Lysosomes are membrane-bound organelles responsible for the transport and degradation of intracellular and extracellular cargo. The intracellular motion of lysosomes is both diffusive and active, mediated by motor proteins moving lysosomes along microtubules. We sought to determine how lysosome diameter influences lysosome transport. We used osmotic swelling to double the diameter of lysosomes, creating a population of enlarged lysosomes. This allowed us to directly examine the intracellular transport of the same organelle as a function of diameter. Lysosome transport was measured using live cell fluorescence microscopy and single particle tracking. We find, as expected, the diffusive component of intracellular transport is decreased proportional to the increased lysosome diameter. Active transport of the enlarged lysosomes is not affected by the increased lysosome diameter.

FRET-based genetically encoded metal-ion sensors coupled with fluorescence microscopy provide an important tool for real-time imaging of metal-ion homeostasis. The heterogeneity and in vivo kinetics are important sensor properties, yet are less explored because of lacking available experimental methods. We present a high-throughput microfluidic method capable of characterizing the FRET kinetics of metal-ion sensors in mammalian cells, at a throughput of 15 cells/sec with a time window of a few ms to several seconds. Using this method, we screened the HeLa cell Zn 2þ sensor library and measured the FRET distribution at single cell level. We also report the quantitative highthroughput cellular-level heterogeneity measurement of cell populations, the cluster map of the Zn 2þ sensor FRET change resolves 4 subpopulations with different metal response. Finally, we measured the in vivo sensor kinetics induced by changes in [Zn 2þ ] and [Ca 2þ ]. We observed a > 30fold rate difference between the extracellular and intracellular sensors, and the kinetics are ionophore-dependent.

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TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractDuring the development of a secondary recovery project by water injection in a Colombian field called Casabe it was observed that the packed production wells presented an abnormal declination on production rates. This was initially attributed to the completion type: slotted liners or screen packed with 10/20 or 20/40 gravel. The packings have an average length of 1,200 ft. The partial recovery of a slotted liner and screen demonstrated that there was an impermeable material that plugging the external phase of the pipe by 90%, not allowing the oil to flow into the wells. The phenomena in question seriously compromised the volumes of production and the life span of the injection project since plugging in the wells generates loss of productivity and represuring in the field causing premature casing collapse. This article shows the methodology used by teamwork in charge of defining the cause for the plugging in the wells, designing a treatment that would lessen the problem and establishing an operational technique to selectively stimulate the intervals present in the packed wells.

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