In metamorphosing wing discs, progression through the cell cycle takes place, as in larval discs, in nonclonally derived clusters of cells synchronized in the same cell cycle stage. Contrary to early ...discs, there are temporal and spatial heterogeneities in cell proliferation associated with wing margin, vein, intervein, and middle intervein territories. Within these territories, there are no indications of a wave progression of the cell cycle. Mitotic orientations are, as in early discs, at random but there is a preferential allocation of postmitotic cells along the proximodistal axis, thus explaining the elongated shape of the resulting clones along this axis. Shapes of clones in mature discs and in evaginated wings are similar, thus excluding major morphogenetic movements during evagination. After the proliferative period, all the cells are arrested in G1 phase. The final number of cells of the wing is fixed independently of experimental perturbations that alter the cell division schedule. These results are discussed in the context of a model of wing morphogenesis.
In this paper we present an application of the Support Vector Regression algorithm (SVMr) to the prediction of hourly ozone values in Madrid urban area. In order to improve the training capacity of ...SVMrs, we have used a recently proposed approach, based on reductions of the SVMr hyper-parameters search space. Using the modified SVMr, we study different influences which may modify the ozone prediction, such as previous ozone measurements in a given station, measurements in neighbors stations, and the influence of meteorologic variables. We use statistical tests to verify the significance of incorporating different variables into the SVMr. A comparison with the results obtained using a neural network (multi-layer perceptron) is also carried out. This study has been carried out in 5 different stations of the air pollution monitoring network of Madrid, so the conclusions raised are backed by real data. The final result of the work is a robust and powerful software for tropospheric ozone prediction in Madrid. Also, the prediction tool based on SVMr is flexible enough to incorporate any other prediction variable, such as city models, or traffic patters, which may improve the prediction obtained with the SVMr.
Organ shape depends on the coordination between cell proliferation and the spatial arrangement of cells during development
1–3. Much is known about the mechanisms that regulate cell proliferation, ...but the processes by which the cells are orderly distributed remain unknown. This can be accomplished either by random division of cells that later migrate locally to new positions (cell allocation)
4 or through polarized cell division (oriented cell division; OCD). Recent data suggest that the OCD is involved in some morphogenetic processes such as vertebrate gastrulation
5, neural tube closure
6, and growth of shoot apex in plants
7; however, little is known about the contribution of OCD during organogenesis. We have analyzed the orientation patterns of cell division throughout the development of wild-type and mutant imaginal discs of
Drosophila. Our results show a causal relationship between the orientation of cell divisions in the imaginal disc and the adult morphology of the corresponding organs, indicating a key role of OCD in organ-shape definition. In addition, we find that a subset of planar cell polarity genes is required for the proper orientation of cell division during organ development.
Table olives are one of the most representatives and consumed fermented vegetables in Mediterranean countries. However, there is an evident lack of standardization of production processes and HACCP ...systems thus implying the need of establishing decision-making tools allowing their commercialization and shelf-life extension. The present work aims at developing a decision-making scoring system by means of a probabilistic assessment to standardize production process of
table olives based on the identification of potential hazards or deficiencies in hygienic processes for the subsequent implementation of corrective measures. A total of 658 microbiological and physico-chemical data were collected over three consecutive olive campaigns (2014-2016) to measure the variability and relative importance of each elaboration step on total hygienic quality and product safety. Three representative companies were visited to collect samples from food-contact surfaces, olive fruits, brines, air environment, olive dressings, water tanks, and finished/packaged products. A probabilistic assessment was done based on the establishment of Performance Hygiene and Safety Scores (PHSS 0-100%) through a standardized system for evaluating product acceptability. The mean value of the global PHSS for the
table olives processing (PHHS
) was 64.82% (90th CI: 52.78-76.39%) indicating the high variability among facilities in the evaluated processing steps on final product quality and safety. Washing and cracking, and selection and addition of olive dressings were detected as the most deficient ones in relation to PHSS
values (
< 0.05) (mean = 53.02 and 56.62%, respectively). The relative contribution of each processing step was quantified by different experts (
= 25) from the
table olive sector through a weighted PHSS (PHSS
). The mean value of PHSS
was 65.53% (90th CI: 53.12-77.52%). The final processing steps obtained higher values for PHSS
being the finished product the most relevant one (mean = 18.44%; 90% CI: 10.34-25.33%). Sensitivity analysis concluded that intervention measures focused on reducing the contamination of washing brines could lead to an improvement of PHSS
value to 67.03%. The present work can be potentially applied in the
table olive food sector for improving food quality and safety assurance.
The Entelechia model is a generative model of morphogenesis where individual cells exhibit surface labels that express scalar difference and planar polarity along two orthogonal axes X and Y. The ...amount of surface label depends on the level of Martial (M) gene product within each cell. The model assumes that the confrontation of cells on both sides of compartment borders causes an increase in their level of M gene expression. The resulting disparity between the M value of border cells and that of their neighbors induces the latter to divide. After each division the daughter cells increase their own M value, and allocate to the best matching value position. The increase in M value at the borders therefore extends through the anlage in a cascade of proliferation. The Entelechia condition is reached when the border cells attain the species-specific maximal M values, and the value differences between adjacent cells become indistinguishable. Computer simulations reveal that this model accounts for a variety of observations made on imaginal discs, e.g., 1) each disc attains a constant size in terms of number of cells, independently of the growing conditions; 2) clonal restrictions separate populations of cells which proliferate by intercalar growth; 3) dissociated cells are capable of reconstructing original patterns upon reaggregation, and 4) genetic mosaics of morphogenetic mutations show local effects that may differ depending on the position of the mutant cells in the growing anlage.
