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Biomedical subjects

I Gibson

Publications and source records attributed to I Gibson.

At least 19 recordsLinked to original sources
PubMed2006

A new look at chronic fatigue syndrome/myalgic encephalomyelitis.

It has been 3 years since the Chief Medical Officer reported on chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME) and the time has come for a thorough investigation by an All Party Group drawn from the House of Commons and the House of Lords. We have received many written submissions and are engaged in taking oral evidence in 2-h sessions, which we open to the public as well as interested groups. The group has received a fantastic response to its requests for written evidence over the past few months. Questions that arise for a government response are the lack of provision and support for patients with CFS/ME, the issue of the clinical definition of CFS/ME, the need for a diagnostic test for CFS/ME, effectiveness of the National Institute for Clinical Excellence guidelines, and criteria used to decide which treatments are best for patients with CFS or myalgic encephalomyelitis.

Biomedical Research↗
PubMed2005

A novel artificial prosthetic replacement for the proximal interphalangeal joint of the hand--from concept to prototype.

This article describes the development of a proximal interphalangeal (PIP) joint prosthesis based on the principles of replicating anatomical surface components, the use of macrolocking intramedullary stem and the use of a cobalt-chrome alloy material. The design features are intended to obtain an optimal range of motion while retaining stability and longevity. The final prototype, for which a patent has been filed, is described.

Chromium Alloys↗
PubMed2003

Calcium phosphate coatings obtained by Nd:YAG laser cladding: physicochemical and biologic properties.

The plasma spray (PS) technique is the most popular method commercially in use to produce calcium phosphate (CaP) coatings to promote fixation and osteointegration of the cementless prosthesis. Nevertheless, PS has some disadvantages, such as the poor coating-to-substrate adhesion, low mechanical strength, and brittleness of the coating. In order to overcome the drawbacks of plasma spraying, we introduce in this work a new method to apply a CaP coating on a Ti alloy using a well-known technique in the metallurgical field: laser surface cladding. The physicochemical characterization of the coatings has been carried out by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray analysis (EDX). The biologic properties of the coatings have been assessed in vitro with human osteoblast-like MG-63 cells. The overall results of this study affirm that the Nd:YAG laser cladding technique is a promising method in the biomedical field.

Alloys↗
PubMed1999

Comparison of binding of N3'-->P5' phosphoramidate and phosphorothioate oligonucleotides to cell surface proteins of cultured cells.

The binding of uniformly modified N3'-->P5' phosphoramidate and stereorandom and stereopure phosphorothioate oligonucleotides (ODN) to cell surface proteins was studied, using both a fibroblast and an epithelial cell line, to assess the effect of different analog backbone types and base composition on cell surface protein binding. Marked differences were observed, both quantitative and qualitative, in the proteins to which individual ODN bound. One phosphoramidate, antisense to the insulin-like growth factor-1 (IGF-1) receptor (IGF-1R), bound to different proteins than did either a 6-base mismatch phosphoramidate IGF-1R sequence or a sense N-ras sequence. The latter bound poorly to the fibroblast line and predominantly to a 46 kDa protein in the epithelial line, as did many of the other ODN. This binding was not so marked as that of the isosequential end-capped phosphodiester N-ras sequence, which bound to this protein in both cell lines. Stereopure and stereorandom phosphorothioates containing a G-quartet (shown in other studies to form high-order tetrad structures), antisense to c-myc, exhibited considerable nonspecific binding to many proteins, as did the isosequential phosphoramidate. In particular, this ODN sequence gave notable binding to high molecular weight proteins. In general, binding of the c-myc ODN to proteins of 28-30, 46, 67, and 70-90 kDa was found in this study.

3T3 Cells↗
PubMed1999

Pharmacokinetics of enrofloxacin and danofloxacin in plasma, inflammatory exudate, and bronchial secretions of calves following subcutaneous administration.

