[Effect of enkephalins on central neuronal activity in the snail Helix pomatia and the white mouse].
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Animals↗
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Effect of oestrogenic, and androgenic and gestagenic hormones on the gametogenesis (oogenesis and spermatogenesis) in the snail Helix pomatia.
In the ovotestis of Helix pomatia both oogenesis and spermatogenesis were influenced by treatments with steroid hormones produced in the gonads of higher vertebrates. Testosterone influenced gametogenesis to a small degree. Progesterone and oestrone-acetate at first stimulated ovogenesis, but they also acted on spermatogenesis. All three hormones examined influenced oogenesis in a conspicuous and significant way, while their effect on spermatogenesis was indistinct.
Animals↗
Light- and electron-microscopic investigations into the gastro-intestinal nervous system of the vineyard snail (Helix pomatia).
In the wall of the intestinal tract, two neural plexuses run though. Both of them consist of nerve cells and nerve fibres. The cells belong to the intestinal wall. One part of the fibres is from the nervus intestinalis, the other part belongs to the process system of the parietal ganglion cells. Most of the nerve cells have a unipolar or a bipolar form, but the multipolar forms don't fall within rarities, either. In the cytoplasm, under an electron microscope, there are several endoplasmatic reticula of wide lumina and free ribosomes or those, coordinated in series. And there are but a few mitochondria. The neurosecretory granules, joined by dense-core forms and homogeneous oval granules, are characteristic. The chromatin sits closely on the nuclear membrane in the form of serrated lobes. The greatest part of the nerve fibres are full of neurosecretory granules, there are in the others elliptical granules of large format, the third is dominated by densecore forms. There are added to the nerve fibres of granule content the agranular fibres, containing no granules, as well as glia cells and glial fibrils. In the latter ones, there are plenty of glycogenous granules. Their characteristic constituents are the homogeneous and elliptical gliogranules of large size.
Animals↗
[Stages of organogenesis and cytodifferentiation of the albumen gland in the snail Helix aspersa Muller].
The differentiation of the albumen gland of the pulmonate stylommatophora Helix aspersa has been divided into five stages. An ultrastructural study showed, the differentiation of undifferentiated epithelial cells into two cell types: ciliated cells and secretory cells. The glandular differentiation of epithelial cells was characterized by the development of ergastoplasma and the Golgi apparatus which were both involved in protein and galactogen synthesis.
Animals↗
Light and electron microscopic investigation of the sensory dendrites in the epidermis of the foot of the snail, Helix pomatia L.
The fine structure of epithelial cells, supporting cells and the sensory dendrites running toward the surface between the former two was investigated in the epidermis of the foot of Helix pomatia. Cilia orienting in regular lines and possessing 9 + 2 tubular structure occur on the surface of the cylindrical epithelial cells lying on the basal lamina. The cilia terminate in basal bodies. The epithelial cells can first of all be characterized by a well-developed Golgi-apparatus and endoplasmic reticulum system as well as a developed tonofibrillar system. The supporting cells differ from the epithelial cells mainly in the poorly-developed tonofibrillar system and small number of cilia. Septate desmosome and zonula adherens are the common connecting structures between the cells composing the epithelium. According to the surface specialization, two types of sensory dendrites running toward the surface were distinguished: dendrites with and dendrites without cilia. On the surface of the former cilia with 9 + 2 tubular structure are randlomly distributed and are present in varying number. In their cytoplasm there are many mitochondria, few clear vesicles and multivesicular bodies. From the surface of the dendrites without cilia, microvilli of different diameter originate and sometimes a centriole was observed below the distal membrane. Their cytoplasm contains many clear vesicles, a well developed smooth endoplasmic reticulum system and few mitochondria. Comparing our results with literary data, we suppose that the differences between the two dendrite types in the presence and number of cilia as well as in the diameter of the microvilli show different forms of appearance of one type of dendritic terminal.
