Effect of ciprofloxacin on subcutaneous abscesses induced with Staphylococcus epidermidis and a foreign body implant in the mouse

Subcutaneous abscesses were induced in mice with Staphylococcus epidermidis strain G19-85 and a foreign body implant. The MIC of ciprofloxacin for this strain was 0.25 microgram/ml. The ciprofloxacin dosage, 120 mg/kg/day, was divided into three injections, administered to the mice subcutaneously at 8 h intervals. Serum concentration kinetics in normal mice (n = 50) were determined. The peak serum level of ciprofloxacin was 3.18 micrograms/ml at the 15 min sampling time; the trough level was 0.53 micrograms/ml at 8 h. Abscesses were found in 96% (n = 49) of the untreated, infected control mice. Three modes of treatment with ciprofloxacin were tested: (1) four prophylactic injections of ciprofloxacin prior to infection reduced abscess formation to 64% (p less than or equal to 0.0002, n = 50). (2) Eleven therapeutic injections, initiated 4 days after infection, reduced abscess formation to 86% (p less than or equal to 0.17, n = 49). (3) One prophylactic injection prior to surgery and five therapeutic injections after infection reduced abscess formation to 43% (p less than or equal to 0.0001, n = 49). Culture results correlated with the abscess formation rates.     

Muramic Acid Assay in Sediments

An improved chromatographic assay for muramic acid which is sufficiently sensitive for marine sandy sediments is described; it involves acid hydrolysis, thin-layer chromatography, and gas-liquid chromatography.     

Rhabdospora thelohani Laguessé, 1895 (Apicomplexa): new host and geographic records with taxonomic considerations.

New fish species and geographic records for Rhabdospora thelohani Laguessé, 1895 (rodlet cells) are presented. Additionally, the ultrastructure of R. thelohani in Alburnoides bipunctatus ohridanus Karaman, Borostomias antarcticus (L?nnberg), Leuciscus cephalus albus Bonaparte and Rutilus rubilio (Bonaparte) is compared with that reported by other authors and with members of Subphylum Apicomplexa. The ultrastructure of R. thelohani was similar in all the fish species examined; however, the organism was not present in all members of any single species and had intertissue density variations. Rhabdospora thelohani is pyriform, averaging in size 7 X 12 micrometer, with a basal nucleus. The surface complex is composed of a layer (0.5 micrometer diameter) formed by microfilaments (9.3 nm) and an outer trilaminar membrane (9.3 nm). The cytoplasm contains structures identical to rhoptries, micronemes and subpellicular microtubules. Mitochondria, Golgi apparatus, and rough endoplasmic reticulum were not observed, althouth free ribosomes were present and arranged in a vesicular pattern. The observations suggest that the organism moves between cell of epithelial layers and is either released into a lumen intact or passively or actively discharges its contents into a lumen. Results from this study indicate that R. thelohani should be considered a member of Apicomplexa unless definitive evidence is presented to the contrary.     

Occurrence,localization, and possible significance of an ornithine-containing lipid in Paracoccus denitrificans

A ninhydrin-positive, phosphorus-negative lipid from Paracoccus denitrificans ATCC 13543 has been isolated and purified by mild alkaline methanolysis followed by silicic acid column chromatography and preparative thin-layer chromatography. The lipid was identified as an ornithine-containing lipid. The major ester-linked fatty acid was cis vaccenic acid. Major amide-linked fatty acids were 3-OH-20:1 and 3-OH-18:0. Ornithine-containing lipid was a major lipid component of P. denitrificans. Phospholipids made up about 57% and ornithine-containing lipid about 14% of the weight of the total lipid of the organism. The ratios of lipid ornithine: lipid phosphorus were 0.23, 0.65 and 0.58 in cytoplasmic membrane, outer membrane, and an NaCl extract, which is thought to represent chiefly outer membrane, respectively. Thus ornithine-containing lipid appears to be present in larger amounts in outer membrane than cytoplasmic membrane. No substantial variations in lipid ornithine levels were noted in stationary phase versus exposnential phase organisms, organisms grown in complex medium versus organisms grown in minimal medium with and without amino acid supplements, or in organisms grown in low phosphate-containing medium.Non standard abbreviations TLC thin-layer chromatography - Tris-HCl tris(hydroxymethyl)aminomethane hydrochloride - TMS trimethylsilyl - TFA triluoroacetyl - NPPN ninhydrin-positive, phosphorus-negative - ECL equivalent chain length     

