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Biomedical subjects

G C Liggins

Publications and source records attributed to G C Liggins.

At least 127 records · Page 7Linked to original sources
PubMed1977

Pulmonary metabolism during diving: conditioning blood for the brain.

During experimental diving by the awake Weddell seal, blood glucose concentration falls consistently. A large fraction of the glucose consumed from the central circulating blood appears as lactate. During diving, the lung utilizes blood lactate in preference to blood glucose as a source of both carbon and energy, and it is able to release glucose into pulmonary venous blood to supplement the supply available for brain metabolism.

Animals↗
PubMed1977

Human amnion metabolism. I. In vitro maintenance.

The energy stores of human term amnion include glycogen (2.2 +/- 0.3 mumoles of glucose per gram, mean +/- S.E.) and ATP (0.13 +/- 0.2 MM.). Histologic structure and biochemical functions were preserved during incubations of amnion for 120 minutes at 37 degrees C. in a defined medium simulating amniotic fluid; glycogen concentrations were maintained at control values, and the concentration of ATP usually remained at 85 to 100 per cent of control values. Glucose utilization during the first 60 minutes of incubation was linear at a rate of 70.0 +/- 3.0 nmoles per minute per gram of tissue. It is concluded that amnion is a highly metabolically active tissue that can be maintained in a viable state in a suitable medium.

Adenosine Triphosphate↗
PubMed1977

Human amnion metabolism. II. Incorporation of fatty acids into tissue phospholipids in vitro.

The rate of incorporation of 3H-arachidonic acid and 14C-palmitic acid into 15 term amniotic membranes was studied during incubation of tissues in an artificial amniotic fluid medium. Phospholipids were extracted from the amnions, separated by thin-layer chromatography, and both the radioactivity and the phosphorus associated with each phospholipid species were determined. The distribution of amnion phospholipids was: lecithin, 47 per cent; phosphatidyl ethanolamine, 30 per cent; sphingomyelin, 7 per cent; phosphatidyl inositol, 5 per cent; lysolecithin, 4 per cent; and other phospholipids, 6 per cent. During incubation, the specific activities of the phospholipids became maximal after 2 hours and remained constant for at least the next 2 hours. Arachidonic acid was incorporated mainly into lecithin (53 per cent) and phosphatidyl ethanolamine (27 per cent) whereas palmitic acid was incorporated mainly into lecithin (70 per cent). Incorporation of fatty acids was 33 per cent higher in amnions obtained after vaginal delivery than in those obtained before labor. From the known fatty acid composition of amnion phospholipids, it is concluded that there is a high rate of turnover of arachidonic acid relative to palmitic acid in lecithin.

Amnion↗
PubMed1977

Parturition in the sheep.

Parturition in sheep is initiated by a sharp rise in the rate of secretion of cortisol by the fetal adrenal. Increased secretion is due partly to enhanced responsiveness to corticotropin (ACTH) and partly to increased fetal concentrations of corticotropin. Cortisol acts on placental enzymes active in the biosynthesis of oestrogens from progesterone. Thus placental secretion of oestrogen increases and that of progesterone decreases. This change in the ratio of oestrogen: progesterone, particularly the rise in oestrogen, stimulates release of prostaglandin F2alpha (PGF2alpha) from the maternal placenta and to a lesser extent from the myometrium. PGF2alpha enhances the myometrial response to oxytocin and, after a latent period, stimulates contractions. The onset of parturition is normally associated with softening of the cervix, the mechanism of which is uncertain. Uterine contractions in the presence of a distensible cervix lead to parturition.

Adrenocorticotropic Hormone↗
PubMed1976

Adrenocortical-related maturational events in the fetus.

In various organs in fetal animals, maturation is inducible by corticosteroids and delayed by hypophysectomy. A surge of corticosteroid in the fetal circulation preceding parturition may cause rapid organ maturation and enhanced viability. Since this phase of accelerated maturation is linked to the parturitional mechanisms, the changes can be termed collectively "preparation for birth." Support for similar adrenocortical-related maturation of organs in the human fetus is less clear-cut. Nevertheless, evidence is accumulating to suggest that a similar concept can be usefully applied in man.

Adrenal Cortex Hormones↗
PubMed1976

Phospholipase A activity in human and ovine uterine tissues.

