Search

We investigate the converse of the known fact that if the Gershgorin discs of a real n-by-n matrix may be separated by positive diagonal similarity, then the eigenvalues are real. In the 2-by-2 case, with appropriate signs for the off-diagonal entries, we find that the converse is correct, which raises several questions. First, in the 3-by-3 case, the converse is not generally correct, but, empirically, it is frequently true. Then, in the n-by-n case, $ n\ge 3 $ n ≥ 3 , we find that if all the 2-by-2 principal submatrices have inseparable discs ('strongly inseparable discs'), the full matrix must have a nontrivial pair of conjugate complex eigenvalues (i.e. cannot have all real eigenvalues). This hypothesis cannot generally be weakened. [ABSTRACT FROM AUTHOR]

Endotoxin exists on the outer membrane of Gram‐negative bacteria and poses risks to human health by triggering a series of immune responses. Therefore, its accurate detection is essential. The Limulus amoebocyte lysate (LAL) test is the most pharmacopeia‐recognized and popular technique for endotoxin detection. Despite its wide industry adoption, the low endotoxin recovery (LER) phenomenon can compromise the LAL test's reliability. This review summarizes the possible reasons attributing to the LER phenomenon from three different perspectives: the endotoxin standards used in hold time study, protein active pharmaceutical ingredients, and excipients. Potential mechanisms and strategies to mitigate the LER phenomenon are also discussed as presented by different research groups. [ABSTRACT FROM AUTHOR]

Production of artemisinin in genetically modified microorganisms is an attractive option to enable sufficient supply of the effective antimalarial agent. Although a sundry of artemisinin precursors are available from engineered bacteria or yeast, no artemisinin has been manufactured by engineering any microbial platforms due to inaccessibility to unidentified steps. To this end, it is essential to consider how to convert artemisinin precursors to artemisinin, either biochemically or chemically. To establish a novel procedure of artemisinin production, we incubate the mixture of artemisinin precursors from engineered Sacchromyces cerevisiae with the cell-free enzyme extract of Artemisia annua. For the single gene-expressing strain INVScI (pYES-ADS), amorpha-4,11-diene accumulation within 48 h or 14 days led to higher artemisinin content than the control. In the multiple gene-expressing strain YPH501 (pYES-ADS:: pESC-CYP71AV1-DBR2), artemisinin accumulation from the 14-day-induced yeast precursor mixture was nearly equivalent between the single gene-transferred strain and the multiple gene-transferred strain. Alternatively, biotransformation of 48-hour-induced yeast amorpha-4,11-diene mixture by the cold-acclimated A. annua cell-free extract that possesses the abundant enzymes relevant to artemisinin biosynthesis gave rise to considerable elevation of artemisinin content up to 0.647% in maximum, accounting to 15-folds increase as the A. annua cell-free extract without cold-acclimation (0.045%), thereby providing a practical protocol for artemisinin overproduction through the interplay of engineered microbial artemisinin precursors with upregulated plant enzymes. [ABSTRACT FROM AUTHOR]

Schwann cells elaborate myelin sheaths around axons by spirally wrapping and compacting their plasma membranes. Although actin remodeling plays a crucial role in this process, the effectors that modulate the Schwann cell cytoskeleton are poorly defined. Here, we show that the actin cytoskeletal regulator, neural Wiskott-Aldrich syndrome protein (N-WASp), is upregulated in myelinating Schwann cells coincident with myelin elaboration. When N-WASp is conditionally deleted in Schwann cells at the onset of myelination, the cells continue to ensheath axons but fail to extend processes circumferentially to elaborate myelin. Myelin-related gene expression is also severely reduced in the N-WASp-deficient cells and in vitro process and lamellipodia formation are disrupted. Although affected mice demonstrate obvious motor deficits these do not appear to progress, the mutant animals achieving normal body weights and living to advanced age. Our observations demonstrate that N-WASp plays an essential role in Schwann cell maturation and myelin formation. [ABSTRACT FROM AUTHOR]