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Biomedical subjects

S C Brooks

Publications and source records attributed to S C Brooks.

At least 109 records · Page 6Linked to original sources
PubMed1979

The cyclic relationship of estrogen sulfurylation to the nuclear receptor level in human endometrial curettings.

Human endometrial curettings were selected principally from patients undergoing tubal ligations for elective sterilization. Specimens were analyzed for the metabolism of 17beta-[6,7-3H]estradiol and Na2 35SO4; assayed for the nuclear receptor content with 17beta-[6,7-3H]estradiol; and examined for the cytosol receptor content with 17beta-[2,4,6,7-3H]estradiol. The results of these experiments demonstrated that a) estrogen sulfotransferase activity is greatly stimulated during the secretory phase; b) although estrogen dehydrogenase is active throughout the menstrual cycle, the formation of estrone is elevated in concert with sulfurylation; and c) this increased metabolism of 17beta-estradiol is accompanied by a decreased nuclear uptake of the estrogen receptor complex. The importance of this endometrial estrogen metabolism in the maintenance of a secretory tissue is discussed.

Animals↗
PubMed1979

Characteristics of the dextran-coated charcoal assay for estradiol receptor in breast cancer preparations.

The measurement of E2 receptor (E2R) in human breast cancer cytosol is significantly influenced by conditions usually employed in the dextran-coated charcoal assay. The incubation time and temperature have an influence on the rate of binding and stability of the receptor. Since lower temperatures preserve the integrity of the receptor, a 2 hr incubation at 4 degrees was selected as the standard incubation procedure. These conditions allow for the detection of at least 80% of the E2R. With supernatants from high-speed centrifugation of HBT biopsies or the human breast cancer cell line MCF-7, reducing agents increased the apparent E2R binding in the order: DTT greater than G-SH greater than MTG. The maximum enhancement of specific E2R binding by a given thiol agent was dependent on its concentration in the incubation medium. The optimum DTT level (7.5 mM) for MCF-7 cell homogenization and cytosol equilibration with tritiated E2 increased E2R to two times control (no DTT). For the HBT 150,000 g supernatant, 1 mM DTT was required to optimize the E2R quantitation. The duration of the dextran-coated charcoal extraction of the cytosol-[3H]E2 incubation had no effect on the level of E2R up to 21 hr. Minimum levels of nonspecific binding of [3H]E2 could be obtained after 4 hr extraction. Maximum depletion of specific [3H]E2 binding could be obtained by adding between 200- and 1000-fold molar excess of unlabeled E2. Greater amounts of unlabeled steroid displaced the radioactive E2 from the dextran-coated charcoal, thereby artifactually increasing the apparent nonspecific binding. This phenomenon may be overcome by utilizing more dextran-coated charcoal in the extraction. However, there was a 9% loss of specifically bound [3H]E2 per milligram of dextran-coated charcoal (1:10 dextran to charcoal by weight) when the cytosol protein was below 90 microgram per incubation. Supplementation with 200 microgram or more albumin per incubation prevented this loss. The dextran:charcoal ratio also prevented E2R loss in the order: 1:1 greater than 1:10 greater than 1:100. One milligram of dextran-coated charcoal (1:10) has the capacity to adsorb 0.3 to 0.4 microgram of free E2. Other unlabeled competitors are capable of displacing [3H]E2 on the receptor. Although DES was as effective as E2, U11,100A and estrone were inefficient competitors. It appeared that the levels of these two estrogen analogues required to maximally displace [3H]E2 on receptor also eluted labeled E2 from the dextran-coated charcoal. DES, however, was unable to displace significant quantities of the [3H] E2 from dextran-coated charcoal even at a molar excess of 50,000:1.

Biopsy↗
PubMed1978

IV. Synthesis and assay of analogs of adenosine 3',5'-diphosphate as inhibitors of bovine adrenal estrogen sulfotranferase.

Analogs of adenosine 3',5'-diphosphate are described which aid in the characterization of the inhibition of estrone sulfurylation by 3'-phosphoadenosine 5'-phosphosulfate as mediated by bovine adrenal estrogen sulfotransferase (3'-5'-phosphosulfate:estrone 3-sulphotransferase, EC 2.8.2.4). The facile conversion of ribonucleosides to 2',3'-cyclic phosphate 5'-phosphate in neat pyrophosphoryl chloride is utilized to provide a reliable route to the requisite intermediates for enzymatic regiospecific conversion to ribonucleoside 3',5'- and 2',5'-diphosphates. The importance of the 3'-phosphate ester to inhibition of estrone sulfurylation is confirmed by Ki measurements. Replacement of the 6-amino group by hydrogen or oxygen leads to considerable loss in affinity for the enzyme as does also dimethylation of the exocylic amino group. Alterations in the pyrimidine ring are not well tolerated by the sulfotransferase but modifications in the imidazole ring as in tubercidin (7 -deazaadenosine) and 8-bromoadenosine 3',5'-diphosphate lead to an enhanced affinity. The latter findings are discussed in terms of an hypothesis of stacking of the aromatic ring of the estrogen substrate and the purine moiety and its analogs.

