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W W Carmichael

Publications and source records attributed to W W Carmichael.

At least 55 records · Page 3Linked to original sources
PubMed1990

Isolation and characterization of the minor components associated with microcystins LR and RR in the cyanobacterium (blue-green algae).

Two structurally similar analogues of microcystins LR and RR, cyclic peptide hepatotoxins from Microcystis, were isolated by chromatographic methods. Although they have the same mol. wt and amino acid compositions as those of the parent toxins, they do not possess similar toxicities. Ultraviolet and 1H-NMR spectral data for both components demonstrate clear structural difference of these cyclic peptides from the parent toxins, which are probably responsible for the marked decreases in their observed toxicities.

Amino Acids↗
PubMed1990

Pathophysiologic effects of anatoxin-a(s) in anaesthetized rats: the influence of atropine and artificial respiration.

The pathophysiologic effects of anatoxin-a(s) from the cyanobacterium Anabaena flos-aquae NRC-525-17 were investigated in anaesthetized adult male Sprague Dawley rats given the toxin by continuous intravenous infusion until death. Rats (n = 6) pretreated with atropine sulfate (50 mg/kg) intraperitoneally survived significantly longer (P less than 0.05) than non-atropinized rats (n = 6), suggesting that the muscarinic effects of anatoxin-a(s) were important in the lethal syndrome. In contrast to rats only given toxin, rats that were pretreated with atropine had a decrease in heart rate and mean blood pressure that followed profound reductions in respiratory tidal and minute volume, suggesting that neuromuscular blockade of the muscles of respiration was the cause of death. Even when survival time of rats was increased by pretreatment with atropine, phrenic nerve amplitude increased, indicating a lack of a depressive effect of anatoxin-a(s) on central mediation of respiration. Rats (n = 3) continuously ventilated during toxin infusion survived a dose more than 4 fold greater than a consistently lethal dose of the toxin. Thus, the cardiovascular effects of anatoxin-a(s) alone could not account for the death of rats. Electromyographic activity recorded from the diaphragms of rats (n = 5) during continuous toxin administration revealed an increase in muscular electrical activity that became more random and finally decreased prior to death, suggesting a toxin-induced neuromuscular blockade in vivo which ultimately was the cause of death of the anatoxin-a(s) dosed rats.

Anesthesia, Inhalation↗
PubMed1990

Isolation and characterization of hepatotoxic microcystin homologs from the filamentous freshwater cyanobacterium Nostoc sp. strain 152.

A strain of the filamentous cyanobacterium Nostoc sp. isolated from a lake in Finland was found to produce at least nine hepatotoxic peptides with chemical and toxicological properties similar to those of the hepatotoxic hepta- and pentapeptides produced by other cyanobacteria. Toxins were isolated and purified by high-performance liquid chromatography. Amounts available for five of the purified toxins (P6, P14, P15, P16, and P18) were adequate for high-performance liquid chromatography amino acid analysis and determination of molecular weight by fast-atom bombardment-mass spectrometry (FAB-MS). Quantities of three toxins (P14, P15, and P16) were adequate for further analysis by high-resolution FAB-MS, FAB-MS/MS, and 1H-nuclear magnetic resonance. Analysis showed that the toxins are new types of microcystin-LR homologs. Microcystin-LR contains equimolar amounts of D-alanine, L-leucine, D-erythro-beta-methylaspartic acid, L-arginine, ADDA (3-amino-9-methoxy-2,6,8-trimethyl-10-phenyl-4,6-decadienoic acid), D-glutamic acid, and N-methyldehydroalanine (molecular weight [MW], 994). Nostoc sp. strain 152 was found to produce the following microcystin-LR homologs: (i) P6 contains an extra methylene group most probably due to the presence of N-methyldehydrobutyrine instead of N-methyldehydroalanine (MW, 1,008); (ii) P14 is O-acetyl-O-demethyl ADDA-microcystin-LR (MW, 1,022); (iii) P15 is 3-demethyl-O-acetylADDA-homoarginine-microcystin-LR (MW, 1,036); (iv) P16 is 3-demethyl-O-acetyl-O-demethylADDA-microcystin-LR (MW, 1,008); (v) P18 is 3-demethyl-O-acetyl-O-demethylADDA-homoarginine-microcystin- LR (MW, 1,022). The toxicities of the new microcystin homologs were not significantly different from those of microcystin-LR or demethylmicrocystin-LR.