Enrofloxacin (2.5 mg/kg of body weight) and danofloxacin (1.25 mg/kg) were administered subcutaneously to ruminating calves (n = 8) fitted with subcutaneous tissue cages. Concentrations of enrofloxacin, its metabolite ciprofloxacin, and danofloxacin in blood (plasma), tissue cage exudate (following intracaveal injection of 0.3 ml of 1% [vol/wt] carrageenan), and bronchial secretions were measured by high-performance liquid chromatography (HPLC) and microbiological assay (enrofloxacin plus ciprofloxacin and danofloxacin). Mean maximum concentrations (C(max)) +/- standard deviations of enrofloxacin (0.24 +/- 0.08 microg/ml), ciprofloxacin (0.11 +/- 0.03 [total, 0.34 +/- 0.10] microg/ml), and danofloxacin (0.23 +/- 0.05 microg/ml) were detected in the plasma of calves by HPLC. The C(max) were 0.49 +/- 0.17 microg/ml (enrofloxacin equivalents) and 0.24 +/- 0.03 microg/ml (danofloxacin) when they were measured by microbiological assay. Mean C(max) in exudate (HPLC) were 0.18 +/- 0.07 microg/ml (enrofloxacin), 0.10 +/- 0.04 microg/ml (ciprofloxacin), 0.27 +/- 0.09 microg/ml (enrofloxacin plus ciprofloxacin), and 0.19 +/- 0.05 microg/ml (danofloxacin), and concentrations in exudate exceeded those in plasma from 8 h (enrofloxacin and ciprofloxacin) or 6 h (danofloxacin) after drug administration. The C(max) were 0.34 +/- 0.09 microg/ml (enrofloxacin equivalents) and 0.22 +/- 0.04 microg/ml (danofloxacin) in exudate when they were measured by the microbiological assay. The maximum mean concentration achieved in bronchial secretions (HPLC) were 0.07 +/- 0.04 microg/ml (enrofloxacin), 0.04 +/- 0.07 microg/ml (ciprofloxacin), 0.10 +/- 0. 05 microg/ml (enrofloxacin plus ciprofloxacin), and 0.12 +/- 0.09 microg/ml (danofloxacin). The maximum mean concentration in bronchial secretions from a limited number of animals from which samples were available for microbiological assay were 0.27 +/- 0.11 microg/ml (n = 4 [enrofloxacin equivalents]) and 0.14 +/- 0.02 microg/ml (n = 3 [danofloxacin]). With predictive models of efficacy (C(max)/MIC and area under the concentration-time curve/MIC ratios in plasma) for Pasteurella multocida (MIC of enrofloxacin, 0.06 microg/ml [24]; MIC of danofloxacin, 0.06 microg/ml [6]), enrofloxacin produced scores of 8.17 and 52.00, respectively, compared to those of danofloxacin, which were 4.02 and 23.05, respectively. With the dosing rates recommended in some markets by manufacturers, enrofloxacin and danofloxacin achieved concentrations above the MICs for important pathogenic organisms in plasma, tissue cage exudate, and bronchial secretion. Since fluoroquinolones display concentration-dependent activities, C(max)/MIC ratios may be critical to efficacy. In the United States enrofloxacin is currently the only fluoroquinolone licensed for food animals and dosages for acute respiratory disease are 2.5 to 5 mg/kg for 3 days or 7.5 to 12. 5 mg/kg once. The higher dosages on a single occasion are likely to confer C(max)/MIC ratios that are associated with greater clinical efficacy.

Animals↗
PubMed1998

The therapeutic potential of ribozymes.

Ribozymes are catalytic RNA molecules that recognize their target RNA in a highly sequence-specific manner. They can therefore be used to inhibit deleterious gene expression (by cleavage of the target mRNA) or even repair mutant cellular RNAs. Targets such as the mRNAs of oncogenes (resulting from base mutations or chromosome translocations, eg, ras or bcr-abl) and viral genomes and transcripts (human immunodeficiency virus-type 1 [HIV-1]) are ideal targets for such sequence-specific agents. The aim of this review is therefore to introduce the different classes of ribozymes, highlighting some of the chemistry of the reactions they catalyze, to address the specific inhibition of genes by ribozymes, the problems yet to be resolved, and how new developments in the field give hope to the future for ribozymes in the therapeutic field.

Gene Expression Regulation↗
PubMed1997

Inhibition of bacteriophage T7 RNA polymerase in vitro transcription by DNA-binding pyrrolo[2,1-c][1,4]benzodiazepines.

