F.N.A.M. van Pelt

Shellfish toxicity: human health implications of marine algal toxins

Five major human toxic syndromes caused by the consumption of shellfish contaminated by algal toxins are presented. The increased risks to humans of shellfish toxicity from the prevalence of harmful algal blooms (HABs) may be a consequence of large-scale ecological changes from anthropogenic activities, especially increased eutrophication, marine transport and aquaculture, and global climate change. Improvements in toxin detection methods and increased toxin surveillance programmes are positive developments in limiting human exposure to shellfish toxins.

The effects of salinity on the Manila clam (Ruditapes philippinarum) using the neutral red retention assay with adapted physiological saline solutions

This study investigated the internal osmotic regulatory capabilities of the Manila clam (Ruditapes philippinarum) following in vivo exposure to a range of salinities. A second objective was to measure the health status of the Manila clam following exposure to different salinities using the neutral red retention (NRR) assay, and to compare results using a range of physiological saline solutions (PSS). On exposure to seawater of differing salinities, the Manila clam followed a pattern of an osmoconformer, although they seemed to partially regulate their circulatory haemolytic fluids to be hyperosmotic to the surrounding aqueous environment. Significant differences were found when different PSS were used, emphasizing the importance of using a suitable PSS to reduce additional osmotic stress. Using PSS in the NRR assay that do not exert additional damage to lysosomal membrane integrity will help to more accurately quantify the effects of exposure to pollutants on the organism(s) under investigation.

The effects of concurrent atorvastatin therapy on the pharmacokinetics of intravenous midazolam.

Midazolam is a commonly used anaesthetic agent and is metabolised by the 3A4 isoform of the cytochrome P450 enzyme system. Atorvastatin is also metabolised by cytochrome P450 3A4 and, in vitro, atorvastatin inhibits the cytochrome P450 3A4‐mediated metabolism of mexazolam. We hypothesised that concurrent administration of atorvastatin and midazolam would result in altered midazolam pharmacokinetics. Fourteen patients scheduled to undergo general anaesthesia for elective surgery were recruited in a matched pair design to receive intravenous midazolam (0.15 mg.kg−1). Of these patients, seven were taking long‐term atorvastatin. Atorvastatin patients demonstrated a greater area under the curve (889.4 (standard deviation 388.6) ng‐h.ml−1) vs. control patients (629.1 (standard deviation 197.2) ng‐h.ml−1) (p < 0.05). Patients taking atorvastatin also demonstrated a decreased clearance (0.18 (standard deviation 0.08) l‐kg. h−1) vs. control patients (0.27 (standard deviation 0.08) l‐kg.h−1) (p < 0.05). This study suggests that chronically administered atorvastatin decreases the clearance of intravenously administered midazolam.

Effect of atorvastatin and fluvastatin on the metabolism of midazolam by cytochrome P450 in vitro.

We have investigated the effects of the statins atorvastatin and fluvastatin on the cytochrome P450 3A4 enzyme (CYP 3A4)‐mediated metabolism of midazolam in vitro, using pooled human liver microsomes. Midazolam was metabolised by human hepatic microsomes with a Michaelis–Menten constant (Km) of 5.25 (SD 1.2) μmol.l−1. Atorvastatin was a moderate competitive inhibitor of CYP 3A4 with an inhibitory constant (Ki) of 12.4 (95% CI 4.65–20.06) μmol.l−1. Fluvastatin was a weak non‐competitive inhibitor of CYP 3A4 with a Ki of 94.3 (95% CI 55.01–133.5) μmol.l−1. Both atorvastatin and fluvastatin inhibit the CYP 3A4‐mediated metabolism of midazolam in vitro.

Effects of contaminated sediment from Cork Harbour, Ireland on the cytochrome P450 system of turbot.

Hatchery-reared juvenile turbot (Scophthalmus maximus L.) were exposed for 3 weeks, under laboratory conditions, to inter-tidal sediments collected from polluted sites in Cork Harbour (Whitegate and Agahda) and a reference site at Ballymacoda Co., Cork, Ireland. The potential of the sediment exposure to induce cytochrome P450 activities and CYP1A1 in the fish was assessed. Chemical analysis revealed that the sediments originating from the reference and harbour sites were contaminated principally with PAHs-the harbour sites having double the levels of those at the reference site. Following 3 weeks exposure to the sediments western blotting demonstrated a strong immunogenic response for CYP1A1 in the liver, but not for gill or intestine. P450 activities were generally significantly higher than those exposed to reference site sediment. Liver was the most responsive tissue with significantly greater P450 activities compared with gill and intestinal tissues.

Two-dimensional electrophoresis analysis of glutathione affinity-selected proteins from the clam Tapes semidecussatus: Evidence for tissue-specific expression of redox proteins

Proteins from gill, digestive gland and mantle of the clam Tapes semidecussatus were selected on glutathione (GSH) agarose to simplify proteomic comparison. Analysis by two-dimensional gel electrophoresis (2D SDS PAGE) revealed tissue-specific patterns of protein expression with some spots common to all tissues. Immunoblotting of gill and digestive gland separations identified some spots as glutathione transferases (GSTs). In gill and digestive gland several spots were immunoblotted with Pi class GSTs indicating multiple isoenzymes. Selected spots were excised, digested with trypsin and analyzed by reversed phase C-18 high performance liquid chromatography and tandem mass spectrometry. This confirmed that gill and digestive gland share some GST isoenzymes. Our results suggest that this clam expresses a complex tissue-specific pattern of GSH-binding proteins, which may reflect different redox requirements in each tissue.