The extracellular matrix protein MAGP-2 interacts with Jagged1 and induces its shedding from the cell surface

Elastic fibers are composed of the protein elastin and a network of 10-12-nm microfibrils, which are composed of several glycoproteins, including fibrillin-1, fibrillin-2, and MAGP1/2 (microfibril-associated glycoproteins-1 and -2). Although fibrillins and MAGPs covalently associate, we find that the DSL (Delta/Serrate/LAG2) protein Jagged1, an activating ligand for Notch receptor signaling, also interacts with MAGP-2 in both yeast two-hybrid and coimmunoprecipitation studies. Interaction between Jagged1 and MAGP-2 requires the epidermal growth factor-like repeats of Jagged1. MAGP-2 was found complexed with the Jagged1 extracellular domain shed from 293T cells and COS-7 cells coexpressing full-length Jagged1 and MAGP-2. MAGP-2 shedding of the Jagged1 extracellular domain was decreased by the metalloproteinase hydroxamate inhibitor BB3103 implicating proteolysis in its release. Although MAGP-2 also interacted with the other DSL ligands, Jagged2 and Delta1, they were not found associated with MAGP-2 in the conditioned media, identifying differential effects of MAGP-2 on DSL ligand shedding. The related microfibrillar protein MAGP-1 was also found to interact with DSL ligands but, unlike MAGP-2, was unable to facilitate the shedding of Jagged1. Our findings suggest that in addition to its role in microfibrils, MAGP-2 may also affect cellular differentiation through modulating the Notch signaling pathway either by binding to cell surface DSL ligands or by facilitating release and/or stabilization of a soluble extracellular form of Jagged1.     

Definition and validation of operating equations for poly(vinyl alcohol)‐poly(lactide‐co‐glycolide) microfiltration membrane‐scaffold bioreactors

The aim of this work is to provide operating data for biodegradable hollow fiber membrane bioreactors. The physicochemical cell culture environment can be controlled with the permeate flowrate, so this aim necessitates the provision of operating equations that enable end‐users to set the pressures and feed flowrates to obtain their desired culture environment. In this paper, theoretical expressions for the pure water retentate and permeate flowrates, derived using lubrication theory, are compared against experimental data for a single fiber poly(vinyl alcohol)–poly(lactide‐co‐glycolide) crossflow module to give values for the membrane permeability and slip. Analysis of the width of the boundary layer region where slip effects are important, together with the sensitivity of the retentate and permeate equations to the slip parameter, show that slip is insignificant for these membranes, which have a mean pore diameter of 1.1 µm. The experimental data is used to determine a membrane permeability, of k = 1.86 × 10^?16 m², and to validate the model. It was concluded that the operating equation that relates the permeate to feed ratio, c, lumen inlet flowrate, Q _l,in, lumen outlet pressure, P ₁, and ECS outlet pressure, P ₀, is (1) where A and B are constants that depend on the membrane permeability and geometry (and are given explicitly). Finally, two worked examples are presented to demonstrate how a tissue engineer can use Equation (1) to specify operating conditions for their bioreactor. Biotechnol. Bioeng. 2010;107: 382–392. © 2010 Wiley Periodicals, Inc.     

Development of a process for the production of the anticancer lead compound pleurotin by fermentation of Hohenbuehelia atrocaerulea

Pleurotin is a naphthoquinone antibiotic originally isolated from Pleurotus griseus. Two pleurotin producing strains of Hohenbuehelia atrocaerulea have been identified, which, on solid substrate fermentation for 2 months yield 1-2 mg/l of the antibiotic. Described here is the lengthy developmental process which resulted in a production protocol being developed which reliably yields pleurotin from liquid fermentation at >300 mg/l. Critical to obtaining this increase in titer was inclusion in the media of an aqueous extract of alder wood.     

Ecosystem productivity can be predicted from potential relative growth rate and species abundance

We show that ecosystem-specific aboveground net primary productivity (SANPP, g g⁻¹ day⁻¹, productivity on a per gram basis) can be predicted from species-level measures of potential relative growth rate (RGR_max), but only if RGR_max is weighted according to the species' relative abundance. This is in agreement with Grime's mass-ratio hypothesis. Productivity was measured in 12 sites in a French Mediterranean post-agricultural succession, while RGR_max was measured on 26 of the most abundant species from this successional sere, grown hydroponically. RGR_max was only weakly correlated ( r ² = 0.12, P  < 0.05) with field age when species abundance was not considered, but the two variables were strongly correlated ( r ² = 0.81, P  < 0.001) when the relative abundance of species in each field was taken into account. SANPP also decreased significantly with field age. This resulted in a tight relationship ( r ² = 0.77, P  < 0.001) between productivity and RGR_max weighted according to species relative biomass contribution. Our study shows that scaling-up from the potential properties of individual species is possible, and that information on potential and realized species traits can be integrated to predict ecosystem functioning.     

