Interleukin-2 (IL-2), which is a growth factor for T lymphocytes, can also sometimes be inhibitory. Thus, the proliferation of CD8+ T cells in vivo is increased after the injection of a monoclonal antibody that is specific for IL-2 (IL-2 mAb), perhaps reflecting the removal of IL-2-dependent CD4+ T regulatory cells (T regs). Instead, we show here that IL-2 mAb augments the proliferation of CD8+ cells in mice simply by increasing the biological activity of preexisting IL-2 through the formation of immune complexes. When coupled with recombinant IL-2, some IL-2/IL-2 mAb complexes cause massive (>100-fold) expansion of CD8+ cells in vivo, whereas others selectively stimulate CD4+ T regs. Thus, different cytokine-antibody complexes can be used to selectively boost or inhibit the immune response. 相似文献
Natural regeneration ofP. abies(L.) H. Karst. may reach high densities in lower mountain elevations. The highest densities were found in sites with moderate light availability, with low pH, and not near the riverbank. However, age-height classes differed in the predicted magnitude of response, but were consistent in response directions. Mosses and understory species typical of coniferous forests were positively correlated with regeneration density.
? Context
Norway spruce Picea abies (L.) H. Karst. in Central Europe is at risk under climate change scenarios, particularly in mountain regions. Little is known about the impact of environmental factors on the natural regeneration of P. abies in low-elevation mountain forests.
? Aims
We aimed to assess impacts of distance from the riverbank, soil pH, and light availability on natural P. abies regeneration. We hypothesized that (1) natural P. abies regeneration would depend on light availability and soil pH and (2) there are understory plant species which may indicate the microsites suitable for natural regeneration of P. abies.
? Methods
The study was conducted in the Sto?owe Mountains National Park (SW Poland, 600–800 m a.s.l.). We established 160 study plots (25 m2) for natural regeneration, light availability, soil pH, and understory vegetation assessment.
? Results
The highest densities of natural regeneration of P. abies were observed in sites with moderate light availability (0.1–0.2 of open sky) and low pH (3.5–4.5), and located relatively far from the riverbank. Cover of 22 understory plant species were correlated with natural P. abies regeneration densities, mostly positively.
? Conclusion
Different stages of natural regeneration of P. abies revealed different regeneration niches. Most understory plant species (bryophytes and herbs typical of coniferous forests) do not compete with natural regeneration of P. abies.
After exposure in the field and laboratory soil block culture testing, the void content of wood–plastic composite (WPC) decking boards was compared to unexposed samples. A void volume analysis was conducted based on calculations of sample density and from micro-computed tomography (microCT) data. It was found that reference WPC contains voids of different sizes from the micrometer range up to several cubic millimeters. Large voids were unevenly distributed within the composite sample. Void size and volume increased after conditioning the WPC in water at 70°C. Depending on the effect of exposure conditions, fungal decay during laboratory soil block testing increased the size and volume of voids. For laboratory samples, the calculated void volume was much higher compared to microCT-detected voids because of the limited resolution of the instrument on relatively large samples with many nano- and microvoids present in the material. In both laboratory and field samples, the creation of the voids resulted in a significant decrease in composite density. Decay damage observed as an increase in the size and volume of voids was particularly severe for boards exposed in the field. The calculated void volume in such samples was in reasonable agreement with voids detected by microCT. 相似文献
From a root culture of Salvia austriaca, transformed with Agrobacterium rhizogenes, a new diterpenoid was isolated and its chemical structure was determined as 7-(2-oxohexyl)-11-hydroxy-6, 12-dioxo-7,9(11),13- abietatriene [= 7-(2-oxohexyl)-taxodione] on the basis of spectroscopic methods, especially 1D and 2D NMR, and by comparison with structurally related compounds. This compound represents a hitherto unknown 2-oxohexyl diterpenoid derivative. Cytotoxic studies revealed that the new compound exhibited high cytotoxic activity against three cancer cell lines with IC(50) values ranging from 0.63 to 0.72μM. Its cytotoxic effectiveness against the cancer cells was ten fold higher than that of taxodione. 相似文献
Conventions and policies for biodiversity conservation and climate change mitigation state the need for increased protection, restoration and climate change adaptation of forests. Much degraded land may be targeted for large-scale forest restoration, yet challenges include costs, a shortage of regeneration material and the need for restored forests to serve as a resource for communities. To ensure ecosystem function for the future, forest restoration programs must: (1) learn from the past; (2) integrate ecological knowledge; (3) advance regeneration techniques and systems; (4) overcome biotic and abiotic disturbances and (5) adapt for future forest landscapes. Historical forest conditions, while site-specific, may help to identify the processes that leave long-term legacies in current forests and to understand tree migration biology/population dynamics and their relationship with climate change. Ecological theory around plant–plant interactions has shown the importance of negative (competition) and positive (facilitation) interactions for restoration, which will become more relevant with increasing drought due to climate change. Selective animal browsing influences plant–plant interactions and challenges restoration efforts to establish species-rich forests; an integrated approach is needed to simultaneously manage ungulate populations, landscape carrying capacity and browse-tolerant regeneration. A deeper understanding of limiting factors that affect plant establishment will facilitate nursery and site preparation systems to overcome inherent restoration challenges. Severe anthropogenic disturbances connected to global change have created unprecedented pressure on forests, necessitating novel ecological engineering, genetic conservation of tree species and landscape-level approaches that focus on creating functional ecosystems in a cost-effective manner.
