Characterization of pNiXa,a serpin of Xenopus laevis oocytes and embryos,and its histidine-rich,Ni(II)-binding domain

A Ni(II)-binding serpin, pNiXA, is abundant in Xenopus oocytes and embryos. Kinetic assays show that purified pNiXa strongly inhibits bovine α-chymotrypsin (K₁ = 3 mM), weakly inhibits porcine elastase (K₁ = 0.5 μM), and does not inhibit bovine trypsin. The reversible, slow-binding inhibition of α-chymotrypsin by pNiXa is unaffected by Ni(II). Ovochymase in egg exudates is inhibited by pNiXa, but to a limited extent, even at high pNiXa concentrations. An octadecapeptide that models the His-rich domain (-HRHRHEQQGHHDSAKHGH-) of pNiXa forms six-coordinate, octahedral Ni(II)-complexes when the N-terminus is acetylated, and a square-planar Ni(II)-complex when the N-terminus is unblocked. Spectroscopy reveals two distinct types of octahedral Ni(II)-coordination to the N-acetylated octadecapeptide, involving, respectively, 3–4 and 5–6 imidazole nitrogens; the octadecapeptide undergoes partial, reversible precipitation in pH-and Ni(II)-dependent fashion, suggesting an insoluble, Ni(II)-coupled (Hx)_n-dimer. Such (Hx)_n-peptide interaction is confirmed by an enzyme-linked biotin-avidin assay with N-biotin-KHRHRHE-amide and N-acetyl-KHRHRHE-resin beads, which become coupled after adding Ni(II) or Zn(II). H₂O₂ oxidation of 2′-deoxyguanosine to mutagenic 8-hydroxy-2′deoxyguanosine is enhanced by the octahedral Ni(II)-octadecapeptide complex, although the effect is more intense with the square-planar Ni(II) octadecapeptide complex. Immunoperoxidase staining of whole mounts wish pNiXa antibody shows that pNiXa is distributed throughout gastrula-stage embryos and is localized during organogenesis in the brain, eye, spinal cord, myotomes, craniofacial tissues, and other sites of Ni(II) induced anomalies. Patterns of pNiXa staining are similar in controls and Ni(II)-exposed embryos. Binding of Ni(II) to pNiXa may cause embryotoxicity by enhancing oxidative reactions that produce tissue injury and genotoxicity. Although the natural target proteinases for pNiXa inhibition have not been established, pNiXa may be an important regulator of proteolysis during embryonic development. © 1996 Wiley-Liss, Inc.     

Chorology of the Euxinian and Hyrcanian element in the woody flora of Asia

The Euxinian and the Hyrcanian floristic province are analysed in respect to their trees and shrubs. These provinces mark the southern limit of the Euro-Siberian Region in SW. Asia. Mesophyllic forests dominate; they are deciduous, but there is a substantial component of evergreen shrubs in the understorey. Characteristics species frequently have a relic nature. Species lists and some exemplary distribution maps are presented for the Euxinian and the Hyrcanian element, both with endemic and more wide-spread species, including the characteristic Euxine-Hyrcanian group.     

The 33 kDa protein of photosystem II is a low-affinity calcium- and lanthanide-binding protein

We have shown that the isolated 33 kDa protein of photosystem II contains one calcium and one lanthanide low-affinity binding site with binding constants (K(D)) on the order of 10(-5) M. Binding of calcium or lanthanides to this site induces conformational changes in the protein that manifest in fluorescence emission spectra of the protein, circular dichroism spectra, and calorimetric thermograms where the phase transitions are shifted to lower temperatures. The role of calcium binding to the 33 kDa protein in the attainment of its native structure and the significance of this interaction for the oxygen evolution process are discussed.     

Characteristics of action potentials in Helianthus annuus

The action potentials induced by nondamaging electrical stimuli in 16- to 22-day-old plants of Helianthus annuus were examined. Typical recordings are presented. Mean values of their amplitudes and conduction velocities in the stem, the strength-duration relation, the 'all-or-none' law and the refractory periods have been determined. The amplitude and velocity of propagation were essentially identical in the upward and downward direction, but greater in the upper than in the lower half. In 'electrically active' plants, the rheobase value is 2 V, the minimum period for stimulation is 1.8 s. and the chronaxie 2.3 s. It is noted that the excitability level between similar plants on the same day and in the same plant on different days is highly variable and undergoes periodic changes.     

