Gerd Magdowski

Scanning electron microscopic analysis of foldable acrylic and hydrogel intraocular lenses

Objective: To analyze the surface quality of foldable acrylic and hydrogel intraocular lenses (IOLs). Setting: Cullen Eye Institute, Baylor College of Medicine, Houston, Texas, and Institute of Anatomy and Cellular Biology, University of Giessen, Germany. Methods: We studied eight foldable IOL models with optics made of six different acrylate/methacrylate polymers: Acrylens ACR360 (loptex), AcrySof MA60BM (AIcon), MemoryLens U940A (Mentor), 92S and 92C (Morcher), Hydroview H60M (Storz), HydroSof SH30BC (Alcon), and ISH66 (Corneal). Four IOLs of each design were examined. Light and scanning electron microscopy were performed before and after IOL folding with forceps. Results: All IOL models had excellent optic and haptic surfaces. The haptic‐optic junctions revealed minimal empty spaces or irregularities in three of the five three‐piece IOLs and smooth surfaces in all one‐piece IOLs. Minimal surface alterations and superficial defects caused by folding were detectable in the two acrylate (acrylic) IOLs (loptex ACR360, Alcon MA60BM) with low water content. Conclusion: Intraocular lenses of acrylate/methacrylate polymers had excellent surface quality. The acrylic IOLs were vulnerable to mild folding or forceps defects; however, these were less marked than those previously noted with poly(methyl methacrylate) IOLs.

Scanning electron microscopic characteristics of Phakic intraocular lenses

OBJECTIVE To analyze the surface quality of new generation phakic intraocular lenses (IOLs). DESIGN Experimental materials study. MATERIALS Three different new generation phakic IOLs: angle-fixated anterior chamber lens Chiron Vision NuVita MA20 (polymethylmethacrylate [PMMAD, iris-fixated anterior chamber lens Ophtec Artisan Iris-Claw (PMMA), posterior chamber lens Staar ICM (polymer from porcine collagen and 2-hydroxyethyl methacrylate [HEMA]). METHODS Representative samples of three different phakic IOLs underwent surface and edge-finish examination with light microscopy (LM). The phakic IOLs were then examined by use of scanning electron microscopy (SEM), and particular attention was given to optic surface quality, edge finish, haptic, and optic/haptic junction. RESULTS In all IOLs the LM examination showed a smooth and homogeneous surface. No irregularities, particularly at the optic front and back surface, optic edge, haptic, and the optic/haptic junctions, were detected by SEM. One exception was a minor surface roughness at the claws of an Artisan iris-fixated anterior chamber IOL. CONCLUSIONS Phakic IOLs are implanted either in the anterior or posterior chamber of healthy eyes, and high standards for their surface quality are required. The evaluation of surface properties with LM and SEM did not reveal any defects that contraindicate the implantation of phakic IOLs.

Harbour seal (Phoca vitulina) PMN and monocytes release extracellular traps to capture the apicomplexan parasite Toxoplasma gondii.

Extracellular traps (ETs) are composed of nuclear DNA as backbone adorned with histones, cytoplasmic antimicrobial peptides/proteins which are released from a range of vertebrate and invertebrate host immune cells in response to several invading pathogens. Until now this ancient novel innate defence mechanism has not been demonstrated in any marine mammal. Interactions of harbour seal (Phoca vitulina)-PMN and -monocytes with viable tachyzoites of Toxoplasma gondii were investigated in this respect in vitro. For the demonstration and quantification of harbour seal PMN- and monocyte-derived ETs, extracellular DNA was stained with Sytox Orange. Fluorescence assays as well as scanning electron microscopy (SEM) analyses demonstrated PMN- and monocyte-promoted ET formation rapidly being induced upon contact with T. gondii-tachyzoites. The co-localisation of extracellular DNA decorated with histones (H3), neutrophil elastase (NE) and myeloperoxidase (MPO) in parasite entrapping structures confirmed the classical characteristics of PMN- and monocyte-promoted ETs. Exposure of harbour seal PMN and monocytes to viable tachyzoites resulted in a significant induction of ETs when compared to negative controls. Harbour seal-ETs were efficiently abolished by DNase I treatment and were reduced after PMN and monocytes pre-incubation with the NADPH oxidase inhibitor diphenilane iodondium. Tachyzoites of T. gondii were firmly entrapped and immobilised within harbour seal-ET structures. To our best knowledge, we here report for the first time on T. gondii-induced ET formation in harbour seal-PMN and -monocytes. Our results strongly indicate that PMN- and monocyte-triggered ETs represent a relevant and ancient conserved effector mechanism of the pinniped innate immune system as reaction against the pathogenic protozoon T. gondii and probably against other foreign pathogens occurring in the ocean environment.

