Global variability in leaf respiration in relation to climate, plant functional types and leaf traits

• Leaf dark respiration (Rdark) is an important yet poorly quantified component of the global carbon cycle. Given this, we analyzed a new global database of Rdark and associated leaf traits. • Data for 899 species were compiled from 100 sites (from the Arctic to the tropics). Several woody and nonwoody plant functional types (PFTs) were represented. Mixed-effects models were used to disentangle sources of variation in Rdark. • Area-based Rdark at the prevailing average daily growth temperature (T) of each site increased only twofold from the Arctic to the tropics, despite a 20°C increase in growing T (8–28°C). By contrast, Rdark at a standard T (25°C, Rdark25) was threefold higher in the Arctic than in the tropics, and twofold higher at arid than at mesic sites. Species and PFTs at cold sites exhibited higher Rdark25 at a given photosynthetic capacity (Vcmax25) or leaf nitrogen concentration ([N]) than species at warmer sites. Rdark25 values at any given Vcmax25 or [N] were higher in herbs than in woody plants. • The results highlight variation in Rdark among species and across global gradients in T and aridity. In addition to their ecological significance, the results provide a framework for improving representation of Rdark in terrestrial biosphere models (TBMs) and associated land-surface components of Earth system models (ESMs)

J. Clin. Endocrinol. Metab.

Objective: Congenital hypothyroidism occurs in 1:3500 live births and is therefore the most common congenital endocrine disorder. A spectrum of defective thyroid morphology, termed thyroid dysgenesis (TD), represents 80% of permanent congenital hypothyroidism cases. Although several candidate genes have been implicated in thyroid development, comprehensive screens failed to detect mutation carriers in a significant number of patients with nonsyndromic TD. Due to the sporadic occurrence of TD, de novo chromosomal rearrangements are conceivably representing one of the molecular mechanisms participating in its etiology. Methods: The introduction of array comparative genomic hybridization (CGH) has provided the ability to map DNA copy number variations (CNVs) genome wide with high resolution. We performed an array CGH screen of 80 TD patients to determine the role of CNVs in the etiology of the disease. Results: We identified novel CNVs that have not been described as frequent variations in the healthy population in 8.75% of all patients. These CNVs exclusively affected patients with athyreosis or thyroid hypoplasia and were nonrecurrent, and the regions flanking the CNVs were not enriched for segmental duplications. Conclusions: The high rate of chromosomal changes in TD argues for an involvement of CNVs in the etiology of this disease. Yet the lack of recurrent aberrations suggests that the genetic causes of TD are heterogenous and not restricted to specific genomic hot spots. Thus, future studies may have to shift the focus from singling out specific genes to the identification of deregulated pathways as the underlying cause of the disease

Respiratory alkalosis in children with febrile seizures

Purpose: Febrile seizures (FS) are the most common type of convulsive events in children. FS are suggested to result from a combination of genetic and environmental factors. However, the pathophysiologic mechanisms underlying FS remain unclear. Using an animal model of experimental FS, it was demonstrated that hyperthermia causes respiratory alkalosis with consequent brain alkalosis and seizures. Here we examine the acid-base status of children who were admitted to the hospital for FS. Children who were admitted because of gastroenteritis (GE), a condition known to promote acidosis, were examined to investigate a possible protective effect of acidosis against FS. Methods: We enrolled 433 age-matched children with similar levels of fever from two groups presented to the emergency department. One group was admitted for FS (n = 213) and the other for GE (n = 220). In the FS group, the etiology of fever was respiratory tract infection (74.2%), otitis media (7%), GE (7%), tonsillitis (4.2%), scarlet fever (2.3%) chickenpox (1.4%), urinary tract infection (1.4%), postvaccination reaction (0.9%), or unidentified (1.4%). In all patients, capillary pH and blood Pco(2) were measured immediately on admission to the hospital. Key Findings: Respiratory alkalosis was found in children with FS (pH 7.46 +- 0.04, [mean +- standard deviation] Pco(2) 29.5 +- 5.5 mmHg), whereas a metabolic acidosis was seen in all children admitted for GE (pH 7.31 +- 0.03, Pco(2) 37.7 +- 4.3 mmHg; p < 0.001 for both parameters). No FS were observed in the latter group. A subgroup (n = 15; 7%) of the patients with FS had GE and, notably, their blood pH was more alkaline (pH 7.44 +- 0.04) than in the GE-admitted group. During the enrollment period, eight of the patients were admitted on separate occasions because of FS or GE. Consistent with the view that generation of FS requires a genetic susceptibility in addition to acute seizure triggering factors, each of these patients had an alkalotic blood pH when admitted because of FS, whereas they had an acidotic pH (and no FS) when admitted because of GE (pH 7.47 +- 0.05 vs. pH 7.33 +- 0.03, p < 0.005). Significance: The results show that FS are associated with a systemic respiratory alkalosis, irrespective of the severity of the underlying infection as indicated by the level of fever. The lack of FS in GE patients is attributable to low pH, which also explains the fact that children with a susceptibility to FS do not have seizures when they have GE-induced fever that is associated with acidosis. The present demonstration of a close link between FS and respiratory alkalosis may pave the way for further clinical studies and attempts to design novel therapies for the treatment of FS by controlling the systemic acid-base status

Tree parameters

Tree parameters (stem diameter, height and crown radii in eight cardinal directions) for 12 mangrove forest stands located along a soil salinity gradient within the mangrove forest of the Lagoon of La Mancha, located in the central Gulf Coast of Mexico. The data set was used to study the responses of tree crowns to asymmetric neighbourhood pressure and dominant wind direction. The data set was created in collaboration between The Institute of Ecology (INECOL, Mexico), and the Technische Universitaet Dresden (Dresden, Germany), under the scope of the Coastal Research Network for Environmental Change (CREC), financed by the European Commission

