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M Borrás

Publications and source records attributed to M Borrás.

At least 19 recordsLinked to original sources
PubMed1997

Effects of time of storage, albumin, and osmolality changes on outflow facility (C) of bovine anterior segment in vitro.

PURPOSE: To analyze the influence of time of storage, the presence of albumin at physiological concentrations, and the perfusion with anisosmotic media on the aqueous humor outflow facility (C) of isolated bovine anterior segments (AS). METHODS: Anterior segments dissected from cow eyes were perfused at a constant pressure of 10 mm Hg with Dulbecco's modified Eagle's medium (DMEM; osmolality 300 mOsm/kg), with hyposmotic media (150, 210, and 270 mOsm/kg), or with hyperosmotic media (360, 420, and 480 mOsm/kg). Outflow facility was calculated every 5 seconds as the ratio between average inflow from the reservoir (in microliters per minute) and the perfusion pressure (in millimeters of mercury). Three groups were studied: a 0-hour group, with AS perfused with DMEM 1 to 3 hours after enucleation; a 0-hour alb-group, with AS perfused with DMEM plus 0.1 mg/ml albumin 1 to 3 hours after enucleation; and a 24-hour group, with AS perfused after storage for 24 hours in DMEM. In the 0-hour groups, perfusion with increasingly hyposmotic or hyperosmotic media was also made in 30-minute steps, followed by a return to isosmotic medium for 90 minutes. RESULTS: Perfusion of AS with DMEM for 9 hours caused a progressive increase in C that was statistically significant at 225 minutes in the 0-hour group perfused with DMEM and at 195 minutes in the 24-hour group perfused with DMEM. The 0-hour alb-group perfused with DMEM did not show changes in C throughout the 9-hour perfusion period. Perfusion with increasingly hyposmotic media induced a progressive decrease in C that did not recover on return to isotonic medium. Hyperosmotic media caused a progressive increase in C that returned to control values when isotonic medium was again perfused. CONCLUSIONS: Preservation of tissue for C measurements is best achieved with short storage time (1 to 3 hours). Physiological concentrations of albumin (0.1 mg/ml) prevent development of washout, suggesting that albumin or an albumin-bound factor in aqueous humor may play a role in the maintenance of outflow resistance. Outflow facility also may be influenced by volume changes in the trabecular meshwork.

Animals↗
PubMed1996

Estrogenic and antiestrogenic regulation of the half-life of covalently labeled estrogen receptor in MCF-7 breast cancer cells.

Effect of estrogens and antiestrogens (AEs) on estrogen receptor (ER) half-life was analyzed in MCF-7 cells by assessing its progressive disappearance after covalent labeling in situ with [3H]tamoxifen aziridine ([3H]TAZ). Cells were incubated for 1 h with 20 nM [3H]TAZ either in the absence or presence of a 500-fold excess of unlabeled estradiol (E2) (non-specific binding). The entire ER population was labeled by this method as established by subsequent incubation of the cells with [125I]E2. [3H]TAZ labeled cells were maintained in culture for additional 5 h in the absence (control) or presence of increasing amounts (0.1 nM - 1 microM) of either a given estrogen (E2, estrone, diethylstilbestrol, bisphenol), a pure AE (RU 58 668, ICI 164 384) or an AE with residual estrogenic activity (RU 39 411, 4-hydroxytamoxifen, keoxifene). The progressive disappearance of nuclear and cytosolic [3H]TAZ-ER complex during 5 h incubation were assessed by their immunoprecipitation with anti-ER monoclonal antibody (H 222) followed by scintillation counting or SDS-PAGE and fluorography. Fading of labeled receptors was extremely slow (approximately 10% loss after 6 h) in absence of any hormone/antihormone indicating a long half-life of the [3H]TAZ-ER complex. Addition of estrogens as well as pure AEs led to a dramatic reduction of the half-life while AEs with residual estrogenic activity were extremely less efficient in this regard providing an explanation for the ability of latter compounds to up-regulate the receptor since they do not affect ER mRNA synthesis and stability. Receptor disappearance induced by estrogens was closely related to their binding affinity for ER. Newly synthesized ER emerged during the treatment with hormones or antihormones seems to be implicated in the phenomenon since [3H]TAZ was covalently bound and could, therefore, not be displaced by these compounds. Induction of synthesis of a short half-life peptide(s) with degradative activity was demonstrated by addition of cycloheximide or puromycine (both at 50 microM) which completely blocked ER disappearance. The fact that no cleavage products of ER were detected by SDS-PAGE suggested a lysosomial hydrolysis. Hence, hormonal modulation of only a part of ERs may down-regulate their total population until it reaches the steady-state level.

