This application claims priority of German patent application no. 10 2005 037 060.8 filed Aug. 5, 2005, which is incorporated by reference herein.
The invention relates to a device for sectioning specimens, in particular a microtome or an ultramicrotome.
Microtomes and ultramicrotomes are usually equipped with at least one knife that serves to produce thin sections of the specimen. Microtomes and/or ultramicrotomes are surrounded by a cold chamber. It is already known to place microtomes or ultramicrotomes in a glovebox (see page 128 of “Nanostructural Study of Raney-Type Nickel Catalysts,” Francois Devred, September 2004, Delft University Press, ISBN: 9040725039). The purpose previously was that materials that reacted chemically with nitrogen, or with the oxygen residues in nitrogen gas, were being investigated. The cold nitrogen gas was therefore not directed into the glovebox, but instead was guided out of the glovebox via a sealed connection. The glovebox itself was filled with ultrapure gases via a separate supply conduit. The complexity in this instance is extreme, since the glovebox must be sealed and it is necessary to use ultrapure gases and sealed airlocks.
The Leica EM UC6 (the new ultramicrotome) and the Leica EM FC6 (the new cold chamber) (brochure entitled “The new ultramicrotome for room-temperature section and cryosectioning”) possess a tank that is filled with liquid nitrogen from a reservoir vessel. Evaporation of the liquid nitrogen creates a continuous flow of dry, cold gas that is directed into the cold chamber. The homogeneous gas flow escapes from the chamber, which is open at the top. The homogeneous purging is intended to prevent the entry of moisture. Ice formation occurs, however, at the boundary layer between the upper side of the cold chamber and the laboratory environment, and can result in the deposition of ice crystals onto the specimen or the cut sections.
An ultramicrotome of the RMC company is known (see “Ultramicrotomes” catalog), having a cryobox placed onto the housing of the ultramicrotome. Devices of the RMC company of the MTX type, having CRX cold chambers, are of similar construction, so that here as well the entry of ice crystals into the cold chamber cannot be entirely prevented.
The devices of the existing art have the critical disadvantage that in the context of a cold chamber without a glovebox, purging with dry gas cannot completely prevent the formation of ice deposits. A boundary layer with the atmosphere forms at the upper side of the cold chamber, and can also be detected visually by the formation of a slight mist. Very small ice crystals form in this boundary layer, fall into the cold chamber, and collect during sectioning on the knife and also on the sections. These ice crystals interfere with subsequent observation under the electron microscope. Large areas of the section can be unusable.
An improvement in terms of ice formation on the cold chamber can furthermore be achieved with complex air-conditioning systems, by setting a very low relative humidity (e.g. 10%). It is not very pleasant for the user to work under these conditions, however, and the air-conditioning system consumes a great deal of energy and is also expensive to acquire and install.
Various embodiments of gloveboxes may be inferred, for example, from page 579 of the Cole-Parmer catalog.
It is therefore the object of the present invention to create a device with which it is possible to create a low relative humidity in the environment of the cold chamber, in order to prevent ice contamination in the cold chamber. The intention is for the environment around the cold chamber to be produced in simple fashion.
This object is achieved, according to the present invention, by a device according to the present invention. The invention has the advantage that a device for sectioning specimens is provided. The device comprises a sectioning apparatus, namely a microtome or an ultramicrotome, for generating thin specimen pieces. A table is provided on which the microtome or ultramicrotome is placed, the microtome or ultramicrotome possessing a knife holder and a specimen holder. The knife holder and specimen holder are surrounded by a cold chamber. A glovebox surrounds the microtome or ultramicrotome and the cold chamber, and stands on the table. A coolant hose connects the reservoir vessel with coolant to the cold chamber, so that coolant flows out of the reservoir vessel into the cold chamber, and the coolant evaporating out of the cold chamber fills the glovebox. The glovebox has a rim at which the glovebox contacts the table, and no seal is provided between the rim and the table. The glovebox is fastened to the table with multiple fastening elements. The glovebox is embodied with a passthrough for cables and a passthrough for the coolant hose.
The microtome or ultramicrotome possesses a stereomicroscope for observation of the specimen, the stereomicroscope being sealed by means of an elastic bellows between the interior of the glovebox and the laboratory environment.
The glovebox is embodied with openings which are configured in such a way that a user can introduce his or her arm into the glovebox without causing a substantial leak.
The glovebox possesses an outlet valve or a defined opening, so that no substantial overpressure builds up in the interior of the glovebox, and so that a defined outflow of the evaporating coolant is possible.
The glovebox is equipped with an airlock that permits the introduction of tools and specimens into the interior of the glovebox without thereby allowing a large amount of moisture to enter the interior of the glovebox.
The glovebox can furthermore also be equipped with an airlock that permits the introduction of a cryosample holder of an electron microscope into the interior of the glovebox, and allows the cryosample holder to be loaded with sample carriers and sections.
Further advantages and advantageous embodiments of the invention may be inferred from the dependent claims, and are the subject matter of the Figures below as well as their descriptions.
In the individual Figures:
Device 1 is made up of a sectioning apparatus 3, which may be either a microtome or an ultramicrotome, that is equipped with a cold chamber 30 that surrounds a knife holder and a specimen holder of sectioning apparatus 3. A rail 23 is mounted on table 5. Arm supports 20 and 21 are horizontally displaceable in rail 23. A stereomicroscope 10 is joined to sectioning apparatus 3 for observation of the sectioning operation by the user. Cold chamber 30 likewise comprises supports 31 and 32 for a user's hands. When a microtome or ultramicrotome is used as sectioning apparatus 3 together with a cold chamber 30, the user places his or her hands onto supports 31 and 32 on cold chamber 30, and rests his or her elbows on arm supports 20 and 21 of table 5.
The manner in which device 1 functions may be described as follows. When cooling of cold chamber 30, and of the specimen holders present therein, begins, more than a liter of liquid coolant from reservoir vessel 35 is needed. The initially warm cold chamber 30 is thereby brought to operating temperature. The liquid coolant is liquid nitrogen. This means that approximately one cubic meter of gas (gaseous nitrogen) is produced, which is used to displace the atmosphere out of glovebox 42 and replace it with nitrogen gas. Only a slight overpressure occurs in this context, since a desired leakage rate exists because glovebox 42 is installed on table 5 without a seal. The flow of dry nitrogen gas is consequently sufficient to maintain this state.
It is possible to work in cold chamber 30 for many hours with no occurrence of ice contamination. Operation is independent of external laboratory conditions.
A laterally mounted airlock 50 serves for the introduction and removal of samples, knives, and accessories.
It is also conceivable to couple a cryosample holder of an electron microscope to glovebox 42 via airlock 50, so that transfer of the screen with the sections to the cryosample holder can likewise be performed in the dry nitrogen gas.
Number | Date | Country | Kind |
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10 2005 037 060.8 | Aug 2005 | DE | national |