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Abstract
The equilibrium assembly of purified GDP-tubulin into microtubules induced by taxol and Taxotere has been studied as a function of solution variables, ligand, and nucleotide, in 10 mM sodium phosphate buffers. Assembly is coupled to the binding of one taxoid molecule per tubulin heterodimer, while binding to the unassembled protein is not detected within ligand solubility limits. Linked functions analysis has indicated that two Mg2+ and no more H+ ions are bound per tubulin-taxoid polymerized, and the heat capacity change is negligible within experimental error (determined by van't Hoff analysis and by differential scanning calorimetry), in contrast with drug-free control microtubule assembly and with the abnormal polymerization of the tubulin-colchicine complex. The apparent enthalpy change is ca. 240 kJ mol-1 (calorimetry), and the process is entropy driven. The apparent standard free energy change of taxoid-induced elongation at 2 mM free Mg2+, pH 6.1-6.7, and 37 degrees C is -29.5 +/- 0.4 (taxol) or -31.5 +/- 0.4 kJ mol-1 (Taxotere). This is independent of taxoid excess, which has indicated that the process measured corresponds to the elongation equilibrium of the fully liganded protein. Comparison to elongation in the absence of drug suggests an apparent linkage free energy change of binding and polymerization of -11.3 +/- 1.2 kJ mol-1. The taxoid-induced elongation of GTP-tubulin proceeds with an increment of apparent free energy change of -2.5 +/- 0.4 kJ mol-1 over GDP-tubulin. It is proposed that the taxoid binding changes the conformation of GDP-tubulin from inactive to active, allowing productive binding and elongation at the microtubule end. Among several possible model mechanisms discussed, it is particularly attractive to think of taxoids as double-sided ligands, which bind to tubulin at the microtubule end and participate in a lateral contact interface with the newly added tubulin molecule. In the kinetic pathway of assembly, these ligands should bind first to inactive Mg(2+)-induced linear GDP-tubulin oligomers and transform them into active bidimensional polymerization nuclei.
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152
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Menéndez M, Garay M, Verdasco E, González Ureña A. On the determination ofD00(CaCl) from translational energy threshold measurements. J Chem Phys 1993. [DOI: 10.1063/1.465184] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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153
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Sanz JM, García JL, Laynez J, Usobiaga P, Menéndez M. Thermal stability and cooperative domains of CPL1 lysozyme and its NH2- and COOH-terminal modules. Dependence on choline binding. J Biol Chem 1993; 268:6125-30. [PMID: 8454587] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Differential scanning calorimetry (DSC) has been employed to characterize the thermal denaturation of CPL1 lysozyme and its isolated fragments in the absence and presence of choline. The heat capacity function of CPL1 lysozyme shows two peaks with Tm values of 43.5 and 51.4 degrees C. At saturating concentrations of choline the second transition disappears, and the Tm is shifted to higher temperatures. The DSC thermogram of the C-CPL1 protein corresponding to the carboxyl-terminal domain of CPL1 lysozyme has a single peak with a Tm of 42.9 degrees C. The effect of choline is very similar to that observed for the whole CPL1 lysozyme. The NH2-terminal fragment obtained by proteolytic digestion shows a Tm of 52 degrees C, close to that of 51.4 degrees C found for the second transition of CPL1, and choline does not affect the Tm nor the denaturation enthalpy. These data suggest that choline is bound to the COOH-terminal domain of the protein. Deconvolution of the excess heat capacity curve of the CPL1 lysozyme shows that the data can be fitted to two two-state independent transitions. The analysis of the DSC curves showed that the NH2-terminal unfolding enthalpy steadily decreases with increasing concentrations of choline. These results indicate that, under saturating concentrations of choline, whole CPL1 could unfold as a single cooperative unit.
