Peptidyl Arginine Deiminases in Chronic Diseases: A Focus on Rheumatoid Arthritis and Interstitial Lung Disease.

Protein citrullination is accomplished by a broad enzyme family named Peptidyl Arginine Deiminases (PADs), which makes this post-translational modification in many proteins that perform physiological and pathologic mechanisms in the body. Due to these modifications, citrullination has become a significant topic in the study of pathological processes. It has been related to some chronic and autoimmune diseases, including rheumatoid arthritis (RA), interstitial lung diseases (ILD), multiple sclerosis (MS), and certain types of cancer, among others. Antibody production against different targets, including filaggrin, vimentin, and collagen, results in an immune response if they are citrullinated, which triggers a continuous inflammatory process characteristic of autoimmune and certain chronic diseases. PAD coding genes (PADI1 to PADI4 and PADI6) harbor variations that can be important in these enzymes' folding, activity, function, and half-life. However, few studies have considered these genetic factors in the context of chronic diseases. Exploring PAD pathways and their role in autoimmune and chronic diseases is a major topic in developing new pharmacological targets and valuable biomarkers to improve diagnosis and prevention. The present review addresses and highlights genetic, molecular, biochemical, and physiopathological factors where PAD enzymes perform a major role in autoimmune and chronic diseases.

Aerobic exercise and insulin resistance indicators in sedentary woman / Ejercicio aeróbico e indicadores de resistencia a la insulina en sedentarios mujer

The aim of this study is to determine the concordance between the insulin resistance indicators, HOMA and TyG, because ofa moderate intensity aerobic exercise session in sedentary young women. Methods: A total of 22 sedentary women between 18 and 35 years of age participated in this research. HOMA and TyG indiceswere determined before and after a moderate intensity aerobic exercise (MIAE), based on Heart Rate reserve. Spearman andKendall’s Tau-b were used to evaluate the association between those variables. Values were compared using the Bland &Altman graphs: Kappa Coefficient was used to estimate the proportion of concordance observed between both indicators. Significant differences were considered at a p≤0.01.Results: Spearman's Rho correlation and Kendall's Tau-b before MIAE were significant and direct (r=0.634, p<0.001 andr=0.480, p<0.01; respectively) with a Cohen's Kappa index of k=0.585. After MIAE, Spearman's Rho correlation and Kendall'sTau-b were also significant and direct r=0.650, p<0.001 and r=0.504, p<0.001, respectively, with a lower Cohen's Kappa index(k=0.390). Conclusions: TyG index is a good indicator to evaluate insulin resistance at baseline situations. However, this index doesn’tproperly determine insulin resistance after a MIAE.(AU)

Reaction of NO2 with Groups IV and VI Transition Metal Oxide Clusters.

The addition of NO2 to Group IV (MO2)n and Group VI (MO3)n (n = 1-3) nanoclusters was studied using both density functional theory (DFT) and coupled cluster theory (CCSD(T)). The structures and overall binding energetics were predicted for Lewis acid-base addition without transfer of spin (a physisorption-type process) and the formation of either cluster-ONO (HONO-like or bidentate bonding) or NO3- formation where for both the spin is transferred to the metal oxide clusters (a chemisorption-type process). Only chemisorption of NO2 is predicted to be thermodynamically allowed at temperatures ≥298 K for Group IV (MO2)n clusters with the formation of surface chemisorbed NO2 being by far the most energetically favorable. The ligand binding energies (LBEs) for physisorption and chemisorption on the TiO2 nanoclusters are consistent with computational studies of the bulk solids. Chemisorption is only predicted to occur for (CrO3)n clusters in the form of a terminal nitrate containing species whereas the larger chemisorbed nitrate structures for (MoO3)n and (WO3)n were found to be metastable and unlikely to form in any appreciable amount at temperatures of 298 K and higher. NO2 is predicted to only be capable of physisorbing to (MoO3)n and (WO3)n at lower temperatures and therefore unlikely to bind NO2 at temperatures ≥298 K. Correlations between the (MO3)nNO2 ligand bond energies and the chemical properties of the parent (MO3)n clusters (Lewis acidity, ionization potentials, excitation energies, and M = O/M-O bond strengths) are described.

Heterozygous Genotype rs17580 AT (PiS) in SERPINA1 is Associated with COPD Secondary to Biomass-Burning and Tobacco Smoking: A Case-Control and Populational Study.

