Pulsed-field gel electrophoresis for genotypic comparison of Rhizobium bacteria that nodulate leguminous trees

Abstract Pulsed-field gel electrophoresis (PFGE) was applied to characterize Rhizobium bacteria isolated from the root nodules of Acacia senegal and Prosopis chilensis trees growing in Sudan and Keya. For the electrophoresis, the total DNA of 42 isolates, embedded in agarose, was digested by a rare-cutting restriction endonuclease, Xba I. The PFGE run resulted in good resolution of the DNA fragments and gave the strains distinctive fingerprint patterns. The patterns were analysed visually and using automated clustering analysis, which divided the strains into groups resembling the results generated by numerical taxonomy. However, several strains had unique banding patterns, which indicates that these strains are genetically very diverse.     

An acetyl esterase of Trichoderma reesei and its role in the hydrolysis of acetyl xylans

Summary An acetyl esterase was purified from Trichoderma reesei by cation and anion exchange chromatography. The enzyme had a molecular weight of 45 000 as determined by SDS-electrophoresis, or 67 000 as determined by gel filtration. In chromatofocusing the enzyme was shown to consist of two isoenzymes with isoelectric points of 6.8 and 6.0. The enzyme showed activity towards naphthyl acetate, triacetin and glucose-and xylose acetates. However, it liberated acetic acid from acetylated xylo-oligomers only to a small extent. The liberation of acetic acid from the oligomeric substrate was enhanced by addition of endoxylanase and -xylosidase.     

The size of a vendace, Coregonus albula L., stock in a deep lake basin monitored by hydroacoustic methods

An acoustic estimate of the number and biomass of a vendace stock (age >2 + years) in a deep basin of Lake Karjalan Pyhäjärvi was made in August 1985. The acoustic data were collected at night during the summer stagnation. The vendace were on the lake bottom during the day and rose by midnight to the hypolimnion; they did not rise to the thermocline or water layers above it. In the research area the mean number of vendace was 1900 fish ha ⁻¹ and the mean biomass was 76 kg ha ⁻¹. Total vendace biomass was 151 in the whole 200-ha research area.     

Virulence plasmid-associated autoagglutination in Yersinia spp.

The autoagglutination of Yersinia enterocolitica was dependent on the presence of the virulence plasmid and on the active growth of bacteria in tissue culture media at 37 degrees C. Cultures with a high initial concentration of bacteria failed to autoagglutinate , indicating that synthesis of new virulence plasmid-associated surface factors was essential for autoagglutination. The synthesis of a plasmid-encoded polypeptide (molecular weight, 240,000), designated P1, that could be dissociated under strongly reducing conditions into subunits of 52,500 daltons was found to be correlated with autoagglutination. Further, a strain of Yersinia pseudotuberculosis [ YPIII ( PIB102 )], which has Tn5 inserted within the structural gene of P1 that prevents the synthesis of P1, failed to autoagglutinate , in contrast to the wild-type strain, strongly indicating that P1 is involved in this phenomenon. It was also found by immunoblotting that in addition to the common response to temperature, the P1 proteins of Y. enterocolitica and Y. pseudotuberculosis were immunologically related.     

Adenylyl Cyclases: mRNA and Characteristics of Enzyme Activity in Three Areas of Brain

Abstract: Arachidonic acid and oleoylacetylglycerol enhance depolarization-evoked glutamate release from hippocampal mossy fiber nerve endings. It was proposed this is a Ca²⁺-dependent effect and that protein kinase C is involved. Here we report that arachidonic acid and oleoylacetylglycerol synergistically potentiate the glutamate release induced by the Ca²⁺ ionophore ionomycin. The Ca²⁺ dependence of this effect was established, as removal of Ca²⁺ eliminated evoked release and the lipid-dependent potentiation. Also, Ca²⁺ channel blockers attenuated ionomycin- and KCI-evoked exocytosis, as well as the facilitating effects of the lipid mediators. Although facilitation required Ca²⁺, it may not involve an enhancement of evoked Ca²⁺ accumulation, because ionomycin-dependent glutamate release was potentiated under conditions that did not increase ionomycin-induced Ca²⁺ accumulation. Also, the facilitation may not depend on inhibition of K⁺ efflux, because enhanced release was observed in the presence of increasing concentrations of 4-aminopyridine and diazoxide did not reduce the lipid-dependent potentiation of exocytosis. In contrast, disruption of cytoskeleton organization with cytochalasin D occluded the lipid-dependent facilitations of both KCI- and ionomycin-evoked glutamate release. In addition, arachidonic acid plus glutamatergic or cholinergic agonists enhanced glutamate release, whereas a role for protein kinase C in the potentiation of exocytosis was substantiated using kinase inhibitors. It appears that the lipid-dependent facilitation of glutamate release from mossy fiber nerve endings requires Ca²⁺ and involves multiple presynaptic effects, some of which depend on protein kinase C.     

