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A T Darnule

Publications and source records attributed to A T Darnule.

11 recordsLinked to original sources
PubMed1994

A nonexchangeable apolipoprotein E peptide that mediates binding to the low density lipoprotein receptor.

ApoE is a 34-kDa apoprotein that mediates lipoprotein binding to the low density lipoprotein (LDL) receptor and to the LDL receptor-related protein. Receptor binding is mediated by a highly basic, alpha-helical sequence of approximately 15 amino acids that interacts with cysteine-rich repeat regions of the receptor. To determine the relationship between the receptor binding and lipid associating properties of apoE, we have synthesized a series of apoE peptides containing all (residues 129-169) or part (residues 139-169, 144-169, and 148-169) of the receptor-binding domain. The lipophilicity of these peptides was increased by modification of their N termini by acylation with either palmitic acid (C16-apoE peptide) or the N,N-distearyl derivative of glycine (diC18-Gly-apoE peptide). The unmodified peptides demonstrated low affinity for lipid surfaces (Kd > 10(-5) M) and moderate alpha-helicity in the presence of lipid (40%) and had no effect on LDL uptake by fibroblasts. N-Palmitoyl peptides had increased affinity for lipid (Kd approximately 10(-6) M) and increased alpha-helicity (55%) in the presence of lipid. The addition of the C16-apoE-(129-169)-peptide to 125I-LDL enhanced its uptake and degradation by fibroblasts 8-10-fold; however, < 50% of the degradation was mediated by the LDL receptor. By contrast, the diC18-Gly-apoE-(129-169)-peptide was essentially nonexchangeable (Kd < or = 10(-9) M) and highly helical (78%) in the presence of lipid. The addition of the diC18-Gly-apoE-(129-169)-peptide to 125I-LDL enhanced the specific uptake and degradation of LDL by both LDL receptor-mediated and non-LDL receptor-mediated mechanisms. Uptake and degradation of methylated LDL containing diC18-Gly-apoE-(129-169) revealed that the lipoprotein-bound peptide is the active agent. In agreement with this finding, a mutant diC18-Gly-apoE peptide (Arg142-->Gln) was much less effective than the wild-type peptide in potentiating binding, uptake, and degradation of 125I-LDL. Complexes of diC18-Gly-apoE-(129-169), apoA-I, and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine containing four to six copies of the peptide/particle displayed an affinity for the LDL receptor similar to that of apoE-L-alpha-dimyristoylphosphatidylcholine discs containing four copies of apoE.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗
PubMed1992

Maternal serum alpha-fetoprotein, beta-human chorionic gonadotropin, and unconjugated estriol levels in midtrimester trisomy 18 pregnancies.

OBJECTIVE: The purpose was to evaluate the levels of maternal serum human chorionic gonadotropin, alpha-fetoprotein, and unconjugated estriol in trisomy 18 pregnancies compared with normal singleton pregnancies. STUDY DESIGN: Sera from 14 trisomy 18 pregnancies (13 retrospectively and one prospectively ascertained) were analyzed for human chorionic gonadotropin, alpha-fetoprotein, and unconjugated estriol. RESULTS: The alpha-fetoprotein levels in the 10 trisomy 18 pregnancies without open neural tube or ventral wall defect had a median of 0.65 multiple of the median, although two had alpha-fetoprotein levels above 2.5 multiples of the median. The human chorionic gonadotropin levels had a median of 0.32 multiple of the median and the unconjugated estriol levels had a median of 0.56 multiple of the median. Although most women with trisomy 18 pregnancies had serum human chorionic gonadotropin levels that were less than 1.0 multiple of the median, three had markedly elevated human chorionic gonadotropin levels (greater than 5.0 multiples of the median). CONCLUSION: Our data are partially consistent with those previously published but suggest the possibility of a bimodal distribution of alpha-fetoprotein and human chorionic gonadotropin levels in trisomy 18-affected pregnancies, unrelated to a neural tube or abdominal wall defect. The efficiency of screening for trisomy 18 prospectively, using the three serum markers, requires further evaluation.

Adult↗
PubMed1983

Identification of surface antigens of endothelial cells.

A monolayer of a clone of endothelial cells derived from rat lung cells (RLE) was overlaid with 1 M urea to extract the surface proteins. Hydrolysis and SDS-gel electrophoresis of the urea extracted cell surface proteins (UCSP) yielded four peptides of 350,000, 84,000, 66,000 and 18,500 molecular weight. Of these only the 66,000 and 18,500 molecular weight peptides reacted with antibodies raised in rabbit against rat lung endothelial cells (RLE). The 18,500 mol. wt. antigenic peptide was a serum protein associated with the cell surface, whereas the 66,000 mol. wt. peptide was the surface antigen synthesized and released into the medium by the rat lung endothelial cells. On rocket immunoelectrophoresis, the 66,000 mol. wt. rat kidney fibroblast surface peptide produced only a single rocket whereas peptides of RLE produced two rockets, suggesting the presence of an additional antigenic peptide which could serve as a marker for endothelial cells.

Animals↗
PubMed1978

Antiserum to surface antigens as a marker for cultured rat lung endothelial cells (1).

Antibodies were developed in rabbits against an established line of endothelial cells from normal adult rat lung. Pre- and postimmunization sera were tested for antibody activity by the indirect immunofluorescence technique. Preimmunization serum failed to react with the endothelial cells, whereas the antibody titer of postimmunization serum from two rabbits was 1:512. Organ specificity and species specificity were assessed by absorbing the serum with packed dissociated cells from different organs of the rat and lung cells of other species. Only cells obtained from rat lung absorbed the antibodies completely. The antiserum showed some crossreactivity with the other cultured cells but the pattern of fluorescence was different. In the presence of complement the antiserum was found to be cytotoxic to cultured rat lung endothelial cells but not to the other crossreacting cells.

Animals↗