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Biomedical subjects

J M Corbett

Publications and source records attributed to J M Corbett.

28 records · Page 2Linked to original sources
PubMedDate not supplied

Electrophoretic and computer analysis of skeletal muscle used for cardiac assistance.

Skeletal muscle has an inherent plasticity which allows it to undergo fibre type transformation when induced by a specific stimulus. Electrical stimulation has been used here to induce transformation of a predominantly fast type skeletal muscle towards a slow, more fatigue-resistant phenotype, which is more suitable for use in long-term cardiac assistance. Muscle samples from animals electrically stimulated for periods up to 6 months have been analysed by electrophoresis for myosin heavy chain (MHC) and myosin light chain (MLC) fast and slow isoforms. Densitometry and computer analysis have been used to determine the pattern of transformation of the different myosin subunits over this time period. MHC and MLC 2 fast to slow isoform switching preceded that of the alkali light chains (MLC1 and MLC3). After 3 months of stimulation the MHC slow isoform was found to have doubled in concentration relative to the unstimulated control muscle and by 4 months accounted for almost 50% of the total MHC content. The slow isoform accounted for 75% of the MLC2 after 4 months of stimulation. The protein products of mRNA isolated from stimulated muscle samples, translated in vitro and separated by electrophoresis, showed that transformation at the mRNA level preceded that at the protein level. By 2-4 weeks of stimulation MLC2 slow isoform mRNA represented over 60% of the total MLC2 mRNA population. An understanding of the molecular structure of muscle during transformation provides insight into its haemodynamic performance in cardiac assistance.

Animals↗
PubMedDate not supplied

A human myocardial two-dimensional electrophoresis database: protein characterisation by microsequencing and immunoblotting.

This communication briefly describes how a human heart two-dimensional electrophoresis (2-DE) protein database is being established in our laboratory. The database contains more than 1500 polypeptides and approximately fifty proteins from 2-DE gels of human myocardial tissue have been characterised. Information about the proteins has been compiled including molecular weight (M(r)), isoelectric point (pI), sample spot (SSP) number, protein name, partial sequence, and antibody reacting with the protein. The first stage of this project involves the investigation of protein with pIs in the range pH 4-7. Future studies will employ immobilised pH gradient (IPG) gels as the first dimension of the 2-DE to examine basic proteins. The ultimate goal of this project is to establish a global picture of human heart protein expression in both normal and disease conditions.

Amino Acid Sequence↗
PubMedDate not supplied

Electrophoretic analysis of electrically trained skeletal muscle.

Sheep latissimus dorsi muscle was electrically trained, thereby inducing fast-to-slow fibre-type transformation. Using a combination of one- and two-dimensional gel electrophoresis techniques with computer analysis, we have analysed altered expression of contractile protein isoforms at protein and mRNA level over a time course of electrical training extending to 5 months. Myosin heavy chain and regulatory myosin light chain analysis showed predominant expression of their slow isoforms (86% and 92%, respectively) after 3 months of training. At the same time point, however, tropomyosin analysis revealed that the slow isoform of the alpha-subunit accounted for 64% of the total alpha expression. Troponin T isoform switching proceeded more slowly over the same time course than tropomyosin and the thick filament proteins studied. Troponin T analysis revealed 5 fast and 2 slow isoforms in the sheep, of which the second slow isoform only became clearly visible after 5 months' training. At this time point the two slow isoforms were more predominant than their fast counterparts. This suggests that a wide heterogeneity of fast and slow isoform combinations are possible in the thin filament of skeletal muscle.

Animals↗
PubMedDate not supplied

Positional reproducibility of protein spots in two-dimensional polyacrylamide gel electrophoresis using immobilised pH gradient isoelectric focusing in the first dimension: an interlaboratory comparison.

An intra- and interlaboratory comparison of positional reproducibility of protein spots in two-dimensional electrophoresis using immobilised pH gradients (IPG) in the first dimension (IPG-DALT) was made. Aliquots of two different samples, human cardiac and barley leaf proteins, were separated in two different laboratories (London and Munich), using 180 mm long IPG gel strips, pH 4-8, for the first dimension and homogeneous SDS-PAGE gels (12% T) for the second dimension. Subsets of 340 (cardiac) and 200 (barley) well-resolved spots distributed across the 2-D gel patterns were selected for computer analysis (PDQUEST) of positional reproducibility. The IPG-dimension was highly reproducible in each laboratory, with a mean standard deviation of about 1 mm for both types of sample. Interlaboratory comparisons revealed identical results for barley with a mean standard deviation along the x-axis of about 1 mm, whereas the cardiac matchset showed slightly more variability (mean standard deviation approximately 1.5 mm). Nevertheless, IPG-DALT provides significantly improved reproducibility of spot positions compared to conventional isoelectric focusing with synthetic carrier ampholytes.

Electrophoresis, Gel, Two-Dimensional↗
PubMedDate not supplied

The analysis of myocardial proteins by infrared and ultraviolet laser desorption mass spectrometry.

The use of infrared (IR) and ultraviolet (UV) matrix-assisted laser desorption (MALDI) mass spectrometry to analyse myocardial proteins separated by two-dimensional (2-D) polyacrylamide gel electrophoresis (PAGE) is discussed. Proteins were electroblotted onto a FluoroTrans polyvinylidene difluoride (PVDF) membrane in order to facilitate analysis by MALDI, which represented the most efficient means of extracting large numbers of proteins simultaneously. Once on a FluoroTrans membrane, IR-MALDI was used to obtain spectra from selected protein spots, but no useful signals were obtained with UV MALDI. Spectra were generated from 46 of 50 spots analysed with protein masses from 13 to 82 kDa and isoelectric points (pI) 4.7-7.8. For those protein spots that had previously been characterised, and for which both sequence and post-translational modification data were known, IR-MALDI data was within plus or minus 0.5% of the expected mass. Some spots contained more than one protein signal, illustrating the increased information obtainable from MALDI, but also suggesting the limit of resolution of 2-D gels for separating large numbers of proteins. Attempts to digest proteins with specific proteases and generate peptide mass fingerprints by MALDI analysis on the membrane were unsuccessful with either IR or UV lasers. The peptides were extracted from the membrane and readily analysed by UV MALDI for peptide spectra. Poor data was obtained for peptide digests with IR-MALDI, probably because of matrix suppression by digest buffer. In order to obtain the maximum amount of information from blotted proteins, both IR and UV MALDI were required.

Electrophoresis, Gel, Two-Dimensional↗
PubMedDate not supplied

Construction of HSC-2DPAGE: a two-dimensional gel electrophoresis database of heart proteins.

The dissemination of information relating to the characterisation of proteins from two-dimensional electrophoresis (2-DE) gel databases is essential for their effective utilisation in the study of protein expression in cell biology. Since the inception of the World Wide Web and the pioneering development of SWISS-2DPAGE as a tool for retrieving information on proteins separated by 2-DE, the Internet has become the method of choice for disseminating and accessing information on 2-DE protein databases. At Harefield we have established HSC-2DPAGE which is an advanced interface for accessing protein database relating to heart disease. The Web site currently includes databases of proteins from human, dog and rat ventricular tissue and a human endothelial cell line. The databases are searchable individually or as a whole by remote keyword searches. Each database is represented by both synthetic (computer generated) and real (scanned gel) clickable images upon which characterised protein spots are highlighted by hyperlinked symbols. The database conforms to all the rules proposed for federated 2-DE protein databases and individual protein entries are linked to other protein databases such as SWISS-PROT by active cross-references. This paper describes the construction of HSC-2DPAGE, its maintenance, and access via the Internet.

Animals↗