Purpose: The protease inhibitor S (PiS) and Z (PiZ) variants have been stated as the only genetic cause of chronic obstructive pulmonary disease (COPD) in Caucasians. However, its frequency in admixed populations is low. We aimed to identify genetic susceptibility between PiS (rs17580) and PiZ (rs28929474) polymorphisms with COPD related to tobacco smoking and biomass-burning smoke as well as to determine its frequencies in Mestizo and Amerindian populations from Mexico. Patients and Methods: One thousand and eight hundred seventy-eight subjects were included in two comparisons of cases and controls, (1) smokers with and without COPD (COPD-S, n=399; SWOC, n=1106); (2) Biomass-burning smoke-exposed subjects with and without COPD (COPD-BS, n=98; BBES, n=275). In addition, 2354 Mexican subjects identified as Mestizos (n=1952) and Amerindian (n=402) were included. The population structure was evaluated using 59 informative ancestry markers. Results: The AT genotype of rs17580 is associated with COPD in both comparisons (COPD-S vs SWOC p<0.001, OR=2.16; COPD-BS vs BBES p<0.0001, OR=11.50). The population of the Mexico-North has a greater Caucasian contribution (54.7%) compared to the center (46.9%) and southeast (42.7%). Conclusion: The rs17580, AT genotype, is associated with COPD in Mexican-Mestizo smokers and exposed to biomass-burning smoke. The rs17580 AT is more frequent in the Mexican-Mestizo population of the North of the country, which has a high Caucasian component.

HLA Allele and Haplotype Frequencies in Three Urban Mexican Populations: Genetic Diversity for the Approach of Genomic Medicine.

Genetic variability defends us against pathogen-driven antigens; human leucocyte antigens (HLA) is the immunological system in charge of this work. The Mexican mestizo population arises mainly from the mixture of three founder populations; Amerindian, Spaniards, and a smaller proportion of the African population. We describe allele and haplotype frequencies of HLA class I (-A and -B) and class II (-DRB1 and -DQB1), which were analyzed by PCR-SSP in Mexican mestizo from three urban populations of Mexico: Chihuahua-Chihuahua City (n = 88), Mexico City-Tlalpan (n = 330), and Veracruz-Xalapa (n = 84). The variability of the allele HLA class I and class II among the three regions of Mexico are in four alleles: HLA-A*24:02 (36.39%), -B*35:01 (16.04%), -DRB1*04:07 (17.33%), and -DQB1*03:02 (31.47%), these alleles have been previously described in some indigenous populations. We identified 5 haplotypes with a frequency >1%: HLA-A*02:01-B*35:01-DRB1*08:02-DQB1*04:02, A*68:01-B*39:01-DRB1*08:02-DQB1*04:02, A*02:01-B*35:01-DRB1*04:07-DQB1*03:02, A*68:01-B*39:01-DRB1*04:07-DQB1*03:02, and A*01:01-B*08:01-DRB1*03:01-DQB1*02:01. Also, the haplotype A*02:01-B*35:01-DRB1*08:02-DQB1*04:02 was identified in Tlalpan and Xalapa regions. Haplotype A*01:01-B*08:01-DRB1*03:01-DQB1*02:01 was found only in Tlalpan and Chihuahua. In the Xalapa region, the most frequent haplotype was A*24:02-B*35:01-DRB1*04:07-DQB1*03:02. These alleles and haplotypes have been described in Amerindian populations. Our data are consistent with previous studies and contribute to the analysis of the variability in the Mexican population.

Predicting the Formation of Sulfur-Based Brønsted Acids from the Reactions of SOx with H2O and H2S.

