Interchangeable Whole-Body and Nose-Only Exposure System

This invention relates to an exposure system for laboratory animals which can be utilized alternatively or simultaneously for whole-body and nose-only exposure of the animals to gases or aerosols, hereinafter termed gaseous materials, and an animal container for use therein.

Existing exposure systems for laboratory animals are of two main types. The first is a large chamber in which a considerable number of animals are contained in groups and the entire body exposed to a flow of gaseous material. Such chambers are exemplified by those shown in U.S. Pat. Nos. 4,216,741 and 4,398,498. In another type exemplified by U.S. Pat. No. 4,721,660, the animals are individually contained in relatively small chambers and the gaseous material is supplied in such a manner that only the nose and closely adjacent portions of the animal receive the gas or aerosol. The need has arisen, however, for systems which are more versatile in that they can be used for whole-body exposure or nose-only exposure as desired. It is particularly desirable that the system be suitable for simultaneously exposing some animals to the whole-body treatment and others to the nose-only in order to determine possible differences in effect depending on the mode of exposure to the same atmosphere. This invention is adapted to accomplish those objectives.

U.S. Pat. No. 4,721,060 referenced above discloses an exposure system of the "nose-only" type. In this system gaseous material from a central chamber flows through a number of small tubes to the inlet of bottles in which the experimental animals are contained. Gas is drawn from these bottles to an outer chamber from which it is exhausted to a disposal system. The present system operates in the same general manner as the prior system, but at least some of the bottles or other containers for the animals are so designed that the gas or aerosol passes over the entire body of the animal before going into the exhaust chamber. Since the basic system is the same, it is only necessary to interchange the type of animal containers in order to change between nose-only and whole-body exposure of the animals. As a secondary matter, the invention includes improvements in the circulation system for the atmosphere to which the animal is exposed.

In more detail, the animal container is, in general, of the bottle type but contains a wire cage or wire mesh restrainer or holder which is spaced from the walls of the bottle so that gaseous material may flow about the entire animal. A return passage is provided from the end of the container back to the exhaust manifold. Preferably, this is accomplished by making the container of double-walled construction with the inner wall forming the primary container and connected to the inlet manifold and the space between the walls connected to the exhaust manifold. The inner wall terminates short of the outer wall and is open at its end remote from the manifolds. The inlet and exhaust manifolds may be concentric as described in the above U.S. Pat. No. 4,721,060, or they may be of box-like (and/or) tubular construction. The choice will depend on the particular laboratory environment in which the system is to be used.

In one embodiment of the last named type, the animal container and the inlet tubes supplying the gas to the animals and the exhaust ports leading from the containers are arranged in vertical columns. A tubular horizontal inlet manifold extends along the top, and vertical sub-manifolds are connected to the inlet manifold. Valve connections extend from the inlet manifold to each of the vertical sub-manifolds so that gas or aerosol can be supplied selectively to any or all of the columns of containers. A single large exhaust manifold surrounds the inlet tubes and is connected to the exhaust ports from the containers. The entire system may be mounted on a cart for ready movement about the laboratory.

In the drawings,

FIG. 1 is a perspective view of the cart-mounted model with parts omitted for clarity and other parts broken away to show interior structure.

FIG. 2 is a horizontal section through one of the containers of FIG. 1, showing its connection to the exhaust manifold.

FIG. 3 is a section taken on line 3--3 of FIG. 2.

FIGS. 4, 5, and 6 are diagramatic views of the air system and the air flow with different settings of a valve 28.

Referring to FIG. 1, this embodiment of our exposure system is mounted on a cart 2 having wheels or castors 4. The exposure system comprises a vertical panel 6. At the top of the panel is an inlet manifold 8 which extends the entire width of the panel 6. It is provided with an inlet 10 for gaseous material, and feeds to a plurality of vertical sub-manifolds 12, each of which feeds to a plurality of inlet tubes 14 (FIGS. 1, 2, and 4); each of the latter is surrounded by an exhaust port 16. The inlet tubes and exhaust ports are in turn each connected to one of the plurality of animal containers 18.

These containers and their connections are best shown in FIG. 2 and 3. Referring to these figures, each container comprises an outer shell 20 and an inner shell 22, and it will be noted that the inner shell terminates short of the outer shell at the end of the container remote from the manifold. The remote end of the outer shell is closed by a removable plug 24 through which extends a tube 25 made of metal having high thermal conductivity, e.g., aluminum. It will be noted that each of these shells includes a relatively large diameter portion and a relatively small diameter portion connected by a frusto-conical section. The small diameter portion of the outer shell 20 fits within the exhaust port -6 while the small diameter portion of the inner shell 22 fits over an inlet tube 14. Exhaust manifold 26 extends the entire width and height of the panel 6 and surrounds all the inlet tubes 14. It connects with all the exhaust ports 16. As has been noted, each of the inlet tubes 14 is connected to a vertical sub-manifold 12.

Referring to FIGS. 4, 5, and 6, each of the sub-manifolds 12 is provided with a valve 28 which connects with the inlet manifold 8. Depending on the setting of the valve, gaseous material can be emitted directly to a sub-manifold 12 (FIG. 6), admitted thereto by way of filter 30 (FIG. 5), or shut off (FIG. 4).

Returning to FIGS. 2 and 3, each container 18 is provided with an animal restrainer or cage 32, preferably formed of wire mesh and spaced from inner casing 22 by spacers 34. Preferably, these restrainers are provided with positioning flanges 27 secured to tail cylinders 25. As disclosed in U.S. Pat. No. 4,721,060, tubes 25 are slidable in plugs 24 so that flanges 27 hold the animals in the desired positions. Tubes 25 receive the tails of rodents and dissipate heat, as described in that patent, column 2, lines 27-47.

In use, animals (e.g., rats) are placed in restrainers 32. Gaseous material is admitted to manifold 8 through inlet 10 and is distributed by sub-manifolds 12 through the containers 18. It flows through the inner shell 22 to the space between the shells, and finally to the exhaust manifold 26 from which it is withdrawn. By proper manipulation of valves 28, it can be selectively admitted to individual sub-manifolds either directly or through filters 30, or it can be shut off from a particular manifold. Furthermore, some or all of the containers 18 may be replaced by those of the type shown at 40 in U.S. Pat. No. 4,721,060. When the latter type are used, only the nose of the animal receives the gaseous material. Hence, it is possible to treat the animals in either the "whole-body" or "nose-only" mode. This may vary from animal to animal.

Alternatively, the apparatus shown in U.S. Pat. No. 4,721,060 may be employed, with the containment 18, described above, replacing some or all of the bottles 40 of that patent.

While we have described certain embodiments of our invention in considerable detail, it will be apparent to those skilled in the art that variations are possible. Therefore, we wish our invention to be limited solely to the scope of the appended claims.