Differential appearance of dynamin in constitutive and regulated exo-endocytosis: a single-cell multiplex RT-PCR study

Neurons in the central nervous system establish, via their axons and dendrites, an extended network that allows synaptic transmission. During developmental maturation and process outgrowth, membrane turnover is necessary for the enlargement and subsequent growth of axons and dendrites from the perikarya to the target cell (constitutive exocytosis/endocytosis). After targeting and synapse formation, small synaptic vesicles are needed for the quantal release of neurotransmitters from the presynaptic terminal with subsequent recycling by regulated exocytosis/endocytosis. An investigation of the onset of the appearance of mRNA and protein in dissociated cultures of neurons from mouse hippocampus or from chick retina has shown an early abundance of proteins involved in exocytosis, such as syntaxin 1, SNAP-25, and synaptotagmin 1, whereas dynamin 1, a protein necessary for clathrin-mediated endocytosis, can be detected only after neurons have established contacts with neighboring cells. The results reveal that constitutive membrane incorporation and regulated synaptic transmitter release is mediated by the same neuronal proteins. Moreover, the data exclude that dynamin 1 takes part in constitutive recycling before synapse formation, but dynamin 2 is present at this stage. Thus, dynamin 2 may be the constitutive counterpart of dynamin 1 in growing neurons. Synapse establishment is linked to an upregulation of dynamin 1 and thereby represents the beginning of the regulated recycling of membranes back into the presynaptic termina

Expression of SV2 in the developing chick cerebellum: comparison with Calbindin and AMPA glutamate receptors 2/3

The well-organized cerebellum is an ideal model to investigate the developmental appearance and localization of pre- and postsynaptic structures. One of the synaptic proteins abundant in the central nervous system and localized in presynaptic vesicle membranes is the synaptic vesicle protein 2 (SV2). SV2 was shown to be involved in priming and modulating synaptic vesicles and having an effect in epileptic diseases. So far there are no data available describing the developmental localization of this protein in the cerebellum. We followed the expression pattern of SV2 and compared it with the expression of the neuronal calcium-binding protein Calbindin and the AMPA glutamate receptor subunits 2/3 (GluR 2/3), both shown to be early expressed in the developing chick cerebellum predominantly in Purkinje cells. We detected the expression of SV2 in presynaptic terminals (mainly from climbing and mossy fibers) as soon as they are formed at embryonic day 16 in the inner molecular layer. Purkinje cells express Calbindin and GluR 2/3 in the soma and postsynaptically in the primary dendrites at this stage. With ongoing development, the pattern of SV2 expression follows the development of Purkinje cell dendrites in the molecular layer, suggesting a synaptic refinement of labeled climbing and later parallel fibers

Detection of electrical spin injection by light-emitting diodes in top- and side-emission configuration

Detection of the degree of circular polarization of the electroluminescence of a light-emitting diode fitted with a spin injecting contact (a spin-LED) allows for a direct determination of the spin polarization of the injected carriers. Here, we compare the detection efficiency of (Al,Ga)As spin-LEDs fitted with a (Zn,Be,Mn)Se spin injector in top- and side-emission configuration. In contrast with top emission, we cannot detect the electrical spin injection in side emission from analysing the degree of circular polarization of the electroluminescence. To reduce resonant optical pumping of quantum-well excitons in the side emission, we have analysed structures with mesa sizes as small as 1 micron.Comment: 15 pages with 3 figure

Self Assembled II-VI Magnetic Quantum Dot as a Voltage-Controlled Spin-Filter

A key element in the emergence of a full spintronics technology is the development of voltage controlled spin filters to selectively inject carriers of desired spin into semiconductors. We previously demonstrated a prototype of such a device using a II-VI dilute-magnetic semiconductor quantum well which, however, still required an external magnetic field to generate the level splitting. Recent theory suggests that spin selection may be achievable in II-VI paramagnetic semiconductors without external magnetic field through local carrier mediated ferromagnetic interactions. We present the first experimental observation of such an effect using non-magnetic CdSe self-assembled quantum dots in a paramagnetic (Zn,Be,Mn)Se barrier.Comment: 4 pages, 4 figure

