The pentylenetetrazole-kindling model of epilepsy in SAMP8 mice: behavior and metabolism

This work describes a novel epilepsy model, combining pentylenetetrazole (PTZ) kindling with the senescence-accelerated mouse P8 (SAMP8) a model for aging. The 2- and 8-month-old SAMP8 mice were treated with PTZ, phenobarbital plus PTZ or saline every 48 h during a period of 40 days. Both 2- and 8-month-old PTZ-kindled mice showed a behavioral pattern that was very similar to severe chronic epilepsy with secondary generalized seizures. Two out of six 8-month-old animals died in the PTZ group. Interestingly, atypical absence seizures were limited to the 8-month-old PTZ group. Furthermore, 8-month-old mice were more sensitive to the sedative effect of phenobarbital. The concentrations of several amino acids were examined by HPLC. Lower levels of amino acids were found in the 8-month-old compared to the 2-month-old control animals. No biochemical changes were observed between the groups of 2-month-old animals, while in the 8-month-old animals both treatment groups showed significantly higher concentrations of GABA, glutamine and glutathione. Thus, it could be shown that cerebral metabolism of 8-month-old SAMP8 mice was more sensitive to PTZ and phenobarbital than metabolism of 2-month-old mice. Furthermore, it is suggested that glutamate metabolism in brains of 8-month-old SAMP8 mice is altered and that excessive glutamate is transformed, in considerable amounts, into glutamate related metabolites, possibly in astrocytes.     

Preparation and characterisation of chitosans with oligosaccharide branches

The trimer 2-acetamido-2-deoxy-D-glucopyranosyl-beta-(1-->4)-2-acetamido-2-deoxy-D-glucopyranosyl-beta-(1-->4)-2,5-anhydro-D-mannofuranose (A-A-M) was reductively N-alkylated onto a fully de-N-acetylated chitosan (F(A)<0.001, DP(n)=25) to obtain branched chitosans with degree of substitution (DS) of 0.070, 0.23 and 0.40, as determined by 1H NMR spectroscopy. The apparent pK(a) values of the primary and secondary amines of the chitosans substituted with the trimer A-A-M were determined by monitoring the chemical shift of the H-2 of GlcN, and were determined as 6.5-6.9 for the primary (unsubstituted) amines and as 5.0-5.2 for the secondary (substituted) amines. The intrinsic pK(a) values (pK(int)) were found to be 7.3-7.4 for the substituted and 8.7 for the unsubstituted amines. The chitosan branched with A-A-M (DS 0.40) was found to be soluble in aqueous solution over the entire pH range. SEC-MALLS (size-exclusion chromatography with a multi-angle laser light scattering detector) further showed that addition of branches did not affect the molar hydrodynamic volume of the chitosan.     

Evolution of Cyanobacteria by Exchange of Genetic Material among Phyletically Related Strains

