This video demonstrates two key techniques for sampling and processing biobank porcine tissue specimens. The submersion technique reliably estimates total organ and tissue volume and the orientator technique generates random isotropic tissue sections for unbiased estimation of quantitative morphological parameters. The main advantage of the submersion technique for tissue density determination is that it can be applied to any kind of tissue and that it produces reliable results for small as well as for large samples.
The advantages of the orientator technique are that it is highly efficient and also works with large tissue samples. To begin volumetry for a large organ excise an appropriately sized piece of tissue from the organ. Carefully swab the sample with a paper towel to remove excess blood and tissue fluid.
Then weigh the sample on a precision scale and record the weight of the sample. Add 0.9%saline to a beaker of suitable size. Do not completely fill the beaker to prevent overflow during tissue emersion.
Place the beaker on the scale then submerge a forceps or a self-constructed sample holder in the saline until the mark on the forceps or sample holder reaches the liquid. Next, reset the display of the scale to zero. Carefully attach the tissue sample to the forceps or sample holder and completely submerge the sample in the saline until the marked position is reached.
To record reliable density measurements it is important to ensure that the sample is completely submerged and to avoid any contact of the submerged sample to the inner walls or the bottom of the beaker. While holding the sample in position, record the weight displayed on the scale. Use this measurement and the density of saline at room temperature to calculate the volume of the sample.
Then calculate the density of the tissue sample from the weight of the sample and its volume. For large organs and tissues, such as this kidney, perform repeated measurements with multiple samples and calculate the average density from the single measurements. For small samples and small organs measured in total such as the pituitary gland, repeat the measurement three times before calculating the average organ density from the single measurement values.
Finally, calculate the total volume of the organ, tissue or organ compartment from its weight and density. Place a fixed tissue specimen on a print of an equiangular circle with one edge parallel to the zero to 180 degree direction. Then use a random number table to determine a random angle.
Find the corresponding marks on the scale of the equiangular circle. Using these marks, cut a section through the sample with the section plane oriented parallel to the direction of the random angle indicated on the scale of the equiangular circle and a vertical to the resting surface of the sample. Place the tissue block with the section surface facing down on a cosine weighted circle.
With the edge of the resting surface placed parallel to the one-to-one direction. Now cut a new section through the sample at a random angle determined using the random number table. The resulting section plane is an isotropic uniform random section.
This table shows the representative densities of several porcine tissues and organs determined using the submersion technique. Most porcine tissues display density values slightly higher than one referring to the density of water. Whereas tissues swimming in saline, such as adipose tissue for example, display densities lower than one.
This figure shows four representative IUR sections of porcine left ventricular myocardium prepared with the orientator technique. Note the changed cutting angles in the different IUR sections. Once mastered, the submersion technique for tissue density determination can be done in a few minutes.
If it is performed properly. Isotropic uniform random tissue sections generated with the orientator technique are suitable for estimation of any quantitative morphological parameters using appropriate stereological analysis methods. digital music.
