Toxicity thresholds for juvenile freshwater mussels Echyridella menziesii and crayfish Paranephrops planifrons, after acute or chronic exposure to Microcystis sp

Survival of juvenile freshwater mussels (Echyridella menziesii (Gray, 1843) formerly known as Hyridella menziesi) and crayfish (Paranephrops planifrons, White, 1842) decreased after four days exposure to microcystin-containing cell-free extracts (MCFE) of Microcystis sp. at concentrations typical of severe cyanobacterial blooms. Crayfish survival was 100, 80, and 50% in microcystin concentrations of 1339, 2426, and 11146 μg L(-1) respectively, and shade- and shelter-seeking behavior was negatively affected when concentrations were ≥2426 μg L(-1) . Mussel survival decreased to 92% and reburial rates decreased to 16% after exposure for 96 h to MCFE containing microcystins at concentrations of 5300 μg L(-1) . Crayfish survival was 100% when fed freeze-dried Microcystis sp. incorporated into an artificial diet (6-100 μg microcystin kg(-1) ww) at dietary doses from 0.03 to 0.55 μg g(-1) body weight d(-1) for 27 days. Specific growth rate was significantly lower in crayfish fed ≥0.15 μg g(-1) body weight day(-1) compared with controls, but not compared with a diet incorporating nontoxic cyanobacteria. Microcystins accumulated preferentially in crayfish hepatopancreas and mussel digesta as MCFE or dietary concentrations increased. These laboratory data indicate that, assuming dissolved oxygen concentrations remain adequate, and no simultaneous exposure to live Microcystis sp. cells, cell-free microcystins will only be a significant stressor to juvenile crayfish and mussels in severe Microcystis sp. blooms. In contrast, crayfish were negatively affected by relatively low concentrations of microcystins in artificial diets compared with those measured locally in benthic cyanobacterial mats.

Alterations in rectal sensitivity and motility in childhood irritable bowel syndrome

BACKGROUND & AIMS

Children with chronic abdominal pain have a heterogeneous clinical presentation, but no organic cause can be identified in most of them. Some children present with symptoms of irritable bowel syndrome (IBS). We hypothesized that visceral hypersensitivity and motor abnormalities may be underlying mechanisms in these children.

METHODS

Rectal sensation and rectal contractile response to a meal were studied in 8 children with IBS and 8 children with functional abdominal pain (FAP) and were compared with those of 9 healthy volunteers (HVs).

RESULTS

The threshold for pain, but not that for first sensation and urge to defecate, was significantly decreased in IBS patients (6 +/- 1 mm Hg) compared with FAP patients and HVs (17 +/- 1 and 22 +/- 2 mm Hg, respectively). In HVs and patients with FAP, ingestion of a meal induced a decrease in rectal volume with an early and late component. This motor pattern was absent in children with IBS. In IBS patients, no rapid volume waves were observed during fasting in contrast to FAP patients (2.7 +/- 0.3/10 min) and HVs (1.8 +/- 0.5/10 min).

CONCLUSIONS

Children fulfilling the Rome II criteria for IBS have a significantly lowered threshold for pain and a disturbed contractile response to a meal. Comparable to results reported in adults, sensory and motor abnormalities might play a pathophysiologic role in childhood IBS.

The repatriation of anthropology: Some observations on Endo-ethnography

For a few decades, anthropologists have increasingly turned to the study of their own society and culture. This article addresses the problems and the relative advantages and disadvantages of endogenous ethnography. It devotes special attention to the experiences of medical anthropologists who have conducted fieldwork at home. It is concluded that anthropology at home has no special epistemological position compared with anthropological research abroad, though there may be differences at the practical level of fieldwork and publishing.