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Capillary regression in the human placental stem villi
A.52
Placenta (1993), Vol 14
CAPILLARY REGRESSION IN THE HUMAN PLACENTAL STEM VILLI. V.A. Mironov I, G. Kosanke I, G. Kohnen I, R. Leiser 2, R. Demir 3, and P. Kaufmann 1. Dept. of Anatomy I, Technical University of Aachen, FRG; Dept. of Veterinary Anatomy 2, University of Giessen, FRG; Dept. of Histology 3, University of Antalya, Turkey. The development of the feto-placental vessel system is a complex morphogenetic process which includes formation of new vessels as well as differentiation or regression of existing ones. The differentiation of the reticular stroma into fibrous stroma and the formation of large caliber vessels with a tunica media are the key events indicating transformation of immature intermediate villi (iiv) into stem villi (sv); concerning this transformation, it was proposed that the so-called paravascular capillary network of the stem villi is a rudiment of the capillary plexus of the immature intermediate villi. We investigated i w a n d sv from 1st trimester and term placentas using serial semithin sections, scanning electron microscopy of vessel casts, and immunohistochemistry of proliferation markers PCNA and MIB 1 on paraf~fin sections. The capillary plexus of the iiv of early human placenta were composed of densely arranged vessels mainly located just beneath the trophoblastic layer. Some of the endothelial cells were immunostained by proliferation markers. In contrast, the paravascular capillary net of the stem villi usually was irregUlar and was reduced with increasing calibers of the sv. Proliferating endothelial cells have not been noted. In vessel casts as well as in serial sections of stem villi, conus-like, blind ending capillaries have been observed. Their presence is closely related to increased numerical densities of stromal macrophages as well as to increased amounts of perivillous fibrinoid replacing the trophoblast layer of the sv. The data demonstrate a regression of the paravascular net during maturation of stem villi. They support the hypothesis that these capillaries are remnants of an originally dense capillary net of the immature intermediate villi.
THE BLOOD FLOW VELOCITY WAVE IN THE UMBILICAL ARTERIES OF THE ANAESTHETISED GUINEA PIG RELATED TO THE DISTRIBUTION OF RESISTANCE AND COMPLIANCE IN THE FETAL ARTERIAL SYSTEM AND TO MYOCAR.DIAL EJECTION VELOCITY. W. Moll, O. Aedtner and A. Grillh6sl, Institute of Physiology, University of Regensburg, D-8400 Regensburg, FRG. In anaesthetised guinea pigs near term, the blood flow velocity wave (BFVW) was registered in the umbilical arteries, using a computer-assisted continuous DOPPLER system. Arterial diameter was calculated from external diameter and weight per length in the range of physiological pressures and used to determine arterial flow rate and compliance. Velocity wave data were compared to simulated data obtained by a model of fetal circulation. The BFVW showed a slow initial rise, however significant pulsatility: fetal umbilical blood flow velocity was 17 cm/s + 5 cm/s (N=6) during systole and 8 cm/s +3 cm/s (6) during diastole with a mean of 12 cm/s + 4 crrds. With 1.1 mm + 0.2 mm internal diameter of fresh, untreated umbilical arteries, mean combined umbilical flow rate was 14 ml/min (fetal weight 80 g), around 80% of that in the abdominal aorta and around 50 % of cardiac output as evaluated previously. The compliance of the (intraabdominai and extraabdominal) umbilical arteries with placental arteries was found to be 1.2 ixl/mm Hg, that of the combined aorta and pulmonary artery 2,5 ~l/mm Hg. The empirical BFVW d_ata were produced by the model for a rather slow ventricular ejection rate and for total fetal body compliance around twice the value found in the combined aorta and pulmonary artery. We conclude that the BFVW can be understood as determined by rather low ventricular ejection rate, low placental resistance and high compliance in the fetal arterial system.
Placenta (1993), Vol 14
CAPILLARY REGRESSION IN THE HUMAN PLACENTAL STEM VILLI. V.A. Mironov I, G. Kosanke I, G. Kohnen I, R. Leiser 2, R. Demir 3, and P. Kaufmann 1. Dept. of Anatomy I, Technical University of Aachen, FRG; Dept. of Veterinary Anatomy 2, University of Giessen, FRG; Dept. of Histology 3, University of Antalya, Turkey. The development of the feto-placental vessel system is a complex morphogenetic process which includes formation of new vessels as well as differentiation or regression of existing ones. The differentiation of the reticular stroma into fibrous stroma and the formation of large caliber vessels with a tunica media are the key events indicating transformation of immature intermediate villi (iiv) into stem villi (sv); concerning this transformation, it was proposed that the so-called paravascular capillary network of the stem villi is a rudiment of the capillary plexus of the immature intermediate villi. We investigated i w a n d sv from 1st trimester and term placentas using serial semithin sections, scanning electron microscopy of vessel casts, and immunohistochemistry of proliferation markers PCNA and MIB 1 on paraf~fin sections. The capillary plexus of the iiv of early human placenta were composed of densely arranged vessels mainly located just beneath the trophoblastic layer. Some of the endothelial cells were immunostained by proliferation markers. In contrast, the paravascular capillary net of the stem villi usually was irregUlar and was reduced with increasing calibers of the sv. Proliferating endothelial cells have not been noted. In vessel casts as well as in serial sections of stem villi, conus-like, blind ending capillaries have been observed. Their presence is closely related to increased numerical densities of stromal macrophages as well as to increased amounts of perivillous fibrinoid replacing the trophoblast layer of the sv. The data demonstrate a regression of the paravascular net during maturation of stem villi. They support the hypothesis that these capillaries are remnants of an originally dense capillary net of the immature intermediate villi.
THE BLOOD FLOW VELOCITY WAVE IN THE UMBILICAL ARTERIES OF THE ANAESTHETISED GUINEA PIG RELATED TO THE DISTRIBUTION OF RESISTANCE AND COMPLIANCE IN THE FETAL ARTERIAL SYSTEM AND TO MYOCAR.DIAL EJECTION VELOCITY. W. Moll, O. Aedtner and A. Grillh6sl, Institute of Physiology, University of Regensburg, D-8400 Regensburg, FRG. In anaesthetised guinea pigs near term, the blood flow velocity wave (BFVW) was registered in the umbilical arteries, using a computer-assisted continuous DOPPLER system. Arterial diameter was calculated from external diameter and weight per length in the range of physiological pressures and used to determine arterial flow rate and compliance. Velocity wave data were compared to simulated data obtained by a model of fetal circulation. The BFVW showed a slow initial rise, however significant pulsatility: fetal umbilical blood flow velocity was 17 cm/s + 5 cm/s (N=6) during systole and 8 cm/s +3 cm/s (6) during diastole with a mean of 12 cm/s + 4 crrds. With 1.1 mm + 0.2 mm internal diameter of fresh, untreated umbilical arteries, mean combined umbilical flow rate was 14 ml/min (fetal weight 80 g), around 80% of that in the abdominal aorta and around 50 % of cardiac output as evaluated previously. The compliance of the (intraabdominai and extraabdominal) umbilical arteries with placental arteries was found to be 1.2 ixl/mm Hg, that of the combined aorta and pulmonary artery 2,5 ~l/mm Hg. The empirical BFVW d_ata were produced by the model for a rather slow ventricular ejection rate and for total fetal body compliance around twice the value found in the combined aorta and pulmonary artery. We conclude that the BFVW can be understood as determined by rather low ventricular ejection rate, low placental resistance and high compliance in the fetal arterial system.