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At least 487 records · Page 27Linked to original sources
PubMed1981

Uptake of tritium-labelled biogenic amines by the prostomium of the polychaete Nereis virens (Sars) (Annelida).

The uptake of tritium-labelled 5-HT, noradrenaline, 5-hydroxytrytophan, DOPA and dopamine by the cerebral ganglion and prostomial nervous system of the polychaete Nereis virens has been examined using radioautography at the level of the light microscope. Pronounced uptake of (3)H-5HT occurred in the antennal, palpal, tegumentary and nuchal nerves as well as in ganglionic nuclei 13, 14, 15, 16, 17, 20, 24 and 25, the mid-brain neuropile, the neurosecretory neuropil and the infracerebral organ; (3)H-NA uptake was observed in small cells in the prostomial epidermis, and the infracerebral organ; (3)H-dopamine only in one of two common types of epidermal mucus cells. Prostomial muscles labelled generally with (3)H-NA and at specific sites with (3)H-5HT. These observations support the concept of an efferent serotonergic system originating in several cerebral ganglionic nuclei and serving prostomial muscle and epidermis. Evidence for an afferent adrenergic system is less substantial. The role of dopamine remains obscure.

5-Hydroxytryptophan↗
PubMed1983

A fine structural study of the calcareous opercular plate and associated cells of a polychaete annelid.

The structure of the organic material and inorganic elements of the opercular plate and associated cells in the serpulid annelid, Pomatoceros lamarckii Quatrefages, have been described by transmission and scanning electron microscopy. After decalcification the organic material of the opercular plate was found to consist of three major structurally different components, an outer, thin, electron-dense layer, parallel rows of rectangular profiles partitioned into large units by cross-walls, and layers of orthogonally arranged fibres. The inorganic aragonite components were found, in contrast, to consist of two structurally different elements namely, highly ordered crystals with a prismatic-like morphology and smaller needle-like crystallites. Two morphologically distinct cell types, columnar opercular rim and cuboidal opercular plate cells, are responsible for the formation of the opercular rim and cuboidal opercular plate cells, are responsible for the formation of the opercular plate. Both possess membrane-bound bodies containing filamentous material. However, in addition, membrane-bound bodies, containing calcium carbonate crystals, are found in some cells. Such bodies are seen to be closely related to the Golgi system. Based on the cytoarchitecture of the cells, the mechanisms involved in the formation and calcification of the opercular plate are discussed.

Animals↗
PubMed1984

The role of the heart-body and of the extravasal tissue in disposal of foreign cells in two polychaete annelids.

Sheep red cells injected into the coelom of the polychaetes Neoamphitrite figulus and Arenicola marina are phagocytosed by coelomocytes and conveyed to the heart-body and extravasal ('chloragogen') tissue respectively. In the former case the phagocytes creep into the vessels, penetrate the heart-body tissue and bequeath the sheep red cells to the heart body cells. In Arenicola the phagocytes accumulate on the tips of the blind ending vessels and the red cells are similarly transferred to the extravasal tissues. These observations confirm that the heart-body and extravasal cells function not only in production of haemoglobin but in sequestering foreign material.

Animals↗
PubMed1984

Novel organelle associations in photoreceptors of a serpulid polychaete worm.

Cerebral and branchial eyes of serpulid polychaetes have been studied by electron microscopy for the first time. In one species both eye types possess a novel ultrastructure. The receptor cells of the simple cerebral ocelli are rhabdomeric and display a close structural and functional relationship between ciliary rootlets and mitochondria. The receptors of the compound branchial eyes contain both a rhabdom and a stack of photosensitive ciliary membranes.

Animals↗
PubMed1985

Calcium-containing granules in myoepithelial cells of the polychaete Syllis spongiphila: possible ionic modulators.

Myoepithelial cells of the polychaete Syllis spongiphila have a central core containing abundant membrane-bound granules. Examination of isolated and in situ granules using radioactive labelling, X-ray energy dispersive spectrometry, and scanning and transmission electron microscopy indicated that the granules contain high levels of Ca and P, and take up free Ca ions with a time course of 15-30 min. The granules appear to contribute to the dynamic calcium metabolism of the myoepithelial cells.

Animals↗
PubMed1982

Induction of ion-permeable channels by the venom of the fanged bloodworm Glycera dibranchiata.

