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排序方式: 共有189条查询结果,搜索用时 390 毫秒
61.
The development of biofilms in polyethylene sheets and particles was studied using downflow reactors with synthetic nutrient media made up of a mixture of volatile fatty acids. Results suggest a preferential immobilization of acetoclastic organisms in the inner space of the surfaces and the colonization by the butyrotrophic bacteria in the outer layers. After 101 days the bioparticles reached a specific acetociastic activity of 72.45mol acetic acid/g protein ·h while the biofilms had 58.80 mol acetic acid/g protein attached ·h. Due to the low density of the polyethylene particles low fluidization velocities would be needed (2m/h) in a downflow fluidized bed reactor. 相似文献
62.
Influence of photosynthesis and chlorophyll synthesis on polypeptide accumulation in greening euglena 总被引:1,自引:1,他引:0 下载免费PDF全文
Two-dimensional gel electrophoresis resolves total cellular protein from Euglena gracilis klebs var bacillaris Cori into 640 polypeptides, 79 of which are induced by light exposure. The inhibition of chloroplast translation by streptomycin, the direct inhibition of photosynthesis as well as the indirect inhibition of chlorophyll synthesis by 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) and the specific inhibition of photosynthesis but not chlorophyll synthesis by DCMU in the presence of 17 millimolar ethanol failed to inhibit the accumulation of 40 polypeptides. These polypeptides appear to be synthesized on cytoplasmic ribosomes and their accumulation is independent of the developmental status of the chloroplast. Streptomycin but not DCMU completely inhibited the accumulation of six polypeptides which are undetectable in mutants lacking chloroplast DNA suggesting that these polypeptides are translated on chloroplast ribosomes. The accumulation of seven polypeptides which are detectable in mutants lacking chloroplast DNA was also inhibited by streptomycin but not by DCMU suggesting that the accumulation of these polypeptides is dependent upon stabilization by a chloroplast translation product. The accumulation of 12 polypeptides was inhibited by streptomycin and by DCMU under conditions in which chlorophyll synthesis was inhibited, but not under conditions in which chlorophyll synthesis was unaffected by DCMU. The inhibition by DCMU of the accumulation of these polypeptides appears to be due to the inhibition of chlorophyll synthesis suggesting that they are components of pigment protein complexes. The accumulation of six polypeptides was inhibited under all conditions in which photosynthesis was inhibited suggesting that the accumulation of these polypeptides is dependent upon a product of photosynthesis. 相似文献
63.
Alberto Monroy Elio Parisi Floriana Rosati 《Differentiation; research in biological diversity》1982,23(1-3):179-183
Abstract. In this paper we argue that the mechanisms underlying the segregation of the somatic and germ cell lines are basically similar. The interaction of the genome with specific cytoplasmic factors is responsible for the restriction of their developmental potencies in the somatic cell lines, and for the prevention of such a restriction in the germ cell line. In particular, it is suggested that meiosis is part of the differentiation program of the germ cells. 相似文献
64.
65.
Iván López-Montero Laura R. Arriaga Germán Rivas Marisela Vélez Francisco Monroy 《Chemistry and physics of lipids》2010,163(1):56-63
Lipid monolayers can be laterally dilated under the action of the barriers in a Langmuir trough thus allowing for measurements of their mechanical response. We study the stress response of Escherichia coli polar lipid extract and POPC against oscillatory deformations stressed up to a 20% of the initial area. For E. coli monolayers a nonlinear regime described by a series of Fourier harmonics of the excitation mode is found beyond a critical strain (uC ≈ 1%). In contrast, the mechanical response of POPC monolayers is found linear upon much larger deformations. For E. coli monolayers the stress–strain plot reflects stress softening (plastic-like) behaviour whilst POPC behaves as a linear elastic body. No viscous delay with respect to the applied strain is detected in both systems, as expected for high fluid materials. The presence of phase coexistence domains as lipid reservoirs to facilitate lateral diffusion is claimed as a plausible mechanism underlying the observed mechanical plasticity. 相似文献
66.
67.
