The potential cytoprotective effects of estrogen in the brain are of special interest in aging, neurodegenerative diseases, exposure to toxins, and trauma. Estrogen effects on neurons have been widely explored, but less is known about estrogen effects on glia. Glial cells are primary targets of ammonia toxicity, which arises from liver disease or failure (such as from cirrhosis in alcoholics), urea cycle disorders, or inborn errors of metabolism. We examined the ability of estrogen to protect glial cells from ammonium chloride toxicity using an in vitro model system. C6-glioma cells in later passage have many astrocytic characteristics and provided a convenient and well established model system for this work. When C6-glioma cells were exposed to 15 mM ammonium chloride, we observed major cell death (only 32% cell survival relative to control) within 72 h. Pretreatment with 17beta-estradiol (10 microM) significantly protected C6-glioma cells from ammonia toxicity (99% cell survival relative to control). In addition to enhancing the viability of C6-glioma cells against ammonia challenge, estrogen pretreatment was also found to protect mitochondrial function as assayed using the MTT reduction assay. Mitochondrial function was reduced to 39% of control levels in ammonia-challenged cultures and was mostly protected by estrogen (72% of control levels). The findings are potentially relevant for the development of therapeutic strategies to protect glial cells against ammonia toxicity resulting from hepatic failure or other causes. 相似文献
Astringency of aqueous solutions of phenolic compounds (grape seed tannins,
tannic acid, catechin and gallic acid) increased upon addition of citric
acid, whereas the astringency of alum was reduced. Astringency of alum was
decreased equivalently by addition of equi-sour levels of lactic acid,
citric acid or hydrochloric acid. The difference between alum and the
phenolic compounds is speculated to result from chemical modifications
affecting binding of the astringents with oral proteins rather than
cognitive differences. Chelation of the aluminum ion in alum by acids
reduces its availability for interacting with salivary proteins or
epithelial proteins. In contrast, the increased astringency produced upon
acidification of phenolic compounds is speculated to result from the pH
driven increase in the affinity of the phenols for binding with proteins.
These results suggest that alum cannot be used interchangeably with
phenolic astringents in psychophysical studies.
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Two-cell mouse conceptuses were cultured in media that contained various concentrations of inorganic ions and amino acids. Substrates of the amino acid transport system Gly were detrimental to development at slightly hyposmotic concentrations of other ions. In contrast, these amino acids increased the frequency at which two-cell conceptuses developed into blastocysts at total ion concentrations of 355 to 405 mM. Data reported elsewhere is consistent with the possibility that the total ion concentration in oviductal fluid exceeds 360 mM, whereas the concentration of glycine in this fluid may be on the order of 10 mM. Therefore, a high ion concentration and glycine may counteract the potentially harmful effects of each other in situ. Like some marine organisms, preimplantation mouse conceptuses may use glycine as an intracellular osmolite because accumulation of inorganic ions could perturb the activities of some enzymes. 相似文献
This report describes a lysozyme expressed at high levels in the stomach of
the hoatzin, the only known foregut-fermenting bird. Evolutionary
comparison places it among the calcium-binding lysozymes rather than among
the conventional types. Conventional lysozymes were recruited as digestive
enzymes twice in the evolution of mammalian foregut fermenters, and these
independently recruited lysozymes share convergent structural changes
attributed to selective pressures in the stomach. Biochemical convergence
and parallel amino acid replacements are observed in the hoatzin stomach
lysozyme even though it has a different genetic origin from the mammalian
examples and has undergone more than 300 million years of independent
evolution.
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AIM: To investigate the effect of stem cells from human exfoliated deciduous teeth(SHED) transplanted for bone regeneration in the dog mandibular defect.METHODS: In this prospective comparative study, SHEDs had been isolated 5 years ago from human exfoliated deciduous teeth. The undifferentiated stem cells were seeded into mandibular bone through-andthrough defects of 4 dogs. Similar defects in control group were filled with cell-free collagen scaffold. After 12 wk, biopsies were taken and morphometric analysis was performed. The percentage of new bone formation and foreign body reaction were measured in each case. The data were subject to statistical analysis using the Mann-Whitney U and Kruskalwalis statistical tests. Differences at P 0.05 was considered as significant level.RESULTS: There were no significant differences between control and SHED-seeded groups in connective tissue(P = 0.248), woven bone(P = 0.248) and compact bone(P = 0.082). There were not any side effects in transplanted SHED group such as teratoma or malignancy and abnormalities in this period.CONCLUSION: SHEDs which had been isolated and characterized 5 years ago and stored with cryopreservation banking were capable of proliferation and osteogenesis after 5 years, and no immune response was observed after three months of seeded SHEDs. 相似文献
1. 1. The feasibility of controlling the ventilation system using the occupant-generated carbon dioxide as an indicator of ventilation rate and indoor air quality has been investigated in an eleven storey office building.
2. 2. The study compares the indoor environment created by two different types of ventilation control systems.
3. 3. The two ventilation systems tested consisted of: a conventional system controlled by outdoor temperatures, and a demand-controlled system regulated by indoor carbon dioxide concentration.
4. 4. The results show that the CO2-based demand-controlled ventilation system does not worsen indoor air quality and thermal comfort. It was also noticed that an energy saving of 12% was achieved using the CO2 control system.
5. 5. The occupants perceived that their productivity is proportional to their perception of the indoor environment; indicating that higher productivity rates can be achieved by better controlling the working environment above satisfactory levels.
Effective drug discovery and optimization can be accelerated by techniques capable of deconvoluting the complexities often present in targeted biological systems. We report a single-molecule approach to study the binding of an alternative splicing regulator, muscleblind-like 1 protein (MBNL1), to (CUG)n = 4,6 and the effect of small molecules on this interaction. Expanded CUG repeats (CUGexp) are the causative agent of myotonic dystrophy type 1 by sequestering MBNL1. MBNL1 is able to bind to the (CUG)n–inhibitor complex, indicating that the inhibition is not a straightforward competitive process. A simple ligand, highly selective for CUGexp, was used to design a new dimeric ligand that binds to (CUG)n almost 50-fold more tightly and is more effective in destabilizing MBNL1–(CUG)4. The single-molecule method and the analysis framework might be extended to the study of other biomolecular interactions. 相似文献
We report observations on the dynamics of bacterial communities in response to methane stimulus in laboratory microcosm incubations prepared with lake sediment samples. We first measured taxonomic compositions of long-term enrichment cultures and determined that, although dominated by Methylococcaceae types, these cultures also contained accompanying types belonging to a limited number of bacterial taxa, methylotrophs and non-methylotrophs. We then followed the short-term community dynamics, in two oxygen tension regimens (150 μM and 15 μM), observing rapid loss of species diversity. In all microcosms, a single type of Methylobacter represented the major methane-oxidizing partner. The accompanying members of the communities revealed different trajectories in response to different oxygen tensions, with Methylotenera species being the early responders to methane stimulus under both conditions. The communities in both conditions were convergent in terms of their assemblage, suggesting selection for specific taxa. Our results support prior observations from metagenomics on distribution of carbon from methane among diverse bacterial populations and further suggest that communities are likely responsible for methane cycling, rather than a single type of microbe. 相似文献