The cyanobacterial radiation consists of several lineages of phyletically (morphologically and genetically) related organisms. Several of these organisms show a striking resemblance to fossil counterparts. To investigate the molecular mechanisms responsible for stabilizing or homogenizing cyanobacterial characters, we compared the evolutionary rates and phylogenetic origins of the small-subunit rRNA-encoding DNA (16S rDNA), the conserved gene rbcL (encoding d-ribulose 1,5-bisphosphate carboxylase-oxygenase large subunit), and the less conserved gene rbcX. This survey includes four categories of phyletically related organisms: 16 strains of Microcystis, 6 strains of Tychonema, 10 strains of Planktothrix, and 12 strains of Nostoc. Both rbcL and rbcX can be regarded as neutrally evolving genes, with 95 to 100% and 50 to 80% synonymous nucleotide substitutions, respectively. There is generally low sequence divergence within the Microcystis, Tychonema, and Planktothrix categories both for rbcLX and 16S rDNA. The Nostoc category, on the other hand, consists of three genetically clustered lineages for these loci. The 16S rDNA and rbcLX phylogenies are not congruent for strains within the clustered groups. Furthermore, analysis of the phyletic structure for rbcLX indicates recombinational events between the informative sites within this locus. Thus, our results are best explained by a model involving both intergenic and intragenic recombinations. This evolutionary model explains the DNA sequence clustering for the modern species as a result of sequence homogenization (concerted evolution) caused by exchange of genetic material for neutrally evolving genes. The morphological clustering, on the other hand, is explained by structural and functional stability of these characters. We also suggest that exchange of genetic material for neutrally evolving genes may explain the apparent stability of cyanobacterial morphological characters, perhaps over billions of years.The current species diversity of the cyanobacterial radiation comprises several lineages of phyletically (morphologically and genetically) related organisms (26). An intriguing question is whether this reflects stability of cyanobacterial characters or whether the phyletic similarities originate from relatively recent common ancestors. Analyses of precambrian microfossils (superficially, hardly distinguishable from recent cyanobacteria) support the view of retention of cyanobacterial properties (1, 11, 28). However, on the basis of molecular data, a 2-billion-year-old mutual ancestor for prokaryotes has been suggested (5), implying that the similarities between the earliest records of cyanobacteria and present-day species do not reflect homologies but rather indicate analogies. In this context, the phyletically clustered groups may reflect a relatively recent divergence of the modern species.In this work we have addressed, by molecular evolutionary studies, the mechanisms responsible for conserving or homogenizing phyletical characters within groups of cyanobacteria. We investigated the evolutionary rates and origins for two genomic regions, by analyzing strains both within and among groups of phyletically related organisms. This was done by comparative analysis of the small-subunit rRNA-encoding DNA (16S rDNA), which is conserved by the RNA function (37), and the rbcLX region with both conserved and less conserved elements. The rbcLX region contains an intergenic spacer (with no identified functional units), the gene rbcX with a possible chaperonin-like function (18), and the 3′ end of rbcL (encoding the highly conserved d-ribulose 1,5-bisphosphate carboxylase-oxygenase large subunit [LSU]) (23). We analyzed a data set consisting of four phyletically clustered cyanobacterial strain categories, as inferred from microscopic observations and 16S rDNA analysis (26, 31). The data set includes the Microcystis category (16 strains), consisting of unicellular organisms, the Tychonema (6 strains) and Planktothrix (10 strains) categories, which contain multicellular, filamentous organisms, and the Nostoc category (12 strains), which includes both morphologically and genetically slightly divergent organisms (26, 34). The strains in this last category share among other features the ability of cellular differentiation to produce heterocysts with nitrogenase activity.Our sequence data suggest an evolutionary model involving several events of gene transfer between phyletically closely related organisms but not between less related organisms. We propose that this gene transfer has led to the observed sequence homogeneity for the groups of related organisms and that exchange of genetic material stabilizes the function and structure of proteins encoded by neutrally evolving genes. Our gene transfer model may explain the similarity between the fossil and the recent species.     

An ultrastructural overview of tubificid spermatozoa

The spermatozoa of seven species of tubificid oligochaete were compared to those already described in order to supply spermatozoal characters for systematic work on Tubificidae. The spermatozoa of Clitellio arenarius (subfamily Tubificinae) resemble those of the two other known members of the subfamily (Tubifex tubifex and Tubificoides amplivasatus) in being of two different types and in showing the same morphology of acrosomes and nuclei. Among Phallodrilinae, the three gutless species Inanidrilus bulbosus, Inanidrilus leukodermatus and Olavius planus share with Bathydrilus formosus the shape of the nucleus and various characters of the acrosome, whereas Thalassodrilus prostatus is particular in having the acrosome vesicle external to the tube and the longest middle piece recorded in oligochaetes. Monopylephorus limosus and Rhizodrilus russus (Rhyacodrilinae) differ widely in acrosomal and nuclear characters: M. limosus has a twisted nucleus, whereas R. russus has an apically flanged nucleus with a conspicuous apical concavity and an endonuclear canal. The data published on spermatozoa of the Limnodriloidinae are reviewed.Department of Zoology University of Göteborg     

Differentiation in floral scent chemistry among populations of Conopodium majus (Apiaceae)

The floral scent of Conopodium majus was trapped by head-space adsorption, and analysed by GC-MS. Two chemotypes of flower scent could be distinguished, both differing from a background of leaves. Characteristic of one chemotype were 4-oxoisophorone and pyridin-3-carboxaldehyde, and characteristic of the other were some sesquiterpenes. In addition, samples of infructescences emitted none or lower amounts of the compounds above. The difference in scent composition was large enough to distinguish three studied populations from each other, and from the blanks, in a principal component analysis. It was concluded that despite its sexually "promiscuous" flowers, C. majus shows differentiation in scent chemistry that might reflect an ecotypic response to local faunae of pollinators of major importance. Whether pollination ecotypes occur deserves further studies.     

