Absence of snow cover reduces understory plant cover and alters plant community composition in boreal forests

Snow regimes affect biogeochemistry of boreal ecosystems and are altered by climate change. The effects on plant communities, however, are largely unexplored despite their influence on relevant processes. Here, the impact of snow cover on understory community composition and below-ground production in a boreal Picea abies forest was investigated using a long-term (8-year) snow cover manipulation experiment consisting of the treatments: snow removal, increased insulation (styrofoam pellets), and control. The snow removal treatment caused longer (118 vs. 57 days) and deeper soil frost (mean minimum temperature −5.5 vs. −2.2°C) at 10 cm soil depth in comparison to control. Understory species composition was strongly altered by the snow cover manipulations; vegetation cover declined by more than 50% in the snow removal treatment. In particular, the dominant dwarf shrub Vaccinium myrtillus (−82%) and the most abundant mosses Pleurozium schreberi (−74%) and Dicranum scoparium (−60%) declined strongly. The C:N ratio in V. myrtillus leaves and plant available N in the soil indicated no altered nitrogen nutrition. Fine-root biomass in summer, however, was negatively affected by the reduced snow cover (−50%). Observed effects are attributed to direct frost damage of roots and/ or shoots. Besides the obvious relevance of winter processes on plant ecology and distribution, we propose that shifts in the vegetation caused by frost damage may be an important driver of the reported alterations in biogeochemistry in response to altered snow cover. Understory plant performance clearly needs to be considered in the biogeochemistry of boreal systems in the face of climate change.     

Association Analysis of Genetic Variants in the Myosin IXB Gene in Acute Pancreatitis

Introduction

Impairment of the mucosal barrier plays an important role in the pathophysiology of acute pancreatitis. The myosin IXB (MYO9B) gene and the two tight-junction adaptor genes, PARD3 and MAGI2, have been linked to gastrointestinal permeability. Common variants of these genes are associated with celiac disease and inflammatory bowel disease, two other conditions in which intestinal permeability plays a role. We investigated genetic variation in MYO9B, PARD3 and MAGI2 for association with acute pancreatitis.

Methods

Five single nucleotide polymorphisms (SNPs) in MYO9B, two SNPs in PARD3, and three SNPs in MAGI2 were studied in a Dutch cohort of 387 patients with acute pancreatitis and over 800 controls, and in a German cohort of 235 patients and 250 controls.

Results

Association to MYO9B and PARD3 was observed in the Dutch cohort, but only one SNP in MYO9B and one in MAGI2 showed association in the German cohort (p < 0.05). Joint analysis of the combined cohorts showed that, after correcting for multiple testing, only two SNPs in MYO9B remained associated (rs7259292, p = 0.0031, odds ratio (OR) 1.94, 95% confidence interval (95% CI) 1.35-2.78; rs1545620, p = 0.0006, OR 1.33, 95% CI 1.16-1.53). SNP rs1545620 is a non-synonymous SNP previously suspected to impact on ulcerative colitis. None of the SNPs showed association to disease severity or etiology.

Conclusion

Variants in MYO9B may be involved in acute pancreatitis, but we found no evidence for involvement of PARD3 or MAGI2.     

Carrion fly‐derived DNA as a tool for comprehensive and cost‐effective assessment of mammalian biodiversity

Large‐scale monitoring schemes are essential in assessing global mammalian biodiversity, and in this framework, leeches have recently been promoted as an indirect source of DNA from terrestrial mammal species. Carrion feeding flies are ubiquitous and can be expected to feed on many vertebrate carcasses. Hence, we tested whether fly‐derived DNA analysis may also serve as a novel tool for mammalian diversity surveys. We screened DNA extracted from 201 carrion flies collected in tropical habitats of Côte d'Ivoire and Madagascar for mammal DNA using multiple PCR systems and retrieved DNA sequences from a diverse set of species (22 in Côte d'Ivoire, four in Madagascar) exploiting distinct forest strata and displaying a broad range of body sizes. Deep sequencing of amplicons generated from pools of flies performed equally well as individual sequencing approaches. We conclude that the analysis of fly‐derived DNA can be implemented in a very rapid and cost‐effective manner and will give a relatively unbiased picture of local mammal diversity. Carrion flies therefore represent an extraordinary and thus far unexploited resource of mammal DNA, which will probably prove useful for future inventories of wild mammal communities.     

