Intraventricular (i3vt) ghrelin increases food intake in fatty Zucker rats

Ghrelin is an orexigenic peptide secreted from the stomach and also made in the brain. Ghrelin receptors are expressed on hypothalamic cells important in appetite and energy balance. We determined that intra-3rd-ventricular (i3vt) ghrelin dose-dependently increases acute (1 and 2 h) food intake in lean and fatty Zucker rats (0, 0.01, 0.1 and 1.0 nmol ghrelin). The percentage increase of food intake in fatty Zucker rats was significantly greater than that in lean rats. Fatty Zucker rats had 4.5 times more ghrelin receptor mRNA in the hypothalamus than lean Zucker rats, suggesting a possible mechanism for the increased sensitivity.     

Leaching of contaminated leaves following uptake and phytoremediation of RDX, HMX, and TNT by poplar

The uptake and fate of 2,4,6-trinitrotoluene (TNT), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) by hybrid poplars in hydroponic systems were compared and exposed leaves were leached with water to simulate potential exposure pathways from groundwater in the field. TNT was removed from solution more quickly than nitramine explosives. Most of radioactivity remained in root tissues for 14C-TNT, but in leaves for 14C-RDX and 14C-HMX. Radiolabel recovery for TNT and HMX was over 94%, but that of RDX decreased over time, suggesting a loss of volatile products. A considerable fraction (45.5%) of radioactivity taken up by whole plants exposed to 14C-HMX was released into deionized water, mostly as parent compound after 5 d of leaching. About a quarter (24.0%) and 1.2% were leached for RDX and TNT, respectively, mostly as transformed products. Leached radioactivity from roots was insignificant in all cases (< 2%). This is the first report in which small amounts of transformation products of RDX leach from dried leaves following uptake by poplars. Such behavior for HMX was reported earlier and is reconfirmed here. All three compounds differ substantially in their fate and transport during the leaching process.     

Poly(amidoamine) dendrimer peripherally modified with 4-N,N-dimethylaminoethyleneamino-1,8-naphthalimide as a sensor of metal cations and protons.

A new poly(amidoamine) dendrimer from second generation whose periphery comprises sixteen fluorescent 4-N,N-dimethylaminoethylamino-1,8-naphthalimide units has been synthesized and characterized. In DMF, the dendrimer shows sensitivity to the presence of Cu(2+), Fe(3+) and protons. The changes in the fluorescence intensity of the material are in opposite directions if acids or metals are present. Fluorescence enhancements (FE from 5 to 9 depending on solvent) are recorded when the photoinduced electron transfer (PET) originating from the donating amine to the electron accepting naphthalimide is inhibited by the protonation of the N,N-dimethylamino groups. In the case of Cu(2+) cations, a fluorescence quenching (FQ of 6) is first observed, followed by fluorescence partial restoration. In the Fe(3+) case, the same behaviour is observed with a final FE of 2. The successive complexations of these cations by the dendrimer core and by the external rim of the dendrimer may explain the results.     

Formation, maintenance and consequences of the imprint at the mating-type locus in fission yeast

Mating-type switching in the fission yeast Schizosaccharomyces pombe is initiated by a strand-specific imprint located at the mating-type (mat1) locus. We show that the imprint corresponds to a single-strand DNA break (SSB), which is site- but not sequence-specific. We identified three novel cis-acting elements, involved in the formation and stability of the SSB. One of these elements is essential for a replication fork pause next to mat1 and interacts in vivo with the Swi1 protein. Another element is essential for maintaining the SSB during cell cycle progression. These results suggest that the DNA break appears during the S-phase and is actively protected against repair. Consequently, during the following round of replication, a polar double-strand break is formed. We show that when the replication fork encounters the SSB, the leading-strand DNA polymerase is able to synthesize DNA to the edge of the SSB, creating a blunt-ended recombination intermediate.     

Distinct contractile and cytoskeletal protein patterns in the Antarctic midge are elicited by desiccation and rehydration

Desiccation presents a major challenge for the Antarctic midge, Belgica antarctica. In this study, we use proteomic profiling to evaluate protein changes in the larvae elicited by dehydration and rehydration. Larvae were desiccated at 75% relative humidity (RH) for 12 h to achieve a body water loss of 35%, approximately half of the water that can be lost before the larvae succumb to dehydration. To evaluate the rehydration response, larvae were first desiccated, then rehydrated for 6 h at 100% RH and then in water for 6 h. Controls were held continuously at 100% RH. Protein analysis was performed using 2‐DE and nanoscale capillary LC/MS/MS. Twenty‐four identified proteins changed in abundance in response to desiccation: 16 were more abundant and 8 were less abundant; 84% of these proteins were contractile or cytoskeletal proteins. Thirteen rehydration‐regulated proteins were identified: 8 were more abundant and 5 were less abundant, and 69% of these proteins were also contractile or cytoskeletal proteins. Additional proteins responsive to desiccation and rehydration were involved in functions including stress responses, energy metabolism, protein synthesis, glucogenesis and membrane transport. We conclude that the major protein responses elicited by both desiccation and rehydration are linked to body contraction and cytoskeleton rearrangements.     

