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Biomedical subjects

M C Elphick

Publications and source records attributed to M C Elphick.

33 records · Page 2Linked to original sources
PubMed1977

Quantitative recovery of free and esterified fatty acids from thin-layer plates coated with silica gel.

A method is described for the recovery of fatty acids from silica gel on thin-layer plates. The method is simple and rapid and depends on the conversion of silica gel to potassium silicate, using potassium hydroxide, followed by acidification in such a way that the silicic acid is kept in solution. Fatty acids are then extracted by shaking with solvent. Fatty acid recovery from free fatty acid, phospholipid, glyceride and cholesterol ester zones is more than 90% efficient. There is no oxidation or isomerization of unsaturated fatty acids.

Chromatography, Thin Layer↗
PubMed1977

The transfer of free fatty acids across the rabbit placenta.

1. The passage of fatty acids across the placenta was studied in 28 day pregnant rabbits (i) by comparing the fatty acid distribution in plasma free fatty acids (FFA) of umbilical cord artery and vein with that in maternal plasma and (ii) by infusing the doe at a constant rate with labelled palmitic, linoleic or arachidonic acids. During the infusion maternal and foetal plasma FFA specific activities were measured. 2. The mean levels of all the fatty acids studied (from twelve to twenty carbon atoms) were similar in both the umbilical vein plasma and maternal arterial plasma FFA, except for arachidonic acid, which was higher in foetal blood. The relative distribution of the fatty acids in umbilical arterial plasma similar to that in the vein, but at lower concentrations. The mean cord venous-arterial difference for each fatty acid correlated positively with the mean maternal arterial levels, with the exception of arachidonic acid. 3. During the constant infusion experiments the specific activities of the fatty acids in the maternal and foetal circulating FFA pools rose rapidly during the first 4 min then rose only slowly. Palmitic and linoleic acids were cleared from the maternal circulation in a similar manner and crossed the placenta at similar rates. 4. The average foetal specific activity in plasma FFA reached 15% of the maternal level for both palmitate and linoleate. The figure for arachidonic acid was half that for palmitic acid infused at the same time. 5. It is concluded that (i) all the major fatty acids present in foetal adipose tissue cross the placenta, (ii) the net transport of each fatty acid depends in part on maternal concentrations, (iii) the rate of metabolism of palmitic and linoleic acids is the same and both cross the placenta at the same rate. Proportionately less foetal arachidonic acid is derived from maternal FFA, and (iv) the results suggest a second placental source of arachidonic acid and possibly also of otherfatty acids.

Animals↗
PubMed1977

Rabbit placental clearing-factor lipase and transfer to the foetus of fatty acids derived from triglycerides injected into the mother.

1. Lipase activity was measured in rabbit placental tissue fragments in late pregnancy. The activity in incubated tissue was greater with heparin (69%), reduced by NaCl (90%), but not affected by acetone or ether. 2. Pregnant rabbits (28-days gestation) were given triglyceride emulsions intravenously and the change in profile of fatty acids in the maternal and umbilical artery and vein plasma free fatty acid (FFA) measured. 3. Those fatty acids predominant in the emulsion were higher in concentration in the umbilical vein FFA than in the maternal plasma FFA and the venous-arterial difference was altered such that the placental transfer of FFA was enriched in a pattern corresponding to the profile of the fatty acids in the emulsion. 4. It is concluded that (i) the rabbit placenta shows considerable lipase activity and the lipase has the same characteristics as clearing-factor (lipoprotein) lipase, (ii) triglyceride infused into the mother is taken up by the placenta and hydrolysed, and (iii) the fatty acids so released pass through the placenta and are taken up by the foetus.

Animals↗
PubMed1977

Incorporation in vivo of 1-14C-palmitic acid into placental and fetal liver lipids of the rabbit.

The incorporation of free fatty acid into the placental and fetal liver lipids of rabbits was studied after fetal injections of albumin-bound 1-14C-palmitic acid. The fetuses were killed either 5--10 or 10--20 min after the injection. The placentas and livers were extracted for lipids and the specific activities of triglycerides (TG), phospholipids (PL), free fatty acids (FFA), monoglycerides (MG) and diglycerides (DG) measured. The lipids of the liver and placenta took up 17.0 and 3.6% of the dose, respectively, and of that liver TG accounted for 74% and the placental TG 34% of the label in each tissue. Most of the remaining counts were in the PL fraction with the rest more or less evely distributed between the FFA, DG and MG fractions. No activity was recorded in the cholesterol esters. The placental TG, PL, DG and MG specific activities reached the same level as that of the placental FFA, while in the liver these esters had higher specific activities (than the liver FFA). The liver TG, DG and PL had higher specific activities when compared with those of the placenta. The specific activity of the placental FFA was lower at 10--20 min than at 5--10 min; the opposite was seen for the placental TG. No time-related changes were seen in the liver lipids. It is concluded that (i) both placenta and fetal liver incorporate FFA into glycerides and PL; (ii) the liver incorporates FFA more rapidly and to a greater extent than the placenta; (iii) most of the FFA is incorporated into TG and to a lesser extent (PL; (iv) in both organs hydrolysis of PL or TG occurs. These results are discussed with reference to placental transport of FFA and fetal fat metabolism.

Animals↗
PubMed1977

Distribution of label in maternal plasma, placenta, fetal plasma and tissues after injection of 14C-palmitate into the circulation of 21- and 28-day-pregnant rabbits.

