Contact inhibition of locomotion and mechanical cross-talk between cell-cell and cell-substrate adhesion determines the pattern of junctional tension in epithelial cell aggregates

We generated a computational approach to analyze the biomechanics of epithelial cell aggregates, either island or stripes or entire monolayers, that combines both vertex and contact-inhibition-of-locomotion models to include both cell-cell and cell-substrate adhesion. Examination of the distribution of cell protrusions (adhesion to the substrate) in the model predicted high order profiles of cell organization that agree with those previously seen experimentally. Cells acquired an asymmetric distribution of basal protrusions, traction forces and apical aspect ratios that decreased when moving from the edge to the island center. Our in silico analysis also showed that tension on cell-cell junctions and apical stress is not homogeneous across the island. Instead, these parameters are higher at the island center and scales up with island size, which we confirmed experimentally using laser ablation assays and immunofluorescence. Without formally being a 3-dimensional model, our approach has the minimal elements necessary to reproduce the distribution of cellular forces and mechanical crosstalk as well as distribution of principal stress in cells within epithelial cell aggregates. By making experimental testable predictions, our approach would benefit the mechanical analysis of epithelial tissues, especially when local changes in cell-cell and/or cell-substrate adhesion drive collective cell behavior.Comment: 39 pages, 8 Figures. Supplementary Information is include

Mapping of serotype-specific, immunodominant epitopes in the NS-4 region of hepatitis C virus (HCV):use of type-specific peptides to serologically differentiate infections with HCV types 1, 2, and 3

The effect of sequence variability between different types of hepatitis C virus (HCV) on the antigenicity of the NS-4 protein was investigated by epitope mapping and by enzyme-linked immunosorbent assay with branched oligopeptides. Epitope mapping of the region between amino acid residues 1679 and 1768 in the HCV polyprotein revealed two major antigenic regions (1961 to 1708 and 1710 to 1728) that were recognized by antibody elicited upon natural infection of HCV. The antigenic regions were highly variable between variants of HCV, with only 50 to 60% amino acid sequence similarity between types 1, 2, and 3. Although limited serological cross-reactivity between HCV types was detected between peptides, particularly in the first antigenic region of NS-4, type-specific reactivity formed the principal component of the natural humoral immune response to NS-4. Type-specific antibody to particular HCV types was detected in 89% of the samples from anti-HCV-positive blood donors and correlated almost exactly with genotypic analysis of HCV sequences amplified from the samples by polymerase chain reaction. Whereas almost all blood donors appeared to be infected with a single virus type (97%), a higher proportion of samples (40%) from hemophiliacs infected from transfusion of non-heat-inactivated clotting factor contained antibody to two or even all three HCV types, providing evidence that long-term exposure may lead to multiple infection with different variants of HCV

Lateral dimerization is required for the homophilic binding activity of C-cadherin

Regulation of cadherin-mediated adhesion can occur rapidly at the cell surface. To understand the mechanism underlying cadherin regulation, it is essential to elucidate the hemophilic binding mechanism that underlies all cadherin-mediated functions. Therefore, we have investigated the structural and functional properties of the extracellular segment of Xenopus C-cadherin using a purified, recombinant protein (CEC 1-5). CEC 1-5 supported adhesion of CHO cells expressing C-cadherin. The extracellular segment was also capable of mediating aggregation of microspheres. Chemical cross-linking and gel filtration revealed that CEC 1-5 formed dimers in the presence as well as absence of calcium. Analysis of the functional activity of purified dimers and monomers demonstrated that dimers retained substantially greater homophilic binding activity than monomers. These results demonstrate that lateral dimerization is necessary for hemophilic binding between cadherin extracellular segments and suggest multiple potential mechanisms for the regulation of cadherin activity

Biomonitoring of trace metals (Fe, Cu and Ni) in the mangrove area of Peninsular Malaysia, using different soft tissues of flat-tree oyster Isognomon alatus.

It is well documented that marine oysters are net bioaccumulators of trace metals and they can be employed as biomonitors of time-integrated measurements of bioavailable metal fractions over their lifetime. In this study, the Malaysian mangrove flat tree oyster Isognomon alatus collected from the estuaries of Lukut River (five sites), Sepang Besar River (one site), and one metal-polluted site at Kg. Pasir Puteh were dissected into muscle, mantle plus gills, byssus, and remaining soft tissues. All the four different soft tissues were analyzed for Fe, Cu, and Ni. Significant spatial differences in the accumulated metal concentrations of the oysters were found between sampling sites, and these could be attributed to anthropogenic inputs including discharges of shrimp ponds (Lukut), animal husbandry (Sepang Besar), sewage, shipping, and industrial effluents (Kg. Pasir Puteh). For Fe, the tissue distribution followed: byssus > mantle plus gill >muscle > remaining soft tissues, while for Cu and Ni, both followed byssus > remaining soft tissues > mantle plus gill > muscle. This indicated that byssus could act as an excretion route for the metals. Based on a correlation analysis between oyster tissues and sediments, selected tissues of I. alatus were shown to be good biomonitors of Ni and Cu contamination, while high regulative capacity of Fe in the oyster tissues could hardly reflect the actual Fe levels in the surroundings. However, the clustering patterns based on metal levels in the four different soft tissues were not in agreement with those based on the geochemical fractions of sediment data. This phenomenon which was due to the metal contamination might not necessarily create high bioavailabilities of metals to the biomonitor I. alatus, which might involve differences in uptake, excretion, and sequestration of metals. Similarly to the Mussel Watch approach, this study points to the very potential use of the different soft tissues of I. alatus as biomonitors for regular biomonitoring in the mangrove area of Peninsular Malaysia

