G1 and G2 arrest achieved in root meristems by black light irradiation under anoxia, after DNA bromosubstitution

Irradiation under anoxic conditions with near-UV light (300-400 nm walength) of Allium cepa L. root meristems whose cycling cells have their DNA bromosubstituted brings about accumulation of cells in both G1 and G2 stages, in frequencies similar to those found in dormant roots. On the other hand, cells in mitosis nearly disappear from the 12th hour onwards after light irradiation. Since fidelity of transcription is lost after such treatment, the data suggest that altering the pattern of gene expression in the cell cycle is a way to achieve dormancy in these previously proliferating meristems

Cis-acting loci involved in the induction and reversal of chromosome condensation in plant prophase, determined by their different replication times

Anoxic UVA irradiation (300-400 nm) of cells in prophase induced their chromatin to return to the interphase decondensed form when their DNA was unifiliarly bromosubstituted. This immediate effect may be related to the incompetence of chromatin with Br-DNA when irradiated to bind proteins which induce its condensation. Hence, inhibition of protein synthesis also causes chromatin decondensation in cells with native DNA. Bromosubstitution of DNA sequences replicated in the last two thirds of the S period was as efficient as bromosubstitution of the whole genome for such an effect to take place in a nucleus. On the other hand, the irradiation accelerated the entrance into prophase of those cells in which only sequences replicated in the first third of S were bromosubstituted. Thus, early replicating loci may act as attachment sites for binding proteins preventing the induction of chromatin condensation. DNA bromosubstitution during portions of S was carried out in synchronous cell populations labelled as binucleate by a previous short caffeine treatment, in Allium cepa L. root meristems

Impaired chromosome segregation in plant anaphase after moderate hypomethylation of DNA

16 p.-8 fig.-2 tab.10 M and 10 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 M treatment gave rise to multiple chromosomal anomalies in mitosis before any fall in the mitotic index was detectable, but no chromosomal breaks were ever seen. Serious lesions involved in chromatids and segregation in anaphase were preferentially found after hypomethylation of DNA sequences replicated in the second half of the previous S period: (i) sister telomeres remained unresolved at the cell equator while kinetochores had reached the poles, (ii) whole unsegregated chromosomes were pulled to one of the poles by obviously disfunctional kinetochores, resulting in an unbalanced distribution of chromatids, (iii) unsegregated chromosomes in other cells remained at the spindle equator as if kinetochores were nonfunctional, while cytoplasmic division took place before their migration to the poles. Frequently, a growing cytokinetic plate randomly cut the unsegregated chromosomes, giving rise to aneuploid nuclei. These anaphase failures are a firm basis to explain why the 10 M treatment selectively depressed the rate of cell proliferation in these cells in the long run. On the other hand, if hypomethylation occurred at the first half of the previous S period, enlarged chromosomal segments were evident in most metaphases, while chromosome laggards and bridges were recorded in anaphase at rather similar frequencies after the different 5‐azacytidine treatments. These data were consistently obtained both in the native mononucleate cells of meristems and in one subpopulation of synchronous cells labelled as binucleate by 5 mm caffeine

Determination of the replication time of nucleolar organizer DNA after 5-azacytidine treatment for restricted parts of the S period

In vivo exposure to 5-azacytidine (10-6M) depressed the incorporation of methyl groups to GC rich regions of Allium 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 shortened from 2.7 to 1.6 h in synchronous binucleate cells after 5-azacytidine treatment lasting the whole S period of their previous interphase. By hypomethylating DNA sequences replicated at different times during the S period, it could be inferred that the cistron replication took place in early S. Thus, nucleogenesis was shortened to only 0.6 h after such treatment. Sequential short treatment periods using [3H]thymidine confirmed that the nucleolar organizer regions of the chromosomes replicate in early S

Preferences of Underserved Chilean Women on a Mobile Technology Intervention for Cervical Cancer Screening: Qualitative Study

Background: In Chile and Latin America, cervical cancer disproportionately affects women of low socioeconomic status. Mobile technology (mobile health, mHealth) may be able to address this disparity by targeting women in underserved populations. However, there is a lack of information regarding barriers to the implementation of mHealth interventions in underserved populations. Objective: The objective of this study was to investigate the use of cell phones and text messaging (short message service, SMS) in Latina women from disadvantaged communities to design an mHealth intervention for improving cervical cancer screening rates. Methods: We conducted 9 focus groups among women aged 25-64 years to better understand the implementation barriers and perceptions of a text message (SMS)–based intervention designed to improve cervical cancer screening rates. We used the PRECEDE-PROCEED model to categorize identified themes using template analysis. Results: Focus group results indicated that older women use mobile phones to receive calls from family and friends but seldom send text messages. Furthermore, they prefer personal contact with their health care providers regarding Papanicolaou (Pap) testing. Younger women, on the other hand, find text messaging easy to use and frequently send texts to family and friends. Importantly, women of all ages mentioned they would like to receive text messages about Pap tests. Factors that facilitate the uptake of the intervention include ease of access to Pap testing, inclusion of family members, and reminder messaging. Potential barriers include cost and the impersonal nature of messaging. Health team members support an mHealth intervention even though they acknowledge the potential barriers to this strategy. Overall, these results support the implementation of an mHealth intervention to increase cervical cancer screening rates. Conclusions: This study describes the opinions of women nonadherent to Pap testing on the potential use of mobile technologies for cervical cancer screening. Although the overall acceptance was positive, older women prefer personal contact and phone calls over text messaging. Information surrounding these preferences will aid in the implementation of effective strategies to improve cancer screening in underserved populations