The neuroblast and angioblast chemotaxic factor SDF-1 (CXCL12) expression is briefly up regulated by reactive astrocytes in brain following neonatal hypoxic-ischemic injury

Background  

Stromal cell-derived factor 1 (SDF-1 or CXCL12) is chemotaxic for CXCR4 expressing bone marrow-derived cells. It functions in brain embryonic development and in response to ischemic injury in helping guide neuroblast migration and vasculogenesis. In experimental adult stroke models SDF-1 is expressed perivascularly in the injured region up to 30 days after the injury, suggesting it could be a therapeutic target for tissue repair strategies. We hypothesized that SDF-1 would be expressed in similar temporal and spatial patterns following hypoxic-ischemic (HI) injury in neonatal brain.     

Internal energy content of n-butylbenzene, bromobenzene, iodobenzene and aniline molecular ions generated by two-photon ionization at 266 nm. A photodissociation study

A technique to investigate photodissociation kinetics on a nanosecond time scale has been devised for molecular ions generated by multiphoton ionization (MPI) using mass-analyzed ion kinetic energy spectrometry. The branching ratio or rate constant has been determined for the photodissociation of the n-butylbenzene, bromobenzene, iodobenzene, and aniline molecular ions generated by MPI at 266 nm. The ion internal energies have been estimated by comparing the measured kinetic data with the previous energy dependence data. The analysis has shown that only those molecular ions generated by two-photon ionization contribute to the photodissociation signals. Around half of the available energy has been found to remain as molecular ion internal energy in the two-photon ionization process. Copyright 1999 John Wiley & Sons, Ltd.     

Biotransformation of (R)-(+)- and (S)-(-)-citronellol by Aspergillus sp. and Penicillium sp., and the use of solid-phase microextraction for screening

The biotransformation of (R)-(+)- and (S)-(-)-citronellol by fungi was studied. For screening experiments, solid-phase microextraction (SPME) was used as analytical sampling technique. It was found that sporulated surface cultures of Aspergillus niger were able to convert the substrate into cis- and trans-rose oxides and nerol oxide. The relative contents in the headspace SPME extract of the three bioconversion products cis- and trans-rose oxide and nerol oxide were up to 54, 21 and 12%, respectively. Rose oxide is found in minor amounts in some essential oils, such as Bulgarian rose oil and geranium oil and contributes to its unique odor. It is one of the most important fragrance materials in perfumery in creating rosy notes. Other bioconversion products were 6-methyl-5-hepten-2-one, 6-methyl-5-hepten-2-ol, limonene, terpinolene, linalool and alpha-terpineol. These bioconversion reactions were confirmed by sporulated surface cultures on larger scale and sampling by dynamic headspace sweep and steam distillation solvent extraction. The same conversions were noticed with A. tubingensis and Penicillium roqueforti. This bioconversion was enantioselective since more of the chiral cis- than trans-rose oxide was obtained (cisitrans ratio up to 95/5). Submerged liquid cultures of P. roqueforti yielded two unidentified metabolites after conversion of citronellol (yield up to 5%). The stability and acid-catalyzed conversion of citronellol was also investigated. No chemical oxidation or auto-oxidation products were detected in acidified liquid control broths up to pH 3.5. However, when control tests were run with solid media, acid-catalyzed conversion of the substrate to small amounts of cis- and trans-rose oxides, nerol oxide, linalool and alpha-terpineol was observed at pH 3.5 and when heat treatment (steam distillation solvent extraction) was applied.     

An alternating direction scheme on a nonuniform mesh for reaction-diffusion parabolic problems

In this paper we develop a numerical method for two-dimensionaltime-dependent reaction-diffusion problems. This method, whichcan immediately be generalized to higher dimensions, is shownto be uniformly convergent with respect to the diffusion problems.This method, which can immediately be generalized to higherdimensions, is shown to be uniformly convergent with respectto the diffusion parameter.