Biomedical subjects

O Echeverría

Publications and source records attributed to O Echeverría.

6 recordsLinked to original sources

PubMed1999

Evidence for estrogen receptor expression in germ cell and somatic cell subpopulations in the ovary of the newly hatched chicken.

Estrogens are involved in the gonadal morphogenesis of vertebrates, and almost all hormonal effects of 17beta-estradiol are mediated through specific receptors. At the time of sexual differentiation in the chicken, or even before, there is evidence of the presence of estrogen receptors and the secretion of 17beta-estradiol. However, no information is available regarding the cellular types that express the estrogen receptor in the immature chick ovary. The present study analyzes estrogen receptor expression in germ and somatic cells of the ovary in the newly hatched chicken. Highly purified cell subpopulations of germ and somatic cells were evaluated for specific 17beta-estradiol nuclear binding. In addition, the estrogen receptor was localized at the ultrastructural level by the immunogold technique. Finally, reverse transcription and polymerase chain reaction procedures detected a steady-state level of mRNA for the estrogen receptor. Somatic cells including typical steroidogenic cells showed specific 17beta-estradiol nuclear binding, displayed the estrogen receptor, and possessed estrogen receptor transcripts. The same result was observed in primary oocytes, together with the ultrastructural localization of estrogen receptor in extended chromatin filaments. Our experimental data support the hypothesis that estrogens are involved in the function of somatic and germ cells subpopulations in the immature chicken ovary.

Animals↗

PubMed1999

Correlation of the changes of the frequency of perichromatin granules with the RNA content of the interchromatin region of uterine cells in normal and ovariectomized rats. A high resolution in situ hybridization and stereological study.

The changes in the number of perichromatin granules (PCG) and the alterations in the RNA content of the interchromatin and perichromatin regions caused by ovariectomy and estradiol injection were studied in rat endometrial fibroblast and myometrial muscle cells. Twelve rats were divided in four groups. A group of rats was fixed without any treatment, the other three groups were ovariectomized and processed 21 days after the operation. One of them was studied without further treatment, and two groups were injected intraperitoneally with 20 micrograms of 17 beta-estradiol hemisuccinate and fixed 0.5 and 2 h after the injection. The frequency of PCG was evaluated in preparations stained with EDTA procedure preferential for RNP. The alterations of RNA content were estimated by post-embedding high resolution in situ hybridization using a total DNA probe labeled with biotinilated nucleotides revealed by streptavidin coupled with 10 nm gold grains. Most of the non-nucleolar labeling is associated to RNP containing fibrils. Perichromatin and interchromatin granules are labeled to a lesser extent. Castration brings about a reduction of the number of PCG and of the numerical density of labeling in endometrial fibroblasts. The injection of estradiol causes a rapid increase in both parameters. On the contrary, the frequency of PCG and intensity of labeling of epithelial endometrial cells and in muscle cells increase after ovariectomy and are reduced by estradiol administration. These results suggest that estradiol may affect differentially various types of target cells in the same organ, and also that PCG are not the only nuclear compartment of pre-mRNA or mRNA altered by the changes in estradiol, the RNP containing fibrils located in the perichromatin and in the interchromatin regions are also involved.

Animals↗

PubMed1996

Three-dimensional analysis of the arrangement of compact chromatin in the nucleus of G0 rat lymphocytes.

The arrangement of compact chromatin of G0 lymphocytes was studied in three-dimensional reconstructions of the ensemble of the chromatin and of individual compact chromatin bodies. Rat spleen was serially cut and sections were contrasted with procedures preferential for DNA. Electron microscopy images were digitized, processed, and displayed using a commercial software package, complemented by a system for three-dimensional reconstruction and analysis developed by us on an IBM-compatible microcomputer provided with an image acquisition board. The reconstructions showed a continuous layer of compact chromatin in contact with the nuclear envelope that prevents the automatic recognition of individual chromatin clumps. The ensemble of the arrangement of compact chromatin was found to be very similar in different lymphocytes. After morphological filtering procedures, the initial mass was divided into individual bodies of compact chromatin, which were tagged. Most of these bodies contact the nuclear envelope. The number of bodies as well as the number of contacts with the envelope are similar and correspond to a haploid number of chromosomes. The largest body is always the one containing nucleolus-associated chromatin. When the cell has two nucleoli, the nucleolus-associated chromatin bodies contact the envelope in diametrically opposed areas. This feature was also described in rat liver cells. It is concluded that: (a) the individualized compact chromatin bodies do not correspond to an entire chromosome or to a pair of chromosomes; (b) the arrangement of compact chromatin is not identical in each G0 lymphocyte, but there are patterns that are repeated with limited changes; and (c) there are common features that appear in different cell types of individuals of the same species.

