SEARCH · Search PubMed

Results for “ARCHITECTURE”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 991 records · Page 55Linked to original sources

PubMed2003

Formation of corporal tissue architecture in vivo using human cavernosal muscle and endothelial cells seeded on collagen matrices.

We explored the feasibility of developing corporal tissue, consisting of human cavernosal smooth muscle and endothelial cells in vivo, using three-dimensional acellular collagen matrices, which are similar in architecture to native corpora. Acellular collagen matrices were derived from processed donor rabbit corpora, using cell lysis techniques. Human corpus cavernosal muscle and endothelial cells were seeded on the acellular matrices. A total of 80 matrices, 20 without cells and 60 with cells, were implanted subcutaneously in athymic mice. An additional 36 matrices seeded with cells were maintained in culture for up to 4 weeks. Hydroxyproline quantification, Western blot analysis, RT-PCR, and scanning electron microscopy of the matrices, with and without cells, were performed at various time points. Animals were killed 3 days and 1, 2, 3, 4, 6, and 8 weeks after implantation. Immunocytochemical and histological analyses were performed to confirm the muscle and endothelial phenotype. Organ bath studies were performed in order to determine the degree of tissue contraction. Western blot analysis detected alpha-actin, myosin, and tropomyosin proteins from human corporal smooth muscle cells. Expression of muscarinic acetylcholine receptor (mAChR) subtype m4 mRNA was demonstrated by RT-PCR from corporal muscle cells before and 8 weeks after seeding. The implanted matrices showed neovascularity into the sinusoidal spaces by 1 week after implantation. Increasing organization of smooth muscle and endothelial cells lining the sinusoidal walls was observed at 2 weeks and continued with time. The matrices were covered with the appropriate cell architecture 4 weeks after implantation. The matrices showed a stable collagen concentration over 8 weeks, as determined by hydroxyproline quantification. Immunocytochemical studies using alpha-actin and factor VIII antibodies confirmed the presence of corporal smooth muscle and endothelial cells, both in vitro and in vivo, at all time points. There was no evidence of cellular organization in the control matrices. Organ bath studies showed that the cell-seeded corporal tissue matrices responded to electrical field stimulation, whereas the unseeded implants failed to respond. This study demonstrates that human cavernosal smooth muscle and endothelial cells seeded on three-dimensional acellular collagen matrices derived from donor corpora are able to form well-vascularized corporal tissues in vivo.

Animals↗

PubMed2006

Polyelectrolyte nano-scaffolds for the design of layered cellular architectures.

The design of in vitro multilayered cellular architectures that resemble the stratified, lattice-like structure in tissues poses a significant challenge for tissue engineering. There is currently no generally applicable methodology to design multilayered cellular constructs that mimic the structure of tissues in vivo. We report a novel and generalizable approach to create multilayered cellular constructs that addresses these issues. These in vitro constructs comprise alternating layers of cells and nano-scale biocompatible polyelectrolyte (PE) scaffolds. We apply this methodology to address two specific problems in hepatic tissue engineering: the design of in vitro liver sinusoidal structures and the critical need to increase viable cell mass in extracorporeal liver-assist devices. We assembled ultrathin polymer scaffolds on the top of a confluent monolayer of cells by the sequential deposition of oppositely charged PEs. The thickness of the PE scaffold lies in the nanometer range. The PE scaffold plays a dual role. First, it is a technique to culture hepatocytes in vitro that maintains their morphology, cytoskeletal structure, and liver-specific functions. Second, the nano-scaffold provides a cell-adhesive surface on which a second layer of cells can be cultured, resulting in layered architectures. We have used this approach to design layered three-dimensional hepatocyte-PE-hepatocyte constructs, hepatocyte-PE-endothelial cell constructs, and hepatocyte-PE-fibroblast constructs. As a result of its versatility, this approach can, in principle, be used to design layered cellular constructs of any tissue type, and therefore has potentially wide applications in tissue engineering, bioreactor devices, and in drug delivery. This methodology has the potential to generate realistic in vitro constructs of any tissue type.

