Biomedical subjects
Publications and source records attributed to J S Slater.
A method for flunixin detection in equine serum extracts involving thin layer chromatography, spraying the chromatogram with alkaline sodium hypochlorite solution and heating with a detection limit of 50 ng ml-1 is described.
The relation of leisure time and occupational physical activity to the risk of death from ischemic heart disease was investigated in a cohort of 15,088 persons aged 30-59 years who had no history of cardiovascular disease or other condition which hindered physical activity. Two population samples were randomly chosen from eastern Finland. During a six-year follow-up, persons who were sedentary in leisure time (relative risk = 1.3, 95% confidence interval (CI) = 1.1-1.6) or at work (relative risk = 1.3, 95% CI = 1.1-1.6) had an excess risk of ischemic heart disease death when adjusted for age, health status, family history, and body mass index in multivariate logistic models. Adjustment for years of education, social network participation, cigarette consumption, serum cholesterol level, and blood pressure level weakened the residual association of low leisure time physical activity with the risk of ischemic heart disease death (relative risk = 1.2, 95% CI = 1.0-1.5), whereas the association for low occupational physical activity remained unchanged. The lack of leisure time physical activity and a sedentary occupation are associated with an increased risk of ischemic heart disease death, and the excess risk due to lack of leisure time physical activity is, in part, accounted for by other ischemic heart disease risk factors.
Within-day variations in the concentrations of glucose, fructose, lactate, urea, insulin, thyroxine, corticosteroids and individual amino acids in maternal and fetal plasma from 12 Scottish Blackface ewes between 125 and 134 days of pregnancy were examined during a period of six days. In six ewes maintained on an adequate diet given at hourly intervals the concentrations of almost all the plasma constituents remained within the limits of analytical error during the period of observation. The advantages of this method of feeding in attaining the 'steady state' commonly required for kinetic experiments using isotopically labelled metabolites are discussed. In six ewes given similar rations but fed once daily substantial postprandial changes occurred in both maternal and fetal plasma composition and persisted for at least 15 hours after feeding. In maternal plasma the concentrations of glucose, lactate, insulin, thyroxine, alanine, glutamic acid, glutamine and asparagine increased after feeding and the concentrations of urea, glycine, taurine, citrulline and the essential amino acids decreased. Changes in fetal plasma were generally similar but some differences from maternal plasma, mainly in the timing and duration of postprandial changes, suggested that fetal plasma composition was primarily affected by factors within the fetus. Only six amino acids gave significant correlations between their maternal and fetal plasma concentrations. It is suggested that maternal effects on fetal amino acid metabolism and possibly protein turnover are imposed indirectly through an autonomous fetal endocrine response stimulated in part by variations in the supply of glucose from the mother.
Concentrations of amino acids, urea, glucose, fructose and corticosteroids were measured in maternal and fetal plasma from nine Scottish Blackface ewes during the last 35 days of pregnancy. During this period maternal plasma levels of most amino acids did not change significantly. In fetal plasma the concentrations of most amino acids decreased or remained relatively constant until about 20 days before birth (day -20) and then increased as term approached. Glucose levels in plasma from both sources did not change, but urea concentrations rose to maximum values about day -20. Except for valine and isoleucine, the concentrations of amino acids in fetal plasma varied independently of levels in maternal plasma up to day -20, but thereafter 10 amino acids, including seven essential amino acids, showed a significant positive correlation with maternal values. Possible causes of the observed variations in fetal plasma composition are discussed.
Total plasma amino acid concentrations (TAA) in 12 Scottish Blackface ewes between 80 and 140 days of pregnancy were unaltered by two days of starvation, but concentrations of essential amino acids (EAA) increased and non-essential amino acid (NAA) levels decreased. These trends were more pronounced later in pregnancy. Ewes fasted before surgery to implant fetal catheters showed marked reductions in mean TAA levels (--26 per cent, n-5) on the day after operation (day+ 1). Half of this decrease was accounted for by glycine. Mean concentrations of NAA increased after day +1 but by day +6 were still 15 per cent below baseline values. In contrast mean plasma concentrations of EAA were 31 per cent above prestarvation levels on day +6 and maximal on day +4(+39 per cent). Following a two-day fast, sheep given half rations and simultaneously infused with adrenocorticotrophin showed changes in plasma-free amino acid composition like those observed during the two days after operation. Disturbances to plasma amino acid concetrations persisted for up to 12 days after operation and are attributed to the preoperative starvation and the combined effects of irregular feeding patterns and elevated plasma corticosteroid levels during and after operation.
At ambient temperatures of 17-22 degrees C hypoglycaemia (plasma glucose levels smaller than 45 mg/100 ml) in pregnant sheep was associated with rising potassium concentrations in allantoic fluid, while at temperatures below 12 degrees C glucose levels were higher and coincided with falling potassium values. It is suggested that the fetus is sensitive to changes in maternal glucose balance induced by variations in anbient temperature, and this indicates the need to consider the environmental temperature in metabolic studies of fetal sheep.
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1. The fluid sacs and bladders of sixteen foetuses in fourteen ewes were catheterized between 81 and 92 days gestational age and the rumens of four ewes were also catheterized.2. Between 95 and 145 days gestational age in forty-six 24 hr experiments hourly samples of maternal plasma and foetal urine were obtained and in fifteen experiments foetal fluid samples were also taken at 4- to 6-hr intervals.3. The osmolality, pH, and concentrations of sodium, potassium, chloride, glucose, fructose and urea were measured on all samples.4. During experiment there was no significant variation in the composition of amniotic or allantoic fluid. Marked changes in osmolality occurred in maternal plasma and foetal urine when ewes drank after feeding, but not in ewes that received water intrarumenally via catheter while feeding or in fasting ewes. Post-prandial changes in maternal plasma osmolality may have altered transplacental water fluxes and as a result foetal plasma volume and osmolality.5. The results suggest that the foetus alters renal water retention by varying antidiuretic hormone (ADH) secretion in response to changes in blood volume and at later gestational ages plasma osmolality as well.6. Post-prandial changes in the [Na(+)]/[K(+)] ratio of foetal urine suggested that foetal adrenocorticotrophin (ACTH) secretion is influenced by variations in foetal blood volume and glucose concentrations.7. The post-prandial changes in foetal urine composition observed here support previous suggestions (Mellor & Slater, 1972) about the role of foetal urine in foetal fluid formation which were based on gestational changes in the composition of foetal fluids and urine sampled once daily during the post-absorptive state.
