Neuroprotective Effects of Cactus Polysaccharide on Oxygen and Glucose Deprivation Induced Damage in Rat Brain Slices

1. The neuroprotective effect of cactus polysaccharide (CP) on oxygen and glucose deprivation (OGD) and reoxygenation (REO)-induced damage in the cortical and hippocampal slices of rat brain was investigated. 2. Cell viability was evaluated by using the 2, 3, 5-triphenyl tetrazolium chloride (TTC) method. The fluorescence of propidium iodide (PI) staining was used for quantification of cellular survival, and lactate dehydrogenase (LDH) activity in incubation medium was assessed by LDH assay to evaluate the degree of injury. 3. The OGD ischemic condition significantly decreased cellular viability and increased LDH release in the incubation medium. CP (0.2 mg/l∼2 mg/l) protected brain slices from OGD injury in a dosage dependent manner as demonstrated by increased A 490 value of TTC, decreased PI intensity and LDH release. At the above concentration, CP also prevented the increase of nitric oxide (NO) content and inducible nitric oxide synthase (iNOS) activity induced by OGD. 4. CP can protect the brain slices (cortical and hippocampus) against injury induced by OGD. Its neuroprotective effect may be partly mediated by the NO/iNOS system induced by OGD insult. Xianju Huang and Qin Li have contributed equally to this article.     

Diversity of Bacterial Isolates from Commercial and Homemade Composts

The diversity of heterotrophic bacterial isolates of three commercial and two homemade composts was studied. The commercial composts were produced from poultry litter (PC), sewage sludge (SC), municipal solid waste (MC), and homemade composts (thermal compost [DC] and vermicompost [VC]) from food wastes. The taxonomic and physiological diversity of the heterotrophic culturable bacteria was assessed using phenotypic and genotypic characterization and the analysis of the partial 16S rRNA gene sequence. Composts DC and SC presented the higher genotypic diversity, as could be inferred from the number of distinct genotypic patterns observed, 28 and 21, respectively. Gram-positive bacteria, mainly Firmicutes, were predominant in all the composts. Some organisms related with taxa rarely reported in composts, as Rhodanobacter spathiphylli, Moraxella osloensis, Lysobacter, Corynebacterium, Pigmentiphaga kullae, and new taxa were also isolated. The highest relative proportion of isolates able to degrade starch was found in compost SC (>70%), to degrade gelatine in compost DC (>70%), to degrade Tween 80 in compost PC (>90%), and to degrade poly-epsilon-caprolactones in compost DC (>80%). Compost MC presented the lowest relative proportions of isolates able to degrade starch (<25%), gelatine (<20%), and poly-epsilon-caprolactone (<40%). When compared with the others, the homemade composts presented higher relative proportions of Gram-positive isolates able to inhibit the target organisms Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, or Pseudomonas aeruginosa. In compost MC, none of the Gram-positive isolates was able to inhibit those targets.     

Influences of calcium deficiency and cerium on the conversion efficiency of light energy of spinach

Chloroplast absorbs light energy and transforms it into electron energy, and then converts it into active chemical energy and stable chemical energy. In the present paper, we investigated the effects of Ce(3+), which has the most significant catalytic effects and similar characteristics with Ca(2+), on light energy conversion of spinach chloroplasts under Ca(2+)-deficient stress. The results illuminated that the Hill reaction activity, electron flow both photosystems and photophosphorylation rate of spinach chloroplasts reduced significantly under Ca(2+)-deficient condition, and activities of Mg(2+)-ATPase and Ca(2+)-ATPase on the thylakoid membrane were severely inhibited. Meanwhile, the activity of Rubisco, which is the key enzyme of photosynthetic carbon assimilation, was also prohibited. However, Ce(3+) decreased the inhibition of calcium deprivation the electron transport rate, the oxygen evolution rate, the cyclic and noncyclic photophosphorylation, the activities of Mg(2+)-ATPase, Ca(2+)-ATPase and Rubisco of spinach chloroplasts. All above implied that Ca(2+)-depletion could disturb light energy conversion of chloroplasts strongly, which could be reversed by Ce(3+).     

