Ultrastructure of the pericardium in chitons (Mollusca: Polyplacophora), in relation to filtration and contraction mechanisms

Summary The pericardium in Lepidopleurus asellus (Spengler), Tonicella marmorea (Fabricius), T. rubra L., Ischnochiton albus L., and Calleochiton laevis (Montagu), species taxonomically far apart, is described. It consists of a flat, simple epithelium facing the pericardial cavity, a basement membrane, a muscle layer with two types of muscle fibres, nerve processes, glio-interstitial cells, and fibrocytes, embedded in a loose collagen matrix. The epithelium in L. asellus and I. albus have convoluted lateral cell borders, and in L. asellus very long basal cell processes are seen. Type 1 muscle fibres resemble smooth molluscan muscle. Type 2 muscle fibres resemble cardiac muscle fibres in chitons. Nerve processes associated with glio-interstitial cells and cell processes, run free in the matrix. Synapses in type 1 fibres are covered with glio-interstitial cell processes, lacking in type 2 muscle fibres synapses.This work was supported by grants from the Norwegian Research Council for Science and the Humanities     

Bootstrap methods for estimating spatial synchrony of fluctuating populations

We describe and examine methods for estimating spatial correlations used in population ecology. We base our analyses on a hypothetical example of a species that has been censured at 30 different locations for 20 years. We assume that the population fluctuations can be described by a simple linear model on logarithmic scale. Stochastic simulations is utilized to check how seven different ways of resampling perform when the goal is to find nominal 95% confidence intervals for the spatial correlation in growth rates at given distances. It turns out that resampling of locations performs badly, with true coverage level as low as 30–40%, especially for small correlations at long distances. Resampling of timepoints performs much better, with coverage varying from 80 to 90%, depending on the strength of density regulation and whether the spatial correlation is estimated for the response variable or for the error terms in the model. Assuming that the underlying model is known, the best results are achieved for parametric bootstrapping, a result that strongly emphasize the importance of defining and estimating a proper population model when studying spatial processes.     

Water-soluble polysaccharides of Opuntia ficus-indica cv “Burbank's Spineless”

Carbohydrate-containing polymers have been extracted with water from the fleshy, lobed stems of Opuntia ficus-indica cv “Burbank's Spineless”. By ion exchange chromatography, the material was separated into one neutral and two acidic fractions. Each fraction was separated in two by gel filtration. The neutral fractions consisted of two glucans and a glycoprotein, containing arabinose and galactose. All four acidic fractions contained galacturonic acid, arabinose, rhamnose, galactose and xylose in different proportions. The cell wall structure of O. ficus-indica is discussed.     

Reversal of response to artificial selection on body size in a wild passerine

A general assumption in quantitative genetics is the existence of an intermediate phenotype with higher mean individual fitness in the average environment than more extreme phenotypes. Here, we investigate the evolvability and presence of such a phenotype in wild bird populations from an eleven‐year experiment with four years of artificial selection for long and short tarsus length, a proxy for body size. The experiment resulted in strong selection in the imposed directions. However, artificial selection was counteracted by reduced production of recruits in offspring of artificially selected parents. This resulted in weak natural selection against extreme trait values. Significant responses to artificial selection were observed at both the phenotypic and genetic level, followed by a significant return toward preexperimental means. During artificial selection, the annual observed phenotypic response closely followed the predicted response from quantitative genetic theory ( = 0.96, = 0.56). The rapid return to preexperimental means was induced by three interacting mechanisms: selection for an intermediate phenotype, immigration, and recombination between selected and unselected individuals. The results of this study demonstrates the evolvability of phenotypes and that selection may favor an intermediate phenotype in wild populations.     

Complete mitochondrial genome sequences of the Arctic Ocean codfishes <Emphasis Type="Italic">Arctogadus glacialis</Emphasis> and <Emphasis Type="Italic">Boreogadus saida</Emphasis> reveal oriL and tRNA gene duplications

We have determined the complete mitochondrial genome sequences of the codfishes Arctogadus glacialis and Boreogadus saida (Order Gadiformes, Family Gadidae). The 16,644 bp and 16,745 bp mtDNAs, respectively, contain the same set of 37 structural genes found in all vertebrates analyzed so far. The gene organization is conserved compared to other Gadidae species, but with one notable exception. B. saida contains heteroplasmic rearrangement-mediated duplications that include the origin of light-strand replication and nearby tRNA genes. Examination of the mitochondrial control region of A. glacialis, B. saida, and four additional representative Gadidae genera identified a highly variable domain containing tandem repeat motifs in A. glacialis. Mitogenomic phylogeny based on the complete mitochondrial genome sequence, the concatenated protein-coding genes, and the derived protein sequences strongly supports a sister taxa affiliation of A. glacialis and B. saida.     

