Stretch receptors in the eye muscles of a teleost fish

Summary Extraocular muscles of a teleost fish,Girella tricuspidata, contain a predominantly phasic stretch receptor, which consists of fine beaded nerve terminals within the red portion of the muscle.The authors are grateful to Mr V. Straznik for supplying the fish, and to Mrs M. Fisher for histological assistance. Financial support for this work was received from the New Zealand Medical Research Council and the Auckland University Research Committee and University Grants Committee.     

Eine bisher unbekannte endokrine Drüse im Kopf vonScutigera coleoptrata L. (Chilopoda,Notostigmophora)

Summary A hitherto unknown endocrine gland in the head ofScutigera coleoptrata is described. It is attached to a small blood vessel. Its cells are typical podocytes. Between the pedicells and along the lateral cell membranes, there are many intercellulary spaces. The fine structure of the gland is very similar to that of the collar gland in the diplopodPolyxenus lagurus.     

Redundant and unique roles of coronin proteins in <Emphasis Type="Italic">Dictyostelium</Emphasis>

Dictyostelium discoideum harbors a short (CRN12) and a long coronin (CRN7) composed of one and two beta-propellers, respectively. They are primarily present in the cell cortex and cells lacking CRN12 (corA ⁻) or CRN7 (corB ⁻) have defects in actin driven processes. We compared the characteristics of a mutant cell line (corA ⁻ /corB ⁻) lacking CRN12 and CRN7 with the single mutants focusing on cytokinesis, phagocytosis, chemotaxis and development. Cytokinesis, uptake of small particles, and developmental defects were not enhanced in the corA ⁻ /corB ⁻ strain as compared to the single mutants, whereas motility and phagocytosis of yeast particles were more severely impaired. It appears that although both proteins affect the same processes they do not act in a redundant manner. Rather, they often act antagonistically, which is in accordance with their proposed roles in the actin cytoskeleton where CRN12 acts in actin disassembly whereas CRN7 stabilizes actin filaments and protects them from disassembly.     

Contribution à l'étude de la morphogenèse du thalle duStigeoclonium farctum berth (Chaetophorale)

Summary All inhibitors or any modifications of the cultural conditions lead to partial or total isolation of the cells of filaments ofStigeoclonium farctum. The suppression of the intracellular correlation leads to the ramification of the filaments.     

Zur wirkung hypertoner Lösungen auf die markhaltige Nervenfaser

Summary The effect of hypertonic solutions on the action potential of single myelinated nerve fibres is described. Hypertonicity mainly changes the duration of the action potential: Short action potentials obtained in normal Ringer's solution at room temperature are prolonged, long action potentials due to 0.1–1.0 mM NiCl₂-Ringer's solution and low temperature are shortened by hypertonicity. The changes in action potential duration are accompanied by small changes in action potential amplitude. In addition, hypertonicity reduces the depolarization produced by 20 mM KCl; inactivation of the sodium-carrying system under cathodal polarization is enhanced.

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Die Untersuchungen wurden mit Unterstützung der Deutschen Forschungsgemeinschaft ausgeführt.     

Myosins from plants

Molecular cloning and sequence analysis of myosin genes from Arabidopsis thaliana and electron microscopic observation of a myosin from characean alga have revealed that overall structure of plant unconventional myosins is similar to that of the class V myosins. These plant unconventional myosins have two heads, a coiled-coil tail of varied length and a globular tail piece at the end. The tail piece is probably a site for membrane interaction. Characean myosin is of special interest because it can translocate actin filaments at a velocity several times faster than muscle myosin, which must have evolved to support the quick movement of animals in the struggle for their lives.     

Detection of fusaric acid in the mycelium and conidia ofFusarium oxysporum f.vasinfectum

Résumé Le champignonFusarium oxysporum f.vasinfectum contient de l'acide fusarique (l'acide 5-n-butyle picolinique) dans les filaments et spores.     

Heat shock proteins in three relatedDrosophila species belonging to theobscura group

The effect of heat shock on protein synthesis in three relatedDrosophila species belonging to theobscura group was analyzed on SDS-acrylamide gels. Four major heat shock proteins (hsps) were found in these species, in which synthesis reaches a maximum at 34°C. Although the higher molecular weight proteins are conserved, differences in size were found for the small hsps in these species. By means of in situ hybridization usingD. melanogaster probes for the small hsp genes, it was inferred that the small hsp genes of theobscura group species are clustered at the 27A locus in all three species.     

Cholinergic control of extracardiac pulsations in insects

Summary The autonomic nerve system which controls extracardiac pulsations of hemolymph pressure appears to be quite susceptible to cholinesterase inhibitors (physostigmine, organophosphorus insecticides). In pupae ofTenebrio molitor L. andGalleria mellonella L., the treatment induced large peaks in hemolymph pressure (over 4 kPa). The peaks were repeated at more-or-less constant, 30-s intervals for several hours or days. Removal of the pupal brain neither affected extracardiac pulsations nor influenced the specific responses to the investigated drugs or insecticides.     

