clasificacion de cientificos

http://bitesizebio.com/2007/12/11/a-classification-system-for-scientists/

Caspasas

En la revista Cell Death and Differentiation, se publicó una revisión especial para caspasas (Volume 14, Issue 1).
This review series includes comprehensive articles by experts in the caspase field, and covers the basic biology of caspases, their mechanisms of activation, cellular substrates, natural and synthetic inhibitors, apoptopic and non-apoptopic functions and role in inflammation and immunity.

Otro de esos efectos alternos de NFkB

En este caso, al ser secuestrado en el nucleolo, ya no puede activar transcripcion (o inhibirla, como en el post pasado), promoviendo la apoptosis.

clipped from www.google.com The proapoptotic effects of sulindac, sulindac sulfone and indomethacin are mediated by nucleolar translocation of the RelA(p65) subunit of NF-κB from Oncogene by L A Stark The proapoptotic effects of sulindac, sulindac sulfone and indomethacin are mediated by nucleolar translocation of the RelA(p65) subunit of NF-κB Oncogene advance online publication, December 3, 2007. doi:10.1038/sj.onc.1210891 Authors: C J Loveridge, A D H MacDonald, H C Thoms, M G Dunlop & L A Stark

Un bonito ejemplo del efecto antiapoptotico de NFkB

En este caso, en vez de activar la transcripcion de genes antiapoptoticos, inhibe la de un gen proapoptotico

clipped from www.google.com RelA/NF-κB recruitment on the bax gene promoter antagonizes p73-dependent apoptosis in costimulated T cells from Cell Death and Differentiation by L Tuosto RelA/NF-κB recruitment on the bax gene promoter antagonizes p73-dependent apoptosis in costimulated T cells Cell Death and Differentiation advance online publication, November 23, 2007. doi:10.1038/sj.cdd.4402264 Authors: R Cianfrocca, M Muscolini, V Marzano, A Annibaldi, B Marinari, M Levrero, A Costanzo & L Tuosto

Nuevo participante en la jugada, che!

Este articulo nos habla de un nuevo participante en la respuesta apoptotica al daño al ADN, como en la quimioterapia, funcionando rio arriba de la expresion de las IAPs, que a su vez son reguladas por NFkB. Esto nos provee de nuevas preguntas en nuestro tema

Che-1 activates XIAP expression in response to DNA damage Cell Death and Differentiation advance online publication 30 November 2007; doi: 10.1038/sj.cdd.4402284

X-linked inhibitor of apoptosis protein (XIAP) is a member of the inhibitor of apoptosis proteins family that selectively binds and inhibits caspase-3, -7 and -9. As such, XIAP is an extremely potent suppressor of apoptosis and an attractive target for cancer treatment. Che-1 is an antiapoptotic agent involved in the control of gene transcription and cell proliferation. Recently, we showed that the checkpoint kinases ATM/ATR and checkpoint kinase 2 physically and functionally interact with Che-1 and promote its phosphorylation and accumulation in response to DNA damage. These Che-1 modifications induce transcription of p53, and Che-1 depletion strongly sensitizes tumor cells to anticancer drugs. Here we show that Che-1 activates XIAP expression in response to DNA damage. This effect is mediated by Che-1 phosphorylation and requires NF-B. Notably, we found that XIAP expression is necessary for antiapoptotic activity of Che-1 and that in vivo downregulation of Che-1 by small interference RNA strongly enhanced the cytotoxicity of anticancer drugs.

Un panorama de la genomica en mexico

Es bueno enterarse de lo que se ha hecho y lo que se esta haciendo en Mexico. Echenle un vistazo.

clipped from compbiol.plosjournals.org Development of Genomic Sciences in Mexico: A Good Start and a Long Way to Go Rafael Palacios*, Julio Collado-Vides Citation: Palacios R, Collado-Vides J (2007) Development of Genomic Sciences in Mexico: A Good Start and a Long Way to Go. PLoS Comput Biol 3(9): e143 doi:10.1371/journal.pcbi.0030143

Regulacion de Smac por AMPc

Un articulo interesante en el que comprueban nuestros resultados previos, lo que es importante para asegurar la fiabilidad de la ciencia que hacemos . El AMP ciclico regula smac para inducir apoptosis.

clipped from www.ncbi.nlm.nih.gov Gene expression signatures of cAMP/PKA-promoted, mitochondrial-dependent apoptosis: Comparative analysis of wild-type and cAMP-deathless S49 lymphoma cells. 1: J Biol Chem. 2007 Nov 29 [Epub ahead of print]

