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Biomedical subjects

C S Scott

Publications and source records attributed to C S Scott.

At least 19 recordsLinked to original sources
PubMed1992

Classification of large granular lymphocyte (LGL) and NK-associated (NKa) disorders.

Literature trends indicate an increasing awareness regarding the frequency, nature and clinical associations of abnormal and persistent expansions of lymphocytes with cytoplasmic granulation. These particular cells, which represent a minor normal lymphoid subpopulation and are widely referred to as large granular lymphocytes (LGL), generally (but not invariably) express monoclonal antibody-defined membrane NK-associated (NKa) determinants and appear to functionally correspond to those populations involved in cellular cytotoxicity. Increased proportions or absolute numbers of blood lymphocytes with LGL morphology and/or NKa+ phenotypes are associated with a diverse spectrum of clinical (haematological and non-haematological) disorders and may be broadly viewed as secondary (acute and chronic reactive) or primary in nature. Both primary and secondary LGL/NKa+ expansions may be persistent in type and the clinical distinction between the two may be difficult. A number of investigators have proposed schemes for the classification of these disorders but, because of their diversity, abnormal LGL/NKa+ expansions often defy rigid compartmentalisation. This communication examines the general basis of these classifications and illustrates their limitations by reviewing the data for 97 patients recorded in the largest (Yorkshire Leukaemia Group) survey to date of persistent LGL/NKa+ expansions.

Antigens, CD↗
PubMed1992

Purification of human monocyte-specific esterase (MSE): molecular and kinetic characteristics.

Human monocyte-specific esterase (MSE) derived from leukaemic AMoL-M5 blast cells was purified to homogeneity by the sequential application of anion-exchange, hydrophobic interaction, affinity and gel filtration chromatographic procedures. The resulting enzymatically active MSE primarily existed as an apparent trimer which, under both reducing and non-reducing conditions, dissociated to an inactive 63.4 kD glycoprotein monomer. Electrophoretic studies further confirmed that purified MSE comprised a narrow series of pI (5.5-6.1) forms and one main charge species. Neuraminidase failed to modify observed pI values for individual MSE isoenzymes, and endoglycosidase H treatment revealed that the deglycosylated form of MSE had an apparent molecular weight of 60.1 kD. In support of the known cytochemical characteristics of human MSE, substrate kinetic studies demonstrated that purified enzyme hydrolysed esters of higher acyl chain length (butyrate > propionate > acetate) but did not show peptidase activity. Amino acid sequencing of the MSE N-terminus further revealed that there was almost complete identity with human alveolar macrophage esterase and close similarities with rat and rabbit liver carboxylesterases. These kinetic and molecular studies are particularly important in elucidating the biological and functional role(s) of one of the few haemopoietic cell enzymes that can be considered truly lineage-specific.

Amino Acid Sequence↗
PubMed1992

A distinct large granular lymphocyte (LGL)/NK-associated (NKa) abnormality characterized by membrane CD4 and CD8 coexpression. The Yorkshire Leukaemia Group.