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1. The fluid sacs and bladders of ten foetuses and the allantoic sacs of five foetuses were catheterized between 79 and 96 days gestational age and daily samples were withdrawn until lambs were born naturally at approximately 147 days. Maternal jugular plasma obtained daily allowed the nutritional status of each ewe to be regulated and monitored. All lambs were observed for 7 weeks, and at post-mortem no abnormalities were seen in those operated upon in utero.2. The osmolality, [Na(+)], [K(+)], [Cl(-)], [glucose], [fructose], [urea], [amino acid] and pH of all samples were measured.3. Foetal surgery seemed to affect the actual concentrations of some solutes, but gestational trends in foetal fluid composition were unaltered.4. Until about 7 days before birth the foetal urine osmolality, [Na(+)], [Cl(-)] and [fructose] decreased, its [urea], [amino acid] and pH remained relatively constant, and from about 120 days gestational age the [K(+)] increased. During the last 7 days there was a marked increase in the osmolality and the concentrations of all these solutes, and a decrease in pH.5. Entry of foetal urine into the fluid sacs tended to decrease the osmolality, [Na(+)], [K(+)], [Cl(-)] and [glucose] of both foetal fluids and the [amino acid] of allantoic fluid, and tended to increase the [fructose] and [urea] of both fluids and the [amino acid] of amniotic fluid.6. Changes in urine composition suggested large daily variations in the secretion of foetal antidiuretic hormone and also a rapid increase in its secretion during the last 7 days, and particularly the last 2-4 days before birth.7. Changes in the [Na(+)]/[K(+)] ratios of foetal urine and allantoic fluid were parallel during post-operative recovery, during the course of pregnancy and immediately before birth, and this was consistent with a simultaneous action of foetal plasma corticosteroids on the foetal kidneys and chorioallantois.8. Variations in the [fructose] of foetal urine and allantoic fluid were parallel to changes in their [Na(+)]/[K(+)] ratios and suggested an involvement of foetal corticosteroids in the regulation of the [fructose] of foetal plasma.9. Further evidence has been presented supporting the hypothesis that maternal induced foetal hypoglycaemia effects a relative increase in the secretion of foetal corticosteroids having an action on the chorioallantois. Also, high concentrations of maternal plasma corticosteroids may decrease the permeability of the placenta to glucose.
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1. Catheters were inserted into the maternal and foetal vasculatures of ten ewes, 100-139 days pregnant, and daily samples of uterine and umbilical blood and maternal jugular vein blood were taken for periods of 5-27 days after operation.2. Catheters were inserted into the fluid sacs of nineteen foetuses, 60-97 days post-conception, and daily samples were withdrawn for up to 90 days from amniotic sacs (eleven foetuses) and for up to 70 days from allantoic sacs (eight foetuses). Maternal jugular plasma was obtained 3 times weekly and an approximation from its composition to that of uterine and umbilical plasma was made using results from the ewes and foetuses with vascular catheters.3. The pH, osmolality, [Na(+)], [K(+)], [Cl(-)], [urea] and [amino acid] of all samples were measured.4. The nutritional status of all ewes was monitored throughout pregnancy. Most lambs were born naturally at approximately 147 days post-conception and their subsequent progress was observed.5. Results at operation and from acute experiments were compared with those from conscious ewes and foetuses of the same gestational age to assess the nature and extent of the influence of the operative procedures on foetal fluid composition. The composition of amniotic fluid was influenced mainly by the anaesthetic and surgical procedures while that of allantoic fluid was affected largely by starvation of the ewe.6. Changes during recovery from operation were followed and indicated that maternal and foetal plasma required about 3 days and the foetal fluids up to 7 days before stability of composition was achieved.7. After recovery from operation, daily changes in the composition of each foetal fluid showed the same general pattern in all foetuses, but the absolute values of constituents sometimes showed large differences.8. It is suggested that flow of foetal urine into the amniotic sac increased from 80 days gestational age, that urine flow into the allantoic sac decreased until about 100 days but did not cease thereafter, and that relative to foetal urine the influence of foetal pulmonary fluid on amniotic fluid composition was not great.9. A relative impermeability of the amnion appeared to be a major factor influencing amniotic fluid composition, whereas pumping mechanisms in the chorioallantois seem to have been responsible largely for changes in the composition of allantoic fluid.10. The quantity of solute relative to that of water within each sac appears to be a major determinant of changes in foetal fluid volumes.11. Changes in the [Na(+)] and [K(+)] of allantoic fluid during the normal course of pregnancy were consistent with an increasing action of mineralo-corticoids on pumping mechanisms in the chorioallantois. Similar but more rapid changes seemed to be associated with acute and chronic episodes of maternal hypoglycaemia. Under these circumstances foetal hypoglycaemia may effect a relative increase in the secretion of foetal corticosteroids having an action on the chorioallantois.12. The results from this study demonstrate clearly the value of using chronically catheterized animals, and it is suggested that their use in physiological studies on the conceptus must eventually supersede that of acute, anaesthetized preparations.
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