Spatial structure in ecological communities – a quantitative analysis

The spatial structure of communities has recently gained much attention in ecology. Spatial structure comprises an important element in communities, but the literature lacks a thorough investigation about possible among‐organism or among‐ecosystem differences in the degree of spatial structure. Here, I conducted a quantitative review to determine if the degree of spatial structure varied predictably between the major organism types and ecosystems. Spatial structure was quantified as the relative fraction of community variation explained purely by spatial variables (fraction S/E). I integrated data from 322 variation partition analyses both in a generalized linear model (GLM) and using a boosted regression tree method, and showed that a mean of 11.0% of the variation in community composition was explained purely by spatial variables. Across all taxa, a body size–S/E relationship was positive. In GLM, fraction S/E increased highly significantly with study extent, it was highest among terrestrial taxa and higher in ectotherms than in homoiotherms. Spatial structure was also higher in omnivores than in autotrophs. These results suggest that the degree of spatial structure is jointly driven by extrinsic factors such as study extent and ecosystem type, and intrinsic factors such as body size, thermoregulation and interactions between body size and dispersal mode. These results should be important not only for basic research, but also conservation and bioassessment programs would benefit from the information about the magnitude of spatial variation in nature. Synthesis Spatial processes comprise an important element in most ecological communities, but the degree to which spatial structure varies across organisms or ecosystems is poorly known. Here, a quantitative review of 322 variation partition analyses indicated that spatial component varied predictably across ecological communities – it was driven by study extent and ecosystem type as well as by species traits such as body size and thermoregulation. These results give deep insights into the magnitude of spatial variation in nature and should be highly beneficial for conservation and bioassessment programs that are built on the information about how communities vary in space.     

Loss of assembly of the main basement membrane collagen, type IV, but not fibril-forming collagens and embryonic death in collagen prolyl 4-hydroxylase I null mice

Collagen prolyl 4-hydroxylases (C-P4Hs) catalyze the formation of the 4-hydroxyproline residues that are essential for the generation of triple helical collagen molecules. The vertebrate C-P4Hs I, II, and III are [alpha(I)]2beta2, [alpha(II)]2beta2, and [alpha(III)]2beta2 tetramers with identical beta subunits. We generated mice with targeted inactivation of the P4ha1 gene encoding the catalytic alpha subunit of C-P4H I to analyze its specific functions. The null mice died after E10.5, showing an overall developmental delay and a dilated endoplasmic reticulum in their cells. The capillary walls were frequently ruptured, but the capillary density remained unchanged. The C-P4H activity level in the null embryos and fibroblasts cultured from them was 20% of that in the wild type, being evidently due to the other two isoenzymes. Collagen IV immunofluorescence was almost absent in the basement membranes of the null embryos, and electron microscopy revealed disrupted basement membranes, while immunoelectron microscopy showed a lack of collagen IV in them. The amount of soluble collagen IV was increased in the null embryos and cultured null fibroblasts, indicating a lack of assembly of collagen IV molecules into insoluble structures, probably due to their underhydroxylation and hence abnormal conformation. In contrast, the null embryos had collagen I and III fibrils with a typical cross-striation pattern but slightly increased diameters, and the null fibroblasts secreted fibril-forming collagens, although less efficiently than wild-type cells. The primary cause of death of the null embryos was thus most likely an abnormal assembly of collagen IV.     

Effects of weaning age and formic acid-based feed additives on pigs from weaning to slaughter

Two hundred and forty piglets were used in a 2 x 6 factorial experiment to study the effects of weaning age (26 or 36 d) and four formic acid-based feed additives on the performance of pigs from weaning to slaughter. Either formic acid (F) or a mixture of formic acid, propionic acid, and potassium sorbate (FPS) or a mixture of formic acid, propionic acid, and sodium benzoate (FPB) or formic acid in a diatomaceous earth carrier (FD) were added to the diets of weaned piglets (from weaning to 60 d of age) and growing (18-46 kg) and finishing pigs (46-107 kg) to provide 8, 6, and 6 g acid per kg feed, respectively. The negative control treatment's (C) diets contained no growth promoters, whereas the positive control treatment's weaner and grower diets were supplemented with 40 mg/kg of avilamycin (A). The piglets weaned at the age of 26 and 36 d weighed 7.6 and 10.7 kg at weaning (p < 0.001), and 18.5 and 17.9 kg at the age of 60 d (p > 0.05), respectively. There was a weaning age x feed additive interaction in the weight gain of piglets after weaning (p < 0.05). The weight gain of piglets weaned on day 26 was enhanced by A, FPS, and FD (p < 0.05), and that of piglets weaned on day 36 by A and FPB (p < 0.05). The feed conversion ratio was not affected by weaning ages but was decreased in groups A, F, FBS, and FPB (p < 0.05). The severity of post-weaning diarrhoea was less in groups A, F, FPS, and FD than in C (p < 0.05). In piglets weaned on day 26, faecal water content and the total Escherichia coli count were highest 9 d after weaning. The total E. coli count was reduced only by FD (p < 0.05). Increased faecal water content was characterized by increased faecal Na+ and decreased K+ concentrations. Weaning age did not influence performance or carcass quality in the growing-finishing pigs. Feed additives did not affect weight gain in the growing pigs, but FPS and FPB enhanced weight gain during finishing period and total fattening (p < 0.05). In summary, the pigs' growth performance from weaning to slaughter was not affected by weaning age but it was enhanced by mixtures of formic and propionic acids with small amounts of sorbate or benzoate.     

