Atomic force microscopy study of living diatoms in ambient conditions.

We present the first in vivo study of diatoms using atomic force microscopy (AFM). Three chain-forming, benthic freshwater species -Eunotia sudetica, Navicula seminulum and a yet unidentified species - are directly imaged while growing on glass slides. Using the AFM, we imaged the topography of the diatom frustules at the nanometre range scale and we determined the thickness of the organic case enveloping the siliceous skeleton of the cell (10 nm). Imaging proved to be stable for several hours, thereby offering the possibility to study long-term dynamic changes, such as biomineralization or cell movement, as they occur. We also focused on the natural adhesives produced by these unicellular organisms to adhere to other cells or the substratum. Most man-made adhesives fail in wet conditions, owing to chemical modification of the adhesive or its substrate. Diatoms produce adhesives that are extremely strong and robust both in fresh- and in seawater environments. Our phase-imaging and force-pulling experiments reveal the characteristics of these natural adhesives that might be of use in designing man-made analogues that function in wet environments. Engineering stable underwater adhesives currently poses a major technical challenge.

Iron as catalyst for oxidative stress in the pathogenesis of Parkinson's disease?

The mechanisms leading to degeneration of melanized dopaminergic neurons in the brain stem, and particularly in the substantia nigra zona compacta (SNZC) in patients with Parkinson's disease (PD) are still unknown. Demonstration of increased iron Fe(III) in SNZC of PD brain has suggested that Fe-melanin interaction may contribute to oxidative neuronal damage. Energy dispersive X-ray electron microscopic analysis of the cellular distribution of trace elements revealed significant Fe-peaks, similar to those of a synthetic melanin-Fe(III) complex in intracytoplasmic electron-dense neuromelanin granules of SNZC neurons, with highest levels in a case of PD and Alzheimer's disease (AD). No Fe increase was found in Lewy bodies or in SN neurons of control specimens. The relevance of chemical reactions of dopamine (DA), 5-hydroxydopamine (5-OHDA), and 6-hydroxydopamine (6-OHDA) with Fe(III) and with dioxygen for the pathogenesis of PD was investigated. An initiating mechanism related to interaction between Fe and neuromelanin is suggested which results in accumulation of Fe(III) and a continuous production of cytotoxic species inducing a cascade of pathogenic reactions ultimately leading to neuronal death.

The role of transition metals in the pathogenesis of Parkinson's disease.

The mechanisms that lead to degeneration of melanized dopaminergic neurons in the brain stem, and particularly in the substantia nigra (SN) in patients with Parkinson's disease (PD) are still unknown. Demonstration of increased iron (Fe) in SN of PD brain has suggested that Fe-melanin interaction may contribute to oxidative neuronal damage. Energy dispersive X-ray electron microscopic analysis of the cellular distribution of trace elements revealed significant Fe peaks, similar to those of a synthetic melanin-Fe3+ complex, in intraneuronal electron-dense neuromelanin granules of the SN zona compacta, with highest levels in a case of PD and Alzheimer's disease (AD). No Fe increase was found in Lewy bodies or in SN neurons of control specimens. The relevance of the in vitro chemical reactions of dopamine (DA), 5-hydroxydopamine (5-OHDA), and 6-hydroxydopamine (6-OHDA) with Fe3+ and with dioxygens for the pathogenesis of PD was investigated. An initiating mechanism for a chain reaction is suggested by which excessive Fe3+ arises. Melanin can act as an efficient antioxidant and in the presence of Fe can promote the formation of cytotoxic hydroxyl free radicals (.OH) which, in turn, initiate lipid peroxidation and consequent cell damage. While in vitro studies indicate that DA oxidation leading to melanin formation is independent of metal ions, saturation of melanin with large amounts of Fe3+ causes a significant generation of free .OH radicals. The relevance of the events induced by the melanin-Fe complex for the degeneration of dopaminergic neurons in PD is discussed. Free redox-active metal ions in the cytoplasm may cause site-specific peroxidation and thus exert neurotoxic effects. Excessive hydrogen peroxide in post mortem frontal cortex of a patient with PD and AD could be shown by confocal fluorescence microscopy, and this observation may be a direct indicator of oxidative stress.

