Biomedical subjects
M C Sánchez
Publications and source records attributed to M C Sánchez.
Cooperative Jahn-Teller phase transition in LaMnO3 studied by X-ray absorption spectroscopy.
The local structure of LaMnO3 across the Jahn-Teller (JT) transition at T(JT)=750 K was studied by means of x-ray absorption near edge structure and extended x-ray absorption fine structure at the Mn K-edge. Our results indicate a similar electronic local structure for Mn atoms above and below T(JT) and a dynamical tetragonal JT distortion of MnO6 octahedra above T(JT). The structural transition is originated by the ordering of tetragonally distorted octahedra. The entropy content of the transition is analyzed within the framework of the three-state Potts model with nearest neighbor antiferrodistortive coupling.
Prospective, randomised study with three HRT regimens in postmenopausal women with an intact uterus.
OBJECTIVE: To compare compliance, symptom control, bleeding patterns, lipid and biochemical changes in postmenopausal women treated with three regimens of HRT. METHODS: In a prospective, randomised, group comparative study, with 165 patients, the effects on the aforementioned parameters, as well as treatment compliance and side effects were studied with oral tibolone 2.5 mg per day, with cyclic combined regimen of transdermal oestrogen and progestogen (transdermal patch of 17beta-oestradiol 50 microg/day during 14 days and transdermal patch of 17beta-oestradiol 50 microg/day plus 0.25 mg/day NETA during the following 14 days), and with intermittent progesterone regimen (transdermal 17beta-oestradiol 50 microg/day and oral micronised natural progesterone 200 mg twice a week). Statistical analysis was carried out using the Fisher-test, analysis of the variance (ANOVA) and the Bouferoni test. RESULTS: Ten women dropped out of the tibolone group, 11 dropped out of the intermittent dosing group and 21 dropped out of the cyclid combined group. Irregular bleeding occurred at more rates in the cyclid combined group. Similar reductions in climacteric symptoms were found in the three groups. No differences were observed with respect to biochemical analysis. CONCLUSIONS: Efficacy and safety of the three treatment regimens being comparable, but the patients in our study preferred those that did not produce bleeding episodes.
Differential binding properties of human pregnancy zone protein- and alpha2-macroglobulin-proteinase complexes to low-density lipoprotein receptor-related protein.
Human pregnancy zone protein (PZP) is a major pregnancy-associated plasma protein strongly related to alpha2-macroglobulin (alpha2-M). Both alpha-macroglobulins (alpha-Ms) covalently bind proteinases, which is accompanied by the exposure of carboxy terminal receptor recognition domains important for the rapid clearance from the circulation and tissues. It is accepted that the molecule responsible for the clearance of alpha2-M- and PZP-proteinase complexes is the low-density lipoprotein receptor-related protein (LRP). Although both alpha-M-proteinase complexes bind to the same receptor, differences in the binding properties have been reported. In addition, although it is known that the binding of alpha2-M-proteinase complexes to LRP can be blocked by Ni2+, the effect on PZP-proteinase has never been examined. In order to investigate differences in the binding properties of both alpha-Ms to the receptor, we purified LRP from human placenta by affinity chromatography and then analyzed the specificity and affinity of binding of alpha2-M- and PZP-proteinase complexes to the receptor by enzyme immunoassay. Our results clearly established that although both alpha-M-proteinase complexes specifically bind to LRP, PZP-chymotrypsin complexes bind to the receptor with lesser apparent affinity (Kd approximately equal 320 nM) than alpha2-M-chymotrypsin complexes (Kd approximately equal 40 nM). We also demonstrated that Ni2+ blocks the binding of alpha2-M-chymotrypsin complexes, but not PZP-chymotrypsin complexes, to LRP. These data suggest that the binding to LRP involves conformational differences between both alpha-Ms in a region immediately upstream of the carboxy terminal receptor recognition domain. The possibility that PZP-proteinase complexes interact with other receptors not available to alpha2-M-proteinase complexes could be considered.
Pregnancy zone protein-tissue-type plasminogen activator complexes bind to low-density lipoprotein receptor-related protein (LRP).
