Circadian regulation of mammalian target of rapamycin signaling in the mouse suprachiasmatic nucleus

Circadian (24-h) rhythms influence virtually every aspect of mammalian physiology. The main rhythm generation center is located in the suprachiasmatic nucleus (SCN) of the hypothalamus, and work over the past several years has revealed that rhythmic gene transcription and post-translational processes are central to clock timing. In addition, rhythmic translation control has also been implicated in clock timing; however the precise cell signaling pathways that drive this process are not well known. Here we report that a key translation activation cascade, the mammalian target of rapamycin (mTOR) pathway, is under control of the circadian clock in the SCN. Using phosphorylated S6 ribosomal protein (pS6) as a marker of mTOR activity, we show that the mTOR cascade exhibits maximal activity during the subjective day, and minimal activity during the late subjective night. Importantly, expression of S6 was not altered as a function of circadian time. Rhythmic S6 phosphorylation was detected throughout the dorsoventral axis of the SCN, thus suggesting that rhythmic mTOR activity was not restricted to a subset of SCN neurons. Rather, rhythmic pS6 expression appeared to parallel the expression pattern of the clock gene period1 (per1). Using a transgenic per1 reporter gene mouse strain, we found a statistically significant cellular level correlation between pS6 and per1 gene expression over the circadian cycle. Further, photic stimulation triggered a coordinate upregulation of per1 and mTOR activation in a subset of SCN cells. Interestingly, this cellular level correlation between mTOR activity and per1 expression appears to be specific, since a similar expression profile for pS6 and per2 or c-FOS was not detected. Finally, we show that mTOR activity is downstream of the ERK/MAPK signal transduction pathway. Together these data reveal that mTOR pathway activity is under the control of the SCN clock, and suggests that mTOR signaling may contribute to distinct aspects of the molecular clock timing process.

Photoelectron Emission from the Cesiated Diamond (110) Surface

Cesiation of type IIB diamond (110) crystals was studied using a combination of ultraviolet photoemission spectroscopy, x-ray photoemission spectroscopy, and low energy electron diffraction. The diamond (110) crystal was hydrogen treated by exposure to a hydrogen microwave discharge. Although cesium was largely unreactive with the hydrogenated diamond surface, cesiation yielded a large enhancement in the secondary electron yield of the diamond surface and the negative electron affinity (NEA) condition. An increase in the downwards band bending of approximately 0.75-0.9 eV was inferred from the shift in the valence band edge following cesiation. In addition, (lx 1) LEED patterns were observed at all cesium coverages. Exposure of the cesiated diamond surface to molecular oxygen significantly reduced the NEA peak (relative to the secondary electron background); however, recovery of the NEA peak was observed when the molecular oxygen source was removed.

In vivo angiogenesis and lymphangiogenesis models

Angiogenesis research has become one of the most important areas in biomedical research. At the time of writing this review, there were approximately 3536 articles published in the year of 2008 alone on the topic of angiogenesis. The fast expansion of this research field demands development of rigorous, reliable, stable, convenient, and clinically relevant assay systems for disease diagnosis, prognosis, therapeutic evaluation, drug discovery, and mechanistic studies at the molecular level. Here, we discuss several commonly used in vivo angiogenesis models by systematically analyzing and pointing out pitfalls of each assay. Owing to existence of numerous assays and the limitation of text, it is impossible to discuss all these assays in this article. Here we select several most commonly used angiogenesis assays performed in various species including mice, chicks and zebrafish for further in-depth discussion. We hope this information will be valuable for improving current angiogenesis research.

Temperature dependent pinning phenomenon in superconducting Nb films with triangular and honeycomb pinning arrays

The pinning phenomena in superconducting Nb films with triangular and honeycomb pinning arrays were explored. Special temperature dependent phenomena were found for both films. For the film with a triangular pinning array, the pronounced matching peaks in the critical currents as a function of magnetic field reduce from six to three within a narrow temperature range. This temperature dependent matching effect is explained by considering the dramatic change of coherent length with temperature when the temperature is close to T(c). In order to compare with the film with a triangular pinning array, we fabricated a film with a honeycomb pinning array with similar pinning site spacing and pinning size. Special prominent matching peaks at H = 3.5H(1) were found for this film. Molecular dynamic simulations were made to study this phenomenon. The ground state distribution of vortices obtained from simulations reasonably explains the prominent matching peaks. Pronounced temperature dependent matching effects were also found for the film with a honeycomb pinning array.