10 reglas para hacer la mejor ciencia

1. Drop modesty (strive for excellence)
2. Prepare your mind (luck favors the prepared minds)
3. Age is important (research strategies should be different depending on your age, although I'm not sure I agree with that one)
4. Brains are not enough, you also need courage (I assume this means taking risks)
5. Make the best of your working condition (don't let your environment limit you, but exploit the advantages you have)
6. Work hard and effectively (all the successful scientists I know are workaholics)
7. Believe and doubt your hypothesis at the same time (so be skeptical and accept data for what it is, but don't give up on ideas before you test them)
8. Work on the important problems in your field (work on something interesting and relevant, no matter what the current trends are)
9. Be committed to your problem (because it might take a looong time to solve it)
10. Leave your door open (interact as much as you can with other people, you never know where the insights might come from)

De PLOS Computational Biology

HIV via Haiti

Al parecer se ha encontrado la migracion del HIV, viniendo de Africa via Haiti a los Estados Unidos.
http://www.sciencenews.org/articles/20071103/fob1.asp
Esto es interesante por muchas razones, una de las cuales es localizar el inicio de la infeccion por los 60s (el paso al humano ya habia sido calculado por los 30s)

Lineas contaminadas, incluyendo KB y Hep2

List of contaminated cell lines

From Wikipedia, the free encyclopedia

This is a list of cell cultures which have been cross-contaminated and overgrown by other cells. A project is currently underway to enumerate and rename contaminated cell lines to avoid errors in research caused by misattribution (Masters, 2002). Estimates based on screening of leukemia-lymphoma cell lines suggest that about 15% of these cell lines are not representative of what they are usually assumed to be (Drexler et al., 2002).

Contaminated cell lines have been extensively used in research without knowledge of their true character. For example, most if not all research on the "endothelium" ECV-304 or the "megakaryocyte" DAMI cell lines has in reality been conducted on bladder carcinoma and erythroleukemia cells, respectively. Thus, all research on endothelium- or megakaryocyte-specific functions utilizing these cell lines has turned out to be worthless, except as a warning example.

There are two principal ways a cell line can become contaminated: cell cultures are often exchanged between research groups; if, during handling, a sample gets contaminated and then passed on, subsequent exchanges of cells will lead to the contaminating population being established, although parts of the supposed cell line are still genuine. More serious is contamination at the source: during establishment of the original cell line, some contaminating cells are accidentally introduced into the cultures, where they in time outgrow the desired cells. The initial testing, in this case, still suggested that the cell line is genuine and novel, but in reality, it has disappeared soon after being established and all samples of such cell lines are actually the contaminant cells. It requires lengthy research to determine the precise point where cell lines have become contaminated.

Estándares para Experimentos en Biología (incluyendo para RNAi)

Un estándar se define como una serie de especificaciones uniformes para parte o todos los aspectos de un producto o actividad que promueve la cooperación y la interoperabilidad [1].

Desde hace unos años existe un impetu en la biología para crear estándares para los reportes experimentales, sobre todo para experimentos tipo hightroughput (microarreglos, proteómica, etc). Uno de los principales problemas de los experimentos hightrougput es la reproductibilidad entre diversos laboratorios o plataformas (ej. un microarreglo de Affimetrix vs uno hecho con un chip Perkin Elmer). El objetivo de lograr estándares es facilitar el reporte, la reproductibilidad y lograr compartir los datos entre diversas plataformas. Se espera además que la implementación de estos estándares faciliten la interoperabilidad entre datos genómicos, proteómicos y metabolómicos. Tales iniciativas son por ejemplo MIAME (Minimal Information about a Microarray Experiment), PSI (Proteomics Standards Initiative), etc. [1]

Es interesante para nuestro laboratorio notar que existe una iniciativa para reportar RNAi llamada Minimum Information About an RNAi Experiment (MIARE)

El URL de esa iniciativa es http://miare.sourceforge.net/HomePage

En el siguiente link a mi página pongo un archivo de excel provisto por MIARE para reportar experimentos de RNAi y un PDF con info general de MIARE. Además incluyo información de MIARE de como reportar los reactivos usados para construir el RNAi:

http://franzpruefer.googlepages.com/rnaiguidelines

Ref:
1) Standard operating procedures.Nat Biotechnol. 2006 Nov;24(11):1299.

microRNAs

Nature Reviews presenta una colección sobre microRNAs.
Estos artículos fueron seleccionados para proporcionar una introducción en los diversos aspectos de la biología del microRNA, incluyendo su biogénesis, su función en el desarrollo normal y cáncer, y las implicaciones en el impacto de la regulación genética.

www.nature.com/reviews/focus/microrna

IAP1 es indispensable para la angiogenesis

Este nuevo articulo señala la importancia de IAP1 y NFkB en la angiogenesis, lo que nos provee de un nuevo blanco terapeutico.

