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991.
Mass mortalities of larval cultures of Chilean scallop Argopecten purpuratus have repeatedly occurred in northern Chile, characterized by larval agglutination and accumulation in the bottom of rearing
tanks. The exopolysaccharide slime (EPS) producing CAM2 strain was isolated as the primary organism from moribund larvae in
a pathogenic outbreak occurring in a commercial hatchery producing larvae of the Chilean scallop Argopecten purpuratus located in Bahía Inglesa, Chile. The CAM2 strain was characterized biochemically and was identified by polymerase chain reaction
amplification of 16S rRNA as Halomonas sp. (Accession number DQ885389.1). Healthy 7-day-old scallop larvae cultures were experimentally infected for a 48-h period
with an overnight culture of the CAM2 strain at a final concentration of ca. 105 cells per milliliter, and the mortality and vital condition of larvae were determined by optical and scanning electron microscopy
(SEM) to describe the chronology of the disease. Pathogenic action of the CAM2 strain was clearly evidenced by SEM analysis,
showing a high ability to adhere and detach larvae velum cells by using its “slimy” EPS, producing agglutination, loss of
motility, and a posterior sinking of scallop larvae. After 48 h, a dense bacterial slime on the shell surface was observed,
producing high percentages of larval agglutination (63.28 ± 7.87%) and mortality (45.03 ± 4.32%) that were significantly (P < 0.05) higher than those of the unchallenged control cultures, which exhibited only 3.20 ± 1.40% dead larvae and no larval
agglutination. Furthermore, the CAM2 strain exhibited a high ability to adhere to fiberglass pieces of tanks used for scallop
larvae rearing (1.64 × 105 cells adhered per square millimeters at 24 h postinoculation), making it very difficult to eradicate it from the culture
systems. This is the first report of a pathogenic activity on scallop larvae of Halomonas species, and it prompts the necessity of an appraisal on biofilm-producing bacteria in Chilean scallop hatcheries. 相似文献
992.
This study explored a consumer-resource model including reproductive and nonreproductive subpopulations of the consumer to
consider whether resource-dependent reproductive adjustment by the consumer would stabilize consumer-resource dynamics. The
model assumed that decreasing (increasing) resource availability caused reproductive suppression (facilitation), and that
the reproductive consumer had a higher mortality rate than the nonreproductive one (i.e., a trade-off between reproduction
and survival). The model predicted that the variability would be reduced when the consumer had a strong tendency to suppress
reproduction in response to low resource availability or when the cost of reproduction was high, although consumer extinction
became more likely. Furthermore, when the consumer-resource dynamics converged to limit cycles, reproductive adjustment enhanced
the long-term average of the consumer density. It was also predicted that if reproductive suppression enhanced resource consumption
efficiency (i.e., a trade-off between reproduction and foraging), then it would destabilize the system by canceling the stabilizing
effect of the reproductive adjustment itself. These results suggest that it is necessary not only to identify the costs of
reproduction, but also to quantify the changes in individual-level performances due to reproduction in order to understand
the ecological consequences of reproductive adjustment. 相似文献
993.
Liu Y Yu Y Yang S Zeng B Zhang Z Jiao G Zhang Y Cai L Yang R 《Cancer immunology, immunotherapy : CII》2009,58(5):687-697
An elevated number of Gr-1+CD11b+ myeloid-derived suppression cells (MDSCs) has been described in mice and human bearing tumor and associated with immune suppression.
Arginase I production by MDSCs in the tumor environment may be a central mechanism for immunosuppression and tumor evasion.
In this study and before, we found that Gr-1+CD11b+ MDSCs from ascites and spleen of mice bearing ovarian 18D carcinoma express a high level of PD-1, CTLA-4, B7-H1 and CD80
while other co-stimulatory molecules, namely CD40, B7-DC and CD86 are not detected. Further studies showed that PD-1 and CTLA-4
on the Gr-1+CD11b+ MDSCs regulated the activity and expression of arginase I. The blockage and silencing of PD-1, CTLA-4 or both PD-1 and CTLA4
molecules could significantly reduce arginase I activity and expression induced with tumor-associated factor. Similar results
were also observed while their ligands B7-H1 and/or CD80 were blocked or silenced. Furthermore, CD80 deficiency also decreased
the arginase I expression and activity. Antibody blockade or silencing of PD-1, CTLA-4 or both reduced the suppressive potential
of PD-1+CTLA-4+MDSCs. Blockade of PD-1, CTLA-4 or both also slowed tumor growth and improved the survival rate of tumor-bearing
mice. Thus, there may exist a coinhibitory and costimulatory molecules-based immuno-regulating wet among MDSCs.
This research was supported by Nankai University grant, NSFC grant “30771967”, “985” grant,The Ministry of Science and Technology
grant “2006AA020502”“06C26211200695”, Tianjin Grant “07JCZDJC03300” and “06ZHCXSH04800”. 相似文献
994.
The existence and implications of alternative stable states in ecological systems have been investigated extensively within
deterministic models. However, it is known that natural systems are undeniably subject to random fluctuations, arising from
either environmental variability or internal effects. Thus, in this paper, we study the role of noise on the pattern formation
of a spatial predator–prey model with Allee effect. The obtained results show that the spatially extended system exhibits
rich dynamic behavior. More specifically, the stationary pattern can be induced to be a stable target wave when the noise
intensity is small. As the noise intensity is increased, patchy invasion emerges. These results indicate that the dynamic
behavior of predator–prey models may be partly due to stochastic factors instead of deterministic factors, which may also
help us to understand the effects arising from the undeniable susceptibility to random fluctuations of real ecosystems. 相似文献
995.
