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991.
992.
Bradykinin is a potent mediator of inflammation that has been shown to participate in allergic airway inflammation. The biologic effects of bradykinin are mediated by binding and activation of its cognate receptor, the B(2) receptor (B(2)R). In the lung fibroblast cell line IMR-90, binding of bradykinin to B(2)R triggers down-regulation of receptor surface expression, suggesting that bradykinin-induced inflammation is transient and self-limited. Notably, subjects with chronic airway inflammation continue to respond to BK following a first challenge. B(2)Rs are expressed on many different lung cell types, including airway epithelial cells. We therefore compared IMR-90 cells with the human lung epithelial cell line BEAS2B and found that B(2)R expression in the two cell types is differently regulated by BK. Whereas BK induces down-regulation of B(2)R in IMR-90 cells, the same treatment leads to up-regulation of the receptor in BEAS2B cells. These results provide a possible explanation for the potency of bradykinin in inducing ongoing airway inflammation. 相似文献
993.
Extreme genetic similarity does not predict non‐breeding distribution of two closely related warblers 下载免费PDF全文
Ruth E. Bennett Sara Barker Swarthout Jeffrey S. Bolsinger Amanda D. Rodewald Kenneth V. Rosenberg Ronald W. Rohrbaugh 《Journal of Field Ornithology》2017,88(2):156-168
Detailed knowledge of migratory connectivity can facilitate effective conservation of Neotropical migrants by helping biologists understand where and when populations may be most limited. We studied the migratory behavior and non‐breeding distribution of two closely related species of conservation concern, the Golden‐winged Warbler (Vermivora chrysoptera) and Blue‐winged Warbler (Vermivora cyanoptera). Although both species have undergone dynamic range shifts and population changes attributed to habitat loss and social interactions promoting competition and hybridization, full life‐cycle conservation planning has been limited by a lack of information about their non‐breeding ecology. Because recent work has demonstrated that the two species are nearly identical genetically, we predicted that individuals from a single breeding population would have similar migratory timing and overwintering locations. In 2015, we placed light‐level geolocators on 25 males of both species and hybrids in an area of breeding sympatry at the Fort Drum Military Installation in Jefferson and Lewis counties, New York. Despite extreme genetic similarity, non‐breeding locations and duration of migration differed among genotypes. Golden‐winged Warblers (N = 2) overwintered > 1900 km southeast of the nearest Blue‐winged Warbler (N = 3) and spent nearly twice as many days in migration; hybrids (N = 2) had intermediate wintering distributions and migratory timing. Spring migration departure dates were staggered based on distance from the breeding area, and all birds arrived at the breeding site within 8 days of each other. Our results show that Golden‐winged Warblers and Blue‐winged Warblers in our study area retain species‐specific non‐breeding locations despite extreme genetic similarity, and suggest that non‐breeding locations and migratory timing vary along a genetic gradient. If the migratory period is limiting for these species, our results also suggest that Golden‐winged Warblers in our study population may be more vulnerable to population decline than Blue‐winged Warblers because they spend almost twice as many days migrating. 相似文献
994.
Gustavo Emilio Santos-Medrano Daniel Robles-Vargas Saraí Hernández-Flores Roberto Rico-Martínez 《Hydrobiologia》2017,796(1):169-179
We conducted life table experiments on the freshwater rotifer Asplanchna brightwellii to analyze its demography when fed with prey items from several taxonomic groups (cladocerans, protozoans, and rotifers) and under two different temperature regimes (20 and 25°C); the aim of the study was to determine the preferred prey for A. brightwellii in terms of fitness (evaluated as reproductive success) among five cladoceran, protozoan, and rotifer preys, and to test which temperature (20 or 25°C) is better for life table parameters of Asplanchna. Our analysis identified Brachionus calyciflorus as the preferred prey for A. brightwellii based on life table statistics, ingestion rate and electivity indices. The greatest values for net reproductive rate and intrinsic growth rate were achieved when A. brightwellii was fed B. calyciflorus. Greater reproductive values (R o and r) were found at 25°C than at 20°C for A. brightwellii across the five prey species. We found significant differences in the ingestion rate and electivity index among zooplanktonic and benthic preys. The influence of temperature, the cost of predation, and how prey selection by A. brightwellii is influenced by: biomass, size, and swimming speed; they are discussed hoping to gain a better understanding of trophic transfers in zooplankton communities. 相似文献
995.
