Herbert Stachelberger

Iron‐Melanin Complex in Substantia Nigra of Parkinsonian Brains: An X‐Ray Microanalysis

Abstract: 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 Parkinsons disease (PD) [one with Alzheimers 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.

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 Parkinsons 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 Alzheimers 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.

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.

In vivo nanoscale atomic force microscopy investigation of diatom adhesion properties

Abstract Most state of the art adhesives fail to bond under wet conditions. Therefore, knowledge of the intrinsic properties of natural adhesives might give valuable information for future engineering approaches. This work investigates the adhesive that Eunotia sudetica, a species of benthic freshwater diatoms, produces to attach itself to a substrate. Atomic force spectroscopy under aqueous solution reveals the modular, self-healing properties of this natural adhesive.

Exploring the Innovational Potential of Biomimetics for Novel 3D MEMS

A novel way to describe the complexity of biological and engineering approaches depending on the number of different base materials is proposed: Either many materials are used (material dominates) or few materials (form dominates) or just one material (structure dominates). The complexity of the approach (in biology as well as in engineering) increases with decreasing number of base materials. Biomimetics, i.e., technology transfer from biology to engineering, is especially promising in MEMS development because of the material constraints in both fields. The Biomimicry Innovation Method is applied here for the first time to identify naturally nanostructured rigid functional materials, and subsequently analyse their prospect in terms of inspiring MEMS development.

Biomimetics in Tribology

Science currently goes through a major change. Biology is evolving as new Leitwissenschaft, with more and more causation and natural laws being uncovered. The term ‘technoscience’ denotes the field where science and technology are inseparably interconnected, the trend goes from papers to patents, and the scientific ‘search for truth’ is increasingly replaced by search for applications with a potential economic value. Biomimetics, i.e. knowledge transfer from biology to technology, is a field that has the potential to drive major technical advances. The biomimetic approach might change the research landscape and the engineering culture dramatically, by the blending of disciplines. It might substantially support successful mastering of current tribological challenges: friction, adhesion, lubrication and wear in devices and systems from the meter to the nanometer scale. A highly successful method in biomimectics, the biomimicry innovation method, is applied in this chapter to identify nature’s best practices regarding two key issues in tribology: maintenance of the physical integrity of a system, and permanent as well as temporary attachment. The best practices identified comprise highly diverse organisms and processes and are presented in a number of tables with detailed references.

Biomimetics: Its Technological and Societal Potential

This introductory chapter contains a short discussion of the topic of biomimetics with special emphasis on background and goals together with an overview of the book. Biomimetics is described as information transfer from biology to the engineering sciences. Methods and preconditions for this interdisciplinary scientific subject are mentioned briefly focusing on the educational issues and the pathway to product development. To provide the reader with a preliminary information, an overview of the book is given devoted to a brief description of the remaining chapters which are allocated to three main sections “Material & Structure”, “Form & Construction”, and “Information & Dynamics”.

Neuromelanin and Nigrostriatal Dopamine Neuron Degeneration

To the Editors: The contribution of neuromelanin (NM) to the progressive degeneration of the nigrostriatal dopamine neurons and the pathogenesis of Parkinsons disease (PD) has been a topic of discussion for some time. Recently Kastner et al. (1 992) reported that the vulnerability of the dopaminergic neurons in PD is related to their high NM content in the substantia nigra. They were able to measure the NM content of individual cells. An inverse relationship was reported between the percentage of surviving neurons and NM content in PD as compared with controls. They went on to suggest that other factors besides NM may be involved in the differential vulnerability of the dopamine neurons in PD. However, they did not fully explain how this could occur. The authors referred to the possible interaction of melanin with drugs and metals, e.g., iron, to induce oxygen free radicals and initiate membrane lipid peroxidation by refemng to our article (Youdim et al., 1989). In the latter publication we proposed the hypothesis of oxidative stress and iron-melanin interaction. These authors failed to discuss the recent reports of increased iron content in parkinsonian substantia nigra zona compacta (SNC) (for review, see Youdim et al., 1993) as well as the demonstration by Scatchard analysis of high-affinity binding sites on synthetic dopamine melanin for s9Fe3+ (Ben-Shachar et al., 199 1). We further showed that synthetic dopamine melanin, in the absence of iron, inhibited basal membrane lipid peroxidation and formation of oxygen free radicals using rat cortical membrane preparations. However, in the presence of Fe3+ it potentiates lipid peroxidation, and this could be inhibited by iron-chelating agents such as desfemoxamine. Indeed, at the 10th International Conference on Parkinsons Disease, held in 199 1 in Tokyo (Jellinger et al., 1993) and more recently (Jellinger et al., 1992) we demonstrated for the first time using x-ray microanalysis (a) the accumulation of iron in the remaining dopamine neurons of SNC of parkinsonian brains and (b) showed that iron was bound to NM in a manner almost identical to that observed for its binding to synthetic dopamine melanin. Iron was not found in matched control brains and NM-containing neurons. It is generally accepted that in normal circumstances melanin is cytoprotective where it is formed (Schwabe et al., 1989; Youdim et al., 1989; Scalia et al., 1990; Ben-Shachar et al., 1991). However, in the presence of femc iron [predominantly formed in the SNC in PD (Sofic et al., 1988)], melanin can derive a Fenton reaction to generate cytotoxic hydroxyl radical (OH ) (Pilas et al., 1988) and initiate membrane lipid peroxidation (Ben-Shachar et al., 199 1). The demonstration that the highly melanized dopamine neurons are more vulnerable to degeneration may stem from the above reaction of iron-melanin interaction. Furthermore, it must be noted that the formation of melanin from autooxidation of dopamine could very well depend on the accumulation of iron within the neuron. Transition metals, e.g., Fe, Cu. and Mn, are known to participate in the autooxidation of catecholamines to give rise to cytotoxic semiquinones (Halliwell, 1989), which form the backbone of the melanin structure (Larrson and Tjalve, 1979).

Identifizierung von Abbauprodukten der Zellulose in mit Kupferpigmenten illuminierten Graphiken

Degradation products of cellulose resulting fromFehlings reaction in the course of paper destruction by copper-containing pigments have been detected in aqueous eluates of pigment-damaged areas of illuminated manuscripts by GLC ofO-trimethylsilylaldonic acid trimethylsilyl esters.

Quantitative Bestimmung einiger biogener Amine in Bananen, Datteln und Feigen

Brands of bananas, dates, and figs were examined on the presence of serotonin, dopamine, noradrenaline, and adrenaline. Quantitative determination of the detected biogenic amines was performed by thin-layer chromatographic separation of their dansyl-derivatives followed by ultraviolet spectrophotometric measurement of the eluted substances. In bananas (eatable portion) could be found 77,5 µg/g serotonin, 650,5 µg/g dopamine, and 105,5 µg/g noradrenaline; in dates and figs only serotonin was detectable the amount of which has been 8,5 µg/g and 12,2 µg/g respectively.