The trophic interactions between 15 native and two introduced fish species, silverside Odontesthes bonariensis and rainbow trout Oncorhynchus mykiss, collected in a major fishery area at Lake Titicaca were explored by integrating traditional ecological knowledge and stable‐isotope analyses (SIA). SIA suggested the existence of six trophic groups in this fish community based on δ13C and δ15N signatures. This was supported by ecological evidence illustrating marked spatial segregation between groups, but a similar trophic level for most of the native groups. Based on Bayesian ellipse analyses, niche overlap appeared to occur between small O. bonariensis (<90 mm) and benthopelagic native species (31·6%), and between the native pelagic killifish Orestias ispi and large O. bonariensis (39%) or O. mykiss (19·7%). In addition, Bayesian mixing models suggested that O. ispi and epipelagic species are likely to be the main prey items for the two introduced fish species. This study reveals a trophic link between native and introduced fish species, and demonstrates the utility of combining both SIA and traditional ecological knowledge to understand trophic relationships between fish species with similar feeding habits. 相似文献
68.
Ceramide: From lateral segregation to mechanical stress 总被引:1,自引:0,他引:1
Ceramide is a sphingolipid present in eukaryotic cells that laterally segregates into solid domains in model lipid membranes. Imaging has provided a wealth of structural information useful to understand some of the physical properties of these domains. In biological membranes, ceramide is formed on one of the membrane leaflets by enzymatic cleavage of sphyngomyelin. Ceramide, with a smaller head size than its parent compound sphyngomyelin, induces an asymmetric membrane tension and segregates into highly ordered domains that have a much high shear viscosity than that of the surrounding lipids. These physical properties, together with the rapid transmembrane flip-flop of the locally produced ceramide, trigger a sequence of membrane perturbations that could explain the molecular mechanism by which ceramide mediates different cell responses. In this review we will try to establish a connection between the physical membrane transformations in model systems known to occur upon ceramide formation and some physiologically relevant process in which ceramide is known to participate. 相似文献
69.
Bethany Richards Nicholas M de la Rúa Carlota Monroy Lori Stevens Patricia L Dorn 《Memórias do Instituto Oswaldo Cruz》2013,108(4):395-398
Triatoma dimidiata is the most important Chagas disease insect
vector in Central America as this species is primarily responsible for
Trypanosoma cruzi transmission to humans, the protozoan
parasite that causes Chagas disease. T. dimidiata sensu lato is
a genetically diverse assemblage of taxa and effective vector control requires a
clear understanding of the geographic distribution and epidemiological
importance of its taxa. The nuclear ribosomal internal transcribed spacer 2
(ITS-2) is frequently used to infer the systematics of triatomines. However,
oftentimes amplification and sequencing of ITS-2 fails, likely due to both the
large polymerase chain reaction (PCR) product and polymerase slippage near the
5'' end. To overcome these challenges we have designed new primers that amplify
only the 3''-most 200 base pairs of ITS-2. This region distinguishes the ITS-2
group for 100% of known T. dimidiata haplotypes. Furthermore,
we have developed a PCR-restriction fragment length polymorphism (RFLP) approach
to determine the ITS-2 group, greatly reducing, but not eliminating, the number
of amplified products that need to be sequenced. Although there are limitations
with this new PCR-RFLP approach, its use will help with understanding the
geographic distribution of T. dimidiata taxa and can facilitate
other studies characterising the taxa, e.g. their ecology, evolution and
epidemiological importance, thus improving vector control. 相似文献
70.
Jenna A. Monroy Matthew E. Carter Kimberly E. Miller Ellen Covey 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2011,197(5):459-467
Big brown bats form large maternity colonies of up to 200 mothers and their pups. If pups are separated from their mothers,
they can locate each other using vocalizations. The goal of this study was to systematically characterize the development
of echolocation and communication calls from birth through adulthood to determine whether they develop from a common precursor
at the same or different rates, or whether both types are present initially. Three females and their six pups were isolated
from our captive breeding colony. We recorded vocal activity from postnatal day 1 to 35, both when the pups were isolated
and when they were reunited with their mothers. At birth, pups exclusively emitted isolation calls, with a fundamental frequency
range <20 kHz, and duration >30 ms. By the middle of week 1, different types of vocalizations began to emerge. Starting in
week 2, pups in the presence of their mothers emitted sounds that resembled adult communication vocalizations, with a lower
frequency range and longer durations than isolation calls or echolocation signals. During weeks 2 and 3, these vocalizations
were extremely heterogeneous, suggesting that the pups went through a babbling stage before establishing a repertoire of stereotyped
adult vocalizations around week 4. By week 4, vocalizations emitted when pups were alone were identical to adult echolocation
signals. Echolocation and communication signals both appear to develop from the isolation call, diverging during week 2 and
continuing to develop at different rates for several weeks until the adult vocal repertoire is established. 相似文献