Case Study

Case 1

Two series of experiments were performed with an aim to determine the effect of a new antibiotic drug on the skin epithelium. In in vivo studies using rats the solution of the tested drug was applied to the skin surface. The employed dose of the antibiotic was much higher than the therapeutic one. The results of this experiment were assessed by in vivo microscopy studies which were performed during the first 24 hours after the end of drug application with 8-hour intervals. In the in vitro experiments the tested drug was added to the suspension of epithelial cells isolated from the same stock of rats. Six hours later the cells were washed out by repetitive centrifugation and suspending in the same media containing no tested drug. The effects of the antiobiotic were studied at the same time points using regular light microscopy and electron microscopy.

The results of the experiments:

1. In vivo: 8 hours after the completion of the drug application the morphological analysis of the epithelial cells revealed the signs of dystrophy and focal necrosis; the extent of pathologic alterations increased by the end of the 24 hour observation period.

2. In vitro: no signs of the cellular or subsellular damage were seen in the isolated epithelial cells after the drug treatment. The only changes observed included a reversible cell aggregation found in the first test (8 hours after the drug withdrawal), but not in analyses that followed.

Questions:

1. How can you explain the difference in results of the in vivo and in vitro experiments?

2. Was damage to the epithelial cells in the in vivo test direct or indirect? Explain your point of view.

What are the possible mechanisms of the injurious action of the drug on the epithelium?

4. Taking into account the results of the in vitro experiments, which of these mechanisms are the most likely?

5. What processes or cell functions should be studied in the further in vivo experiments to confirm your presumptions about the mechanisms of the pathogenic effect of the tested drug?

Case 2

A technician of the chemical laboratory was not careful working with a toxic volatile chemical. He dropped a flask containing the toxic substance, and smashed it. Before he left the room he had inhaled the noxious vapors of the chemical. Two days later he was admitted to hospital with the following complaints: malaise, somnolence, headache, nausea, back pains, blood in the urine. Blood analysis: erythrocytes 2.7*10¹²/L, Hb 100 g/L, platelets 120*10⁹/L, leucocytes 3.1*10⁹/L; compensated acidosis (metabolic and renal).

The results of the special blood biochemistry analysis: increased concentration of free fatty acid, lipid hydroperoxides, and adenosinephosphate; elevated total creatine phosphate kinase (CPK) activity and potassium content.

Questions: