Optogenetics and electron tomography for structure-function analysis of cochlear ribbon synapses

Ribbon synapses of cochlear inner hair cells (IHCs) are specialized to indefatigably transmit sound information at high rates. To understand the underlying mechanisms, structure-function analysis of the active zone (AZ) of these synapses is essential. Previous electron microscopy studies of synaptic vesicle (SV) dynamics at the IHC AZ used potassium stimulation, which limited the temporal resolution to minutes. Here, we established optogenetic IHC stimulation followed by quick freezing within milliseconds and electron tomography to study the ultrastructure of functional synapse states with good temporal resolution in mice. We characterized optogenetic IHC stimulation by patch-clamp recordings from IHCs and postsynaptic boutons revealing robust IHC depolarization and neurotransmitter release. Ultrastructurally, the number of docked SVs increased upon short (17–25 ms) and long (48–76 ms) light stimulation paradigms. We did not observe enlarged SVs or other morphological correlates of homotypic fusion events. Our results indicate a rapid recruitment of SVs to the docked state upon stimulation and suggest that univesicular release prevails as the quantal mechanism of exocytosis at IHC ribbon synapses

Nanomachinery Organizing Release at Neuronal and Ribbon Synapses

A critical aim in neuroscience is to obtain a comprehensive view of how regulated neurotransmission is achieved. Our current understanding of synapses relies mainly on data from electrophysiological recordings, imaging, and molecular biology. Based on these methodologies, proteins involved in a synaptic vesicle (SV) formation, mobility, and fusion at the active zone (AZ) membrane have been identified. In the last decade, electron tomography (ET) combined with a rapid freezing immobilization of neuronal samples opened a window for understanding the structural machinery with the highest spatial resolution in situ. ET provides significant insights into the molecular architecture of the AZ and the organelles within the presynaptic nerve terminal. The specialized sensory ribbon synapses exhibit a distinct architecture from neuronal synapses due to the presence of the electron-dense synaptic ribbon. However, both synapse types share the filamentous structures, also commonly termed as tethers that are proposed to contribute to different steps of SV recruitment and exocytosis. In this review, we discuss the emerging views on the role of filamentous structures in SV exocytosis gained from ultrastructural studies of excitatory, mainly central neuronal compared to ribbon-type synapses with a focus on inner hair cell (IHC) ribbon synapses. Moreover, we will speculate on the molecular entities that may be involved in filament formation and hence play a crucial role in the SV cycle

Nanomachinery Organizing Release at Neuronal and Ribbon Synapses

A critical aim in neuroscience is to obtain a comprehensive view of how regulated neurotransmission is achieved. Our current understanding of synapses relies mainly on data from electrophysiological recordings, imaging, and molecular biology. Based on these methodologies, proteins involved in a synaptic vesicle (SV) formation, mobility, and fusion at the active zone (AZ) membrane have been identified. In the last decade, electron tomography (ET) combined with a rapid freezing immobilization of neuronal samples opened a window for understanding the structural machinery with the highest spatial resolution in situ. ET provides significant insights into the molecular architecture of the AZ and the organelles within the presynaptic nerve terminal. The specialized sensory ribbon synapses exhibit a distinct architecture from neuronal synapses due to the presence of the electron-dense synaptic ribbon. However, both synapse types share the filamentous structures, also commonly termed as tethers that are proposed to contribute to different steps of SV recruitment and exocytosis. In this review, we discuss the emerging views on the role of filamentous structures in SV exocytosis gained from ultrastructural studies of excitatory, mainly central neuronal compared to ribbon-type synapses with a focus on inner hair cell (IHC) ribbon synapses. Moreover, we will speculate on the molecular entities that may be involved in filament formation and hence play a crucial role in the SV cycle

Single top quark events at Fermilab

According to a press release dated 9 March 2009, the two experiments CDF (Collider Detector at Fermilab) and DZero have announced the discovery of ‘single top quark’ events, which represent a spectacular discovery and confirmation of the standard model of elementary particle physics. The results of their findings are now available as preprints which have been submitted for publication in Physical Review Letters1,2

SCREENING OF NINE HERBAL PLANTS FOR ALPHA-AMYLASE INHIBITION

Objective: To evaluate the α-amylase inhibitory potential of nine herbal plants in regulating postprandial hyperglycemia.Materials and Methods: In vitro α-amylase inhibition assay using starch-iodine was performed. α-amylase inhibition delays breakdown of starch andprevents glucose release to reduce postprandial hyperglycemia.Results: The plants screened were Artocarpus altilis, Aconitum heterophyllum, Acorus calamus, Berberis aristata, Cassia auriculata, Cyprus rotundus,Mesua ferrea, Plumbago zeylanicum and Terminalia arjuna. Positive control Acarbose showed IC50 at 14.24 μg/ml. Methanolic extract of C. auriculata(flower), T. arjuna (bark) and P. zeylanicum (rhizome) exhibited the best inhibitory activity with IC50 value of 37.28 μg/ml, 48.75 μg/ml and68.66 μg/ml, respectively.Conclusion: From the present study, we conclude that C. auriculata flower had displayed maximum inhibition against α-amylase.Keywords: Herbal plants, Hyperglycemia, α-amylase inhibition

Downregulation of Wnt/β-catenin self-renewal pathway in cervical cancer cells by polyphenolic compounds

673-680Cervical cancer is the second most common cancer in woman of developing countries. Wnt/β-catenin self-renewal pathway is important for cervical cancer initiation and progression. Plumbagin, Pongapin and Karanjin are three plant polyphenols with known anticancer activities. Thus, this study aims to analyze the effects of these compounds on Wnt/β-catenin pathway in cervical cancer cells (HeLa), due to their high sensitivity in this cell line. The compounds significantly downregulated the co-receptor LRP6 (low density lipoprotein receptor related protein 6) expression (mRNA/ protein) in HeLa cells without any change in the expression of receptor FZD7 (Frizzled class receptor 7). The low membrane expression of LRP6 seen in the immunocytochemical analysis might be due to upregulation of its antagonist Dickkopf 1 (DKK1) protein. The compounds could also increase the expression ofFZD7 antagonists, SFRP1/2 (mRNA/protein) in HeLa cells. The upregulation of SFRPs (secreted frizzled-related protein) was due to their promoter hypomethylation through downregulation of DNMT1 (DNA methyltransferase 1) protein by the compounds. As a result, there was downregulation of effector protein β-catenin and activated phospho-β-catenin (Y654) of the pathway in HeLa cells by these compounds. Thus, the polyphenols differentially inhibit the Wnt/β-catenin pathway to restrict cervical cancer proliferation, suggesting their therapeutic importance

Specifically Designed Ionic Liquids—Formulations, Physicochemical Properties, and Electrochemical Double Layer Storage Behavior

Two key features—non-volatility and non-flammability—make ionic liquids (ILs) very attractive for use as electrolyte solvents in advanced energy storage systems, such as supercapacitors and Li-ion batteries. Since most ILs possess high viscosity and are less prone to dissolving common electrolytic salts when compared to traditional electrolytic solvents, they must be formulated with low viscosity thinner solvents to achieve desired ionic conductivity and dissolution of electrolyte salts in excess of 0.5 M concentration. In the past few years, our research group has synthesized several specifically designed ILs (mono-cationic, di-cationic, and zwitterionic) with bis(trifluoromethylsulfonyl)imide (TFSI) and dicyanamide (DCA) as counter anions. This article describes several electrolyte formulations to achieve superior electrolytic properties. The performance of a few representative IL-based electrolytes in supercapacitor coin cells is presented