Dihydroxy and monohydroxy fatty acids in Legionella pneumophila

Five strains of Legionella pneumophila were examined for the presence of hydroxy fatty acid. The cellular distribution of the fatty acids was also determined, as was the variation of hydroxy acid production on five growth media. The strains tested all produced approximately 5 mol% of hydroxy fatty acid, most of which was found in the nonextractable, alkali-stable, acid-labile (wall-associated, amide-linked) fraction. Three major hydroxy acids were found, along with several minor components. The major hydroxy acids were analyzed by thin-layer chromatography, gas-liquid chromatography, mass spectrometry, and infrared spectrophotometry. These compounds were tentatively identified as 3-hydroxy-12-methyltridecanoate, 3-hydroxy-n-eicosanoate, and a novel dihydroxy acid, 2,3-dihydroxy-12-methyltridecanoate. The total amount of hydroxy acid produced, as well as the profile of the hydroxy acids, remained relatively unchanged with respect to strain and growth medium.     

Plant cap-binding complexes eukaryotic initiation factors eIF4F and eIFISO4F: molecular specificity of subunit binding

The initiation of translation in eukaryotes requires a suite of eIFs that include the cap-binding complex, eIF4F. eIF4F is comprised of the subunits eIF4G and eIF4E and often the helicase, eIF4A. The eIF4G subunit serves as an assembly point for other initiation factors, whereas eIF4E binds to the 7-methyl guanosine cap of mRNA. Plants have an isozyme form of eIF4F (eIFiso4F) with comparable subunits, eIFiso4E and eIFiso4G. Plant eIF4A is very loosely associated with the plant cap-binding complexes. The specificity of interaction of the individual subunits of the two complexes was previously unknown. To address this issue, mixed complexes (eIF4E-eIFiso4G or eIFiso4E-eIF4G) were expressed and purified from Escherichia coli for biochemical analysis. The activity of the mixed complexes in in vitro translation assays correlated with the large subunit of the respective correct complex. These results suggest that the eIF4G or eIFiso4G subunits influence translational efficiency more than the cap-binding subunits. The translation assays also showed varying responses of the mRNA templates to eIF4F or eIFiso4F, suggesting that some level of mRNA discrimination is possible. The dissociation constants for the correct complexes have K(D) values in the subnanomolar range, whereas the mixed complexes were found to have K(D) values in the ～10 nm range. Displacement assays showed that the correct binding partner readily displaces the incorrect binding partner in a manner consistent with the difference in K(D) values. These results show molecular specificity for the formation of plant eIF4F and eIFiso4F complexes and suggest a role in mRNA discrimination during initiation of translation.     

Effect of membrane stiffness and cytoskeletal element density on mechanical stimuli within cells: an analysis of the consequences of ageing in cells

A finite element model of a single cell was created and used to compute the biophysical stimuli generated within a cell under mechanical loading. Major cellular components were incorporated in the model: the membrane, cytoplasm, nucleus, microtubules, actin filaments, intermediate filaments, nuclear lamina and chromatin. The model used multiple sets of tensegrity structures. Viscoelastic properties were assigned to the continuum components. To corroborate the model, a simulation of atomic force microscopy indentation was performed and results showed a force/indentation simulation with the range of experimental results. A parametric analysis of both increasing membrane stiffness (thereby modelling membrane peroxidation with age) and decreasing density of cytoskeletal elements (thereby modelling reduced actin density with age) was performed. Comparing normal and aged cells under indentation predicts that aged cells have a lower membrane area subjected to high strain as compared with young cells, but the difference, surprisingly, is very small and may not be measurable experimentally. Ageing is predicted to have a more significant effect on strain deep in the nucleus. These results show that computation of biophysical stimuli within cells are achievable with single-cell computational models; correspondence between computed and measured force/displacement behaviours provides a high-level validation of the model. Regarding the effect of ageing, the models suggest only small, although possibly physiologically significant, differences in internal biophysical stimuli between normal and aged cells.