Spatial and environmental components of variation in the distribution patterns of subarctic plant species at Kevo, N Finland — a case study at the meso-scale level

This study presents a quantitative partitioning of the total variance in the patterns of occurrence of 231 vascular plant taxa in 362 1 × 1 km grids in the Kevo Nature Reserve into four independent components: purely spatial variation, spatially structured environmental variation, non-spatial environmental variation, and unexplained variation. This partitioning is done with (partial) constrained ordinations (canonical correspondence analysis) and associated Monte Carlo permutation tests. The numerical results suggest that most of the biological variance captured by the external explanatory variables is related to 'local' meso-scale environmental factors, as 12.6% of the variation in the species data is explained solely by the environmental variables. Part of the variance (6%) represents a spatially covarying environmental component, but only a very small part, ca 2%, is related to purely spatial variation. The amount of unexplained variation is very high (>75%). The results are compared and discussed in relation to the relative amounts of these four variance components at broader- and finer-scales and to the concepts of domains and transition zones of scales in biological patterning.     

Alu-Alu recombination results in a duplication of seven exons in the lysyl hydroxylase gene in a patient with the type VI variant of Ehlers-Danlos syndrome.

The type VI variant of the Ehlers-Danlos syndrome (EDS) is a recessively inherited connective-tissue disorder. The characteristic features of the variant are muscular hypotonia, kyphoscoliosis, ocular manifestations, joint hypermobility, skin fragility and hyperextensibility, and other signs of connective-tissue involvement. The biochemical defect in most but not all patients is a deficiency in lysyl hydroxylase activity. Lysyl hydroxylase is an enzyme that catalyzes the formation of hydroxylysine in collagens and other proteins with collagen-like amino acid sequences. We have recently reported an apparently homozygous large-duplication rearrangement in the gene for lysyl hydroxylase, leading to the type VI variant of EDS in two siblings. We now report an identical, apparently homozygous large duplication in an unrelated 49-year-old female originally analyzed by Sussman et al. Our simple-sequence-repeat-polymorphism analysis does not support uniparental isodisomy inheritance for either of the two duplications. Furthermore, we indicate in this study that the duplication in the lysyl hydroxylase gene is caused by an Alu-Alu recombination in both families. Cloning of the junction fragment of the duplication has allowed synthesis of appropriate primers for rapid screening for this rearrangement in other families with the type VI variant of EDS.     

Collagenous transmembrane proteins: collagen XVII as a prototype.

Collagenous transmembrane proteins are an emerging group of biologically versatile molecules which function as both cell surface receptors and matrix molecules. The seven group members have interesting structural similarities: they are integral membrane proteins in type II orientation and have one or more collagenous domains in the extracellular C-terminus; interspersed by non-collagenous stretches which confer structural flexibility to the ectodomain. A conserved coiled-coil sequence (linker domain) immediately adjacent to the extracellular face of the cell membrane presumably serves as a nucleus for trimerization and triple-helix folding of each collagen. Intriguingly, the ectodomains of at least some of these molecules are proteolytically shed from the cell surface, releasing a shorter form of the collagen into the extracellular matrix. Collagenous transmembrane proteins are expressed in many different tissues and cells, and are involved in a broad spectrum of biological functions, reaching from epithelial and neural cell adhesion, and epithelial-mesenchymal interactions during morphogenesis to host defense against microbial agents. Several group members are involved in the molecular pathology of genetic and acquired human diseases including epidermolysis bullosa, ectodermal dysplasia, bullous pemphigoid or Alzheimer disease. An extensively investigated member is collagen XVII, a keratinocyte surface protein, which attaches the epidermis to the basement membrane in the skin. In this review, the structure and functions of the currently known collagenous transmembrane proteins are summarized and, as a 'prototype' of the group, collagen XVII and its biology and pathophysiology are delineated.     

Two New Species of Aphelenchoididae (Nemata) from Declining Red Pines in Maryland

Aphelenchoides resinosi n. sp. and Ektaphelenchus joyceae n. sp. are described and illustrated from red pines of the Allegheny plateau of Maryland, USA. The new species were found in trees infested with Bursaphelenchus xylophilus. Primary diagnostic characters of A. resinosi females are constriction of the head, basal stylet knobs, tong postuterine sac, two incisures in the lateral field, and conical tail four to five anal body widths long with a simple terminal mucro. Diagnostic characters of the males are two pairs of subventral caudal papillae and spicule shape: Primary diagnostic characters of E. joyceae females are a slight constriction of the head, six similar lips, conical tail, and short postuterine sac. Diagnostic characters of the males are spicule size and shape, a single row of spermatocytes, and one pair of caudal papillae. Within-tree distributions of A. resinosi and E. joyceae are presented. A total of 70% of both red-needled and chlorotic-needled trees in the study were positive for A. resinosi and E. joyceae. Branch hierarchy was related to the percentage of samples positive for A. resinosi.     

CO2 exchange in the Empetrum nigrum-Sphagnum fuscum community

Summary The CO₂ exchange of the Empetrum nigrum-Sphagnum fuscum community of a raised bog was studied in the laboratory at different temperature (from 5 to 30° C) and irradiance (up to 128 W m^-2) combinations during one growing season. The total CO₂ exchange was divided into three components, namely those due to Empetrum nigrum, Sphagnum fuscum, and peat, respectively. At the optimum temperature (10 to 15° C) the maximum net CO₂ exchange of Empetrum nigrum was c. 200 and that of Sphagnum fuscum c. 250 mg CO₂ m^-2h^-1. The total respiration in peat increased exponentially from 50 to 350 mg CO₂ m^-2h^-1 with increasing temperature from 5 to 30° C. About 40% of the CO₂ fixed by the community in optimal temperature and irradiation conditions was released immediately.