In a study of 870 individual patients with either lymphocytosis (excluding known lymphoproliferative disease), increased proportions of blood lymphocytes with granular morphology (LGL), or neutropenia, 14 cases were found with abnormally increased CD3+CD4+CD8+ components. Eleven of these were further investigated and 10 shown in follow-up studies to be persistent in nature. Morphological assessments revealed increased LGL in 9/11 cases, and in seven of these > 50% lymphocytes had discernable cytoplasmic granulation. Immunophenotypic studies indicated that CD8 expression by CD4+ lymphocytes in these patients was of low density (CD8dim+), and that both the CD4+CD8- and CD4+CD8dim+ fractions in each patient was characterized by a CD11b+CD16-CD56+CD57+ composite NK-associated (NKa) phenotype (in contrast to normal CD4+CD8- blood lymphocytes and CD4+CD8+ thymocytes which were consistently CD11b-CD16-CD56-CD57-). TCR genotypic studies revealed rearranged components (beta plus gamma, or beta alone) in 5/11 cases, but there were no obvious relationships between TCR configuration (including rearranged band densities) and immunophenotypes, absolute lymphocyte or neutrophil numbers, the proportions of blood LGL, or the proportions of CD4+ cells coexpressing CD8. The occurrence of identical NKa phenotypic profiles in both germline and rearranged TCR cases does, however, suggest the possibility of an evolutionary process from a non-clonal expansion to a clonal state. Serum studies, including soluble CD4, CD8 and IL2-R concentrations and autoantibody investigations, of representative germline and rearranged TCR cases failed to indicate any consistent abnormalities, but there was some suggestion for the existence of a chronic reactive process in some of the patients with germline TCR. These findings suggest that expanded LGL/NKa+ components with phenotypic evidence of CD4/CD8 coexpression should be regarded as a distinct diagnostic category and that persistent CD4+CD8+ abnormalities with germline TCR should be monitored for possible clonal transition.

Antigens, CD↗
PubMed1992

Abnormal CD45R expression in patients with common variable immunodeficiency and X-linked agammaglobulinaemia.

This study has investigated the patterns of membrane 2H4 (CD45RA) and UCHL1 (CD45RO) expression by CD4+ and CD8+ lymphocyte subpopulations in 10 adults and seven children with common variable immunodeficiency (CVI) and X-linked hypogammaglobulinaemia (XLA). Of the 10 adults (CVI, n = 8; XLA, n = 2), only one with a diagnosis of CVI showed normal CD45R expression. For the remaining seven adult CVI patients the abnormal CD45R profiles were primarily associated with CD4+ lymphocytes in three and CD8+ lymphocytes in four. Specific increases in CD45RA- CD45RO+ fractions were found in four CVI patients and in all of these there was a concomitant reduction in circulating CD19+ B-cell numbers. Two of the CVI cases were identical twin sisters and both had the same CD45R abnormality. The two adults with XLA also showed abnormal CD45R expression (increased CD45RA+ CD45RO- components) but of particular note, in view of the fact that these were brothers, one was associated with the CD4+ subpopulation and the other with the CD8+ fraction. Similar analyses for the paediatric group revealed, in distinct contrast to the adult patients, no significant abnormalities of CD45R expression suggesting that these defects may not become apparent until a later age. Further investigations of in vitro lymphocyte proliferation (PHA and PWM) in the eight adults with CVI showed a significant correlation between abnormal responses and disordered CD45R expression. It is proposed that these abnormal patterns of CD45R expression by lymphocyte subpopulations in CVI and XLA may be of fundamental importance with respect to the pathogenesis of these particular immunodeficiencies.

Adolescent↗
PubMed1992

Chinese medical school exit objectives: a multi-institutional survey of teacher opinion.

This paper describes a collaborative survey of Chinese medical school teacher opinion concerning clinical behaviours and skills that Chinese students should be expected to demonstrate prior to graduation from medical school. Selected teachers from four Chinese medical schools indicated whether each of 77 objectives was: essential for every student to know or demonstrate prior to graduation; useful but not essential; or not applicable to their educational programmes. Results show teachers' expectations regarding some of the behaviours and skills Chinese medical school teachers consider to be important for students to learn. Forty-nine per cent of the exit objectives were regarded as essential by 75% or more of the teachers. The most essential objectives involved performing clinical procedures, collaborating and communicating with health care professionals, conducting organ system examinations, formulating hypotheses and defining problems. Other essential objectives were concerned with communicating with patients and their families, maintaining currency within the discipline, and recognition, evaluation and triage of patients with life-threatening or chronic conditions. Exit objectives related to health promotion and risk assessment were regarded as useful but not essential at the undergraduate level. Implications for Chinese medical education are discussed.

China↗
PubMed1992

Human NK cells in health and disease: clinical, functional, phenotypic and DNA genotypic characteristics.

