Morphological traffic between the inflorescence and the vegetative shoot in helobial monocotyledons

Previous studies of reproductive structures in the helobial monocotyledons (Alismatidae) indicate that partitioning between flower and inflorescence is not always clear (e.g.,Lilaea,Scheuchzeria) and that this may be the result of ancestral, unisexual modules coming together to form flowers and/or inflorescences. Later evolutionary changes may have included the inflorescence becoming involved or mixed in with vegetative growth. Substitution of vegetative buds for flowers is the simplest version, and there can be additional modifications to the growth behavior of the inflorescence, such as horizontal growth and dorsiventrality. In the Alismataceae and Limnocharitaceae the derivation of stolonlike structures from inflorescences is obvious: vegetative features have been incorporated into structures that are recognizably inflorescences. In the Hydrocharitaceae the interrelationships between the inflorescence and the vegetative body are much less well defined. We previously suggested forHydrocharis, where a single axillary complex can contain both inflorescence and stolons, that the stolon is basically a sterilized inflorescence and that features of the inflorescence have become incorporated into the vegetative body. Here we will explore this theme further for the Hydrocharitaceae, using information from within and outside the family.     

Infection Control Measures to Prevent Invasive Mould Diseases in Hematopoietic Stem Cell Transplant Recipients

Invasive mould diseases, particularly aspergillosis, are important causes of morbidity and mortality in allogeneic stem cell transplant recipients. Mould spores are ubiquitous in the environment. Guidelines established by the Centers for Disease Control (CDC) and other authoritative organizations focus on approaches to reduce exposure to mould spores. These recommendations include avoidance of areas and activities expected to result in high levels of mould spores (e.g., construction, gardening) and use of specially designed units (protected environments) where additional standards (e.g., HEPA-filtered rooms) are in place to minimize mould exposure. These recommendations are based on consensus criteria and limited clinical data largely derived from single-center retrospective studies. In addition, highly immunocompromised stem cell transplant recipients are commonly managed as outpatients, where engineering standards of the inpatient protected environment are not feasible. In the absence of an outbreak with an identified environmental source (e.g., a contaminated air vent), it is not possible to reliably distinguish community-acquired from nosocomial aspergillosis. Adherence to infection control guidelines, acknowledging their limitations, combined with evidence-based targeted antifungal prophylaxis for the highest risk transplant recipients, is likely to be the most effective approach to prevent invasive mould diseases.     

Power Dissipation in the Cochlea Can Enhance Frequency Selectivity

The cochlear cavity is filled with viscous fluids, and it is partitioned by a viscoelastic structure called the organ of Corti complex. Acoustic energy propagates toward the apex of the cochlea through vibrations of the organ of Corti complex. The dimensions of the vibrating structures range from a few hundred (e.g., the basilar membrane) to a few micrometers (e.g., the stereocilia bundle). Vibrations of microstructures in viscous fluid are subjected to energy dissipation. Because the viscous dissipation is considered to be detrimental to the function of hearing—sound amplification and frequency tuning—the cochlea uses cellular actuators to overcome the dissipation. Compared to extensive investigations on the cellular actuators, the dissipating mechanisms have not been given appropriate attention, and there is little consensus on damping models. For example, many theoretical studies use an inviscid fluid approximation and lump the viscous effect to viscous damping components. Others neglect viscous dissipation in the organ of Corti but consider fluid viscosity. We have developed a computational model of the cochlea that incorporates viscous fluid dynamics, organ of Corti microstructural mechanics, and electrophysiology of the outer hair cells. The model is validated by comparing with existing measurements, such as the viscoelastic response of the tectorial membrane, and the cochlear input impedance. Using the model, we investigated how dissipation components in the cochlea affect its function. We found that the majority of acoustic energy dissipation of the cochlea occurs within the organ of Corti complex, not in the scalar fluids. Our model suggests that an appropriate dissipation can enhance the tuning quality by reducing the spread of energy provided by the outer hair cells’ somatic motility.     

Mikromorphologie der Samenoberflächen der GattungEuphorbia

Seed coat surfaces of 127 species, representing 23 sections of the genusEuphorbia L. (Euphorbiaceae) have been examined with the scanning electron microscope (SEM). Various surface patterns and cell wall structures are described. In some groups the seed coat is rather uniform (e.g. in sect.Euphorbium), in other sections even closely related species can be separated by seed coat morphology (e.g.Tithymalus). The taxonomic application of testa micromorphology and the possible systematic position of certain taxa are briefly discussed. The seed coat cells of all species in sect.Tithymalus show remarkable intercellulares filled with small particles, which are described in detail for the first time.

