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Biomedical subjects

S C Brooks

Publications and source records attributed to S C Brooks.

At least 73 records · Page 4Linked to original sources
PubMed1988

The release of residual monomeric methyl methacrylate from acrylic appliances in the human mouth: an assay for monomer in saliva.

A gas-liquid chromatography assay has been developed for the estimation of methyl methacrylate monomer (MMA) in whole saliva, with a lower limit of detection in the order of 1 microgram/mL. Healthy human dentate subjects wore recently made autopolymerized or heat-polymerized polymethyl methacrylate (PMMA) palatal appliances. MMA released into saliva was detected for up to one week after insertion of autopolymerized appliances, with a maximum concentration of 45 micrograms/mL in whole saliva or 180 micrograms/mL in the salivary film on the fitting surface. The MMA was not detected in blood or urine. MMA was also present in the saliva of volunteers wearing appliances which had been heat-polymerized at 70 degrees C for one hr but not cured at 70 degrees C for three hr. The maximum amount of monomer released by an autopolymerized base plate was 29.5 micrograms in the first hour, which, while not a toxic or primary irritant dose, could possibly sensitize patients or elicit an allergic reaction. For minimization of monomer release, autopolymerized appliances should be immersed for 24 hr in water before being worn.

Acrylic Resins↗
PubMed1987

A-ring substituted estrogens as inhibitors of the MXT transplantable mammary ductal carcinoma.

A-ring substituted estrogens have been examined as growth inhibitors of the hormone dependent MXT murine mammary tumor. Certain of these estrogen analogues inhibited the growth of newly implanted as well as established MXT tumors when administered either by s.c. or i.p. injections or by intubation. These compounds were nontoxic over a broad range of active levels. Amino and nitro groups, introduced at position-4 of estrone 3-methyl ether were particularly carcinostatic, a property not shared by 4-bromoestrone 3-methyl ether. In addition tumor inhibition was greatly diminished by placing the nitro group at the other ortho position (i.e., carbon-2). Evidence indicates that the A-ring substituted estrogens may function as growth inhibitors via the estrogen receptor mechanism in the case of 4-nitro- and 4-aminoestrone. The 3-methyl ethers of these compounds also blocked tumor growth, possibly through in vivo dealkylation leading to the free phenolic A-ring substituted estrogens. On the other hand, A-ring substituted 3-deoxyestrogens (particularly 4-nitro- and 4-aminoestratrien-17 beta-ol), which do not bind to receptor, were also excellent inhibitors of hormone dependent MXT breast tumors and therefore must express their activity by mechanisms other than that mediated by receptor. The A-ring substituted estrogens are unlike tamoxifen and diethylstilbestrol which (a) display toxicity at optimum inhibitory doses and (b) are inactive or marginally active in rodent breast cancer models.

Animals↗
PubMed1987

Endocrine steroid sulfotransferases: porcine endometrial estrogen sulfotransferase.

Porcine endometrial estrogen sulfotransferase has been isolated and its properties examined. This enzyme only appeared in uteri from ovariectomized gilts which had been primed with estrogen and treated with progesterone. The most stable form of the enzyme was obtained via chromatofocusing of the 100,000 g supernatant from secretory endometrium. A molecular weight of 31 KDa was determined for this sulfotransferase by molecular sieve (Sephadex G-200 Superfine) and disk-gel electrophoresis. The active protein displayed a pI of 6.1, pH optimum of 7.6-7.8 and a requirement of 10 mM Mg2+ for maximum transfer of sulfate from 3'-phosphoadenosine-5'-phosphosulfate (PAPS) to estrone (E1). Km of the reaction was 24 +/- 4.7 microM for PAPS and 24 +/- 9.8 nM for E1 as substrate. Porcine endometrial sulfotransferase thus displayed a much greater affinity for E1 than a similar enzyme previously isolated from bovine adrenals. As has been observed of sulfotransferases from other tissues, an endogenous substrate (presumed to be E1) accompanies the enzyme throughout its purification.

