KATP channels in the nodose ganglia mediate the orexigenic actions of ghrelin

Ghrelin is the only known hunger signal derived from the peripheral tissues. Ghrelin overcomes the satiety signals evoked by anorexigenic molecules, such as cholecystokinin (CCK) and leptin, to stimulate feeding. The mechanisms by which ghrelin reduces the sensory signals evoked by anorexigenic hormones, which act via the vagus nerve to stimulate feeding, are unknown. Patch clamp recordings of isolated rat vagal neurons show that ghrelin hyperpolarizes neurons by activating K+ conductance. Administering a KATP channel antagonist or silencing Kir6.2, a major subunit of the KATP channel, abolished ghrelin inhibition in vitro and in vivo. Patch clamp studies show that ghrelin inhibits currents evoked by leptin and CCK‐8, which operate through independent ionic channels. The inhibitory actions of ghrelin were abolished by treating the vagal ganglia neurons with pertussis toxin, as well as phosphatidylinositol 3‐kinase (PI3K) or extracellular signal‐regulated kinase 1 and 2 (Erk1/2) small interfering RNA. In vivo gene silencing of PI3K and Erk1/2 in the nodose ganglia prevented ghrelin inhibition of leptin‐ or CCK‐8‐evoked vagal firing. Feeding experiments showed that silencing Kir6.2 in the vagal ganglia abolished the orexigenic actions of ghrelin. These data indicate that ghrelin modulates vagal ganglia neuron excitability by activating KATP conductance via the growth hormone secretagogue receptor subtype 1a–Gαi–PI3K–Erk1/2–KATP pathway. The resulting hyperpolarization renders the neurons less responsive to signals evoked by anorexigenic hormones. This provides a mechanism to explain the actions of ghrelin with respect to overcoming anorexigenic signals that act via the vagal afferent pathways.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/113677/1/tjp6781.pd

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Strategic Charitable Giving and R&D Innovation of High-Tech Enterprises: A Dynamic Perspective Based on the Corporate Life Cycle

As important components of differentiation strategy, charitable giving and R&D innovation can have a profound impact on the survival and growth of high-tech enterprises. However, the strategic interaction between them has not been studied in depth using the whole-life-cycle perspective. With Chinese A-share-listed high-tech enterprises in the 2015–2020 period as the research sample, the Tobit model was used to empirically test the interaction between charitable giving and R&D innovation and analyze differences in their utility over different life cycles. The results show that there was a strategic synergy between charitable giving and R&D innovation and charitable giving could significantly improve R&D innovation, but its utility was affected by changes in the life cycle of firms. Among them, the synergy utility was highest for maturing firms, followed by declining firms, but not significant for growing firms. A further study on the synergistic utility of mature firms found that, for non-state firms where executives have an R&D background, charitable giving could promote integration of external advantageous resources and R&D innovation development. Finally, the regression findings remained significant after accounting for possible endogeneity and heteroskedasticity between charitable giving and R&D innovation

Mechanisms regulating somatostatin release and somatostatin-induced acetylcholine release from the myenteric plexus

The present studies were performed to characterize the molecular form(s) of somatostatin present in the myenteric plexus and to examine some aspects of the regulatory mechanisms underlying somatostatin release and somatostatin-induced release of acetylcholine from this tissue. We observed the following: (1) Somatostatin-like immunoreactivity (SLI) is present in the myenteric plexus of the guinea pig ileum with somatostatin-14 being the predominant molecular form. (2) Somatostatin-like immunoreactivity is released from isolated myenteric ganglia after stimulation with veratridine or the ganglionic agonist dimethylphenylpiperazinium (DMPP). (3) Calcium entry via the N-type channel appears to play a dominant role in DMPP-induced release of SLI. (4) Somatostatin regulates its own release via a pertussis toxin-sensitive mechanism. (5) Under basal conditions somatostatin-14 stimulates release of acetylcholine in a concentration-dependent manner. (6) Calcium entry via L-type channels is associated with the release of acetylcholine evoked by somatostatin-14.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/28401/1/0000176.pd