Thermal analysis and electrochemical study of Hg reactions on Pt-30% Ir alloy electrode

Thermogravimetry (TG), cyclic voltammetry (CV) and other analytical techniques were used to study the reactions of mercury with Pt-30% Ir alloy. The results allowed to suggest that an electrodeposited mercury film interacts with the substrate and when subjected to heat or electrochemical removal at least four mass loss steps or five peaks appeared during the mercury desorption process. The first two steps were attributed to Hg(0) removal probably from the bulk and from the adsorbed monolayer which wets the electrode surface. These two processes are responsible for peaks D and F in the cyclic voltammograms. The last two peaks (G, H) in CV were ascribed to the intermetallic compound decomposition. In TG curves, the last two steps were attributed to the PtHg4 (third step), and PtHg2 decomposition followed by Hg removal from the subsurface. The PtHg2 was formed by an eutectoide reaction: PtHg -> PtHg2+Hg(Pt-Ir). The Hg diffused to the subsurface was not detectable by cyclic voltammetry.

Soil compaction and soybean root growth

Soil compaction has a negative effect and Ca was shown to enhance root growth. The effects of soil subsurface compaction and liming on root growth and nutrient uptake by soybean were studied at the Department of Agriculture and Plant Breeding, São Paulo State University, Brazil. A Dark Red Latosol, sandy loam (Haplortox) was limed to raise base saturations to 40.1, 52.4 and 66.7%. The experimental pots were made of PVC tubes with 100 mm of diameter. Three rings with 150, 35 and 150 mm long were fixed one on the top of the other. In the central ring of 35 mm, the soil was compacted to bulk densities of 1.06, 1.25, 1.43 and 1.71 g.cm(-3). There was no effect of base saturation on soybean root and shoot growth and nutrition. Subsurface compaction led to an increase in root growth in the superficial layer of the pots with a correspondent quadratic decrease in the compacted layer. There was no effect of subsoil compaction on total root length and surface, soybean growth and nutrition. Soybean root growth was decreased by 10% and 50% when the soil penetrometer resistances were 0.52 MPa (bulk density of 1.45 g.cm(-1)) and 1.45 MPa (bulk density of 1.69 g.cm(-3)), respectively. In spite of the poor root growth in the compacted layer, once it nas overcome the root system showed an almost complete recovery.

Cytogenetic studies on holocentric chromosomes of five species of triatomines (Heteroptera: Reduviidae)

The chromosome number and meiotic cycle of triatomines were investigated. All five species presented the same diploid chromosome number, 2n = 22 (20A + XY in the male). Phylogenetic relationships based on chromosomal evidence and C-banded karyotypes in the subfamily are discussed. It is suggested that differences in DNA content are mainly due to variations in the amount of C-heterochromatin, which may be interpreted as loss and/or gain of C-regions. This interpretation is supported by the presence of meiotic and mitotic chromocentres which facilitate the transfer of C-positive material.

Chromosomal studies on five species of the genus Leptodactylus Fitzinger, 1826 (Amphibia, Anura) using differential staining

Cytogenetic studies were carried out on five species of Leptodactylus, namely L. fuscus, L, notoaktites, L. labyrinthicus, L. ocellatus, and L. podicipinus, after standard staining, Ag-NOR and C-banding as well as BrdU incorporation for three of them. The species had 2n = 22 chromosomes and two basic karyotype patterns. Chromosome 8 was a marker bearing a secondary constriction. In all species, this secondary constriction corresponded to the Ag-NOR site. The species had centromeric C-bands in all chromosomes of the complement, but some interstitial or telomeric bands seemed to differentiate some karyotypes, either at the species or the population level. In L. ocellatus, the C-banding pattern confirmed the occurrence of a heteromorphic pericentric inversion in chromosome 8 in specimens from one of the populations. The BrdU incorporation technique showed no detectable difference in the replication patterns of the major bands in the chromosomes of L. noroaktites, L. labyrinthicus, and L. ocellatus.

Cytogenetics of three breeds of river buffalo (Bubalus bubalis L.), with evidence of a fragile site on the X chromosome

The cytogenetic study of 182 river buffalo (Bubalus bubalis L., 2n=50) of Murrah, Mediterranean and Jaffarabadi breeds, from the State of São Paulo, was carried out to characterize their chromosomes and to detect possible chromosomal abnormalities. The karyotypes were indistinguishable with conventional staining as well as with C and replication R banding techniques. In about 44% of the sample (8 males and 72 females), an X marker chromosome due to a fragile site was shown. The frequency of metaphases expressing the fragility site on the X was highly variable, from 2.86 to 41.03%. In females, the fragile site, rarely appeared on both X chromosomes. Most of the metaphases showed only 1 marker chromosome. In R-banded metaphases using 5-bromodeoxyuridine (BrdU) treatment, it corresponded in general to the late replicating X chromosome. No correlation between the X fragile site and altered phenotype was found. Structural and numerical chromosome rearrangements were ruled out in the present sample of buffalo. (C) 1998 by Elsevier B.V.

