Toksičnost talija u humanoj populaciji

Thallium is a naturally occurring trace element, widely distributed in the earth’s crust, but at very low concentrations. It does not have a known biological use and does not appear to be an essential element for life. It has been considered one of the most toxic heavy metals. Occasionally, there are reports on thallium poisoning as results of suicide or murder attempt or accident. The main threat to humans is through occupational exposure, environmental contamination, and accumulation in food, mainly in vegetables grown on contaminated soil. Increasing use in emerging new technologies and demanding high-tech industry constantly raise concern about exposure risk to all living organisms. Thallium is considered a cumulative poison that can cause adverse health effects and degenerative changes in many organs. The effects are the most severe in the nervous system. The exact mechanism of thallium toxicity still remains unknown, although impaired glutathione metabolism, oxidative stress, and disruption of potassium-regulated homeostasis may play a role. The lack of data about mutagenic, carcinogenic, or teratogenic effects of thallium compounds in humans calls for further research.Talij je u prirodi široko rasprostranjen teški metal, prisutan u vrlo niskim koncentracijama pa ga stoga ubrajamo u elemente u tragovima. Budući da organizmima nije potreban ni u jednoj razvojnoj fazi, ne ubrajamo ga u grupu esencijalnih elemenata. Talij zbog njegovih svojstava ubrajamo među najtoksičnije teške metale. Povremeno se još uvijek pojavljuju slučajevi u kojima je talij upotrijebljen kao sredstvo za pokušaj ubojstva, odnosno samoubojstva, ali i slučajevi nenamjernog, slučajnog trovanja talijem. U današnje vrijeme potencijalna o asnost od trovanja talijem postoji zbog profesionalne izloženosti, izbijanja ekološke katastrofe ili zbog akumulacije u hranidbenim lancima, uglavnom zbog uzgoja hrane na onečišćenom tlu. Sve češća uporaba talija u visokotehnološkoj industriji kao odgovor na zahtjeve moderne tehnologije neprestano povećava rizik od izloženosti svih živih organizama štetnim utjecajima talija u okolišu. Talij ima izuzetno negativan učinak na različite organske sustave, a osobito na živčani sustav. Mehanizmi toksičnosti talija još uvijek nisu u potpunosti razjašnjeni, premda važnu ulogu imaju poremećaji metabolizma glutationa, oksidativni stres i narušavanje homeostaze posredovane ionima kalija. Nedostatak podataka o mutagenim, kancerogenim ili teratogenim učincima talija i njegovih spojeva u ljudi opravdava buduća istraživanja ovog vrlo toksičnog metala

Toksičnost talija u humanoj populaciji

Thallium is a naturally occurring trace element, widely distributed in the earth’s crust, but at very low concentrations. It does not have a known biological use and does not appear to be an essential element for life. It has been considered one of the most toxic heavy metals. Occasionally, there are reports on thallium poisoning as results of suicide or murder attempt or accident. The main threat to humans is through occupational exposure, environmental contamination, and accumulation in food, mainly in vegetables grown on contaminated soil. Increasing use in emerging new technologies and demanding high-tech industry constantly raise concern about exposure risk to all living organisms. Thallium is considered a cumulative poison that can cause adverse health effects and degenerative changes in many organs. The effects are the most severe in the nervous system. The exact mechanism of thallium toxicity still remains unknown, although impaired glutathione metabolism, oxidative stress, and disruption of potassium-regulated homeostasis may play a role. The lack of data about mutagenic, carcinogenic, or teratogenic effects of thallium compounds in humans calls for further research.Talij je u prirodi široko rasprostranjen teški metal, prisutan u vrlo niskim koncentracijama pa ga stoga ubrajamo u elemente u tragovima. Budući da organizmima nije potreban ni u jednoj razvojnoj fazi, ne ubrajamo ga u grupu esencijalnih elemenata. Talij zbog njegovih svojstava ubrajamo među najtoksičnije teške metale. Povremeno se još uvijek pojavljuju slučajevi u kojima je talij upotrijebljen kao sredstvo za pokušaj ubojstva, odnosno samoubojstva, ali i slučajevi nenamjernog, slučajnog trovanja talijem. U današnje vrijeme potencijalna o asnost od trovanja talijem postoji zbog profesionalne izloženosti, izbijanja ekološke katastrofe ili zbog akumulacije u hranidbenim lancima, uglavnom zbog uzgoja hrane na onečišćenom tlu. Sve češća uporaba talija u visokotehnološkoj industriji kao odgovor na zahtjeve moderne tehnologije neprestano povećava rizik od izloženosti svih živih organizama štetnim utjecajima talija u okolišu. Talij ima izuzetno negativan učinak na različite organske sustave, a osobito na živčani sustav. Mehanizmi toksičnosti talija još uvijek nisu u potpunosti razjašnjeni, premda važnu ulogu imaju poremećaji metabolizma glutationa, oksidativni stres i narušavanje homeostaze posredovane ionima kalija. Nedostatak podataka o mutagenim, kancerogenim ili teratogenim učincima talija i njegovih spojeva u ljudi opravdava buduća istraživanja ovog vrlo toksičnog metala

