The neurobiology of Etruscan shrew active touch

The Etruscan shrew, Suncus etruscus, is not only the smallest terrestrial mammal, but also one of the fastest and most tactile hunters described to date. The shrew's skeletal muscle consists entirely of fast-twitch types and lacks slow fibres. Etruscan shrews detect, overwhelm, and kill insect prey in large numbers in darkness. The cricket prey is exquisitely mechanosensitive and fast-moving, and is as big as the shrew itself. Experiments with prey replica show that shape cues are both necessary and sufficient for evoking attacks. Shrew attacks are whisker guided by motion- and size-invariant Gestalt-like prey representations. Shrews often attack their prey prior to any signs of evasive manoeuvres. Shrews whisk at frequencies of approximately 14 Hz and can react with latencies as short as 25-30 ms to prey movement. The speed of attacks suggests that shrews identify and classify prey with a single touch. Large parts of the shrew's brain respond to vibrissal touch, which is represented in at least four cortical areas comprising collectively about a third of the cortical volume. Etruscan shrews can enter a torpid state and reduce their body temperature; we observed that cortical response latencies become two to three times longer when body temperature drops from 36°C to 24°C, suggesting that endothermy contributes to the animal's high-speed sensorimotor performance. We argue that small size, high-speed behaviour and extreme dependence on touch are not coincidental, but reflect an evolutionary strategy, in which the metabolic costs of small body size are outweighed by the advantages of being a short-range high-speed touch and kill predator.     

Volkamer Lemon Tetraploid Rootstock Transmits the Salt Tolerance When Grafted with Diploid Kinnow Mandarin by Strong Antioxidant Defense Mechanism and Efficient Osmotic Adjustment

Salinity restricts plant growth and production by specific ions toxicity to particular plants. Cl ion is exceptionally toxic to citrus. Citrus rootstock and scion has a significant effect on each other under unfavourable conditions. Nevertheless, their specific response can be different depending on the way to translocate and compartment the toxic ions, or to induce antioxidant systems. In this paper, we studied the behaviour of diploid (2x) and tetraploid (4x) Volkamer lemon rootstocks grafted with commercial cultivar Kinnow mandarin (KM/VM2x and KM/VM4x, respectively) when exposed to moderate (75 mM) and high salt stress (150 mM). Both genotypes showed a decrease in their photosynthetic variables (Pn, gs, E, Fv/Fm, Fv′/Fm′, NPQ), and the decline was more significant in KM/VM2x plants as compared to KM/VM4x. The highest increase in the concentration of stress indicators (MDA and H₂O₂) was observed in leaves and roots of KM/VM2x at 75 and 150 mM of salt stress. The KM/VM4× showed the maximum increase in antioxidative enzymes (SOD, CAT, POD, APx, GR) and osmolytes (PRO, GB) in leaves and roots at 75 and 150 mM. Minerals (Cl ion, Na, K, P, N, Ca) accumulation was also significantly affected in leaves and roots of KM/VM2x and KM/VM4x under moderate and high NaCl stress. Overall, our results showed that Cl ion accumulation presents a robust correlation with stress indicators and their scavenging enzymes in leaves and roots. Moreover, 2x scion significantly mitigated by the 4x rootstock and showed more tolerance as compared to grafted on 2x rootstock.

     

Nematicidal Triterpenoids from Lantana camara

A new triterpene, lancamarolide ( 1 ), and seven known triterpenes, oleanonic acid ( 2 ), lantadene A ( 3 ), 11α‐hydroxy‐3‐oxours‐12‐en‐28‐oic acid ( 4 ), betulinic acid ( 5 ), lantadene B ( 6 ), and lantaninilic acid ( 7 ) were isolated from the aerial parts of Lantana camara in the course of bioassay‐guided isolation, and their nematicidal activities against Meloidogyne incognita, the root knot nematode, were carried out. Oleanonic acid was found to be the most active compound and exhibited 80% mortality after 72 h at 0.0625% concentration, which is comparable with that of the standard furadan.     

Study of the migration behaviours of imidazoline corrosion inhibitor in concrete using UV–vis spectrophotometry

In this study, UV–visible light spectrophotometry was used for the first time to examine the migration behaviours of cationic and nonionic imidazoline corrosion inhibitors in concrete. Imidazoline can react with bromocresol purple resulting in a reduction in absorbance, which can be used to calculate quantitatively imidazoline concentration. The results showed that the migration rate of nonionic imidazoline was faster than that of cationic imidazoline with or without the presence of an electric field, possibly because of the better water solubility of nonionic imidazoline. The electric field could significantly accelerate the migration rate of the cationic and nonionic imidazoline. However, the penetration performance of nonionic imidazoline was much improved compared with that of cationic imidazoline in concrete. From X‐ray photoelectron spectroscopy analysis, the N element could be detected on steel, verifying the migration behaviour of the nonionic imidazoline. This nonionic imidazoline could markedly retard steel corrosion according to potentiodynamic polarization.     