3T3 Cells↗

PubMed2001

Amino-terminal polypeptides of vimentin are responsible for the changes in nuclear architecture associated with human immunodeficiency virus type 1 protease activity in tissue culture cells.

Electron microscopy of human skin fibroblasts syringe-loaded with human immunodeficiency virus type 1 protease (HIV-1 PR) revealed several effects on nuclear architecture. The most dramatic is a change from a spherical nuclear morphology to one with multiple lobes or deep invaginations. The nuclear matrix collapses or remains only as a peripheral rudiment, with individual elements thicker than in control cells. Chromatin organization and distribution is also perturbed. Attempts to identify a major nuclear protein whose cleavage by the protease might be responsible for these alterations were unsuccessful. Similar changes were observed in SW 13 T3 M [vimentin(+)] cells, whereas no changes were observed in SW 13 [vimentin(-)] cells after microinjection of protease. Treatment of SW 13 [vimentin(-)] cells, preinjected with vimentin to establish an intermediate filament network, with HIV-1 PR resulted in alterations in chromatin staining and distribution, but not in nuclear shape. These same changes were produced in SW 13 [vimentin(-)] cells after the injection of a mixture of vimentin peptides, produced by the cleavage of vimentin to completion by HIV-1 PR in vitro. Similar experiments with 16 purified peptides derived from wild-type or mutant vimentin proteins and five synthetic peptides demonstrated that exclusively N-terminal peptides were capable of altering chromatin distribution. Furthermore, two separate regions of the N-terminal head domain are primarily responsible for perturbing nuclear architecture. The ability of HIV-1 to affect nuclear organization via the liberation of vimentin peptides may play an important role in HIV-1-associated cytopathogenesis and carcinogenesis.

Animals↗

PubMed2004

Nucleoporins as components of the nuclear pore complex core structure and Tpr as the architectural element of the nuclear basket.

The vertebrate nuclear pore complex (NPC) is a macromolecular assembly of protein subcomplexes forming a structure of eightfold radial symmetry. The NPC core consists of globular subunits sandwiched between two coaxial ring-like structures of which the ring facing the nuclear interior is capped by a fibrous structure called the nuclear basket. By postembedding immunoelectron microscopy, we have mapped the positions of several human NPC proteins relative to the NPC core and its associated basket, including Nup93, Nup96, Nup98, Nup107, Nup153, Nup205, and the coiled coil-dominated 267-kDa protein Tpr. To further assess their contributions to NPC and basket architecture, the genes encoding Nup93, Nup96, Nup107, and Nup205 were posttranscriptionally silenced by RNA interference (RNAi) in HeLa cells, complementing recent RNAi experiments on Nup153 and Tpr. We show that Nup96 and Nup107 are core elements of the NPC proper that are essential for NPC assembly and docking of Nup153 and Tpr to the NPC. Nup93 and Nup205 are other NPC core elements that are important for long-term maintenance of NPCs but initially dispensable for the anchoring of Nup153 and Tpr. Immunogold-labeling for Nup98 also results in preferential labeling of NPC core regions, whereas Nup153 is shown to bind via its amino-terminal domain to the nuclear coaxial ring linking the NPC core structures and Tpr. The position of Tpr in turn is shown to coincide with that of the nuclear basket, with different Tpr protein domains corresponding to distinct basket segments. We propose a model in which Tpr constitutes the central architectural element that forms the scaffold of the nuclear basket.

HeLa Cells↗

PubMed1991

Correlation between visual clues, objective architectural features, and interobserver agreement in prostate cancer.

