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91.
Frizzled/planar cell polarity (Fz/PCP) signaling controls the orientation of sensory bristles and cellular hairs (trichomes) along the anteroposterior axis of the Drosophila thorax (notum). A subset of the trichome-producing notum cells differentiate as "tendon cells," serving as attachment sites for the indirect flight muscles (IFMs) to the exoskeleton. Through the analysis of chascon (chas), a gene identified by its ability to disrupt Fz/PCP signaling under overexpression conditions, and jitterbug (jbug)/filamin, we show that maintenance of anteroposterior planar polarization requires the notum epithelia to balance mechanical stress generated by the attachment of the IFMs. chas is expressed in notum tendon cells, and its loss of function disturbs cellular orientation at and near the regions where IFMs attach to the epidermis. This effect is independent of the Fz/PCP and fat/dachsous systems. The chas phenotype arises during normal shortening of the IFMs and is suppressed by genetic ablation of the IFMs. chas acts through jbug/filamin and cooperates with MyosinII to modulate the mechanoresponse of notum tendon cells. These observations support the notion that the ability of epithelia to respond to mechanical stress generated by one or more interactions with other tissues during development and organogenesis influences the maintenance of its shape and PCP features. 相似文献
92.
Several alternatives to the conventional alginate beads formulation were studied for encapsulation of invertase. Pectin was added to the alginate/enzyme solution while trehalose and β-cyclodextrin were added to the calcium gelation media. The effect of composition changes, freezing, drying methods (freeze, vacuum, or air drying), and thermal treatment were evaluated on invertase stability and its release kinetics from beads. The enzyme release mechanism from wet beads depended on pH. The addition of trehalose, pectin, and β-cyclodextrin modified the bead structure, leading in some cases to a release mechanism that included the relaxation of the polymer chains, besides Fickian diffusion. Enzyme release from vacuum-dried beads was much faster than from freeze-dried beads, probably due to their higher pore size. The inclusion of β-cyclodextrin and especially of pectin prevented enzyme activity losses during bead generation, and trehalose addition was fundamental for achieving adequate invertase protection during freezing, drying, and thermal treatment. Present results showed that several alternatives such as drying method, composition, as well as pH of the relese medium can be managed to control enzyme release. 相似文献
93.
Patricio R. Mu?oz Del Valle Dudley A. Huber John R. Butnor 《Tree Genetics & Genomes》2011,7(1):183-192
A single test, including one pseudo-backcross (Pinus elliottii x Pinus taeda) x P. elliottii and open-pollinated families of the pure species progenitors, was established in North Central Florida in December 2007 to
study the transfer of the fast-growing characteristics from a P. taeda L. (loblolly pine) parent into the P. elliottii Engelm. (slash pine) background. Several traits were measured in the first growing season: height growth, phenology, tip
moth incidence, stem traits, crown architectural and needle traits. Heterosis was evaluated for each trait using analyses
of variance by fitting a linear mixed model. All traits were significantly (p value < 0.05) different among families while the significance for heterosis varied by trait. Positive heterosis was found
for average rate of shoot elongation (ASRE), total growth (TG), total height and number of needles per fascicle while the
opposite was true for base diameter, top diameter, fascicle length, fascicle diameter, crown projected area and phenological
traits (cessation, duration and day to reach 50% of the height). Average performance (i.e., no heterosis) was found for initiation
of growth, number of branches, number of nodes, tip moth incidence, sheath length and specific leaf area. The analyses indicated
that introgression of loblolly pine alleles into slash pine was effective and novel trait combinations were achieved. The
pseudo-backcross had larger variation in early height growth than the slash pine families and was taller than all open-pollinated
families at the end of the first season. Tip moth incidence was much lower than the loblolly pine family. 相似文献
94.
Kazuyuki Kudô Shinsaku Koji Sidnei Mateus Ronaldo Zucchi Koji Tsuchida 《Population Ecology》2011,53(2):297-306
Neotropical swarm-founding wasps build nests enclosed in a covering envelope, which makes it difficult to count individual
births and deaths. Thus, knowledge of worker demography is very limited for swarm-founding species compared with that for
independent-founding species. In this study, we explored the worker demography of the swarm-founding wasp Polybia paulista, the colony size of which usually exceeds several thousand adults. We considered each wasp colony as an open-population and
estimated the survival probability, recruitment rate, and population size of workers using the developments of the Cormack–Jolly–Seber
model. We found that capture probability varied considerably among the workers, probably due to age polyethism and/or task
specialization. The daily survival rate of workers was high (around 0.97) throughout the season and was not related to the
phase of colony development. On the other hand, the recruitment rate ranged from 0 to 0.37, suggesting that worker production
was substantially less important than worker survival in determining worker population fluctuations. When we compared survival
rates among worker groups of one colony, the mean daily survival rate was lower for founding workers than for progeny workers
and tended to be higher in progeny workers that emerged in winter. These differences in survivorship patterns among worker
cohorts would be related to worker foraging activity and/or level of parasitism. 相似文献
95.
