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Query: UMLS:C1832526 (PCC)
 5,967 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

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.
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PMID:Blood pressure and hepatocellular effects of the cyclic heptapeptide toxin produced by the freshwater cyanobacterium (blue-green alga) Microcystis aeruginosa strain PCC-7820. 314 Apr 25

An ATP-dependent Ca2+ uptake activity was identified in plasma membrane vesicles prepared from Synechococcus sp. strain PCC 7942. This activity was insensitive to agents which collapse pH gradients and membrane potentials but sensitive to vanadate, indicating that the activity is catalyzed by a P-type Ca(2+)-ATPase. A gene was cloned from Synechococcus sp. strain PCC 7942 by using a degenerate oligonucleotide based on a sequence conserved among P-type ATPases. This gene (pacL) encodes a product similar in structure to eukaryotic Ca(2+)-ATPases. We have shown that pacL encodes a Ca(2+)-ATPase by demonstrating that a strain in which pacL is disrupted has no Ca(2+)-ATPase activity associated with its plasma membrane. In addition, Ca(2+)-ATPase activity was restored to the delta pacL strain by introducing pacL into a second site in the Synechococcus sp. strain PCC 7942 chromosome.
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PMID:The pacL gene of Synechococcus sp. strain PCC 7942 encodes a Ca(2+)-transporting ATPase. 802 Dec 28

In cyanobacteria the protein on the outside of the gas vesicle, GvpC, is characterised by the presence of a 33 amino acid residue repeat (33RR), which in some genera is highly conserved. The number of 33RRs correlates with the diameter of the gas vesicle and inversely with its strength. Gas vesicles isolated from Microcystis aeruginosa strain PCC 7806 were found to be wider and have a lower critical collapse pressure than those from Microcystis sp. strain BC 8401. The entire gas-vesicle gene cluster of the latter strain was sequenced and compared with the published sequence of the former: the sequences of nine of the ten gvp genes differed by only 1-5% between the two strains; the only substantial difference was in gvpC which in strain BC 8401 lacked a 99-nucleotide section encoding a 33RR. This observation further narrows the correlation of gas vesicle width to the number of 33RRs and suggests how Microcystis strains might be used in experimental manipulation of gas vesicle width and strength.
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PMID:The diameter and critical collapse pressure of gas vesicles in Microcystis are correlated with GvpCs of different length. 1592 45

The cyanobacterium Microcystis is a potent producer of microcystins and cyanopeptolins and causes most of the toxicity outbreaks in freshwaters worldwide. Microcystins are mainly stored in the cells and little is found in the water. The intracellular concentration of microcystins in Microcystis PCC 7806 was at least 0.9 mM, although the solubility of microcystins in water was only about 10 microM. This low solubility does not allow the solubilisation of such high amounts of microcystins in the cytosol of Microcystis. Differential fractionation of cell constituents showed that microcystins and cyanopeptolins were bound to a protein fraction primarily composed of phycobilins. The percentage of microcystins and cyanopeptolins found in the thylakoid membranes was very low. Phycobilins may be the major proteins that have binding sites for these oligopeptides. A molar ratio near to 6 was observed for microcystins to the phycobilin (alphabeta) monomer. The binding of the microcystins to the protein was rather weak and allowed rapid dissociation of microcystins from the protein-matrix. Toxicity assays with Thamnocephalus platyurus showed that native microcystin when still bound to cyanobacterial protein was more toxic than an equivalent amount that has been desorbed from the protein by treatment with methanol. It is suggested that phycobilins serve in the gut of grazers as carrier molecules for the rapid transport of microcystin from lysed cells of Microcystis to the epithelium where the uptake of microcystins occurs. Because protein-bound microcystin does not bind to C18 cartridges, this behaviour can be the cause of many analytical discrepancies observed. The blue-coloured water observed upon the collapse of Microcystis blooms may be extremely toxic because the released phycobilins may carry the major fraction of microcystins.
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PMID:Topology and enhanced toxicity of bound microcystins in Microcystis PCC 7806. 1806 36

Although microcystins (MCs) are the most commonly studied cyanotoxins, their significance to the producing organisms remains unclear. MCs are known as endotoxins, but they can be found in the surrounding environment due to cell lysis, designated as extracellular MCs. In the present study, the interactions between MC producing and the non-producing strains of Microcystis aeruginosa, PCC 7806 and PCC 7005, respectively, and a green alga, Desmodesmus subspicatus, were studied to better understand the probable ecological importance of MCs at the collapse phase of cyanobacterial blooms. We applied a dialysis co-cultivation system where M. aeruginosa was grown inside dialysis tubing for one month. Then, D. subspicatus was added to the culture system on the outside of the membrane. Consequently, the growth of D. subspicatus and MC contents were measured over a 14-day co-exposure period. The results showed that Microcystis negatively affected the green alga as the growth of D. subspicatus was significantly inhibited in co-cultivation with both the MC-producing and -deficient strains. However, the inhibitory effect of the MC-producing strain was greater and observed earlier compared to the MC-deficient strain. Thus, MCs might be considered as an assistant factor that, in combination with other secondary metabolites of Microcystis, reinforce the ability to outcompete co-existing species.
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PMID:Desmodesmus subspicatus co-cultured with microcystin producing (PCC 7806) and the non-producing (PCC 7005) strains of Microcystis aeruginosa. 3135 71