Number Of Metacentric Chromosomes Research Articles

Intrinsic Radiosensitivity and Cellular Characterization of 27 Canine Cancer Cell Lines.

Canine cancer cell lines have progressively been developed, but are still underused resources for radiation biology research. Measurement of the cellular intrinsic radiosensitivity is important because understanding the difference may provide a framework for further elucidating profiles for prediction of radiation therapy response. Our studies have focused on characterizing diverse canine cancer cell lines in vitro and understanding parameters that might contribute to intrinsic radiosensitivity. First, intrinsic radiosensitivity of 27 canine cancer cell lines derived from ten tumor types was determined using a clonogenic assay. The 27 cell lines had varying radiosensitivities regardless tumor type (survival fraction at 2 Gy, SF2 = 0.19–0.93). In order to understand parameters that might contribute to intrinsic radiosensitivity, we evaluated the relationships of cellular radiosensitivity with basic cellular characteristics of the cell lines. There was no significant correlation of SF2 with S-phase fraction, doubling time, chromosome number, ploidy, or number of metacentric chromosomes, while there was a statistically significant correlation between SF2 and plating efficiency. Next, we selected the five most radiosensitive cell lines as the radiosensitive group and the five most radioresistant cell lines as the radioresistant group. Then, we evaluated known parameters for cell killing by ionizing radiation, including radiation-induced DNA double strand break (DSB) repair and apoptosis, in the radiosensitive group as compared to the radioresistant group. High levels of residual γ-H2AX foci at the sites of DSBs were present in the four out of the five radiosensitive canine cancer cell lines. Our studies suggested that substantial differences in intrinsic radiosensitivity exist in canine cancer cell lines, and radiation-induced DSB repair was related to radiosensitivity, which is consistent with previous human studies. These data may assist further investigations focusing on the detection of DSB for predicting individual response to radiation therapy for dogs, regardless of tumor type.

Robertsonian translocation in the house mouse: a tale of chromosomal speciation

The subspecies Mus musculus domesticus has a very high chromosome number variability for the presence, in different populations, of different numbers of metacentric chromosomes. These metacentrics are derived by Robertsonian fusion, i.e. the joining of two acro/telocentrics at the centromeres. Since the discovery in 1969 by Alfred Gropp of the first chromosomal variant in an isolated mouse population of the Swiss Poschiavo Valley, more than 100 geographically distinct chromosomal races with metacentrics fixed in homozygosity have been described. The friendship and the common scientific interests among Alfred Gropp, Ernesto Capanna and Maria Gabriella Manfredi Romanini have primed a wealth of studies on the “Robertsonian phenomenon” in this species. These studies have contributed to elucidate i) the molecular bases of metacentric chromosomes formation, ii) the establishment of metacentric races and iii) the impact that chromosome heterozygosities exert on reproductive isolation and speciation.

Cytological studies in Salmo trutta and Salmo alpinus.

Ten populations of Salmo trutta and six populations of Salmo alpinus have been studied cytologically. Both species have the chromosome number 2n = 80. In Salmo trutta the number of metacentric chromosomes varies between 15 and 24 with an average mean of 20, which gives a nombre fondamental (N. F.) of 100. Meiosis has been studied in six of the ten populations of Salmo trutta. Five of these populations have a regular meiosis with 40 bevalents whereas one population had one quadrivalent and 38 bivalents. Five populations of Salmo alpinus have been studied, all having 80 chromosomes somatically. Meiosis has been studied in two of these populations. Both were regular with 40 bivalents. The normal number of metacentric chromosomes in Salmo alpinus is 20, which gives an N. F. of 100 even in this species.

Cytological studies in the smelt (Osmerus eperlanus L.).

The cytology of the smelt, Osmerus eperlanus, has been studied. This salmonid has 2n = 54 with 8 pairs of metacentric and 19 pairs of acrocentric chromosomes, which gives an N. F. value of 70, the lowest value so far observed in the family. At meiosis 27 bivalents are formed, most of which are rod-shaped. Chromosome numbers, number of metacentric chromosomes and N. F. values in the Scandinavian salmonid species so far studied by our group are reported.

