RESUMEN

B chromosomes occur in different species of the small characid fishes of the genus Moenkhausia. These supernumerary elements, that do not recombine with chromosomes of the standard A complement and follow their own evolutionary mechanism vary in number, morphology, and distribution. Here, we show karyotypic data of individuals of 2 populations of Moenkhausia oligolepis of the Brazilian Amazon (Pedro Correia and Taboquinha streams, Tocantins river basin), both with a diploid number of 50 chromosomes and karyotypic formula of 10m + 32sm + 8a. In addition to the normal complement, we also observed the occurrence of B chromosomes in the 2 populations with intra- and interindividual variation ranging from 0 to 10 Bs, independent of sex. The C-banding pattern evidenced heterochromatic blocks located mainly in the pericentromeric region of the chromosomes, while the B chromosomes appeared euchromatic. Silver-stained nucleolus organizer regions were identified in multiples sites, and some of these blocks were positive when stained with chromomycin A3. The karyotype analysis and the application of whole-chromosome painting in populations of M. oligolepis reinforce the conservation of the basal diploid number for the genus, as well as the evolutionary tendency in these fishes to carry B chromosomes. Both populations turned out to be in different stages of stability and expansion of their B chromosomes. We further suggest that the origin of these chromosomes is due to the formation of isochromosomes. Here, we identified a pair of complement A chromosomes involved in this process.

Asunto(s)

Characidae/genética , Inestabilidad Cromosómica , Cromosomas/química , Cariotipificación/métodos , Animales , Brasil , Cromomicina A3/química , Bandeo Cromosómico , Mapeo Cromosómico , Femenino , Colorantes Fluorescentes/química , Hibridación Fluorescente in Situ , Cariotipo , Masculino , Mitosis , Ploidias

RESUMEN

Notolathyrus is a section of South American endemic species of the genus Lathyrus. The origin, phylogenetic relationship and delimitation of some species are still controversial. The present study provides an exhaustive analysis of the karyotypes of approximately half (10) of the species recognized for section Notolathyrus and four outgroups (sections Lathyrus and Orobus) by cytogenetic mapping of heterochromatic bands and 45S and 5S rDNA loci. The bulk of the parameters analyzed here generated markers to identify most of the chromosomes in the complements of the analyzed species. Chromosome banding showed interspecific variation in the amount and distribution of heterochromatin, and together with the distribution of rDNA loci, allowed the characterization of all the species studied here. Additionally, some of the chromosome parameters described (st chromosomes and the 45S rDNA loci) constitute the first diagnostic characters for the Notolathyrus section. Evolutionary, chromosome data revealed that the South American species are a homogeneous group supporting the monophyly of the section. Variation in the amount of heterochromatin was not directly related to the variation in DNA content of the Notolathyrus species. However, the correlation observed between the amount of heterochromatin and some geographical and bioclimatic variables suggest that the variation in the heterochromatic fraction should have an adaptive value.

Asunto(s)

ADN Ribosómico/genética , Evolución Molecular , Heterocromatina/genética , Cariotipo , Lathyrus/genética , Cromomicina A3/química , Mapeo Cromosómico , ADN de Plantas/genética , Hibridación Fluorescente in Situ , Indoles/química , Lathyrus/clasificación , América del Sur

RESUMEN

The present study highlights the biological effects of chromomycin A2 toward metastatic melanoma cells in culture. Besides chromomycin A2, chromomycin A3 and demethylchromomycin A2 were also identified from the extract derived from Streptomyces sp., recovered from Paracuru Beach, located in the northeast region of Brazil. The cytotoxic activity of chromomycin A2 was evaluated across a panel of human tumor cell lines, which found IC50 values in the nM-range for exposures of 48 and 72 h. MALME-3M, a metastatic melanoma cell line, showed the highest sensitivity to chromomycin A2 after 48h incubation, and was chosen as a model to investigate this potent cytotoxic effect. Treatment with chromomycin A2 at 30 nM reduced cell proliferation, but had no significant effect upon cell viability. Additionally, chromomycin A2 induced accumulation of cells in G0/G1 phase of the cell cycle, with consequent reduction of S and G2/M and unbalanced expression of cyclins. Chromomycin A2 treated cells depicted several cellular fragments resembling autophagosomes and increased expression of proteins LC3-A and LC3-B. Moreover, exposure to chromomycin A2 also induced the appearance of acidic vacuolar organelles in treated cells. These features combined are suggestive of the induction of autophagy promoted by chromomycin A2, a feature not previously described for chromomycins.

