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Ecophysiology and trace metal uptake in crabs and other crustaceans
S 124
Abstracts / Comparative Biochemist*3" oral Phy,siology, Part A 126 (2000) SI S163
ECOPHYSIOLOGY AND TRACE METAL UPTAKE IN CRABS AND OTHER CRUSTACEANS R a i n b o w P.S. The Natural History Museum, Cromwell Road, London SW7 5BD, UK The uptake of dissolved trace metals by crustaceans is potentially affected both by the physicochemistry of the metal in solution, and by any physiological change by the crustacean, such as with stage of the moult cycle or in response to change in salinity. The physicochemistry of the aquatic medium controls the speciation of the dissolved metal, not least the activity of the hydrated free metal ion and its degree of complexation by organic or inorganic chelating agents, especially chloride in marine conditions. Thus physicochemistry controls the complexation of dissolved cadmium, determining the relative proportions present of the free cadmium ion, and charged or neutral chloride complexes. Different routes are potentially available for the uptake of dissolved cadmium; a neutral complex may diffuse across the lipophilic membrane, and the free metal ion may be transported via a protein career, potentially also via a calcium channel. While physicochemistry controls the chemical nature of the metal available for uptake from solution, the physiology of the crustacean affects the activities and relative contributions of different uptake routes available. Thus newly moulted crustaceans take up zinc and cadmium at an increased rate before the 'permeability' of the crustacean cuticle is reduced again to intermoult levels. An ecological series of crabs from the sea through an estuary to freshwater shows decreased metal uptake rates, correlated with differences in apparent water permeability; moreover metal uptake rates change in a euryhaline crab as the crab adapts physiologically to reduced salinity. Examples are given of crustaceans in which metal uptake rates are differentially affected by the ability of the crustacean to respond physiologically to environmental changes, gaining some control of metal uptake otherwise determined by physicochemistry. Such physiological intercession may, however, be as rare as the crustaceans concerned are cornmon.
METAL-RESPONSIVE GENES FROM AQUATIC INSECTS AS BIOMARKERS OF METAL POLLUTION Mattingly K.S., M a c k i e R.S., O r a y C., M c G a w M., K l i m o w s k i L., Carlson J.O., Beaty B.J. and R a y m s - K e l l e r A. Arthropod-Borne & Infectious Disease Laboratory, Center for Environmental Toxicology & T e c h n o l o g y D e p a r t m e n t of M i c r o b i o l o g y . C o l o r a d o State University. Fort Collins, C o l o r a d o 80523 .USA Water contamination is one of the most serious consequences of chemicals emanating from hazardous waste sites. In Colorado, it is estimated that heavy metals pollution impact over 2,600 km of streams. Aquatic insects have been extensively utilized as bioindicators of meal pollution. Sensitive, faster, and easier to screen biomarkers are sorely needed. Heavy metal responsive genes, such as the metallothioneins, have been isolated and characterized from variety of organism. Yet, despite their importance, no metal responsive genes from an aquatic insects has been isolated to this date. Here we report the molecular cloning of two cDNA from two aquatic insects whose RNA and /or protein product abundance are increased in individuals exposed to heavy metals. We have isolated a cDNA from the tropical mosquito Aedes aegypti that is transcribed in the larval midgut in response to metal exposure, and in the adult female midgut, where basal transcription is increased by iron or cadmium exposure, or a blood meal. The cDNA encodes a protein, designated Aedes aegypti intestinal mucin 1 (AEIMUCI), that has similarities with invertebrate intestinal mucins and peritrophins (proteins that compose the peritrophic matrix) and vertebrate mucins. As a biomarker of metal pollution, AEIMUC1 RNA abundance's was 100-fold more sensitive than traditional bioassays. We have isolated a cDNA from the aquatic insect Chironomus tentans termed CTTUB 1 which has significant similarities with invertebrate and vertebrate alpha tubulins. CTTUB 1 is very abundantly transcribed in embryos, and to a lesser extent in adults, In larvae, exposure to cadmium or copper increased the abundance of CTTUB 1 RNA and protein. The pattern of cellular distribution of CTTUB1 protein in the midgut epithelial cells was radically affected by cadmium. In unexposed larvae CTTUB 1 protein was more abundant in the perinuclear region. In contrast, in the midgut cells of cadmium-exposed larvae, CTTUB 1 protein was most concentrated near the plasma membrane. This is the first report on the isolation of a metal-responsive genes from aquatic insects. Metal responsive genes of aquatic insect may prove to be a powerful tool to dissect the underlying molecular mechanism of heavy metal toxicity, and sensitive biomarkers of metal exposure.
