Alterations in glial cell metabolism during recovery from chronic osmotic stress

Analysis of the changes in the 1H NMR spectral pattern of perchloric acid extracts of C6 cells with growth

The aim of this work was to identify spectral markers of cell proliferation that could be of use in clinical MRS. Cultured C6 ATCC rat glioma cells were used as models for this purpose and metabolites were extracted with perchloric acid at three different growth curve stages: log, confluence and post-confluence. 1D and 2D in vitro(1)H NMR spectra were recorded at 9.4 T. Statistically significant changes in myo-inositol and glutamine concentrations between log phase and post-confluence were found when normalized to the creatine ratio. The myo-inositol/creatine ratio was 2.76 +/- 0.82 at log phase increasing to 7.43 +/- 1.34 at post-confluence, while the glutamine/creatine ratio decreased from 0.22 +/- 0.03 to 0.10 +/- 0.02. No significant differences were recorded for other metabolites investigated. The fact that both myo-inositol and glutamine are detectable by in vivo MRS at clinical fields makes their changes relevant as potential astrocytic tumour proliferation rate markers in clinical MRS.

Therapeutic effectiveness of novel 5-fluorouracil-loaded poly(methylidene malonate 2.1.2)-based microspheres on F98 glioma-bearing rats

BACKGROUND

Drug delivery to the central nervous system (CNS) remains a real challenge for neurosurgeons and neurologists, because many molecules cannot cross the blood-brain barrier (BBB). In recent years, solid polymeric materials have been implanted into animal and human brains either by surgery or using stereotactic methods to assure the controlled release of a drug over a determined period, thus circumventing the difficulties posed by the BBB. Poly(methylidene malonate 2.1.2) (PMM 2.1.2) is a new polymer that was described a few years ago and that allows the fabrication of novel, 5-fluorouracil (5-FU)-loaded PMM 2.1.2 microspheres. The objective of the current study was to assess the therapeutic effectiveness of those particles in a rat brain tumor model, the F98 glioma.

METHODS

Forty-three rats were used in this study. First, a histologic evaluation of the F98 tumor model was performed on Fischer female rats. Thereafter, different groups of rats were injected and were treated with 5-FU microspheres in 2 different suspension media: carboxymethylcellulose (CMC) aqueous solution with or without 5-FU.

RESULTS

The tumor was confirmed as extremely aggressive and invasive, even in early development. The 5-FU-loaded microspheres improved rat median survival significantly compared with untreated animals, CMC-treated animals, and 5-FU solution-treated animals when injected in CMC without 5-FU, demonstrating the interest of a sustained release and the efficacy of intratumoral chemotherapy against an established tumor.

CONCLUSIONS

PMM 2.1.2 microspheres appeared to be a promising system, because their degradation rate in vivo was longer compared with many polymers, and they may be capable of long-term delivery.

Is myo-inositol a measure of glial swelling after stroke? A magnetic resonance study

PURPOSE

To determine whether the hypothesis that the phenomenon of persistent cytotoxic edema in the subacute stage of ischemic stroke is in fact associated with the glial population. This is done by assessing the evolution of both the apparent diffusion coefficient (ADC) and the glial-specific marker myo-inositol (Ins) in a group of patients, and by comparing the results with the total cellular density by means of the creatine (Cre) level.

MATERIAL AND METHODS

Twenty-two patients with stroke in the territory of the middle cerebral artery were each examined once only at a time ranging from eight hours to six days following the onset of symptoms. Lesion-to-contralateral values of ADC were obtained based on diffusion-weighted echo-planar imaging. Short TE single-voxel proton magnetic resonance ((1)H MR) spectroscopy was used for quantification of cerebral metabolites in infarcted regions. Their levels were also compared with those in homotopic contralateral regions.

RESULTS

In the stroke lesion, there was a significant correlation between ADC and the Ins level, albeit less pronounced than that for Cre. During different pathophysiological stages between 12 hours and three days, the Ins-to-Cre ratio increased by a factor of two and returned to apparently normal thereafter.

CONCLUSION

Our study provides the first demonstration of a relationship between persistent cytotoxic edema and the glial population in the context of cell swelling due to osmotic imbalance in stroke patients.

The role of taurine in diabetes and the development of diabetic complications

The ubiquitously found beta-amino acid taurine has several physiological functions, e.g. in bile acid formation, as an osmolyte by cell volume regulation, in the heart, in the retina, in the formation of N-chlorotaurine by reaction with hypochlorous acid in leucocytes, and possibly for intracellular scavenging of carbonyl groups. Some animals, such as the cat and the C57BL/6 mouse, have disturbances in taurine homeostasis. The C57BL/6 mouse strain is widely used in diabetic and atherosclerotic animal models. In diabetes, the high extracellular levels of glucose disturb the cellular osmoregulation and sorbitol is formed intracellularly due to the intracellular polyol pathway, which is suspected to be one of the key processes in the development of diabetic late complications and associated cellular dysfunctions. Intracellular accumulation of sorbitol is most likely to cause depletion of other intracellular compounds including osmolytes such as myo-inositol and taurine. When considering the clinical complications in diabetes, several links can be established between altered taurine metabolism and the development of cellular dysfunctions in diabetes which cause the clinical complications observed in diabetes, e.g. retinopathy, neuropathy, nephropathy, cardiomyopathy, platelet aggregation, endothelial dysfunction and atherosclerosis. Possible therapeutic perspectives could be a supplementation with taurine and other osmolytes and low-molecular compounds, perhaps in a combinational therapy with aldose reductase inhibitors.