Role of recycling endosomes and lysosomes in dynein-dependent entry of canine parvovirus

Canine parvovirus (CPV) is a nonenveloped virus with a 5-kb single-stranded DNA genome. Lysosomotropic agents and low temperature are known to prevent CPV infection, indicating that the virus enters its host cells by endocytosis and requires an acidic intracellular compartment for penetration into the cytoplasm. After escape from the endocytotic vesicles, CPV is transported to the nucleus for replication. In the present study the intracellular entry pathway of the canine parvovirus in NLFK (Nordisk Laboratory feline kidney) cells was studied. After clustering in clathrin-coated pits and being taken up in coated vesicles, CPV colocalized with coendocytosed transferrin in endosomes resembling recycling endosomes. Later, CPV was found to enter, via late endosomes, a perinuclear vesicular compartment, where it colocalized with lysosomal markers. There was no indication of CPV entry into the trans-Golgi or the endoplasmic reticulum. Similar results were obtained both with full and with empty capsids. The data thus suggest that CPV or its DNA was released from the lysosomal compartment to the cytoplasm to be then transported to the nucleus. Electron microscopy analysis revealed endosomal vesicles containing CPV to be associated with microtubules. In the presence of nocodazole, a microtubule-disrupting drug, CPV entry was blocked and the virus was found in peripheral vesicles. Thus, some step(s) of the entry process were dependent on microtubules. Microinjection of antibodies to dynein caused CPV to remain in pericellular vesicles. This suggests an important role for the motor protein dynein in transporting vesicles containing CPV along the microtubule network.     

Ecological status of some Finnish rivers evaluated using benthic diatom communities

The applicability of some diatom methods to quality assessment of differenttypes of Finnish rivers was compared using dominant taxa of diatomcommunities and nutrient level estimations using Trophic Diatom Index(TDI) and a new Phosphorus Diatom Equation (PDE) [Tot. P_calc (g l^-1) = 39 – 0.278 ol-% – 0.117 olme-% – 0.346me-% – 0.006 meeu-% + 1.193 eu-%; n = 97; r² = 0.742;SE = 17.4]. The overall quality estimations were done by Index ofPollution Sensitivity (IPS) and by Generic Diatom Index (GDI); limit valuesfor quality classes are proposed.     

Cleavage of the cyclin-dependent kinase 5 activator p35 to p25 does not induce tau hyperphosphorylation

Hyperphosphorylated tau protein is the primary component of neurofibrillary tangles observed in several neurodegenerative disorders. It has been hypothesized that in certain pathological conditions, the calcium activated protease, calpain, would cleave the cyclin-dependent kinase 5 (cdk5) activator p35 to a p25 fragment, which would lead to augmented cdk5 activity, and cdk5-mediated tau hyperphosphorylation. To test this hypothesis, we induced calpain-mediated p35 cleavage in rat hippocampal neuronal cultures and studied the relationship between p25 production, cdk5 activity, and tau phosphorylation. In glutamate-treated cells p35 was cleaved to p25 and this was associated with elevated cdk5 activity. However, tau phosphorylation was concomitantly decreased at multiple sites. The calpain inhibitor MDL28170 prevented the cleavage of p35 but had no effect on tau phosphorylation, suggesting that calpain-mediated processes, i.e., the cleavage of p35 to p25 and cdk5 activation, do not contribute to tau phosphorylation in these conditions. Treatment of the neuronal cultures with N-methyl-D-aspartic acid or with calcium ionophores resulted in an outcome highly similar to that of glutamate. We conclude that, in neuronal cells, the cleavage of p35 to p25 is associated with increased activity of cdk5 but not with tau hyperphosphorylation.     

Effect of training in Greco-Roman wrestling on neck strength at the elite level

Special training methods in wrestling have been assumed to improve the stability and tolerance of the neck. The aim of this study was to measure the neck strength levels reached in an extremely physically demanding sport. A neck strength measurement system was used to measure various parameters of maximal isometric neck strength in Finnish senior wrestlers competing at the international level. The results were compared with those achieved by junior wrestlers and a control group. The means (SD) of the maximal isometric neck strength for cervical rotation were 0.4 (0.1) Nm.kg(-1) for the senior wrestlers, 0.3 (0.1) Nm.kg(-1) for the junior wrestlers, and 0.2 (0.1) Nm.kg(-1) for the nonsportsmen. The respective results for cervical flexion were 4.4 (1.4), 3.8 (0.7), and 2.3 (0.8) Nm.kg(-1); for extension, 6.0 (1.1), 5.9 (0.7), and 4.0 (0.9) Nm.kg(-1). Neck strength in flexion seems to improve more than in extension as the result of wrestling. The greatest difference was found in rotation, which in the senior wrestlers was almost 3 times that in the nonsportsmen. There was great individual variation within all groups, and the results revealed weaknesses in all directions. Maximal neck strength measurements provide information useful in planning training programs to correct possible muscle deficiency and imbalance.     

