Biomedical subjects
Publications and source records attributed to M L Mello.
Vesicular inclusions observed in Malpighian tubes of hemipterans have been associated with a virus-like infection rather than a lysosomal-type activity, which is the case of the identical cytoplasmic structures.
The digitized nuclear images of some Feulgen-stained primary and secondary spermatocytes of Triatoma infestans were analyzed with computer programs. Different cell types could be mathematically discriminated in terms of distance of the condensed chromatin areas from the center of the nucleus, relative circumference of these areas, and staining intensity ratio of the condensed chromatin areas with respect to the whole nucleus. The method appears promising for further comparative studies involving the whole spermatogenetic process of T. infestans. It is probably advantageous for the analysis of other hemipteran (and even non-hemipteran) spermatogeneses.
When the heterochromatin and euchromatin of Triatoma infestans are maximally depurinated, their Feulgen-DNA spectral profiles exhibit a shoulder at about lambda = 530 nm. The shoulder is especially prominent in the curves of the heterochromatin. It is assumed that this pattern is related to richness in repetitive DNA in the heterochromatin, favoring appearance of Schiff reagent molecules di-substituted with adjacent apurinic acid aldehydes.
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Feulgen-DNA values were evaluated cytophotometrically in the Malpighian tubes of T. infestans at the nymphal, adult and ageing life periods. In all cases the total nuclear Feulgen-DNA contents were found to be distributed within the 32C and 64C classes. However, part of the Feulgen-DNA values is shifted to lower intervals in ageing insects, as compared with nymphal and adult individuals, promoted by decrease in Feulgen-DNA values of the euchromatins. Changed response to Feulgen reaction due to some aging-induced alteration in DNP complexes, and/or breaks and loss of DNA in the euchromatins, as part of the senescence process, are ascribed to be responsible for such phenomenon.
In cells of the Malpighian tubes of Triatoma infestans Klug, the histone content reactive to the alkaline fast green method does not remarkably differ when nuclei with various heterochromatic patterns (T1 and T8) are compared to each other. The fast green-histone values for the euchromatins (and heterochromatins) of both nucleus types also appear not differing. However, the possibility that these histones are differently linked to DNA in euchromatin or heterochromatin variants is not to be ruled out. Cytochemical evidence is suggestive of a lysine-richness in the histones of the mentioned hetero- and euchromatins.
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