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Biomedical subjects

G Ball

Publications and source records attributed to G Ball.

66 records · Page 4Linked to original sources
PubMed1970

Effet of prostaglandin E1 alone and in combination with theophylline or aspirin on collagen-induced platelet aggregation and on platelet nucleotides including adenosine 3':5'-cyclic monophosphate.

1. Human platelet nucleotides were labelled by incubating platelet-rich plasma with [U-(14)C]adenine. With such platelets, the effects of prostaglandin E1, theophylline and aspirin were determined on collagen-induced platelet aggregation and release of platelet ATP and ADP. Intracellular changes of platelet radioactive nucleotides, particularly 3':5'-cyclic AMP, were also determined both with and without collagen treatment. 2. Prostaglandin E1, theophylline and aspirin inhibited collagen-induced aggregation of platelets in a dose-dependent manner. Collagen-induced release of ATP and ADP and breakdown of radioactive ATP were also inhibited in a dose-dependent manner. 3. Prostaglandin E1 stimulated the formation of platelet radioactive 3':5'-cyclic AMP in a dose-dependent manner. With a given dose of prostaglandin E1, maximum formation of radioactive 3':5'-cyclic AMP occurred by 10-30s and thereafter the concentrations declined. The degree of inhibition of aggregation produced by prostaglandin E1, however, increased with its time of incubation in platelet-rich plasma before addition of collagen, so that there was an inverse relationship between the radioactive 3':5'-cyclic AMP concentration measured at the time of collagen addition and the subsequent degree of inhibition of aggregation obtained. 4. Neither theophylline nor aspirin at a concentration in platelet-rich plasma of 1.7mm altered platelet radioactive 3':5'-cyclic AMP contents. In the presence of prostaglandin E1, theophylline increased the concentration of radioactive 3':5'-cyclic AMP over that noted with prostaglandin E1 alone, but aspirin did not. 5. Mixtures of prostaglandin E1 and theophylline had a synergistic effect on inhibition of platelet aggregation. The same was true to a lesser extent with mixtures of prostaglandin E1 and aspirin. Such mixtures also inhibited collagen-induced release of platelet ATP and ADP and breakdown of platelet radioactive ATP. 6. Certain concentrations of either theophylline or aspirin and mixtures of small concentrations of prostaglandin E1 with either theophylline or aspirin caused little or no increase of radioactive 3':5'-cyclic AMP at the time of collagen addition, but inhibited aggregation to a marked degree, whereas higher concentrations of prostaglandin E1 alone caused a much greater increase of radioactive 3':5'-cyclic AMP at the time of collagen addition but inhibited aggregation to a lesser extent. With these compounds there does not appear to be a correlation between these parameters.

Adenine Nucleotides↗
PubMedDate not supplied

Use of thin-section, multidetector row helical CT images for coronal oblique reformations for optimal visualization of structures in the hepatoduodenal ligament.

Multidetector row computed tomography (CT) can acquire abdominal images of unprecedented thinness in a single breath-hold. This study investigated whether acquiring source axial images at 1.25 mm as opposed to 2.5 mm would result in a perceptible difference in image quality for coronal oblique reformations. Similarly, the hypothesis that a slice pitch of 3:1 would be superior to 6:1 was evaluated. Twenty-nine CT studies were retrospectively evaluated. The images were divided into four groups: 1.25-mm axial images, pitch 3:1; 2.5-mm axial images, pitch 3:1; 1.25-mm axial images, pitch 6:1; and 2.5-mm axial images, pitch 6:1. Three radiologists evaluated by consensus the coronal oblique reformations for overall image quality and image quality of structures in the hepatoduodenal ligament and of nodal groups. Use of 1.25-mm rather than of 2.5-mm source axial images resulted in statistically significant better scores for overall image quality and visualization of the hepatic artery, portal vein, pancreatic duct, and nodal groups. However, a pitch of 3:1 rather than of 6:1 did not result in significant differences in ratings of image quality. Use of 1.25-mm rather than of 2.5-mm source axial images improves image quality when creating coronal oblique reformations for abdominal anatomy.

Adult↗
PubMedDate not supplied

Use of colicin-based genetic tools for studying bacterial protein transport.

Transport of proteins across the envelope of Gram-negative bacteria is a very challenging domain of investigation, which involves membrane-embedded proteinaceous complexes at which specific targeting occurs. These transporters (translocon or secreton) have been studied both with genetics and biochemistry. In this review we report recent developments that should help to identify novel interactions that exist within these complexes, and to decipher the signals that specifically direct transported proteins to the cognate system. These developments are exclusively based on the re-routing of colicins to these molecular machineries. The re-routing induces a lethal situation in the case of efficient or inefficient transport, depending on the system, thus creating a genetic tool for selection of mutations that correct or generate a transport default.

Bacterial Proteins↗
PubMedDate not supplied

NMR relaxation studies of porous sol-gel glasses.

2H relaxation times T1, T1 rho and T2 for D2O in silica sol-gels are used to monitor porosity and surface interactions within the silica framework as a function of aging. Tetramethoxysilane gels are compared with composites containing low levels of poly(vinyl alcohol) (PVA) prepared under acidic conditions. Non-exponential decay of magnetisation in T1 rho and T2 experiments is attributed to the fractal nature of the pore structure.

Fractals↗