Katharina Braun

Distribution of parvalbumin, cytochrome oxidase activity and 14C-2-deoxyglucose uptake in the brain of the zebra finch

SummaryThe auditory and vocal motor systems of adult zebra finches were investigated 1) immunocytochemically for the distribution of the Ca2+-binding protein parvalbumin, 2) for the activity of the respiratory enzyme cytochrome oxidase, and 3) for the uptake of 2-deoxyglucose. All auditory nuclei (field L, nucleus ovoidalis, ansa lenticularis, nucleus spiriformis lateralis, nucleus mesencephalicus lateralis-pars dorsalis, nucleus tegmenti pedunculo-pontinus) and vocal motor nuclei (nucleus magnocellularis of the anterior neostriatum, area X, nucleus interfacialis, hyperstriatum ventrale-pars caudalis, nucleus robustus archistriatalis, nucleus intercollicularis) showed high levels of parvalbumin and cytochrome oxidase. Auditory nuclei in addition showed high spontaneous 2-deoxyglucose uptake, while the vocal motor nuclei either remained at background intensity (nucleus magnocellularis of the anterior neostriatum, hyperstriatum ventrale-pars caudalis, nucleus interfacialis and nucleus intercollicularis) or even below background levels (area X, nucleus robustus archistriatalis). Cytochrome oxidase activity supposedly reflects the energy demand of various aspects of metabolism, while 2-deoxyglucose uptake is primarily related to the demands of electrical activity and the Na+-K+ pump. Consequently, it is argued (i) that the congruently high cytochrome oxidase activity and 2-deoxyglucose uptake in the auditory system are due to the high spontaneous electrical activity of neurons, and (ii) that high cytochrome oxidase activity in vocal motor nuclei is related to other than electrical events since 2-deoxyglucose uptake is low. There is evidence of Ca2 + potentials in some parvalbumin-positive neuron types. Ca2+ potentials must lead to Ca2+ flooding of the cytoplasm which could be buffered by parvalbumin thus preventing interference with Ca2+ dependent metabolic reactions or shuttling the ion to sites of such reactions. The unique morphological plasticity reported from the parvalbumin-positive vocal motor nuclei may put a strain on microtubular transport which is Ca2+ dependent. This leads to the idea that parvalbumin reflects local buffering and redistribution mechanisms for Ca2+, and that cytochrome oxidase indicates the underlying energy demand.

Calcium regulation by calcium-binding proteins in neurodegenerative disorders

1. Introduction.- 2. Structures of EF-Hand Ca2+-Binding Proteins and Annexins.- 3. Gene Structures and Chromosomal Assignments of EF-Hand Ca2+-Binding Proteins.- 4. Localization of EF-Hand Ca2+-Binding Proteins in the CNS.- 5. Biological Functions of EF-Hand Ca2+-Binding Proteins.- 6. EF-Hand Ca2+-Binding Proteins in Neurodegenerative Disorders and Their Use as Diagnostic Tools.

Cellular localization of the Ca2+-binding protein parvalbumin in the developing avian cerebellum

SummaryThe appearance and distribution of the calciumbinding protein parvalbumin was investigated immunocytochemically at different postnatal developmental stages of the zebra finch cerebellum. Purkinje, basket and stellate, but not granule neurons or glial cells were labeled by an antiserum against chicken parvalbumin. At all developmental stages investigated immunostained Purkinje cells were found in clusters separated by spaces containing unstained large cells, probably Purkinje and Golgi type-II cells, and unstained smaller cells resembling granule neurons. Perisomatic processes, dendrites and spines of Purkinje cells were heavily immunoreactive. Axons of Purkinje cells were observed to be parvalbumin-positive throughout their entire length until developmental stage D 24, i.e., 10 days after hatching. Their immunoreactivity gradually decreased up to adulthood, when only their proximal portions, in addition to a few punctate structures in the internal granular layer and in the deep cerebellar nuclei presumably representing the synaptic terminals, remained immunoreactive. This decrease in immunoreactivity might be related to progressive maturation and/or degree of myelination. The developmental expression of parvalbumin immunoreactivity and its ultrastructural localization in spines, postsynaptic densities and on microtubular elements leads to several suggestions concerning the possible function of parvalbumin in neurons. In outgrowing dendrites and axons the protein might be involved in the regulation of the synthesis of membrane components, their intracellular transport and fusion of new membrane components into the plasmalemma, events that are Ca- and/or Mg-dependent. In spines and postsynaptic densities parvalbumin might be involved in the development and regulation of synaptic activities in Ca-spiking elements such as the inhibitory Purkinje cells, and possibly also in stellate and basket cells. Furthermore, in developing and adult neurons parvalbumin might be involved in the Ca-/Mg-regulation of a variety of enzymatic activities and hence influence the alteration of the intracellular metabolic potential in response to extracellular signals.

System-specific distribution of zinc in the chick brain

SummaryThe brain of young domestic chicks was investigated using a Timm sulfide silver method. Serial Vibratome sections were analyzed under the light microscope, and the localization of zinc-positive structures in selected areas was determined at the ultrastructural level. Both strong and differential staining was visible in the avian telencephalon whereas most subtelencephalic structures showed a pale reaction. The highest staining intensity was found in the nonprimary sensory regions of the telencephalon such as the hyperstriatum dorsale, hyperstriatum ventrale, hippocampus, palaeostriatum augmentatum, lobus parolfactorius and caudal parts of neostriatum. There was an overall gradient of staining intensity in neostriatal areas from rostral to caudal with the heaviest zinc deposits in the caudal neostriatum. Primary sensory projection areas, such as the ectostriatum (visual), hyperstriatum intercalatum superius (visual), nucleus basalis (beak representation), the input layer L2 of the auditory field L and the somatosensory area rostral to field L were selectively left unstained. Fiber tracts throughout the brain were free of zinc deposits except for glial cells. In electron micrographs of stained regions, silver grains were localized in some presynaptic boutons of asymmetric synapses (Gray type I), within the cytoplasm of neuronal somata and sporadically in the nucleus. The possible involvement of zinc in synaptic transmission and other processes is discussed.

