Biomedical subjects

J A Poulis

Publications and source records attributed to J A Poulis.

5 recordsLinked to original sources

PubMed2005

Adhesion performance of UHMWPE after different surface modification techniques.

A novel design of an ultra-high molecular weight polyethylene (UHMWPE) glenoid component has been proposed, based on adhesion to PMMA bone cement. However, due to the non-polar nature of UHMWPE, surface modification techniques are needed to obtain good adhesion and thus for the design to be viable. The aim of the study is to investigate adhesion of UHMWPE after different surface treatments. Three gas-phase surface modification techniques were investigated, namely UV/Ozone, corona discharge and radio frequency glow discharge plasma, as well as abrasion. The surface treated samples were examined using water contact angle, surface energy and roughness measurements, as well as single lap-joint shear testing using polymethylmethacrylate (PMMA) bone cement and methylmethacrylate (MMA) adhesive. The effect of aging on bonded samples has also been investigated. Corona and glow discharge treatments were found to activate the surface as shown by an increase in surface energy of over 100% in an order of less than a minute, corresponding to an increase in ultimate shear stress from 0.12 to 0.40 MPa. In contrast, UV/Ozone required exposure times in the order of minutes to have an effect that was still incomparable to the other gas-phase treatments examined. Abrasion produced slightly better adhesion properties for single lap-joints bonded with PMMA compared to the corona treatment. The best treatment was found to be a combined treatment of surface roughening for 10 s, and subsequently a 90 s glow discharge treatment, resulting in failure of the UHMWPE sheet material.

Adhesiveness↗

PubMed1993

Assessment of cleaning and disinfection in the food industry with the rapid ATP-bioluminescence technique combined with the tissue fluid contamination test and a conventional microbiological method.

A quantitative ATP bioluminescence procedure has been used to determine the cleanliness of food processing factories and the results have been compared with those from conventional microbiological culture methods. ATP measurements were combined with the tissue or tissue fluid contamination (TTFC) assessment method to obtain an impression of the amount of inanimate contamination on the sampled surfaces. It was found that, in the sampled food factories, there was poor relation between the two assessment techniques: ATP bio-luminescence combined with TTFC and contact plating. However, either method in its own right is useful to check cleanliness of food industries. ATP measurements do have in addition the great advantage that it is a fast method and is easy to perform.

Adenosine Triphosphate↗

PubMed1986

Circadian urinary excretion rhythms in adrenalectomized rats.

The impact of the adrenal system on urinary rhythms was investigated in adrenalectomized (ADX) rats under various experimental conditions. During a 12:12 light-dark cycle the acrophases were shifted in ADX rats with respect to control rats. Under constant light conditions ADX rats displayed free-running rhythms, similar to those of control rats. The periods were stable in blind rats but not in rats maintained on a constant light cycle. The abrupt change in period, which occurred after approximately 8 days, suggests a stage of internal desynchronization. A 6-h delay in the administration of corticosterone to ADX rats caused a delay shift of the acrophases. A single intraperitoneal injection of corticosterone in blind free-running ADX rats caused delay or advance shifts so that we could construct phase-response curves for the various excretory rhythms. These observations indicate that the adrenals are not essential for the establishment of the urinary rhythms; however, corticosterone influences the phase setting of these rhythms. The site of action is probably the X pacemaker (controlling the body temperature rhythm), although we cannot totally exclude an additional effect on secondary (renal) oscillators.

Adrenalectomy↗

PubMed1982

Measurements of the elasticity of monolayers consisting of lipids from nerve membranes.

For measurement of viscoelastic properties of monolayer-covered interfaces a longitudinal wave is generated in the plane of the interface, using a horizontal oscillating barrier. The wave propagation depends on the values of the viscoelastic parameters of the monolayer. The technique is applied here to study the surface elasticity of layers consisting of lipids extracted from nerve membranes. It is concluded that mechanical disturbances are propagated as longitudinal waves. The possibility that longitudinal waves occur in nerve membranes and the role they might play in the transmission of information in biological membranes is discussed.

Animals↗

PubMed1980

Characterization of Tn904 insertions in octopine Ti plasmid mutants of Agrobacterium tumefaciens.

Seven Tn904 insertion mutants of pTi Ach5 affecting Agrobacterium tumefaciens virulence were studied. The mutant character was shown to be plasmid borne. Four of these mutants were avirulent and carried an insertion in restriction endonuclease HpaI fragment 12, a 3.3-megadalton fragment, which therefore appears to be a Ti plasmid region essential for virulence. Two mutants were attenuated in virulence. The inserts mapped close to HpaI fragment 12. One mutant giving rise to small tumors with excessive adventitious root formation on Kalanchoe daigremontiana carried an insertion in the right side of the common sequence in the deoxyribonucleic acid of the Ti plasmid detected in crown gall tumors. The insertion behavior of Tn904 was studied by analyzing 11 independently isolated and randomly chosen mutants. The Tn904 inserts did not affect oncogenicity, tumor morphology, bacterial transfer functions, octopine catabolism functions, or vital parts of the Ti plasmid, such as the origin of replication. Most of the Tn904 inserts were concentrated in a small part of the map. The size of additional deoxyribonucleic acid as a result of Tn904 inserts varied between 5 and 15 megadaltons. In two cases a Ti plasmid was found with two Tn904 insertions at different positions.

Arginine↗