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Biomedical subjects

C Sumner

Publications and source records attributed to C Sumner.

8 recordsLinked to original sources
PubMed2001

Biosensor based on enzyme-catalysed degradation of thin polymer films.

A biosensor based on the enzyme-catalysed dissolution of biodegradable polymer films has been developed. Three polymer-enzyme systems were investigated for use in the sensor: a poly(ester amide), which is degraded by the proteolytic enzyme alpha-chymotrypsin; a dextran hydrogel, which is degraded by dextranase; and poly(trimethylene) succinate, which is degraded by a lipase. Dissolution of the polymer films was monitored by Surface Plasmon Resonance (SPR). The rate of degradation was directly related to enzyme concentration for each polymer/enzyme couple. The poly(ester amide)/alpha-chymotrypsin couple proved to be the most sensitive over a concentration range from 4 x 10(-11) to 4 x 10(-7) mol l(-1) of enzyme. The rate of degradation was shown to be independent of the thickness of the poly(ester amide) films. The dextran hydrogel/dextranase couple was less sensitive than the poly(ester amide)/alpha-chymotrypsin couple but showed greater degradation rates at low enzyme concentrations. Enzyme concentrations as low as 2 x 10(-11) mol l(-1) were detected in less than 20 min. Potential fields of application of such a sensor system are the detection of enzyme concentrations and the construction of disposable enzyme based immunosensors, which employ the polymer-degrading enzyme as an enzyme label.

Biodegradation, Environmental↗
PubMed2000

A transducer based on enzyme-induced degradation of thin polymer films monitored by surface plasmon resonance.

A novel transducer based on the dissolution of biodegradable polymer films as a direct result of enzymatic reaction has been developed. Three polymers were investigated for use in the transducer: a poly(ester amide), which is degraded by the proteolytic enzyme alpha-chymotrypsin; a dextran hydrogel, which is degraded by dextranase; and poly(trimethylene) succinate, which is degraded by a lipase. Degradation of the polymer films was monitored by surface plasmon resonance (SPR) and impedance measurements. SPR was shown to be suitable for a greater variety of materials, since it does not require the polymer film to be electrically insulating. Rate of degradation was shown to be directly related to enzyme concentration for each polymer/enzyme couple. The poly(ester amide)/alpha-chymotrypsin couple proved to be the most sensitive. Degradation of the films was complete in less than 20 min for enzyme concentrations greater than 9 x 10(-9) mol dm-3. Enzyme concentrations as low as 4 x 10(-11) mol dm-3 were detected in less than 30 min. The transducer has great potential for the detection of enzyme concentrations as well as for use in immunosensing where the enzyme degrading the polymer would be the enzyme label.

Chymotrypsin↗
PubMed1999

Postoperative deposits on the Acrysof intraocular lens.

PURPOSE: To report a commonly occurring change on the anterior surface of the Acrysof intraocular lens which is presumed to be due to the proliferation of lens epithelial cells from the capsulo-rhexis margin. METHOD: Forty-one consecutive cases (31 patients) of Acrysof intraocular lens implantation were followed prospectively. Clinical charts were reviewed for changes on or within the lens and visual acuity and refractive changes recorded. All cases were dilated at 3-5 weeks postoperatively to facilitate observation of changes. Representative slit lamp photos were taken. RESULTS: Deposits on the intraocular lens surface were noted on 18 of 41 lenses at 3-5 weeks post surgery. Deposits were not found on examinations conducted during the first postoperative week. All changes had fully resolved by 3 months. CONCLUSIONS: The changes recorded had no impact on visual acuity. The deposits noted do not represent clinically important pathology. They may be an unusual marker of biocompatibility with this lens. Surgeons using this lens should be aware of these changes.

Biofilms↗
PubMed1996

Expression of multiple classes of the nuclear factor-1 family in the developing human brain: differential expression of two classes of NF-1 genes.

Nuclear factor-1 (NF-1) is a multifunctional protein that participates in both transcription and replication. NF-1 proteins exist as a family of proteins that share some common structural and functional features but also demonstrate organ and cell type specific expression. Based upon these characteristics, the family of NF-1 proteins is divided into four classes, A, B, C and D. Several NF-1 binding sites have been identified in the regulatory sequences of the human polyomavirus, JCV, which multiplies most efficiently in glial cells derived from human fetal brain. Nuclear proteins from these cultures bind specifically to these NF-1 sites. It is not known, however, which member(s) of the NF-1 family is expressed in cells susceptible to JCV infection. We have examined glial cells as well as HeLa cells, which are not permissive to JCV, for NF-1 expression. By RT-PCR analysis, all four classes of NF-1 are expressed in human fetal glial cells and HeLa cells. However, by Northern analysis the expression of class D gene is much higher in the glial cells than HeLa cells. Expression of the class C gene, first identified in HeLa cells as NF-1/CTF1, is barely detectable in glial cells but highly expressed in HeLa cells. The screening of cDNA libraries from two early human brain tissues resulted in the identification of a number of clones which appear to be related and belong to a single class of the NF-1 family, class D. Nucleotide sequence of one clone, designated NF-1/AT1, confirms this. The NF-1/AT1 protein was overexpressed in E coli and found to bind specifically to an NF-1 probe by gel shift analysis. Southern analysis of human fetal glial cells indicates that the NF-1/AT1 gene, class D, is derived from a different gene than NF-1/CTF1. These results suggest the possibility that genes or viruses, like JCV, which use NF-1 for their expression in human brain derived cells may preferentially use the NF-1 class D protein.

Amino Acid Sequence↗
PubMed1975

Granulocyte function in myeloblastic leukaemia.

A study of granulocyte function in myeloblastic leukaemia is reported. Function was assessed by the ability of peripheral blood granulocytes to ingest and kill Candida albicans in bitro. Depressed cidal activity was observed in 11 patients with smouldering leukaemia and in 19 patients with acute myeloid leukaemia. Cidal activity was lowest in the untreated acute disease; this improved during cytoreduction therapy and was maintained when remission occurred. Leukaemic plasma depressed the function of control granulocytes; the possible role of a plasma "factor" is discussed.

BCG Vaccine↗
PubMed1975

Stimulation of protein synthesis in vivo in immature mouse testis by FSH.

Human pituitary FSH was found to increase the incorporation of tritiated lysine into testicular protein in prepubertal mice in vivo. Radioactivity was measured in washed trichloracetic acid precipitates prepared from crude testicular homogenates. The time of maximum response was 8 to 16 hr after subcutaneous injection of the hormone. This was considerably later than the maximum response in vitro reported by other workers. Neither HCG nor dibutyryl cyclic 3',5'-adenosine monophosphate had a significant effect on the incorporation of lysine.

Age Factors↗