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Biomedical subjects

J M Anderson

Publications and source records attributed to J M Anderson.

At least 235 records · Page 13Linked to original sources
PubMed1992

Long-term histopathological study of new polypeptidic biomaterials.

The long-term histopathological evaluation of a new class of synthetic polypeptides, the poly(tert-butyloxycarbonylmethyl glutamates), as implantable drug delivery systems is addressed. This evaluation was performed in rat muscles over one year. The histological analysis included the measurement of many parameters, such as the type and thickness of the collagen capsule. The influence of the presence of progesterone, the selected active drug, could also be monitored over time.

Animals↗
PubMed1992

Optimal electrolytic chloriding of silver ink electrodes for use in electrical impedance tomography.

The electrode-electrolyte interface impedance may be simplistically modelled by an equivalent circuit comprising a resistance, RTOTAL, in series with an empirical, constant phase angle impedance, ZCPA. This pseudo-capacitance can be thought of as representing empirically the non-faradaic, double layer capacitance in the presence of specific adsorption and surface roughness effects. RTOTAL is the sum of the lead and electrolyte resistances. Depositing a thin layer of silver chloride on silver electrodes can yield improved electrical performance characteristics (potential and impedance) when used in conjunction with a chloride gel. An electrolytically deposited AgCl layer tends to have a rough surface profile thus leading to an increase in the effective interface area. This gives rise to a decrease in RTOTAL and ZCPA, both of which are desirable. Unfortunately AgCl is a relatively poor conductor. Increasing layer thickness causes RTOTAL to increase, thus adversely affecting the inter-electrode impedance at high frequencies. Electrode systems for use in electrical impedance tomography therefore require only relatively thin layers of AgCl.

Electric Conductivity↗
PubMed1992

The accuracy of decision-making of a semi-automatic defibrillator during cardiac arrest.

The accuracy of decision-making of a semi-automatic defibrillator was assessed at 57 cardiac arrests in 55 patients. The initial rhythm was ventricular fibrillation at 40 arrests and was correctly identified in 37 (sensitivity 92.5%). In the other 17 arrests initial rhythms were not ventricular fibrillation and 16 were correctly identified (specificity 94%). Continuous electrocardiographic recordings of the arrests were analysed in 8-12 s segments: of 432 segments showing ventricular fibrillation, 352 were correctly identified (sensitivity 81%); 3895 of 4139 segments showing rhythms other than ventricular fibrillation were correctly identified (specificity 94%). The percentage accuracy of detection of ventricular fibrillation varied from 0-100% (mean 91%) and for non-ventricular fibrillation from 51-100% (mean 92%). When 104 segments of ventricular fibrillation and 470 segments of non-ventricular fibrillation with cardiopulmonary resuscitation artefact were excluded from the analysis, a sensitivity of 91% and specificity of 96% were obtained. Thus the detection of cardiac arrest rhythms using a microprocessor based detection system for patients with cardiac arrest has a high sensitivity for ventricular fibrillation and specificity for non-ventricular fibrillation.

Cardiopulmonary Resuscitation↗
PubMed1992

Localization and differential expression of two isoforms of the tight junction protein ZO-1.

ZO-1 is a peripheral membrane protein of approximately 225 kDa located on the cytoplasmic side of all tight junctions. ZO-1 cDNA sequencing disclosed the presence of a 240-bp sequence in only some of the ZO-1 cDNAs studied. This 240-bp region encoded an inframe insertion of 80 amino acids, named motif-alpha. Expression of the predicted transcripts in normal rat and human tissues and in human epithelial cell lines (Caco-2, T84, Hep G2) was shown by reverse transcription of RNA and then DNA amplification. Immunoblot analysis showed both protein isoforms were present; however, in different cell lines, their amounts differed markedly relative to each other. Immunolocalization at light and ultrastructural levels, using antibodies generated against motif-alpha or shared sequences flanking it, indicated both forms localized indistinguishably to tight junctions. These observations demonstrate the existence and variable expression of ZO-1 isoforms and raise the question whether these isoforms contribute to tight junction diversity in different epithelia.

Amino Acid Sequence↗
PubMed1992

The immobilization of glucose oxidase onto radio-frequency plasma-modified poly(etherurethaneurea).

