Mitochondria a key role in microcystin-LR kidney intoxication

Microcystins (MCs) are a group of closely related cyclic heptapeptides produced by a variety of common cyanobacteria. These toxins have been implicated in both human and livestock mortality. Microcystin-LR could affect renal physiology by altering vascular, glomerular and urinary parameters, indicating that MC-LR could act directly on the kidney. The aim of the current work was to examine the effect of MC-LR on mitochondrial oxidative phosphorylation of rat kidney isolated mitochondria.Furthermore, microcystin-LR decreased both state 3 and carbonylcyanide p-trifluoromethoxyphenylhydrazone (FCCP)-uncoupled respiration. The transmembrane potential was strongly depressed by MC-LR in a concentration dependent manner, pointing to an uncoupling effect; however, microcystin-LR did not increase the permeability of the inner mitochondria membrane to protons. Therefore, the transmembrane decrease was a consequence of a strong inhibitory effect on redox complexes. The addition of uncoupling concentrations of MC-LR to Ca(2+)-loaded mitochondria treated with ruthenium red resulted in mitochondrial permeability transition pore (MPTP) opening, as evidenced by mitochondrial swelling in isosmotic sucrose medium. Mitochondrial swelling in the presence of Ca(2+) was prevented by cyclosporin A and was drastically inhibited by catalase and dithiothreitol, indicating the participation of mitochondrial generated reactive oxygen species in this process. From this study it can be concluded that the bioenergetic lesion promoted by microcystin-LR seems to be sufficient to explain renal injury.

DNA image cytometry in bladder cancer: state of the art

The most recent Consensus Review of the Clinical Utility of DNA Cytometry in Bladder Cancer, which took place in Maine back in 1992, focused solely on flow cytometry results. Since then, there have been a significant number of articles published on the use of image cytometry to evaluate DNA content in bladder cancer. This has meant that a large proportion of the information collected is scattered across the published literature. The purpose of this article was to organize the data referred to in those articles published since the 1992 Consensus Review, and organise it under three major topic headings: a) DNA image cytometry versus flow cytometry, (b) specimen sources, and (c) its clinical utility with regard to improving prognosis and recurrence detection. A variety of factors and issues are discussed and points have been raised for discussion. Prospects for the future and potential research areas are also suggested.

A phyllodes tumor of the urinary bladder in a rat

AIM

The aim of this short communication was to describe a case of phyllodes tumor of the urinary bladder discovered in a female Fisher 344 rat that died during an experimental protocol to induce and study urothelial lesions by N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN).

METHODOLOGY

From a group of several female rats exposed to BBN via drinking water over the course of 20 weeks, one animal died. At necropsy, a solid mass was identified in the urinary bladder lumen, with a diameter of 0.8 x 0.7 cm. This tumor was processed for histopathological examination and Feulgen coloration.

RESULTS

Microscopically, the mass in the bladder was observed to be a phyllodes tumor. DNA content measured by image analysis of a Feulgen-stained section of the tumor and stroma cells displayed diploid DNA content in both components of the tumor.

CONCLUSION

This is the first reported phyllodes tumor in a rat's urinary bladder. The exact prognosis and histogenesis of phyllodes tumors of the urinary bladder remains to be determined by the accumulation of data from additional cases.

DNA study of bladder papillary tumours chemically induced by N-butyl-N-(4-hydroxybutyl) nitrosamine in Fisher rats

To examine DNA abnormalities in bladder papillary tumours induced by N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN) in female rats, using image cytometric DNA analysis and cytogenetics. Thirty female rats were exposed to BBN in their drinking water for 20 weeks. One group of 10 animals served as controls. The animals exposed to BBN were killed at a rate of two per week, with the bladder being collected under aseptic conditions and those tumours with exophytic growth removed. The nuclear DNA content of the tumours was evaluated using image cytometric analysis. In two rats part of the tumour pieces was stipulated for culturing. Cytogenetic analysis was performed on at least 30 cells from each cell population and on both tumours. Papillary carcinomas were classified as low grade and high grade. DNA ploidy studies were carried out on 28 low-grade and 21 high-grade papillary carcinomas. Histograms obtained by image analysis showed that a normal urothelium was diploid; 28.6% and 100% of low-and high-grade papillary carcinomas were aneuploid respectively. Both tumours used for cell culture showed multiple numerical and structural chromosome alterations and several marker chromosomes. Image cytometric DNA analysis proved to be a good and reliable method for examining DNA alterations in papillary bladder carcinomas. The present findings establish that the DNA content is statistically different between low-grade and high-grade papillary carcinomas and that deviation from the diploid number is markedly higher in the high-grade ones. In addition, the occurrence of marker chromosomes seems to be related to the aggressiveness of the tumour.