Breast Neoplasms↗
PubMed1995

Antiestrogenic activity of two 11 beta-estradiol derivatives on MCF-7 breast cancer cells.

Two 11 beta-derivatives of estradiol (E2) were tested for their potential antiestrogenic activity in the MCF-7 breast cancer model: one contained a phenoxydimethylaminoethyl side-chain (RU 39,411), the other a pentafluoropentylsulfinyl side-chain (RU 58,668). The former compound displayed mixed estrogenic/antiestrogenic properties, while the latter indicated only an antiestrogenic activity. Both the compounds produced a growth inhibition of MCF-7 cells at doses related to their binding affinity for the estrogen receptor (ER); E2 suppressed this inhibition. The compounds also down-regulated the estrogen binding capacity of the cells but failed to reduce ER mRNA levels, indicating that the grafting of their side-chains prevented this antagonistic effect usually observed with steroidal estrogens. Assessment of ER levels by enzyme immunoassay revealed a marked increase with RU 39,411 and a decrease with RU 58,668; different mechanisms of action should, therefore, be considered. Finally, the estrogenic activity of RU 39,411 was demonstrated by its strong ability to induce synthesis of the progesterone receptor; RU 58,668 failed to display this agonistic activity.

Antineoplastic Agents↗
PubMed1994

Estradiol-induced down-regulation of estrogen receptor. Effect of various modulators of protein synthesis and expression.

Incubation of MCF-7 cells with estradiol (E2) down-regulates estrogen receptor (ER) resulting in a progressive reduction of the capacity of cells to concentrate selectively [3H]E2. Scatchard plot analysis failed to detect any transformation of residual receptors into peptides of lower binding affinity. [3H]Estrone gave an identical ER disappearance pattern with an ER half-life comprised between 2 and 3 h. A similar value was established by incubating the cells with [3H]tamoxifenaziridine ([3H]TAZ) for 1 h before the addition of excessive unlabeled E2 which induced ER-down regulation and impeded any further labeling of the residual receptors. Submission of the [3H]TAZ labeled cell extracts to SDS-PAGE revealed no progressive emergence of low molecular weight cleavage products of the receptor (< 67 kDa). Two inhibitors of protein kinases, H-7 at 40 microM and H-89 at 20 microM, failed to block the E2-induced ER down-regulation. On the contrary, the protein phosphatases 1 and 2A inhibitor, okadaic acid, was effective with concentrations higher than 0.1 microM indicating that a dephosphorylation mechanism was involved in this phenomenon. Cycloheximide (CHX) also significantly reduced the receptor decrease at concentrations higher than 1 microM. G-C specific intercalating agents [actinomycin D (AMD) and chromomycin A3 at 1 microM] also prevented ER disappearance; ethidium bromide (EB) and quinacrine were ineffective. AMD and CHX operated immediately after their addition to the medium indicating an inhibitory action on the synthesis of an RNA and/or a peptide with high turnover rate involved in ER decline. Moreover, AMD produced its suppressive effects under conditions impeding any labeling of newly synthetized receptors (i.e. [3H]TAZ with an excess of unlabeled E2) rejecting the possibility of an increasing ER production which may partially hamper its disappearance. Finally, E2-induced ER mRNA down-regulation was similarly abolished by AMD while EB and CHX were devoid of effect.

Cycloheximide↗
PubMed1993

Mass transfer coefficient: comparison between methods.

