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1.
C-6-carboxylated chitosan obtained by oxidation of chitosan was selectively modified in order to obtain derivatives similar to bacterial antigens. Selective O-acetylation of 6-carboxyl chitosan afforded a modified polysaccharide with the 2-amino group available for further modifications to create carbonyl groups. A deaminative degradation reaction allowed the formation of oligosaccharides with terminal aldehyde groups. Reductive alkylation with lactose introduced lactityl branches which were oxidized with galactose oxidase to give aldehyde groups in its
-galactose residues. 相似文献
2.
Beretta A Clerici M Hasson H Fumagalli L Trabattoni D Lillo F Ferrante P Saniabadi AR Adachi M Lazzarin A 《Journal of biological regulators and homeostatic agents》2000,14(1):27-31
AIDS pathogenesis results from a complex array of immune alterations which include, among others, changes in the pattern of cytokine production. Some monocyte-derived cytokines, like TNFalpha play a major role in HIV pathogenesis. TNFalpha transactivates HIV NF-kB thereby inducing viral replication, potentiates HIV replication in lymphomonocytes TNFalpha is one of the main factors of HIV-induced cachexia and might be involved in HAART-associated lipodystrophy. In addition, monocytes are infectable by HIV in vitro and infected monocytes can be recovered from the blood of HIV infected patients. For these reasons, we tested whether renewal of the pool of circulating monocytes by selective monocyte apheresis may improve the immune reconstitution which follows treatment with highly active anti-retrovirals (HAART). HIV-infected HAART receiving (> 1 year) patients who were either virologically non-responders (HIV-1 RNA >50,000 copies/ml) or immunologically non-responders (CD4 counts < 200) were treated with a novel monocyte apheresis device (G-1 Adacolumn). Plasma HIV viral load, proviral DNA and phenotypic and functional immunological analyses were performed. G-1 apheresis was well tolerated, not accompanied by adverse responses, and followed by clinical improvement. TNFalpha production was suppressed and CD4 T cell counts increased. In one G-1 patient with elevated HIV-1 proviral DNA a significant reduction (from 1,500 to 40 copies/10(5) cells) was observed. Neither immunologic nor virologic parameters were modified in the control patients who received HAART alone. Thus, purging of circulating monocytes by G-1 apheresis has a dramatic suppressive effect on TNFalpha production and is followed by both clinical and immunovirological improvement. G-1 apheresis should be considered in patients in whom HAART is only partially effective. 相似文献
3.
The effect of media components and environmental factors on growth and organogenesis of protoplast-derived calli of curly kale and cabbage were tested. Optimal growth (fresh weight increase of calli, shoots and roots) was found at 60 mM sucrose. Lower sucrose concentrations (3–30 mM) were favourable for shoot formation. Nitrate concentrations from 23 to 100 mM in combination with 8 or 21 mM ammonium were optimal for shoot formation. However, growth was reduced by high (100 mM) nitrate concentration. The effects of various organic nitrogen compounds at 0.5 and 2 mM were tested. Glutamine did not influence shoot formation and barely growth. Proline at 0.5 mM stimulated growth of cabbage calli but decreased growth of curly kale calli, and at 2 mM, proline also inhibited shoot production. Adenine sulphate decreased growth of cabbage calli at 0.5 mM, and at 2 mM shoot production was also reduced. Spermidine and spermine inhibited both growth and differentiation. Putrescine resulted in about 50% higher fresh weights, and also increased the number of calli producing shoots by about 35%. More calli produced shoots in white light than in blue or red light or in darkness. The length of the photoperiod or intensity of light was not critical for shoot production. 相似文献
4.
Cathrine Lillo Lucy H. Smith Hugh G. Nimmo Malcolm B. Wilkins 《Physiologia plantarum》1996,98(1):140-146
Nitrate reductase (NR, EC 1.6.6.1) was tested in crude extracts of leaves from Bryophyllum fedtschenkoi plants growing under alternating light/darkness as well as in excised leaves kept in continuous light or darkness. In most extracts NR activity was inhibited 20–80% by 5 m M Mg2+ A light or darkness shift (30 min darkness) during the first part of the photoperiod gave an increase in the Mg2+ inhibition and a decrease in NR activity. Magnesium ion inhibition of NR also showed diurnal variations. Strongest inhibition was found in extracts made during the latter part of the photoperiod and start of the dark period. Pre-incubation of crude extracts with ATP increased Mg2+ inhibition, indicating that phosphorylation of NR is involved in regulation of NR in Crassulacean acid metabolism (CAM) plants. In continuous light an increase in Mg2+ inhibition occurred after 20 h and 40 h, indicating a rhythm in the phosphorylation of NR. A delay in the production of nitrite in the assay (hysteresis) was generally seen in extracts susceptible to Mg2+ inhibition. The rhythms related to NR activity showed the same period length (20 h) as the rhythm in CO2 exchange. However, in contrast to the rhythm in CO2 exchange, NR rhythms were strongly damped in continuous light. In constant darkness the rhythms were even more damped. The results show that post-translational modification of CAM NR is influenced by light/darkness and by an endogenous rhythm. 相似文献
5.