Asunto(s)

Autofagia/efectos de los fármacos , Melanoma/tratamiento farmacológico , Plicamicina/análogos & derivados , Brasil , Ciclo Celular/efectos de los fármacos , Línea Celular Tumoral , Proliferación Celular/efectos de los fármacos , Supervivencia Celular/efectos de los fármacos , Cromomicina A3/metabolismo , Cromomicinas/farmacología , Células HCT116 , Células HL-60 , Humanos , Melanoma/metabolismo , Proteínas Asociadas a Microtúbulos/metabolismo , Plicamicina/farmacología , Streptomyces/química

RESUMEN

Heteroptera is the most numerous and diverse suborder of Hemiptera, with about 38,000 species. This diversity also involves cytogenetic features, including chromosome number and a sex determining system. Information about heterochromatin occurrence and distribution is scarce in heteropterans, but still, there is some evidence of variability. We determined the chromosome number and CMA3/DAPI-banding pattern of 179 individuals of 25 heteropteran species from Brazil. Eight species of Pentatomidae exhibited a constant chromosome number (2n = 12 + XY), but in Coreidae (12 species), Largidae (1 species), Rhopalidae (1 species), and Pyrrhocoridae (3 species), the numbers ranged from 2n = 10 + 2m + X0 to 2n = 24 + 2m + X0. Although there were no large differences in the chromosome size between species, the CMA3/DAPI-banding patterns differed markedly. Among the genera, species of Edessa, Spartocera, Hypselonotus, Phtia,Holhymenia and Euryophthalmus showed a large accumulation of heterochromatin, while the other species exhibited few or no heterochromatic bands. In general, when heterochromatin was more accumulated, this occurred preferentially at terminal positions, except in Holhymenia histrio, which exhibited intercalary bands. This study made it possible to identify some chromosome rearrangements and to enhance our knowledge of the evolutionary mechanisms that determine karyotype differentiation in Heteroptera.

Asunto(s)

Bandeo Cromosómico/métodos , Cromosomas de Insectos/ultraestructura , Heterópteros/genética , Animales , Evolución Biológica , Cromomicina A3 , Colorantes Fluorescentes , Heterocromatina/ultraestructura , Indoles , Cariotipo , Especificidad de la Especie , Coloración y Etiquetado/métodos

RESUMEN

The common bean (Phaseolus vulgaris) and lima bean (P. lunatus) are among the most important legumes in terms of direct human consumption. The present work establishes a comparative cytogenetic map of P. lunatus, using previously mapped markers from P. vulgaris, in association with analyses of heterochromatin distribution using the fluorochromes chromomycin A3 (CMA) and 4',6-diamidino-2-phenylindole (DAPI) and localization of the 5S and 45S ribosomal DNA (rDNA) probes. Seven BACs selected from different common bean chromosomes demonstrated a repetitive pericentromeric pattern corresponding to the heterochromatic regions revealed by CMA/DAPI and could not be mapped. The subtelomeric repetitive pattern observed for BAC 63H6 in most of the chromosome ends of common bean was not detected in lima bean, indicating lack of conservation of this subtelomeric repeat. All chromosomes could be identified and 16 single-copy clones were mapped. These results showed a significant conservation of synteny between species, although change in centromere position suggested the occurrence of pericentric inversions on chromosomes 2, 9 and 10. The low number of structural rearrangements reflects the karyotypic stability of the genus.