Tissue-type plasminogen activator (t-PA), is a serine proteinase that catalyzes the initial and rate-limiting step in the fibrinolytic cascade. Its plasma activity is determined by the rate of release into the bloodstream, the rate of inhibition by plasminogen-activator inhibitor type 1 (PAI-1) and the rate of hepatic clearance. Two receptor systems contribute to the clearance of t-PA: the mannose receptor and the low-density lipoprotein receptor-related protein (LRP) that removes free t-PA as well as t-PA-PAI-1 complexes from the blood. During pregnancy a significant rise in the plasma levels of pregnancy zone protein (PZP) is observed, while alpha(2)-macroglobulin (alpha(2)-M) remains constant. Interestingly, the fibrinolytic activity is decreased during this period. In this context, we have recently demonstrated the in vitro formation of PZP-t-PA complexes. Here, we purified LRP from human placenta by affinity chromatography and then analyzed the binding specificity and affinity of PZP-proteinase complexes to the receptor by enzyme immunoassay (EIA). Our results clearly established that the binding of PZP-t-PA complexes to LRP was specific, saturable, and with K(d) = 337 +/- 31 nM. Moreover, by using the same EIA, we further observed that this binding was inhibited by receptor-associated protein. These data suggest that PZP, by binding to t-PA and promoting its clearance via LRP, might contribute in vivo to the downregulation of the fibrinolytic activity during pregnancy.
Local structure and oxidation state of Mn and Ni atoms in LaNi1-xMnxO3+delta perovskites.
X-ray absorption spectroscopy has been used to study LaNi1-x Mn(x)O3+delta perovskites (x = 0.1, 0.25, 0.5, 0.75, 0.9). We have analysed both, the oxidation state and the local structure around the transition metal atoms. XANES spectra of these samples suggest a mixed valence state for both transition metal atoms. The Mn K-edge is shifted to high energies as the Ni content is increased up to x=0.5. The opposite behavior is found instead, for the Ni K-edge. Samples with x=0.5 and x=0.25 present the Mn K-edge at the same energy but the absorption features are different for both samples. The local structure has also been studied by means of the EXAFS technique. The first coordination shell nicely reflects the structural change observed in this series from rhombohedral perovskites (x>0.5) to orthorhombic perovskites x<0.5). The changes in the local structure for Ni and Mn atoms agree with the variation of the oxidation state observed in the XANES spectra.
Geometric local structure at the Mn site in charge-ordered mixed valence manganites.
An extensive study of Mn K-edge absorption sepctroscopy has been carried out in La(1-x)Ca(x)MnO3 and Tb(1-x)Ca(x)MnO3 (x=0, 0.33, 0.5, 0.67, 1) series as a function of temperature. The EXAFS analysis for the charge ordering compounds (x > or = 0.5) shows the presence of a static distortion of the MnO6 octahedron in the whole temperature range. However, this local distortion is lower than the distortion found for Jahn-Teller compounds. Magnetoresistive compounds (x=0.33) show a regular octahedron in the low temperature metallic phase. Instead, no changes are found for the first coordination shell (Mn-O) across the charge ordering transition while Mn-Mn distribution shows minor variations with the temperature. The structural analysis of the second coordination shell suggests that the Mn-O-Mn angle is the most relevant parameter to describe the electric and magnetic behaviour of these compounds.
Mn K-edge XANES spectra of manganites measured by Kbeta emission.
The electronic state of Mn atoms in mixed valence manganites has been studied by means of X-ray absorption spectroscopy at the Mn K-edge. Higher resolution than in conventional measurements has been achieved by measuring the Mn Kbeta fluorescence line. We have found a unique resonance at the edge in the XANES spectra of intermediate composition RE1-xCa(x)MnO3 samples. The features of these XANES spectra do not depend on small changes in the local structure around the Mn atom. However, the spectra of the intermediate composition samples can not be reproduced by a linear combination of REMnO3 and CaMnO3 spectra. Accordingly, the electronic state of Mn atoms in these compounds can not be considered as a mixture of Mn3+ and Mn4+ pure states.
Has charge ordering actually been observed in manganites by resonant X-ray scattering?
The comparison between X-ray resonant scattering experiments and X-ray absorption data shows that no real Mn3+/Mn4+ charge ordering occurs in manganites with Mn3+/Mn4+=1 ratio. However, these experiments demonstrate the presence of two different types of manganese atoms with a different local geometrical structure. A structural model, which accounts for both X-ray absorption and resonant scattering experiments, is proposed.
[Women's attitudes to menopause and predictive variables].