Photo-induced effects in Ge25Ga10S65 glasses studied by XPS and XAS

The present paper focuses on the structural, electronic, and compositional properties of Ge25Ga10S65 glasses before and after UV illumination in air using X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) techniques. The XPS Ge 3d spectra reveal the existence of Ge-O bonds in the surface region of illuminated glass. In the case of this sample, XAS O K-edge spectra showed the formation of an enriched region of oxygen atoms in the glass bulk, indicating a different bonding structure of oxygen at the surface and in the bulk of the glass. Moreover, the structural changes that occur after UV illumination in the glass sample are identified as the formation of a homogeneous germanium oxide surface layer followed by an intermediary Ge25Ga10S65-yOz subsurface region. (c) 2005 Elsevier B.V. All rights reserved.

Chromosomal analysis of the leptodactylids Pleurodema diplolistris and Physalaemus nattereri (Amphibia, Anura)

Detailed characterizations of the karyotypes of the Brazilian leptodactylid frogs Pleurodema diplolistris, the only species of Pleurodema not studied cytogenetically so far, and Physalaemus nattereri, a species in the Ph. biligonigerus group, are presented. Both karyotypes had 2n = 22 and their chromosomes had a very similar morphology, except for pair 11, which was metacentric in Pl. diplolistris and telocentric in Ph. nattereri. The localization of nucleolar organizer regions (NORs) and heterochromatic bands allowed the differentiation of chromosomes that were morphologically indistinguishable between these species, such as pairs 1, 3 and 10, which showed interstitial C-bands in Ph. nattereri, and pair 8, that had an NOR and an adjacent C-band in Pl. diplolistris. Pair 8 also has NOR-bearing chromosomes in many other Pleurodema species. However, in these species, the NOR is located proximal to the centromere on the short arm, while in Pl. diplolistris it occurred distally on the long arm, a condition that may be considered a derived state. In Ph. nattereri, the NOR occurred on chromosome I 1 and differed from the other species of the Ph. biligonigerus group. In contrast, C-banding revealed a heterochromatic block near the centromere on the short arm of pair 3, a characteristic common to all members of this group of Physalaemus.

CYTOGENETIC AND DNA CONTENT IN 6 GENERA OF THE FAMILY CALLICHTHYIDAE (PISCES, SILURIFORMES)

Cytogenetic studies involving conventional Giemsa staining, C-banding analysis and silver staining of NORs were performed on nine species belonging to six genera of the family Callichthyidae. The diploid number ranged from 2n = 44 to 2n = 100, the number of chromosomal pairs with NORs ranged from 1 to 4 and constitutive heterochromatin was mainly distributed in the centromeric and/or pericentromeric position of the chromosomes. The DNA content of erythrocytes from six species studied ranged from 1.18 +/- 0.07 to 2.77 +/- 0.22 pg/nucleus. The extensive variability in karyotypes and in nuclear DNA content detected are in accordance with the initial hypothesis that chromosome rearrangements and polyploidy have played a significant role in the evolutionary history of Callichthyidae.

CYTOGENETIC REPORT OF A MALE BREAST-CANCER

The cytogenetic findings on G-banding in an infiltrating ductal breast carcinoma in a 69-year-old man are reported. The main abnormalities observed were trisomy of chromosomes 8 and 9 and structural rearrangement in the long arm of chromosome 17 (add(17)(q25)). Our results confirm the trisomy of chromosome 8 in the characterization of the subtype of ductal breast carcinomas and demonstrate that chromosome 17, which is frequently involved in female breast cancers, is also responsible for the development or progression of primary breast cancers in males.

Genetic relationships between Brazilian species of Molossidae and Phyllostomidae (Chiroptera, Mammalia)

A comparative analysis of G-banded karyotypes was performed for seven species of Chiroptera, representing two families (Phyllostomidae and Molossidae). Despite the differences in diploid and fundamental numbers, extensive homologies between six karyotypes were identified: A . planirostris, P. lineatus, S. lilium, G. soricina, P. hastatus (Phyllostomidae) and M. rufus (Molossidae). Robertsonian rearrangements and pericentric inversions account for the differences between the karyotypes of phyllostomid and molossid species. The homologies and rearrangements observed reinforce the monophiletic origin of phyllostomids and the inclusion of species in different subfamilies. In situ hybridization with genomic DNA revealed considerable conservation of the karyotypes, including C. perspicillata, that did not show G-band homologies with the other species analyzed. For the first time, chromosomal evidence is presented of a common origin for Phyllostomidae and Molossidae.