Glucose oxidase was covalently immobilized onto a radio-frequency plasma-modified poly(etherurethaneurea). Thin (90-100 nm) plasma-polymerized N-vinyl-2-pyrrolidone films were deposited onto poly(etherurethaneurea) films. Active sites for the immobilization were obtained via reduction with aqueous sodium borohydride and activation with 1-cyano-4-dimethylaminopyridinium tetrafluoroborate. Modified poly(etherurethaneurea) films were assayed for binding and activity of the immobilized glucose oxidase layer. The results of a modified radioimmunoassay and an 'immunochemical stain' indicated that washing in 900 ml of continuously stirred 2% sodium dodecyl sulfate, 2% Triton X-100, and 20 mM sodium phosphate, pH 7.0, for 24 h each at 4 degrees C was necessary to remove physically adsorbed glucose oxidase from the solid supports. An amperometric activity determination in 9 ml of well-stirred 20 mM sodium phosphate-0.1 M sodium chloride, pH 7.4, gave a qualitative demonstration of the activity of the immobilized enzyme on 18.75 cm2 of modified poly(etherurethaneurea) film. A colorometric activity determination using the coupled reaction with o-dianisidine and peroxidase indicated that glucose oxidase covalently immobilized on approximately 2.4 cm2 of modified poly(etherurethaneurea) film had an activity approximately equal to that of 13.4 nM glucose oxidase in 50 mM sodium acetate, pH 5.1, with a specific activity of approximately 32.0 U/mg at pH 5.1 and room temperature.

Biocompatible Materials↗
PubMed1992

Polarized functions and permeability properties of rat epididymal epithelial cells in vitro.

Cultured rat caput and cauda epididymidal epithelial cells are shown to exhibit polarized properties characteristic of functioning epithelia. When grown on plastic substrates coated with reconstituted basement membrane, confluent monolayers of cells from both regions formed domes characteristic of other transporting epithelia. Immunocytochemical localization of three proteins characteristically associated with epithelial junctional complexes revealed that uvomorulin, zonula occludens 1 and cingulin were present in cultured epididymal epithelial cells and that their distribution was similar to that in the epididymal epithelium in vivo. These three molecules were not found in epididymal stromal cells. Cells from both regions growing in two compartment chambers developed an electrical resistance across the monolayer with a magnitude characteristic of high resistance epithelia. The optimal plating density of cells was 0.75 x 10(6) cells cm-2. The presence of reconstituted basement membrane on the filters did not affect the resistance of the cells. Inulin passage from basal to apical chambers was less than 2% over 24 h. These results show that several polarized functions of epididymal epithelial cells can be maintained in culture and that this type of culture system is useful for studying the function of the epididymis in vitro.

Animals↗
PubMed1992

The altered glomerular filtration slits seen in puromycin aminonucleoside nephrosis and protamine sulfate-treated rats contain the tight junction protein ZO-1.

Nephrosis induced in rats by puromycin aminonucleoside treatment (PAN) results in the apical displacement of the glomerular filtration slit membrane by newly formed, intercellular occluding-type junctions. Similar changes can also be induced by acute kidney perfusion with protamine sulfate (PS). We have investigated the molecular nature of these altered junctions using an antibody to ZO-1, a protein found exclusively in tight junctions. Immunoblotting demonstrates ZO-1, a 225-kd band, in glomerular extracts of normal, PAN-, and PS-treated rats. By immunofluorescence, ZO-1 was localized at the base of podocytes outlining the capillary loops of glomeruli from all three experimental groups. At the electron microscope level, using immunoperoxidase or immunogold labeling, ZO-1 was concentrated along the cytoplasmic surfaces of the slit diaphragms of normal rats. In PAN or PS rats, it was concentrated along both the newly formed occluding-type junctions and the remaining slit diaphragms. When podocalyxin (the major membrane sialoprotein of the podocyte) was similarly localized, it was found exclusively apical to the displaced slit membrane. Based on morphology and the presence of ZO-1, the altered junctions seen in PAN and PS rats appear to represent bona fide tight junctions. Their rapid (15-minute) induction in PS-treated rats suggests that on neutralization of the cell surface charge by polycation perfusion, discontinuous tight junctions form from a preexisting pool of junctional proteins. These findings raise the possibility that glomerular hydraulic conductivity may be regulated in part by regulating the relative patency and width of the filtration slits through focal tight junction assembly.

Animals↗
PubMed1992

Immunoelectrophoretic and immunohistochemical characterizations of fibrinogen derivatives in atherosclerotic aortic intimas and vascular prosthesis pseudo-intimas.