Animals↗
PubMed1986

Endocrine steroid sulfotransferases: steroid alcohol sulfotransferase from human breast carcinoma cell line MCF-7.

Steroid alcohol sulfotransferase (SAS) has been isolated from the cytosol of a human breast carcinoma cell line, MCF-7. This enzyme from Sephadex G-200 chromatography displayed a mol. wt of 118 KDa. The conditions for optimal enzymic activity of SAS were determined to be 20 min incubations at 45 degrees C in 0.2 M Tris buffer (pH 7.5) containing 0.06 M Mg2+. Chromatofocusing chromatography also yielded a single peak of SAS with a pI of 5.8. Results from the incubations of a series of androstane analogues revealed that SAS required a 3 beta-hydroxyl on a steroid with the trans bridge between the A and B rings. Neither the 3 beta-allylic hydroxyl group nor the A-ring phenolic 3-hydroxyl accepted the sulfate group from 3'-phosphoadenosine-5'-phosphosulfate. D-ring beta-hydroxyl groups were tolerated by the enzyme, however, alpha-hydroxyl groups on the D-ring appeared to interfere with the reaction. Sulfurylation of steroids by SAS was related inversely to the sum of the displacements of the 3-hydroxyl plus that of the 17-hydroxyl groups relative to the plane of symmetry of the dehydroepiandrosterone nucleus. This enzyme was also capable of sulfurylating short chain aliphatic alcohols, although at greatly reduced rates. 3 beta-Chloro-5-androstene-17-one and 2-nitroestradiol. 17 beta proved to be the best inhibitors of SAS.

Breast Neoplasms↗
PubMed1986

In vitro inhibition of estrogen sulfoconjugation by some 2- and 4-substituted estra-1,3,5(10)-trien-17 beta-ols1a.

Hormone-responsive rat and human mammary tumor, unlike normal epithelium, actively sulfoconjugates estrogens. The title compounds (9-11) were synthesized in search of specific inhibitors of estrogen sulfotransferase as a possible means of developing effective chemotherapeutic agents for treatment of hormone-dependent human mammary cancer. 4-Nitroestrone 3-triflate (7a) was converted to the corresponding estradiol derivative (8a) in 93% yield by reduction with NaBH4 under phase-transfer conditions. Catalytic reduction (10% Pd/C) of the latter gave 4-aminoestra-1,3,5(10)-trien-17 beta-ol (9a) in 77% yield. These same reactions were applied consecutively to 4-nitroestrone 3-nonaflate (7b) to give 9a in 56% overall yield. The amino steroid (9a) was converted to 4-fluoroestra-1,3,5(10)-trien-17 beta-ol (10a) via a Balz-Schiemann reaction, in 17% overall yield. Successive NaBH4 and (10% Pd/C) catalytic reductions of 4-fluoroestrone 3-O-(1-phenyl-1H-tetrazol-5-yl) ether (2b) provided a less satisfactory route to 10a. MCPBA oxidation of 9a gave 4-nitroestra-1,3,5(10)-trien-17 beta-ol (11a) in 56% yield. The same series of reactions were applied to 2-nitroestrone 3-triflate (7c) to give 2-amino- (9b), 2-fluoro- (10b), and 2-nitro- (11b) estra-1,3,5(10)-trien-17-ols in comparable yields. Substitution in the A ring results in improved inhibition of porcine endometrial sulfotransferase sulfoconjugation of estradiol relative to estra-1,3,5(10)-trien-17 beta-ol (4a). Moreover, electronegative substitution at C-4 of 4a is more effective than at C-2. In particular, the Ki (2.43 +/- 0.16 microM) of 11a is sixfold smaller than that of the unsubstituted steroid (4a).

Animals↗
PubMed1985

Racial differences in breast cancer patients.

