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PubMed1994

Functional aspects of central electrical coupling in mechanoreceptor afferents of crayfish.

Cuticular stress detector afferents (CSD1 and CSD2) in the walking legs of crayfish have been studied in an in vitro preparation allowing intracellular recordings of single neurones during mechanical stimulation of the organs. Lucifer yellow staining of single fibres showed them to be dye-coupled through junctions presumably located near their point of entry into the ganglion. In intracellular recordings from identified sensory fibres with 30-80-mV impulses, coupled afferent spikes were seen as depolarizing potentials of short duration but smaller amplitude. Coupling sometimes involved fibres with quite different response characteristics to mechanical stimuli. Coupled spikes summated during strong mechanical stimuli. In silent CSD fibres, antidromic spikes could occur which were triggered by the depolarization due to coupling. Antidromic spikes were more frequent during strong stimuli and were in some cases shown to be triggered in a cooperative way when two afferent spikes synchronously reached the ganglion. Our results suggest that central coupling of primary afferents may be a widespread phenomenon in Crustacea and that it provides a threshold mechanism for selective amplification of strong stimuli.

Animals↗
PubMed1993

Structure and localization of mRNA encoding a pigment dispersing hormone (PDH) in the eyestalk of the crayfish Orconectes limosus.

The pigment-dispersing hormone (PDH) is produced in the eyestalks of Crustacea where it induces light-adapting movements of pigment in the compound eye and regulates the pigment dispersion in the chromatophores. To study this hormone at the mRNA level, we cloned and sequenced cDNA encoding PDH in the crayfish Orconectes limosus. The structure of the PDH preprohormone consists of a signal peptide, a PDH precursor-related peptide (PPRP) and the highly conserved PDH peptide at the carboxy-terminal end. In situ hybridization in combination with immunocytochemistry revealed four cell clusters expressing PDH in the optic ganglia of the eyestalk. Three clusters stained both with the PDH cRNA probe and the PDH antiserum, however, the perikarya in the lamina ganglionaris (LG) only stained with the PDH antiserum, suggesting the presence of a PDH-like peptide in the LG.

Amino Acid Sequence↗
PubMed1983

Species and tissue distribution of cholecystokinin/gastrin-like substances in some invertebrates.

Twenty-six species of invertebrates representing eight phyla were surveyed for the presence of cholecystokinin/gastrin-like (CCK/gastrin-like) peptides by radioimmunoassay of various tissue extracts. This is the first report of the presence of CCK/gastrin-like peptides in representatives of the phylum Ectoprocta, the arthropodan classes Crustacea and Merostomata, and in the nervous systems of the gastropod mollusc Aplysia californica and the oligochaete annelid Lumbricus terrestris. It has been proposed that CCK/gastrin evolved in the invertebrates as a neural peptide and was subsequently exploited by the vertebrates as a regulatory peptide in both the nervous system and the gastrointestinal endocrine system. The present results indicate that some gastropod molluscs, a merostomatan arthropod, and an annelid have detectable CCK/gastrin in both nervous and gut tissue. However, extractable CCK/gastrin was found only in gut tissue and not in the central nervous system of a crustacean arthropod. The tissue origin of the extracted CCK/gastrin in Bugula (phylum Ectoprocta) was not determined. Final resolution of the question of the nervous versus gut endocrine cellular origin of CCK/gastrin in invertebrates awaits further investigation. CCK/gastrin-like peptides are widely distributed among the invertebrates, which thus provide a rich source of comparative material for study of these regulatory substances.

Animals↗
PubMed1982

The structure of Artemia sp. haemoglobins-I. Isolation and characterization of oxygen binding domains obtained by limited tryptic digestion.

Limited tryptic digestion of the extracellular haemoglobins of the crustacea Artemia sp. result in series of discrete fragments which are multiples of 16,000 d. 2. These 16,000 d fragments, together with 50,000 d and 80,000 d fragments have similar amino acid composition and tryptic peptide maps as the intact globin chains. 3. The haem content of the 16,000 d fragments is the same as this of the intact pigment and they can bind oxygen in a non cooperative way. 4. These results strongly support that the 16,000 d fragments represent structural and functional units or domains from which the globin chains are built up.

Amino Acids↗
PubMed1984

Crustecdysone-induced modulation of electrical coupling and gap junction structure in crayfish hepatopancreatocytes.

