The Purkinje fiber-myocardial cell region in the goat heart as studied by combined scanning electron microscopy and chemical digestion

The 3-dimensional architecture of the junctional region between Purkinje fibers and ordinary myocardial cells has been closely studied by combined scanning electron microscopy and chemical digestion in the goat heart. It was revealed that the Purkinje fibers forming the terminal arborization of the atrioventricular bundle are followed by transitional cells which are in contact with ordinary myocardial cells.     

Selective representation of vibrissa at the level of cerebellar Purkinje cells by way of climbing fibers in rats]

In the Rat peripheral information from snout vibrissae are transmitted to cerebellar Purkinje cells of Crus I and II by both mossy and climbing fibers. The climbing fiber pathway is organized in a very precise manner, a particular Purkinje cell being preferentially activated by a single vibrissa.     

Potassium currents in cardiac cells

The kinetic properties of the inwardly rectifying K current and the transient outward current in cardiac cells were investigated. In sheep Purkinje fibers superfused with Na-free K-free solution, time-dependent changes in the conductance of the inward rectifier are described. In patch clamp experiments the inward rectifier inactivates during hyperpolarization, as can be seen by a decrease in the open state probability. Using whole cell clamp on ventricular myocytes it is demonstrated that the inactivation during hyperpolarization is due to blocking of the channel by external Na, Mg and Ca. The channels responsible for the transient outward current in cow, sheep and rabbit Purkinje fibers are identified using single channel recording. It is demonstrated that in all three preparations the channels are K-selective. The channel in cow Purkinje cells has a large conductance and is regulated by voltage and internal Ca concentration. The channels identified in the sheep and rabbit cells have a much smaller conductance.     

Role of granular cells in the placement and distribution of synapses between ascending fibers and Purkinje cells of the rat cerebellum]

The study of rats irradiated during development shows that the establishment of the one-to-one relationship in the adult between climbing fibers and Purkinje cells which follows the immature multiply innervated stage mainly depends on granule cells formed before day 8. Climbing fibers ending upon a multiply innervated cell are intermingled on the same dendritic segments.     

Mechanisms of glial-guided neuronal migration in vitro and in vivo

Summary Our laboratory has developed an in vitro model system in which glial-guided neuronal migration can be observed in real time. Cerebellar granule neurons migrate on astroglial fibers by apposing their cell soma against the glial arm, forming a specialized migration junction, and extending a motile leading process in the direction of migration. In vitro assays indicate that the neuronal antigen astrotactin functions as a neuron-glia ligand, and is likely to play a role in the movement of neurons along glial fibers. In heterotypic recombinations of neurons and glia from mouse cerebellum and rat hippocampus, neurons migrate on heterotypic glial processes with a cytology, speed and mode of movement identical to that of neuronal migration on homotypic glial fibers, suggesting that glial fibers provide a permissive pathway for neuronal migration in developing brain. In vivo analyses of developing cerebellum demonstrate a close coordination of afferent axon ingrowth relative to target cell migration. These studies indicate that climbing fibers contact immature Purkinje neurons during the migration and settling of Purkinje cells, implicating a role for afferents in the termination of migration.     

Mechanisms of glial-guided neuronal migration in vitro and in vivo

Our laboratory has developed an in vitro model system in which glial-guided neuronal migration can be observed in real time. Cerebellar granule neurons migrate on astroglial fibers by apposing their cell soma against the glial arm, forming a specialized migration junction, and extending a motile leading process in the direction of migration. In vitro assays indicate that the neuronal antigen astrotactin functions as a neuron-glia ligand, and is likely to play a role in the movement of neurons along glial fibers. In heterotypic recombinations of neurons and glia from mouse cerebellum and rat hippocampus, neurons migrate on heterotypic glial processes with a cytology, speed and mode of movement identical to that of neuronal migration on homotypic glial fibers, suggesting that glial fibers provide a permissive pathway for neuronal migration in developing brain. In vivo analyses of developing cerebellum demonstrate a close coordination of afferent axon ingrowth relative to target cell migration. These studies indicate that climbing fibers contact immature Purkinje neurons during the migration and settling of Purkinje cells, implicating a role for afferents in the termination of migration.     