Lipovitellin—phosvitin crystals with orthorhombic features: Thin-section electron microscopy, gel electrophoresis, and microanalysis in teleost and amphibian yolk platelets and a comparison with other vertebrates

Yolk-platelet crystals in the teleosts Pelvicachromis pulcher and Noemacheilus barbatulus and the amphibians Xenopus laevis, Rana temporaria, R. esculenta, and Triturus sp. have been studied by electron diffraction and imaging using a standardized processing (glutaraldehyde-osmium tetroxide fixation, glutaraldehyde-urea embedding, thin-section staining), by X-ray microanalysis, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis of their constituents. The crystal lattice is orthorhombic having--following standardized processing--in three amphibians a = 9.0 nm, b = 17.6 nm, c = 19.2 nm, and in the two teleosts a = 8.9 nm, b = 17.6 nm, c = 20.0 nm (averages). These values are very close to X-ray data from wet crystals (Xenopus laevis). Crystal images in the three axial projections point to the presence of space group P212121 (or an approximation of it since the lipovitellin dimers cannot be fully equivalent in some cases), to differences between the phosvitins of the two teleosts, and to a highly unusual stain exclusion from large crystal constituents interpreted as representing lipovitellin dimers. Microanalysis in ultrathin cryosections and other preparations revealed K and Cl to be the prominent ions in the crystals (and in the superficial layer of the platelet). Gel electrophoresis (including data of cyclostomes) showed considerable molecular variations despite a closely similar crystal architecture, emphasizing a physiological significance of the architecture, which may have remained conserved for nearly 400 million years according to paleontologic views.

Myocardial remodelling in left ventricular atrophy induced by caloric restriction

Changes in body weight due to changes in food intake are reflected by corresponding changes in the cardiac phenotype. Despite a growing body of literature on cardiac hypertrophy associated with obesity, little is known on the atrophic remodelling of the heart associated with calorie restriction. We hypothesized that, besides the cardiomyocyte compartment, capillaries and nerve fibres are involved in the atrophic process. C57Bl6 mice were kept on normal diet (control group) or at a calorie‐restricted diet for 3 or 7 days (n = 5 each). At the end of the protocol, mice were killed and the hearts were processed for light and electron microscopic stereological analysis of cardiomyocytes, capillaries and nerve fibres. Body, heart and left ventricular weight were significantly reduced in the calorie‐restricted animals at 7 days. Most morphological parameters were not significantly different at 3 days compared with the control group, but at 7 days most of them were significantly reduced. Specifically, the total length of capillaries, the volume of cardiomyocytes as well as their subcellular compartments and the interstitium were proportionally reduced during caloric restriction. No differences were observed in the total length or the mean diameter of axons between the cardiomyocytes. Our data indicate that diet‐induced left ventricular atrophy leads to a proportional atrophic process of cardiomyocytes and capillaries. The innervation is not involved in the atrophic process.

Crystalline preparations of rhombohedral porcine insulin as studied by electron diffraction.

Porcine rhombohedral insulin crystals, mainly of the varieties containing 2.5 and 0.8% Zn, were studied by electron diffraction in the fixed, embedded, and thin-sectioned state. Stable and reproducible diffraction patterns (resolution limit 0.8 nm) were obtained only with 2.5% Zn-insulin crystals. Suitable fixatives were combinations of OsO 4 and glutaraldehyde; suitable embedding media were an epoxy resin and a glutaraldehyde-urea resin. The crystals, in the embedded state, were trigonal (rhombohedral cell) with a H = 7.4 nm, c = 3.1 nm as measured in the diffraction patterns. In discussing these values, a number of possible errors are considered, i.e., reciprocal lattice spikes, section compression, and mass loss from sections due to irradiation. For comparison wet unfixed 2.5% Zn-insulin crystals were also studied in X-ray powder patterns (Guinier, low angle), yielding a H = 8.2 nm, c = 3.3 nm (rhombohedral cell). These values indicate a close resemblance to porcine 2 Zn-insulin crystals (0.4% Zn), apparently shown here for the first time. Confidence intervals for a H and c were computed by use of their asymptotic distribution. The results are discussed in view of electron microscope studies of intracellular protein crystals, where, in conclusion, a reduction in length of approximately 8% is to be expected in reference to the hydrated state.

Computerized three-dimensional reconstructions of serial sections in electron microscopy

To improve reconstructive 3D electron microscopy novel methods are discussed to represent and process serial section images in a cuberille environment. This includes the analysis of the transfer characteristics of the image detection system, the use of laser-induced fiducials for deformation correction and alignment, the control of section thickness by EELS and the use of ESI to image thick sections.

The cephalic aorta of Sepia officinalis (Cephalopoda, Dibranchiata): structural muscular specialisations of a high-pressure vessel

Abstract Electron microscopic studies on the cephalic aorta of Sepia officinalis characterise the tunica media as a highly specialised type of cross-striated muscle with complex cord-like and branched-off z-patches. These contain 10-nm filaments and show a lattice-like substructure which is evidence that they play a role in the particular viscoelastic function of this vessel. Analyses of freeze-etched preparations as well as TEM sections demonstrate desmosome-like contacts and largely extended gap junction areas between the closely interdigitated muscle cells. They suggest that the tunica media represents a functional syncytium in which the marginal muscle cells, the only ones to be innervated, can be seen as pace-maker cells in modulating the tonus of the vessel.