Crustecdysone, the hormone responsible for onset and regulation of the molt cycle in Crustacea, causes an increase in ionic coupling of cells of the hepatopancreas concomitant with the events of the molt. Hepatopancreatic tissue incubated for up to 4 hr in modified Eagle Basal Medium containing crustecdysone, exhibited an approximate 29% decrease in intercellular resistance as compared with tissue incubated in control medium. This represents a 29% increase in ionic coupling between hepatopancreatocytes following treatment with crustecdysone. Examination of platinum replicas of freeze-fractured, crustecdysone-treated hepatocyte plasma membrane revealed that most of the gap junction plaques were round with tightly packed intramembrane particles; a condition indicative of highly coupled cells. Similar preparations of control plasmalemmae demonstrated many gap junction plaques which were round or irregular in shape with very loosely packed particles and were indicative of uncoupled junctions. Results of this study are identical to those from a previous investigation of the electrophysiology and freeze-fracture morphology of hepatopancreatocytes during the molt cycle (McVicar and Shivers, 1984), and are thus presumed to reflect a crustecdysone-controlled increase in cell communications in vivo.

Animals↗
PubMed1991

[Toxicity of the molluscicidal plant, Ambrosia maritima L., to aquatic non-target organisms].

The toxicity of the molluscicidal plant, Ambrosia maritima L., has been evaluated in fish, crustacea and algae. The LC50 for fries of the guppy, Lebistes reticulatus, was respectively 650 and 450 mg/litre using a powder or an ether-methanol-hexane extract from the leaves of the plant. This concentration is much higher than the molluscicidal concentration (LC90) of 35 to 70 mg/litre, which is used in the field (irrigation canals in Egypt). Preliminary tests showed that juveniles of L. reticulatus and Tilapia aurea were as sensitive as the fries. Using the same extract of A. maritima the LC50 for Daphnia magna was 766 mg/litre and no toxic effects could be observed in algae Selenastrum capricornutum at 1 g/litre. It can be concluded that A. maritima has a very low toxicity to aquatic non-target organisms. It is not toxic when used at the molluscicidal concentration of 35 to 70 mg/litre.

Animals↗
PubMed1994

The intrarhabdomal filters in the retinas of mantis shrimps.

The intrarhabdomal filters in the photoreceptors of compounds eyes of 32 species of mantis shrimps (Crustacea: Stomatopoda), representing seven families within the superfamilies Lysiosquilloidea and Gonodactyloidea, were surveyed by microspectrophotometry of filters in fresh cryosections of the retina. A total of up to four classes of filters exist in stomatopods: two each in Rows 2 and 3 of the midband. All lysiosquilloid species lacked the proximal filter in Row 3; a few also lacked the proximal Row 2 class. While most gonodactyloid species had all four possible classes, in some species the proximal filters of Row 3 and (in one case) Row 2 were missing. In all, at least 11 distinct spectral classes of pigments were found. Absorption spectra suggested that the filter pigments were probably carotenoids or carotenoproteins, although the distal filter of Row 3 was often exceptional, appearing to contain a mixture of pigments. While the types of pigments found in the filters of the various species generally followed taxonomic lines, numerous exceptions were found that were apparently related to the ecological requirements of the various species.

Animals↗
PubMed1995

Acute and prolonged toxicity to aquatic organisms of new and existing chemicals and pesticides.

The relation of acute to prolonged toxicity of existing and new chemicals and active ingredients of numerous pesticides in the aquatic environment have been compared with their physico-chemical properties. The data had been presented to the authorities in behalf of the pesticide registrations, the notification of new chemicals or research projects. The ecotoxicity ratios are expressed as acute to prolonged ratios (APR). They are determined for fish and crustacea with existing and new chemicals and pesticides. In the case of the pesticides the data are subsummarized into fungicides, herbicides, insecticides. The variability of the APR is evaluated. According to the statistic evaluation of the data it must be summarized, that the toxic effects are often extremely specific and depend not only on the substance, but also on the aquatic species, the duration of the exposure, and the endpoint of the test. In general, a factor of 100 between the EC/LC50 of acute toxicity and NOEC of prolonged toxicity is scientifically justified. The data indicate that there is no significant correlation between lipophilic properties (logPow) or water solubility and toxicity in aquatic organisms. For that reason structure-activity relationships based on lipophilic properties of the substance cannot lead to reasonable results. It must be stated, that the prolonged ecotoxicity can not be exactly extrapolated from acute toxicity data on the basis of physico-chemical properties.