Natural killer (NK) cells are the subject of great current interest because of their possible (in vivo) role in tumour cell surveillance and killing, and because of the potential application of cytokine-modulated NK cells in cancer immunotherapy. In addition, clonal proliferations of NK-associated (NKa) cell populations represent a high proportion of chronic (non-B) lymphoid malignancies and abnormal (both clonal and non-clonal) NKa components are being increasingly reported in association with diverse clinical pictures such as autoimmune disease. This communication extensively reviews what is presently known regarding normal and leukaemic NKa phenotypic diversity, the mechanisms of NK-mediated cytolysis, the role of NK cells in malignancy, and the diagnostic and cellular aspects of malignant NKa proliferations.

Antibody-Dependent Cell Cytotoxicity↗
PubMed1992

Patterns of membrane CD45 isoform expression by leukaemic blasts and normal mature myeloid cells.

The membrane expression of CD45R isoforms by leukaemic blasts from 92 cases of acute myeloid (AML) and 12 cases of lymphoblastic leukaemia was analysed by single and two-colour flow cytometry. Compared to normal mature granulocytes, which invariably expressed UCHL1 (CD45RO) but not 2H4 (CD45RA), leukaemic myeloid blasts showed 2H4+ UCHL1- and 2H4- ++UCHL1- composite patterns of expression with the first of these phenotypes being associated in particular with the most immature AML subtype (M0). Similar analyses of blast cell fractions from monocytic AML variants, revealed wide variation in CD45R expression in cases of M4, whereas M5 leukaemias were typically 2H4+ ++UCHL1+ with minor 2H4- UCHL1- components. As most normal mature monocytes were also 2H4+ ++UCHL1+, this suggested that monocytic myeloid differentiation was primarily associated with the "acquisition" of UCHL1 and the development of 2H4/UCHL1 co-expressing cells. The expression of membrane CD45RA by leukaemic blasts is an abnormal characteristic and may be related to the maintenance of an undifferentiated state by malignant myeloid precursors.

Adult↗
PubMed1991

Inhibitor studies of purified haemopoietic (myeloid) cell esterases. Evidence for the existence of distinct enzyme species.

Human myeloid cells synthesize and express two major species of esterase, defined by isoelectric focusing (IEF). The first of these (MonEst) is specifically associated with haemopoietic cells of monocytic lineage, whereas the other species (ComEst) is common to all myeloid cells (granulocytes and monocytes) irrespective of lineage affiliation. Having recently purified these two species of human myeloid cell esterase, this present study extensively investigated the effects of 17 different inhibitors on their ability to hydrolyse the synthetic substrate alpha-naphthyl acetate (alpha NA). Significant inhibition of both ComEst and MonEst was exerted by 1% sodium dodecyl sulphate (SDS) and 1.0 mM diethyl pyrocarbonate (DEPC), but the patterns of inhibition for the two esterase species with the remaining compounds studied differed considerably; for example, 0.2 mM phenylmethylsulphonyl fluoride (PMSF), 5.0 x 10(-3) M dichloroisocoumarin (DCIC) and 0.1 mM N-tosyl-L-phenylalanine chloromethyl ketone (TPCK) all inhibited MonEst but not ComEst. Mechanisms of inhibition were also examined and these studies established that SDS, PMSF, DCIC and TPCK irreversibly inactivated MonEst whilst the inhibition of ComEst by SDS was reversible. Analysis of inhibition kinetics further showed that (a) the reversible inhibition of both ComEst and MonEst by sodium fluoride (NaF) was noncompetitive (with Ki values of 1.28 and 0.01 mM, respectively, indicating a marked difference in sensitivity); (b) the inhibition of MonEst by PMSF was of 'mixed' noncompetitive-competitive type; and (c) that DEPC exerted noncompetitive inhibition with similar Ki values (0.05 mM) for both esterase species. These observations unequivocably demonstrate that ComEst and MonEst are unrelated enzyme species, with a common ability to hydrolyse alpha NA, and that these esterase show marked differences with respect to their active sites as adjudged by inhibitor sensitivities. These observations are particularly relevant to the histochemical analysis of these enzymes and to the elucidation of their in vivo functions.