Venom from the poison glands of the polychaete annelid Glycera convoluta has been reported to dramatically increase the frequency of miniature end-plate potentials at the frog and crayfish neuromuscular junctions, without causing detectable ultrastructural changes. We report here that addition of venom from the related annelid Glycera dibranchiata to one side of a lipid bilayer results in the formation of ion-permeable channels in the membrane. The channel forming activity was found in the void volume of a Sephadex G-25 column (mol. wt. greater than 5000). The conductance of a single channel is about 350 pmho in 0.1 M NaCl and is ohmic. The channels exhibit moderate (but not ideal) cation selectivity in NaCl or KCl gradients. Other selectivity measurements suggest that Ca2+ and Mg2+ are also permeable. The channels show a slight voltage sensitivity. The steady state conductance at--70 mV (side opposite venom) is about 5 times the conductance at + 70 mV. We suggest that these channels in the venom may evoke transmitter release at neuromuscular junctions either by (1) depolarizing the pre-synaptic terminal and thus opening voltage-dependent Ca2+ channels, or (2) directly allowing Ca2+ to enter the terminal. Black widow spider venom is known to produce similar effects on neuromuscular junctions and lipid bilayers. The single channel conductances and ionic selectivities of the channels found in the venoms of Glycera and Latrodectus are strikingly similar. Taken together, these results suggest that channel formation can explain the electrophysiologic effects of these two different venoms.

Animals↗
PubMed1985

Absence of toxin-producing parapodial glands in amphinomid polychaetes (fireworms).

Amphinomid polychaetes (fireworms) have been responsible for 'bristleworm stingings' and their large setae are reputed to be filled with toxin. The setae and parapodia of Eurythoe complanata, Chloeia flava and Pherecardia striata were examined using histological and scanning electron microscope techniques. No evidence was found for hypothesised toxin-producing glands communicating with the parapodial setae. Setae were hollow, but empty. It is suggested that these polychaetes are urticating rather than toxic.

Animals↗
PubMed1980

Variations in accessibility of DNA during traumatic regeneration by Owenia fusiformis (polychaete annelid).

One of the earliest events observed in the 'dedifferentiation phase' of traumatic regeneration is an in vivo increase in transcription. In order to see whether that increase corresponds to a variation at the level of genetic material, we prepared chromatin from normal and regenerating animals (12 h after amputation) for transcription in vitro by E. coli RNA polymerase. The template activity of regenerating chromatin was 2.1-fold higher than normal under standard conditions and showed an altered response to variation of the ionic strength of the medium. The accessibility of DNA in the chromatin was tested using mild digestion by DNAase II. Almost twice as much DNA was solubilised from regenerating chromatin as from normal chromatin. These data were correlated with morphological changes (decondensation) observed by electron microscopy.

Animals↗
PubMed1983

Suppression of ribosomal gene expression in oocytes and nurse cells of a polychaete as a result of polyamine synthesis inhibition.

The role of the polyamines in ribosomal gene expression was evaluated in the polychaete Ophryotrocha labronica by analyzing the effects of polyamine synthesis inhibition on RNA synthesis during oogenesis, a period characterized by intense nucleolar activity. At various stages of oogenesis adult polychaete females were blocked in their polyamine synthesis by the addition of 10 mM DL-alpha-difluoromethylornithine (DFMO) to the sea water in which they were cultivated. To monitor RNA synthesis during DFMO treatment the animals were pulse-labeled with [5-3H]uridine and processed for autoradiography. Light and electron microscope autoradiographs demonstrate that DFMO treatment suppresses incorporation of label into nucleolar RNA (rRNA) both in the oocytes and their associated nurse cells. The ultrastructural appearance of both cell types reveals interference with nucleolar and ribosomal activity; the endoplasmic reticulum is deprived of ribosomes, and the production of protein granules (vitellogenesis) is reduced. The high specificity of DFMO for polyamine synthesis and the fact that the effects of DFMO were counteracted by addition of a low concentration (10 microM) of putrescine shows that the observed interference with ribosomal gene expression is indeed due to polyamine deficiency.

Age Factors↗
PubMed1987

Free diffusion coefficient of ionic calcium in cytoplasm.

The free diffusion coefficient of ionic Ca was measured in isolated samples of Myxicola axoplasm by following the migration of 45Ca. When precautions were taken to minimize the sequestration and chelation of 45Ca (i.e., using inhibitors, energy deprivation, and saturation of Ca chelation sites), a diffusion coefficient of 5.3 x 10(-6) cm2 s-1 was measured. The diffusion coefficient was not appreciably changed by lowering free calcium from 100 microM to approximately 10 microM or by increasing the diffusion time from ten to twenty minutes. In untreated cytoplasm taken directly from the giant axon of Myxicola, the migration of Ca was more complex and could not be described by a single diffusion coefficient. This result is interpreted to suggest that bulk movement of Ca-buffers may occur in untreated Myxicola axoplasm, a system that contains few microtubules.

