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861.
The contribution of different membrane constituents to the bloodgroup P1 activity of human erythrocytes was investigated. Pronase digestion of native red cell stroma or partition between butanol and water had no serologically detectable effect, whereas pronase-treatment of previously butanol-extracted membranes liberated virtually all blood-group P1 determinants from the ghosts. On Laemmli gels, all P1 activity was found in the band 4.5 region. Thus it is concluded that, in addition to the well-documented P1 glycolipid, also membrane glycoproteins are carriers of blood-group P1 determinants. 相似文献
862.
The role of C, N and P in dissolved and particulate organic matter as a nutrient source for phytoplankton growth, including toxic species 总被引:3,自引:0,他引:3
Phytoplankton have traditionally been regarded as strictly phototrophic, with a well defined position at the base of pelagic food webs. However, recently we have learned that the nutritional demands of a growing number of phytoplankton species can be met, at least partially, or under specific environmental conditions, through heterotrophy. Mixotrophy is the ability of an organism to be both phototrophic and heterotrophic, in the latter case utilizing either organic particles (phagotrophy) or dissolved organic substances (osmotrophy). This finding has direct implications for our view on algal survival strategies, particularly for harmful species, and energy- and nutrient flow in pelagic food webs. Mixotrophic species may outcompete strict autotrophs, e.g. in waters poor in inorganic nutrients or under low light. In the traditional view of the ‘microbial loop’ DOC is thought to be channeled from algal photosynthesis to bacteria and then up the food chain through heterotrophic flagellates, ciliates and mesozooplankton. Are mixotrophic phytoplankton that feed on bacteria also significantly contributing to this transport of photosynthetic carbon up the food chain? How can we estimate the fluxes of carbon and nutrients between different trophic levels in the plankton food web involving phagotrophic algae? These questions largely remain unanswered. In this review we treat evidence for both osmotrophy and phagotrophy in phytoplankton, especially toxic marine species, and some ecological implications of mixotrophy. 相似文献
863.
864.
Anita Aisenberg Natalia Estramil Carlos Toscano-Gadea Macarena González 《Journal of Ethology》2009,27(1):43-50
Males can change their copulatory or sperm transfer patterns in response to sperm competition risk. Schizocosa malitiosa performs long copulations, which include two consecutive patterns (Patterns 1 and 2). Virgin females are very sexually receptive,
but mated females diminish their receptiveness. Female unreceptivity has been attributed to the action of receptivity-inhibiting
substances, mainly transferred during Pattern 1. We tested: (1) if females who mated only with Pattern 1 were immediately
unreceptive; (2) male and female behaviours when the copulating couple was exposed to another male. For (1), we interrupted
mating when Pattern 1 finished and immediately exposed the female to a second male. For (2), we introduced a second male when
the couple was starting (Ei) or finishing copulation (Li). Females were unreceptive immediately after finishing Pattern 1.
Males from Ei and Li dismounted and approached the second males. Ei males diminished the frequencies of insertion after perceiving
the presence of a second male and dismounted less frequently when copulating with heavy females. The study provides insights
about the timing of sexual unreceptivity in S. malitiosa under possibilities of sperm competition, discussing male adjustment of copulatory behaviour in the presence of rival males.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
865.
866.
A 1 μM solution of ammoniates [ZnCu(NH3)n]2+(CO3)2− was inserted into a cut shoot of flax with the transpiration stream of water. Analysis of the 14C content after 14CO2 assimilation by the shoot showed that ammoniates increased radioactive label contents in the tissues (especially in the young
leaves and stem). In the leaves the higher sucrose to hexoses ratio, an increased radioactivity of glycerate and malate and
decreased incorporation of 14C into oligosaccharides and pigments were observed. These effects were more pronounced in the young leaves. Spraying of plants
with 20 mM solution resulted in an increase of plant height and leaf number. 相似文献
867.
Cáit Coyle Pat Duggan Margery Godinho Dr. Dave McGrath 《International journal of phytoremediation》1999,1(2):189-202
The proposed phytoremediation technique is based on the successful exploitation and optimization of oxidative coupling, mediated by horseradish peroxidase. Susceptibility to degradation of a selection of phenolic compounds, in solution, by horseradish peroxidase appears to be structurally related and was found to be of the order 2,4-dichlorophenol (2,4-DCP) > 4-chlorophenol (4-CP) > 2-chlorophenol (2-CP). Only 1.89% of 2,4-DCP, at an initial concentration of 5 mM, remained unchanged at the end of the experiment. Reaction rates between purified horseradish peroxidase and 2,4-DCP were found to be extremely rapid with 74% of the substrate removed from solution during the first 30 s. Inhibition of the reaction by the heavy metals Cd, Zn, Ni, and Pb at concentrations of 100 mg/l is of concern because these metals are often present in contaminated soils. H2O2 has a dominant role in optimizing peroxidase activity in crude horseradish extracts. Fluctuations in temperature and pH, normally experienced in soils, did not appear to have a detrimental impact on peroxidase activity. However, the functioning of the enzyme is seriously affected at a pH ≤ 3. All reactions in this study were carried out in solution. 相似文献
868.