We have performed an extensive computational investigation of the potential energy surfaces for the reactions of SOx (x = 2 or 3) with H2S and H2O in the gas phase and in aqueous solution at the CCSD(T)/CBS level of theory plus a self-consistent reaction field approach. Formation of a gas-phase H2SO4 from the hydrolysis of SO3 at lower temperatures requires the presence of additional water molecules. When additional waters are introduced, the barrier for H2SO4 formation is significantly reduced, and a barrierless transition occurs with only three excess waters as well as in aqueous solution. In a mixture of H2O, H2S, and SO3, formation of H2S2O3 has a lower barrier in the gas phase than does the formation of H2SO4. In aqueous solution, no barrier is predicted, and both are likely to be formed. Introduction of an additional water to the SO3 + H2S reaction results in a decrease in barrier height, nearly identical to the ∼18 kcal/mol catalytic effect of the first additional water in SO3 hydrolysis, with the barrier for H2S2O3 formation disappearing altogether in aqueous solution. Formation of H2SO3 by the way of SO2 hydrolysis is unlikely. Excess waters reduce the barrier for SO2 hydrolysis; however, the overall endothermicity is increased as waters are added. The formation of H2S2O2 from SO2 and H2S via an isostructural pathway to SO2 hydrolysis is unlikely, with additional water molecules resulting in a small increase in the overall endothermicity and a catalytic effect smaller than that observed for the SO3 reactions. The results of this work have implications pertaining to the formation of H2SO4, H2S2O3, H2SO3, and H2S2O2 in the atmospheres of Earth and Venus. These results also question the existence of H2S2O2 as an intermediate in the Claus process.

Carotenoid and Tocochromanol Profiles during Kernel Development Make Consumption of Biofortified "Fresh" Maize an Option to Improve Micronutrient Nutrition.

Biofortification is a strategy to reduce micronutrient malnutrition. The aim of this study was to investigate whether consumption of biofortified fresh maize can supply nutritionally meaningful amounts of provitamin A carotenoids (PVA), zinc, lysine, and tryptophan. The accumulation patterns for PVA and tocochromanol compounds in developing grain of 23 PVA hybrids was studied, and nutritionally meaningful amounts of those compounds were found in grain by milk stage, when fresh maize is eaten. The highest PVA and tocochromanol accumulation occurred by physiological maturity. The percent apparent retention in boiled fresh maize was 92%, 117%, 99%, and 66% for PVA, zinc, lysine, and tryptophan, respectively. Consumption of 0.5 to 2 ears of fresh maize daily could supply 33-62.2%, 11-24% and more than 85% of the estimated average requirement of PVA, tryptophan, and zinc, respectively. The results indicate that eating biofortified fresh maize can contribute to improved micronutrient nutrition.

Reaction of CO2 with UO3 Nanoclusters.

Adsorption of CO2 to uranium oxide, (UO3)n, clusters was modeled using density functional theory (DFT) and coupled cluster theory (CCSD(T)). Geometries and reaction energies were predicted for carbonate formation (chemisorption) and Lewis acid-base addition of CO2 (physisorption) to these (UO3)n clusters. Chemisorption of multiple CO2 moieties was also modeled for dimer and trimer clusters. Physisorption and chemisorption were both predicted to be thermodynamically allowed for (UO3)n clusters, with chemisorption being more thermodynamically favorable than physisorption. The most energetically favored (UO3)3(CO2)m clusters contain tridentate carbonates, which is consistent with solid-state and solution structures for uranyl carbonates. The calculations show that CO2 exposure is likely to convert (UO3)n to uranyl carbonates.

Data on polymorphisms in CYP2A6 associated to risk and predispose to smoking related variables.

This article contains data on the single nucleotide polymorphisms (SNPs) rs1137115, rs1801272 and rs28399433 rs4105144 in CYP2A6 associated to smoking related variables in Mexican Mestizo smokers (Pérez-Rubio et al., 2017) [1]. These SNPs were selected due to previous associations with other populations. Mexican Mestizo smokers were classified according their smoking pattern. A genetic association test was performed.

Reaction of CO2 with Groups 4 and 6 Transition Metal Oxide Clusters.

Density functional theory (DFT) and coupled cluster theory (CCSD(T)) were used to study the addition of CO2 to group 4 (MO2)n and group 6 (MO3)n (n = 1, 2, 3) nanoclusters. The structures and energetics arising from Lewis acid-base addition (physisorption) and formation of CO32- (chemisorption) of CO2 to these clusters were predicted. Physisorption and chemisorption of CO2 are predicted to be thermodynamically allowed for group 4 (MO2)n clusters, with chemisorption being more favored energetically. Correlations of the ligand binding energies (LBEs) for the group 4 clusters are made with the fluoride affinities and M-O and M═O bond strengths of the clusters. The LBEs for chemisorption on the Zr and Ti clusters are consistent with published experimental and computational studies of bulk solids. Physisorption LBEs for the Ti and Zr clusters are more exothermic than the bulk values, as the cluster models allow for better relaxation at the metal sites. Chemisorption is not predicted to occur with group 6 (MO3)n clusters, as the larger chemisorbed structures were all found to be metastable. CO2 is predicted to weakly physisorb to (WO3)n with physisorption correlating with the Lewis acidity of the metal site.