A comparative study of the innervation of the choroid plexus in amphibia

Summary The aminergic and cholinergic innervation of choroid plexuses in three species of amphibia was investigated. Plexuses of the Japanese toad and the bullfrog had poor innervation by adrenergic nerves of sympathetic origin, but in the clawed toad, these plexuses were heavily innervated by adrenergic axons from ganglion cells located in the plexus stroma. Nerve fibers positive for acetylcholinesterase were not found in the plexuses, except for a few fibers with very weak enzyme activity in the clawed toad.Acknowledgment. The authors are very grateful to Prof. T. Wasano (Professor emeritus of Kyushu University) for his encouragement and advice during the course of the present work.     

Comparative ultrastructural and cytochemical analysis of the cephalopod systemic heart and its innervation

Summary The present knowledge of the morphology of cephalopod central hearts is presented. The cytological characteristics of the epicardial, myocardial and endothelial tissue layers are reviewed. Myocardial cells are characterized as obliquely striated myocytes with a high level of oxidative metabolism. The voluminous myocardium is intensively penetrated by nerve fibers controlling the myogenic heart rhythm by different chemical transmitter systems. Catecholaminergic fluorophores and acetylcholinesterase activity could be localized by means of histochemical and cytochemical investigations. A glio-interstitial cell system is shown to be present in connection with nerve fibers and also uncombined between heart muscle cells. Its content of large different-sized inclusions is described and their function discussed.     

Antiarrhythmic peptide has no direct cardiac actions

The electrophysiologic, inotropic, and muscarinic effects of antiarrhythmic peptide (AAP) were examined in canine cardiac Purkinje fibers, ferret papillary muscle, and canine cardiac membranes, respectively. Aside from a prolongation of time to peak force in papillary muscle, no biologically significant effects of AAP could be determined in any preparation, suggesting that its antiarrhythmic effects are not mediated by direct membrane actions.     

Junctions of polytene chromosomes and the inner nuclear membrane

Summary Polytene chromosomes in salivary gland nuclei from chironomid larvae of defined stages are connected along their entire length, by some 100 chromatin fibers, to the inner nuclear membrane.Dedicated to Professor Friedrich Mechelke on the occasion of his 60th anniversary.     

Antiarrhythmic peptide has no direct cardiac actions

Summary The electrophysiologic, inotropic, and muscarinic effects of antiarrhythmic, peptide (AAP) were examined in canine cardiac Purkinje fibers, ferret papillary muscle, and canine cardiac membranes, respectively. Aside from a prolongation of time to peak force, in papillary muscle, no biologically significant effects of AAP could be determined in any, preparation, suggesting that its antiarrhythmic, effects are not mediated by direct membrane actions.     

Facilitation of synaptic transmission by diazepam in a perfused frog cerebellum

Summary The action of diazepam on the parallel fibres-Purkinje cell synapse was studied in a perfused frog cerebellum. Diazepam facilitates the excitatory input to Purkinje cells and hence increases the inhibition produced by Purkinje cells activity.Supported by a grant from the Israel Center of Psychobiology.This work is part of M. D. Thesis by Y. B. N.     

Differential distribution of TASK-1, TASK-2 and TASK-3 immunoreactivities in the rat and human cerebellum

In this work, the distributions of some acid-sensitive two-pore-domain K⁺ channels (TASK-1, TASK-2 and TASK-3) were investigated in the rat and human cerebellum. Astrocytes situated in rat cerebellar tissue sections were positive for TASK-2 channels. Purkinje cells were strongly stained and granule cells and astrocytes were moderately positive for TASK-3. Astrocytes isolated from the hippocampus, cerebellum and cochlear nucleus expressed TASK channels in a primary tissue culture. Our results suggest that TASK channel expression may be significant in the endoplasmic reticulum of the astrocytes. The human cerebellum showed weak TASK-2 immunolabelling. The pia mater, astrocytes, Purkinje and granule cells demonstrated strong TASK-1 and TASK-3 positivities. The TASK-3 labelling was stronger in general, but it was particularly intense in the Purkinje cells and pia mater.Received 25 February 2004; received after revision 19 April 2004; accepted 28 April 2004     