Large Hawk‐Cuckoo Hierococcyx sparverioides parasitism on the Chinese Babax Babax lanceolatus may be an evolutionarily recent host–parasite system

We documented brood parasitism by the poorly studied Large Hawk‐Cuckoo on a previously unknown host species, the Chinese Babax. Furthermore, we describe a new egg colour for the Large Hawk‐Cuckoo. The parasitism rate of Chinese Babax nests over 4 years was 6.9% (11 of 159 nests), with significant temporal variation. The Large Hawk‐Cuckoo laid immaculate white eggs that appeared non‐mimetic to the blue Babax eggs, an impression that was confirmed by avian visual modelling. Nevertheless, most Cuckoo eggs were accepted by the host, suggesting that this host–parasite system may be evolutionarily recent.     

The Intercostal NMJ Assay: a new alternative to the conventional LD50 assay for the determination of the therapeutic potency of botulinum toxin preparations

Therapeutic botulinum neurotoxin type A preparations have found an increasing number of clinical uses for a large variety of neuromuscular disorders and dermatological conditions. The accurate determination of potency in the clinical application of botulinum toxins is critical to ensuring clinical efficacy and safety, and is currently achieved by using a lethal dose (LD50) assay in mice. Ethical concerns and operational constraints associated with this assay have prompted the development of alternative assay systems that could potentially lead to its replacement. As one such alternative, we describe the development and evaluation of a novel ex vivo assay (the Intercostal Neuromuscular Junction [NMJ] Assay), which uses substantially fewer animals and addresses ethical concerns associated with the LD50 assay. The assay records the decay of force from electrically-stimulated muscle tissue sections in response to the toxin, and thus combines the important mechanisms of receptor binding, translocation, and the enzymatic action of the toxin molecule. Toxin application leads to a time-related and dose-related reduction in contractile force. A regression model describing the relationship between the applied dose and force decay was determined statistically, and was successfully tested as able to correctly predict the potency of an unknown sample. The tissue sections used were found to be highly reproducible, as determined through the innervation pattern and the localisation of NMJs in situ. Furthermore, the efficacy of the assay protocol to successfully deliver the test sample to the cellular target sites, was critically assessed by using molecular tracer molecules.     

Age impairs Flk-1 signaling and NO-mediated vasodilation in coronary arterioles

Impairment of flow-induced vasodilation in coronary resistance arterioles may contribute to the decline in coronary vasodilatory reserve that occurs with advancing age. This study investigated the effects of age on flow-induced signaling and activation of nitric oxide (NO)-mediated vasodilation in coronary resistance arterioles. Coronary arterioles were isolated from young (approximately 6 mo) and old (approximately 24 mo) male Fischer-344 rats to assess vasodilation to flow, vascular endothelial growth factor (VEGF), and ACh. Flow- and VEGF-induced vasodilation of coronary arterioles was impaired with age (P相似文献   

Unique neuronal tracers show migration and differentiation of SVZ progenitors in organotypic slices

Continual neurogenesis in the subventricular zone (SVZ) of postnatal and adult mammalian forebrain has been well documented, but the mechanisms underlying cell migration and differentiation in this region are poorly understood. We have developed novel in vivo and in vitro methods to investigate these processes. Using stereotaxic injections of a variety of tracers/tracker [Cholera Toxin β subunit (CTb‐), Fluorogold (FG), and Cell Tracker Green (CTG)], we could efficiently label SVZ cells. Over several days, labeled cells migrate along the rostral migratory stream (RMS) to their final differentiation site in the olfactory bulb (OB). The compatibility of these tracers/trackers with immunohistochemistry allows for cell labeling with multiple dyes (e.g., CTb and CTG) and/or specific cell antigens. To investigate the dynamics of migration we labeled SVZ progenitor cells with small injections of CTG and monitored the movements of individual cells in fresh parasagittal brain slices over several hours using time‐lapse confocal microscopy. Our observations suggest that tangential cell migration along the RMS occurs more rapidly than radial cell migration into the OB granule cell layer. To investigate migration over longer time periods, we developed an in vitro organotypic slice in which labeled SVZ progenitors migrate along the RMS and differentiate within the OB. The phenotypic characteristics of these cells in vitro were equivalent to those observed in vivo. Taken together, these methods provide useful tools investigating cell migration and differentiation in a preparation that maintains the anatomical organization of the RMS. © 2001 John Wiley & Sons, Inc. J Neurobiol 49: 326–338, 2001     

Parnassia palustris: a genetically diverse species in Scandinavia

Patterns of variation at nine enzyme loci were examined in 528 plants representing diploid and tetraploid populations of Parnassia palustris s. l. in Europe to assess genetic variation patterns and migration history. Half of the plants showed a unique multilocus phenotype and 75% of all phenotypes occurred only in Scandinavia. Diploid populations showed similar levels of genetic diversity as other widespread outbreeding species with animal-mediated pollination and F -statistics indicated excessive heterozygosity and low rates of gene flow among them. In spite of dramatic population histories caused by the ice ages, diploid populations have maintained the same genetic diversity in Scandinavia as in central and southern Europe. Northern populations have apparently been established through the gradual advance of genetically variable populations and patterns of variation at individual loci indicate different migration routes, from the south-south-west and the east-north-east, respectively. The data strongly support a repeated autoploid origin of the tetraploid cytotype which has been much more successful than the diploid progenitors in colonizing new land since the last ice age. High genetic diversity in Scandinavia has apparently been obtained by a combination of immigration of plants from different source areas and recurrent formation of autotetraploids from diploid progenitors.  © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society , 2003, 142 , 347−372.