Search PubMed⌕ Search

Biomedical subjects

J M Wilkinson

Publications and source records attributed to J M Wilkinson.

At least 127 records · Page 7Linked to original sources
PubMed1983

Differentiation antigens identify subpopulations of rabbit T and B lymphocytes. Definition by flow cytometry.

A panel of six monoclonal antibodies produced against cell surface glycoproteins of a rabbit T lymphocyte line was used with flow cytometry to define rabbit lymphocyte subpopulations. Four thymocyte populations were characterized by size and expression of cell surface antigens and appear to represent stages in thymocyte differentiation. Rabbit spleen contained five subpopulations: two of T lineage, two of B, and a null cell subset. Bimodal distribution of staining of thymocytes and peripheral T cells was observed using an antibody (9AE10) directed against a Thy-1 analogue in the rabbit, suggesting two separate T cell lineages. One of the monoclonal reagents, L11/135, reacted strongly with peripheral rabbit T cells as shown by two-color immunofluorescence. In functional studies, only the L11/135-bearing cells responded to the T cell mitogens concanavalin A and phytohemagglutinin and to allogeneic splenocytes. The thymocyte subpopulations and the peripheral T and B cell subsets differ from those described in mouse and man.

Animals↗
PubMed1983

The use of Selectron afterloading equipment to simulate and extend the Manchester System for intracavitary therapy of the cervix uteri.

When Selectron afterloading machines were introduced in the Christie Hospital the first aim was to reproduce, as closely as possible, the isodose distributions achieved with the traditional Manchester Radium System. This resulted in the establishment of standard pellet loading patterns, and standard treatment times, for programming the Selectron channels. However, the availability of whole-body CT scanning facilities provides a method of accurately locating the source positions with respect to the local anatomy and hence the possibility of dosage control based on doses to specific pelvic structures. Various computer programs have been written to extract source position data from the CT images, to allow the operator to propose pellet loading patterns and treatment times, and ultimately to display the resultant isodose distribution superposed on the cross-sectional scans. The effects on the dose distribution arising from changing the number of pellets, the pellet positions within the applicators, and the treatment times, are briefly discussed.

Brachytherapy↗
PubMed1983

Cost benefit analysis of radiological protection: a case study of remote after-loading in gynaecological radiotherapy.

The ICRP system of dose limitation requires radiation exposures to be kept "as low as reasonably achievable" (ALARA). The International Commission on Radiological Protection (ICRP) advocates a form of cost benefit analysis for this purpose, in which a comparison is made between the costs of protective measures and the benefits of reduced radiation exposure. In the UK, the National Radiological Protection Board (NRPB) has been developing a framework for the practical application of cost benefit techniques to aid the evaluation of investments in radiological protection. One such investment, being undertaken at a number of radiotherapy centres, concerns remote after-loading equipment to replace the use of radium in the treatment of gynaecological cancers. The introduction of such equipment can offer a complete solution to the radiological protection problems associated with manual radium insertions but involves large capital expenditures on equipment and shielded treatment rooms. This paper describes a cost benefit analysis of introducing remote after-loading equipment at the Christie Hospital and Holt Radium Institute in Manchester. In accordance with the NRPB framework, it is shown that the introduction of after-loading equipment, when housed in appropriately protected rooms, should result in a substantial net benefit and would therefore be justified on radiological protection grounds according to the ALARA principle.

Bed Occupancy↗
PubMed1982

Rabbit MHC antigens: occurrence of non-beta-2-microglobulin-associated class I molecules.

Two monoclonal antibodies, L12/36 and L13/112, prepared from spleens of BALB/c mice immunized with extracts of the rabbit lymphoid cell line RL-5, precipitate a 42,000 mol. wt molecule from detergent lysates of this cell line. This molecule is not associated with beta-2-microglobulin (beta 2m) and has been shown by sequential precipitation experiments to be antigenically distinct from the population of class I rabbit MHC (RLA) molecules that is associated with beta 2m. In spite of this antigenic difference, amino acid sequence analyses indicate that the RLA heavy chain precipitated with anti-beta 2m and that precipitated with the monoclonal antibodies, have identical N-terminal sequences. The sequence determined to position 36 is GSHSMRYFYTSVSRPGLGXPRFIIVGYVXXTXFVRF. The isoleucine assigned to position 24 is the first species-specific residue found for RLA class I molecules. Analysis of the beta 2m associated and non-associated molecules by two-dimensional gel electrophoresis revealed no differences between the RLA heavy chains. Differences in the subcellular locations of the determinants were indicated by fluorescence microscopy and confirmed by immunoelectron microscopy. It was shown that the specificity recognized by the monoclonal antibodies is principally located on the cytoplasmic face of the plasma membrane whereas the majority of anti-beta 2m reactive specificities are on the extracellular side of the cell membrane.

Amino Acid Sequence↗
PubMed1981

Arthrodesis of the metatarsophalangeal joint of the great toe.