Asunto(s)

Citogenética , Fabaceae/genética , Phaseolus/genética , Centrómero/ultraestructura , Cromomicina A3/metabolismo , Mapeo Cromosómico/métodos , Cromosomas/ultraestructura , ADN Ribosómico/genética , Genes de Plantas , Heterocromatina/genética , Heterocromatina/metabolismo , Hibridación Fluorescente in Situ , Indoles/química , Cariotipificación , Modelos Genéticos , Telómero/ultraestructura

RESUMEN

A large number of genera in the tropical fish family Characidae are incertae sedis. Cytogenetic analysis was made of four of these species: Astyanax eigenmanniorum, Deuterodon stigmaturus, Hyphessobrycon luetkenii, and H. anisitsi, collected from various hydrographic basins: hydrographic system from Laguna dos Patos/RS, Tramandaí basin/RS and Tibagi River basin/PR. The first two species were collected in their type locality in the State of Rio Grande do Sul. The 2n = 48 karyotype was observed only in A. eigenmanniorum, while the other species had 2n = 50 chromosomes, with different karyotypic formulas. There was weak heterochromatin staining in the pericentromeric region of A. eigenmanniorum, D. stigmaturus and H. luetkenni chromosomes. In H. anisitsi, heterochromatin appeared to be more abundant and distributed in the pericentromeric and terminal regions of the chromosomes; three pairs showed more evident heterochromatic blocks. There were multiple Ag-NORs in all populations, visualized by FISH with an 18S rDNA probe. While D. stigmaturus and H. luetkenii had conserved AgNOR, CMA3 and 18S rDNA sites, the other two species showed intra- and interindividual variation at these sites. The karyotype variability was high, as is common in this group of fish. Different species arising from isolated hydrographic basins maintain an elevated level of karyotype differentiation, mainly with respect to chromosome structure, heterochromatin distribution and rDNA localization. This is the first report with cytogenetic data for D. stigmaturus and H. luetkenii.

Asunto(s)

Antígenos Nucleares/genética , Characidae/clasificación , Characidae/genética , Cromomicina A3/metabolismo , ADN Ribosómico/genética , Variación Genética , Cariotipificación , Animales , Brasil , Bandeo Cromosómico , Cromosomas/genética , Femenino , Geografía , Hibridación Fluorescente in Situ , Indoles/metabolismo , Masculino , Metafase/genética , Ríos , Especificidad de la Especie

RESUMEN

B chromosomes are additional chromosomes widely studied in a diversity of eukaryotic groups, including fungi, plants and animals, but their origin, evolution and possible functions are not clearly understood. To further understand the genomic content and the evolutionary history of B chromosomes, classical and molecular cytogenetic analyses were conducted in the cichlid fish Astatotilapia latifasciata, which harbor 1­2 B chromosomes. Through cytogenetic mapping of several probes, including transposable elements, rRNA genes, a repeated DNA genomic fraction (C0t - 1 DNA), whole genome probes (comparative genomic hybridization), and BAC clones from Oreochromis niloticus, we found similarities between the B chromosome and the 1st chromosome pair and chromosomes harboring rRNA genes. Based on the cytogenetic mapping data, we suggest the B chromosome may have evolved from a small chromosomal fragment followed by the invasion of the proto-B chromosome by several repeated DNA families.

