Effect of sequential heat and cold shocks on nuclear phenotypes of the blood-sucking insect, Panstrongylus megistus (Burmeister) (Hemiptera, Reduviidae)

• Published in: Memórias do Instituto Oswaldo Cruz 2002-12, Vol.97 (8), p.1111-1116
• Main Authors: Garcia, Simone L, Pacheco, Raquel M, Rodrigues, Vera L C C, Mello, Maria Luiza S
• Format: Article
• Language: English
• Subjects: Analysis of Variance; Animals; Cell Death; Cell Nucleus - physiology; Cell Survival; cold shock; Cold Temperature; Epithelial Cells - physiology; heat shock; Heat-Shock Response - physiology; Hot Temperature; Male; Malpighian Tubules - cytology; nuclear phenotypes; Panstrongylus - physiology; Panstrongylus megistus; PARASITOLOGY; Phenotype; sequential shocks; TROPICAL MEDICINE
• ISSN: 0074-0276; 1678-8060; 0074-0276; 1678-8060
• DOI: 10.1590/S0074-02762002000800008

Thermal shocks induce changes in the nuclear phenotypes that correspond to survival (heterochromatin decondensation, nuclear fusion) or death (apoptosis, necrosis) responses in the Malpighian tubules of Panstrongylus megistus. Since thermal tolerance increased survival and molting rate in this species following sequential shocks, we investigated whether changes in nuclear phenotypes accompanied the insect survival response to sequential thermal shocks. Fifth instar nymphs were subjected to a single heat (35 or 40 degrees C, 1 h) or cold (5 or 0 degrees C, 1 h) shock and then subjected to a second shock for 12 h at 40 or 0 degrees C, respectively, after 8, 18, 24 and 72 h at 28 degrees C (control temperature). As with specimen survival, sequential heat and cold shocks induced changes in frequency of the mentioned nuclear phenotypes although their patterns differed. The heat shock tolerance involved decrease in apoptosis simultaneous to increase in cell survival responses. Sequential cold shocks did not involve cell/nuclear fusion and even elicited increase in necrosis with advancing time after shocks. The temperatures of 40 and 0 degrees C were more effective than the temperatures of 35 and 5 degrees C in eliciting the heat and cold shock tolerances, respectively, as shown by cytological analysis of the nuclear phenotypes. It is concluded that different sequential thermal shocks can trigger different mechanisms of cellular protection against stress in P. megistus, favoring the insect to adapt to various ecotopes.