Mechanisms for carbon and nutrient release and retention in beech forest gaps

Nutrient cycling and water balance in forest gaps has received little attention until now, although gap regeneration is important to natural dynamics of temperate forests. Gaps of 30 m diameter, cut in a mature beech forest, exhibited a distinct change in microclimatic conditions in comparison with the surrounding stand. Soil moisture in gaps remained very high throughout the observation period. Disruption of the N cycle in gaps led to substantial nitrate losses; seepage water nitrate concentrations were 10–18 mg NO₃-N L^-1. Excess nitrification was a significant cause of soil acidification and aluminium release. The pH in subsoil seepage water decreased by 0.25. Liming in gaps promoted the establishment of a herbaceous vegetation, which functioned as an important nutrient sink, and thus is recommended for tree regeneration in highly acidified forest ecosystems as it increases the resilience of the ecosystem to nutrient losses.     

From three-dimensional morphology to effective diffusivity in filamentous fungal pellets

Filamentous fungi are exploited as cell factories in biotechnology for the production of proteins, organic acids, and natural products. Hereby, fungal macromorphologies adopted during submerged cultivations in bioreactors strongly impact the productivity. In particular, fungal pellets are known to limit the diffusivity of oxygen, substrates, and products. To investigate the spatial distribution of substances inside fungal pellets, the diffusive mass transport must be locally resolved. In this study, we present a new approach to obtain the effective diffusivity in a fungal pellet based on its three-dimensional morphology. Freeze-dried Aspergillus niger pellets were studied by X-ray microcomputed tomography, and the results were reconstructed to obtain three-dimensional images. After processing these images, representative cubes of the pellets were subjected to diffusion computations. The effective diffusion factor and the tortuosity of each cube were calculated using the software GeoDict. Afterwards, the effective diffusion factor was correlated with the amount of hyphal material inside the cubes (hyphal fraction). The obtained correlation between the effective diffusion factor and hyphal fraction shows a large deviation from the correlations reported in the literature so far, giving new and more accurate insights. This knowledge can be used for morphological optimization of filamentous pellets to increase the yield of biotechnological processes.     

Anterior cruciate ligament constructs fabricated from human mesenchymal stem cells in a collagen type I hydrogel

BACKGROUND: Disruptions of the anterior cruciate ligament (ACL) of the knee joint are common and are currently treated using ligament or tendon grafts. In this study, we tested the hypothesis that it is possible to fabricate an ACL construct in vitro using mesenchymal stem cells (MSC) in combination with an optimized collagen type I hydrogel, which is in clinical use for autologous chondrocyte transplantation (ACT). METHODS: ACL constructs were molded using a collagen type I hydrogel containing 5 x 10(5) MSC/mL and non-demineralized bone cylinders at each end of the constructs. The constructs were kept in a horizontal position for 10 days to allow the cells and the gel to remodel and attach to the bone cylinders. Thereafter, cyclic stretching with 1 Hz was performed for 14 days (continuously for 8 h/day) in a specially designed bioreactor. RESULTS: Histochemical analysis for H and E, Masson-Goldner and Azan and immunohistochemical analysis for collagen types I and III, fibronectin and elastin showed elongated fibroblast-like cells embedded in a wavy orientated collagenous tissue, together with a ligament-like extracellular matrix in the cyclic stretched constructs. No orientation of collagen fibers and cells, and no formation of a ligament-like matrix, could be seen in the non-stretched control group cultured in a horizontal position without tension. RT-PCR analysis revealed an increased gene expression of collagen types I and III, fibronectin and elastin in the stretched constructs compared with the non-stretched controls. DISCUSSION: In conclusion, ACL-like constructs from a collagen type I hydrogel, optimized for the reconstruction of ligaments, and MSC have been fabricated. As shown by other investigators, who analyzed the influence of cyclic stretching on the differentiation of MSC, our results indicate a ligament-specific increased protein and gene expression and the formation of a ligament-like extracellular matrix. The fabricated constructs are still too weak for animal experiments or clinical application and current investigations are focusing on the development of a construct with an internal augmentation using biodegradable fibers.     