The mass transfer area coefficient (MTC) is the best parameter for solute transport evaluation in continuous ambulatory peritoneal dialysis (CAPD) patients. We compared three simplified MTC methods (calculated according Garred, Krediet, or Lindholm) and the peritoneal equilibration test (PET) (Twardowski) to complex MTC (MTCX) (Randerson and Farrell) for urea and creatinine, by means of 29 tests performed in 24 stable CAPD patients. There were no significant differences (paired t-test) between MTCX and each of the simplified MTC, except for creatinine MTC calculated by Krediet's method, which was significantly different (MTCX: 9.36 +/- 4.32, K-MTC: 10.48 +/- 4.55, p < 0.05). Likewise, there was an acceptable correlation between complex MTC and each of the simplified methods including the PET. However, a more detailed study of the MTC's categorizations shows poor agreement with complex MTC categorization. Better results are obtained by PET categorization, which reaches good likelihood ratios either for positive or negative events. We conclude that simplified MTC or the dialysate/plasma ratio at 240 minutes for urea and creatinine has an acceptable correlation with complex MTC and can be useful in clinical practice. There is poor agreement between solute transport categorizations of simplified MTC and complex MTC. There is a better coincidence between the PET (D/P at 240 minutes) and complex MTC categorizations.

Adolescent↗
PubMed1992

Modulatory effect of nonesterified fatty acids on structure and binding characteristics of estrogen receptor from MCF-7 human breast cancer cells.

Arachidonic, docosahexaenoic and oleic acids were found to produce a dose-dependent cytotoxic effect on MCF-7 cells; palmitic and stearic acids were totally ineffective in this regard suggesting that solely unsaturated fatty acids were able to arrest mammary tumor cell growth. Similarly, only former acids were able to decrease the binding capacity and affinity (increase Kd value) of the cells for 3H-E2 in a dose-dependent manner. In the case of arachidonic acid (the reference fatty acid), this decrease was associated with a slight cleavage of the native 67 KDa estrogen receptor (ER) into 50 and 25-30 KDa peptides as demonstrated by sequential labeling of high-salt cell extracts with 3H-tamoxifen aziridine, specific immunoadsorption with H-222 anti-ER monoclonal antibody, SDS-PAGE and fluorography. Both, modifications in binding characteristics of ER and cleavage of the native 67 KDa receptor were found to be extremely marked when unsaturated fatty acids were directly added to the high-salt cell extracts. This clear influence on the ER structure was reflected on enzyme immunological assay (EIA) by a reduction of ER immunoreactivity of approximately 50% in presence of arachidonic acid. Our observations are discussed in terms of possible interference of unsaturated fatty acids either through transmembrane modulation of phosphokinases and/or phospholipases implicated in ER mechanism of action, or through an intracellular interaction between ER and these acids acting as second messengers in regulation of cellular functions.

Breast Neoplasms↗
PubMed1992

Peritoneal function tests: usefulness of simplified methods.

The Peritoneal Equilibration Test (PET) as standardized by Twardowski (T) and simplified Mass Transfer Coefficients (MTC) as per Garred (G) and Krediet (K) have been employed in our patients to assess: 1) the reproducibility of results, 2) correlation between methods, and 3) usefulness of patient categorization by simplified methods in contrast to PET patterns. We have performed 29 standardized PET (Dianeal 2.5%) in 24 stable CAPD patients. We have collected dialysate samples at 0, 30, 60, 120, 180 and 240 minutes. With this data we were able to calculate the dialysate/plasma ratio for PET, MTC as per Garred and MTC as per Krediet. Our results were not significantly different from data reported by the original authors, except for PET D/P urea at 240': 0.91 +/- 0.07(T) vs. 0.87 +/- 0.08 (our), p < 0.05. In our patients, good correlation was found between PET and MTC for urea, creatinine, and glucose, using both formulae (G and K). Patient categorization as High, High Average, Low Average, and Low by MTCs can well predict PET categorization with acceptable sensitivity and good specificity. We conclude there is good reproducibility of the methods. There is also a close correlation between PET, K and G methods for solute transport evaluation and patient categorization. Simplified methods can be substituted for the more complex ones.

Adolescent↗
PubMed1990

Liver, brain, and heart metallothionein induction by stress.

To date, stress has been reported to induce metallothionein (MT) synthesis in the liver only. In the present experiment, the effects of food and water deprivation alone or of immobilization stress plus food and water deprivation on liver, brain, and heart MT have been studied in adult male rats. Liver and brain MT levels were increased by immobilization stress as soon as 6 h after the onset of stress. Eighteen hours of immobilization, which is accompanied by food and water deprivation, further increased liver and brain MT levels and significantly increased heart MT content. A specific effect of immobilization was evident in all three tissues, because the effect of food and water deprivation alone was significantly lower than that of immobilization plus starvation. Changes in MT apparently were not related to changes in cytosolic Zn.

Animals↗