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Biomedical subjects

M D Penney

Publications and source records attributed to M D Penney.

At least 55 records · Page 3Linked to original sources
PubMed1990

The mathematical basis of multivariate risk screening: with special reference to screening for Down's syndrome associated pregnancy.

The underlying mathematical techniques behind the multivariate normal distribution are explained in principle and expanded in detail for up to three variables. The application of multivariate distributions to screening programs is described with particular reference to the calculation of risk ratios for the detection of Down's syndrome between 15 and 19 weeks of gestation.

Adolescent↗
PubMed1989

Fractional measurements of sweat osmolality in patients with cystic fibrosis.

After pilocarpine iontophoresis the change of sweat concentration during collection was studied by vapour pressure osmometry in 24 patients with cystic fibrosis and 24 healthy controls. There was a continuous but proportionate fall in sweat concentrations during the collection period. Mean (SD) initial sweat concentration in the control group was 154.4 (32.6) mmol/kg falling, after 50 microliters of sweat produced, to 92.9 (15.8) mmol/kg. In the cystic fibrosis group it was 315.9 (35.8) mmol/kg falling to 247.4 (24.9) mmol/kg. Despite different rates of fall in concentrations, separation of the two groups was maintained throughout. We conclude that there are implications for the potential improvement of the predictive value of the sweat test.

Adolescent↗
PubMed1987

Arginine vasopressin in manic-depressive psychosis.

Urinary excretions of arginine vasopressin (AVP), sodium, potassium, osmoles and creatinine were measured in three in-patients with bipolar manic-depressive psychosis on at least eight 24-hour periods in each affective phase. Mood and body weight were recorded twice daily. The excretion by each patient of sodium, water and osmoles was greater in mania than during depression. Comparison of electrolytes and osmoles suggested that the increase was due to increased intake of salt and water rather than of total diet. There was a fall of mean AVP excretion during mania, the magnitude of the fall being related to the increase of water throughput. Compared with controls, AVP excretion was high and variable. It did not show the normal relationship to urine osmolality. Days with very high AVP were not associated with any characteristic feature of the other measurements; nor were they confined to any one point in the manic-depressive cycle. AVP does not appear to play a major role in the salt and water changes characteristic of manic-depressive psychosis and we have no evidence of its having any direct relationship to mood changes. We suggest that the observed abnormalities of AVP excretion are another manifestation of the central defect of this disease.

Arginine Vasopressin↗
PubMed1987

Correlation of specific gravity and osmolality of urine in neonates and adults.

There is good correlation between the specific gravity and osmolality of urine obtained from neonates and adults, if specimens contain neither protein nor glucose. The regression equations between specific gravity and osmolality, however, differ considerably between the two age groups, maturation to the adult regression occurring within the first 5 years of life. Specifically derived regression equations should therefore be used when predicting urine osmolality from measurement of specific gravity in neonates.

Adolescent↗
PubMed1987

Total or free thyroxin as a primary test of thyroid function.

We compared measurement of free thyroxin (fT4) and total thyroxin (tT4) in serum as a primary screening test of thyroid function, based solely on biochemical diagnostic classification. The normal 95% reference intervals for fT4 and tT4 were equated by probit transformation, which allowed us directly to compare the efficiency of the biochemical classification. fT4 showed a small but distinct advantage over tT4 in the diagnosis of hyperthyroidism, but narrowing the reference interval proportionally for fT4 and tT4 to improve the sensitivity of the screening test resulted in the loss of this advantage. No clear advantage of fT4 over tT4 for the initial diagnosis of hypothyroidism was found at any reference interval.

Diagnostic Errors↗
PubMed1986

Arginine infusion blocks the action of parathyroid hormone but not arginine vasopressin on the renal tubule in man.

Six male volunteers were infused with arginine (0.5 g/kg body weight) over 30 min, after an overnight fast and water deprivation. There was a significant decrease in renal phosphate clearance (P less than 0.025) and urinary cyclic adenosine monophosphate (cAMP) output (P less than 0.025) during the 60- to 90-min period after the beginning of the infusion; both returned to the preinfusion basal levels within 150 min. The plasma levels of parathyroid hormone (PTH) were not affected by the infusion and remained unchanged during the subsequent 150 min. Plasma levels of arginine vasopressin (AVP) were also not significantly affected although plasma osmolality increased by 6-9 mmol/kg in all subjects. The infusion resulted in a diuresis, and a fall in urine osmolality but a decrease in free-water clearance; creatinine clearance was not affected. Six other subjects were given a bolus of 230 i.u. PTH intravenously, and 20 days later this was repeated during an infusion of arginine (0.5 g/kg body weight). There was a significant decrease in urinary phosphate (P less than 0.025) and cAMP excretion (P less than 0.05) when PTH was given with arginine. It is suggested that arginine blocks the action of PTH on the proximal renal tubule but not that of vasopressin on the distal nephron and collecting ducts.

Arginine↗
PubMed1983

Thirst, resetting of the osmostat, and water intoxication following encephalitis.

A young man developed pathological thirst and hyperdipsia, hyperphagia, disordered temperature regulation, a lowered threshold for aggressive behavior, apathy, impaired memory, and seizures following encephalitis. He had marked hyponatremia. Bouts of water drinking produced water intoxication and precipitated status epilepticus. Studies of water handling with measurements of plasma osmolality and arginine vasopressin (AVP) revealed a very low thirst threshold (below 242 mOsm/kg) with resetting of the osmostat to a new level (255 mOsm/kg) but normal control of plasma osmolality at that level with adequate AVP release.

Adult↗
PubMed1983

Analysis of the components of the hypercalcaemia in a 14-year-old boy following prolonged immobilisation.

A fourteen-year-old boy developed severe symptomatic hypercalcaemia following prolonged supine bed rest for major trauma. Treatment consisted initially of intravenous saline and frusemide together with oral phosphate, followed by intramuscular salmon calcitonin. Only after mobilisation and weight bearing was a sustained fall of plasma calcium to normal achieved. Plasma immunoreactive parathormone levels using both N-terminal and mixed terminal specific antisera were always undetectable and urinary cyclic AMP levels were within the normal range throughout. However, before mobilisation, the tubular reabsorption of phosphate was reduced and that of calcium was increased thus indirectly suggesting increased parathormone activity. The hypercalcaemia was due to a combination of increased calcium release from bone and increased tubular reabsorption. We suggest that a factor other than parathormone is responsible for altered tubular handling of calcium and phosphate which develop following prolonged immobilisation in these patients.

Adolescent↗
PubMed1981

The relationship between plasma lithium and the renal responsiveness to arginine vasopressin in man.

1. Arginine vasopressin (AVP) was measured in morning samples of urine from 58 patients treated with lithium for unipolar or bipolar affective disorders and from 25 healthy control subjects. 2. The AVP excretion rate was increased in the patients treated with lithium and was related to the plasma lithium concentration. The increase in AVP excretion is the result of a renal resistance to AVP so that what has been observed is an effect of lithium in vivo related to its plasma level over the therapeutic range.

Arginine Vasopressin↗
PubMed1979

Resetting of osmoreceptor response as cause of hyponatraemia in acute idiopathic polyneuritis.

In a patient with hyponatraemia associated with acute idiopathic polyneuritis plasma concentrations of antidiuretic hormone increased when hypertonic saline was infused intravenously, and urine osmolality rose concomitantly. A water load was excreted normally, while the plasma remained extremely hypo-osmolal. It is concluded that osmoregulation was functioning normally but was set abnormally low, possibly owing to a disturbance of the peripheral volume receptors.

Acute Disease↗