Birc2 (cIap1) regulates endothelial cell integrity and blood vessel homeostasis

Nature Genetics 39, 1397 (2007). doi:10.1038/ng.2007.8 Authors: Massimo M Santoro, Temesgen Samuel, Tracy Mitchell, John C Reed & Didier Y R Stainier

Integrity of the blood vessel wall is essential for vascular homeostasis and organ function. A dynamic balance between endothelial cell survival and apoptosis contributes to this integrity during vascular development and pathological angiogenesis. The genetic and molecular mechanisms regulating these processes in vivo are still largely unknown. Here, we show that Birc2 (also known as cIap1) is essential for maintaining endothelial cell survival and blood vessel homeostasis during vascular development. Using a forward-genetic approach, we identified a zebrafish null mutant for birc2, which shows severe hemorrhage and vascular regression due to endothelial cell integrity defects and apoptosis. Using genetic and molecular approaches, we show that Birc2 positively regulates the formation of the TNF receptor complex I in endothelial cells, thereby promoting NF-κB activation and maintaining vessel integrity and stabilization. In the absence of Birc2, a caspase-8–dependent apoptotic program takes place that leads to vessel regression. Our findings identify Birc2 and TNF signaling components as critical regulators of vascular integrity and endothelial cell survival, thereby providing an additional target pathway for the control of angiogenesis and blood vessel homeostasis during embryogenesis, regeneration and tumorigenesis.

NF-kappa B y ciclo celular

Este es un nuevo articulo muy interesante. Aunque ya se sabia que NF-kappa B algo tenia que ver con el ciclo celular (entre otros ver 'Int J Biochem Cell Biol.Tissue inhibitor of metalloproteinases-2 growth-stimulatory activity is mediated by nuclear factor-kappa B in A549 lung epithelial cells.Lizárraga F, Maldonado V, Meléndez-Zajgla J. ) este es uno de los mecanismos empleados para tal efecto.

A cell cycle regulatory network controlling NF-B subunit activity and function EMBO J advance online publication

Abstract

Aberrantly active NF-B complexes can contribute to tumorigenesis by regulating genes that promote the growth and survival of cancer cells. We have investigated NF-B during the cell cycle and find that its ability to regulate the G1-phase expression of key proto-oncogenes is subject to regulation by the integrated activity of IB kinase (IKK), IKK, Akt and Chk1. The coordinated binding of NF-B subunits to the Cyclin D1, c-Myc and Skp2 promoters is dynamic with distinct changes in promoter occupancy and RelA(p65) phosphorylation occurring through G1, S and G2 phases, concomitant with a switch from coactivator to corepressor recruitment. Akt activity is required for IKK-dependent phosphorylation of NF-B subunits in G1 and G2 phases, where Chk1 is inactive. However, in S-phase, Akt is inactivated, while Chk1 phosphorylates RelA and associates with IKK, inhibiting the processing of the p100 (NF-B2) subunit, which also plays a critical role in the regulation of these genes. These data reveal a complex regulatory network integrating NF-B with the DNA-replication checkpoint and the expression of critical regulators of cell proliferation.

Jefes de laboratorio

Creo que esto les puede interesar.
Saludos
http://scienceblogs.com/insolence/2007/10/what_kind_of_pi_am_i.php

Revision de IAPs

Una introduccion al tema que nos interesa, junto con la revision de survivina, para los interesados.

clipped from clincancerres.aacrjournals.org The Inhibitor of Apoptosis Proteins as Therapeutic Targets in Cancer poptosis is a cell suicide process with a major role in development and homeostasis in vertebrates and invertebrates. Inhibition of apoptosis enhances the survival of cancer cells and facilitates their escape from immune surveillance and cytotoxic therapies. Among the principal molecules contributing to this phenomenon are the inhibitor of apoptosis (IAP) proteins, a family of antiapoptotic regulators that block cell death in response to diverse stimuli through interactions with inducers and effectors of apoptosis. IAP proteins are expressed in the majority of human malignancies at elevated levels and play an active role in promoting tumor maintenance through the inhibition of cellular death and participation in signaling pathways associated with malignancies. Here, we discuss the role of IAP proteins in cancer and options for targeting IAP proteins for therapeutic intervention.

