Christopher W Waters

California Institute of Technology, Pasadena, California, United States

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Publications (5)8.51 Total impact

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    ABSTRACT: Multiphoton microscopy is becoming a popular mode of live and fixed cell imaging. This mode of imaging offers several advantages due to the fact that fluorochrome excitation is a nonlinear event resulting in excitation only at the plane of focus. Multiphoton excitation is enhanced by the use of ultrafast lasers emitting in the near IR, offering better depth penetration coupled with efficient excitation. Because these lasers, such as titanium:sapphire lasers, offer tunable output it is possible to use them to collect multiphoton excitation spectra. We use the software-tunable Coherent Chameleon laser coupled to the Zeiss LSM 510 META NLO to acquire x-y images of biological samples at multiple excitation wavelengths, creating excitation lambda stacks. The mean intensity of pixels within the image plotted versus excitation wavelength reveals the excitation spectra. Excitation lambda stacks can be separated into individual images corresponding to the signal from different dyes using linear unmixing algorithms in much the same way that emission fingerprinting can be used to generate crosstalk free channels from emission lambda stacks using the META detector. We show how this technique can be used to eliminate autofluorescence and to produce crosstalk-free images of dyes with very close overlap in their emission spectra that cannot be separated using emission fingerprinting. Moreover, excitation finger- printing can be performed using nondescanned detectors (NDDs), offering more flexibility for eliminating autofluorescence or crosstalk between fluorochromes when imaging deep within the sample. Thus, excitation fingerprinting complements and extends the functions offered by the META detector and emission fingerprinting. We correct biases in the laser and microscope transmission to acquire realistic multiphoton excitation spectra for fluorochromes within cells using the microscope, which enables the optimization of the excitation wavelength for single and multilabel experiments and provides a means for studying the influence of the biological environment on nonlinear excitation.
    No preview · Article · Aug 2003 · Journal of Biomedical Optics
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    ABSTRACT: Due to the internal nature of mammalian development, much of the research performed is of a static nature and depends on interpolation between stages of development. This approach cannot explore the dynamic interactions that are essential for normal development. While roller culture overcomes the problem of inaccessibility of the embryo, the constant motion of the medium and embryos makes it impossible to observe and record development. We have developed a static mammalian culture system for imaging development of the mouse embryo. Using this technique, it is possible to sustain normal development for periods of 18-24 h. The success of the culture was evaluated based on the rate of embryo turning, heart rate, somite addition, and several gross morphological features. When this technique is combined with fluorescent markers, it is possible to follow the development of specific tissues or the movement of cells. To highlight some of the strengths of this approach, we present time-lapse movies of embryonic turning, somite addition, closure of the neural tube, and fluorescent imaging of blood circulation in the yolk sac and embryo.
    No preview · Article · Dec 2002 · genesis
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    ABSTRACT: Fluorescent proteins have emerged as an ideal fluorescent marker for studying cell morphologies in vital systems. These proteins were first applied in whole organisms with established germ-line transformation protocols, but now it is possible to label cells with fluorescent proteins in other organisms. Here we present two ways to introduce GFP expressing plasmids into avian embryos for vital confocal and two-photon imaging. First, electroporation is a powerful approach to introduce GFP into the developing neural tube, offering several advantages over dye labeling. Second, we introduce a new lipid-based transfection system for introducing plasmid DNA directly to a small group of injected cells within live, whole embryos. These complementary approaches make it possible to transfect a wide-range of cell types in the avian embryo and the bright, stable, uniform expression of GFP offers great advantages for vital fluorescence imaging.
    No preview · Article · Jul 2002 · Differentiation
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    ABSTRACT: Multi-color fluorescence microscopy has become a popular way to discriminate between multiple proteins, organelles or functions in a single cell or animal and can be used to approximate the physical relationships between individual proteins within the cell, for instance, by using Fluorescence Resonance Energy Transfer (FRET). However, as researchers attempt to gain more information from single samples by using multiple dyes or fluorescent proteins (FPs), spectral overlap between emission signals can obscure the data. Signal separation using glass filters is often impractical for many dye combinations. In cases where there is extensive overlap between fluorochromes, separation is often physically impossible or can only be achieved by sacrificing signal intensity. Here we test the performance of a new, integrated laser scanning system for multispectral imaging, the Zeiss LSM 510 META. This system consists of a sensitive multispectral imager and online linear unmixing functions integrated into the system software. Below we describe the design of the META device and show results from tests of the linear unmixing experiments using fluorochromes with overlapping emission spectra. These studies show that it is possible to expand the number of dyes used in multicolor applications.
    No preview · Article · Jun 2002 · Proceedings of SPIE - The International Society for Optical Engineering
  • M E Dickinson · C W Waters · G Bearman
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    ABSTRACT: Multi-color fluorescence microscopy has become a popular way to discriminate between multiple proteins, organelles or functions in a single cell or animal and can be used to approximate the physical relationships between individual proteins within the cell, for ...
    No preview · Article · Jan 2002 · Proc SPIE