《Saudi Journal of Biological Sciences》2020,27(1):500-517
ObjectiveHere, the aim is to improve the bioavailability of Naringenin (NRG) in brain and to establish the highest remedial benefit from a novel anti-ischemic medicine i.e. NRG.MethodsA novel Naringenin-loaded-nanoemulsion (NE)-(in situ)-gel (i.e. thermoresponsive), was formulated with the help of Poloxamer-407 (20.0% w/v). Chitosan (CS, 0.50% w/v) was used to introduce the mucoadhesive property of NE-(in situ)-gel and finally called as NRG-NE-gel + 0.50%CS. A novel UHPLC-ESI-Q-TOF-MS/MS-method was optimized and used for NRG-NE-gel + 0.50%CS to quantify the Pharmacokinetic-(PK)-parameters in plasma as well as brain and to evaluate the cerebral ischemic parameters after MCAO i.e. locomotor activity, grip strength, antioxidant activity, and quantity the infarction volume in neurons with the safety/toxicity of NRG-NE-gel + 0.50%CS after i.n. administration in the rats.ResultsThe mucoadhesive potency and gelling temperature of NRG-NE-gel + 0.50%CS were observed 6245.38 dynes/cm2 and 28.3 ± 1.0 °C, respectively. Poloxamer-407 based free micelles size was observed 98.31 ± 1.17 nm with PDI (0.386 ± 0.021). The pH and viscosity of NRG-NE-gel + 0.50%CS were found to be 6.0 ± 0.20 and 2447 ± 24cp (at 35.0 ± 1.0 °C temperature), respectively. An elution time and m/z NRG were observed 1.78 min and 270.97/150.96 with 1.22 min and m/z of 301.01/150.98 for Quercetin (IS) respectively. Inter and intra %precision and %accuracy was validated 1.01–3.37% and 95.10–99.30% with a linear dynamic range (1.00 to 2000.00 ng/ml). AUC0-24 of plasma & brain were observed 995.60 ± 24.59 and 5600.99 ± 144.92 (ng min/ml g) in the rats after the intranasal (i.n.) administration of NRG-NE-gel + 0.50%CS. No toxicological response were not found in terms of mortalities, any-change morphologically i.e. in the microstructure of brain as well as nasal mucosa tissues, and also not found any visual signs in terms of inflammatory or necrosis.ConclusionIntranasally administered NRG-NE-gel + 0.50%CS enhanced the bioavailability of Naringenin in the brain. In the cerebral ischemic rats, significantly improved the neurobehavioral activity (locomotor & grip strength) followed by antioxidant activity as well as infarction volume. Finally, the toxicity studies carried out and established the safe nature of optimized-NRG-NE-gel + 0.50%CS. 相似文献
869.
John R. Whitaker 《Enzyme and microbial technology》1984,6(8):341-349
The pectic substances, located primarily in the middle lamella between cells in higher plant tissues, are complex polysaccharides. They include the negatively charged rhamnogalacturonans, and the neutral arabinogalactans I and II and l-arabinans. These polysaccharides add viscosity to juices but may also form hazes and precipitates and retard maximum recovery of juices from the fruit. The rhamnogalacturonans are degraded by the enzymes pectin methylesterase and polygalacturonase normally present in plant tissues and by these enzymes and pectate lyase in microbially derived commercial pectic enzymes added during processing. The presence of a?abinofuranosidase, which degrades l-arabinans, in commercial pectic enzyme preparations, can cause haze formation in juices such as apple and pear. 相似文献
870.
Detlef Keller Ulrich Wahnschaffe Gerhard Rosner Inge Mangelsdorf 《The International Journal of Life Cycle Assessment》1998,3(2):80-85
Characterization of toxic chemicals with relevance to human exposure does normally not belong to Life Cycle Assessments (LCA)
and is still a topic of research. The concept of hazard potential classes proposed in this paper is primarily based on threshold
limit values that are considered to be a measure of the severity of potential effects. In the absence of threshold limit values
the R-phrases of the ordinance of dangerous substances are used. Substances are assigned to five hazard potential classes
(A to E). Potentially dangerous chemicals are identified and substances of low toxicological relevance are excluded from further
evaluation. The location where a probable exposure might occur (indoor versus outdoor) and inter-media transport of substances
is considered. The product comparison is based both on the results of the proposed “semi-quantitative screening method” and
on toxicological expert knowledge. 相似文献