Autoradiographic and cytochemical studies of phagocytic cells in selected fibre tracts of the mouse periodontium.

Proliferative and protein synthetic activities of phagocytic cells of specific fibre tracts of the periodontium of C57Bl mice were employing autoradiographic techniques; these were combined with a histochemical technique for horseradish peroxidase (HRP) as a marker for phagocytic activity. Animals were injected either with [3H]thymidine as a marker for proliferative activity, or with [3H]proline as a marker for protein synthetic activity prior to HRP injection. Blocks from the maxillae of experimental and control animals were fixed, decalcified, and sectioned at 50 micrometers. These were incubated with HRP localization media, dehydrated and flat embedded in Epon 812 wafers. The entire length of the periodontium, including adjacent tooth and bone, were selectively cut from the wafers, mounted on epoxy blocks and serially sectioned at 2 micrometers. Slides containing these sections were then dipped in NTB-3 nuclear track emulsion, and after appropriate exposure times, were developed and post-stained. Sections were examined microscopically, employing an ocular grid, and phagocytic cells within each area examined were delineated as either 'fibroblast-like' (FL cells) or 'endothelial/macrophage-like' (EML cells) according to criteria such as morphology, location, orientation and proximity to a vascular channel. They were then subclassified as labelled or unlabelled with respect to the autoradiographic markers. The thymidine labelling index obtained for non-phagocytic FL cells was 3.09%; this was more than twice that for phagocytic FL cells (1.35%). Similarly phagocytic FL cells in all regions studied incorporated less than half as much [3H]proline as did their non-phagocytic counterparts. This was determined by silver grain counts over HRP-stained and unstained cells using a matched pair system. In addition, the variation of the relative number of phagocytic FL cells in specific fibre tracts suggested a relationship to functional demand. The distribution of these cells was closely related to experimentally determined rates of protein turnover. Phagocytic FL cells have a markedly reduced proliferative rate and synthesize proline-containing proteins at a reduced rate. This may reflect protein production primarily for the purpose of cell maintenance. These findings are consistent with the presence of subpopulations of fibroblasts (or fibrocytes) developmentally or functionally modified for phagocytosis; alternatively, this could signify modulation of fibroblasts from primarily biosynthetic activities to degradative functions in response to varying microenvironmental conditions.

Number and shape of tears in aphakic retinal detachment: its relationship with different surgical techniques of cataract extraction.

An analysis is made of retinal detachments which occurred in patients operated upon for cataract with different surgical techniques, as well as the degree of operating experience of the surgeons. The main clinical features of the detachments are recorded such as number, shape, localization of retinal tears, type and extension. The different surgical techniques are explained and a statistical comparison of the incidence of detachments is set up.

Argon laser barrage as complementary therapy in surgery with minimal plombage.

A group of patients with retinal detachments was selected whose characteristics allowed the employment of much less traumatizing surgical techniques, such as localized plombs, cryotherapy or diathermy. Once the patient was operated and the retina flattened out itself completely, usually after 1 or 2 days, we proceeded to photocoagulate the degenerative areas of the retina which were usually present with argon laser. Also, a laser barrier was performed, generally at the equatorial level in order to avoid manipulative techniques in the operating room as much as possible. The study comprises the main clinical features of the detachment, the surgical technique employed, and the commented results. The follow-up time of the group in study ranged from 6 months to 2 years.

Laser tuners using circular piezoelectric benders.

This paper presents the results of an experimental evaluation of a new type of piezoelectric ceramic device designed for use as a laser mirror tuner. Thin plates made from various materials were assembled into a circular bimorph configuration and tested for linearity of movement, maximum travel, and resonant frequency for varying conditions of clamping torque and mirror loading values. Most of the devices tested could accept mirror diameters up to approximately 1.3 cm and maintain a resonant frequency above 2 KHz. Typical mirror translation without measurable tilt was +/-20 microm or greater for applied voltages of less than +/-300 V.

Temperature-dependent etalon effects in laser systems.

This paper deals theoretically with the variety of temperature-dependent extracavity and intracavity etalon effects that must be considered in the design of laser systems. All examples refer to carbon dioxide lasers and materials appropriate for use with carbon dioxide lasers, although the analyses and results are valid for other lasers as well. Etalon effects in extracavity flats and lenses are examined, and the temperature-dependent transmittance is calculated. It is shown that the transmission of a ten-surface optical system, assumed to be uniform in temperature with 1% antireflectance coatings on each surface, can vary 18% as the system temperature varies. Temperature-dependent variations in the performance of a carbon dioxide laser are analyzed with respect to etalon effects of the laser resonator and with respect to etalon-within-an-etalon effects due to intracavity elements, e.g., an electrooptic modulator crystal. It is shown that etalon effects can produce line hopping that cannot be prevented by tuning of the laser.