Understanding Carbon Dioxide Solubility in Ionic Liquids by Exploring the Link with Liquid Clathrate Formation.

The solubilities of the quadrupolar molecules benzene and CO2 in various ionic liquids (ILs) are compared in order to determine the connection between aromatic liquid clathrate formation and CO2 dissolution in ILs. It was found that both CO2 Henry's law constants and benzene solubility are remarkably well correlated with each other and with IL molar volume, suggesting both phenomena depend more on the strength of interionic interactions between the ions of an IL rather than the identity of either ion. However, IL ion-quadrupole interactions were found to have an effect for dicyanamide ([N(CN)2 ]- ), where solubility of CO2 and benzene are affected by destabilizing and stabilizing interactions with [N(CN)2 ]- , respectively. The results suggest both solubility phenomena are related to the incorporation of the solute into an IL host network. Aromatic liquid clathrate formation thus has potential as a facile experimental probe for predicting the relative ability of ILs to physisorb CO2 .

Distribution of polymorphic variants of CYP2A6 and their involvement in nicotine addiction.

Tobacco consumption has become a major public health issue, which has motivated studies to identify and understand the biological processes involved in the smoking behavior for prevention and smoking cessation treatments. CYP2A6 has been identified as the main gene that codifies the enzyme that metabolizes nicotine. Many alleles have been identified after the discovery of CYP2A6, suggesting a wide interethnic variability and a diverse smoking behavior of the allele carrying individuals. The main purpose of this review is to update and highlight the effects of the CYP2A6 gene variability related to tobacco consumption reported from diverse human populations. The review further aims to consider CYP2A6 in future studies as a possible genetic marker for the prevention and treatment of nicotine addiction. Therefore, we analyzed several population studies and their importance at addressing and characterizing a population using specific parameters. Our efforts may contribute to a personalized system for detecting, preventing and treating populations at a higher risk of smoking to avoid diseases related to tobacco consumption.

Polymorphisms in HTR2A and DRD4 Predispose to Smoking and Smoking Quantity.

BACKGROUND: Genes encoding the receptors involved in the dopaminergic and serotonergic pathways are potential candidates in the mechanisms of nicotine addiction. AIMS: To identify genetic variants in the promoter regions and exons of the DRD4 and HTR2A genes associated with tobacco smoking and the degree of nicotine addiction in Mexican mestizos. METHODS: The study included 438 non-smokers (NS) and 1,157 current smokers, ranked based on their consumption of cigarettes per day (cpd): 574 heavy smokers (HS, >20 cpd) and 583 light smokers (LS, 1-10 cpd). Genotyping was performed for 4 and 8 single nucleotide polymorphisms (SNPs) in the DRD4 and HTR2A genes, respectively. RESULTS: The C allele of rs1800955 in DRD4 was found to be associated with cigarette smoking in the HS vs. NS and LS vs. NS comparisons (p = 2.34E-03 and p = 1.13E-03, respectively); the association was maintained in the homozygous CC genotype (p = 5.00E-04 and p = 2.00E-04, respectively). The T allele of rs6313 in HTR2A was significantly associated with cigarette smoking and a greater degree of nicotine addiction (p = 4.77E-03, OR = 1.55); the association was maintained in the homozygous genotype (TT) (p = 4.90E-03, OR = 1.96). The A allele of rs6313 was associated with cigarette smoking in the HS vs. NS comparison (p = 1.53E-02, OR = 1.36); the risk was nearly doubled in the homozygous AA genotype (p = 1.30E-03, OR = 1.83) compared with the heterozygous GA genotype (OR = 1.38). CONCLUSIONS: Among Mexican mestizos, the C allele of rs1800955 in the DRD4 gene and the A allele of rs6311 in the HTR2A gene are associated with cigarette smoking, whereas the T allele of rs6313 in HTR2A is associated with cigarette smoking and the degree of nicotine addiction.

Corrigendum: Virtual Avatar for Emotion Recognition in Patients with Schizophrenia: A Pilot Study.

