Bright and ultrafast electron point source made of LaB6 nanotip

The development of time-resolved transmission electron microscopy (TEM), ultrafast electron spectroscopy and pulsed X-ray sources relies on the realization of stable and high brightness sources of ultra-short electron bunches with a long service time. The flat photocathodes implanted in thermionic electron guns have been replaced by Schottky-type or cold-field emission sources driven by ultra-fast laser. Recently, lanthanum hexaboride (LaB₆) nanoneedles have been reported to have high brightness and high emission stability when working in a continuous emission mode. Here, we prepare nano-field emitters from bulk LaB₆ and we report on their use as ultra-fast electron sources. Using a high repetition rate laser in the infrared range, we present different field emission regimes as a function of the extraction voltage and laser intensity. The properties of the electron source (brightness, stability, energy spectrum and emission pattern) are determined for the different regimes. Our results show that LaB₆ nanoneedles can be used as ultrafast and ultra-bright sources for time-resolved TEM, with better performances as compared to metallic ultra-fast field-emitters.

Functional balance between Tcf21-Slug defines cellular plasticity and migratory modalities in high grade serous ovarian cancer cell lines

Cellular plasticity and transitional phenotypes add to complexities of cancer metastasis that can be initiated by single cell epithelial to mesenchymal transition (EMT) or cooperative cell migration (CCM). Our study identifies novel regulatory cross-talks between Tcf21 and Slug in mediating phenotypic and migration plasticity in high-grade serous ovarian adenocarcinoma (HGSC). Differential expression and subcellular localization associate Tcf21, Slug with epithelial, mesenchymal phenotypes, respectively; however, gene manipulation approaches identify their association with additional intermediate phenotypic states, implying the existence of a multistep epithelial-mesenchymal transition program. Live imaging further associated distinct migratory modalities with the Tcf21/Slug status of cell systems and discerned proliferative/passive CCM, active CCM and EMT modes of migration. Tcf21-Slug balance identified across a phenotypic spectrum in HGSC cell lines, associated with microenvironment-induced transitions and the emergence of an epithelial phenotype following drug exposure. Phenotypic transitions and associated functionalities following drug exposure were affirmed to ensue from occupancy of Slug promoter E-box sequences by Tcf21. Our study effectively provides a framework for understanding the relevance of ovarian cancer plasticity as a function of two transcription factors.

Gender affects the pattern of neuroendocrine response to head-up tilt

One of the major concerns in space medicine is post-mission postural hypotension. Since the beginning, most of the studies have been aimed at the identification of mechanical and neuroautonomic mechanisms within the cardiovascular system potentially involved in this phenomenon. Some gender differences in the cardiovascular reactivity to changing posture have been described so far, which still need better clarification. Moreover, the neuroendocrine contribution to postflight readaptation deserves more indepth studies. Sudden passive head-up tilting is considered to be a good simulation method for hemodynamic changes occurring during transition from 0xg to 1xg. The aim of this study was to verify whether cardiovascular or neuroendocrine changes occurring after sudden passive +70 degrees head-up tilt (HUT) became already evident within 10 min and were similar in healthy young-adult men and women.

Changes in human adrenal and gonadal function onboard Spacelab

Astronauts have to face chronic stress during the mission period. This might cause: (i) increased adrenocortico-trophin (ACTH) and cortisol (Cort) secretion; (ii) impaired luteinizing hormone (LH) output with consequent testosterone (T) hyposecretion in men. Moreover, should the subjects prove not to synchronize their inner clocks to the time shift protocols defined by NASA, most results would be questionable. The aim of this study was to verify if plasma testicular androgens were lower than baseline and Cort biorhythm was preserved in male astronauts during a short duration flight.

Thyrotropin-releasing hormone enhances event-related brain potentials and growth hormone release in man

Changes in contingent negative variation (CNV), a brain-evoked potential related in arousal, as well as in serum triiodothyronine (T3), thyroxine (T4), thyroid-stimulating hormone (TSH), prolactin (PRL), cortisol and growth hormone (GH) levels were recorded in 12 male volunteers receiving either thyrotropin-releasing hormone (TRH) or saline infusion. Only during TRH administration an increase in CNV (P less than 0.02) and, 30 min later, in GH (P less than 0.05) occurred; thyroid hormones and PRL increased as well, in the absence of any correlation with CNV areas. Cortisol was not affected by TRH. As dopamine (DA) agonistic drugs notoriously increase both CNV areas and GH levels and experimental evidence for prodopaminergic properties of TRH has accumulated in animal models, a possible explanation of the results here presented might be the activation of DA pathways by TRH also in the human.