Revision de la importancia de la survivina en el cancer

No solo para diagnostico y tratamiento, sino para inmunoterapia. Magali tenia la idea de hacer un kit de ELISA para detectar survivina o sus anticuerpos en pacientes. Podria ser interesante

clipped from clincancerres.aacrjournals.org The Universal Character of the Tumor-Associated Antigen Survivin Several clinical trials targeting survivin with a collection of different approaches from small molecule antagonists to immunotherapy are currently under way. With regard to the latter, spontaneous anti-survivin T-cell reactivity has been described in cancer patients suffering from a huge range of cancers of different origin, e.g., breast and colon cancer, lymphoma, leukemia, and melanoma. Thus, survivin may serve as a universal target antigen for anticancer immunotherapy. Accordingly, down-regulation of survivin as a means of immune escape would severely inflict the survival capacity of tumor cells, which highlights this protein as a prime target candidate for therapeutic vaccinations against cancer. Data from several ongoing phase I/II trials targeting survivin for patients with advanced cancer will provide further information about this idea.

Estructura tridimensional de proteinas pasajeras cromosomales

Han cristalizado este complejo, que incluye survivina y que podria ser clave para la decision de apoptosis por la misma. El articulo completo en Jeyaprakash, A.A., Klein, U.R., Lindner, D., Ebert, J., Nigg, E.A., and Conti, E. (2007). Cell Vol 131, 230-231, 19 October 2007

clipped from images.cell.com

Ten Simple Rules for Getting Published

Este es un video interesante, por favor echenle un vistazo. Esta en ingles, pero lo principal aparece escrito. Es importante considerar este tipo de cuestiones para tener una carrera exitosa en la ciencia.
http://www.scivee.tv/pubcast/16261197

Celulas mesenquimales stem de MEDULA, podrian afectar el desarrollo del cancer

Cada vez se encuentran mas datos de la participacion del resto de la economia de nuestro organismo en la iniciacion y progresion del cancer.

clipped from 132.248.107.22:2062 New work with human breast cancer cells shows that they cooperate with mesenchymal stem cells (MSCs) derived from the bone marrow to advance metastasis. The breast cancer cells prompt MSCs to produce a cytokine, CCL5, that acts on cancer cells to promote their invasion and metastasis. Significantly, the MSC-stimulated cancer cells do not acquire a stable metastatic phenotype; rather they revert to their pre-malignant state in the absence of contextual signals. This raises the possibility that metastatic programming of cancer cells may be reversed therapeutically by targeting CCL5 or its receptor. Article: Mesenchymal stem cells within tumour stroma promote breast cancer metastasis doi:10.1038/nature06188 4 October 2007

ademas

clipped from news.yahoo.com The Nobel is a particularly striking achievement for Capecchi, (pronounced kuh-PEK'-ee). A native of Italy, he was separated from his mother at age 4 when she was taken to the Dachau concentration camp as a political prisoner during World War II. For four years, Capecchi lived on the street or in orphanages, "and most of the time hungry," he recalled in a University of Utah publication in 1997. Malnutrition sent him to a hospital where his mother found him on his ninth birthday. Within two weeks they left for the United States, where he went to school for the first time, starting in third grade despite not knowing English.

Nobel de medicina

clipped from news.yahoo.com STOCKHOLM, Sweden - Two American scientists and a Briton won the 2007 Nobel Prize in medicine on Monday for groundbreaking discoveries that led to a powerful technique for manipulating mouse genes. The prize is shared by Mario R. Capecchi, 70, of the University of Utah in Salt Lake City; Oliver Smithies, 82, a native of Britain now at University of North Carolina in Chapel Hill, and Sir Martin J. Evans, 66, of Cardiff University in Wales.

Y finalmente, cual es el elemento mas importante?

En este paper, Kroemer nos demuestra la importancia de la respuesta inmune en el efecto de las drogas antineoplasicas, la cual podria ser uno de los determinantes de las diferencias en las respuestas particulares de cada paciente y, evidentemente, un blanco a explotar. Apetoh, L. et al. Toll-like receptor 4-dependent contribution of the immune system to anticancer chemotherapy and radiotherapy. Nature Med. 13, 1050–1059 (2007) | Article | PubMed |

clipped from www.signaling-gateway.org Immunology: 'Danger' signals Chemotherapy-induced cell death triggers the release of the high-mobility group box 1 protein (HMGB1), which stimulates Toll-like receptor 4 (TLR4) and elicits an immune response that is required for the success of the therapy.

