Interactions of colipase with bile salt micelles. 1. Ultracentrifugation studies.

A detailed investigation by ultracentrifugation of the colipase-taurodeoxycholate system showed the formation of well-defined mixed associations with a sedimentation coefficient of about 2.2S. The fact that these associations were only detectable above the critical micelle concentration of the salt indicated that micelles rather than monomers were bound to the cofactor. Two technical difficulties must be overcome before the weight of the associations could be measured with a reasonable accuracy. Firstly, the partial specific volume of the associations was determined using a digital microdensimeter and the interferometric system of the ultracentrifuge for concentration determinations. Secondly, due to the fact that micelle concentrations could not be equilibrated by dialysis, even after an extended period of time, an appropriate dilution of the ligand in the buffer compartment was necessary in order to compensate for its fixation by colipase in the solution. Then, the ionic strength dependence of the weight of the associations was found to vary in parallel with that of the micelles and to be in each case equal to the sum of the weights of one colipase molecule and one micelle. Therefore, colipase can be expected to contain a single high affinity site for bile salt micelle binding.     

Fatty acids, part 51. The long-chain oxo acids (argemonic acid) in Argemone mexicana seed oil

The crystalline material which separates from Argemone mexicana seed oil is a mixture of 9-and 11-oxo-octacosanoic and 11-oxotriacontanoic acids.     

Interaction between the Effects of Inside and Outside Na and K on Bullfrog Skin Potential

The composition of the solution bathing one border of the isolated frog skin affects the response of the potential across the skin to changes in the composition of the solution bathing the opposite border. Increasing the K concentration of the inside (corium) bathing solution decreased the sensitivity of the potential to a change in outside Na concentration. Decreasing the outside Na concentration decreased the sensitivity of the potential to a change in inside K concentration. Increasing the total ionic strength of the outside bathing solution or of both bathing solutions decreased the sensitivity of the potential to a change in outside Na concentration.     

Curare and modern medicine

This deadly arrow-poison of South American Indians, concocted from the juices of a variety of plants, has found modern clinical use in the treatment of human ailments.     

EFFECTS OF ARSENATE ON GROWTH OF NITROGEN-AND PHOSPHORUS-LIMITED CHLORELLA VULGARIS (CHLOROPHYCEAE) ISOLATES1

The effects of arsenate on the growth characteristics of five isolates of the freshwater alga, Chlorella vulgaris Beij., were examined. Two field isolates originated from arsenic-contaminated sites in Yukon, Canada and Kyushi, Japan; two reference isolates were obtained from the University of Texas Culture Collection. One isolate was selected for arsenic-tolerance in the laboratory. All five strains survived in culture solutions containing high arsenate concentrations. Arsenate (1–25 mM As) reduced photosynthesis and cell growth, as reflected by induced lag periods, slower growth rates, and lower stationary cell yields. Field isolates had shorter lag periods, higher growth rates, and enhanced cell yields compared to lab isolates when exposed to the same arsenic concentrations. Growth of the phosphorus-limited field strains was stimulated by the addition of arsenic. The cell yield of phosphorus-limited C. vulgaris Yukon, when treated with arsenic, was two times that of the phosphorus-limited control. This pattern was not evident when photosynthesis was used as a measure of cell response.     

Termite Prey Specialization in the Pitcher Plant Nepenthes albomarginata--Evidence from Stable Isotope Analysis

Old World pitcher plants (Nepenthes spp., Nepenthaceae) trapand digest invertebrate prey to derive nutrients, primarilynitrogen (N). In the majority of lowland Nepenthes species studiedto date, ants (Hymenoptera, Formicidae) are numerically thedominant prey taxon. Nepenthes albomarginata is unusual in showingan apparent bias towards the capture of termites (Isoptera).We tested the hypothesis that N. albomarginata derives N fromtermite capture, by comparison of foliar stable N isotope abundance(