Three pathologists evaluated a number of designated architectural features to assign grades to 41 cases of well- to moderately differentiated adenocarcinoma, and their opinions were compared. The consensus opinion was obtained and evaluated against objective measurements of glandular architecture that were obtained by morphometric techniques. The observers agreed on gland size, gland uniformity, and the number of glands per field in only 49%, 31%, and 39% of cases, respectively. There were significant differences in the Gleason grades assigned by observers. Paired matching of individual Gleason grades showed agreement among observers in 44% (18 of 41), 56% (23 of 41), and 75% (31 of 41) of cases, respectively. This level of interobserver disagreement occurred even though cases with predominant patterns were selected carefully and those with variable patterns were excluded. A direct relationship appears to exist between increasing Gleason grade and increasing glandular variability, and there is an inverse relationship between Gleason grade, gland lumen area, and the number of glandular nuclei, as assessed by a group of pathologists.

Humans↗

PubMed2003

Branch architecture, light interception and crown development in saplings of a plagiotropically branching tropical tree, Polyalthia jenkinsii (Annonaceae).

To investigate crown development patterns, branch architecture, branch-level light interception, and leaf and branch dynamics were studied in saplings of a plagiotropically branching tree species, Polyalthia jenkinsii Hk. f. & Thoms. (Annonaceae) in a Malaysian rain forest. Lengths of branches and parts of the branches lacking leaves ('bare' branches) were smaller in upper branches than in lower branches within crowns, whereas lengths of 'leafy' parts and the number of leaves per branch were larger in intermediate than in upper and lower branches. Maximum diffuse light absorption (DLA) of individual leaves was not related to sapling height or branch position within crowns, whereas minimum DLA was lower in tall saplings. Accordingly, branch-level light interception was higher in intermediate than in upper and lower branches. The leaf production rate was higher and leaf loss rate was smaller in upper than in intermediate and lower branches. Moreover, the branch production rate of new first-order branches was larger in the upper crowns. Thus, leaf and branch dynamics do not correspond to branch-level light interception in the different canopy zones. As a result of architectural constraints, branches at different vertical positions experience predictable light microenvironments in plagiotropic species. Accordingly, this pattern of carbon allocation among branches might be particularly important for growth and crown development in plagiotropic species.

Light↗

PubMed2003

Exploring within-tree architectural development of two apple tree cultivars over 6 years.

The present study addresses the prediction of apple tree development, taking into account both the number and within-tree position of tree components. The architectural development of two trees per scion cultivar, 'Fuji' and 'Braeburn', was studied by describing all shoots over 6 years. Flowering and fruiting were observed over 3 years. The description included different scales [entire trees, axes, growth units (GUs) and metamers], and the analysis compared all axes of the trees as a function of their branching order and age. Three main aspects of vegetative development were investigated: the quantity of primary growth; the number and nature of developing axillary shoots; and meristem death. Results confirm the existence of within-tree morphological gradients, and show that the decrease in growth was comparable in magnitude for all axes and GUs, irrespective of their position. This decrease results from a reduction in the number of metamers per GU, which was modelled by an exponential function. The decrease in growth involved changes in the number and nature of the axillary shoots, which could be described by simple functions. The probability of spur death was constant over the years but differed according to cultivar and type of bearing shoot. The within-tree probability of flowering and fruiting was predictable for 'Braeburn' because axes, regardless of their position and type, had a high probability of flowering and a low probability of fruit set which led to a regular bearing habit. In contrast, 'Fuji' had an alternating bearing behaviour that was more complex to predict. This appeared to result from a synchronized increase in the probability that all GUs at tree scale are floral, combined with a high probability of fruit set. The consequences of these results for both yield prediction and architectural simulations are discussed.

Flowers↗

PubMed2003

Reconstructing tumor genome architectures.