Associations of Variants in FTO and Near MC4R With Obesity Traits in South Asian Indians

Recent genome‐wide association studies show that loci in FTO and melanocortin 4 receptor (MC4R) associate with obesity‐related traits. Outside Western populations the associations between these variants have not always been consistent and in Indians it has been suggested that FTO relates to diabetes without an obvious intermediary obesity phenotype. We investigated the association between genetic variants in FTO (rs9939609) and near MC4R (rs17782313) with obesity‐ and type 2 diabetes (T2DM)‐related traits in a longitudinal birth cohort of 2,151 healthy individuals from the Vellore birth cohort in South India. The FTO locus displayed significant associations with several conventional obesity‐related anthropometric traits. The per allele increase is about 1% for BMI, waist circumference (WC), hip circumference (HC), and waist—hip ratio. Consistent associations were observed for adipose tissue‐specific measurements such as skinfold thickness reinforcing the association with obesity‐related traits. Obesity associations for the MC4R locus were weak or nonsignificant but a signal for height (P < 0.001) was observed. The effect on obesity‐related traits for FTO was seen in adulthood, but not at younger ages. The loci also showed nominal associations with increased blood glucose but these associations were lost on BMI adjustment. The effect of FTO on obesity‐related traits was driven by an urban environmental influence. We conclude that rs9939609 variant in the FTO locus is associated with measures of adiposity and metabolic consequences in South Indians with an enhanced effect associated with urban living. The detection of these associations in Indians is challenging because conventional anthropometric obesity measures work poorly in the Indian “thin‐fat” phenotype.     

Hydroclimatic and hydrochemical controls on Plecoptera diversity and distribution in northern freshwater ecosystems

Freshwater ecosystems in the mid- to upper-latitudes of the northern hemisphere are particularly vulnerable to the impact of climate change as slight changes in air temperature can alter the form, timing, and magnitude of precipitation and consequent influence of snowmelt on streamflow dynamics. Here, we examine the effects of hydro-climate, flow regime, and hydrochemistry on Plecoptera (stonefly) alpha (α) diversity and distribution in northern freshwater ecosystems. We characterized the hydroclimatic regime of seven catchments spanning a climatic gradient across the northern temperate region and compared them with estimates of Plecoptera genera richness. By a space-for-time substitution, we assessed how warmer temperatures and altered flow regimes may influence Plecoptera alpha diversity and composition at the genus level. Our results show wide hydroclimatic variability among sites, including differences in temporal streamflow dynamics and temperature response. Principal component analysis showed that Plecoptera genera richness was positively correlated with catchment relief (m), mean and median annual air temperature (°C), and streamflow. These results provide a preliminary insight into how hydroclimatic change, particularly in terms of increased air temperature and altered streamflow regimes, may create future conditions more favorable to some Plecopteras in northern catchments.     

Ankyrin B modulates the function of Na,K-ATPase/inositol 1,4,5-trisphosphate receptor signaling microdomain

Na,K-ATPase and inositol 1,4,5-trisphosphate (IP3) receptor (IP3R) can form a signaling microdomain that in the presence of ouabain triggers highly regular calcium oscillations. Downstream effects include NF-kappaB activation. Here we report that ankyrin B (Ank-B), expressed in most mammalian cells, plays a pivotal role in the function of the Na,K-ATPase/IP3R signaling microdomain. In studies performed on a monkey kidney cell line, we show that Ank-B co-precipitates with both Na,K-ATPase and IP3R. We identify the N terminus tail of the Na,K-ATPase catalytic subunit and the N-terminal portion 1-604 of the IP3R as novel binding sites for Ank-B. Knockdown of Ank-B with small interfering RNA reduced the expression of Ank-B to 15-30%. This down-regulation of Ank-B attenuated the interaction between Na,K-ATPase and IP3R, reduced the number of cells responding to pm doses of ouabain with calcium oscillations, altered the calcium oscillatory pattern, and abolished the ouabain effect on NF-kappaB. In contrast, Ank-B down-regulation had no effect on the ion transporting function of Na,K-ATPase and no effect on the distribution and apparent mobility of Na,K-ATPase in the plasma membrane.     

Osmotic water permeability measurements using confocal laser scanning microscopy

 We have developed a method for measurement of plasma membrane water permeability (P _f) in intact cells using laser scanning confocal microscopy. The method is based on confocal recording of the fluorescence intensity emitted by calcein-loaded adherent cells during osmotic shock. P _f is calculated as a function of the time constant in the fluorescence intensity change, the cell surface-to-volume ratio and the fractional content of the osmotically active cell volume. The method has been applied to the measurement of water permeability in MDCK cells. The cells behaved as linear osmometers in the interval from 100 to 350 mosM. About 57% of the total cell volume was found to be osmotically inactive. Water movement across the plasma membrane in intact MDCK cells was highly temperature dependent. HgCl₂ had no effect on water permeability, while amphotericin B and DMSO significantly increased P _f values. The water permeability in MDCK cells transfected with aquaporin 2 was an order of magnitude higher than in the intact MDCK cell line. The water permeability of the nuclear membrane in both cell lines was found to be unlimited. Thus the intranuclear fluid belongs to the osmotically active portion of the cell. We conclude that the use of confocal microscopy provides a sensitive and reproducible method for measurement of water permeability in different types of adherent cells and potentially for coverslip-attached tissue preparations. Received: 12 June 1999 / Revised version: 21 February 2000 / Accepted: 25 February 2000     