Amino Acids↗
PubMed1990

Microcystin-LR-induced ultrastructural changes in rats.

The ultrastructure of hepatic, pulmonary, and renal lesions was evaluated in rats injected intraperitoneally with a lethal dose of microcystin-LR (MCLR, 160 micrograms/kg), a cyclic heptapeptide hepatotoxin produced by the blue-green algae, Microcystis aeruginosa. Hepatic lesions were first seen at 10 minutes post-dosing and consisted of mild widening of hepatocyte intercellular spaces centrilobularly. At 20 minutes post-dosing, hepatocyte plasma membrane alterations were more pronounced, consisting of plasma membrane invagination with formation of variably sized and shaped intracytoplasmic vacuoles, loss of microvilli along the sinusoidal face, and widespread, pronounced hepatocyte separation. By 30 minutes, the space of Disse was markedly widened. At 60 minutes post-dosing, centrilobular areas contained necrotic cells and apparently intact, isolated, organelles intermingled with erythrocytes and platelets. In less severely affected regions there was prominent hepatocyte rounding, and erythrocytes and platelets were present in the widened space of Disse. Large amounts of hepatocellular debris and intact hepatocytes were present in the pulmonary vasculature, while smaller amounts of debris were also seen in the glomerular and peritubular capillaries of the renal cortex. This study shows that initial lesions are confined to shape changes in the plasma membrane of hepatocytes. These changes are consistent with the hypothesis that microcystin-LR induces alterations in the hepatocyte cytoskeleton. Later changes consist of hepatocyte disassociation and necrosis, as well as endothelial damage, which allow release of hepatocytes and debris into the circulation with microembolism in lungs and kidneys.

Animals↗
PubMed1989

A new procedure for the analysis and purification of naturally occurring anatoxin-a from the blue-green alga Anabaena flos-aquae.

Anabaena flos-aquae produces at least two neurotoxins termed anatoxin-a (ANTX-a) and -a(s) [ANTX-a(s)]. ANTX-a is a potent postsynaptic depolarizing neuromuscular blocking agent. Its structure is the secondary amine, 2-acetyl-9-azabicyclo[4.2.1]non-2-ene. Known isolation and analysis methods have not always given satisfactory results. Therefore, an improved procedure was developed for both isolation and analysis of ANTX-a which involves four steps; extraction, clean-up, separation and determination. Extraction was efficiently done with 0.05 M acetic acid, and a reversed phase. ODS (octadecylsilanized) and a cation exchanger (COOH) organosilans bonded to silica gels were applied to a clean-up step. Separation and determination were then performed using two TLC and HPLC chromatographies.

Bacterial Toxins↗
PubMed1989

Regional brain cholinesterase activity in rats injected intraperitoneally with anatoxin-a(s) or paraoxon.

Adult male Long-Evans rats were injected intraperitoneally with 1.5, 3.0 or 9.0 micrograms/kg of anatoxin-a(s) that had been extracted from laboratory-grown Anabaena flos-aquae NRC-525-17, 800 micrograms/kg of paraoxon, or a control solution. Blood, anterior spinal cord, and brain cerebellar, cortical, medullary, midbrain, hippocampal, hypothalamic, olfactory and striatal cholinesterase activity was determined in rats that died prior to 2 hours or were anesthetized and killed at 2 hours. Unlike paraoxon, anatoxin-a(s) did not cause detectable inhibition of cholinesterase in the central nervous system, but did cause inhibition of cholinesterase in blood, suggesting that anatoxin-a(s) is strictly a peripheral cholinesterase inhibitor.

