RESUMEN
The plant hormone abscisic acid (ABA) regulates potassium and chloride ion channels at the plasma membrane of guard cells, leading to stomatal closure that reduces transpirational water loss from the leaf. The tobacco Nt-SYR1 gene encodes a syntaxin that is associated with the plasma membrane. Syntaxins and related SNARE proteins aid intracellular vesicle trafficking, fusion, and secretion. Disrupting Nt-Syr1 function by cleavage with Clostridium botulinum type C toxin or competition with a soluble fragment of Nt-Syr1 prevents potassium and chloride ion channel response to ABA in guard cells and implicates Nt-Syr1 in an ABA-signaling cascade.
Asunto(s)
Ácido Abscísico/farmacología , Canales de Cloruro/fisiología , Proteínas de la Membrana/fisiología , Nicotiana/fisiología , Reguladores del Crecimiento de las Plantas/farmacología , Hojas de la Planta/fisiología , Plantas Tóxicas , Canales de Potasio/fisiología , Secuencia de Aminoácidos , Animales , Toxinas Botulínicas/metabolismo , Membrana Celular/fisiología , Genes de Plantas , Prueba de Complementación Genética , Activación del Canal Iónico/efectos de los fármacos , Proteínas de la Membrana/química , Proteínas de la Membrana/genética , Datos de Secuencia Molecular , Oocitos , Técnicas de Placa-Clamp , Proteínas Qa-SNARE , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/crecimiento & desarrollo , Transducción de Señal , Nicotiana/genética , XenopusRESUMEN
This study aim to determine the proportion of traffic rule infractions in Cali, Colombia, in places where a road traffic injury (RTI) occurred. Description of videotaping of sites where a person was injured in an RTI in 2009. Counts of road users and infractions were established for each road user group and were compared using a Z-test. They were found 13,491 users, distributed as follow: 8.9% were pedestrians, 4.6% cyclists, 24.6% motorcyclists, and 61.8% were automobile drivers. The most frequent traffic violation among motorcyclists was transiting on lines designated for other vehicles (55.2%). Among cyclists, the most frequent violations were transiting without a helmet (99.2%) and not wearing the designated vest (100%). Among pedestrians, crossing streets at prohibited places (77.3%), even at sites where a pedestrian bridge was present (72.7%), represented two common violations. Vulnerable road users committed more traffic infractions than automobile drivers (p < 0.001). High rates of traffic rule infractions among vulnerable road users were observed. Studies to better understand the occurrence of these behaviours and the promotion of effective interventions are warranted.
Asunto(s)
Accidentes de Tránsito , Conducción de Automóvil , Regulación Gubernamental , Colombia/epidemiología , Humanos , Motocicletas , Prevalencia , Seguridad , Grabación de Cinta de Video , Heridas y LesionesRESUMEN
The ENA1 gene of Saccharomyces cerevisiae encodes a putative ATPase necessary for Na+ efflux. Plasma membranes and intracellular membranes of a yeast strain overexpressing the ENA1 gene contain significant amounts of ENA1 protein. Consequences of the overexpression with reference to the wild-type strain are: (1) a 5-fold higher content of the ENA1-protein in plasma membranes; (2) lower Na+ and Li+ effluxes; (3) slightly higher Na+ tolerance; and (4) much higher Li+ tolerance. The ENA1-specific ATPase activity in plasma membrane preparations of the overexpressing strain was low, but an ENA1 phosphoprotein was clearly detected when the plasma membranes were exposed to ATP in the presence of Na+ or to Pi in the absence of Na+. The characteristics of this phosphoprotein, which correspond to the acyl phosphate intermediaries of P-type ATPases, the absolute requirement of Na+ or other alkali cations for phosphorylation, and the Na+ and pH dependence of phosphorylation from ATP and Pi suggest that the product of the ENA1 gene may be a Na,H-ATPase, which can also pump other alkali cations. The role of the intracellular membranes structures produced with the overexpression of ENA1 in Na+ and Li+ tolerances and the existence of a beta-subunit of the ENA1 ATPase are discussed.
