GB1578029A

GB1578029A - Production of samples for microscopy

Info

Publication number: GB1578029A
Application number: GB2869276A
Authority: GB
Original assignee: British American Tobacco Co Ltd
Current assignee: British American Tobacco Investments Ltd
Priority date: 1977-06-29
Filing date: 1977-06-29
Publication date: 1980-10-29

Description

(54) IMPROVEMENTS IN THE PRODUCTION OF SAMPLES FOR MICROSCOPY (71) We, BRITISH-AMERICAN TOBACCO COMPANY LIMITED, a Com- pany incorporated under the laws of Great Britain, of Westminster House, 7, Millbank, London, S.W. 1., do hereby declare the invention for which we pray that a Patent may be granted to us and the method by which it is to be performed to be particularly described in and by the following statement: This invention concerns improvements relating to the production of samples for microscopy after any necessary preliminary treatment.

Tissues for histological examination are embedded in wax and made into blocks from which sections are cut for mounting on microscope slides. To ensure even penetration of the wax into the tissue pieces, wax embedding is usually done under vacuum in order to remove air bubbles from the material being processed, the vacuum and the length of time for which it is applied being urder manual control. This simple procedure is satisfactory for many types of tissue, but some, notably those of lung and bone, often give unacceptable wax specimens, so that time-consuming and tedious repetitive treatments are required.

The present invention seeks to provide an automatic method and apparatus which will allow precise control of the application of the vacuum and of the number of the repeated treatments necessary to achieve satisfactory embedding of substanially all types of tissue.

According to the invention there is provided an apparatus for embedding tissue in an embedding medium comprising a vacuum embedding unit including a vacuum embedding chamber in which the tissue can be immersed in the medium and which can be selectively connected to a vacuum supply, and programmable control means which automatically regulate the initiation of vacuum application to the embedding chamber and the reduction of the vacuum of a plurality of evacuation cycles to which the chamber is subjected, the control means including a pre-settable counting means which determines the number of said cycles to be applied to the vacuum embedding chamber.

In one embodiment of the invention, the control means includes means for holding the vacuum applied to the chamber for a predetermined period before initiation of each vacuum-reduction phase.

The invention also provides a method of embedding tissue in an embedding medium, comprising immersing said tissue in a vacuum embedding chamber and subjecting the tissue to a plurality of evacuation cycles, each cycle comprising a vacuum-application phase and a vacuum-reducing phase, each cycle being performed automatically in response to programmable control means which control the initiation of the vacuum-application phase, the degree of vacuum applied and the rate of vacuum reduction of the vacuum-reducing phase for each of said cycles, the number of said cycles applied to said chamber being determined by presettable counting means of said control means. The method of the invention may also include a vacuum holding phase prior to the release of the vacuum.

It is possible to ensure consistent and reliable results, avoiding variations which may arise with manual control. Indeed excellent replicas suitable even for general electronmicroscopy can be reliably produced.

One manner of carrying the invention into effect will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is an electrical circuit diagram of a convenient form of the apparatus, Figure 2 is a diagram for pneumatic components of the apparatus, Figure 3 is a schematic side elevation of a tissue processor of which the apparatus of this invention forms a part, and Figure 4 is a partial top plan view of the processor shown in Figure 3.

Referring to Figures 1 and 2, the sequence of cycles of operation to be described are controlled by means of a timer T in the form of a synchronous motor whose output shaft rotates at one revolution in 10 minutes and a presettable counter C of known type through whose contacts C1, C2 the motor can be connected to a source of supply at L, N, E, these contacts being only closed when a number of repeated cycles of operation, for example, six cycles, required for a particular treatment, has been entered into the counter. The motor T drives three cams which operate switches M1, M2 and M3 in predetermined sequence and for predetermined durations.The switch M1, which is closed for, say, 1 minute at the commencement of each cycle, controls the supply of current, via a socket S, to a motor driving a vacuum pump P (Figure 2), which may be of known type, and to the winding VW1 of a two-way solenoid valve V1 connected between the pump and, via a two-way solenoid valve V2, to a line L connected to a vacuum-embedding nuit including a vacuum embedding chamber, which may also be of known type. Closure of the switch M1 will cause the pump P to be switched on and connected to the embedding unit through the valves Vl and V2.