Revision cultivo 3D

Para los que esten interesados. Esta es una revision del cultivo 3D (como los esferoides). Queremos utilizar lo mas posible este tipo de cultivo y aqui podran leer los beneficios

clipped from www.nature.com Nature Reviews Molecular Cell Biology 8, 839-845 (October 2007) | doi:10.1038/nrm2236 Essay: The third dimension bridges the gap between cell culture and live tissue We believe that 3D cultures will have a strong impact on drug screening and will also decrease the use of laboratory animals, for example, in the context of toxicity assays.

Nuevos controles para nuestro experimentos?

Por favor lean este articulo. Podriamos cambiar nuestros controles de carga (GAPDH, etc) para adecuarlos mejor. Por favor opinen al respecto.

clipped from www.plosone.org Evidence Based Selection of Housekeeping Genes For accurate and reliable gene expression analysis, normalization of gene expression data against housekeeping genes (reference or internal control genes) is required. It is known that commonly used housekeeping genes (e.g. ACTB, GAPDH, HPRT1, and B2M) vary considerably under different experimental conditions and therefore their use for normalization is limited. Here we show novel candidate housekeeping genes (e.g. RPS13, RPL27, RPS20 and OAZ1) with enhanced stability among a multitude of different cell types and varying experimental conditions.

You are what you ate!

¿Les gustan las pastas, pizza, papas fritas, arroz o pan?
Lean este atículo.

Evolutionary genetics: You are what you ate.

Sadaf Shadan. Nature 13 September 2007 Volume 449 Number 7159, p155

A multiplicity of cell death pathways

En abril de este año se llevó acabo el congreso de "The Keystone Symposium on Apoptotic and Non-Apoptotic Cell Death Pathways".
Los doctores Golstein y Guido Kroemer publicaron un artículo en donde reportan algunos de los trabajos presentados en este congreso. Les anexo la cita. Está interesante.

A multiplicity of cell death pathways. Symposium on Apoptotic and Non-Apoptotic Cell Death Pathways.
EMBO Rep. 2007 Sep;8(9):829-833. Epub 2007 Jul 27.

Como crear calendario

Por favor creen su calendario en google (pueden entrar directamente desde gmail, picandole en el tab a la izq arriba que dice calendar).
Al accesar, presionen añadir en la barra de la izq abajo (abajo del minicalendario de la izq y arriba de donde dice mis calendarios) y seleccionar añadir un calendario nuevo. Pongale nombre (su nombre) y si quieren descripcion. Agreguen en la parte de abajo (compartir) mi nombre (correo), el de Vilma y el de Magali. Piquenle en crear calendario. Luego presionen el cuadro de la hora en que esten del calendario grande nuevo creado, pongan su nombre personal en evento y acepten. Se creara el evento. Al picarle nuevamente dos veces pueden editarlo, picandole en cuando y poniendo repetir diaro (o semanalmente, etc). Repetir hasta completar su horario. Recuerden compartilo con nosotros tres o mas gente si lo desean.

Deshonor para el laboratorio!!!

Calificaciones examen de alumnos de doctorado paper estadistica (el que esta señalado un poco mas abajo en el blog)
En escala 1 a 10

Franz 2.5
Gustavo 0
Varenka 2.5

Resultado igual o menor a echar una moneda al aire :). Necesitamos reinvindicar esto. Lean con mas cuidado el articulo y lo discutimos en algun momento.

RNAi que activa?

Por favor lean el siguiente articulo>

Nature 448, 855-858 (23 August 2007) | doi:10.1038/448855a; Published online 22 August 2007

RNA interference: Hitting the on switch

Estos dos investigadores han descubierto que RNAi dirigido a un promotor activa en vez de inhibir el gen. Esto es muy controversial y vale la pena leer este articulito para que vean lo que han sufrido estos dos investigadores con su linea (y como les han rechazado varios articulos en nature, a pesar de que ahora pongan un articulo de como les ha ido)
No olviden el ejercicio que les deje en el post pasado!!!

Celulas stem

Este es un articulo muy interesante

Is Bacterial Persistence a Social Trait?