Animals↗
[Immunohistochemical study of protein S-100 in the neurons and glia of the grape snail (Helix pomatia)].
Indirect Coons' method was used to study the localization of the brain-specific S-100 protein in the neurons and the glia of Helix pomatia. This protein was demonstrated to be present in the cytoplasm of the nerve and glial cells, in the nuclei and the outer membrane of the neurons.
Animals↗
[HCS1--a new gene specific for gigantic interneurons of the pleural and parietal ganglia from the nervous system of the grape snail Helix lucorum L].
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Amino Acid Sequence↗
[Excitatory and inhibitory monosynaptic peptidergic transmissions in the CNS of the edible snail Helix pomatia].
Dual action of peptidergic interneuron stimulation was described in the CNS of Helix, being excitatory on bursting neurons and inhibitory on beating ones. The properties of postsynaptic responses were studied.
Animals↗
[Generalized and local changes in the choline sensitivity of snail (Helix lucorum taurica Kryn) neurons after the single or tetanic local applications of acetylcholine].
Single or tetanic local applications of acetylcholine to the soma of command Helix lucorum identified neurons LPa3 and RPa3 induce general and local changes in somatic cholinosensitivity. The general decrease in cholinosensitivity depends on a distance of the tested membrane zones to the site of conditioning stimulation and its intensity. The qualitative and quantitative differences in general and local chemosensitivity have been revealed which can determine the selectivity in changes of chemoreceptor membrane reactivity.
Acetylcholine↗
Up- and down-regulation of Helix command-specific 2 (HCS2) gene expression in the nervous system of terrestrial snail Helix lucorum.
A novel gene named Helix command-specific 2 (HCS2) was shown to be expressed predominantly in four giant parietal interneurons involved in withdrawal behavior of the terrestrial snail Helix lucorum L. and several single neurons in other ganglia. Decrease in spontaneous electrophysiological activity of neurons in the isolated CNS by 24h incubation in saline with elevated Mg(2+) concentration significantly decreased the number of HCS2-expressing neurons. Five short-term serotonin applications (each of 10microM), during a 24h incubation of the nervous system in saline induced expression of the HCS2 gene in many cells in cerebral, parietal, pleural and pedal ganglia. Dopamine applications under similar conditions were not effective. Application of anisomycin or cycloheximide, known to block protein synthesis, did not prevent the induction of HCS2 expression under serotonin influence. Skin injury elicited a significant increase in the number of HCS2-expressing cells 24h later in pleural and cerebral ganglia. Incubation of the isolated nervous system preparations for three days in culture medium elicited close to a maximum increase in number of HCS2-expressing cells. Elevation of the normal Mg(2+) concentration in the culture medium significantly decreased the number of cells demonstrating HCS2 expression. Application of the cAMP activator forskolin (10microM) increased the expression under Mg(2+), indicating that cAMP was involved in the up-regulation of HCS2. Application of thapsigargin (10microM), known to release Ca(2+) from intracellular stores, was also effective in increasing expression, suggesting participation of Ca(2+) in regulation of HCS2 expression. Cellular groups expressing the HCS2 gene under different conditions seem to be functionally related since it was demonstrated earlier that some neurons constituting these clusters are involved in the withdrawal behavior and the response of the organism to stress stimuli. From these results we suggest that the HCS2 pattern of expression can be down-regulated by a decrease in synaptic activity in the nervous system, and up-regulated by external noxious inputs, as well as the application of neurotransmitters and second messengers known to be involved in the withdrawal behavior and maintenance of isolated ganglia in culture medium. When up-regulated, the HCS2 expression appears, at least in part in neurons, to be involved in the withdrawal behavior.
Animals↗
Brain cells that command sexual behavior in the snail Helix aspersa.
