Biomedical subjects

I Martínez-Flores

Publications and source records attributed to I Martínez-Flores.

8 recordsLinked to original sources

PubMed2005

Chromosome 18 pairing behavior in human trisomic oocytes. Presence of an extra chromosome extends bouquet stage.

Little is known about the first meiotic prophase stages in the human female because these occur during fetal life, and only a few studies have addressed aneuploid human oocytes. In this paper, the synaptic process in the meiotic prophase in three 47, XX+18 cases is analyzed. A complete study of the dynamics of centromeres and telomeres, cohesin core and synapsis development in aneuploid female meiosis was performed. Investigation of chromosome dynamics in prophase of trisomy 18 oocytes show that these events follow the major patterns seen earlier in euploid oocytes. However, there is a significant delay in the resolution of bouquet topology which could relate to the presence of a surplus chromosome 18 axial element in zygotene oocytes. Pachytene oocytes displayed normal synapsis among the three chromosome 18s. However, in some oocytes the surplus chromosome 18 core was aligned to the bivalent 18. As ataxia telangiectasia and Rad3 related kinase (ATR) has been described as a marker for late-pairing chromosomes in mice, ATR distribution was analyzed in human meiocytes--spermatocytes, euploid oocytes and trisomic oocytes. In contrast to the observations made in mice, no preferential staining for late-pairing chromosomes was observed in humans. In the cases studied, bivalent synapses progressed as in a normal ovary, contrasting with the hypothesis that a surplus chromosome can modify pairing of other chromosomes.

Ataxia Telangiectasia Mutated Proteins↗

PubMed2003

Synaptic process in the rat (Rattus norvegicus): Influence of methodology on results.

Synaptonemal complex (SC) analysis is a widely used method for assessing the effects of genotoxic agents in germ cells. Although the evolution of the SCs and their related annexed structures, such as nucleoli, has been well established, sometimes it is difficult to assess whether the abnormal features observed correspond to genotoxic effects or to an artefact related to the method used to obtain the SC preparations. In this article, we describe a new method of obtaining SC preparations for electron microscopy, as well as the results of a study of the first meiotic prophase in oocytes and spermatocytes of the rat (Rattus norvegicus Sprague Dawley) in which we analysed how the methodology used can influence the results. Besides important sex-specific differences, mainly during desynapsis (diplotene), a relationship between several bivalents and nucleolar structures, that in some cases could disturb the synaptic process, was observed in oocytes. At the same time, the characteristic SC fragmentation in oocytes was verified, but this fragmentation, in addition to a sex-specific component, was influenced by the method itself. By reducing to a minimum the artefacts produced by the method, it is possible to optimise the analysis of SCs as a method of testing genotoxic effects in the germ line.

Animals↗

PubMed2001

Embryolethality induced by metronidazole (MTZ) in Rattus norvegicus.

Parasitic illnesses is increasing all over the world, especially in developing countries, and metronidazole (MTZ) is the therapeutic agent usually administered to children as well as adults at the reproductive age. In this work, we propose an evaluation of MTZ in order to analyze the potential reproductive damage in females by using Rattus norvegicus (Sprague-Dawley) as an animal model. Adult female rats were mated after MTZ treatments, and they were sacrificed at 21 days of gestation. Different types of damage were evaluated by using mortality, phenotypic abnormalities and reproductive capacity as parameters, and were studied and scored in 70 adult specimens (450 g/bw). They were divided into five groups: a) untreated females as a control group; females treated with b) DMSO as a solvent control group or c) 500 mg/kg/bw of MTZ per day for 7 days as therapeutic dose (TD); d) a half therapeutic dose (HD); and e) a double therapeutic dose (DD). Pre-implantation death in MTZ-treated groups was not significantly different from controls. However, drug treatments significantly increased the frequency of post-implantation deaths and the dominant lethals were ranged between 12.0 % and 17.8 %.

Animals↗

PubMed2001

Synaptic behaviour of some structural and numerical chromosome anomalies in female and male rats (Rattus norvegicus).

The processes of synapsis and synaptic adjustment have been detected in some structural and numerical anomalies in two female rat foetuses and in one male rat in the course of a study on X-ray genotoxicity. The synaptic characteristics and adjustment of one pericentric inversion and a deletion have been analysed by electron microscopy in synaptonemal complex spreads from two female foetuses, and the synaptic behaviour of a trisomy has been studied in a testicular biopsy from an adult male. In a large proportion (from 50% to 90%) of the analysed cells, the abnormal meiotic configuration could not be detected either because the anomaly was present in mosaic from trisomy or because synaptic adjustment had already taken place (inversion) or as result of a combination of two of the above (deletion).

