Biology Reference
In-Depth Information
Incidences of human poisoning relate both to the recreational and drinking waters. Toxicity due
to blooms of Anabaena and Microcystis in recreational waters was reported from North America,
United Kingdom, the Netherlands, and Australia. Though no fatalities were reported from these
countries, illness due to cyanobacterial poisoning in Saskatchewan (Canada) developed stomach
cramps, vomiting, diarrhoea, fever, headache, pains in muscles and joints and weakness (Dillenberg
and Dehnel, 1960). Ingestion of lake water that developed toxic blooms of M . aeruginosa resulted in
hospitalization of two military recruits with atypical pneumonia in United Kingdom but yet majority
of them developed abdominal pain, nausea, vomiting and diarrhoea (Turner et al ., 1990). Besides
these symptoms, dermal irritation, sore red eyes, sore throat and allergic responses have also been
noted in some patients in Australia (Ressom et al ., 1994). Characteristic symptoms of MC-poisoning
in human beings upon drinking water loaded with cyanobacterial toxins are weakness, anorexia,
cold extremities, pallor, apathy, respiratory problems, gastroenteritis, vomiting and diarrhoea.
These symptoms are associated with necrosis of the liver leading to death by either haemorrhagic
shock or liver failure (Gorham and Carmichael, 1988; Codd, 1995, 2000; Dow and Swoboda, 2000;
de Figueiredo et al ., 2004). The outbreak of Palm Island mystery disease in Australia (Byth, 1980;
Hawkins et al ., 1985) was in fact associated with the development of hepatoenteritis in 140 school
children and 10 adults due to intake of lake water treated with copper sulphate that suffered the
bloom of C . raciborskii (Chorus and Bartram, 1999). It was suggested that the addition of copper
sulphate to control the bloom alga caused lysis of the cyanobacterial cells releasing more toxin into
the waters. Due to drinking of lakewater that developed immense cyanobacterial bloom, more
than 2000 cases of gastroenteritis in children were reported from Brazil in 1988, of these 88 of them
succumbed to death (Teixera et al ., 1993). The death of 76 hemodialysis patients in a dialysis center
at Caruaru, Brazil is a glaring example of human misery suffered due to hepatotoxins. This was
due to use of dialysate contaminated with cyanobacterial cells and toxins. This was designated as
'Caruaru syndrome' (Pouria et al ., 1998; Jochimsen et al ., 1998). Subsequent studies on the examination
of liver tissues by light microscopy and electron microscopy revealed a number of histopathological
changes. The characteristics of 'Caruaru syndrome' are painful, extreme hepatomegaly, jaundice, a
bleeding diathesis, disruption of liver plates, liver cell deformity, necrosis, apoptosis and injuries to
cell organelles. The serum samples from diseased patients and the carbon fi lters of the dialysis unit
revealed the existence of variants of MCs, i.e. MC-YR, MC-LR and MC-AR. The concentration of
MCs in liver samples from 39 patients, collected after the death of 52 patients in between February
to December, 1996, was found to be 223 ng g -1 liver tissue (Carmichael et al ., 2001).
v) Carcinogenicity : The hepatocellular specificity of MC-LR has been confirmed by
immunohistochemical studies in rats, mice and trout (Solter et al ., 1998; Yoshida et al ., 1998; Fischer
et al ., 2000). Upon chronic administration (20 kg -1 body weight, 100 times over 28 weeks), MCs
promoted the formation of multiple neoplastic nodules in the liver of mice (Ito et al ., 1997). Other
pathological symptoms reported in mice for chronic administration are increased liver weight and
hepatohistological damage (Heinze, 1999) and kidney damage in rats (Milutinovi et al ., 2002). The
carcinogenicity of MCs has been tested in vivo animal experiments. These involve testing DNA-
damaging chemicals that can initiate cancer development while other classes of chemicals are able
to promote cancer (Boutwell, 1974; Yamasaki, 1988; Fitzgerald and Yamasaki, 1990). The potential
of MCs as cancer promoting substances was thus tested in vivo on skin, liver and intestines of mice.
Initial application of 7,12-dimethyl benzanthracene (DMBA) as a single dose (500 µg) on dorsal skin
of mice followed by Microcystis extract (80 mg MC-YM L -1 ) increased the frequency of skin papillomas
(Falconer, 1991). In another carcinogenic bioassy, DEN was given i.p. at a dose of 200 mg kg -1 body
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