Although cancer progression is often associated with genome rearrangements, little is known about the detailed genomic architecture of tumor genomes. The attempt to reconstruct the genomic organization of a tumor genome recently resulted in the development of the End Sequence Profiling (ESP) technique, and the application of this technique to human MCF7 tumor cells. We formulate the ESP Genome Reconstruction Problem, and develop an algorithm to solve this problem in the case of sparse ESP data. We apply our algorithm to analyze human MCF7 tumor cells, and obtain the first reconstruction of the putative architecture of human MCF7 tumor genome. Our results assist in the ongoing ESP analysis of MCF7 tumors by suggesting additional ESP experiments for the completion of a reliable reconstruction of the MCF7 tumor genome, and by focusing BAC re-sequencing efforts.

Algorithms↗

PubMed2004

An architecture for biological information extraction and representation.

MOTIVATIONS: Technological advances in biomedical research are generating a plethora of heterogeneous data at a high rate. There is a critical need for extraction, integration and management tools for information discovery and synthesis from these heterogeneous data. RESULTS: In this paper, we present a general architecture, called ALFA, for information extraction and representation from diverse biological data. The ALFA architecture consists of: (i) a networked, hierarchical, hyper-graph object model for representing information from heterogeneous data sources in a standardized, structured format; and (ii) a suite of integrated, interactive software tools for information extraction and representation from diverse biological data sources. As part of our research efforts to explore this space, we have currently prototyped the ALFA object model and a set of interactive software tools for searching, filtering, and extracting information from scientific text. In particular, we describe BioFerret, a meta-search tool for searching and filtering relevant information from the web, and ALFA Text Viewer, an interactive tool for user-guided extraction, disambiguation, and representation of information from scientific text. We further demonstrate the potential of our tools in integrating the extracted information with experimental data and diagrammatic biological models via the common underlying ALFA representation. CONTACT: aditya_vailaya@agilent.com.

Abstracting and Indexing↗

PubMed2004

Architecture of basic building blocks in protein and domain structural interaction networks.

MOTIVATION: The structural interaction of proteins and their domains in networks is one of the most basic molecular mechanisms for biological cells. Topological analysis of such networks can provide an understanding of and solutions for predicting properties of proteins and their evolution in terms of domains. A single paradigm for the analysis of interactions at different layers, such as domain and protein layers, is needed. RESULTS: Applying a colored vertex graph model, we integrated two basic interaction layers under a unified model: (1) structural domains and (2) their protein/complex networks. We identified four basic and distinct elements in the model that explains protein interactions at the domain level. We searched for motifs in the networks to detect their topological characteristics using a pruning strategy and a hash table for rapid detection. We obtained the following results: first, compared with a random distribution, a substantial part of the protein interactions could be explained by domain-level structural interaction information. Second, there were distinct kinds of protein interaction patterns classified by specific and distinguishable numbers of domains. The intermolecular domain interaction was the most dominant protein interaction pattern. Third, despite the coverage of the protein interaction information differing among species, the similarity of their networks indicated shared architectures of protein interaction network in living organisms. Remarkably, there were only a few basic architectures in the model (>10 for a 4-node network topology), and we propose that most biological combinations of domains into proteins and complexes can be explained by a small number of key topological motifs. CONTACT: doheon@kaist.ac.kr.

Animals↗

PubMedDate not supplied

Circuitry, architecture, and functional dynamics of visual cortex.

A fundamental understanding of the mechanisms of cortical processing requires an examination of the relationships of cortical circuitry, functional architecture, and receptive field properties. Ultimately, this kind of analysis can be utilized to explore the neurobiological basis of psychophysics and perception. At the onset our studies were intended to account for the then known receptive field properties of cortical cells in terms of their underlying circuitry, but surprisingly a good part of the cortical circuit appeared to be in violation of the principles of cortical architecture, and this led us to explore the possibility of new, more complex properties of cortical cells. It has become increasingly possible to relate the responsive specificity of cortical cells, and the circuitry underlying this specificity, to the perceptual capabilities of the visual system by performing analogous experiments on single cells and in human psychophysics.

Animals↗

PubMed2002

Molecular architecture and mechanism of an icosahedral pyruvate dehydrogenase complex: a multifunctional catalytic machine.