Abstracts / Comparative Biochemist*3" oral Phy,siology, Part A 126 (2000) SI S163
ECOPHYSIOLOGY AND TRACE METAL UPTAKE IN CRABS AND OTHER CRUSTACEANS R a i n b o w P.S. The Natural History Museum, Cromwell Road, London SW7 5BD, UK The uptake of dissolved trace metals by crustaceans is potentially affected both by the physicochemistry of the metal in solution, and by any physiological change by the crustacean, such as with stage of the moult cycle or in response to change in salinity. The physicochemistry of the aquatic medium controls the speciation of the dissolved metal, not least the activity of the hydrated free metal ion and its degree of complexation by organic or inorganic chelating agents, especially chloride in marine conditions. Thus physicochemistry controls the complexation of dissolved cadmium, determining the relative proportions present of the free cadmium ion, and charged or neutral chloride complexes. Different routes are potentially available for the uptake of dissolved cadmium; a neutral complex may diffuse across the lipophilic membrane, and the free metal ion may be transported via a protein career, potentially also via a calcium channel. While physicochemistry controls the chemical nature of the metal available for uptake from solution, the physiology of the crustacean affects the activities and relative contributions of different uptake routes available. Thus newly moulted crustaceans take up zinc and cadmium at an increased rate before the 'permeability' of the crustacean cuticle is reduced again to intermoult levels. An ecological series of crabs from the sea through an estuary to freshwater shows decreased metal uptake rates, correlated with differences in apparent water permeability; moreover metal uptake rates change in a euryhaline crab as the crab adapts physiologically to reduced salinity. Examples are given of crustaceans in which metal uptake rates are differentially affected by the ability of the crustacean to respond physiologically to environmental changes, gaining some control of metal uptake otherwise determined by physicochemistry. Such physiological intercession may, however, be as rare as the crustaceans concerned are cornmon.
METAL-RESPONSIVE GENES FROM AQUATIC INSECTS AS BIOMARKERS OF METAL POLLUTION Mattingly K.S., M a c k i e R.S., O r a y C., M c G a w M., K l i m o w s k i L., Carlson J.O., Beaty B.J. and R a y m s - K e l l e r A. Arthropod-Borne & Infectious Disease Laboratory, Center for Environmental Toxicology & T e c h n o l o g y D e p a r t m e n t of M i c r o b i o l o g y . C o l o r a d o State University. Fort Collins, C o l o r a d o 80523 .USA Water contamination is one of the most serious consequences of chemicals emanating from hazardous waste sites. In Colorado, it is estimated that heavy metals pollution impact over 2,600 km of streams. Aquatic insects have been extensively utilized as bioindicators of meal pollution. Sensitive, faster, and easier to screen biomarkers are sorely needed. Heavy metal responsive genes, such as the metallothioneins, have been isolated and characterized from variety of organism. Yet, despite their importance, no metal responsive genes from an aquatic insects has been isolated to this date. Here we report the molecular cloning of two cDNA from two aquatic insects whose RNA and /or protein product abundance are increased in individuals exposed to heavy metals. We have isolated a cDNA from the tropical mosquito Aedes aegypti that is transcribed in the larval midgut in response to metal exposure, and in the adult female midgut, where basal transcription is increased by iron or cadmium exposure, or a blood meal. The cDNA encodes a protein, designated Aedes aegypti intestinal mucin 1 (AEIMUCI), that has similarities with invertebrate intestinal mucins and peritrophins (proteins that compose the peritrophic matrix) and vertebrate mucins. As a biomarker of metal pollution, AEIMUC1 RNA abundance's was 100-fold more sensitive than traditional bioassays. We have isolated a cDNA from the aquatic insect Chironomus tentans termed CTTUB 1 which has significant similarities with invertebrate and vertebrate alpha tubulins. CTTUB 1 is very abundantly transcribed in embryos, and to a lesser extent in adults, In larvae, exposure to cadmium or copper increased the abundance of CTTUB 1 RNA and protein. The pattern of cellular distribution of CTTUB1 protein in the midgut epithelial cells was radically affected by cadmium. In unexposed larvae CTTUB 1 protein was more abundant in the perinuclear region. In contrast, in the midgut cells of cadmium-exposed larvae, CTTUB 1 protein was most concentrated near the plasma membrane. This is the first report on the isolation of a metal-responsive genes from aquatic insects. Metal responsive genes of aquatic insect may prove to be a powerful tool to dissect the underlying molecular mechanism of heavy metal toxicity, and sensitive biomarkers of metal exposure.