Robertsonian translocation as a result of telomere shortening during replicative senescence and immortalization of bovine oviduct epithelial cells

We investigated chromosome (Chr) aberrations in the process of replicative senescence and immortalization of cultured bovine oviduct epithelial cells (BOEC) before and after transfecting vectors SV40 large T or human telomerase reverse transcriptase (hTERT). We found that a gradual increase in the number of metacentric chromosomes occurred during replicative senescence but not immortalization of BOEC. The accumulation of metacentric chromosomes was concomitant with decreases in the number of acrocentric autosomes, strongly suggesting that Robertsonian (Rb) translocation frequently occurred in cultured BOEC. The process was also correlated with an accumulation of extremely shortened telomeres (<4 kb). The maximum number of metacentric chromosomes reached a plateau (8.75 +/- 0.53) in the senescent BOEC (approximately 48 population doublings), and the value was stably maintained in all immortalized lines. These results suggest that not all autosomes may be involved in Rb translocation. Fluorescence in situ hybridization analysis using probes specific for Chr1, Chr29, telomeres, and x-chromosomes of bovine confirmed the presence of t(1;29) with other unidentified fused chromosomes. There was no evidence for duplication of sex chromosomes. Because no detectable fluorescence in situ hybridization signals at the centromere for telomeres were indicative of no direct integration of telomere sequences in the Rb translocated chromosomes, these results raise a possibility that Rb translocation between certain autosomes of bovine cells is partly but critically dependent upon a physical state of telomere attrition. The cells and cell lines established in this study could provide a promising system for further studies on the mechanisms of chromosomal translocation because of centromeric fusion in bovine cells.

Citogenética e qualidade da forragem de espécies de Adesmia DC. nativas no Rio Grande do Sul

Accessions of Adesmia DC. species of bicolores and psoraleoides series, native of Rio Grande do Sul State were studied regarding to chromosome numbers (in 11 acessions of 5 species), karyotypes (in 5 accessions of a 4 species), meiotic behaviour (in 8 accessions of 5 species), forage quality through analysis of crude protein (CP) and in vitro organic matter digestibility (IVOMO) (in 9 accessions of 5 species). Some studied accessions were conducted in field for collections of inflorescences to meiosis and forage quality analysis. In the determination of the chromosome numbers and analyse of karyotypes roots were used with 2-5mm pretreated in tap water at 0°C for 14 hours, fixed in (3: 1) ethanol:acetic acid for 4 hours at room temperature, and stored in 70% ethanol in the refrigerator. In the preparation of slides an enzymatic digestion of cellular parede in 2% pectinase + celulase, squashes in 45% acetic acid and staining in 2% acetic orcein was applied. To the analysis of meiotic behaviour the inflorescences were fixed in (3: 1) ethanol-acetic acid at 4°C for 24 hours. The stain used was 1 % acetic orcein. The analysis of forage quality were conducted in plants cutted when the first inflorescence of each accession appeared. All species studied regarding to the chromosome numbers are diploid and in A. incana var. incana besides two diploid races, there was one tetraploid race. A. incana shouldn't considered a only tetraploid species, as it had been considered till now. The species analysed regarding to Karyotypes presents differences related with the number of metacentric chromosomes, size of chromosomes and total size of complement (TSC), witch allow the karyotype distinction among some of them. A. bicolor seems be the more ancient among the analysed species due to its high karyotype symmetry and its high TSC, among the diploid accessions. A. tristis seems be the more recent among the analysed species, because it's high karyotype asymmetry. The meiotic behaviour of the species in essentially normal, with meiotic index (MI) over 90%, with exception af A. latifolia M1568 (MI=88.92%), and high pollen grain viability, suggesting meiotically stable and potentially fertile plants, probably without problems for utilization in programs of selection and erossing and viable seeds produetion. There is big variability among the accessions of A. latifolia and A. incana var. incana regarding to the IVOMO, wich can will be explorated in breeding programs. The IVOMD are related with the way of growing of the plants, being high in prostrated species.

Cytogenetic evaluation of four canine mast cell tumors

We evaluated four canine cutaneous mast cell tumors cytogenetically. All four tumors contained both hypodiploid and hyperdiploid cells, an increase in the number of metacentric chromosomes, exchange configurations, and cells showing loss of an X chromosome. All tumors contained metaphases with chromosome gaps and breaks at frequencies greater than observed spontaneous chromosome breaks in normal cultured canine peripheral blood lymphocytes. Three of the four tumors had a normal modal chromosome number of 78. The fourth tumor had a modal chromosome number of 93, which represented 15% of the cells evaluated from this tumor.