Pena SD Di Pietro G Fuchshuber-Moraes M Genro JP Hutz MH Kehdy Fde S Kohlrausch F Magno LA Montenegro RC Moraes MO de Moraes ME de Moraes MR Ojopi EB Perini JA Racciopi C Ribeiro-Dos-Santos AK Rios-Santos F Romano-Silva MA Sortica VA Suarez-Kurtz G 《PloS one》2011,6(2):e17063
Based on pre-DNA racial/color methodology, clinical and pharmacological trials have traditionally considered the different geographical regions of Brazil as being very heterogeneous. We wished to ascertain how such diversity of regional color categories correlated with ancestry. Using a panel of 40 validated ancestry-informative insertion-deletion DNA polymorphisms we estimated individually the European, African and Amerindian ancestry components of 934 self-categorized White, Brown or Black Brazilians from the four most populous regions of the Country. We unraveled great ancestral diversity between and within the different regions. Especially, color categories in the northern part of Brazil diverged significantly in their ancestry proportions from their counterparts in the southern part of the Country, indicating that diverse regional semantics were being used in the self-classification as White, Brown or Black. To circumvent these regional subjective differences in color perception, we estimated the general ancestry proportions of each of the four regions in a form independent of color considerations. For that, we multiplied the proportions of a given ancestry in a given color category by the official census information about the proportion of that color category in the specific region, to arrive at a "total ancestry" estimate. Once such a calculation was performed, there emerged a much higher level of uniformity than previously expected. In all regions studied, the European ancestry was predominant, with proportions ranging from 60.6% in the Northeast to 77.7% in the South. We propose that the immigration of six million Europeans to Brazil in the 19th and 20th centuries--a phenomenon described and intended as the "whitening of Brazil"--is in large part responsible for dissipating previous ancestry dissimilarities that reflected region-specific population histories. These findings, of both clinical and sociological importance for Brazil, should also be relevant to other countries with ancestrally admixed populations. 相似文献
96.
Brulc JM Yeoman CJ Wilson MK Berg Miller ME Jeraldo P Jindou S Goldenfeld N Flint HJ Lamed R Borovok I Vodovnik M Nelson KE Bayer EA White BA 《PloS one》2011,6(10):e25329
Background
The bovine rumen maintains a diverse microbial community that serves to break down indigestible plant substrates. However, those bacteria specifically adapted to degrade cellulose, the major structural component of plant biomass, represent a fraction of the rumen microbiome. Previously, we proposed scaC as a candidate for phylotyping Ruminococcus flavefaciens, one of three major cellulolytic bacterial species isolated from the rumen. In the present report we examine the dynamics and diversity of scaC-types both within and between cattle temporally, following a dietary switch from corn-silage to grass-legume hay. These results were placed in the context of the overall bacterial population dynamics measured using the 16S rRNA.Principal Findings
As many as 117 scaC-types were estimated, although just nineteen were detected in each of three rumens tested, and these collectively accounted for the majority of all types present. Variation in scaC populations was observed between cattle, between planktonic and fiber-associated fractions and temporally over the six-week survey, and appeared related to scaC phylogeny. However, by the sixth week no significant separation of scaC populations was seen between animals, suggesting enrichment of a constrained set of scaC-types. Comparing the amino-acid translation of each scaC-type revealed sequence variation within part of the predicted dockerin module but strong conservation in the N-terminus, where the cohesin module is located.Conclusions
The R. flavefaciens species comprises a multiplicity of scaC-types in-vivo. Enrichment of particular scaC-types temporally, following a dietary switch, and between fractions along with the phylogenetic congruence suggests that functional differences exist between types. Observed differences in dockerin modules suggest at least part of the functional heterogeneity may be conferred by scaC. The polymorphic nature of scaC enables the relative distribution of R. flavefaciens strains to be examined and represents a gene-centric approach to investigating the intraspecific adaptation of an important specialist population. 相似文献97.
98.
99.
Martínez-Ramos I Maya-Mendoza A Gariglio P Aranda-Anzaldo A 《Journal of cellular biochemistry》2005,96(1):79-88
DNA of higher eukaryotes is organized in supercoiled loops anchored to a nuclear matrix (NM). The DNA loops are attached to the NM by means of non-coding sequences known as matrix attachment regions (MARs). Attachments to the NM can be subdivided in transient and permanent, the second type is considered to represent the attachments that subdivide the genome into structural domains. As yet very little is known about the factors involved in modulating the MAR-NM interactions. It has been suggested that the cell is a vector field in which the linked cytoskeleton-nucleoskeleton may act as transducers of mechanical information. We have induced a stable change in the typical morphology of cultured HeLa cells, by chronic exposure of the cells to the polar compound dimethylsulfoxide (DMSO). Using a PCR-based method for mapping the position of any DNA sequence relative to the NM, we have monitored the position relative to the NM of sequences corresponding to four independent genetic loci located in separate chromosomes representing different territories within the cell nucleus. Here, we show that stable modification of the NM morphology correlates with the redefinition of DNA loop structural domains as evidenced by the shift of position relative to the NM of the c-myc locus and the multigene locus PRM1 --> PRM2 --> TNP2, suggesting that both cell and nuclear shape may act as cues in the choice of the potential MARs that should be attached to the NM. 相似文献
100.
M.?Josefina?Poupin Patricio?Arce-JohnsonEmail author 《In vitro cellular & developmental biology. Plant》2005,41(2):91-101
Summary Traditional breeding has been widely used in forestry. However, this technique is inefficient because trees have a long and
complex life cycle that is not amenable to strict control by man. Fortunately, the development of genetic engineering is offering
new ways of breeding and allowing the incorporation of new traits in plant species through the introduction of foreign genes
(transgenes). The introduction of selected traits can be used to increase the productivity and commercial value of trees and
other plants. For example, some species have been endowed with resistance to herbicide and pathogens such as insects and fungi.
Also, it has been possible to introduce genes that modify development and wood quality, and induce sexual sterility. The development
of transgenic trees has required the implementation of in vitro regeneration techniques such as organogenesis and somatic embryogenesis. Release of transgenic species into the agricultural
market requires a standardized biosafety regulatory frame and effective communication between the scientific community and
society to dissipate the suspicions associated with transgenic products. 相似文献