SummaryThe general topic of supercritical fluid chromatography (SFC) is introduced, and historical aspects of its development are discussed. The physical properties of supercritical fluids, gases and liquids are tabulated. SFC is compared and contrasted with the classical forms of chromatography -gas chromatography (GC) and high performance liquid chromatography (HPLC). The selectivity of SFC, GC, and HPLC are discussed and compared. Instrumentation employed for supercritical fluid chromatography is depicted. A wide variety of SFC applications are introduced. New examples of the use of SFC for analysis of a variety of complex oligomeric mixtures including polypropylene glycol, polysiloxanes, fluorocarbon oligomers (i.e. -3M's fluorochemical surfactant Fluorad 171, and Kel-F) and high molecular weight normal alcohols areshown. Theuseof SFC for separation of mono-, di-, and triglycerides at low operating temperatures is described. Lastly, the use of SFC for separations of complex hydrocarbon mixtures from liquid fuels, polycyclic aromatic hydrocarbons, synthetic alpha-olefins, and petroleum functional group separations are depicted.

Background: Time-lapse microscopic imaging provides a powerful approach for following changes in cell phenotype over time. Visible responses of whole cells can yield insight into functional changes that underlie physiological processes in health and disease. For example, features of cell motility accompany molecular changes that are central to the immune response, to carcinogenesis and metastasis, to wound healing and tissue regeneration, and to the myriad developmental processes that generate an organism. Previously reported image processing methods for motility analysis required custom viewing devices and manual interactions that may introduce bias, that slow throughput, and that constrain the scope of experiments in terms of the number of treatment variables, time period of observation, replication and statistical options. Here we describe a fully automated system in which images are acquired 24/7 from 384 well plates and are automatically processed to yield high-content motility and morphological data.

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SummaryThe separation of mixed mono-, di-, and triglycerides by capillary supercritical fluid chromatography is described. The separations were performed at low operating temperatures, using a carbon dioxide mobile phase, a conventional flame ionization detector, and two different stationary phases, DB-5 (95% dimethyl-(5%)-diphenylpolysiloxane) and DB-225 (50% cyanopropyl-methyl-(5O0/~)-methylphenylpolysiloxane). Because the separations were performed at low operating temperatures, no thermal degradation of the glycerides wasobserved. Even under these mild operating conditions, trinewonin, a triglyceride having a molecular weight over 11 00 amu, was readily eluted. When rapid pressure programming of the carbon dioxide mobile phase was employed, trinervonin was eluted in less than two minutes. On DB-5, the mono-, di-, and triglycerides eluted in order of increasing molecular weight. A graph of t i (on DB-5) versus molecular weight is linear. When DB-225 was used as the stationary phase, triglycerides eluted in the order of increasing unsaturation-Thus, theorder of elution on 138-225 was tristearin, triolein, trilinolein, and trilinolenin.

A deeper understanding of stem cell-niche engagement and subsequent behaviors would be enhanced by technologies enabling the tracking of individual stem cells at the clonal level in long-term co-culture (LTC), which mimics the complexity of the bone marrow microenvironment in vivo. Here, we report the application of time-lapse imaging with intermittent fluorescence for tracking well-defined populations of GFP+ murine hematopoietic stem cells (HSCs) using LTC for more than 5 weeks. Long-term (LT) and short-term (ST) repopulating HSCs and hematopoietic progenitor cells (HPCs) were compared. The transition from cobblestone areas (CA) under the stromal cell mantle into dispersed migrating cells on top of the stroma (COS) were directly observed. The ST-HSC and LT-HSC were able to initiate multiple waves of CA formation and COS expansion beyond 2 and 4 weeks, respectively. Retrospective tracking of individual CA forming cell (CAFC) revealed a preference for residing under stroma prior to the first division and a longer interval before first division for LT-HSC. Inability to maintain quiescence in subsequent divisions was revealed. Our study represents an important starting point from which the LTC system can be augmented to provide a better in vitro model for bone marrow stem cell niches.