And Storage Of Lung Slices

BARIUM SULFATE IMPREGNATION This method renders pulmonary tissue opaque and thus makes it considerably easier to quantitate lung changes such as in pulmonary emphysema. After impregnation with barium sulfate, the lung slices sink in water and can easily be photographed and studied with the naked eye or with a dissecting microscope.

Fig. 4-4. Perfusion system for lungs and other organs. (A) Four plastic containers are stacked on adjustable shelves. An electric pump is mounted to one of the center rails. Some of the tubing between the containers is visible. The large flask in the upper left corner of the picture contains neutral buffered 10% formalin solution that is used to gravitate-perfuse the specimens before they are placed in the containers with the circulating fixative (see text). The floor space occupied by the system is 160 x 60 cm. (B) Schematic drawing of perfusion system. P, electric pump (TEEL magnetic drive pump with 5/8' outer diameter inlet and outlet, Dayton Electric Manufacturing Co., Chicago, IL). The direction of the fixative flow is indicated by arrows. The solution cascades from containers A to E, flowing through any organ that is attached to one of the nozzles. The distance between one container and the next lower one is 30-33 cm, and thus the perfusion pressure is 30-33 cm H2O. If an outflow opening in one of the containers becomes plugged, the fluid level rises until it reaches the opening to the overflow tube, O, which leads into the next-lower container. Tube O of container E drains into a large base pan that is normally empty. However, that pan has a drain that can be opened manually. Note the nozzles inside containers B to E. In the example drawn, one pair of lungs, three livers, and two hearts are attached to the system. Adapted with permission from ref. (5).

Fig. 4-4. Perfusion system for lungs and other organs. (A) Four plastic containers are stacked on adjustable shelves. An electric pump is mounted to one of the center rails. Some of the tubing between the containers is visible. The large flask in the upper left corner of the picture contains neutral buffered 10% formalin solution that is used to gravitate-perfuse the specimens before they are placed in the containers with the circulating fixative (see text). The floor space occupied by the system is 160 x 60 cm. (B) Schematic drawing of perfusion system. P, electric pump (TEEL magnetic drive pump with 5/8' outer diameter inlet and outlet, Dayton Electric Manufacturing Co., Chicago, IL). The direction of the fixative flow is indicated by arrows. The solution cascades from containers A to E, flowing through any organ that is attached to one of the nozzles. The distance between one container and the next lower one is 30-33 cm, and thus the perfusion pressure is 30-33 cm H2O. If an outflow opening in one of the containers becomes plugged, the fluid level rises until it reaches the opening to the overflow tube, O, which leads into the next-lower container. Tube O of container E drains into a large base pan that is normally empty. However, that pan has a drain that can be opened manually. Note the nozzles inside containers B to E. In the example drawn, one pair of lungs, three livers, and two hearts are attached to the system. Adapted with permission from ref. (5).

Method of Heard (9) A slice of fixed lung is placed in a solution of 75 g of barium nitrate dissolved in 1 L of warm water. The lung tissue is slightly squeezed so that the solution penetrates the tissue. After about 1 min, the slice is taken out of this solution and excess fluid is squeezed out.

Next, the tissue is submerged in a solution of 100 g sodium sulfate dissolved in 1 L of warm water. The lung tissue is again slightly squeezed and then taken out of the solution, drained, and returned to the barium nitrate bath. This procedure is repeated several times until all air bubbles have been squeezed out and the barium sulfate precipitate has rendered the lung tissue opaque and grayish white (Fig. 4-6).

STORAGE Fresh lungs can be stored in a refrigerator for a few days at temperatures just above the freezing point. Fresh lungs also can be kept deep frozen for months but it is recommended to obtain samples for histologic study prior to snap-freezing. Fixed lungs are best sliced and stored flat in heat-sealed plastic bags filled with 5-20% formalin solution. Several slices can be stored in a stack without distorting the lung tissue.

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