[This corrects the article on p. 421 in vol. 10, PMID: 27616987.].

Virtual Avatar for Emotion Recognition in Patients with Schizophrenia: A Pilot Study.

Persons who suffer from schizophrenia have difficulties in recognizing emotions in others' facial expressions, which affects their capabilities for social interaction and hinders their social integration. Photographic images have traditionally been used to explore emotion recognition impairments in schizophrenia patients, but they lack of the dynamism that is inherent to facial expressiveness. In order to overcome those inconveniences, over the last years different authors have proposed the use of virtual avatars. In this work, we present the results of a pilot study that explored the possibilities of using a realistic-looking avatar for the assessment of emotion recognition deficits in patients who suffer from schizophrenia. In the study, 20 subjects with schizophrenia of long evolution and 20 control subjects were invited to recognize a set of facial expressions of emotions showed by both the said virtual avatar and static images. Our results show that schizophrenic patients exhibit recognition deficits in emotion recognition from facial expressions regardless the type of stimuli (avatar or images), and that those deficits are related with the psychopathology. Finally, some improvements in recognition rates (RRs) for the patient group when using the avatar were observed for sadness or surprise expressions, and they even outperform the control group in the recognition of the happiness expression. This leads to conclude that, apart from the dynamism of the shown expression, the RRs for schizophrenia patients when employing animated avatars may depend on other factors which need to be further explored.

Myopia in schoolchildren in a rural community in the State of Mexico, Mexico.

PURPOSE: This study sought to determine the prevalence of myopia in schoolchildren of a rural population in Mexico. METHODS: A cross-sectional study was conducted in 317 children between 6 and 12 years old. A complete refractive examination was performed, including static retinoscopy without cycloplegic agents. All procedures were conducted according to the Declaration of Helsinki. RESULTS: In total, 9.7% (95% CI: 13.07-6.52) of the examined children were myopic (spherical equivalent ≤ -0.50 D), 4.4% (95% CI: 6.66-2.14) presented astigmatism (cylinder ≤ -1.50 D), and 5.4% (95% CI: 7.89-2.91) presented hyperopia (spherical equivalent ≥ +0.50 D). CONCLUSION: Additional research is required to assess the prevalence of refractive errors in rural areas in Mexico, to analyze the associated risk factors, and to implement appropriate eye care plans for this population.

Benzene solubility in ionic liquids: working toward an understanding of liquid clathrate formation.

The solubility of benzene in 15 imidazolium, pyrrolidinium, pyridinium, and piperidinium ionic liquids has been determined; the resulting, benzene-saturated ionic liquid solutions, also known as liquid clathrates, were examined with (1) H and (19) F nuclear magnetic resonance spectroscopy to try and understand the molecular interactions that control liquid clathrate formation. The results suggest that benzene interacts primarily with the cation of the ionic liquid, and that liquid clathrate formation (and benzene solubility) is controlled by the strength of the cation-anion interactions, that is, the stronger the cation-anion interaction, the lower the benzene solubility. Other factors that were determined to be important in the final amount of benzene in any given liquid clathrate phase included attractive interactions between the anion and benzene (when significant), and larger steric or free volume demands of the ions, both of which lead to greater benzene solubility.

Boron nanoparticles with high hydrogen loading: mechanism for B-H binding and potential for improved combustibility and specific impulse.

Ball milling of boron in an H2 atmosphere was found to result in hydrogen uptake of up to 5% by weight (36 mol %). The nature of the hydrogen binding to boron was probed by a combination of ab initio theory, IR spectroscopy, thermogravimetric analysis, and mass spectral measurements of gases evolved during sample heating. The dominant binding mode is found to be H atoms bound to B atoms in the surface layer of the particles, and the high hydrogen loading results from production of very high surface area, indicating that gaseous H2 is an effective agent promoting size reduction in milling. Hydrogen incorporated in the samples was found to be stable for at least a month under ambient conditions. Desorption is observed beginning at ∼60 °C and continuing as the temperature is increased, with broad desorption features peaking at ∼250 and ∼450 °C, and ending at ∼800 °C. Unprotected hydrogenated boron nanoparticles were found to be reactive with O2 producing a hydrated boron oxide surface layer that decomposed readily at 100 °C leading to desorption of H2O. Hydrogenated boron nanoparticles were found to promote a higher flame height in the hypergolic ignition of ionic liquids upon contact with nitric acid.