Prácticas de física : laboratorio II

1 archivo PDF (86 páginas)Manual de laboratorio de prácticas de física

Fluid release from the subducted Cocos plate and partial melting of the crust deduced from magnetotelluric studies in southern Mexico: implications for the generation of volcanism and subduction dynamics

In order to study electrical conductivity phenomena that are associated with subduction related fluid release and melt production, magnetotelluric (MT) measurements were carried out in southern Mexico along two coast to coast profiles. The conductivity-depth distribution was obtained by simultaneous two-dimensional inversion of the transverse magnetic and transverse electric modes of the magnetotelluric transfer functions. The MT models demonstrate that the plate southern profile shows enhanced conductivity in the deep crust. The northern profile is dominated by an elongated conductive zone extending >250 km below the Trans-Mexican Volcanic Belt (TMVB). The isolated conductivity anomalies in the southern profile are interpreted as slab fluids stored in the overlying deep continental crust. These fluids were released by progressive metamorphic dehydration of the basaltic oceanic crust. The conductivity anomalies may be related to the main dehydration reactions at the zeolite → blueschist → eclogite facies transitions and the breakdown of chlorite. This relation allows the estimation of a geothermal gradient of ∼8.5°C/km for the top of the subducting plate. The same dehydration reactions may be recognized along the northern profile at the same position relative to the depth of the plate, but more inland due to a shallower dip, and merge near the volcanic front due to steep downbending of the plate. When the oceanic crust reaches a depth of 80–90 km, ascending fluids produce basaltic melts in the intervening hot subcontinental mantle wedge that give rise to the volcanic belt. Water-rich basalts may intrude into the lower continental crust leading to partial melting. The elongated highly conductive zone below the TMVB may therefore be caused by partial melts and fluids of various origins, ongoing migmatization, ascending basaltic and granitic melts, growing plutons as well as residual metamorphic fluids. Zones of extremely high conductance (>8000 S) in the continental crust on either MT profile might indicate extinct magmatism

SOMACLONAL VARIATION OF Phanaenopsis sp. var. Dudu PLANTS REGENERATED BY DIRECT SOMATIC EMBRIOGENESIS

