Classification of leaf epidermis microphotographs using texture features

We present the results of a Gray Level Co-occurrence Matrix (GLCM) analysis for two sets of leaf epidermis images for the adaxial (20×_H) and abaxial sides (20×_E). The leaves were collected from a dry forest in Mona Island which is located between the Dominican Republic and Puerto Rico. For each set of images (GLCM) texture features were calculated namely the energy, correlation, contrast, absolute value, inverse difference, homogeneity, and entropy. From the calculated statistics a features matrix was obtained for each image and randomly divided into training set and test set using the hold-out method. In this method 70% of the images were considered as a training set and 30% as the test set. For each training and test set a linear discrimination analysis (LDA) was performed resulting in a average correct classification percent of 90% for the abaxial side in comparison with 80% for the adaxial side.     

Analysis of Early Embryogenesis in Rainbow and Banded Darters (Percidae: Etheostoma) Reveals Asymmetric Postmating Barrier

This study examines early embryogenesis in two species of darters, Etheostoma caeruleum and E. zonale (Teleostei: Percidae), and their hybrids. Results document the course of ontogeny from fertilization until the onset of pigmented eyes. Comparing fertilization and developmental success of conspecific versus heterospecific crosses revealed an asymmetric postmating reproductive barrier. E. caeruleum eggs treated with E. zonale sperm exhibited fertilization and developmental success similar to that of conspecific crosses. In contrast, E. zonale eggs treated with E. caeruleum sperm exhibited reduced fertilization relative to conspecific crosses and abnormal development. Development in this latter cross was compromised at all stages, but appeared to be concentrated around epiboly, or cell migration. As epiboly represents the stage of ontogeny when zygotic genes of both species jointly contribute to embryogenesis, results provide insight into the genetic mechanisms underlying postmating barriers in Etheostoma. Finally, the observed asymmetry in fertilization success is consistent with predictions based on the behavioral ecology of these species. Etheostoma zonale spawn in the open water column, whereas E.␣caeruleum bury their eggs under the substrate. The observed fertilization barrier may have therefore resulted from selection favoring increased fertilization specificity in E. zonale.     

As integrated culture system for outdoor production of microalgae and cyanobacteria

Cultivation of microalgae in closed photobioreactors suffers from high temperatures, whereas in open raceway ponds the optimal temperature is seldom reached. With an integrated device coupling a raceway pond with a suitably sized and positioned closed system (alveolar panel), the heat accumulated in the panel was efficiently transferred to the pond and a near-optimum temperature regimen for Arthrospira platensis was maintained, with no need for any additional cooling device. The productivity obtained in the integrated system was higher than the sum of the productivities (g reactor⁻¹ day⁻¹) of the pond and panel systems operating separately. This revised version was published online in September 2006 with corrections to the Cover Date.     

Chemical crosslinking of cell membranes

Summary The complexity of cell membranes makes the resolution of their macromolecular topology one of the more challenging problems in modern molecular and cellular biochemistry. Despite the difficulties inherent in any such analysis, a surprisingly simple yet powerful approach exists that has consistently yielded valuable results. This method is chemical crosslinking, in which cell membranes are treated with crosslinking reagents (usually bifunctional) which produce covalent linkages between membrane components. The resultant complexes are usually then separated and identified by electrophoresis. This review is intended to provide a guide to the i.nvestigator who is unfamiliar with this approach. The overall strategy of crosslinking is discussed including selection of reagents, conditions to optimize crosslinking and the cleavage of crosslinked complexes to regenerate the original target for identification purposes. The crosslinking of biological membranes is then reviewed with special emphasis on recent advances including macromolecular photoaffinity labeling, kinetic analysis to probe symmetry properties and potential artifacts that may complicate interpretation of results. Examples of specific applications of crosslinking to membranes are presented in tabular form. The final portion of the review discusses the synthesis and properties of the most widely employed crosslinking reagents. Available reagents are summarized in a series of comprehensive tables. It is hoped that our discussion will provide the uninitiated investigator with sufficient information to ascertain the applicability of chemical crosslinking to particular areas of interest.     

