Search PubMed⌕ Search

Biomedical subjects

C Turner

Publications and source records attributed to C Turner.

At least 199 records · Page 11Linked to original sources
PubMed1983

Oral essential aminoacid and ketoacid supplements in children with chronic renal failure.

The effects on growth, body composition, and metabolism of a protein-restricted diet supplemented with essential aminoacids, the calcium-ketoacids of valine, leucine, isoleucine, and phenylalanine, and the calcium-hydroxyacid of methionine, were investigated in seven growth-retarded children with chronic renal failure. During 0.4 to 1.0 years of treatment there were significant increases in growth velocity and upper arm circumference SD scores, body cell mass (intracellular water calculated as tritium space minus corrected sodium bromide space) and serum transferrin. Blood urea and urea:creatinine ratio fell in all children. Renal function assessed from plasma creatinine and 51Cr EDTA clearance did not change significantly. During treatment there was an increase in plasma calcium, high levels necessitating brief interruption of therapy in two children, and a decrease in plasma phosphate. Levels of serum parathormone fell in all children, and were correlated inversely with plasma calcium and positively with plasma phosphate. Abnormalities compared to control children in blood aminoacid and branched-chain ketoacid levels were unaffected by treatment. These results suggest that a protein-restricted diet supplemented with essential aminoacids and calcium-keto and hydroxyacids may be useful to improve linear growth and nutritional status in children with chronic renal failure, and that a reduction in hyperparathyroidism may be partly responsible for some of the beneficial effects observed.

Amino Acids, Essential↗
PubMed1983

Effect of a 2 week course of oral salbutamol on adrenomedullary function in normal subjects.

1 The adrenal medullary response to intravenous histamine infusions (0.1 and 0.4 micrograms kg-1 min-1 histamine base) was studied in six normal subjects. 2 After a 2 week course of oral salbutamol (8 mg slow release twice daily) plasma adrenaline levels, thought to reflect adrenomedullary function, were unchanged both at rest and in response to histamine infusion. 3 The present study does not support our original hypothesis that salbutamol may be capable of suppressing the adrenal medulla in normal subjects.

Administration, Oral↗
PubMed1983

The effect of posture on the sympathoadrenal response to theophylline infusion.

We studied the effect of posture on the sympathoadrenal response to intravenous theophylline in six normal subjects. On three separate occasions they received an intravenous infusion of either theophylline (6 mg/kg) while supine, theophylline (6 mg/kg) while standing or saline as placebo while standing. With the subjects standing theophylline caused tremor, a peak heart rate of 99 +/- 6 beats/min, and an elevation of plasma cyclic AMP from 9.3 +/- 0.7 to 15.1 +/- 1.7 nmol/1 (mean +/- s.e. mean). There was a small, but significant, elevation of plasma adrenaline, noradrenaline and glucose. The elevation in plasma catecholamines was insufficient to explain either the sympathomimetic effects of theophylline or the rise in plasma cyclic AMP. Theophylline had little or no effect with the subjects supine. The mean peak theophylline concentration following infusion was significantly higher with the subjects upright than when supine (18.3 c.f. 12.4 mg/l, P less than 0.025). However, adequate plasma levels of theophylline were obtained in all subjects when lying or supine. Analysis of individual data suggests that differences in plasma levels of theophylline are unlikely to account for the increased effects seen on standing. The mechanism of action of theophylline cannot be explained by increased secretion of catecholamines alone. Theophylline appears to amplify the increased sympathetic activity associated with standing and this is probably by phosphodiesterase inhibition.

Adrenal Glands↗
PubMed1983

Pure tone pitch perception and low-frequency hearing loss.

