Isolation and sequence of a tropomyosin-binding fragment of turkey gizzard calponin

Limited chymotryptic cleavage of turkey gizzard calponin yields a 13 kDa fragment which could be purified by its ability to bind to Sepharose-immobilized tropomyosin. This 13 kD polypeptide is shown to be derived from a 22 kDa fragment. Complete amino acid sequence analysis of the 13 kD and 22 kD fragments reveals high homology with the formerly characterized smooth muscle-specific protein SM22 alpha (Pearlstone, J.R., Weber, M., Lees-Miller, J.P., Carpenter, M.R. and Smillie L.B., 1987, J. Biol. Chem. 262, 5985-5991) and the product of gene mp20 of Drosophila (Ayme-Southqate, A., Lasko, P., French, C, and Pardue, M.L. [(1989) J. Cell Biol. 108, 521-531]. Futhermore we recognize sequence elements of a putative actin-binding domain of alpha-actinin, the calpactin I or p 36 sequence, and a consensus motif present in the repeats of the gene product of the candidate unc-87 gene of C. elegans (S.D. Goetinck and R.H. Waterston, personal communication).     

Synthetic high density lipoprotein particles. Application to studies of the apoprotein specificity for selective uptake of cholesterol esters

Particles closely resembling rat high density lipoproteins (HDL) in terms of equilibrium density profile and particle size were prepared by sonication of apoA-I with a microemulsion made with egg lecithin and cholesterol oleate. These particles, like authentic HDL, allowed selective uptake of their cholesterol ester moieties by cultured cells without parallel uptake of the particle itself. That uptake was saturable and competed by HDL. In rats, the plasma decay kinetics and sites of uptake of a cholesteryl ether tracer were similar whether that tracer was incorporated into synthetic or authentic HDL. Synthetic particles containing other apoproteins were made by generally the same method, but using in place of apoA-I either a mixture of rat apoCs or apoE that was either competent or reductively methylated to prevent interaction with the B/E receptor. These particles, of lower density and larger Stokes radius than those made with apoA-I, also allowed selective uptake of cholesterol esters, albeit with a lower degree of selectivity than in the case of apoA-I. Thus a specific apoprotein component in the subject lipoprotein particle is not required for selective uptake. However, selective uptake was shown to be a function of particle density or size, and part of the difference in rates of selective uptake from the particles made with various apoproteins was explained by their differences in density or size.     

M241 (CD1) expression on B lymphocytes

The human thymus leukemia-like antigens (CD1a-c) consist of three similar glycoproteins found on subpopulations of normal thymocytes, T cell acute leukemias, and cutaneous dendritic cells. The CD1c antigen recognized by the M241 monoclonal antibody was detected on the circulating mononuclear cells of three children with severe combined immunodeficiency disease (SCID). Two-color immunofluorescence analysis demonstrated that M241 expression (43 to 95%) was limited to cells expressing the B cell-restricted antigens B4 (CD19), B1 (CD20), and surface immunoglobulin. To confirm M241 expression on normal cells of the B lineage rather than aberrant expression limited to SCID B cells, its expression was demonstrated serologically and biochemically on purified B cells from spleen, tonsil, and peripheral blood. Parallel analyses with monoclonal antibodies NA1/34 and 4A76 demonstrated that the CD1a and CD1b molecules were negative on all B cells that were studied. It has been hypothesized that the CD1 molecules represent the human counterpart of the murine thymus leukemia antigens due to their similar size, limited tissue distribution, and association with beta 2-microglobulin. This study suggests that a subset of CD1 antigens detected by M241 (CD1c) may represent a human analog of a murine Qa antigen due to its extended distribution on normal peripheral B cells.     

Structure and polymorphism of 18-carbon fatty acyl triacylglycerols: effect of unsaturation and substitution in the 2-position

The polymorphic behavior of symmetric diacid triacylglycerols (TGs), 1,3-dioleoyl-2-stearoyl (OSO), 2-elaidoyl (OEO), and 2-vaccinoyl (OVO) glycerols were studied by differential scanning colorimetry (DSC) and X-ray diffraction and compared with the corresponding monoacid TGs triolein (OOO), tristearin (SSS), trielaidin (EEE), and trivaccinin (VVV). The monoacid TGs formed a bilayered structure in all the polymorphic forms. On quenching from the melt, the diacid TGs OEO and OVO formed a bilayered (D = 45 A) beta'-phase with the exception of OSO, which formed a hexagonally packed bilayered (D = 52 A) alpha-phase. At -7 degrees C, the alpha-phase of OSO quickly transformed to a bilayered (D = 45 A) beta'-phase. Incubation at the beta'-phase melting temperature transformed OVO, OEO, and OSO into a trilayered (D = 65 A) beta-phase, where the 1,3-dioleoyl chains are segregated from the vaccinoyl, elaidoyl, or stearoyl chains into alternating layers. In summary, when all the acyl chains in a TG are the same (saturated, cis or trans unsaturated), the stable beta-phase packs into a bilayered structure. However, when the 1- and 3-acyl chains are cis unsaturated (bent) and the 2-acyl chain is either saturated or trans-unsaturated (straight), a bilayered beta'-phase can form, but transforms to a stable trilayered beta-phase, where the 2-acyl chains form a layer between two different layers of 1,3-oleoyl chains.     

