13,587 research outputs found
Pseudevoplitus vittatus Grazia, Becker & Thomas 1994
No full textPseudevoplitus vittatus Grazia, Becker & Thomas, 1994 Distribution. A—Amazonas and Rondônia. C—Ecuador (Grazia et al. 1994, 2016).Published as part of Silva, Valeria Juliete Da, Santos, Cleverson Rannieri Meira Dos & Fernandes, Jose Antonio Marin, 2018, Stink bugs (Hemiptera: Pentatomidae) from Brazilian Amazon: checklist and new records, pp. 401-455 in Zootaxa 4425 (3) on page 444, DOI: 10.11646/zootaxa.4425.3.1, http://zenodo.org/record/126751
Vegetation-environment relationships in a heavy metal-dry grassland complex
No full textHeavy-metal content is assumed to be the most important edaphic factor that determines vegetation composition on contaminated soil. We compared the effects of heavy metals on species composition and species richness in the heavy metal-dry grassland complex of the Bottendorf Hills (Central Germany) with those of other environmental factors. Based on 206 releves, we distinguished nine communities of the classes Koelerio-Corynephoretea and Festuco-Brometea. Four communities in which the metallophytes Armeria maritima subsp. halleri and Minuartia verna subsp. hercynica occurred with high frequency were classified as heavy metal subassociations of four different dry grassland associations because of the dominance of dry grassland species. We measured the soil content of copper, zinc and lead, and the carbonate content, C/N ratio, pH and conductivity of the soil, soil depth and incident radiation per site. The first axis resulting from a DCA was positively correlated with the cover and height of the herb layer, the soil depth and soil carbonate content, and negatively with the soil content of copper, the proportion of rocks, the soil C/N ratio and incident radiation per site. The number of vascular plants, bryophyte and lichen species per plot increased with pH up to 7.5 and then decreased slightly. Species richness increased with carbonate content and conductivity of the soil and decreased with the soil C/N ratio. Heavy metal content of the soil and species richness were not correlated. The occurrence of the metallophytes was strongly related to the copper content of the soil. In conclusion our study has shown that heavy metal content is not necessarily the main factor determining the total composition and richness of grasslands on soil containing heavy metals. Heavy metal grasslands are not necessarily floristically distinct from "normal" dry grasslands
Spinal motor neurons are regenerated after mechanical lesion and genetic ablation in larval zebrafish
No full textIn adult zebrafish, relatively quiescent progenitor cells show lesion-induced generation of motor neurons. Developmental motor neuron generation from the spinal motor neuron progenitor domain (pMN) sharply declines already at 48 hours post-fertilisation (hpf). After that, mostly oligodendrocytes are generated from the same domain. We demonstrate here that within 48 h of a spinal lesion or specific genetic ablation of motor neurons at 72 hpf, the pMN domain reverts to motor neuron generation at the expense of oligodendrogenesis. By contrast, generation of dorsal Pax2-positive interneurons was not altered. Larval motor neuron regeneration can be boosted by dopaminergic drugs, similar to adult regeneration. We use larval lesions to show that pharmacological suppression of the cellular response of the innate immune system inhibits motor neuron regeneration. Hence, we have established a rapid larval regeneration paradigm. Either mechanical lesions or motor neuron ablation is sufficient to reveal a high degree of developmental flexibility of pMN progenitor cells. In addition, we show an important influence of the immune system on motor neuron regeneration from these progenitor cells
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No full textImproving the meal and protein quality for feed and food purposes is of increasing importance in canola (Brassica napus L.). The phenolic acid ester content contributes to the bitter taste, astringency, and dark color of rapeseed meal products. The predominant phenolic acid esters are sinapate esters (SE), which make up 1 to 2% of the seed dry matter. The objective of the present study was to analyze the genetic variation and the genotype X environment interactions for SE content and composition in three populations of doubled haploid lines. The populations were grown in three to four environments in Germany. The following SE were analyzed by HPLC: sinapoylcholine (sinapine), sinapoylglucose, and a minor group of other SE which includes sinapate. The three populations showed a highly significant variation for the total SE content, and sinapine was the predominant sinapate ester compound. The analysis of variance showed highly significant effects for the genotype (G), the environment (E) and the G X E interactions for all three populations. In two of the populations the G X E interaction variance components were less than half of the genetic variance, in one population it was slightly higher. The estimates for heritability of the individual and total SE were generally high and ranged from 0.57 to 0.93. A reduction of sinapate ester content was not associated with a change in oil, protein, and glucosinolate content
The dynamics of wealth inequality under endogenous fertility: A remark on the Barro-Becker model with heterogenous endowments
No full textSeveral contributions have already pointed out that initial wealth in- equalities do persist in the long run in the Ramsey model with heteroge- nous agents. We show that this result is not robust to the introduction of endogenous fertility. Our argument builds on the Barro-Becker (1989) seminal model extended to allow for heterogenous agents with dierent capital endowments. Strikingly enough, individual consumption levels, fertility rates and capital stocks are shown to be equalized after only one adjustment period. This property is shown to hold irrespective of the production sector specication.endogenous fertility, heterogeneous households, optimal growth
Plant diversity differs between young and old mesic meadows in a central European low mountain region
