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Biomedical subjects

K Dickerson

Publications and source records attributed to K Dickerson.

11 recordsLinked to original sources
PubMed2001

Polycyclic aromatic hydrocarbons, aliphatic hydrocarbons, trace elements, and monooxygenase activity in birds nesting on the North Platte River, Casper, Wyoming, USA.

Tree swallow (Tachycineta bicolor) and house wren (Troglodytes aedon) eggs and chicks were collected near a refinery site on the North Platte River, Casper. Wyoming, USA and at a reference site 10 km upstream. Total polycyclic aromatic hydrocarbon (PAH) concentrations in swallow and wren chicks were higher at the refinery site than at the reference site. Polycyclic aromatic hydrocarbon concentrations in sediment and chick dietary samples were consistent with these findings. The general lack of methylated PAHs in sediment, diet, and bird carcasses suggested that the PAHs were derived from combustion and not from petroleum. The predominance of odd-numbered aliphatic hydrocarbons and the low ratios (< or =0.25) of pristane:n-C17 and phytane:n-C18 in chick and diet samples also suggested that swallow and wren chicks were not being chronically exposed to petroleum. Mean ethoxyresorufin-O-dealkylase and benzyloxyresorufin-O-dealkylase activities in tree swallow livers averaged nine times higher at the refinery site than at the reference site and were probably induced by exposure to PAHs. Trace element concentrations in eggs and livers of swallows and wrens were similar or greater at the reference site than at the refinery site. Selenium, strontium, and boron concentrations were elevated in eggs and livers of swallows and wrens at both the refinery and reference sites.

Alkanes↗
PubMed1994

On the spectral properties of Doppler thread phantoms.

It is shown that some of the threads used in Doppler phantoms have a repetitive structure which leads to peaks in the angular distribution of the backscattered power at beam axis-to-flow angles of theta = 90 degrees and approximately theta = 70 degrees. This nonuniform scattering does not significantly interfere with modelling the Doppler spectrum peak as a function of velocity and beam-to-thread angle, but makes it impossible to model the spectral width as a function of these parameters. A new plaited structure is described which has a periodicity too small to lead to subsidiary reflection peaks, and which has a more uniform backscattering profile than the other threads studied.

Blood Flow Velocity↗
PubMed1991

Cell attachment activity of cementum: bone sialoprotein II identified in cementum.

Considerable research effort has been directed at preparing root surfaces in a fashion that would promote cell attachment leading to periodontal regeneration; however, no methods have proven to be clinically predictable. Identification of attachment protein(s) associated with the root surface matrix of cementum may prove valuable for developing effective clinical treatments. In this study cementum proteins were extracted from bovine and human teeth by sequential chaotropic extraction using guanidine followed by guanidine/EDTA. The guanidine/EDTA extract, but not guanidine extract, was found to promote attachment of fibroblasts. This attachment activity was inhibitable with synthetic peptide containing the attachment sequence arginine-glycine-aspartic acid (RGD). Fractionation of the guanidine/EDTA extract revealed several fractions with attachment activity. Immunoblot analysis demonstrated that two of these fractions contain the bone-associated RGD containing attachment protein, bone sialoprotein-II (BSP-II). In addition, attachment activity was also noted in other fractions that could not be attributed to BSP-II or fibronectin. These studies indicate that a component of the attachment activity of cementum is likely to be due to BSP-II and that cementum contains additional, as yet undetermined, attachment proteins.

Amino Acid Sequence↗
PubMed1990

The human alpha 2-macroglobulin receptor: identification of a 420-kD cell surface glycoprotein specific for the activated conformation of alpha 2-macroglobulin.

Ligand affinity chromatography was used to purify a cell surface alpha 2-macroglobulin (alpha 2M) receptor. Detergent extracts of human placenta were applied to an affinity matrix consisting of alpha 2M, previously reacted with methylamine, coupled to Sepharose. Elution with EDTA specifically released polypeptides with apparent molecular masses of 420 and 39 kD. In some preparations, small amounts of a 90-kD polypeptide were observed. The 420- and 39-kD polypeptides appear specific for the forms of alpha 2M activated by reaction with proteinases or methylamine and do not bind to an affinity matrix consisting of native alpha 2M coupled to Sepharose. Separation of these two polypeptides was accomplished by anion exchange chromatography, and binding activity was exclusively associated with the 420-kD polypeptide. The purified 420-kD protein binds to the conformationally altered forms of alpha 2M that are known to specifically interact with alpha 2M receptors and does not bind to native alpha 2M. Binding of the 420-kD polypeptide to immobilized wheat germ agglutinin indicates that this polypeptide is a glycoprotein. The cell surface localization of the 420-kD glycoprotein was confirmed by affinity chromatography of extracts from surface radioiodinated fibroblasts. These properties suggest that the 420-kD polypeptide is a cell surface receptor for the activated forms of alpha 2M.

Animals↗
PubMed1990

Fibulin is an extracellular matrix and plasma glycoprotein with repeated domain structure.

We have studied the expression of fibulin in cultured fibroblasts and determined its primary structure by cDNA cloning. Our results show that fibulin is a secreted glycoprotein that becomes incorporated into a fibrillar extracellular matrix when expressed by cultured cells or added exogenously to cell monolayers. In addition, we find that fibulin is present in plasma at a level of 33 +/- 3 micrograms/ml. Sequencing of multiple fibulin cDNAs indicates that a process of alternative splicing results in the expression of three fibulin transcripts. The transcripts encode overlapping polypeptides differing only in carboxy-terminal segments. Common to the three predicted forms of fibulin is a unique 537-amino acid-long cysteine-rich polypeptide and a 29-residue signal peptide. The amino-terminal portion of fibulin contains a repeated element with potential disulfide loop structure resembling that of the complement component anaphylatoxins C3a, C4a, and C5a as well as proteins of the albumin gene family. The bulk of the remaining portion of the molecule is a series of nine EGF-like repeats.