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154
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Menéndez M, Garay M, Verdasco E, Ureña AG. Collision energy and product polarization effects in the Ca*(1D2)+ HCl → CaCl*(A, B)+ H reaction. ACTA ACUST UNITED AC 1993. [DOI: 10.1039/ft9938901493] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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155
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Arriaga P, Menéndez M, Villacorta JM, Laynez J. Differential scanning calorimetric study of the thermal unfolding of beta-lactamase I from Bacillus cereus. Biochemistry 1992; 31:6603-7. [PMID: 1633173 DOI: 10.1021/bi00143a034] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The irreversible thermal unfolding of the class A beta-lactamase I from Bacillus cereus has been investigated at pH 7.0, using differential scanning calorimetry (DSC) and inactivation kinetic techniques. DSC transitions showed a single peak with a denaturation enthalpy of 646 kJ.mol-1 and were moderately scan rate dependent, suggesting that the process was partially kinetically controlled. The inactivation kinetics at constant temperature showed that the irreversible denaturation of the enzyme occurs as the sum of two exponential terms whose amplitudes are strongly temperature dependent within the transition range so that, at the lowest temperatures within this interval, irreversible inactivation would proceed mainly through the slow phase. The fraction of irreversibly denatured enzyme (D) as a function of temperature for a given scanning rate was calculated by numerical integration of the kinetic equation with temperature, using previously determined kinetic parameters. This D form was the most populated of the unfolded states only at temperatures well above the maximum in the calorimetric transition. Combination of the results of kinetic and DSC experiments has allowed us to separate the contribution of the final D state to the excess enthalpy change from the contribution arising from the reversibly denatured forms of the enzyme (I(i), i = 1,..., n), with the resulting conclusion that the scan rate dependence of the calorimetric traces was the result of two different dynamic effects, viz., the irreversible step and a slow relaxation process during formation of the reversibly denatured intermediate states. Finally, the problems of using results obtained at a single scan rate to validate the two-state kinetic model are commented on.
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156
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Bilbao R, Lezaun J, Menéndez M, Izquierdo M. Segregation of straw/sand mixtures in fluidized beds in non-steady state. POWDER TECHNOL 1991. [DOI: 10.1016/0032-5910(91)80061-m] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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157
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Royo C, Menéndez M, Santamaría J. Kinetics of catalyst regeneration by coke combustion. I. Increased reaction rate due to the presence of chromium. ACTA ACUST UNITED AC 1991. [DOI: 10.1007/bf02073013] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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158
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Rodriguez MA, Martinez MC, Martinez-Ruiz D, Paz Giménez M, Menéndez M, Repetto M. Death following crude oil aspiration. J Forensic Sci 1991; 36:1240-5. [PMID: 1919482] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
This is a report on three deaths following oil aspiration by workers in petrol tankers. Lung aspiration was demonstrated by the presence of a yellowish-brown material in the alveolar spaces, which was difficult to identify by optic microscopy. Volatile hydrocarbons from petroleum were identified in lung samples by gas chromatography/mass spectrometry.
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159
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González Ureña A, Menéndez M, Solé Sabaté A, Aguilar Navarro A. The influence of rotational energy on the cross-section of direct reactions: comparison of a simple model with classical trajectories. Chem Phys Lett 1991. [DOI: 10.1016/0009-2614(91)90036-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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160
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Bañares L, Menéndez M, Whitehead J, Muga J, Ureña A. Classical trajectory studies versus statistical model predictions of the reagent rotational energy dependence for the reaction Cl+ICH3→ClI+CH3. Chem Phys 1990. [DOI: 10.1016/0301-0104(90)90012-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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161
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Menéndez M, Laynez J, Medrano FJ, Andreu JM. A thermodynamic study of the interaction of tubulin with colchicine site ligands. J Biol Chem 1989; 264:16367-71. [PMID: 2777794] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The bicyclic colchicine analogue 2-methoxy-5-(2',3',4'-trimethoxyphenyl)-2,4,6-cycloheptatrien-1-on e (MTC) has been used to study the thermodynamics of specific ligand binding to the colchicine site of tubulin, employing isothermal reaction microcalorimetry. The binding of MTC to purified calf brain tubulin, in 10 mM sodium phosphate buffer, pH 7.0, is characterized by delta H degree = -19 +/- 1 kJ.mol-1, delta G degree = -31.8 +/- 0.6 kJ.mol-1, and delta S degree = 43 +/- 5 J.mol-1.K-1 at 298 K, with a slight variation in the temperature range from 283 to 308 K. The binding thermodynamics of colchicine and allocolchicine are similar to MTC under the conditions examined, suggesting related molecular interactions of the three ligands with the protein binding site. The standard enthalpy changes of binding of colchicine and MTC at 308 K coincide within experimental error. Therefore the more favorable free energy change of binding of colchicine must come from a larger binding entropy change (by about 20 J.mol-1.K-1). This difference could be attributed to the presence of the middle ring of colchicine, which is absent in MTC. Consistently, a similar entropy change is observed by the comparison of allocolchicine to MTC binding at several temperatures. In addition, allocolchicine binding is about 6 kJ.mol-1 less exothermic than MTC binding, which could be attributed to the presence in allocolchicine of a substituted phenyl ring instead of the colchicine-MTC tropolone ring. The present results and analysis are fully compatible with the previously proposed bifunctional binding of colchicine and MTC (through their trimethoxybenzene and tropolone moieties) to a bifocal protein binding site, and also with a partial immobilization of intramolecular rotation of MTC upon binding, which in colchicine is already constrained by its middle ring (Andreu, J. M., Gorbunoff, M. J., Lee, J. C., and Timasheff, S. (1984) Biochemistry 23, 1742-1752).
