Inhibition of mTOR affects protein stability of OGT

Autophagy regulates cellular homeostasis through degradation of aged or damaged subcellular organelles and components. Interestingly, autophagy-deficient beta cells, for example Atg7-mutant mice, exhibited hypoinsulinemia and hyperglycemia. Also, autophagy response is diminished in heart of diabetic mice. These results implied that autophagy and diabetes are closely connected and affect each other. Although protein O-GlcNAcylation is up-regulated in hyperglycemia and diabetes, and O-GlcNAcylated proteins play an important role in metabolism and nutrient sensing, little is known whether autophagy affects O-GlcNAc modification and vice versa. In this study, we suppressed the action of mTOR by treatment of mTOR catalytic inhibitors (PP242 and Torin1) to induce autophagic flux. Results showed a decrease in global O-GlcNAcylation, which is due to decreased OGT protein and increased OGA protein. Interestingly, knockdown of ATG genes or blocking of lysosomal degradation enhanced protein stability of OGT. In addition, when proteasomal inhibitor was treated together with mTOR inhibitor, protein level of OGT almost recovered to control level. These data suggest that mTOR inhibition is a more efficient way to reduce protein level of OGT rather than that of CHX treatment. We also showed that not only proteasomal degradation regulated OGT stability but autophagic degradation also affected OGT stability in part. We concluded that mTOR signaling regulates protein O-GlcNAc modification through adjustment of OGT stability.     

Contractile behavior of the forelimb digital flexors during steady-state locomotion in horses (Equus caballus): an initial test of muscle architectural hypotheses about in vivo function

The forelimb digital flexors of the horse display remarkable diversity in muscle architecture despite each muscle-tendon unit having a similar mechanical advantage across the fetlock joint. We focus on two distinct muscles of the digital flexor system: short compartment deep digital flexor (DDF(sc)) and the superficial digital flexor (SDF). The objectives were to investigate force-length behavior and work performance of these two muscles in vivo during locomotion, and to determine how muscle architecture contributes to in vivo function in this system. We directly recorded muscle force (via tendon strain gauges) and muscle fascicle length (via sonomicrometry crystals) as horses walked (1.7 m s(-1)), trotted (4.1 m s(-1)) and cantered (7.0 m s(-1)) on a motorized treadmill. Over the range of gaits and speeds, DDF(sc) fascicles shortened while producing relatively low force, generating modest positive net work. In contrast, SDF fascicles initially shortened, then lengthened while producing high force, resulting in substantial negative net work. These findings suggest the long fibered, unipennate DDF(sc) supplements mechanical work during running, whereas the short fibered, multipennate SDF is specialized for economical high force and enhanced elastic energy storage. Apparent in vivo functions match well with the distinct architectural features of each muscle.     

From descriptive to predictive distribution models: a working example with Iberian amphibians and reptiles

Background

The two sympatric species of Tunisian desert ants, Cataglyphis bicolor and C. mauritanica, do not exhibit any differences in their foraging ecology, e.g. in food preferences and in their spatial and temporal activity patterns. Here we show that instead the two species markedly differ in their life histories.

Results

We analysed mtDNA of specimens that were collected along a 250-km transect. C. bicolor exhibited a genetically unstructured population (with the genetic and geographic distances among colonies not being correlated). On the contrary the populations of the polygynous C. mauritanica were clearly structured, i.e. exhibited a strong correlation between genetic and geographic distances. This difference is in accordance with large queen dispersal distances due to far-reaching mating flights in C. bicolor and small queen dispersal distances due to colony foundation by budding in C. mauritanica. Furthermore, wherever we found populations of both species to coexist within the same habitat, the habitat was used agriculturally. Mapping nest positions over periods of several years showed that plowing dramatically decreased the nest densities of either species.