Animals↗

PubMed2000

Effects of ionizing radiation on oocytes of prepubertally irradiated rats.

PURPOSE: To characterize the effects of ionizing radiation on the immature oocytes of prepubertal rats aged 16-20 days old. MATERIALS AND METHODS: The abdomen of Sprague Dawley (SD) female rats was exposed to 0, 1 and 2 Gy of X-rays. The effects were analysed when the animals became adults (80 days old) using as parameters the number of implantation sites, embryonic loss, dominant lethality and the synaptonemal complex (SC) analysis of F1 female foetuses. RESULTS: A statistically significant decrease in the fertility of the 2 Gy irradiated rats was observed. However, the SC analysis of F1 female foetuses showed no cytogenetic damage that could be attributed to radiation. CONCLUSIONS: A reproductive effect was demonstrated but no inherited genetic damage was detected by SC analysis in female foetuses of irradiated mothers.

Animals↗

PubMed1999

The ompB operon partially determines differential expression of OmpC in Salmonella typhi and Escherichia coli.

Expression of the Escherichia coli OmpC and OmpF outer membrane proteins is regulated by the osmolarity of the culture media. In contrast, expression of OmpC in Salmonella typhi is not influenced by osmolarity, while OmpF is regulated as in E. coli. To better understand the lack of osmoregulation of OmpC expression in S. typhi, we compared the expression of the ompC gene in S. typhi and E. coli, using ompC-lacZ fusions and outer membrane protein (OMP) electrophoretic profiles. S. typhi ompC expression levels in S. typhi were similar at low and high osmolarity along the growth curve, whereas osmoregulation of E. coli ompC in E. coli was observed during the exponential phase. Both genes were highly expressed at high and low osmolarity when present in S. typhi, while expression of both was regulated by osmolarity in E. coli. Complementation experiments with either the S. typhi or E. coli ompB operon in an S. typhi DeltaompB strain carrying the ompC-lacZ fusions showed that both S. typhi and E. coli ompC were not regulated by osmolarity when they were under the control of S. typhi ompB. Interestingly, in the same strain, both genes were osmoregulated under E. coli ompB. Surprisingly, in E. coli DeltaompB, they were both osmoregulated under S. typhi or E. coli ompB. Thus, the lack of osmoregulation of OmpC expression in S. typhi is determined in part by the ompB operon, as well as by other unknown trans-acting elements present in S. typhi.

Amino Acid Sequence↗

PubMed1998

Effects on female fertility and germinal cells in prepubertal and adult rats (Rattus norvegicus) after X-ray irradiation.

In this work we analyse the effects of ionizing radiation in prepubertal and adult female rats, using as parameters, implantation sites, embryonic loss, and synaptonemal complex (SC) analysis of the female F1 of the pregnant rats. Our preliminary results show a decrease statistically significant in fertility of irradiated groups, but cytogenetic analysis did not shown any inherited damage attributed to radiation. At the same time, our results seem to indicate a higher resistance of oocytes from prepubertal rats and support the possible use of GnRH agonists as oestrus cycle suppressors to turn adult rats into gonadal quiescence.

Aging↗

PubMed1998

The synaptic process in Locusta migratoria spermatocytes by synaptonemal complex analysis.

We describe the synaptic process during meiotic prophase in spermatocytes from Locusta migratoria, using synaptonemal complex (SC) spreads analyzed by light (LM) and electron (EM) microscopy. At leptotene, a stage of short duration, unpaired axial elements begin to be assembled. Synapsis starts at zygotene, beginning usually at the terminal regions of the bivalents, either at the proximal, centromeric end or at the distal, non-centromeric end; interstitial initiation of synapsis was only occasionally observed in the longer chromosomes. Pairing is asynchronous, and shorter chromosomes are the first to complete synapsis. At pachytene all bivalents are fully synapsed. Diplotene is characterized by the progressive fragmentation of SCs; fragmentation is asynchronous, and affects mainly the longer chromosomes, while the shorter ones maintain their morphology up to late diplotene.

Animals↗