One thousand seventy-eight patients diagnosed with primary breast cancer were examined for racial differences in histopathologic and clinical parameters. There were no observed differences in tumor histopathologic type or tumor endocrine status between races. There were no differences with respect to time to breast tumor recurrence observed between black and white patients. However, differences were observed in factors that contributed to tumor stage at diagnosis and to tumor grade. Survival differences observed in univariant analysis of blacks vs. whites were explainable by the presence of more severe skin involvement, tumor grade, and tumor size at diagnosis in the black patients.

Black People↗
PubMed1985

Presurgical serum immunoglobulin concentrations and the prognosis of operable breast cancer in women.

Serum concentrations of IgG, IgA, IgM, IgE, and allergen-specific IgE were measured in presurgical serum samples from 400 women admitted to a multidisciplinary study of primary breast cancer. The relationships between the serum immunoglobulins and patient survival were analyzed with the use of a Cox proportional hazards linear model. After adjustment for TNM stage, tumor histopathologic grade, and estrogen receptor (E2R) status, lower IgM concentrations were associated with longer survival. Lower IgE concentrations were also associated with longer survival, but only in patients whose tumors were E2R positive. IgG and IgA were not related to survival. Serum IgM and IgE concentrations, allergen-specific IgE scores, and the tumor E2R status were combined to construct a three-level risk classification that was more prognostic than any of the individual components. Cox model analysis demonstrated that this combination of immunologic and hormonal variables provided significant new information beyond that obtained from TNM staging and histopathologic grading of the tumors (P = .01). This new information may be useful to physicians in advising patients with primary, operable breast cancer about the relative risks and benefits of adjuvant therapy and in designing clinical trials of adjuvant therapy.

Breast Neoplasms↗
PubMed1984

Stereochemistry of poly(methyl methacrylate) acrylic resin denture base material.

Nuclear magnetic resonance (NMR) 13C has been used to determine the tacticity of poly(methyl methacrylate) (PMMA) denture base materials. Curing cycle has no effect on tacticity. A tendency towards a mainly syndiotactic arrangement is shown. Industrially produced PMMA showed the same tacticity as the dental products.

Acrylic Resins↗
PubMed1984

Effect of growth on the estrogen receptor levels in MCF-7 cells.

MCF-7 cells have been shown to contain estrogen receptor in several cell fractions following homogenization: nuclei, microsomes, and cytosol. The amount of 17 beta-estradiol-binding capacity found in each cellular compartment depended on the inclusion of detergent in homogenization buffers and on the use of 0.25 M sucrose in the nuclear washes. 17 beta-Estradiol receptor (E2R) associated with nuclei (whole nuclei exchange assay, 0.6 M KCl soluble, and that found on membranes sheared from crude nuclear pellets by centrifugation in 0.25 M sucrose buffer) displayed a dissociation constant (Kd) of 0.77 +/- 0.01 (S.D.) nM (n = 7). KdS of the cytoplasmic (microsomes and soluble) receptors were determined to be 0.33 +/- 0.10 nM (n = 9). Exchangeable ligand on partially purified nuclei assumed its highest level in MCF-7 cells during logarithmic growth in serum-containing media (0.8 pmol/micrograms DNA) but declined after the culture reached confluence (0.2 pmol/micrograms DNA). Seventy-five % of the nuclear E2R declined linearly after feeding MCF-7 cells in logarithmic growth phase an estrogen- and serum-free medium (t1/2 3.5 days). Another class of salt-extractable nuclear receptor (0.2 pmol/micrograms DNA) persisted in postconfluent cultures whether fed estrogen (serum-containing media) or not (serum-free media). This residual binding capacity remained in nuclei of MCF-7 cells for an extended period of time. MCF-7 cells demonstrated functionality of E2R throughout their growth phases as evidenced by the replenishment of cytosolic E2R and the induction of progesterone receptor when given 17 beta-estradiol.

Breast Neoplasms↗