Acetylesterase↗
PubMed1991

A highly sensitive E.L.I.S.A. for endopeptidase-24.11, the common acute-lymphoblastic-leukaemia antigen (CALLA, CD-10), applicable to material of porcine and human origin.

Endopeptidase-24.11 is a widely distributed cell-surface enzyme with a key role in the metabolism of neuropeptides. It is now known to be identical with CD-10, the common acute-lymphoblastic-leukaemia antigen (CALLA). An e.l.i.s.a. is described which utilizes two antibodies, one monoclonal, the other polyclonal, generated to pig endopeptidase-24.11. These antibodies cross-reacted with human endopeptidase-24.11, thus making the assay applicable to both species. By using optimum conditions for the e.l.i.s.a., as little as 25 pg of pure pig endopeptidase-24.11 could be quantified at 95% confidence limits. E.l.i.s.a. of tissue homogenates from a variety of pig tissues and of human kidney correlated well with enzymic assays. However, the use of detergents to solubilize the antigen greatly decreased the sensitivity of the e.l.i.s.a. The e.l.i.s.a. is 1000-fold more sensitive than the immunoradiometric assay and has advantages in specificity over enzymic assays. Daudi cells, some leukaemic cells shown to be CALLA-positive, and Caco-2 cells, could also be assayed, but N2 cavitation was necessary to fragment the cells, and only part of the total endopeptidase-24.11 activity in Daudi cells was recognized by the e.l.i.s.a.

Animals↗
PubMed1991

Oral contraceptive use and coronary risk factors in women.

The relationship between oral contraceptive use and other coronary artery disease risk factors was examined in 215 nonsmoking women grouped as never, current, or previous users. Current oral contraceptive users had higher triglyceride levels (p less than or equal to 0.001) than other groups, higher systolic blood pressure, and lower plasma HDL-cholesterol levels (p less than or equal to 0.05) than previous users. The effect of oral contraceptive use on plasma triglyceride values persists on multivariate regression analysis independently of age, body mass index, dietary sodium and cholesterol intake, cigarette smoking, and level of physical activity. Oral contraceptive use also has an independent relationship to the plasma total cholesterol/HDL- cholesterol ratio. These findings indicate that oral contraceptive use is adversely associated with plasma lipid and lipoprotein values.

Adult↗
PubMed1991

Clinical behaviors and skills that faculty from 12 institutions judged were essential for medical students to acquire.

This paper describes a 1988-1989 collaborative mail survey of faculty opinion about clinical behaviors and skills that students should be expected to demonstrate prior to graduation from undergraduate medical school (hereafter called "exit objectives"). Selected faculty from 12 American and Canadian medical schools indicated whether each of 77 objectives was essential for every student to know or demonstrate prior to graduation; useful but not essential at the undergraduate level; or not applicable to their undergraduate program. Their responses provide a glimpse into faculty expectations regarding some of the exit behaviours and skills they deemed essential. Forty-two percent (32) of the 77 objectives were regarded as essential by 75% or more of the faculty members who responded. Essential objectives involved conducting organ system examinations, formulating problems and hypotheses, and gathering fundamental interview, physical, and screening examination data, including emergency examinations of the airway and circulatory systems. Other essential objectives involved collaboration and communication, demonstrating concern for legal and ethical values, and keeping abreast of current information within the discipline. Exit objectives related to the diagnosis and management of specific conditions were regarded as useful but not essential at the undergraduate level. Implications for medical education are discussed.

Canada↗
PubMed1991

Patterns of CD16 and CD56 expression in persistent expansions of CD3+NKa+ lymphocytes are predictive for clonal T-cell receptor gene rearrangements. The Yorkshire Leukaemia Group.