Tissue and plasma samples were obtained from fetuses removed 1--20 min after injection of 14C-palmitate into the doe at day 21 or day 28 of gestation. Specific activity of maternal plasma free fatty acids (FFA) was higher, but that of fetal plasma FFA lower in 21- than 28-day-pregnant rabbits. In 21-day fetuses, total radioactivity in the liver never exceeded that in the placenta; in 28-day fetuses, the liver radioactivity exceeded that in the placenta after 3 min. Total radioactivity in the fetal brown adipose tissue (BAT) never exceeded that in the placental. Most of the placental radioactivity was initially in the FFA, but at later time intervals the majority of the label was in the phospholipids. The fetal liver and BAT rapidly esterified label into triglycerides. It is concluded that transport of FFA across the placenta is greater at 28 days than at 21 days gestation. The evidence suggests that a pool of placental FFA, which equilibrates rapidly with the maternal plasma FFA, is a possible source of fetal plasma FFA. The rapidity and quantity of label appearing in the fetal liver suggest that fatty acids may first be processed by the liver before transport to extrahepatic tissues.

Adipose Tissue↗
PubMed1976

Concentrations of free fatty acids in maternal and umbilical cord blood during elective Caesarean section.

The concentration of free fatty acids was measured in blood taken from the umbilical artery and vein of 29 infants during elective Caesarean section and compared with levels in maternal venous blood. The mean venous-arterial (v-a) difference was 0.07 mEq/l. There was a direct and significant correlation between the umbilical v-a difference and maternal venous concentrations.

Adolescent↗
PubMed1975

Transfer of fatty acids across the rabbit placenta.

1. Transfer of fatty acids across the placenta was studied in anaesthetized rabbits at 28-days gestation by measuring umbilical venous-arterial differences, by injection of labelled palmitate into the mother and observing its appearance in the foetus, by injection of labelled palmitate into the foetus and measuring its appearance in the mother and the foetal clearance rate. 2. The release of fatty acids and glycerol by foetal adipose tissues was investigated in vitro by measuring the effect of addition of noradrenaline to the incubation medium and in vivo by measuring the effect of noradrenaline infusion into the foetus on circulating glycerol and free fatty acid concentrations. 3. In anaesthetized rabbits at 28-days gestation the maternal circulating free fatty acid concentrations were high and there was a positive umbilical venous-arterial difference. High maternal free fatty acid concentrations were associated with high umbilical venous-arterial differences. 4. Label was present in the foetus in 2 min and reached a peak in 3 min after injection of labelled palmitate into the mother. Label appeared in the maternal circulation in 1 min after injection into the foetus. The half-life of labelled palmitate was of the order of 30-60 sec in both mother in foetus. 5. Foetal white adipose tissue released both free fatty acids and glycerol into the medium and the rate of release increased four to five fold after addition of noradrenaline. Infusion of noradrenaline in the foetus led to a rise in glucose and glycerol concentrations, but the change in free fatty acid concentrations was not significant. 6. It was concluded that (i) free fatty acids can cross the rabbit placenta in amounts sufficient to provide the fatty acid components of stored triglyceride and structural lipids; (ii) placental transport of free fatty acids depends in part on maternal blood concentration and on foetal uptake; (iii) foetal circulating free fatty acids are continually exchanging with fatty acid pools in the placenta and with the maternal circulating free fatty acids.

Adipose Tissue↗
PubMed1975

Automated modification of Duncombe's method for the ultramicro determination of serum free fatty acids.

An automated continuous-flow method is described for estimating free fatty acids in serum using 25-mul samples. The procedure depends on the formation of copper soaps on the surface of a semipermeable membrane, their transfer into chloroform, and subsequent determination of dissolved copper. The membrane separating copper reagent and chloroform is supported between thin-channel dialysis plates. Chloroform extracts of serum free fatty acids are passed through the dialysis unit, and dissolved copper in the outflow is estimated colorimetrically. The procedure gives values that agree with a standard titrimetric method.

Autoanalysis↗
PubMed1971

Microscope slide electrophoresis of serum lipoproteins in agarose gel.

An ultramicro electrophoretic technique for the separation of serum lipoproteins is described using agarose gel on microscope slides.The interaction between the agarose gel and lipoproteins has been reduced and the separation between beta- and pre-beta-lipoproteins has been improved over existing methods. A semiquantitative assay of the lipoproteins can be done in a densitometer. It is suggested that the interaction between agarose gel and lipoproteins, which, without albumin in the system, results in distortion of the lipoprotein bands, may be mediated by free fatty acids.

Blood Protein Electrophoresis↗
PubMed1968

Modified colorimetric ultramicro method for estimating Nefa in serum.

A method is described for the estimation of serum free fatty acids based on the ultramicro method of Novák. The difficulty of obtaining an accurate standard graph has been overcome and the interfering effects of phospholipids have been reduced. The method is simple to perform and gives accurate, precise results in 50 mul samples; it is thus suitable for work on newborn babies and small laboratory animals.

Animals↗
PubMedDate not supplied

Evidence for fatty acid transfer across the human placenta.

Lipid analysis of blood from umbilical artery and vein, experiments on artificially perfused human placentas, measurements of fetal blood triglyceride concentrations and the relative percentage of essential fatty acids in fetal adipose tissue are all consistent with the view that fatty acids cross the human placenta and that the flow to the fetus is influenced by maternal blood concentrations of free fatty acids and triglycerides.

Adipose Tissue↗