Asunto(s)

Cromosomas/genética , Cíclidos/genética , Genómica , Animales , Cromomicina A3/metabolismo , Bandeo Cromosómico , Evolución Molecular , Femenino , Masculino , ARN Ribosómico 18S/genética

RESUMEN

Most species of Citrus and related genera display a similar karyotype with 2n = 18 and a variable number of terminal heterochromatic blocks positively stained with chromomycin A(3) (CMA(+) bands). Some of these blocks are 45S rDNA sites, whereas others may correspond to the main GC-rich satellite DNA found in several Citrus species. In the present work, the distribution of the 45S rDNA and the main satellite DNA isolated from C. sinensis (CsSat) were investigated by in situ hybridization in seven species of Citrus, two species of closely related genera (Fortunella obovata and Poncirus trifoliata) and four species of the subfamily Aurantioideae, which were less related to Citrus (Atalantia monophylla, Murraya paniculata, Severinia buxifolia, and Triphasia trifolia). In Citrus, Fortunella, and Poncirus, most CMA(+) bands colocalized only with CsSat sites, whereas others colocalized only with rDNA sites. However, some of these species displayed a few CMA(+) bands that colocalized with sites of both probes and other CMA(+) bands that did not colocalized with any of the probes. On the other hand, in the four species less related to Citrus, no CsSat signal was found on chromosomes. On Southern blot, the CsSat probe hybridized with genomic DNA from Citrus, Fortunella, and Poncirus at high stringency only, while under the less stringent conditions, it also hybridized with distantly related species. Therefore, CsSat sequences are the principal component of the heterochromatic blocks of Citrus, Poncirus, and Fortunella, whereas CsSat-like sequences seem to be widespread in the subfamily Aurantioideae. These data further suggest that the variable number of terminal CMA(+) bands observed on chromosomes of Citrus and related genera are probably the consequence of amplification or reduction in the number of CsSat-like sequences distributed on chromosome termini, paralleled by mutation and homogenization events, as proposed by the library hypothesis.

Asunto(s)

Evolución Biológica , Cromomicina A3 , Mapeo Cromosómico/métodos , Cromosomas de las Plantas , Citrus/genética , ADN Satélite , Hibridación Fluorescente in Situ , ARN Ribosómico

RESUMEN

Under specific technical conditions chromosome staining with 4',6-diamidino-2-phenylindole (DAPI) permits characterization of heterochromatic regions as AT-rich (DAPI(+)) or AT-poor (DAPI(-)), especially when the chromosomes are counterstained with chromomycin A(3) (CMA), which preferentially binds to GC-rich DNA. DAPI(+) bands also often have been observed after C-banding or FISH. In these cases, however, it is not clear whether only AT-rich regions stain positively with DAPI or other heterochromatins with different base compositions also are stained. We evaluated the meaning of DAPI bands observed after C-banding and FISH using three plant species bearing different types of heterochromatin: DAPI(+)/CMA(-), DAP(-)/CMA(+) and DAPI(0)/CMA(0) (neutral bands). Additional tests were performed using propidium iodide, a fluorochrome without preferential affinity for AT or GC. Our results indicate that AT-rich heterochromatin stains as DAPI(+) bands after C-banding or FISH, but other kinds of heterochromatin also may be stained by DAPI.

Asunto(s)

Bandeo Cromosómico/métodos , Heterocromatina/química , Indoles/química , Plantas/genética , Secuencia Rica en At , Cromomicina A3/química , Colorantes Fluorescentes , Secuencia Rica en GC , Hibridación Fluorescente in Situ , Sustancias Intercalantes , Propidio/química

RESUMEN

Cytogenetic analyses were performed in Astyanax jacuhiensis from lago Guaíba, Brazil. The diploid number was 50, with a karyotype composed of 8m+30sm+4st+8a chromosomes, FN = 92. The AgNORs were observed in 2 to 5 chromosomes, with intra- and interindividual variation. The sm pair 8 observed always carried NORs on the short arms, presenting size heteromorphism between homologous. Fluorescence in situ hybridization (FISH) with an 18S rDNA probe only confirmed the location of ribosomal cistrons in the sm pair 8, and heteromorphism of these regions between the homologous chromosomes. C-banding revealed the occurrence of weak C-positive heterochromatin in the pericentromeric regions of several chromosomes, in addition to more evident bands interstitially located on some chromosome pairs and in the terminal region of the short arms in pair 8. C-banding plus CMA3 revealed light fluorescent signals in different chromosomes of the karyotype, with a strong terminal site in pair 8, indicating the occurrence of several GC-rich heterochromatic regions in this species. Our results provide the first description of the Astyanax jacuhiensis karyotype, showing karyotype similarities when compared to various populations of A. altiparanae and A. bimaculatus, indicating that chromosomal features are very similar for these three species.(AU)

