Download Biochemical Studies on the Carrier State in the

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The significance of these results will be discussed in
relation to specific features of the marrow depression
caused by these drugs.
12. IMMUNOCHEMICAL STUDIES OF MAMMALIAN GLYCOPROTEINS WITH BLOOD
GROUP I ACTIVITY
T. FEIZI
Division of Communicable Diseases, MRC Clinical
Research Centre, Warford Road, Harrow, Middlesex
HA1 3UJ
(Introduced by A. S. TAVILL)
The blood group I antigen is present on the erythrocytes of the vast majority of adults. Antibodies
directed against this antigen may give rise to autoimmune haemolytic anaemia. These antibodies are
cold agglutinins and often arise following atypical
pneumonia (due to Mycophma pneumoniae infection) or are associated with lymphoproliferative
disorders. Recent studies have shown that I antigen is
a glycoprotein consisting of at least six antigenic
determinants and that it is closely related to the
precursors of ABH and Lewis blood group substances.
One of these determinants has been characterized.
13. THE INTERACTION OF HYDROGEN IONS
AND CALCIUM IONS ON THE ATPase
ACTIVITY OF CARDIAC MYOFIBRILS
G. J. WILLIAMS,
M. R. STEPHENSand J. R. MUIR
Department of Cardiology, Welsh National School of
Medicine, Medical Teaching Centre, Heath Park,
Cardiff
The concentration of lactic acid rises in ischaemic
myocardium (Cornblatt, Ronelle, Parmeggioni &
Morgan, 1963, Journal of Biological Chemistry, 238,
1592; Williamson, 1966, Journal of Biological
Chemistry, 241, 5026) and it has therefore been
supposed that intracellular pH falls under these
conditions. Katz & Hecht (1969, American Journal of
Medicine, 47, 497) have suggested that the reduced
myocardial performance associated with ischaemia
is due to hydrogen ions competing with calcium ions
for binding sites on the regulatory protein, troponin.
Such competition would result in a reduction as the
pH fell in the number of active actin-myosin interactions at any given [&++] and therefore in the
myofibrillar ATPase activity and in the force of
contraction. Unfortunately experimental data on this
point is conflicting (Muhlrad & Hegyn, 1965, Biochimica et Bwphysica Acta, 105, 341 ; Schieller, 1967,
Pfliigers Archiv fur die gesamte Physiologie, 2%,70).
The interaction of [a++]
and [H+] on cardiac
myofibrillar A T P m activity was therefore studied,
both [Ca+ +] and [H+]being accurately controlled by
L
1 7 ~
buffers. Myofibrils were prepared from left ventricles
of normal dogs by a standardized technique (Muir,
Weber & Olson, 1971, Biochimica et Biophysica Acta,
234, 199). ATPase activity was measured over a
pH range 6.5-7.4, the [Ca++I in each range varying
from zero to 1.5 x l o 4 M . It was not possible to
exceed this pH range as the buffering action of
EGTA for calcium is ineffective outside this range.
ATPase of dog cardiac myofibrils, and rabbit cardiac
myosin and actomyosin was also measured in the
absence of [Ca+1‘ over the pH range 6-9. In addition
the influence of pH on the K,ATP of cardiac myofibrils was studied.
In the absence of ionic calcium, myofibrillar,
myosin and actomyosin ATPase activities are
maximal at pH 8.0. In addition the myofibrillar
ATPase activity for any given calcium ion concentration is depressed by lowering the pH. However, the
effect of pH on the K,ATP ( 1 x
M) shows that
the inhibition is non-competitive.
These results suggest that a fall in intracellular pH
could reduce cardiac myofibrillar ATPase activity
but that the effect is probably complex, competition
between calcium and hydrogen ions for binding sites
on troponin being only one factor.
14. BIOCHEMICAL
STUDIES
ON
THE
CARRIER STATE IN THE LESCH-NYHAN
SYNDROME
R. 0. MCKERAN,T. M. ANDREWS,
A. HOWELL,
D. A.
GmBs and R. W. E. W A ~
Division of Inherited Metabolic Diseases, MRC
Clinical Research Centre, Warford Road, Harrow,
Middesex HA1 3UJ
The Lesch-Nyhan syndrome (choreoathetosis, compulsive self-mutilation, mental retardation and
excessive uric acid production) is associated with the
absence of detectable IMP: pyrophosphate phosphoribosyltransferase (EC 2.4.2.8.) from the patient’s
tissues (‘complete HGPRT deficiency’). Occasional
cases of severe gout with gross uricacid overproduction
and sometimes minor neuropsychiatric abnormalities
have very low levels of HGPRT activity (‘incomplete
HGPRT deficiency’). These two conditions are
genetically separate, although both are X-linked. The
female carriers of the complete HGPRT deficiency
have previously been identified by the mosaicism of
their fibroblasts in tissue culture. We have studied
presumed carriers of the complete and incomplete
HGPRT deficiencies in a search for additional and
more easily obtainable evidence for the presence
of two cell populations in these women. The following
tissues were studied in addition to fibroblasts: hair
follicles, phytohaemagglutinin stimulated lymphocytes, cultured bone marrow cells and jejunal mucosa
biopsies. Our findings confirm that hair follicles can be
used to assist the diagnosis of the carrier state for the
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complete HGPRT deficiency. We found some evidence
for the presence of a subpopulation of HGPRT
deficient cells in the other tissues studied.
