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At least 271 records · Page 15Linked to original sources
PubMed2006

Assessment of biochemical components and enzyme activities in the estuarine crab Scylla tranquebarica from naphthalene contaminated habitants.

To document the impact of naphthalene, a comparative toxicological research was performed in the estuarine crab Scylla tranquebarica habitant of Ennore creek (polluted site) and Kovalam creek (pristine site) for a period of 6 months. The biochemical constituents, such as protein, carbohydrate, lipid and enzyme activities like acid and alkaline phosphatase, aspartate and alanine transaminase were analysed in hepatopancreas, heamolymph and ovary of the female crabs collected from the two creeks. The results revealed that there was a significant measurable difference in these parameters in the tissues of crabs sampled from the polyaromatic hydrocarbon (PAH) polluted site (Ennore creek) when compared with the reference site (Kovalam creek). In addition naphthalene was detected in gill, hepatopancrease, heamolymph and ovary of the crabs sampled from the polluted creek. The results indicate that the indicators selected for toxic impact in S. tranquebarica may be related to the uptake of naphthalene in the tissues examined and support the feasibility of employing these types of analyses as biochemical biomarkers for PAH contaminant-exposed organisms.

Animals↗
PubMed1989

Danger stimulus-induced analgesia in the crab Chasmagnathus granulatus.

When a danger stimulus (a passing shadow) is presented to the crab Chasmagnathus granulatus, an escape response is elicited that habituates after repeated stimulation. Results from previous work suggest that this habituation might be mediated by endogenous opiates and, thus, that after an habituation session an analgesic effect on the response to a painful stimulus should be found. The purpose here was to test this contention. Each crab was lodged in an actometer where two 2-trial sessions with electrical shock stimulation were given (SS1, SS2), the intersession interval being 60 or 105 min, and the response activity recorded. In some experiments, repeated shadow stimulation was inserted during the interval, and the response activity also recorded. In Expt. 1, shadow sessions of 15 and 30 trials were tested and a significant decrease of the reactivity to the shock was only shown with 30 trials. In Expt. 2, crabs were immediately injected after SS1 with distilled water (d.w.) or naloxone (NX) (3.2 micrograms/g), and a shadow session of 30 trials was given to half of the d.w. animals and to half of the NX ones. NX injected crabs showed an increased responsiveness to the danger stimulus during the shadow session but no inhibitory effect on pain reactivity to the subsequent painful stimulus. Issues concerning dependence of the analgesia on danger stimulus iteration and on stimulus controllability, as well as the opioid nature of the analgesia, are discussed.

Analgesia↗
PubMed1986

Regulation of the stress-responsive X-organ--Y-organ axis by 5-hydroxytryptamine in the crab, Cancer antennarius.

Eyestalk-intact, but not de-eyestalked, crabs (Cancer antennarius) given five injections of 5-hydroxytryptamine (5HT, 750 micrograms per injection) in 48 hr showed significant reductions in hemolymph ecdysteroid titers within the first 12 hr which continued through Hour 72; the effect was reversible (Hours 72-144). The 5HT synthesis inhibitor p-chlorophenylalanine (PCPA; 60 micrograms) or the 5HT receptor antagonist cyproheptadine (CPH; 100 micrograms) caused significant rises in serum ecdysteroids in intact, but not in de-eyestalked, crabs; with four injections over 48 hr, a rise was evident at 12 hr, continued through 72 hr, and returned to control levels within 4 days post-treatment. Stress due to handling depressed ecdysteroid levels, an effect that was reversed by PCPA and CPH; values in the treated groups returned to prestress levels within 24 hr and were significantly greater than prestress levels within 48 hr. 5HT treatment did not further decrease stress-reduced ecdysteroid titers. Normal behaviors are described in posturing and in defensive responses to stress; these were changed in both intact and de-eyestalked crabs by 5HT treatment (but not by PCPA or CPH). These findings support the hypothesis that release of molt-inhibiting hormone (MIH) from crab eyestalks is mediated by 5HT and suggest that stress induces 5HT-mediated MIH release.

Animals↗
PubMed1991

Effects of dopamine and acclimation to reduced salinity on the concentration of cyclic AMP in the gills of the green crab, Carcinus maenas (L).

Injection of 10(-5) M dopamine into adult green crabs increased the concentration of cyclic AMP (cAMP) in all gills tested. Short-term acclimation (24 hr) of crabs to 40% seawater (sw) also increased the cAMP content of the posterior gills as compared to controls, an effect similar to that seen with injection of dopamine. However, when crabs were acclimated to reduced salinity for 2 weeks, the concentration of cAMP in the gills was not statistically different from that of gills from crabs in 100% sw. It is likely that the physiological effects of dopamine on gills are important in the early stages of acclimation and that they depend upon an increase in concentration of cAMP, which interacts with cellular proteins.

