Search PubMed⌕ Search

Biomedical subjects

M J Carter

Publications and source records attributed to M J Carter.

117 records · Page 7Linked to original sources
PubMed1970

The purification and properties of carbonic anhydrases from guinea-pig erythrocytes and mucosae of the gastrointestinal tract.

Procedures for isolating carbonic anhydrase (EC 4.2.1.1) enzymes from the erythrocytes and the mucosae of the gastrointestinal tract of guinea pigs are described. From a haemolysate, haemoglobin was removed by the addition of ammonium sulphate, and also by two other methods, namely by gel filtration or by adsorption on DEAE-Sephadex. The crude enzyme thus obtained was resolved into the different isoenzymes by chromatography with DEAE-cellulose. From particle-free supernatants of homogenates of some gastrointestinal tissues, carbonic anhydrases were purified by ammonium sulphate fractionation, gel filtration, and ion-exchange chromatography with DEAE-cellulose. The major isoenzymes from blood, stomach, proximal colonic mucosa and caecal mucosa were homogeneous during ion-exchange chromatography, acrylamide-gel electrophoresis, and centrifugal examination. From these tissues, carbonic anhydrase was isolated as two major isoenzymes. They resemble the pairs of isoenzymes discovered in the bloods of other species. The carbon dioxide hydratase activity of one isoenzyme (;high activity' carbonic anhydrase) was 40 times that of the other isoenzyme (;low activity' carbonic anhydrase), as measured at a single substrate concentration. Two other minor components of the enzyme are also found in guinea-pig erythrocytes. All of the enzymes isolated had molecular weights of nearly 30000 (sedimentation equilibrium). ;High activity' carbonic anhydrases from blood and gastrointestinal tissues were indistinguishable according to some chemical, physical and kinetic measurements; similarly ;low activity' carbonic anhydrases from those tissues were indistinguishable. ;High activity' carbonic anhydrase was markedly different from the ;low activity' carbonic anhydrase with respect to its amino acid composition, chromatographic behaviour and isoelectric pH value. Marked differences were also found in the tissue concentrations of the major isoenzymes. It is suggested that the characteristic and selective distribution of the different forms of carbonic anhydrase in the guinea-pig tissues is related to the specific and different physiological functions of the enzymes.

Amino Acids↗
PubMedDate not supplied

Defective translation of measles virus matrix protein in a subacute sclerosing panencephalitis cell line.

Subacute sclerosing panencephalitis (SSPE) is a slowly progressing fatal human disease of the central nervous system (CNS) that is associated with measles virus persistence. Virus nucleocapsids are present in the brain and the patient is in a state of hyperimmunization towards this agent. However, although all other structural polypeptides are recognized by the immune system, there is a markedly decreased antibody response towards virus matrix or membrane protein. Matrix protein has not been detected in brain cells and infectious virus is not present. The absence of this virus structural polypeptide is thought to account for the apparent restriction in virus maturation both in vivo and in vitro. SSPE viruses can only rarely be rescued from brain tissue by co-cultivation or cell fusion techniques using tissue culture cell lines susceptible to measles virus infection. Often this procedure fails to yield a lytic budding virus but produces instead a carrier cell line in which the agent is cell associated. These lines (known as SSPE cell lines) also do not contain matrix protein. However, the reason for this deficiency is unknown. We have therefore now examined an SSPE cell line which does not yield infectious virus in order to define this process further. We found that although messenger RNA for membrane protein was present, it was unable to form normal matrix protein in translation reactions.

Cell Line↗
PubMedDate not supplied

Determination of measles virus protein molecular weights on high percentage, highly cross-linked SDS polyacrylamide gels.

A recent examination of measles virus mRNA molecules has shown that the nucleocapsid and haemagglutin messengers are of the size expected from a consideration of their protein products. However, the mRNA for membrane protein is approximately 50% larger than the size required. The molecular weight of matrix protein has been determined by SDS-polyacrylamide gel electrophoresis, and this procedure can lead to an underestimation of the true size of hydrophobic molecules which show increased SDS binding. It is therefore appropriate to examine the molecular weight determination of this protein to exclude such an artefactual discrepancy in mRNA and protein sizes. We report here that measles virus membrane protein does not shown such anomalous behaviour and confirm that the size discrepancy is a true phenomenon.

Cross-Linking Reagents↗