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Biomedical subjects

J M Davison

Publications and source records attributed to J M Davison.

At least 109 records · Page 6Linked to original sources
PubMed1982

Response of the renin-aldosterone system and antidiuretic hormone to oral water loading and hypertonic saline infusion during and after pregnancy.

Amongst the man physiological changes in human pregnancy are the sustained stimulation of the renin-angiotensin system and a decreases in plasma osmolality (Posm). In this study the effect osmolar and water loading on the renin-angiotensin system and arginine vasopressin (AVP) secretion has been tested in seven women during the third trimester and again 8-10 weeks after delivery. Pregnant women had markedly increased plasma renin substrate (PRS), plasma renin activity (PRA) and plasma renin concentration (PRC) values as well as aldosterone levels when compared to their post-partum values. Osmolar loading with intravenous infusion of hypertonic saline resulted in a decrease in PRA and aldosterone levels both during and after pregnancy but even at the end of the infusion the pregnant women still had values greater than the pre-infusion levels obtained post-partum. Surprisingly, oral water loading also significantly decreased PRA and aldosterone levels in pregnancy, possibly related to the redistribution of extracellular fluid centrally when the pregnant women were in left lateral recumbency. Despite the decreased basal Posm of pregnancy, urinary AVP increased and decreased appropriately during osmolar and water loading. Exact characterisation of the resetting of the threshold for AVP secretion in pregnancy awaits the development of a reliable radioimmunoassay for the determination of AVP in human pregnancy plasma.

Aldosterone↗
PubMed1981

Serial changes in 24 hour creatinine clearance during normal menstrual cycles and the first trimester of pregnancy.

Serial changes in 24-hour creatinine clearance were determined in 11 women during several menstrual cycles before conception, the conceptional cycle and the first trimester of pregnancy. During the menstrual cycle, a 20 per cent mean increase occurred between the week of menstruation and the late luteal phase. Following conception, this increase continued such that a 45 per cent mean increase was evident by the ninth week of gestation. In two women who aborted spontaneously, the change in 24-hour creatinine clearance in early pregnancy was not as great nor as sustained, this feature being apparent at least three weeks before any clinical abnormality. Possible reasons for the changes in glomerular filtration rate in early pregnancy and its clinical implications are discussed.

Abortion, Spontaneous↗
PubMed1981

Non-postural serial changes in renal function during the third trimester of normal human pregnancy.

Seventeen healthy women were investigated near the beginning and again near the end of the third trimester of their normal pregnancies. Infusion studies were performed in the left lateral position. There was a highly significant decrease in effective renal plasma flow but not in glomerular filtration rate, measured as inulin clearance. Plasma creatinine concentration increased significantly, but the renal handling of creatinine was unchanged; simultaneous 24-hour creatinine clearance showed a tendency to decrease. Serum urate concentration also increased significantly, apparently due to an increase in net tubular reabsorption of urate.

Adult↗
PubMed1981

Plasma osmolality and urinary concentration and dilution during and after pregnancy: evidence that lateral recumbency inhibits maximal urinary concentrating ability.

In nine women studied serially before conception and through the first trimester, plasma osmolality (Posm) started to decline with the first missed menstrual period, was significantly decreased by the fifth week of pregnancy and was 10 mosmol/kg lower than preconception values by the tenth week, changing little thereafter. Changes in plasma sodium (and its attendant anion) accounted for the majority of the decrement. In separate studies, urinary concentration and dilution, assessed by water deprivation and loading, studied in nine women during their last trimester and again 10-12 weeks post partum. Basal Posm was 9 mosmol/kg lower in the last trimester than post partum (p less than 0.001) but the results of concentration and dilution tests were similar during and after pregnancy. Basal urinary arginine vasopressin (AVP) excretion was similar during and after pregnancy and water loading suppressed AVP excretion in both pregnant and postpartum women. An unanticipated observation was that lateral recumbency interfered with urinary concentration tests in both pregnant and postpartum women. The results demonstrate that the decrement in Posm during pregnancy is an early event. The data (urinary AVP excretion, its suppression by water loading and normal concentration and dilution despite a lower plasma tonicity) also suggest that human pregnancy is accompanied by a resetting of the threshold for vasopressin secretion to a lower Posm.

