269 research outputs found
Effects of Resident Species on Recruitment into a Community: Larval Settlement Versus Post-Settlement Mortality in the Oyster Crassostrea virginica
Laboratory and field experiments revealed that a variety of species of common, sessile invertebrates, including barnacles, ascidians, and bryozoans, affected the settlement and post-settlement abundance of the oyster Crassostrea virginica (Gmelin). While the nature of the effects varied, most species both reduced oyster settlement by covering and removing substrate available for attachment, and increased settlement on adjacent surfaces. The solitary ascidians Ciona intestinalis (L.) and Styela clava (Herdman), were found to be predators of oyster larvae. Post-settlement survivorship and growth were also strongly affected by the presence of sessile species. In most cases the effects were negative and correlated with the abundances of the species. Data suggest that competition for planktonic food was the mostly likely cause of reduced growth and survivorship. For many resident species, the combination of reduced oyster settlement on their own exposed surfaces, increased settlement on substrate adjacent to them, and decreased post-settlement survivorship in their presence resulted in these species having little effect on net recruitment. These results demonstrate the need for distinguishing interactions among benthic invertebrate populations during the period from settlement to recruitment
Effects of Inter-Specific Density and Food Supply on Survivorship and Growth of Newly Settled Benthos
Using a laboratory model system comprised of newly settled oysters Crassostrea virginica and established fouling species (Botrylloides sp. initially, and others including Styela clava and Ciona intestinalis as the experiment progressed), we tested how differences in food supply and competitor density may affect post-settlement surivorship and growth of sessile marine invertebrates over a 44 d period. After 15 d, results were mixed but indicated that both food and density conditions affected growth and survivorship significantly, with some suggestion of high food levels ameliorating high density effects However, 44 d after settlement, oysters had reduced survivorship and growth when competitors were present regardless of food level. This study suggests that localized food depletion by juveniles and/or adults of resident species may have a negative effect on recruitment in fouling communities, even when space is not limiting
Structures of Two Melanoma-Associated Antigens Suggest Allosteric Regulation of Effector Binding
The MAGE (melanoma associated antigen) protein family are tumour-associated proteins normally present only in reproductive tissues such as germ cells of the testis. The human genome encodes over 60 MAGE genes of which one class (containing MAGE-A3 and MAGE-A4) are exclusively expressed in tumours, making them an attractive target for the development of targeted and immunotherapeutic cancer treatments. Some MAGE proteins are thought to play an active role in driving cancer, modulating the activity of E3 ubiquitin ligases on targets related to apoptosis. Here we determined the crystal structures of MAGE- A3 and MAGE-A4. Both proteins crystallized with a terminal peptide bound in a deep cleft between two tandem-arranged winged helix domains. MAGE-A3 (but not MAGE-A4), is pre- dominantly dimeric in solution. Comparison of MAGE-A3 and MAGE-A3 with a structure of an effector-bound MAGE-G1 suggests that a major conformational rearrangement is required for binding, and that this conformational plasticity may be targeted by allosteric binders
Interfacial water as a “hydration fingerprint” in the noncognate complex of BamHI. Biophys
ABSTRACT The molecular code of specific DNA recognition by proteins as a paradigm in molecular biology remains an unsolved puzzle primarily because of the subtle interplay between direct protein-DNA interaction and the indirect contribution from water and ions. Transformation of the nonspecific, low affinity complex to a specific, high affinity complex is accompanied by the release of interfacial water molecules. To provide insight into the conversion from the loose to the tight form, we characterized the structure and energetics of water at the protein-DNA interface of the BamHI complex with a noncognate sequence and in the specific complex. The fully hydrated models were produced with Grand Canonical Monte Carlo simulations. Proximity analysis shows that water distributions exhibit sequence dependent variations in both complexes and, in particular, in the noncognate complex they discriminate between the correct and the star site. Variations in water distributions control the number of water molecules released from a given sequence upon transformation from the loose to the tight complex as well as the local entropy contribution to the binding free energy. We propose that interfacial waters can serve as a ''hydration fingerprint'' of a given DNA sequence
Production of ascorbic acid releasing biomaterials for pelvic floor repair
Objective: An underlying abnormality in collagen turnover is implied in the occurrence of complications
and recurrences after mesh augmented pelvic floor repair surgeries. Ascorbic acid is a potent stimulant of
collagen synthesis. The aim of this study is to produce ascorbic acid releasing poly-lactic acid (PLA) scaffolds
and evaluate them for their effects on extracellular matrix production and the strength of the materials.
Materials and methods: Scaffolds which contained either L-ascorbic acid (AA) and Ascorbate-2-Phosphate
(A2P) were produced with emulsion electrospinning. The release of both drugs was measured by UV
spectrophotometry. Human dermal fibroblasts were seeded on scaffolds and cultured for 2 weeks. Cell
attachment, viability and total collagen production were evaluated as well as mechanical properties.