hTERT mRNA dendritic cell vaccination: complete response in a pancreatic cancer patient associated with response against several hTERT epitopes

Immunotherapy targeting the hTERT subunit of telomerase has been shown to induce robust immune responses in cancer patients after vaccination with single hTERT peptides. Vaccination with dendritic cells (DCs) transfected with hTERT mRNA has the potential to induce strong immune responses to multiple hTERT epitopes and is therefore an attractive approach to more potent immunotherapy. Blood samples from such patients provide an opportunity for identification of new, in vivo processed T-cell epitopes that may be clinically relevant. A 62-year-old female patient underwent radical surgery for a pancreatic adenocarcinoma. After relapse, she obtained stable disease on gemcitabine treatment. Due to severe neutropenia, the chemotherapy was terminated. The patient has subsequently been treated with autologous DCs loaded with hTERT mRNA for 3 years. Immunomonitoring was performed at regular intervals following start of vaccination and clinical outcome measured by CT and PET/CT evaluation. The patient developed an immune response against several hTERT-derived Th and CTL epitopes. She presently shows no evidence of active disease based on PET/CT scans. No serious adverse events were experienced and the patient continues to receive regular booster injections. We here provide evidence for the induction of hTERT-specific immune responses following vaccination of a pancreas cancer patient with DCs loaded with hTERT mRNA. These responses are associated with complete remission. A thorough analysis of this patient immune response has provided a unique opportunity to identify novel epitopes, associated with clinical effects. These will be included in future hTERT vaccines.     

Trans-splicing of a mutated glycosylasparaginase mRNA sequence by a group I ribozyme deficient in hydrolysis.

RNA reprogramming represents a new concept in correcting genetic defects at the RNA level. However, for the technique to be useful for therapy, the level of reprogramming must be appropriate. To improve the efficiency of group I ribozyme-mediated RNA reprogramming, when using the Tetrahymena ribozyme, regions complementary to the target RNA have previously been extended in length and accessible sites in the target RNAs have been identified. As an alternative to the Tetrahymena model ribozyme, the DiGIR2 group I ribozyme, derived from a mobile group I intron in rDNA of the myxomycete Didymium iridis, represents a new and attractive tool in RNA reprogramming. We reported recently that the deletion of a structural element within the P9 domain of DiGIR2 turns off hydrolysis at the 3' splice site (side reaction) without affecting self-splicing [Haugen, P., Andreassen, M., Birgisdottir, A.B. & Johansen, S.D. (2004) Eur. J. Biochem. 271, 1015-1024]. Here we analyze the potential of the modified ribozyme, deficient in hydrolysis at the 3' splice site, for application in group I ribozyme-mediated trans-splicing of RNA. The improved ribozyme catalyses both cis-splicing and trans-splicing in vitro of a human glycosylasparaginase mRNA sequence with the same efficiency as the original DiGIR2 ribozyme, but without detectable levels of the unwanted hydrolysis.     

Harvest‐induced phenotypic selection in an island population of moose,Alces alces

Empirical evidence strongly indicates that human exploitation has frequently led to rapid evolutionary changes in wild populations, yet the mechanisms involved are often poorly understood. Here, we applied a recently developed demographic framework for analyzing selection to data from a 20‐year study of a wild population of moose, Alces alces. In this population, a genetic pedigree has been established all the way back to founders. We demonstrate harvest‐induced directional selection for delayed birth dates in males and reduced body mass as calf in females. During the study period, birth date was delayed by 0.81 days per year for both sexes, whereas no significant changes occurred in calf body mass. Quantitative genetic analyses indicated that both traits harbored significant additive genetic variance. These results show that selective harvesting can induce strong selection that oppose natural selection. This may cause evolution of less favorable phenotypes that become maladaptive once harvesting ceases.     

Effective size of density‐dependent populations in fluctuating environments

Reliable estimates of effective population size are of central importance in population genetics and evolutionary biology. For populations that fluctuate in size, harmonic mean population size is commonly used as a proxy for (multi‐) generational effective size. This assumes no effects of density dependence on the ratio between effective and actual population size, which limits its potential application. Here, we introduce density dependence on vital rates in a demographic model of variance effective size. We derive an expression for the ratio in a density‐regulated population in a fluctuating environment. We show by simulations that yearly genetic drift is accurately predicted by our model, and not proportional to as assumed by the harmonic mean model, where N is the total population size of mature individuals. We find a negative relationship between and N. For a given N, the ratio depends on variance in reproductive success and the degree of resource limitation acting on the population growth rate. Finally, our model indicate that environmental stochasticity may affect not only through fluctuations in N, but also for a given N at a given time. Our results show that estimates of effective population size must include effects of density dependence and environmental stochasticity.