Dequalinium-Induced Cell Death of Yeast Expressing α-Synuclein-GFP Fusion Protein

Intracellular toxic effects of the dequalinium-induced protofibrils of alpha-synuclein have been investigated with the yeast system expressing alpha-synuclein-GFP fusion protein in single copy, which appears in the green halo around the plasma membrane. Intracellular responses of the green fluorescent protein were analyzed as the cells were treated with dequalinium (DQ) and lactacystin. Yeast cells expressing alpha-synuclein-GFP were susceptible to both compounds in alpha-synuclein-dependent manner. Upon DQ treatment, the green halo became smeared throughout the cytoplasm while lactacystin induced a few discrete green dots, reflecting intracellular formation of the protofibrils and the protein inclusions, respectively. The DQ-treated yeast cells were intensely stained with the nucleic acid stains of cell-permeable Hoechst 33342 and cell-impermeable propidium imidione, indicating that nucleus has been disrupted in addition to plasma membrane destabilization. Those DQ-treated yeast cells, however, still contained active mitochondria identified with MitoTracker Red. Therefore, the DQ-induced protofibrillar state of alpha-synuclein-GFP has been suggested to cause the nuclear damage either independently or in combination with the membrane destabilization without affecting mitochondria.     

Entangled Matters—Alzheimer’s,Interiority, and the ‘Unflattening’ of the World

When, in the 1980s, Alzheimer's disease became a disease of major public concern, 'personhood' also became an important, related topic of discussion. Those in caring professions (psychology, social work, etc.) and caregiver groups advocated for the 'person within' who was getting lost in a forgetful body and in a reductionist biomedical system. This essay aims to critically approach the dualism of this kind of argument by focusing on the moral positioning of claims such as personhood or biomedical reductionism.     

Air pollution and mutations in the germline: are humans at risk?

Genotoxic air pollution is ubiquitous in urban and industrial areas. A variety of studies has linked human exposure to air pollution with a number of different somatic cell endpoints including cancer. However, the potential for inducing mutations in the human germline remains unclear. Sentinel animal studies of germline mutations at tandem-repeat loci (specifically minisatellites and expanded simple tandem repeats) have recently provided proof of principle that germline mutations can be induced in vertebrates (birds and mice) by air pollution under ambient conditions. Although humans may also be susceptible to induced germline mutations in polluted areas, uncertainties regarding causative agents, doses, and mutational mechanisms at repetitive DNA loci currently preclude extrapolation from animal data to the evaluation of human risk. Nevertheless, several recent studies have linked air pollution exposure to DNA damage in human sperm, indicating that our germ cells are not impervious to the genotoxic effects of air pollution. Thus, both sentinel animal and human studies have raised the possibility that ambient air pollution may increase human germline mutation rates, especially at repetitive DNA loci. Given that some human genetic conditions appear to be modulated by length mutations at tandem-repeat loci (e.g. HRAS1 cancers, type 1 diabetes, etc.), there is an urgent need for extensive study in this area. Research should be primarily focused upon: (1) the direct measurement of mutation frequencies at repetitive DNA loci in human male germ cells as a function of air pollution exposure, (2) large-scale epidemiology studies of inherited disorders and tandem-repeat associated genetic conditions and air pollution, and (3) the characterization of mutational mechanisms at hypervariable tandem-repeat loci.