Animals↗
PubMed1989

Structural characterization of toxic cyclic peptides from blue-green algae by tandem mass spectrometry.

Combined use of chemical degradation, derivatization, and tandem mass spectrometry for rapid structural characterization of toxic cyclic peptides from blue-green algae at the nanomole level is described. Previously, all blue-green algal toxins were thought to belong to a family of seven-residue cyclic peptides, having the general structure cyclo-D-Ala-L-Xaa-erythro-beta-methyl-D-isoaspartic acid-L-Yaa-Adda-D-isoglutamic acid-N-methyldehydroalanine, where Xaa and Yaa represent variable amino acids of the L configuration and Adda is 3-amino-9-methoxy-2,6,8-trimethyl-10-phenyl-deca-4,6-dienoic acid. Structural characterization of two additional toxins indicates that further variability can exist within this family of naturally occurring toxic cyclic peptides. Isoaspartic acid and dehydroalanine can substitute for beta-methylisoaspartic acid and N-methyldehydroalanine, respectively.

Amino Acid Sequence↗
PubMed1989

A model system for studying the bioavailability of intestinally administered microcystin-LR, a hepatotoxic peptide from the cyanobacterium Microcystis aeruginosa.

Sprague-Dawley rats were used to evaluate a model system for studying the hepatotoxicity caused by microcystin-LR (MCYST-LR), a toxin produced by the cyanobacterium (blue-green alga) Microcystis aeruginosa, and for evaluating the in vivo therapeutic potential of cholestyramine resin (CTR) which was found to bind the toxin in vitro. Female rats were treated with either toxin or an equivalent volume of the saline vehicle by direct administration into the lumen of an in situ isolated ileal loop. Male rats were dosed with toxin as described above, and then animals were dosed in the ileal loop with either cholestyramine resin (CTR, 50 mg/rat) or an equivalent vehicle. The survivors in both studies were killed six hours after dosing and hepatotoxicity was assessed by change in relative liver weights. In all groups given toxin alone, there was a significant increase in liver weight and males and females were equally susceptible. Liver weights of the toxin plus CTR treated rats were similar to those in vehicle-treated rats. When the toxin was administered into a similarly isolated jejunal loop, liver weight was significantly less than that found when an equivalent dose was administered into the ileal loop suggesting an intestinal site specificity for toxin absorption.

Animals↗
PubMed1989

Production and characterization of antibodies against microcystins.

Antibodies against a microcystin (MCYST) leucine-arginine variant (MCYST-LR) were demonstrated 4 weeks after immunization of rabbits with either MCYST-LR-polylysine- or MCYST-LR-ethylenediamine-modified bovine serum albumin. A radioimmunoassay (RIA), a direct competitive enzyme-linked immunosorbent assay (ELISA), and an indirect competitive ELISA were developed for characterization of the antibodies. Indirect ELISA and RIA revealed that MCYST-LR-ethylenediamine-bovine serum albumin was a better immunogen. Competitive RIA and direct ELISA revealed that the antibodies had good cross-reactivities with an MCYST-arginine-arginine variant (MCYST-RR), MCYST-LR, an MCYST-tyrosine-arginine variant (MCYST-YR), and nodularin (NODLN); but they had lower reactivities with variants MCYST-leucine-tyrosine (MCYST-LY) and MCYST-leucine-alanine (MCYST-LA). The antibodies did not cross-react with ozonolyzed MCYST-LR. The concentrations causing 50% inhibition of binding of reduced MCYST-LR to the antibodies by MCYST-RR, MCYST-LR, MCYST-YR, NODLN, MCYST-LA, and MCYST-LY in the RIA were 43, 105, 112, 503, 671, and 1,920 ng/ml, respectively. The concentrations causing 50% inhibition of binding of MCYST-LR-horseradish peroxidase to the antibodies by MCYST-RR, MCYST-LR, MCYST-YR, NODLN, MCYST-LY, and MCYST-LA in the ELISA were 1.75, 2.2, 3.4, 4.6, 50, and 114 ng/ml, respectively.