Determination of total aluminum, chromium, copper, iron, manganese, and nickel and their fractions leached to the infusions of black tea, green tea, Hibiscus sabdariffa, and Ilex paraguariensis (mate) by ETA-AAS

Total aluminum, chromium, copper, iron, manganese, and nickel were determined in black tea, green tea, Hibiscus sabdariffa, and Ilex paraguariensis (mate) by electrothermal atomic absorption spectrometry after nitric/perchloric acid digestion. In each case, one ground sample of commercially available leafy material was prepared and three 0.5-g subsamples were run in parallel. The infusions were also analyzed and the percentage of each element leached into the liquor was evaluated. The obtained results indicated that hibiscus and mate contained lower levels of aluminum (272±19 μg/g and 369±22 μg/g, respectively) as referred to black tea (759±31 μg/g) or green tea (919±29 μg/g) and suggested that mate drinking could be a good dietary source of essential micronutrient manganese (total content 2223±110 μg/g, 48.1% leached to the infusion). It was also found that the infusion of hibiscus could supply greater amounts of iron (111±5 μg/g total, 40.5% leached) and copper (5.9±0.3 μg/g total, 93.4% leached) as compared to other infusions. Moreover, it was found that the percentage of element leached to the infusion was strongly related to the tannins content in the beverage (correlation coefficients >0.82 with the exception for nickel); for lower tannins level, better leaching was observed.     

Hexavalent chromium removal in vitro and from industrial wastes, using chromate-resistant strains of filamentous fungi indigenous to contaminated wastes

Two chromate-resistant filamentous fungi, strains H13 and Ed8, were selected from seven independent fungal isolates indigenous to Cr(VI)-contaminated soil because of their ability to decrease hexavalent chromium levels in the growth medium. Morphophysiological studies identified strain H13 as a Penicillium sp. isolate and Ed8 as an Aspergillus sp. isolate. When incubated in minimal medium with glucose as a carbon source and in the presence of 50 microg/mL Cr(VI), these strains caused complete disappearance of Cr(VI) in the growth medium after about 72 h of incubation. Total chromium concentration in growth medium was constant during culture growth, and no accumulation of chromium in fungal biomass was observed. Quantitative determinations of oxidized and reduced chromium species during the reduction process revealed stoichiometric conversion of Cr(VI) to Cr(III). A decrease in Cr(VI) levels from industrial wastes was also induced by Ed8 or H13 biomass. These results indicate that chromate-resistant filamentous fungi with Cr(VI)-reducing capability could be useful for the removal of Cr(VI) contamination.     

Molecular and phenotypic characterisation of Bacillus thuringiensis isolated during epizootics in Cydia pomonella L

Twelve Bacillus thuringiensis strains were isolated from intestinal tracts of Cydia pomonella larvae during epizootics in different laboratory insect culture lines. Phenotypic and genetic similarity of these isolates, together with two cultured from Leucoma salicis larvae and 14 reference B. thuringiensis strains were determined. The epizootic bacteria did not form a single group based on numerical analysis of biochemical properties. Simple RAPD method with only one primer does not allow estimating the genetic similarity of B. thuringiensis strains. We propose a novel strategy based on combining several DNA patterns obtained by RAPD technique with different primers for B. thuringiensis typing. Majority of infections in the C. pomonella culture lines were caused by bacteria with different genotypes. However, two isolates cultured from infected insects at different time (one strain was isolated in 1990 and the other in 1992) had identical DNA fingerprint that suggested a possibility of these bacteria to survive in the laboratory and to cause infections in different years. The results of SDS-PAGE of whole-cell proteins revealed a possibility to apply protein profile analysis in epidemiological investigations of infections caused by B. thuringiensis. Strains with identical DNA patterns had very similar whole-cell protein profiles.     

Interchromosomal duplication of major histocompatibility complex class I regions in rainbow trout (Oncorhynchus mykiss), a species with a presumably recent tetraploid ancestry

Salmonid fishes are among the few animal taxa with a probable recent tetraploid ancestor. The present study is the first to compare large (>100 kb) duplicated genomic sequence fragments in such species. Two contiguous stretches with major histocompatibility complex (MHC) class I genes were detected in a rainbow trout BAC library, mapped and sequenced. The MHC class I duplicated regions, mapped by fluorescence in situ hybridization (FISH), were shown to be located on different metaphase chromosomes, Chr 14 and 18. Gene organization in both duplications is similar to that in other fishes, in that the class I loci are tightly linked with the PSMB8, PSMB9, PSMB10 and ABCB3 genes. Whereas one region, Onmy-IA, has a classical MHC class I locus (UBA), Onmy-IB encodes only non-classical class Ib proteins. The nucleotide diversity between the Onmy-IA and Onmy-IB noncoding regions is about 14%. This suggests that the MHC class I duplication event has occurred about 60 mya close to the time of an hypothesized ancestral tetraploid event. The present article is the first convincing report on the co-existence of two closely related MHC class I core regions on two different chromosomes. The interchromosomal duplication and the homology levels are supportive of the tetraploid model.Nucleotide sequence data reported are available in the DDBJ/EMBL/GenBank database under the accession numbers AB162342, AB162343 and from AY525774 to AY525776.