by TheStar 6 Replies latest jw friends
I have heard that although the the WTBTS admits that plasma proteins transfer from mother to fetus, blood also transfers from mother to fetus and of course they don't admit to that.
Does anyone know if this is true and if so where I can go to get more information on this? I have already looked at the twins case but is it only in the case of twins or always?
If anyone knows something about this please help. Thanks
Actually, the idea that fetal blood and maternal blood mix during pregnancy is a bit more complex than what the WTS describes.
Both maternal and fetal blood circulate via the placenta, however, under normal circumstances no actual "mixing" occurs. The placental barrier serves as a filter whereby waste products from the fetus cross into the maternal circulation by osmosis, and nutrients pass to the fetus from the mother in the same manner. Oxygen and carbon dioxide diffuse across the membrane via differences in partial pressures. Drugs pass across the placental barrier relative to their molecular weight (lower MW drugs - like alcohol - pass more readily than higher MW substances - such as insulin).
http://arbl.cvmbs.colostate.edu/hbooks/pathphys/reprod/placenta/transport.html
Transport Across the PlacentaThe issue of twin-to-twin transfusion is extremely rare, and very serious to the babies, even though they may be genetically identical. I don't have time to address this right now, but I'll come back later and post again, if you still have questions. Feel free to e-mail me if you like.The primary function of the placenta in all species is to promote selective transport of nutrients and waste products between mother and fetus. Such transport is facilitated by the close approximation of maternal and fetal vascular systems within the placenta. It is important to recognize that there normally is no mixing of fetal and maternal blood within the placenta. Entry of small amounts of fetal blood into the maternal circulation does occasionally occur, and can evoke an immune response in the mother that affects that fetus after birth or fetuses in subsequent pregnancies that are sired by the same father.
The placenta is a complex tissue and should not be envisioned as simple permiable membrane. In addition to transporting some molecules unaltered between fetal and maternal blood, it also consumes a large fraction of certain types of cargo - glucose and oxygen being good examples. Additionally, a number of molecules that cross the placenta are metabolized to other things during passage.
There are a number of differences among species in the characteristics of transport across the placenta, which should not be a big surprise considering the differences in structure of the placental interface. The following discussions reflect general principles of placental transport.
Transport of Gases
Gases like oxygen and carbon dioxide diffuse through and across tissues in response to differences in partial pressure.In late pregnancy, the mean partial pressure of oxygen (P02) in maternal blood is considerably higher than in fetal blood. As a consequence, oxygen readily diffuses across the placenta from maternal to fetal blood. Despite its low PO2, fetal blood is able to transport essentially the same quantity of oxygen to tissues as maternal blood. This is because the hemoglobin concentration in fetal blood is about 50% higher than in maternal blood, and the majority of hemoglobin in the fetus is fetal hemoglobin, which has a higher oxygen carrying capacity than adult hemoglobin.
Carbon dioxide is produced abundantly in the fetus, and the PCO2 of fetal blood is higher than maternal blood. Carbon dioxide therefore diffuses from fetal blood, through the placenta, into the maternal circulation, and is disposed of by expiration from the mother's lungs.
Nutrients
Glucose is the major energy substrate provided to the placenta and fetus. It is transported across the placenta by facilitated diffusion via hexose transporters that are not dependent on insulin (GLUT3 and GLUT1). Although the fetus receives large amounts of intact glucose, a large amount is oxidized within the placenta to lactate, which is used for fetal energy production.Amino acid concentrations in fetal blood are higher than in maternal blood. Amino acids are therefore transported to the fetus by active transport. A family of at least 10 sodium-dependent amino acid transporters have been identified in placenta that serve this function. There is substantial metabolism of some amino acids as they cross the placenta - for example, much of the serine taken up by the placenta is converted to glycine prior to delivery to the fetus.
There is much more variability among species in placental permiability to fatty acids than to glucose or amino acids. In some animals, there is little transport of fatty acids from mother to fetus, while in others a significant amount of transport takes place.
Antibodies
There are marked differences among species in whether immunoglobulins are transported across the placenta. In primates and rodents, there is substantial transfer of immunoglobulin G from maternal to fetal circulations prior to birth. This process requires immunoglobulin-binding proteins in the placenta.In contrast, there is no transplacental transfer of immunoglobulins in animals like cattle, sheep, horses and pigs. In those species, the neonate is essentially devoid of circulating antibodies until it absorbs them from colostrum (first milk).
Other Molecules
Bilirubin is a waste product derived from the heme in hemoglobin. This lipophilic molecule is conjugated in the liver to make it water-soluble, and eliminated by excretion into bile. The fetus also produces bilirubin, but conjugates only a small fraction. This is good because conjugated bilirubin is transported across the placenta very poorly. In contrast, unconjugated fetal bilirubin is readily transported from the fetal circulation, across the placenta, for elimination by the mother.Many drugs are eliminated in bile through pathways similar to bilirubin. The relative inability of the fetal liver to metabilize and conjugate means that it is impaired for eliminating such molecules compared to adults.
Love, Scully RN
Maternal-Newborn Care
Try
Whole blood transfer
- http://www.geocities.com/osarsif/twins.htm
and
Red Blood cell and White Blood cell transfer
- http://www.ajwrb.org/basics/crumbles.shtml
hawk
Observer.org has a technical document that SIMPLIFIED says:
IDENTICAL TWINS HAVE THE SAME PLACENTA AS FETUSES AND MOST SUCH IDENTICAL TWINS TRANSFER "WHOLE BLOOD" BACK AND FORTH TO EACH OTHER THROUGH ARTERIES AND VEINS THEY SHARE
That article may also be on ajwrb.org or used to be
In 1992 a female lab tech who had donated a blood specimen for analysis was found to have "Y" DNA circulating in her blood stream. Researchers were baffled until it was disclosed that she was 6 weeks pregnant. The source of the "Y" DNA was her unborn son. Cells in the blood stream including fetal nucleated red blood cells, were crossing the placental barrier. This was reported by Diane Bianchi in Johns Hopkins University Press Week. Since then, fetal erythroblasts, trophoblasts, granulocytes and lymphocytes have all been isolated in maternal blood. In 1995 it was demonstrated that a woman can still have fetal cells in her blood stream more than 30 years after her last pregnancy. This has been reported in a number of medical and scientific journals since then. . (See for example Science News 2/10/1996 p. 85)
Thanks All who have replied. I greatly appreciate it!
Hi Anewperson,
That article may also be on ajwrb.org or used to beNo, unfortunately my article is only on Osarsif's site and Kent's Observer site.
AJWRB has said they will publish it at their web site but they told me that they are too busy with other stuff and won't be able to publish it on their site for a while - seeing I'm a member of AJWRB too I kinda go hmmmm but then again I haven't seen many updates on the web site for some time ...
hawk