The developing porcine fetus offers an excellent opportunity for the study of lymphocyte development. Studies on B cell, alphabeta T cells and gammadelta T cells in the last decade have expanded our knowledge of lymphocyte development in pigs. These studies have revealed several interesting differences between swine, mice and humans. For example, porcine peripheral lymphocytes include CD4+CD8+ alphabeta T cells and an abundance of gammadelta T cells that may even prevail over the alphabeta population. There are numerous CD2- gammadelta T cells in the blood and a large number of CD8alphaalpha-bearing cells that include NK cells, conventional gammadelta and alphabeta T cells. All porcine B lymphocytes are CD25(lo) and sIgM+ B cells may differ in the expression of CD2 antigen. Unlike mice, porcine B cells appear approximately 2 weeks before T cells and progenitors undergo VDJH rearrangement at 20th day of gestation (DG20) in the yolk sac and DG30 in the fetal liver before consummating high level lymphogenesis in the bone marrow after DG45. Early B cells show an unexpectedly high proportion of in-frame rearrangements, undergo switch recombination in thymus on DG60 and use N-region insertion from the time of the earliest VDJ rearrangement. The genomic repertoire of VH, DH and JH genes is small compared to mice and humans and swine appear to depend on junctional diversity for the majority of their repertoire. The limited VH repertoire of swine contrasts sharply with the porcine TCRbeta repertoire, which is extensive, extraordinarily conserved and nearly identical to that in humans. Therefore, swine present an example of two highly related receptor systems that have diverged in the same species. 相似文献
Evaporative cooling of rose plants ‘Baccara’ and ‘Marimba’ by “fan and pad” resulted in a substantial increase in shoot water potential, a decrease in leaf diffusive resistance, and an increase in CO2 fixation. The mid-day increase in the leaf diffusive resistance was not accompanied by a decrease in the CO2 uptake. This phenomenon is attributed to the existence of continuous air flow through the plant canopy. Evaporative cooling also increased leaf area and the fresh weight and dry matter content of flower buds and stems. 相似文献
Difficulty in recognition of some diaphragmatic hernias in dogs have stimulated the authors to develop a diagnostic method consisting of selective angiography of the cranial mesenteric and celiac arteries. The basis for the experimen was that each herniated visceral organ is usually displaced with its vessels. The experiment was carried out on 14 mongrel dogs. Four dogs served as controls. Different kinds of diaphragmatic hernias were surgically created in 10 dogs. Survey abdominal radiographs, gastrointestinal tract contrast studies and selective abdominal angiography were performed 14 days later. In angiograms of dogs with omental diaphragmatic hernias, displacement of branches of the left gastroepiploic artery into the thorax was seen. In angiograms of dogs with hepatic diaphragmatic hernias, branches of the common hepatic artery were seen to enter the thorax. In dogs with herniated small intestine, the jejunal branches of the cranial mesenteric artery were seen entering the thorax. Potential possibilities of selective abdominal angiography for diagnosis of diaphragmatic hernias are discussed. 相似文献
The varied bioavailability and different effects of organic forms of copper on the immune system of poultry have prompted the search for new feed additives based on copper compounds containing modified chelate complexes. The aim of the study was to determine the effect of inorganic and organic forms of copper on selected parameters of the cellular and humoral immune response in broiler chickens by determining the percentages of CD3+CD4+, CD3+CD8+ and CD25+ lymphocytes, cells with MHC Class II expression, and BU‐1+ cells, as well as the concentrations of SOD, IL‐2, IL‐10 and TNF‐α in the peripheral blood. The experiments were conducted using 500 one‐day‐old Ross 308 roosters divided into five groups. Cu was added in inorganic form (CuSO4), in inorganic form with the addition of phytase (CuSO4 + F), in organic form in combination with glycine (Cu‐Gly) and in organic form in combination with glycine and a phytase supplement (Cu‐Gly+F). The results of the study indicate an increase in the percentage of CD3+CD4+ and CD3+CD8+ T lymphocytes, CD25+ T cells, and cells expressing MHC class II molecules, and in the concentration of ceruloplasmin, activity of superoxide dismutase and the concentration of IL‐2 in the groups that received copper, particularly copper‐glycine chelates. Based on the study, we can conclude that supplementation of poultry feed with copper chelates activates mainly the Th1 cellular immune response and the response of peripheral blood T lymphocytes. Furthermore, it promotes secretion of cytokines, which are involved in potentiation and regulation of the immune response in birds. 相似文献