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A C Richards

Publications and source records attributed to A C Richards.

14 recordsLinked to original sources
PubMed1999

Adsorption of water by anhydrous nedocromil sodium from 20 to 40 degrees C.

Three different powder preparations of the drug disodium 9-ethyl-4, 6-dioxo-10-propyl-4H,6H pyrano[3,2-g]quinoline-2,8-dicarboxylic trihydrate, Nedocromil sodium (trade name Tilade), have been fully dehydrated in a vacuum and their water vapor adsorption characteristics quantitatively assessed at different water vapor pressures over a temperature range 20 to 40 degrees C. At saturated vapor pressures, 100% RH, rates of adsorption are around 0.1 s(-1/2). Graphs of square root of time against reduced mass during uptake of water vapor at vapor pressures in the range 20 to 47 mm of Hg, all equivalent to 100% RH, indicate control by a diffusion mechanism with activation energies in the range 8 to 24 kJ mol(-1), dependent on the powder preparation method. In two of the powders nonlinear Arrhenius-type plots are interpreted as showing that control of the process is dependent on the surface's ability to hold water molecules at the experimental temperature. The variation in activation energies and the calculated values for diffusivities, around 1 x 10(-13) m(2) s(-1), are used to explore structural involvement in the overall water adsorption process. The measured values of water vapor diffusivity into the structure have been used to predict the water solubility of nedocromil sodium trihydrate, and the results show good agreement to reported solubilities. This approach to solubility prediction is an alternative to the Noyes and Whitney method where ions leaving the surface are monitored.

Adsorption↗
PubMed1989

Atrial natriuretic peptide inhibits the release of endothelium-derived relaxing factor from blood vessels of the rabbit.

We investigated the effects of atrial natriuretic peptide (ANP) on release of endothelium-derived relaxing factor (EDRF) from rabbit aorta and central ear artery using inhibition of platelet aggregation and vascular smooth muscle relaxation respectively as measures of EDRF activity. ANP at concentrations greater than 10(-9) M inhibited carbachol-induced EDRF release from rabbit aorta and acetylcholine-induced EDRF release from the central ear artery. These findings are consistent with previous observations that 8-bromo cyclic GMP inhibits EDRF release from rabbit aorta and ANP inhibits release of EDRF from cultured endothelial cells.

Adenosine Diphosphate↗
PubMed1978

Automatic collector of expired 14CO2 for liquid scintillation counting.

A filtration technique was employed to trap 14CO2 continuously for liquid scintillation counting. Devices for delivering scintillator and ethanolamine solutions were combined symmetrically with two fritted-glass aspirators for alternating operation. The collector was regulated by a fraction collector timer. Trial and animal tests indicated that the described method was efficient, reliable, and more convenient for frequent collection over long periods than alternative methods. The automatic collector was used for metabolic studies of [1-14C] arachidonic acid in rats kept in metabolic cages and the results were processed by multicompartmental analysis.

Animals↗
PubMed1976

The binding of Met-tRNAf to isolated 40-S ribosomal subunits and the formation of Met-tRNAf - 80-S-ribosome initiation complexes.

Different forms of 40-S ribosomal subunit, distinguishable by their buoyant densities on CsCl equilibrium density gradients, are formed when derived 40-S ribosomal subunits are incubated with partially purified reticulocyte ribosomal wash proteins. One of these subunits, the 1.37-g-cm-3 form is not present in the cell but the other two forms, the 1.40-g-cm-3 and 1.40-g-cm-3 subunits, are present in cell extracts. 35S label is bound to 1.37-g-cm-3 and 1.40-g-cm-s subunits when [35S]Met-tRANf, GTP and poly(A,U,G) are included in the incubations. The 35S-labelled 40-S subunits recovered, and the amount of 35S label bound to them, are changed if the [35S]Met-tRNAf-40-S-subunit-poly(A,U,G) complexes are first purified on sucrose gradients before analysing them on CsCl. The 1.37-g-cm-3 particle is no longer seen and the total quantity of 35S label on the 40-S subunits is 90% lower after sucrose gradient purification. Between 30% and 40% of the 40-S subunits bind [35S]Met-tRNAf when 1 mM GTP, an excess of ribosomal wash proteins and [35S]Met-tRNAf over derived 40-S subunits, and poly(A,U,G) or AUG is included in the incubations. The omission of poly(A,U,G) or AUG from the incubations substantially lowers the amount of subunit-bound 35S label ultimately recovered. With these incubations less than 10% of the 40-S subunits have bound [35S]Met-tRNAf. [35S]Met-tRNAf binding is affected by the nature of the RNA added. The addition of poly(U), rRNA and native 9-S golbin mRNA is without effect, whereas denatured globin mRNA is stimulatory. Maximum binding is obtained however with AUG. Poly(A,U,G) is less stimulatory than AUG but more stimulatory than denatured mRNA, suggesting that the number as well the accessibility of the AUG initiations condons determines the amount of 35S label bound. Similar results are obtained for the ribosomal-wash-dependent binding of [35S]Met-tRNAf to 80-S ribosomes. Contrary to the binding results, the ability of mRNA to stimulate protein synthesis is dependent on the integrity of the mRNA. Thus, native 9-S globin mRNA but not poly(A,U,G) stimulatex protein synthesis in the wheat germ system. HCHO-treated globin mRNA, although stimulatory, is 45% less effective than native mRNA. The addition of AUG, derived 60-S subunits and extra ribosomal wash is required for the formation of [35S]Met-tRNAf-80-S-ribosome complexes from sucrose-gradient-purified [35S]Met-tRNAf-40-S-subunit complexes. The 80-S ribosome complexes are able to form peptide bonds. Thus, if puromycin is added to the full incubations at zero time, no 35S label is present on the 80-S ribosome. 35S label is released as methionyl-puromycin. If the [35S]Met-tRNAf-40-S-subunit complexes are assembled with poly(A,U,G) or AUG in the incubations and then purified, only derived 60-S subunits are required to form [35S]Met-tRNAf-80-S-ribosome complexes. 35S label is not released from them when puromycin is added to the incubations unless extra ribosomal wash is also added.

Animals↗
PubMedDate not supplied

Complement activation, its consequences, and blockade by gene transfer.

The success of xenotransplanting vascularized pig organs into humans is limited owing to the immediate immune reaction, termed hyperacute rejection (HAR). This reaction is primarily mediated by naturally occurring xenoreactive antibodies binding to the graft and activating the complement system, resulting in organ dysfunction. Pig membrane-bound complement regulatory proteins efficiently control autologous complement only and are unable to protect against human complement-mediated damage. One line of current research to overcome HAR of pig organs involves the expression of human complement regulatory proteins by pig cells. In vitro data have demonstrated that pig endothelial cells expressing human regulators of complement activation (RCAs) are resistant to human complement-mediated attack, which has led to the successful production of pigs transgenic for human RCAs. Ex vivo perfusion studies using fresh human blood with organs from these animals has shown an improvement in graft function and survival through expression of human RCAs compared to that of nontransgenic pig organs. Similar results have been observed in primate models, where expression of human RCA proteins on the pig donor organ has resulted in protection against HAR and prolongation of graft survival. The initial complement-mediated immunologic barrier of HAR has been overcome through this genetic incorporation of human RCAs into pigs, and it is now possible to study the subsequent mechanisms of xenograft rejection in the pig-to-human combination.

Acute Disease↗