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R Miró

Publications and source records attributed to R Miró.

At least 37 records · Page 2Linked to original sources
PubMed1998

A new assay to asses aneuploidy in human-hamster embryos.

Fluorescent in situ hybridization using three chromosome-specific centromeric human DNA probes was used to analyze the aneuploidy frequency in human-hamster two-cell embryos. With these techniques first mitotic division errors due to the effects of physical or chemical agents on human spermatozoa, such as non-disjunction and anaphase lag, can be easily detected. In control samples the estimated frequency of non-disjunction and anaphase lag was 3.4%. This assay can also detect premeiotic or meiotic errors. We estimated the same frequency (3.4%) for disomy, whereas monosomy was not found.

Aneuploidy↗
PubMed1998

Analysis of 3p allelic losses in renal cell carcinomas: comparison with cytogenetic results.

We performed a study of loss of heterozygosity (LOH) at 3p by restriction fragment length polymorphism analysis in a series of 22 renal tumors. In 11 cases, molecular results could be compared with those of cytogenetic studies. The highest frequency of allelic losses at 3p was seen in clear cell non-papillary renal tumors, whereas none of the papillary renal cell carcinomas showed LOH at 3p. Allelic losses on 3p were found to be independent of tumor grade or stage or both. One case analyzed showed a discrepancy between cytogenetic and LOH studies. This tumor displayed rearrangements of chromosome 3 and no LOH at the c-RAF-1 (close to the Von Hippel Lindau gene) locus.

Carcinoma, Renal Cell↗
PubMed1997

Biological dosimetry in simulated in vitro partial irradiations.

The assessment by biological dosimetry of the dose received in cases of partial-body exposure to ionizing radiation can be underestimated because irradiated lymphocytes are mixed with non-irradiated ones. To determine if the exposure affects the whole body or only part of it, it may be useful to know the distribution of cells with more than one dicentric chromosome. We established a dose-effect calibration curve for X-rays by analysis of chromosome aberrations. Moreover, in the present work, 20 partial irradiations for four different doses of X-rays (2, 3, 4 and 5 Gy) have been simulated by mixing irradiated and non-irradiated blood in different proportions. In all cases, the 95% confidence intervals of the estimated dose included the real dose of irradiation. However, some difficulties were found for the estimation of the fraction of irradiated cells. In the present study, D0 = 3.8 allows to obtain the best fit between the estimated and the real fraction of irradiated cells.

Cells, Cultured↗
PubMed1997

Hamster origin of metaphases with multiple chromosome rearrangements in first cleavage human-hamster embryos.

Laboratories using the human sperm-hamster egg fertilization system to analyse sperm chromosomes obtain, sporadically, metaphases with multiple aberrations. Due to the high number of aberrations, these metaphases cannot be fully karyotyped. In some of them, one or several human chromosomes can be identified, guaranteeing the human origin of the whole metaphase. However, in others, none of the chromosomes can be recognized as human. This latter type of grossly rearranged metaphases is characterized by complex chromatid exchanges, multifragmented chromosomes and pulverized chromosome material. Using fluorescent in-situ hybridization techniques (FISH) with either human or hamster genomic DNA probes, we examined the origin of this second type of metaphase with multiple chromatid exchanges and fragmented chromosomes. Our study demonstrates that all of them hybridize with hamster genomic DNA probes and not with human DNA, proving their hamster origin. Since some of these metaphases seem to be diploid, we suggest that they may arise from hamster eggs that have failed to complete meiosis and have not extruded the second polar body.

Animals↗
PubMed1997

Familial complex chromosome rearrangement ascertained by in situ hybridisation.

A complex familial chromosome translocation has been ascertained by combining classical cytogenetics and CISS (chromosomal in situ suppression). Cytogenetic analysis of a chorionic villus sample with G banding showed a 47,XX,-2, +der(2)t(2;22),+der(22)t(2;22) karyotype. Analysis of peripheral blood lymphocytes from the parents by G banding and CISS showed a more complex translocation in the father: 46,XY,-2,-11,-22, +der(2) t(2;11)(q13;q23), +der(11) t(11;22) (q23;q11.2), +der(22) t(2;22) (q13;q11.2). Definitive analysis of cultured amniotic fluid cells showed a double partial trisomy of chromosomes 11 and 22. The couple decided to continue the pregnancy. The fetal karyotype was confirmed at birth. Clinical abnormalities present in our patient were typical of an unbalanced 11;22 translocation. Our findings confirm that chromosome painting techniques allow a better characterisation of complex chromosome rearrangements which may be difficult to detect in G banded karyotypes.

Abnormalities, Multiple↗
PubMed1997

Dose-response relationship for the induction of chromosomal abnormalities in gamma-irradiated human spermatozoa.

