The relationship between adrenal vascular events and steroid secretion: the role of mast cells and endothelin.

The actions of ACTH on the adrenal cortex are known to be 2-fold. In addition to increased steroidogenesis, ACTH also causes marked vasodilation, reflected by an increased rate of blood flow through the gland. Our studies, using the in situ isolated perfused rat adrenal preparation, have shown that zona fasciculata function and corticosterone secretion are closely related to vascular events, with an increase in perfusion medium flow rate causing an increase in corticosterone secretion, in the absence of any known stimulant. These observations give rise to two important questions: how does ACTH stimulate blood flow; and how does increased blood (or perfusion medium) flow stimulate steroidogenesis? Addressing the first question, we have recently identified mast cells in the adrenal capsule, and shown that Compound 48/80, a mast cell degranulator, mimics the actions of ACTH on adrenal blood flow and corticosterone secretion. We have also demonstrated an inhibition of the adrenal vascular response to ACTH in the presence of disodium cromoglycate, which prevents mast cell degranulation. We conclude, therefore, that ACTH stimulates adrenal blood flow by its actions on mast cells in the adrenal capsule. Addressing the second question, we looked at the role of endothelin in the rat adrenal cortex. Endothelin 1, 2 and 3 caused significant stimulation of steroid secretion by collagenase dispersed cells from both the zona glomerulosa and the zona fasciculata. A sensitive response was seen, with significant stimulation at an endothelin concentration of 10(-13) mol/l or lower. Endothelin secretion by the in situ isolated perfused rat adrenal gland was measured using the Amersham assay kit. Administration of ACTH (300 fmol) caused an increase in the rate of immunoreactive endothelin secretion, from an average of 28.7 +/- 2.6 to 52.6 +/- 6 fmol/10 min (P less than 0.01, n = 5). An increase in immunoreactive endothelin secretion was also seen in response to histamine, an adrenal vasodilator, which stimulates corticosterone secretion in the intact gland, but has no effect on collagenase-dispersed cells. From these data we conclude that endothelin may mediate the effects of vasodilation on corticosterone secretion, and this mechanism may explain some of the differences in response characteristics between the intact gland and dispersed cells.     

Determination of axonal transport velocities via image cross- and autocorrelation

On their way to the synapse and back, neuronal proteins are carried in cargo vesicles along axons and dendrites. Here, we demonstrate that the key parameters of axonal transport, i.e., particle velocities and pausing times can be read out from CCD-camera images automatically. In the present study, this is achieved via cross- and autocorrelation of kymograph columns. The applicability of the method was measured on simulated kymographs and data from axonal transport timeseries of mRFP-labeled synaptophysin. In comparing outcomes of velocity determinations via a performance parameter that is analogous to the signal-to-noise ratio (SNR) definition, we find that outcomes are dependent on sampling, particle numbers and signal to noise of the kymograph. Autocorrelation of individual columns allows exact determination of pausing time populations. In contrast to manual tracking, correlation does not require experience, a priori assumptions or disentangling of individual particle trajectories and can operate at low SNR. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. O. Welzel and D. Boening contributed equally to this work.     

A review of the ecosystem functions in oil palm plantations,using forests as a reference system

Oil palm plantations have expanded rapidly in recent decades. This large‐scale land‐use change has had great ecological, economic, and social impacts on both the areas converted to oil palm and their surroundings. However, research on the impacts of oil palm cultivation is scattered and patchy, and no clear overview exists. We address this gap through a systematic and comprehensive literature review of all ecosystem functions in oil palm plantations, including several (genetic, medicinal and ornamental resources, information functions) not included in previous systematic reviews. We compare ecosystem functions in oil palm plantations to those in forests, as the conversion of forest to oil palm is prevalent in the tropics. We find that oil palm plantations generally have reduced ecosystem functioning compared to forests: 11 out of 14 ecosystem functions show a net decrease in level of function. Some functions show decreases with potentially irreversible global impacts (e.g. reductions in gas and climate regulation, habitat and nursery functions, genetic resources, medicinal resources, and information functions). The most serious impacts occur when forest is cleared to establish new plantations, and immediately afterwards, especially on peat soils. To variable degrees, specific plantation management measures can prevent or reduce losses of some ecosystem functions (e.g. avoid illegal land clearing via fire, avoid draining of peat, use of integrated pest management, use of cover crops, mulch, and compost) and we highlight synergistic mitigation measures that can improve multiple ecosystem functions simultaneously. The only ecosystem function which increases in oil palm plantations is, unsurprisingly, the production of marketable goods. Our review highlights numerous research gaps. In particular, there are significant gaps with respect to socio‐cultural information functions. Further, there is a need for more empirical data on the importance of spatial and temporal scales, such as differences among plantations in different environments, of different sizes, and of different ages, as our review has identified examples where ecosystem functions vary spatially and temporally. Finally, more research is needed on developing management practices that can offset the losses of ecosystem functions. Our findings should stimulate research to address the identified gaps, and provide a foundation for more systematic research and discussion on ways to minimize the negative impacts and maximize the positive impacts of oil palm cultivation.     