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Análises citogenéticas foram realizadas em Astyanax jacuhiensis do lago Guaíba, Brasil. O número diplóide foi 50, sendo o cariótipo composto por 8m+30sm+4st+8a cromossomos, NF = 92. As regiões organizadoras de nucléolos (AgNORs) foram observadas em 2 a 5 cromossomos, evidenciando uma variação intra e interindividual nesta espécie. O par sm 8 foi constantemente detectado com NORs nos braços curtos, mostrando um heteromorfismo de tamanho entre os homólogos. Entretanto, a hibridação in situ fluorescente (FISH) com sonda de DNAr 18S, localizou cístrons ribossômicos apenas no par 8, confirmando o heteromorfismo de tamanho entre os homólogos. O bandamento C revelou a presença de bandas discretas de heterocromatina na região pericentromérica da maioria dos cromossomos, além de algumas bandas mais evidentes intersticiais, bem como na região terminal dos braços curtos do par 8. A associação de BC+CMA3 evidenciou marcações fluorescentes mais discretas em diferentes cromossomos e uma forte marcação terminal no par 8, confirmando vários sítios de heterocromatina GC-rica nessa espécie. Nossos resultados fornecem a primeira descrição do cariótipo de Astyanax jacuhiensis, apresentando semelhanças em relação ao cariótipo de diferentes populações de A. altiparanae e A. bimaculatus, indicando que as características cromossômicas são muito semelhantes para estas três espécies.(AU)

Asunto(s)

Animales , Región Organizadora del Nucléolo/genética , Variación Genética/genética , Cromomicina A3/análisis , Análisis Citogenético/veterinaria , Peces/genética , Hibridación Fluorescente in Situ/veterinaria

RESUMEN

Karyotype and chromosomal characteristics from 3 allopatric populations of Hoplias malabaricus, cytogenetically the most studied Erythrinidae taxon, were investigated using different staining techniques (C-, Ag-, and CMA(3) banding) as well as fluorescent in situ hybridization (FISH) to detect 18S rDNA, 5S rDNA, and 5SHindIII satellite DNA sites. The isolation, cloning and characterization of an 18S rDNA probe from H. malabaricus genome were also performed for the first time in order to develop a more specific probe. The 3 populations, named PR, CR, and DR, showed identical karyotypes, with 2n = 42 chromosomes composed of 11 m pairs and 10 sm pairs, without heteromorphic sex chromosomes, which characterize the populations as belonging to karyomorph A. In all populations C-positive heterochromatin was situated in the centromeric/pericentromeric regions of the chromosomes, as well as in the telomeric region of several pairs. A conspicuous proximal heterochromatic block on the long arm of pair No. 16 was the only GC-rich segment in the karyotypes. 5SHindIII satellite DNA was always mapped in the centromeric region of several chromosomes. The 18S rDNA sites were situated on the telomeric or centromeric regions, whereas the 5S rDNA showed an interstitial or proximal location in some pairs. Several chromosomes bearing these repetitive DNA sequences were shared by the 3 populations, alongside with some exclusive chromosomal markers. In this sense, population CR was the most differentiated one, including a syntenic condition for the 18S and 5S rDNA probes, as confirmed by double FISH. Thus, despite their inclusion in the same major karyotypic group, the distinct populations cannot be considered an absolute evolutionary unit, as evidenced by their inner chromosomal differentiations.