Andy Gardner^1,2*, Stuart A. West², Ashleigh S. Griffin²

1 St John's College, Oxford University, Oxford, United Kingdom, 2 Institute of Evolutionary Biology, University of Edinburgh, Edinburgh, United Kingdom

The ability of bacteria to evolve resistance to antibiotics has been much reported in recent years. It is less well-known that within populations of bacteria there are cells which are resistant due to a non-inherited phenotypic switch to a slow-growing state. Although such ‘persister’ cells are receiving increasing attention, the evolutionary forces involved have been relatively ignored. Persistence has a direct benefit to cells because it allows survival during catastrophes–a form of bet-hedging. However, persistence can also provide an indirect benefit to other individuals, because the reduced growth rate can reduce competition for limiting resources. This raises the possibility that persistence is a social trait, which can be influenced by kin selection. We develop a theoretical model to investigate the social consequences of persistence. We predict that selection for persistence is increased when: (a) cells are related (e.g. a single, clonal lineage); and (b) resources are scarce. Our model allows us to predict how the level of persistence should vary with time, across populations, in response to intervention strategies and the level of competition. More generally, our results clarify the links between persistence and other bet-hedging or social behaviours.

Esto lleva a un blog a postular un posible parecido con las celulas stem, lo cual es muy interesante para el caso del cancer. Seria posible que las celulas stem cancerosas puedan tener este comportamiento? Es decir comportarse como stem por razones fenotipicas y no genotipicas y cambiar de un estado a otro. Esto explicaria el articulo de k. polyak que difiere de la mayoria y podria dar una teoria que cubriera todo.

Que se les ocurre hacer para comprobar esta hipotesis? Me gustaria que todos intentaran contestar (en comentarios). Es mas, lo hacemos obligatorio como un ejercicio. No se preocupen de poner algo que consideren tonto, solo asi se aprende.

Mutaciones en NF-kappa B

Es muy conocido que NF-kappa B se encuentra activado en practicamente todos los tumores. Sin embargo, la razon especifica para esta activacion no ha sido aclarada para cada tipo tumoral. Dos nuevos articulos en Cancer Cell (August 2007, 12(2)) reportan que alrededor del 20% de los mielomas multiples presentan mutaciones en diversos componentes de la cascada canonica o no canonica, incluyendo mutaciones con perdida de funcion en reguladores negativos como TRAF2, TRAF3, IAP1 y 2 y CYLD como mutaciones activantes en genes positivos como amplificacion de NIK, NFkB1 (p50/105) NFkB2 (p52/100), CD40, LTBR, etc.
Es mas, al inhibir la activacion de NFkB en lineas con estas alteraciones se induce apoptosis. Adicionalmente, uno de los articulos valida el uso de microarreglos de expresion para identificar mutaciones, algo mucho mas facil que aproximaciones genomicas (CGH, etc).

Avance cientifico. Teoria del Cha-cha-cha

Filosofia de la ciencia.
Este articulo en el ultimo numero de Science (Science 10 August 2007: Vol. 317. no. 5839, pp. 761 - 762) es interesante. Es un homenaje al recientemente fallecido ex-editor de Science, en el que categoriza el avance cientifico en tres tipos:

""Charge" discoveries solve problems that are quite obvious--cure heart disease, understand the movement of stars in the sky--but in which the way to solve the problem is not so clear. In these, the scientist is called on, as Nobel laureate Albert Szent-Györgyi put it, "to see what everyone else has seen and think what no one else has thought before." Thus, the movement of stars in the sky and the fall of an apple from a tree were apparent to everyone, but Isaac Newton came up with the concept of gravity to explain it all in one great theory.

"Challenge" discoveries are a response to an accumulation of facts or concepts that are unexplained by or incongruous with scientific theories of the time. The discoverer perceives that a new concept or a new theory is required to pull all the phenomena into one coherent whole. Sometimes the discoverer sees the anomalies and also provides the solution. Sometimes many people perceive the anomalies, but they wait for the discoverer to provide a new concept. Those individuals, whom we might call "uncoverers," contribute greatly to science, but it is the individual who proposes the idea explaining all of the anomalies who deserves to be called a discoverer.

"Chance" discoveries are those that are often called serendipitous and which Louis Pasteur felt favored "the prepared mind." In this category are the instances of a chance event that the ready mind recognizes as important and then explains to other scientists. This category not only would include Pasteur's discovery of optical activity (D and L isomers), but also W. C. Roentgen's x-rays and Roy Plunkett's Teflon. These scientists saw what no one else had seen or reported and were able to realize its importance."