Adaptation, Physiological↗
PubMed1988

Appearance and partial purification of a high molecular weight protein in crabs exposed to saxitoxin.

This paper provides evidence for a protein component which appears to be involved in the seasonal resistance of small shore crabs, Hemigrapsus oregonesis and Hemigrapsus nudus to saxitoxin, a principle neurotoxin involved in paralytic shellfish poisoning (PSP). This unique protein complex was isolated and partially purified by ion exchange chromatography using DEAE-cellulose from visceral tissue extracts of resistant crabs. The complex was absent in control crabs that were sensitive to saxitoxin. In addition, the protein complex was induced in the crab after acute administration of low doses of saxitoxin. Results indicate that the protein complex is acidic in nature and has an apparent mol. wt of 145,000.

Animals↗
PubMed1995

Guanidine neurotoxins are released with the digestive fluid of crabs (Crustacea, Brachyura).

During agonistic interactions intertidal crabs, when exposed to air, produce a foam made of digestive secretions, sea water and air bubbles. They also may release their digestive secretions in water when disturbed. Crabs belonging to the families Majidae, Xanthidae and Portunidae from Atlantic and Pacific areas, not related with human poisoning, possess substances in their digestive secretion which are neurotoxic to mice, block action potentials in nerve preparations, and are reversible on washing. After purification in Bio-gel P-2 chromatography and HPLC analysis, the spontaneously regurgitated secretion, the digestive secretion collected by stomach cannulation of crabs, and the water aquarium replete of intertidal crabs kept overnight show the presence of guanidine neurotoxins.

Animals↗
PubMed1996

Occurrence of paralytic toxin in Taiwanese crab Atergatopsis germaini.

Paralytic toxicity was detected by paralytic shellfish poison bioassay for all 17 specimens of the xanthid crab A. germaini collected from northern Taiwan in November 1993. The average toxicity of crab specimens was 3809 +/- 2591 mouse units (mean +/- S.D.). The toxin was partially purified from ethanolic extract of the crab by ultrafiltration and Bio-Gel P-2 column chromatography. Electrophoresis, TLC, HPLC, ultraviolet spectrum and GC-MS analyses indicated that the crab toxin was composed of gonyautoxin 3 (50%), neosaxitoxin and saxitoxin (7%), a novel paralytic shellfish poison-like toxin (40%) and tetrodotoxin (3%).

Animals↗
PubMed1992

Opiate effect on the threat display in the crab Carcinus mediterraneus.

The well-known defense response of a crab (laterus merus display, LMD) was easily evoked in Carcinus mediterraneus by striking the cephalothoraxic protogastric region between the eyestalks. Following a program aimed at investigating the regulatory action of diverse neuromodulators on the LMD of this crab, a study on the role of opioids was started by testing the effect of morphine administration. Injection of morphine HC1 (MP) (40, 50, 60, 70, or 100 micrograms/g) produced a dose-dependent reduction of the LMD so elicited that dissipated with the postinjection time. Only MP doses higher than 50 micrograms/g were effective 30 min after drug administration. The MP-induced inhibition of LMD was blocked by a 4.8-micrograms naloxone HC1/g dose injected 10 min before MP. These results and those previously obtained as the action of GABA on the LMD of this crab are discussed in connection with results reporting a similar effect of these drugs on another agonistic item of behavior in the crab Chasmagnatus granulatus. The possibility of demonstrating habituation of the LMD to an iterated stimulation in C. mediterraneus and of using such a process to elucidate the acting paths of the drugs is discussed.

Aggression↗
PubMed1984

Occupational asthma in snow crab-processing workers.

The prevalence of occupational asthma was studied in two snow crab-processing industries in operation since 1980. Before the 1982 season, all except 10 of the 313 employees were investigated by a questionnaire, prick skin tests with common allergens, crab n and crab-boiling water extracts, and spirometry. The diagnosis was confirmed in 46 (15.6%) workers (including 33 of 64 subjects with a history highly suggestive of occupational asthma in the previous seasons) by (1) specific inhalation challenges in 33 subjects (one immediate, nine dual, and 23 late asthmatic responses) and/or (2) a combination of monitoring of peak expiratory flow rates (n = 12) and significant changes in bronchial responsiveness to histamine (n = 16) as well as in spirometry (n = 18) after reappearance of symptoms on return to work. Positive skin tests to crab (p less than 0.001) and, to a lesser degree, smoking history (p = 0.03) but not atopy (p greater than 0.05) were related to the presence of occupational asthma. A high prevalence of rhinoconjunctivitis (35 of 46) and urticaria (16 of 46) was also documented in the affected individuals.

Asthma↗
PubMed1985

Follow-up of occupational asthma caused by crab and various agents.

