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Biomedical subjects

D C Watts

Publications and source records attributed to D C Watts.

At least 127 records · Page 7Linked to original sources
PubMed1984

Human 'creatine kinase conversion factor' identified as a carboxypeptidase.

The effect of partially purified 'creatine kinase conversion factor' on rabbit muscle creatine kinase is shown to be that of a carboxypeptidase, removing the C-terminal lysine residue from both subunits. These changes fully explain the three-banded electrophoretic patterns of the partially and the fully modified rabbit and human enzymes. The factor also produces a similar electrophoretic pattern with haemoglobin A; comparison with the effects of carboxypeptidases A and B permits the inference that the C-terminal residues of both alpha- and beta-subunits are removed. Small synthetic peptides are poor or non-substrates. A low activity with hippuryl-L-lysine may be due to contamination of the preparation with carboxypeptidase N. The possibility has been excluded that the action of conversion factor on creatine kinase involves modification of the protein thiol groups. Mr, substrate-specificity, pH-activity profile and the effects of metal ions distinguish creatine kinase conversion factor from carboxypeptidases A, B and N. On the basis of this evidence it is proposed to give the conversion factor the provisional name of carboxypeptidase K.

Animals↗
PubMed1984

Pyruvate kinase in fetal plasma and amniotic fluid unsuccessful for the prenatal diagnosis of Duchenne muscular dystrophy.

A specific spectrophotometric assay of muscle-pyruvate kinase (M-PK) was used to measure the activity of this isozyme in fetal muscle, fetal plasma and amniotic fluid at about 17-24 wk of gestational age to assess its predictive value for the prenatal diagnosis of Duchenne muscular dystrophy (DMD). Fetal muscle obtained after termination was found to contain a high M-PK specific activity. No significant activity was detected in amniotic fluid from normal or at-risk fetuses. Pure fetal blood was obtained in utero by fetoscopy; significant plasma levels of M-PK activity were measured in a series of control samples, but at-risk fetal plasma contained no higher levels. We conclude that M-PK is of no use for the prenatal diagnosis of DMD.

Amniotic Fluid↗
PubMed1984

Anion activation of monkey muscle creatine kinase.

Creatine kinase from rhesus monkey skeletal muscle is activated by acetate and other short chain fatty acids. Activation is associated with lower Km and higher Vmax values at less than saturating substrate concentrations but does not occur when both substrates are saturating. No co-operativity between subunits is evident in the activation process. It appears that acetate promotes the mutual enhancement by substrates in their binding by inducing the optimum enzyme conformation normally associated with substrate saturation. Conservation of this activation effect through the evolution of the phosphagen kinases implies that it may well be of physiological significance.

Acetates↗
PubMed1984

The diagnostic value of plasma myoglobin levels in the adult and fetus at-risk for Duchenne muscular dystrophy.

In boys with Duchenne muscular dystrophy (DMD) plasma myoglobin levels remained approximately constant with age while creatine kinase (CK) activity progressively decreased. For carrier detection, plasma myoglobin level was found to be less reliable than CK activity. The myoglobin level was raised only in some of those subjects who also showed a raised CK activity and was normal in those with a normal CK activity. The myoglobin level in fetal muscle at 18-22 weeks gestational age was found to be low compared with adult skeletal muscle levels and, consequently, the myoglobin level in fetal plasma and in amniotic fluid was found to be negligible. It is concluded that measurement of myoglobin offers no advantage over CK for the investigation of any aspect of DMD.

Adolescent↗
PubMed1984

Developmental changes in lactate dehydrogenase and aldolase activity of the A2G-adr mouse with abnormal muscle function: further comparison with the 129Re-dy mutant.

