An extended panel of single nucleotide polymorphisms in Atlantic salmon (<Emphasis Type="Italic">Salmo salar</Emphasis> L.) mitochondrial DNA

A total of 6,324 base pairs, distributed on eight different regions of the mitochondrial DNA (mtDNA) were re-sequenced for 32 specimens of Norwegian farmed and wild Atlantic salmon. A total of 16 new and three previously reported single nucleotide polymorphisms (SNPs) were detected. These SNPs were validated using 240 farm and 119 wild Norwegian salmon. Alignments of sequences obtained in this study and previously published sequences revealed another 15 previously unreported SNPs. The panel of mitochondrial SNPs detected in the present study will, in combination with previously identified SNPs, prove useful in designing efficient assays for analyzes of mtDNA variation.     

Nanoparticles of compacted DNA transfect postmitotic cells

Charge-neutral DNA nanoparticles have been developed in which single molecules of DNA are compacted to their minimal possible size. We speculated that the small size of these DNA nanoparticles may facilitate gene transfer in postmitotic cells, permitting nuclear uptake across the 25-nm nuclear membrane pore. To determine whether DNA nanoparticles can transfect nondividing cells, growth-arrested neuroblastoma and hepatoma cells were transfected with DNA/liposome mixtures encoding luciferase. In both models, growth-arrested cells were robustly transfected by compacted DNA (6,900-360-fold more than naked DNA). To evaluate mechanisms responsible for enhanced transfection, HuH-7 cells were microinjected with naked or compacted plasmids encoding enhanced green fluorescent protein. Cytoplasmic microinjection of DNA nanoparticles generated a approximately 10-fold improvement in transgene expression as compared with naked DNA; this enhancement was reversed by the nuclear pore inhibitor, wheat germ agglutinin. To determine the upper size limit for gene transfer, DNA nanoparticles of various sizes were microinjected into the cytoplasm. A marked decrease in transgene expression was observed as the minor ellipsoidal diameter approached 25 nm. In summary, suitably sized DNA nanoparticles productively transfect growth arrested cells by traversing the nuclear membrane pore.     

Pikas (Ochotona princeps : Lagomorpha) as allogenic engineers in an alpine ecosystem

Pikas (Ochotona princeps: Lagomorpha) build caches of vegetation (“haypiles”), which serve as a food source during winter in alpine and subalpine habitats. Haypiles appear to degrade over time and form patches of nutrient-rich soils in barren talus and scree areas. We sampled soils underneath and next to haypiles, and plants growing on and near haypiles in an alpine cirque in northwestern Wyoming, USA, to determine the effects of pika food caches on N, C, and C/N ratios in soils and plants. We found that (1) haypile soils had significantly higher carbon and nitrogen levels and lower C/N ratios than both adjacent soils and soils in the general study area, (2) two of three plant species tested (Polemonium viscosum and Oxyria digyna) had significantly higher levels of tissue percent N when growing on haypile soils, and (3) total standing plant biomass at the study site increased with soil percent N suggesting that vegetation was nitrogen limited. Pikas may therefore function as allogenic ecosystem engineers by modulating nutrient availability to plants. Received: 5 July 1997 / Accepted: 30 November 1997     

Ecology,sexual dimorphism,and jumping evolution in anurans

Sexual dimorphism (SD) is a common feature of animals, and selection for sexually dimorphic traits may affect both functional morphological traits and organismal performance. Trait evolution through natural selection can also vary across environments. However, whether the evolution of organismal performance is distinct between the sexes is rarely tested in a phylogenetic comparative context. Anurans commonly exhibit sexual size dimorphism, which may affect jumping performance given the effects of body size on locomotion. They also live in a wide variety of microhabitats. Yet the relationships among dimorphism, performance, and ecology remain underexamined in anurans. Here, we explore relationships between microhabitat use, body size, and jumping performance in males and females to determine the drivers of dimorphic patterns in jumping performance. Using methods for predicting jumping performance through anatomical measurements, we describe how fecundity selection and natural selection associated with body size and microhabitat have likely shaped female jumping performance. We found that the magnitude of sexual size dimorphism (where females are about 14% larger than males) was much lower than dimorphism in muscle volume, where females had 42% more muscle than males (after accounting for body size). Despite these sometimes-large averages, phylogenetic t-tests failed to show the statistical significance of SD for any variable, indicating sexually dimorphic species tend to be closely related. While SD of jumping performance did not vary among microhabitats, we found female jumping velocity and energy differed across microhabitats. Overall, our findings indicate that differences in sex-specific reproductive roles, size, jumping-related morphology, and performance are all important determinants in how selection has led to the incredible ecophenotypic diversity of anurans.     

Survival following renal transplantation in Saskatchewan, 1970--74: follow-up study using medical insurance records.