Sixty-three subjects with occupational asthma caused by crab (n = 31) and various other agents (n = 32) were studied after cessation of exposure at work for mean +/- SD intervals of 12.3 +/- 5.5 and 24.5 +/- 18.7 months (greater than 6 months in every subject), respectively. Nineteen of the subjects with asthma caused by crab and 30 of the subjects with asthma caused by various agents were still symptomatic of asthma, nine subjects of the latter group requiring bronchodilators (with inhaled beclomethasone in five) regularly. No significant changes in baseline spirometry were observed at the time of follow-up as compared with initial assessment, nine subjects (all in the asthma group caused by various agents) demonstrating significant bronchial obstruction. Improvement in bronchial responsiveness to histamine was significant (p less than 0.01) in the group with asthma caused by crab but not in the other group. Forty-eight of 52 subjects still had significant airway hyperexcitability. Subjects with asthma caused by crab who were asymptomatic and those subjects with asthma caused by various agents who used bronchodilators only if they were needed had worked for shorter intervals after onset of symptoms (p less than 0.01 and p less than 0.05, respectively). It is concluded that subjects with occupational asthma caused by various agents can remain symptomatic of asthma and demonstrate a persistence of bronchial obstruction and hyperexcitability for prolonged intervals after cessation of exposure.

Adult↗
PubMed1992

Multitrial inhibitory avoidance learning in the crab Chasmagnathus.

Chasmagnathus crabs placed in the dark compartment (DC) of a double-chamber device and given electrical shocks whenever they entered or remained in the light compartment (LC), showed an LC-avoidance behavior when tested 24 h after a training session of three 30-min periods with 60-min intervals. The avoidance behavior depended neither on the shock number nor on the distribution at training but only on exposure to the LC-shock contingency, thus suggesting that crabs learn to associate the LC with an aversive situation. The learning outcome disclosed a higher degree of refraining from entering the LC rather than a faster escaping to the DC. Distributed practice proved more effective on crab avoidance learning than massive practice. Retention of the learned behavior occurred after a 24-h rest interval in an environment different from that of the training apparatus. Experimental devices previously used in avoidance learning studies with crabs were improved here by automating both the computation of latency values and the event recording.

Animals↗
PubMed1984

A spectroscopic study of rat liver and Scylla serrata crab metallothioneins.

The absorption, circular dichroism (CD) and magnetic circular dichroism (MCD) spectra of native rat liver and crab (Scylla serrata) Cd,Zn-metallothionein have been measured and the data are compared. The MCD data indicate that there are close similarities in the geometries of the cadmium-binding sites in both of these proteins; however, the CD spectra are quite different for the rat liver and crab proteins. The CD spectrum for the crab metallothionein is unlike any previously reported for a cadmium-containing metallothionein. This suggests that the CD spectrum is sensitive to the different bridging pattern used in the binding sites in the crab compared with the rat-liver metallothionein. Cadmium binding to the metal-free metallothionein is demonstrated for both proteins and it is shown that there are only minor structural differences between the native and remetallated proteins. The structural changes that occur near to the cadmium-binding sites during cadmium loading to the native proteins have been followed using absorption and CD spectroscopy. Marked changes are observed in the CD spectrum which can be associated with a two-phase reaction: initially Zn2+ is displaced by the Cd2+, then at higher concentrations of Cd2+ the tetrahedral geometry of the Cd2+-binding sites is lost as more Cd2+ is bound using the same thiolate groups. While this latter reaction results in considerable change to the CD spectrum, only minor changes are observed in the absorption spectrum. A significant red shift is observed in the S leads to Cd charge transfer transition region of the MCD spectrum (230-270 nm) following both cadmium loading of native rat liver, Cd,Zn-metallothionein and the metallation of metal-free metallothionein with cadmium. There are two contributions to this effect in Cd,Zn-metallothionein: (i) there is a S leads to Zn band underlying the S leads to Cd band; and (ii) the occupation of zinc sites by cadmium changes the energy of the S leads to Cd transition.

Animals↗
PubMed1994

Substrate specificity of collagenolytic proteases from the king crab Paralithodes camtschatica.

Substrate specificity of two collagenolytic proteases from the king crab Paralithodes camtschatica has been studied. Both proteases are shown to hydrolyze effectively type I and III collagens, gelatin and fibrinogen. The variety of products formed during the enzymatic hydrolysis of the proteins appeared to be different for crab proteases A and C. Studies on peptide hydrolysis demonstrated that protease A cleaves preferably peptide bonds with Arg and Lys as carbonyl components, while protease C prefers hydrophobic amino acids. Kinetic constants of hydrolysis for low molecular weight substrates in the presence of crab proteases have been determined. This allowed us to characterize collagenolytic protease A as a trypsin-like protease. By contrast, collagenolytic protease C was classified as chymotrypsin-like protease although this protease and bovine chymotrypsin are not completely similar. Collagenase substrates Pz-Pro-Leu-Gly-Pro-D-Arg and Z-Gly-Pro-Ala-Gly-Pro-Ala were found to be resistant to both crab proteases.

