Fluorescence in situ hybridization with rDNA probes on chromosomes of two nucleolus organizer region phenotypes of a species of Eigenmannia (Pisces, Gymnotoidei, Sternopygidae)

Nucleolus organizer regions (NORs) were analysed in two related and geographically close populations of Eigenmannia sp.1 (Pisces, Gymnotoidei, Sternopygidae) using silver staining and fluorescence in situ hybridization (FISH). The two populations differed in their AS-NOR phenotypes, displaying fixed differences in the NOR-bearing chromosome pairs. FISH with rDNA probes showed that these differences were due to the location of rDNA cistrons. This finding, showing fixed NOR differences between two populations belonging to the same species in a connected river system, is highly significant in terms of evolutionary change, possibly indicating an initial step of genetic differentiation. This result also has important implications from the cytosystematic point of view, as NORs usually have a very constant karyotypic location in fish species and have been used as species-specific chromosome markers.

Nuclear DNA content of thirty species of neotropical fishes

The present paper reports nuclear DNA content in 30 Neotropical freshwater fish species and summarizes the data on other Neotropical species presented in the literature. Among Neotropical fishes, the nuclear DNA content ranges from 1.04 ± 0.09 pg/nucleus in Corydoras cf. simulatus (2n = 62) to 248.0 pg/nucleus in Lepidosiren paradoxa (2n = 38). A general analysis of the data obtained in the present study for each species showed that DNA measurements were practically constant at the individual level, while significant differences were observed among individuals of the same population. This observation was valid for all species analyzed and was more evident in those species that presented other karyotypic particularities such as sex chromosomes or supernumerary chromosomes. The importance of changes in nuclear DNA content in the evolutionary process of Neotropical fishes is discussed.

Optimized delta expansion for relativistic nuclear models: Renormalization of vacuum fluctuations

We use the optimized linear δ expansion and functional methods to study vacuum contributions in nuclear matter up to the lowest non-trivial order which includes exchange terms. We show that well known results (MFT, RHA and HF) can be easily reproduced when appropriate limits are taken. Neglecting vacuum contributions we explicitly show that the δ expansion goes beyond the traditional loop approximation previously used to study two loop vacuum contributions in nuclear matter. We then evaluate and renormalize vacuum exchange contributions showing that they are numerically very large, as predicted by the ordinary loop approximation.

Droplet formation in cold asymmetric nuclear matter in the quark-meson-coupling model

The quark-meson-coupling model is used to study droplet formation from the liquid-gas phase transition in cold asymmetric nuclear matter. The critical density and proton fraction for the phase transition are determined in the mean field approximation. Droplet properties are calculated in the Thomas-Fermi approximation. The electromagnetic field is explicitly included and its effects on droplet properties are studied. The results are compared with the ones obtained with the NL1 parametrization of the non-linear Walecka model. © 2000 Elsevier Science B.V.

Effects of nuclear structure on parity nonconservation in atomic cesium in relativistic mean field theory

We use relativistic mean field theory, which includes scalar and vector mesons, to calculate the binding energy and charge radii in 125Cs - 139Cs. We then evaluate the nuclear structure corrections to the weak charges for a series of cesium isotopes using different parameters and estimate their uncertainty in the framework of this model.

Nucleotide sequence of 5S rDNA and localization of the ribosomal RNA genes to metaphase chromosomes of the Tilapiine cichlid fish, Oreochromis niloticus

In this study, we report the cloning and nucleotide sequence of PCR-generated 5S rDNA from the Tilapiine cichlid fish, Oreochromis niloticus. Two types of 5S rDNA were detected that differed by insertions and/or deletions and base substitutions within the non-transcribed spacer (NTS). Two 5S rDNA loci were observed by fluorescent in situ hybridization (FISH) in metaphase spreads of tilapia chromosomes. FISH using an 18S rDNA probe and silver nitrate sequential staining of 5S-FISH slides showed three 18S rDNA loci that are not syntenic to the 5S rDNA loci.

Long-term starvation effects on Mus musculus hepatocyte nuclear phenotypes

Starvation is a physiologic stress and can significantly alter the structure of hepatic cells. This work aims to detect morphological changes in mice hepatocyte under starvation physiologic stress, based on silver staining technique. Fourteen 21 day old male mice (Mus musculus) were used, 5 as control, 5 submitted to 72 hours of starvation, and 4 were refed during 72 hours after 72 hours of starvation. After liver imprint, 15 nuclei per mouse and their respective nucleoli were outlined in millimetric paper and their areas were obtained. The results, in mm2, were transformed into μm2. The number of nucleoli per nuclei were also counted. After starvation, a statistically significant rise in nuclear and nucleolar areas occurred and no significant increase in the number of nucleoli was observed. The refeeding caused a partial recovery of the nuclear area, no significant change in the nucleolar area and a statistically significant increase in the number of nucleoli. Therefore, starvation can be considered as a modifier agent of the chromatinic structure, leading to an increase of the nuclear and nucleolar areas probably due to an increment of RNA and protein synthesis. The recovery of the stress (refeeding) did not presented a decrease of nucleolar area and evidenced a nucleoli fragmentation, probably to increase more the protein synthesis and/or due to its cycle during the interphase.