Electron cryo-microscopy of 'single particles' is a powerful method to determine the three-dimensional (3D) architectures of complex cellular assemblies. The pyruvate dehydrogenase multi-enzyme complex couples the activity of three component enzymes (E1, E2 and E3) in the oxidative decarboxylation of pyruvate to generate acetyl-CoA, linking glycolysis and the tricarboxylic acid cycle. We report here a 3D model for an 11 MDa, icosahedral pyruvate dehydrogenase sub-complex, obtained by combining a 28 A structure derived from electron cryo-microscopy with previously determined atomic coordinates of the individual E1 and E2 components. A key feature is that the E1 molecules are located on the periphery of the assembly in an orientation that allows each of the 60 mobile lipoyl domains tethered to the inner E2 core to access multiple E1 and E2 active sites from inside the icosahedral complex. This unexpected architecture provides a highly efficient mechanism for active site coupling and catalytic rate enhancement by the motion of the lipoyl domains in the restricted annular region between the inner core and outer shell of the complex.

Catalysis↗

PubMed2003

The nuclear actin-related proteins Arp7 and Arp9: a dimeric module that cooperates with architectural proteins for chromatin remodeling.

Nuclear actin-related proteins (ARPs) are essential components of chromatin remodeling and modifying complexes, but their functions and relationship to actin remain elusive. The yeast SWI/SNF and RSC complexes contain Arp7 and Arp9, and are shown to form a stable heterodimer with the properties of a functional module. Arp7 and Arp9 rely on their actin-related regions for heterodimerization, and their unique C-termini cooperate for assembly into RSC. We suggest that regulated ARP-ARP (and possibly ARP-beta-actin) heterodimerization might be a conserved feature of chromatin complexes. A RSC complex lacking Arp7/9 was isolated that displays robust nucleosome remodeling activity, suggesting a separate essential role for ARPs in the regulation of chromatin structure. A screen for suppressors of arp mutations yielded the DNA bending architectural transcription factor Nhp6, which interacts with RSC complex physically and functionally and shows facilitated binding to nucleosomes by RSC. We propose that Arp7/9 dimers function with DNA bending proteins to facilitate proper chromatin architecture and complex- complex interactions.

Actins↗

PubMed2026

DENND3-p.R534S disrupts dyadic microdomain architecture to drive potentially pro-arrhythmic calcium and electrophysiologic instability.

AIMS: Inherited ventricular arrhythmias (VAs) frequently occur in the absence of pathogenic variants in canonical ion channel genes, suggesting alternative mechanisms of electrical instability. DENND3 is a guanine nucleotide exchange factor that regulates Rab GTPase-mediated trafficking, but its role in cardiac excitation-contraction coupling and membrane microdomain organization remains undefined. METHODS AND RESULTS: We studied induced pluripotent stem cell-derived cardiomyocytes generated from a CRISPR/CAS9-engineered ultra-rare DENND3-p.R534S variant-inserted line (previously identified in an idiopathic ventricular fibrillation pedigree) and matched isogenic controls. Multielectrode array recordings, live-cell calcium imaging, super-resolution imaging using expansion microscopy, and biochemical analyses were used to assess electrical activity, calcium handling, membrane architecture, and calcium release unit organization. Potentially therapeutic studies were performed using genetic and pharmacologic inhibition of Rab11b. DENND3-p.R534S induced pluripotent stem cell-derived cardiomyocytes exhibited multicellular electrical instability characterized by increased beat-to-beat variability, arrhythmic activity, conduction slowing, and prolonged excitation-contraction delay. These abnormalities were accompanied by heterogeneous and dyssynchronous calcium cycling despite preserved expression of major calcium-handling proteins. Super-resolution imaging revealed disruption of BIN1-dependent membrane architecture and nanoscale uncoupling of Cav1.2 and RyR2. Inhibition of Rab11b restored BIN1 organization, re-established dyadic coupling, normalized calcium cycling, and improved electrical stability. CONCLUSION: These findings support a model in which altered trafficking balance contributes to disruption of membrane microdomain organization, leading to dyadic uncoupling, calcium instability, and electrical dysfunction. Modulation of the Rab11b-mediated trafficking pathway restored structural and functional abnormalities, supporting the trafficking-associated pathway as a potential therapeutic target in DENND3-associated ventricular arrhythmia.

