Consultar ensayos de calidad


Histología



MIME-Version: 1.0 Content-Location: file:///C:/B1334A59/119.htm Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset="us-ascii"

Histología


La histología (del griego ι&= #963;τÏŒς: histós 'tejido' y «-λογÎ¯α» -logía, tratado, estudio, ciencia) es la ciencia que estudia todo lo referente a los tejidos organicos: su estructura microscópica, su desarrollo y sus funciones. La histología se identifica a veces con lo que se ha llamado anatomía microscópica, pues su estudio no se detiene en los tejidos, sino que= va mas alla, observando también l= as células interiormente y otros corpúsculos, relacionand= ose con la bioquímica y la citología.


Las primeras investigaciones histológicas fueron posibles a partir <= st1:place w:st=3D"on">del año 1600, cuando se incorporó el microscopio a los estudios anatómicos. Marcello Malpighi es el fundador de la histología y su nombre aún esta ligado a varias estructuras histológicas. En 1665 se descubre la existencia de unidades pequeñas dentro de los tejidos y reciben la denominaciónde células. En&nb= sp;1830, acompañando a las mejoras que se introducen en la microscopía óptica, se logra distinguir el núcleo celular. En 1838 se introduce el concepto de la teoría celular.
En los años siguientes, Virchow introduce el concepto de q= ue toda célula se origina de otra célula (omnis cellula ex cellu= la).
El desarrollo tecnológico moderno de las herramientas de investigación permitió un enorme a= vance en el conocimiento histológico. Entre ellos pode= mos citar a la microscopía electrónica, la inmunohistoquímica, la técnica de hibridaci&oacu= te;n in situ. Las técnicas recientes sumado a = las nuevas investigaciones dieron paso al surgimiento de la biología celular.
La histología jamas había tenido la importancia en el = plan de estudios de medicina y biología que ha alcanzado hoy día. = La histología es el estudio de la estructura microscópica del




be used to produce hydrogen or methane. In Chapter 7 “Waste to Renewable Energy: A Sustainable and Green Approach Towards Production of Biohydrogen by Acidogenic Fermentation”, Mohan provides a detailed review of the state of the art with regard to biological hydrogen production using waste and wastewater as substrates with dark fermentation processes. Many biological processes use mixed cultures operating under non-sterile conditions (e.g. biological hydrogen and methane production, as discussed above). Watanabe et al. in Chapter 8 “Bacterial Communities in Various Conditions of the Composting Reactor Revealed by 16S rDNA Clone Analysis and Denaturing Gradient Gel Electrophoresis” demonstrate the utility of 16S rRNA analysis and denaturing gradient gel electrophoresis (DGGE) techniques for tracking microbialcommunities within a mixed and changing culture. Their work uses a composting process, which offers a typically cost-effective alternative to incineration for the remediation of contaminated soil. The production of liquid fuel from biomass necessitates the consideration of various issues such as the effects on the food supply, the rainforest, and greenhouse gas production, as well as carbon sustainability certiï¬cation. Some of these issues may require appropriate regulations and in Chapter 9 “Perspectives on Bioenergy and Biofuels”, Scott et al., examine these issues closely. In addition to its environmental advantages, the use of renewable energy resources offers the potential for stimulation of the economies of the nations where they are produced. The potential products of these renewable materials extend well beyond liquid fuels alone. Owing partly to the enormous volume of their production, fuels are sold for relatively low prices, and the successful implementation of renewable fuels depends, at least initially, on their ability to compete in the marketplace. To this end, it is particularly important to maximize the efï¬ciency of their production in bioreï¬neries where secondary products would be derived from the same feedstock as the fuels. As an example, petroleum reï¬neries have been in operation for over 150 years and now produce lubricants, plastics, solvents, detergents, etc., all from the starting crude oil [6]. Similarly, biomass, in addition to being used for the production of fuels, can be used as a starting material for the production of other value-addedproducts of microbial bioconversion processes such as fermentable sugars, organic acids and enzymes. In Chapter 10 “Perspectives on Chemicals from Renewable Resources”, Scott et al. describe how, with the aid of biotechnology, Protamylase R generated from starch production, can be used as a medium for the production of a cynophycin polymer, which is a major source of arginine and aspartic acid for the production of many industrially useful compounds including 1 -butanediamine and succinic acid. In Chapter 11 “Microbial Lactic Acid Production from Renewable Resources”, Li and Cui describe the production of lactic acid from renewable resources such as starch biomass, cheese whey etc. Lactic acid has recently gained attention due its application to the manufacture of biodegradable polymers. Among other renewable resources, Chapter 12 “Microbial Production of Potent Phenolic-Antioxidants Through Solid State Fermentation”, Martin et al. describe the role of agroindustrial residues including plant tissues rich in polyphenols for the microbial bioconversion of potent phenolics under solid state



fermentation conditions. Hence, combined with the economy of scale derived from large reï¬neries, secondary products could be key to bridging the price gap between fossil fuels and renewables. One critical advantage of biofuels is their potential to achieve a reduction in greenhouse gas releases, since the plants from which they are produced derive their carbon from the atmosphere. The overallbalance of greenhouse gases however, depends in large measure on the particular feedstocks used and the methods by which they are produced. Corn ethanol for instance, while being potentially carbon neutral, is not likely to achieve an overall reduction in greenhouse gas release due to its requirement for nitrogenous fertilizer and the associated release of nitrous oxide [7]. An interesting approach to the production of biodiesel is the use of algae to synthesize oil from the CO2 they capture for growth. Algae cultivation offers a potential low-cost alternative to physical methods of carbon sequestration such as pumping liquid CO2 underground or underwater or chemical methods such as base-mediated capture of CO2 and subsequen material biológico y de la forma en que se relacionan tanto estructu= ral y funcionalmente los distintos componentes individuales. Es crucial para la medicina y para la biología porque se encuentra en las intersecciones entre la bioquímica, la biología molecular y la fisiología por un lado y los procesos patológicos y sus consecuencias por el otro.<= br> Los histólogos prestan cada día mayor atención a los problemas químicos. Así por ejem= plo, cunde entre ellos la aspiración a determinar con exactitud la composición química de determinadas estructuras de la masa vi= va, al estudiar las enzimas, iones, proteínas, hidratos de carbono, grasas y lipoides, fermentos, etc. en las células y en los tejidos con el auxilio del microscopio




Política de privacidad });