Acquisition of multiple image stacks with a confocal laser scanning microscope

Image acquisition at high magnification is inevitably correlated with a limited view over the entire tissue section. To overcome this limitation we designed software for multiple image-stack acquisition (3D-MISA) in confocal laser scanning microscopy (CLSM). The system consists of a 4 channel Leica CLSM equipped with a high resolution z- scanning stage mounted on a xy-monitorized stage. The 3D- MISA software is implemented into the microscope scanning software and uses the microscope settings for the movements of the xy-stage. It allows storage and recall of 70 xyz- positions and the automatic 3D-scanning of image arrays between selected xyz-coordinates. The number of images within one array is limited only by the amount of disk space or memory available. Although for most applications the accuracy of the xy-scanning stage is sufficient for a precise alignment of tiled views, the software provides the possibility of an adjustable overlap between two image stacks by shifting the moving steps of the xy-scanning stage. After scanning a tiled image gallery of the extended focus-images of each channel will be displayed on a graphic monitor. In addition, a tiled image gallery of individual focal planes can be created. In summary, the 3D-MISA allows 3D-image acquisition of coherent regions in combination with high resolution of single images.

Detection of Dendritic Spines in 3-Dimensional Images

This paper demonstrates a method to analyse connections in biological neural networks. The signal flow from one neuron to another is established by an axon which carries the output of a neuron, a synapse which is divided into presynapse and postsynapse, and a dendrite which collects numerous signals from a large number of synapses and delivers them to the destination neuron. The postsynapse including its connection to the dendrite is denoted as a dendritic spine. Due to the observation that shape and size of dendritic spines as well as their distribution along a dendrite vary with behavioral experience and age, a relation between learning processes and the morphology of spines can be conjectured. This can be verified only by statistical analysis. Therefore, a pattern recognition system is required which automatically clusters the set of spines into classes in an unsupervised learning process and selects the features to discriminate them. Our approach is based on the idea that the skeletons of the spines including radius information will constitute all significant information.

Localization of EF-Hand Ca2+-Binding Proteins in the CNS

The intention of this chapter is not to provide a complete review of all the anatomical literature dealing with the distribution of Ca2+-binding proteins in the central nervous system, rather an attempt is made to survey the distribution and cellular localization of Ca2+-binding proteins in selected brain systems of the mammalian brain. Special emphasis is placed on brain systems that are affected in certain neurodegenerative diseases of the human brain, such as hippocampus, cerebellum, basal ganglia and cortical areas. Since, for most of these brain regions, excellent, extensive, and very detailed descriptions of cell types, their distribution and pathways containing different Ca2+-binding proteins have already been published (for reviews see refs. 1–6), the following description is restricted to brain areas and their neurons and functional pathways, which are related to the pathology of brain diseases.

3D Formrekonstruktion an der Auflösungsgrenze konfokaler Laserscan-Mikroskope

Bei Arbeiten an der Auflosungsgrenze eines konfokalen Laserscan-Mikroskops ist wegen der wenigen Abtastwerte und uberlagerter Storungen eine modellgestutzte bzw. wissensbasierte Herangehensweise zur Formrekonstruktion zweckmasig. Das vorhandene a-priori Wissen kann auf diese Weise effektiv verwendet werden. Als Beispiel wurde die Formrekonstruktion dendritischer Spines untersucht. In einem ersten Schritt erfolgt die Einteilung der Formenvielfalt in verschiedene Klassen, die jeweils ahnliche Formen enthalten. Dann konnen die Generalisierungseigenschaften neuronaler Netze genutzt werden, um die Form einzelner Spines mit erheblich verbesserter Auflosung zu rekonstruieren. Ein modifizierter Assoziativspeicher wird mit den zur Verfugung stehenden Daten der jeweiligen Spineklasse trainiert. Beim Recall glattet, korrigiert und interpoliert der Assoziativspeicher die Form einzelner Spines mit Hilfe des gespeicherten a-priori Wissens uber die gesamte Klasse.

Gene Structures and Chromosomal Assignments of EF-Hand Ca2+-Binding Proteins

The genes of only a few members of the EF-hand family have been analyzed.1,2 Based on these data it is suggested that these proteins have evolved from a single ancestral EF-hand motif. During evolution multiple reiterations of this primordial gene gave rise to genes coding for proteins with multiple EF-hands. Subsequent gene duplication led to the large family of proteins with different expression patterns and functions.

3D Bildrekonstruktion mit Hilfe geometrischer Modelle

Durch den Einsatz von geometrischen Modellen ist es moglich, auf einfache Weise a-priori Wissen uber den zu erwartenden Bildinhalt in die Bildrekonstruktion einfliesen zu lassen. Dabei konnen sowohl die Abbildungseigenschaften des Bildaufnahmesystems als auch statistische und geometrische Zusammenhange zwischen den Bildpunkten berucksichtigt werden. Durch die Wahl der Modellparameter und Vorgabe ihrer Fehlergrenzen last sich die Gute der Approximation beeinflussen. Im Ergebnis erhalt man geometrische Modelle der im Bild vorhandenen Objekte, die in den gewahlten Grenzen der Modellierung eine optimale Rekonstruktion darstellen. Aus den Parametern der Modelle lassen sich morphologische Eigenschaften wie Langen, Durchmesser, Volumen und Lagebeziehungen ableiten. Die Modelle konnen einfach und schnell visualisiert werden.