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Influence of light on ascorbate formation and metabolism in apple fruits

To further understand the regulatory mechanism of light on the formation of ascorbic acid (AsA) in the sink organs of plants, a systematical investigation on AsA levels, activities of two key biosynthsis enzymes and their mRNA expression as well as the recycling was performed in the fruits of apple (Malus domestica Borkh), under different levels of shade. After the whole trees were shaded with the sun-light about 50–55% for 20 days, AsA levels were significantly decreased in fruit peel, flesh and leaves, while mRNA expression levels and activities of l-galactose dehydrogenase (l-GalDH, EC 1.1.1.117) and l-galactono-1,4-lactone dehydrogenase (l-GalLDH, EC 1.3.2.3) as well as activities of recycling enzymes was clearly declined in the leaf and peel but not in the flesh. By shading fruits only for 20 days, AsA levels, relative mRNA levels and activities of l-GalDH and l-GalLDH as well as activities of recycling enzymes all showed obvious decrease in the peel, but not in the flesh. However, their levels in the peel were markedly increased after the full shade was removed and re-exposed these fruits on natural light for 5 days. It is concluded that light affects AsA biosynthesis and recycling in the peel and leaf, but did not in the fresh. Results also suggest that apple fruit is potential to biosynthesize AsA via the l-galactose pathway, and AsA content in the fruits may depend partly on levels of AsA or other photochemistry controlled by light in the leaves.     

Evaluation of the toxicity of stress-related aldehydes to photosynthesis in chloroplasts

Aldehydes produced under various environmental stresses can cause cellular injury in plants, but their toxicology in photosynthesis has been scarcely investigated. We here evaluated their effects on photosynthetic reactions in chloroplasts isolated from Spinacia oleracea L. leaves. Aldehydes that are known to stem from lipid peroxides inactivated the CO₂ photoreduction to various extents, while their corresponding alcohols and carboxylic acids did not affect photosynthesis. α,β-Unsaturated aldehydes (2-alkenals) showed greater inactivation than the saturated aliphatic aldehydes. The oxygenated short aldehydes malondialdehyde, methylglyoxal, glycolaldehyde and glyceraldehyde showed only weak toxicity to photosynthesis. Among tested 2-alkenals, 2-propenal (acrolein) was the most toxic, and then followed 4-hydroxy-(E)-2-nonenal and (E)-2-hexenal. While the CO₂-photoreduction was inactivated, envelope intactness and photosynthetic electron transport activity (H₂O → ferredoxin) were only slightly affected. In the acrolein-treated chloroplasts, the Calvin cycle enzymes phosphoribulokinase, glyceraldehyde-3-phosphate dehydrogenase, fructose-1,6-bisphophatase, sedoheptulose-1,7-bisphosphatase, aldolase, and Rubisco were irreversibly inactivated. Acrolein treatment caused a rapid drop of the glutathione pool, prior to the inactivation of photosynthesis. GSH exogenously added to chloroplasts suppressed the acrolein-induced inactivation of photosynthesis, but ascorbic acid did not show such a protective effect. Thus, lipid peroxide-derived 2-alkenals can inhibit photosynthesis by depleting GSH in chloroplasts and then inactivating multiple enzymes in the Calvin cycle.     

Excitable Population Dynamics,Biological Control Failure,and Spatiotemporal Pattern Formation in a Model Ecosystem

Biological control has been attracting an increasing attention over the last two decades as an environmentally friendly alternative to the more traditional chemical-based control. In this paper, we address robustness of the biological control strategy with respect to fluctuations in the controlling species density. Specifically, we consider a pest being kept under control by its predator. The predator response is assumed to be of Holling type III, which makes the system’s kinetics “excitable.” The system is studied by means of mathematical modeling and extensive numerical simulations. We show that the system response to perturbations in the predator density can be completely different in spatial and non-spatial systems. In the nonspatial system, an overcritical perturbation of the population density results in a pest outbreak that will eventually decay with time, which can be regarded as a success of the biological control strategy. However, in the spatial system, a similar perturbation can drive the system into a self-sustained regime of spatiotemporal pattern formation with a high pest density, which is clearly a biological control failure. We then identify the parameter range where the biological control can still be successful and describe the corresponding regime of the system dynamics. Finally, we identify the main scenarios of the system response to the population density perturbations and reveal the corresponding structure of the parameter space of the system. A. Morozov is on leave from Shirshov Institute of Oceanology, Russian Academy of Science, Nakhimovsky Prosp. 36, Moscow 117218, Russia.