Results: No significant differences were observed between AA, A2P, Vehicle and PLA scaffolds in terms of
fibre diameter and pore size. The encapsulation efficiency and successful release of both AA and A2P were
demonstrated. Both AA and A2P containing scaffolds were significantly more hydrophilic and stronger in
both dry and wet states compared to PLA scaffolds. Fibroblasts produced more collagen on scaffolds containing
either AA or A2P compared to cells grown on control scaffolds.
Conclusion: This study is the first to directly compare the two ascorbic acid derivatives in a tissue engineered
scaffold and shows that both AA and A2P releasing electrospun PLA scaffolds increased collagen
production of fibroblasts to similar extents but AA scaffolds seemed to be more hydrophilic and stronger
compared to A2P scaffolds
Increasing elastin fibre production in a tissue engineered mesh for pelvic floor surgery
yesPolypropylene mesh for pelvic floor surgery is associated with serious complications ( e.g. erosion). A biodegradable tissue engineered mesh composed of a polylactic acid (PLA) scaffold seeded with autologous cells is a promising alternative.
However, thus far elastin content (important for elastic recoil) in this tissue has been low. We aimed to increase elastin expression and test the resultant tensile properties
Effect of mild cortisol cosecretion on body composition and metabolic parameters in patients with primary hyperaldosteronism
Objective
To investigate the effects of simultaneous cortisol cosecretion (CCS) on body composition in computed tomography (CT)-imaging and metabolic parameters in patients with primary aldosteronism (PA) with the objective of facilitating early detection.
Design
Retrospective cohort study.
Patients
Forty-seven patients with PA and CCS confirmed by 1-mg dexamethasone suppression test (DST) with a cutoff of ≥1.8 µg/dL were compared with PA patients with excluded CCS (non-CCS, n = 47) matched by age and sex.
Methods
Segmentation of the fat compartments and muscle area at the third lumbar region was performed on non-contrast-enhanced CT images with dedicated segmentation software. Additionally, liver, spleen, pancreas and muscle attenuation were compared between the two groups.
Results
Mean cortisol after DST was 1.2 µg/dL (33.1 nmol/L) in the non-CCS group and 3.2 µg/dL (88.3 nmol/L) in the CCS group with mild autonomous cortisol excess (MACE). No difference in total, visceral and subcutaneous fat volumes was observed between the CCS and non-CCS group (p = .7, .6 and .8, respectively). However, a multivariable regression analysis revealed a significant correlation between total serum cholesterol and results of serum cortisol after 1-mg DST (p = .026). Classification of the patients based on visible lesion on CT and PA-lateralization via adrenal venous sampling also did not show any significant differences in body composition.
Conclusion
MACE in PA patients does not translate into body composition changes on CT-imaging. Therefore, early detection of concurrent CCS in PA is currently only attainable through biochemical tests. Further investigation of the long-term clinical adverse effects of MACE in PA is necessary
pH-Dependent Spectroscopy and Electronic Structure of the Guanine Analogue 6,8-Dimethylisoxanthopterin †
Effects of adhesive types and structural configurations on shear performance of laminated board from two Gigantochloa bamboos
Semantan (Gigantochloa scortechinii) and beting (Gigantochloa levis) bamboo are the two Malaysian bamboo that are suitable to be converted into laminated bamboo boards. One of the main criteria for laminated board is its good bondability, which is determined by shear performance. The shear performance of laminated board is influenced by several factors such as the species used, adhesive types and lamination configurations. Therefore, in this study, laminated bamboo boards were produced using Semantan and Beting bamboo bonded with phenol–resorcinol–formaldehyde (PRF) and polyurethane (PUR) adhesives. Different configurations (lay-up patterns and strip arrangements) were used during the consolidation of the laminated boards. The bamboo strips were arranged in three different arrangements, namely vertical, horizontal and mixed, and then assembled into a three-layered structure with two lay-up patterns, which are perpendicular and parallel. Shear performances, such as shear strength, bamboo failure and delamination of the boards, were evaluated. The results revealed that the adhesive type and lay-up pattern were the most influential factors on the shear performance. PRF-bonded laminated bamboo boards outperformed PUR-bonded laminated bamboo boards in terms of shear strength and bamboo failure but PUR bonding had better bond durability as indicated by its low delamination. Boards laminated parallelly significantly outperformed those bonded perpendicularly. As for strip arrangement, PRF-bonded laminated boards were less influenced by it compared to PUR-bonded laminated boards. The results suggested that PRF is a better adhesive for bamboo lamination due to its higher shear performance and more consistent performance across structural configurations (lay-up patterns and strip arrangements)
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