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At least 199 records · Page 11Linked to original sources
PubMed2005

GABAergic and glutamatergic inhibition of nonspiking local interneurons in the terminal abdominal ganglion of the crayfish.

Nonspiking local interneurons in the terminal abdominal ganglion of the crayfish Procambarus clarkii receive inhibitory inputs from mainly glutamatergic spiking local interneurons and GABAergic nonspiking interneurons. In this study, the inhibitory responses of nonspiking interneurons to local application of glutamate and GABA into the neuropil were compared. Glutamate and GABA injection mediated the hyperpolarization of the nonspiking interneurons with an increase in membrane conductance. The glutamate-mediated membrane hyperpolarization was reversed by injection of 1 or 2 nA hyperpolarizing current. By contrast, more than 3 nA hyperpolarizing current was frequently necessary to reverse the GABA-mediated hyperpolarization. Bath application of a chloride channel blocker, 50 microM picrotoxin (PTX), reduced the glutamate-mediated hyperpolarization, but had no effect on the GABA-mediated hyperpolarization. The GABA-mediated hyperpolarization was not consistently affected by bath application of low chloride solution. These results suggest that the glutamate-mediated inhibition was related to the gating of a Cl(-) conductance, while the GABA-mediated inhibition was not. Electrical stimulation of sensory afferents innervating the exopodite elicited ipsps in uropod opener motor neurons. These sensory-evoked ipsps were also PTX-insensitive, suggesting GABAergic nonspiking interneurons could be the predominant premotor elements in organizing the uropod motor control system.

Animals↗
PubMed2005

Ontogeny of the Marmorkrebs (marbled crayfish): a parthenogenetic crayfish with unknown origin and phylogenetic position.

Development, growth, and egg production of the Marmorkrebs (marbled crayfish), a crayfish with parthenogenetic reproduction, uncertain geographic origin, and taxonomic position, was studied under laboratory conditions. Length and weight increments strongly depended on temperature being highest at 30 degrees C, and lowest at 15 degrees C. At 25 degrees C, cephalothorax length and weight increased by 17.5 mm and 1700 mg, respectively, in the course of 150 d, whereas at 15 degrees C these parameters increased by only 7 mm and 100 mg during the same period of time. Photoperiod slightly affected growth at 25 degrees C. During growth experiments, mortality was lower at 20 degrees C compared to higher (25 degrees , 30 degrees C) or lower temperatures (15 degrees C), and lower under short-day than under long-day conditions. Females matured early (at an age of 141-255 d, a cephalothorax length of 14-21.5 mm, and a weight of 0.63-2 g) compared to other crayfish species. Reproductive females with a cephalothorax length of between 25-35 mm produced large clutches (up to 416 eggs) and brooding periods varied between 22 and 42 d. In order to establish a staging scheme for Marmorkrebs embryos, embryos were photographed, externally visible ontogenetic events charted, and dissected embryos stained with a nuclear dye. These experiments indicate that their development is virtually identical to that of other crayfish. In conclusion, these results and others show that the Marmorkrebs may be taken as a representative valid model organism for future developmental studies on Crustacea.

Acclimatization↗
PubMed2004

Molecular cloning of a putative membrane form guanylyl cyclase from the crayfish Procambarus clarkii.

Available data indicate that crustacean hyperglycemic hormone (CHH) stimulates membrane-bound guanylyl cyclase (GC), producing cyclic guanosine 3',5'-monophosphate, which in turn mediates the effect of CHH on carbohydrate metabolism. In the present study, we report the cloning of a cDNA (PcGC-M2) encoding a putative membrane form GC from the muscle of the crayfish, Procambarus clarkii. Analysis of the deduced amino acid sequence shows that PcGC-M2 contains the signature domains characteristic of membrane form GCs, including an extracellular ligand-binding domain, a single transmembrane, and intracellular kinase-like and cyclase catalytic domains. In addition, a C-terminal domain of 247 residues is present following the cyclase catalytic domain. PcGC-M2 is most closely related (33% identity) to a Drosophila membrane form GC (DrGC-1), and an Anopheles gambiae membrane form GC (AgaGC); the three GCs also share a similar distribution pattern of conserved cysteine residues in the extracellular domain. The PcGC-M2 transcript is expressed in several CHH target tissues, including muscle, hepatopancreas, heart, ovary, testis, and gill, suggesting that PcGC-M2 may participate in the signaling cascade activated by CHH.

Amino Acid Sequence↗
PubMed2004

Brood care in freshwater crayfish and relationship with the offspring's sensory deficiencies.