Coupling mechanical deformations and planar cell polarity to create regular patterns in the zebrafish retina

The orderly packing and precise arrangement of epithelial cells is essential to the functioning of many tissues, and refinement of this packing during development is a central theme in animal morphogenesis. The mechanisms that determine epithelial cell shape and position, however, remain incompletely understood. Here, we investigate these mechanisms in a striking example of planar order in a vertebrate epithelium: The periodic, almost crystalline distribution of cone photoreceptors in the adult teleost fish retina. Based on observations of the emergence of photoreceptor packing near the retinal margin, we propose a mathematical model in which ordered columns of cells form as a result of coupling between planar cell polarity (PCP) and anisotropic tissue-scale mechanical stresses. This model recapitulates many observed features of cone photoreceptor organization during retinal growth and regeneration. Consistent with the model's predictions, we report a planar-polarized distribution of Crumbs2a protein in cone photoreceptors in both unperturbed and regenerated tissue. We further show that the pattern perturbations predicted by the model to occur if the imposed stresses become isotropic closely resemble defects in the cone pattern in zebrafish lrp2 mutants, in which intraocular pressure is increased, resulting in altered mechanical stress and ocular enlargement. Evidence of interactions linking PCP, cell shape, and mechanical stresses has recently emerged in a number of systems, several of which show signs of columnar cell packing akin to that described here. Our results may hence have broader relevance for the organization of cells in epithelia. Whereas earlier models have allowed only for unidirectional influences between PCP and cell mechanics, the simple, phenomenological framework that we introduce here can encompass a broad range of bidirectional feedback interactions among planar polarity, shape, and stresses; our model thus represents a conceptual framework that can address many questions of importance to morphogenesis.     

Macrophages mediate lung inflammation in a mouse model of ischemic acute kidney injury

Serum IL-6 is increased in acute kidney injury (AKI) and inhibition of IL-6 reduces AKI-mediated lung inflammation. We hypothesized that circulating monocytes produce IL-6 and that alveolar macrophages mediate lung inflammation after AKI via chemokine (CXCL1) production. To investigate systemic and alveolar macrophages in lung injury after AKI, sham operation or 22 min of renal pedicle clamping (AKI) was performed in three experimental settings: 1) systemic macrophage depletion via diphtheria toxin (DT) injection to CD11b-DTR transgenic mice, 2) DT injection to wild-type mice, and 3) alveolar macrophage depletion via intratracheal (IT) liposome-encapsulated clodronate (LEC) administration to wild-type mice. In mice with AKI and systemic macrophage depletion (CD11b-DTR transgenic administered DT) vs. vehicle-treated AKI, blood monocytes and lung interstitial macrophages were reduced, renal function was similar, serum IL-6 was increased, lung inflammation was improved, lung CXCL1 was reduced, and lung capillary leak was increased. In wild-type mice with AKI administered DT vs. vehicle, serum IL-6 was increased. In mice with AKI and alveolar macrophage depletion (IT-LEC) vs. AKI with normal alveolar macrophage content, blood monocytes and lung interstitial macrophages were similar, alveolar macrophages were reduced, renal function was similar, lung inflammation was improved, lung CXCL1 was reduced, and lung capillary leak was increased. In conclusion, administration of DT in AKI is proinflammatory, limiting the use of the DTR-transgenic model to study systemic effects of AKI. Mice with AKI and either systemic mononuclear phagocyte depletion or alveolar macrophage depletion had reduced lung inflammation and lung CXCL1, but increased lung capillary leak; thus, mononuclear phagocytes mediate lung inflammation, but they protect against lung capillary leak after ischemic AKI. Since macrophage activation and chemokine production are key events in the development of acute lung injury (ALI), these data provide further evidence that AKI may cause ALI.     