The interactions of several pyrrolo[2, 1-c][1,4]benzodiazepine (PBD) antitumor antibiotics with linearized plasmid pGEM-2-N-ras DNA have been analyzed by quantitative in vitro transcription (QIVT) and in vitro transcription footprinting (IVTF) methods. A concentration-dependent inhibitory effect of the PBDs on transcription is observed using both techniques. The rank order for overall inhibition of transcription by the QIVT method is found to be: sibiromycin > tomaymycin > anthramycin > DC-81 > neothramycin, whereas the IVTF experiments show a different ranking: sibiromycin > anthramycin > neothramycin > tomaymycin. In addition, stimulation of transcription was observed at low PBD concentrations in both the QIVT and IVTF experiments. These results demonstrate unequivocally that the formation of PBD-DNA adducts at AGA-5' base sequences on the transcribed strand results in transcription blockage for all PBDs examined. Furthermore, the sequence of flanking base pairs appears to influence the degree of blocking, with the sequences ACAGAAA-5', AAAGATG-5', AGAGATA-5', and CAAGAAC-5' providing the most pronounced blocks for all PBDs studied in this system. Neothramycin and tomaymycin cause additional blocks at some GGA-5' and TGA-5' sequences. Parallel MPE-Fe(II) footprinting studies have revealed PBD binding sites on both the transcribing and nontranscribing strands, although all transcription blocks determined from the IVTF assays are due to drug bound on the transcribing DNA template strand.

Anthramycin↗
PubMed1996

Antisense approaches to the gene therapy of cancer--'Recnac'.

This review has looked at the wide-ranging research initiatives in the field of antisense technology. It starts with the philosophy behind antisense DNA and the production of antisense RNA from genetic constructs and raises the various problems which are being addressed. These include uptake into cells, targeting the substrate sequence and cells, the stability of the antisense molecules and pharmokinetic considerations within animals. The review talks of the positive results attained in vitro and in vivo in animal and plant experiments but also addresses the problems many workers have faced in the field. It attempts to resolve these differences in terms of the need for further understanding of the mechanisms by which the positive results have been obtained. The novel use of catalytic ribozymes (RNA) in downregulating genes is also discussed in similar terms to antisense DNA and RNA. By taking a case study with a human leukaemia the review delves into the mysteries of how different results can be resolved by improving the design of ribozymes thereby increasing specificity and preventing aberrant reactions. It is concluded that despite a lack of understanding of how the biological effects have come about in vitro and in vivo the clinical and research developments should resolve the issue of antisense potential for rational drug development.

Base Sequence↗
PubMed1996

Interaction of oligodeoxynucleotides with mammalian cells.

Many previous studies have demonstrated that antisense oligodeoxynucleotides (ODNs) bind to surface proteins in a manner compatible with receptor-mediated endocytosis and, unless specifically modified, are internalized into endosomes with little access to the cytoplasmic structures or to the nucleus. Reports vary as to the specific proteins involved in the mechanism, and this study examines the conditions of binding, some proteins that might contribute to the process, and whether changes in binding patterns occur during differentiation. Native gel electrophoresis was used to optimize the surface binding of a phosphorothioate end-capped 16-mer to T15 mouse fibroblast cells, and comparisons are made with some human epithelial tumor cell lines. Binding to individual proteins was visualized using SDS-PAGE and autoradiography. Binding at 4 degrees C was almost exclusively to a 46 kDa protein and decreased in the presence of an excess of unlabeled ODN and heparin but not ATP. Increasing the temperature of ODN binding from 4 degrees C to 37 degrees C for 10 minutes changed the binding pattern observed. ODN binding to the total cytoplasmic and membrane proteins immobilized on a membrane showed a greater number of binding proteins, the most prominent being one of 30 kDa. Examination of the effects of serum on binding were made using the human lung carcinoma cell line COR-L23, which can be grown in serum-free conditions. Serum starvation led to an increased total binding seen on native gels coinciding with increased binding to a 46 kDa protein. Demonstration that changes in binding proteins occur when cells differentiate was made using the premacrophage cell line THP-1. Differentiation of these cells increased the total ODN binding and appeared to initiate the synthesis of some new binding proteins, although binding to a 46 kDa protein was reduced.