     

A Method for Material Parameter Determination for the Human Mandible Based on Simulation and Experiment

In cranio-maxillofacial surgery planning and implant design, it is important to know the elastic response of the mandible to load forces as they occur, e.g., in biting. The goal of the present study is to provide a method for a quantitative determination of material parameters for the human jaw bone, whose values can, e.g., be used to devise a prototype plastic model for the mandible. Non-destructive load experiments are performed on a cadaveric mandible using a specially designed test bed. The identical physiological situation is simulated in a computer program. The underlying mathematical model is based on a two component, linear elastic material law. The numerical realization of the model, difficult due to the complex geometry and morphology of the mandible, is via the finite element (FE) method. Combining the validated simulation with the results of the tests, an inverse problem for the determination of Young's modulus and the Poisson ratio of both cortical and cancellous bone can then be solved.     

A method for material parameter determination for the human mandible based on simulation and experiment

In cranio-maxillofacial surgery planning and implant design, it is important to know the elastic response of the mandible to load forces as they occur, e.g., in biting. The goal of the present study is to provide a method for a quantitative determination of material parameters for the human jaw bone, whose values can, e.g., be used to devise a prototype plastic model for the mandible. Non-destructive load experiments are performed on a cadaveric mandible using a specially designed test bed. The identical physiological situation is simulated in a computer program. The underlying mathematical model is based on a two component, linear elastic material law. The numerical realization of the model, difficult due to the complex geometry and morphology of the mandible, is via the finite element (FE) method. Combining the validated simulation with the results of the tests, an inverse problem for the determination of Young's modulus and the Poisson ratio of both cortical and cancellous bone can then be solved.     

Genetic analysis of floral symmetry in Van Gogh's sunflowers reveals independent recruitment of CYCLOIDEA genes in the Asteraceae

The genetic basis of floral symmetry is a topic of great interest because of its effect on pollinator behavior and, consequently, plant diversification. The Asteraceae, which is the largest family of flowering plants, is an ideal system in which to study this trait, as many species within the family exhibit a compound inflorescence containing both bilaterally symmetric (i.e., zygomorphic) and radially symmetric (i.e., actinomorphic) florets. In sunflower and related species, the inflorescence is composed of a single whorl of ray florets surrounding multiple whorls of disc florets. We show that in double-flowered (dbl) sunflower mutants (in which disc florets develop bilateral symmetry), such as those captured by Vincent van Gogh in his famous nineteenth-century sunflower paintings, an insertion into the promoter region of a CYCLOIDEA (CYC)-like gene (HaCYC2c) that is normally expressed specifically in WT rays is instead expressed throughout the inflorescence, presumably resulting in the observed loss of actinomorphy. This same gene is mutated in two independent tubular-rayed (tub) mutants, though these mutations involve apparently recent transposon insertions, resulting in little or no expression and radialization of the normally zygomorphic ray florets. Interestingly, a phylogenetic analysis of CYC-like genes from across the family suggests that different paralogs of this fascinating gene family have been independently recruited to specify zygomorphy in different species within the Asteraceae.     

Scattering of exciting light by live cells in fluorescence confocal imaging: phototoxic effects and relevance for FRAP studies

As exciting light in a scanning confocal microscope encounters a cell and its subcellular components, it is refracted and scattered. A question arises as to what proportion of the exciting light is scattered by subcellular structures and whether cells in the vicinity of the imaged area, i.e., cells that are not directly illuminated by the laser beam, can be affected by either an exposure to scattered light and ensuing phototoxic reactions, or by the products of photoactivated reactions diffusing out of the directly illuminated area. We have designed a technique, which allows us to detect subtle cell photodamage and estimate the extent and range of phototoxic effects inflicted by interaction between scattered exciting light and fluorescent probes in the vicinity of the illuminated area. The technique is based on detecting an increased influx of acridine orange into photodamaged cells, which is manifested by a change of color. We demonstrate that phototoxic effects can be exerted not only on the illuminated cell, but also on fluorescently labeled neighboring cells. The damage inflicted on neighbors is due to exposure to light scattered by the imaged (i.e., directly illuminated) cell, but not phototoxic products diffusing out of the directly illuminated area. When light encounters a cell nucleus, scattering is so intense that photodamage can be inflicted even on fluorescently labeled cells located within a radius of approximately 90 microm, i.e., several cell diameters away. This range of scattering is comparable with that caused by the glass bead resting on a coverslip (up to 120 microm). The intense scattering of exciting light imposes limits on FRAP, FLIP, and other techniques employing high intensity laser beams.     

