Human placental serum

R.G. Richards, S.M. Hartman, and S. Handwerger. Human cytotrophoblast cells cultured in maternal serum progress to a differentiated syncytial phenotype expressing both human chorionic gonadotropin and human placental lactogen. Endocrinology. 135 321-329 (1994). 

The properties of membranes can also be used for analytical purposes. A radioreceptor assay for somatomalin A has been developed using human placental membrane. This assay is more sensitive and simpler than the chick bioassay and requires only 40 pi of serum. It is not species-specific... 

The application of quality control procedures to ensure that satisfactory analytical performance of enzyme assays is maintained on a day-to-day basis is complicated by the tendency of enzyme preparations to undergo denaturation with loss of activity. This maltes it difficult to distinguish between poor analytical performance and denaturation as possible causes of a low result obtained for a control sample introduced into a batch of analyses. Assured stability within a defined usable time span is therefore the prime requirement for enzyme control materials, as it is for enzyme calibrators. However, specifications for the two types of materials can differ in other respects. Because the function of a calibrator is to provide a stated activity under defined assay conditions, it is not necessary for it to show sensitivity to changes in the assay system identical to those of the samples under test therefore within certain Umits, enzymes from various sources can be considered in the search for stability. However, it is the function of a control to reveal small variations in reaction conditions, so it must mimic the samples being analyzed. The preparation of enzymes from human sources is not by itself a guarantee of an effective control. For example, human placental ALP is very stable, but it differs significantly in kinetic properties from the liver and bone enzymes that contribute most of the ALP activity of human serum samples it is therefore not an ideal enzyme for use in control material for the determination of ALP. 

Takami M, Kasuya I, Mizumoto K, et al. 1988. A receptor for formaldehyde-treated serum albumin on human placental brush-border membrane. Biochim Biophys Acta 945 291-297. 

The inhibitory properties of PED were also shown in the pregnant-mare-serum-gonadotropin-stimulated rat ovarian microsomes (PMSGSROM). Comparison of the inhibitory kinetic parameters of PED in the human placental and PMSGSROM preparations showed close resemblance time-dependent Ki of 5 nM and 14.5 nM and t i2 of inactivation of 11.8 min and 16.2 min, respectively. The Fmax of human placental microsomes was, however, 10 times higher than that of PMSGSROM (51.8 9.4 vs 4.2 0.9 pmol/min/mg protein, respectively, with testosterone as substrate). The affinities of aromatase from the two sources were also similar Johnston and coworkers showed that baboon placental aromatase, but not the rhesus placental enzyme, was similar in activity to the human placental preparation. 

Serum alkaline phosphatase elevations have been reported following administration of salt-poor albumin (B5). Placenta is very rich in a heat-stable alkaline phosphatase, and albumin prepared from placental blood has a high activity of this enzyme. In one cirrhotic patient who received 1-6 units per day of albumin obtained from pooled human blood and/or human placenta, the alkaline phosphatase before infusion was 5 Bodansky units and by the thirteenth day of administration had reached a value of 160 units. The physician administering the albumin at first thought the patient was having a severe toxic liver reaction and stopped the therapy. The alkaline phosphatase then started to go down and within 10 days returned to normal levels. Analysis of the albumin indicated that it contained 470 units of alkaline phosphatase activity and was probably responsible for the observed elevations in the serum enzyme activity. Albumin prepared from venous blood did not cause an alkaline phosphatase elevation, but placenta-albumin caused elevations with a half-life of about 8 days (Ml). 

Serum half-life values have been estimated using human data from the Michigan PBB cohort. A median half-life of 12-13 years was estimated. Just like polychlorinated biphenyls (PCBs), PBBs are capable of crossing the placental barrier and can concentrate in breast milk. Infants born to and nursing from PBB-exposed mothers may uptake and accumulate PBBs. Lactation constitutes the most important route of excretion of PBB in lactating women. Numerous studies reported PBB levels in breast milk from Michigan women. PBB levels in breast milk on a lipid... 

Pregnancy. Serotransferrin is involved in the process of iron transfer to the foetus by a placental receptor-mediated mechanism. The three glycovariants of serotransferrin and their binding to human syncytiotrophoblast microvillar membranes have been studied by Leger et al. [108]. The results obtained by these authors and others [243,244] showed that in the serum of pregnant women, especially in the last... 

MeHg" " is distributed throughout the body, and easily penetrates the blood-brain and blood-placental barriers (Clarkson 1993, Hansen et al. 1989, Suzuki et al. 1984). The transport of MeHg" " into tissues is mediated by the formation of a MeHg-cysteine complex (Aschner and Aschner 1990, Tanaka et al. 1991, Kerper et al. 1992). Soon after application, McHg" " is found in the blood, predominantly in the red cells. In humans, the ratio of MeHg in red blood cells to serum is approximately 20 1 (Kershaw et al. 1980). Short-chain alkyl-mercury compounds such as methylmercury or ethylmercury are rather stable in the body, whereas long-chain alkylmercury or arylmercury compounds such as phenylmercury may be metabolized relatively quickly to Hg " " ions (Roberts et al. 1979) and, therefore, show similar behavior to the Hg " " ion (Pfab et al. 

Human serum transferrin is an iron(m) tr ispoTt protein which gives up Fe + ions to bone marrow and placental tissues in preference to other cells such as liver cells the protein can bind two iron atoms per molecule but an anion such as HCOa" must be present for binding to occur. Vanadyl ion has been used (as an e.s.r. spin label) to show that the two metal-binding sites are non-equivalent and the same conclusion has been drawn from studies on the dissociation of labelled protein-bound iron. On the other hand, Harris and Aisen have obtained evidence from radiotracer experiments that the two sites are kinetically equivalent. The kinetics of iron(in) (in the form of ferric citrate) binding to the analogous apoprotein from hen s egg (apo-ovotransferrin) have been reported and the following minimum mechanistic scheme has been proposed ... 

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