Tsui-Ling C. Hsu Daniel S. Engebretson Sara A. Helvoigt Daniel G. Nocera 《Inorganica chimica acta》1995,240(1-2):551-557
The quadruple metal-metal bonded complexes, W2Cl4(PR3)4 (PR3 = PMe3, PMe2Ph, PBu3), photoreact in dichloromethane with near-UV excitation (λ>375 nm) to yield a mixed valence W2(II,III) photoproduct. Electronic absorption and EPR spectra of photolyzed solutions are identical to those obtained from the thermal oxidation of W2Cl4(PR3)4 by PhICI2, which is known to yield W2Cl5(PR3)3. Subsequent reaction of the photolyzed solution yields the oxidized, confacial biotahedral W2(III,III) halophosphine. Analysis of the organic photoproduct reveals that the halocarbon solvent is reduced by one electron to yield the chloromethyl radical. When the radical is produced in low yields, hydrogen abstraction from solvent appears to be sufficiently efficient to compete with dimerization and only chloromethane is observed; however, at higher concentrations, the chloromethyl radicals couple to produce dichloroethane. Photoreaction is observed only with near-UV excitation of the LMCT absorption manifold of W2Cl4(PR3)4. At lower energy wavelengths, transient absorption spectroscopy shows the production of the 1δδ* excited state, which decays to ground state over times commensurate with the decay of 1δδ* luminescence. In hydrocarbon solutions, no transient intermediate or photochemistry is observed, indicating that the LMCT excited state, although capable of reducing a C---X bond, cannot activate the stronger C---H bonds of hydrocarbons. The photochemistry and transient absorption spectroscopy results of the W2Cl4(PR3)4 complexes are compared to our previous studies of the
homologs. 相似文献
996.
Hillard S. Kaplan Jane B. Lancaster Sara E. Johnson John A. Bock 《Human nature (Hawthorne, N.Y.)》1995,6(4):325-360
Our objective is to test an optimality model of human fertility that specifies the behavioral requirements for fitness maximization
in order (a) to determine whether current behavior does maximize fitness and, if not, (b) to use the specific nature of the behavioral deviations from fitness maximization towards the development of models of evolved
proximate mechanisms that may have maximized fitness in the past but lead to deviations under present conditions. To test
the model we use data from a representative sample of 7,107 men living in Albuquerque, New Mexico, between 1990 and 1993.
The model we test proposes that low fertility in modern settings maximizes number of grandchildren as a result of a trade-off
between parental fertility and next generation fertility. Results do not show the optimization, although the data do reveal
a trade-off between parental fertility and offspring education and income.
We propose that two characteristics of modern economies have led to a period of sustained fertility reduction and to a corresponding
lack of association between income and fertility. The first is the direct link between costs of investment and wage rates
due to the forces of supply and demand for labor in competitive economies. The second is the increasing emphasis on cumulative
knowledge, skills, and technologies in the production of resources. Together they produce historically novel conditions. These
two features of modern economies may interact with evolved psychological and physiological mechanisms governing fertility
and parental investment to produce behavior that maximizes the economic productivity of lineages at the expense of fitness.
If cognitive processes evolved to track diminishing returns to parental investment and if physiological processes evolved
to regulate fertility in response to nutritional state and patterns of breast feeding, we might expect non-adaptive responses
when returns from parental investment do not diminish until extremely high levels are reached. With high economic payoffs
from parental investment, people have begun to exercise cognitive regulation of fertility through contraception and family
planning practices. Those cognitive processes maynot have evolved to handle fitness trade-offs between fertility and parental investment.
A preliminary presentation of this data was published in R. I. M. Dunbar, ed.,Human Reproduction Decisions: Biological and Social Perspectives. New York: St. Martin’s Press, 1995. Support for the research project, “Male Fertility and Parenting in New Mexico,” began
with two seed grants from the University of New Mexico’s Biomedical Research Grants Program, 1988 and 1989, and one from the
University of New Mexico Research Allocations Committee, 1988. Further seed money as well as interim funding came from the
William T. Grant Foundation (#89130589 and #91130501). The major support for the project came from the National Science Foundation
from 1990 to 1993 (#BNS-9011723 and #DBS-911552). Both National Science Foundation grants included Research Experience for
Undergraduates supplements.
Hillard S. Kaplan is an Associate Professor of Anthropology at the University of New Mexico. His earlier research and publications
focused on food sharing, time allocation, parental investment, and reproductive strategies among Ache hunter-gatherers in
Paraguay, Machiguenga and Piro forager-horticulturalists in Peru, and villagers of several ethnicities in Botswana. New research
and theory concern fertility, parental investment, and mating strategies in developed and developing nations. This research
formulates a new theory of reproductive decision-making and the demographic transition, integrating human capital and parental
investment theory in a synthesis of economic and evolutionary approaches.