Das beim Gefrieren von Gelen entstehende Eis

Summary Highly swollen gels which contain, in addition to a large amount of solvent, a spatial network formed by chains of a high polymer, show an abnormal lowering of the freezing point. This is caused by the fact that the network prevents the formation of macroscopically undisturbed crystals.If, in the course of freezing at this lower temperature, a conglomerate of microcrystals were created corresponding in size to the width of the network, one should be able to observe a broadening of the X-ray interference lines. Experiments have shown that no measurable broadening takes place.This is explained by the assumption that a crystal which is prevented from growing in the normal way by the surrounding filaments of the gel, when cooled to a suitably low temperature grows crystallites with a small cross-section corresponding to the mesh size. The crystallites thus formed are orientated in a crystallographically exact manner toward their supporting crystal and parallel to each other. Therefore, when reaching the necessary height, they unite to larger, ordered crystalline regions which incorporate the polymeric filaments. This explains the observed sharpness of the X-ray interferences as well as the observation that, upon heating of a frozen gel, the melting does not occur at the same low temperature as the freezing, but closer to the melting point of macroscopic ice.     

Nervenzellen im Bereich des ösophagus der Grillen und ihre mögliche Funktion

Summary Multiterminal nerve cells have been found in the foregut of crickets (Acheta domesticus (L.),Gryllus campestris L.) which are sensitive to stretching the wall of the gut. These cells are spontaneously active and they respond to stretch in a phasic-tonic way. Within the ventricular nerves there are also neurones being spontaneously active.     

A low molecular weight tracer molecule for immunocytochemistry. Identification of cytoplasmic actin

Summary Anti actin Fab-fragments were tagged to a small electron dense tracer molecule; ferrocene monocarboxylic acid (230 daltons). The conjugate stains actin filaments, which were found mainly in the core of microvilli.     

Der Ursprung des dorsalen Herznervs der Lithobiiden (Chilopoda)

Summary InLithobius piceus Koch the dorsal cardiac nerve is a branch of the nervus connectivus, and thus a nerve of the stomatogastric system. It arises from the frontal ganglion.     

Cyanobacterial symbiont biosynthesis of chlorinated metabolites fromDysidea herbacea (Porifera)

The tropical marine spongeDysidea herbacea contains large numbers of a symbiotic filamentous cyanobacterium identified on the basis of a detailed ultrastructural study asOscillatoria spongeliae. We report the flow-cytometric separation of the symbiont from the sponge cells, and demonstrate by chemical analyses that a unique group of polychlorinated compounds isolated from the whole sponge tissue is limited to the cyanobacterial filaments, whereas the accompanying sesquiterpenoids are found only in the sponge cells. This is the first demonstration that secondary metabolites ascribed to a sponge are localized in prokaryotic symbiont cells.     

Identification of the nerve bundle in the tractus olfactorius of the tench,Tinca tinca L., which conducts the nervous excitation elicited by the alarm substance

Summary In a total of 29 tench (Tinca tinca L., Cyprinidae, Ostariophysi, Pisces) we operatively impaired either 1 or 2 of the 3 nerve bundles of both tractus olfactorii. Through behavioral experiments, using the fright reaction as a test, we found out which nerve bundle of the tractus olfactorius conducts the excitation elicited by the alarm substance. According to the results the conducting bundles are exclusively the lateral bundles in both tractus olfactorii.     

Variations de salinité chez la Tanche (Tinca tinca L.): Effet de la vagotomie sur l'intensité respiratoire et la teneur en eau et cations (Na+ et K+) du tissu hépatique

Summary Vagus nerve section was performed on a stenohaline species: the tench (Tinca tinca L.). The oxygen consumption and Na⁺ content increased in both tap water and after transfer to salt water. It is suggested that the vagus nerve plays a role in water and electrolyte flux in this fish.     

Untersuchungen zur Neurosekretion beiAcheta domesticus L

Summary PAF-positive material, which is found in the brain and stomatogastric system of adultAcheta domesticus, can in addition be demonstrated in the Nervus corporis allati II. In the suboesophageal ganglion and the ventral nerve cord 3 different types of neurosecretory cells are described.     

Erregungsübertragung von Riesenfasern auf Motoneurone bei der SchabePeriplaneta americana L.

Summary The spike-frequency in a motor fibre of the 5th leg nerve ofPeriplaneta americana L. is shown to be approximately stable for several hours. It can be increased by electrical stimulation of the thoracic or the abdominal nerve cord or of the homolateral cercal nerves.     

Regulation of cross-bridge detachment by Ca ions at high ionic strength in molluscan catch muscle

Summary Changes in the profile of equatorial intensities of X-ray diffraction from an intact, anterior byssal retractor muscle (ABRM) ofMytilus were examined at rest, during contracture brought about by acetylcholine (ACh) and a subsequent rigor-like contraction caused by raising the tonicity of the external solution, and after returning the tonicity to normal. The results suggest that the cross-bridges formed between thick and thin actin filaments during the ACh-contracture were maintained in the hypertonic solution and broken on decreasing the tonicity before the recovery of spacing of the actin filament lattice. A similar rigor-like contraction was induced in glycerinated ABRM by increasing salt concentration during active contraction. The rigor-like force declined rapidly when Ca⁺⁺ concentration decreased. The results suggest that the detachment of the cross-bridge from the actin filament is regulated by Ca⁺⁺ at high ionic strength in the ABRM.