XX:XY sex chromosome system with X heterochromatinization: an early stage of sex chromosome differentiation in the Neotropic electric eel Eigenmannia virescens

An early stage of sex chromosome differentiation is reported to occur in the electric eel Eigenmannia virescens (Pisces, Sternopygidae) from populations of two tributaries of the Paraná river system (Brazil). Cytogenetic studies carried out in the two populations showed that the Mogi-Gua?u population is characterized by 2n = 38 chromosomes and undifferentiated sex chromosomes and the Tietê population presents 2n = 38 both for males and females and an XX:XY sex chromosome system. The X-chromosome is acrocentric, easily recognized by the presence of a conspicuous heterochromatin block in its distal portion; the Y-chromosome is probably one of the medium sized acrocentrics present in the male karyotype. BrdU induced R-bands of the two populations did not reveal any difference in the euchromatic regions of the chromosomes. AluI and HaeIII restriction enzyme digestion patterns and chromomycin A3 staining of the X-chromosome are presented. The possible role of heterochromatinization in the evolution of sex chromosomes in fish is discussed.     

Genetica

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Genetica     

Life cycle of an endogenous retrovirus, ZAM, in Drosophila melanogaster

ZAM is an env-containing member of the gypsy family of retrotransposons that represents a possible retrovirus of invertebrates. In this paper, we traced ZAM mobilization to get information about a potential path a retroelement may take to reach the germ line of its host. In situ hybridization on whole-mount tissues and immunocytochemistry analyses with antibodies raised against ZAM Gag and Env proteins have shown that all components necessary to assemble ZAM viral particles, i.e., ZAM full-length RNAs and Gag and Env polypeptides, are coexpressed in a small set of follicle cells surrounding the oocyte. By electron microscopy, we have shown that ZAM viral particles are indeed detected in this somatic lineage of cells, which they leave and enter the closely apposed oocyte. Our data provide evidence that the vesicular traffic and yolk granules in the process of vitellogenesis play an important role in ZAM transfer to the oocyte. Our data support the possibility that vitellogenin transfer to the oocyte may help a retroelement pass to the germ line with no need of its envelope product.     

Mitochondrial DNA Variation, Phylogenetic Relationships, and Evolution of Four Mediterranean Genera of Soles (Soleidae, Pleuronectiformes)

To increase knowledge about the systematics and evolution of Mediterranean soles, we assessed mitochondrial DNA variation, molecular phylogeny, and evolution in eight species from the genera Solea, Microchirus, Monochirus, and Buglossidium by large ribosomal subunit (16S) and cytochrome b (cytb) sequence analysis. Relevant molecular features are the great variation of base composition among species at the third codon in cytb and the heterogeneity of the nucleotide substitution rate. Phylogenies recovered using 16S nucleotide and cytb amino acid sequences agree with those based on morphology in assessing monophyly of Solea species and ancestry of Buglossidium luteum, but they are against the intergeneric differentiation of Microchirus and Monochirus. Conversely, phylogenetic trees based on cytb nucleotide sequences yielded relationships among taxa regardless of their evolutionary histories. The incongruities between morphological and molecular issues suggest the need for reassessing the systematic value of some morphological characters. Approximate estimates of the divergence time of Mediterranean soleid lineages range from 40 to 13 Mya (Oligocene–Miocene), indicating an ancient origin for the group. Received August 31, 1999; accepted December 17, 1999.     

In vitro proliferation and in vivo malignancy of cell lines simultaneously derived from a chemically-induced heterogeneous rat mammary tumor

