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81.
82.
René R Balandrán-Quintana Ana Ma Mendoza-Wilson Gerardo Alvarez-Manilla Carl W Bergmann Irasema Vargas-Arispuro Miguel Angel Martínez-Téllez 《Biochemical and biophysical research communications》2002,290(1):577-584
The effect of pectic oligomers (OG) on ethylene biosynthesis, electrolyte leakage (EL), and CO(2) production was studied in discs excised from zucchini fruit (Cucurbita pepo L.) and stored at 20 or 2.5 degrees C. At 20 degrees C, OG enhanced ethylene biosynthesis and had a transient effect on decreasing EL, but showed little effect on respiratory rate; both the amount and size of the oligomer were important in changing both ethylene synthesis and EL. At 2.5 degrees C, OG increased both ethylene biosynthesis and respiratory rate with a maximum effect at 100 microg of oligomer and peaking at 6 h; shorter oligomers demonstrated an even greater effect on ethylene biosynthesis, but differences were smaller in respiratory rate. EL at 2.5 degrees C was affected most by 1 microg of OG and by monomeric galacturonic acid, with transient increases that peaked at 8 h. We suggest a signaling role for OG in the early steps of cold acclimation or chilling injury. 相似文献
83.
Pemán J Cantón E Orero A Viudes A Frasquet J Gobernado M 《Revista iberoamericana de micología》2002,19(1):30-35
The results of the epidemiological study on candidemias with the highest number of cases carried out in Spain is presented. This study is included in the Epidemiological Survey of Candidemia in Europe supported by the ECMM in which another five countries take part. In the Spanish study, 19 hospitals participated, 290 candidemia episodes were analysed (80 in children under 15 years and 210 in adults), 293 strains of yeasts being isolated. Both in children and in adults, the risks factors more frequently observed were the intravenous catheter and previous antibiotic therapy. In adults, the most habitual underlying disease was the solid tumor and, in children, hematological diseases. Candida albicans was the most prevalent species isolated in adults (46.1%) and Candida parapsilosis in children (50%). As part of the therapy, the intravenous line was removed and antifungal treatment was prescribed to 74% and 92.5% of children, respectively and to 43.8% and 73.8% of adults. The antifungal agent of election in adults was fluconazole (54.8%) and liposomal amphotericin B (58.1%) in children. The global mortality of the study was 38.9%, which for ages was major in adults (41.4%) than in children (38.7%). The geographical distribution of the isolated species was homogeneous, C. albicans being the predominant species, with the exception of Galicia and Extremadura where C. parapsilosis was the most frequent. 相似文献
84.
Antibodies against pure discoidin I have been used as a tool to ascertain the role of this lectin in aggregation of Dictyostelium discoideum. Discoidin I is widely expressed over the cell surface of aggregation-competent AX-2 cells, as ascertained by indirect immunofluorescence with specific (antidiscoidin I) antibodies. Univalent antidiscoidin I antibodies (Fab fragments) inhibit the aggregation-specific intercellular adhesion of D discoideum AX-2 cells in an in vitro assay. This inhibition depends on antibody concentration and cell density; a 50% inhibition of cell aggregation was obtained at antidiscoidin I Fab concentration of 4.5 mg/ml and 1 X 10(6) cells/ml. Aggregation and morphogenesis on solid support is also effectively inhibited when AX-2 cells are starved in the presence of antidiscoidin I Fab fragments. The inhibition of morphogenesis is also dose dependent and more effective than in the in vitro assay. No inhibition of aggregation either in the in vitro assay or on morphogenesis on solid support was observed with preimmune Fab fragments at any of the concentrations tested (up to 9.6 mg/ml). 相似文献
85.
Zafar U. Khan Antonia Gutiérrez Celia P. Miralles Angel L. De Blas 《Neurochemical research》1996,21(2):147-159
Subunit-specific antibodies to all the γ subunit isoforms described in mammalian brain (γ1, γ2S, γL, and γ3) have been made. The proportion of GABAA receptors containing each γ subunit isoform in various brain regions has been determined by quantitative immunoprecipitation.
