Guide to the practical teaching
of biology and genetics

Influence of surroundings onto the bioplasm

TASK 1: Photodynamy

NP: hay infusion, eosin

Prepare two slides, one with one drop of hay infusion, the other with two drops. Add eosin to one of the two drops on one slide (experiment) and to the single drop on the other slide (control). Expose the slide with two drops to light and place the other slide into dark. Observe specimen after 3 min. intervals and compare it to controls. The photodynamy causes excitation of the ciliates and their rapid movement, followed by inhibition and death.

TASK 2: The effect of ionizing irradiation on the testes of rat and fowl

PP: testes of rat (normal tissue and tissue after irradiation with dose of 6.5 Gy) - "varle krysa, varle krysa 6,5 Gy", testes of fowl (normal tissue, tissue 4 and 8 days after irradiation with doses of 12 Gy) - "varle kohout, varle kohout - 4 dny, varle kohout - 8 dnů". Specimens are stained with haematoxylin-eosin.

Observe the testes under small and then larger magnification and compare the normal tissue with the tissue after irradiation. You can find damaged tubules and space around them. It is difficult to differentiate individual stages of spermatogenesis inside the tubules, because cells are damaged. In fowl, you can observe signs of reparation eight days after irradiation.

Fig.: The effect of ionizing irradiation on the testes of rat: A – normal tissue (small and large magnification), B – tissue after irradiation (small and large magnification).

TASK 3: Oligodynamic action (the effect of heavy metal ions dissolved in water solution (water upon mercury) on a survival of Protozoa

NP: hay infusion, water upon mercury (Hg)

Put a drop of hay infusion and a drop of water upon the mercury on the slide. Observe a specimen in 3 min. interval and compare it with control (only hay infusion). You can observe excitation of ciliates and their rapid movement, followed by inhibition and death.

TASK 4: The effect of CdCl₂ (cadmium chloride) on the testes of rat

PP: testes of rat (normal tissue and tissue of rat that was fed with CdCl₂) - "varle po CdCl₂". Specimens are stained with haematoxylin-eosin.

Observe the testes of a rat that was fed with CdCl₂ (under small and large magnification) and compare it with normal testes. Focus on the seminiferous tubules (their number and structure) and spermatogenesis.

TASK 5: The effect of phytoncides on survival of Protozoa

NP: hay infusion

Cut an onion into small pieces and then crush it using sea sand and a mortar. Drop hay infusion on the slide and observe the presence of protozoa. Then put the specimen into the Petri dish and place crushed onion under it (see the picture). Control reactions and movement of the protozoa in 3-5 min. intervals and compare it with control (hay infusion without the effect of phytoncides). Note the time of protozoa’s death.