Summary Identification of clones in primary tumors responsible for proliferation, invasion, and metastasis was carried out. Four different aneuploid established cell lines derived from a ductal infiltrating mammary rat tumor induced by 7,12-dimethylbenz[a]anthracene were studied for proliferative and growth features in vitro and for tumorigenic and metastatic potential in vivo in nude mice. Clones, named RM1, RM2, RM3, and RM4, were characterized by different proliferative activity. Clone RM1 showed the highest proliferative activity by both tritiated thymidine incorporation and S-phase flow cytometry, followed by clone RM4. Conversely, clones RM2 and RM3 showed a lower proliferation rate. Growth-promoting activity, tested on 3T3 Swiss cells, was high in all clones, although RM1 showed significantly lower growth factors—releasing activity. Nude mice tumorigenesis demonstrated a strong tumor induction of line RM1 (100% of the mice after 47±7 d) and a slightly lower tumor induction of line RM4 (70% of the mice after 69±9 d). Line RM3 showed tumor induction in 40% of the mice after 186±16 d. Lines RM2 showed no tumor induction. Metastasis occurred in mice treated with line RM1 only. Therefore, tumorigenesis and metastasis correlate with proliferation but not with the release of growth factors. In conclusion, flow cytometry monitoring of clones from heterogeneous primary tumors proved to be a suitable model for the study of in vivo malignancy and in vitro proliferation.     

Development of microsatellite markers using next-generation sequencing for the fish <Emphasis Type="Italic">Colossoma macropomum</Emphasis>

Tambaqui (Colossoma macropomum) is a fish species from the Amazon and Orinoco Rivers, with favorable characteristics to the cultivation system and great market acceptance in South America. However, the construction of a genetic map for the genetic improvement of this species is limited by the low number of molecular markers currently described. Thus, this study aimed to validate gene-associated and anonymous (non-genic) microsatellites obtained by next generation sequencing (RNA-seq and whole genome shotgun—WGS, respectively), for future construction of a genetic map and search for quantitative trait loci (QTL) in this species. In the RNA-seq data, the observed and expected heterozygosity (H_o and H_e) ranged from 0.09 to 0.73, and 0.09 to 0.85, respectively. In the WGS data, H_o and H_e ranged from 0.33 to 0.95, and 0.28 to 0.92, respectively. In general, the evaluation of 200 markers resulted in 45 polymorphic loci, of which 14 were gene-associated (RNA-Seq) and 31 were anonymous (WGS). Moreover, some markers were related to genes of the immune system, biological regulation/control and biogenesis. This study contributes to increase the number of molecular markers available for genetic studies in C. macropomum, which will allow the development of breeding programs assisted by molecular markers.     

Minimizing the Electrolyte Volume in Li–S Batteries: A Step Forward to High Gravimetric Energy Density

Sulfur electrodes confined in an inert carbon matrix show practical limitations and concerns related to low cathode density. As a result, these electrodes require a large amount of electrolyte, normally three times more than the volume used in commercial Li‐ion batteries. Herein, a high‐energy and high‐performance lithium–sulfur battery concept, designed to achieve high practical capacity with minimum volume of electrolyte is proposed. It is based on deposition of polysulfide species on a self‐standing and highly conductive carbon nanofiber network, thus eliminating the need for a binder and current collector, resulting in high active material loading. The fiber network has a functionalized surface with the presence of polar oxygen groups, with the aim to prevent polysulfide migration to the lithium anode during the electrochemical process, by the formation of S–O species. Owing to the high sulfur loading (6 mg cm^?2) and a reduced free volume of the sulfide/fiber electrode, the Li–S cell is designed to work with as little as 10 µL cm^?2 of electrolyte. With this design the cell has a high energy density of 450 Wh kg^?1, a lifetime of more than 400 cycles, and the possibility of low cost, by use of abundant and eco‐friendly materials.     

Can proton pumping by SERCA enhance the regulatory role of phospholamban and sarcolipin?