An investigation of the evolutionary origin of reciprocal communication using simulated autonomous agents

How does communication originates in a population of originally non-communicating individuals? Providing an answer to this question from a neo-Darwinian epistemological perspective is not a trivial task. The reason is that, for non-communicating agents, the capabilities of emitting signals and responding to them are both adaptively neutral traits if they are not simultaneously present. Research studies based on rather general and theoretically oriented evolutionary simulation models have, so far, demonstrated that at least two different processes can account for the origin of communication. On the one hand, communicative behaviour may first evolve in a non-communicative context and only subsequently acquire its adaptive function. On the other hand, communication may originate thanks to cognitive constraints; that is, communication may originate thanks to the existence of neural substrates that are common to the signalling and categorising capabilities. This article provides a proof-of-concept demonstration of the origin of communication in a novel-simulated scenario in which groups of two homogeneous (i.e. genetically identical) agents exploit reciprocal communication to develop common perceptual categories and to perform a collective task. In particular, in circumstances in which communication is evolutionarily advantageous, simulated agents evolve from scratch social behaviour through acoustic interactions. We look into the phylogeny of successful communication protocol, and we describe the evolutionary phenomena that, in early evolutionary stages, paved the way for the subsequent development of reciprocal communication, categorisation capabilities and successful cooperative strategies.     

Lack of correlation between overall protein synthesis and the onset of cell elongation in germinating embryos of Haplopappus gracilis

10⁻⁵M abscisic acid (ABA) completely inhibits germination or (if seeds deprived of integuments are used) embryo elongation in Haplopappus gracilis (Nutt.) Gray. Nevertheless, considerable rates of protein and RNA synthesis were found in embryos grown in abscisic acid, at least during the early hours after sowing. On the contrary, seeds grown in cycloheximide + fusicoccin (a powerful promoter of cell expansion), where protein synthesis is almost completely inhibited, show full protrusion of radicle, thus simulating a "germination" process. These results suggest that some of the most important events involved in seed germination, i.e. protein and RNA synthesis, and cell elongation which leads to radicle protrusion, may not necessarily be linked together and are possibly regulated by different control mechanisms. Moreover, when seeds or embryos are grown in abscisic acid + fusicoccin, protein synthesis is considerable, cell elongation is greater than in water controls at least for 12 h, and germination in its early stages appears to be normal; but DNA synthesis and cell division are not resumed, possibly since some other factor is required. All these findings propose a reevaluation of criteria for defining successful germination.     

Synthesis of thiazole and selenazole derivatives with affinity for the odorant-binding protein.

Three new ligands for odorant-binding proteins (OBPs) have been prepared, to be used in protein structure studies: the photoaffinity label 2-azido-4-butyl-5-propylthiazole, the NMR probe 2-trifluoromethyl-4-butyl-5-propylthiazole and the X-ray probe 2-amino-4-butyl-5-propylselenazole. All three compounds bind the bovine OBP with dissociation constants in the micromolar range.     

Cell cycle reactivation in cultured pea embryo axes. Effect of abscisic acid

Summary We used cultured pea embryo axes to study the effect of exogenous abscisic acid (ABA) on the reactivation of cell proliferation at germination. ABA (100 μM) was administered in a complete medium or in a medium without KNO₃ (the main source of K⁺ in the complete medium). In the presence of ABA, only a few meristematic root tip nuclei progressed through the cell cycle during the first 24 h of germination. Compared to the control the percentage of G₀/G₁ cells remained high. In the absence of KNO₃, the inhibitory effect of ABA on the cell cycle increased and the transition from G₁ to S was almost completely inhibited after 24 h of germination. Moreover, the amount of a 47 kDa nuclear protein remained high in embryos treated with ABA whereas it decreased in the control.     

Cell cycle kinetic analysis with flow cytometry in pea root meristem synchronized with aphidicolin

Meristematic cells in pea root were synchronized after treatment with aphidicolin. Flow cytometric analysis of DNA content variations revealed a variety of information: ca 50% of the cells were synchronized in the first part of the S phase; kinetic studies of the S-phase traverse revealed an increase of the DNA synthesis rate from early to late S; some of the cells in the meristem were non-cycling, arrested in Gl (19%) and G2 (12%). The possibility of using such a synchronized system in cytogenetic and biomolecular studies is discussed.     

Trans-ethnic variation in germline variants of patients with renal cell carcinoma

1. Download : Download high-res image (104KB)
2. Download : Download full-size image