Animals↗
PubMed1983

Metabolism of arsenobetaine in mice, rats and rabbits.

The distribution, retention and biotransformation of arsenobetaine, the most common organic arsenic compound in fish and crustacea, have been studied in mice, rats and rabbits by use of synthesized 73As-labelled arsenobetaine. Orally administered arsenobetaine was almost completely absorbed from the gastro-intestinal tract in mice. The urinary excretion for 3 days following intravenous injection was about 75% of the dose in the rabbits and more than 98% in the mice and rats. The rate of excretion in mice was independent of the dose level in the range 4 to 400 mg As/kg body weight. In both animal species the tissue distribution differed widely from that observed following exposure to inorganic arsenic. The clearance of arsenobetaine from plasma and most tissues was fast (somewhat faster in mice than in rabbits) and seemed to follow first-order kinetics. The clearance from cartilage, testes, epididymis, and in the rabbits also the muscles, was slower and consisted of more than one phase. 73As-arsenobetaine was the only labelled arsenic compound detected in urine and soluble extract of tissues, indicating that no biotransformation occurred.

Animals↗
PubMed1992

Selenium and arsenic in biology: their chemical forms and biological functions.

Based on the recent development of analytical methods, sensitive systems for the analysis and speciation of selenium and arsenic have been established. A palladium addition technique was developed for the accurate determination of selenium in biological samples using graphite furnace atomic absorption analysis. For the speciation of the elements, combined methods of HPLC either with ICP-AES or with ICP-MS were found to work well. These systems were applied to the elucidation of the chemical form of the elements in natural samples. Some chemical properties of the selenium-mercury complex in dolphin liver were elucidated: i.e., it was a cationic, water-soluble, low molecular weight compound containing selenium and mercury in a 1:1 molar ratio, and was shown to be different from a known selenium-mercury complex, bis(methylmercuric)selenide. The major selenium compound excreted in human urine was revealed to be other than any of those previously identified (TMSe, selenate, and selenite). TMSe, a suspected major metabolite in urine, was found, if at all, in low levels. The major water-soluble, and lipid-soluble arsenic compounds in a brown seaweed, U. pinnatifida (WAKAME), were rigorously identified, and the results were compared with other data on marine algae and animals. The major organic arsenic compounds (termed "arseno-sugars") in marine algae commonly contain 5-deoxy-5-dimethylarsinyl-ribofuranoside moiety. There are various kinds of arseno-sugar derivatives containing different side-chains attached to the anomeric position of the sugar, and the distribution of each arsenic species seems to be related to algal species. The arseno-sugar (A-XI) is present in every alga so far examined, is metabolized to lipids, and possibly may play some specific role in the algal cells. On the other hand, the major arsenic compound in fish, crustacea and molluscs has been identified as arsenobetaine, which is an arseno-analog of glycinebetaine, a very common osmo-regulator in living organisms. Arsenobetaine is not detected in marine algae while arseno-sugars are not present in marine animals except for some molluscs which contain both compounds in considerable amounts. Arsenobetaine is present in the urine of human beings who have eaten foods derived from marine animals.

Animals↗
PubMed1984

Recognition of xenogeneic proteins by the blue crab: dissociation of the clearance and degradation reactions and lack of involvement of circulating hemocytes and humoral factors.

Blue crabs clear foreign proteins from the circulation to the gills in a manner that can be explained by postulating the participation of a finite number of naturally occurring quasi-specific receptors. The rate of this clearance reaction is not increased by previous exposure to the foreign protein although recovery to the normal rate of clearance after high level blockade is quite rapid. The cleared foreign proteins are degraded in the gills in a relatively nonspecific fashion suggestive of a clear distinction between the clearance and degradation reactions. The results of perfusion experiments indicate that neither circulating hemocytes nor specific humoral factors are responsible for the foreign protein clearance reaction in blue crabs. Thus it is concluded that fixed cells, most likely in the gills, are responsible for this means of dealing with nonself proteins in blue crabs and possibly other crustaceae .

Animals↗
PubMed1983

The significance of the accumulation of cadmium by aquatic organisms.

