ChIP-Seq and In Vivo Transcriptome Analyses of the Aspergillus fumigatus SREBP SrbA Reveals a New Regulator of the Fungal Hypoxia Response and Virulence

The Aspergillus fumigatus sterol regulatory element binding protein (SREBP) SrbA belongs to the basic Helix-Loop-Helix (bHLH) family of transcription factors and is crucial for antifungal drug resistance and virulence. The latter phenotype is especially striking, as loss of SrbA results in complete loss of virulence in murine models of invasive pulmonary aspergillosis (IPA). How fungal SREBPs mediate fungal virulence is unknown, though it has been suggested that lack of growth in hypoxic conditions accounts for the attenuated virulence. To further understand the role of SrbA in fungal infection site pathobiology, chromatin immunoprecipitation followed by massively parallel DNA sequencing (ChIP-seq) was used to identify genes under direct SrbA transcriptional regulation in hypoxia. These results confirmed the direct regulation of ergosterol biosynthesis and iron uptake by SrbA in hypoxia and revealed new roles for SrbA in nitrate assimilation and heme biosynthesis. Moreover, functional characterization of an SrbA target gene with sequence similarity to SrbA identified a new transcriptional regulator of the fungal hypoxia response and virulence, SrbB. SrbB co-regulates genes involved in heme biosynthesis and demethylation of C4-sterols with SrbA in hypoxic conditions. However, SrbB also has regulatory functions independent of SrbA including regulation of carbohydrate metabolism. Loss of SrbB markedly attenuates A. fumigatus virulence, and loss of both SREBPs further reduces in vivo fungal growth. These data suggest that both A. fumigatus SREBPs are critical for hypoxia adaptation and virulence and reveal new insights into SREBPs\u27 complex role in infection site adaptation and fungal virulence

Acute Effects of Whole-Body Vibration on Lower Extremity Muscle Performance in Persons With Multiple Sclerosis

Background and Purpose: Whole-body vibration (WBV) is a relatively new form of exercise training that may influence muscle performance. This study investigated the acute effects of high (26 Hz) and low (2 Hz) frequency WBV on isometric muscle torque of the quadriceps and hamstrings in persons with multiple sclerosis (MS). Participants and Method: Fifteen individuals (mean age = 54.6 years, SD = 9.6) with MS and Expanded Disability Status Scale (EDSS) scores ranging from 0-6.5 (mean = 4.2, SD = 2.3) participated in this randomized cross-over study. Following baseline measures of isometric quadricep and hamstring torque, subjects were exposed to 30 seconds of WBV at either 2 or 26 Hz. Torque values were measured again at 1, 10 and 20 minutes post vibration. Subjects returned one week later to repeat the same protocol at the alternate vibration frequency. Results: There were no significant differences in isometric torque production between the 2 and 26Hz WBV conditions. There was also no significant difference between baseline torque values and those measured at 1, 10 and 20 minutes following either vibration exposure. However, there was a consistent trend of higher torque values following the 26 Hz WBV when compared to the 2 Hz condition for both quadriceps and hamstrings. Discussion and Conclusion: Although not statistically significant, peak torque values for both quadriceps and hamstrings were consistently higher following 30 seconds of WBV at 26 vs. 2 Hz. Whether or not WBV presents a viable treatment option as either a warm-up activity or a long-term exercise intervention is yet to be determined. Future studies should include a wider variety of WBV parameters and the use of functional outcome measures

Applications of off-gas mass spectrometry in fed-batch mammalian cell culture

Off-gas analysis using a magnetic sector mass spectrometer was performed in mammalian cell cultures in the fed-batch mode at the 5 L bench and 50 L pilot scales. Factors affecting the MS gas traces were identified during the duration of the fed-batch cultures. Correlation between viable cell concentration (VCC) and oxygen concentration of the inlet gas into the bioreactor (O2-in) resulted in R2 ≈ 0.9; O2-in could be used as a proxy for VCC. Oxygen mass transfer (kLa) was also quantified throughout the culture period with antifoam addition at different time points which is shown to lower the kLa. Real-time specific oxygen consumption rate (qO2) of 2–20 pmol/cell/day throughout the bioreactor runs were within the range of values reported in literature for mammalian cell cultures. We also report, to our knowledge, the first instance of a distinct correlation between respiration quotient (RQ) and the metabolic state of the cell culture with regard to lactate production phase (average RQ > 1) and consumption phase (average RQ < 1)