Kiyoon Kang Sangkyu Park Young Soon Kim Sungbeom Lee Kyoungwhan Back 《Applied microbiology and biotechnology》2009,83(1):27-34
Serotonin derivatives belong to a class of phenylpropanoid amides found at low levels in a wide range of plant species. Representative
serotonin derivatives include feruloylserotonin (FS) and 4-coumaroylserotonin (CS). Since the first identification of serotonin
derivatives in safflower seeds, their occurrence, biological significance, and pharmacological properties have been reported.
Recently, serotonin N-hydroxycinnamoyl transferase (SHT), which is responsible for the synthesis of serotonin derivatives, was cloned from pepper
(Capsicum annuum) and characterized in terms of its enzyme kinetics. Using the SHT gene, many attempts have been made to either increase the
level of serotonin derivatives in transgenic plants or produce serotonin derivatives de novo in microbes by dual expression of key genes such as SHT and 4-coumarate-CoA ligase (4CL). Due to the strong antioxidant activity
and other therapeutic properties of serotonin derivatives, these compounds may have high potential in treatment and prophylaxis,
as cosmetic ingredients, and as major components of functional foods or feeds that have health-improving effects. This review
examines the biosynthesis of serotonin derivatives, corresponding enzymes, heterologous production in plants or microbes,
and their applications. 相似文献
996.
Ectomycorrhizal (ECM) syntheses between four ECM fungi, Laccaria amethystina, Hebeloma mesophaeum, Thelephora terrestris, and Tomentella sp., and Populus maximowiczii seedlings that are known to form ECM at a denuded area of Mt. Usu were performed in volcanic debris in a controlled growth
chamber. The percentage of ECM colonization and seedling growth were determined 3 months after inoculation. Seedlings were
successfully colonized by the inoculated ECM fungi with low contamination ratios. Seedling height and biomass were larger
in the inoculated seedlings than in the control, although the effects of inoculation on seedling growth varied with the ECM
fungus. 相似文献
997.
Ligia Noronha 《EcoHealth》2004,1(2):SU16
This article briefly discusses the evolution of ecosystem approaches, and illustrates the use of ecosystem approaches to assess human health and well-being in a mining context. It discusses the various elements that help distinguish such approaches from other approaches. Well-being here is understood broadly in terms of its “constituents” and “determinants,” of which health is an important constituent. Ecological, health, and social assessments highlighted a number of impacts from mining activity in Goa, India. These generated a list of issues of concern that were validated by stakeholders—community, industry, and government—which served as a basis for the development of tools to track mining-induced changes in health and well-being. The article concludes by reflecting on some of the challenges posed by the use of ecosystem approaches to assessing human health and well-being. 相似文献
998.
Utíkal P Köcher M Bachleda P Drác P Cerná M Buriánková E 《Biomedical papers of the Medical Faculty of the University Palacky, Olomouc, Czechoslovakia》2004,148(2):175-178
The authors describe the method of surgical aortic banding for better stent-graft fixation in cases of problematic aortic neck in the endovascular infrarenal aneurysms repair. 相似文献
999.
Yocum D 《Arthritis research & therapy》2004,6(Z2):S24-S30
Tumor necrosis factor (TNF) antagonists are biologic response modifiers that have significantly improved functional outcomes in patients with rheumatoid arthritis (RA). RA is a progressive disease in which structural joint damage can continue to develop even in the face of symptomatic relief. Before the introduction of biologic agents, the management of RA involved the use of disease-modifying antirheumatic drugs (DMARDs) early in the course of disease. This focus on early treatment, combined with the availability of the anti-TNF agents, has contributed to a shift in treatment paradigms favoring the early and timely use of DMARDs with biologic therapies. Improvement in symptom control does not always equate to a reduction in disease progression or disability. With the emergence of structure-related outcome measures as the primary means for assessing the effectiveness of antirheumatic agents, the regular use of X-rays is recommended for the continued monitoring and evaluation of patients. In addition to the control of symptoms and improvement in physical function, a reduction in erosions and joint-space narrowing should be considered among the goals of therapy, leading to a better quality of life. Adherence to therapy is an important element in optimizing outcomes. Durability of therapy with anti-TNF agents as reported from clinical trials can also be achieved in the clinical setting. Concomitant methotrexate therapy might be important in maintaining TNF antagonist therapy in the long term. Overall, the TNF antagonists have led to improvements in clinical and radiographic outcomes in patients with RA, especially those who have failed to show a complete response to methotrexate. 相似文献
1000.
Inflorescence apices are suitable explants for the rapid in vitro propagation of Musa spp. However, the diploid and triploid banana cultivars showed different in vitro responses with respect to the hormone combinations
in Murashige and Skoog medium. The diploid cultivar (Sannachenkadali, AA) induced a maximum number of multiple shoots in 8.9 μM
6-benzyl adenine (BA) whereas the triploid cultivar (Red banana, AAA) exhibited maximum multiplication in 22.2 μM 6-benzyl
adenine. MS medium supplemented with 11.4 μM indole acetic acid and 17.8 μM BA was also suitable for shoot proliferation in
triploid cultivar but not in the diploid cultivar. The regenerated shoots were rooted in Murashige and Skoog basal medium
within 10–15 days. The rooted plantlets were transferred to vermiculite and maintained at a temperature of 25 ± 2°C for 10 days
and then at room temperature (30–32°C) for 2 weeks before transferring to potted soil compost mixture. The plantlets showed
100% survival. 相似文献