from modeling by the Gemini 8-Meter Telescopes Project. The overall Strehl ratios and OTF's that are due to the combined effect of these error sources are well approximated as products of separate factors for the static and time-varying aberrations, as long as the overall Strehl ratio that is due to both errors is greater than approximately 0.1. For lower Strehl ratios, the products provide lower bounds on the actual values of the Strehl ratio and the OTF. The speckle transfer function is also well approximated by a product of two functions, but only where AO compensation is sufficiently good that speckle imaging techniques are usually not required.

Linear reconstruction of compensated images: theory and experimental results.

Linear image reconstruction techniques are proposed for postprocessing astronomical images measured with compensated imaging systems. Linear techniques use averaging to overcome the effects of noise and deconvolution to remove system effects. Experimental results from compensated image measurements of four single stars and one binary star at visible wavelengths are reported for the first time, to our knowledge, and a previously derived analytic expression relating the statistics of the compensated optical transfer function to the compensated image spectrum signal-to-noise ratio is verified. The performance of deconvolution on a bright binary star with angular subtense previously estimated to be 0.52 arcsec (2.52 microrad) is demonstrated.

Compensated speckle imaging: theory and experimental results.

Previous analyses have predicted that improved power-spectrum estimation results from application of speckle-imaging postprocessing to compensated astronomical images. We report the first results, to our knowledge, of compensated-speckle-imaging experiments, conducted at a compensated telescope operated by the U.S. Air Force, that confirm these predictions. The power-spectrum signal-to-noise ratio is used as the metric for evaluating the performance. We report the results of power-spectrum estimation for a single star and three binary stars, and we reconstruct images of the binary stars using the bispectrum method to obtain the Fourier phase of the object. Compensated and uncompensated results are compared. A previously derived expression that expresses the power-spectrum signal-to-noise ratio in terms of the compensated optical transfer function statistics and object parameters is verified by experimental data.