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1.
Leandro Neves Faria Marlon Gomes Da Rocha Quirijn De Jong Van Lier Derblai Casaroli 《Plant and Soil》2010,331(1-2):299-311
Correct modeling of root water uptake partitioning over depth is an important issue in hydrological and crop growth models. Recently a physically based model to describe root water uptake was developed at single root scale and upscaled to the root system scale considering a homogeneous distribution of roots per soil layer. Root water uptake partitioning is calculated over soil layers or compartments as a function of respective soil hydraulic conditions, specifically the soil matric flux potential, root characteristics and a root system efficiency factor to compensate for within-layer root system heterogeneities. The performance of this model was tested in an experiment performed in two-compartment split-pot lysimeters with sorghum plants. The compartments were submitted to different irrigation cycles resulting in contrasting water contents over time. The root system efficiency factor was determined to be about 0.05. Release of water from roots to soil was predicted and observed on several occasions during the experiment; however, model predictions suggested root water release to occur more often and at a higher rate than observed. This may be due to not considering internal root system resistances, thus overestimating the ease with which roots can act as conductors of water. Excluding these erroneous predictions from the dataset, statistical indices show model performance to be of good quality. 相似文献
2.
During the steady-state continuous culture of Saccharomyces cerevisiae on sugar cane blackstrap molasses under different experimental conditions, oscillatory variations of the invertase activity of the intact yeast cells were observed. The continuous morphological changes of the cells wall and of the periplasmic space affecting the interaction between invertase and sucrose molecules could be responsible by the observed oscillatory phenomena. The average invertase activity at the steady state is linearly correlated to the cell's growth rate. 相似文献
3.
Margarita F. Renart Leandro Sastre Víctor Díaz Jésus Sebastián 《Molecular and cellular biochemistry》1985,66(1):21-29
Summary A purification procedure to obtain RNA polymerases I (or A) and II (or B) from Dictyostelium discoideum amoeba has been developed. The enzymes were solubilized from purified nuclei and separated by DEAF-Sephadex chromatography. RNA polymerases I and II were further purified by a second chromatography on DEAE-Sephadex followed by chromatographies on phosphocellulose and heparin-sepharose. The specific activities of purified RNA polymerases I and II are 92 units/ mg protein and 70 units/ mg protein, respectively. The subunit structure of both RNA polymerases were analyzed by polyacrylamide gel electrophoresis under denaturing conditions after glycerol gradient centrifugation of the enzymes. The putative subunits of RNA polymerase I have molecular weights of 180 000,125 000,43 000,40 000,34 000, 31 000, 25 000,19 000, 17 000 and 14 000. The putative subunits of RNA polymerase II have molecular weights of 200 000 (170 000), 130 000, 33 000, 25 000, 19 000, 17 000, 15 000, 13 000. There are three polypeptides with common molecular weight in Dictyostelium RNA polymerases I and 11. The subunit of 25 000 daltons of both enzymes has common immunological determinants with RNA polymerase II from crustacean Artemia.Abbreviations TLCK
tosyl-lysine-chloromethyl-ketone
- DPT
diazophenylthioether 相似文献
4.
J A Hamilton N Veis A M Bordun G Vairo T J Gonda W A Phillips 《Journal of cellular physiology》1989,141(3):618-626
Murine bone marrow-derived macrophages (BMM) undergo DNA synthesis in response to growth factors such as colony stimulating factor-1 (CSF-1) and granulocyte-macrophage CSF (GM-CSF). These macrophages can also be "activated," but without subsequent DNA synthesis, by a number of other agents, including lipopolysaccharide (LPS), concanavalin A, zymosan, formyl-methionyl-leucyl-phenylalanine (FMLP), and the Ca2+ ionophore, A23187. When BMM are treated with a range of stimuli, there is some, although not perfect, correlation between transient elevations in both c-myc mRNA and c-fos mRNA levels and increases in DNA synthesis. However, enhanced DNA synthesis and oncogene expression are readily dissociated from rises in inositol phosphates and, by implication, phospholipase C-mediated hydrolysis of phosphatidyl inositol 4,5-bisphosphate. Superoxide formation in BMM can also be dissociated from the other responses and does not necessarily depend on protein kinase C activation. 相似文献
5.