Evidence is presented indicating that the mesocerebrum of the terrestrial snail, Helix aspersa, has a major role in the control of sexual behavior. Morphological and physiological results demonstrate a right-sided bias in the mesocerebrum that is consistent with the fact that sexual behavior is executed almost entirely on the animal's right side. Thus, the right lobe has 23% more neurons than the left lobe, and they are 24% larger. Excitatory synaptic inputs derive predominately from neurons on the right side. The axons of right-side mesocerebral neurons go to the right pedal ganglion almost without exception, and even the axons of left-side neurons travel mostly in right-side connective nerves. Direct evidence for a role of the mesocerebrum in commanding sexual behavior comes from experiments with electrical stimulation. Extracellular stimulation of the right mesocerebrum, but not the left mesocerebrum, resulted in movements of the "love dart" sac and the penis. Intracellular stimulation of neurons in the right mesocerebrum evoked measurable movements of either the dart sac or the penis, or both, in 17% of the cells tested. The latencies ranged between 5 and 50 s. In an intact animal, these movements would cause a release of the dart and an eversion of the penis. The motor effects were mediated through the right cerebropedal connective and the pedal nerve NCPD, with the motorneurons probably situated in the right pedal ganglion.
Animals↗
D-Mannitol oxidation in the land snail, Helix aspersa.
Respiration by mitochondrial preparations from hepatopancreas tissue of the land snail Helix aspersa is stimulated by D-mannitol. The rate of mannitol-stimulated respiration is approximately one-half that given by succinate, the most effective substrate thus far tested with these preparations. Mannitol-stimulated respiration is cyanide-insensitive but is not inhibited by salicylhydroxamate. The product of the membrane-bound mannitol-oxidizing activity was shown to be D-mannose by thin layer chromatography, high voltage electrophoresis of the germanate and borate complexes, gas chromatography of the trimethylsilyl derivative, low resolution mass spectrometry of the trimethylsilyl derivative, and by an enzymatic method dependent upon phosphomannose isomerase. The reaction mannitol + O2 leads to mannose is stoichiometric; however, it is not known whether O2 is the immediate electron acceptor. The activity in Helix mitochondria is thus unique among most alditol-oxidizing enzymes in not being pyridine nucleotide linked and in acting on carbon 1 rather than carbon 2.
Alcohol Oxidoreductases↗
[Immunocytologic detection of material related to various vertebrate peptides in the nerve ring of the snail (Helix aspersa Müller)].
The immunocytological method applied to the brain of the snail (Helix aspersa Müller) reveals positive antigenic sites with several antibodies raised against vertebrate peptides: somatostatin, ACTH-17-39, beta-MSH, beta-endorphin, methionine-enkephalin. The distribution of the positive structures (perikarya, fibers) in the ganglia, in the commissure or in the cerebral vessels is given and the presence of these substances is discussed.
Animals↗
Haemocyanin synthesis in pore cells of the terrestrial snail Helix aspersa.
Ultrastructural evidence is presented that the pore cells of the interrestrial snail Helix aspersa are involved in the production and secretion of haemocyanin.
Animals↗
Degradation of bacterial lipopolysaccharide by gut juice os the snail Helix pomatia.
Lipopolysaccharides from several bacteria were selectively degarded by gut juice of the snail Helix pomatia with extensive loss of anticomplementary activity and changes in the electrophoretic pattern in polyacrylamide gels. The gut juice had little effect on ketodeoxyoctonate content or immunodominant sugars. The lipid A moiety of the lipopolysaccharide appeared to be the main site of attack.
Animals↗
Control of the delayed outward potassium currents in bursting pace-maker neurones of the snail, Helix pomatia.