Jane B. Lancaster is a Professor of Anthropology at the University of New Mexico. Her research and publications are on human
reproductive biology and behavior, especially human parental investment; women’s reproductive biology of pregnancy, lactation,
and child-spacing; and male fertility and investment in children. Current research with Hillard S. Kaplan is on male life
history strategies among a large sample of men in New Mexico. She has coedited three books on human parental investment:School-Age Pregnancy and Parenthood (with B. Hamburg),Parenting across the Life Span (with J. Altmann, A. Rossi, and L. Sherrod), andOffspring Abuse and Neglect (with R. Gelles). She is scientific editor of a quarterly journal,Human Nature: An Interdisciplinary, Biosocial Perspective published by Aldine de Gruyter. She is also a council member of the newly formed Human Behavior and Evolution Society.
John A. Bock is Andrew W. Mellon Post-Doctoral Fellow in Epidemiology and Population Health at the National Centre for Epidemiology
and Population Health, The Australian National University. His research focuses on the allocation of parental investment and
the determinants of children’s activities, integrating aspects of economic and evolutionary theory. He has ongoing field research
with Bantu and Bushmen agro-pastoralists and forager-horticulturalists in the Okavango Delta, Botswana. He is also collaborating
with Lancaster and Kaplan on the determinants of progeny distribution and homosexuality among New Mexican men.
Sara E. Johnson is a Ph.D. candidate at the University of New Mexico. Her major research trajectory focuses on trade-offs
in life history characters. Her research experience includes participation in a study of variation in growth and development
among children in a multi-ethnic community in the Okavango Delta, Botswana, in addition to her dissertation work on individual
variation in growth and mortality among juvenile baboons. She is collaborating with Lancaster and Kaplan on the association
between survival and fertility among Albuquerque men. 相似文献
997.
Various approaches to identify potential vaccine candidates against onchocerciasis resulted in the cloning of recombinant proteins, which confer protection in vaccinated mice. The development of an effective vaccine against onchocerciasis has been the focus of a research program supported by the Edna McConnell Clark Foundation from 1985 to 1999. The approaches used to clone potential protective antigens and the successful vaccination of animals with some of the antigens are summarized here. 相似文献
998.
Mammalian ykt6 is a neuronal SNARE targeted to a specialized compartment by its profilin-like amino terminal domain 下载免费PDF全文
Hasegawa H Zinsser S Rhee Y Vik-Mo EO Davanger S Hay JC 《Molecular biology of the cell》2003,14(2):698-720
SNAREs are required for specific membrane fusion throughout the endomembrane system. Here we report the characterization of rat ykt6, a prenylated SNARE selectively expressed in brain neurons. Immunofluorescence microscopy in neuronal and neuroendocrine cell lines revealed that membrane-associated ykt6 did not colocalize significantly with any conventional markers of endosomes, lysosomes, or the secretory pathway. However, ykt6-containing membranes displayed very minor overlaps with lysosomes and dense-core secretory granules and were similar to lysosomes in buoyant density. Thus, ykt6 appears to be specialized for the trafficking of a unique membrane compartment, perhaps related to lysosomes, involved in aspects of neuronal function. Targeting of this SNARE to the ykt6 compartment was mediated by its profilin-like amino-terminal domain, even in the absence of protein prenylation. Although several other R-SNAREs contain related amino-terminal domains, only the ykt6 version was able to confer the specialized localization. Rat ykt6, which contains an arginine in its SNARE motif zero-layer, was found to behave like other R-SNAREs in its SNARE assembly properties. Interestingly, cytosolic ykt6, constituting more than half of the total cellular pool, appeared to be conformationally inactive for SNARE complex assembly, perhaps indicative of a regulatory mechanism that prevents promiscuous and potentially deleterious SNARE interactions. 相似文献
999.
Folkert Reck Alun Bermingham Johanne Blais Vladimir Capka Taryn Cariaga Anthony Casarez Richard Colvin Charles R. Dean Alex Fekete Wanben Gong Ellie Growcott Hongqiu Guo Adriana K. Jones Cindy Li Fengxia Li Xiaodong Lin Mika Lindvall Sara Lopez Qingming Zhu 《Bioorganic & medicinal chemistry letters》2018,28(4):748-755
Metallo-β-lactamases (MBLs), such as New Delhi metallo-β-lactamase (NDM-1) have spread world-wide and present a serious threat. Expression of MBLs confers resistance in Gram-negative bacteria to all classes of β-lactam antibiotics, with the exception of monobactams, which are intrinsically stable to MBLs. However, existing first generation monobactam drugs like aztreonam have limited clinical utility against MBL-expressing strains because they are impacted by serine β-lactamases (SBLs), which are often co-expressed in clinical isolates. Here, we optimized novel monobactams for stability against SBLs, which led to the identification of LYS228 (compound 31). LYS228 is potent in the presence of all classes of β-lactamases and shows potent activity against carbapenem-resistant isolates of Enterobacteriaceae (CRE). 相似文献
1000.