Trap-nesting bees and wasps colonizing set-aside fields: succession and body size,management by cutting and sowing

Trap-nesting bees and wasps (Hymenoptera Aculeata) colonizing crop and fallow fields in an agricultural landscape were studied using 20 sown fields (pea, barley, rye, clover-grass mixtures, Phacelia tanacetifolia) and 20 fields with naturally developed vegetation (1- and 2-year old fields, both mown and unmown, and old meadows). Fourteen species of Apoidea, 4 of Sphecidae, 1 of Eumenidae and 4 of parasitoids were reared from reed nests exposed in these 40 fields of 10 field-types. Fields with naturally developed vegetation had twice as many species as sown fields, due to the distribution pattern of the 14 bee species, whereas the 9 predatory species (wasps and parasitoids) showed a rather uniform distribution. None of the trap-nesting bees were found in Phacelia fields, despite contrasting expectations of beekeepers. Old meadows showed a particularly high abundance and species richness, since only 10% of all traps were exposed, but 32% of all bee nests were sampled in old meadows, including 4 bee species that were not found elsewhere. Accordingly, species richness of fields with naturally developed vegetation showed a significant increase with age. Variability in Hymenoptera species numbers could be explained by corresponding differences in plant species numbers. The alternative hypothesis that field size or field connectivity influenced species richness was not supported. Habitats with great floral diversity appeared to offer better and richer food resources for the flower-visiting bees, whereas food availability apparently did not influence predatory wasps. The bees Osmia caerulescens and Megachile versicolor that had colonized early-successional fields took twice as long to provision cells as those that colonized late-successional meadows characterized by a greater plant species richness. In contrast, the eumenid wasp Ancistrocerus gazella took a similar period of time to provision cells in both field types. In addition, bee and wasp species of plant-species-poor fields were on average significantly larger than those of plant-species-rich fields. Thus, body size appeared to be a good predictor of colonization ability. Management by cutting greatly increased plant species richness in early-successional set-aside fields and thus doubled species richness of bees. Cutting of early-successional habitats can be expected to benefit insects and plants in general, whereas older grassland should show the greatest insect diversity when both mown and unmown parts are present.     

Landscape perspectives on agricultural intensification and biodiversity – ecosystem service management

Understanding the negative and positive effects of agricultural land use for the conservation of biodiversity, and its relation to ecosystem services, needs a landscape perspective. Agriculture can contribute to the conservation of high‐diversity systems, which may provide important ecosystem services such as pollination and biological control via complementarity and sampling effects. Land‐use management is often focused on few species and local processes, but in dynamic, agricultural landscapes, only a diversity of insurance species may guarantee resilience (the capacity to reorganize after disturbance). Interacting species experience their surrounding landscape at different spatial scales, which influences trophic interactions. Structurally complex landscapes enhance local diversity in agroecosystems, which may compensate for local high‐intensity management. Organisms with high‐dispersal abilities appear to drive these biodiversity patterns and ecosystem services, because of their recolonization ability and larger resources experienced. Agri‐environment schemes (incentives for farmers to benefit the environment) need to broaden their perspective and to take the different responses to schemes in simple (high impact) and complex (low impact) agricultural landscapes into account. In simple landscapes, local allocation of habitat is more important than in complex landscapes, which are in total at risk. However, little knowledge of the relative importance of local and landscape management for biodiversity and its relation to ecosystem services make reliable recommendations difficult.     

Population size and the risk of local extinction: empirical evidence from rare plants

Due to habitat fragmentation many plant species today occur mainly in small and isolated populations. Modeling studies predict that small populations will be threatened more strongly by stochastic processes than large populations, but there is little empirical evidence to support this prediction for plants. We studied the relationship between size of local populations (number of flowering plants) and survival over ten years for 359 populations of eight short-lived, threatened plants in northern Germany ( Lepidium campestre , Thlaspi perfoliatum , Rhinanthus minor , R . serotinus , Melampyrum arvense , M . nemorosum , Gentianella ciliata and G . germanica ). Overall, 27% of the populations became extinct during the study period. Probability of survival of a local population increased significantly with its size in all but one species ( R. minor ). However, estimated population sizes required for 90% probability of survival over 10 years varied widely among species. Survival probability increased with decreasing distance to the nearest conspecific population in R . serotinus , but not in the other species. The mean annual growth rate of surviving populations differed greatly between species, but was only for G . germanica significantly lower than 1, suggesting that there was no general deterministic decline in the number of plants due to deteriorating habitat conditions. We conclude that the extinction of populations was at least partly due to stochastic processes. This is supported by the fact that in all species a considerable proportion of small populations survived and developed into large populations.     