Iron-melanin complex in substantia nigra of parkinsonian brains: an x-ray microanalysis.

Using energy-dispersive x-ray analysis on an electron microscope working in the scanning transmission electron microscopy mode equipped with a microanalysis system, we studied the subcellular distribution of trace elements in neuromelanin-containing neurons of the substantia nigra zona compacta (SNZC) of three cases of idiopathic Parkinson's disease (PD) [one with Alzheimer's disease (AD)] and of three controls, in Lewy bodies of SNZC, and in synthetic dopamine-melanin chemically charged or uncharged with Fe. Weak but significant Fe peaks similar to those of a synthetic melanin-Fe3+ complex were seen only in intraneuronal highly electron-dense neuromelanin granules of SNZC cells of PD brains, with the highest levels in a case of PD plus AD, whereas a synthetic melanin-Fe2+ complex showed much lower iron peaks, indicating that neuromelanin has higher affinity for Fe3+ than for Fe2+. No detectable Fe was seen in nonmelanized cytoplasm of SNZC neurons and in the adjacent neuropil in both PD and controls, in Lewy bodies in SNZC neurons in PD, and in synthetic dopamine-melanin uncharged with iron. These findings, demonstrating for the first time a neuromelanin-iron complex in dopaminergic SNZC neurons in PD, support the assumption that an iron-melanin interaction contributes significantly to dopaminergic neurodegeneration in PD and PD plus AD.

[Detection of blood plasma in heat-treated meat products by ultrathin-layer isoelectric focusing]. / Nachweis von Blutplasma in erhitzten Fleischwaren mittels Ultradünnschicht-isoelektrischer Focussierung.

The detection of blood plasma in heat-treated meat products was performed by means of ultrathin-layer isoelectric focusing. Because of the poor solubility of denatured blood plasma in water or diluted salt solutions the extracts were concentrated by adsorption of the protein on hydroxyl apatite and subsequent elution. Desalting of the samples was done by gel chromatography. Gels with a thickness of 150 micron were used for isoelectric focusing because of their excellent resolution as well as low expenditure of time and cost. 0.2% of dry blood plasma in sausages were still detectable by the method described.

[Can silicon diffusion from silicone rubber catheters cause urethral stricture?]. / Kann eine Siliziumdiffusion aus Silikonkautschukkathetern Harnröhren-strikturen verursachen?

Silicon-leakage out of alloplastic Silicon containing implants induces myofibroblast proliferation and constricting scar tissue. Therefore the possible Silicon-leakage out of Silicon rubber Foley-Catheters was of major interest. This cathaters were often used after internal urethrotomies of recurrent urethral strictures. Pieces of Silicon rubber Foley-Catheters of 18 F, 2 cm in length, were implanted subcutaneously and intraperitoneally in rats. Using Scanning electron microscopy and EDXA (energy dispersiv x-ray microanalysis) Silicon could not be identified in tissues around the implants 6 and 12 weeks after implantation. Therefore Silicon-leakage out of Silicon rubber Foley-Catheters is not responsible for recurrent urethral strictures.

Detection of aluminum oxide and polyethylene wear particles from joint endoprostheses using cathodoluminescence and x-ray analysis in SEM.

A highly sensitive method to localize aluminum oxide or polyethylene wear particles in biological tissues is presented. Using the scanning electron microscope (SEM) with a special cathodoluminescence detector system, small amounts of these foreign materials can be visualized in simple frozen sections by their bright luminescence, even at low magnifications (200X). At higher magnifications, a differentiation of free as well as phagocytized aluminum oxide and polyethylene particles can be made due to their different behavior in light emission. In addition, aluminum oxide such as other metals can be identified by x-ray microprobe analysis. This combination of SEM with microprobe analysis and with the highly sensitive cathodoluminescence mode enables to detect and identify wear products from all the materials, commonly used in manufacturing artificial joint replacements.

