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J Sans

Publications and source records attributed to J Sans.

13 recordsLinked to original sources
PubMed1992

Early and late replicating DNA involved in the G1 to S transition in Allium cepa L meristematic cells.

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. Sequences replicated in late S appeared to be involved in the positive regulation of the initiation of replication. Hence, cells were prevented from initiating replication if irradiated at mid G1 only when the DNA sequences replicated in the last third of the previous S period were bromosubstituted. Cycloheximide-induced inhibition of protein synthesis at late G1 also prevented the G1 to S transition. Sequences replicated in mid S appeared unrelated to any control of the initiation of replication. On the other hand, sequences replicated in the first third of the S period seemed to be involved in the negative regulation of the initiation of replication, since irradiation after previous bromosubstitution of early replicating DNA sequences advanced G1 cells into the next S phase and increased the proliferative fraction of the population. Finally, the simultaneous inactivation of DNA sequences involved in both positive and negative regulation of replication allowed the cells to enter into S.

Allium↗
PubMed1992

Impaired response to recombinant hepatitis B vaccine in HIV-infected persons.

We studied the immunogenicity of the standard schedule of recombinant hepatitis B vaccine (20 micrograms per dose at months 0, 1, and 6) in 21 anti-human immunodeficiency virus (HIV)-positive persons. Relatively low titers of anti-HBs developed in only five subjects (23.8%) 1 month after the third dose; all five had T4 cell counts greater than 700 cells/mm and none of the 11 subjects with a T4 cell count below this value responded. Five of the 16 nonresponders to the vaccine later had acquired immunodeficiency syndrome (AIDS)-related complex (two) and AIDS (three), while none of the responders did. Our results show that anti-HIV-positive persons are poor responders to the recombinant hepatitis B vaccine, and that the absence of a response is an indicator of a more severe immune deficiency and of a poor prognosis. An optimal regimen of hepatitis B vaccination in HIV-infected persons is still to be established.

Follow-Up Studies↗
PubMed1992

Effect of caffeine and isobutyl-methyl-xanthine on production of binucleate cells and on post-replicative repair.

Caffeine (CAF) but not 3-isobutyl 1-methyl-xanthine (IBMX) displayed a strong DNA anti-repair effect in G2 prophase, as estimated by the frequency of abnormal chromosomes in anaphase-telophase found shortly after treatment. IBMX is more effective than CAF in inhibiting cytokinesis, while the binucleate cells formed by a short treatment with any of these two xanthines have similar cycle kinetics.

1-Methyl-3-isobutylxanthine↗
PubMed1991

Genome size variation and its phenotypic consequences in Phyllotis rodents.

Constitutive heterochromatin and genome size were studied in Phyllotis darwini, three Phyllotis xanthopygus subspecies, and their interspecific laboratory hybrids. P. darwini, with no or only small C-bands, had the smallest genome size; P. xanthopygus rupestris and P. x. vaccarum, with large C-bands in all the chromosomes, had the largest; and P. x. xanthopygus, with heterochromatin only in a few chromosomes, showed intermediate genome size. To examine some phenotypic consequences of nuclear DNA content, we measured nuclear and cellular surfaces and volumes. Linear regression analyses showed that all these cellular characters had a highly significant direct relationship with genome size. Hybrids had always the expected intermediate parental characteristics. Previous results indicate that P. x. vaccarum should have longer mitotic cycles and lower reproductive capacity than P. darwini. Our findings suggest that the "nucleotypic DNA" hypothesis, which considers genome size as an adaptive feature in higher plants and lower vertebrates, could be extended to these mammals. The analysis of heterochromatin and nuclear DNA amounts of other phyllotine and akodontine rodents supports the idea that small C-bands and genomes are ancestral conditions, from which independent and parallel events occurred until large genomes were produced.

Animals↗
PubMed1991

[Isochromosome 17q as the sole alteration in 2 patients with a myelodysplastic syndrome and its relation to myeloperoxidase activity].

Two patients diagnosed of myelodysplastic syndrome with an isochromosome i (17q) as the only chromosomal alteration are presented. The MAC method (i.e., morphology, antibodies, chromosomes) was applied in the study of one of the patients, it being found that all the myeloperoxidase-positive cells carried the i (17q) anomaly. Such finding might suggest that those patients with i (17q) as the only chromosomal alteration could have specific clinical and cytological features.

Aged↗
PubMed1979

Proliferative index estimated by chromatin pattern analysis.

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 G2 to 4C cells, when cells also digress from the post-replicative stage of the cycle). The method is based in the fact that G1 and G2 cells have larger projected nuclear area and smaller dense chromatin area than their conterpart non-proliferating G0 and G0,2 cells.

Cell Cycle↗
PubMed1979

Cell proliferation in the mouse parotid gland after unilateral parotidectomy.

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 independent. On the other hand, the response decreased with age. RNA and protein synthesis inhibitors showed that the stimulation of DNA synthesis depends on early protein synthesis, which seems to be synthesized on a preexisting template.

Animals↗
PubMed1979

Go and Go,2 cells as identified by their chromatin pattern in dormant and proliferating meristems.

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 proliferate compartment from those in the non-proliferative compartment (Go and Go,2 cells).

Cell Cycle↗
PubMedDate not supplied

X to Y spermatozoal ratio in normal and oligozoospermic human semen and its relationship to fertility parameters.

The ratio of X to Y spermatozoa in normo and oligozoospermic human semen is established with a fluorescent technic using quinacrine. The relationship between concentration of X and Y spermatozoa to factors that potentially control the fertilizing ability of spermatozoa (i.e. sperm count, vitality, motility and morphology) is analyzed. Out of a total of 44 samples (22 normo and 22 oligozoospermic samples) a ratio of 1:1 in X to Y spermatozoa is found in both groups. The frequency of X to Y spermatozoa in the evaculate is not related to sperm count. It is also independent from morphology, motility, and vitality of spermatozoa.

Cell Count↗