Pereyra Paula Evelyn Rubira Hallwass Gustavo Begossi Alpina Giacomin Leandro Lacerda Silvano Renato Azevedo Matias 《Ecosystems》2023,26(5):1095-1107
Ecosystems - Frugivory and seed dispersal by fish is an important mutualistic interaction in complex and species-rich tropical rivers. The local ecological knowledge (LEK) held by fishers can... 相似文献
6.
The wintering diet of Common Terns Sterna hirundo was studied by using 714 pellets collected on roosting sites at the mouth of the Lagoa dos Patos and on adjacent coastal beaches, in Rio Grande do Sul, southern Brazil, from March 1999 to February 2000. A total of 12 340 individual prey items of 35 different food types was found. Fish was the most important food type in the diet, constituting 32% by number and 93% by mass. Insects contributed 67% by number but only 3% by mass. The main food types were sciaenid fishes Paralonchurus brasiliensis, Micropogonias furnieri, Cynoscion guatucupa and Macrodon ancylodon. Several of these are important commercial species; fisheries potentially impact food availability to the terns, and terns may contribute significantly to the natural mortality of these fishes. Clupeiform fishes, the urophycid fish Urophycis brasiliensis and flying ants (Camponotus sp.) were also important. Species composition of the diet (food types), both by number and by mass, differed significantly between months. Prey sizes ranged in length from 12.7 mm to 217.4 mm. The average estimated total length of fish taken was 77.7 mm, but the mean differed significantly among prey species. The importance of demersal sciaenids to the diet of the Common Tern, a surface predator, may be explained by their association with aquatic predators, especially adult Bluefish Pomatomus saltatrix and Striped Weakfish Cynoscion guatucupa, and the Franciscana Dolphin Pontoporia blainvillei, which drive these fish to the surface. The occurrence of flying ants in the diet was related to offshore winds, which carried these insects out to sea. The occasional high availability of insects possibly changed the cost/benefit relationship of several food types, causing diet changes. The high number of prey species, the temporal variations in the composition of the diet and the wide range of prey sizes are evidence of the high dietary plasticity of the Common Tern, at wintering areas in southern Brazil. 相似文献
7.
Carlos F. de Mello Diego D. De La Vega Leandro T. Pizutti Fabiane P. Lopes Maribel A. Rubin Jaime G. Homerich Dr. Carlos R. Melo Joana E. Somer Diogo O. Souza Moacir Wajner 《Neurochemical research》1995,20(12):1437-1441
The effect ofl-pyroglutamic acid, a metabolite that accumulates in pyroglutamic aciduria, on different neurochemical parameters was investigated in adult male Wistar rats. Glutamate binding, adenylate cyclase activity and G protein coupling to adenylate cyclase were assayed in the presence of the acid.l-pyroglutamic acid decreased Na+-dependent and Na+-independent glutamate binding Basal and GMP-PNP stimulated adenylate cyclase activity were not affected by the acid. Furthermore, rats received unilateral intrastriatal injections of 10–300 nmol of bufferedl-pyroglutamic acid. Vehicle (0.25 M Tris-Cl, pH 7.35–7.4) was injected into the contralateral striatum. Neurotoxic damage was assessed seven days after the injection by histological examination and by weighing both cerebral hemispheres. No difference in histology or weight could be identified between hemispheres. These results suggest that, although capable of interfering with glutamate binding, pyroglutamate did not cause a major lesion in the present model of neurotoxicity. 相似文献
8.
