Biomedical subjects

F J Michel

Publications and source records attributed to F J Michel.

36 records · Page 2Linked to original sources

PubMed1990

Purification, partial characterization, and development of a specific radioimmunoassay for goat placental lactogen.

Placental lactogen (PL) was isolated from goat cotyledonary tissue by a combination of mild alkaline extraction, anion and cation exchange chromatography, chromatofocussing and molecular filtration. The product, enriched 15,000-fold from the initial extract, was homogeneous when examined by SDS-gel electrophoresis (Mr 22,500) and isoelectricfocussing indicated a pI of 8.35 with a trace contaminant of pI 8.0. When assessed by relative binding activity in radioreceptor assays (RRA), goat PL exhibited somatotropic activity equivalent to 2.2 units/mg dry weight and lactogenic activity equivalent to 28.5 units/mg. A radioimmunoassay (RIA) for goat PL is described that is highly sensitive (190 pg/tube) and has acceptable repeatability within and between assays (6 and 13%, respectively). The assay is not affected by goat pituitary extracts or partly purified goat growth hormone and prolactin. Despite the marked increase in sensitivity of the RIA over that previously available when goat PL was measured by RRA, the hormone was not detected in jugular plasma of goats before Day 44 of pregnancy; concentrations increased thereafter and highest levels were measured during the last third of pregnancy in animals bearing triplets. Measurements by RIA are in general agreement with those obtained earlier in several studies in which RRAs were used. The hormone was detected in amniotic fluid. Maternal concentrations of goat PL declined before parturition and were undetectable by 18 h post partum.

Animals↗

PubMed1988

Endocrine changes, with special emphasis on oestradiol-17 beta, prolactin and oxytocin, before and during labour and delivery in goats.

Jugular plasma concentrations of oestradiol-17 beta, prolactin, progesterone and 13,14-dihydro-15-keto-prostaglandin F-2 alpha (PGFM) were measured at 2-h intervals during the last 4 days of pregnancy in 6 goats. During advanced labour and delivery, samples were obtained more frequently and assayed for oxytocin. The animals were housed in a barn with continuous dim lighting. A distinct pattern of oscillation in prolactin concentrations, with peaks during the late afternoon, was apparent during the last 3 days. Geometric means of peak concentrations doubled each day and became of longer duration; night-time nadir values remained low except during the last night before parturition. A progressive increase in oestradiol-17 beta, with mean levels doubling every 36 h, was apparent during the last 3 days. There was no sharp pre-partum increase in oestradiol-17 beta. Correlated (r = 0.83) with the increase in oestradiol-17 beta was a gradual increase in PGFM and when the latter reached approximately 1000 pg/ml, the non-reversible decline in progesterone reflecting pre-partum luteolysis occurred. Subsequent changes in PGFM related closely to an approximately 20-fold increase in the ratio of oestradiol-17 beta to progesterone until maximal PGFM levels of 26.5 +/- 4.2 ng/ml were reached at delivery. Basal concentrations of oxytocin (8-15 microU/ml) were measured before the last 60 min and markedly higher, though erratic, concentrations were detected at various times before appearance of the allantochorion. Maximal oxytocin values (range 180-1570 microU/ml) occurred within minutes before or after delivery of the first fetus. The results suggest that increased pre-partum production of oestradiol-17 beta, in addition to provoking sufficient release of prostaglandins to cause luteolysis, may modulate either the sensitivity or set-points for an endogenous rhythm in prolactin secretion at the end of pregnancy. The nature of the oxytocin changes suggest that, after labour has evolved sufficiently, delivery is precipitated by an abrupt increase in oxytocin secretion.

Animals↗

PubMed1988

Elevated concentrations of 13,14-dihydro-15-keto-prostaglandin F-2 alpha in maternal plasma during prepartum luteolysis and parturition in dogs (Canis familiaris).

Concentrations of progesterone and of 13,14-dihydro-15-keto-prostaglandin F-2 alpha (PGFM) were measured in plasma collected from 6 bitches every 3 h starting 2.8-4.6 days before parturition (birth of first pup) and continuing until 0.4-0.8 days post partum, and in additional samples collected less frequently. Progesterone concentrations at 48, 24, 12 and 3 h pre partum averaged 2.8 +/- 0.3, 2.2 +/- 0.4, 1.0 +/- 0.3 and 0.7 +/- 0.2 ng/ml. At those times PGFM values averaged 380 +/- 80, 800 +/- 220, 1450 +/- 450 and 1930 +/- 580 pg/ml, respectively. Mean concentrations of PGFM increased about 2.5-fold between 48 and 15 h pre partum in association with the onset of luteolysis, and then increased another 2.5 times before parturition as progesterone fell to nadir values. Peak levels of PGFM ranged from 1060 to 7150 pg/ml (2100 +/- 600 pg/ml) and occurred within 1-9 h after the birth of the first pup and before the birth of the last pup. These results suggest that prepartum luteolysis in dogs is initiated by increases in maternal concentrations of PGF, and that progesterone withdrawal causes a further increase in PGF which completes luteolysis and provides a major portion of the uterotonic activity causing expulsion of pups.

Animals↗

PubMed1976