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41.
Derivatives of ethanologenic Escherichia coli K011 were constructed for D: (-)-lactate production by deleting genes encoding competing pathways followed by metabolic evolution, a growth-based selection for mutants with improved performance. Resulting strains, SZ132 and SZ186, contain native genes for sucrose utilization. No foreign genes are present in SZ186. Strain SZ132 also contains a chromosomally integrated endoglucanase gene (Erwinia chrysanthemi celY). Strain SZ132 produced over 1 mol lactate per liter of complex medium containing 10% (w/v) sugar (fermentation times of 48 h for glucose, 120 h for sucrose). Both strains produced 667-700 mmol lactate per liter of mineral salts medium. Yields for metabolized sugar ranged from 88% to 95% in both media.  相似文献   
42.
Pexiganan (Gly-Ile-Gly-Lys-Phe-Leu-Lys-Lys-Ala-Lys-Lys-Phe-Gly-Lys-Ala-Phe-Val-Lys-Ile-Leu-Lys-Lys), a 22 amino acid peptide, is an analogue of the magainin family of antimicrobial peptides present in the skin of the African clawed frog. Conformational analysis of pexiganan was carried out in different solvent environments for the first time. Organic solvents, trifluoroethanol (TFE) and methanol, were used to study the secondary structural preferences of this peptide in the membrane-mimicking environments. In addition, aqueous (D2O) and dimethyl sulfoxide (DMSO) solutions were also investigated to study the role of hydrogen bonding involved in the secondary structure formation. Fourier transform infrared absorption, vibrational circular dichroism (VCD), and electronic circular dichroism (ECD) measurements were carried out under the same conditions to ascertain the conformational assignments in different solvents. All these spectroscopic measurements suggest that the pexiganan peptide has the tendency to adopt different structures in different environments. Pexiganan appears to adopt an alpha-helical conformation in TFE, a sheet-stabilized beta-turn structure in methanol, a random coil with beta-turn structure in D2O, and a solvated beta-turn structure in DMSO.  相似文献   
43.
The benefits to captive animals of environmental enrichment (EE) are widely recognized. Few studies have, however, studied how to maximise the effect of EE. One issue with EE programs seems to be habituation to the enrichment device. To study the effect of habituation to EE, 14 captive sloth bears (Melursus ursinus) were subjected to two different EE treatments. Treatment one presented EE (logs with honey containing holes) for five consecutive days, whereas treatment two presented EE on intermittent days for five days. Intermittent presentations tended to reduce habituation toward the EE. Both consecutive and intermittent presentations significantly reduced stereotypies; however, the consecutive presentations had a longer‐lasting effect. Explorative behaviors increased in both treatments, consistent with earlier findings that EE increase levels of natural behaviors. Other behaviors were unaffected by the EE presentations. The results show that intermittent presentation of EE objects may secure the interest of the animals, but continuous access to enrichment may be more efficient in reducing stereotypies in the long run. Zoo Biol 29:705–714, 2010. © 2010 Wiley‐Liss, Inc.  相似文献   
44.
The present study was aimed to investigate the chemopreventive potential of carnosic acid in 7,12-dimethylbenz(a)anthracene (DMBA)-induced hamster buccal pouch carcinogenesis. The chemopreventive potential was assessed by analyzing the tumor incidence, tumor volume and burden as well as by measuring the status of lipid peroxidation, non-enzymatic and enzymatic antioxidants and phase I and phase II detoxification enzymes. Oral squamous cell carcinoma was developed in the buccal pouch of golden Syrian hamsters by painting with 0.5% DMBA in liquid paraffin three times a week for 14 weeks. In the present study, 100% tumor formation was observed in hamsters treated with DMBA alone. Also, the status of lipid peroxidation, antioxidants and phase I and phase II detoxification enzymes were significantly altered during DMBA-induced oral carcinogenesis. Oral administration of carnosic acid at a dose of 10 mg/kg body weight/day to DMBA-treated animals completely prevented the tumor formation in the hamsters’ buccal pouches. Also, carnosic acid exerted potent anti-lipid peroxidative function and stimulated the detoxification cascade during DMBA-induced hamster buccal pouch carcinogenesis. The results of the present study suggest that the chemopreventive potential of carnosic acid is probably due to its anti-lipid peroxidative potential and modulating effect on carcinogen detoxification enzymes during DMBA-induced oral carcinogenesis.  相似文献   