No full textEffects of habitat age on species diversity are an important issue in plant conservation. However, effects of habitat age on mesic meadows are poorly investigated. Here we compare plant species richness between old mesic meadows (> 150 years) and young mesic meadows (40-60 years) in a low mountain region (Thuringian Forest, Germany). Species richness and species traits were determined in 20 old and 20 young mountain meadows (alliances Polygono-Trisetion, Violion caninae) which were defined using historical maps and compared using species indicator analysis and ANOVA. Additionally we quantified changes in the extent of the area of young and old meadows using a Geographical Information System. Species richness of vascular plants on 20 m(2) plots was significantly higher in old than in young meadows, while evenness did not differ between young and old meadows. Endangered plant species were restricted to old meadows. which also contained a higher proportion of habitat specialists. The terminal velocity index of seeds was lower and seed weight was higher in old meadows, indicating a lower importance of wind dispersal in old meadows. This was also indicated by a higher proportion of species with seeds adapted to wind dispersal in young meadows. In old meadows there was a higher proportion of species with seeds adapted to ant dispersal and a lower proportion of species with seeds adapted to animal dispersal. In a representative sub-area of the study region, the total area of meadows has increased by 88% during the 20th century due to transformation of arable fields into meadows, while the area of old meadows declined by 36% during the same time due to abandonment and afforestation. We conclude that the age of the habitat is highly important in order to maintain plant diversity of mesic meadows. Therefore, higher priority should be given to old meadows. (C) 2008 Elsevier B.V. All rights reserved.Evangelisches Studienwerk Villigs
Ck Weakly Holomorphic Functions on an Analytic Curve
No full textPaper by Joseph Becker and John C. Polkin
Cellular and axonal plasticity in the lesioned spinal cord of adult zebrafish
No full textZebrafish, in contrast to mammals, are capable of functional regeneration after complete transection of the spinal cord. In this system I asked:
(1) Which spinal cell types regenerate in the lesioned spinal cord? (2) To what extent do the dopaminergic and 5-HT systems regenerate and (3) do dopaminergic axons from the brain influence cellular regeneration in the spinal cord?
(1) Lost motor neurons are replaced by newly born motor neurons that mature and are integrated into the spinal circuitry after a spinal lesion in adult zebrafish. Using immunohistochemical and transgenic markers in combination with BrdU labeling, we showed that also 5-HT, parvalbuminergic, Pax2+ and Vsx1+ cells are newly born after lesion. Thus, my work shows that diverse cell types are newly generated in the lesioned spinal cord of adult zebrafish.
(2) After spinal cord lesion, zebrafish completely recover locomotion within six weeks. Previous work suggested that axonal regeneration is crucial for functional recovery. Here I analyzed changes in the density of 5-HT and dopaminergic axon terminals in the lesioned spinal cord during recovery. Rostral to the lesion site, I observed die-back and sprouting of dopaminergic axons within two weeks post-lesion. Caudal of the lesion, axons are lost indicating Wallerian degeneration. At six weeks post-lesion I tested functional recovery with a behavioral swim test. In recovered fish, a third of the axonal density was restored just caudal of the lesion site, but not at far caudal levels. In contrast, in fish that had non-recovered, only few axons had bridged the lesion site. Thus dopaminergic axon regrowth correlates with functional recovery. Re-transection of the spinal cord in recovered animals abolished re-gained swimming capability, suggesting that behavioral recovery critically depends on axons that crossed the spinal lesion site and not on an intraspinal circuit. 5-HT axon terminals are of both intra- and supraspinal origin. The overall time course of changes in axon terminal density during recovery is similar to that of dopaminergic axon terminals and also correlates with functional recovery. Overall, the organization of the spinal dopaminergic and 5-HT systems, consisting of neuronal somata in the spinal cord and descending axons, differs significantly from their unlesioned organization. I observe sprouting rostral to the lesion site and limited innervation of the caudal spinal cord, as axons do not regrow into the far distal spinal cord.
(3) We further hypothesized that signals released by descending axons are involved in cellular regeneration around the lesion site. Dopaminergic axons of supraspinal origin sprout rostral, but are almost completely absent caudal to the lesion site at two weeks post-lesion. Moreover, we observe that expression of the dopamine receptor drd4a is only increased rostral to the lesion site in the ventricular zone of progenitor cells, including olig2 expressing motor neuron progenitor cells. Correlated with these rostro-caudal differences, numbers of regenerating motor neurons are almost two-fold higher rostral than caudal of the lesion site. To functionally test whether dopamine is involved in motor neuron regeneration, we ablated tyrosine hydroxylase positive, mostly dopaminergic axons by injecting the toxin 6-hydroxydopamine. This treatment significantly reduced motor neuron numbers only rostral to the lesion site. As a gain-of-function experiment, we injected the dopamine agonist NPA after spinal lesion, which increased motor neuron numbers only rostral to the lesion site at two weeks post-lesion. These results suggest that dopamine released by descending axons, augments the generation of motor neurons in the lesioned spinal cord of adult zebrafish. In summary, during spinal cord regeneration I observe generation of various cell types and plastic changes of descending axonal projections. Dopamine released by descending axons is able to increase motor neuron regeneration, showing for the first time that signals from descending axons influence cellular regeneration in the spinal cord
Seal of Rt. Rev. Thomas A. Becker, Bishop of Savannah, Georgia, and Letter, To: Eleanor C. Donnelly From: Thomas A. Becker, May 31, 1898.
No full textAn Augmented Becker-DeGroot-Marschak Mechanism for Transaction Cycles
No full textWe introduce an augmented Becker-DeGroot-Marschak mechanism for the revelation of willingness-to-accept and willingness-to-pay in transaction cycles. The mechanism can be used to test for a behavioral anomaly. (C) 2011 Elsevier B.V. All rights reserved.OE
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