Hematopoietic Stem Cells in Neonates: Any Differences between Very Preterm and Term Neonates?

Background

In the last decades, human full-term cord blood was extensively investigated as a potential source of hematopoietic stem and progenitor cells (HSPCs). Despite the growing interest of regenerative therapies in preterm neonates, only little is known about the biological function of HSPCs from early preterm neonates under different perinatal conditions. Therefore, we investigated the concentration, the clonogenic capacity and the influence of obstetric/perinatal complications and maternal history on HSPC subsets in preterm and term cord blood.

Methods

CD34+ HSPC subsets in UCB of 30 preterm and 30 term infants were evaluated by flow cytometry. Clonogenic assays suitable for detection of the proliferative potential of HSPCs were conducted. Furthermore, we analyzed the clonogenic potential of isolated HSPCs according to the stem cell marker CD133 and aldehyde dehydrogenase (ALDH) activity.

Results

Preterm cord blood contained a significantly higher concentration of circulating CD34+ HSPCs, especially primitive progenitors, than term cord blood. The clonogenic capacity of HSPCs was enhanced in preterm cord blood. Using univariate analysis, the number and clonogenic potential of circulating UCB HSPCs was influenced by gestational age, birth weight and maternal age. Multivariate analysis showed that main factors that significantly influenced the HSPC count were maternal age, gestational age and white blood cell count. Further, only gestational age significantly influenced the clonogenic potential of UCB HSPCs. Finally, isolated CD34+/CD133+, CD34+/CD133– and ALDH^high HSPC obtained from preterm cord blood showed a significantly higher clonogenic potential compared to term cord blood.

Conclusion

We demonstrate that preterm cord blood exhibits a higher HSPC concentration and increased clonogenic capacity compared to term neonates. These data may imply an emerging use of HSPCs in autologous stem cell therapy in preterm neonates.     

Functional group diversity of bee pollinators increases crop yield

Niche complementarity is a commonly invoked mechanism underlying the positive relationship between biodiversity and ecosystem functioning, but little empirical evidence exists for complementarity among pollinator species. This study related differences in three functional traits of pollinating bees (flower height preference, daily time of flower visitation and within-flower behaviour) to the seed set of the obligate cross-pollinated pumpkin Cucurbita moschata Duch. ex Poir. across a land-use intensity gradient from tropical rainforest and agroforests to grassland in Indonesia. Bee richness and abundance changed with habitat variables and we used this natural variation to test whether complementary resource use by the diverse pollinator community enhanced final yield. We found that pollinator diversity, but not abundance, was positively related to seed set of pumpkins. Bees showed species-specific spatial and temporal variation in flower visitation traits and within-flower behaviour, allowing for classification into functional guilds. Diversity of functional groups explained even more of the variance in seed set (r2=45%) than did species richness (r2=32%) highlighting the role of functional complementarity. Even though we do not provide experimental, but rather correlative evidence, we can link spatial and temporal complementarity in highly diverse pollinator communities to pollination success in the field, leading to enhanced crop yield without any managed honeybees.     

Sustainable pest regulation in agricultural landscapes: a review on landscape composition, biodiversity and natural pest control

Agricultural intensification has resulted in a simplification of agricultural landscapes by the expansion of agricultural land, enlargement of field size and removal of non-crop habitat. These changes are considered to be an important cause of the rapid decline in farmland biodiversity, with the remaining biodiversity concentrated in field edges and non-crop habitats. The simplification of landscape composition and the decline of biodiversity may affect the functioning of natural pest control because non-crop habitats provide requisites for a broad spectrum of natural enemies, and the exchange of natural enemies between crop and non-crop habitats is likely to be diminished in landscapes dominated by arable cropland. In this review, we test the hypothesis that natural pest control is enhanced in complex patchy landscapes with a high proportion of non-crop habitats as compared to simple large-scale landscapes with little associated non-crop habitat. In 74% and 45% of the studies reviewed, respectively, natural enemy populations were higher and pest pressure lower in complex landscapes versus simple landscapes. Landscape-driven pest suppression may result in lower crop injury, although this has rarely been documented. Enhanced natural enemy activity was associated with herbaceous habitats in 80% of the cases (e.g. fallows, field margins), and somewhat less often with wooded habitats (71%) and landscape patchiness (70%). The similar contributions of these landscape factors suggest that all are equally important in enhancing natural enemy populations. We conclude that diversified landscapes hold most potential for the conservation of biodiversity and sustaining the pest control function.