Saudi gazelle (Gazella saudiya) is not a subspecies of Dorcas gazelle

AbstractKaryotypes of Saudi gazelle (2n = 47 female, 2n = 50/51 male) are presented for the first time. The three karyotypes shown here vary in the numbers of metacentric chromosomes, but the cause of this variation is not yet known. Although Saudi gazelle are often regarded as a subspecies of Dorcas gazelle, the chromosome numbers and karyotypes of Saudi gazelle are too different from Dorcas gazelle (2n = 30 female, 2n = 31 male) for them to be considered a subspecies. It is also unlikely that these species would interbreed. In view of the present findings, the taxonomic status of this highly endangered gazelle needs to be resolved as soon as possible.

Novel Antigen Expression on Syngeneic Somatic Cell Hybrids of Murine Spontaneous Mammary Tumor Cells&lt;xref ref-type="fn" rid="FN1"&gt;2&lt;/xref&gt;

Spontaneous mammary carcinoma cells of C3H/He mice were fused with syngeneic L-cells, and two types of hybrid cell clones were obtained. In group A, hybrid cells showed contact inhibition, and parental H-2k and L-antigens were well expressed. Metacentric chromosomes of L-cell origin and estrogen dependency were also well preserved in this group. However, in group B, hybrid cells proliferated to pile up, and the expression of parental antigens, H-2 and L-cell antigens, was strongly suppressed. But, mouse mammary tumor antigens (MM-antigens), which were expressed on ascites mammary tumor cells with hypotetraploidy of C3H/He origin and which were not expressed on both parent cells, were newly expressed. The number of metacentric chromosomes was decreased, and estrogen dependency was lost in this group. The relationship between the expression of MM-antigens and that of H-2 antigens was reciprocal, and tumorigenicity was independent of cellular behavior in vitro and of MM-antigen expression. MM-antigen-positive hybrid cell clones were frequently obtained when tumor cells were fused with metaphase-rich L-cells.

Genotypic and Phenotypic Evolution of a Murine Tumor During Its Progression In Vivo Toward Metastasis23

To follow the cellular progeny of the multiple-drug-marked benign murine tumor cell line MDW4 during its progression in vivo toward metastatic spread in DBA/2 mice, the following parameters were analyzed: retention of the drug-resistant markers ouabain resistance (OuaR) and thioguanine resistance (ThgR), lectin-resistance pattern (WGAR), and the karyotype of cell populations (and clones derived from these cells) removed at intervals from the solid tumor growing at the site of inoculation, as well as distant metastatic nodules. It was determined that the initially homogeneous inoculum composed of OuaR, ThgR, and WGAR hypotetraploid cells (mode: 68 +/- 2 chromosomes) was gradually overgrown and replaced by a new population of cells that were either OuaR or ouabain-sensitive but that became thioguanine-and lectin-sensitive and hyperploid (mode: 95 +/- 5). Regardless of the composition of the individual drug marker combinations, only cells with high chromosome contents were found to be able to disseminate to distant visceral organs and to rapidly produce metastases upon sc or iv reinjection. The presence of the same number of metacentric chromosomes in metastatic cells as in MDW4 and the coextinction of two recessive drug-resistant markers (WGAR and ThgR) suggested that cells endowed with invasive-metastatic potential represent the product of spontaneous somatic hybridization between the original nonmetastatic MDW4 cells and normal host cells of unknown origin. Such a fusion was followed by more or less extensive chromosome segregation that accounts for the karyotype mosaicism and the occasional drug marker heterogeneity identified in cell populations of metastatic nodules.

Karyotype studies in thirteen species of fishes.

The karyotypes of thirteen species of fishes belonging to nine families, studied in spermatogonial cells and in primary and secondary spermatocytes are reported. All these fishes were collected from the river Jumna near Delhi (India). The diploid number of chromosomes of these species ranges between 86 (Wallago attu) and 40 (Ompak bimaculatus). The karyotypes of seven species are characterized by exclusively possessing acrocentric chromosomes, while the remaining six species have varying numbers of metacentric chromosomes in addition to acrocentric chromosomes. Species belonging to the same family, and even the same genus, have been found to differ in chromosome number and morphology. On the basis of the data available, the author has endeavoured to discuss the relationship between cytologically known fish species and the various complications involved in their classification. The validity of the “nombre fondamental” hypothesis of Matthey in fish karyotypes has also been discussed.