PubMed Health⌕ Search

Biomedical subjects

L Tseng

Publications and source records attributed to L Tseng.

At least 73 records · Page 4Linked to original sources
PubMed1982

Estrogen synthesis in normal and malignant human endometrium.

The ability of human endometrium to synthesize estrogen from testosterone (T) was investigated. Normal and malignant endometrial specimens were incubated in a complete nutrient medium with 1 muC/ml (approximately 10 pmol/ml) of [3H]T for 20 hrs. Various estrogens: estrone (E1), estradiol (E2), estrone sulfate (E1S), and estradiol-3-sulfate (E2S) were isolated from cultured tissue and medium. The capacity of aromatization, expressed in pmol of estrogen formed/g of tissue, of proliferative endometria was found to be significantly higher than that of secretory endometria (prol. n=12, 0.53 +/- 0.21, vs sec. n=13, 0.15 +/- 0.09, mean +/- s.d., P less than 0.005). In nine cancer endometrial specimens studied, the estrogen produced varied from 0.3 to 15 pmol/g of tissue. These studies represent the first evidence that human endometrium is capable of synthesizing estrogens from delta 4 androgens at a concentration similar to plasma level. The changes of the capacity of aromatization during the two phases of the menstrual cycle indicate that the estrogen synthesis in endometrium is apparently regulated by hormones. The presence of aromatase in cancer endometria may play an important role in promoting the cell growth in estrogen sensitive endometrial cancer.

Aromatase↗
PubMed1981

In vitro inhibition of endometrial cancer growth by a neonatal rat testicular secretory product.

The ability of a neonatal testicular product to inhibit cancer cell line growth of Mullerian origin was tested in an "in vitro" system. Preliminary experiments indicated that increasing concentration of neonatal rat testicular homogenates showed increasing endometrial cancer (HEC-1) cell growth inhibition. Further investigation revealed that testes organ culture, similarly, inhibited HEC-1 cell growth. It is, therefore, concluded that neonatal rat testes elaborated a substance (or substances) which may be effective as an anti-tumor agent.

Animals↗
PubMed1981

Stimulation of arylsulfotransferase activity by progestins in human endometrium in vitro.

The effect of progestin on the rate of estradiol (E2) sulfurylation in human endometrium was studied in two culture systems: 1) in intact endometrial tissue fragments and 2) in isolated endometrial epithelial glands and stromal cells. Human endometrial tissue fragments were cultured in medium in the presence and absence of progesterone (P) for 24-48 h. The arylsulfotransferase activity was determined in the cytosol of the tissue homogenate by measuring the rate of conversion of E2 to E2-3 sulfate (E2S) in the presence of an excess amount of substrate and cofactor (adenosine-3'-phosphate-5'-phosphosulfate). The enzyme activity was found to be stimulated in the sample cultured with P. The increase in activity correlated with the dose of P and period of culture. Stimulation of endometrial estradiol dehydrogenase activity by P, which has been reported in a series of previous publications, was also evident in the current study. Human endometrial glandular epithelial and stromal cells were cultured separately in medium in the presence and absence of medroxyprogesterone acetate (MPA). The cultured cells were incubated with E2 (0.4-0.6 nM) for 2 h. The formation of estrogen sulfates, [estrone sulfate (E1S) and E2S] was greatly increased in all the proliferative glandular epithelial cells cultured with MPA. However, the rate of sulfurylation was not appreciably affected by MPA in stromal cells and in glandular epithelial cells from secretory endometrium. The oxidation of E2 in these cultured cells was also influenced by P but not to the extent of sulfurylation. These results indicate that arylsulfotransferase in endometrium originates from glandular epithelial cells and can be stimulated by progestin.

Arylsulfotransferase↗
PubMed1981

Substrate-directed modulation of elastin oxidation by lysyl oxidase.

The oxidation of an elastin substrate by highly purified bovine aortic lysyl oxidase (LO) is markedly influenced by amphiphilic molecules known to bind to elastin. Negatively charged elastin ligands, including fatty acids, bile salts or sodium dodecyl sulfate can completely inhibit the oxidation of lysine in elastin, the cationic amphiphilic ligands stimulate the enzymatic reaction five-fold, while small hydrophilic molecules of either charge or neutral detergents have no effect. In addition, evidence has been obtained that changes in the conformation of a synthetic polypeptide substrate markedly alter its susceptibility to LO. The coacervated state of the substrate is most readily oxidized and crosslinked by the enzyme. These results point to the importance of small ligands, electrostatic charge, and conformation as substrate-directed influences which can control the expression of LO activity.

Amino Acid Oxidoreductases↗
PubMed1980

Repeat polypeptide models of elastin as substrates for lysyl oxidase.

Synthetic repeat polypeptides analogous in sequence to the valine-rich regions of elastin have been tested as substrates for purified bovine aorta lysyl oxidase. These polypeptides, HCO(phi-Pro-Gly-Gly)n-Val-OMe, HCO(Val-Pro-Gly-phi-Gly)n-Val-OMe, and HCO-Val-(Ala-Pro-Gly-phi-Gly-Val)n-OMe, where phi = Val or Lys at approximately a 4:1 ratio and where n greater than or equal to 40, are models of the tetra-, penta-, or hexapeptide repeat sequences found in elastin. alpha-Aminoadipic delta-semialdehyde is generated in each of these upon incubation with lysyl oxidase at 37 degrees C, whereas the aldol and anhydrolysinonorleucine bifunctional cross-linkages were formed only in the incubation of enzyme with polypentapeptide. Incubation of the polypentapeptide at 55 degrees C, which enhances coacervation of the peptide, increases aldehyde formation and generates a much higher ratio of cross-linkages to aldehyde than occurred at 37 degrees C. These results demonstrate that lysyl oxidase can oxidize lysine in synthetic polypeptides and suggest important conformational aspects of lysyl oxidase substrates which may control substrate potential as well as the ability of peptidyl aldehyde, once formed by the enzyme, to condense to cross-linkage products.

