When density dependence is not instantaneous: theoretical developments and management implications

Most organisms live in changing environments or do not use the same resources at different stages of their lives or in different seasons. As a result, density dependence will affect populations differently at different times. Such sequential density dependence generates markedly different population responses compared to the unrealistic assumption that all events occur simultaneously. Various field studies have also shown that the conditions that individuals experience during one period can influence success and per capita vital rates during the following period. These carry-over effects further complicate any general principles and increase the diversity of possible population dynamics. In this review, we describe how studies of sequential density dependence have diverged in directions that are both taxon-specific and have non-overlapping terminology, despite very similar underlying problems. By exploring and highlighting these similarities, we aim to improve communication between fields, clarify common misunderstandings, and provide a framework for improving conservation and management practices, including sustainable harvesting theory.     

Predictors of the first cardiovascular event in patients with systemic lupus erythematosus - a prospective cohort study

Introduction

Cardiovascular disease (CVD) is a major cause of premature mortality among Systemic lupus erythematosus (SLE) patients. Many studies have measured and evaluated risk factors for premature subclinical atherosclerosis, but few studies are prospective and few have evaluated risk factors for hard endpoints, i.e. clinically important cardiovascular events (CVE). We investigated the impact of traditional and lupus associated risk factors for the first ever CVE in a longitudinal cohort of SLE patients.

Methods

A total of 182 SLE patients (mean age 43.9 years) selected to be free of CVE were included. Cardiovascular and autoimmune biomarkers were measured on samples collected after overnight fasting at baseline. Clinical information was collected at baseline and at follow up. End point was the first ever CVE (ischemic heart, cerebrovascular or peripheral vascular disease or death due to CVD). Impact of baseline characteristics/biomarkers on the risk of having a first CVE was evaluated with Cox regression.

Results

Follow up was 99.5% after a mean time of 8.3 years. Twenty-four patients (13%) had a first CVE. In age-adjusted Cox regression, any positive antiphospholipid antibody (aPL), elevated markers of endothelial activation (von Willebrand factor (vWf), soluble vascular cellular adhesion molecule-1 (sVCAM-1)) and fibrinogen predicted CVEs. Of SLE manifestations, arthritis, pleuritis and previous venous occlusion were positively associated with future CVEs while thrombocytopenia was negatively associated. Among traditional risk factors only age and smoking were significant predictors. In a multivariable Cox regression model age, any positive aPL, vWf and absence of thrombocytopenia were all predictors of the first CVE.

Conclusions

In addition to age, positive aPL, biomarkers indicating increased endothelial cell activity/damage, and absence of thrombocytopenia were independent predictors of CVEs in this prospective study. Our results indicate that activation of the endothelium and the coagulation system are important features in SLE related CVD. Furthermore, we observed that the risk of CVEs seems to differ between subgroups of SLE patients.     

<Emphasis Type="Italic">Leptospira</Emphasis> seroprevalence and associations between seropositivity,clinical disease and host factors in horses

Background  

A cross-sectional study was carried out to determine the seroprevalence of different serovars of Leptospira spp. and their association with clinical disease and host factors in Swedish horses.     

Engineered xyloglucan specificity in a carbohydrate-binding module

The field of plant cell wall biology is constantly growing and consequently so is the need for more sensitive and specific probes for individual wall components. Xyloglucan is a key polysaccharide widely distributed in the plant kingdom in both structural and storage tissues that exist in both fucosylated and non-fucosylated variants. Presently, the only xyloglucan marker available is the monoclonal antibody CCRC-M1 that is specific to terminal alpha-1,2-linked fucosyl residues on xyloglucan oligo- and polysaccharides. As a viable alternative to searches for natural binding proteins or creation of new monoclonal antibodies, an approach to select xyloglucan-specific binding proteins from a combinatorial library of the carbohydrate-binding module, CBM4-2, from xylanase Xyn10A of Rhodothermus marinus is described. Using phage display technology in combination with a chemoenzymatic method to anchor xyloglucan to solid supports, the selection of xyloglucan-binding modules with no detectable residual wild-type xylan and beta-glucan-binding ability was achieved.     