Animals↗
PubMed1988

A Ca2+ influx in response to hypo-osmotic stress may alter osmolyte permeability by a phenothiazine-sensitive mechanism.

The phenomenon of cell volume recovery following a hypo-osmotic stress mediated by intracellular osmolyte regulation is well known. In many, perhaps all, cell types, the osmolytes involved are usually inorganic ions and amino acids. The details of the regulatory mechanisms for the organic-type osmolytes are not well known. We have found that an immediate influx of external Ca2+ occurs coincident with the application of a hypo-osmotic stress into red cells of two invertebrate species. In both, the influx is initiated by the osmotic stress, not the concomitant ionic decrease. Volume recovery in clam red blood cells is blocked by phenothiazines. In addition, the effect of the phenothiazines is to reduce the amino acid efflux; the ionic portion of the volume response is unaffected. In contrast, the phenothiazines potentiate the volume recovery in worm red coelomocytes. A23187 also potentiates the volume recovery of the worm red cells. The results suggest that the Ca2+ influx is involved in the mechanism that alters cell membrane permeability permitting the amino acid efflux by a mechanism that may involve calmodulin.

Amino Acids↗
PubMed1990

Ca2+ binding by Myxicola neurofilament proteins.

Titrimetric, 45Ca dialysis, and autoradiographic methods were used to examine how axoplasmic proteins from the giant neuron of the marine annelid Myxicola infundibulum bind calcium. Following the autoradiographic method of Maruyama et al., the 150-160 kD neurofilament subunits were identified as prominent intracellular Ca-binding peptides. Using equilibrium dialysis, extracts of axoplasmic proteins (greater than 50% neurofilament subunits) were examined in 300 mM KCl at different concentrations of free Ca and Mg, and at different pH. Axoplasmic proteins showed a high affinity Ca binding site (K1/2 3-6 microM, capacity 3-7 mumole g-1 protein) at pH 6.8 or pH 7.5. Changing the Mg concentration from 0 to 5 mM had no effect on the Ca binding. Elevating the dialysis pH from 7.0 to 9.0 reduced the apparent number of binding sites for Ca. Using microelectrodes to record the free Ca, microtitrations of axoplasmic proteins were completed by adding small amounts of CaCl2 to 100 microliters volumes of protein solutions. In a medium containing ionic constituents closely resembling those of the Myxicola axon, a Ca binding capacity of 5.0 mumole g-1 protein and a K1/2 of approximately 1 microM were measured.

Animals↗
PubMed1990

Properties of calcium binding by Myxicola axoplasmic protein.

The 45Ca2+ binding properties of axoplasmic protein from the Myxicola giant axon have been investigated using a centrifugal/concentration-dialysis technique. Scatchard plot analysis of these binding data suggest that Ca2+ is attached to a site with an equilibrium dissociation constant of 7.7 +/- 0.5 microM and a capacity of 4.4 +/- 0.2 mumol/g axoplasmic protein (n = 11). Addition of other cations--Cd2+, Mn2+, Al3+, Cu2+, Ba2+, and Zn2(+)--at concentrations up to 10 microM did not displace 0.2 microM 45Ca2+ from its binding site, probably because of buffering of these cations by amino acid residues within the protein solutions. The protein could be stored at 4 degrees C for up to 16 days with no appreciable change in the number of calcium sites. Ca2+ binding equilibrium took place in less than 30 min of incubation. Increasing the incubation temperature from 4 degrees C to 37 degree C reduced the number of Ca2+ sites. The binding capacity was reduced by one-half when the protein was dialyzed with 4 M urea or high ionic strength KCl (2 M). Calcium binding was examined as a function of pH. When the protein was dialyzed overnight at different pH values and all the binding was done at pH 7.0, the apparent number of Ca2+ sites decreased as the pH of the dialysis medium was increased. When the protein was dialyzed overnight at pH 7.0 and the binding was done at different pH values, the apparent binding capacity increased as pH increased.(ABSTRACT TRUNCATED AT 250 WORDS)

Aluminum↗
PubMed1995

Cytoplasmic calcium buffer capacity determined with Nitr-5 and DM-nitrophen.