Norwegian water quality criteria — ecosystems approach

General water quality criteria for Norwegian Waters were developed by the State Pollution Control Authority in the earch 1980s. The need for further refinement of these criteria became apparent in the mid-1980s. New water quality criteria were developed in conjunction with the development of a system for assessment of water uses. Two fundamental principles are outlined for determining the classification of water quality in Norway:

1. The classification for polluted water. The basis for this system is the natural water quality without any form of influence from man. It is the influence of pollution on the water quality, or the difference between the natural water quality and the water quality today that is classified.
2. The system for assessment of water quality for various uses is based both on the existing water quality and some physical and practical properties of the environment. The water quality criteria are specific for various uses.

Comprehensive planning in Norway should include physical planning and areal planning of rivers, lakes, and coastal areas. Water use planning will become an indtegral part of comprehensive master planning. This paper describes the system for assessment of water resources uses. Explaining the principles of the system is the main feature of this paper.     

Can sunspot activity and ultraviolet-B radiation explain cyclic outbreaks of forest moth pest species?

Cyclic outbreaks of forest moth pest species have long remained a puzzle for foresters and ecologists. This paper presents time-series exhibiting a strong negative relationship between sunspot numbers and population indices of autumnal and winter moths, both in a mountain birch forest in central Norway and in a mixed lowland forest in southern Norway. In the latter area, also the population level of a moth species feeding entirely on lichens was negatively related to sunspot numbers. Low sunspot activity leads to a thinner ozone layer and thus higher surface ultraviolet (UV)-B radiation. As winter moth larvae prefer leaves subjected to enhanced UV-B radiation, we suggest that the causal relationship between sunspots and moths is that the metabolic costs of producing UV-B-protective pigments during periods of low sunspot activity reduce trees' and lichens' resistance to herbivores, and thus increase the survival of moth larvae. Higher peak densities of moth cycles in mountain forests could be explained by the general higher UV-B radiation at higher altitudes.     

Optimisation of the surface electrostatics as a strategy for cold adaptation of uracil-DNA N-glycosylase (UNG) from Atlantic cod (Gadus morhua)

Cold-adapted enzymes are characterised by an increased catalytic efficiency and reduced temperature stability compared to their mesophilic counterparts. Lately, it has been suggested that an optimisation of the electrostatic surface potential is a strategy for cold adaptation for some enzymes. A visualisation of the electrostatic surface potential of cold-adapted uracil-DNA N-glycosylase (cUNG) from Atlantic cod indicates a more positively charged surface near the active site compared to human UNG (hUNG). In order to investigate the importance of the altered surface potential for the cold-adapted features of cod UNG, six mutants have been characterised and compared to cUNG and hUNG. The cUNG quadruple mutant (V171E, K185V, H250Q and H275Y) and four corresponding single mutants all comprise substitutions of residues present in the human enzyme. A human UNG mutant, E171V, comprises the equivalent residue found in cod UNG. In addition, crystal structures of the single mutants V171E and E171V have been determined. Results from the study show that a more negative electrostatic surface potential reduces the activity and increases the stability of cod UNG, and suggest an optimisation of the surface potential as a strategy for cold-adaptation of this enzyme. Val171 in cod UNG is especially important in this respect.     

Directed evolution and identification of control regions of ColE1 plasmid replication origins using only nucleotide deletions

Genes can be mutated by altering DNA content (base changes) or DNA length (insertions or deletions). Most in vitro directed evolution processes utilize nucleotide content changes to produce DNA libraries. We tested whether gain of function mutations could be identified using a mutagenic process that produced only nucleotide deletions. Short nucleotide stretches were deleted in a plasmid encoding lacZ, and screened for increased beta-galactosidase activity. Several mutations were found in the origin of replication that quantitatively and qualitatively altered plasmid behavior in vivo. Some mutations allowed co-residence of ColE1 plasmids in Escherichia coli, and implicate hairpin structures II and III of the ColE1 RNA primer as determinants of plasmid compatibility. Thus, useful and unexpected mutations can be found from libraries containing only deletions.