Blood↗
PubMed1980

24-hour creatinine clearance during the third trimester of normal pregnancy.

Serial changes in 24-hour creatinine clearance were determined in 10 healthy women during late pregnancy and after the puerperium. A decrease occurred in all subjects during the six weeks preceding delivery, so that mean values for the last three weeks of pregnancy did not differ from the non-pregnant mean. Possible reasons for this phenomenon and its clinical implications are discussed.

Adult↗
PubMed1980

Changes in renal haemodynamics and kidney weight during pregnancy in the unanaesthetized rat.

1. Glomerular filtration rate ([(3)H]inulin clearance) and renal plasma flow (PAH clearance) were measured in unanaesthetized Sprague-Dawley rats early in pregnancy (8-10 days) and near term (18-20 days); the results were compared with studies in virgin litter-mates. Evidence of kidney growth was sought by analysing renal dry weights as well as [(14)C]choline incorporation into membrane phospholipids of renal cortical slices.2. Inulin clearances were similar early in pregnancy (pregnant 2.36 +/- 0.12 (S.E. of mean) vs. non-pregnant 2.33 +/- 0.10 ml./min) but near term values were significantly increased (pregnant 2.80 +/- 0.05 vs. non-pregnant 2.39 +/- 0.05 ml./min, P < 0.001). PAH clearances were similar in pregnant and litter-mate control animals at each stage of the study.3. Total renal weight increased significantly both early and late in pregnancy, but renal dry weights as well as [(14)C]choline incorporation were similar in pregnant and non-pregnant animals both at 8-10 days gestation and near term.4. Data confirm our previous findings on renal haemodynamics in anaesthetized rats. Observations that renal dry weight and [(14)C]choline incorporation into phospholipids are similar in litter-mate pregnant and control animals suggests that renal enlargement in this species is due to increments in water content and not to accelerated growth.

Animals↗
PubMed1977

Relation of immediate post-transplant renal function to long-term function in cadaver kidney recipients.

Renal function studies 12 to 41 months after transplantation have been performed on seven cadaver renal allograft recipients who demonstrated immediate primary function after transplant (group A) and seven similar recipients who had delayed primary function (group B). The groups were matched as closely as possible for major physical characteristics and their postoperative management; in particular, only one patient had a post-transplant renal biopsy. Glomerular filtration rate was determined by 24-hr creatinine clearance, endogenous creatinine clearance, and inulin clearance was usually lower in those patients having delayed primary function and they excreted more glucose per 24 hr and reabsorbed a smaller proportion of the filtered glucose load under infusion conditions. These results are discussed in relation to the effect of immediate and delayed primary function on the long-term prognosis of such patients.

Adult↗
PubMed1977

The effect of normal pregnancy upon the renal handling of uric acid.

Twenty-four women were investigated serially during and after normal pregnancy. Plasma uric acid concentration appeared to be inversely related to uric acid clearance under infusion conditions, and comparison with simultaneous inulin clearance suggested an alteration in renal function resulting in increased 'net tubular reabsorption' of uric acid as pregnancy progressed. No difference was detected between primigravidae and multigravidae. The implications of these changes are discussed with reference to the renal handling of uric in pre-eclampsia.

Adult↗
PubMed1977

The excretion of gamma-glutamyl transferase in pregnancy.

A cross-sectional study of gamma-glutamyl transferase (gamma-GT) excretion in 316 healthy pregnant women showed the enzyme excretion (mU per mmol creatinine) was significantly higher than that of a non-pregnant control group. The increase was apparent before the end of the first trimester and continued therafter. These changes may be indicative of hypertrophy and/or hyperplasia of the nephron and be part of the overall renal adaptation to normal pregnancy. Even higher levels were recorded in three obstetric patients in whom renal complications were to be expected and this may indicate a specific type of renal damage.

Creatinine↗