The regeneration of neuromuscular junctions during spontaneous re-innervation of the rat diaphragm

Summary Electron microscopic observations have been made on the regeneration of neuromuscular junctions during spontaneous re-innervation of the rat diaphragm, following unilateral transsection of the phrenic nerve. 3 and 4 weeks after denervation motor end plates displayed the pattern of almost complete degeneration, i.e. persisting subneural foldings, deprived of neural contact and covered with collagen fibrils and fibrocytes. From observations at 5, 10 and 24 weeks after denervation the following sequence of events could be established: a few small axon terminals, accompanied by Schwann cells, became apposed to subneural folds, while most foldings were covered initially by Schwann cells or still by collagen fibrils. Gradually an increasing number of subneural folds came into contact with axon terminals. At 24 weeks all junctions displayed the pattern of a mature motor end plate. In the majority of regenerating neuromuscular junctions single dense-cored vesicles of approximately 900–1200 Å were present in axon terminals.It is concluded that under the present conditions restoration of neuromuscular transmission is accomplished by a re-innervation of the preserved subneural apparatuses of former junctions by regenerating axons. The significance of the occurrence of dense-cored vesicles in regenerating motor end plates is discussed.This work was supported by the Deutsche Forschungsgemeinschaft and the Stiftung Volkswagenwerk.     

On the ultrastructure of the rat anococcygeus muscle

Cell and Tissue Research - The rat anococcygeus muscle, which is known from previous functional and histochemical investigations to be a smooth muscle with a dense adrenergic innervation, was...     

A new method to measure nitrate/nitrite with a NO-sensitive electrode

There are different methods to measure the unstable moleculenitric oxide (NO). We will describe a new sensitive method to measure NO by reconversion of nitrate/nitrite to NO, which will bedetermined with an amperometric Clark-type electrode. Nitrate andnitrite are the degradation products of NO. First, nitrate isenzymatically converted to nitrite with the use of the nitrate reductase. Second, nitrite is reduced to equimolar NO concentrations byan acidic iodide solution. The detection limit of the electrode in anaqueous solution was 2 nmol/l NO (meaning the threshold was dependingon the volume added: 500 µl of a 0.2 µmol/l nitrite solution addedto a 10-ml bath). This method provides the ability to assess basal andagonist-stimulated NO releases of different biological models. Wemeasured basal and carbachol-stimulated NO release of nativeendothelial cells from porcine coronary arteries and porcine aorticendothelial cell cultures. Moreover, it was possible to measure thenitrate/nitrite concentration in the coronary effluent of a guinea pigheart. In conclusion, we present a valid, highly sensitive new methodof measuring nitrite/NO in biological systems with a commerciallyavailable electrode.

     

Aufenthaltsdauern explorierender Meisen: Habitat- und Artspezifit?t

Ohne Zusammenfassung

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Patch residence times of exploring tits: habitat and species specificity

     

Frequent diploidisation of haploid Armillaria ostoyae strains in an outdoor inoculation experiment

Very little is known about the biology and ecology of haploid Armillaria strains in nature. In this outdoor inoculation experiment, we assessed the virulence of six haploid Armillariaostoyae strains along with their diploid parent towards 2-year-old seedlings and 4-year-old saplings of Norway spruce (Picea abies), and determined their ability to colonise freshly cut stumps. As inoculum source an Armillaria-colonised hazelnut (Corylus avellana) stem segment was inserted into the soil substrate. Re-isolations from mycelial fans at the root collar of infected trees or stumps were made. Surprisingly, not a single haploid re-isolate could be recovered. Microsatellite genotyping of 133 re-isolates suggests that the inoculated haploid strains were diploidised either by mating propagules (basidiospores or haploid mycelia) already present in the soil substrate or naturally disseminated in the course of the experiment from nearby forests. Consequently, no conclusion about the infectious ability of haploid Armillaria mycelia under natural conditions can be drawn. Nonetheless, the diploid half-sib families resulting from the diploidisation showed varying degrees of virulence, with a high correlation between the experiment with 2-year-old seedlings and 4-year-old saplings. Despite extensive genotyping of re-isolates, no evidence for somatic recombination between haploid mating propagules and diploidised mycelia was detected, suggesting that this is an uncommon phenomenon in A. ostoyae.     

Über die Differenzierungsleistungen undeterminierten Ektodermmaterials nach Transplantation in erwachsene Organismen

Ohne Zusammenfassung     

Flavone C-glycosides of Apometzgeria pubescens

Eleven flavone di-C-glycosides, including nine which are new, have been identified in gametophytic material of Apometzgeria pubescens. Tricetin 6,8-di-C-glucoside and tricin 6-C-arabinoside-8-C-pentoside are the major compounds. Another identified was ferulylisoschaftoside. The chemotaxonomic relevance of the flavonoid pattern of Apometzgeria pubescens is briefly discussed.