Lipid binding by fragments of apolipoprotein C-III-1 obtained by thrombin cleavage.

We have used thrombin to cleave apolipoprotein C-III-1 into two fragments constituting residues 1-40 (apoLP-C-III-A) and 41-79 (apoLP-C-III-B). The lipid binding properties of these fragments with dimyristoyl- and 1-palmitoyl-2-oleoylphosphatidylcholines have been determined using circular dichroic and intrinsic tryptophan fluorescence spectroscopy. The peptide-phospholipid mixtures were fractionated by density gradients of cesium chloride. ApoLP-C-III-A showed disordered structure in the absence and presence of DMPC and no significant amount of peptide-phospholipid complex was isolated. ApoLP-C-III-B showed conformational changes in the circular dichroic spectrum and a shift in the intrinsic tryptophan fluorescence spectrum. Ultracentrifugation in cesium chloride gradients yielded peptide-phospholipid complexes isolated between density 1.10 and 1.18. The molar ratio of lipid to protein was 12:1. The results of these studies and the examination of space filling models of apoLP-C-III provide evidence that an amphipathic alpha helix which contains a nonpolar face and a polar face is the basic structural unit for binding of phospholipid by the plasma apolipoproteins. These results also provide direct evidence that the hydrophobicity of the nonpolar face is important in lipid binding since the nonpolar face of residues 1-40 is considerably less hydrophobic than the nonpolar face of residues 41-79.     

Thin-layer chromatography with agarose gels: A quick,simple method for evaluating liposome size

Thin-layer gels can be made with agarose and used to assess within a few minutes the efficiency with which multilamellar vesicles are converted to small unilamellar ones by sonication. A fluorescent lipid marker or vesicle-encapsulated solute permits continuous monitoring of the chromatography. Advantages over agarose gel column chromatography include speed of analysis, small sample size, the possibility of running multiple samples simultaneously, and direct accessibility to fluorescence microscopy. This approach should also be useful in the study of liposome-lipoprotein interactions and in affinity chromatography of liposomes.     

Competitive interactions and the availability of sleeping sites for a diurnal coral reef fish

A field study was made to test whether the population size of a diurnal reef fish, the wrasse Thalassoma bifasciatum (Bloch), was limited by inter- or intraspecific competition for sleeping shelter. T. bifasciatum is often attacked at dusk by two small territorial damselfishes, Eupomacentrus dorsopunicans (Poey) and E. planifrons (Cuvier). Although these three species sleep in the same general habitats, there are qualitative differences in the types of holes they use and how they use them. Wrasse holes are usually in these damselfishes' territories, but damselfish attacks do not prevent wrasses entering holes. Wrasses infrequently defend their holes intraspecifically. They regularly change their holes, with little intra- or interspecific aggressive interaction. When its hole is removed, a wrasse is late in retiring but finds a hole near its old one with little aggressive interaction, and does not have a higher mortality rate. Empty wrasse holes are rarely refilled, and then only by conspecifics. Wrasses added to reefs find unoccupied holes and do not usurp other fishes' holes. Damselfish defend their eggs and food against the wrasse, but not their sleeping shelter, nor living space per se. Sleeping sites are not limiting the wrasse, but are present in a surplus. Intraspecific hole defense by a wrasse prevents a delay in its retiring that would increase the risk of crepuscular predation on it.     

Daytime births in captive patas monkeys

Daytime births in two patas colonies were the rule rather than the exception.     

Synchronization of Drosophila cells in culture.

We synchronized Drosophila cell lines (Schneider's line 2 and Kc) by allowing the cells to enter the stationary phase of growth and then diluting them into fresh culture medium. The cells of both cell lines entered S phase, after an 8- to 14-hr delay, in a state of partial synchrony; 60 to 80% of the cell population accumulated in S phase. Measurements of the cell cycle phases of Schneider's line 2 cells (S = 14 to 16 hr; G2 = 6 to 8 hr; M = 0.4 hr) were similar to those of Kc cells.     

Fusion of Mycoplasma fermentans strain incognitus with T-lymphocytes.

The ability of Mycoplasma fermentans (strain incognitus) to fuse with cultured lymphocytes was investigated and the fusion process was characterized. Fusion was measured using an assay to determine lipid mixing based on the dequenching of the fluorescent probe, octadecylrhodamine (R18), that was incorporated into the mycoplasma cells. Fusion of M. fermentans was detected with both CD4+ (Molt 3) and CD4- (12-E1) cells. The amount of fusion induced was relatively low and ranged from 5-10% with either cell culture. When primary peripheral blood lymphocytes were used the fusion yield was somewhat higher, reaching 12% of the cell population. Similar findings were obtained with fluorescent microscopy analysis suggesting that a predetermined, but unidentified subpopulation of cultured lymphocytes, were being fused. The rate of fusion was temperature dependent. Following a short lag period fusion at 37 degrees C was virtually completed in 60 min. The lymphocytes remained intact throughout the fusion process, as determined by the Trypan blue staining procedure. Fusion was almost completely inhibited by anti-M. fermentans antisera and by pretreatment of M. fermentans cells with proteolytic enzymes, suggesting that a surface-exposed proteinaceous component is involved in the fusion process.     

HLA-DR2, [HLA-B7, SC31, DR2], and [HLA-B8, SC01, DR3] haplotypes distinguish subjects with asthma from those with rhinitis only in ragweed pollen allergy.

MHC haplotypes were determined for 52 patients with ragweed pollen allergy, with and without asthma, and 27 non-atopic controls. Total IgE levels were unimodally distributed in all study groups and were higher in atopic patients in general compared with non-atopics. There was no difference in total IgE levels in patients with rhinitis only compared with those with rhinitis and asthma. IgE anti-Amb a V was detected (after subtraction of values representing the means + 2 SD of the non-atopics) in 9 of 20 asthmatics but only 3 of 32 patients with only rhinitis and was thus associated with asthma. Mean anti-Amb a V was much higher in the antibody-positive asthmatics (1710 U/ml) than in the positive patients with rhinitis only (469 U/ml). The extended MHC haplotype [HLA-B7, SC31, DR2] and its possible DR-containing fragment (SC31, DR2), were found almost exclusively among the patients with IgE anti-Amb a V and were significantly elevated in patients with asthma. DR2 in general, but not DR2 without SC31, was significantly increased in frequency in patients with anti-Amb a V. In contrast, the extended haplotype [HLA-B8, SC01, DR3] and DR3 in general were increased among patients with rhinitis only and patients without IgE anti-Amb a V compared with general controls. Thus, [HLA-B8, SC01, DR3] and DR3 appear to be "protective" for the production of this antibody and the occurrence of asthma. The findings are consistent with an MHC-linked gene or genes on [HLA-B7, SC31, DR2] (but not necessarily DR2, Dw2, or DQw6 in general) controlling the IgE immune response to Amb a V and associated with asthma in ragweed pollen-sensitive subjects. In patients with rhinitis alone and generally undetectable levels of IgE anti-Amb a V, the increase in [HLA-B8, SC01, DR3] and DR3 may mark a response to an as yet unidentified Ag associated with ragweed allergy and rhinitis only.     

Osage orange (Maclura pomifera): History and economic uses

Osage orange, a tree native to Texas, Oklahoma, and Arkansas, was planted widely in the United States as a living fence from 1850–1875. It has naturalized over much of its planted range and is an early successional species. Economically the tree has had a wide number of uses including for bows, yellow dye, and building materials. It is used for fence posts and is a potential source for a proteolytic enzyme. Its taxonomy, anatomy, morphology, chemical constitutents, medicinal uses, and toxicity are discussed in this paper and related to its economic importance.