Conclusion

We conclude that owing to its greater queen dispersal potential C. bicolor might be more successful in quickly re-colonizing disturbed areas, while the slowly dispersing C. mauritanica could later out-compete C. bicolor by adopting its effective nest-budding strategy. According to this scenario the observed sympatry of the two species might be an intermediate stage in which faster colonization by one species and more powerful exploitation of space by the other species have somehow balanced each other out. In conclusion, C. bicolor and C. mauritanica represent an example where environmental disturbances in combination with different life histories might beget sympatry in congeneric species with overlapping niches.     

Oscillatory increases in alkalinity anticipate growth and may regulate actin dynamics in pollen tubes of lily

Lily (Lilium formosanum or Lilium longiflorum) pollen tubes, microinjected with a low concentration of the pH-sensitive dye bis-carboxyethyl carboxyfluorescein dextran, show oscillating pH changes in their apical domain relative to growth. An increase in pH in the apex precedes the fastest growth velocities, whereas a decline follows growth, suggesting a possible relationship between alkalinity and cell extension. A target for pH may be the actin cytoskeleton, because the apical cortical actin fringe resides in the same region as the alkaline band in lily pollen tubes and elongation requires actin polymerization. A pH-sensitive actin binding protein, actin-depolymerizing factor (ADF), together with actin-interacting protein (AIP) localize to the cortical actin fringe region. Modifying intracellular pH leads to reorganization of the actin cytoskeleton, especially in the apical domain. Acidification causes actin filament destabilization and inhibits growth by 80%. Upon complete growth inhibition, the actin fringe is the first actin cytoskeleton component to disappear. We propose that during normal growth, the pH increase in the alkaline band stimulates the fragmenting activity of ADF/AIP, which in turn generates more sites for actin polymerization. Increased actin polymerization supports faster growth rates and a proton influx, which inactivates ADF/AIP, decreases actin polymerization, and retards growth. As pH stabilizes and increases, the activity of ADF/AIP again increases, repeating the cycle of events.     

In vivo analysis of fracture toughness of thyroid gland tumors

Background

Human solid tumors that are hard or firm on physical palpation are likely to be cancerous, a clinical maxim that has been successfully applied to cancer screening programs, such as breast self-examination. However, the biological relevance or prognostic significance of tumor hardness remains poorly understood. Here we present a fracture mechanics based in vivo approach for characterizing the fracture toughness of biological tissue of human thyroid gland tumors.

Methods

In a prospective study, 609 solid thyroid gland tumors were percutaneously probed using standard 25 gauge fine needles, their tissue toughness ranked on the basis of the nature and strength of the haptic force feedback cues, and subjected to standard fine needle biopsy. The tumors' toughness rankings and final cytological diagnoses were combined and analyzed. The interpreting cytopathologist was blinded to the tumors' toughness rankings.

Results

Our data showed that cancerous and noncancerous tumors displayed remarkable haptically distinguishable differences in their material toughness.

Conclusion

The qualitative method described here, though subject to some operator bias, identifies a previously unreported in vivo approach to classify fracture toughness of a solid tumor that can be correlated with malignancy, and paves the way for the development of a mechanical device that can accurately quantify the tissue toughness of a human tumor.     

Survival of F-Specific RNA Coliphage, Feline Calicivirus, and Escherichia coli in Water: a Comparative Study

The relationship between the survival of enteric viral pathogens and their indicators (coliform bacteria and coliphages) is not well understood. We compared the survival rates of feline calicivirus (FCV), Escherichia coli, and a male-specific RNA coliphage MS2 at 4, 25, and 37°C for up to 28 days in dechlorinated water. The survival rates of E. coli and FCV, a surrogate of noroviruses (NV), had a high degree of correlation at 4 and 25°C, while MS2 phage survived significantly longer (P < 0.05) at these two temperatures. At 37°C, the survival rates for all three organisms were highly correlated. Decimal reduction values indicating the number of days needed for 90% reduction in titer (D values) decreased for all three organisms as storage temperatures increased. FCV had the shortest D value among all three organisms at all temperatures investigated. These findings indicate that F-specific RNA phages may be useful indicators of NV in the environment.