North Carolina macular dystrophy is assigned to chromosome 6.

North Carolina macular dystrophy (NCMD) is an autosomal dominant macular dystrophy causing impaired central vision at an early age, is completely penetrant, and is present in a single large family. With the development of the hypervariable microsatellite (CA repeats) markers in the human genome, it was possible to relatively rapidly screen most of the genome for linkage to the NCMD gene. After utilizing 124 genetic markers, which excluded over 95% of the human genome, three Marshfield microsatellites located at 6q13-q21 were linked to the NCMD locus. Marshfield marker (MFD) 131 gave a lod score of Z(theta) = 4.36 at theta = 0.137; MFD 171 gave a Z(theta) = 8.42 at theta = 0.004; and MFD 97 gave a Z(theta) = 13.10 at theta = 0.017. Other retinal diseases have been reported on 6q stressing the importance of this region and possibly suggesting that these diseases may be allelic or located in part of a large macular gene family. Locating and characterizing the NCMD gene may be an important step in understanding this group of maculopathies as well as age-related macular degeneration (AMD), a common cause of blindness in the elderly.     

Demographic responses of arctic hares Lepus arcticus placed on two predominantly forested islands in Newfoundland

During January-April 1989. we monitored survival, reproduction, and body condition of 19 radio-collared arctic hares Lepus areticus introduced to two predominantly (80%) forested islands. Merchant (66 1 ha) and Burke (82 6 ha), in Placentia Bay, Newfoundland By late April, bone-marrow fat (42 7%) and kidney fat indices were lower than found in populations on the mountain barrens of western Newfoundland However, most island hares gained weight overwinter, and litter sizes (mean. 4 2 in utero) and testis weights (mean, 8 3 g) were as large or larger than recorded from other introduced and natural populations in Newfoundland The distribution of telemetry locations, tracks and feeding sites indicated that hares frequented the scattered barrens (totalling c 30 ha) on both islands in greater proportion than available These results suggest that, in the absence of snowshoe hares and mammalian predators, forested regions interspersed with small patches of barrens can sustain arctic hares     

Inhibition of lettuce seed germination by cycloheximide and chloramphenicol is alleviated by kinetin and oxygen

Kinetin alleviates cycloheximide inhibition and oxygen alleviates chloramphenicol inibition of germination of lettuce seeds (Lactuca sativa L. cv Grand Rapids). The effect is not due to increased but rather a substitution for protein synthesis. A cytokinin and energy supply appear prime requirements for germination.     

The ionization and distribution behavior of oleic acid in chylomicrons and chylomicron-like emulsion particles and the influence of serum albumin

A reproducible, fairly narrow-sized population of rat lymph chylomicrons, approximately 100 nm, was isolated by centrifugation and combined with low levels of [1-13C]oleic acid for NMR studies. The carboxyl chemical shift was monitored as a function of aqueous pH to characterize the ionization behavior of the fatty acid in these particles. The titration curves were very similar to those for oleic acid in equivalent-sized emulsion particles composed of egg phosphatidylcholine and triolein. A simple partition-ionization model was fitted to the data to derive values for apparent ionization constant, expressed as pKapp, of 7.4-7.5 and the "true" surface to core partition coefficient of approximately 7 for oleic acid in chylomicrons. The fatty acid in chylomicrons thus appeared to be largely associated with the surface regions of these particles. Addition of bovine serum albumin to the samples showed that near physiologic pH much of the fatty acid was bound to the albumin at fatty acid to albumin-binding stoichiometries as high as 5.1 and with mass ratios of greater than 2 in favor of the lipid or lipoprotein particles. Lowering the pH of the medium shifted the distribution of fatty acid away from albumin so that at pH 5 with the emulsion, virtually all the fatty acid was associated with the lipid. The behavior observed under physiologic conditions is consistent with the rapid clearance and redistribution of fatty acid generated in these particles by lipolytic processes. However, under conditions of severe acidosis, hyperlipidemia, and hypoalbuminemia a significant portion of fatty acids might be retained in triglyceride-rich lipoproteins and their remnants and affect subsequent metabolism.