Phenotypic characteristics, and correlations between the expression of membrane NK-associated (NKa) determinants (CD11b, CD16, CD56 and CD57) and T cell receptor (TCR) genotypic patterns, were examined in 25 patients with persistent (greater than 6 months) expansions of CD3+WT31+NKa+ (CD8+ and CD8dim+) lymphocytes. These studies showed that distinct NKa phenotypic profiles were restricted to cases with rearranged TCR configurations and that clonal CD3+NKa+ components could be predicted in most cases by assessing relationships between membrane CD16 and CD56 expression. For all normal NKa subpopulations, there was a high correlation (P less than 0.0001; n = 31) between the expression of these two membrane determinants. Markedly increased CD16 expression by CD3+NKa+ cells, in relation to CD56 (i.e. a high CD16:CD56 ratio), was found exclusively in cases with rearranged TCR (13/16 cases); 2/3 of the remaining cases showing significantly reduced CD16:CD56 ratios and high (greater than 2.0) CD3+CD56+ absolute numbers. In contrast, 7/9 of the germline TCR cases had a normal CD16:CD56 ratio and 2/9 a decreased ratio with low (less than 1.0) CD3+CD56+ absolute numbers. A high ratio of CD16:CD56 expression by CD3+NKa+ lymphocytes was therefore informative for 82% of TCR rearrangements in this series; and analysis of CD16 and CD56 expression was predictive for germline and rearranged TCR configurations in 24/25 persistent CD3+NKa+ expansions.

Adult↗
PubMed1991

Variant CD45R expression with autosomal dominant inheritance affects both helper/inducer (CD4+) and suppressor/cytotoxic (CD8+) T cell populations.

The differential expression of various membrane CD45R isoforms by normal lymphocyte populations is known to be closely associated with distinct immunoregulatory functions. Abnormal patterns of CD45R expression have been reported in patients with common variable immunodeficiency and HIV infection, and recent evidence has suggested the possibility that one type of variant CD45R expression may be inheritable. By multiple colour flow cytometry, we studied the immunological characteristics of CD4+ helper/inducer and CD8+ suppressor/cytotoxic T cells in a family with variant CD45R expression over three generations. This variant pattern of CD45R expression was shown to affect both CD4+ and CD8+ lymphocyte populations in individual family members and was immunologically characterized by a failure of the normal reciprocal expression of the CD45RA and CD45RO isoforms. Family studies also revealed that this trait had an autosomal dominant mode of inheritance and, in the heterozygous state, appeared not to be associated with major clinical abnormalities. The different isoforms of CD45 show distinct patterns of expression during lymphocyte ontogeny and activation, and these patterns appear to closely reflect function. Despite their diverse immunological roles, our finding that both CD4+ and CD8+ T cells in affected family members showed the same defect suggests a common regulatory mechanism(s) for both these lymphocyte populations. The recognition of this abnormality, particularly in homozygous individuals, will be of great importance in understanding the role of these molecules in immune function and disease.

Adolescent↗
PubMed1991

Current practice patterns and training status of selected graduates at the King Abdulaziz University College of Medicine, Saudi Arabia.

Graduate doctors are the primary output of medical education programmes. It is important for institutions to identify systematically the types of medical activities in which their former students are involved in order to determine the effectiveness of the curriculum, assessing academic standards and reviewing admissions policies. Information was obtained from a survey of men and women graduates from three of the early graduation classes of King Abdulaziz University College of Medicine in Saudi Arabia about postgraduate medical training, certification, practice patterns, and other curriculum issues. Information collected from 151 graduates (90%) indicated that 96% were practising medicine in a variety of medical specialties and subspecialties. Six were not practising at the time of the study. Significant differences were found in the specialties being practised when men and women were compared. Men tended to practise in medicine, surgery, dermatology, urology, ENT, ophthalmology and orthopaedics, while women concentrated in obstetrics and gynaecology and paediatrics. Certification beyond medical school was earned by 49% with no significant difference being found comparing men to women. Men earned the majority of their postgraduate certifications outside Saudi Arabia while most women earned theirs in Saudi Arabia. Graduates indicated that departments in the basic sciences were least helpful in preparing them as doctors, while selected clinical departments were most helpful. It was concluded from the study that the curriculum goals of the College of Medicine, namely a curriculum of international standards producing graduates to take leadership roles in both teaching and medical practice, were realized in part by the graduates surveyed.