Myocytes, Cardiac↗

PubMedDate not supplied

Pleiotropy, epistasis and new QTL: the genetic architecture of honey bee foraging behavior.

The regulation of division of labor in social insects, particularly in the honey bee (Apis mellifera L.), has received considerable attention from a number of biological subdisciplines, including quantitative and behavioral genetics, because of the high complexity of the behavioral traits involved. The foraging choices of honey bee workers can be accurately quantified, and previous studies have made the foraging behavior of honey bees one of the best studied naturally occurring behavioral phenotypes. Three quantitative trait loci (QTL) have been identified that influence a set of foraging variables, including the concentration of nectar collected and the amount of pollen and nectar brought back to the hive. This study extends previous genetic investigations and represents the most comprehensive investigation of the genetic architecture of these foraging variables. We examined the effects of markers for the three established QTL and for one further candidate gene (Amfor), in two reciprocal backcross populations. These populations were also used to carry out two new QTL mapping studies, with over 400 Amplified Fragment Length Polymorphism (AFLP) markers in each. We detected a variety of effects of the genetic markers for the established QTL and the candidate gene, which were mostly epistatic in nature. A few new QTL could be detected with a variety of mapping techniques. Our results add complexity to the genetic architecture of the foraging behavior of the honey bee. Specifically, we support the hypotheses that pln1, pln2, pln3, and Amfor are involved in the regulation of foraging behavior in the honey bee and add some new factors that deserve further study in the future.

Animals↗

PubMed2004

The nest architecture of the Florida harvester ant, Pogonomyrmex badius.

The architecture of the subterranean nests of the Florida harvester ant, Pogonomyrmex badius, was studied through excavation and casting. Nests are composed of two basic units: descending shafts and horizontal chambers. Shafts form helices with diameters of 4 to 6 cm, and descend at an angle of about 15-20 degrees near the surface, increasing to about 70 degrees below about 50 cm in depth. Superficial chambers (< 15 cm deep) appear to be modified shafts with low angles of descent, and are distinct from deeper chambers. In larger nests, they have a looping, connected morphology. Chambers begin on the outside of the helix as horizontal-floored, circular indentations, becoming multi-lobed as they are enlarged. Chamber height is about 1 cm, and does not change with area. Chamber area is greatest in the upper reaches of the nest, and decreases with depth. Vertical spacing between chambers is least in the upper reaches and increases to a maximum at about 70 to 80% of the maximum depth of the nest. The distribution of chamber area is top-heavy, with about half the total area occurring in the top quarter of the nest. Each 10% depth increment of the nest contains 25 to 40% less area than the decile above it, no matter what the size of the nest. Nests grow by simultaneous deepening, addition of new chambers and/or shafts and enlargement of existing chambers. As a result, the vertical spacing between chambers is similar at all nest sizes, and the relative distribution of chamber area with relative nest depth did not change during colony growth (that is, the size-free nest shape was the same at all colony sizes). Total chamber area increased somewhat more slowly than the population of workers excavating the nest. The branching of shafts was consistently shallow (< 40 cm), somewhat more so in large nests than small. Large colonies rarely had more than 4 shaft/chamber series. Each new series contributed less to the total chamber area because its chambers were smaller. Incipient colonies were usually 40 to 50 cm deep while mature colonies were commonly 2.5 to 3.0 m deep. Workers captured near the top of a mature nest (and therefore older) and penned in escape proof enclosures, excavated larger nests than did young workers captured from the bottom of the nest. Most of this difference was due to a larger fraction of older workers engaging in digging, rather than an increase in their rate of work. All ages of workers produced similar top-heavy nests. When different ages of workers from different levels of a mature colony were allowed to re-assort themselves in a vertical test apparatus buried in the soil, older workers moved upward to assume positions in the upper parts of the nest, much as in the colonies from which they were taken. The vertical organization of workers based on age is therefore the product of active movement and choice. A possible template imparting information on depth is a carbon dioxide gradient. Carbon dioxide concentrations increased 5-fold between the surface and the depths of the nest. A preference of young workers for high carbon dioxide concentrations, and a tendency for workers to dig more under low carbon dioxide concentrations could explain both the vertical age-distribution of workers, and the top-heaviness of the nest's architecture.