OBJECTIVE: To find what women's attitudes to the menopause are and how these attitudes relate to certain personal variables. DESIGN: Multi-centre, transversal study. SETTING: 5 clinics at three urban and teaching health centres in Granada. PARTICIPANTS: A systematic randomised sample of women = 18 who attended on demand in June 1998: alpha = 0.05, accuracy = 3 and standard deviation from the scale of attitudes (SA), found through prior sampling, was 15.4. N = 101 women. INTERVENTIONS: Questionnaire through interview after consultation. MEASUREMENTS AND MAIN RESULTS: Dependent variable: scale of attitudes to the menopause with 29 items. INDEPENDENT VARIABLES: age, marital status, educational qualifications, work situation, cultural group, religion, continuity with her doctor, utilisation, menopausal status, perception of autonomy, opinion of the menopause, feelings towards the menopause, perceived health. ANALYSIS: homogeneity and validity of SA. Descriptive, univariate analysis of SA with independent variables. Multiple linear regression: we found 7 factors that explained 66.5% of variance. Age 43.4 +/- 17.5. 50.5% had not reached the menopause; 10.9% were in the peri-menopause; and 37.6% in the menopause. 70.3% had feelings of relief or were neutral; 54.5% had a positive view; and 21.8% expressed no opinion. The variables explaining attitudes were feeling, continuity, opinion, utility, autonomy and perceived health. CONCLUSIONS: Women had positive or neutral feelings and opinions about the menopause. Their attitudes to it were related to these variables and not to other social or demographic variables or to their menopausal status.
Cultures of human osteoblastic cells from dialysis patients: influence of bone turnover rate on in vitro selection of interleukin-6 and osteoblastic cell makers.
The factors contributing to renal osteodystrophy are still incompletely characterized. A variety of cytokines and growth factors appear to have ill-defined roles in this disease. Our aim is to compare osteoblastic cell growth and different osteoblastic markers in vitro with histomorphometric bone parameters and some serum bone-turnover markers in vivo in dialysis patients with either high- (HTBD) or low-turnover (LTBD) bone disease. Six patients were diagnosed to have LTBD, and another five patients, HTBD. Intact parathyroid hormone (PTH) and osteocalcin (OC) levels in serum were greater in patients with HTBD than in those with LTBD. Osteoblastic cells isolated from iliac crest biopsy specimens were grown in culture medium for different times up to 13 days. Osteoblastic cell growth (cell number and area under the cell growth curve) was greater in patients with HTBD than in those with LTBD. Static and dynamic bone formation parameters correlated with serum PTH levels. No correlation was found between PTH and osteoblastic cell proliferation. OC, C-terminal type I procollagen, and alkaline phosphatase osteoblastic secretion in vitro were similar in the HTBD and LTBD groups. However, interleukin-6 (IL-6) secretion was greater in cells isolated from patients with LTBD. Our results indicate that osteoblastic cell growth and osteoblastic IL-6 secretion are related to bone turnover in patients with osteodystrophy. Our findings support the hypothesis that factors other than PTH level might have an important role in affecting osteoblastic function in renal osteodystrophy.
Stabilization of homogeneous preparations of pregnancy zone protein lyophilized in the presence of saccharose. Structural and functional studies.
Human pregnancy zone protein (PZP) is a macromolecule of 360 kDa, organized as a disulfide-linked homodimer of two 180 kDa subunits, with an amino acid sequence and structure remarkably similar to that of human alpha2-Macroglobulin. Homogeneous PZP samples undergo fast aging forming oligomeric aggregates of high molecular weight. This aged PZP loses its ability to interact with proteinases and consequently, non-recognition of receptors occurs. In the present work, we assessed the effect of saccharose on the stability of native PZP on lyophilized samples kept for a long period of time. Herein, we demonstrate that the addition of 0.25 M saccharose to homogeneous PZP and further lyophilization is enough to prevent aging and preserve functional activity for more than 1 year. Hence, high quality samples, in terms of purity, stability and functional activity will allow to develop biochemical studies in order to know the PZP role in physiological and pathological states where the protein levels are increased, such as pregnancy and tumoral disorders.
Resonant "forbidden" reflections in magnetite.
Resonant x-ray scattering was used to investigate electronic fluctuations of the octahedral iron atoms in magnetite. We measured the (002) and (006) "forbidden" x-ray diffraction reflections permitted by the anisotropy of the iron anomalous scattering factor. The energy and azimuthal angle dependencies of these reflections, and the polarization analysis, are shown and discussed. The results clearly show p and d iron empty states ordering in magnetite at room temperature. Moreover, the octahedral iron atoms are electronically equivalent in a time scale lower than 10(-16) sec. Therefore, magnetite should be considered as an itinerant magnet and not as a fluctuating mixed valence material.
