Cloning and characterization of a 70 kd heat shock cognate (hsc70) gene from the zebrafish (Danio rerio)

The heat shock 70 family of proteins is one of the most highly conserved among all species. The genes encoding these proteins have been cloned and sequenced from bacterial species to humans with a high degree of homology preserved throughout evolution. Here we describe the cloning and characterization of a cDNA encoding a 70 kd heat shock cognate (hsc70) gene from the zebrafish (Danio rerio). A high degree of conservation is observed among hsc70 genes of other species as shown by phylogenetic analysis. The characterization of a hsc70 gene in the zebrafish provides a marker for studying the role of a constitutively expressed member of the hsp70 family in an important developmental and evolutionary model system.     

Mathematical model for the ecosystem response of Lake Ladoga to phosphorus loading

The ecosystem response model described in this paper combines an ecosystem model and a three-dimensional circulation model of Lake Ladoga developed earlier by the authors. The ecosystem model describes the process of Lake Ladoga eutrophication, and its biological submodel describes changes in the phyto- and zooplankton. In the earlier model version, lake circulation was determined using a two-dimensional hydrodynamical model which was not completely adequate. The present model allows calculation of the distributions of phyto- and zooplankton and mineral phosphorus and nitrogen. One of its main advantages is that reliable computations of the ecosystem dynamics over an extended period of time are possible. The response of the ecosystem to different levels of phosphorus pollution loading and to weather conditions is studied.     

Typing of Verotoxins by DNA Colony Hybridization with Poly- and Oligonucleotide Probes,a Bead-Enzyme-Linked Immunosorbent Assay,and Polymerase Chain Reaction

To identify the type of Verotoxins (VT) produced by Verocytotoxin-producing Escherichia coli (VTEC), a sensitive bead-enzyme-linked immunosorbent assay and polymerase chain reaction with common and specific primers to various VTs (VT1, VT2, VT2vha, VT2vhb, and VT2vp1) were developed. Together with colony hybridization tests with oligo- and polynucleotide probes, these methods were applied to VTEC isolates to type the VT produced. The toxin types of 26 of 37 strains were identified, but the reaction profiles in assays of the remaining 11 strains suggested the existence of new VT2 variants. The application of these identification procedures may be useful as a tool for clinical and epidemiological studies of VTEC infection.     

In vitro culture selection increases glyphosate tolerance in barley

In vitro culture of barley calluses has been used to produce plants with increased glyphosate tolerance. Calluses from immature embryos of barleyHordeum vulgare L. (Jeff) were cultured on Murashige and Skoog medium with 10^-6, 10^-5, 10^-4, 5×10^-4, 10^-3, or 10^-2M glyphosate for one, four or thirty months. Plants were regenerated from calluses maintained in glyphosate medium at 10^-6, 10^-5 or 10^-4M for four months, at 10^-5 or 5×10^-4M for one month and at 10^-5M for thirty months. The progeny of each regenerated plant was analyzed for response to glyphosate. Some progenies showed increased tolerance to glyphosate.     

Structural and functional homology between the 29 kD rat liver nucleoprotein and the high mobility group 1 protein

A 29 kD soluble rat liver nucleoprotein (p29) has increased binding affinity for the hormone responsive element (RE) of the rat haptoglobin (Hp) gene during the acute-phase reaction. In this work the possibility of its structural and functional homology to the high mobility group 1 (HMG1) nonhistone protein constituent of chromatin was examined. The results of two-dimensional gel electrophoresis, Southwestern and Western immunoblot analyses, showed that p29 and HMG1 are homologous protein species. On the basis of in vitro and in vivo phosphorylation/dephosphorylation experiments, we discuss the modulatory role of phosphate groups in view of the structure and function of p29.     