Effects of pCai and pHi on cell-to-cell coupling

Internal longitudinal resistance (ri), a determinant of cardiac conduction, is affected by changes in intracellular calcium and protons. However, the role and mechanism by which H+ and Ca2+ may modulate ri is uncertain. Cable analysis was performed in cardiac Purkinje fibers to measure ri during various interventions. In some experiments, intracellular pH (pHi) was recorded simultaneously to study the pHi-ri relation. Both intracellular Ca2+ and H+ independently modified ri. However, internal resistance of cardiac fibers was insensitive to pHi changes compared to other tissues. A latent period preceded the pHi-related changes in ri and the amount of change depended upon methodology. The results suggest that direct action of protons or ri may be subordinate to other regulatory processes. Ionic regulation of internal longitudinal resistance may occur by more than one mechanism: i) direct cationic binding to sites on junctional membrane proteins; and ii) H+- or Ca2+-dependent phosphorylation of junctional proteins.     

Interaction of vasoactive intestinal peptide (VIP) with cholinergic stimulation of glucagon secretion

Summary VIP-containing nerve fibers as well as cholinergic nerve fibers have a ubiquitous distribution in the body and both types of nerves have been demonstrated to innervate the pancreatic islets. The present study shows, in the intact, conscious mouse, that VIP and the cholinergic agonist carbachol stimulate glucagon secretion in a dose-dependent manner. Furthermore VIP and carbachol were found to exert potentiating interactions on glucagon secretion. These results suggest the existence of an interactive neural regulation of glucagon secretion, exerted by acetylcholine and VIP.We thank Professor V. Mutt, Karolinska Institutet, Stockholm, for giving us VIP. The skilful technical assistance of Lena K vist and Peter Okmark is gratefully acknowledged. This study was supported by grants from the Swedish Medical Research Council (14P-4289, 14X-4286) and the Medical Faculty, University of Lund, Sweden.     

Calcium binding in chemically skinned fibers of rat myocardium during force development

The amount of bound calcium and force were measured in chemically skinned rat myocardial fibers during isometric contraction at different concentrations of free Ca2+. The data obtained suggest that calcium binding by cardiac myofibrils is cooperative and probably depends on mechanical tension.     

Effects of altered thyroid state on the inhibition produced by locus coeruleus in purkinje cells in the rat

Summary The number of cerebellar Purkinje cells inhibited after locus coeruleus stimulation was found to be greater in hyperthyroid rats than in control healthy animals; these in turn showed a higher percentage of inhibited cells than hypothyroid rats. It is concluded that thyroid hormone is capable of modulating synaptic activity in the LC-PC pathway.     

Technique d'enregistrement de l'activité unitaire du cortex cérébelleux,chez le chat chronique

Summary A technique is described for chronic implantation of movable micro-electrodes in cerebellum of the cat, which is especially adapted for recording unit patterns (Purkinje cells) on the unrestrained animal during a learned motor sequence.     

Presence of giant mitochondria during cerebellar ontogenesis in reptiles

Summary Giant mitochondria were observed in the perikarya and dendrites of Purkinje cells in the developing cerebellar cortex of the lizardGallotia galloti at sevral stages previous to hatching. Such mitochondria are absent from the adult cerebellum.4 December 1986The authors would like to thank Prof. L. Puelles (Murcia University) for his critical assistance and the Edafology Department of La Laguna University for facilities offered, specially for the use of the electron microscope. This work has been pertially suported by a CAICYT research grant No. 909-2.     

Effect of tannic acid on the Ehrlich ascites tumor cells

Summary Tannic acid was used to fix and stain Ehrlich ascites tumor cells in suspension. An increase in surface microvilli and cytoplasmic blebs in the tumor cells was observed. The mechanism of tannic acid induced surface morphological changes in tumor cells and the formation of a precipitate of protein-tannic acid-heavy metal complex are discussed.Acknowledgment. The author is grateful to Professor F. P. Lisowski for his advice and helpful criticism and to Mr Y. S. Tong for his expert technical assistance. This project was supported by a grant from the Hong Kong University Research Grants Committee.