New Microscope Reveals Ultrastructure of Cells 58
An anonymous reader writes "For the first time, there is no need to chemically fix, stain or cut cells in order to study them. Instead, whole living cells are fast-frozen and studied in their natural environment. The new method delivers an immediate 3-D image, thereby closing a gap between conventional microscopic techniques. The new microscope delivers a high-resolution 3-D image of the entire cell in one step. This is an advantage over electron microscopy, in which a 3-D image is assembled out of many thin sections. This can take up to weeks for just one cell. Also, the cell need not be labeled with dyes, unlike in fluorescence microscopy, where only the labeled structures become visible. The new X-ray microscope instead exploits the natural contrast between organic material and water to form an image of all cell structures. Dr. Gerd Schneider and his microscopy team at the Institute for Soft Matter and Functional Materials have published their development in Nature Methods (abstract)."
natural environment? (Score:3, Insightful)
... whole living cells are fast-frozen and studied in their natural environment.
Um, unless we're talking about species native to Antarctica, I wouldn't think that frozen would be their "natural environment".
Freezing is known (and not just by the State of California ;-) to do damage to many cell structures. For example, they no longer qualify as "living".
Somehow, I think this could have been better expressed with different words.
*not* immediate (Score:4, Insightful)
Here's the relevant passage from the article with the juicy bits:
We acquired X-ray microscope images of these vitrified mammalian cells at tilt angles from 60 to +60 in increments of 1 at a pixel size of either 9.8 nm (25-nm zone plate objective) or 15.6 nm (40-nm zone plate objective). Exposure times for each tilt angle were 224 s. The total X-ray exposure (~109 Gy) produced negligible radiation damage, as we detected no difference in image quality between images acquired at the beginning and end of the tilt series (Supplementary Fig. 3). We processed the images using a reciprocal space algorithm11 to generate a 3D tomogram composed of cubic voxels whose side lengths were either 9.8 nm (25-nm zone plate objective) or 15.6 nm (40-nm zone plate objective).
So they took 121 x-ray images of the specimen, with each image taking 2-24 seconds, and then stitched them together using a tomography technique to obtain their 3D volume. It's certainly faster than a few weeks, but this is not what I would consider "immediate". The article also points out that poor cryopreservation led to some artifacts and that the resolution in this technique was still not as good as the TEM; not having an entire 180 degree rotation of the object led to artifacts as well:
We did not detect some structures by X-ray tomography that we detected by TEM, such as ribosomes and the double membrane of the mitochondrial cristae. These probably fall below the current resolution limit (see below). An additional limitation was the restricted tilt angle range (±60) used in these experiments. This led to poorer resolution in the z dimension, as indicated by a distortion in the 3D shape of some organelles, which appeared more cylindrical in x-z views (Fig. 3b) as well as an inability to obtain face-on views of the nuclear pores (data not shown) or follow the complete circumference of the nuclear membrane (Supplementary Fig. 5b).