The effect of the incorporation of phosphorylated phospholamban (pPLN) and sarcolipin (SLN) in mercury-supported self-assembled lipid monolayers and in lipid bilayers tethered to mercury via a hydrophilic spacer was investigated by voltammetric techniques and electrochemical impedance spectroscopy. It was shown that pPLN and SLN do not permeabilize lipid bilayers toward ions at physiological pH. However, they exert a permeabilizing action toward inorganic monovalent cations such as K⁺ and Tl⁺, but not toward divalent cations such as Ca²⁺ and Cd^2 +, following a small decrease in pH. This behavior can be associated with their regulatory action on the Ca-ATPase of the sarcoplasmic reticulum (SERCA). SERCA pumps two Ca²⁺ ions from the cytosol to the lumen of the sarcoplasmic reticulum (SR) and two protons in the opposite direction, causing a transient decrease of pH in the immediate vicinity of its cytoplasmic domain. This decrease is expected to activate the liberated pPLN molecules and SLN to make the SR membrane leakier toward K⁺ and Na⁺ and the SLN ion channel to translocate small inorganic anions, such as Cl⁻. The effect of pPLN and SLN, which becomes synergic when they are both present in the SR membrane, is expected to favor a rapid equilibration of ions on both sides of the membrane.     

Sviluppo Vegetativo E Riproduttivo Di Alcune Longidiurne in Rapporto All'Azione Dell'Acido Gibberellico

Summary

Continuing the experiments on the action of Gibberellic acid on growth and development of herbaceous plants, the Authors have examined once more several species which require “long day” for espletion of some phases of their reproductive development.

The principal aim was to bring into evidence whether Gibberellic acid can really substitute for some manifestations of the reproductive development itself, or whether some apparent manifestations of reproductive development provoked by this substance are due primarily to modifications of vegetative processes determinated by it.

The experiments were carried out on Papaver somniferum L., Centaurea calcitrapa L., Oenothera acaulis L., Aethusa Cynapium L. and Myosurus minimus L.

Results obtained on Papaver somniferum demonstrate that Gibberellic acid accelerates the macroscopic flowering manifestations under short day conditions of plants already induced to flowering, substituting in this for the effect of “long day” factor in so far as concerns the lengthening of the floral axis. No experiments which can establish whether Gibberellic acid may have an action on specific processes involved in the transition to the reproductive stage, have so far been conducted on Papaver.

Experiments on Centaurea calcitrapa have revealed that Gibberellic acid, treatment though promoting in plants manteined in short-day conditions a “bolting” effect simulating that obtained usually only at long-day, does not succeed in flowering this is true in our experimental conditions (experiments limit: 10 weeks; (photo-phase at light intensity inferior to 2000 lux). Experiments on Centaurea were also supplemented with histological observation of esperimental material.

In the experiments on Oenothera acaulis, a long-day plant only for the macroscopic development phase of floral apparatus, and indeterminate for the formation of floral primordia, has been noted that Gibb. acid can, in the long run, partly substitute for the long-day effect. However, development of floral structures at shortday, is more easily obtained if the plants are supplied, besides with Gibberellic acid, also with other stimulating and trophic substances. This and others observations may indicate that Gibberellic acid represent only one of the substances involved in the metabolism of plants under long-day conditions.

Aethusa Cynapium has furnished results similar to those obtained with Centaurea, even if within very long experimental limits some apparently indirect action of Gibberellic acid towards flowering may occurs.

Preliminary experimental data on logday Myosurus minimus L. show that Gibberellic acid can substitute sooner or later for longday requirements in flowering. In fact, two months old plants flower when Gibberellic acid is supplied under 9 hr. shortday conditions while the controls in shorday remain vegetative. We must note that Myosurus flowers better when light extension is prevalently constituted by far red radiation the effect of which is apparently substituted more easily by Gibberellic acid even if its action appears less afficient and rapid than that of supplementary illumination.     

Inibizione della nodulazione radicale nel pisello meteor come conseguenza del trattamento nictofasico intermittente con luce rosso-estrema

Abstract

INHYBITION OF NODULATION IN METEOR PEA, BY NICTOPHASIC TREATMENT WITH FAR-RED RADIATION. — A remarkable inhybiting effect of far-red light (given to the aerial part of the plants as a flash befor and during the nictophase) on Pea root nodulation, has been achivied through some preliminary experiments. The relations between irradiated aerial parts and the activities of the underground organs in general, are being studied in the picture of photo-chromoperiodism.

Relations with the action of gibberellic acid (GA) are preliminary attempted. The inhibiting action of GA is far less striking in comparison with that of far-red radiation. Kinetin favores, at some extent, the nodulation process.