The separation of ribonucleic acids from Escherichia coli on lysin-agarose.

Lysine-agarose provides a simple means of separating RNA species of different moleecular weight. When RNA from Escherichia coli is added to a small column of lysine-agarose and elution is carried out at neutral pH with a shallow linear gradient of NaCl the RNA species are eluted according to size; 4S and 5S RNA species are completely separated and after a delay the 16S and 23S species are eluted as separate peaks. The process is very reproducible and the different species are eluted at a fixed salt concentration even when changes are made in the gradient, provided other conditions, under which the column is run remain constant.     

Geometry of the human erythrocyte. I. Effect of albumin on cell geometry.

The effects of albumin on the geometry of human erythrocytes have been studied. Individual red cells, hanging on edge from coverslips were photographed. Enlarged cell profiles were digitized using a Gradicon digitizer (Instronics Ltd., Stittsville, Ontario). Geometric parameters including diameter, area, volume, minimum cylindrical diameter, sphericity index, swelling index, maximum and minimum cell thickness, were calculated for each cell using a CDC 6400 computer. Maximum effect of human serum albumin was reached at about 1 g/liter. Studies of cell populations showed decreases in mean cell diameter of up to 6%, area 6%, and volume 15%, varying from sample to sample. The thickness of the rim was increased while that at the dimple was decreased. Studies of single cells showed that area and volume changes do not occur equally in all cells. Cells with lower sphericity indices showed larger effects. In the presence of albumin, up to 50% of the cells assumed cup-shapes (stomatocytes). These cells had smaller volumes but the same area as biconcave cells. Mechanical agitation could reversibly induce biconcave cells to assume cup shapes without area or volume changes. Experiments with de-fatted human albumins showed that the presence of bound fatty acids in varying concentrations does not alter the observed effects. Bovine serum albumin has similar effects on human erythrocytes as human serum albumin.     

200 injuries caused by playground equipment.

Two-hundred children with injuries caused by playground equipment were studied. Whereas only about 9% of the total casualty attendances are for fractures, 26-5% (53) of these children had fractures. The climbing frame and the slide seemed to be associated with more severe injuries than the swing or other equipment, but more cases need to be studied to confirm this. The youngest children were at particular risk on equipment such as the wooden rocking horse or roundabout, when the speed of operation could be controlled by older children. Many of the injuries to the very youngest children occurred when they were walking behind a moving swing. Faulty equipment did not seem to be a major factor in causing accidents, but the use by older children of apparatus designed for young ones led to accidents. There was supervision, either at home, in a school playground, or in a park, in 62% of the cases. Many of the accidents were the result of the normal desire of children for experimentation and adventure.     

Prostaglandins and renal function II. The effect of prostaglandin inhibition on autoregulation of blood flow in the intact kidney of the dog

In order to evaluate the effect of prostaglandin release on renal autoregulation in the intact kidney of the dog, pressure-flow curves were obtained before and after the administration of either indomethacin or meclofenamate, two potent prostaglandin synthetase inhibitors. After drug administration renal venous prostaglandin E decreased in each of eight studies with a mean change from 286 to 141 pg/ml (p < .001). In addition, prostaglandin inhibition was associated with a 31 percent decrease in renal blood flow and a 58 percent increase in renal resistance. Yet, as renal perfusion pressure was decreased by aortic constriction, the change in flow per pressure reduction and the percent change in renal resistance were not significantly different after prostaglandin inhibition when compared to control values in the same animals. The magnitude of the pressure range over which autoregulation was maintained was also similar in the two groups although both the initial and lowest level of autoregulation were slightly higher after prostaglandin inhibition. It is concluded that the administration of these prostaglandin synthetase inhibitors does not significantly impair renal autoregulation in the intact dog kidney.     

Essai chimiosystématique sur la tribu des Lotées

A survey of the leaves and flowers of 62 representatives of the tribe Loteae (Leguminosae) showed the presence of several classes of flavonoids: flavonol 7-methyl ethers (rhamnocitrin, rhamnetin), 8-O-substituted flavonols (gossypetin, limocitrin, sexangularetin, corniculatusin), 3′,4′,5′-tri-O-substituted flavonols (myricetin, mearnsetin, syringetin, laricitrin), proanthocyanidins and flavone-C-glycosides. The trisubstitution of the B-ring and the 8-O-substitution of the A-ring allow the definition of a major group including the genera Dorycnium, Bonjeania, Lotus and Tetragonolobus. The presence of proanthocyanidins and 7-O-methylation determine a second group consisting of the genus Anthyllis. Finally, Securigera, on the basis of its flavonoid chemistry, appears to be rather remote from other members of the tribe.     

Cooperativity of ligand binding as a function of monomer-dimer equilibrium parameters and acceptor concentration

A general monomer-dimer equilibrium system involving ligand interactions ispresented. Cooperativity features of specific limited models are analyzed by selecting the appropriate family of equilibrium constants from this general scheme. Each system is then characterized in terms of Hill coefficient dependency on alterations in values of equilibrium constants and total acceptor concentration. This method permits comparison of predicted cooperativity trends between systems. Contrasting reports concerning cooperativity dependencies for certain defined equilibrium systems are compared and the discrepancies resolved. Characteristics of cooperativity binding patterns are shown to include symmetry about dimerization association constant values, both positive and negative cooperativity for a single set of parameters, and significant changes in cooperativity features with relatively small changes in equilibrium parameters.