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161.
Hernández-Hernández A Rincón-Arano H Recillas-Targa F Ortiz R Valdes-Quezada C Echeverría OM Benavente R Vázquez-Nin GH 《Chromosoma》2008,117(1):77-87
The synaptonemal complex (SC) is an evolutionarily conserved structure that mediates synapsis of homologous chromosomes during
meiotic prophase I. Previous studies have established that the chromatin of homologous chromosomes is organized in loops that
are attached to the lateral elements (LEs) of the SC. The characterization of the genomic sequences associated with LEs of
the SC represents an important step toward understanding meiotic chromosome organization and function. To isolate these genomic
sequences, we performed chromatin immunoprecipitation assays in rat spermatocytes using an antibody against SYCP3, a major
structural component of the LEs of the SC. Our results demonstrated the reproducible and exclusive isolation of repeat deoxyribonucleic
acid (DNA) sequences, in particular long interspersed elements, short interspersed elements, long terminal direct repeats,
satellite, and simple repeats. The association of these repeat sequences to the LEs of the SC was confirmed by in situ hybridization
of meiotic nuclei shown by both light and electron microscopy. Signals were also detected over the chromatin surrounding SCs
and in small loops protruding from the lateral elements into the SC central region. We propose that genomic repeat DNA sequences
play a key role in anchoring the chromosome to the protein scaffold of the SC.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
162.
Nitric oxide (NO) is an important molecule that acts in many tissues to regulate a diverse range of physiological processes.
It is becoming apparent that NO is a ubiquitous signal in plants. Since the discovery of NO emission by plants in the 1970s,
this gaseous compound has emerged as a major signalling molecule involved in multiple physiological functions. Research on
NO in plants has gained significant awareness in recent years and there is increasing indication on the role of this molecule
as a key-signalling molecule in plants. The investigations about NO in plants have been concentrated on three main fields:
The search of NO or any source of NO generation, effects of exogenous NO treatments, NO transduction pathways. However we
have limited information about signal transduction procedures by which NO interaction with cells results in altered cellular
activities. This article reviews recent advances in NO synthesis and its signalling functions in plants. First, different
sources and biosynthesis of NO in plants, then biological processes involving NO signalling are reviewed. NO signalling relation
with cGMP, protein kinases and programmed cell death are also discussed. Besides, NO signalling in plant defense response
is also examined. Especially NO signalling between animal and plant systems is compared. 相似文献
163.
Eftimie R Dushoff J Bridle BW Bramson JL Earn DJ 《Bulletin of mathematical biology》2011,73(12):2932-2961
Recent advances in virology, gene therapy, and molecular and cell biology have provided insight into the mechanisms through
which viruses can boost the anti-tumor immune response, or can infect and directly kill tumor cells. A recent experimental
report (Bridle et al. in Molec. Ther. 18(8):1430–1439, 2010) showed that a sequential treatment approach that involves two viruses that carry the same tumor antigen leads to an improved
anti-tumor response compared to the effect of each virus alone. In this article, we derive a mathematical model to investigate
the anti-tumor effect of two viruses, and their interactions with the immune cells. We discuss the conditions necessary for
permanent tumor elimination and, in this context, we stress the importance of investigating the long-term effect of non-linear
interactions. In particular, we discuss multi-stability and multi-instability, two complex phenomena that can cause abrupt
transitions between different states in biological and physical systems. In the context of cancer immunotherapies, the transitions
between a tumor-free and a tumor-present state have so far been associated with the multi-stability phenomenon. Here, we show
that multi-instability can also cause the system to switch from one state to the other. In addition, we show that the multi-stability
is driven by the immune response, while the multi-instability is driven by the presence of the virus. 相似文献
164.
We introduce a novel computational approach to predict effective genome size (EGS; a measure that includes multiple plasmid copies, inserted sequences, and associated phages and viruses) from short sequencing reads of environmental genomics (or metagenomics) projects. We observe considerable EGS differences between environments and link this with ecologic complexity as well as species composition (for instance, the presence of eukaryotes). For example, we estimate EGS in a complex, organism-dense farm soil sample at about 6.3 megabases (Mb) whereas that of the bacteria therein is only 4.7 Mb; for bacteria in a nutrient-poor, organism-sparse ocean surface water sample, EGS is as low as 1.6 Mb. The method also permits evaluation of completion status and assembly bias in single-genome sequencing projects. 相似文献
165.
166.