Cadaveric aortic intimas with uncomplicated atherosclerosis were examined to determine the distribution and polypeptide chain composition of fibrinogen-related protein. Immunohistochemical staining showed deposits rich in fibrinopeptides A and B. The deposits were usually disseminated throughout intimas of moderate thickness < 0.7 mm, but were distributed focally in elongate patches bounded both lumenally and medially by deposit-free tissue in thick atheromas. Saline extracts generally showed undegraded monomers and dimers by electrophoresis. The residual protein contained A alpha and gamma-chains that were cross-linked predominantly (>80%) into unresolved high M(r) (>200 kd) derivatives, whereas B beta-chains were left non-cross-linked, as occurs in late stages of cross-linking by transglutaminases. The resolved components had electrophoretic mobilities corresponding to characteristic products of both factor XIIIa and tissue-transglutaminase. A greater incorporation of alpha- rather than gamma-chains into cross-linked products implicated tissue-transglutaminase as contributing heavily. By contrast, vascular graft pseudo-intimas and a cadaveric clot were rich in degraded fibrin devoid of fibrinopeptide A, and cross-linked in patterns typical of XIIIa with gamma 2 dimers constituting the principal product. The findings indicate that the fibrinogen in the aortic intima is comparatively well protected from thrombin and plasmin, and that much of it is deposited through direct cross-linking by tissue-transglutaminase without being converted to fibrin.

Antibodies, Monoclonal↗
PubMed1991

Inhibition of the activation of Hageman factor (factor XII) by human vascular endothelial cell culture supernates.

The supernatant fluid (conditioned medium) of cultured human vascular endothelial cells inhibits activation of Hageman factor (factor XII), whether by ellagic acid, bovine brain sulfatides, or bismuth subgallate; inhibition appears to be a property of one or more proteins in the culture supernates. This phenomenon may contribute to maintaining the fluidity of circulating blood by inhibiting surface activation of the intrinsic pathway of coagulation.

Cells, Cultured↗
PubMed1991

The tight-junction-specific protein ZO-1 is a component of the human and rat blood-brain barriers.

Continuous tight junctions between vascular endothelial cells, the principal anatomical basis for the blood-brain barrier, have been investigated functionally and morphologically but their molecular components have not been defined. This communication reports that the protein ZO-1, a specific constituent of epithelial tight junctions, is found in human and rat brain vasculature. ZO-1-positive immunocytochemical staining forms a tightly banded pattern outlining individual endothelial cells in blood vessels of the human cerebral cortex. Rat brain exhibits a similar staining of blood vessels as well as ZO-1-positive staining around individual epithelial cells of the choroid plexus. The antiserum used for immunocytochemistry recognizes a protein of about 200 kDa in rat brain microvessels by Western blot. These findings indicate that ZO-1 is located at the interendothelial junctions of brain vasculature, implicating its importance as a component of the blood-brain barrier.

Animals↗
PubMed1991

Reduction in cab and psb A RNA transcripts in response to supplementary ultraviolet-B radiation.

The cab and psb A RNA transcript levels have been determined in Pisum sativum leaves exposed to supplementary ultraviolet-B radiation. The nuclear-encoded cab transcripts are reduced to low levels after only 4 h of UV-B treatment and are undetectable after 3 days exposure. In contrast, the chloroplast-encoded psb A transcript levels, although reduced, are present for at least 3 days. After short periods of UV-B exposure (4 h or 8 h), followed by recovery under control conditions, cab RNA transcript levels had not recovered after 1 day, but were re-established to ca. 60% of control levels after 2 more days. Increased irradiance during exposure to UV-B reduced the effect upon cab transcripts, although the decrease was still substantial. These results indicate rapid changes in the cellular regulation of gene expression in response to supplementary UV-B and suggest increased UV-B radiation may have profound consequences for future productivity of sensitive crop species.

Blotting, Northern↗
PubMed1991

Molecular characterization of the gene encoding a rice endosperm-specific ADPglucose pyrophosphorylase subunit and its developmental pattern of transcription.

The gene encoding a rice endosperm-specific ADPglucose pyrophosphorylase (AGPP) subunit was isolated and its structure determined by nucleotide (nt) sequencing. A comparison of the genomic and cDNA nt sequences revealed a complex gene structure with ten exons and nine introns spanning over 6 kb. The exons ranged in size from 293 to 99 nt and the introns were between 1435 and 84 nt in size, with the first intron being the largest. All of the intron splice sites, except intron-2, contained GT/AG borders and were similar to the published splice site consensus sequences. Intron-2 had CA/CC borders at the 5' and 3' ends, but sequences adjacent to the splice site borders shared homology to the splice site consensus sequence, suggesting that the overall splice region, rather than the specific GT/AG sequence, determines the splice site. Several sequence motifs which may play a role in the regulation of plant genes were evident upstream from the transcriptional start point. Analysis of the developmental pattern of expression revealed a maximum level of mRNA transcripts for AGPP at five days after flowering coincident with starch accumulation. This result suggests that starch biosynthesis is controlled at the transcriptional level during seed development.