The net outward current in bursting pace-maker neurones of the snail (Helix pomatia) during sustained and repeated voltage clamp pulses was studied. The properties of currents remaining in cobalt-Ringer or after TEA injection were compared with those in untreated cells. 2. With sustained voltage clamp depolarizations the net outward current first increases to a maximum at 150 msec and then declines to 60% or less of its peak intensity. This depression, which is greater during repetition of short pulses (e.g. 100 msec pulses at 0-5 sec intervals), represents a true decrease in the outward flow of K (designated IK) and is not due to a decreased driving force resulting from extracellular K accumulation. The steady-state current-voltage (I-V) relationship for IK is N-shaped (Heyer & Lux, 1976). 3. A component of IK persists when Ca and Mg in the medium are replaced by Co (ICo-res). With voltage clamp depolarizations ICo-res increases rapidly to a maximum and then partially inactivates with voltage dependent time constants of hundredths or tenths of seconds. Repolarization removes the inactivation. Thus, repeated stimulation with short pulses does not increase the depression of ICo-res-ICo-res (e.g. measured during voltage steps from holding potentials of -50 to near 0 mV) is smaller in test pulses preceded by depolarization and larger in pulses preceded by hyperpolarization. The steady state I-V relationship is not N-shaped. ICo-res is blocked by intracellular injection of tetraethylammonium (TEA). 4. Repeated voltage clamp depolarization to near 0 mV with 100 msec pulses for neurones with large Ca currents in normal Ringer produces a long-term depression which is maximal with 300-400 msec repolarizations (to -50 mV) between pulses. This corresponds with stimulus parameters for the maximum Ca current (Heyer & Lux, 1976). Intracellular injection of Ca2+ (also Ba2+ and Co2+) likewise reduces the total net outward current and especially the delayed outward current under voltage clamp. 5. The component of IK which is removed by Co is identified as Ca dependent and designated IK(Ca). With single voltage clamp pulses IK(Ca) follows the approximate time course and voltage dependence of the slow inward Ca current (Iin slow; Heyer & Lux, 1976). Several lines of evidence suggest that Ca ions moving through the membrane activate IK(Ca). 6. Part of IK cannot be blocked by intracellular TEA injection. In different neurones the magnitude of the IK component resistant to TEA (ITEA-res) is approximately proportional to the relative magnitudes of Iin slow.ITEA-res does not inactivate with sustained depolarization and shows pronounced long-term depression with repetitive stimulation at intermediate intervals and an increased outward current at the onset of the second and subsequent pulses following short repolarizations. The steady-state I-V relationship is N-shaped. ITEA-res is abolished by extracellular Co. 7. A net inward current with low depolarizations can be measured after TEA injection...
Animals↗
Gut endocrine cells in the snail Helix aspersa.
A microscopic study of the endocrine cells present in the gut of the snail Helix aspersa is made. Electron microscopy is necessary in most cases to identify the enteroendocrine cells, since neither silver impregnations nor immunocytochemical staining have rendered positive results. Endocrine cells are scarce and rest on the basement membrane. They display a clear cytoplasm and variable amounts of small (143 nm) secretory granules of diverse electron-density. They are ovoid or rounded and possess apical processes which extend into the lumen of the gut. The nucleus, located in the basal region of the cell, presents characteristic cytoplasmic indentations. Intraepithelial nerve bundles in contact with endocrine cells are present.
Animals↗
Partial characterization of a novel cardioinhibitory peptide from the brain of the snail Helix aspersa.
1. We report the isolation of a peptide from the brain of the snail Helix aspersa by radioimmunoassay using an antisomatostatin. 2. The sequencing of an immunopositive fraction showed the presence of a new tridecapeptide, termed Helix cardioinhibitory peptide (HCIP), with the following primary structure: H-Val-Phe-Gln-Asn-Gln-Phe-Lys-Gly-Ile-Gln-Gly-Arg-Phe-NH2. It is structurally related to the Achatina cardioexcitatory peptide (ACEP-1) and the terminal-amino acid sequence of HCIP is identical to that of FMRFamide family peptides. 3. The synthetic HCIP was tested on heart and neuronal activities and it was found to have inhibitory actions not only on the ventricle but also on visceral neurons of the central nervous system of Helix. Immunocytochemical investigation indicates its presence in visceral and parietal ganglia, in which cells taking part in the regulation of the heartbeat have been previously identified.
Amino Acid Sequence↗