Animals↗
PubMed1996

The influence of polarized epithelial (Caco-2) cell differentiation on the cellular binding of phosphodiester and phosphorothioate oligonucleotides.

Cell aging and the degree of cellular differentiation are thought to be important variables governing uptake of oligonucleotides but remain poorly understood. The Caco-2 colon carcinoma cell line has the ability to spontaneously differentiate into enterocytes in vitro and serves as a useful model to further investigate the effect of differentiation on oligonucleotide binding and uptake. In this study, we report that the extent of oligonucleotide association and the expression of cell surface binding proteins are governed by the age and thus the degree of differentiation of Caco-2 epithelial cells in culture. Cellular association (normalized for cell number) of an all phosphodiester (PO), all phosphorothioate (PS), and a phosphodiester oligonucleotide containing two terminal phosphorothioate internucleotide linkages at the 3' end (EC-PO) gradually increased from day 3 to around day 17 of the culture, followed by a plateau, or slight decrease, up to day 21 of the cell aging study. Overall, a threefold to fourfold increase in binding was observed from day 3 to day 17. Oligonucleotide binding was temperature and pH dependent, but the magnitude of the effect was influenced by cell aging and the degree of differentiation. PS oligonucleotides exhibited greater binding (up to threefold) at the basolateral surface compared with the apical surface within the pH range 5-7. These findings could be directly correlated with the expression levels of cell surface oligonucleotide binding proteins during the aging study. A Caco-2 cell surface protein binding complex of around 46 kDa was identified as the major site of binding for both PO and PS oligonucleotides, although the latter also bound to several other proteins, especially at low pH.

Caco-2 Cells↗
PubMed1996

Investigating and improving the specificity of ribozymes directed against the bcr-abl translocation.

Chronic myelogenous leukaemia (CML) is associated with a translocation between the ABL and BCR genes on chromosomes 9 and 22, t(9;22). The resulting transcription and translation products, bcr-abl mRNA and p210bcr-abl, are unique to the malignant cells and as such are ideal targets for specific chemicals or drugs. We have designed hammerhead ribozymes to cleave the two predominant forms of bcr-abl mRNA, b2a2 and b3a2. Synthetic bcr-abl RNA substrates were cleaved by the ribozymes in vitro, but so was a wild-type abl RNA sequence. bcr RNA was not cleaved in vitro and mutant ribozymes showed no cleavage activity. Ribozymes designed to cleave 9 nucleotides (nt) from either of the fusion points were non-specific for the bcr-abl substrate, but a ribozyme designed to cleave 3 nt upstream of the b3a2 fusion point was specific for b3a2 RNA. However, this ribozyme was less efficient than the others. The shortening of one of the ribozymes arms from 10 nt to 4 nt resulted in a ribozyme that was more specific without losing any efficiency. We conclude that it is possible to specifically cleave bcr-abl RNA in vitro by using hammerhead ribozymes.

Base Sequence↗
PubMed1995

The effects of N-ras oncogene expression on PDGF-BB stimulated responses in cultured mouse myoblasts.

The role of the ras oncogene in the signalling pathway triggered by platelet-derived growth factor BB (PDGF-BB) has been investigated in a cell line which normally differentiates into myotubes. Following the activation of the N-ras oncogene, however, the cells proliferate and form foci. PDGF-BB stimulated the phosphorylation of tyrosine in several cellular proteins of molecular weight 185, 160, 94, 54, 44, 42 kDa and furthermore Ca2+ was released from internal stores. Activation of the N-ras gene by treatment of cells with dexamethasone (DEX) inhibited these responses to PDGF-BB. On the other hand, both ras-induced and -non induced cells responded to bradykinin (BK), foetal calf serum (FCS) and ionomycin (ION) by releasing Ca2+ from intracellular stores. The inhibition of the response to PDGF-BB in ras-activated cells has been further investigated. The binding of [125I]-PDGF-BB to its receptors was low and western blotting showed a low level of PDGF-BB receptor protein. This was in marked contrast to the receptor number seen in cells grown in growth medium or fusion promoting medium. These results indicate that cells transformed with the N-ras oncogene fail to respond to platelet-derived growth factor and exhibit a very low level of PDGF receptors. This suggests a role for the ras oncogene in the earliest steps of the signalling pathway.

Animals↗