Genetic diversity revealed by physiological behavior of citrus genotypes subjected to salt stress

Different physiological behavior of a wide range of varieties and species belonging to the Citrus genus was analyzed when subjected to salt stress with the aim to seek new sources of tolerance that might be specie-specific. Our goal was to use physiological results obtained along a salt stress in order to clarify if it would be possible to associate them with the known citrus genetic diversity. For that purpose, we have selected 20 different genotypes representing the major species on the basis of the genetic diversity of Citrus genus complemented with one intergeneric hybrid Carrizo citrange (C. sinensis × P. trifoliata). A moderate salt stress of 75 mM of NaCl was applied for 12 weeks. For control plants, the main parameters contributing for more than 25 % to the diversity on the two axes of principal component analysis (PCA) were chlorophyll content, photosynthesis and Fv/Fm under light. However, the dispersal of species and varieties on the PCA did not show any particular structure. Under salt stress condition, four parameters (leaf chloride content, leaf chlorophyll content, photosynthesis and stomatal conductance) contributed more specifically to the dispersion on PCA representation with more than 15 % of contribution for each parameter. Large differences were observed within citrus genus: mandarin and pummelo presented good tolerance to salt stress while citron was very sensitive. Furthermore, all secondary genotypes that presented good tolerance to salt tolerance shared mandarin or pummelo as female parent.     

Cadmium causes oxidative stress in mung bean by affecting the antioxidant enzyme system and ascorbate-glutathione cycle metabolism

Ascorbate (AsA)-glutathione (GSH) cycle metabolism is an essential mechanism for the resistance of plants under stress conditions. In a greenhouse pot experiment, the influence of cadmium (Cd) (25, 50, and 100 mg/kg soil) on plant dry weight and leaf area, photosynthetic parameters (net photosynthetic rate (P_N) and chlorophyll (Chl) content) and oxidative stress, and the possible protective role of AsA-GSH cycle metabolism was studied in two mung bean (Vigna radiata (L.) Wilczek.) cvs. Pusa 9531 (Cd-tolerant) and PS 16 (Cd-susceptible) at 30 days after sowing. The contents of thiobarbituric acid-reactive substances (TBARS), H₂O₂, and the leakage of ions were the highest at 100 mg Cd/kg soil, and the effect was more pronounced in cv. PS 16 than in cv. Pusa 9531. This was concomitant with the strongest decreases in P_N, plant dry weight, and leaf area. The changes in the AsA-GSH redox state and an increase in AsA-GSH-regenerating enzymes, such as glutathione reductase, monodehydroascorbate reductase, dehydroascorbate reductase, and other antioxidant enzymes, such as superoxide dismutase and ascorbate peroxidase, strongly supported over-utilization of AsA-GSH in Cd-treated plants. However, the oxidative stress caused by Cd toxicity was partially overcome by AsA-GSH-based detoxification mechanism in the two genotypes studied because an increases in lipid peroxidation (TBARS, ion leakage) and H₂O₂ content were accompanied by a corresponding decrease in reduced AsA and GSH pools. Thus, changes in AsA-GSH pools and the coordination between AsA-GSH-regenerating enzymes and other enzymatic antioxidants of the leaves suggest their relevance to the defense against Cd stress.     

Effect of Zinc and Iron Fortification of the Feed on Liver and Thyroid Function in Rats

Changes in plasma glutamate oxaloacetate transaminase (GOT), glutamate pyruvate transaminase (GPT), triiodothyronine (T3), and thyroxin (T4) of male rats, following 8?weeks of administration of different concentrations of elemental iron (EI), sodium iron ethylenediaminetetraacetate (NaFeEDTA), zinc sulfate (ZnSO(4)), and zinc oxide (ZnO) in whole wheat flour were investigated. Liver enzymes and thyroid hormones were determined using colorimetric methods and enzyme immune assay, respectively. Ingestion of fortified diets by the male rats did not show a marked effect on GOT and GPT, the exception being NaFeEDTA fed alone and EI with ZnO-fortified diets indicating a significant (p?相似文献   