Amino Acid Sequence↗
PubMed1991

Fibroblast stimulation by monocytes cultured on protein adsorbed biomedical polymers. I. Biomer and polydimethylsiloxane.

The studies presented in this paper evaluate the modulatory role of protein pre-adsorbed polydimethylsiloxane (PDMS) and Biomer on the secretion of fibroblast stimulating growth factors from human monocytes/macrophages. The results of these studies show that Biomer and PDMS selectively activate human monocytes to produce fibroblast "progression-like" and to a lesser extent "competence-like" stimulating growth factors. Polydimethylsiloxane stimulated the monocytes/macrophages to produce more "progression-like" fibro-blast stimulating growth factors than Biomer. The induction of "competence-like" fibroblast stimulating activity from the monocytes was enhanced by preadsorption of PDMS with human derived fibrinogen, fibronectin, IgG, hemoglobin, or albumin. This phenomenon was not observed with protein pre-adsorbed Biomer. These studies support the hypothesis that protein pre-adsorbed polymers will selectively modulate monocyte/macrophage activation and induction of growth factors which have the potential to participate in tissue-implant interactions in vivo.

Adult↗
PubMed1991

Effect of some additives on the biostability of a poly(etherurethane) elastomer.

Four materials based on a single poly-(etherurethane) (PEU) prepared from MDI and PTMEG but differing in additives were studied in the cage implant system. The two additives studied were Santowhite powder at the 1% level and Methacrol 2138F 5%. Methacrol 2138F appeared to be immiscible with the base PEU and was dispersed in discrete domains about 0.5-micron in size. The retrieved PEU specimens were also cleaned and examined in the optical and scanning electron microscopes, and the size and density of adherent foreign body giant cells (FBGCs) were measured at implantation times up to 10 weeks. Methacrol 2138F had no effect on the density, coverage or size distribution of adherent FBGCs, but leaching of Methacrol 2138F was considered to be responsible for extensive pitting of the PEU surface. On the other hand, Santowhite powder appeared to inhibit formation of FBGCs, and while surface cracking and flaking were observed as early as 3 weeks postimplantation on some PEUs, the Santowhite powder effectively inhibited surface cracking and flaking up to the longest implantation time studied.

Amines↗
PubMed1991

Protein adsorption from human plasma is reduced on phospholipid polymers.

Protein adsorption from human plasma was investigated on phospholipid polymers, poly (2-methacryloyloxyethyl phosphorylcholine (MPC)-co-n-butyl methacrylate (BMA) or glass by radioimmunoassay and immunogold labeling techniques. In the present studies the focus was to determine the composition and distribution of proteins at the surface of these materials after contact with human blood plasma. On all materials, protein adsorption was detected and included identification of albumin, IgG, fibrinogen, fibronectin, Hageman factor (factor XII), factor VIII/von Willebrand factor, high-molecular-weight kininogen (HMWK) and the complement protein C5. The amount of protein adsorbed decreased with an increase in the MPC composition and appeared to adsorb to the surfaces in a uniform and evenly distributed manner. Therefore, we suggest that MPC moieties play an important role in suppression of protein adsorption. From these findings, it is concluded that the reduction of protein adsorption at the blood contacting surface of phospholipid polymers may result in the inhibition of thrombus formation.

Adsorption↗
PubMed1991

Comparison of the primary sequences of two potato tuber ADP-glucose pyrophosphorylase subunits.

Near-full-length cDNA clones to the small and large subunit of the heterotetrameric potato tuber ADP-glucose pyrophosphorylase have been isolated and characterized. The missing amino terminal sequence of the small subunit has also been elucidated from its corresponding genomic clone. Primary sequence comparisons revealed that each potato subunit had less identity to each other than to their homologous subunit from other plants. It also appeared that the smaller subunit is more conserved among the different plants and the larger subunit more divergent. Amino acid comparisons of both potato tuber sequences to the Escherichia coli ADP-glucose pyrophosphorylase sequence revealed conserved regions important for both catalytic and allosteric function of the bacterial enzyme.

Amino Acid Sequence↗