Growth estimation of mangrove cockle Anadara tuberculosa (Mollusca: Bivalvia): application and evaluation of length-based methods.

Growth is one of the key processes in the dynamic of exploited resources, since it provides part of the information required for structured population models. Growth of mangrove cockle, Anadara tuberculosa was estimated through length-based methods (ELEFAN I y NSLCA) and using diverse shell length intervals (SLI). The variability of L(infinity), k and phi prime (phi') estimates and the effect of each sample were quantified by jackknife techniques. Results showed the same L(infinity) estimates from ELEFAN I and NSLCA across each SLI used, and all L(infinity) were within the expected range. On the contrary, k estimates differed between methods. Jackknife estimations uncovered the tendency of ELEFAN I to overestimate k with increases in SLI, and allowed the identification of differences in uncertainty (PE and CV) between both methods. The average values of phi' derived from NSCLA1.5 and length-age sources were similar and corresponded to ranges reported by other authors. Estimates of L(infinity), k and (phi' from NSCLA1.5 were 85.97 mm, 0.124/year and 2.953 with jackknife and 86.36mm de L(infinity), 0.110/year de k and 2.914 de phi' without jackknife, respectively. Based on the observed evidence and according to the biology of the species, NSCLA is suggested to be used with jackknife and a SLI of 1.5 mm as an ad hoc approach to estimate the growth parameters of mangrove cockle.

Growth estimation of mangrove cockle Anadara tuberculosa (Mollusca: Bivalvia): application and evaluation of length-based methods

Growth is one of the key processes in the dynamic of exploited resources, since it provides part of the information required for structured population models. Growth of mangrove cockle, Anadara tuberculosa was estimated through length-based methods (ELEFAN I y NSLCA) and using diverse shell length intervals (SLI). The variability of L∞, k and phi prime (Φ`) estimates and the effect of each sample were quantified by jackknife techniques. Results showed the same L∞ estimates from ELEFAN I and NSLCA across each SLI used, and all L∞ were within the expected range. On the contrary, k estimates differed between methods. Jackknife estimations uncovered the tendency of ELEFAN I to overestimate k with increases in SLI, and allowed the identification of differences in uncertainty (PE and CV) between both methods. The average values of Φ`derived from NSCLA1.5 and length-age sources were similar and corresponded to ranges reported by other authors. Estimates of L∞, k and Φ` from NSCLA1.5 were 85.97mm, 0.124/year and 2.953 with jackknife and 86.36mm de L∞, 0.110/year de k and 2.914 de Φ` without jackknife, respectively. Based on the observed evidence and according to the biology of the species, NSCLA is suggested to be used with jackknife and a SLI of 1.5mm as an ad hoc approach to estimate the growth parameters of mangrove cockle. Rev. Biol. Trop. 59 (1): 159-170. Epub 2011 March 01.

El crecimiento es uno de los procesos clave en la dinámica de los recursos explotados. En este estudio se estimó el crecimiento de la concha prieta Anadara tuberculosa por medio de métodos basados en tallas (ELEFAN I y NSLCA) y usando distintos intervalos de clase de talla (ICT). La variabilidad de los estimadores para L∞y k, y el efecto de cada muestra e ICT fueron cuantificados por la técnica de jackknife. ELEFAN I y NSLCA producen una misma estimación de L∞para cada uno de los ICT. Por el contrario, para k ambos métodos estiman diferentes valores. Las estimaciones con jackknife permitieron detectar que ELEFAN I sobreestima k a medida que se aumenta el ICT, y a definir diferencias en el grado de incertidumbre (EP y CV) entre ambos métodos. Los valores promedio de Φ` derivados de NSCLA1.5 son similares a los de tallaedad y están dentro del rango reportado por otros autores. Las estimaciones de NSCLA1.5 fueron 85.97mm de L∞, 0.124/año de k y 2.953 de Φ` con jackknife y 86.36mm de L∞, 0.110/año de k y 2.914 de Φ` sin jackknife. Basado en las evidencias mostradas y acorde a la biología de la especie se sugiere utilizar el NSCLA conjuntamente con jackknife y un ICT de 1.5mm para estimar los parámetros de crecimiento de la concha prieta.