Amino Acid Oxidoreductases↗
PubMed1979

Endometrial estradiol-17 beta-dehydrogenase activity in women wearing Cu-IUD.

In order to determine whether inhibition of the endometrial estradiol-17 beta-dehydrogenase activity by Cu++ could be one of the factors accounting for the enhanced contraceptive efficacy of copper intrauterine devices (Cu-IUD), the activity of the enzyme was measured in endometrial biopsies from women wearing this device. The levels of enzymatic activity found in these specimens were within the range of controls (women without IUD), e.g. 0.1--0.8 and 7--27 nmol E1 formed/mg protein/h in the follicular and luteal phases of the menstrual cycle, respectively. It is concluded that Cu-IUD does not modify significantly either the activity of endometrial-17 beta-dehydrogenase, an enzyme known to regulate the tissular concentration of estradiol, or its response to the inductive effect of progesterone.

17-Hydroxysteroid Dehydrogenases↗
PubMed1978

Aryl hydrocarbon hydroxylase activity and microsomal cytochrome content of human fetal tissues.

Aryl hydrocarbon hydroxylase (AHH) and microsomal cytochromes were measured in tissues of human features aborted by prostaglandins. Cytochrome P-450 concentrations and AHH activity were about 4 times higher in adrenal glands than in liver. AHH was present in testes, ovaries, and vagina and uterus at levels equal to or greater than those in the liver. In lung, kidney, and intestines it was present at levels lower than those in the liver. Mean hepatic AHH and hepatic and adrenal cytochromes P-450 and b5 were not significantly different in prostaglandin and hysterotomy abortuses; mean adrenal AHH was significantly lower in prostaglandin abortuses, but the ranges in both groups were overlapping. Neither fetal sex nor maternal cigarette smoking affected hepatic or adrenal AHH activity or microsomal cytochrome concentrations or difference spectra. Hepatic and adrenal AHH activities were concentrated in microsomes and were correlated with microsomal P-450 content. These findings are constant with P-450 mediation of AHH in human fetal tissues. The data demonstrate the utility of prostaglandin abortuses for studies of fetal tissue mixed-function oxidase activity and point to the endocrine glands and target tissues in addition to the liver as potential sites for activating chemical carcinogens and cytotoxins in the human fetus.

Abortion, Induced↗
PubMed1977

Estrogen metabolism in normal and neoplastic endometrium.

Studies on normal endometrium at different phases of the menstrual cycle have shown that progesterone and synthetic progestins reduce the levels of estradiol receptors in the tissue and increase the activity of estradiol-17beta-dehydrogenase, an enzyme that converts estradiol to estrone. These effects may account for the antiestrogenic characteristics of the progestins. Similar effects were obtained in some postmenopausal patients with endometrial adenocarcinoma treated for two to 10 days with oral medroxyprogesterone acetate. These results point to the potential usefulness of a short-term, in vivo biochemical test which, combined with histologic observations, may identify patients who are likely to respond to treatment with progestins.

Adenocarcinoma↗
PubMed1975

Induction of human endometrial estradiol dehydrogenase by progestins.

Estradiol-17beta dehydrogenase activity in proliferative human endometrium (average of 1.5 nmole of estrone formed from estradiol/mg protein/h) was stimulated as much as as 6-fold during incubations of tissue slices in culture medium containing progesterone. Stimulation was already detectable at 7 h and the highest activity values were reached at 48-72 h of incubation in the presence of excess progesterone. Maximal stimulation was achieved with concentrations of the hormone of 0.25 mug/ml or higher. At concentrations approximately equal to midluteal plasma levels (20 ng/ml) more than 50% of the maximal response was observed. Norgestrel (17alpha-ethynyl-18-methyl-19-nortestosterone) was also effective in inducing enzymatic activity. The similarity of the effects obtained with progesterone (a possible substrate for estradiol dehydrogenase) and the synthetic progestin indicates that the stimulation of enzymatic activity was not due to substrate induction. Addition of estradiol to the culture medium had no influence on the activity of the enzyme. The induction of estradiol dehydrogenase by progesterone was inhibited by puromycin or actinomycin D. These observations indicate that progestational agents increase the rate of de novo synthesis of the enzyme. Stimulation of endometrial estradiol dehydrogenase was also observed after 2-3 day oral administration of medroxyprogesterone acetate to women in the follicular phase. In contrast, the enzymatic activity in endometrium obtained from women taking estrogens was found to be as low as in normal proliferative tissue. These in vitro and in vivo results point to progesterone as the agent responsible for the 10-fold increase in endometrial estradiol dehydrogenase activity observed during the luteal phase in menstruating women. Data obtained from superfusion studies of estrogen dynamics in endometrium indicate that changes in enzyme concentrations may play a physiologic role in the regulation of tissue levels of estradiol.

Adenocarcinoma↗