Gbx2 Identifies Two Amacrine Cell Subtypes with Distinct Molecular, Morphological, and Physiological Properties

The diverse functions of retinal amacrine cells are reliant on the physiological properties of their synapses. Here we examine the role of mitochondria as Ca2+ buffering organelles in synaptic transmission between GABAergic amacrine cells. We used the protonophore p-trifluoromethoxy-phenylhydrazone (FCCP) to dissipate the membrane potential across the inner mitochondrial membrane that normally sustains the activity of the mitochondrial Ca2+ uniporter. Measurements of cytosolic Ca2+ levels reveal that prolonged depolarization-induced Ca2+ elevations measured at the cell body are altered by inhibition of mitochondrial Ca2+ uptake. Furthermore, an analysis of the ratio of Ca2+ efflux on the plasma membrane Na-Ca exchanger to influx through Ca2+ channels during voltage steps indicates that mitochondria can also buffer Ca2+ loads induced by relatively brief stimuli. Importantly, we also demonstrate that mitochondrial Ca2+ uptake operates at rest to help maintain low cytosolic Ca2+ levels. This aspect of mitochondrial Ca2+ buffering suggests that in amacrine cells, the normal function of Ca2+-dependent mechanisms would be contingent upon ongoing mitochondrial Ca2+ uptake. To test the role of mitochondrial Ca2+ buffering at amacrine cell synapses, we record from amacrine cells receiving GABAergic synaptic input. The Ca2+ elevations produced by inhibition of mitochondrial Ca2+uptake are localized and sufficient in magnitude to stimulate exocytosis, indicating that mitochondria help to maintain low levels of exocytosis at rest. However, we found that inhibition of mitochondrial Ca2+ uptake during evoked synaptic transmission results in a reduction in the charge transferred at the synapse. Recordings from isolated amacrine cells reveal that this is most likely due to the increase in the inactivation of presynaptic Ca2+ channels observed in the absence of mitochondrial Ca2+ buffering. These results demonstrate that mitochondrial Ca2+ buffering plays a critical role in the function of amacrine cell synapses.

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Gbx2 identifies two amacrine cell subtypes with distinct molecular, morphological, and physiological properties

10.1101/2020.05.19.104307 ◽

2020 ◽

Author(s):

Patrick C. Kerstein ◽

Joseph Leffler ◽

Benjamin Sivyer ◽

W. Rowland Taylor ◽

Kevin M. Wright

Keyword(s):

Gap Junctions ◽

Amacrine Cell ◽

Bipolar Cells ◽

Mouse Retina ◽

Genetic Approach ◽

Physiological Properties ◽

Dendritic Arbors ◽

Dopamine Signaling ◽

Circuit Function ◽

Novel Model

ABSTRACTOur understanding of how the nervous sytem works is limited by our ability to identify the neuronal subtypes that comprise functional circuits. Using a genetic approach, we show that the transcription factor Gbx2 labels two amacrine cell (AC) subtypes in the mouse retina that have distinct morphological, physiological, and molecular properties. One subtype of Gbx2+ ACs are likely the previously characterized On-type GABAergic CRH-1 AC. The other Gbx2+ AC population is a previously uncharacterized non-GABAergic, non-Glycinergic (nGnG) AC subtype. Gbx2+ nGnG ACs are On-Off type cells with asymmetric dendritic arbors. Gbx2+ nGnG ACs also exhibit tracer coupling to bipolar cells (BCs) through gap junctions that are modulated by dopamine signaling. This study genetically identifies a previously uncharacterized AC subtype and reveals an unusual AC-BC connectivity through gap junctions that may provide a novel model of synaptic communication and visual circuit function.

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IDENTIFICATION AND CHARACTERIZATION OF A PURPLE NONSULFUR BACTERIUM ISOLATED FROM COASTAL AREA OF HAI PHONG FOR USING IN PRODUCTION OF UNSATURATED FATTY ACID (OMEGA 6, 7, 9)

Vietnam Journal of Science and Technology ◽

10.15625/2525-2518/57/6/13711 ◽

2019 ◽

Vol 57 (6) ◽

pp. 665 ◽

Cited By ~ 1

Author(s):

Yen Thi Hoang ◽

Quynh Thi Thu Tran ◽

Ha Hoang Chu ◽

Tuyen Thi Do ◽

Thanh Tat Dang ◽

...

Keyword(s):

Fatty Acid ◽

Unsaturated Fatty Acid ◽

Unsaturated Fatty Acids ◽

Nitrogen Sources ◽

16S Rrna Analysis ◽

Rhodovulum Sulfidophilum ◽

Purple Nonsulfur Bacterium ◽

High Lipid ◽

Physiological Properties ◽

Omega 6

Purple nonsulfur bacteria are a group that has so much biotechnological applications, particularly in producing of functional food rich with unsaturated fatty acids. A purple nonsulfur bacterium (named HPB.6) was chosen based on its strong growth, high lipid and synthesis of unsaturated fatty acid (omega 6,7,9). Studying on basic biological characteristics showed that the cells of HPB.6 were observed as ovoid-rod shape, none motility, Gram negative staining. The diameter of single bacterium was about 0.8-1.0 µm. The cells divide by binary fission and had bacteriochlorophyll a (Bchl a). This bacterium grew well on medium with carbon and nitrogen sources such as acetate, succinate, pyruvate, butyrate, glutamate, arginine, leucine, tyrosine, alanine, methionine, threonine, glutamine, yeast extract and NH4Cl. This selected strain grew well on medium with salt concentrations from 1.5 - 6.0% (optimum 3%), pH from 5.0 to 8.0 (optimum at pH 6.5) and could withstand Na2S at 4.0 - 5.2 mM. Based on morphological, physiological properties and 16S rRNA analysis received demonstrated that HPB.6 strain belongs to the species Rhodovulum sulfidophilum.

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Synthesis of Elaborate Benzofuran-2-Carboxamide Derivatives Through a Combination of 8-Aminoquinoline Directed C–H Arylations and Transamidations

10.26434/chemrxiv.7925489.v1 ◽

2019 ◽

Author(s):

Michael Oschmann ◽

Linus Johansson Holm ◽

Oscar Verho

Keyword(s):

Small Molecule ◽

High Efficiency ◽

Synthetic Strategy ◽

Small Molecule Screening ◽

Physiological Properties ◽

Wide Range ◽

Directing Group ◽

Synthetic Sequence

Benzofurans are everywhere in nature and they have been extensively studied by medicinal chemists over the years because of their chemotherapeutic and physiological properties. Herein, we describe a strategy that can be used to access elaborate benzo-2-carboxamide derivatives, which involves a synthetic sequence of 8-aminoquinoline directed C–H arylations followed by transamidations. For the directed C–H arylations, Pd catalysis was used to install a wide range of aryl and heteroaryl substituents at the C3 position of the benzofuran scaffold in high efficiency. Directing group cleavage and further diversification of the C3-arylated benzofuran products were then achieved in a single synthetic operation through the utilization of a two-step transamidation protocol. By bocylating the 8-aminoquinoline amide moiety of these products, it proved possible to activate them towards aminolysis with different amine nucleophiles. Interestingly, this aminolysis reaction was found to proceed efficiently without the need of any additional catalyst or additive. Given the high efficiency and modularity of this synthetic strategy, it constitute a very attractive approach for generating structurally-diverse collections of benzofuran derivatives for small molecule screening.

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