Hypoxic Excitability Changes and Sodium Currents in Hippocampus CA1 Neurons

1. The objective of the present study was to distinguish if inhibition of neuronal activity by hypoxia is related to a block of voltage-gated Na+ channels. 2. The effect of chemical hypoxia induced by cyanide (0.5 mM, 10 min perfusion) was studied with patch-clamp technique in visualized intact CA1 pyramidal neurons in rat brain slices. Action potentials were elicited in whole cell current-clamp recordings and the threshold was estimated by current pulses of 50-ms duration and incremental amplitudes (n = 31). The effect of cyanide on the Na+ current and conductance was studied in voltage clamp recordings from cell-attached patches (n = 13). 3. Cyanide perfusion during 10 min increased the threshold for excitation by 73 +/- 79 pA (p = 0.001), which differed from the effect in control cells (11 +/- 41 pA, ns). The change in current threshold was correlated to a change in membrane potential (r = -0.88, p < 0.0001). Cyanide had no significant effect on the peak amplitude, duration, or rate of rise of the action potential. 4. Cyanide perfusion did not change the Na+ current size, but caused a small decrease in ENa (-17 +/- 22 mV, ns) and a slight increase in Na+ conductance (+14 +/- 26%, ns), which differed (p = 0.045) from controls (-19 +/- 23 %, ns). 5. In conclusion, chemical hypoxia does not cause a decrease in Na+ conductance. The decreased excitability during hypoxia can be explained by an increase in the current threshold, which is correlated with the effect on the membrane potential.     

Regulation of coenzyme Q biosynthesis and breakdown

All animal cells synthesize sufficient amounts of coenzyme Q (CoQ) and the cells also possess the capacity to metabolize the lipid. The main product of the metabolism is an intact ring with a short carboxylated side chain which glucuronidated in the liver and excreted mainly into the bile (Nakamura et al., Biofactors 9 (1999), 111-119). In other cells CoQ is phosphorylated, transferred into the blood and excreted through the urine. The biosynthesis of this lipid is regulated by nuclear receptors. PPARalpha is not required for the biosynthesis, or induction upon cold exposure, but it is necessary for the elevated CoQ synthesis during peroxisomal induction. RXRalpha is involved in the basal synthesis of CoQ and also in the increased synthesis upon cold treatment but is not required for peroxisomal induction. Dietary CoQ in human appear in the blood and it is taken up by mononuclear but not polynuclear cells. The former cells display a specific phospholipid modification, an increase of arachidonic acid content. In monocytes the CoQ administration leads to a significant decrease of the beta2-integrin CD11b and the complement receptor CD35. CD11b is one of the adhesion factors regulating the entry of these cells into the arterial wall which demonstrates that the anti-atherogenic effect of CoQ is mediated by other mechanisms beside its antioxidant protection.     

Patterns of liver gene expression governed by TRbeta

Several metabolic processes in the liver are regulated by thyroid hormone (T3). Gene expression profiles of livers from normal and TRbeta-deficient mouse strains should allow the classification of rapid and sustained effects of T3, as well as identification of target genes that are dependent on TRbeta. The immediate and long-term T3 regulation of about 4000 genes in livers from hypo- and hyperthyroid wild-type and TRbeta-deficient mice was analyzed using cDNA microarrays. T3 was found to regulate more than 200 genes, and among these, more than 100 were previously not described. Sixty percent of all these genes show dependence on the TRbeta gene for T3 regulation, indicating that TRalpha1 may have previously unknown functions in the liver. Analysis of the gene expression patterns showed a clear functional distinction between rapid (2 h) actions of T3 and late effects, seen after 5 d of sustained T3 treatment. Many metabolic actions were rapidly executed, whereas effects on mitochondrial function, for example, were seen after the sustained T3 treatment. As compared with wild-type controls, TRbeta-/-mice exhibited elevated expression of some target genes and reduced levels of others, indicating that both direct and indirect gene regulation by TRs in liver is complex and involves both ligand-dependent and -independent actions by the major TR isoforms.