The neuroprotective effect of long-term n-3 polyunsaturated fatty acids supplementation in the cerebral cortex and hippocampus of aging rats.

The purpose of this study was to determine whether hippocampus and cerebral cortex fatty acids (FA) composition can be altered as a result of n-3 enriched diet, or modifications in FA can affect the age-related histological changes in these brain tissues. The study was performed on eighteen rats which were fed control (CD) or fish oil supplemented diet (FOD) for 12 months. We investigated the n-3 and n-6 brain FA profile by gas-chromatography analysis. Histomorphometry included the measurement of the quantity of pyramidal cells in the cerebral cortex (layer II-III) and in the hippocampal formation (CA1, CA3 and DG). The number of apoptotic cells (neuron and glial cells) was also calculated separately in three hippocampal areas and in the pyramidal cerebral cortex layer. Rats fed supplemented diet showed a significantly poorer content of the arachidonic acid (AA, 20:4n6) in all brain regions when compared to the control group. Furthermore, the level of the docosahexaenoic acid (DHA, 22:6n3) was significantly higher in the cerebral cortex in fish oil fed rats vs. the control group. The neurons of the pyramidal cortex showed significant changes in cell density in control animals when compared to the group of fish oil fed rats. Furthermore, the number of positive apoptotic cells was significantly higher in the CA1 area and cerebral pyramidal layer in rats fed control diet. Following dietary n-3 fatty acids supplementation, the increase in DHA content in the cerebral cortex resulted in consequential changes in histology of this tissue. The results obtained indicate that dietary intake of fish n-3 fatty acids may reduce the risk of age-related brain impairments.

Molecular speciation and mesoscale clustering in formaldehyde-methanol-water solutions in the presence of sodium carbonate.

Nanoporous organic gels can be synthesized from aqueous solutions of formaldehyde and resorcinol in the presence of basic electrolytes such as sodium carbonate. It is well known that formaldehyde is present in the form of methylene glycols or methoxy-glycols in aqueous and methanolic solutions, but influence of pH or electrolytes on speciation in these solutions has not been previously studied. Here we investigated effects of sodium carbonate on the speciation and colloidal scale clustering in formaldehyde-methanol-water solutions in the absence of resorcinol. We used (13)C NMR spectroscopy to quantitatively characterize molecular speciation in solutions and to estimate corresponding equilibrium constants for glycol dimerization and methoxylation. We found that species distribution is essentially independent of carbonate concentration for pH values between 3.4 (no carbonate) and 10.6. This was also consistent with ATR IR measurements of the same solutions. However, NMR spin-spin relaxation time measurements showed an unexpected behavior for glycols and especially for diglycol (but not for methanol), with relaxation times strongly decreasing with increasing carbonate concentration, indicating differences in local molecular environment of glycols. We further used dynamic light scattering to confirm the presence of mesoscale clustering in formaldehyde-methanol-water (for both H2O and D2O) solutions in the presence of sodium carbonate. We propose that the observed phenomena are due to glycol-rich cluster mesospecies in equilibrium bulk solution, together forming a thermodynamically stable mesostructured liquid phase.

Mechanism and kinetics of nanostructure evolution during early stages of resorcinol-formaldehyde polymerisation.

Resorcinol and formaldehyde react in aqueous solutions to form nanoporous organic gels well suited for a wide range of applications from supercapacitors and batteries to adsorbents and catalyst supports. In this work, we investigated the mechanism and kinetics of formation of primary clusters in the early stages of formation of resorcinol-formaldehyde gels in the presence of dissolved sodium carbonate. Dynamic Light Scattering measurements showed that size of freely diffusing primary clusters was independent of both reactant and carbonate concentrations at a given temperature, reaching the mean hydrodynamic radius of several nanometres before further changes were observed. However, more primary clusters formed at higher carbonate concentrations, and cluster numbers were steadily increasing over time. Our results indicate that the size of primary clusters appears to be thermodynamically controlled, where a solubility/miscibility limit is reached due to formation of certain reaction intermediates resulting in approximately monodisperse primary clusters, most likely liquid-like, similar to formation of micelles or spontaneous nanoemulsions. Primary clusters eventually form a particulate network through subsequent aggregation and/or coalescence and further polymerisation, leading to nanoscale morphologies of resulting wet gels. Analogous formation mechanisms have been previously proposed for several polymerisation and sol-gel systems, including monodisperse silica, organosilicates and zeolites.

Age-related changes in the central nervous system in selected domestic mammals and primates.

Aging is a process which operates at many levels of physiological, genetic and molecular organization and leads inevitably to death. Brain macroscopic changes by MRI investigation during aging were observed in humans and dogs but chimpanzees did not display significant changes. This suggestion led to the statement that brain aging is different in various species. Although human brain changes, e.g. ß-amyloid storage, neurofibrillary tangle formation, lipofuscin, are relatively well known, we are still looking for a suitable animal model to study the mechanisms of aging and neurodegenerative diseases. Therefore, this paper presents a comparative analysis of the changes described in the brains of senile dog, horse and gorilla. In addition we present the latest, non-invasive methods that can be applied in the diagnosis of old age in mammals. Our considerations have shown that the best animal model for further studies and observations on aging is the dog.