J A Hamilton G Vairo B G Cocks 《Journal of immunology (Baltimore, Md. : 1950)》1992,148(12):4028-4035
Some of the important controlling events regulating eukaryotic S-phase progression are considered to occur late in the G1 stage of the cell cycle. We show here that stimulation of DNA synthesis in bone marrow-derived macrophages (BMM) by macrophage CSF-1 is preceded by G1 expression of three genes which encode proteins associated with the DNA synthesis machinery--the M1 and M2 subunits of ribonucleotide reductase and proliferating cell nuclear Ag (PCNA). Increased expression for these genes correlated well with the mitogenic response and sustained expression required de novo RNA and protein synthesis and also the presence of CSF-1 for at least most of G1. Inhibitors of BMM proliferation (LPS, TNF-alpha, IFN-gamma, and cAMP elevating agents) suppressed CSF-1-induced expression of M1, M2, and PCNA mRNA measured at 22 h. This suppression occurred even when added up to 12 h after the CSF-1, a period coinciding with the G1/S-phase boundary. The delayed kinetics of this effect parallels the ability of these agents to maximally inhibit CSF-1-induced BMM DNA synthesis when added at similar times. Decreased expression of M1, M2, and PCNA was not merely a consequence of DNA synthesis inhibition because the S-phase inhibitor, hydroxyurea, did not suppress CSF-1-induced gene expression. These results suggest that inhibition of DNA synthesis by antiproliferative agents involves inhibition of expression of several genes associated with the DNA synthesis machinery. 相似文献
9.
Walter Borzani Haroldo Hiss Teresinha W. de Santos Marina L. R. Vairo 《Biotechnology letters》1992,14(10):981-984
Summary A mathematical model is proposed to explain the influence of the volume fraction of inoculum on the fermentation time and ethanol productivity in semicontinuous ethanol fermentation of sugar cane blackstrap molasses by pressed yeast.Nomenclature a, b, c, d
constants, see equation (5)
- Eo
initial ethanol concentration
- Ef
final ethanol concentration
- K1, K2, K3
constants, see equation (1)
- P
ethanol productivity
- Pc
calculated values of P
- Pe
experimental values of P
- r
correlation coefficient
- So
initial TRS concentration
- Sm
TRS concentration of the feeding mash
- T
fermentation time (average of the experimental values)
- Tc
calculated value of T
- Te
experimental value of T
- TRS
total reducing sugars calculated as glucose
- Uo
initial urea concentration
- Um
urea concentration of the feeding mash
- V
reactor working volume
- Vi
volume of the inoculum
-
volume fraction of inoculum=Vi/V 相似文献
10.
Ismael Galván Eduardo Aguilera Francisco Atiénzar Emilio Barba Guillermo Blanco José L. Cantó Verónica Cortés Óscar Frías István Kovács Leandro Meléndez Anders P. Møller Juan S. Monrós Péter L. Pap Rubén Piculo Juan C. Senar David Serrano José L. Tella Csongor I. Vágási Matthias Vögeli Roger Jovani 《Journal of avian biology》2012,43(3):273-279
Feather mites are arthropods that live on or in the feathers of birds, and are among the commonest avian ectosymbionts. However, the nature of the ecological interaction between feather mites and birds remains unclear, some studies reporting negative effects of feather mites on their hosts and others reporting positive or no effects. Here we use a large dataset comprising 20 189 measurements taken from 83 species of birds collected during 22 yr in 151 localities from seven countries in Europe and North Africa to explore the correlation between feather mite abundance and body condition of their hosts. We predicted that, if wing‐dwelling feather mites are parasites, a negative correlation with host body condition should be found, while a mutualistic interaction should yield positive correlation. Although negative relationships between feather mite abundance and host body condition were found in a few species of birds, the sign of the correlation was positive in most bird species (69%). The overall effect size was only slightly positive (r =0.066). The effect of feather mite abundance explained <10% of variance in body condition in most species (87%). Results suggest that feather mites are not parasites of birds, but rather that they hold a commensalistic relationship where feather mites may benefit from feeding on uropygial gland secretions of their hosts and birds do not seem to obtain a great benefit from the presence of feather mites. 相似文献