The cytogenetic effects of in vitro irradiation on human spermatozoa have been studied by the interspecific in vitro fertilization system between human sperm and hamster oocytes. Semen samples from three healthy men were irradiated at doses of 0.00, 0.10, 0.25, 0.50, 1.00, 2.00, and 4.00 Gy. A total of 340 chromosome complements derived from non-irradiated human spermatozoa and 987 complements from irradiated spermatozoa were analyzed after sequential uniform stain-G banding. Both the frequency of spermatozoa with structural chromosome abnormalities, and the incidence of such abnormalities per cell, showed strong dose-effect relationships that were best expressed by linear-quadratic equations: Y = 0.06413(+/-0.00475) + 0.1982(+/-0.00833)D - 0.00763(+/-0.00204)D2 and Y = 0.07385(+/-0.00838) + 0.23329(+/-0.03124)D + 0.02317(+/-0.00955)D2, respectively. When analyzing separately unrejoined and rejoined structural abnormalities, we found that the incidence of unrejoined lesions was four times higher than the incidence of rejoined anomalies. The induction of unrejoined abnormalities showed a linear, dose-dependent increase, whereas the incidence of rejoined abnormalities showed a quadratic, dose-dependent increase. The distribution of radiation-induced breakpoints was also analyzed. Breakpoints were found to be randomly distributed among chromosomes, but a clustering of breakpoints in G-negative bands was found: 71.5% of breakpoints were located in G-negative bands, and 28.5% in G-positive bands.

Adult↗
PubMed1996

Decreased sensitivity to the cytogenetic effects of bleomycin in individuals occupationally exposed to ionizing radiation.

In the present work, 12 individuals occupationally exposed to ionizing radiation and 11 unexposed ones were studied to determine the cytogenetic effect of a challenge dose of bleomycin on their phytohemagglutinin stimulated lymphocytes. After bleomycin treatment, the frequencies of chromatid breaks and gaps were significantly lower in the exposed population (p < 0.025 for both types of chromatid alterations). These results could indicate that occupational exposure to ionizing radiation can induce an adaptive response that can be detected by a subsequent treatment with bleomycin.

Adaptation, Physiological↗
PubMed1996

Chromosome aberrations in human spermatozoa treated with Ca2+ ionophore A23187.

Incorporation of A23187 ionophore into the human-hamster fertilization system clearly improves the ability of human spermatozoa to penetrate zona-free hamster oocytes. Thus, an increasing number of laboratories working in human sperm cytogenetics have substituted classical incubation with Biggers-Whitten-Whittingham (BWW) medium plus human serum albumin (HSA) by pretreatment of spermatozoa with calcium ionophore A23187 which directly induces the acrosome reaction in spermatozoa. However, there have been no formal studies on the effects of this ionophore pretreatment. To determine whether calcium ionophore could affect the cytogenetic characteristics of human spermatozoa we compared A23187-treated spermatozoa with controls (only incubated with BWW + HSA) by analysing a total of 447 sperm chromosome complements from two normal donors. Our results show that there are no statistical differences in the frequency and the types of human sperm chromosomal abnormalities between the two methods of sperm treatment. Thus, ionophore A23187 seems not to affect the cytogenetic characteristics of human spermatozoa, and the results of laboratories using either sperm capacitation in BWW + HSA or acrosome reaction by calcium ionophore can be compared.

Acrosome↗
PubMed1996

Analysis of radiation-induced micronuclei in two-cell human-hamster embryos using telomeric and centromeric FISH probes.

Simultaneous, fluorescent in situ hybridization using a centromeric human alpha satellite DNA probe and a telomeric DNA probe was used to analyze the chromosome content of micronuclei induced in two-cell human-hamster embryos by in vitro gamma-ray irradiation of human spermatozoa. In unirradiated samples, about 26% of micronuclei were centromere positive, indicating that both structural chromosome aberrations and numerical changes are involved in the spontaneous production of micronuclei. After exposure of spermatozoa to radiation, a significant increase in the number of micronuclei was found. About 77% of induced micronuclei contained only telomeric signals suggesting that they originated from acentric fragments. However, both centromere-positive and centromere-negative micronuclei increased with radiation dose. These results are consistent with the well known clastogenic effect of ionizing radiation and with its weak aneugenic effect.

Animals↗
PubMed1995

Cytogenetic characterization of a familial papillary renal cell carcinoma.

We describe the first case of a familial renal cell carcinoma cytogenetically characterized as a papillary renal cell carcinoma. Cytogenetic and molecular studies were performed on primary renal cell carcinomas and normal kidney tissue from two members of the same family. Both patients showed a normal constitutional karyotype. The two tumors analyzed from the first patient showed the numerical chromosome alterations characteristic of papillary renal cell carcinomas. From the four tumors analyzed in the second patient, three of them presented the cytogenetic pattern of papillary renal cell tumors, and the fourth showed only structural chromosome abnormalities with the presence of a del(7)t(7;7) or dup(7) in all metaphases analyzed. Chromosome 3 was cytogenetically unaffected in all tumors from both patients, and restriction fragment length polymorphism analysis performed with probe pEFD145 (3p21.1-p23) did not detect any loss of heterozygosity.