We have examined intracellular calcium buffer capacity of cytoplasm from the giant axon of the marine invertebrate Myxicola infundibulum by photolytically releasing calcium from 'caged' compounds, while monitoring free calcium, [Ca2+], with Ca-sensing electrodes. In cytoplasm containing intact organelles, two features of the [Ca2+] response were seen upon light exposure: an initial spike from basal [Ca2+], followed by a slower phase recovery. Both the amplitude of the spike in [Ca2+] and the recovery were reduced by removal of MgATP. If organelles were removed from the cytoplasm, light exposure caused only a step-like change in [Ca2+] with no recovery. Apparent buffer capacities (delta bound Ca/delta free Ca) were unaffected by changing pH from 7.0 to 7.5; however, raising basal free calcium above 3 microM significantly reduced this parameter. The buffer capacity measured after the initial spike varied by as much as an order of magnitude from one giant axon to another but averaged approximately 50 in the absence and approximately 100 in the presence of 1 mM MgATP for [Ca2+] below 3 microM.

Acetates↗
PubMed1995

Calcium diffusion coefficient in Myxicola axoplasm.

Calcium diffusion coefficients were measured in Myxicola axoplasm and in agar controls by two independent techniques: one utilizing 45Ca, and one utilizing Ca-specific mini-electrodes. The lowest value, approximately 0.1 x 10(-6) cm2.s-1, was measured, using the mini-electrode technique, in axoplasm with intact Ca-sequestering organelles. With ATP-depleted axoplasm, diffusion coefficients of 0.5-2 x 10(-6) cm2.s-1 were obtained by both isotope and mini-electrode techniques. In organelle-free axoplasm with a protein concentration roughly half that in the intact axoplasm, diffusion coefficients of 1.4-3 x 10(-6) cm2.s-1 were measured at 0.7 microM Ca and 7 x 10(-6) cm2.s-1 at 3-5 microM Ca. When compared with measurements of the calcium buffering capacity [Al-Baldawi NF. Abercrombie RF. (1995) Cytoplasmic Ca buffer capacity determined with Nitr-5 and DM-nitrophen. Cell Calcium, 17, 409-422], these diffusion coefficients require that part of the buffer capacity be located on mobile Ca-binding sites.

Agar↗
PubMed1982

Evidence for the presence of subpopulations of Arenicola marina coelomocytes identified by their selective response towards Gram+ve and Gram-ve bacteria.

In Arenicola marina (L.), in vitro attachment and phagocytosis of bacteria appears to be serum-independent and thus, non-specific. Mixtures of Gram+ve and Gram-ve bacterial species (Gram+ve/-ve, of two Gram+ve (Gram+ve/+ve) and of two Gram-ve bacterial species (Gram-ve/-ve)were overlaid on coelomocyte monolayers, in order to introduce competition for cell surface 'receptors'. An enhanced total phagocytosis was only recorded in the Gram+ve/-ve mixtures in comparison with their controls. The results are interpreted in terms of coelomocyte subpopulations and indicate that A. marina coelomocytes may possess specific carbohydrate/glycoprotein determinants capable of recognizing basic carbohydrate differences between the cell walls of Gram+ve and Gram-ve bacteria.

Alcaligenes↗
PubMed1988

Distribution and nature of membrane receptors for different plant lectins in the coelomocyte subpopulations of the Annelida Nereis diversicolor.

Studies on membrane receptors have been performed on the Nereis coelomocytes using various lectins. In the agglutination assay, only LCA and WGA appeared nonreactive. Fluorescent lectins showed the poor reactivity of the eleocytes and the diversity of the receptors according to the granulocyte types. Types I-granulocytes reacted only with Con A. Type II-granulocyte membrane contained mannose and galactose receptors (reactivity with Con A, PNA and SBA). The type III-granulocyte membrane revealed the presence of mannose and fucose receptors (UEA, AAA). Electron microscope investigations with HRP-DAB or mannosyl labelled Con A, RCAI and LTA have confirmed the distribution of the membrane receptors.

Animals↗
PubMedDate not supplied

Adaptability of the coccidian Coelotropha to parasitism.

The coccidian, Coelotropha durchoni, manages to develop in its host, the polycheate annelid, Nereis diversicolor, because of its ability to circumvent the host's internal defence system. First, it avoids phagocytes by penetrating other cells, principally eleocytes and muscular cells, where it undergoes a phase of intracellular development. After becoming extracellular, a thick coat protects it from being attacked by granulocytes. This coat then breaks and is shed from its surface to permit fertilization. Parasites that have lost their coats and remain unfertilized are surrounded with granulocytes and destroyed by encapsulation. A strict hormonal correlation exists between the biological cycles of the parasite and its host. Thus, the mature spores of the coccidian parasite are disseminated when the worm lays its gametes by rupture of teguments. C. durchoni and N. diversicolor have established a biological equilibrium that permits mutual survival of both partners and constitutes a simple model for the study of the host-parasite relationship.

Adaptation, Physiological↗