Complete replacement of the mitochondrial genotype in a Bos indicus calf reconstructed by nuclear transfer to a bos taurus oocyte

Due to the exclusively maternal inheritance of mitochondria, mitochondrial genotypes can be coupled to a particular nuclear genotype by continuous mating of founder females and their female offspring to males of the desired nuclear genotype. However, backcrossing is a gradual procedure that, apart from being lengthy, cannot ascertain that genetic and epigenetic changes will modify the original nuclear genotype. Animal cloning by nuclear transfer using host ooplasm carrying polymorphic mitochondrial genomes allows, among other biotechnology applications, the coupling of nuclear and mitochondrial genotypes of diverse origin within a single generation. Previous attempts to use Bos taurus oocytes as hosts to transfer nuclei from unrelated species led to the development to the blastocyst stage but none supported gestation to term. Our aim in this study was to determine whether B. taurus oocytes support development of nuclei from the closely related B. indicus cattle and to examine the fate of their mitochondrial genotypes throughout development. We show that indicus:taurus reconstructed oocytes develop to the blastocyst stage and produce live offspring after transfer to surrogate cows. We also demonstrate that, in reconstructed embryos, donor cell-derived mitochondria undergo a stringent genetic drift during early development leading, in most cases, to a reduction or complete elimination of B. indicus mtDNA. These results demonstrate that cross-subspecies animal cloning is a viable approach both for matching diverse nuclear and cytoplasmic genes to create novel breeds of cattle and for rescuing closely related endangered cattle.

Analysis of chromatin and nuclear area alterations in triatomines during starvation

In the present study changes in nuclear area and chromatin distribution in the Malpighian tubules of a blood-feeding insect, the vector of Chagas' disease were analysed. Male and female adult insects were dissected, after a starving period of up to 28 days. The Malpighian tubules were fixed and stained by orcein lacto-acetic. The nuclei were analyzed by photomicrography, karyometry and a statistical analysis was performed. It was observed that with the increase of the starvation period there were alterations in the nuclear phenotype, that is, changes in the nuclear area and chromatin extenuation. In males, starting from the second week of starvation, chromatin extenuation was accentuated, and the beginning of nuclear coalition occurred more frequently in the third and fourth starvation weeks. In females, the accentuated chromatin extenuation was observed after the third starvation week, and irregularities in nuclear borders were more frequent. The descriptive statistical analysis of the male and temale nuclear areas revealed that the nuclear areas continued to increase during starvation reaching highest values in the third week. Another outstanding aspect is that in the third starvation week karyometry presented larger heterogeneity with higher standard deviation values for both genders. Therefore, nuclear alterations related to the distribution and extenuation chromatin and increase in nuclear area were observed. These aspects suggest the presence of nuclear metabolic mechanisms that lead to synthesis of specific proteins necessary for the protection and maintenance of the cell during physiologic stress.

Quantum vacuum in hot nuclear matter: A non-perturbative treatment

We derive the equation of state for hot nuclear matter using the Walecka model in a non-perturbative formalism. We include here the vacuum polarization effects arising from the nucleon and scalar mesons through a realignment of the vacuum. A ground state structure with baryon-antibaryon condensates yields the results obtained through the relativistic Hartree approximation of summing baryonic tadpole diagrams. Generalization of such a state to include the quantum effects for the scalar meson fields through the σ -meson condensates amounts to summing over a class of multiloop diagrams. The techniques of the thermofield dynamics method are used for the finite-temperature and finite-density calculations. The in-medium nucleon and sigma meson masses are also calculated in a self-consistent manner. We examine the liquid-gas phase transition at low temperatures (≈ 20 MeV), as well as apply the formalism to high temperatures to examine a possible chiral symmetry restoration phase transition.

Biophysical Characterization of Interactions Involving Importin-α during Nuclear Import

Proteins containing the classical nuclear localization sequences (NLSs) are imported into the nucleus by the importin-α/β heterodimer. Importin-α contains the NLS binding site, whereas importin-β mediates the translocation through the nuclear pore. We characterized the interactions involving importin-α during nuclear import using a combination of biophysical techniques (biosensor, crystallography, sedimentation equilibrium, electrophoresis, and circular dichroism). Importin-α is shown to exist in a monomeric autoinhibited state (association with NLSs undetectable by biosensor). Association with importin-β (stoichiometry, 1:1; K D = 1.1 × 10 -8 M) increases the affinity for NLSs; the importin-α/β complex binds representative monopartite NLS (simian virus 40 large T-antigen) and bipartite NLS (nucleoplasmin) with affinities (K D = 3.5 × 10 -8 M and 4.8 × 10 -8 M, respectively) comparable with those of a truncated importin-α lacking the autoinhibitory domain (T-antigen NLS, K D = 1.7 × 10 -8 M; nucleoplasmin NLS, K D = 1.4 × 10 -8 M). The autoinhibitory domain (as a separate peptide) binds the truncated importin-α, and the crystal structure of the complex resembles the structure of full-length importin-α. Our results support the model of regulation of nuclear import mediated by the intrasteric autoregulatory sequence of importin-α and provide a quantitative description of the binding and regulatory steps during nuclear import.