Insulin-like growth factor 1 (IGF-1) mediates many of the actions of growth hormone. Overexpression of IGF-1 was reported to have endocrine and paracrine/autocrine effects on somatic growth in transgenic mice. To study the paracrine/autocrine effects of IGF-1 in mammary gland, transgenic mice were produced by pronuclear microinjection of a construct containing a bovine alpha-lactalbumin (alpha-LA) promoter linked to an ovine IGF-1 cNDA. This alpha-LA promoter has previously been shown to direct expression of a human factor VIII gene specifically to the mammary gland of transgenic mice. Three transgenic mouse lines were established as a result of microinjection of 398 embryos. Transgene expression was found in mammary gland at day 1 of lactation from these three lines. Progeny test were carried out by mating two transgenic males/one transgenic female to two nontransgenic females/one nontransgenic male. Mice from one line (line 1225) were all nonexpressors and the other (line 1372) failed to produce offspring. Milk yield was analyzed in the line 1137 that produced 10 mice, of which three were transgenic females and three nontransgenic females. All of the three transgenic females showed integration of the transgene and expressed transgene IGF-1 mRNA in the mammary gland. Milk yields from days 5, 10, and 15 of lactation were significant greater in transgenic expressors than in their nontransgenic littermates. Specifically, there is 17.9% increase in total milk yield from these three days for transgenics compared with nontransgenics. These results demonstrate that local overexpression of IGF-1 in transgenic mice is capable to stimulating milk yield during the first lactation. 相似文献
167.
Don A. Driscoll Annabel L. Smith Samantha Blight John Maindonald 《Biodiversity and Conservation》2012,21(6):1607-1625
Altered fire regimes are a driver of biodiversity decline. To plan effective management, we need to know how species are influenced
by fire and to develop theory describing fire responses. Animal responses to fire are usually measured using methods that
rely on animal activity, but animal activity may vary with time since fire, potentially biasing results. Using a novel approach
for detecting bias in the pit-fall trap method, we found that leaf-litter dependent reptiles were more active up to 6 weeks
after fire, giving a misleading impression of abundance. This effect was not discovered when modelling detectability with
zero-inflated binomial models. Two species without detection bias showed early-successional responses to time since fire,
consistent with a habitat-accommodation succession model. However, a habitat specialist did not have the predicted low abundance
after fire due to increased post-fire movement and non-linear recovery of a key habitat component. Interactions between fire
and other processes therefore must be better understood to predict reptile responses to changing fire-regimes. We conclude
that there is substantial bias when trapping reptiles after fire, with species that are otherwise hard to detect appearing
to be abundant. Studies that use a survey method based on animal activity such as bird calls or animal movements, likely face
a similar risk of bias when comparing recently-disturbed with control sites. 相似文献
168.
Little information exists on mixed-species groups between primates and other mammals in Neotropical forests. In this paper, we describe three such associations observed during an extensive large-vertebrate survey in central Amazonia, Brazil. Mixed-species groups between a primate species and another mammal were observed on seven occasions between squirrel monkeys (Saimiri cf. ustus) and either South American coatis (Nasua nasua) or tayras (Eira barbara) and between brown capuchins (Cebus apella) and coatis. All associations were restricted to floodplain forest during its dry stage. We suggest that the associations involving the coatis are connected to foraging and vigilance but may be induced by a common alternative food resource at a time of food shortage. 相似文献
169.
Lentiviral vectors have been used for gene transfer into the liver but their ability to efficiently transduce quiescent hepatocytes
remains controversial. Lentivirus-mediated gene transfer is more efficient in cycling cells. We determine the effect of H-IL6
in the lentiviral transduction. The lentiviral vector was used to transduce HepG2 cells and mice liver cells, previously treated
with H-IL6. The highest transduction level was observed in HepG2 cells treated with 30 ng/mL H-IL6 and in the mice that received
4 μg H-IL6. Our results suggest that H-IL6 is an inducer of lentiviral gene transfer into the liver cells without any toxicity. 相似文献
170.
Thomas Proft 《Biotechnology letters》2010,32(1):1-10
Sortases are transpeptidases produced by Gram-positive bacteria to anchor cell surface proteins covalently to the cell wall.
The Staphylococcus aureus sortase A (SrtA) cleaves a short C-terminal recognition motif (LPXTG) on the target protein followed by the formation of an amide bond with the pentaglycine
cross-bridge in the cell wall. Over recent years, several researchers have exploited this specific reaction for a range of
biotechnology applications, including the incorporation of non-native peptides and non-peptidic molecules into proteins, the
generation of nucleic acid–peptide conjugates and neoglycoconjugates, protein circularisation, and labelling of cell surface
proteins on living cells. 相似文献