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11.
It has been postulated that sulphatides may be the K+ binding site of the sodium pump. In order to test this hypothesis we studied the binding of K+ to bilayer membranes containing sulphatides or phosphatidylserine. The adsorption constants of Na+, K+ and Ca2+ to planar bilayers containing these acidic lipids were determined from changes in the electrostatic potential at the membrane surface. Our results indicate that univalent cations adsorb weakly to both lipids and Ca2+ binds more strongly. The sequence of ion binding was Ca2+ greater than Na+ greater than K+. These results indicate that K+ does not bind specifically to sulphatides or phosphatidylserine and rule out the proposal that sulphatides by themselves provide the K+ binding site of the sodium pump. 相似文献
12.
M F Canto M M Oliva J J Potter E Mezey V W Yang 《Biochemical and biophysical research communications》1992,188(2):684-689
The activity of the rat class I alcohol dehydrogenase (ADH) is enriched in certain tissues including the liver, intestine and testis. The tissue-specific expression of the gene encoding ADH in the rat was studied and found to closely correlate with tissue isozymic activity. A factor designated enhancer-site downstream binding protein (EDBP) was recently identified in the rat liver and found to interact with the proximal promoter of the class I ADH gene. The distribution of EDBP in nuclear extracts obtained from various tissues was examined based on its sequence-specific DNA binding property and found to correlate with tissue ADH expression. These findings suggest that EDBP is potentially a positive regulatory factor which is involved in controlling the tissue-specific expression of the ADH gene. 相似文献
13.
14.
Decomposition is a key process driving carbon and nutrient cycling in ecosystems worldwide. The home field advantage effect (HFA) has been found to accelerate decomposition rates when litter originates from “home” when compared to other (“away”) sites. It is still poorly known how HFA plays out in tropical, riparian forests, particularly in forests under restoration. We carried out three independent reciprocal litter transplant experiments to test how litter quality, soil nutrient concentrations, and successional stage (age) influenced HFA in tropical riparian forests. These experimental areas formed a wide gradient of soil and litter nutrients, which we used to evaluate the more general hypothesis that HFA varies with dissimilarity in soil nutrients and litter quality. We found that HFA increased with soil nutrient dissimilarity, suggesting that litter translocation uncouples relationships between decomposers and litter characteristics; and with litter N:P, indicating P limitation in this system. We also found negative HFA effects at a site under restoration that presented low decomposer ability, suggesting that forest restoration does not necessarily recover decomposer communities and nutrient cycling. Within each of the independent experiments, the occurrence of HFA effects was limited and their magnitude was not related to forest age, nor soil and litter quality. Our results imply that HFA effects in tropical ecosystems are influenced by litter nutrient limitation and soil nutrient dissimilarity between home and away sites, but to further disentangle major HFA drivers in tropical areas, a gradient of dissimilarity between litter and soil properties must be implemented in future experimental designs. 相似文献
15.
VIP stimulates adenylate cyclase activity of male and female rat anterior pituitaries and human prolactinomas, while dopamine inhibits the enzyme activity of female rat pituitaries and prolactinomas. A dopamine inhibited cyclase can be detected also in male rats provided the enzyme activity is increased by VIP. The analysis of the dose-response curves for one agent (VIP or dopamine) in the absence or in the presence of the other indicates that the two agents exhibit a different pattern of interaction in the different systems. In fact, in female rat pituitaries and in human prolactinomas, the curves for dopamine±VIP and for VIP±dopamine were parallel, indicating that the two agents exherted their effects independently from one another. On the contrary, in male rat pituitaries, the curves were definitively non parallel, that is, the inhibitory effect of dopamine was greatly amplified by VIP. In no case was the apparent affinity (EC50) of one agent modified by the presence of the other. It is concluded that two different modes of interaction between stimulatory and inhibitory neurohormones might exist at the level of adenylate cyclase from anterior pituitary cells. 相似文献
16.
A Oliva G Cacciapuoti G Romeo M Porcelli 《Bollettino della Società italiana di biologia sperimentale》1979,55(19):2019-2024
The paper reports the preparation and the chromatographic separation of new deaminated analogs of S-adenosyl(5')-3-methylthiopropylamine, i.e. S-adenosyl(5')-3-methylthiopropanol and S-inosyl(5')(-3-methylthiopropanol. These compounds can be used as specific inhibitors of polyamine biosynthesis. It is also reported the characterization of new sulfonium compounds by U.V. spectrophotometry, thin layer chromatography, high voltage electrophoresis, hydrolysis to known fragments. 相似文献
17.