In all tested regions of the rat brain, the γ1, and γ3 subunits are present in considerable smaller proportion of GABAA receptor than the γ2 subunit. Immunocytochemistry shows that γ1 immunoreactivity concentrates in the stratum oriens and stratum radiatum of the CA1 region of the hippocampus. In the dentate
gyrus, γ1 immunoreactivity concentrates on the outer 2/3 of the molecular layer coinciding with the localization of the axospinous
synapses of the perforant pathway. In contrast, γ3 immunoreactivity concentrates on the basket cells and other GABAergic local circuit neurons of the hilus. These cells are
also rich in γ2S. In the cerebellu, γ1 immunolabeling was localized on the Bergmann glia. The γ2S and γ2L subunits are differentially expressed in various brain regions. Thus the γ2S is highly expressed in the olfactory bulb and hippocampus whereas the γ2L is very abundant in inferior colliculus and cerebellum, particularly in Purkinje cells, as immunocytochemistry, in situ hybridization
and immunoprecipitation techniques have revealed. The γ2S and γ2L coexist in some brain areas and cell types. Moreover, the γ2S and γ2L subunits can coexist in the same GABAA receptor pentamer. We have shown that this is the case in some GABAA receptors expressed in cerebellar granule cells. These GABAA receptors also have α and β subunits forming the pentamer. Immunoblots have shown that the rat γ1, γ2S, γ2L and γ3 subunits are peptides of 47, 45, 47 and 44 kDa respectively. Results also indicate that there are aging-related changes in
the expression of the γ2S and γ2L subunits in various brain regions which suggest the existence of aging-related changes in the subunit composition of the
GABAA receptors which in turn might lead to changes in receptor pharmacology. The results obtained with the various γ subunit isoforms
are discussed in terms of the high molecular and binding heterogeneity of the native GABAA receptors in brain.
Special issue dedicated to Dr. Kinya Kuriyama 相似文献
86.
Mariona Parera Bonaventura Clotet Miguel Angel Martínez 《Journal of molecular biology》2009,392(2):243-10
A central goal in molecular evolution is to understand how genetic interactions between protein mutations shape protein function and fitness. While intergenic epistasis has been extensively explored in eukaryotes, bacteria, and viruses, intragenic epistatic interactions have been insufficiently studied. Here, we employ a model system in which lambda phage fitness correlates with the enzymatic activity of human immunodeficiency virus type 1 (HIV-1) protease to systematically determine the epistatic interactions between intragenic pairs of deleterious protein substitutions. We generated 114 genotypes of the HIV-1 protease, each carrying pairs of nucleotide substitution mutations whose separated and combined deleterious effects on fitness were then determined. A high proportion (39%) of pairs displayed lethality. Several pairs exhibited significant interactions for fitness, including positive and negative epistasis. Significant negative epistatic interactions predominated (15%) over positive interactions (2%). However, the average ± SD epistatic effect, ē = 0.0025 ± 0.1334, was not significantly different from zero (p = 0.8368). Notably, epistatic interactions, regardless of epistatic direction, tend to be more frequent in the context of less deleterious mutations. In the present study, the high frequencies of lethality and negative epistasis indicate that the HIV-1 protease is highly sensitive to the effects of deleterious mutations. Therefore, proteins may not be as robust to mutational change as is usually expected. 相似文献
87.
Gutiérrez AM Reboredo GR Mosca SM Catalá A 《Molecular and cellular biochemistry》2006,282(1-2):109-115
Birds – particularly long-lived species – have special adaptations for preventing tissue damage caused by reactive oxygen
species. The objective of the present study was to analyse the fatty acid composition and non-enzymatic lipid peroxidation
of mitochondria and microsomes obtained from liver, heart and brain of quail (Coturnix coturnix japonica), a short-lived bird. Fatty acids located in total lipids of rat liver, heart and brain mitochondria and microsomes were
determined using gas chromatography and lipid peroxidation was evaluated using a chemiluminescence assay. The unsaturated
fatty acid content found in mitochondria and microsomes of all tissue examined was approximately 50 and 40%, respectively
with a prevalence of C18:1 n9. The C18:2 n6 content in brain mitochondria was significantly lower as compared to liver and
heart mitochondria. Whereas the C20:4 n6 content in mitochondria from all tissues examined and brain microsomes was approximately
6%, liver and heart microsomes exhibited lower values. C22:6 n3 was absent in liver mitochondria, very low content in liver
microsomes and heart organelles (between 0.5 and 1%) and high content in brain organelles, with mitochondria having the highest
value (11%). Whereas liver and heart organelles were not affected when subjected to lipid peroxidation, brain mitochondria
were highly affected, as indicated by the increase in chemiluminescence and a considerable decrease of C20:4 n6 and C22:6
n3. These results indicate that a low degree of fatty acid unsaturation in liver and heart organelles of quail, a short-lived
bird, may confer advantage by decreasing their sensitivity to lipid peroxidation process. 相似文献
88.
