Biomedical subjects

A Genescà

Publications and source records attributed to A Genescà.

At least 19 recordsLinked to original sources

PubMed2003

Radiation-induced chromosome breaks in ataxia-telangiectasia cells remain open.

PURPOSE: To determine if broken chromosome-end healing mechanisms through the addition of new telomeric sequences exist in cells having difficulties in rejoining the ends of broken chromosomes. MATERIALS AND METHODS: A full-colour painting protocol of all human chromosomes by FISH was combined with a telomeric and centromeric labelling using PNA probes to characterize the rejoining pattern and telomere status of radiation-induced chromosome breaks in ataxia-telangiectasia (A-T) and normal lymphoblastoid cell lines. RESULTS: It was first established that the cell lines used for chromosome healing analysis were chromosomally stable. FISH analysis provided evidence that the frequency of deleted chromosomes, apparently unrejoined, was much higher in A-T than in normal cells, as expected by the role of ATM in cell-cycle control, as well as in DNA repair. In spite of their high frequency, broken chromosome ends in A-T cells do not seem to act as substrates for telomerase since additional terminal telomere sequences (more than the 92 expected pairs) indicative of chromosome healing were never observed. Broken chromosome ends in A-T cells remained open. CONCLUSION: The disability of cells to rejoin broken chromosome ends does not lead to the healing of DSBs by the acquisition of new telomeric sequences.

Ataxia Telangiectasia↗

PubMed2001

Non-disjunction and chromosome loss in gamma-irradiated human lymphocytes: a fluorescence in situ hybridization analysis using centromere-specific probes.

Centromere-specific DNA probes for chromosomes 4, 7 and 18 were used to simultaneously analyze chromosome loss, non-disjunction, breaks within the labeled region, and nucleoplasmic bridges induced by gamma rays in binucleated human lymphocytes. The doses used were 0, 1, 2 and 4 Gy, and approximately 1000 cells were scored per dose. Micronucleus frequency increased in a linear-quadratic fashion. For chromosome loss, significant increases were observed at 2 and 4 Gy, whereas for non-disjunction significant increases were observed at 1 Gy; thus non-disjunction allowed us to detect the effects of radiation at a lower dose than chromosome loss. The use of centromere-specific probes allowed discrimination between the clastogenic and aneugenic effects of ionizing radiation. The analysis of chromosome loss, not taking fragmented signals into account, ensures the detection of an aneugenic effect, which was not possible using pancentromeric probes. The frequency of chromosome breakage within the labeled regions was higher in nuclei than in micronuclei, suggesting an increase in the engulfment of chromosomal material by nuclei as a consequence of the presence of cytochalasin B in the cultures. Chromatin filaments connecting main nuclei, the so-called nucleoplasmic bridges, were observed in irradiated samples, and are a manifestation of rearranged chromosomes producing anaphase bridges.

Centromere↗

PubMed1999

Absence of chromosomal instability in spermatozoa of men affected by testicular cancer.

Testicular germ cell cancer affects mainly young men. It is the most frequent type of cancer in 20-35 year old men. Since cancer treatment using antineoplasic drugs and ionizing radiation has a negative effect on the function of the gonads, testicular cancer patients are offered the opportunity to cryopreserve their semen samples before the beginning of therapy. For this reason it would be of interest to know whether there is chromosome instability in their spermatozoa prior to any treatment. Using the interspecific human-hamster fertilization system, we have analysed a total of 340 chromosome complements from spermatozoa of control donors and 320 chromosome complements from testicular cancer patients. There were no significant differences in the frequencies of chromosomal aberrations between controls and cancer patients (9.7 and 10.3% respectively; P = 0.4921). Our results indicate that spermatozoa from untreated testicular cancer patients do not show an increased chromosomal instability as compared to control donors.

Adult↗

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↗

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

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

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

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

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↗

PubMed1992

Cytogenetic studies in motile sperm from normal men.

Most studies on human sperm chromosomes from normal men involve the heterologous fertilization of zona free hamster eggs by unselected human sperm. In this work, we have performed cytogenetic studies of highly motile sperm, selected by a swim-up method. A total of 505 motile human sperm complements from three normal donors was analysed. The total frequency of sperm with chromosomal abnormalities (10.9%; 6.9% structural aberrations and 4.0% aneuploidy) and the sex ratio (50.4% X:49.6% Y) were similar to those obtained from whole semen samples. Our results indicate that the selection of motile sperm does not imply chromosomal selection.

Adult↗

PubMed1992

Repair of human sperm chromosome aberrations in the hamster egg.

In order to study the repair capacity of fertilized hamster eggs for the lesions present or induced in human sperm, we have examined the potentiating effect of caffeine, a DNA repair inhibitor, on the frequency and types of sperm chromosome aberrations. Sperm samples were donated by an individual treated with chemotherapy for a testicular cancer 3 years previously. Exposure of spermatozoa and inseminated oocytes to caffeine led to an increase of sperm chromosome aberrations, indicating that the damage to human sperm can be repaired in untreated hamster egg cytoplasm. The potentiating effect of caffeine was mainly reflected in an increase of unrejoined aberrations, indicating that the formation of chromosomal rearrangements is also inhibited. Since both chromatid-type and chromosome-type aberrations increase after treatment with caffeine, damage to human sperm can probably be repaired inside the hamster egg cytoplasm by pre- and post-replication repair mechanisms.

