Comparative feeding ecology of four syntopic Hypostomus species in a Brazilian southeastern river.

Though their broad distribution in most Brazilian rivers, scarce studies concerning ecological interactions on Hypostomus species are available. This study observes the diet, the trophic interactions and some morphological aspects of four syntopic species of Hypostomus. These fishes were studied at the superior part of the Corumbataí river, at São Paulo state, southeastern Brazil.

Morphological aspects in the ontogeny of Salminus hilarii Valenciennes, 1850 (Ostaryophysi: Characidae).

This study compared various morphological characteristics of S. hilarii, in order to verify possible variations over the life of the fish. It was used individuals collected from the Tietê river basin (sub-basins of Sorocaba, Jacaré Pepira and Corumbataí rivers) and from the Rio Grande basin (sub-basins of Pardo and Mogi Guaçu rivers).

Differences in the feeding of Rhamdia quelen (Siluriformes, Heptapteridae) in four distinct lotic systems.

The aim of this study was to compare the food composition of Rhamdia quelen in four distinct order rivers. It was performed at a low part at the basin of the Sorocaba river in systems classified as first (Anastácio stream), second (Nego stream), fifth (Tatuí river) and sixth (Sorocaba river) orders. Collections were performed every month between January and December of 2011.

Variations of Salminus hilarii diet (Ostariophysi, Characidae): seasonal and ontogenetic effects.

This study described the variations seasonal and ontogenetic of Salminus hilarii diet. Samples were collected in the Sorocaba River, São Paulo, Brazil, one of the few rivers where individuals of the species still occur in a higher frequency. The preys consumed were analyzed by Importance Alimentary Index (AIi).

Reproductive biology of the smooth butterfly ray Gymnura micrura.

This study provides the first detailed information on the reproductive biology of the smooth butterfly ray Gymnura micrura. A total of 905 individuals were sampled, 377 of which were used for the reproductive study. Juveniles accounted for 75% of the sample, but all life cycle stages were present in the study area.

Biological aspects of Schizodon nasutus Kner, 1858 (Characiformes, Anostomidae) in the low Sorocaba river basin, São Paulo state, Brazil.

Four biological aspects of Schizodon nasutus in the low Sorocaba river basin, São Paulo, Brazil were analysed. These were accomplished during the year seasons. The fish diet and the feeding activity were investigated by studying the repletion index, which showed no significant differences between seasons.

Diet and feeding activity of Acestrorhynchus lacustris (Lütken, 1875) (Characiformes, Acestrorhynchidae) in the water reservoir at Ribeirão Claro, SP.

A. lacustris is a widely distributed species in the São Francisco and Paraná river basins, mainly in lentic waters. Specimens were captured monthly, over a whole year in a reservoir built by damming the Ribeirão Claro stream (SP).

Diet and capture of Hypostomus strigaticeps (Siluriformes, Loricariidae) in a small Brazilian stream: relationship with limnological aspects.

The purpose of this study is to ascertain whether variations in the limnological parameters of the Corumbataí river resulting from the discharge of a variety of wastes into its waters may be responsible for spatial shifts in the diet and capture of the armored catfish Hypostomus strigaticeps (Regan, 1907). Individuals were collected over a period of two years from two sites with similar physical, albeit distinct limnological characteristics. As a whole, the environmental variables (temperature, pH, dissolved oxygen, electrical conductivity, and total coliforms and fecal coliforms) of the two sites were found to vary significantly.

Food resource utilization of the skates Rioraja agassizii (Müller & Henle, 1841) and Psammobatis extenta (Garman, 1913) on the continental shelf off Ubatuba, South-eastern Brazil.

The feeding habits of Rioraja agassizii (syn. Raja agassizii) and Psammobatis extenta (syn. Psammobatis glansdissimilis) of the South-eastern Brazilian coast were studied by means of stomach content analysis.