[Interaction between blood platelets and capillary kidney in haemodialysis (author's transl)]. / Die Interaktion zwischen Thrombozyten und Kapillarniere im Rahmen der Hämodialyse.

In haemodialysis an interaction between platelets and the dialysator membrane occurs, which is not prevented by heparin. This can be demonstrated by parietal depositions of platelets in the capillaries of the artificial kidney by scanning electron microscopy, as well as in a marked increase of reversible platelet microaggregates during the first phase of dialysis. Some patients are prone to develop thrombosis of the capillary kidneys in spite of a high-dose heparinization. In these cases the use of diclofenac, a cyclooxygenase inhibitor, prevents these adverse platelet reactions.

Effect of proteoglycans (Pg) and glycosaminoglycans (GAG) on prostacyclin (PGI2) and PGI2-formation of rat arteries.

Heparin had no effect on PGI2-activity if heparin and PGI2 have been incubated-together in an ice bath for 3 minutes. But heparin was able - unlike the other Pg or GAG - to abolish PGI2-activity if it had been incubated with PGI2 in an ice bath for 15 minutes. Pg and GAG, which had been isolated from bovine aortas according to the method of Hascall, and commerically available GAG (hyaluronic acid, chondroitin-40-sulfate, chondroitin-6-sulfate and heparin) had no effect on PGI2-formation of rat aortas in short time incubation (3 min). After long time incubation (15 min) or rat aortas in heparin less PGI2 was detectable compared to a buffer incubation. These data suggest that Pg and GAG do not influence PGI2-formation of arteries. The diminished PGI2-activity after long time incubation should be due to the PGI2-degrading effect of heparin.

Influence of proteoglycans (PG) and glycosaminoglycans (GAG) on ADP-, collagen- and thrombin-induced platelet aggregation.

PGs and GAGs have been isolated from fresh bovine aortas according to the method of Hascall and chemically characterized. These PGs and GAGs had only little effects on ADP- and collagen-induced platelet aggregation, but had very potent inhibitory action on thrombin-induced platelet aggregation and prolonged thrombin-clotting-time. Of the standard GAGs investigated hyaluronic acid, chondroitin-4-sulfate and chondroitin-6-sulfate had only little inhibitory action on thrombin-induced platelet aggregation, whereas heparin was very potent in this respect. The unsaturated disaccharides originating after degradation of GAGs with chondroitinases had no effect on platelet aggregation. No differences between PGs and GAGs in inhibiting thrombin-induced platelet aggregation could be detected.

Scanning electron microscopic study of hyperacute rejection in the inbred rat.

Twenty skin-presensitised Lewis rats received kidney transplants from (Lewis X BN)f1 rats. Two grafts each were withdrawn at intervals from 1--120 min and examined using a scanning electron microscopic (SEM). A series of Lewis to Lewis isografts served as control. In hyperacute rejection at just 1 min spider-like fibrin fibres and platelets could be observed in small arteries, where the endothelium was severely altered. In these regions at 2 and particularly 5 min a fibrin network often contained platelet aggregates, mechanically altered erythrocytes as well as different kinds of leucocytes. This coagulation process progressed with time and resulted in a complete vascular occlusion at 30--60 min.

[Investigations on the molecular weight distribution of wheat glutenin subunits (author's transl)]. / Untersuchungen über die Molekulargewichtsverteilung der Untereinheiten des Weizenglutenins.

Comparative investigations on the molecular weight distribution of the reduced glutenins from untreated and petroleum ether resp. chloroform-methanol defatted wheat flour by means of SDS-PAGE have shown that the molecular weight distribution and the intensity ratios of the electrophoretic bands are strongly influenced by the removal of lipids. It could be shown that defatting of flour causes a decrease in the yield of high molecular components in the course of AUC-extraction. The examination of a glutenin prepared by extraction under reducing conditions (0, 2 percent NaHSO3 in 60 percent propanol-2) has revealed that there is evidence for the participation of gliadin-like subunits in the glutenin structure.