Ontogeny of synaptophysin and synaptoporin in the central nervous system

The expression of the synaptic vesicle antigens synaptophysin (SY) and synaptoporin (SO) was studied in the rat striatum, which contains a nearly homogeneous population of GABAergic neurons. In situ hybridization revealed high levels of SY transcripts in the striatal anlage from embryonic day (E) 14 until birth. In contrast. SO hybridization signals were low, and no immunoreactive cell bodies were detected at these stages of development. At E 14, SY-immunoreactivity was restricted to perikarya. In later prenatal stages of development SY-immunoreactivity appeared in puncta (identified as terminals containing immunostained synaptic vesicles), fibers, thick fiber bundles and ‘patches’. In postnatal and adult animals, perikarya of striatal neurons exhibited immunoreaction for SO; ultrastructurally SO antigen was found in the Golgi apparatus and in multivesicular bodies. SO-positive boutons were rare in the striatum. In the neuropil, numerous presynaptic terminals positive for SY were observed. Our data indicate that the expression of synaptic vesicle proteins in GABAergic neurons of the striatum is developmentally regulated. Whereas SY is prevalent during embryonic development, SO is the major synaptic vesicle antigen expressed postnatally by striatal neurons which project to the globus pallidus and the substantia nigra. In contrast synapses of striatal afferents (predominantly from cortex, thalamus and substantia nigra) contain SY

Business accountability in the Anthropocene

The arrival of the Anthropocene requires a profound rethinking of business accountability. A central challenge in this age is the possibility of pushing past planetary boundaries, which may irreversibly propel the Earth system into a new equilibrium that is less hospitable for human civilization. Businesses drive many of the processes contributing to such boundaries, and are powerful political actors who may shape or obstruct the necessary transformations to our socio-economic systems. We therefore need to reconsider their accountability, focused on the following guiding question: Who (in business) should be accountable to whom for what? The answer to this question has important implications for environmental policy and governance. Drawing on a range of recent conceptual and policy developments, I present four major lines of thinking for reconsidering business accountability in the Anthropocene context: to rethink the purpose of business; to acknowledge companies' expanded but shared accountability for productive activities; to heighten collective and individual liability for past and future actions linked to overshooting planetary boundaries; and to recognize business accountability for influencing political and societal processes. Each of these lines of thinking imply policy changes related to, inter alia, corporate governance, due diligence, liability, and lobbying laws. I further call on businesses to actively participate in the large-scale transformation necessary to keep within planetary boundaries by changing not only their production processes, but also product portfolios, business models, legal forms, and political and societal engagement; and highlight avenues for future research.info:eu-repo/semantics/publishedVersio

Designer enzymes for industrial applications

Arzeda is harnessing the power of computational and synthetic biology to design new enzymes and chemical products. In partnership with Fortune 500 companies and industrial leaders, we have developed a portfolio of enzymes and specialty chemicals for polymers, advanced materials and health and nutrition products. Arzeda’s proprietary platform and validation process rapidly and reliable engineers new enzyme - key to enabling customized bio-processes. We will illustrate how Arzeda’s computational design technology is applied to engineer enzymes features for applications in bio-based chemical production and agricultural traits

How can sustainable business models distribute value more equitably in global value chains? Introducing “value chain profit sharing” as an emerging alternative to fair trade, direct trade, or solidarity trade

Global supply chains often distribute value inequitably among the Global North and South. This perpetuates poverty and contributes to indecent work in raw material-producing countries, thus creating challenges to sustainable development. For decades, corporate social responsibility, social entrepreneurship, and sustainable business model innovations have aimed to distribute value more equitably across global value chains, for instance via fair trade, alternative trade, and direct trade. This article examines a novel and hitherto understudied innovation for equitable value distribution in global supply chains: “value chain profit sharing.” We draw on interview and archival data from two cases of social entrepreneurs working in the coffee sector to develop a generalized model. One of the model's key features is that the entrepreneur pays suppliers in multiple installments that reflect market conditions (as opposed to a single lump sum based on prediction). We show how this can increase value creation, appropriation, and equitable distribution. Although our research suggests that this model may be highly contingent on leaders' skills, resources, sense of place, and accountability to suppliers, we find no evidence that its applications are limited to specific countries or sectors. Our research further extends extant theory by showing how “value chain profit sharing” may relieve some of the tensions often associated with sustainable business models, including distributing value to suppliers while maintaining financial solvency; creating value while pursuing a social mission; providing benefits to suppliers without curtailing their market opportunities; responding to market conditions while maintaining commitments to suppliers; and scaling without diluting benefits. It thereby contributes to the literatures on sustainable business model innovations, equitable value distribution in global supply chains, novel application of revenue-sharing contracts, and innovative methods of profit sharing. It furthermore provides actionable guidance for social entrepreneurs, corporate social responsibility practitioners, and supplier cooperatives aiming to achieve more equitable value distribution and sustainable supply chains.info:eu-repo/semantics/publishedVersio