Identification of PENDRIN (SLC26A4) mutations in patients with congenital hypothyroidism and "apparent" thyroid dysgenesis

Context: Congenital hypothyroidism (CH), the most frequent endocrine congenital disease, can occur either based on a thyroid hormone biosynthesis defect or can predominantly be due to thyroid dysgenesis. However, a genetic cause could so far only be identified in less than 10% of patients with a thyroid dysgenesis. Objectives: Exome-sequencing was used for the first time to find additional genetic defects in thyroid dysgenesis. Patients and Methods: In a consanguineous family with thyroid dysgenesis exome-sequencing was applied and findings were further validated by Sanger sequencing in a cohort of 94 patients with thyroid dysgenesis. Results: By exome-sequencing we identified a homozygous missense mutation (p.Leu597Ser) in the SLC26A4 gene of a patient with hypoplastic thyroid tissue, who was otherwise healthy. In the cohort of patients with thyroid dysgenesis we observed a second case with a homozygous missense mutation (p.Gln413Arg) in the SLC26A4 gene, who was additionally affected by severe hearing problems. Both mutations were previously described as loss-of-function mutations in patients with Pendred syndrome and nonsyndromic EVA (enlarged vestibular aqueduct). Conclusion: We identified unexpectedly SLC26A4 mutations, that were hitherto diagnosed in thyroid dyshormonogenesis patients, now for the first time in patients with structural thyroid defects. This result resembles the historic description of thyroid atrophy in patients with the so-called myxedematous form of cretinism following severe iodine deficiency. Most likely, the thyroid defect of the two homozygous SLC26A4 gene mutation carriers represents a kind of secondary thyroid "atrophy", rather than a primary defect of thyroid development in the sense of thyroid "agenesis". Our study extends the variable clinical spectrum of patients with SLC26A4 mutations and points out the necessity to analyze the SLC26A4 gene in patients with "apparent" thyroid dysgenesis in addition to the known candidate genes TSHR, PAX8, NKX2.1, NKX2.5 and FOXE1

The mangrove forest dynamics model mesoFON

This study presents mesoFON, an individual-based mangrove forest dynamics model that advances beyond current models by describing crown plasticity of mangrove trees. The crown plasticity routines take advantage of the fields-of-neighborhood (FON) approach and account for the trunk bending and the differential side branch growth mechanism. Competition for above-/below-ground resources is dealt with separately in this model. Offspring production depends on tree growth and rises with tree ontogeny. An extensive sensitivity analysis revealed that mesoFON resembles the behavior of known mangrove forest dynamics and is ready for application. In this study we exposed two plant functional types (PFTs) of the red mangrove (Rhizophora mangle L.) either in monoculture or as a community to two disturbance regimes, namely (1) without disturbances and (2) with hurricane impacts returning every 5 years. While one functional type possesses plastic crowns, the other PFT has rigid crowns. For the first time, long-term interaction of lateral crown displacement and disturbance was examined using a comprehensive comparative analysis including point patterns and canopy coverage. In the monoculture experiments disturbance strongly promoted the beneficial effects of crown plasticity. Without disturbance crown movements merely increased stand-based stem volume by 6.7% despite considerable displacement distances. We attribute this to the overall high competitive strength that constrained the effects of plasticity in the dense stands. Yet, in disturbed stands the plastic behavior raised stem volume and tree density by 12.5% and 7.5%, respectively, as a result of substantially reduced local competition (by 20.1%). In this treatment crown shifts are particularly advantageous because of their contribution to gap closure. Generally, the Clark Evans aggregation index of crown centers tended to be higher than that of stem bases indicating a more regular distribution of crown centers. The same was true for the canopy coverage of crowns located at their centers implying better space usage by shifted crowns. Pair-correlation functions revealed a plasticity-induced trend toward more regular distribution at low tree-to-tree distances and less aggregation at intermediate distances. The trend was stronger in disturbed communities. The plastic PFT was finally able to out-compete the rigid PFT in all community experiments. Hurricane impacts, however, accelerated the time to the extinction of the rigid PFT by a factor of 2.4. © 2014 Elsevier B.V.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Molecular analysis of the PDS gene in Pendred syndrome (sensorineural hearing loss and goitre)

Pendred syndrome is an autosomal recessive disorder characterized by the association between sensorineural hearing loss and thyroid swelling or goitre and is likely to be the most common form of syndromic deafness. Within the thyroid gland of affected individuals, iodide is incompletely organified with variable effects upon thyroid hormone biosynthesis, whilst the molecular basis of the hearing loss is unknown. The PDS gene has been identified by positional cloning of chromosome 7q31, within the Pendred syndrome critical linkage interval and encodes for a putative ion transporter called pendrin. We have investigated a cohort of 56 kindreds, all with features suggestive of a diagnosis of Pendred syndrome. Molecular analysis of the PDS gene identified 47 of the 60 (78%) mutant alleles in 31 families (includes three homozygous consanguineous kindreds and one extended family segregating three mutant alleles). Moreover, four recurrent mutations accounted for 35 (74%) of PDS disease chromosomes detected and haplotype analysis would favour common founders rather than mutational hotspots within the PDS gene. Whilst these findings demonstrate molecular heterogeneity for PDS mutations associated with Pendred syndrome, this study would support the use of molecular analysis of the PDS gene in the assessment of families with congenital hearing loss.link_to_OA_fulltex