Reconciling taxonomy and phylogenetic inference: formalism and algorithms for describing discord and inferring taxonomic roots

Although taxonomy is often used informally to evaluate the results of phylogenetic inference and find the root of phylogenetic trees, algorithmic methods to do so are lacking. In this paper we formalize these procedures and develop algorithms to solve the relevant problems. In particular, we introduce a new algorithm that solves a "subcoloring" problem for expressing the difference between the taxonomy and phylogeny at a given rank. This algorithm improves upon the current best algorithm in terms of asymptotic complexity for the parameter regime of interest; we also describe a branch-and-bound algorithm that saves orders of magnitude in computation on real data sets. We also develop a formalism and an algorithm for rooting phylogenetic trees according to a taxonomy. All of these algorithms are implemented in freely-available software.Comment: Version submitted to Algorithms for Molecular Biology. A number of fixes from previous versio

Search for the blind vampire: First record of Eoctenes Kirkaldy in Southern Luzon, (Hemiptera: Polyctenidae), with key to the Cimicoidea, ectoparasitic on bats in the Philippines

Polyctenidae Westwood, also known as bat bugs, is a haematophagous group of hemipterans exclusively ectoparasitic on bats and is closely related to Cimicidae Latreille. These bugs are dorsoventrally flattened with conspicuous ctenidia, apterous, anophthalmus, possess well-developed legs, and reproduce via pseudoplacental viviparity. They are rare compared to other insect taxa ectoparasitic on bats as evinced by a relatively small number of museum collections and described taxa. Worldwide, it is represented by 2 subfamilies, 5 genera, and 32 species. In the Philippines, it is only represented by two species from the genus Eoctenes Kirkaldy: E. spasmae (Waterhouse) and E. intermedius (Speiser). The first Philippine record for the genus was reported in 1961 from Northern Luzon. This paper presents the first record of Eoctenes in Southern Luzon, with key to the Cimicoidea ectoparasitic on bats in the Philippines

Uses of cetyl cacaoateTM in lipstick development: sensory evaluation

The use of Cetyl CacaoateTM in lipstick formulation was evaluated by varying the porpotion of waxes mixture among carnauba wax, jojoba ester and Cetyl CacaoateTM based on Simplex centroid {3,3} experimental design. Sensory evaluation was carried out by nine trained panels using quantitative descriptive analysis (QDA) method. The attributes agreed in the sensory languages development session were easy to apply, off flavor, hardness, texture, moist, appearance on lip after use, glossy, oily, comfortability after use, and long lasting. Results showed that Cetyl CacaoateTM increased the score of easy to apply but decreased the score for hardness. Cetyl CacaoateTM in the lipstick formulation increased the oily feels whereas carnauba wax gave less oily effect. No off flavor was detected for all the samples. However, the panels had different perception on comfortability after use, and long lasting. The ratio of cosmetic waxes in lipstick formulation which gave scores close to reference sample were 1/2 Cetyl CacaoateTM : 1/2 jojoba ester and 2/3 Cetyl CacaoateTM : 1/6 jojoba ester : 1/6 lilin carnauba

Use of different tissues of flat-tree oyster Isognomon alatus as biomonitors of bioavailabilities and contamination by Zn in the mangrove area of Peninsular Malaysia

Oyster is a net accumulator of metals, especially Zn, which can be used as a biomonitor of time—integrated records of bioavailable Zn fractions over its life time. Total soft tissues of oysters have been frequently used in metal bio-monitoring study. However, a lot of environmental and biological effects could iniluence the metal data. ln order to reduce such confounding factors, the use of different soft tissues in oysters is proposed in this study. The muscle, mantle plus gills, byssus and remaining soft tissues of flat-tree oyster Lwgnomon alatus, collected from the estuaries of Lukut (5 sites), Sepang Besar (2 sites) and one polluted site at Kg. Pasir Puteh, were analysed for Zn. Signiticant spatial differences in the accumulated Zn concentrations of the oysters (and hence bioavailabilities) were found between sampling sites and estuaries, and these could be attributed to anthropogenic inputs, including discharges of shrimp ponds (Lukut), animal husbandry (Sepang Besar), sewage, shipping and industrial efliuents (Kg. Pasir Puteh). The use of different soft tissues of I. alatus as biomonitors of bioavailability and contamination by Zn in the mangrove area of Peninsular Malaysia is proposed. The erroneous results due to spawning and the problem of defaecation before dissection could be potentially reduced by using the oyster muscle. Hence, a more accurate interpretation of the bioavailability and contamination by heavy metals in coastal waters could be obtained. Overall, the present baseline data based on different soft tissues of the oysters can be used for regular biomonitoring, considering the rapid land-based development in the coastal area of Peninsular Malaysia