An adjustable needle valve NV provided on the suction side of the pump P permits the degree of vacuum applied, indicated by a guage G, to be preset for the operation to be performed. When the switch M1 is opened after the appropriate vacuum, for example 20 in.Hg has been established, the pump is switched off causing the vacuum valve V1 to be de-energised and to assume its other position in which the line L is isolated from the pump P and the pump is connected to atmosphere through the valve NV to reduce the vacuum. The vacuum release in the embedding unit is controlled by the length of time during which the switch M2 is closed.

This switch controls the energisation of the winding VW2 of the valve V2 and its closure causes that valve to assume its other position, in which the embedding unit is connected to atmosphere through an adjustable needle valve NA. Air enters the unit, causing the vacuum therein to reduce at a rate predetermined by the setting of the valve NA. The setting of the valve NA may be such, for example, that the vacuum in the embedding chamber rises to atmospheric pressure during a period of one minute. The switch M3, which is closed momentary just before the switch M2 is re-opened, controls the energisation of a winding CW which, on such closure, causes the number of cycles set in the counter C to be reduced by one in known manner.

Opening of the switch M2 causes the valve V2 to be returned to its initial position, in which the embedding unit is reconnected to the valve V1. The above-described cycle will then be repeated, commencing with the closure of the switch M1, until the preset counter reaches zero, whereupon the contacts C1, C2 are opened, causing the motor T to stop and the embedding operation to be automatically terminated.

Neon lamps L1 and L2 serve by their illumination to indicate the vacuum and air stages of each cycle and neon lamp L3 is operated by the counter through contacts C2 and C3 to indicate completion of the whole operation.

Advantageously, manually operable switches SW1 and SW2, controlling vacuum and air respectively, may be provided to allow manual control of cycles of a vacuum-embedding operation if such should be required. As will be seen operation of either switch SW1 and SW2 also interrupts the supply circuit to the motor T.

Switch M2 is open during the establishment of the vacuum in the embedding unit and after a predetermined period, the switch M2 is closed to allow the vacuum to be released through the needle valve NA.

The apparatus of this invention can be operatively incorporated in a tissue processor.

One example of such an arrangement is shown schematically in Figures 3 and 4 and as illustrated in this example, the processor comprises a base housing 1 supporting a circular platform 2 and a vertical shaft 3 which extends centrally upwards from the platform 2. At its upper end, the shaft 3 carries a spider frame 4, having in this example, twelve, radial spokes.

Upon the platform 2 rest twelve containers, at twelve treatment stations a--l respectively.

From each of eleven of the spokes of the frame 4 there is suspended a carrier supporting a disc for closure of a corresponding one of the containers. From the remaining spoke there is suspended a carrier provided with a motor 5 and a wire-mesh basket 7. A closure disc 6 is located intermediate the motor 6 and the basket 7.

Within the housing 1 is a further motor (not shown) arranged to produce relative indexing rotation between the shaft 3 and the platform 2, and a lifting-and-lowering mechanism (also not shown) which is drivable by the further motor to raise and lower the shaft 3 axially, so that the basket 7 is raised out of that one of the containers in which it is disposed between the shaft 3 or the platform 2 is caused to rotate, the shaft or platform is rotated by a fixed amount and the basket 7 is lowered into an adjacent container after cessation of the relative rotation.

The housing also contains programming means (also not shown) pre-settable by means of a setting disc 8.

The containers provided at stations i and k are for holding an embedding medium such as molten wax and each is provided with heating means for maintaining the wax in a molten condition. At station 1, there is positioned a vacuum embedding chamber, the timing means of which can advantageously be enclosed in the hosing 1. The vacuum pump may be a separate unit which is suitably connected for use to the apparatus. In the latter case the vacuum pump could be located in the housing 1.

In use of the apparatus to prepare tissue for sectioning, containers at stations a-g hold alcohol solutions of progressively increasing concentrations. Containers at h and i hold fat solvents, and containers at j and k hold molten wax. A tissue sample is placed in the basket 7 and the setting disc 8 is set so that the sample is immersed for set times in the liquid contents of the containers a-k in turn. By means of operation of the motor 6, the basket is slowly rotated whilst being disposed in these containers. The basket 7 will then be transferred to the vacuum chamber at station 1 and will reside there for a time which is controlled by the vacuum embedder timer. During this time the closure dise 6 serves to hermetically seal the vacuum chamber.

