Quantitative evaluation of the regenerated dura mater in a decompressive skull trepanation model in rats / Evaluación cuantitativa de la duramadre regenerada en un modelo de perforación cranial descompresiva en ratas

SUMMARY: Regeneration of the dura mater following duraplasty using a collagen film, a chitosan film, or a combination of both with gelatin, was studied in a craniotomy and penetrating brain injury model in rats. Collagen autofluorescence in the regenerated dura mater was evaluated using confocal microscopy with excitation at λem = 488 nm and λem = 543 nm. An increase in regeneration of the extracellular matrix of connective tissue and an increase in matrix fluorescence were detected at 6 weeks after duraplasty. The major contributors to dura mater regeneration were collagen films, chitosan plus gelatin-based films, and, to a much lesser extent, chitosan-based films. By using autofluorescence densitometry of extracellular matrix, the authors were able to quantify the degree of connective tissue regeneration in the dura mater following duraplasty.

RESUMEN: Se estudió la regeneración de la duramadre después de una duraplastía utilizando una lámina de colágeno, una lamina de quitosano o una combinación de ambas con gelatina en un modelo de craneotomía y lesión cerebral en ratas. La autofluorescencia del colágeno en la duramadre regenerada se evaluó mediante microscopía confocal con excitación a λem = 488 nm y λem = 543 nm. Se observó un aumento en la regeneración de la matriz extracelular del tejido conectivo y un aumento en la fluorescencia de la matriz a las 6 semanas después de la duraplastía. Se observe un efecto significativo en la regeneración de la duramadre con las láminas de colágeno, las láminas en base de quitosano más gelatina y, en un menor grado, las láminas a base de quitosano. Mediante el uso de densitometría de autofluorescencia de la matriz extracelular, los autores lograron cuantificar el grado de regenera- ción del tejido conectivo en la duramadre después de la duraplastía.

Mechanochemical synthesis of carbon-stabilized Cu/C, Co/C and Ni/C nanocomposites with prolonged resistance to oxidation.

Metal-carbon nanocomposites possess attractive physical-chemical properties compared to their macroscopic counterparts. They are important and unique nanosystems with applications including in the future development of nanomaterial enabled sensors, polymer fillers for electromagnetic radiation shields, and catalysts for various chemical reactions. However, synthesis of these nanocomposites typically employs toxic solvents and hazardous precursors, leading to environmental and health concerns. Together with the complexity of the synthetic processes involved, it is clear that a new synthesis route is required. Herein, Cu/C, Ni/C and Co/C nanocomposites were synthesized using a two-step method including mechanochemical treatment of polyethylene glycol and acetates of copper, nickel and cobalt, followed by pyrolysis of the mixtures in an argon flow at 700 °C. Morphological and structural analysis of the synthesized nanocomposites show their core-shell nature with average crystallite sizes of 50 (Cu/C), 18 (Co/C) and 20 nm (Ni/C) respectively. The carbon shell originates from disordered sp2 carbon (5.2-17.2 wt.%) with a low graphitization degree. The stability and prolonged resistance of composites to oxidation in air arise from the complete embedding of the metal core into the carbon shell together with the presence of surface oxide layer of metal nanoparticles. This approach demonstrates an environmentally friendly method of mechanochemistry for controllable synthesis of metal-carbon nanocomposites.

Heat Shock Proteins in the "Hot" Mitochondrion: Identity and Putative Roles.

The mitochondrion is known as the "powerhouse" of eukaryotic cells since it is the main site of adenosine 5'-triphosphate (ATP) production. Using a temperature-sensitive fluorescent probe, it has recently been suggested that the stray free energy, not captured into ATP, is potentially sufficient to sustain mitochondrial temperatures higher than the cellular environment, possibly reaching up to 50 °C. By 50 °C, some DNA and mitochondrial proteins may reach their melting temperatures; how then do these biomolecules maintain their structure and function? Further, the production of reactive oxygen species (ROS) accelerates with temperature, implying higher oxidative stresses in the mitochondrion than generally appreciated. Herein, it is proposed that mitochondrial heat shock proteins (particularly Hsp70), in addition to their roles in protein transport and folding, protect mitochondrial proteins and DNA from thermal and ROS damage. Other thermoprotectant mechanisms are also discussed.

Liquid exfoliation of mechanochemically nanostructured tungsten disulfide to a graphene-like state.