Protein-inhibitor flexible docking by a multicanonical sampling: native complex structure with the lowest free energy and a free-energy barrier distinguishing the native complex from the others

Flexible docking between a protein (lysozyme) and an inhibitor (tri-N-acetyl-D-glucosamine, tri-NAG) was carried out by an enhanced conformational sampling method, multicanonical molecular dynamics simulation. We used a flexible all-atom model to express lysozyme, tri-NAG, and water molecules surrounding the two bio-molecules. The advantages of this sampling method are as follows: the conformation of system is widely sampled without trapping at energy minima, a thermally equilibrated conformational ensemble at an arbitrary temperature can be reconstructed from the simulation trajectory, and the thermodynamic weight can be assigned to each sampled conformation. During the simulation, exchanges between the binding and free (i.e., unbinding) states of the protein and the inhibitor were repeatedly observed. The conformational ensemble reconstructed at 300 K involved various conformational clusters. The main outcome of the current study is that the most populated conformational cluster (i.e., the cluster of the lowest free energy) was assigned to the native complex structure (i.e., the X-ray complex structure). The simulation also produced non-native complex structures, where the protein and the inhibitor bound with different modes from that of the native complex structure, as well as the unbinding structures. A free-energy barrier (i.e., activation free energy) was clearly detected between the native complex structures and the other structures. The thermal fluctuations of tri-NAG in the lowest free-energy complex correlated well with the X-ray B-factors of tri-NAG in the X-ray complex structure. The existence of the free-energy barrier ensures that the lowest free-energy structure can be discriminated naturally from the other structures. In other words, the multicanonical molecular dynamics simulation can predict the native complex structure without any empirical objective function. The current study also manifested that the flexible all-atom model and the physico-chemically defined atomic-level force field can reproduce the native complex structure. A drawback of the current method is that it requires a time consuming computation due to the exhaustive conformational sampling. We discussed a possibility for combining the current method with conventional docking methods.     

Taxonomic studies in the Miconieae (Melastomataceae). VII. Miconia howardiana,a new speices from Hispaniola

Miconia howardiana, which is known only from a diverse moist montane forest in the vicinity of Loma Trocha de Pey (or “Monteada Nueva”), the easternmost peak of the Sierra de Baoruco, is described and illustrated. It is compared to phenetically similar (and probably phylogenetically related) species of theMiconia favosa complex, i.e.,M. favosa, M. xenotricha, M. campanensis M. Sintenisii, M. foveolata, andM. pycnoneura. The species of this complex are characterized by bullate leaves with frequently cordate bases and often six secondary veins. Most species also have large berries and flowers, 5-locular ovaries, large inflorescence bracts and bracteoles, and more or less dendritic multicellular hairs.     

DEVELOPMENT OF THE EPIPHYLLOUS INFLORESCENCE OF HELWINGIA JAPONICA (HELWINGIACEAE)

The inflorescence of Helwingia japonica (Thunb.) Dietr. is initiated adjacent to the leaf axil on the adaxial side of the base of a leaf primordium during its second plastochron. The inflorescence which develops from the resulting primordium comes to be situated on the midrib of the mature fertile leaf, through the action of a basal, intercalary meristem. In fertile leaves this meristem develops beneath, as well as above, the insertion of the inflorescence primordium on the leaf primordium. The same meristem is present in sterile leaves as well. A separate, adaxial vascular bundle departs from the leaf trace in the base of the petiole and leads to the inflorescence, in the mature fertile leaf. This adaxial vascular bundle is absent in sterile leaves. It is argued that the vascular anatomy does not conclusively confirm the hypothesis that the epiphyllous inflorescence is the congenital fusion product of a leaf and an axillary inflorescence. Instead, it is suggested that the interplay of changes in the position of primordium initiation, and intercalary growth, offers an ontogenetic explanation of the situation, which in turn may be related to the phylogeny of the species in question. It appears to be misguided and futile to look for homologies (i.e., 1:1 correspondences) between fertile and sterile leaves, since 1:1 correspondences do not exist in this case.     