Adenine Nucleotides↗
PubMed1978

Nuclear and cytosolic estrogen receptor in gilt endometrium throughout the estrous cycle.

The levels of nuclear and uncharged cytoplasmic estrogen receptors were determined in gilt endometrium throughout the estrous cycle. Nuclear estrogen receptor was found to reach its highest level of 1.3 (range, 1.0-1.5) pmol/mg DNA on day 1 of the cycle just before ovulation (day 2), after which the values dropped sharply to 0.3 (range, 0.1-0.4) pmol/mg DNA. This level of nuclear receptor was consistently found through day 9. Between days 9-14, the estrogen receptor present in the nucleus decreased to zero, where it remained until the return of estrus (day 1). The dissociation constant (Kd +/- SD) for the nuclear estrogen receptor was 1.6 (+/- 1.4) x 10(-9) M. Initially, the nuclear estrogen receptor peak at day 1 was preceded by elevation (0.04-0.05 pmol/mg DNA) in cytoplasmic receptor at day 19, which declined when the receptor appeared in the nucleus. There was an even larger peak (range of maximal values, 0.07-0.26 pmol/mg DNA) of uncharged receptor in the cytosol near day 5. Throughout the rest of the cycle the values ranged from 0.01-0.03 pmol/mg DNA. Kd( +/- SD) for the cytoplasmic estrogen receptor was 2.4 (+/- 1.5) x 10(-9) M. The fluctuations of these two pools of endometrial estrogen receptor are discussed in relation to the previously observed cyclic variations in porcine uterine oxidation and sulfurylation of 17 beta-estradiol (Pack and Brooks, Endocrinology 95: 1680, 1974).

Animals↗
PubMed1978

Prognostic value of estrogen receptor determinations in patients with breast cancer.

The estrogen receptor content of human breast cancer specimens is related to the degree of differentiation (grade) of the tumor. In addition, patients with estrogen receptor-positive tumors experience fewer recurrences and remain disease free for a longer priod of time than do patients with receptor-negative tumors. The presence of estrogen receptor is not correlated with lymph node infiltration.

Adult↗
PubMed1978

Serotonin, folic acid, and uric acid metabolism in the diagnosis of neuropsychiatric disorders.

Metabolic compensation appears possible within the serotonergic, folate, purine system and it seems possible that clinical illness may result when the system can no longer compensate. For example, elevated serotonin, induced by stress accumulation of tryptophan, could be compensated by a lowered folate ratio, normalizing the beta-carboline index and preventing hallucinations. Conversely, deficient serotonin, induced by a psychological loss or transport deficit, could be compensated by raising the folate ratio, which would normalize the beta-carboline index and prevent further depression. Increased purine turnover would seemingly lower the folate ratio, compensating perhaps for hallucinatory activity or mania. Several genetic defects of enzymes or transport proteins could seemingly preclude normal compensations within the system.

Adolescent↗
PubMed1977

Studies on bovine adrenal estrogen sulfotransferase. Inhibition and possible involvement of adenine-estrogen stacking.

The inhibition of bovine adrenal estrogen sulfotransferase has been studied utilizing representative androgens and estrogens with structural changes in rings A, B, and D. These investigations have shown oxygen functions in positions 3, 16, or 17 to be required for the binding of estrogens or androgens to the enzyme. 5alpha-Androstanes (all transfused rings) are weak noncompetitive inhibitors and bind more tightly than the 5beta isomers (cis-fused A and B rings). The competitive inhibition observed with the estrogens does not require a free 3-phenolic hydroxyl, however, groups larger than 3-methoxy limit binding. While the product, estrone sulfate, is not inhibitory, phosphate esters on positions 3- or 17beta or a sulfate moiety on the 17beta-hydroxyl group of estrogens slightly inhibit the enzyme. The stacking of adenine (in adenosine 3'-phosphate-5'-phosphosulfate) with the A ring of estrogens is postulated for the enzyme-bound transition state. This structure, which facilitates the hydrogen bonding between the 6-amino group of adenine and the 4-nitro, 4-bromo, or 6-keto substituents on estrogens, readily explains the unusual substrate and inhibitory properties of these compounds. Certain of these estrogen derivatives, which possess little or no hormonal activity, are efficient inhibitors of estrogen sulotransferase.

Adenine Nucleotides↗
PubMed1977

Effect of prolactin on growth and the estrogen receptor level of human breast cancer cells (MCF-7).

