Developmental Characterization of Tail Movements in the Appendicularian Urochordate Oikopleura dioica.

Using high-speed video cinematography, we characterized kinematically the spontaneous tail movements made by the appendicularian urochordate Oikopleura dioica. Videos of young adult (1-day-old) animals discriminated 4 cardinal movement types: bending, nodding, swimming and filtering, each of which had a characteristic signature including cyclicity, event or cycle duration, cycle frequency, cycle frequency variation, laterality, tail muscle segment coordination and episode duration. Bending exhibited a more common, unilateral form (single bending) and a rarer, bilateral form (alternating bending).

Modification of the larval swimming behavior in Oikopleura dioica, a chordate with a miniaturized central nervous system by dsRNA injection into fertilized eggs.

Using RNA interference, we have selectively perturbed neurotransmitter-related features of the larval swimming behavior of Oikopleura dioica, a tunicate with a central nervous system comprising about 130 neurons. We injected dsRNA into fertilized eggs to knockdown the expression of the genes, respectively, encoding ChAT (choline acetyltransferase) and GAD (glutamic acid decarboxylase), enzymes critical for the biosynthesis of acetylcholine and GABA. These two neurotransmitters have conserved roles during evolution, particularly within chordate motor systems, where they mediate respectively neuromuscular and central inhibitory signals.

Astrocytes in the retrotrapezoid nucleus sense H+ by inhibition of a Kir4.1-Kir5.1-like current and may contribute to chemoreception by a purinergic mechanism.

Central chemoreception is the mechanism by which CO(2)/pH sensors regulate breathing in response to tissue pH changes. There is compelling evidence that pH-sensitive neurons in the retrotrapezoid nucleus (RTN) are important chemoreceptors. Evidence also indicates that CO(2)/H(+)-evoked adenosine 5'-triphosphate (ATP) release in the RTN, from pH-sensitive astrocytes, contributes to chemoreception.

Glucose increases activity and Ca2+ in insulin-producing cells of adult Drosophila.

We sought to understand the mechanisms underlying glucose sensing in Drosophila melanogaster. We found that insulin-producing cells (IPCs) of adult Drosophila respond to glucose and glibenclamide with a burst-like pattern of activity. Under controlled conditions IPCs have a resting membrane potential of -62+/-4 mV.

Increased uncoupling protein (UCP) activity in Drosophila insulin-producing neurons attenuates insulin signaling and extends lifespan.

To understand the role of mitochondrial uncoupling protein (UCP) in regulating insulin signaling and glucose homeostasis, we created transgenicDrosophila lines with targeted UCP expression in insulin producing cells (IPCs). Increased UCP activity in IPCs results in decreased steady state Ca(2+) levels in IPCs as well as decreased PI3K activity and increased FoxO nuclear localization in periphery. This reduced systemic insulin signaling is accompanied by a mild hyperglycemia and extended life span.

Current ideas on central chemoreception by neurons and glial cells in the retrotrapezoid nucleus.

Central chemoreception is the mechanism by which CO2/pH-sensitive neurons (i.e., chemoreceptors) regulate breathing in response to changes in tissue pH.

AMP-activated protein kinase inhibits TREK channels.

AMP-activated protein kinase (AMPK) is a serine/threonine kinase activated by conditions that increase the AMP : ATP ratio. In carotid body glomus cells, AMPK is thought to link changes in arterial O(2) with activation of glomus cells by inhibition of unidentified background K(+) channels. Modulation by AMPK of individual background K(+) channels has not been described.