Splicing components are excluded from the transcriptionally inactive XY body in male meiotic nuclei.

The study of the effect of programmed cessation of transcription in a large nuclear domain, on the distribution of elements of the pre-mRNA splicing machinery, is the main aim of this paper. To this end, we took advantage of the nuclear partitioning of mouse spermatocytes early in meiosis into autosomal transcribing and XY nontranscribing compartments. This system also allows to extend this study to stages in sperm differentiation that are accompanied by reduction and eventual cessation of transcription.

Endoreduplication and polyploidy in fragile X cells induced by methotrexate and fluorodeoxyuridine: implications for diagnosis.

Lymphoblastoid cell lines from fragile X patients and amniotic cells from fragile X embryos, when cultured with methotrexate (MTX) or fluorodeoxyuridine (FUdR), showed a significant increase in endoreduplication and polyploidy. This phenomenon was not observed in fragile X lymphocytes or in lymphoblastoid cell lines and amniotic cells of normal control individuals. The relationship between the inducible fragile site at Xq27.

Isolation and characterization of the Drosophila nuclear envelope otefin cDNA.

We have recently identified and characterized a 53-kDa inner nuclear membrane-associated protein in Drosophila and termed it otefin. Here we report the isolation and characterization of cDNA and genomic clones of the otefin gene. Based on sequence analysis, we deduced that the primary translation product has a calculated mass of 45 kDa, contains many serine and threonine residues, and is mostly hydrophilic.

Regulation of mouse satellite DNA replication time.

The satellite DNA sequences located near the centromeric regions of mouse chromosomes replicate very late in S in both fibroblast and lymphocyte cells and are heavily methylated at CpG residues. F9 teratocarcinoma cells, on the other hand, contain satellite sequences which are undermethylated and replicate much earlier in S. DNA methylation probably plays some role in the control of satellite replication time since 5-azacytidine treatment of RAG fibroblasts causes a dramatic temporal shift of replication to mid S.

DNase I sensitivity of Microtus agrestis active, inactive and reactivated X chromosomes in mouse-Microtus cell hybrids.

We isolated Microtus agrestis-mouse somatic cell hybrid clones which had retained either the active or the inactive M. agrestis X chromosome. In both hybrid clones the X chromosomes retained their original chromatin conformation as studied by the in situ nick translation technique--the active X chromosome retained its high sensitivity to DNase I while the inactive one remained insensitive.

Cytological evidence of defective template in the fragile X chromosome.

In cells of fragile X patients, the changed X segment may appear as a poorly staining region or a gap, or as a deletion, involving one or both chromatids. To find out whether the fragile site represents an incompletely replicated DNA sequence, as has been suggested recently, we analyzed the four chromatids of methotrexate-induced endoreduplicated fragile X chromosomes. Our main observations were: (1) a deleted chromatid was never internal to a poorly staining one; (2) an endoreduplicated X chromosome with a fragile site never included a normal chromatid.

Evaluation of a laboratory system intended for use in physicians' offices. II. Reliability of results produced by health care workers without formal or professional laboratory training.

The Kodak DT-60 tabletop chemistry analyzer was evaluated with standardized protocols to determine the system's precision and accuracy when operated by four volunteers (a secretary, a licensed practical nurse, and two family medicine residents) in a simulated office laboratory. The variability of the results was found to be significantly greater than the variability of results produced by medical technologists who analyzed the same samples during the same study period with another DT-60 placed in the hospital laboratory. The source(s) of increased variance needs to be identified so the system can be modified or new control procedures can be developed to ensure the reliability of results used in patient care.

Evaluation of a laboratory system intended for use in physicians' offices. I. Reliability of results produced by trained laboratory technologists.

The accuracy and precision of the Kodak DT-60 tabletop chemistry analyzer were evaluated in the clinical laboratory at the Portland (Ore) Veterans Administration Medical Center, and its operational throughout and cost were estimated. All DT-60 tests that were studied exhibited clinically acceptable precision and, except for the glucose method, accuracy. The accuracy of the glucose method was indeterminate with the available data.