Prolonged brood care is one of the evolutionary clues for the successful colonization of freshwater habitats by freshwater crayfish (Astacida). By means of macrophotography, light microscopy, and scanning electron microscopy we investigated all phases of brood care in freshwater crayfish, with particular emphasis on the morphological structures involved. We selected the recently discovered parthenogenetic marbled crayfish (species identity not yet known) as a model organism due to its fast reproduction and high resistance to handling stress. In order to examine if there is a causal relationship between brood care and the developmental status of the offspring's sensory apparatus, we additionally investigated major sense organs of juvenile Stages 1-5 in comparison with those of the adults. Brood care in the marbled crayfish is characterized by initial and final "active" phases dominated by specific maternal or juvenile behavior and a medial "passive" phase based more on the action of temporarily developed structures rather than on behavior. The most remarkable feature of this period, which includes permanent carrying of the eggs and the first two juvenile stages under the mother's abdomen, is safeguarding of hatching by a telson thread that keeps the helpless newborn hatchlings linked to the egg cases on the maternal pleopods and thus prevents them from being lost. Further important transient structures are the recurved hooks on the first pereiopods of Stage 1 and 2 juveniles that are used to firmly attach these nonfeeding stages to the mother's abdomen. In hatchlings all sense organs necessary for an independent life, such as eyes, olfactory aesthetascs, gustatory fringed setae, hydrodynamic receptor hairs, and statocysts are not developed or are underdeveloped, making brood care indispensable. Most of these sense organs appear in Stage 2 juveniles, but only from Stage 3, the first freelancing and feeding stage, are all sense organs well developed and operating, thus reducing brood care in this final period to temporary provisioning of shelter. Brooding of the eggs and postembryonic brood care are to some extent also found in other freshwater Decapoda like freshwater crabs and aeglid anomurans, but safeguarding of hatching is confined to the Astacida only. This sophisticated mode of passive brood care is unique in the animal kingdom and is apparently related to the sensory deficiencies of the first juvenile stage.

Animals↗
PubMed1982

Development of the crayfish retina: a light and electron microscopic study.

The development of the crayfish retina was examined in embryos and first, second and third instars with both and light and electron microscope. Light microscopic observations indicate that differentiation begins at the posterior portion of the optic disc and progresses in an anterior direction. Development of screening pigment, dioptric elements, and rhabdoms all parallel this posterior to anterior gradient in the retina. Tracer studies in early embryos reveal that the retina is separated from the proximal neuropil regions by a distinct vascular space. This observation suggests that the source of new cells for the retina may not be the more proximal cell proliferation zone as previously indicated. It is proposed that mitotic activity within the retina and/or differentiation of cells from the anterior surface layer of the eye may be sources for addition of new cells to the retina. Proto-ommatidial clusters of seven retinula cells occur very early at the posterior region of the embryonic retina. Initially the receptor cells extend throughout the entire thickness of the retina, but later they withdraw from beneath the cornea to occupy only the proximal portion of the retina. Microvilli of the rhabdom arise from the centrally opposed membranes of the retinula cells in each cell cluster. Each new microvillus contains a core of fine filaments which extend out into the cytoplasm at its base. As development of the microvilli continues, the core filaments appear to be lost or altered, but the cytoplasmic bundles at the base of the microvilli persist.

Animals↗
PubMed2005

PDT-induced death of sensory neurons and glial cells in the isolated crayfish stretch receptor after proteolytic treatment.

To study the involvement of neuroglial interactions in photodynamic damage of crayfish stretch receptor, which consists of only two neurons surrounded by satellite glial cells (SGCs), we attempted to proteolytically uncouple neurons and glia and then compare the responses of these cells to photosensitization when intercellular communications were intact or impaired. After incubation of isolated stretch receptors with pronase or collagenase they were photosensitized with Photosens, a mixture of sulfonated alumophthalocyanines AlPcS(n) (n = 2, 3, and 4; mean n = 3.1). In the next 6 hr the preparations were double fluorochromed with propidium iodide and Hoechst-33342 to visualize necrotic and apoptotic cells. Proteolytic treatment shortened bioelectric neuron response and precipitated its functional inactivation; however, it did not significantly impair neuron morphology and did not induce its necrosis either in the darkness or under photosensitization. Photodynamic treatment induced necrosis of neurons and SGC and apoptosis of glial cells. Pronase but not collagenase increased percent of necrotic and apoptotic SGCs in the darkness and thus reduced the number of glial cells around the neuron; however, both pronase and collagenase prevented photodynamically induced apoptosis of glial cells. The involvement of neuron-to-glia signaling interactions in this phenomenon is suggested.

Action Potentials↗
PubMed1975

Studies on neuronal lipid.

The procedure for bulk preparation of nerve-cell perikarya from pig brain-stem is briefly described. This method has definite merits with regard to the preservation of the intracellular structures as well as the preservation of the processes. The chemical composition of the isolated nerve-cell perikarya is presented. The nerve-cell perikarya are characterized by the absence of cerebroside and sulfatide. Diffuse distribution of ganglioside on the cell surface is suggested. The lipid content of the nerve-cell perikarya isolated by different methods is discussed. Lipid composition of the invertebrate nervous tissue is discussed. The submicrosomal membranes of rat brain are isolated, and their chemical and morphological properties are discussed. Ribosome-free membranes are characterized by the high content of glycolipids including gangliosides, as well as by the high activity of Na, K-ATPase, whereas ribosome-bound membranes are characterized by the absence of glycolipids, as well as by the low activity of Na, K-ATPase. The molecular organizations of lipid in submicrosomal membranes are demonstrated.