45.
The present study was designed to identify the urinary volatiles across various reproductive stages of female mice in order to detect estrus-specific chemical signal. The urine of adult female mice were extracted with dichloromethane (1:1 ratio, v/v) and analyzed by gas chromatography linked mass-spectrometry (GC-MS). Numerous compounds were identified during estrus cycle of female mice urine. Among these, the compounds, namely, isocroctylhydrazine, 4-methyl-2-heptanone and auzulene were specific to proestrus stage and the compounds, 1-H-cyclopop-e.auzulene, caryophyllene, copanene were specific to estrus stage. However, the compound, 1-iodo-2methyl undecane (1I2MU) was observed both in proestrus and estrus phases and was absent in all other phases. The volatile signal produced at the end of proestrus and the beginning of estrus phase appears to be behaviourally important in the attraction of males. Moreover, the behaviour assay revealed that the compound, 1I2MU, is involved in attracting the male mice. This result concludes that the 1-iodo-2methyl undecane is considered as a putative estrus-specific chemo-signal.  相似文献   
46.
Gastric cancer (GC) is a lethal malignancy and the second most common cause of cancer-related deaths. Although treatment options such as chemotherapy, radiotherapy, and surgery have led to a decline in the mortality rate due to GC, chemoresistance remains as one of the major causes for poor prognosis and high recurrence rate. In this study, we investigated the potential effects of isorhamnetin (IH), a 3′-O-methylated metabolite of quercetin on the peroxisome proliferator-activated receptor γ (PPAR-γ) signaling cascade using proteomics technology platform, GC cell lines, and xenograft mice model. We observed that IH exerted a strong antiproliferative effect and increased cytotoxicity in combination with chemotherapeutic drugs. IH also inhibited the migratory/invasive properties of GC cells, which could be reversed in the presence of PPAR-γ inhibitor. We found that IH increased PPAR-γ activity and modulated the expression of PPAR-γ regulated genes in GC cells. Also, the increase in PPAR-γ activity was reversed in the presence of PPAR-γ-specific inhibitor and a mutated PPAR-γ dominant negative plasmid, supporting our hypothesis that IH can act as a ligand of PPAR-γ. Using molecular docking analysis, we demonstrate that IH formed interactions with seven polar residues and six nonpolar residues within the ligand-binding pocket of PPAR-γ that are reported to be critical for its activity and could competitively bind to PPAR-γ. IH significantly increased the expression of PPAR-γ in tumor tissues obtained from xenograft model of GC. Overall, our findings clearly indicate that antitumor effects of IH may be mediated through modulation of the PPAR-γ activation pathway in GC.  相似文献   
47.
Zinc is an essential micronutrient for plants, but it is toxic in excess concentrations. In Arabidopsis, additional iron (Fe) can increase Zn tolerance. We isolated a mutant, zinc tolerance induced by iron 1, designated zir1, with a defect in Fe-mediated Zn tolerance. Using map-based cloning and genetic complementation, we identified that zir1 has a mutation of glutamate to lysine at position 385 on γ-glutamylcysteine synthetase (GSH1), the enzyme involved in glutathione biosynthesis. The zir1 mutant contains only 15% of the wild-type glutathione level. Blocking glutathione biosynthesis in wild-type plants by a specific inhibitor of GSH1, buthionine sulfoximine, resulted in loss of Fe-mediated Zn tolerance, which provides further evidence that glutathione plays an essential role in Fe-mediated Zn tolerance. Two glutathione-deficient mutant alleles of GSH1, pad2-1 and cad2-1, which contain 22% and 39%, respectively, of the wild-type glutathione level, revealed that a minimal glutathione level between 22 and 39% of the wild-type level is required for Fe-mediated Zn tolerance. Under excess Zn and Fe, the recovery of shoot Fe contents in pad2-1 and cad2-1 was lower than that of the wild type. However, the phytochelatin-deficient mutant cad1-3 showed normal Fe-mediated Zn tolerance. These results indicate a specific role of glutathione in Fe-mediated Zn tolerance. The induced accumulation of glutathione in response to excess Zn and Fe suggests that glutathione plays a specific role in Fe-mediated Zn tolerance in Arabidopsis. We conclude that glutathione is required for the cross-homeostasis between Zn and Fe in Arabidopsis.  相似文献   
48.