Cadmium, by virtue of its toxicity, persistence, and bioaccumulation appears on the "black list" of all the international conventions aimed at protecting the aquatic environment from pollution. Although there is no doubt that cadmium is both persistent and toxic to aquatic life at relatively low concentrations, its bioaccumulation potential appears to have been somewhat exaggerated. Median concentration factors for both marine and freshwater organisms are less than 100 times and for vertebrate (fish) species concentration factors are less than 20 times. There is no evidence in the literature for biomagnification of cadmium and bioconcentration is only likely to be of significance in a restricted range of gastropod mollusks and some crustacea.

Animals↗
PubMed1989

Structural and functional diversity of copper-metallothioneins from the American lobster Homarus americanus.

The role of copper metallothionein (CuMT) in copper metabolism and metalloenzyme activation is poorly understood. We have chosen marine crustaceans, in which a direct correlation exists between levels of Cu(I)MT and Cu(I)-hemocyanin during the molt cycle (Engel and Brouwer, Biol. Bull. 173, 239-251, 1987) as unique model systems to study the involvement of MTs in metalloprotein activation and degradation. We have isolated three low-molecular weight, cysteine-rich copper proteins from the American lobster Homarus americanus, which we designate as CuMT-1, CuMT-2, and CuMT-3, respectively. As a first attempt to fully characterize these proteins, we have determined the sequence of the first 56 amino acids of CuMT-1. The results show this protein to belong to the class I MTs, i.e., related in primary structure to equine renal MT. CuMT-1 cannot transfer its copper to copper-depleted apohemocyanin. CuMT-2 belongs to the same class of MTs as CuMT-1, but CuMT-3 does not. The latter can reactivate lobster hemocyanin containing reduced amounts of Cu(I). Spectroscopic studies show that Cu(I) transfer from CuMT-3 to apohemocyanin initially results in the formation of distorted binuclear-copper sites, which subsequently slowly return to their native stereochemical configuration. Finally, we present evidence that shows that the class I MTs in marine crustacea are involved in the sequestration of elevated levels of heavy-metal ions. These observations strongly suggest that the different forms of MT have different biological functions.

Amino Acid Sequence↗
PubMed1991

A method for the determination of projection areas of GABA immunoreactive neurons in the invertebrate nervous system.

Axonal transport of metallic salts (nickel or cobalt chloride) has been widely used for the anatomical mapping of neural pathways. We show here that when nickel is introduced into GABAergic neurons it completely eliminates GABA immunolabelling. We have used this property to determine the axonal projections of GABAergic neurons in the stomatogastric system of Crustacea. For example, following nickel backfills from either cut axons or from terminals, GABA immunostaining labels only those GABA-immunoreactive neurons which had not been retrogradely labelled with nickel and hence did not project in the cut nerve or to the neuropile uptake site. By comparing such immunolabelled preparations with those not pretreated with nickel the projection patterns of all the GABA immunoreactive neurons in a given system can be revealed. This effect of nickel appears to be selective for GABA immunostaining, insofar as it does not interfere with the immunodetection of either the peptide proctolin or a FMRFamide-like peptide. This method may prove to be a useful tool for analyzing GABAergic neuronal pathways in the nervous systems of invertebrates.

Animals↗
PubMed1991

The midgut chymotrypsins of shrimps (Penaeus monodon, Penaeus japonicus and Penaeus penicillatus).

The midgut chymotrypsins (EC 3.4.4.5) of three species of shrimps, Penaeus monodon, Penaeus japonicus and Penaeus penicillatus were purified and studied in detail to clarify previous ambiguity in their identification. In each of the species there are two major forms of chymotrypsin, both single-chained with three disulfide bonds. One has a pI of 3.2 and Mr 27,000 or 28,000, while the other has a pI of 3.0 and Mr 25,000 or 26,000. The N-terminal amino acid sequences of the P. monodon enzymes are homologous to those of the crab (Uca pugilator) collagenase and to the other chymotrypsins. However, the active sites of the shrimp chymotrypsins are different from that of the well studied bovine alpha-chymotrypsin in some respects: (1) in spite of showing the typical specificity of chymotrypsin, the shrimp enzymes are more stringently selective for substrates with extended polypeptide chain; (2) some titration agents of alpha-chymotrypsin, including t-cinnamoylimidazole, 4-nitrophenyl guanidinobenzoate and its fluorescent derivative, do not react with the shrimp enzymes, neither do some of the alpha-chymotrypsin inhibitors: Tosyl-PheCH2Cl, methyl-4-nitrobenzenesulfonate and benzeneboronic acid; (3) the shrimp chymotrypsins are more reactive than the bovine enzyme toward native protein substrates including collagen; (4) the kinetic-salt-effects of the shrimp enzyme toward N-succinyl- and acetyl-Ala-Ala-Pro-Phe-4-nitroanilide mainly reflect electrostatic rather than hydrophobic interactions between the substrates and the enzyme. The shrimp enzymes are acid-labile but resistent to autolysis. Our results suggest that most Crustacea decapods contain chymotrypsins as one of the major digestive endopeptidases.