A review of the literature attests to a place for arthrodesis of the metatarsophalangeal joint of the great toe in the management of hallux valgus and rigidus. The predictability and consistency of the result of arthrodesis is noted with good results in approximately 90% of cases. The functional excellence and durability of such a result are impressive. The procedure is particularly indicated in patients with hallux rigidus and hallux valgus associated with metatarsalgia. There are a number of operative techniques, but the cone arthrodesis procedure described by Wilson is probably nearest to the ideal.

Arthrodesis↗
PubMed1980

Troponin C from rabbit slow skeletal and cardiac muscle is the product of a single gene.

Troponin C has been isolated from rabbit slow skeletal and cardiac muscle and the complete amino acid sequence of the slow muscle protein determined. Amino acid analysis and peptide mapping of the cardiac protein showed it to be very similar to, if not identical with, the slow muscle protein. This identity has been proved by the isolation and characterisation of tryptic peptides from the cardiac protein. It seems very likely that troponin C from these two tissues is the product of a single gene, in contrast to troponin I and troponin T which are the products of different genes. The amino acid sequences shows only one difference from that of bovine cardiac troponin C, the highly conservative replacement of an aspartic for a glutamic acid at position 115. No differences were found in the N-terminal region where these proteins appear to have a lost one of the Ca2+ binding sites found in fast skeletal muscle troponin C. The possible significance of this finding in relation to the binding of troponin C to the different types of troponin I is discussed.

Amino Acid Sequence↗
PubMed1980

Dose-rate considerations in the introduction of low-dose-rate afterloading intracavitary techniques for radiotherapy.

An investigation has been made into the changes in total dose required as a consequence of proposed increases in dose-rate in low-dose-rate treatments of cancer of the uterine cervix. The relationship between total irradiation time and dose-rate has been measured using an assay based on mouse-tail radionecrosis, with irradiation schedules similar to existing and proposed human cervix treatments. This relationship, which is similar to that observed in other biological systems, predicts that the total dose for epithelial tolerance should be reduced by about one third when the dose-rate is increased from 1.0 to 3.5 Gy per hour. The clinical implications of this finding are discussed.

Animals↗
PubMed1978

The amino-acid sequence of chicken fast-skeletal-muscle troponin I.

The amino acid sequence of troponin I from chicken breast and leg muscle has been determined using tryptic and CNBr peptides. The protein contains 182 residues and has a molecular weight of 21136. The N-terminus is blocked and is probably acetylated. 35 of the residues have acidic and 45 have basic side chains giving an overall net positive charge of 9. The CNBr peptides from both breast and leg troponin I have been shown to be identical and no heterogeneity has been found in the tryptic peptides isolated from a mixture of the two proteins. It may thus be taken that the two proteins are identical. Comparison with the sequence of troponin I from rabbit fast skeletal muscle shows strong homology with 34 differences out of 182 residues. The major difference is in a deletion of three residues, from 152 to 154, in the rabbit protein.

Amino Acid Sequence↗
PubMed1978

The components of troponin from chicken fast skeletal muscle. A comparison of troponin T and troponin I from breast and leg muscle.

The three components of troponin were prepared from chicken breast and leg muscle. The troponin I and T components were separated by chromatography on DEAE-cellulose after citraconylation and without the use of urea-containing buffers. The troponin I and C components were similar to their counterparts from rabbit fast skeletal muscle, and a comparison of the troponin I components from breast and leg muscle by amino acid analysis, gel electrophoresis and peptide 'mapping' provides strong evidence for the identity of these proteins. The molecular weights of the troponin T components from breast and leg muscle were 33 500 and 30 500 respectively, determined by gel filtration. A comparison of these two proteins by methods similar to those used for the troponin I components suggested that they differed only in the N-terminal region of the sequence, the breast-muscle troponin T having an extra length of polypeptide chain of approx. 24 residues that is rich in histidine and alanine. The N-terminal hexapeptide sequence, however, is the same in both proteins and is (Ser,Asx,Glx)Thr-Glu-Glu. The genetic implications of these findings are considered.

Amino Acid Sequence↗
PubMed1977

The amino acid sequence of rabbit slow-muscle troponin I.