Predictors of post-stroke body temperature elevation

Background

Growing evidence indicates that elevated body temperature after stroke is associated with unfavorable outcome. The aim of the current study was to investigate which factors predict temperature elevation within 48 h of stroke onset. Specifically, we hypothesized that temperature elevation would be associated with stroke symptom severity and that hemorrhagic stroke would cause a more pronounced temperature increase compared to ischemic stroke.

Methods

The medical records of 400 stroke patients were retrospectively reviewed. Multiple linear regression analysis was used to determine which factors were associated with elevated body temperature.

Results

Several factors were significantly associated with peak body temperature (the highest recorded body temperature) within 48 h of stroke onset: stroke severity measured by the National Institutes of Health Stroke Scale (NIHSS) (regression coefficient; (RC) 0.022), female gender (RC 0.157), tympanic/non-rectal temperature reading (RC ?0.265), swallowing difficulties (RC 0.335), intubation (RC 0.470), antipyretic treatment (RC 0.563), and C-reactive protein?>?50 or signs of infection at admission (RC 0.298). Contrary to our expectations, patients with intracerebral hemorrhage did not have higher peak body temperatures than patients with ischemic stroke.

Conclusions

In conclusion, temperature elevation within the first 48 h of stroke onset is common, can be partially predicted using information at admission and is strongly associated with stroke severity. The strong association with stroke severity may, at least partly, explain the previously described association between post-stroke temperature elevation and unfavorable outcome.

     

Statin consumption as a risk factor for developing colorectal cancer: a retrospective case study

Background

Statins are the backbone of lipid-lowering therapy and are among the most commonly prescribed drugs in the elderly population in Sweden today. Colorectal cancer is the second most common cancer in men and women, after prostate and breast cancer, respectively, with a median age of 72 years at diagnosis. Statins induce mitochondrial damage leading to accumulation of reactive oxygen species in the cell. Reactive oxygen species can cause mutations in mitochondrial as well as nuclear DNA leading to the development of cancer. Our hypothesis was that statins increase the risk for colorectal cancer.

Methods

A case study was performed on consecutive cases of colorectal cancer diagnosed at Norrlands University Hospital (NUS) in Umeå between 2012 and 2015 (n?=?325). Patients diagnosed with diabetes mellitus type II (DM II n?=?65) were excluded in the primary endpoint analysis (occurrence of colorectal cancer). As control, three databases were used to create an age-matched population in order to calculate the proportion of inhabitants using statins in the county of Västerbotten, Sweden. A secondary endpoint was cancer-specific survival among our study group of colorectal cancer patients, including those with DM II, investigating whether there was a difference if the patient was a ‘recent’ statin user or not at the time of diagnosis.

Results

Statin use at the time of colorectal cancer diagnosis in the study group was 23.8%. The corresponding figure in an age-matched population in Västerbotten was 24.6%. Using a one-proportional one-sided z test, there was no significant difference between these (23.8%, 95% CI 18.6–29.0%, p?=?0.601). When comparing groups 20–64 years of age, the difference was greater with recent statin use in 17.8% in the study population and 11.9% in Västerbotten (17.8%, 95% CI 9.0–26.6%, p?=?0.059). When considering cancer-specific survival, no significant difference in survival was seen when comparing ‘former/never’ statin users as reference category with ‘recent’ users diagnosed with colorectal cancer (HR 1.39, 95% CI 0.89–2.16).

Conclusions

No significant increase in risk for developing colorectal cancer among patients (type II diabetics excluded) medicated with statins was found. We found no correlation between ‘recent’ statin use at the time of diagnosis and cancer-specific survival.

     

Nesting behavior of greater eelpout (Lycodes esmarkii), identified through a predation event by spotted wolffish (Anarhichas minor)

The stomach of a spotted wolffish (Anarhichas minor) caught in Icelandic waters was found to contain ~727 greater eelpout larvae (Lycodes esmarkii). All the larvae were of similar size and at a similar state of digestion, indicating they were all consumed together. The likely explanation for this observation is that greater eelpout lay their eggs in a nest, with the larvae remaining in the nest for a short period after hatching. The larvae were then predated upon by the spotted wolffish while still in the nest. This study sheds new light on greater eelpout in Icelandic waters, with recently hatched larvae being present in March, breeding at a depth of ~200–250 m, and likely exhibiting nesting behavior, which has not previously been documented.     