Animals↗

PubMed1991

Effects of testosterone on nuclear ribonucleoprotein components of prostate epithelial cells.

The changes of the nuclear components caused by castration and testosterone injection were studied in epithelial cells of the ventral prostate of the rat. Castration drastically diminishes the nuclear and nucleolar volume, as well as the fraction of the nuclear volume occupied by non-nucleolar ribonucleoprotein (RNP) fibrils. However, in castrated animals the frequency of perichromatin granules (PCG) is 79% higher than in controls. Testosterone injection causes a reduction of the number of PCG to 33% of the castrated level in 15 min, and increases the non-nucleolar RNP fibrils. Other parameters such as nuclear and nucleolar volume and the relative volume of the compact chromatin present only small changes in a period of 2 h following the hormone administration. High resolution quantitative autoradiography demonstrates that the transportation of previously synthesized RNA increases steeper than the RNA synthesis. All these effects are similar to those caused by ovariectomy and estradiol injection on the nuclear structures of endometrial epithelial cells. These similarities and other observations suggest that PCGs contain mRNA, of a few genes, stored in the nucleus by a restriction of its transportation to the cytoplasm.

Animals↗

PubMed1989

Evidence of repetitive patterns of chromatin distribution in cell nuclei of rat liver.

Samples of rat livers were fixed in glutaraldehyde, contrasted en bloc with phosphotungstic acid, embedded in an epoxy resin and serially sectioned. The study of three-dimensional models of 20 complete nuclei shows that all of them share some general features: they have more than one nucleolus (2-4), an irregular layer of compact chromatin adjacent to the nuclear membrane and well-delimited clumps of chromatin both in the nuclear sap and surrounding the nucleoli. A space of 8 sections containing the central nucleolus and a lateral one was studied in detail. In this space, 8 clumps of compact chromatin were found in 17 nuclei and 9 clumps in the other 3 nuclei. No other number of clumps was found in those zones. In all the nuclei studied the compact chromatin surrounding the central nucleolus contacts the nuclear envelope. This contact takes place in a region almost diametrically opposed to the lateral nucleolus in 13 nuclei. In 7 nuclei, these structures were at angles between 50 and 125 degrees. These results support the existence of nonrandom repetitive patterns of chromatin distribution in liver cells.

Animals↗

PubMed1987

A simple staining method for chromatin in electron microscopy compatible with serial sectioning.

The study of the disposition of chromatin in the interphasic nucleus requires the combination of serial sectioning and a specific or preferential chromatin staining. The staining of chromatin with phosphotungstic acid (PTA) chromatin was originally employed on sections of glycolmethacrylate-embedded samples. As it is very difficult to obtain ribbons with this resin, we introduced a modification which consisted of staining the tissue after fixation and before dehydration, in order that epoxy resins can be applied. Several procedures were tried and the best results were attained in the following way. Standard fixation of samples no thicker than 1 mm was carried out with 2.5% glutaraldehyde at pH 7.2 for 1 or 2 h at room temperature; tissues were then rinsed three times with 0.2N HCl adjusted to pH 2.1-2.3 with 0.2N NaOH for 15 min. Staining was held with 3% W/V PTA in 1N HCl adjusted to the same pH. Samples were dehydrated in gradual ethyl alcohol concentrations and Epon-embedded. Post-staining on sections with uranyl-acetate and lead-citrate or other methods may be used to demonstrate other cell components and their relations to chromatin.

Animals↗