Subfractional activities and some properties of Β-glucuronidase were studied at different ontogenetic stages of the human placenta. Maximum activity was localized in the 105,000 g supernatant of tissue homogenate. The enzyme activity in all fractions increased gradually, being maximum in the placentas of 22–26 weeks of gestation. At term, Β-glucuronidase activity had diminished to a great extent. The enzyme showed considerable stability after heating at 65 °C for 10 min. The Km value of this enzyme for p-nitrophenyl-Β-.D-glucuronide was 1.02 mM. EDTA inhibited placental Β-glucuronidase. Of the cations tested, Ag+, Fe++ and Co++ were stimulatory, while Zn++ was inhibitory to the enzyme. Only one isoenzyme of (Β-glucuronidase was found in human placenta.
Acid phosphatases from human placenta and fetal liver during ontogénie development
have been studied by electrophoresis on polyacrylamide gels. Three isozymes have been detected
in liver as well as in early and term placenta, and one more in placenta at mid-gestation. These
isozymes behaved differentially towards heat and a number of inhibitors at different weeks of
gestation. Quantitative determination of each isozyme also showed stage-specific variation.
A higher rate of RNA synthesis in human fetal liver cells was found during the early age of gestation, after a drop, it gradually increases to a maximum value between 18 and 22 weeks, followed by a sharp decrease at later period of gestation. Total polyamine content of fetal liver tissue shows a similar trend. However, when liver cell suspension was incubated with exogenous spermine, spermidine and putrescine there is a dose-dependent inhibition in RNA synthesis. Protein synthesis in human fetal liver cells was stimulated with lower doses of spermine, spermidine and putrescine and inhibited at higher doses. The optimum dose for stimulation and the degree of stimulation was, however, not the same for fetuses of different gestational ages.
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