saxitoxin and Eye-Diseases

This study is the first report of saxitoxin in cyanobacterial blooms in Finland. Bloom samples (n = 50) were collected from Finnish freshwater sites during summer months of 2002 and 2003. These samples were screened for the presence of paralytic shellfish toxins (PSTs) using the Jellett rapid PSP screening test. Samples testing positive for PSTs (n = 7) were further analyzed with saxiphilin- and voltage-gated sodium channel [(3)H]-STX-binding radioreceptor assays and liquid chromatography using fluorescence and mass spectrometric analysis. The results indicated that saxitoxin (STX) was the only PST analogue in the samples and that it was present in high concentrations, as much as 1 mg L(-1). Microscopic analysis revealed that 95%-100% of the phytoplankton in the positive samples consisted of Anabaena lemmermannii. The trophic status of lakes in which STX-containing blooms were found varied from oligotrophic to hypertrophic. All the lakes had high nitrogen-to-phosphorus ratios. In some instances, samples had been collected from sites where swimmers had reported adverse health effects, and in three such cases, reported adverse health effects were associated with sites from which samples testing positive for STX had been received. Symptoms of fever, eye irritation, abdominal pains, and skin rash were reported in children aged 2-10 years after exposure to the water. These were not the adverse human symptoms typical of STX poisoning; rather, they represented acute effects often reported following recreational exposure to cyanobacterial blooms.

Topics: Abdominal Pain; Anabaena; Biological Assay; Child; Child, Preschool; Chromatography, Liquid; Environmental Exposure; Eutrophication; Exanthema; Eye Diseases; Female; Fever; Finland; Humans; Male; Public Health; Saxitoxin; Water Supply

Müller cells, the main macroglial cells of the retina, express several types of voltage and ligand-activated ion channels, including Na+ channels. Using the whole-cell voltage-clamp technique, we studied the expression of Na+ currents in acutely isolated, non-cultivated human Müller cells from retinas of healthy organ donors and patients suffering from different eye diseases. In both types of retinas transient Na+ currents could be recorded from Müller cells. The tetrodotoxin-resistant Na+ currents, which were not completely blocked even at a concentration of 10 microM tetrodotoxin, had a mean current density of 3.0 +/- 3.0 pA/pF (mean +/- SD, n = 10) in Müller cells from donor retinas and of 12.2 +/- 9.6 pA/pF (n = 74) in Müller cells from patient retinas. Only 33.3% of healthy but 88.4% of pathological Müller cells depicted such currents. The GNa+/GK+ ratio was very high in several Müller cells from patient retinas, such that action potential-like activity could be generated after prehyperpolarizing current injection in some of these cells. Apparently, the Na+ channels, due to their negative steady-state inactivation curve (Vh = -84.5 mV), do not influence the lowered membrane potential of the pathological cells, since they are inactivated at these voltages. Currently, we do not have an explanation for the increase in amplitude and frequency of Na+ currents in human Müller cells under pathological conditions. However, the up-regulation of Na+ channels may mirror a basic glial response to pathological conditions, since it has also been found previously in human hippocampal astrocytes from epileptic foci and in rat cortex stab wounds lined by an astrocytic scar.

Topics: Electric Conductivity; Eye Diseases; Homeostasis; Humans; Kinetics; Neuroglia; Reference Values; Retina; Saxitoxin; Sodium; Sodium Channel Blockers; Sodium Channels; Tetrodotoxin