Nuclear phenotype changes after heat shock in Panstrongylus megistus (Burmeister)

Abstract

The nuclear phenotypes of Malpighian tubule epithelial cells of male nymphs of the blood-sucking

Changes in nuclear phenotypes following cold shock in Panstrongylus megistus (Burmeister)

“…The increased frequencies of altered nuclear phenotypes following cold shock indicate mechanisms involving cell survival (heterochromatin unravelling, nuclear fusion) and cell death (apoptosis, necrosis). Most of the nuclear changes observed here have also been reported after hyperthermia in P. megistus and T. infestans (Dantas & Mello 1992, Tavares et al 1997, Garcia et al 2000. Heterochromatin unravelling, with its possible role in the activation of silent genes during stress (Simões et al 1975), is longer-lasting in P. megistus compared with T. infestans, irrespective of the eliciting temperature used (Dantas & Mello 1992).…”

“…The control specimens of P. megistus studied here had lower nuclear frequency than that reported for fully-nourished, laboratory-reared specimens (Mello et al 1986, Garcia et al 2000. This may reflect nuclear fusion and cell death induced by other stressing agents (such as fasting) prior to the shock.…”

“…The frequency of giant nuclei in P. megistus nymphs increased slightly just after the short cold shock but remained very low with increasing time after the shock. This finding contrasts with the situation found after short heat shock when there was an increase in the absolute frequency of giant nuclei 10 days after a 1 h-treatment and a decreased frequency thereafter (Garcia et al 2000). The activation of nuclear and/or cell fusion which generates giant nuclei (Wigglesworth 1967) was found to be less effective or necessary in response to cold shock than that elicited by heat shock.…”

“…Organs from at least three specimens under experimental and control groups were used. The control groups were the same as those used for study of the heat shock effects (Garcia et al 2000), since heat and cold shock experiments were processed simultaneously, although cold shock results were analyzed later. The organs were mounted on histological slides, fixed in absolute ethanol: glacial acetic acid (3:1, v/v) for 1 min, rinsed in 70% ethanol for 5 min and air dried at room temperature.…”

“…Considering that changes in nuclear phenotypes indicative of cell survival and cell death are induced by heat shock in 5th instar nymphs of P. megistus (Garcia et al 2000), we have examined the cellular effects of cold shock in specimens of the same developmental phase of this species for comparison purposes.…”