Asunto(s)
Adenosina Trifosfatasas/metabolismo , Adenosina Trifosfato/metabolismo , Proteínas de Transporte de Catión , Fosfatos/metabolismo , Proteínas de Saccharomyces cerevisiae , Saccharomyces cerevisiae/enzimología , Membrana Celular/enzimología , Litio/metabolismo , Fosfoproteínas/metabolismo , Proteínas Recombinantes/metabolismo , Sodio/metabolismo , ATPasa Intercambiadora de Sodio-Potasio , Fracciones Subcelulares/enzimologíaRESUMEN
In this study, we examined the lipid composition of rat caecal mucosa, including the fatty acid composition of major phospholipid classes. Phospholipids accounted for 90% of the total lipid, with cholesterol, triacylglycerols, diacylglycerols, fatty acids and cholesterol ester making up the remainder. Therefore, a phospholipid to neutral lipid ration of 9:1 was found. Phosphatidylethanolamine was the predominant phospholipid, with phosphatidylcholine as the second most abundant phospholipid. Cardiolipin, phosphatidylserine, phosphatidylinositol and lysophosphatidylcholine were present in lesser amounts. Sphingomyelin and lysophosphatidylethanolamine were only detected in trace amounts. The major fatty acids present in both the lipid and all phospholipid fractions were palmitate, stearate, oleate, linoleate and arachidonate. Other fatty acids of chain length greater than C20 were only detected in phospholipid fraction and accounted for < 5% of the total fatty acids in this fraction. However, 11.10% of 22:6 (n-3) and 7.17% of 24:0 were detected in phosphatidylserine and lysophosphatidylcholine, respectively. The results are discussed in terms of their possible physiological significance.
Asunto(s)
Ciego/química , Ácidos Grasos/análisis , Mucosa Intestinal/química , Lípidos/análisis , Fosfolípidos/análisis , Animales , Ésteres del Colesterol/análisis , Diglicéridos/análisis , Masculino , Ratas , Ratas Wistar , Triglicéridos/análisisRESUMEN
Na+ efflux and Na+ tolerance depend on a putative P-type ATPase encoded by the gene ENA1(PMR2) in Saccharomyces cerevisiae and on a putative Na+/H+ antiporter encoded by the gene sod2 in Schizosaccharomyces pombe. This report shows that a sod2::ura4 mutant of S. pombe transformed with the ENA1 gene of S. cerevisiae expressed the ENA1 protein, and recovered Na+ efflux and Na+ tolerance. The efflux of Na+ in the wild strain of S. pombe was sensitive to the transmembrane Na+ and H+ gradients, whereas in the sod2::ura4 mutant transformed with ENA1 it was independent of these gradients. The data give further support to the notion that ENA1 and sod2 encode Na+ transporters and not regulators of the process of Na+ export; they show also the physiological consequences of exporting Na+ through an Na(+)-ATPase or an Na+/H+ antiporter.
Asunto(s)
Adenosina Trifosfatasas/genética , Proteínas de Transporte de Catión , Proteínas de Saccharomyces cerevisiae , Saccharomyces cerevisiae/enzimología , Schizosaccharomyces/genética , Transporte Biológico , Clonación Molecular , Concentración de Iones de Hidrógeno , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/crecimiento & desarrollo , Saccharomyces cerevisiae/metabolismo , Schizosaccharomyces/crecimiento & desarrollo , Schizosaccharomyces/metabolismo , Sodio/metabolismo , ATPasa Intercambiadora de Sodio-PotasioRESUMEN
Transport of K+ in higher plants, as in bacteria and fungi, is mediated by two broad classes of transport proteins that operate in the millimolar and micromolar K+ concentration ranges. A search of the Expressed Sequence Tag database using amino acid consensus sequences for the K+ transporters HAK1 from Schwanniomyces and Kup of Escherichia coli yielded two homologous sequences for Arabidopsis. Cloning and sequencing of these genes gave single open reading frames for the putative transporters, AtKT1 and AtKT2, with predicted molecular weights of 79 and 88 kDa. The predicted gene products showed a high degree of homology at the amino acid level (56% identity) and exhibited significant hydrophobic stretches in their N-terminal halves, consistent with 12 membrane-spanning, alpha-helical domains. Database searches using AtKT1 and AtKT2 identified 10 additional sequences in Arabidopsis as well as additional homologous sequences in the plant species Oryza and Allium, the bacterium Lactococcus lactis, and in Homo sapiens. Expression of AtKT2 rescued growth on low millimolar [K+] in Saccharomyces cerevisiae carrying deletions for the genes encoding the K+ transporters TRK1 and TRK2. Rescue was associated with a 2-fold stimulation of Rb+ uptake and was sensitive to competition with external Na+ but not to extracellular pH, indicating that the gene encodes a low-affinity K+ transporter. These and additional results suggest that AtKT1 and AtKT2 belong to a superfamily of cation transporters that have been conserved through evolution.
