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Biomedical subjects

A J Barrett

Publications and source records attributed to A J Barrett.

At least 343 records · Page 19Linked to original sources
PubMed1980

Survival of CFU-C in recipient blood after bone marrow transplantation.

In six patients undergoing allogeneic bone marrow transplantation granulocyte colony and cluster forming units were detectable in the blood up to 24 hours after intravenous marrow infusion. The mean surviving fraction 30 minutes after the end of the infusion was 0.3 for colonies and 0.42 for total aggregates. CFU-C declined logarithmically with time, but a small secondary rise in blood CFU-C occurred 2--6 hours after the end of the marrow infusion. Three patients were plasma-exchanged immediately before the marrow graft for major donor-recipient ABO incompatibility. The proportion of total groups remaining in the blood at 30 minutes was significantly higher in the plasma-pheresed patients (P = less than 0.05), and the secondary rise in CFU-C was less marked, but no correlation of the blood CFU-C decay curve with the subsequent fate of the graft was observed.

Adolescent↗
PubMed1980

The many forms and functions of cellular proteinases.

Mammalian proteases comprise both the peptidases or exopeptidases, which act at the N- or C-terminal positions of polypeptides, and the proteinases or endopeptidases, which are capable of cleaving peptide bonds in the central regions of polypeptides. Presumably the endopeptidases usually act first in the degradation of a protein molecule. The endopeptidases are classified in four distinct groups on the basis of the chemical nature of the groups responsible for catalytic activity. Because these chemical groupings are most reliably recognized by use of active-site directed inhibitors, inhibitors are often more important than substrates in the classification and identification of proteinases. The major characteristics of the serine, thiol, carboxyl, and metallo-proteinases are summarized. The activities of the proteinases in vivo are controlled by a powerful range of inhibitors, as well as other factors, and the properties of these also are summarized.

Animals↗
PubMed1979

The electrophoretically 'slow' and 'fast' forms of the alpha 2-macroglobulin molecule.

alpha 2-Macroglobulin (alpha 2M) was isolated from human plasma by a four-step procedure: poly(ethylene glyco) fractionation, gel chromatography, euglobulin precipitation and immunoadsorption. No contaminants were detected in the final preparations by electrophoresis or immunoprecipitation. The protein ran as a single slow band in gel electrophoresis, and was designated 'S-alpha 2M'. S-alpha 2M bound about 2 mol of trypsin/mol. Treatment of S-alpha 2M with a proteinase or ammonium salts produced a form of the molecule more mobile in electrophoresis, and lacking proteinase-binding activity (F-alpha 2M). The electrophoretic mobility of the F-alpha 2M resulting from reaction with NH4+ salts was identical with that of proteinase complexes. We attribute the change in electrophoretic mobility of the alpha 2M to a conformation change, but there was no evidence of a change in pI or Strokes radius. Electrophoresis of S-alpha 2M in the presence of sodium dodecylsulphate gave results consistent with the view that the alpha 2M molecule is a tetramer of identical subunits, assembled as a non-covalent pair of disulphide-linked dimers. Some of the subunits seemed to be 'nicked' into two-thires-length and one-third-length chains, however. This was not apparent with F-alpha 2M produced by ammonium salts. F-alpha 2M produced by trypsin showed two new bands attributable to cleavage of the subunit polypeptide chain near the middle. Immunoassays of F-alpha 2M gave 'rockets' 12-29% lower than those with S-alpha 2M. The nature of the interactions between subunits in S-alpha 2M and F-alpha 2M was investigated by treating each form with glutaraldehyde before electrophoresis in the presence of sodium dodecyl sulphate. A much greater degree of cross-linking was observed with the F-alpha 2M, indicating that the subunits interact most closely in this form of the molecule. Exposure of S-alpha 2M to 3 M-urea or pH3 resulted in dissociation to the disulphide-bonded half-molecules; these did not show the proteinase-binding activity characteristic of the intact alpha 2M. F-alpha 2M was less easily dissociated than was S-alpha 2M. S-alpha 2M was readily dissociated to the quarter-subunits by mild reduction, with the formation of 3-4 new thiol groups per subunit. Inact reactive alpha 2M could then be regenerated in high yield by reoxidation of the subunits. F-alpha 2M formed by reaction with a proteinase or ammonium salts was not dissociated under the same conditions, although the interchain disulphide bonds were reduced. If the thiol groups of the quarter-subunits of S-alpha 2M were blocked by carboxymethylation, oxidative reassociation did not occur. Nevertheless treatment of these subunits with methylammonium salts or a proteinase caused the reassembly of half-molecules and intact (F-) tetramers. It is emphasized that F-alpha 2M does not have the properties of a denatured form of the protein...

Antigens↗
PubMed1979

Cathepsin D: the lysosomal aspartic proteinase.

Cathepsin D was originally known simply as 'cathepsin' and was first purified in the late 1930s. Nowadays the enzyme is purified by conventional column chromatography, and by isoelectric focusing (which resolves isoforms), but affinity chromatography with pepstatin--Sepharose is also important. Cathepsin D is a glycoprotein of about 42,000 molecular weight; sometimes it comprises a single polypeptide chain but often this is found to have been 'nicked' about two-thirds of the way from one end. Cathepsin D is an 'aspartic proteinase' and may be one of the more primitive members of the family. The activity of cathepsin D is expressed exclusively at acidic pH values and the specificity shows a strong preference for cleavage near hydrophobic amino acids. Specific inhibition of cathepsin D with antibodies and pepstatin has provided strong evidence that the enzyme plays a part in intralysosomal proteolysis but there is as yet little evidence for extracellular activity.