CATEGORIES OF DISCOVERY
Problem that needed solving	Discovery	Discoverer	Category of discovery
Movement of stars, Earth, and Sun	Gravity	Newton	Charge
Structure of C6H6	Benzene structure	Kekulé	Challenge
Clear spots on petri dish	Penicillin	Fleming	Chance
Constant speed of light	Special relativity	Einstein	Challenge
Preventing heart attacks	Cholesterol metabolism	Brown & Goldstein	Charge
Crystals of D- and -L tartaric acid	Optical activity	Pasteur	Chance
Atomic spectra that could not be explained	Quantum mechanical atom	Bohr	Challenge
How DNA replicates and passes on coding	Base pairing in double helix	Watson & Crick	Challenge
Reagent "stuck" in storage cylinder	Teflon	Plunkett	Chance
Why offspring look like their parents	Laws of heredity	Mendel	Charge

Smac/DIABLO se fosforila

Phosphorylation of Smac by JNK3 attenuates its interaction with XIAP.

Biochem Biophys Res Commun. 2007 Jul 31;

Authors: Park BD, Ham YM, Jeong HJ, Cho SJ, Je YT, Yoo KD, Lee SK

Here we demonstrate that JNK3 can phosphorylate Smac. Smac phosphorylation attenuates its ability to activate apoptosome activity in HeLa S-100 cell lysates. Addition of the X-linked inhibitor of apoptosis protein (XIAP) to the S-100 markedly suppresses apoptosome activity, and this suppressive effect of XIAP is neutralized by adding unphosphorylated Smac, but not phosphorylated Smac. Furtherover, JNK3-mediated phosphorylation of Smac markedly attenuates the interaction between Smac and XIAP, as measured by BIACORE assays and non-denaturing gel shift assays. When JNK3 activity is down-regulated in etoposide-induced HeLa cells by transiently overexpressing a dominant negative version of JNK3 (DN-JNK3), the caspase-3 activity as well as PARP cleavages are markedly enhanced. And the interaction of Smac with XIAP also increases by down-regulating JNK3 activity under the same conditions. These results suggest that JNK3 activity can attenuate the progression of apoptosis through a novel mechanism of action, the down-regulation of interaction between Smac and XIAP

p53. Efectos supresores independientes de apoptosis?

Una hipotesis muy arraigada es que la capacidad de p53 para suprimir tumores de p53 esta mediada por su habilidad para inducir apoptosis en celulas que tienen su ADN dañado. Este nuevo articulo contribuye a la idea de que esto no es universal, y que pueden existir tumores especificos en donde p53 suprime por otro mecanismo:

Nature Medicine 13, 992 - 997 (2007)
David G Kirsch

A spatially and temporally restricted mouse model of soft tissue sarcoma

Soft tissue sarcomas are mesenchymal tumors that are fatal in approximately one-third of patients. To explore mechanisms of sarcoma pathogenesis, we have generated a mouse model of soft tissue sarcoma. Intramuscular delivery of an adenovirus expressing Cre recombinase in mice with conditional mutations in Kras and Trp53 was sufficient to initiate high-grade sarcomas with myofibroblastic differentiation. Like human sarcomas, these tumors show a predilection for lung rather than lymph node metastasis. Using this model, we showed that a prototype handheld imaging device can identify residual tumor during intraoperative molecular imaging. Deletion of the Ink4a-Arf locus (Cdkn2a), but not Bak1 and Bax, could substitute for mutation of Trp53 in this model. Deletion of Bak1 and Bax, however, was able to substitute for mutation of Trp53 in the development of sinonasal adenocarcinoma. Therefore, the intrinsic pathway of apoptosis seems sufficient to mediate p53 tumor suppression in an epithelial cancer, but not in this model of soft tissue sarcoma.
Por ende, p53 emplea otro mecanismo de supresion en el caso de estos sarcomas

Nuevo papel de p53

El gen supresor p53, conocido como "el guardián del genoma", tiene un papel fundamental en la respuesta al daño al ADN (como el producido por las drogas antineoplásicas), al activar ya sea el proceso de arresto celular, si el daño es reparable, o apoptosis, si no lo es. Más del 50% de los tumores tienen mutado o perdido este gen, lo que resalta su importancia. Acaban de describir una nueva función de p53, como un inhibidor de la migración, lo que tiene mucho sentido para la fisiopatología del cáncer.

p53 and RhoA signalling: A round about way for tumour invasion

Cell Migration Gateway (August 2007) | doi:10.1038/cmg051

Knocking out the tumour suppressor p53 causes cells to shift from an elongated to a rounded morphology, which is associated with increased motility and tumour invasiveness.