Animals↗
PubMed1989

Occurrence of the hepatotoxic cyanobacterium Nodularia spumigena in the Baltic Sea and structure of the toxin.

Water blooms formed by potentially toxic species of cyanobacteria are a common phenomenon in the Baltic Sea in late summer. Twenty-five cyanobacterial bloom samples were collected from open and coastal waters of the Baltic Sea during 1985 to 1987, and their toxicity was determined by mouse bioassay. All of 5 bloom samples from the southern Baltic Sea, 6 of 6 from the open northern Baltic Sea (Gulf of Finland), and 7 of 14 Finnish coastal samples were found to contain hepatotoxic cyanobacteria. Nodularia spumigena and Aphanizomenon flos-aquae occurred together in high amounts in blooms from the open-sea areas. In addition, coastal samples contained the species Anabaena lemmermannii, Microcystis aeruginosa, and Oscillatoria agardhii. Eighteen hepatotoxic N. spumigena cultures were isolated from water bloom and open-sea water samples. High-pressure liquid chromatographic analysis of both hepatotoxic bloom samples and Nodularia strains showed a single toxic fraction. The toxin concentrations of the blooms were less than or equal to 2.4 mg/g of freeze-dried material, and those of laboratory-grown cultures were 2.5 to 8.0 mg/g of freeze-dried cells. A single toxin was isolated from three N. spumigena-containing bloom samples and three N. spumigena laboratory isolates. Amino acid analysis and low- and high-resolution fast-atom bombardment mass spectroscopy indicated that the toxin from all of the sources was a cyclic pentapeptide (molecular weight, 824) containing glutamic acid, beta-methylaspartic acid, arginine, N-methyldehydrobutyrine, and 3-amino-9-methoxy-2,6,8-trimethyl-10-phenyl-4,6-decadienoic acid.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗
PubMed1989

Toxicity of microcystin LR, a cyclic heptapeptide hepatotoxin from Microcystis aeruginosa, to rats and mice.

Rats (Sprague-Dawley) and mice (Balb/c) were given microcystin LR intraperitoneally and were killed at intervals up to 24 hr (rats) or 90 min (mice) and necropsied. The lowest consistently lethal dose was 160 micrograms/kg in rats and 100 micrograms/kg in mice. Rats that were clinically unaffected had no lesion. All clinically affected rats in all dose groups died (from 20 to 32 hr after toxin) and had similar hepatic lesions. Livers were enlarged and dark red beginning 40 to 60 min after toxin. Mild disassociation and rounding of centrilobular hepatocytes developed within 20 min. By 60 min after toxin, degeneration and necrosis of hepatocytes involved most of the lobules except for small periportal zones. Weights of livers and kidneys were significantly increased. Eosinophilic fibrillar material filled renal glomerular capillaries as early as 9 hr after toxin. At 18 to 24 hr there was moderate vacuolation of proximal tubular epithelium with mild tubular dilatation. Beginning at 1 hr, intact hepatocytes and hepatic debris were present in pulmonary vessels. Analysis of serum revealed an increase in alanine aminotransferase 40 min after toxin; at 6 to 12 hr there were significant increases in alkaline phosphatase, total bilirubin, blood urea nitrogen, and creatinine. Mice survived only 60 to 90 min after toxin. Hepatic lesions were similar to those in rats, but renal and pulmonary lesions were not seen.

Animals↗
PubMed1988

Analysis and purification of toxic peptides from cyanobacteria by reversed-phase high-performance liquid chromatography.

A simple, rapid and reliable chemical analysis method for microcystins (cyanoginosins) has been studied. Three different mobile phases for high-performance liquid chromatography were selected and optimized. Also the adsorptive powers of three commercially available C18 cartridges were compared and the results successfully applied to the clean up of three of the toxins. Finally a total system for the analysis and isolation of microcystins was established.