Model-Assisted Analysis of Sugar Metabolism throughout Tomato Fruit Development Reveals Enzyme and Carrier Properties in Relation to Vacuole Expansion

A kinetic model combining enzyme activity measurements and subcellular compartmentation was parameterized to fit the sucrose, hexose, and glucose-6-P contents of pericarp throughout tomato (Solanum lycopersicum) fruit development. The model was further validated using independent data obtained from domesticated and wild tomato species and on transgenic lines. A hierarchical clustering analysis of the calculated fluxes and enzyme capacities together revealed stage-dependent features. Cell division was characterized by a high sucrolytic activity of the vacuole, whereas sucrose cleavage during expansion was sustained by both sucrose synthase and neutral invertase, associated with minimal futile cycling. Most importantly, a tight correlation between flux rate and enzyme capacity was found for fructokinase and PPi-dependent phosphofructokinase during cell division and for sucrose synthase, UDP-glucopyrophosphorylase, and phosphoglucomutase during expansion, thus suggesting an adaptation of enzyme abundance to metabolic needs. In contrast, for most enzymes, flux rates varied irrespectively of enzyme capacities, and most enzymes functioned at <5% of their maximal catalytic capacity. One of the major findings with the model was the high accumulation of soluble sugars within the vacuole together with organic acids, thus enabling the osmotic-driven vacuole expansion that was found during cell division.     

Reconstituting Corticostriatal Network on-a-Chip Reveals the Contribution of the Presynaptic Compartment to Huntington’s Disease

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Protein kinase D1 is essential for contraction-induced glucose uptake but is not involved in fatty acid uptake into cardiomyocytes

Increased contraction enhances substrate uptake into cardiomyocytes via translocation of the glucose transporter GLUT4 and the long chain fatty acid (LCFA) transporter CD36 from intracellular stores to the sarcolemma. Additionally, contraction activates the signaling enzymes AMP-activated protein kinase (AMPK) and protein kinase D1 (PKD1). Although AMPK has been implicated in contraction-induced GLUT4 and CD36 translocation in cardiomyocytes, the precise role of PKD1 in these processes is not known. To study this, we triggered contractions in cardiomyocytes by electric field stimulation (EFS). First, the role of PKD1 in GLUT4 and CD36 translocation was defined. In PKD1 siRNA-treated cardiomyocytes as well as cardiomyocytes from PKD1 knock-out mice, EFS-induced translocation of GLUT4, but not CD36, was abolished. In AMPK siRNA-treated cardiomyocytes and cardiomyocytes from AMPKα2 knock-out mice, both GLUT4 and CD36 translocation were abrogated. Hence, unlike AMPK, PKD1 is selectively involved in glucose uptake. Second, we analyzed upstream factors in PKD1 activation. Cardiomyocyte contractions enhanced reactive oxygen species (ROS) production. Using ROS scavengers, we found that PKD1 signaling and glucose uptake are more sensitive to changes in intracellular ROS than AMPK signaling or LCFA uptake. Furthermore, silencing of death-activated protein kinase (DAPK) abrogated EFS-induced GLUT4 but not CD36 translocation. Finally, possible links between PKD1 and AMPK signaling were investigated. PKD1 silencing did not affect AMPK activation. Reciprocally, AMPK silencing did not alter PKD1 activation. In conclusion, we present a novel contraction-induced ROS-DAPK-PKD1 pathway in cardiomyocytes. This pathway is activated separately from AMPK and mediates GLUT4 translocation/glucose uptake, but not CD36 translocation/LCFA uptake.     

Is coarse-to-fine strategy sensitive to normal aging?

Theories on visual perception agree that visual recognition begins with global analysis and ends with detailed analysis. Different results from neurophysiological, computational, and behavioral studies all indicate that the totality of visual information is not immediately conveyed, but that information analysis follows a predominantly coarse-to-fine processing sequence (low spatial frequencies are extracted first, followed by high spatial frequencies). We tested whether such processing continues to occur in normally aging subjects. Young and aged participants performed a categorization task (indoor vs. outdoor scenes), using dynamic natural scene stimuli, in which they resorted to either a coarse-to-fine (CtF) sequence or a reverse fine-to-coarse sequence (FtC). The results show that young participants categorized CtF sequences more quickly than FtC sequences. However, sequence processing interacts with semantic category only for aged participants. The present data support the notion that CtF categorization is effective even in aged participants, but is constrained by the spatial features of the scenes, thus highlighting new perspectives in visual models.