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162
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Menéndez M, Laynez J, Medrano FJ, Andreu JM. A thermodynamic study of the interaction of tubulin with colchicine site ligands. J Biol Chem 1989. [DOI: 10.1016/s0021-9258(19)84714-2] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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163
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Bilbao R, Lezaun J, Menéndez M, Abanades J. Model of mixing—segregation for straw/sand mixtures in fluidized beds. POWDER TECHNOL 1988. [DOI: 10.1016/0032-5910(88)80026-3] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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164
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Berger DK, Perez G, Bistritz J, Menéndez M, Kelly M, Pincus M. Hepatitis B virus markers and persistent antigenemia in adolescents. JOURNAL OF ADOLESCENT HEALTH CARE : OFFICIAL PUBLICATION OF THE SOCIETY FOR ADOLESCENT MEDICINE 1988; 9:374-7. [PMID: 3170302 DOI: 10.1016/0197-0070(88)90031-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Adolescents attending a municipal outpatient adolescent clinic in New York City were evaluated for the prevalence of hepatitis B virus (HBV) markers and persistent antigenemia. Among 313 teenagers tested in 1 year, 11.8% were HBV marker positive, and 4.8% had persistent antigenemia. Hispanic teens had a marker rate of 6.4% and an antigenemia rate of 1.4%. Dominican Republic teens had a significantly higher marker rate than Puerto Rican teens. Among Hispanics, sexual activity status and foreign- vs. U.S.-born status were not significantly related to the presence of HBV markers. Asian teenagers had a 50% marker rate and a 27.2% rate for persistent antigenemia. Marker and antigenemia rates were highest in the most recent immigrants. Unexplained persistent hematuria occurred more frequently in patients with HBV markers than in patients without markers. We recommend routine hepatitis B surface antigen screening in Hispanic and Asian adolescents. The greatest at-risk groups are Asians, especially recent immigrants, immigrants from the Dominican Republic, and probably patients with unexplained persistent hematuria.
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165
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Alonso J, Banares L, Menéndez M, Ureña AG. Variational transition state calculation: collision energy dependence of the M + RX → MX + R (M = alkali, X = halogen, R = radical) reaction family. CAN J CHEM 1988. [DOI: 10.1139/v88-228] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A variational transition state theory has been developed to account for the kinetic energy dependence of the reaction cross-section which is valid for the case where experiments are carried out at different, but fixed, collision energies. One of the main aspects of the present work is the inclusion of non-collinear configurations for the transition state.Analytical expressions for σR(ET) averaged over the angle of attack are presented and several model calculations where carried out for the M + RX → MX + R reaction family with an orientational dependence of the energy barrier. The relative success of the present model calculations has been rationalized considering the possibility that long range interactions, via alignment forces, would favour the collinear approach regardless of the initial angle of attack.
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166
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Menéndez M, Bañares L, Alonso J, Ureña A. Kinematics and dynamical effects in the total and differential excitation functions. A variational transition state theory analysis. Chem Phys 1988. [DOI: 10.1016/0301-0104(88)87173-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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167
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Berger DK, Perez G, Kyman W, Perez L, Garson J, Menéndez M, Bistritz J, Blanchard H, Dombrowski C. Influence of family planning counseling in an adolescent clinic on sexual activity and contraceptive use. JOURNAL OF ADOLESCENT HEALTH CARE : OFFICIAL PUBLICATION OF THE SOCIETY FOR ADOLESCENT MEDICINE 1987; 8:436-40. [PMID: 3667398 DOI: 10.1016/0197-0070(87)90233-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
We evaluated whether family planning counseling (FPC) in an adolescent clinic promoted the onset of sexual activity among the non-sexually active teens and/or increased contraceptive use among the sexually active teens. The FPC focused on the teens' establishing sexual values, the right to say "no," abstinence and alternate forms of intimacy, consequences of intercourse, and the various contraceptive methods. Data for one year were collected on the adolescents' first and subsequent visits to a medically oriented, municipal outpatient adolescent clinic. There were 383 teenagers who qualified for the study. Of these, 35% (134) reported premarital sexual activity. During the study period, 3% (8) of the 249 nonsexually active teens reported becoming sexually active. Among the 134 sexually active teens at clinic entry, 27% reported using a contraceptive method at their most recent sexual encounter. Among the 142 sexually active adolescents at the conclusion of the study, 76% reported contraceptive use at their most recent sexual encounter (p less than 0.001). We conclude that the provision of FPC to nonsexually active and sexually active teens does not appear to promote the onset of sexual activity significantly among the non-sexually active group, although it significantly increases contraceptive use among the sexually active group.