The intracellular specific 17beta-estradiol binding in the human breast cancer cell line, MCF-7, was shown to be modified by prolactin. Both ovine and human prolactin doubled the estradiol receptor (E2R) level, but the latter was at least 10 times more stimulatory on a concentration basis. Most of the E2R complex (approximately 80%) was transported to the nucleus, and the prolactin stimulation was reflected in an elevated nuclear uptake of the tritiated 17beta-estradiol. Neither ovine nor human prolactin altered the growth rate of the cells when E2R stimulation was maximal. Insulin (10 mug/ml) stimulated tritiated thymidine incorporation and total DNA content but had no apparent effect on E2R concentration. At 10(-4) M, N6,O2'-dibutyrylcyclicadenosine 3':5'-monophosphate increased insulin stimulation of tritiated thymidine incorporation and brought about a prolactin stimulation of apparent DNA synthesis. Theophylline (10(-3) M) blocked both of these effects of N6,O2'-dibutyrylcyclicadenosine 3':5'-monophosphate. The possible mechanism implicating prolactin as an effector of differentiation and growth of MCF-7 cells is discussed.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1976

Estrogen receptor and natural course of breast cancer.

The tumors from approximately 50% of patients with breast cancer contained estrogen receptor (ER). ER appeared more often and at higher levels in the tumors of postmenopausal women. Eleven out of 12 patients who had multiple ER assays from various metastatic sites showed no significant discrepancies in ER values. ER level appears to decrease as the duration of metastatic cancer increase. Patients with ER in the tumor more frequently have bone metastases than those without ER. Visceral metastases occurred more often with ER negative patients and appeared to have a more malignant course with significant shorter survival.

Breast Neoplasms↗
PubMed1976

The fate of 17 beta-estradiol in the plasma of premenopausal and postmenopausal patients with cancer.

The patterns of radioactive estrogen metabolities in the plasma of patients with a variety of malignancies were determined after the injection of physiological amounts of 17 beta-estradiol-6,7-3H or of estrone-6,7-3H. The metabolites were separated and isolated from the plasma by the following procedures: a) alumina chromatography, b) modified Brown procedure, and c) gas liquid chromatography. This study showed that the conjugated state of the estrogens varied with the subjects's age. There was a dramatic decrease in the relative quantity of the plasma free estrogens which are converted to sulfates as the age of the patient increased. This change was noted just prior to menopause, suggesting that there are alterations in the conjugation of plasma estrogens which are detectable before clinical menopause.

Adenocarcinoma↗
PubMed1976

The surgical implications of estrophile protein estimations in carcinoma of the breast.

Assays of estrophile protein (ER) in 161 patients with no previous additive or ablative hormonal therapy have been analyzed; 47.2 percent were ER positive; 52.8 percent ER negative. A total of 37.5 percent of premenopausal and 50.8 percent of postmenopausal patients had ER-positive tumors. The effects of additive and ablaive hormonal therapy were observed in 75 patients; 63.5 percent of the ER-positive group and 8.6 percent of the ER-negative group responded, but the incidence in the ER-negative group is thought to be spuriously high. The level of the ER content in the ER-positive group did not influence the degree of response. The ER-negative group had a shorter life span after discovery of the tumor and was more likely to develop dominant visceral metastases. Of 15 patients followed with sequential ER assays after hormonal therapy (additive and/or ablative), 14 demonstrated substantial falls in ER levels but these did not correlate with the clinical response. Tumor assayed in nine patients after irradiation of the lesion contained no demonstrable ER. ER assays of breast cancer tissue proved to be a useful but imperfect tool in predicting clinical progress following hormonal maneuvers but some readings may be spuriously low due to imperfect techniques of measurement, prior exogenous hormonal administration or hormonal ablation, and previous irradiation of the tumor.

Adrenalectomy↗
PubMed1975

The steroid alcohol and estrogen sulfotransferases in rodent and human mammary tumors.

Rodent and human mammary tumor systems were investigated to relate the steroid alcohol and estrogen sulfotransferase activities to the hormoanl dependency of the tumor as determined by estrogen receptor content. Unlike the normal mammary gland or the hyperplastic alveolar nodule, rodent mammary neoplasms displayed significant levels of these two sulfotransferases. In the hormone-independent mouse tumors produced from out-growth lines D1, D2, and D8, high dehydroepiandrosterone sulfotransferase activity was characteristic of the rapidity with which hyperplastic alveolar nodules developed into a neoplasms (V-max = 52.8 versus 1.8 fmoles/min/mg protein) while estrone sulfotransferase activity was either not detectable or low (V-max = 5.5 fmoles). After oophorectomy of mice bearing slowly developing tumors, both sulfotransferases in the nonregressing neoplasms showed marked increases in activity (V-max dehydroepiandrosterone = 30.0 fmoles; V-max estrone = 18.5 fmoles). Strain differences not the estrogen receptor content of hormone-dependent rat mammary tumors. In Wistar-Lewis rats the steroid alcohol sulfotransferase activity was at least 35 times higher than in the Sprague-Dawley strain. As was observed in the mouse mammary tumor, Sprague-Dawley rat neoplasms that grew in the absence of ovarian hormones contained significantly greater levels of the steroid alcohol sulfotransferase. Possible correlaion between presence of the steroid alcohol sulfotransferase and the estrogen receptor protein was observed in a limited number of human breast carcinomas.

Alcohols↗