5-aza-C-induced changes in the time of replication of the X chromosomes of Microtus agrestis are followed by non-random reversion to a late pattern of replication.

Treatment with 5-azacytidine (5-aza-C) causes an advance in the time of replication and enhances the DNase-I sensitivity of the inactive X chromosome in Gerbillus gerbilllus fibroblasts. We found that these changes were not stably inherited and upon removal of the drug the cells reverted to the original state of one active and one inactive X chromosome. In order to determine whether this reversion was random, we used a cell line of female Microtus agrestis fibroblasts in which the two X chromosomes are morphologically distinguishable.

DNA hypomethylation causes an increase in DNase-I sensitivity and an advance in the time of replication of the entire inactive X chromosome.

We have examined the effect of 5-azacytidine (5-aza-C) induced hypomethylation of DNA on the time of replication and DNase I sensitivity of the X chromosomes of female Gerbillus gerbillus (rodent) lung fibroblast cells. Using in situ nick translation to visualise the potential state of activity of large regions of metaphase chromosomes we show that 5-aza-C causes a dramatic increase in the DNase-I sensitivity of the entire inactive X chromosome of female G. gerbillus cells and this increase in nuclease sensitivity correlates with a large shift in the time of replication of the inactive X chromosome from late S phase to early S phase.

DNase I sensitivity in facultative and constitutive heterochromatin.

In situ nick translation allows the detection of DNase I sensitive and insensitive regions in fixed mammalian mitotic chromosomes. We have determined the difference in DNase I sensitivity between the active and inactive X chromosomes in Microtus agrestis (rodent) cells, along both their euchromatic and constitutive heterochromatic regions. In addition, we analysed the DNase I sensitivity of the constitutive heterochromatic regions in mouse chromosomes.

Mapping of DNAase I sensitive regions on mitotic chromosomes.

We have shown that in fixed mitotic chromosomes from female G. gerbillus cells the inactive X chromosome is distinctly less sensitive to DNAase I than the active X chromosome, as demonstrated by in situ nick translation. These results indicated that the specific chromatin conformation that renders potentially active genes sensitive to DNAase I is maintained in fixed mitotic chromosomes.

Analysis of a Chinese hamster temperature-sensitive cell cycle mutant arrested in early S phase.

E36 ts24 is a temperature-sensitive cell cycle mutant which has been derived from the Chinese hamster lung cell line E36. This mutant is arrested in phase S when incubated at the restrictive temperature (40.3 degrees C) for growth.

Patterns of heterochromatin replication and condensation correlate in rat kangaroo PtK2 cells.

Chromosome replication in mammalian cells in an ordered phenomenon. This is true also for the condensation in G2 of the heterochromatic chromosomal regions in mouse cells. The generality of this phenomenon and its mechanism are not known, nor is it known whether the order of condensation of the heterochromatic chromosomal segments in G2 reflects the order of replication or is independent of it.

In situ nick-translation distinguishes between active and inactive X chromosomes.

Template-active regions of chromatin are structurally distinct from nontranscribing segments of the genome. Recently, it was suggested that the conformation of active genes which renders them sensitive to DNase I may be maintained even in fixed mitotic chromosomes. We have developed a technique of mitotic cell fixation and DNase I-directed nick-translation which distinguishes between active and inactive X chromosomes.

A temperature sensitive mutant of a Chinese hamster cell line exhibiting high chromosomal breakage.

A temperature sensitive mutant exhibiting a very high level of chromosomal aberrations has been isolated from the Chinese hamster cell line E36. The chromosome aberrations, which include chromosome and chromatid breaks, multiradial configurations, dicentrics, and pulverizations, start to appear 1 h after a shift in temperature from 34 degrees C to 40.5 degrees C.