Pitch perception for pure tones was investigated in a group of listeners with low-frequency sensorineural hearing loss. Pitch judgments from each listener were compared with results from psycho-acoustic tasks which provide information on the "place" of cochlear response. The pitch measures employed were: (1) binaural pure-tone pitch matching in a listener with unilateral hearing loss, (2) octave judgments in listeners with musical ability, and (3) pitch-intensity functions in other listeners. Cochlear place of response was inferred from psychophysical tuning curves (PTC's). Two distinct types of PTC's for low-frequency probe tones were observed. Three listeners demonstrated "abnormally tuned" PTC's. For these listeners the frequencies that were most effective at masking the probe were considerably higher than the probe frequency. The three remaining listeners demonstrated "normally tuned" PTC's. Listeners with abnormally tuned PTC's were suspected of having an extremely abnormal place of response for low-frequency tones; this response pattern being located more toward the base of the cochlea than in the listeners with normally tuned PTC's. Sensitivity thresholds measured in the presence of high-pass masking noise supported this hypothesis. Small pitch-frequency irregularities were observed in many listeners, although they were not consistently related to the inferred place of response for that frequency. The individual listeners' pitch judgments failed to distinguish between two types of PTC's. In particular, listeners who demonstrated abnormally tuned PTC's did not exhibit correspondingly large pitch irregularities. These results are difficult to explain on the basis of a classical "place" theory of pitch perception.

Adult↗
PubMed1983

Secondary hyperparathyroidism and glucose intolerance in children with uremia.

Glucose metabolism was studied using the glucose clamp technique in 8 children with CRF (4 pubertal and 4 prepubertal) before and after correction of secondary hyperparathyroidism (HPD) by a regime of phosphate binders and dietary phosphate restriction. Glucose metabolic rate (M) increased by 34%, insulin response (I) increased by 32%, and insulin sensitivity (M/I) did not change. Compared to corresponding normal values, these patients were glucose-intolerant (low M) before treatment and became glucose-tolerant after treatment (normal M). They were insulin-resistant (low M/I) before treatment and remained so after treatment. The 5 uremic children without secondary HPD were treated with the same regime to prevent the secondary HPD. Their M, I, and M/I did not change after treatment. The change in I correlated closely with the change in M in all 13 patients. One pubertal patient with uremia was studied on three occasions. Initially, without secondary HPD, he had a normal M and a low M/I. When he developed secondary HPD, M decreased by 39%, I decreased by 37%, and M/I did not change. Treatment of his secondary HPD restored M and I values back to initial levels, and M/I again did not change. Treatment of secondary HPD by correction of phosphate retention led to an improvement of glucose intolerance with an increase in insulin secretion.

Adolescent↗
PubMed1982

The activation segment of procarboxypeptidase A from porcine pancreas constitutes a folded structural domain.

The controlled action of trypsin on porcine pancreatic procarboxypeptidase A releases a large activation peptide which contains the activation segment of the proenzyme. Circular dichroism studies indicate that the isolated activation peptide contains a high percentage of residues in ordered secondary structures (mainly alpha-helix). This result agrees with predictions of secondary structure carried out on the published amino acid sequence of the homologous rat proenzyme. Moreover, proton magnetic resonance spectroscopy shows that the peptide adopts a thermostable tertiary structure with characteristics typical of globular proteins. The results as a whole indicate that the activation segment of porcine pancreatic procarboxypeptidase A constitutes a folded structural domain.

Animals↗
PubMed1981

The 20,000 molecular weight variant of human growth hormone. Preparation and some physical and chemical properties.

Extracts of frozen human pituitary glands contain, in addition to normal growth hormone (hGH (Mr = 22,005), a variant of lower molecular weight (approximately 20,000) (Singh, R. N. P., Seavey, B. K. and Lewis, U. J. (1974) Endocrinol. Res. Commun. 1, 449-464). This material, designated 20K hGH, occurs in various forms with the majority present as a heterologous dimer of Mr = 20,000 hGH and hGH. The purification scheme for obtaining the variant from these fractions is described. Analysis of Mr = 20,000 hGH in the sequenator has confirmed that residues 32-46 of hGH are absent in Mr = 20,000 hGH. The structures of hGH and Mr = 20,000 hGH have been compared by 1H nuclear magnetic resonance spectroscopy, circular dichroism, spectrophotometric titration, and nitration of the tyrosine residues by tetranitromethane. The results indicate that the folding of the polypeptide chain of the two proteins is similar but not identical.

Amino Acid Sequence↗
PubMed1979

A simple micromethod for 25-hydroxyvitamin D estimation.

A quick and simple method for estimating 25-hydroxyvitamin D is described, It involves dichloromethane extraction followed by competitive protein-binding assay without chromatography. This assay can be performed on 100 microliter of serum and enables 50 samples to be estimated in one working day. The simplicity, speed, and sample size of this method make it very suitable for use in a routine clinical biochemistry laboratory. It is particularly useful when calcium disorders secondary to abnormalities in vitamin D intake and metabolism are suspected.