We study the problem of the emergence of cooperation in the spatial Prisoner's Dilemma. The pioneering work by Nowak and May [1992. Evolutionary games and spatial chaos. Nature 415, 424-426] showed that large initial populations of cooperators can survive and sustain cooperation in a square lattice with imitate-the-best evolutionary dynamics. We revisit this problem in a cost-benefit formulation suitable for a number of biological applications. We show that if a fixed-amount reward is established for cooperators to share, a single cooperator can invade a population of defectors and form structures that are resilient to re-invasion even if the reward mechanism is turned off. We discuss analytically the case of the invasion by a single cooperator and present agent-based simulations for small initial fractions of cooperators. Large cooperation levels, in the sustainability range, are found. In the conclusions we discuss possible applications of this model as well as its connections with other mechanisms proposed to promote the emergence of cooperation. 相似文献
89.
J. Angel Soto‐Centeno Lisa N. Barrow Julie M. Allen David L. Reed 《Ecology and evolution》2013,3(6):1603-1613
We evaluated the mtDNA divergence and relationships within Geomys pinetis to assess the status of formerly recognized Geomys taxa. Additionally, we integrated new hypothesis‐based tests in ecological niche models (ENM) to provide greater insight into causes for divergence and potential barriers to gene flow in Southeastern United States (Alabama, Florida, and Georgia). Our DNA sequence dataset confirmed and strongly supported two distinct lineages within G. pinetis occurring east and west of the ARD. Divergence date estimates showed that eastern and western lineages diverged about 1.37 Ma (1.9 Ma–830 ka). Predicted distributions from ENMs were consistent with molecular data and defined each population east and west of the ARD with little overlap. Niche identity and background similarity tests were statistically significant suggesting that ENMs from eastern and western lineages are not identical or more similar than expected based on random localities drawn from the environmental background. ENMs also support the hypothesis that the ARD represents a ribbon of unsuitable climate between more suitable areas where these populations are distributed. The estimated age of divergence between eastern and western lineages of G. pinetis suggests that the divergence was driven by climatic conditions during Pleistocene glacial–interglacial cycles. The ARD at the contact zone of eastern and western lineages of G. pinetis forms a significant barrier promoting microgeographic isolation that helps maintain ecological and genetic divergence. 相似文献
90.
Shaimaa Abdelmohsen Carol Verheecke-Vaessen Esther Garcia-Cela Angel Medina Naresh Magan 《Fungal biology》2021,125(1):62-68
Penicillium verrucosum contaminates temperate cereals with ochratoxin A (OTA) during harvesting and storage. We examined the effect of temperature (25 vs 30 oC), CO2 (400 vs 1000 ppm) and matric/solute stress (-2.8 vs -7.0 MPa) on (i) growth, (ii) key OTA biosynthetic genes and (iii) OTA production on a milled wheat substrate. Growth was generally faster under matric than solute stress at 25 oC, regardless of CO2 concentrations. At 30 oC, growth of P. verrucosum was significantly reduced under solute stress in both CO2 treatments, with no growth observed at -2.8 MPa (=0.98 water activity, aw) and 1000 ppm CO2. Overall, growth patterns under solute stress was slower in elevated CO2 than under matric stress when compared with existing conditions. The otapksPV gene expression was increased under elevated CO2 levels in matric stress treatments. There was fewer effects on the otanrpsPV biosynthetic gene. This pattern was paralleled with the production of OTA under these conditions. This suggest that P. verrucosum is able to actively grow and survive in both soil and on crop debris under three way interacting climate-related abiotic factors. This resilience suggests that they would still be able to pose an OTA contamination risk in temperate cereals post-harvest. 相似文献