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168
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Corella J, Menéndez M. The modelling of the kinetics of deactivation of monofunctional catalysts with an acid strength distribution in their non-homogeneous surface. Application to the deactivation of commercial catalysts in the FCC process. Chem Eng Sci 1986. [DOI: 10.1016/0009-2509(86)87061-0] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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169
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García-Cubillana JM, Barrionuevo B, Menéndez M, Santiago F, Alvarez Silván AM. [Intraspinal mediastinal tumor. Pott's disease]. ANALES ESPANOLES DE PEDIATRIA 1985; 23:449-52. [PMID: 4091346] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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170
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Ramos E, Rodríguez-Vigil E, Alonso A, Suárez E, Poo P, Sánchez M, Miguel MA, Menéndez M, Castillo J. [Aicardi syndrome]. ANALES ESPANOLES DE PEDIATRIA 1982; 16:352-7. [PMID: 7125395] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The association in young girls of flexion spasms of early beginning, partial or total agenesis of the corpus callosum, severe chororetinopathy and frequent skeletal anomalies is known as the Aicardi syndrome. On occasion of two observations a review of the literature is made.
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171
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Rodríguez-Vigil Lorenzo E, Antuña García MJ, Menéndez M, Poo Argüelles P, Sobrino González A, Suárez Calvo E, Méndez Méndez J, Ramos Polo E, Roza Suárez M. [Clinical-therapeutical correlations in meningococcal infection: prophylactic heparin therapy (author's transl)]. ANALES ESPANOLES DE PEDIATRIA 1981; 15:343-8. [PMID: 7337300] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
A number of 241 patients with meningococcal infection, treated between 1972 and 1978, is analysed. Some new therapeutic patterns are established based on the application of the prognosis score of Stiehm. With these patterns consisting in the use of volume expansors with anti-aggregating properties and low dosage prophylactic heparin administration, authors have considerably improved their results reported in 1972, succeeding in diminishing the global mortality to 3.73%, a figure inferior to that of all known series to date.
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172
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Menéndez M, Galbe M, Antuńa MJ, Del Campo MA, Rodríguez-Vigil E. [Acute poisoning by I.M. iron. Report of a fatal case (author's transl)]. ANALES ESPANOLES DE PEDIATRIA 1978; 11:347-50. [PMID: 697206] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The case of a five months-old child who received 44 mg/Kg of Fe-sorbitol I.M. by mistake is reported. That dose is about ten times the usual standard dosage. After an initial vague symptomatology, followed by transitory improvement, she developed a serious metabolic acidosis, renal and hepatic failure and generalized convulsions. The clinical picture could not be controlled by general supportive treatment, desferroxamine administration and exanguino-transfusion.
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173
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Repetto M, Menéndez M. [Indixes of the quality of the environment]. REVISTA DE SANIDAD E HIGIENE PUBLICA 1975; 49:773-82. [PMID: 1236204] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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174
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Repetto M, Menéndez M. [Drug addiction to cannabis]. REVISTA DE SANIDAD E HIGIENE PUBLICA 1972; 46:155-67. [PMID: 4660995] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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175
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Repetto MJ, Menéndez M. [Identification of cannabis products on the fingers and in the blood of smokers]. EUROPEAN JOURNAL OF TOXICOLOGY 1971; 4:502-4. [PMID: 5155776] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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176
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Repetto M, Menéndez M. [Air pollution in Seville, 1970-71]. REVISTA DE SANIDAD E HIGIENE PUBLICA 1971; 45:921-54. [PMID: 4111884] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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