Troponin I was isolated from six red muscles in the hind leg of the rabbit. Soleus, semi-tendinosus, vastus intermedius and adductor longus muscles contained primarily slow-muscle troponin I, vastus lateralis contained fast-muscle troponin I and quadratus femoris contained a mixture of the two. The complete amino acid sequence of the troponin I from slow muscle was determined. Seven CNBr fragments were isolated and sequenced by using the dansyl-Edman technique after digestion with proteolytic enzymes. The CNBr fragments were ordered by isolation of tryptic peptides containing carboxy[(14)C]methyl-methionine. Direct evidence for the conjunction of residues 8 and 9 has not been obtained, and one of the carboxyl groups between residues 71 and 79 may carry an amide group. Slow-muscle troponin I is a single polypeptide chain of 184 residues with a mol.wt. of 21146. It has a net overall positive charge of 18 at pH7, and an absorption coefficient, A(1%,1cm) (280), of 5.43. The protein was isolated with both a blocked and an unblocked N-terminus, although the nature of the blocking group was not determined. Proline was found to be the N-terminal amino acid. Two forms of the protein could also be distinguished by the presence of an extra two residues at the C-terminus. Comparison of sequences of troponin I from rabbit slow, fast and cardiac muscle shows that homology is most marked in the C-terminal half of the molecules. Towards the N-terminus the homology becomes much less marked. Detailed evidence on which the sequence is based has been deposited as Supplementary Publication SUP 50079 (32 pages) at the British Library (Lending Division), Boston Spa, Wetherby, West Yorkshire LS23 7BQ, U.K., from whom copies may be obtained in the terms given in Biochem. J. (1977), 161, 1.

Amino Acid Sequence↗
PubMed1976

The connective tissue coverings of leech peripheral nerves: anatomical evidence for the absence of cerebrospinal fluid in the leech.

The central nervous system of Hirudo medicinalis is contained within a blood vessel, the ventral longitudinal sinus, but the nervous system is separated from the blood by the visceral endothelium. The visceral endothelium possesses many pinocytotic vesicles and basal infoldings and thus appears active whereas the parietal endothelium appears inactive. The junction between the visceral and parietal endothelia is abrupt. Peripheral nerves in this animal, as in vertebrates, are covered by endoneurium, perineurium, and epineurium. The endoneurium is continous with the fibrous tissue of the segmental ganglia. The perineurium, consisting of a single layer of flattened cells that surrounds the peripheral nerve like a sleeve, is not continuous with the endothelium of the ventral sinus, but is separated from it by 5-10 microns. Therefore, at the point where the peripheral nerve joins the segmental ganglion, the extracellular spaces of the central nervous system, the peripheral nervous system, and the body wall are all confluent. Thus, there are only two compartments of the extracellular space in the leech: the blood, which is enclosed by the endothelia of the coelomic sinuses, and the extracellular fluid of the body, which includes the extracellular fluid of the nervous system. There seems to be no equivalent of cerebrospinal fluid in the gnathobdellid leech.

Animals↗
PubMed1976

The amino acid sequence of rabbit cardiac troponin I.

The complete amino acid sequence of troponin I from rabbit cardiac muscle was determined by the isolation of four unique CNBr fragments, together with overlapping tryptic peptides containing radioactive methionine residues. Overlap data for residues 35-36, 93-94 and 140-145 are incomplete, the sequence at these positions being based on homology with the sequence of the fast-skeletal-muscle protein. Cardiac troponin I is a single polypeptide chain of 206 residues with mol.wt. 23550 and an extinction coefficient, E 1%,1cm/280, of 4.37. The protein has a net positive charge of 14 and is thus somewhat more basic than troponin I from fast-skeletal muscle. Comparison of the sequences of troponin I from cardiac and fast skeletal muscle show that the cardiac protein has 26 extra residues at the N-terminus which account for the larger size of the protein. In the remainder of sequence there is a considerable degree of homology, this being greater in the C-terminal two-thirds of the molecule. The region in the cardiac protein corresponding to the peptide with inhibitory activity from the fast-skeletal-muscle protein is very similar and it seems unlikely that this is the cause of the difference in inhibitory activity between the two proteins. The region responsible for binding troponin C, however, possesses a lower degree of homology. Detailed evidence on which the sequence is based has been deposited as Supplementary Publication SUP 50072 (20 pages), at the British Library Lending Division, Boston Spa, Wetherby, West Yorkshire LS23 7QB, U.K., from whom copies may be obtained on the terms given in Biochem. J. (1976) 153, 5.

Amino Acid Sequence↗
PubMed1976

The relationship between biological activity and primary structure of troponin I from white skeletal muscle of the rabbit.

1. A series of defined peptides which span the complete sequence were produced from troponin I isolated from white skeletal muscle of the rabbit. 2. Two peptides, CF1 (residues 64-133) and CN4 (residues 96-117) inhibited the Mg2+-stimulated adenosine triphosphatase of desensitized actomyosin. This inhibition was potentiated by tropomyosin and the Mg2+-stimulated adenosine triphosphatase of desensitized actomyosin. This inhibition, unlike that of troponin I and peptides derived from it, was not potentiated by tropomyosin. 4. The most active inhibitor, peptide CN4, was 45-75% as effective as troponin I when compared on a molar basis. The inhibitory peptide, CN4, and also whole troponin I were shown by affinity chromatography to interact specifically with actin. 5. A strong interaction with troponin C was demonstrated with peptide CF2 (residues 1-47), from the N-terminal region of troponin I. Somewhat weaker interactions were shown with peptides CN5 (residues 1-21) and with the inhibitory peptide CN4. 6. The significance of these interactions for the mechanisms of action of troponin I is discussed.

Actins↗