The significance of these results will be discussed in
relation to the presence or absence of mosaicism for
X-linked traits in different tissues.
15. THE FORMATION O F OXALATE FROM
GLYOXYLATE BY THE SUBCELLULAR
PARTICLES O F LIVER TISSUE
DOROTHY
A. GIBBS
Division of Inherited Metabolic Diseases, MRC
Clinical Research Centre, Watford Road, Harrow,
Middlesex HA1 3UJ
(Introduced by R. W. E. WATTS)
The work to be reported was undertaken as part of a
project to determine which enzyme or enzymes are
responsible for the oxidation of glyxoylate in man and
the rat. Having identified the enzyme one would then
be in a better position to prepare an inhibitor of the
reaction as a means of treatment in primary hyperoxaluria and possibly for oxalate renal stone from
other causes.
Recent publications from this laboratory (Gibbs,
1971, Clinical Science, 41, 38; Gibbs & Watts, 1973,
Clinical Science, 44, 227) reported the results of the
separation and identification of the enzymes in the
1OOOOO g supernatant fraction of human liver and
heart which can catalyse the oxidation. The present
work extends that investigation to the subcellular
particles of rat liver tissue. The particles were isolated
by sucrose density gradient centrifugation, either in a
zonal rotor or in tubes, by methods which will be
described. Nuclei, peroxisomes and rough endoplasmic reticulum contain enzyme systems which are
able to catalyse the oxidation of glyoxylate to oxalate
but lysosomes and mitochondria do not. Evidence for
the identity of the enzymes will be presented.
16. TUMOUR RESISTANCE IN OVUM FUSION
DERIVED TETRAPARENTAL AKR MOUSE
CHIMAERAS
R. D. BARNES
Division of Infant Development, MRC Clinical
Research Centre, Watford Road, Harrow, Middlesex
HA1 3UJ
Susceptibility to tumours is strain dependent in mice
and this probably reflects the influence of polygenic
factors. To examine this we have studied the interaction between tumour susceptibility and resistant
factors in ovum fusion derived tetraparental mouse
chimaeras. Here we have examined the ovum fusion
derived tetraparental AKRtKBA/H-T6T6 chimaeras
(c) indicates chimaera between strains). Whilst the
AKR invariably develop thymic lymphomas, the
CBA are resistant to tumours. Results in eighteen
mixed coat-colour AKRcrCBA/H-T6T6 chimaeras
suggest a marked delay and the likely inhibition of the
lymphomas.
Other workers have suggested that strain susceptibility to tumour development was apparently uninfluenced by ovum fusion and it therefore appeared
that the genetic locus controlling the localized
susceptibility of the cells destined for tumour development remained dominant. Our results question
this assumption and have suggested that localized
genotypic tumour susceptibility can be influenced by
as yet unknown factors present in the other strain.
Although the loss of one or other parental cell
population occasionally occurs in tetraparental
chimaeras, the absence of AKR cells cannot explain
the absence of tumours in certain of the AKRcrCBA
chimaeras. Chromosomal analysis in fact has shown
a marked preponderance (> 99%) of AKR lymphocytes in PHA stimulated peripheral blood cultures of
each chimera. This argues active (? CBA) suppression
of AKR lymphomas in AKR-CBA chimaeras.
17. CONTROL MECHANISMS IN INFECTIOUS
MONONUCLEOSIS
A. M. DENMAN,
B. PELTON
and B. BAZERBASHI
Division of Immunology MRC Clinical Research
Centre, Watford Road, Harrow, Middlesex HA1 3 UJ
(Introduced by A. S. TAVILL)
The pathogenesis of autoimmune disease in man has
been ascribed to a breakdown in normal control
mechanisms. In order to test this theory we have
looked for evidence for a host reaction to the abnormal
cells which are prominent in the blood of patients
with infectious mononucleosis, a self limited proliferative disease of lymphoid cells accompanied by
autoantibody production. The peripheral blood
cells of patients with this disease were separated by
velocity sedimentation, a technique which allows
such cells to be separated on the basis of differences in
volume. By this method, the atypical cells were
readily isolated from populations of lymphocytes
and macrophages.
The atypical and normal cells were characterized
with respect to their surface properties &nd immunological reactivity. In addition, the inter-reaction
between the normal and atypical cells was studied with
respect to antigen recognition by mixed lymphocyte
reactions and with respect to growth inhibition by
cytotoxicity and thymidine incorporation assays.
Reactivity against the atypical cells was noted in
many patients with infectious mononucleosis. Serum
factors were of occasional importance. In contrast,
spontaneous reactivity between surviving populations
of normal lymphocytes and malignant cells was not
observed in patients with progressive lymphomas.