Niedoszłe przejście graniczne Wołosate–Łubnia. Refleksja nad bieszczadzkim odcinkiem pogranicza polsko-ukraińskiego

The author writes about an initiative to open a border crossing between Poland and Ukraine in the Bieszczady village of Wołosate, concentrating particularly on the social actors involved and showing their positions: the Bieszczady National Park, the Bieszczady Border Guard Division, local society, the Polish state, and also tourists, ecologists, and other activists engaged in the affair. The author’s reflections are based on statements gathered during a stay in Wołosate and Ustrzyki Górne in July 2014 and on other opinions regarding the question. These considerations differentiate, at the theoretical level, between the border administration and society, and enable the marked specificity of this fragment of the Polish-Ukrainian border to be perceived.

Structural insight intoL-ribulose 3-epimerase fromMesorhizobium loti

L-Ribulose 3-epimerase (L-RE) fromMesorhizobium lotihas been identified as the first ketose 3-epimerase that shows the highest observed activity towards ketopentoses. In the present study, the crystal structure of the enzyme was determined to 2.7 Å resolution. The asymmetric unit contained two homotetramers with the monomer folded into an (α/β)8-barrel carrying four additional short α-helices. The overall structure ofM. lotiL-RE showed significant similarity to the structures of ketose 3-epimerases fromPseudomonas cichorii,Agrobacterium tumefaciensandClostridium cellulolyticum, which use ketohexoses as preferred substrates. However, the size of the C-terminal helix (α8) was much larger inM. lotiL-RE than the corresponding helices in the other enzymes. InM. lotiL-RE theα8 helix and the following C-terminal tail possessed a unique subunit–subunit interface which promoted the formation of additional intermolecular interactions and strengthened the enzyme stability. Structural comparisons revealed that the relatively small hydrophobic pocket of the enzyme around the substrate was likely to be the main factor responsible for the marked specificity for ketopentoses shown byM. lotiL-RE.

Contracaecumovale (Nematoda: Anisakidae) from Rollandia rolland Quoy & Gaimard 1824 (Aves, Podicipedidae) in Argentina

Necropsy on 15 specimens of white-tufted grebe, Rollandiarolland, caught in the Mar Chiquita and Chascomús lagoons (Buenos Aires province), revealed the presence of Contracaecumovale (Linstow, 1907). This nematode shows a marked specificity for podicipediform birds. The specimens were identified from morphological study on features such as cephalic and esophageal structures and caudal papillae, using both optical and scanning electron microscopy. This is the first record of C. ovale parasitizing R. rolland in Argentina.

Identification and Characterization of a nodH Ortholog from the Alfalfa-Nodulating Or191-Like Rhizobia

Nodulation of Medicago sativa (alfalfa) is known to be restricted to Sinorhizobium meliloti and a few other rhizobia that include the poorly characterized isolates related to Rhizobium sp. strain Or191. Distinctive features of the symbiosis between alfalfa and S. meliloti are the marked specificity from the plant to the bacteria and the strict requirement for the presence of sulfated lipochitooligosac-charides (Nod factors [NFs]) at its reducing end. Here, we present evidence of the presence of a functional nodH-encoded NF sulfotransferase in the Or191-like rhizobia. The nodH gene, present in single copy, maps to a high molecular weight megaplasmid. As in S. meliloti, a nodF homolog was identified immediately upstream of nodH that was transcribed in the opposite direction (local synteny). This novel nodH ortholog was cloned and shown to restore both NF sulfation and the Nif+Fix+ phenotypes when introduced into an S. meliloti nodH mutant. Unexpectedly, however, nodH disruption in the Or191-like bacteria did not abolish their ability to nodulate alfalfa, resulting instead in a severely delayed nodulation. In agreement with evidence from other authors, the nodH sequence analysis strongly supports the idea that the Or191-like rhizobia most likely represent a genetic mosaic resulting from the horizontal transfer of symbiotic genes from a sinorhizobial megaplas-mid to a not yet clearly identified ancestor.

Cyst wall synthase: N-acetylgalactosaminyltransferase activity is induced to form the novel N-acetylgalactosamine polysaccharide in the Giardia cyst wall

