Electrical method for detection of endothelial cell shape change in real time: assessment of endothelial barrier function.

We have developed an electrical method to study endothelial cell shape changes in real time in order to examine the mechanisms of alterations in the endothelial barrier function. Endothelial shape changes were quantified by using a monolayer of endothelial cells grown on a small (10(-3) cm2) evaporated gold electrode and measuring the changes in electrical impedance. Bovine pulmonary microvessel endothelial cells and bovine pulmonary artery endothelial cells were used to study the effects of alpha-thrombin on cell-shape dynamics by the impedance measurement. alpha-Thrombin produced a dose-dependent decrease in impedance that occurred within 0.5 min in both cell types, indicative of retraction of endothelial cells and widening of interendothelial junctions because of "rounding up" of the cells. The alpha-thrombin-induced decrease in impedance persisted for approximately 2 hr, after which the value recovered to basal levels. Pretreatment of endothelial cells with the protein kinase C inhibitor, calphostin C, or with 8-bromoadenosine 3',5'-cyclic monophosphate prevented the decreased impedance, suggesting that the endothelial cell change is modulated by activation of second-messenger pathways. The alpha-thrombin-induced decrease in impedance was in agreement with the previously observed increases in transendothelial albumin permeability and evidence of formation of intercellular gaps after alpha-thrombin challenge. The impedance measurement may be a valuable in vitro method for the assessment of mechanisms of decreased endothelial barrier function occurring with inflammatory mediators. Since the rapidly occurring changes in endothelial cell shape in response to mediators such as thrombin are mediated activation of second-messenger pathways, the ability to monitor endothelial cell dynamics in real time may provide insights into the signal-transduction events mediating the increased endothelial permeability.     

Characterization and screening of bacteria from rhizosphere of maize grown in Indonesian and Pakistani soils

Thirty rhizobacteria isolated from maize grown in Pakistani and Indonesian soils were evaluated for their morphological characteristics, nitrogen fixation, P-solubilization, indole acetic acid (IAA) and siderophores production. Nitrogenase activity was detected in nineteen isolates ranging from 21.8-3624 n moles C2H4 produced/h/mg protein. Most of the isolates produced IAA, ten were capable of siderophore production while four were P-solubilizers. Ultrastructural studies of Pseudomonas sp. F14 indicated characteristic rhizospheric colonization within 48 h that was observed to change considerably with the passage of time from few bacteria to micro colonies. Random amplified polymorphic DNA (RAPD) analysis of 30 bacterial strains using 30 oligonucleotide primers resulted in considerable level of genetic diversity, with genetic distance ranging from 2-16%. Indonesian isolates were found to be more diverse as compared to Pakistani isolates. The characterization and screening of rhizobacteria of maize rhizosphere has helped in selection of isolates F7, LS-1, 3.1.1.C, F2, F3 and F13 as superior strains for use as bioinoculant. Moreover isolate F14 identified, as Pseudomonas fulgida by partial 16S rRNA sequence analysis is a novel strain regarding its tremendous potentials for inoculum production to enhance the yield of maize.     

Misidentification of toxigenic Corynebacterium diphtheriae as a Corynebacterium species with low virulence in a child with endocarditis.

A 6-year-old boy presented to a university hospital in Malaysia with infective endocarditis complicating cyanotic congenital heart disease. Blood cultures showed a gram-positive, aerobic, coryneform-like bacillus identified by the hospital laboratory as Corynebacterium xerosis, but a reference laboratory identified the organism as a toxigenic strain of Corynebacterium diphtheriae. The two laboratories concurred on all biochemical test results except for sucrose fermentation.     