Nucleolar changes in malpighian tubules cells of Rhodnius prolixus during starvation

This study focused on nuclear and nucleolar area changes in Malpighian tubule cells of Rhodnius prolixus, an hematophagous insect, vector of Chagas' disease. Male and female adult insects were dissected after a 28-day starvation period, as well as insects which had been fed again after a 30-day starvation period. Malpighian tubules were fixed and silver stained. In both, males and females, nucleolar fusions and regions of nucleolar corpuscles were observed to be differentially impregnated by silver during feeding stress. In the males and females that were fed again, nucleolar corpuscles were partially fusioned, indicating a slight recovery upon the 30-day starvation period. The changes observed in the nucleolar phenotype and in both nuclear and nucleolar areas indicated that, as a result of stress, a more intense, compensatory activity occurred to supply the metabolic rate. The mechanism of this phenomenon may be associated to the decondensation and activation of chromatin that carries rDNA in order to increase rRNA transcription, and,consequently, protein synthesis.

Structural characterization of nuclear phenotypes during Scinax fuscovarius spermatogenesis (Anura, Hylidae)

In anuran amphibian Scinax fuscovarius, the spermatogenesis occurs in structures called seminiferous loculi, in which germ epithelium is organized in spermatocysts. Each cyst contains cells in the same stage of cytodifferentiation. Characteristics of each cellular type and their groups made the identification and differentiation of the germ lineage cells possible. In the basis of the epithelium there are the spermatogonia I, the biggest cells and always associated with the Sertoli cell. After the phase of mitotic proliferation, the cysts containing variable number of spermatogonia II are originated, quite smaller and with cellular boundaries a little distinct. After differentiation and growth in volume, the spermatocytes I appear, the nuclei of which are spherical and with different degrees of compaction of the nuclear material. Starting the meiotic process, the spermatocytes II are originated, which by means of the second meiotic division become haploid cells, the spermatids I. These two last spermatocysts are very similar. In this phase, the cells will go through a prominent process of differentiation until they form the spermatids II, which are elongated and begin to be organized in bundles supported by prominent Sertoli cells. With the process of spermiogenesis, spermatozoa appear, usually observed in compact bundles with tails turned to the lumen and their heads fitted in their support cells. In more advanced stages, the spermatozoa can be observed free in the locular lumen, ready to follow the spermatic path.

Nuclear phenotypes and morphometry of human secretory prostate cells: A comparative study of benign and malignant lesions in Brazilian patients

Prostatic lesions in Brazilian patients with benign prostatic hyperplasia (BPH, 26 cases) or adenocarcinoma (AC, 25 cases) were compared by qualitative microscopy and morphometric analysis. In 12 cases of BPH, prostate regions with no histological alterations were considered as controls (Ct). Archival material consisted of formalin-fixed, paraffin-embedded specimens obtained from prostatic transurethral resection and radical prostatectomy. Haematoxylin/eosin (HE)-stained sections were used to estimate the nuclear areas, perimeters and form factor values. HE-stained sections from AC specimens were also used for Gleason grading. BPH, AC and Ct could be discriminated by their nuclear areas and nuclear perimeters, but not by the nuclear form factor parameter. No significant differences were found when the AC data were compared using the combined version or the predominant grade version of the Gleason score (p = 0.8380 for nuclear area; p = 0.6076 for nuclear perimeter; p = 0.9202 for nuclear form factor; n = 200 nuclei per patient). This finding indicates that there is extensive heterogeneity in the size and shape of the nucleus in AC cells. These results also show that although the nuclear morphometry served to discriminate BPH and AC from each other and from Ct, it was not sufficient to correlate AC lesions with their respective Gleason scores in the human population analyzed.

Análise filogenética de Phytophthora capsici Leonian do estado de São Paulo baseada na seqüência de nucleotídeos da região ITS-5.8S rDNA

Phylogenetic analysis through morphological and cultural traits is considered inconsistent and hard to be scientifically accepted once there is no way to establish the direction of evolution on morphological traits. Molecular markers are suitable for phylogenetic analysis. The sequencing of ITS1 and ITS2 (internal transcribed spacers) regions and of 5.8S gene from ribosomal DNA were used to estimate the genetic variation and distance of 10 Phytophthora capsici isolates. The amount of genetic variation amongst isolated P. capsici from distinct regions of São Paulo State was 0.1 to 1.6 and 0.1 to 1.1% at ITS1 and ITS2, respectively, and a phylogenetic distance of about 78.5% between P. capsici and Phytophthora spp. was observed.