Background

Effective fixation of fracture requires careful selection of a suitable implant to provide stability and durability. Implant with a feature of locking plate (LP) has been used widely for treating distal fractures in femur because of its favourable clinical outcome, but its potential in fixing proximal fractures in the subtrochancteric region has yet to be explored. Therefore, this comparative study was undertaken to demonstrate the merits of the LP implant in treating the subtrochancteric fracture by comparing its performance limits against those obtained with the more traditional implants; angle blade plate (ABP) and dynamic condylar screw plate (DCSP).

Materials and Methods

Nine standard composite femurs were acquired, divided into three groups and fixed with LP (n?=?3), ABP (n?=?3) and DCSP (n?=?3). The fracture was modeled by a 20?mm gap created at the subtrochanteric region to experimentally study the biomechanical response of each implant under both static and dynamic axial loading paradigms. To confirm the experimental findings and to understand the critical interactions at the boundaries, the synthetic femur/implant systems were numerically analyzed by constructing hierarchical finite element models with nonlinear hyperelastic properties. The predictions from the analyses were then compared against the experimental measurements to demonstrate the validity of each numeric model, and to characterize the internal load distribution in the femur and load bearing properties of each implant.

Results

The average measurements indicated that the constructs with ABP, DCPS and LP respectively had overall stiffness values of 70.9, 110.2 and 131.4?N/mm, and exhibited reversible deformations of 12.4, 4.9 and 4.1?mm when the applied dynamic load was 400?N and plastic deformations of 11.3, 2.4 and 1.4?mm when the load was 1000?N. The corresponding peak cyclic loads to failure were 1100, 1167 and 1600?N. The errors between the displacements measured experimentally or predicted by the nonlinear hierarchical hyperelastic model were less than 18?%. In the implanted femur heads, the principal stresses were spatially heterogeneous for ABP and DCSP but more homogenous for LP, meaning LP had lower stress concentrations.

Conclusion

When fixed with the LP implant, the synthetic femur model of the subtrochancteric fracture consistently exceeds in the key biomechanical measures of stability and durability. These capabilities suggest increased resistance to fatigue and failure, which are highly desirable features expected of functional implants and hence make the LP implant potentially a viable alternative to the conventional ABP or DCSP in the treatment of subtrochancteric femur fractures for the betterment of clinical outcome.  相似文献   
49.
Paenibacillus sp. strain JDR-2, an aggressively xylanolytic bacterium isolated from sweetgum (Liquidambar styraciflua) wood, is able to efficiently depolymerize, assimilate and metabolize 4-O-methylglucuronoxylan, the predominant structural component of hardwood hemicelluloses. A basis for this capability was first supported by the identification of genes and characterization of encoded enzymes and has been further defined by the sequencing and annotation of the complete genome, which we describe. In addition to genes implicated in the utilization of β-1,4-xylan, genes have also been identified for the utilization of other hemicellulosic polysaccharides. The genome of Paenibacillus sp. JDR-2 contains 7,184,930 bp in a single replicon with 6,288 protein-coding and 122 RNA genes. Uniquely prominent are 874 genes encoding proteins involved in carbohydrate transport and metabolism. The prevalence and organization of these genes support a metabolic potential for bioprocessing of hemicellulose fractions derived from lignocellulosic resources.  相似文献   
50.
Amyloid precursor protein (APP) fragment containing amino acids 667–676, (APP667–676), is a substrate for β-secretase which is responsible for generating amyloid β peptides. Conformational analysis of APP667–676 peptide [Ac-Ser-Glu-Val-Lys-Met-Asp-Ala-Glu-Phe-Arg-NH2] and the effect of substitution of Asp672 with d-Asp and iso-l-Asp, studied for the first time, demonstrate that the peptide backbone of APP667–676 is flexible and adopts different conformations in different solvent environments (water, trifluoroethanol and dimethylsulfoxide). A major conformational difference was observed in trifluoroethanol solvent when Asp672 is substituted with d-Asp and iso-Asp. These conformational changes involved in APP667–676 may assist in understanding the interactions between β-secretase and APP667–676, with relevance to Alzheimer’s disease.  相似文献   
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