Asunto(s)

Cromosomas , ADN Satélite/genética , Peces/genética , ARN Ribosómico 18S/genética , ARN Ribosómico 5S/genética , Secuencias Repetitivas de Ácidos Nucleicos , Animales , Brasil , Cromomicina A3 , Endonucleasas/metabolismo , Femenino , Cariotipificación , Masculino , Mapeo Físico de Cromosoma , ARN Ribosómico 18S/metabolismo , ARN Ribosómico 5S/metabolismo

RESUMEN

Sperm chromatin integrity is essential for accurate transmission of male genetic information, and normal sperm chromatin structure is important for fertilization. Protamine is a nuclear protein that plays a key role in sperm DNA integrity, because it is responsible for sperm DNA stability and packing until the paternal genome is delivered into the oocyte during fertilization. Our aim was to investigate protamine deficiency in sperm cells of Bos indicus bulls (Nelore) using chromomycin A3 (CMA3) staining. Frozen semen from 14 bulls were thawed, then fixed in Carnoy's solution. Smears were prepared and analyzed by microscopy. As a positive control of CMA3 staining, sperm from one bull was subjected to deprotamination of nuclei. The percentage of CMA3-positive bovine sperm did not vary among batches. Only two bulls showed a higher percentage of CMA3-positive sperm cells compared to the others. CMA3 is a simple and useful tool for detecting sperm protamine deficiency in bulls.

Asunto(s)

Cromomicina A3 , Protaminas/análisis , Espectrometría de Fluorescencia/métodos , Espermatozoides/química , Femenino , Fertilización In Vitro , Colorantes Fluorescentes , Humanos , Masculino , Sensibilidad y Especificidad , Recuento de Espermatozoides , Motilidad Espermática , Espermatozoides/fisiología , Coloración y Etiquetado/métodos

RESUMEN

Mandarin is the common name of a heterogeneous group of Citrus species with a large range of variation in morphological and molecular characters as well as in number of species. Aiming to identify chromosome markers and to clarify the relationship within this group, the karyotype of 13 mandarin accessions were analyzed using CMA/DAPI staining and in situ hybridization with 5S and 45S rDNA probes. The CMA band pattern together with the position of rDNA sites revealed that mandarins can be separated karyologically into three groups: a) C. sunki and C. reshni; b) the Mediterranean mandarin, C. deliciosa, and the closely related C. tangerina cv. Dancy and C. reticulata cv. Cravo; c) the remaining cultivars, which are cytologically heterozygous and most probably interspecific hybrids. The former two groups are assumed to be pure species together with C. medica and C. grandis. A chromosome marker for mandarin species was identified and the relationship among the pure species and some hybrids is discussed.

Asunto(s)

Cromosomas de las Plantas/genética , Citrus/genética , Hibridación Genética , Cromomicina A3/metabolismo , Bandeo Cromosómico , ADN Ribosómico/metabolismo , Marcadores Genéticos , Cariotipificación , Especificidad de la Especie

RESUMEN

Organophosphorus (OP) pesticides, widely used in agriculture and pest control, are associated with male reproductive effects, including sperm chromatin alterations, but the mechanisms underlying these effects are unknown. The main toxic action of OP is related to phosphorylation of proteins. Chemical alterations in sperm nuclear proteins (protamines), which pack DNA during the last steps of spermatogenesis, contribute to male reproductive toxicity. Therefore, in the present study, we tested the ability of diazinon (DZN), an OP compound, to alter sperm chromatin by phosphorylating nuclear protamines. Mice were injected with a single dose of DZN (8.12 mg/kg, i.p.), and killed 8 and 15 days after treatment. Quality of sperm from epididymis and vas deferens was evaluated through standard methods and chromatin condensation by flow cytometry (DNA Fragmented Index parameters: DFI and DFI%) and fluorescence microscopy using chromomycin-A(3) (CMA(3)). Increases in DFI (15%), DFI% (4.5-fold), and CMA(3) (2-fold) were observed only at 8 days post-treatment, indicating an alteration in sperm chromatin condensation and DNA damage during late spermatid differentiation. In addition, an increase of phosphorous content (approximately 50%) in protamines, especially in the phosphoserine content (approximately 73%), was found at 8 days post-treatment. Sperm viability, motility, and morphology showed significant alterations at this time. These data strongly suggest that spermatozoa exposed during the late steps of maturation were the targets of DZN exposure. The correlation observed between the phosphorous content in nuclear protamines with DFI%, DFI, and CMA(3) provides evidence that phosphorylation of nuclear protamines is involved in the OP effects on sperm chromatin.