Characterization of the dimerization interface of membrane type 4 (MT4)-matrix metalloproteinase

MT4-MMP (MMP17) belongs to a unique subset of membrane type-matrix metalloproteinases that are anchored to the cell surface via a glycosylphosphatidylinositol moiety. However, little is known about its biochemical properties. Here, we report that MT4-MMP is displayed on the cell surface as a mixed population of monomeric, dimeric, and oligomeric forms. Sucrose gradient fractionation demonstrated that these forms of MT4-MMP are all present in lipid rafts. Mutational and computational analyses revealed that Cys(564), which is present within the stem region, mediates MT4-MMP homodimerization by forming a disulfide bond. Substitution of Cys(564) results in a more rapid MT4-MMP turnover, when compared with the wild-type enzyme, consistent with a role for dimerization in protein stability. Expression of MT4-MMP in Madin-Darby canine kidney cells enhanced cell migration and invasion of Matrigel, a process that requires catalytic activity. However, a serine substitution at Cys(564) did not reduce MT4-MMP-stimulated cell invasion of Matrigel suggesting that homodimerization is not required for this process. Deglycosylation studies showed that MT4-MMP is modified by N-glycosylation. Moreover, inhibition of N-glycosylation by tunicamycin diminished the extent of MT4-MMP dimerization suggesting that N-glycans may confer stability to the dimeric form. Taken together, the data presented here provide a new insight into the characteristics of MT4-MMP and highlight the common and distinct properties of the glycosylphosphatidylinositol-anchored membrane type-matrix metalloproteinases.     

Genetic variability of NaCl tolerance in tomato

Cultivation of crops in soils with high salt (NaCl) content can affect plant development. We examined the morphological and physiological mechanisms of salt tolerance in tomato. The responses of 72 accessions of tomato (Solanum lycopersicum) to salinity were compared by measuring shoot and root lengths, and fresh shoot and root weights relative to those of controls (plants grown in normal salt levels). All traits were reduced at the seedling stage when salinity levels were increased. The accession x salinity interaction was significant for all traits. Root length had higher heritability than other traits and was used as a selection criterion to identify salt-tolerant and -non-tolerant accessions. On the basis of root length, accessions LA2661, CLN2498A, CLN1621L, BL1176, 6233, and 17870 were considered to be more tolerant than accessions 17902, LO2875 and LO4360. The degree of salt tolerance was checked by analyzing K+ and Na+ concentrations and K+/Na+ ratio in tissues of plants treated with 10 and 15 dS/m salinity levels. Tolerance of these accessions to salinity was most associated with low accumulation of Na+ and higher K+/Na+ ratios.     

Receptor-specific mechanisms regulate phosphorylation of AKT at Ser473: role of RICTOR in β1 integrin-mediated cell survival

A tight control over AKT/PKB activation is essential for cells, and they realise this in part by regulating the phosphorylation of Ser473 in the "hydrophobic motif" of the AKT carboxy-terminal region. The RICTOR-mTOR complex (TORC2) is a major kinase for AKT Ser473 phosphorylation after stimulation by several growth factors, in a reaction proposed to require p21-activated kinase (PAK) as a scaffold. However, other kinases may catalyse this reaction in stimuli-specific manners. Here we characterised the requirement of RICTOR, ILK, and PAK for AKT Ser473 phosphorylation downstream of selected family members of integrins, G protein-coupled receptors, and tyrosine-kinase receptors and analysed the importance of this phosphorylation site for adhesion-mediated survival. siRNA-mediated knockdown in HeLa and MCF7 cells showed that RICTOR-mTOR was required for phosphorylation of AKT Ser473, and for efficient phosphorylation of the downstream AKT targets FOXO1 Thr24 and BAD Ser136, in response to β1 integrin-stimulation. ILK and PAK1/2 were dispensable for these reactions. RICTOR knockdown increased the number of apoptotic MCF7 cells on β1 integrin ligands up to 2-fold after 24 h in serum-free conditions. β1 integrin-stimulation induced phosphorylation of both AKT1 and AKT2 but markedly preferred AKT2. RICTOR-mTOR was required also for LPA-induced AKT Ser473 phosphorylation in MCF7 cells, but, interestingly, not in HeLa cells. PAK was needed for the AKT Ser473 phosphorylation in response to LPA and PDGF, but not to EGF. These results demonstrate that different receptors utilise different enzyme complexes to phosphorylate AKT at Ser473, and that AKT Ser473 phosphorylation significantly contributes to β1 integrin-mediated anchorage-dependent survival of cells.