Phospholipase A was assayed in crude lysosomal fractions of human decidua, amnion, chorion and myometrium. Activity was present in all the tissues and was highest in decidua and amnion which contained enzymes with pH optima of 6.5-8.0 and 7.2 respectively. Comparison of the activities in tissues obtained before labor with others obtained during labor showed no differences. In sheep, the fetal membranes contained a greater activity of phospholipase A than placenta and myometrium. Stimulation of the fetal adrenals with corticotrophin caused a marked increase in activity in both amnion and chorioallantois. It is concluded that the human amnion and the ovine amnion and chorioallantois could participate in the biosynthesis of prostaglandins by releasing stored arachidonic acid.

Adrenocorticotropic Hormone↗
PubMed1976

The effect of labour on uterine blood flow in the pregnant ewe.

The effect of labour on cardiac output and uterine blood flow was measured in pregnant ewes at a mean gestation of 124 days using radioactive microspheres labelled with 169Yb and 85Sr. Labour was induced by a continuous infusion of ACTH into the foetal circulation. Cardiac ouput measured before ACTH infusion in seven ewes was 5234 +/- 175-9 ml./min (mean +/- S.E.) and total uterine blood flow was 732 +/- 57-9 ml./min (mean +/- S.E.). Measurements during labour in six ewes showed a significant increase in cardiac output to 6175 +/- 149-6 ml./min (P less than 0-005) but no significant change in uterine blood flow. However, the partition of blood flow was altered; thus myometrial flow increased by 67% from 114 +/- 15-4 ml./min to 190 +/- 13-2 ml./min (P less than 0-005) while placental blood flow decreased, although not significantly, from 618 +/- 55-9 ml./min to 575 +/- 40-7 ml./min. Similar changes were observed in one ewe in spontaneous labour at term and in another ewe receiving an infusion of 4 mg oestradiol 17beta over a 24 hr period. It is concluded that labour is not associated with any major alternation in total uterine blood flow although myometrial blood flow is increased. It is not known whether this is due to the rise in circulating oestrogens which occurs prior to parturition in the ewe, or to other factors such as the work of uterine muscle during labour.

Adrenocorticotropic Hormone↗
PubMed1975

Protein binding of plasma cortisol in the foetal lamb near term.

Binding of cortisol to plasma proteins was studied in the foetal lamb by equilibrium dialysis at 37 degrees C. At 122 days of pregnancy the mean level of transcortin expressed as cortisol-binding capacity was 28 +/- 6 (S.D.) ng cortisol/ml plasma. During the last 14 days of pregnancy there was a progressive increase in transcortin-binding capacity to 85 +/- 14 ng cortisol/ml plasma. A sharp increase in the concentration of both protein-bound and unbound cortisol was observed over the same period. A rise in the concentration of total cortisol from around 3 to 42 ng/ml was associated with an increase in unbound cortisol from 0-2 to a maximum of 2-1 ng/ml. The concentration of albumin-bound cortisol was approximately equal to that of unbound cortisol. The mean value for the transcortin-cortisol affinity constant was 1-15 x 10(8) l/mol. It is concluded that an increase in transcortin-binding capacity is partly responsible for the prepartum increase of corticosteroid levels observed in normal foetal lambs.

Animals↗
PubMed1972

Respiratory movements and rapid eye movement sleep in the foetal lamb.

1. In foetal lambs from 40 days gestation (0.27 of term) onwards delivered into a warm saline bath, apparently spontaneous breathing movements were present intermittently. They became deeper and more rapid with increasing age.2. In foetal lambs (from 0.66 of term) in which observations were made for many days after chronic implantation of tracheal, carotid and amniotic catheters, rapid irregular respiratory movements were present up to 40% of the time, and brief gasps also were seen.3. The presence of these movements was unrelated to the foetal carotid blood gas values over a wide range of spontaneous variation.4. These foetal breathing movements were accompanied by comparatively small alterations of pulmonary volume recorded from a tracheal flowmeter, insufficient to clear the tracheal dead space. Occasionally a more prolonged expiration led to the outward flow of fluid.5. A description is given of sleep and wakefulness in foetal lambs from 0.78 of term.6. Rapid irregular breathing was associated with rapid eye movement sleep as seen in a warm saline bath or, in utero, as inferred from records of eye movements and electrocortical activity.7. Respiratory movements were often associated with relatively large variations in foetal heart rate, blood pressure and descending aortic blood flow.8. Rapid irregular foetal breathing was unaffected by section or blockade of the cervical vagi, but was abolished by general anaesthesia.9. It is concluded that respiratory movements are normally but intermittently present in the foetal lamb over the greater part of gestation.

Amniotic Fluid↗