Configuration of the circle of Willis and its two parts among Egyptian: a magnetic resonance angiographic study.

BACKGROUND: We hypothesized that the collateral circulation differs in different ethnic groups. So, the aim of our work was to study variations of the circle of Willis (COW) among Egyptian and to compare our findings with the findings of other nationalities. MATERIALS AND METHODS: One hundred patients were studied using magnetic resonance angiography (3D-TOF-MRA). Frequency and morphologic variations in COW were studied. The diameters of the arteries of the anterior and posterior circle were verified. Finally, the differences among the mean diameters of these arteries regarding age and sex were also studied. RESULTS: Complete, partially complete and incomplete COW were encountered in 28%, 38% and 34% in the studied cases. The incomplete anterior circle was found in 34% (10% isolated incomplete anterior circle and 24% combined incomplete anterior and posterior circles) and the incomplete posterior circle came across in 62% (38% isolated incomplete posterior circle and 24% combined incomplete anterior and posterior circles). Seven anterior circle variations were found. The commonest type was the classical type "a" with a prevalence of 56%, being higher in male (57.1%). The 2nd common type was type "g" (hypoplasia or aplasia of the anterior communicating artery) with a prevalence of 24%, being higher in male (66.7%). Six posterior circle variations were found. The commonest variation was the classic type "a" with a prevalence of 26%, being higher in male (61.5%). Posterior circles types "d, e, h" (18%, 24%, 20%) constituted 62% and were characterised by hypoplasia/absent of the posterior communicating arteries. CONCLUSIONS: The prevalence of complete COW (classic or textbook type) was encountered only 28% of the studied cases. Variations of COW were found to be more common in the posterior circulation (62%). The incomplete anterior circle was found in 34% and it is mostly caused by hypoplasia or aplasia of the anterior communicating artery which was found to be more common compared to the literature.

8-[(1E)-1-(2-Aminophenyl-iminio)eth-yl]-2-oxo-2H-chromen-7-olate.

The title Schiff base, C(17)H(14)N(2)O(3), exists as an NH tautomer with the H atom of the phenol group transferred to the imine N atom. The iminium H atom is involved in a strong intra-molecular N(+)-H⋯O(-) hydrogen bond to the phenolate O atom, forming an S(6) motif. In the crystal structure, N-H⋯O hydrogen bonds form a C(9) chain parallel to [100] and a C(11) chain parallel to [010], while C-H⋯O hydrogen bonds form a C(11) chain parallel to [010]. The combination of N-H⋯O and C-H⋯O hydrogen bonds generates R(4) (3)(30) rings parallel to the ab plane.

Electron spin resonance and magnetic studies on some copper(II) azobarbituric and azothiobarbituric acid complexes.

Electron spin resonance and magnetic susceptibility on some copper(II) complexes prepared from phenylazobarbituric and phenylazothiobarbituric acid compounds containing 2,5-dichloro and 2,5-dimethyl groups were discussed. The thio complexes exist in dimer-monomer mixture. The corresponding copper(II) complexes of the oxygen homologous failed to exhibit association. Singlet-triplet separation values equal to -321 and -263 cm(-1) for the 2,5-dimethyl and 2,5-dichloro complexes, respectively, of the thio series. An empirical measure of the amount of tetrahedral deformation based on the values of g||/A|| assigned the square-planar geometry of the dimethyl-oxygen complex while the other complexes are with tetrahedral planar geometries. The effect of temperature on the ESR data was discussed. The diamagnetic properties of the complexes derived from 2,5-dichloro and 2,5-dimethyl thiobarbituric acid suggested the formation of Cu(I) complexes.

Novel reversion reaction of D-arabino-hexose phenylosotriazole. A useful model in natural glycoside and polysaccharide analysis.

Treatment of D-arabino-hexose phenylosotriazole with conc. hydrochloric acid afforded a new type of alpha- and beta-glycosides of D-erythrose formed by reaction of the 3,6-anhydro derivative with the in situ formed 2-phenyl-4-(formylmethyl)- 1,2,3-triazole.

The WHO Vaccine Trial Registry.

The WHO Vaccine Trial Registry prospectively registers clinical vaccine studies supported by WHO. Through December 1999, the registry includes 103 studies from 43 countries, with nearly 80% in developing countries. The registry documents an expanding research capacity, with an average of 3.9 new studies per year during 1987-1993, rising to 10.7 per year during 1994-2000. The studies concern a broad spectrum of infectious organisms, including: Clostridium tetani (tetanus), dengue virus, enterotoxigenic Escherichia coli (ETEC), Haemophilus influenzae type b (Hib), hepatitis B virus, measles virus, Mycobacterium tuberculosis, Neisseria meningitidis (meningococcus), poliovirus, respiratory syncytial virus (RSV), rotavirus, Salmonella typhi, Shigella, Streptococcus pneumoniae (pneumococcus), and Vibrio cholerae.