Attitude of Health Personnel↗
PubMed1991

The MHC class I associated beta 2-microglobulin (beta 2m) light chain is expressed in a molar excess over HLA-ABC and CD1 on the membrane of leukaemic B cells but not leukaemic T cells: evidence for further beta 2m-associated molecules.

Beta 2-microglobulin (beta 2m) constitutes the common light chain of both the MHC-encoded HLA-ABC molecules and a group of structurally related glycoproteins recognized by antibodies of the first cluster of differentiation (CD1a, CD1b and CD1c). These CD1 antigens appear similar to murine T1 and Qa molecules in terms of structure and tissue distribution, although the question of inter-species homology is controversial. A further group of alloantigens expressed predominantly on T cells has been reported however, with immunogenetic characteristics more closely analogous to the murine T1/Qa system than the CD1 antigens, although their precise identity remains ill-defined. Having previously shown that malignant B cells may express membrane CD1c, we examined leukaemic B-cells corresponding to early lymphoblastic differentiation (null- and common acute lymphoblastic leukaemia) through to the terminal plasma cell stage for the expression of other non-HLA class I beta 2m-associated molecules. It was found that leukaemic B-cells at intermediate/late stages of differentiation, represented by non-Hodgkin's lymphoma (B-NHL) and 'hairy-cell' leukaemia (HCL), had significantly higher beta 2m:HLA-ABC ratios than did the cells from other types of B-cell malignancy. Although leukaemic B cells with a demonstrable non HLA-ABC-associated beta 2m component expressed detectable levels of CD1c, and insignificant levels of CD1a and CD1b, the antigen density was insufficient to account for the excess beta 2m. In vitro stimulation of leukaemic B cells by phorbol ester substantially increased the expression of HLA-ABC and CD1c, but also accentuated further the difference between the expression of these molecules and that of beta 2m. There was no detectable beta 2m other than that associated with HLA-ABC and CD1 on the surface of malignant T cells by contrast. Our findings strongly support the existence, at certain stages of leukaemic B-cell differentiation, of an additional beta 2m component(s) other than that associated with HLA-ABC and CD1.

Antigens, CD↗
PubMed1991

Suppression of natural killer cell activity by rabbit antibody to human beta 2-microglobulin (beta 2m) is an Fc-mediated phenomenon and is not beta 2m specific.

Natural killer (NK) cell cytotoxicity constitutes an important component of the host immune defence system. The NK effector cell has been relatively well defined in terms of immunophenotypic characteristics, but in contrast to the functional T-cell receptor molecule associated with major histocompatibility complex (MHC)-restricted cytotoxic activity, the NK cell receptor has not to date been defined. However, several studies have suggested that the beta 2-microglobulin (beta 2m) molecule is functionally associated with NK cell activity. Using various heterospecific and monoclonal antibodies, this study has shown that intact rabbit IgG antibody bound either directly or indirectly to peripheral mononuclear cell (PMNC) effector populations significantly reduced their lytic activity against K562 targets. Substitution of F(ab)2 fragments for rabbit IgG antibodies, or the use of monoclonal antibodies alone, failed to reduce peripheral blood mononuclear cell (PMNC) lytic activity. Addition of non-NK cell components labelled with rabbit anti-beta 2m to purified NK-enriched effector cell populations also suppressed K562 lysis. In contrast, pre-treatment of a NK-enriched PMNC fraction with rabbit anti-beta 2m enhanced target lysis. These results strongly suggest that antibody-induced suppression of PMNC NK activity is mediated via rabbit Fc attached to co-existing non-NK cells in the mononuclear fraction, and are inconsistent with the previously suggested functional association between NK activity and membrane beta 2m.

Animals↗