RNA interference-based strategies for metabolic syndrome treatment.

RNA interference is a naturally occurring cellular mechanism to inhibit the expression of specific gene products. The technical application of RNA interference offers great potential for the specific treatment of a huge variety of diseases including the metabolic syndrome, one of the most challenging threats to human health associated with our civilization. In order to develop novel and powerful strategies for the treatment of the metabolic syndrome, it is essential to define a set of specific gene products that may be targeted by RNA interference. Based on currently available in vitro and in vivo data, we discuss the feasibility of candidate genes involved in the pathophysiology of the metabolic syndrome as potential targets for a rational RNA interference based therapy in this review.     

Fish eggs and pentacrinoids in Weddell Sea hexactinellids: further examples for the structuring role of sponges in Antarctic benthic ecosystems

 During the CS-EASIZ expedition (ANT XII/3) to the eastern Weddell Sea shelf with RF ‘Polarstern’ in January–March 1996, several hundred hexactinellids from trawl catches were inspected for associated fauna. At one station, fish egg masses were found in the suboscular cavities of 18 specimens of hexactinellid sponges belonging to four different species of the genus Rossella. Egg numbers in intact hexactinellids ranged from about 800 to more than 8000. At two stations, pentacrinoids, the sessile stage of comatulid crinoid development were found attached to the inner dermal membrane of hexactinellids. This is the first time pentacrinoids have been documented from the high Antarctic. The pentacrinoids mostly formed small groups, but single individuals were found as well. Neither fish eggs nor pentacrinoids were observed in or on other structures or animals; these findings stress the overall importance of sponges, especially hexactinellids, as substrates for developmental stages of other members of the ecosystem. Received: 25 May 1996/Accepted: 22 July 1996     

No Association between Antenatal Common Mental Disorders in Low-Obstetric Risk Women and Adverse Birth Outcomes in Their Offspring: Results from the CDS Study in Ghana and C?te D'Ivoire

Background

Evidence linking common mental disorders (CMD) in pregnant women to adverse birth outcomes is inconsistent, and studies often failed to control for pregnancy complications. This study aimed to explore the association between antenatal depression and anxiety symptoms and birth outcomes in a low-obstetric risk sample of mother/child dyads in Ghana and Côte d’Ivoire.

Methods

In 2010-2011, a prospective cohort of 1030 women in their third trimester in Ghana and Côte d’Ivoire was enrolled. Depression and anxiety were assessed in the third trimester using the Patient Health Questionnaire depression module and the 7-item Generalized Anxiety Disorder scale. 719 mother/child dyads were included in the analysis. We constructed multivariate regression models to estimate the association between CMD and low birth weight (LBW), and preterm birth (PTB) to control for potential confounders.

Results

The prevalence of depression and anxiety symptoms were 28.9% and 14.2% respectively. The mean birth weight was 3172.1g (SD 440.6) and the prevalence of LBW was 1.7%. The mean gestational age was 39.6 weeks and the proportion of PTB was 4%. Multivariate linear regression revealed no significant association between maternal depression (B=52.2, 95% CI -18.2 122.6, p=0.15) or anxiety (B=17.1, 95% CI -74.6 108.7, p=0.72) and birth weight. Yet, low socio-economic status, female sex of the child, and younger maternal age were associated with lower birth weight. Multivariate logistic regression suggested no significant association between maternal depression (OR: 2.1, 95% CI 0.8 5.6, p=0.15) or anxiety (OR: 1.8, 95% CI 0.6 5.5, p=0.29) with PTB.

Conclusions

Our data suggests that depression and/or anxiety in the 3^rd trimester of pregnancy are not independent predictors of adverse birth outcomes in low obstetric risk women. The role of pregnancy complications as confounders or effect modifiers in studies of maternal CMD and their impact on birth outcomes should be investigated.