Bulk and Solution Copolymerization of Butyl Acrylate/Methyl Methacrylate at Elevated Temperatures

A series of bulk and solution (in toluene) copolymerizations of butyl acrylate/methyl methacrylate were performed independently at two laboratories. The runs were at elevated temperatures ranging from 90 to 140 °C conducted to high conversion levels, and samples were characterized for conversion, cumulative copolymer composition and number‐ and weight‐average molecular weights and distribution. Variation of the comonomer feed composition, temperature, and the solvent, initiator and chain transfer agent concentrations was studied. Using a mechanistic model, conversion data were predicted to high conversions using terminal model kinetics at 90 and 115 °C. The copolymer composition data conformed to the terminal kinetic model over the entire temperature range. Solvent effects were reflected by changes in the butyl acrylate rate constants.

Composition vs. conversion. Effect of feed composition for runs at 140 °C.     

First external quality assurance of antibody diagnostic for SARS-new coronavirus.

To confirm an infection with the new coronavirus (SARS-CoV) causing the severe acute respiratory syndrome (SARS) diagnostic assays for detection of SARS-CoV specific antibody are necessary. To evaluate the diagnostic performance of laboratories an external quality assurance (EQA) study was performed in 2004. Participating laboratories (9/20) correctly detected anti-SARS antibodies in serum samples without false positive results in an immunofluorescence assay. In contrast, only 4/13 laboratories detected most of the anti-SARS antibody positive samples without false positive results using enzyme immunoassays (EIA) and/or immunoblot. The overall results clearly demonstrate that serological diagnosis of SARS-CoV remains at an early stage of development, with further technical improvements required, particularly with respect to the use of SARS specific EIAs.     

A pharmacological study of group I muscle afferent terminals and synaptic excitation in the intermediate nucleus and Clarke's column of the cat spinal cord

Summary When administered microelectrophoretically GABA and piperidine-4-sulphonic acid depolarized the central terminations of muscle group Ia and Ib afferent fibres in the lumbar intermediate nucleus and Clarke's column of cats anaesthetised with pentobarbitone sodium. Both this depolarization, and primary afferent depolarization, generated by impulses in other primary afferent fibres which produce prolonged bicuculline-sensitive inhibition of the firing of group I afferent fibre-excited interneurones in the intermediate nucleus and cells in Clarke's column, are reduced by microelectrophoretic bicuculline methochloride. Systemically administered (±)-baclofen hydrochloride (maximum dose 8 mg kg^–1) depressed the monosynaptic excitation of Clarke's column neurones by impulses in muscle and cutaneous afferent fibres. Microelectrophoretically administered (–)-baclofen reduced the bicuculline-sensitive primary afferent depolarization of group I terminations without, however, reducing the depolarizing action of GABA or piperidine-4-sulphonic acid. The depression by (–)-baclofen of the group I monosynaptic excitation of intermediate nucleus neurones is not reduced by concentrations of bicuculline methochloride adequate to suppress prolonged inhibition of these neurones     

Differential effects of complement activation induced by cobra venom factor on pulmonary transvascular fluid and protein exchange

Sheep were prepared with lung lymph fistulas for assessment of the effects of complement activation on pulmonary transvascular fluid and protein exchange in the intact animal. Cobra venom factor (CVF 200 +/- 46 U/kg) was injected intravenously for activation of the complement system. In some animals (n = 6), pulmonary lymph flow (Qlym) and pulmonary arterial pressure (Ppa) increased without a change in the lymph-to-plasma protein concentration ratio (L/P) or in pulmonary blood flow (QL), indicating an increase in pulmonary vascular permeability to proteins. In another group (n = 6), Qlym and the L/P did not change, and there were also no changes in Ppa and QL following a similar injection of CVF. Morphologic evidence showed that leukocytes were trapped in pulmonary vessels and interstitium of both groups. Pulmonary edema was also present in both groups. Complement activation does not uniformly increase pulmonary lymph flow despite pathologic evidence of leukocyte sequestration and pulmonary edema. The lack of change in lymph flow in some animals may be due to lymphatic insufficiency, or lack of generation of humoral mediators, and/or a decrease in pulmonary capillary pressure.