Full text in pdf format

Nuclear fusion and change in chromatin packing state in response to starvation in Triatoma infestans

Maria Luiza S. Mello

Departamento de Biologia Celular, Instituto de Biologia, UNICAMP, 13081 Campinas, SP, Brasil

ABSTRACT

Feulgen-stained nuclei of Malpighian tubule epithelial cells of Triatoma infestans 5th instar nymphs under conditions of full nourishment, prolonged starvation, and feeding following starvation ("recovery") were studied with scanning microspectrophotometry and image analysis. The aim was to correlate changes in nuclear phenotypes with any change in DNA content and/or chromocenter structure in response to the fasting stress. In the starved and "recovered" specimens, nuclei resembling those of the control as well as fused and degenerated nuclei were found. Nuclear fusion giving rise to ploidy degrees up to the 1024 C class were detected in nuclei of the starved insects, whereas very giant fused nuclei were absent in the "recovered" specimens, since they possibly degenerate. Changes in nuclear phenotypes involving heterochromatin unravelling could be demonstrated with image analysis for part of the fused and unfused nuclear populations of the starved and "recovered" specimens. The relatively unpacked state of the heterochromatin did not revert on cessation of the stressor action. Although starvation appears to be a specific stress factor capable of inducing nuclear fusion in T. infestans cells in vivo, the phenomenon of heterochromatin unravelling is possibly an attempt to activate (a) dormant gene(s), and should not be considered a fasting-specific response.

Keywords: Nuclear fusion; Chromatin; Response to starvation; Triatoma infestans.

REFERENCES

Andrade, C.G.T.J. and Mello, M.L.S. (1987). Phenotypes and number of Malpighian tubule nuclei in Triatoma infestans Klug along development and starvation. Rev. Bras. Genet. 10: 449-457.

Atkinson, B.G. and Walden, D.B. (1985). Changes in eukaryotic gene expression in response to environmental stress. Academic Press, Orlando, 379 pp.

Brumpt, E. (1914). Importance du canibalisme et de la coprophagie chez reduvidés hematophages (Rhodnius, Triatoma) pour la conservation des trypanosomes pathogénes en dehors de l'hôte vertebré. Bull. Soc. Pathol. Exot. 7: 702-705.

Bucher, O. und Horisberger, B. (1950). Karyometrische Untersuchungen an Gewebekulturen. Acta Anat. 9: 258-278.

Diaz, M., Pavan, C. and Basile, R. (1969). Effect of a virus and microsporidian infections in chromosomes of various tissues of Rhynchosciara angelae. Rev. Bras. Biol. 29: 191-206.

Dolder, H. and Mello, M.L.S. (1978). Virus-like particles in the Malpighian tubes of blood-sucking hemipterans. Cell. Mol. Biol. 23: 299-310.

Kubrusly, F.S. (1984). Ação de cobre e mercúrio sobre estrutura nuclear e atividade de alguns sistemas enzimáticos em Triatoma infestans Klug. Masters Thesis, UNICAMP, Campinas, 71 pp.

Mello, M.L.S. (1971). Nuclear behaviour in the Malpighian tubes of Triatoma infestans (Reduv., Hem iptera). Cytologia 36:42-49.

Mello, M.L.S. (1978). Computer analysis of stained chromatin on Malpighian tubes of Triatoma infestans Klug (Hemiptera, Reduviidae). Mikroskopie 34: 285-299.

Mello, M.L.S. (1983). Cytochemical properties of euchromatin and heterochromatin. Histochem. J. 15:739-751.

Mello, M.L.S., Dolder, H. and Dias, C.A. (1989). Nuclear ultrastructure of Malpighian tubule cells in Triatoma infestans under conditions of full nourishment and starvation. Rev. Bras. Genet. (in press).

Mello, M.L.S. and Raymundo, H.H. (1980). Nuclear fusion in the Malpighian tubes of a bloodsucking hemipteran. Cytologic 45: 203-209.

Mello, M.L.S. and Recco-Pimentel, S.M. (1987). Response to banding and Hoechst 33258 treatment in chromocentres of the malpighian tubule cells of Triatoma infestans. Cytobios 52: 175-184.

Monneron, A. and Bernhard, W. (1969). Fine structural organization of the interphase nucleus in some mammalian cells. J. Ultrastruct. Res. 27: 266-278.

Palkóvits, M. and Fischer, J. (1968). Karyometric investigations. Akademiai Kiadó, Budapest. Puvion, E., Viron, A. and Bernhard, W. (1977). Unusual accumulation of ribonucleoprotein constituents in the nucleus of cultured rat liver cells after hypothermal shock. Biol. Cell. 29:81-88.

Sandritter, W., Kiefer, G., Salm, R., Moore, G.W., Grimm, H. and Kiefer, R. (1974). DNA in heterochromatin: cytophotometric pattern recognition image analysis among cell nuclei in duct epithelium and in carcinoma of the human breast. Beitr. Path. 151:87-96.Simões, L.C.G., Amabis, J.M. and Cestari, A.N. (1975). Puffs in the heterochromatin in chromosomes of Rhynchosciara. Ciênc. Cult. 27: 159-161.

Simões, L.C.G. e Cestari, A.N. (1982). Cromossomos politénicos: sistemas experimentais in vivo e in vitro. Ciênc. Cult. 34:480-485.

Vidal, B.C. (1984). Polyploidy and nuclear phenotypes in salivary glands of the rat. Biol. Cell 50: 137-146.

Vidal, B.C., Schlüter, G. and Moore, G.W. (1973). Cell nucleus pattern recognition: influence of staining. Acta Cytol. 17: 510-521.

Wigglesworth, V.B. (1967). Polyploidy and nuclear fusion in the fat body of Rhodnius (Hemiptera). J. Cell Sci. 2: 603-616.

Zeiss Information (1977). Continuous filter monochromator b with motor drive. Mikro Bull. 18: 1-4.