Observations of apparent C-type particles in baboon (Papio cynocephalus) placentas.

Ultrastructural investigations have revealed the presence of apparent endogenously derived C-type particles in the placental villi of each of 13 baboons studied. Both budding and mature forms were observed in the syncytiotrophoblast of these animals at various stages of pregnancy.

Type-C virus particles in placenta of the cottontop marmoset (Saguinus oedipus).

Electron microscopy of near-term placentas of two cottontop marmosets (Saguinus oedipus) revealed, in one placenta, the presence of budding and mature C-type virus particles associated with the basal trophoblast. The particles were morphologically similar to those observed by other investigators in placentas of other primate species.

Vertical transmission of C-type viruses: their presence in baboon follicular oocytes and tubal ova.

C-type viruses were found in baboon follicular oocytes and tubal ova adjacent to the plasma membrane in the perivitelline space or along the inner margin of the zona pellucida. Their presence support the concept of vertical transmission of C-type viruses.

Angiotensinogen in the developing rat fetal hindbrain and spinal cord from 18th to 20th day of gestation: an immunocytochemical study.

We have detected angiotensinogen immunoreactivity in the hindbrain and in the spinal cord of rat fetuses during the 18th to 20th day of gestation. In the 18th-day fetus, a few immunoreactive angiotensinogen cells are localized in precise brain areas. Their number sharply increase during the 19th and 20th day gestation period when there is an active cell differentiation and cell growth. These observations suggest a role of the renin-angiotensinogen system during cell growth and cell differentiation.

Energy charge monitoring via magnetic resonance spectroscopy 31P in the perfused human placenta: effects of cadmium, dinitrophenol and iodoacetate.

Phosphorus 31 nuclear magnetic resonance spectroscopy as a non-invasive technique was applied to monitor the metabolic activity of the human placenta during perfusion in vitro. During control perfusions (n = 3) there was an initial increase in adenosine triphosphate (ATP) and a fall in inorganic phosphate (Pi). Thereafter, however, the level of both ATP and Pi remained constant throughout the perfusion period (11 h). Additional biochemical parameters such as glucose consumption, lactate production and the release of hormones, human chorionic gonadotrophin (hGC). measured in the perfusate samples, were also used to assess the viability of the placental tissue. As with ATP, all these biochemical parameters under the control conditions showed a stable rate of metabolic activity throughout the length of the experiments. In additional experiments, the effect of the metabolic inhibitor dinitrophenol (n = 2) and dinitrophenol (DNP) together with iodoacetic acid (IOA, n = 2) were studied. DNP (0.1 mM) alone showed a slight decrease of all parameters. In contrast, the addition of IOA (0.1 mM) with DNP (0.1 mM) not only blocked the production of ATP but also produced a substantial impact on placental metabolic activity. The effect of a toxic dose of cadmium (20 nmol/ml) was studied also (n = 3). This dose of cadmium demonstrated no effect on phosphorus metabolism. However, the rate of glucose consumption and the release of hCG were significantly reduced.

Long-term dual perfusion of isolated human placental lobules with improved oxygenation for infectious diseases research.

An improved method for long-term perfusion of the isolated human term placental lobule has been developed to investigate the maternofetal transfer of infectious agents, in particular the human immunodeficiency virus (HIV). The purpose of this paper is to describe those modifications that allow for substantially prolonged perfusions in in a biohazard environment. The method described has been adapted from previous models. The perfusion apparatus has been modified for use within a biohazard hood, and, intravenous bags contain the medium for circulation of perfusates in closed circuits. A Mera Silox-S 0.3 membrane oxygenator delivers more oxygen to the tissue, and, Electromedic Cardioplegia heat exchangers warm the perfusate prior to oxygenation. Viability criteria (glucose consumption, lactate production, de novo production of human placental lactogen (hPL), volume loss, flow, temperature, pressure, oxygen transfer, carbon dioxide production, absence of IgM transfer and light and electron microscopy) demonstrate that the placental tissue remains in a functional state throughout the perfusion. Oxygen and glucose consumption are both stable over time; lactate levels remain constant; and hPL continues to be produced. These significant modifications of the perfusion system have permitted the investigators to increase the duration of perfusion to 48 h while preserving normal metabolic function of ultrastructurally intact tissue as demonstrated by ultra structural observations. This perfusion model device provides biohazard precautions and may be applied to other studies of placental physiology.

