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L D Ward

Publications and source records attributed to L D Ward.

60 records · Page 4Linked to original sources
PubMed1981

Multivalency of the partitioning species in quantitative affinity chromatography. Evaluation of the site-binding constant for the aldolase-phosphate interaction from studies with cellulose phosphate as the affinity matrix.

Theory is presented which describes the competitive interaction of a multivalent solute with a univalent ligand and an affinity matrix. The formulation accounts for cross-linking interactions of the multivalent solute, and of its complexes with ligand, with matrix interaction sites in terms of two site-binding constants pertaining respectively to ligand-solute and solute-matrix interactions. Explicit expression are derived which permit evaluation of these constants from experimental results obtained in partition equilibrium experiments or in frontal affinity chromatography studies. These relations are explored in partition equilibrium experiments conducted with cellulose phosphate as the matrix, aldolase as the solute, and phosphate as the ligand. At pH 7.4, I = 0.15, a value of 350 +/- 60 M-1 was obtained for the aldolase-phosphate site-binding constant, in close agreement with the corresponding value deduced from competitive inhibition studies. It is concluded that the present approach is particularly suited to the elucidation of weak interactions, which cannot be reliably studied by conventional means.

Animals↗
PubMedDate not supplied

Two-dimensional electrophoretic analysis of proteins expressed by normal and cancerous human crypts: application of mass spectrometry to peptide-mass fingerprinting.

Protein patterns of normal human colonic crypts, isolated from different regions of the large intestine, and several colorectal cancer cell lines were compared using two-dimensional electrophoresis gels (2-DE). As detected by intrinsic radiolabeling and Coomassie Brilliant Blue staining, the protein patterns for normal crypts isolated from the ascending, and descending, regions of the colon and the rectum, were almost (> 95%) identical. While 75-80% of the protein spots from normal crypts and the colorectal cancer cell line (LIM 1863), a cell line that grows as organoids and differentiates spontaneously into crypt-like structures in vitro, can be matched, the relative expression levels of a large number of proteins differ. At least two protein spots (undetectable in the protein pattern from normal cells), proteins a (M(r) approximately 18,000, pI 6.7-6.9) and b (M(r) approximately 24,000, pI 5.9-6.0), were detected in the 2-DE gel protein pattern in the three cell lines LIM 1863, LIM 1215 and LIM 1899. The identity of these proteins is not yet known and further studies are required before they can be considered as potential colon tumor markers. Approximately 60% of the cellular proteins from LIM 1215 cells, a colon carcinoma cell line that exhibits many properties associated with columnar cells, can be matched with LIM 1863 cells. The results presented here represent an initial phase in our efforts to develop a comprehensive protein database for normal human colon cells and several colorectal cancer cell lines. While our initial protein identification relied on microsequencing methodologies, we are presently evaluating peptide-mass fingerprinting, utilizing capillary reversed-phase high-performance liquid chromatography (RP-HPLC) and electrospray mass spectrometry, as a means for rapid identification of proteins at subpicomole levels. Using this approach, protein #3 (M(r) approximately 66,000, pI 6.2) was identified as heat shock protein 60 from as few as seven tryptic peptide masses when they were screened against the molecular weight search (MOWSE) peptide-mass database.

Amino Acid Sequence↗
PubMedDate not supplied

Micropreparative protein isolation from polyacrylamide gels following detection by high-resolution dynamic imaging: application to microsequencing.

Polyacrylamide gel electrophoresis is a high-resolving technique for separating proteins. Until recently, its use as a micro-preparative method for isolating microgram amounts of protein in a form suitable for structural analysis was limited by the difficulty in recovering material from the polyacrylamide matrix. This problem has been largely overcome by the development of chemically inert membranes that retain proteins after electroblotting from the polyacrylamide gel. The immobilized proteins are suitable for chemical identification by direct microsequence analysis. Nevertheless, the overall recoveries of proteins using this electrotransfer/blotting approach are low (28%-30%). This paper describes a phase-contrast technique that allows the visualization of proteins during the polyacrylamide gel electrophoresis. This approach is suitable for the quantitative detection of proteins. Since no fixing/staining step is employed, proteins can be recovered in high yield (50%-65%), by passive elution, in a form suitable for microsequence analysis. Methods and strategies for obtaining internal amino acid sequence information from proteins recovered from gels after visualization by high-resolution dynamic imaging are discussed.

Amino Acid Sequence↗
PubMedDate not supplied

Effectiveness of home visits by public health nurses in maternal and child health: an empirical review.

The effectiveness of public health nursing in promoting maternal and child health through home visits is summarized from empirical studies published between 1960 and 1984. Eight reports identified through a comprehensive reference search were first classified according to the components of nursing service studied (assessment, teaching, counseling or support, referral, and clinical services). The results of each study were then analyzed for study population characteristics, the research design and statistical methods employed, the reliability of the measures used, significant treatment effects, sample size, and statistical power. The research is evenly divided among studies employing an experimental design, a quasi-experimental design, and samples of low-income and middle-income mothers. The reliability of the measures was, with one exception, not reported. All but one study had final sample sizes for treatment and control or comparison groups of fewer than 100 subjects. Four of the studies thus had sample sizes sufficiently large to detect a medium treatment effect; power calculations showed that none could measure a small treatment impact. Within the methodological limitations of these studies, our review found that under certain circumstances public health nurses can effectively impart health knowledge to high-risk mothers and can effect positive change in maternal attitudes and parenting practices that in turn can be associated with positive changes in infant health and development. Cumulative knowledge from this body of research suggests that a priority for future evaluations of public health nursing is development of theoretical frameworks that maximize the fit between the needs of the population served and the services provided and between the outcomes measured and the nursing services being assessed.

Adult↗