The relative importance of biological and chemical processes in the release of phosphorus from a highly organic sediment

Bacteria can play an important role in the process of anaerobic phosphorus release: they can act as a direct source of orthophosphates, or as a catalyst of iron hydroxyde reduction. We studied their influence on phosphorus release from highly organic sediments of a Canadian shield lake. Phosphorus and iron release were measured under aerobic and anaerobic conditions, with or without sterilization, and at different pH. We measured also the abundance and activity of bacteria in sediments. The increased P release after sterilization can be explained by cell lysis. Compared to sterilization, changing oxygen concentrations or acidification had little or no effect on P release. In these sediments, phosphorus and iron movements were independent. Most of the total dissolved iron seemed to be linked to humic acids, but not phosphorus.A contribution to the GRIL (Groupe de Recherche Interuniversitaire de Limnologie)     

Significance of dissolved organic carbon in the prediction of thermocline depth in small Canadian shield lakes

Empirical models used to predict thermocline depths of lakes have typically been based on physical and morpho-metric variables. However, lakes with appreciable levels of dissolved organic material, including those found on the Canadian Precambrian Shield (DOC levels 1.4-12.41 mg/l), have seldom been included in these models. Our analysis suggests that for such lakes, thermocline depth is linked strongly to light penetration (Secchi depth r = 0.83, light extinction r = 0.85) which is strongly related to DOC concentration (Secchi depth r = 0.91, light extinction r = 0.97). A multivariate regression based on small Canadian Shield lakes suggests that DOC is the most important predictor of thermocline depth. Maximum effective length, maximum depth, and chlorophyll a contribute significantly to the prediction power of the regression model, but are of secondary importance in the presence of DOC. This revised version was published online in August 2006 with corrections to the Cover Date.     

The use of confocal microscopy in the investigation of cell structure and function in the heart,vascular endothelium and smooth muscle cells

In recent years, fluorescence microscopy imaging has become an important tool for studying cell structure and function. This non invasive technique permits characterization, localisation and qualitative quantification of free ions, messengers, pH, voltage and a pleiad of other molecules constituting living cells. In this paper, we present results using various commercially available fluorescent probes as well as some developed in our laboratory and discuss the advantages and limitations of these probes in confocal microscopy studies of the cardiovascular system.     

C-Terminal Fragments of Amyloid-β Peptide Cause Cholinergic Axonal Degeneration by a Toxic Effect Rather Than by Physical Injury in the Nondemented Human Brain

Previous experimental studies have indicated that amyloid-b peptide (A) may cause axonal degeneration in the brain of individuals with Alzheimer's disease (AD) by physical injury, mass lesion, or membrane perturbation. In this study, acetylcholinesterase histochemical, and A and tau immunohistochemical double-staining were performed in nondemented elderly human hippocampal and entorhinal brain samples, to demonstrate the presence of dystrophic neurites caused by the C-terminal or N-terminal fragments of A. The early interactions between the A-stained senile plaques (SPs) and the enzyme-positive axons were investigated. The double-stained samples revealed that A deposition occurs first, followed by the development of cholinergic axonal damage. Most of the dystrophic axonal processes are incorporated in the peripheral area of the SPs and are positive for phosphorylated tau [pS²⁰²] and tau-5. The result suggests that C-terminal fragments are more harmful than N-terminal fragments of A and may induce the development of dystrophic neurites by a toxic effect rather than by physical injury.     

A novel COL7A1 gene mutation causing pretibial epidermolysis bullosa: Report of a Chinese family with intra-familial phenotypical diversity

Pretibial epidermolysis bullosa (PEB) is an extremely rare subtype of dominant dystrophic epidermolysis bullosa (DDEB) caused by mutation of the COL7A1 gene. More than 730 mutations have been identified in patients with DDEB, but only five mutations have been found to be related to PEB. In this study, a novel heterozygous nucleotide G > T transition at position 6101 in exon 73 of COL7A1 was detected, which resulted in a glycine to valine substitution (G2034V) in the triple-helical domain of type-VII collagen. This is the first report to show that one mutation caused a broad range of severity of disease in one family with PEB. These data suggest that c.6101G > T may influence the phenotype of PEB. They also contribute to the expanding database on COL7A1 mutations.     

A Suggestion fob Prevention of Loose Sections in the Bodian Peotargol Method

Prolonged immersion in an aqueous medium such as the protargol bath in the original Bodian method for paraffin sections may increase any tendency for sections to separate from the slide during their subsequent reduction.     

Zooplankton variability related to environmental changes in a eutrophic coastal lagoon in the Po Delta

Zooplankton variability in a lagoon of the Po Delta, the Sacca di Goro, was studied in relation to changes in its hydrodynamic and hydrological features. From 1987 to 1992 the lagoon was affected each summer by severe anoxia due to the decomposition of dense and widespread beds of Ulva rigida. In August 1992 a canal was opened through the sand bank closing off the lagoon from the sea in order to improve the water circulation. This hydraulic intervention led to significant environmental changes in the lagoon: during the two subsequent years the summer dystrophic crises were brief and less severe, due to a sharp decrease in the Ulva cover. At the same time a clear increase in phytoplankton biomass values was observed. Following the opening of the channel, the most remarkable change in zooplankton was a significant density increase of calanoids, particularly of Acartia tonsa.