Aging↗

PubMed2005

The nest architecture of the ant, Camponotus socius.

The architecture of subterranean nests of the ant Camponotus socius was studied from casts of plaster or metal. Twenty-four such casts are illustrated using stereo pairs of images. After study, plaster casts were dissolved to retrieve the workers embedded in them, providing a census of the ants that excavated the nest. Nests were up to 60 cm deep, and were composed of descending shafts connecting up to about 10 horizontal chambers. Nest volume ranged up to almost 800 cm and total chamber area up to almost 500 cm. Both volume and area were closely and positively related to the number of workers in the nest. Nest enlargement occurred through the simultaneous enlargement of chambers, deepening of the nest and addition of more chambers. Chamber enlargement contributed most to nest growth. Chambers near the surface were elongate and tunnel-like, while deeper chambers were more compact in outline. As chambers were enlarged, their outlines became more complex and lobed. Workers were polymorphic with clearly distinguishable minor and major workers. The headwidth of minors averaged 1.45 to 1.65 mm, and that of majors 2.30 to 2.80 mm. The mean headwidth of minors increased significantly as the proportion of major workers increased, but the trend of major headwidths fell short of significance. The numerical proportion of majors ranged from 3% to 38% and averaged 15% of the workers, while their biomass proportion ranged from 10% to 75%, averaging about 50%. The queen was recovered in 6 of the 14 plaster nests, suggesting that the average colony of this polydomous species has 2.3 nests. Because of the lateness of the season when casts were made (October), only two nests contained significant amounts of brood. The possible functional roles of nest architecture in ants are discussed.

Animals↗

PubMed2004

Hydraulic architecture of plants of Helianthus annuus L. cv. Margot: evidence for plant segmentation in herbs.

The hydraulic architecture of sunflower (Helianthus annuus L. cv. Margot) was studied in terms of the partitioning of the hydraulic conductance (Kleaf) of leaves inserted at progressively more apical nodes both in growing plants (GP) and in plants at full anthesis (mature plants, MP). Leaf conductance to water vapour (gL), leaf water potential (PsiL), leaf water potential at zero turgor (Psi tlp), and leaf osmotic potential at full turgor (pi0) were also measured. Sunflower plants showed gL and Kleaf values significantly increasing in the acropetal direction, while PsiL of basal leaves was significantly more negative than that of distal leaves; Psi tlp markedly decreased in the acropetal direction in MP so that leaves of MP retained increasingly more turgor the more apical they were. This hydraulic pattern, already present in very young plants (GP), strongly favours apical leaves. These data suggest that the progressive leaf dieback starting from the stem base, as observed when the inflorescence of sunflower reached maturity, might be due to time-dependent loss of hydraulic conductance. In fact, Kleaf loss was correlated with PsiL drop and stomatal closure. Leaf dehydration was aggravated by solute exportation from the basal towards the apical leaves, as revealed by the acropetal decrease of pi0. Kleaf was shown to be linearly and positively related to the prevailing ambient irradiance during plant growth, thus suggesting that leaf hydraulics is very sensitive to environmental conditions. It was concluded that the pronounced apical dominance of some sunflower cultivars is determined, among other factors, by plant hydraulic architecture.

Helianthus↗