Multiport-readout frame-transfer 5 megapixel CCD imaging system for TEM applications.

A multiport-readout, frame-transfer charge-coupled device (CCD) digital imaging system has been successfully developed and tested for intermediate-high-voltage electron microscopy (IVEM) applications up to 400 keV. The system employs a back-thinned CCD with 2560 x 1960 pixels and a pixel size of 24 microm x 24 microm. In the current implementation, four of the eight on-chip readout ports are used in parallel each operating at a pixel rate of 1- or 2-MHz so that the entire CCD array can be read out in as short as 0.6 s. The frame-transfer readout functions as an electronic shutter which permits the rapid transfer of charges in the active pixels to four masked buffers where the charges are readout and digitized while the active area of the CCD is integrating the next frame. With a thin film-based phosphor screen and a high-performance lens relay, the system has a conversion factor of 2.1 digital units per incident electron at 400 keV, and a modulation transfer function value of 14% at the Nyquist frequency.

Physicochemical characterization of the nucleational core of matrix vesicles.

While previous studies revealed that matrix vesicles (MV) contain a nucleational core (NC) that converts to apatite when incubated with synthetic cartilage lymph, the initial mineral phase present in MV is not well characterized. This study explored the physicochemical nature of this Ca2+ and Pi-rich NC. MV, isolated from growth plate cartilage, were analyzed directly by solid-state 31P NMR, or incubated with hydrazine or NaOCl to remove organic constituents. Other samples of MV were subjected to sequential treatments with enzymes, salt solutions, and detergents to expose the NC. We examined the NC using transmission electron microscopy, energy-dispersive analysis with x-rays, and electron and x-ray diffraction, Fourier transform-infrared spectroscopy, high performance thin-layer chromatographic analysis, and SDS-polyacrylamide gel electrophoresis. We found that most of the MV proteins and lipids could be removed without destroying the NC; however, NaOCl treatment annihilated its activity. SDS-polyacrylamide gel electrophoresis showed that annexin V, a phosphatidylserine (PS)-dependent Ca2+-binding protein, was the major protein in the NC; high performance thin-layer chromatographic analysis revealed that the detergents removed the majority of the polar lipids, but left significant free cholesterol and fatty acids, and small but critical amounts of PS. Transmission electron microscopy showed that the NC was composed of clusters of approximately 1.0 nm subunits, which energy-dispersive analysis with x-rays revealed contained Ca and Pi with a Ca/P ratio of 1.06 +/- 0. 01. Electron diffraction, x-ray diffraction, and Fourier transform-infrared analysis all indicated that the NC was noncrystalline. 1H-Cross-polarization 31P NMR indicated that the solid phase of MV was an HPO42--rich mixture of amorphous calcium phosphate and a complex of PS, Ca2+, and Pi. Taken together, our findings indicate that the NC of MV is composed of an acid-phosphate-rich amorphous calcium phosphate intermixed with PS-Ca2+-Pi, annexin V, and other proteins and lipids.

Performance of thin foil scintillating screen for transmission electron microscopy.

Scintillating screens made by coating a thin metal foil with a layer of phosphor appear to be attractive for transmission electron microscopy applications. We report here the brightness and resolution in the voltage range of 100-400 kV of such a screen made of a 10 microns layer of P20 phosphor on a 2 microns Al foil. Both brightness and resolution are superior to that of a screen made by coating a glass plate with a similar layer of phosphor. An exciting property of such a device is that its resolution improves slightly at higher voltages. This, combined with its excellent resistivity to radiation damage and stability under the electron beam, makes it a good candidate for high-voltage applications.

Performance characteristics of radioluminescent fiber optics as electron scintillators.

Terbium-activated radioluminescent fiber-optic face plates have been studied for their suitability as electron scintillators. The energy conversion efficiency of such material is determined to be about 2.5% in the electron energy range of 100-400 keV tested. The resolution is approximately 40 microns at electron energy of 100 keV, as measured by the rise width of an edge. The main advantage of such a device is the potential simplification of CCD camera designs, since it functions both as a scintillator as well as a light guide so that it can be coupled direct to a CCD detector.

Cytological examination of reduction bodies of Corvomeyenia carolinensis Harrison (porifera: spongillidae).

Freshwater sponges, Corvomeyenia carolinensis Harrison, were placed into tap water to induce degenerative reduction body formation. Reduction bodies were examined using light and electron microscopy in order to define their histochemical and ultrastructural characteristics. The reduction body of freshwater sponges is an extremely simple developmental system consisting primarily of an archeocyte reserve delimited by a simple squamous pinacoderm. The freshwater sponge reduction body displays many similarities to overwintering phases of marine sponges. The system presents an unusually straightforward vehicle for investigations of degeneration and regeneration as processes in developmental biology and may represent a reasonable vehicle in which to examine the process of the genesis of lysosomes.

The cytology of the testaceous rhizopod Lesquereusia spiralis (Ehrenberg) Penard. I. Cytochemistry.

The cytology of the testaceous ameba, Lesquereusia spiralis (EHRENBERG) PENARD, has been described using a broad spectrum of cytochemical methods. Most cytological characteristics lie within the range of variability reported for free living non-shelled amebas. The shell of L. spiralis is complex, being composed of siliceous platelets positioned in an organic matrix. This interplatelet matrix is composed of sulfomucin complexed with basic protein. The matrix contains a complex of pore-like structures. The structure and possible origins and function of this matrix complex are discussed.