The possibility of the efficient preparation of graphene-like 1H-WS2 by the primary solventless nanostructuration of bulk 2H-WS2 by means of its mechanochemical treatment in the presence of a chemically inert agent (NaCl) and the subsequent liquid exfoliation of the nanostructured 2H-WS2 in an organic solvent is shown for the first time. The shear stresses generated during the grinding of the WS2/NaCl mixture caused the formation of WS2 particles with a reduced number of layers, while the stresses normal to their surface led to their cracking and a significant reduction in lateral size. The graphene-like morphology of the 1H-WS2 nanoparticles in the prepared dispersions is confirmed by atomic force microscopy and Raman spectroscopy. The semiconducting character of 1Н-WS2 is supported by electron absorption and x-ray photoelectron spectroscopy data.

Spectroscopic study of proflavine adsorption on the carbon nanotube surface.

Despite the fact that non-covalent interactions between various aromatic compounds and carbon nanotubes are being extensively investigated now, there is still a lack of understanding about the nature of such interactions. The present paper sheds light on one of the possible mechanisms of interaction between the typical aromatic dye proflavine and the carbon nanotube surface, namely, π-stacking between aromatic rings of these compounds. To investigate such a complexation, a qualitative analysis was performed by means of ultraviolet visible, infrared, and nuclear magnetic resonance spectroscopy. The data obtained suggest that π-stacking brings the major contribution to the stabilization of the complex between proflavine and the carbon nanotube.

Effect of a pH change on the conformational stability of the modified nucleotide queuosine monophosphate.

The naturally occurring modified nucleotide queuosine 5'-monophosphate (QMP) related to biochemical regulatory pathways in the cell was investigated using quantum chemical approaches. The relative stability of biologically relevant conformations of QMP in solvent under a pH change was predicted at the BVP86/TZVP and MP2/TZVP levels of theory. Hydrogen bonding in QMP was studied using Bader's approach. The acidity constants of QMP were estimated using the COSMO-RS theory. It has been found that the neutral and anionic forms of QMP are the most stable in the physiological pH range. These forms correspond to the anti/north conformation and exist as zwitterionic tautomers having a negatively charged phosphate group (-1 for neutral and -2 for anionic) and a positively charged secondary amine group in the side chain. It was also found that QMP possesses the syn conformation in the cationic state at pH < 5.0 and undergoes syn to anti conformation transition when the pH increases, remaining in the anti conformation at the higher pH values. The marker IR bands specific for the anionic and neutral QMP forms in the 2300-2700 cm(-1) region were assigned to H-bonded NH groups of the QMP side chain. The bands between 800 and 1300 cm(-1) of the "fingerprint" (400-1500 cm(-1)) region were assigned to the vibrations of the ribose ring, the phosphate group and the side chain of QMP. The predicted IR spectra can be useful for the assignment of vibration bands in the experiential spectra of QMP or identification of the QMP forms. The revealed peculiarities of the QMP conformation sensitivity to a pH change as well as additional formed H-bonds could be responsible for specific nucleotide interactions with enzymes.

Structural organisation of nucleic acids from tumour cells.

The DNA from Carcinoma Guerina resistant and sensitive cells of Wistar line rats and their interaction with anti-cancer drugs--cis-platin and doxorubicin (DOX)--have been studied in in vivo experiments. Surface enhanced infrared absorption (SEIRA) in reflectance absorption spectroscopy (RAS) mode was applied for registration of conformational change of the DNA induced by cancer process and anti-cancer drugs. We have registered numerous minor changes in infrared spectra of the DNA from sensitive and resistant cells that could reflect essential changes in molecular structure of DNA from cancer cells. The most significant transformation was undergone by the sugar phosphate backbone of the DNA from cancer cells. The DNA from resistant cancer cells could be characterized as rigid structures and look like the canonical helix form of DNA being practically unchangeable after anti-cancer drug application. The structure of DNA from sensitive cancer cells seems to be flexible and after application of anti-cancer drugs drastically changes and approaches to structure of helix form. It has been shown that doxorubicin strongly influences the DNA structure, leading to DNA stabilization and formation of new H-bonds in DNA doxorubicin complex. We have registered slight cis-platin influence on the DNA structure in in vivo experiment. Principal component analysis of SEIRA spectra can select the DNA from cancer cells.