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Biomedical subjects

A Verhoeff

Publications and source records attributed to A Verhoeff.

42 records · Page 3Linked to original sources
PubMed1986

Myometrial activity related to gap junction area in periparturient and in ovariectomized oestrogen treated sheep.

Propagation of electrical (EMG) activity in the myometrium may be facilitated by the presence of gap junctions (GJ), leading to improved synchronization of contractility. EMG and mechanical (IUP) activity in relation to GJ area were studied in 9 periparturient and in 2 ovariectomized (OVX) oestradiol-17 beta (E2) treated ewes, chronically instrumented with bipolar electrodes and intrauterine sponge-tip catheters. Myometrial biopsies were taken under epidural anaesthesia at various time intervals around delivery and after intra-arterial administration of 0.1 mg of E2. In pregnant ewes we found a significant increase in the rate of rise and area of IUP cycles during labour. Both were closely related to a significant increase in GJ area. In E2 treated OVX sheep we found a significant increase in GJ area, with a maximum at 24 hours after injection. The increase in GJ area was associated with a significant increase in the rate of rise of IUP cycles. The results of our study support the hypothesis that gap junctions facilitate the spread of EMG activity across the myometrium, which may improve synchronization of uterine contractility during labour.

Animals↗
PubMed1985

Electrical and mechanical uterine activity and gap junctions in peripartal sheep.

In 10 chronically instrumented pregnant ewes myometrial electrical activity and intrauterine pressure were measured and plasma levels of 17 beta-estradiol and progesterone were determined in late pregnancy and during and after labor. Myometrial biopsies were obtained to determine gap junction area. Plasma progesterone levels fell 4 days before delivery, and 17 beta-estradiol levels rose sharply 12 hours before delivery. Toward delivery the myometrial electrical pattern changed from infrequent bursts of long duration to frequent bursts of short duration, and the active pressure area of the intrauterine pressure cycles, the apparent conduction velocity, and the rate of rise of intrauterine pressure cycles increased associated with the changes in hormone levels. These changes were related to an increase in gap junction area. It is concluded that these results support the hypothesis that changes in concentrations of steroid hormones lead to an increase in myometrial gap junction area, which improves the coordination of contractile activity of the uterus during labor.

Animals↗
PubMed1985

Modulation of spontaneous myometrial activity in chronically instrumented ovariectomized sheep.

The uterine electromyogram (EMG) and intrauterine pressure curves (IUP) were investigated as indicators of myometrial activity in chronically instrumented, ovariectomized ewes. Spontaneous electrical activity was characterized by rhythmic patterns of trains of bursts accompanied by IUP waves. Administration of adrenergic (propranolol or phentolamine) or cholinergic (atropine) blocking agents had no effect on spontaneous uterine activity. Both oxytocin and PGF2 alpha appeared to stimulate spontaneous myometrial activity. 17beta-Estradiol temporarily depressed uterine activity in a dose-dependent fashion. The period of relaxation was followed by a pronounced increase in activity. Progesterone treatment resulted in long-term suppression of myometrial activity. Oxytocin and PGF2alpha increased EMG and IUP activity during estradiol suppression but not after progesterone treatment. These results indicate that the myometrium is active in chronically instrumented, ovariectomized ewes. The autonomic nervous system or its receptors do not play a role in the maintenance of spontaneous myometrial activity, estradiol and progesterone suppress myometrical activity but by different mechanisms.

Action Potentials↗
PubMed1984

Effects of experimental head compression on transcutaneous scalp PO2 in fetal lambs.

Equatorial compression of the fetal head is known to occur during labor; its effect on trancutaneous scalp PO2 (PtCO2) was investigated in acute experiments in four fetal lambs. Fetal PtCO2, and oxygen tension (PaO2) and flow in a carotid artery were continuously measured. Equatorial head compression was obtained by inflating a cuff around the fetal head. A strong relationship was shown to exist between PtCO2 and PaO2 values in the normoxemic and hypoxemic fetus. Stepwise compression of the fetal head resulted in a PtCO2 of zero at cuff pressures of 40 to 50 mmHg. Laborlike fetal head compression with an intensity of 50 to 70 mmHg and a duration of one minute resulted in a 30 to 60% fall in PtCO2. Fetal PaO2 remained stable in all experiments. The present findings indicate that values of PtCO2 during fetal head compression do not reflect fetal arterial oxygen tension. This questions the reliability of transcutaneous PO2 monitoring as a method of intrapartum surveillance.

Animals↗
PubMedDate not supplied

The incidence of major clinical complications in a Dutch transport IVF programme.

Four different major clinical complications were identified in a retrospective analysis of 2495 in-vitro fertilization (IVF) cycles resulting in oocyte retrieval. The severe form of ovarian hyperstimulation syndrome (OHSS) occurred in 18 patients, giving a prevalence for this complication of 0.7%. Seven (39%) of these 18 patients had previously been diagnosed as having polycystic ovaries. Eleven patients were admitted with moderate OHSS. Adnexal torsion was diagnosed in two patients. Ovariectomy was considered necessary in both cases. Complications of the transvaginal procedure occurred in seven cases (0.3%): one patient had an acute appendicitis with puncture holes in the appendix, six patients were admitted shortly after oocyte retrieval with a pelvic inflammatory disease. Of the 624 pregnancies obtained, 13 were ectopic, giving an ectopic pregnancy rate of 2.1%. It is concluded that serious clinical complications of IVF treatment are rare. However, patients should be counselled for the occurrence of serious procedure-related complications before entering an IVF programme.

Adnexal Diseases↗