Interaction of human tissue plasminogen activator (t-PA) with pregnancy zone protein: a comparative study with t-PA-alpha2-macroglobulin interaction.
Human pregnancy zone protein (PZP) is a major pregnancy-associated plasma protein strongly related to alpha2-macroglobulin (alpha2-M). Interactions of tissue plasminogen activator (t-PA) with PZP and alpha2-M were both investigated in vitro and the complexes were analyzed by polyacrylamide gel electrophoresis (PAGE). The results demonstrated that PZP-t-PA complex formation was evident within 1 h of incubation, whereas alpha2-M-t-PA complexes were formed after 18 h. Conclusions were supported by the following evidence: (i) PZP and alpha2-M complexes revealed changes of the mobility rate in non-denaturing PAGE, similar to those observed with alpha-Ms-chymotrypsin; (ii) both PZP and alpha2-M formed complexes of molecular size >360 kDa by SDS-PAGE, in accordance with the covalent binding of t-PA, which was previously reported for other proteinases; and (iii) PZP underwent a specific cleavage of the bait region with appearence of fragments of 85-90 kDa as judged by reducing SDS-PAGE. In contrast, the proteolytic attack on alpha2-M was found to occur more slowly, requiring several hours of incubation with t-PA for generation of an appreciable amount of fragments of 85-90 kDa. The appearance of free SH-groups of alpha-Ms was further investigated by titration with 5, 5'-dithiobis(2-nitrobenzoic acid). The maximal level of SH-groups raised was 3.9 mol/mol of PZP and 3.5 mol/mol of alpha2-M, indicating approximately one SH-group for each 180-kDa subunit. Finally, t-PA activity in PZP-t-PA complex was evaluated by measuring the hydrolysis of the chromogenic substrate Flavigen t-PA. Our results revealed that prolongation of the incubation period of this complex increased t-PA-mediated hydrolysis of Flavigen t-PA until a plateau was reached, approximately between 60 and 120 min. The present study suggests that PZP, by binding to t-PA, may contribute to the control of the activity of proteinases derived from fibrinolytic systems.
Primary sensitization to Morus alba.
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Immunologic contact urticaria caused by asparagus.
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[Pulmonary granulomatosis caused by lentil aspiration].
Pulmonary nodular granulomatosis caused by aspirated lentils is a rare entity. We report the case of a healthy 8 years-old girl who suffered a choking life-threatening choking event during a meal, with cardiorespiratory arrest. After a delay of one month delay without symptoms, she developed respiratory distress with radiologic changes. Lung biopsy disclosed foreing body granulomas. Steroids were not used because of their uncertain effectiveness in these cases. One year later the patient's progress was satisfactory.
[Calibration and safety of sphygmomanometers in health centers of Murcia].
OBJECTIVE: To find the levels of calibration, safety and physical faults in the sphygmomanometers used in Health Centres. DESIGN: A multi-centre, observational, descriptive and crossover study. SITE. 7 Health Centres in the urban zone of Murcia and nearby towns. All the sphygmomanometers in the 7 Health Centres, that is 80 aneroid and 62 mercury ones. MAIN MEASUREMENTS AND RESULTS: It needs high-lighting that 43.7% of the aneroid sphygmomanometers and 12.3% of the mercury ones were wrongly calibrated. We noted that 20% of the measurements made with wrongly calibrated aneroid sphygmomanometers had a margin of error above +/- 8 mmHg, with a tendency towards under-registering. We found very significant differences between the average arterial pressure measured by aneroid instruments as against mercury ones (p < 0.001). The number of sphygmomanometers which show a margin of error greater than +/- 3 mmHg at every level of pressure is significantly greater in aneroid instruments than in mercury ones (p < 0.001). We found physical faults in 23.9% of the instruments. CONCLUSIONS: We consider the number of wrongly calibrated aneroid sphygmomanometers to be excessively high. Therefore mercury ones should be used whenever possible and particularly during diagnosis and treatment. Both aneroid and mercury sphygmomanometers should be regularly checked, using a proper procedure. Mercury instruments set at zero are correctly calibrated and can be used as a model for checking aneroid ones.