Asunto(s)
Proteínas de Arabidopsis , Arabidopsis/química , Proteínas Portadoras/química , Proteínas de Transporte de Catión , Secuencia Conservada , Proteínas de Plantas/química , Potasio/metabolismo , Secuencia de Aminoácidos , Arabidopsis/genética , Arabidopsis/metabolismo , Transporte Biológico , Southern Blotting , Proteínas Portadoras/genética , Proteínas Portadoras/metabolismo , Clonación Molecular , Regulación de la Expresión Génica de las Plantas , Prueba de Complementación Genética , Datos de Secuencia Molecular , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Rubidio/metabolismo , Saccharomyces cerevisiae/genética , Alineación de Secuencia , Análisis de Secuencia de ADNRESUMEN
Vacuolar compartmentation of Na(+) is an essential mechanism for salinity tolerance since it lowers cytosolic Na(+) levels while contributing to osmotic adjustment for cell turgor and expansion. The AtNHX1 protein of Arabidopsis thaliana substituted functionally for ScNHX1, the endosomal Na(+)/H(+) antiporter of yeast. Ion tolerance conferred by AtNHX1 and ScNHX1 correlated with ion uptake into an intracellular pool that was energetically dependent on the vacuolar (H(+))ATPase. AtNHX1 localized to vacuolar membrane fractions of yeast. Hence, both transporters share an evolutionarily conserved function in Na(+) compartmentation. AtNHX1 mRNA levels were upregulated by ABA and NaCl treatment in leaf but not in root tissue.
Asunto(s)
Arabidopsis/genética , Secuencia Conservada/fisiología , Endosomas/química , Saccharomyces cerevisiae/citología , Saccharomyces cerevisiae/genética , Intercambiadores de Sodio-Hidrógeno/metabolismo , Ácido Abscísico/farmacología , Arabidopsis/efectos de los fármacos , Cationes/metabolismo , Cationes/farmacología , Clonación Molecular , Secuencia Conservada/genética , Endosomas/metabolismo , Evolución Molecular , Regulación de la Expresión Génica de las Plantas/efectos de los fármacos , Prueba de Complementación Genética , Concentración de Iones de Hidrógeno , Membranas Intracelulares/química , Membranas Intracelulares/metabolismo , Cinética , Litio/metabolismo , Litio/farmacología , Datos de Secuencia Molecular , Mutación/genética , Concentración Osmolar , Hojas de la Planta/efectos de los fármacos , Hojas de la Planta/genética , Raíces de Plantas/efectos de los fármacos , Raíces de Plantas/genética , Saccharomyces cerevisiae/efectos de los fármacos , Saccharomyces cerevisiae/metabolismo , Sodio/metabolismo , Sodio/farmacología , Intercambiadores de Sodio-Hidrógeno/química , Intercambiadores de Sodio-Hidrógeno/genética , Vacuolas/química , Vacuolas/metabolismoRESUMEN
In this study we examined the effect of 50% distal small bowel resection (DSBR) on the lipid composition of rat colonic mucosa, including the fatty acid composition of major phospholipid classes, phosphatidylethanolamine (PE), phosphatidylcholine (PC), phosphatidylinositol (PI), lysophosphatidylcholine (LPC), and sphingomyelin (SM). Phospholipid, free cholesterol, triacylglycerols, diacylglycerols, and cholesterol ester levels were not affected by the surgical operation. PE together with PC accounted for more than 60% of total phospholipid, in both groups of animals. The relative percentages of PE, PC, PI, SM, and cardiolipin (CL) remained unaffected by DSBR. However, a decrease in the content of LPC was observed in 50%-resected animals. Different fatty acid composition changes in the colonic phospholipid classes were observed after resection. PC fraction contained the highest amounts of saturated fatty acids, but monounsaturated fatty acids were present in high levels in PI fraction, in both groups of animals. DSBR produces different changes in the levels of linoleic and arachidonic acids. These results suggest that the lipid composition and the fatty acid profile of the different phospholipid fractions change in the adaptive response of colon to intestinal resection.
Asunto(s)
Colon/metabolismo , Ácidos Grasos/metabolismo , Mucosa Intestinal/metabolismo , Intestino Delgado/cirugía , Fosfolípidos/metabolismo , Animales , Masculino , Fosfolípidos/química , Ratas , Ratas WistarRESUMEN
The distribution of absorbed dose about models 6711 and 6702 125I seeds in water has been calculated from first principles using the Monte Carlo method. Dose is calculated as a function of angle with respect to the transverse seed bisector for distances from the seed center ranging from 0.1 to 7.5 cm. The computed results are compared to measured data. A truncated Fourier series is used to describe the Monte Carlo data in terms of a small number of coefficients, facilitating accurate and efficient dose calculations for clinical treatment planning.
Asunto(s)
Braquiterapia/métodos , Radioisótopos de Yodo/uso terapéutico , Modelos Teóricos , Método de Montecarlo , Investigación Operativa , Análisis de Fourier , HumanosRESUMEN
The influence of subacute treatment with benzyl viologen (a stimulator of free radical production in cells) on the fatty acid content of rat liver has been analyzed. Lipid storage, essentially characterized by lamellated inclusions, developed as we reported previously (Muriana et al., Exp. Pathol., 32 (1987) 65-72). A substantial increase in liver total lipid, phospholipids and triacylglycerols was found during viologen treatment in rats. The composition in fatty acids was profoundly influenced by the experimental conditions, but to different degrees in different lipid classes.