Adenosine Triphosphatases↗
PubMed1994

Toxic axonal degeneration occurs independent of neurofilament accumulation.

Alteration of neurofilament (NF) proteins is considered a critical component and a causative factor for a number of neuropathologies, especially certain neurotoxicities. Correlative observations have supported this hypothesis; the current study tests this relationship by exposure of neurotoxicants to crayfish, a species lacking NFs. Morphological and immunological tests verified the absence of NFs in crayfish peripheral nerve axons. Tail injections of acrylamide (ACR), 2,5-hexanedione (2,5-HD), or 3,4-dimethyl-2,5-HD (3,4-DMHD) produced ataxia and paralysis. Morphological expression of axonal degeneration in a spatial and temporal pattern of progression comparable to mammalian species possessing NFs was observed. With gamma-diketones, time to onset was slower than observed in mammals but relative potency between neurotoxic analogues was maintained. Non-neurotoxic analogues failed to produce any functional signs of neurotoxicity. These data are consistent with the conclusion that NF accumulations are not cause-effect related to axonal degeneration in these models of neurotoxicity and raise questions as to the relationship between accumulation of NF proteins and axonal degeneration in other neuropathological conditions.

Acrylamides↗
PubMed1995

Selective block of Ca(2+)-dependent K+ current in crayfish neuromuscular system and chromaffin cells by sea anemone Bunodosoma cangicum venom.

The effects of the nematocyst venom of the sea anemone Bunodosoma cangicum on depolarization-activated currents were studies in opener crayfish muscle fibers and in cultured bovine chromaffin cells. The venom selectively and reversibly blocked the Ca(2+)-dependent K+ current (IK(Ca)) present in crayfish muscle in a dose-dependent manner without affecting voltage-gated Ca2+ or K+ currents. Furthermore, the venom also reduced IK(Ca) in chromaffin cells, without modifying voltage-gated Na+, Ca2+, or K+ currents. Synaptic transmission in crayfish muscle was also affected by the venom. Repetitive excitatory and inhibitory postsynaptic currents (each associated with a presynaptic action potential) were evoked by each nerve stimulus, suggesting that presynaptic IK(Ca) may control the electrical activity of excitatory and inhibitory presynaptic fibers. We conclude that B. cangicum venom includes a toxin that selectively and reversibly blocks Ca(2+)-dependent K+ currents in crayfish muscle and in bovine chromaffin cells, and modifies excitatory and inhibitory synaptic transmission, probably abolishing a similar conductance at the presynaptic fibers.

Animals↗
PubMed2002

Immunological evidence for progesterone and estradiol receptors in the freshwater crayfish Austropotamobius pallipes.

In this article, we present evidence for progesterone and estradiol receptors (PR and ER, respectively) in the female of the crayfish Austropotamobius pallipes. To our knowledge, this is the first report of sex steroid receptors in crustaceans. By using immunohistochemistry and Western blotting approaches and employing three different antibodies against PR (human PR, chicken PR-hinge region, and chicken PR A/B domain) and antibodies against human ER, we showed the presence of PR in the ovary and hepatopancreas and ER in the hepatopancreas of the freshwater crayfish A. pallipes. The immunological characteristics and the tissue localization suggest a relatedness with both PR and ER in vertebrates along with their involvement in the modulation of reproductive functions in this crustaceans.

Animals↗
PubMed2004

Vitellogenin mRNA expression in Cherax quadricarinatus during secondary vitellogenic at first maturation females.

PCR products of 1.1 and 0.9 kb were generated using Cherax quadricarinatus genomic DNA in the first case, and hepatopancreas and ovary cDNAs in the second case. These PCR products were cloned and analyzed for nucleotide sequences. The 1.1 kb fragment was used as a probe for Northern hybridization, revealing a transcript of approximately 8 kb in both tissues. Results from both Northern blot and RT-PCR analyses showed that the mRNA enconding the 3' end of the vitellogenin cDNA was present simultaneously in both hepatopancreas and ovary tissues in secondary vitellogenic at first maturation females, but was not detected in male hepatopancreas. The deduced amino acid sequences of Vitellogenin (Vg) cDNAs from ovary and hepatopancreas confirmed the existence at least two different Vg genes, and two different sites of synthesis.

Amino Acid Sequence↗
PubMed1992

Proton relaxation studies of water compartmentalization in a model neurological system.

Proton relaxation measurements from 18 crayfish abdominal nerve cords (a model of human CNS) are used to demonstrate that the transverse (though not the longitudinal) relaxation can be decomposed into four reproducible components that, in conjunction with optical and electron microscopy of the morphology, can be assigned to three water compartments within the cord and possibly to the mobile lipid protons. The assignments are extraaxonal water protons (32 +/- 9% and mean T2 = 600 +/- 200 ms), axonal water protons (59 +/- 12% and mean T2 = 200 +/- 30 ms), intramyelinic water protons (7 +/- 4% and mean T2 = 50 +/- 20 ms), and finally an unsubstantiated assignment of lipid protons (2.0 +/- 2.0% and mean T2 = 7 +/- 4 ms).

Algorithms↗