Kinetic assessment of manganese using magnetic resonance imaging in the dually perfused human placenta in vitro.

The transfer and distribution of paramagnetic manganese was investigated in the dually perfused human placenta in vitro (using 10, 20, 100 microM Mn with and without 54Mn) using magnetic resonance imaging (MRI) and conventional radiochemical techniques. The human placenta concentrated 54Mn rapidly during the first 15 min of perfusion and by 4 hr was four times greater than the concentrations of Mn in the maternal perfusate, while the concentration of Mn in the fetal perfusate was 25% of the maternal perfusate levels. Within placentae, 45% of the 54Mn was free in the 100,000g supernatant, with 45% in the 1,000g pellet. The magnetic field dependence of proton nuclear spin-lattice relaxation time (T1) in placental tissue supports this Mn binding. Mn primarily affected the MRI partial saturation rather than spin-echo images of the human placenta, which provided for the separation of perfusate contributions from those produced by Mn. The washout of the Mn from the placenta was slow compared with its uptake, as determined by MRI. Thus, Mn was concentrated by the human placenta, but transfer of Mn across the placenta was limited in either direction. These studies also illustrate the opportunity for studies of human placental function using magnetic resonance imaging as a noninvasive biomarker.

Continuous measurement of ATP by 31P-NMR in term human dually perfused placenta in vitro: response to ischemia.

ATP was examined in dually perfused term human placentas by using 31P-nuclear magnetic resonance (NMR) spectroscopy. 31P-NMR spectra were acquired every 30 min starting approximately 30 min after establishing fetal and maternal perfusions, and maternal perfusate samples were obtained to monitor glucose utilization, lactate production, and human chorionic gonadotropin (hCG) and human placental lactogen (hPL) release. In continuous-perfusion experiments, placentas were perfused as long as 10 h. ATP increased and Pi fell after initiation of perfusion. Fetal volume loss was < 2 ml/h, and constant production of hCG, hPL, and lactate as well as constant utilization of glucose were observed. In additional experiments, ischemia was produced by halting maternal and fetal perfusion pumps after a 2-h control period. After 2, 3, or 4 h of ischemia, ATP decreased 46 +/- 17, 51 +/- 5, and 85% of control, respectively. When perfusion was reinitiated, ATP increased and was maintained for the duration of the experiment (an additional 2 h). Recovery of ATP after reperfusion was not paralleled by recovery in glucose utilization, lactate production, or hPL and hCG release. However, during the reperfusion period, fetal pressure was < 70 mmHg and fetal volume loss was < 2 ml/h. These investigations suggest that the dually perfused human placental lobule can maintain ATP for > or = 10 h. Although the perfused human placenta recovers ATP and maintains fetal perfusion volume after ischemia lasting up to 4 h, utilization of glucose, production of lactate, and production and release of hCG and hPL are impaired.

Ultrastructure of cleavage stages and preimplantation embryos of the baboon.

The baboon preimplantation stages were examined using light and electron microscopy. Six cases were studied at 2, 3, 4, 5, 7 and 8 days estimated fertilization age. The first 3 specimens were composed of 2, 8 and 24 blastomeres respectively. At 5 days, 30 to 40 cells were counted and more than 60 cells in later stages. Primitive "trophoblast cells" differentiate at 7 days and a crescentic blastocoele appears at 8 days. Shedding of the zona pellucida is not observed in the 7 and 8 day specimens. The preimplantation period is longer in the baboon than in man. C-type viruses are observed in the zona pellucida, in the perivitelline and interblastomeric spaces. Microvilli and caveolae cover ther periphery of the baboon conceptus. As in many other mammals, transformation of the mitochondria, changes in the ribosomes distribution, multivesicular bodies, myelin figures, nucleoli and intranuclear clusters of granules are described in the baboon. Cytoplasmic fibrous strands are not present as in the mouse. Experiments on the influence of hormones and drugs on ultrastructural changes would help to evaluate the importance of biohazards during the early development of primates.