"The role of p53 in controlling cell-cycle arrest and apoptosis has been well-characterised but the tumour suppressor has more recently been linked with cell morphology. Published in The Journal of Cell Biology, Roux and colleagues report that p53 affects cell migration morphology by controlling localisation of the key cytoskeletal regulator RhoA, leading to an increase in cell invasiveness."

".....Thus, p53 modulates cell migration by controlling RhoA localization and regulating the RhoA-ROCK signalling pathway. Loss of p53 results in the aberrant overactivation of RhoA and ROCK-dependent translocation of RhoA to membrane blebbing structures."

Problemas en la lectura de MTT

Los ensayos de citotoxicidad que hacemos involucran varias tecnicas, entre ellas la del MTT. Este articulo señala que el suero fetal bovino, por la cantidad de albumina, podria dar problemas en la lectura.
BioTechniques® August 2007
Volume 43, Number 2: pp 178-186
Serum albumin leads to false-positive results in the XTT and the MTT assay
Dorothee Funk, Hans-Hermann Schrenk, and Eva Frei

Abstract
Tetrazolium salts like 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) or sodium 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H- tetrazolium-5-carboxanilide (XTT) that form formazans after reduction are widely used to investigate cell viability. Besides cellular enzymes, some constituents of cell media and other substances reduce tetrazolium salts, thereby interfering with these assays. We describe here that different preparations of serum albumin from bovine or human origin can lead to a concentration-dependent increase in the signals of the XTT assay; therefore leading to an overestimation of cell numbers and to an underestimation of potential cytotoxic effects of compounds to be tested. The same effect was seen in the MTT assay with human serum albumin (HSA). We demonstrate that this reductive activity cannot be inactivated by proteolytic digestion, but that it is due to the free cysteine residue in albumin, and is also observed when cysteine or glutathione (GSH) are used. Binding of N-ethylmaleimide (NEM) to the free cysteine residue leads to a decrease of the albumin interference in the XTT assay.

"...reduced XTT and MTT to the corresponding formazan and might explain the observation of Zhang and Cox who observed a 20% higher formazan signal when cells were assayed in 10% fetal calf serum (FCS) rather than in 5% FCS (16).Based on these findings, we strongly recommend to be careful with data from XTT and MTT assays when estimating cytotoxicity when albumin or other proteins with free SH groups are present, because the artificial increase in the assay signal, which is not due to cellular reductases, could lead to an underestimation of the cytotoxicity of the compounds to be tested"

CDIP, a novel pro-apoptotic gene.

27Jul07
Magali nos envia este dato:

Identificaron a un nuevo gen proapoptotico que es inducido por p53. La apoptosis dependiente de CDIP esta asociada con la activacion de la caspasa 8.

Les anexo el link.

Otro nivel de control para las IAPs

Para evitar que las celulas mueran por apoptosis por la actividad incontrolada de las caspasas, existe una familia de proteinas inhibidoras conocidas como IAPs:


Las IAPs incluyen proteinas tan importantes como la survivina (en la que trabaja Magali). Su mecanismo de control en general esta mediado por sintesis de novo, es decir, a nivel transcripcional. Sin embargo este nuevo articulo de D. Altieri, muestra que es posible regular a estas proteinas mediante fosforilacion, en particular por PKA (protein cinasa activada por AMPc). Es interesante destacar que Moises, un alumno nuestro de doctorado, encontro que la PKA, inducida por el AMPc, fosforila a CREB para incrementar la transcripcion de Smac/DIABLO que a su vez induce apoptosis (resumen articulo). Esto explicaba parcialmente la capacidad apoptotica del AMPc. Si sumamos a esto que la PKA fosforila a la survivina citosolica (no mitocondrial) y la inhibe, tenemos dos mecanismos sinergicos para inducir apoptosis. Asimismo, esto añade otra dimensión al trabajo de Gisela, otra alumna nuestra, que encontro que la survivina mitocondrial puede evitar la salida de Smac/DIABLO de este organelo. Esto sugeriria que, de ser regulado, el mecanismo de importacion de la Survivina a la mitocondria podria ser importante para la apoptosis y para determinar el umbral a las drogas antineoplasicas.

Descripcion de los datos

Uno de los problemas mas comunes en la descripcion de los resultados que tenemos es el uso correcto de las medidas de dispersion de las graficas que utilizamos. Les dejo el link de un articulo muy bueno que explica esto. El autor es D. L. Vaux, un investigador experto en apoptosis.
http://www.jcb.org/cgi/content/abstract/177/1/7
El texto completo es de libre acceso.
La idea es que presenten sus datos usando este articulo.