The patient history file of a medical care insurance plan can be used for statistical purposes in many ways. This is illustrated by the use of the records of the Saskatchewan Medical Care Insurance Commission to study the survival of patients receiving kidney transplants in the period 1970--74. During this period 48 males and 23 females received at least one renal transplant; these patients represented 34% of all males and 28% of all females undergoing regular renal dialysis. These period prevalence estimates are consistent with calculations based on incidence and point prevalence reported elsewhere. Life-table calculations showed the 4-year survival rate following first kidney transplantation in Saskatchewan to be 45% for all patients, 55% for those less than 45 years of age and 26% for those 45 years of age or older.     

Explorative multifactor approach for investigating global survival mechanisms of Campylobacter jejuni under environmental conditions

Explorative approaches such as DNA microarray experiments are becoming increasingly important in microbial research. Despite these major technical advancements, approaches to study multifactor experiments are still lacking. We have addressed this problem by using rotation testing and a novel multivariate analysis of variance (MANOVA) approach (50-50 MANOVA) to investigate interacting experimental factors in a complex experimental design. Furthermore, a new rotation testing based method was introduced to calculate false-discovery rates for each response. This novel analytical concept was used to investigate global survival mechanisms in the environment of the major food-borne pathogen C. jejuni. We simulated nongrowth environmental conditions by investigating combinations of the factors temperature (5 and 25 degrees C) and oxygen tension (anaerobic, microaerobic, and aerobic). Data were generated with DNA microarrays for information about gene expression patterns and Fourier transform infrared (FT-IR) spectroscopy to study global macromolecular changes in the cell. Microarray analyses showed that most genes were either unchanged or down regulated compared to the reference (day 0) for the conditions tested and that the 25 degrees C anaerobic condition gave the most distinct expression pattern with the fewest genes expressed. The few up-regulated genes were generally stress related and/or related to the cell envelope. We found, using FT-IR spectroscopy, that the amount of polysaccharides and oligosaccharides increased under the nongrowth survival conditions. Potential mechanisms for survival could be to down regulate most functions to save energy and to produce polysaccharides and oligosaccharides for protection against harsh environments. Basic knowledge about the survival mechanisms is of fundamental importance in preventing transmission of this bacterium through the food chain.     

Age, sex ratio and timing of the catch of kelts and ascending Atlantic salmon in the subarctic River Teno

By 15 June, 82% of the catch of Atlantic salmon Salmo salar kelts had been taken from the middle part of River Teno, northern Scandinavia. The median date of capture was 4 June for males and 8 June for females. Salmon of 1–4 sea–winters (SW) of both sexes survived spawning to return to sea as kelts. Among males, 1 SW kelts were caught earliest in the spring and 3 SW latest, but among females 4 SW were earliest, then 3 SW and finally 1 and 2 SW. There were 17 river and sea–age combinations among the kelts compared with 23 among the ascending salmon. The smolt age distribution and the mean smolt age differed significantly only between female 2 SW ascending salmon (3·97 years) and kelts (4·14 years). The proportion of 1 SW females was higher and that of 3 SW males lower among kelts than among ascending salmon. The proportion of males among 1 SW ascending salmon was 80% but among kelts only 57%. Similarly, the proportion of males among 3 SW fish was 21% for ascending salmon but only 7% for kelts. Hence overwinter mortality was higher among males. Male and female kelts of 1 and female kelts of 2 SWhad a greater mean length than ascending salmon in corresponding groups indicating a better survival of larger fish within an age group. Grilse ascend rivers after most kelts have left, but the main catch of ascending 2–3 SW salmon takes place concurrently with kelts leaving the river, inadvertently targeting kelts in the fishery.     

Epithelial Cadherin Determines Resistance to Infectious Pancreatic Necrosis Virus in Atlantic Salmon

Infectious pancreatic necrosis virus (IPNV) is the cause of one of the most prevalent diseases in farmed Atlantic salmon (Salmo salar). A quantitative trait locus (QTL) has been found to be responsible for most of the genetic variation in resistance to the virus. Here we describe how a linkage disequilibrium-based test for deducing the QTL allele was developed, and how it was used to produce IPN-resistant salmon, leading to a 75% decrease in the number of IPN outbreaks in the salmon farming industry. Furthermore, we describe how whole-genome sequencing of individuals with deduced QTL genotypes was used to map the QTL down to a region containing an epithelial cadherin (cdh1) gene. In a coimmunoprecipitation assay, the Cdh1 protein was found to bind to IPNV virions, strongly indicating that the protein is part of the machinery used by the virus for internalization. Immunofluorescence revealed that the virus colocalizes with IPNV in the endosomes of homozygous susceptible individuals but not in the endosomes of homozygous resistant individuals. A putative causal single nucleotide polymorphism was found within the full-length cdh1 gene, in phase with the QTL in all observed haplotypes except one; the absence of a single, all-explaining DNA polymorphism indicates that an additional causative polymorphism may contribute to the observed QTL genotype patterns. Cdh1 has earlier been shown to be necessary for the internalization of certain bacteria and fungi, but this is the first time the protein is implicated in internalization of a virus.