Highly Overlapping Winter Diet in Two Sympatric Lemming Species Revealed by DNA Metabarcoding

Sympatric species are expected to minimize competition by partitioning resources, especially when these are limited. Herbivores inhabiting the High Arctic in winter are a prime example of a situation where food availability is anticipated to be low, and thus reduced diet overlap is expected. We present here the first assessment of diet overlap of high arctic lemmings during winter based on DNA metabarcoding of feces. In contrast to previous analyses based on microhistology, we found that the diets of both collared (Dicrostonyx groenlandicus) and brown lemmings (Lemmus trimucronatus) on Bylot Island were dominated by Salix while mosses, which were significantly consumed only by the brown lemming, were a relatively minor food item. The most abundant plant taxon, Cassiope tetragona, which alone composes more than 50% of the available plant biomass, was not detected in feces and can thus be considered to be non-food. Most plant taxa that were identified as food items were consumed in proportion to their availability and none were clearly selected for. The resulting high diet overlap, together with a lack of habitat segregation, indicates a high potential for resource competition between the two lemming species. However, Salix is abundant in the winter habitats of lemmings on Bylot Island and the non-Salix portion of the diets differed between the two species. Also, lemming grazing impact on vegetation during winter in the study area is negligible. Hence, it seems likely that the high potential for resource competition predicted between these two species did not translate into actual competition. This illustrates that even in environments with low primary productivity food resources do not necessarily generate strong competition among herbivores.     

Mapping a new spontaneous preterm birth susceptibility gene, IGF1R, using linkage, haplotype sharing, and association analysis

Preterm birth is the major cause of neonatal death and serious morbidity. Most preterm births are due to spontaneous onset of labor without a known cause or effective prevention. Both maternal and fetal genomes influence the predisposition to spontaneous preterm birth (SPTB), but the susceptibility loci remain to be defined. We utilized a combination of unique population structures, family-based linkage analysis, and subsequent case-control association to identify a susceptibility haplotype for SPTB. Clinically well-characterized SPTB families from northern Finland, a subisolate founded by a relatively small founder population that has subsequently experienced a number of bottlenecks, were selected for the initial discovery sample. Genome-wide linkage analysis using a high-density single-nucleotide polymorphism (SNP) array in seven large northern Finnish non-consanginous families identified a locus on 15q26.3 (HLOD 4.68). This region contains the IGF1R gene, which encodes the type 1 insulin-like growth factor receptor IGF-1R. Haplotype segregation analysis revealed that a 55 kb 12-SNP core segment within the IGF1R gene was shared identical-by-state (IBS) in five families. A follow-up case-control study in an independent sample representing the more general Finnish population showed an association of a 6-SNP IGF1R haplotype with SPTB in the fetuses, providing further evidence for IGF1R as a SPTB predisposition gene (frequency in cases versus controls 0.11 versus 0.05, P = 0.001, odds ratio 2.3). This study demonstrates the identification of a predisposing, low-frequency haplotype in a multifactorial trait using a well-characterized population and a combination of family and case-control designs. Our findings support the identification of the novel susceptibility gene IGF1R for predisposition by the fetal genome to being born preterm.     

Developmental origins of physical fitness: the Helsinki Birth Cohort Study

Background

Cardiorespiratory fitness (CRF) is a major factor influencing health and disease outcomes including all-cause mortality and cardiovascular disease. Importantly CRF is also modifiable and could therefore have a major public health impact. Early life exposures play a major role in chronic disease development. Our aim was to explore the potential prenatal and childhood origins of CRF in later life.

Methods/Principal Findings

This sub-study of the HBCS (Helsinki Birth Cohort Study) includes 606 men and women who underwent a thorough clinical examination and participated in the UKK 2-km walk test, which has been validated against a maximal exercise stress test as a measure of CRF in population studies. Data on body size at birth and growth during infancy and childhood were obtained from hospital, child welfare and school health records. Body size at birth was not associated with adult CRF. A 1 cm increase in height at 2 and 7 years was associated with 0.21 ml/kg/min (95% CI 0.02 to 0.40) and 0.16 ml/kg/min (95% CI 0.03 to 0.28) higher VO_2max, respectively. Adjustment for adult lean body mass strengthened these findings. Weight at 2 and 7 years and height at 11 years became positively associated with CRF after adult lean body mass adjustment. However, a 1 kg/m² higher BMI at 11 years was associated with −0.57 ml/kg/min (95% CI −0.91 to −0.24) lower adult VO_2max, and remained so after adjustment for adult lean body mass.

Conclusion/Significance

We did not observe any significant associations between body size at birth and CRF in later life. However, childhood growth was associated with CRF in adulthood. These findings suggest, importantly from a public point of view, that early growth may play a role in predicting adult CRF.