Biomedical subjects
D B Morgan
Publications and source records attributed to D B Morgan.
Plasma digoxin: an over-used test?
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The contribution of dietary vitamin D and sunlight to the plasma 25-hydroxyvitamin D in the elderly.
Total plasma 25-hydroxyvitamin D (25-OHD) and its components 25-OHD2 and 25-OHD3 were measured during the winter in young and elderly healthy persons and in elderly women patients in a long-stay mental hospital. The long-stay patients had no exposure to sunlight or other ultraviolet irradiation, but their diet alone maintained an average total 25-OHD level of 16 nmol/l (range, 10.3-26.5 nmol/l), with most values within the ranges observed in the other two groups, although the average value was lower. The plasma 25-OHD2 which is derived exclusively from vitamin D2 in the diet was similar in all three groups and the vitamin D intake was also similar in the two elderly groups. 25-OHD3 is obtained from the diet as well as from the skin and in the elderly patients the diet alone maintained equal concentrations of 25-OHD2 and 25-OHD3. These findings taken together suggest that the diet accounted for 70 per cent of the total 25-OHD in the active elderly in winter compared with 50 per cent in the young subjects. In all our subjects, young or old, the diet was the major source of vitamin D.
Relation between intake and plasma concentration of vitamin C in elderly women.
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The effect of pregnancy and pregnancy induced hypertension on active sodium transport in the erythrocyte.
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Sulphinpyrazone and renal function following myocardial infarction.
The effects of sulphinpyrazone 800 mg daily on renal excretory function were studied in a double-blind placebo-controlled randomised trial of incremental and full doses of the drug in 28 patients with plasma urea concentration less than 10 mmol/l in the period 2-28 days following uncomplicated acute myocardial infarction. Sulphinpyrazone in both dosage regimens increased uric acid excretion and lowered plasma urate concentration. There was no evidence that the drug reduced glomerular filtration rate or damaged the renal tubules. These results suggest that sulphinpyrazone in the doses used in this study is not contraindicated in patients early after acute myocardial infarction even though they may have a moderate rise in the blood urea.
Selection, presentation, and interpretation of biochemical data in renal failure.
There is more information in biochemical laboratory data than is generally appreciated; much can be gained by display and manipulation of data. Patients with renal disease are often under regular clinic review so that many will have sets of sequential data. Display of these data, which requires a computer if it is to be routine, will reveal patterns and define trends which could be otherwise missed or inadequately assessed. Trends are most useful if they are recti-linear and several transforms of the data should be tried to achieve this aim; for plasma creatinine the usual transforms are the reciprocal and the logarithm. The choice of transform is based on usefulness and not on any prior assumption about the underlying pathophysiology. More frequently, however, all that is available is a single measurement, typically the simple plasma creatinine rather than the more complex creatinine clearance. The problem is to balance simplicity against precision and decide what the needs and the reliability of the interpretations of the data are. There is an advantage in manipulation of the data and comparison with standard data; and the possibilities were discussed for the plasma creatinine; these tables are ideally suited to a laboratory computer. It was suggested that complex calculations so easily achieved with a computer should be avoided unless they bring real gains, since complexity tends to hide the basic principles involved.
Erythrocyte sodium and potassium in patients with hypokalaemia.
1. The erythrocyte content of sodium and of potassium were measured in 231 unselected patients with hypokalaemia, and together with net ouabain-sensitive sodium efflux in patients with severe hypokalaemia, before (20 patients) and during potassium repletion (14 patients). 2. The erythrocytes of the patients with hypokalaemia compared with control subjects had on average an increase in sodium content, a decrease in potassium content and a reduction in the rate constant of ouabain-sensitive sodium efflux. All three changes had a similar curvilinear relation to the concentration of potassium in plasma with relatively little change in the measured variable unless the plasma potassium was very low. 3. There was a similar curvilinear relation between the final sodium and potassium content of normal erythrocytes and the potassium concentration of the medium in which they were incubated for 48 h in vitro. 4. These results suggest that the changes in the sodium and potassium content of erythrocytes in hypokalaemia are due to a direct inhibiting effect of the hypokalaemia on the activity of the sodium pump. 5. In many patients with hypokalaemia of moderate degree the increase in erythrocyte sodium content was less than expected from the effect in vitro of a low extracellular potassium concentration. This finding suggests that a compensatory change, presumably an increase in the number of sodium pumps, is a common event even in moderate hypokalaemia.
Effect of hypokalaemia on the ouabain-sensitive sodium transport and the ouabain-binding capacity in human erythrocytes.
1. The sodium content, the ouabain-sensitive sodium efflux and efflux rate constant and the ouabain-binding capacity were measured in the erythrocytes of 53 patients with hypokalaemia and in 37 healthy controls. The sodium content alone was measured in a further 57 patients with hypokalaemia. 2. In the patients with hypokalaemia there was an increase in the average sodium content of the erythrocytes, which was entirely due to a reduction in the ouabain-sensitive efflux rate constant. 3. The ratio of the ouabain-sensitive efflux rate constant to the number of sodium pumps was decreased in the patients with hypokalaemia, and was directly related to the plasma potassium. 4. Many patients with moderate hypokalaemia had normal erythrocyte sodium and potassium contents and normal ouabain-sensitive efflux rate constant. These patients had an increased number of sodium pumps, which compensated for the inhibitory effect of hypokalaemia on each sodium pump. 5. This increase in the number of sodium pumps was common even in patients who had probably had hypokalaemia for less than 2 weeks. This finding suggests that there are latent sodium pumps within the circulating erythrocytes.