CYTOGENETIC ANALYSIS OF THE PAMPAS DEER, OZOTOCEROS-BEZOARTICUS (MAMMALIA, CERVIDAE)

The chromosome constitution of five males and three females of the Pampas deer (Ozotoceros bezoarticus) coming mainly from the region of Corumba-MS, was studied. The diploid number of the species was reconfirmed as 68 chromosomes with Fundamental Number (FN) = 74. The X chromosome was the largest and the Y the smallest in the genome. Constitutive heterochromatin demonstrated by C banding was present in the centromeric region of all chromosomes, except in pair number two, which had none, and in chromosome X which had a stained region in the telomere on the long arm, Chromosomes pairs 3 and 4 bore Ag-NORs. The banding patterns differed from those of previous reports for this species. This may be due to subspecific differences.

KARYOTYPIC ANALYSIS AND CHROMOSOME BIOMETRY OF CELL-CULTURES OF THE YELLOW-THROATED ALLIGATOR (CAIMAN-LATIROSTRIS DAUDIN)

Blood from eight specimens of both sexes of the alligator Caiman latirostris was collected and incubated in culture medium. Conventional as well as chromosomal banding (C and NOR) techniques were used.The diploid number was determined as 42, being 24 telocentric, 12 metacentric and six submetacentric, with real lengths varying from 1.49 to 6.08, 1.63 to 3.71, and 2.41 to 3.19 mum, respectively. The fundamental number was 60. About 81% of the chromosomes were small and 19% medium in size. NOR-banding was presented for the first time for this species and it was verified that only one submetacentric pair (no. 20) was marked on arm q, and under conventional staining it presented a secondary constriction. There was no association between NOR marked chromosomes.

Estudo citogenético em equinos para detecção de portadores de monossomia do cromossomo X

A cytogenetic study of 22 mares with fertility has showed that four of them had 63,X/64,XX mosaicism. The X-chromosome has presented the expected interstitial heterochromatic C - banding located in the long arm, besides of the usual centromeric band. The great variation of clinic signs observed in mares with mosaicism, could be due to the type of zygote or the time the mosaicism occured.

A LINE2 repetitive DNA sequence from the cichlid fish, Oreochromis niloticus: sequence analysis and chromosomal distribution

We report the cloning and characterization of a long interspersed nucleotide element (LINE) fi-om a cichlid fish, Oreochromis niloticus, and show the distribution of this element, called CiLINE2 for cichlid LINE2, in the chromosomes of this species. The identification of an open reading frame in CiLINE2 with amino acid sequence similarity to reverse transcriptases encoded by LINE-like elements in Caenorhabditis elegans, Platemys spixii, Schistosoma mansoni, Gallus gallus (CRI), Drosophila melanogaster (I factor), and Homo sapiens (LINE2), as well as the structure of the element, suggest it is a member of this family of non-long terminal repeat-containing retrotransposons. Search of a DNA sequence database identified sequences similar to CiLINE2 in four other fish species (Haplotaxodon microlepis, Oreochromis mossambicus, Pseudotropheus zebra, and Fugu rubripes). Southern blot hybridization experiments revealed the presence of sequences similar to CiLINE2 in all Tilapiini species analyzed from the genera Oreochromis, Tilapia, and Sarotherodon, and gave an estimated copy number of about 5500 for the haploid genome of O. niloticus. Fluorescent in situ hybridization showed that CiLINE2 sequences were organized in small clusters dispersed over all chromosomes of O. niloticus, with a higher concentration near chromosome ends. Furthermore the long arm of chromosome 1 was strikingly enriched with this sequence. The distribution of LINE2-related elements might underlie the difference in chromosome banding patterns observed between cold-blooded vertebrates and mammals.

Atributos físicos de latossolo vermelho sob pousio ou cultivado com forrageiras tropicais sob pastejo

The objective was to study the physical attributes of an Oxisol under fallow or planted with tropical grasses under grazing. The experiment was conducted under the experimental design of randomized blocks in split-plot 2 x 5, being five types of use of soil (Brachiaria ruziziensis, Panicum maximum cv. Aries, Brachiaria brizantha cv. MG5, Panicum maximum cv. Mombaca and fallow) and two evaluation periods (after the first and after the second grazing), with four replications. We evaluated the characteristics of soil bulk density, total porosity, microporosity and macroporosity, after the first and second grazing, and soil resistance to penetration after the second grazing. In layer of 0.00 to 0.10 m, the macroporosity was affected by the interaction between types of use and evaluation periods, while the microporosity and total porosity were reduced and the density was increased from first to second evaluation time. In the subsurface layer (0.10-0.20 m), there were significant effect only of evaluation time, on the macroporosity, total porosity and density. The porosity were reduced, while the density increased from first to second evaluation time. No significant effects of types of use of soil on penetration resistance in all layers studied. The maintenance of an Oxisol under fallow or cultivation with tropical grasses subjected to grazing cattle causes a reduction in total porosity and increased density of surface soil layers (0 to 0.10 m) and subsurface (0.10 - 0.20 m), without promoting changes on resistance to penetration mechanics.