Dorso‐ventral axis formation in the Drosophila wing requires the localized accumulation of the Apterous LIM/homeodomain protein (Ap) in dorsal cells. Here we report that dLdb/Chip encodes a ...LIM‐binding cofactor that controls Ap activity. Both lack and excess of dLdb/Chip function cause the same phenotype as apterous (ap) lack of function; i.e. dorsal to ventral transformations, generation of new wing margins, and wing outgrowths. These results indicate that the normal function of Ap in dorso‐ventral compartmentalization requires the correct amount of the DLDB/CHIP co‐factor, and suggest that the Ap and DLDB/CHIP proteins form a multimeric functional complex. In support of this model, we show that the dLdb/Chip excess‐of‐function phenotypes can be rescued by ap overexpression.
In bilateral animals, the left and right sides of the body usually present asymmetric structures, the genetic bases of whose generation are still largely unknown CIBA Foundation (1991) Biological ...Asymmetry and Handedness, CIBA Foundation Symposium 162 (Wiley, New York), pp. 1-327. In Drosophila melanogaster, mutations in the rotated abdomen (rt) locus cause a clockwise helical rotation of the body. Even null alleles are viable but exhibit defects in embryonic muscle development, rotation of the whole larval body, and helical staggering of cuticular patterns in abdominal segments of the adult. rotated abdomen is expressed in the embryonic mesoderm and midgut but not in the ectoderm; it encodes a putative integral membrane glycoprotein (homologous to key yeast mannosyltransferases). Mesodermal cells defective in O-glycosylation lead to an impaired larval muscular system. We propose that the staggering of the adult abdominal segments would be a consequence of the relaxation of intrinsic rotational torque of muscle architecture, preventing the colateral alignment of the segmental histoblast cells during their proliferation at metamorphosis.
Mutant larvae for the Drosophila gene lethal giant larva (lgl) develop neoplastic tumors in imaginal discs. However, lgl mutant clones do not form tumors when surrounded by wild-type tissue, ...suggesting the existence of a tumor-suppressing mechanism. We have investigated the tumorigenic potential of lgl mutant cells by generating wing compartments that are entirely mutant for lgl and also inducing clones of various genetic combinations of lgl⁻ cells. We find that lgl⁻ compartments can grow indefinitely but lgl⁻ clones are eliminated by cell competition. lgl mutant cells may form tumors if they acquire constitutive activity of the Ras pathway (lgl⁻ UAS-rasV¹²), which confers proliferation advantage through inhibition of the Hippo pathway. Yet, the majority of lgl⁻ UAS-rasV¹² clones are eliminated in spite of their high proliferation rate. The formation of a tumor requires in addition the formation of a microenvironment that allows mutant cells to evade cell competition.
Live imaging of Drosophila imaginal disc development Aldaz, Silvia; Escudero, Luis M.; Freeman, Matthew ...
Proceedings of the National Academy of Sciences - PNAS,
08/2010, Letnik:
107, Številka:
32
Journal Article
Recenzirano
Odprti dostop
Live imaging has revolutionized the analysis of developmental biology over the last few years. The ability to track in real time the dynamic processes that occur at tissue and cellular levels gives a ...much clearer view of development, and allows greater temporal resolution, than is possible with fixed tissue. Drosophila imaginal discs are a particularly important model of many aspects of development, but their small size and location inside the larva and pupa has prevented live imaging techniques from extensively being used in their study. Here, we introduce the use of viscous culture medium to enable high resolution imaging of imaginal disc development. As a proof of principle, we have analyzed the transformation that occurs during metamorphosis of the wing imaginal disc into the mature wing and report several previously unobserved stages of this model of organogenesis. These imaging methods are especially useful to study the complex and dynamic changes that occur during morphogenesis, but we show that they can also be used to analyze other developmental and cellular events. Moreover, our viscous medium creates a platform for future adaptation of other tissue culture conditions to allow imaging of a wide range of developmental events and systems.
The veins in the Drosophila wing have a characteristic width, which is regulated by the activity of the Notch pathway. The expression of the Notch-ligand Delta is restricted to the developing veins, ...and coincides with places where Notch transcription is lower. We find that this asymmetrical distribution of ligand and receptor leads to activation of Notch on both sides of each vein within a territory of Delta-expressing cells, and to the establishment of boundary cells that separate the vein from adjacent interveins. In these cells, the expression of the Enhancer of split gene m beta is activated and the transcription of the vein-promoting gene veinlet is repressed, thus restricting vein differentiation. We propose that the establishment of vein thickness utilises a combination of mechanisms that include: (1) independent regulation of Notch and Delta expression in intervein and vein territories, (2) Notch activation by Delta in cells where Notch and Delta expression overlaps, (3) positive feedback on Notch transcription in cells where Notch has been activated and (4) repression of veinlet transcription by E(spl)m beta and maintenance of Delta expression by veinlet/torpedo activity.
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