Animals↗

PubMed1991

Chromosome abnormalities in human spermatozoa after albumin or TEST-Yolk capacitation.

Cytogenetic studies were made on 328 spermatozoa from three individuals using either fresh semen samples capacitated in Biggers, Whitten and Whittingham (BWW) medium plus human serum albumin (BWW + HSA) or semen samples preserved at 4 degrees C in TEST-Yolk buffer. A total of 261 sperm karyotypes were obtained in a series of experiments in which half of each sample was capacitated in BWW + HSA and the other half in TEST-Yolk buffer at 4 degrees C for 2 days; 123 and 138 sperm karyotypes were obtained from the two capacitation methods respectively. Neither the frequency of sperm chromosomal abnormalities nor the sex ratio was significantly different after each capacitation methods. In one individual, however, the sex ratio (19X:32Y in the fresh sample and 49X:28Y in the preserved sample) did show a significant difference. In three experiments with semen samples from a single individual capacitated at 4 degrees C for 1, 2 or 3 days in TEST-Yolk buffer we obtained 33, 30 and 34 sperm karyotypes respectively. No significant differences in the sex ratio was exhibited between these experiments; the number of chromosome anomalies was too low to allow statistical analysis. Our results suggest that TEST-Yolk capacitation for 1, 2 or 3 days does not induce significant variations in the frequency and type of chromosomal abnormalities in human spermatozoa.

Animals↗

PubMed1990

Significance of structural chromosome aberrations in human sperm: analysis of induced aberrations.

A significant increase in the incidence of structural chromosome anomalies has been observed in the sperm of patients treated with radio and/or chemotherapy for different types of cancer when analyzed by the interspecific fertilization of hamster eggs. The analysis of these aberrations shows that while in controls only 9.4% of structural abnormalities are of the stable type, in treated patients this figure increases to 39.3%, thus indicating that the anomalies have not been produced during the fertilization of the hamster egg. However, it is possible that part, or even most, of the breaks appear as a result of a reduced repair capacity of sperm chromosomes in the cytoplasm of the hamster egg.

Antineoplastic Agents↗

PubMed1990

Lymphocyte and sperm chromosome studies in cancer-treated men.

To evaluate the reliability of the quantitative extrapolation of the long-term effect of cancer therapies from somatic cells to germ cells, we compared the frequency of chromosome abnormalities in 303 lymphocytes from four individuals treated with radio- and/or chemotherapy 5-18 years earlier with the frequency in 422 spermatozoa from the same individuals. The mean frequency of structurally abnormal complements was much higher in germ cells than in somatic cells (P = 2.08 x 10(-6)). The fact that spermatogenic cells share cytoplasm is suggested as a possible factor in the increased viability of germ cells with chromosome aberrations. In addition, in spermatozoa the incidence of structural chromosome abnormalities was much higher in treated individuals than in controls (P less than 0.00060), while in lymphocytes no statistically significant differences could be observed. This observation and the apparent lack of relationship between individual frequencies in the two kinds of cells suggest that the long-term effect of anti-tumor treatments on germ cells cannot be extrapolated from the analysis of somatic cells.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed1990

Human sperm chromosomes. Long-term effect of cancer treatment.

The long-term cytogenetic effect of radio- or chemotherapy or both on male germ cells was evaluated by study of the chromosomal abnormalities in spermatozoa of four men treated for cancer 5-18 years earlier. The cytogenetic analysis of 422 sperm metaphases showed no differences in the aneuploidy rate. The incidence of structural chromosome aberrations was 14.0%, however, which is much higher than in controls. Thus, the high incidence of structurally aberrant spermatozoa observed in our long-term study indicates that antitumoral treatments affect stem-cell spermatogonia and that aberrant cells can survive germinal selection and produce abnormal spermatozoa.

Antineoplastic Agents↗

PubMed1990

Sperm chromosome studies in individuals treated for testicular cancer.

Sperm chromosome studies have shown that patients treated with chemotherapy for testicular cancer have a much higher incidence of chromosome abnormalities than patients treated for other types of cancer or than controls. In two out of four cases, penetration of zona-free hamster eggs was close to zero, indicating that after 2-7 years after treatment the functional capacity of the sperm had not been recuperated. The cytogenetic study of the spermatozoa shows that many of the abnormalities observed corresponded to structural aberrations that may not have a pathogenic effect in the production of abortions or of children with chromosome abnormalities.

Adult↗

PubMed1989

Expression of fragile sites in human sperm and lymphocyte chromosomes.

Sperm and lymphocyte chromosome studies in a normal, fertile male have shown a high degree of coincidence between chromosome lesions and fragile sites in both types of cells. In this donor we also found that some fragile sites expressed in sperm chromosomes coincided with those expressed in lymphocyte chromosomes. These results indicate that the chromosome lesions expressed in sperm do not occur at random and that they are not technical artifacts. The fragility expression in sperm chromosomes could reflect in vivo conditions. The presence in some sperm metaphases of acentric fragments suggests that chromosome fragility can result in the loss of chromosome fragments or give rise to de novo structural rearrangements. However, the incidence of sperm with chromosomal abnormalities observed in this man was within the normal range.

Adult↗