Lactate dehydrogenase and aldolase activity were reduced in lateral gastrocnemius muscle from two mouse mutants, A2G-adr and 129Re-dy, with abnormal muscle function. The activities of both of these enzymes were significantly reduced in the lateral gastrocnemius muscle from the A2G-adr mice at ages varying from 2 weeks to 32 weeks, whereas the activities in the soleus, heart, liver, and brain were the same as in the control animals. The lactate dehydrogenase isoenzymes in the lateral gastrocnemius and soleus muscles from the A2G mice were quantified, and although those of the soleus were comparable in mutant and control muscle, the lateral gastrocnemius from the adr mutant had reduced activity of LDH 5 and increased activities of the other four isoenzymes. The findings suggest that the adr mutation is expressed in the white (Type II) muscle fibres and not in the red (Type I) fibres or in any of the organs studied. It is suggested that the initiation of differentiation into Type II fibres from the embryonic form is absent or delayed in the A2G mutant. The reduced activities of lactate dehydrogenase and aldolase in 129Re-dy muscle confirm the findings of other workers.

Aging↗
PubMed1984

A visible light-activated direct bonding material: an in vitro comparative study.

This paper reports on the mechanical performance of a visible light cured orthodontic bonding agent. It is concluded that this type of material is as effective as other commercial adhesives and offers certain advantages in handling. Resistance to 4 kg of force in the shear/peel mode within the first 5 minutes of its application is expected from a clinically usable adhesive.

Adhesiveness↗
PubMed1984

Biological features of the new A2G--adr mouse mutant with abnormal muscle function.

A new mouse mutant (A2G-adr) with abnormal muscle function is described and has been compared with the 129 Re dystrophic mouse. The mutation, which is due to an autosomal gene defect, results in myotonic-like spasms, progressive muscle weakness and a reduced lifespan. Affected animals were consistently lighter than normal littermates; comparison of organ weights and organ-to-bodyweight ratios indicated a slower growth rate in the mutants.

Animals↗
PubMed1983

Tetrathionate-blocked creatine kinase as a substrate for human plasma 'creatine kinase conversion factor'.

'Creatine kinase conversion factor' has been partially purified from whole plasma. The preparation has the ability to convert slowly migrating, native CK-MM into a faster electrophoretic form through a form of intermediate mobility. These changes are accompanied by a loss in CK activity. The rates of both electrophoretic conversion and loss of enzyme activity are reduced or prevented by the presence of 2-mercaptoethanol, EDTA, or by formation of the creatine-MgADP-nitrate dead-end complex. When the thiol group essential for enzyme activity found at the CK active site is first blocked by treatment with potassium tetrathionate, full activity may be retained under conditions that fully convert CK to the faster electrophoretic forms. The conversion factor activity was not inhibited by a pre-incubation with the protease inhibitor, PMSF and the converted form of CK showed no evidence of proteolytic cleavage. The molecular basis of the chemical alteration caused by the conversion is discussed.

Creatine Kinase↗
PubMed1983

Equilibrium density gradient analysis of erythrocytes from normal humans and patients with Duchenne muscular dystrophy.

Human red blood cells were fractionated by centrifugation in a continuous Ficoll/Triosil density gradient and the density distribution was determined by scanning the gradient in situ. Variation of some of the conditions used showed that erythrocyte mean cell density is very sensitive to the type of anticoagulant and washing system employed. A population study of mean cell density showed no significant difference between males and females and no correlation with age. Patients with Duchenne muscular dystrophy showed no significant difference from normals in mean cell density but an almost sevenfold increase in the variance. This may explain the disparate findings of different workers.

Adolescent↗
PubMed1983

Plasma creatine kinase and myoglobin levels, before and after abortion, in human fetuses at risk for Duchenne muscular dystrophy.

Plasma levels of creatine kinase (CK) were measured in 14 abortuses, nine of which were at risk for Duchenne muscular dystrophy (DMD). The plasma CK level was found to be increased in all abortuses, compared with the value obtained by fetoscopy before the termination. The causes of the increase in CK level were found to be 1) method of termination, 2) physical state of the abortus at delivery, 3) delay between delivery of the abortus and taking the blood sample, and 4) site of blood sampling. It is concluded that even under optimum conditions of termination the plasma creatine kinase level of the abortus is significantly raised above the true level; hence, this measurement is not reliable as a guide to the genetic status of the fetus. Cardiac leakage was the main source of the raised plasma CK level in the abortus and this was corroborated by measurement of myoglobin levels.

Abortion, Therapeutic↗