Amino Acid Sequence↗
PubMed1983

Muscle nitrogen metabolism of freshwater crab, Oziotelphusa senex senex Fabricius, during acute and chronic sumithion intoxication.

Muscle nitrogen metabolism was studied in the crab, Oziotelphusa senex senex Fabricius, following acute (1 day) and chronic (20 days) exposure to 0.1 ppm sumithion solution. Proteolysis in the muscle tissue in acute exposure was increased after exposure for 24 h. The muscle tissue of chronically exposed crabs seemed to develop a more efficient mechanism for the detoxication of ammonia compared with that of acutely exposed crabs. The survival of crabs after chronic sumithion intoxication has been attributed to adaptive changes involving protein synthesis and the metabolism of ammonia.

Amino Acids↗
PubMed1983

Chronic sumithion toxicity: effect on carbohydrate metabolism in crab muscle.

Chronic sumithion toxicity in experimental crabs was induced by exposing them for 15 and 30 days to 0.04 ppm sumithion solution. The enzymes concerned with glycogenolytic metabolism (phosphorylase), glycolytic metabolism (aldolase), aerobic metabolism [succinate dehydrogenase (SDH), malate dehydrogenase (MDH)], anaerobic metabolism, lactate dehydrogenase (LDH) and alanine amino transaminase (AIAT)], were assayed in the muscle of control and experimental crabs. Glycogen, pyruvic acid, lactic acid were also estimated in the muscle of both control and experimental crabs. The muscle tissue of chronic sumithion-exposed crab exhibited suppressed glycogenolysis and glycolysis with an onset of gluconeogenesis. In general, chronic sumithion exposure seems to result in an elevation of the synthetic phase of muscle carbohydrate metabolism.

Animals↗
PubMed1987

A comparison of dressed crab and a cadmium salt (CdCl2) as cadmium sources in rat diets.

1. A long term low level exposure experiment was conducted on rats in order to determine the metabolic patterns of realistic environmental dietary levels of cadmium from different sources. 2. Male and female rats were fed a diet for 6 months with a high crab content containing 4 mg Cd/kg as organic bound cadmium from dressed crab, a diet with low crab content containing 0.2 mg Cd/kg as organic bound cadmium, a casein based diet containing 4 mg Cd/kg as cadmium chloride and a low cadmium level control diet. 3. Analysis of the cadmium levels in the kidney, liver and spleen showed that uptake from the dressed crab was only half of that from the diet fortified with cadmium chloride.

Animals↗
PubMed1995

A urine collection system for studying the excretion of xenobiotics from Dungeness crabs.

A technique is described for collecting urine from the Dungeness crab, Cancer magister (Dana), a commercially important seafood and an indicator species of aquatic pollution. The technique has been modified from previously published methods to study the role of urinary excretion in the elimination of lipophilic pollutants by the Dungeness crab. The improved urine collection system uses chemically resistant and nonreactive materials that are better suited to pharmacological and toxicological studies than those used in previous methods. The improved method was tested by injecting a vital dye into catheterized Dungeness crabs and by measuring urine flows for 10 days. This technique can be used to determine the urinary excretion of xenobiotics and facilitate the characterization of chemicals and their metabolites accumulated by crabs.

Animals↗
PubMed2004

Use of the CABS methodology to assess biomechanical stress in commercial crab fishermen.

Commercial fishing is a job characterized by long hours in an unpredictable, dynamic natural environment and variable demands placed on the musculoskeletal system, requiring strength, coordination, and endurance. The focus of this project was in the quantification of the biomechanical stresses placed on the lumbar spine during the work activities of commercial crab fishermen. The continuous assessment of back stress (CABS) methodology was used to develop distributions describing the amount of time that each of the crew members on a two- or three-man crabbing crew spend at various levels of low back stress. The results of this analysis, expressed in terms of time-weighted histograms, show significant inter and intra-crewmember variability in the stress measures during regular daily work activities. For the three man crew, the captain has relatively low stress levels throughout the work day, while the mate performs high force (up to 30 kg), dynamic exertions while pulling the crab pots from the water up into the boat and high loads (20-40 kg) during the loading and unloading of the boat in the morning and evening, respectively. The third man of the crew experiences static awkward postures (forward flexed postures held for up to 5 min at a time) as he sorts and packs the crabs. For the two-man crew, the results show a more even distribution of the high stress activities between the crewmembers. The application of the results of this analysis for prioritization of work tasks for ergonomic intervention is discussed.

Biomechanical Phenomena↗