Biomedical subjects
C Heron
Publications and source records attributed to C Heron.
How many tests are required in the diagnosis of palpable breast abnormalities?
Palpable breast nodules in 143 patients attending our primary diagnosis breast clinics were assessed by clinical examination, needle cytology, mammography, ultrasonography and magnetic resonance imaging (MRI). The diagnostic accuracy of all test combinations was compared with the final diagnosis of malignant or benign disease. Two-test combinations increased the sensitivity of diagnosis over that of the individual tests to between 93% and 100% except for MRI/mammography and MRI/cytology. The combinations of three or more tests increased the sensitivity further, but at the expense of an increased false-positive rate. MRI does not appear to have an important role in the primary diagnosis of breast cancer. Mammography is necessary because of the possibility of occult or multifocal disease. Clinical examination was associated with a high false-positive rate. The combination of cytology and ultrasound was best at correctly diagnosing malignancy, but in this series only 42% of patients underwent ultrasound examination. The role of breast ultrasound together with needle aspiration cytology for the diagnosis of malignancy in palpable breast nodules deserves further evaluation.
[Mushroom worker's lung. 1 case].
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An analysis of the polypeptide composition of bovine heart mitochondrial NADH-ubiquinone oxidoreductase by two-dimensional polyacrylamide-gel electrophoresis.
Purified preparations of Complex I (NADH-ubiquinone oxidoreductase) from bovine heart mitochondria may be resolved into 26 polypeptides by two-dimensional analysis combining isoelectric focusing and polyacrylamide-gel electrophoresis in sodium dodecyl sulphate. Similar analyses of the fragments obtained from chaotropic resolution of the enzyme show that each of these fragments contains a distinct and non-overlapping set of polypeptides. Evidence that the polypeptides seen in the intact enzyme are true constituents comes from analyses of immunoprecipitates obtained by allowing Complex I or solubilized submitochondrial particles to react with antisera directed against the whole enzyme and a subfragment of the enzyme.
The effects of lipid phase transitions on the interaction of mitochondrial NADH--ubiquinone oxidoreductase with ubiquinol--cytochrome c oxidoreductase.
1. The endogenous phosphatidylcholine and phosphatidylethanolamine of Complexes I and III from bovine heart mitochondria may be completely replaced with 1,2-ditetradecanoyl-sn-glycero-3-phosphocholine with at least partial retention of activity. 2. The lipid-replaced enzymes associate in 1:1 molar ratio to give a Complex I--III unit catalysing NADH-cytochrome c oxidoreductase activity. 3. On increasing the concentration of ubiquinone-10 and the synthetic phospholipid, the lipid-replaced Complexes appear to operate independently of each other as in the natural membrane. Thus the lipid-replaced enzymes associate in exactly the same ways as the enzymes containing natural phospholipids. 4. Arrhenius plots of NADH--cytochrome c oxidoreductase activity reconstituted from lipid-replaced Complexes I and III exhibit changes in slope at 24 degrees C. When the concentrations of phospholipid and ubiquinone-10 are increased, the Arrhenius plots show discontinuities at 24 degrees C as well as changes in slope. 5. The kinetics of cytochrome b reduction by NADH were measured in mixtures containing 2 mol of Complex III/mol of Complex I. When the enzymes contained natural phospholipids. the reduction kinetics were biphasic. When the enzymes had been supplemented with further phospholipid and ubiquinone-10 the kinetics were monophasic. When lipid-replaced enzymes were supplemented with 1,2-ditetradecanoyl-sn-glycero-3-phosphocholine and ubiquinone-10, reduction of cytochrome b was monophasic above the phase-transition temperature of the lipid but biphasic below it. 6. These findings are interpreted in terms of the model for the interaction of Complexes in the natural membrane proposed by Heron, Ragan & Trum-power [(1978) Biochem. J. 174, 791--800].
The interaction between mitochondrial NADH-ubiquinone oxidoreductase and ubiquinol-cytochrome c oxidoreductase. Evidence for stoicheiometric association.
1. The NADH-ubiquinone oxidoreductase complex (Complex I) and the ubiquinol-cytochrome c oxidoreductase complex (Complex III) combine in a 1:1 molar ratio to give NADH-cytochrome c oxidoreductase (Complex I-Complex III). 2. Experiments on the inhibition of the NADH-cytochrome c oxidoreductase activity of mixtures of Complexes I and III by rotenone and antimycin indicate that electron transfer between a unit of Complex I-Complex III and extra molecules of Complexes I or III does not contribute to the overall rate of cytochrome c reduction. 3. The reduction by NADH of the cytochrome b of mixtures of Complexes I and III is biphasic. The extents of the fast and slow phases of reduction are determined by the proportion of the total Complex III specifically associated with Complex I. 4. Activation-energy measurements suggest that the structural features of the Complex I-Complex III unit promote oxidoreduction of endogenous ubiquinone-10.
The interaction between mitochondrial NADH-ubiquinone oxidoreductase and ubiquinol-cytochrome c oxidoreductase. Restoration of ubiquinone-pool behaviour.
1. In the inner mitochondrial membrane, dehydrogenases and cytochromes appear to act independently of each other, and electron transport has been proposed to occur through a mobile pool of ubiquinone-10 molecules [Kröger & Klingenberg (1973) Eur. J. Biochem. 34, 358--368]. 2. Such behaviour can be restored to the interaction between purified Complex I and Complex III by addition of phospholipid and ubiquinone-10 to a concentrated mixture of the Complexes before dilution. 3. A model is proposed for the interaction of Complex I with Complex III in the natural membrane that emphasizes relative mobility of the Complexes rather than ubiquinone-10. Electron transfer occurs only through stoicheiometric Complex I-Complex III units, which, however, are formed and re-formed at rates higher than the rate of electron transfer.
The phospholipid annulus of mitochondrial NADH-ubiquinone reductase: a dual phospholipid requirement for enzyme activity.
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Impaired acquisition of novel locomotor tasks in aged and norepinephrine-depleted F344 rats.
Performance of rats on a motor learning paradigm that has been demonstrated to be dependent upon cerebellar norepinephrine (NE) was studied in 20-month-old F344 rats. The behavioral task is identical to that described by Watson and McElligott: Rats are trained on a runway consisting of aluminum pegs arranged in a regular pattern. Rats receive a water reward at either end of the runway. Subsequent to training, rats are tested for running times on a runway with irregularly spaced rods. The ability of rats to improve their performance (decrease their running times) on this novel motor task is diminished in young rats that have received 6-hydroxydopamine lesions. Rats at 20 months of age are known to have deficits in cerebellar noradrenergic transmission; thus, the hypothesis to be tested was to determine if aged rats demonstrated performance deficits similar to young rats depleted of central stores of NE. The rate of acquisition of the task was determined by the decrease in running times with successive days of training. The ability of 20-month-old F344 rats to acquire proficiency on the novel motor task was impaired and the rate of acquisition of the novel motor task was not different from the young 6-hydroxydopamine-lesioned rats. In an attempt to distinguish between alterations in motor coordination and motor learning, additional tests of psychomotor performance were assessed for all groups of rats. These tests included a walking on 2.5- and 5-cm rods, speed of running on the motor task, and number and types of mistakes made on the motor learning task.(ABSTRACT TRUNCATED AT 250 WORDS)