Asunto(s)

Cromatina/efectos de los fármacos , Cromatina/metabolismo , Diazinón/efectos adversos , Espermatozoides/anomalías , Espermatozoides/efectos de los fármacos , Animales , Supervivencia Celular/efectos de los fármacos , Supervivencia Celular/fisiología , Cromatina/química , Cromomicina A3 , ADN/efectos de los fármacos , ADN/metabolismo , Fragmentación del ADN/efectos de los fármacos , Diazinón/administración & dosificación , Diazinón/química , Evaluación Preclínica de Medicamentos/métodos , Citometría de Flujo/métodos , Inyecciones Intraperitoneales , Sustancias Intercalantes/efectos adversos , Sustancias Intercalantes/química , Sustancias Intercalantes/metabolismo , Masculino , México , Ratones , Ratones Endogámicos , Microscopía Fluorescente/métodos , Matriz Nuclear/química , Matriz Nuclear/efectos de los fármacos , Matriz Nuclear/metabolismo , Fosforilación/efectos de los fármacos , Fosfotirosina/química , Protaminas/química , Protaminas/efectos de los fármacos , Protaminas/metabolismo , Motilidad Espermática/efectos de los fármacos , Motilidad Espermática/fisiología , Espermatozoides/química , Factores de Tiempo , Pruebas de Toxicidad/métodos

RESUMEN

We analyzed cytogenetically specimens of Pimelodella meeki from Tibagi River at Limoeiro (LM) and from two tributaries, Couro do Boi (CB) and Gabriel da Cunha (GC) Rivers. All specimens presented 2n=46 chromosomes, which were the karyotypes composed by 15 pairs metacentric (M) + 6 pairs submetacentric (SM) + 2 pairs subtelocentric (ST). In specimens of GC, CB, and LM, the results of analyses of the nucleolus organizer regions (NORs), done by means of AgNO3 and CMA3 staining, showed that they are identical, located in terminal position on the short arm of a SM chromosome pair, and they were observed to be a size heteromorphism in some metaphase plates. FISH with 18S rDNA probe yielded evidence for these regions but not for the size variation, indicating that they are not due to a greater number of NOR cistrons in one of the homologue chromosomes. An interesting characteristic of these regions is that they could appear divided in blocks, as evidenced by all the techniques. This work makes clear the necessity for more deeply systematic studies, because of the confused taxonomic situation of the genus Pimelodella.

Asunto(s)

Peces/genética , Animales , Brasil , Cromomicina A3 , Análisis Citogenético , Sondas de ADN , ADN Ribosómico , Femenino , Peces/clasificación , Cariotipificación , Masculino , Región Organizadora del Nucléolo , Tinción con Nitrato de Plata

RESUMEN

Cytogenetic studies were carried out on seven specimens of Pimelodus heraldoi and sixteen specimens of Pimelodus sp., both from the Parana River basin. The two species had the same diploid number of 56 chromosomes: P. heraldoi with 22M+22SM+6ST+6A and FN of 106 and Pimelodus sp. with 24M+26SM+4ST+2A and FN of 110. NORs were found at the terminal position of the long arm of one pair of ST chromosomes. C-banding (CB) showed in the two species heterochromatin distributed in various chromosomes of the complement, mainly in telomeric regions and in a pair of metacentric chromosomes with strong heterochromatic staining in both telomeres. Treatment only with the fluorochrome CMA3 confirmed in Pimelodus heraldoi and Pimelodus sp. the nucleolar chromosome pair and showed other fluorescent bands. Combined treatment with CB+CMA3 enhanced fluorescent staining of chromosomes in the two fish species evidencing several bands, including in P. heraldoi a chromosome pair showing fluorescent staining in both telomeres.