Uridine-5′-diphospho-N-acetylgalactosamine (UDP-GalNAc) is required in the formation of the outer filamentous wall of Giardia and is synthesized by inducible enzymes in the cytosol of encysting trophozoites. In this study, an inducible enzyme activity that is associated with a particle population isolated from encysting Giardia is reported, and this activity exclusively incorporates [1-14C]GalNAc (from UDP-[14C]GalNAc) into an ethanol precipitate with the same properties as the filamentous cyst wall of Giardia. This ethanol precipitate exhibits characteristics of Giardia cyst wall filaments in that both contain GalNAc as the only sugar moieties and are SDS-insoluble, proteinase- and alkali-resistant and acid-hydrolysable. However, since the precise chemical nature of the ethanol precipitate remains unknown, this enzyme activity is referred to tentatively as cyst wall synthase (CWS). CWS activity peaks in cells between 24 and 36 h of encystment and exhibits a high affinity and marked specificity for UDP-GalNAc as its substrate. UDP-N-acetylglucosamine, UDP-glucose, UDP-galactose, d-glucosamine and d-galactosamine were not incorporated into the ethanol precipitate. Partially purified CWS activity exhibits an apparent K m of 0·048 mM for UDP-GalNAc, a V max of 0·70 nmol min−1 (mg protein)−1 and a requirement for divalent cations in the following order of preference: Ca2+, Mg2+>Co2+>>>Mn2+, Zn2+. EDTA inhibits CWS activity.

Insertions of a Novel Class of Transposable Elements With a Strong Target Site Preference at the r Locus of Maize

The r locus of maize regulates anthocyanin synthesis in various tissues of maize through the production of helix-loop-helix DNA binding proteins capable of inducing expression of structural genes in the anthocyanin biosynthetic pathway. The complex r variant, R-r:standard (R-r), undergoes frequent mutation through a variety of mechanisms including displaced synapsis and crossing over, and intrachromosomal recombination. Here we report a new mechanism for mutation at the R-r complex: insertion of a novel family of transposable elements. Because the elements were first identified in the R-p gene of the R-r complex, they have been named P Instability Factor (PIF). Two different PIF elements were cloned and found to have identical sequences at their termini but divergent internal sequences. In addition, the PIF elements showed a marked specificity of insertion sites. Six out of seven PIF-containing derivatives examined had an element inserted at an identical location. Two different members of the PIF element family were identified at this position. The seventh PIF-containing derivative examined had the element inserted at a distinct position within r. Even at this location, however, the element inserted into a conserved target sequence. The timing of PIF excision is unusual. Germinal excision rates can range up to several percent of progeny. Yet somatic sectors are rare, even in lines exhibiting high germinal reversion rates.

Specificity and Differences in Three Methods of Assessing Trainable Mental Retardates' Reaction Time

The purposes of this study were to determine the specificity and differences in reaction time that exist among three manual methods of measurement. This dependent variable was measured from onset of a light stimulus until activation of a microswitch by one of the following methods: depressing or releasing a panel-mounted button or depressing a hand-held button. A rotational order of testing was implemented with 35 trainable mentally retarded subjects. Data indicated marked specificity among the three methods; reaction times were significantly faster with the depressed and hand-held methods than with the released method.

Enzyme-induced inactivation of transminases by acetylenic and vinyl analogues of 4-aminobutyrate

The reactions of two analogues of 4-aminobutyrate, namely 4-aminohex-5-ynoate and 4-aminohex-5-enoate, with three transaminases were studied. Three pure enzymes were used, aminobutyrate transaminase (EC 2.6.1.19), ornithine transaminase (EC 2.6.1.13) and aspartate transaminase (EC 2.6.1.1), and the course of the reactions was studied by observing changes in the absorption spectrum of the bound coenzyme and by observing loss of activity. All of the enzymes were inactivated by either inhibitor, but amino-hexenoate showed a marked specificity for aminobutyrate transaminase. Aminohexynoate was most potent towards ornithine transaminase, and with this enzyme transamination of the inhibitor is an important factor in protecting the enzyme. Most of the reactions could be analysed as first order, with the observed rate constant showing a hyperbolic dependence on inhibitor concentration.

The hydrolysis of phosphatidylinositol by lysosomal enzymes of rat liver and brain

1. Lysosomes from rat liver contain two enzymic systems for hydrolysing phosphatidyl-inositol: a deacylation via lysophosphatidylinositol producing glycerophosphoinositol and non-esterified fatty acid, and a phospholipase C-like cleavage into inositol 1-phosphate and diaclygycerol. 2. The separate enzyme systems involved can be distinguished by gel filtration, differential temperature-stability and the inhibitory action of detergents. 3. The enzyme systems both have pH optima at 4.8 and their attack on a pure phosphatidylinositol substrate is inhibited by many bivalent metals including Ca2+ and Mg2+, and cationic drugs. 4. Whereas the deacylation system will attack other glycerophospholipids, the phospholipase C shows a marked specificity towards phosphatidylinositol, although it will also slowly attach phosphatidylcholine with the liberation of phosphocholine. 5. Gel filtration and temperature-stability distinguish the phospholipase C from lysosomal phosphatidic acid phosphatase, but not from sphingomyelinase. 6. Evidence is presented that an EDTA-insensitive phospholipase C degrading phosphatidylinositol is present in rat brain.