High performance wood composites based on benzoxazine-epoxy alloys

Wood-substituted composites from matrices based on ternary mixtures of benzoxazine, epoxy, and phenolic novolac resins (BEP resins) using woodflour (Hevea brasiliensis) as filler are developed. The results reveal that the addition of epoxy resin into benzoxazine resin can lower the liquefying temperature of the ternary systems whereas rheological characterization of the gel points indicates an evident delay of the vitrification time as epoxy content increased. The gelation of the ternary mixtures shows an Arrhenius-typed behavior and the gel time can be well predicted by an Arrhenius equation with activation energy of 35-40kJ/mol. For wood-substituted composites from highly filled BEP alloys i.e. at 70% by weight of woodflour, the reinforcing effect of the woodflour shows a substantial enhancement in the composite stiffness i.e. 8.3GPa of the filled BEP811 vs 5.9GPa of the unfilled BEP811. The relatively high flexural strength of the BEP wood composites up to 70MPa can also be obtained. The outstanding compatibility between the woodflour and the ternary matrices attributed to the modulus and thermal stability enhancement of the wood composites particularly with an increase of the polybenzoxazine fraction in the BEP alloys.     

Imaging of chemiluminescent reactions in mesoscale silicon-glass microstructures

Chemiluminescent reactions in mesoscale analytical structures (chips) containing micrometer-sized interconnecting channels and chambers (pL-nL total volume) were imaged. The chips were fabricated by bonding Pyrex glass to etched pieces of silicon using a high-temperature diffusive bonding technique. In initial experiments light emission from an enhanced chemiluminescent horseradish peroxidase reaction and from a peroxyoxalate reaction contained in straight channels (300 μm wide × 20μ deep; volume 70.2 nL) and open chambers (812 μm wide, 400 μm deep, 5.2 mm long) linked by channels (100μm wide, 20 μm deep) to an exit and entry port were studied using a specially modified microplate holder and an Amerlite microplate luminometer. Light emission from more complex structures (two chambers interconnected by a branching channel 100 μm wide, 20 μm deep) filled with a solution containing alkaline phosphatase, Emerald, and CSPD^TM was imaged using a Photometrics Star 1 CCD camera. Detailed investigation of the detection and spatial resolution of the signal was performed on a Berthold Luminograph LB 980 using both the enhanced chemiluminescent horseradish peroxidase reaction and a peroxyoxalate reaction. We successfully resolved light emission from silicon structures with dimensions 100 μm wide and 20 μm deep. These simple silicon structures served as models for more complex designs that will be used for simultaneous multi-analyte assays in which an imaging system resolves and quantitates light emission from different locations on a silicon-glass analytical device.     

Determination for inflorescence development is a stable state,separable from determination for flower development in Pisum sativum L. buds

Terminal meristems of Pisum sativum (garden pea) transit from vegetative to inflorescence development, and begin producing floral axillary meristems. Determination for inflorescence development was assessed by culturing excised buds and meristems. The first node of floral initiation (NFI) for bud expiants developing in culture and for adventitious shoots forming on cultured meristems was compared with the NFI of intact control buds. When terminal buds having eight leaf primordia were excised from plants of different ages (i.e., number of unfolded leaves) and cultured on 6-benzylaminopurine and kinetin-supplemented medium, the NFI was a function of the age of the source plant. By age 3, all terminal buds were determined for inflorescence development. Determination occurred at least eight nodes before the first axillary flower was initiated. Thus, the axillary meristems contributing to the inflorescence had not formed at the time the bud was explanted. Similar results were obtained for cultured axillary buds. In addition, meristems excised without leaf primordia from axillary buds three nodes above the cotyledons of age-3 plants gave rise to adventitious buds with an NFI of 8.3 ±0.3 nodes. In contrast seed-derived plants had an NFI of 16.5 ±0.2. Thus cells within the meristem were determined for inflorescence development. These findings indicate that determination for inflorescence development in P. sativum is a stable developmental state, separable from determination for flower development, and occurring prior to initiation of the inflorescence at the level of meristems.     