Asunto(s)

Bagres/genética , Animales , Brasil , Cromomicina A3/química , Bandeo Cromosómico/métodos , Cromosomas/genética , Cromosomas/ultraestructura , Femenino , Cariotipificación , Masculino , Microscopía Fluorescente

RESUMEN

The chromosomes of Steindachneridion sp. (2n = 56) and Rhamdia quelen (2n = 58) were analyzed by C-banding (CB) and Chromomycin A3 (CMA3) and 4,6-diamidino-2-phenylindole (DAPI) staining, separately and consecutively, in order to understand the role of base-specific fluorochrome treatment after CB. Both species' chromosomes shared common staining profiles as follows. CB with Giemsa (CBG) revealed weak heterochromatic blocks in the telomeric regions of some chromosomes and conspicuous bands on the short arms of one chromosome pair, where nucleolar organizer regions (NORs) were evidenced by silver-staining. Without CB pretreatment, the NORs were stained conspicuously with CMA3, but not with DAPI. The latter uniformly stained all chromosomes, but leaving the NORs pale. Combination of CMA3 or DAPI staining with CB showed distinctive fluorescent blocks in the NOR-bearing short arms of the single chromosome pair along with several bright fluorescent signals on other chromosomes, which were not evidenced by single CMA3 or DAPI staining. These results suggest a modification of chromatin structure by CB treatment, which may increase the stainability of CMA3 and DAPI.

Asunto(s)

Bagres/genética , Heterocromatina/genética , Animales , Brasil , Cromomicina A3 , Bandeo Cromosómico , Indoles , Tinción con Nitrato de Plata

RESUMEN

Chromosomes of a species of Eigenmannia presenting a X1X1X2X2:X1X2Y sex chromosome system, resulting from a Y-autosome Robertsonian translocation, were analyzed using the C-banding technique, chromomycin A3 (CMA3) and mithramycin (MM) staining and in situ digestion by the restriction endonuclease AluI. A comparison of the metacentric Y chromosome of males with the corresponding acrocentrics in females indicated that a C-band-positive, CMA3/MM-fluorescent and AluI digestion-resistant region had been lost during the process of translocation, resulting in a diminution of heterochromatin in the males. It is hypothesized that the presence of a smaller amount of G + C-rich heterochromatin in the sex chromosomes of the heteromorphic sex when compared with the homomorphic sex may be associated with the sex determination mechanism in this species and may be a more widely occurring phenomenon in fish with differentiated sex chromosomes than was initially thought.

Asunto(s)

Evolución Biológica , Pez Eléctrico/genética , Cromosomas Sexuales/genética , Animales , Cromomicina A3/química , Femenino , Heterocromatina , Cariotipificación , Masculino , Plicamicina/química , Mapeo Restrictivo , Diferenciación Sexual , Tinción con Nitrato de Plata/métodos , Translocación Genética

RESUMEN

Chromosomes of Poecilia mexicana mexicana, one of the bisexual species involved in the hybrid origin of the unisexual teleost fish species P. formosa, were analyzed by several staining techniques. Sex-specific, differential heterochromatin, found in other congeneric species, was not observed in P. m. mexicana. Nucleolar organizer regions were polymorphic among individual specimens within a given population sample. A single specimen exhibiting intraindividual variability of chromosome pair 1 and a specimen with a triploid karyotype are also described.

Asunto(s)

Bandeo Cromosómico , Heterocromatina , Región Organizadora del Nucléolo , Poecilia/genética , Coloración y Etiquetado , Animales , Cromomicina A3 , Femenino , Colorantes Fluorescentes , Indoles , Masculino , Quinacrina , Tinción con Nitrato de Plata