The control means, or the mounting means thereof, of the vacuum embedding apparatus may be incorporated in the programming means of the tissue processor.

WHAT WE CLAIM IS:- 1. An apparatus for embedding tissue in an embedding medium comprising a vacuum embedding unit including a vacuum embedding chamber, in which the tissue is immersed in the medium and whch can be selectively connected to a vacuum supply, and programmable control means which automatically regulate the initiation of the vacuum application to the embedding chamber and the reduction of the vacuum of a plurality of evacuation cycles to which the chamber is subjected, the control means including a presettable counting means which determines the number of said cycles to be applied to the vacuum embedding chamber.

2. Apparatus according to claim 1, wherein adjustable valve means are provided to regulate the degree of vacuum applied to said chamber.

3. Apparatus according to claim I or claim 2, wherein adjustable valve means are provided to regulate the vacuum reduction phases.

4. Apparatus according to any one of claims 1 to 3, wherein the control means automati cally maintain the vacuum in said chamber for a predetermined period between the vacuum-application and the vacuum-reduction phases of each evacuation cycle.

5. Apparatus according to any one of claims 1 to 4, wherein manually operated means are provided to control each evacuation cycle.

6. A tissue processor operatively associated with a vacuum embedding apparatus according to any one of claims 1 to 5.

7. A tissue processor according to claim 6, comprising a plurality of treatment stations, one of said stations incorporating the vacuum embedding chamber, transporting means operable to sequentially locate tissue at the stations and timing means operable to programme the transporting means.

8. A tissue processor according to claim 7, wherein the transporting means comprises a closure member co-operable with the vacuum embedding chamber to hermetically seal the chamber.

9. A tissue processor according to claim 7 or claim 8 wherein the timing means is combined with the control means of the vacuum embedding apparatus.

10. A method of embedding tissue in an embedding medium, comprising immersing said tissue in said medium in a vacuum embedding chamber and subjecting the chamber to a plurality of evacuation cycles, each cycle coinprising a vacuum-application phase and a vacuum-reducing phase, each cycle being performed auomatically in response to programmable control means which control the initiation of the vacuum application phase, the degree of vacuum applied and the rate of vacuum reduction of the vacuum-reducing phase for each of said cycles, the number of said cycles applied to said chamber being determined by pre-settable counting means of said control means.

11. Method according to claim 10 and including the step of maintaining the vacuum in said chamber for a predetermined period between the vacuum-application and the vacuum-reduction phases of each said evacuarion cycles.

12. A method according to claim 10 or claim 11 wherein the plurality of evacuation cycles comprises a substantially continuous series of said cycles.

13. A method according to any one of claims 10 to 12 wherein the tissue is animal tissue having a major proportion of internal ducts or passages.

14. An apparatus for embedding tissue in an embedding medium, substantially as hereinbefore described and with reference to the accompanying drawings.

15 A method of embedding tissue in an embedding medium substantially as hereinbefore described and with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. pump may be a separate unit which is suitably connected for use to the apparatus. In the latter case the vacuum pump could be located in the housing 1. In use of the apparatus to prepare tissue for sectioning, containers at stations a-g hold alcohol solutions of progressively increasing concentrations. Containers at h and i hold fat solvents, and containers at j and k hold molten wax. A tissue sample is placed in the basket 7 and the setting disc 8 is set so that the sample is immersed for set times in the liquid contents of the containers a-k in turn. By means of operation of the motor 6, the basket is slowly rotated whilst being disposed in these containers. The basket 7 will then be transferred to the vacuum chamber at station 1 and will reside there for a time which is controlled by the vacuum embedder timer. During this time the closure dise 6 serves to hermetically seal the vacuum chamber. The control means, or the mounting means thereof, of the vacuum embedding apparatus may be incorporated in the programming means of the tissue processor. WHAT WE CLAIM IS:-

1. An apparatus for embedding tissue in an embedding medium comprising a vacuum embedding unit including a vacuum embedding chamber, in which the tissue is immersed in the medium and whch can be selectively connected to a vacuum supply, and programmable control means which automatically regulate the initiation of the vacuum application to the embedding chamber and the reduction of the vacuum of a plurality of evacuation cycles to which the chamber is subjected, the control means including a presettable counting means which determines the number of said cycles to be applied to the vacuum embedding chamber.