Chromatography, High Pressure Liquid↗
PubMed1988

Improved method for purification of toxic peptides produced by cyanobacteria.

The improved method consists of ODS-silica gel extraction, and separation on silica gel and HPLC with UV (238 nm) detector. The method has been successfully applied to the isolation of toxic peptides from the Monroe and M-228 strains of Microcystis aeruginosa. This method reduces toxin extraction and separation time, and so enables a rapid isolation of peptide toxins from cyanobacteria.

Chromatography, Gel↗
PubMed1988

Blood pressure and hepatocellular effects of the cyclic heptapeptide toxin produced by the freshwater cyanobacterium (blue-green alga) Microcystis aeruginosa strain PCC-7820.

Laboratory rats and mice were used to investigate the hepatotoxicity caused by the cyclic heptapeptide (mol. wt 994) termed microcystin-LR. Microcystin-LR (also known as cyanoginosin-LR) is produced by the freshwater cyanobacterium (blue-green alga) M. aeruginosa strain PCC-7820. In time course histopathology studies with mice significant liver damage, with an absence of pulmonary emboli, were observed after 15 min. Pulmonary emboli did not appear until 1 hr. In rats, significant liver damage and the presence of occasional emboli were observed at 20 min. Pulmonary emboli did not contain fibrin nor appear life-threatening in any case and resembled the globular eosinophilic debris found in the liver sinusoids and central veins. Measurements of rat femoral arterial, jugular venous and hepatic portal venous blood pressures during the course of toxicity revealed a slowly declining arterial pressure and stable, normal venous pressures. Blood lactic acid levels rose in parallel with the fall in arterial pressure, a pattern typical of hemorrhagic shock. There was no indication of venous congestion that would accompany right heart failure. Isolated, perfused rat livers dosed with toxin showed rapid changes in the liver, including cessation of bile flow within 10 min and complete obliteration of normal lobular architecture within 60 min. No effect of the toxin was observed in isolated perfused rat heart. We conclude that in the mouse and rat, microcystin-LR is a potent, rapid-acting, direct hepatotoxin, with the immediate cause of death in acute toxicities being hemorrhagic shock secondary to massive hepatocellular necrosis and collapse of hepatic parenchyma.

Animals↗
PubMed1988

Comparison of effects of anatoxin-a(s) and paraoxon, physostigmine and pyridostigmine on mouse brain cholinesterase activity.

Anatoxin-a(s), an alkaloid neurotoxin from the freshwater cyanobacterium, Anabaena flos-aquae NRC-525-17, was compared to paraoxon, physostigmine and pyridostigmine for effects on brain cholinesterase after i.p. injection into Balb/c mice. The duration of clinical signs in mice injected with anatoxin-a(s) persisted longer than in mice given the carbamates and was comparable with that of paraoxon. Anatoxin-a(s) did not inhibit brain cholinesterase activity suggesting that this toxin is unable to cross the blood-brain barrier.

Animals↗
PubMed1988

Partial structural determination of hepatotoxic peptides from Microcystis aeruginosa (cyanobacterium) collected in ponds of central China.

Waterbloom samples of the colonial cyanobacterium Microcystis aeruginosa, collected in fish ponds at the Hydrobiological Institute, Wuhan, People's Republic of China, were hepatotoxic to mice. Lyophilized cells had an LD50 (i.p. mouse; 40 mg/kg) and signs of poisoning similar to that reported for other cyanobacterial hepatotoxic peptides. Two toxins, with an LD50 (i.p. mouse) of 40 and 150 micrograms/kg, were isolated using gel filtration and high performance liquid chromatography. The amino acid composition and mol. wt (994) of the 40 micrograms/kg toxin was the same as that for microcystin-LR, while the 150 micrograms/kg toxin had an amino acid composition and mol. wt (1048) different from any of the reported cyanobacteria heptapeptide toxins reported to date.

Amino Acids↗