A viable option for increasing nitrogen (N) use efficiency and mitigation of negative impacts of N on the environment is to capitalize on multi-element interactions through implementation of nutrient management programs that provide balanced nutrition. Numerous studies have demonstrated the immediate efficacy of this approach in the developing regions like China and India as well as developed countries in North America. Based on 241 site-years of experiments in these countries, the first-year N recovery efficiency (RE) for the conventional or check treatments averaged 21% while the balanced treatments averaged 54% RE, for an average increase of 33% in RE due to balanced nutrition. Effective policies to promote adoption are most likely those that enable site-specific approaches to nutrient management decisions rather than sweeping, nation-wide incentives supporting one nutrient over another. Local farmers, advisers and officials need to be empowered with tools and information to help them define necessary changes in practices to create more balanced nutrient management. 相似文献
6.
Barley leaf protoplasts were incubated in light or darkness in the presence of various inhibitors, metabolites or weak acids/bases. Nitrate reductase (NR) and phosphoenolpyruvate carboxylase (PEPCase) were rapidly extracted from the protoplasts and assayed under sub-optimal conditions, i.e. in the presence of Mg2+ and malate, respectively. Under these conditions changes in activities are thought to reflect changes in the phosphorylation states of the enzymes. The NR was activated by illumination to 90% of its maximal activity within 10 min. Photosynthetic electron transport appeared necessary for light activation of NR since activation was inhibited by the photosynthetic electron-transport inhibitor 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), and, additionally, an electron acceptor (HCO
3
-
) was required. The PEPCase was also activated by light. However, this activation was not prevented by DCMU or lack of HCO
3
-
. Loading of protoplasts in the dark with a weak acid resulted in activation of both NR and PEPCase. For NR, full activation was completed within 5 min, whereas for PEPCase a slower, modest activation continued for at least 40 min. Incubation of protoplasts with a weak base also gave activation of PEPCase, but not of NR. On the contrary, base loading counteracted light activation of NR. Since several treatments tested resulted in the modulation of either NR or PEPCase activity, but not both, signal transduction cascades leading to changes in activities appear to be very different for the two enzymes.Abbreviations DCMU
3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron)
- DMO
5,5-dimethyl-2,4 oxazolidinedione
- NR
nitrate reductase
- PEPCase
Phosphoenolpyruvate carboxylase
This work was supported by the Norwegian Research Council by a Grant to C.L: L.H.S. was supported by the Biotechnology and Biological Sciences Research Council. 相似文献
7.
The biocontrol properties of Trichoderma species are well documented, but their effectiveness in antagonism of the problematic Sclerotium cepivorum, the causal agent of white rot in Allium species, appears limited with reports of significant control only relating to deliberately-mutated strains of Trichoderma. Our previous studies have indicated the possibility of using selected naturally-occurring strains of the antagonist in the suppression of other diseases; now in vitro and controlled environment in vivo studies have indicated that a degree of control of Onion White Rot is possible, and that the selected antagonist strains can be used in integrated treatments with Iprodione to good effect. The possible value of such treatments is considered in light of other approaches to the suppression of this continuing problem. 相似文献
8.
PP2A activates brassinosteroid-responsive gene expression and plant growth by dephosphorylating BZR1 总被引:4,自引:0,他引:4
9.
Lillo, R. S., E. C. Parker, and W. R. Porter.Decompression comparison of helium and hydrogen in rats.J. Appl. Physiol. 82(3): 892-901, 1997.The hypothesis that there are differences in decompression riskbetween He and H2 wasexamined in 1,607 unanesthetized male albino rats subjected to dives on2% O2-balance He or 2%O2-balanceH2 (depths 50 ATA, bottom times 60 min). The animals were decompressed to 10.8 ATA with profilesvarying from rapid to slow, with up to four decompression stops of up to 60 min each. Maximum likelihood analysis was used to estimate therelative decompression risk on a per unit pressure basis (termed \"potency\") and the rate of gas uptake and elimination, bothfactors affecting the decompression sickness risk, from a specific dive profile. H2 potency for causingdecompression sickness was found to be up to 35% greater than that forHe. Uptake rates were unresolvable between the two gases with the timeconstant (TC) estimated at ~2-3 min, leading to saturation inboth cases in <15 min. Washout of both gases was significantly slowerthan uptake, with He washout (TC ~1.5-3 h) substantially slowerthan H2 washout (TC ~0.5 h). Itis unknown whether the decompression advantage of the faster washout ofH2 or the disadvantage of itsincreased potency, observed in the rat, would be important for humandiving. 相似文献
10.
This investigation examined the question of whether gas mixtures containing multiple inert gases provide a decompression advantage over mixtures containing a single inert gas. Unanesthetized male albino rats, Rattus norvegicus, were subjected to 2-h simulated dives at depths ranging from 145 to 220 fsw. At pressure, the rats breathed various He-N2-Ar-O2 mixtures (79.1% inert gas-20.9% O2); they were then decompressed rapidly (within 10 s) to surface pressures. The probability of decompression sickness (DCS), measured either as severe bends symptoms or death, was related to the experimental variables in a Hill equation model incorporating parameters that account for differences in the potencies of the three gases and the weight of the animal. The relative potencies of the three gases, which affect the total dose of decompression stress, were determined as significantly different in the following ascending order of potency: He less than N2 less than Ar; some of these differences were small in magnitude. With mixtures, the degree of decompression stress diminished as either N2 or Ar was replaced by He. No obvious advantage or disadvantage of mixtures over the least potent pure inert gas (He) was evident, although limits to the expectation of possible advantage or disadvantage of mixtures were defined. Also, model analysis did not support the hypothesis that the outcome of decompression with multiple inert gases in rats under these experimental conditions can be explained totally by the volume of gas accumulated in the body during a dive. 相似文献