Asunto(s)
Bencil Viológeno/efectos adversos , Ácidos Grasos/metabolismo , Hígado/efectos de los fármacos , Animales , Ésteres del Colesterol/metabolismo , Metabolismo de los Lípidos , Hígado/metabolismo , Masculino , Fosfolípidos/metabolismo , Ratas , Ratas Endogámicas , Triglicéridos/metabolismoRESUMEN
A cDNA library in a yeast expression vector was prepared from roots of Arabidopsis exposed to salt and was used to select Li(+)-tolerant yeast transformants. The cDNA SAL1 isolated from one of these transformants encodes a polypeptide of 353 amino acid residues. This protein is homologous to the HAL2 and CysQ phosphatases of yeast and Escherichia coli, respectively. Partial cDNA sequences in the data bases indicate that rice produces a phosphatase highly homologous to SAL1 and that a second gene homologous to SAL1 exists in Arabidopsis. The SAL1 protein expressed in E. coli showed 3'(2'),5'-bisphosphate nucleotidase and inositol polyphosphate 1-phosphatase activities. In yeast, SAL1 restored the ability of a hal2/met22 mutant to grow on sulfate as a sole sulfur source, increased the intracellular Li+ tolerance, and modified Na+ and Li+ effluxes. We propose that the product of SAL1 participates in the sulfur assimilation pathway as well as in the phosphoinositide signaling pathway and that changes in the latter may affect Na+ and Li+ fluxes.
Asunto(s)
Proteínas de Arabidopsis , Genes de Plantas , Nucleotidasas/metabolismo , Monoéster Fosfórico Hidrolasas/metabolismo , Saccharomyces cerevisiae/crecimiento & desarrollo , Zea mays/enzimología , Zea mays/genética , Secuencia de Aminoácidos , Clonación Molecular , ADN Complementario , Biblioteca de Genes , Cinética , Litio/farmacología , Magnesio/farmacología , Datos de Secuencia Molecular , Nucleotidasas/biosíntesis , Nucleotidasas/genética , Oryza/enzimología , Monoéster Fosfórico Hidrolasas/biosíntesis , Monoéster Fosfórico Hidrolasas/genética , Saccharomyces cerevisiae/efectos de los fármacos , Homología de Secuencia de Aminoácido , Transducción de Señal , Sodio/farmacologíaRESUMEN
The PP2B protein phosphatase, also known as calcineurin, is a regulator of ion homeostasis in yeast cells. We have investigated the physiological consequences of constitutive expression of a recombinant form of calcineurin in which the Ca2+/calmodulin-binding and autoinhibitory domains of the catalytic subunit were deleted. The concomitant expression of the regulatory subunit along with the truncated catalytic subunit resulted in high tolerance to toxic levels of Na+ and Li+. This activated form of calcineurin substituted for the Na+ stress signal to promote the expression of the ENA1 gene, encoding a P-ATPase pump, and to induce the transition of the K+ uptake system to the high affinity mode that restricts influx of Na+ and Li+. In addition, the transcriptional responsiveness of ENA1 to Na+ stress was enhanced. These results demonstrate that calcineurin has a pivotal role in a signaling cascade activated by ion stress in yeast. Moreover, we found that changes in the level of calcineurin activity affected budding pattern and cell morphology. Cells expressing the truncated calcineurin were elongated and budded in an unipolar pattern, whereas calcineurin-deficient mutants budded randomly. These results suggest that calcineurin may also act in the establishment of cell polarity.
Asunto(s)
Proteínas de Unión a Calmodulina/metabolismo , Cationes Monovalentes/toxicidad , Farmacorresistencia Microbiana/fisiología , Homeostasis/fisiología , Fosfoproteínas Fosfatasas/metabolismo , Saccharomyces cerevisiae/fisiología , Transporte Biológico , Calcineurina , Proteínas de Unión a Calmodulina/genética , Cationes Monovalentes/metabolismo , División Celular/fisiología , Litio/metabolismo , Litio/toxicidad , Morfogénesis/fisiología , Fosfoproteínas Fosfatasas/genética , Proteínas Recombinantes/metabolismo , Sodio/metabolismo , Sodio/toxicidad , Relación Estructura-ActividadRESUMEN
The ENA2 gene encoding a P-type ATPase involved in Na+ and Li+ effluxes in Saccharomyces cerevisiae has been isolated. The putative protein encoded by ENA2 differs only in thirteen amino acids from the protein encoded by ENA1/PMR2. However, ENA2 has a very low level of expression and for this reason did not confer significant Li+ tolerance on a Li+ sensitive strain. ENA1 and ENA2 are the first two units of a tandem array of four highly homologous genes with probably homologous functions.