Animals↗
PubMed1977

Relationship between amplitude of pattern displacement and visual evoked potentials.

Thirteen subjects looked at a 7 mm2 black and white checkerboard which was displaced through 0.25, 0.50, 0.75 and full pattern displacement. One hundred and twenty eight averages were taken for each displacement and the peak to peak amplitude of the visual evoked potential was measured. This showed a linear relationship between pattern displacement and size of the evoked potential. Latency was unaffected for 0.25, 0.50 and 0.75 displacement but was significantly longer for the full pattern stimulation.

Adolescent↗
PubMed1977

The effects of nerve section and of colchicine treatment on the density of mechanosensory nerve endings in salamander skin.

We have shown that when one of the spinal nerves supplying the salamander hind limb is cut or treated with colchicine, the fields of the remaining nerves enlarge in area; whereas nerve section produces Wallerian degeneration, the colchicine-treated nerves conducted action potentials normally and their peripheral fields remained unchanged in area (Aguilar, Bisby, Cooper & Diamond, 1973). Since colchicine-treatment reduced neuronal transport, and nerve-section eliminated it, we proposed that nerve sprouting is regulated by factors normally conveyed to the endings by axoplasmic transport. 1. We have now investigated the effects of colchicine on the thresholds and distribution of individual mechanosensory endings in the skin. If reduction of neuronal transport were enough to cause the threshold to be increased to the point of total unresponsiveness, then this could be a sign of an early stage of degernation in those terminals. It could then be hypothesized that products of degeneration were providing a stimulus for adjacent nerves to sprout. 2. Quantitative physiological studies of the effects of colchicine doses known to interfere with fast axoplasmic transport, indicate that in some experiments the terminal field of the treated nerve was invaded by sprouting fibres from neighbouring axons, when its own endings were unchanged in number, distribution and sensory thresholds. In other experiments the colchicine-treated nerve endings showed an increase in threshold but their function was otherwise unchanged; a similar adjacent nerve sprouting occurred. In a final group, colchicine caused total unresponsiveness of some endings of the treated nerve. 3. When a region of skin was partially denervated by nerve section, the physiological analysis indicated that the number of new mechanosensory endings which sprouted from the remaining axons exactly matched the number lost by nerve degeneration: furthermore the distribution of the endings was normal. It therefore appears that sprouting ceased when the original density of mechanosensory endings in the skin was restored. 4. The possibility that the drug induced sprouting as a consequense of a direct action on the skin is unlikely. With [3H]colchicine, we found that the accumulation of label in the skin of the untreated limb, in which sprouting did not occur, equalled that of the opposite limb. 5. The present results lend support to the original hypothesis of Aguilar et al. (1973), which proposed that collateral sprouting of intact nerves occurs when the supply of neuronally transported factors becomes inadequate to balance out the effects of a postulated target-tissue stimulus. In the Discussion other examples of collateral nerve sprouting, such as that following adjacent denervation, are shown to be explainable by this hypothesis.

Action Potentials↗
PubMed1977

Canine kidney preservation: comparison of "intracellular", "extracellular," and high molecular weight dextran flushing solutions.

The effects of modified Collins-2 solution, adjusted lactated Ringer's solution, and a solution containing dextran 70 on kidney preservation and red blood cell (RBC) washout in dogs were evaluated. Excised kidneys were stored on ice for 24 hours and then reimplanted, at which time the contralateral kidney was removed. RBC washout from the preserved kidneys was measured at the time of initial cold flush. For 20 days after transplantation, serial measurements were made of serum creatinine, blood urea nitrogen, creatinine clearance, serum and urine osmolality, blood pH, and dog weight. No one solution cleared RBCs from the kidneys better than the other solutions. Renal function was significantly better in transplanted kidneys flushed and preserved with the Collins-2 solution than that in kidneys flushed and preserved with the other two solutions. There was generally no significant difference in function between kidneys preserved with dextran and those preserved with lactated Ringer's solution. Our findings suggest that the electrolyte composition of the flush solution may be more important than maintaining a high osmolality in the flush solution in the preservation of renal function during 24 hours' cold storage.

Animals↗