Structure,molecular evolution and maintenance of copy number of extended repeated structures in the X-heterochromatin of Drosophila melanogaster

The 60 kb repeats located in the distal heterochromatin of the X chromosome of Drosophila melanogaster were cloned in overlapping cosmids. These regions, designated as SCLRs, comprised the following types of repeated elements Stellate genes, which are known to be involved in spermatogenesis; copia-like retrotransposons; LINE elements, including amplified Type rDNA insertions; and rDNA fragments. The following steps in SCLR formation were hypothesized: insertion of mobile elements into the rDNA and Stellate gene clusters: internal tandem duplication events; recombination between the rDNA cluster and Stellate tandem repeat; and amplification of the whole SCLR structure. There are about nine SCLR copies per haploid genome, but there is approximately a twofold variation in copy number between fly stocks. The SCLR copy number differences between closely related stocks are suggested to be the result of unequal sister chromatid exchange (USCE). The restricted variation in SCLR copy number between unrelated stocks and the absence of chromosomes free of SCLRs suggests that natural selection is active in copy number maintenance.     

Composition and function of cytochrome b559 in reaction centers of photosystem II of green plants

A review of a recent study of the spectral and thermodynamic properties of cytochrome b559 as well as of the electron transfer between b559 and photosystem II reaction center cofactors in isolated D1/D2/cytochrome b559 complex RC-2 is presented. Attention is paid to the existence of intermediary-potential (IP, +150 mV) and extra-low-potential (XLP, –45 mV) hemes located close to the acceptor (quinone) and donor (P680) sides of the reaction center cofactors, respectively. These hemes found in isolated RC-2 probably correspond to the high-potential and low-potential hemes in chloroplasts, respectively. The above location of the hemes is believed to allow the photoreduction of the XLP heme and photooxidation of the IP heme. The electron transfer between the two hemes is discussed in terms of the cyclic electron flow and possible involvement in water splitting.     

Sialosylcholesterol Effects on Reconstitution of Microfilament and Glia Filament

Abstract: The effects of α-sialosylcholesterol (α-SC) on formation of either microfilament or glia filament of rat astrocytes were investigated using a reconstitution system. Polymerization of the depolymerized microfilament preparation that had been extracted from a crude cytoskeletal fraction of rat astrocytes, in the presence of 100 m M KCI and 10 m M MgCI₂, was suppressed in a dose-dependent manner by α-SC. α-SC inhibited polymerization of G-actin in a similar manner. The intensity of a-SC inhibition of G- actin polymerization was as great as that of microfilament polymerization, suggesting that the inhibition of microfilament polymerization by α-SC was due to the direct action of α-SC on actin, the main component of microfilament. α-SC depolymerized partly the polymerized microfilament preparation, which resembled F-actin (microfilament-like filaments). α-SC suppressed, in a dose-dependent manner, polymerization of a glia filament preparation that had been extracted from astrocyte cytoskeletons in the presence of phalloidin. An increase in the amount of added α-SC (up to 15 n M ) decreased the amount of the larger glia filament-like filaments, which were 10 nm thick and centrifuged down at 16,000 g for 30 min, and increased that of smaller ones precipitated only after centrifugation at 100,000 g for 1 h. The lower the concentration of the depolymerized glia filament extract, the greater was the inhibition by α-SC of the polymerization. α-SC repressed polymerization of vimentin, the dominant component of glia filament. Vimentin polymerization was more strongly inhibited by α-SC than polymerization of glia filament was. The findings suggested that α-SC suppressed polymerization of glia filament through a direct action on vimentin and that the glia filament-associated proteins increased its structural stability in the presence of α-SC.     

The T→C mutation at position +96 of the untranslated region 3′ to the terminating codon of the β-globin gene is a rare polymorphism that does not cause a β-thalassemia as previously ascribed

We have observed a TC mutation at position +96 of the untranslated region 3 to the terminating codon of the -globin gene in members of two Czech families and one black family. Data from initial studies suggested that this change was the cause of a -thalassemia, but continued analyses have provided convincing evidence that this mutation is a simple polymorphism.