Amino Acid Sequence↗
PubMed1989

Subunit structure of a laminin-binding integrin and localization of its binding site on laminin.

A laminin receptor was isolated from human MG-63 osteosarcoma cells by affinity chromatography on human laminin. The isolated receptor was defined as the alpha 3 beta 1 integrin by immunoprecipitation with subunit-specific antibodies. A previously unclassified laminin-binding integrin from rat cells was shown also to contain the alpha 3 subunit. Both receptors bound to human and mouse laminin in a radioreceptor assay. They also both bound to some extent to fibronectin in this assay, but only the MG-63 cell receptor showed binding to type IV collagen. The binding of the radiolabeled receptor to insoluble laminin was inhibited by unlabeled receptor, by soluble laminin, and by chymotryptic fragments of laminin that have previously been shown to contain neurite-promoting and cell attachment-promoting activities. Moreover, the receptor binding was also inhibited by monoclonal antibodies capable of inhibiting the neurite-promoting activity of laminin and known to bind to laminin near the junction of the long arm and its terminal globule. One of these antibodies was reactive with fusion proteins expressed from laminin cDNA clones. The immunoreactive clones corresponded to the COOH-terminal end of the B1 subunit. These results identify the integrin-type laminin receptor isolated from the osteosarcoma cells as the alpha 3 beta 1 integrin and localize its binding site in close proximity of the B1 subunit COOH terminus.

Binding Sites↗
PubMed1989

Fibulin, a novel protein that interacts with the fibronectin receptor beta subunit cytoplasmic domain.

A 100 kd protein was isolated from tissue and cell extracts by affinity chromatography on a synthetic peptide representing the cytoplasmic domain of the fibronectin receptor beta subunit. The 100 kd protein also bound to native fibronectin receptor, and this binding could be reversed with EDTA. Calcium may be the divalent cation required for the binding since the 100 kd protein was found to bind 45Ca2+. The N-terminal amino acid sequence of the 100 kd protein was not similar to any sequence in a protein data base. Immunofluorescent staining of cells cultured on fibronectin showed the 100 kd protein coinciding with the fibronectin receptor beta subunit in sites of substrate contact. Therefore this protein, which we term fibulin, interacts with the fibronectin receptor in vitro and associates with the receptor in vivo. Fibulin is a potential mediator of interactions between adhesion receptors and the cytoskeleton.

Amino Acid Sequence↗
PubMed1988

The neurite-promoting domain of human laminin promotes attachment and induces characteristic morphology in non-neuronal cells.

The interaction of cells with laminin and laminin fragments was studied in short-term cell attachment assays. Neurite-promoting chymotrypsin fragments of laminin were isolated using a monoclonal antibody which blocks neurite outgrowth on laminin. The fragments were shown, by electron microscopy after rotary shadowing and by immunological reactivity with different monoclonal antibodies, to contain only the distal end of the long arm. These fragments promoted the attachment and spreading of glioma, sarcoma, carcinoma, muscle, and endodermal cells to the same extent as intact laminin. The attachment was unaffected by peptides containing the RGD sequence. The morphology of the cells on the chymotrypsin fragments was indistinguishable from that on intact laminin but different from the morphology of the same cells on fibronectin. Light microscopy and scanning electron microscopy showed extensive process formation on laminin but not on fibronectin suggestive of increased cell motility in response to laminin. We conclude that the neurite-promoting domain of laminin contains a major site of interaction for non-neuronal cells and that this site induces a cellular response in certain non-neuronal cells that is unique to laminin.

Animals↗
PubMed1986

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National Library of Medicine (U.S.)↗
PubMed1986

Mapping of domains in human laminin using monoclonal antibodies: localization of the neurite-promoting site.

Monoclonal antibodies were made against a truncated form of human laminin isolated from placenta. 12 antibodies were isolated and characterized. All antibodies stained basement membranes in placenta and immunoprecipitated laminin from media of cultured choriocarcinoma cells. Three antibodies, 3E5, 4C7, and 4E10, partially blocked the neurite-promoting activity of laminin. Addition of a second antibody, goat anti-mouse IgG, caused more complete blocking of the activity. Two of the blocking antibodies, 4C7 and 4E10, reacted with epitopes within the globular domain at the end of the long arm of laminin, and the third one, 3E5, reacted at the end of the rod-like portion of the long arm adjacent to the globular domain, as shown by electron microscopy after rotary shadowing. Five nonblocking antibodies used in the same test reacted with epitopes in other domains of the molecule. Blocking antibodies 3E5 and 4E10 could be used in immunoblotting and both antibodies reacted with the same polypeptides in pepsin fragments of human laminin, the predominant polypeptides being approximately 400 kD. When a crude extract of human amnion was used as a source of intact laminin, the 4E10 antibody detected a single polypeptide of approximately 400 kD. A nonblocking antibody, 2E8, which reacted at the center of the laminin cross, reacted predominantly with a 200-kD polypeptide in human laminin fragments and exclusively with a 200-kD polypeptide in amnion extract and in rat laminin. Our results with human laminin match the results by Edgar, D., R. Timpl, and H. Thoenen, 1984, EMBO (Eur. Mol. Biol. Organ.) J., 3:1463-1468, in which the neurite-promoting activity of mouse laminin resides at the end of the long arm, which is also the site for heparin binding. However, since the active fragments of human laminin did not bind to heparin, the neurite-promoting site should be different from the heparin-binding site. Our results further suggest that the neurite-promoting site may be contained in or close to the 400-kD component of laminin.

Animals↗