Actualmente existe una creciente demanda de híbridos de Phalaenopsis sp., por lo cual es necesario desarrollar protocolos de propagación masiva que aseguren altos porcentajes de regeneración clonal tal como la técnica de embriogénesis somática. Así mismo, estudiar la variación genética dentro de las plantas regeneradas ofrece un mayor conocimiento de los alcances del protocolo de micropropagación en relación a la estabilidad genética de los materiales empleados. Objetivo: En el presente trabajo de investigación se evaluó la combinación de tres concentraciones y dos tipos de reguladores de crecimiento vegetal (RCV), la citocinina bencilaminopurina (BA) (1.0, 2.0 y 3.0 mgL-1) en combinación con tres concentraciones de ácido 2,4-diclorofenoxiacético (2,4-D) (3.0, 4.0 y 5.0 mgL-1), para la inducción de embriones somáticos, además, se analizó la estabilidad genética de las plántulas regeneradas mediante marcadores moleculares tipo RAPD (Random Amplified Polymorphic DNA, por sus siglas en inglés). Metodología: La embriogénesis somática se indujo a partir de explantes de hoja con distintos grados de desarrollo: primera hoja se consideró como explante maduro (PH) y la tercera hoja como explante joven (TH), obtenidas de una plántula de Phalaenopsis sp. var. Dudú cultivadas in vitro, de 15-20 cm de altura. Resultados: El mayor número de plantas regeneradas fue de 29.8 a los 135 días después de iniciado el cultivo (ddic) con 2.0 y 5.0 mgL-1 de BA y 2,4-D, respectivamente, utilizando como explante la TH en la respuesta morfogenética de los explantes regenerados, se observó una correlación entre la edad del explante y la concentración de RCV. El análisis de la variación genética mostró cambios en los patrones de bandeo, observando bandas polimórficas con los cuatro iniciadores utilizados, aludiendo variación somaclonal en las plantas regeneradas. Implicaciones: Los resultados obtenidos aportan una alternativa de regeneración, además de ofrecer una metodología para iniciar programas de mejoramiento genético en Phalaenopsis sp. var. Dudú. Conclusiones: Se logró la regeneración in vitro de Phalaenopsis sp. var. Dudú mediante embriogénesis somática, así como la detección de cambios genéticos en el material regenerado.Nowadays, a growing demand for hybrids of Phalaenopsis sp. exists to satisfy this demand it is necessary to develop protocols for massive propagation that ensure high percentages of clonal regeneration, such as somatic embryogenesis. Besides, studying genetic variation within regenerated plants offers a greater understanding of the suitability of the micropropagation protocol in relation with genetic stability of the materials used. Objective: The present research work aimed to evaluate three concentrations of two types of plant growth regulators (RCV). 6- benzylaminopurine cytokinin (BA) (1.0, 2.0 y 3.0 mgL-1) in combination with three concentrations of 2,4- diclorofenoxiacetic acid (2,4-D) (3.0, 4.0, 5.0 mgL-1), for the induction of somatic embryos. In addition, the genetic stability of the regenerated plants was analyzed using molecular markers type RAPD (Random Amplified Polymorphic DNA). Methodology: The induction of somatic embryogenesis was induced from two leaf explants with different stages of develop from 15-20 cm in height Phalaenopsis sp. var. Dudú seedlings, cultivated in vitro; first leaf as mature explant (PH) and third leaf as young explant (TH). Results: The highest number of regenerated plants was 29.8 at 135 days after the start of the culture (ddic) with 2.0 and 5.0 mgL-1 of BA and 2,4-D, respectively, using TH as explant. In the morphogenetic response of the regenerated explants, a correlation was observed between the age of the explant and the RCV concentration. Polymorphic bands were observed with the four primers used, indicating somaclonal variation in regenerated plants. Implications: The results obtained provide an alternative for regeneration, as well as offering a methodology to initiate genetic improvement programs in Phalaenopsis sp. var. Dudú. Conclusions: In vitro regeneration of Phalaenopsis sp. var. Dudú by somatic embryogenesis was achieved, as well as the analysis of the genetic integrity of the regenerated material.UNIVERSIDAD AUTONOMA DEL ESTADO DE MEXIC

Fluid flow evolution in petroleum reservoirs with a complex diagenetic history: An example from Veracruz, Mexico

This paper discusses the fluid flow evolution in the Veracruz petroleum province of eastern Mexico based on results of an integrated diagenetic, sedimentological and structural analysis. The area progressively changed from passive foreland towards an active fold-and-thrust belt into a passive belt with infill of the foreland basin and finally underwent transpressional deformation. This varied kinematic evolution resulted in numerous fluid flow events, among which were four different petroleum migration pulses. © 2006 Elsevier B.V. All rights reserved

Geophysical modeling of Valle de Banderas graben and its structural relation to Bahia de Banderas, Mexico

A gravimetric survey consisting of five lines and 483 stations, as well as a magnetotelluric (MT) survey consisting of 17 observation sites, were made in the Valle de Banderas region for the determination of the structural characteristics of the valley. Additionally, data from a previous aeromagnetic survey were analyzed to correlate them with our geophysical measurements. The gravimetric and MT models confirm that the valley corresponds to a graben structure with slumped blocks that vary from similar to 2000 m deep close to Bahia de Banderas to shallow burial depths (similar to 100 m) toward the NE end of the valley. Faults flanking the valley, inferred from the gravity and magnetic models, trend toward offshore faults in Bahia de Banderas, indicating a structural connection between land and sea. From the MT measurements we conclude that a 2-D resistivity behavior is observed within the graben whereas outside of the graben the behavior is 1-D, in spite of the rough topography of this region. Our gravimetric models also indicate the occurrence of basin-like structures within the graben, coinciding with similar structures reported offshore in the Bahia de Banderas, suggesting that such structures may be typical erosional features of the graben. The aeromagnetic analysis correlates with the gravimetric and W models, and suggests that the graben structure is an extensional zone on granitic crus