Metabolic engineering of Saccharomyces cerevisiae for production of Eicosapentaenoic Acid, using a novel {Delta}5-Desaturase from Paramecium tetraurelia

Very-long-chain polyunsaturated fatty acids, such as arachidonic acid (ARA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA), have well-documented importance in human health and nutrition. Sustainable production in robust host organisms that do not synthesize them naturally requires the coordinated expression of several heterologous desaturases and elongases. In the present study we show production of EPA in Saccharomyces cerevisiae using glucose as the sole carbon source through expression of five heterologous fatty acid desaturases and an elongase. Novel Δ5-desaturases from the ciliate protozoan Paramecium tetraurelia and from the microalgae Ostreococcus tauri and Ostreococcus lucimarinus were identified via a BLAST search, and their substrate preferences and desaturation efficiencies were assayed in a yeast strain producing the ω6 and ω3 fatty acid substrates for Δ5-desaturation. The Δ5-desaturase from P. tetraurelia was up-to-2-fold more efficient than the microalgal desaturases and was also more efficient than Δ5-desaturases from Mortierella alpina and Leishmania major. In vivo investigation of acyl carrier substrate specificities showed that the Δ5-desaturases from P. tetraurelia, O. lucimarinus, O. tauri, and M. alpina are promiscuous toward the acyl carrier substrate but prefer phospholipid-bound substrates. In contrast, the Δ5-desaturase from L. major showed no activity on phospholipid-bound substrate and thus appears to be an exclusively acyl coenzyme A-dependent desaturase.     

Why is timing of bird migration advancing when individuals are not?

Recent advances in spring arrival dates have been reported in many migratory species but the mechanism driving these advances is unknown. As population declines are most widely reported in species that are not advancing migration, there is an urgent need to identify the mechanisms facilitating and constraining these advances. Individual plasticity in timing of migration in response to changing climatic conditions is commonly proposed to drive these advances but plasticity in individual migratory timings is rarely observed. For a shorebird population that has significantly advanced migration in recent decades, we show that individual arrival dates are highly consistent between years, but that the arrival dates of new recruits to the population are significantly earlier now than in previous years. Several mechanisms could drive advances in recruit arrival, none of which require individual plasticity or rapid evolution of migration timings. In particular, advances in nest-laying dates could result in advanced recruit arrival, if benefits of early hatching facilitate early subsequent spring migration. This mechanism could also explain why arrival dates of short-distance migrants, which generally return to breeding sites earlier and have greater scope for advance laying, are advancing more rapidly than long-distance migrants.     

Description of Ulvella elegans sp. nov. and U. islandica sp. nov. (Ulvellaceae,Ulvophyceae) from Iceland – a study based on morphology of species in culture and tufA gene sequences

Two new Ulvella species, U. elegans R. Nielsen & K. Gunnarsson and U. islandica R. Nielsen & K. Gunnarsson are described. These microfilamentous marine green algae were found in the sublittoral zone in northern Iceland, epiphytic on Euthora cristata and associated with a calcareous polychaete tube, respectively. Unialgal cultures were established from field-collected material for morphological observations. In culture, Ulvella elegans was characterized by rosettes of monostromatic pseudoparenchyma consisting of radiating filaments with a margin of mutually free filaments. Each cell had one pyrenoid. Hairs were not observed. Ulvella islandica had a heterotrichous morphology, consisting of dense tufts of upright broad branches and much narrower, rhizoid-like branches. Acrochaete-type hairs occurred; these are hyaline non-septate merocytic extensions from a more or less bulbous base, which may be separated from the vegetative cell below. Most cells had one pyrenoid except for a few broad cells which had two or three. In a phylogenetic reconstruction based on the chloroplast-encoded tufA gene, the sequences for the two species were clearly distinct from any other Ulvella sequence available for this gene. Ulvella islandica was placed in a clade together with U. lens, U. wittrockii, U. reticulata and U. pseudorepens. Ulvella elegans occupied a branch deep in the phylogeny but the position was poorly supported.