Inflorescence patterns in the woody Brazilian genus Diplusodon (Lythraceae)

The Brazilian genus Diplusodon is the second largest genus within Lythraceae. Their 85 species occupy diverse habitats within the ‘cerrado’ vegetation, and range from shrubs and treelets to dwarf, xylopodium-bearing subshrubs. A comparative-morphological survey of their inflorescence structures using Trollian typology is here presented, as well as some evolutionary considerations drawn from mapping inflorescence characters onto a preliminary phylogeny. The inflorescences of Diplusodon are mostly polytelic, ranging from single racemes to more or less complex double-, triple-, and multiple-racemes. Frondose, compound racemes are plesiomorphic within the genus. Nevertheless, an array of derived features has been found among their species, including production of lateral cymes, proliferation of the main axis, diverse patterns of internode elongation, reduction of subtending leaves to bracts, development of accessory branches, paedomorphic flowering, and, in three species, reversion to monotely.     

HETEROMORPHIC FLOWER DEVELOPMENT IN NEPTUNIA PUBESCENS,A MIMOSOID LEGUME

The characteristic of heteromorphic inflorescences in some mimosoid legumes such as Neptunia is a puzzling one which can be approached developmentally. Each spicate inflorescence of Neptunia pubescens includes three types of flowers: perfect in the upper half, functionally male just below the middle, and sterile or neuter at the base. Developmental studies of the inflorescence show that order of initiation of bracts on the inflorescence is acropetal, but that order of subsequent development of flowers is both acropetal and basipetal on the axis. Bract growth and initiation of the axillary floral apices at the base are inhibited or retarded, while those in the middle and upper levels continue development without interruption. The three types of floral primordia are similar during initiatory stages of organ formation and through early development. At mid-development, differences arise in floral symmetry, petal form, stamen form, and size and shape of the carpel. The functionally male flowers become strongly dorsiventral and zygomorphic while the other two morphs remain actinomorphic or nearly so. Heteromorphy arises from a combination of early suppression of organogeny plus mid-stage innovations of zygomorphy and lateral expansion of stamen primordia. These divergent developmental pathways in one inflorescence can be interpreted in part using Gould's concept of heterochrony: changes in timing of developmental events to produce different structures. Other changes in Neptunia cannot be explained by this concept, however; such changes as omission of processes (i.e., meiosis) in some organs, or addition of processes not normally present (i.e., blade formation in stamen primordia which become staminodia). It is becoming evident from work on this and other legume flowers that actual loss of organs is rare, compared to initiation followed by suppression or modification.     

Assessing the causes and consequences of co-polymerization in amyloid formation

How, and why, different proteins form amyloid fibrils is most often studied in vitro using a single purified protein sequence. However, many amyloid diseases involve co-aggregation of different protein species, including proteins with/without post-translational modifications (e.g., different strains of PrP), proteins of different length (e.g., β₂-microglobulin and ΔN6, Aβ40, and Aβ42), sequence variants (e.g., Aβ and Aβ_ARC), and proteins from different organisms (e.g., bovine PrP and human PrP). The consequences of co-aggregation of different proteins upon the structure, stability, species transmission and toxicity of the resulting amyloid aggregates is discussed here, including the role of co-aggregation in expanding the repertoire of oligomeric and fibrillar structures and how this can affect their biological and biophysical properties.     

Maintenance of Functional Stem Cells in Isolated and Cultured Adult Intestinal Epithelium

We have previously described a method for the primary culture of adult large intestinal epithelium, suggesting that stem cells had survived both the isolation and the culture procedures. However, as no markers for such cells exist, confirmation of stem cell survival is difficult-only the functional properties can be used to define them. Unfortunately, many of these (e.g., differentiation, crypt regeneration) do not occur in culture, probably due to suboptimal conditions. To address this problem both freshly isolated and cultured small and large intestinal crypts were grown subcutaneously in an immunocompromized mouse. All initially formed cysts lined by a simple epithelium which gradually became multicellular and formed invaginations containing many mitoses and apoptoses. Epithelial differentiation, as assayed by Goblet cell mucin production, was also apparent. Mucin maturation was also typical of the normal intestine. The lumen was frequently filled with mucin and apoptotic bodies. Interestingly, in grafts displaying pronounced crypt-like morphology the regions of proliferation were situated toward the base of the structure and the Goblet cells toward the lumen, i.e., a typical crypt-like morphology. Hence, functional adult stem cells appear to survive isolation and tissue culture, permitting organotypic regeneration, possibly involving homeobox gene expression. This may now allow direct stem cell characterization and experimental manipulation, such as transfection, and may ultimately permit transplantation and therapeutic gene therapy.