Animals↗
PubMed1979

Variations in granulocyte colony forming cell numbers in adult blood.

Blood granulocyte colony forming units (CFU-C) were studied in normal adults to establish: (i) a normal range; (ii) variability due to the culture technique; (iii) variability of blood CFU-C within individuals. Thirty men studied had 98 (range 8--300) CFU-C X 10(3)/1, and 28 women studied had 44 (range 0--260) CFU-C X 10(3)/1. This difference was significant (P less than 0.001). There was also a significant sex difference in the total number of cells forming colonies and clusters per litre; and in the incidence of colony formers and of cluster formers in buffy coat and mononuclear cell blood fractions. CFU-C were assayed in four subjects over a 10 week period. When buffy coat cells were used as a source of colony stimulation the week to week variation in the combined growth of the four subjects was wide (+/- 36%) but with conditioned medium the variation was smaller (+/- 14%). In all subjects colony and cluster growth varied in the same way (r = 0.77, P = .001) but there was no correlation with the total leucocyte count. A 3--4 week cyclical change in CFU-C/1 was found which was independent of the variation inherent in the technique. The physiological significance of the sex difference and the apparent cyclical changes in blood CFU-C are not explained, but the results emphasize the wide fluctuations in CFU-C that may occur in normal individuals.

Adult↗
PubMed1979

Effect of antilymphocyte globulin on granulocyte precursors in aplastic anaemia.

Granylocyte colony forming units (CFU-C) were studied in 22 patients with severe aplastic anaemia before and after treatment with antilymphocyte globulin (ALG). Nine patients showed a clinical response to ALG characterized by a rise in the granulocyte count to over I X 10(9)/1 within 30 d. These patients were distinguished in vitro from non-responders by an increase in CFU-C numbers after incubation of bone marrow cells with ALG, and by the presence of inhibitors of normal CFU-C in the serum in six out of seven patients tested. In responding patients bone marrow CFU-C rose while most non-responding patients showed no change or a fall in CFU-C after treatment. In addition in three out of four responding patients examined serum inhibitors disappeared after treatment. The horse ALG used in this study also stimulated normal CFU-C in vitro. This evidence is contrary to the hypothesis that ALG stimulates CFU-C in aplasia by inactivating an abnormal suppressor lymphocyte population. The nature of the stimulation by ALG remains unclear. But in practice the effect of ALG on bone marrow cells and study of CFU-C inhibitors in serum could be used to select patients likely to respond to ALG treatment.

Adult↗
PubMed1979

Allogeneic bone marrow transplantation for severe aplastic anaemia--the London experience.

Using the Seattle protocol with minor modifications, 23 patients with severe aplastic anaemia received allogeneic bone marrow transplants from HLA/mixed leucocyte culture matched sibs in three London centres between 1973 and 1977. Ten patients (43.5%) are alive 6 months to 5 years after transplantation, and are well with full haemopoietic reconstitution, two with autologous bone marrow recovery following the graft procedure. A failure of the marrow graft to take, or take followed by rejection occurred in 12 patients (52%). Failure of marrow recovery was associated with a high early mortality from bacterial or fungal infection. The only survivors amongst those who rejected the first graft were four patients in whom a subsequent graft from the same donor was successful, and two in whom autologous recovery occurred. Graft versus host disease (GVHD) occurred in seven patients, and was fatal in one case. The most frequent complication after successful engraftment was varicella-zoster infection which occurred in five patients and was fatal in one patient. The overall results compare favourably with those from other transplant centres, but the high rate of graft rejection and low incidence of GVHD differ from other series. The results should encourage further referral of patients with severe AA for bone marrow transplantation.

Adolescent↗
PubMed1979

Bone marrow culture in aplastic anemia.

Blood and bone marrow granulocyte colony forming units (CFUc) were assayed in 46 patients with aplastic anemia, and the serum was examined for its inhibitory action on normal CFUc growth. All patients showed a gross reduction in colonies and clusters in incidence and absolute number in the bone marrow and blood. Two proliferative abnormalities of CFUc in aplastic anaemia were identified: a significantly higher than normal cluster to colony ratio (P less than 0.05) and a higher than normal ratio of granulocytes to total aggregates in the bone marrow. Eleven out of 34 patients tested had serum inhibitory to normal CFUc. These patients were indistinguishable from the rest on haematological and CFUc culture characteristics, and no correlation between the results of CFUc assay and haematological severity was found. The results suggest that the CFUc is abnormal in aplastic anaemia, the reduction in pool size being related to a failure of self-renewal, but an immunological role in the pathogenesis of aplastic anaemia remains unproven. The close relationship of CFUc incidence to the percentage of granulocyte precursors in the marrow, together with the failure of the CFUc assay to predict clinical severity, limits the practical use of the assay to the confirmation of diagnosis in aplastic anaemia.

Adult↗
PubMed1979

Protein degradation in health and disease. Introduction: the classification of proteinases.

Twenty years after B.S. Hartley's 1960 review, on which the present scheme for classification of the proteinases is based, most of the new information that has been obtained appears fully consistent with Hartley's views. A slight amendment is proposed of the name of the four groups of these enzymes to 'serine', 'cysteine', 'aspartic' and 'metallo'-proteinases.

Animals↗
PubMed1979

Total body irradiation and marrow transplantation for acute leukaemia. The Royal Marsden Hospital experience.

The experience with total body irradiation at the Royal Marsden Hospital is described for an elective program of transplantation in patients with acute myeloid leukaemia (AML) in first remission. Dose rate appears to be a critical factor in the reduction of radiation-associated damage and careful monitoring of the actual dose distribution and dose received is mandatory.

Adolescent↗