Amino Acid Sequence↗
PubMed1987

Glutamate receptors expressed in Xenopus oocyte by messenger RNA from invertebrate muscle.

Glutamate induced responses in the surface membrane of Xenopus oocyte by injection with mRNA from crustacea and insect muscle. Glutamate (10(-5) to 10(-4) M) elicited smooth current responses which resembled those induced by kainate. This smooth current reversed direction at about 0 mV and was blocked by a spider toxin (JSTX). Higher concentrations (more than 1 x 10(-3) M) of glutamate induced JSTX-insensitive oscillatory current responses which may be caused by Cl- activation.

Animals↗
PubMed1985

Strategies for the isolation of insect peptides.

Two distinct diuretic peptides affect the rate of fluid secretion of the Malpighian tubules in Locusta. Diuretic peptide (DP 1) has a molecular mass ca. 4500 and acts via cyclic AMP: the second diuretic peptide (DP 2) has a molecular mass of ca. 1000 and operates via an unknown transduction mechanism; the possible involvement of cGMP, calcium mobilization and the breakdown of phosphoinositides has been investigated. Preliminary sequence data for DP 1 is reported and details are provided concerning the isolation and characterisation of a peptide which is present in large amounts in the storage lobes of the corpora cardiaca and co-chromatographs with DP 1 on high performance size-exclusion chromatography. Adipokinetic hormones (AKH) present in the corpora cardiaca of insects can regulate lipid metabolism. AKH occurs in two forms as AKH I and as AKH II: these hormones have been isolated and characterised in both Locusta and Schistocerca. AKH I is a decapeptide of the following structure: pGlu-Leu-Asn-Phe-Thr-Pro-Asn-Trp-Gly-ThrNH2 and is identical in Locusta and Schistocerca. AKH II is different in these two insects: AKH II-L from Locusta is: pGlu-Leu-Asn-Phe-Ser-Ala-Gly-TrpNH2 and AKH II-S from Schistocerca is: pGlu-Leu-Asn-Phe-Ser-Thr-Gly-TrpNH2. These structures have been established using newly developed quick and simple procedures employing HPLC and gas-phase sequencing which enables full structures to be elucidated from 2-3 nmoles of peptide. Comparisons are made between the structures of AKH and related peptides isolated from insects and crustacea.

Amino Acid Sequence↗
PubMed1987

Comparative effects of mine wastes on the benthos of an acid and an alkaline pond.

Benthic invertebrates collected from an acid (pH 3.2) and an alkaline (pH 7.9) tailing pond in the Rouyn-Noranda mining region were compared with those of a control pond in order to assess the effects of the pH on the benthic community structure and on metal accumulation by invertebrates. The acid pond showed high mean soluble concentrations of aluminium (2600 ppb), copper (230 ppb), iron (6500 ppb) and zinc (4900 ppb) in the water and high mean concentrations of copper (340 ppm), iron (15,238 ppm) and zinc (445 ppm) in the sediments. The benthic fauna was dominated by Chironomus spp and the water beetle Ilybius sp. The Shannon-Weaver diversity index was 0.04. The alkaline pond had high mean sediment concentrations of cadmium (21 ppm), iron (15,823 ppm), manganese (658 ppm) and nickel (146 ppm). A total of 37 insect genera and a diversity index of 3.4 were recorded for this pond. Of the seven metals studied only copper and aluminium showed greater accumulations in the biota of the contaminated ponds than in that of the control. Insects dominated the benthic fauna in both contaminated ponds and crustacea in the control.

Journal Article↗