Improved salvage of complicated microvascular transplants monitored with quantitative fluorometry. 总被引:2,自引:0,他引:2
T M Whitney W C Lineaweaver J B Billys P P Siko G M Buncke B S Alpert A Oliva H J Buncke 《Plastic and reconstructive surgery》1992,90(1):105-111
Quantitative fluorometry has been used to monitor circulation in transplanted toes and cutaneous flaps in our unit since 1982. Analysis of 177 uncomplicated transplants monitored by quantitative fluorometry shows that this technique has low false indication rates for arterial occlusion (0.6 percent of patients) and venous occlusion (6.2 percent of patients). None of these patients was reexplored because of a false monitor reading, and except for single abnormal sequences, monitoring appropriately indicated intact circulation throughout the postoperative period. Quantitative fluorometry has correctly indicated vascular complications in 21 (91.3 percent) of 23 transplants over an 8-year period. The salvage rate (85.7 percent) of the fluorescein-monitored reexplored transplants was significantly higher than the salvage rates of similar reexplored transplants not monitored with fluorescein and of reexplored muscle flaps (which cannot be monitored with the fluorometer used at this unit). These clinical data indicate that quantitative fluorometry is a valid and useful postoperative monitor for transplanted toes and cutaneous flaps. 相似文献
18.
A. Duque P. Manzanares I. Ballesteros M.J. Negro J.M. Oliva F. Saez M. Ballesteros 《Process Biochemistry》2013,48(5-6):775-781
In this work, an integrated one-step alkaline–extrusion process was tested as pretreatment for sugar production from barley straw (BS) biomass. The influence of extrusion temperature (T) and the ratio NaOH/BS dry matter (w/w) (R) into the extruder on pretreatment effectiveness was investigated in a twin-screw extruder at bench scale. A 23 factorial design of experiments was used to analyze the effect of process conditions [T: 50–100 °C; R: 2.5–7.5% (w/w)] on composition and enzymatic digestibility of pretreated substrate (extrudate). The optimum conditions for a maximum glucan to glucose conversion were determined to be R = 6% and T = 68 °C. At these conditions, glucan yield reached close to 90% of theoretical, while xylan conversion was 71% of theoretical. These values are 5 and 9 times higher than that of the untreated material, which supports the great potential of this one-step combined pre-treatment technology for sugar production from lignocellulosic substrates. The absence of sugar degradation products is a relevant advantage over other traditional methods for a biomass to ethanol production process since inhibitory effect of such product on sugar fermentation would be prevented. 相似文献
19.
Juan F. Espínola‐Novelo M. Teresa Gonzlez Aldo S. Pacheco Jos L. Luque Marcelo E. Oliva 《Ecology letters》2020,23(4):631-641
Parasite communities are similar to free‐living communities; decay of similarity over geographic distance, theory of island biogeography, species–area relationships and nestedness have been documented in both communities. Ecological succession has been studied in free‐living communities but has rarely been examined in parasite communities. We use seriation with replication to test the hypothesis that succession of parasite community structure is deterministic, thus developing throughout consecutive changes along the fish ontogeny, via a seriated pattern. 12 306 marine fishes (95 species) were studied. In 40 species, a seriated pattern was detected; 25 had a tendency towards a seriated pattern, and for 31 species, succession was at random. Age‐classes for each host species explained deterministic successional patterns for whole parasite communities and ectoparasites. Richness and number of age‐classes explained this pattern for endoparasites. Seriated successional pattern was evident for parasite communities of long‐lived marine fish, indicating that parasite communities follow sequential changes over time, like many free‐living communities. 相似文献
20.
Emilio García García María-Ángeles Vázquez López Rafael Galera Martínez Irene Alias Manuel Martín González Antonio Bonillo Perales José Eugenio Cabrera Sevilla Icíar García Escobar Sara Gómez Bueno Encarnación López Ruzafa Francisco-Javier Muñoz Vico Patricia Oliva Pérez María Ortiz Pérez Juan Poveda González Marisa Rodríguez Lucenilla Firma-Isabel Rodríguez Sánchez Ana Ruiz Sánchez Lucía Ruiz Tudela Sara Torrico 《Endocrinología y nutrición》2013,60(3):121-126
ObjectivesTo estimate the prevalence of obesity and overweight in children and adolescents in our city and to investigate the associated factors.Subjects and methodsA cross-sectional study of 1317 children and adolescents aged 2-16 years. Multistage probability sampling was used to select three groups of subjects: 411 aged 12 to 16 years, 504 aged 6 to 12 years, and 402 aged 2 to 6 years. Body mass index was calculated, and obesity and overweight were diagnosed using the threshold levels of the International Obesity Task Force for children and adolescents. Parents were asked about eating habits, health, social, and demographic aspects. Results are given as percentages (95% confidence interval). The relationship between obesity and overweight and the different variables was studied using multiple logistic regression. The adjusted odds ratio (OR) was calculated.ResultsAmong children and adolescentes aged 2-16 years, 9.5% (8.0%-11.0%) were obese and 22.4% (23.3%-24.6%) were overweight. Of subjects aged 12-16 years, 8.5% (5.9%-11.2%) were obese and 20.5% (16.7%-24.3%) were overweight. In the groups aged 6-12 years and 2-6 years, rates of obesity and overweight were 11.6% (8.9% -14.3%) and 31.0% (27.0-35.0) and 8.0% (5.4%-10.6%) and 13.6% (10.3%-16.9%) respectively. Obesity or overweight was associated to age (OR 1.21; P< 0.001), maternal obesity (OR 10.99; P= 0.008), a birthweight higher than 4 kg (OR 2.91; p 0.002), and formula feeding (OR 1.82; P= 0.005).ConclusionObesity and overweight in children and adolescents are highly prevalent problems in our city. 相似文献