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The involvement of portions of the genome replicated at different times of the S period in the regulation of the G1 to S transition was analyzed in Allium cepa L meristem cells. For this, DNA bromosubstitution confined to discrete portions of a previous S period followed by anoxic UVA irradiation (300-400 nm light) was performed in synchronous cells.(More)
Tubulin distribution in c-mitoses (induced by 1 mM colchicine) has been studied by indirect immunofluorescence with monoclonal antibodies inAllium cepa L. meristems proliferating under steady state kinetics. Two hours after colchicine treatment was initiated tubulin is detected in approximately 25% of the cells as arrowheads on the kinetochores, as if these(More)
With the aim of finding out factors involved in chromosomal condensation, the kinetics of both metaphase accumulation and the subsequent formation of restitution nuclei in the presence of 1 mM colchicine have been analyzed in Allium cepa L. meristems. Restitution nuclei are formed by decondensation of the chromosomes from the c-mitoses and the reformation(More)
High molecular weight (HMW, >15 kDa) but not low molecular weight (LMW, <15 kDa) polylysines (PLs) bound and induced permeability changes in rat spermatid plasma membranes, estimated by Mn2+ quenching of intracellular indo-1 fluorescence (K(1/2) = 3.3 +/- 0.5 microg/ml) and Co2+ quenching of intracellular calcein. The pharmacology of the Mn2+ entry pathway(More)
10(-6) M and 10(-5) M 5-azacytidine, demethylated around 9% and 17% of the 5-methylcytosine residues found in Allium cepa L. native DNA, respectively. Both treatments stimulated RNA synthesis in the cells of root meristems. On the other hand, the 10(-5) M treatment gave rise to multiple chromosomal anomalies in mitosis before any fall in the mitotic index(More)
Unilateral parotidectomy with or without total submandibulectomy has been used to induce cell proliferation in mouse parotid gland. Maximum DNA synthesis and mitosis were recorded four and five days after the operation. The double operation increased the proliferative response. Such proliferative stimulii was not accompanied by secretion and was sex(More)
Microdensitometry at different density thresholds of Feulgen-stained nuclei shows that both 2C and 4C dormant cells of the unsprouted root of Allium cepa L. bulbs have a smaller nuclear volume and a larger amount of dense chromatin than their counterpart G1 and G2 cells of the proliferating root. The analysis seems to differentiate between cells in the(More)
In vivo exposure to 5-azacytidine (10−6M) depressed the incorporation of methyl groups to GC rich regions ofAllium cepa L. DNA. Nearly 22% of its 5-methylcytosine residues were under-methylated. The treatment stimulated 1.8 times the rate of [3H]uridine incorporation, as measured in meristems proliferating under steady state kinetics. Nucleologenesis was(More)
Chromatin pattern analysis at different density thresholds in Feulgen-stained meristems stimulated to proliferate by water inbibition, allows to estimate a proliferative potential index (PPI) which is a much earlier indicator of changes in proliferation than conventional labelling and mitotic indices. The PPI is but the ratio G1 cells to total 2C cells (or(More)
Dormant meristems of Allium cepa L. root begin to sprout as soon as the water and temperature conditions are right. These cell systems offer many advantages when studying the earliest metabolic events related with the onset of the cell proliferating activity. By electrophoresis in SDS polyacrylamide gels the soluble protein fraction from meristems with(More)