Techniques for determining electron losses at a 1.5 GeV synchrotron light source.

A computer code was developed to simulate the bremsstrahlung dose rate distribution patterns produced by the CAMD electron storage ring. These bremsstralung dose rate distributions were measured along the interior surface of the shield walls (short walls perpendicular to the bending magnets) with TLD chips. Electron losses for each specific magnet was determined by running the computer code and varying the electron loss parameters to fit the measured dose rate distributions. It was determined that (1) bending magnet No. 1 (closest to the injection septum) loses 2.7 x 1010 electrons per minute during electron injection. The loss rate for each of the subsequent seven bending magnets during injection varies from about 25% to 33% of this number; (2) the magnet immediately subsequent to the bending magnet loses more electrons than the magnet immediately prior to the bending magnet does; and (3) the computer code may be used to predict potential problems such as misalignment.

Increased susceptibility of Pseudomonas aeruginosa to ciprofloxacin in the presence of vancomycin.

Vancomycin in combination with ciprofloxacin exhibited synergy against 7 of 10 strains of Pseudomonas aeruginosa. MICs for the microbial strains used in this study ranged from 0.0325 to 3.0 micrograms/ml for ciprofloxacin and from 23.5 to > 188 micrograms/ml for vancomycin. Combinations of these antibiotics, tested in a checkerboard pattern, gave fractional inhibitory concentrations of 0.5 or less for 7 of the 10 strains tested.

Smooth muscle inhibition by an extract of Sesbania drummondii.

The acute effects of an extract of Sesbania drummondii were assessed in vitro on the smooth muscle contractility of intestine and lung parenchyma in the chicken and aortic arch in the rat. Dose-response contraction curves for histamine, carbachol, and norepinephrine were obtained in the ileal, parenchymal, and aortic strips, respectively. After washing was completed, the strips returned to baseline tensions and then were incubated for 10 minutes with an ethyl acetate extraction fraction of S drummondii (molecular weight less than 500). Dose-response curves to the same agonists were repeated at the end of the incubation period. Contractile responsiveness of chicken ileum was little affected by acute incubation of the tissue with the extract. Comparison with the great inhibition of in vitro ileal contractility seen previously in chickens with chronic toxicosis indicated that intestinal inhibition was not due to acute effects of sesbania, but required time for a toxic metabolite to be formed or for damage to occur from affected vasculature. Contractile responsiveness of chicken lung parenchyma to histamine (10(-5) M and 10(-4) M) was significantly decreased, as was rat aortic responsiveness to norepinephrine (10(-7) M to 10(-4) M). Responses in parenchyma were not as greatly inhibited as those in tissue from animals with chronic toxicosis. Greatest inhibition of contractility was seen in the vascular strips, indicating that vascular inhibition has a role in pathologic changes. To test the vasculature inhibition effect in vivo, anesthetized, catheterized rats were given 100-microliter aliquots of dilutions of the extract, IV.(ABSTRACT TRUNCATED AT 250 WORDS)

Structure and cell envelope associations of flagellar basal complexes of Vibrio cholerae and Campylobacter fetus.

To isolate intact flagella with basal complexes from Vibrio cholerae, a rhamnolipid hemolysin from Pseudomonas aeruginosa was used to disrupt the cell envelope and flagellar sheath. The nonionic detergent, Triton X-100, provided similar results for Campylobacter fetus. Each of these basal complexes possessed, in addition to the four classical rings, concentric membrane rings (CMR's) similar to those found in Aquaspirillum serpens. Through the use of stereo imaging (which allows structures to be visualized in three dimensions) of thin sections of cells which had been sequentially treated with a number of envelope perturbants (i.e., ethylenediaminetetraacetate, lysozyme, Triton X-100, rhamnolipid hemolysin, and sodium dodecyl sulfate), we have progressively exposed the component parts of the basal organelles in V. cholerae and C. fetus. Since the action of these envelope perturbants has been well documented, we have been able to determine the associations of the exposed portions of the flagellar basal complex and the layer of the cell envelope in which they would normally reside. From our observations we have concluded that in both V. cholerae and C. fetus the L ring is embedded in the outer membrane and the P ring is associated with the peptidoglycan. The CMR's are bracketed by the L and P rings and are sandwiched between the outer membrane and the peptidoglycan. Elements of both the S and M rings appear to be associated with the plasma membrane.

An alkaline phosphatase mutant of Pseudomonas aeruginosa. 1. Effects of regulatory, structural, and environmental shifts on enzyme function.

An alkaline phosphatase mutant of Pseudomonas aeruginosa exhibiting both regulatory and catalytic changes was isolated. Under repression conditions (i.e. high inorganic phosphate (Pi)) the mutant culture produced an alkaline phosphatase (APase) displaying significant activity against both beta-glycerol phosphate (betaGP) and p-nitrophenyl phosphate (pNPP), while the wild type displayed no activity directed towards these substrates under the same conditions. In vivo, the mutant enzyme's ratio of specific activities was 45:1 in favour of betaGP versus pNPP, whereas this ratio was reversed to 1:9 betaGP versus pNPP for the same enzyme isolated from mutant cells. In addition, the kinetic parameters and stability requirements for the mutant-derived enzyme was altered in comparison with those of the wild type. A study of lipopolysaccharide (LPS) preparations from both the mutant and wild type indicated the mutant to be deficient in the core region of its LPS. The authors propose that the modifications in the catalytic activity of the mutant enzyme, demonstrated in vivo, are due to a change in the enzyme's microenvironment.

Protein-lipopolysaccharide interactions. 1. The reaction of lysozyme with Pseudomonas aeruginosa LPS.

Lysozyme (EC 3.2.1.17) complexes with extracted Pseudomonas aeruginosa LPS in two distinct stages. The initial stage does not produce turbidity detectable by nephelometry (measured as nephelos units (N) per time) but does permit low-speed sedimentation of the lysozyme-lipopolysaccharide (LPS) complex. This association is 100% disrupted by the action of 0.1 M Mg2+. Monovalent cations at equal ionic strength to the Mg2+ concentration used for these studies failed to alter significantly the lysozyme-LPS complex, indicating that the role of Mg2+ was not strictly an ionic one. The study of lysozyme-LPS complexes may provide a model system for investigating in vivo protein-LPS interactions.