Surface ultrastructure of preimplantation baboon embryos.

Scanning and transmission electron microscopy were used to study baboon preimplantation embryos 3 to 5 days E.F.A. (estimated fertilization age), ranging from about 16 to more than 60 cells. The peripheral blastomers were covered with microvilli scattered on the convex outer surface and along the borders of the intercellular furrows. In younger morulae, some longer microvilli may bridge over the furrow separating contiguous blastomeres. A few blastomeres showed poorly developed microvilli. Blastomeres of smaller diameter than the others may arise from more recent cleavage. Cell junctions as well as small intercellular spaces were noted at the apposition of the blastomere plasma membranes whereas surface intercellular ridges were not observed.

Free vitamin B12 and transcobalamin II-vitamin B12 complex uptake by the visceral yolk sac of the Sprague-Dawley rat: effect of inhibitors.

Exogenous free vitamin B12 or B12 bound to human transcobalamin II (TCII) accumulated in the near-term rat visceral yolk sac. The rates of their uptakes in vitro and in vivo increased rapidly with time then reached a plateau, which supports a saturable transport/binding process as the rate-limiting step for the uptake of free and TCII complexed B12. Both uptakes were significantly decreased by trypan blue, colchicine, and low temperature but not by ouabain. Such inhibition suggests that the absorption of free and bound B12 is via an endocytosis process dependent upon energy but not the magnesium-dependent sodium/potassium-activated ATPase. Thus, the role of the visceral yolk sac in vitamin transfer to the conceptus and the alterations in yolk sac function associated with birth defects and diminished growth can be integrally related.

Radionuclide and angiographic studies of placental circulation in man and rhesus monkey.

Imaging maternal and fetal circulation during perfusion of isolated human placental lobules was performed. Radionuclide and contrast angiograms, specimen scans, and histologic preparations obtained on human material during in vitro investigations were compared to the results obtained in vivo on pregnant rhesus monkeys. The distribution of maternal blood flow within the placenta appeared similar in both human and rhesus studies. The 'spurts' of radiopaque medium shown on the contrast angiograms correlated with the appearance of areas of increased radioactivity. These 'hot spots' are located where the uteroplacental spiral arteries open into the intervillous space or where the perfusion cannulae irrigate the maternal side of the placenta. Time-radioactivity curves reached an early peak and remained the same as did their distribution on delayed scans. The 15 to 30 micron microspheres injected into the intervillous spaces are not removed onto the venous side by maternal flow through arteriovenous communications (or 'shunts') but are retained in localized areas of the intervillous space adjacent to the spiral arteries. Many of these microspheres adhere to the 'brush border' of the chorionic villi syncytiotrophoblast. These comparative studies confirm that rhesus monkeys and perfused human placental lobules are relevant models to investigate uteroplacental hemodynamics.

[Visualization of the guinea pig fetus in utero by x-ray densitometry]. / Visualisation du foetus de cobaye in utero par la densitométrie aux rayons X.

The total body X-ray scanner (computer assisted axial tomography) was used to observe the guinea-pig fetus in utero. This new method of investigating obstetrical physiology provides a suitable animal model with quantitative facts about the density of the fetal organs and, using a non-invasive technique, allows precise intrauterine pictures of the anatomy of the fetus to be obtained.

The human placenta. Anatomy and morphology.

This review presents basic aspects of placental morphology with particular reference to the regional specialization of human placental tissues. Intrauterine visualization of the placenta is now possible with new non-invasive methods. Echotomographic ultrasound images of the placenta in vivo and in vitro are of the greatest value for clinical and pathological diagnosis. X-ray computed tomography, though it cannot be applied to pregnant women, is invaluable for the study of circulatory and pathologic changes in the placenta isolated post partum. Nuclear magnetic resonance imaging is another useful adjunct not only for placental localization but also to detect changes of placental morphology with an accuracy almost as good as ultrasonography. Fourier-transform spectroscopy now offers a unique opportunity to obtain computed biochemical data on the metabolic evolution of the human placenta.