Adult↗
PubMed1995

Induction of micronuclei in human sperm-hamster egg hybrids at the two-cell stage after in vitro gamma-irradiation of human spermatozoa.

The efficiency of the micronucleus test to assess radiation-induced chromosomal damage in human spermatozoa has been investigated. Micronuclei were scored in human sperm-hamster egg hybrids at the two-cell stage, after exposure of human spermatozoa to in vitro gamma-rays at doses of 0.00, 0.10, 0.25, 0.50, 1.00, 2.00, and 4.00 Gy. The relationship between the yield of micronuclei per two-cell stage as well as the percentage of two-cell stages with micronuclei and the different doses of irradiation were fitted to linear equations. To evaluate whether scoring micronuclei is useful for the quantification of chromosomal damage occurring in human spermatozoa, induced micronuclei at the different doses of sperm irradiation were compared to the induction of breaks and fragments in sperm-derived chromosomes. After interspecific fertilization of zona-free hamster oocytes by irradiated spermatozoa, a total of 699 fertilized eggs at the two-cell stage and a total of 387 sperm-derived complements were analyzed. The incidence of fertilized eggs with micronuclei at the two-cell stage coincided well with the incidence of sperm-derived chromosome breaks and fragments (e.g., 8.9% vs. 6.7% in the 0.25 Gy group and 52.8% vs. 58.6% in the 4.00 Gy group). A similar correlation was found between the number of micronuclei per two-cell stage and the number of breaks and fragments per sperm complement (0.09 vs. 0.07 in the 0.25 Gy group and 0.71 vs. 0.81 in the 4.00 Gy group). The results show that this test system can be used for the quantification of spontaneous or induced chromosomal damage in human spermatozoa.

Animals↗
PubMed1995

Establishment and validation of a dose-effect curve for gamma-rays by cytogenetic analysis.

A dose-effect curve obtained by analysis of dicentric chromosomes after irradiation of peripheral blood samples, from one donor, at 11 different doses of gamma-rays is presented. For the elaboration of this curve, more than 18,000 first division metaphases have been analyzed. The results fit very well to the linear-quadratic model. To validate the curve, samples from six individuals (three controls and three occupationally exposed persons) were irradiated at 2 Gy. The results obtained, when compared with the curve, showed that in all cases the 95% confidence interval included the 2 Gy dose, with estimated dose ranges from 1.82 to 2.19 Gy.

Blood↗
PubMed1995

Occupational exposure to radiation induces an adaptive response in human lymphocytes.

The in vitro pretreatment of phytohaemagglutinin stimulated human lymphocytes with tritiated thymidine or with low doses of X-rays induces a response that makes these cells less susceptible to further genetic damage induced by subsequent high doses of radiation. This phenomenon has been called 'Adaptive Response' because it is similar to the one described in E. coli. In the present study, we describe that lymphocytes irradiated in vitro at 2 Gy, from individuals occupationally exposed to X and gamma rays, show lower frequencies of dicentrics than those from non-occupationally exposed individuals irradiated in the same conditions. Our results could indicate that an adaptive response can also be induced in lymphocytes in vivo by very low occupational doses of radiation, and that for biological dosimetry purposes it is necessary to know the individual's history of exposure to mutagens.

Adaptation, Physiological↗
PubMed1995

Human origin of micronuclei in human x hamster two-cell embryos.

Using fluorescence in situ hybridization techniques with either human or hamster genomic DNA probes, we studied the origin of micronuclei in two-cell hybrid embryos obtained from hamster oocytes and gamma-irradiated human spermatozoa. Our study demonstrates that over 99% of micronuclei hybridize with human DNA probes and not with hamster DNA, revealing their human origin. Thus, the micronucleus test represents a good method to evaluate genetic damage in human germ cells, since it is simpler and faster than sperm chromosome studies.

Animals↗
PubMed1993

Cytogenetic analysis of lymphocytes from hospital workers occupationally exposed to low levels of ionizing radiation.

Cytogenetic studies were performed in lymphocytes from hospital workers exposed to low doses of radiation (1.6-42.71 mSv). When compared with controls, exposed workers showed a significant increase in structural chromosome-type aberrations, acentric fragments being the most frequent alteration. Our results suggest that acentric fragments are good indicators of exposure to very low doses of radiation, although no dose-effect correlation was observed. The incidence of numerical abnormalities (hyperdiploidy) was significantly increased.

Adult↗
PubMed1993

A case of transitional cell carcinoma of the bladder with a del(9)(q11q21.2).

Monosomy for chromosome 9, as well as loss of heterozygosity for markers on this chromosome, has been detected in a high percentage of transitional cell carcinomas (TCC) of the bladder. We report a case of a TCC of the bladder with an interstitial del(9)(q11q21.2) that could be indicative of the presence of a putative tumor-suppressor gene related to bladder tumor progression. To elucidate the role of chromosome 9 in bladder tumors, it would be interesting to study a possible loss of heterozygosity in this chromosome region.

Carcinoma, Transitional Cell↗