Changes in the number and activity of sodium pumps in erythrocytes from patients with hyperthyroidism.
1. The sodium content, the rate and rate constant of ouabain-sensitive sodium efflux and the number of sodium pumps (indicated by the ouabain-binding capacity) were measured in erythrocytes from patients with hyperthyroidism and compared with values obtained in euthyroid patients and healthy control subjects. Erythrocyte zinc content was measured as a simple estimate of the content of carbonic anhydrase. 2. In the hyperthyroid patients, erythrocyte sodium content was increased, whereas the rate and rate constant of ouabain-sensitive sodium efflux, the ouabain-binding capacity and erythrocyte zinc content were all decreased. 3. The sodium pumps in hyperthyroidism had the same affinity for ouabain and the same rate constant per pump as those in healthy controls. 4. The decrease in the efflux rate constant could be entirely accounted for by the decrease in the number of sodium pumps. 5. Although the sodium efflux was decreased in the hyperthyroid patients, the change was less than expected for the decrease in the efflux rate constant. This suggests that there is an increase in the ground permeability of the erythrocyte membrane in hyperthyroidism. 6. In the hyperthyroid patients the number of sodium pumps and erythrocyte zinc content were inversely related to the plasma levels of thyroxine and tri-iodothyronine, but more closely to the latter. 7. These results suggest that the thyroid hormones may influence the erythrocyte's content of a range of proteins which happens to include the sodium pump.
Estimation of non-fat body tissues from measurements of skinfold thickness, total body potassium and total body nitrogen.
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The impact of ageing--present and future.
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Management of geriatric incontinence in nursing homes.
A behavioral management system designed to reduce urinary incontinence was evaluated in two nursing homes with a pretest-posttest control group design with repeated measures. The primary components of the system were prompting and contingent social approval/disapproval which required approximately 2.5 minutes per patient per hour to administer. The frequency of correct toileting for experimental subjects increased by approximately 45%. The experimental groups were significantly different from the control groups on both incontinence and correct toileting measures. The results are discussed in view of the management issues inherent in nursing home settings.
Plasma vitamin C concentrations in patients in a psychiatric hospital.
Plasma vitamin C was measured in 885 patients in a psychiatric hospital and in 110 healthy controls. The average value was lower in the patients (0.51 mg/100 ml) than in the controls (0.87 mg/100 ml). Length of stay in hospital had little effect on plasma vitamin C in the patients, but the values were marginally lower in males, females on iron therapy and in those with senile dementia. In the patients, many of whom had been offered a similar diet for several years, age was not associated with a change in plasma vitamin C and this suggests that changes in vitamin C with age that have been reported reflect differences in intake. Few patients had values as low as those found in clinical scurvy (less than 0.1 mg/100 ml), but many (32 per cent) had concentrations below the threshold (0.35 mg/100 ml) at which some detrimental effects on health have been reported.
The relation between the membrane cholesterol content and anion exchange in the erythrocytes of patients with cholestasis.
The anion transport system was assessed in erythrocytes from fifteen patients with cholestasis and fifteen healthy subjects as the exchange of intracellular chloride for extracellular pyruvate. The rate constant of pyruvate-chloride exchange was significantly reduced in the patients compared with the controls. The membranes of the erythrocytes of the patients compared with the controls contained more cholesterol and phospholipid and had a higher molar ratio of cholesterol to phospholipid. The rate constant of pyruvate-chloride exchange was directly related to the cholesterol to phospholipid ratio of the membranes in the patients. In vitro loading with cholesterol of erythrocytes from healthy subjects reduced the rate constant of pyruvate-chloride exchange by an amount which was related to the increase in the cholesterol to phospholipid ratio of the cell membrane. The inhibitory effect of cholesterol loading on anion transport was similar to its previously reported inhibitory effect on the furosemide-sensitive sodium transport system in the erythrocytes.
The heterogeneity of essential hypertension. Relation between lithium efflux and sodium content of erythrocytes and a family history of hypertension.
The lithium efflux and sodium content of erythrocytes were measured in 75 patients with untreated essential hypertension. The average values of both were higher than those of normotensive control subjects. Values above the range in the controls were found only in patients with a family history of hypertension, and in these the frequency of raised lithium efflux was 76% and of raised sodium content was 36%. Measurement of lithium efflux and sodium content, together with the family history, allows patients with essential hypertension to be categorised into four groups.
Acute transient hypokalaemia: new interpretation of a common event.
An investigation of 70 unselected hospital inpatients with a plasma potassium of 2.8 mmol/l or less showed that the group contained an excess of women and of the elderly. In nearly half the patients no attempt had been made to correct the hypokalaemia with potassium supplements. 26 of the patients had been recently admitted with an acute medical condition, including stroke and myocardial infarction. Those in this group whose plasma potassium was measured again showed that plasma potassium rose to near or within the normal range in about 4 days, whether or not oral potassium supplements were given. These results suggest that in many cases the hypokalaemia of acutely admitted medical patients, including patients after myocardial infarction, is a spontaneously reversible non-specific event. A likely explanation is that it is due to a transient shift of potassium into the cells.