Normal Human Term Placenta Research Articles

GLUCOSE-6-PHOSPHATASE IN HUMAN PLACENTA: A NEW METHOD FOR THE STUDY OF GLYCOGEN STORAGE DISEASE TYPE I. POSSIBLE IDENTIFICATION OF A HETEROZYGOTE

Glycogen storage disease type I (Von Glerke's disease) is an autosomal recessive disorder characterized by growth retardation hepatomegaly, recurrent episodes of hypoglycemia and acidosis. The enzyme deficiency in this disease has been shown to be glucose 6-phosphatase, which its activity has been reported mainly in liver and kidneys. In order to find a tissue that may exhibit glucose-6-phosphatase activity, full term human placentas were utilized. Placental slices were washed X3 with cold 0.15 M NaCl, then sonicated in 0.1M cacodylate buffer pH 6.5 and centrifuged for 10 min at 10,000 Xg. The supernatant fractions were assayed for glucose 6-phosphatase with glucose 6-phophate. The liberated glucose was determined by glucose oxidase. Normal human term placentas hydrolyze 33.0-80.0 ug glucose/mg/protein/h. D-1-14C-glucose-6-phosphate was used as an additional substrate and 14C-glucose was identified by thin layer chromatography. Extracts of normal term human placentas release 50%-86% of the label/mg protein/h. A pregnancy at risk for glycogen storage disease type I was followed and the full term placenta was assayed for glucose 6-phosphatase. The values obtained from the extracts of the placenta at risk released 16.5 ug glucose/mg protein/h. while a normal control placenta released 34.0 ug glucose/mg protein/h. This finding suggests heterozygous state of the newborn. These data offer a new source for the study of glucose-6-phosphatase and for possible prenatal detection.

Synthesis of human placental lactogen in Xenopus oocytes.

Oocytes from Xenopus laevis were injected with polysomes from normal human term placenta. Synthesis of the protein hormone Human Placental Lactogen (HPL) in the oocytes was demonstrated by specific immunoprecipitation with anti-HPL serum. Analysis of the immunoprecipitates on SDS-polyacrylamide gel revealed one peak, with a migration distance corresponding exactly to that of [14C]-Radioacetylated HPL added as a marker. Two days after injection the mRNA was still able to direct the synthesis of HPL.

Isolation and in vitro translation of human placental lactogen messenger RNA from human term placenta.

A messenger activity for HPL was identified in normal human term placentas. The mRNA was translated in rabbit reticulocyte cell-free system. The HPL synthesized was quantified by a specific immunoprecipitation and further identified by electrophoresis on sodium dodecyl sulfate polyacrylamide gel. The HPL synthesized in the reticulocyte lysate exhibited a molecular weight between 20,000 and 22,000 daltons similar to the active hormone. The messenger RNA activity for HPL corresponded to a sedimentation coefficient of 11-12 S. Furthermore the messenger activity for HPL was preferentially associated with membrane bound polyribosomes than with free polyribosomes.

Glycolytic enzymes in the normal human term placenta.

The enzymes hexokinase (HK), phosphoglucomutase (PGM), pyruvate kinase (PK) and lactate dehydrogenase (LDH) were assayed in villous tissue homogenates and cell fractions of normal human term placentas. Although lowest in activity and probably rate limiting in glycolysis, hexokinase is theoretically adequate to phosphorylate the total amount of glucose metabolized. PGM and PK activity were in the same range exceeding HK by 10-15 times, suggesting a largely increased breakdown of glycogen-derived glucose in situations of need. Substantially higher LDH activities may reflect the placental ability to utilize lactate from both mother and fetus. Of all enzymes only hexokinase was found to be associated with the particulate matter in considerable amounts.

An electron microscopic study of fetal capillary basal laminas of “normal” human term placentas

Electron microscopic examination o f terminal (free-floating) villi o f definable normal human term placentas emphasizes the variable fine structural appearance of the fetal capillary basal lamina (FL). The FL assumes both a unilaminar and multilamellar configuration in each placenta examined; the multilamellar portions are usually composed of individual layers which tend to branch and anastomose. The constant identification of collagen fibrillar profiles between these electron-dense layers argues against the notion that the multilamellar portions o f the FL arise via a simple splitting or disaggregation o f pre-existing unilaminar FL's.

Autoradiographic study of the “X cells” in the human placenta

In vitro autoradiographic studies with tritiated thymidine were applied to normal human term placentas. Labeling patterns were observed in each component of these placentas, especially within the “X-cells.” In foci of fibrin deposits, occasional “X-cells” featured mitotic activity. This suggests that these cells maintain their capacity to replicate, despite apparently poor local conditions. The most active labeling occurred in the cytotrophoblast. There was no activity in the amnion, Hofbauer cells, syncytiotrophoblast, or syncytial giant cells. The finding of “X-cells” in the placenta of the chimpanzee, gorilla, and baboon suggests that placental studies of this subhuman primate may be of further interest.

Basement membranes (amniotic, trophoblastic, capillary) and adjacent tissue in term placenta: An electron microscopic study

Electron microscopic studies of normal human term placenta show that the amniotic epithelium is attached by semidesmosomes to a basement membrane. The latter consists of a 300 to 350 Å thick lamina lucida which is in continuity with the interepithelial space, and an outer 400 to 450 Å thick lamina densa. The thick (1,000 to 3,000 Å) trophoblastic basement membrane is composed of a lamina lucida, 300 to 350 Å in width, and the outer lamina densa, measuring 650 to 2,700 Å in width. The basement membrane of the villous capillary consists of a lamina lucida measuring 300 to 350 Å; the outer lamina densa is usually ill defined. Microfibril-like structures are present at the level of all basement membranes. Typical microfibrils are found in the extracellular space adjacent to all basement membranes examined and throughout the amniotic connective tissue stroma. They are probably responsible for the elastic-like properties of the amnion.