Efficient procedure for c '- 3 substitution and c - 7 n-acylation of 7-aminocepha-losporanic acid (7-aca): Synthesis of cefazolin antibiotic and related compounds

A new preparative method for the C'-3 substitution of 7-aminocepha-losporanic acid (7-ACA), is described. The key feature of our method is based on the protection of the anino group as a Schiff base instead of the usual procedure based on the acylation of the amino group. The relative incapacity of 7-ACA derivatives to produce organic solutions with usual tertiary bases is easily overcome with bicyclic amidines. Catalytic amounts of these bases and N-trimethylsilyl-2-oxazolidinone are used to obtain the silylated products. Activation of sensitive tetrazolylacetic acid by means of N,N-dimethylchloro-sulfitemethaniminium chloride (SOCl₂-DMF) and preparation of cefazolin antibiotic under anhydrous conditions is also described.     

Simultaneous analysis of piperacillin and tazobactam in rabbits: application to pharmacokinetic study

A simple and rapid assay is developed for the simultaneous analysis of piperacillin and tazobactam in rabbit serum and tissue cage fluid (TCF). To eliminate endogenous interferences, a wavelength switch technique was applied, in which the programmable UV detector changed the monitoring wavelength from 218 to 254 nm at 10 min. After liquid-liquid extraction, sample analyses were performed on a C(18) column by gradient elution; the mobile phase consisted of acetonitrile and phosphate buffer (0.014 m, pH 2.4). Owing to the limited amount of rabbit TCF available, a cross-validation of a proxy matrix was evaluated. The relative standard deviation of the between- and within-batch precision of both compounds was less than 5.1%; the relative error of the between- and within-batch accuracy was less than 7.3%. The recoveries of both compounds in serum and TCF were larger than 80%. This assay was successfully applied to simultaneously analyze piperacillin and tazobactam in rabbit serum and TCF samples.     

The Chlorhexidine: beta;-Cyclodextrin Inclusion Compound: Preparation, Characterization and Microbiological Evaluation

The 1 : 2 chlorhexidine : -cyclodextrin(Cx : CD) complex was prepared and characterised using X-ray crystallography, infrared spectroscopy, thermal analysis and nuclearmagnetic resonance. The minimum inhibitory concentration (MIC₅₀) of the chlorhexidine : -cyclodextrin inclusion compoundagainst Streptococcus mutans, Eubacterium Lentum, Fusobacterium nucleatum, Bacteroides fragilis andActinomices actinomycetemcomitans was determined. TheCx : CD inclusion compound inhibited the bacterial growth at a low concentration.     

High-Resolution Magnetic Resonance Angiography of the Mouse Brain: Application to Murine Focal Cerebral Ischemia Models

Three-dimensional time-of-flight high-resolution magnetic resonance angiography was applied to visualize the cerebral vasculature of the mouse brain. In normal mice, angiograms of good quality, showing the essential details of the arterial cerebrovascular anatomy, could be obtained in only 2.5 min without the use of contrast agents. Signals from slowly flowing blood, e.g., in veins, could also be detected after administration of a blood pool contrast agent. The technique was applied to mouse models of permanent and transient brain ischemia, involving the occlusion of the middle cerebral artery. High-resolution magnetic resonance angiography proved to be a very useful tool for verifying the success of the occlusion in these models.     

Staleya guttiformis attachment on poly(tert-butylmethacrylate) polymeric surfaces

The attachment behaviour of Staleya guttiformis DSM 11458^T on poly(tert-butyl methacrylate) (P(tBMA)) polymeric surfaces has been studied. The electrostatic charge of the S. guttiformis cell surface (measured as zeta potential via microelectrophoresis) was −43.18 mV. S. guttiformis cells appeared weakly hydrophilic as the water contact angle measured on lawns of bacterial cells was found to be 55 ± 4.9°. It was found that while attaching on P(tBMA) surfaces, S. guttiformis cells produced extracellular polymeric substances (EPS) as observed from atomic force microscopy (AFM) and scanning electron microscopy (SEM) analysis. The AFM high resolution imaging revealed the nano-topography of the ‘free’ (the EPS that is produced by the bacterial cells, but no longer directly attached to the cells) EPS associated on the cell surface and also found on P(tBMA) surface. The ‘free’ EPS exhibited granular structure with lateral dimensions of 30–50 nm and a vertical nano-roughness of 7–10 nm. Another type of the EPS secreted by S. guttiformis cells appeared as a hydogel substance, presumably polysaccharide that formed a biopolymer network that facilitated bacterial attachment.     

Synthesis of the first nonmetalated triazolephthalocyanine derivatives

The synthesis of nonmetalated triazolephtahlocyanines is described for the first time. These compounds have been prepared by both one-step and stepwise procedures. Their spectroscopic data reveal a nonaromatic cross-conjugated 18pi-electron structure in contrast to their aromatic metalated derivatives.     

Stability of compact actions of ℝ n of codimensional oneof codimensional one

In this paper we study theC ^r stability of locally free compact actions of ℝ ⁿ with compact orbits over manifolds of dimensionn+1. More precisely, we show that in many cases aC ¹ perturbation of an action with all orbits compact must also have all orbits compact and aC ⁰ perturbation usually has many compact orbits.     

Interpolating Blaschke products solving Pick-Nevanlinna problems

We study when a Pick-Nevanlinna problem with more than one solution can be solved by an interpolating Blaschke product. Supported in part by the grant PB85-0374 of the CYCIT, Ministerio de Educación y Ciencia, Spain.     

On some geometrical properties of Seifert bundles

In this paper we use the integration along the leaves introduced by Haefliger in 1980 to obtain a differentiable version of the Gysin sequence and Euler class for compact Hausdorff orientable foliations with generic leaf the sphereS ^p. From this we give a geometrical significance to the vanishing of the Euler class on Seifert bundles. We also obtain an integral formula on Seifert bundles similar to the Gauss-Bonnet one.     

Closures of finitely generated ideals in Hardy spaces

LetH ^∞ be the algebra of bounded analytic functions in the unit diskD. LetI=I(f ₁,...,f _N) be the ideal generated byf ₁,...,f _N∈H ^∞ andJ=J(f ₁,...,f _N) the ideal of the functionsf∈H ^∞ for which there exists a constantC=C(f) such that |f(z)|≤C(|f ₁ (z)|+...;+|f _N (z)|),z∈D. It is clear that , but an example due to J. Bourgain shows thatJ is not, in general, in the norm closure ofI. Our first result asserts thatJ is included in the norm closure ofI ifI contains a Carleson-Newman Blaschke product, or equivalently, if there existss>0 such that