壳寡糖对环江香猪生化参数及肠道菌群组成的影响

为了探讨壳寡糖(COS)用作环江香猪饲料添加剂的可行性,试验选用21日龄断奶的环江香猪12头,随机分为2组,每组6头,分别饲喂添加0.5%COS的基础日粮和添加抗生素的基础日粮,试验期为14 d。试验结束时采集仔猪血液,肝素抗凝,离心分离血浆,测定生化参数;处死后取回肠和盲肠内容物,用荧光定量PCR测定其中双歧杆菌、乳酸杆菌、链球菌、大肠杆菌和总细菌的数量。结果表明,与对照组相比,壳寡糖组仔猪碱性磷酸酶活性显著增加(P<0.05),血氨和尿素氮含量有降低趋势(P>0.05);壳寡糖组回肠乳酸杆菌数量显著增加、链球菌数量显著降低(P<0.05),盲肠双歧杆菌和乳酸杆菌数量显著增加、大肠杆菌和链球菌数量显著降低(P<0.05)。上述结果提示,壳寡糖可在一定程度上改善环江香猪蛋白质代谢和肠道菌群平衡,从而增强其肠道健康。     

海洛因成瘾模型建立及中脑腹侧被盖区Bax的表达

目的探索海洛因对中脑腹侧被盖区细胞Bax表达的影响。方法肌肉注射海洛因,建立成瘾大鼠模型,用免疫组化方法检测中脑腹侧被盖区细胞Bax的表达。结果连续给大鼠注射海洛因7d后,大鼠出现明显的戒断症状;中脑腹侧被盖区细胞Bax表达阳性细胞比对照组明显增多,与对照组相比差异有显著性（P〈0.01）。结论海洛因具有诱导Bax基因表达、损伤脑组织细胞的作用。     

Retrocyclins kill bacilli and germinating spores of Bacillus anthracis and inactivate anthrax lethal toxin

Theta-defensins are cyclic octadecapeptides encoded by the modified alpha-defensin genes of certain nonhuman primates. The recent demonstration that human alpha-defensins could prevent deleterious effects of anthrax lethal toxin in vitro and in vivo led us to examine the effects of theta-defensins on Bacillus anthracis (Sterne). We tested rhesus theta-defensins 1-3, retrocyclins 1-3, and several analogues of RC-1. Low concentrations of theta-defensins not only killed vegetative cells of B. anthracis (Sterne) and rendered their germinating spores nonviable, they also inactivated the enzymatic activity of anthrax lethal factor and protected murine RAW-264.7 cells from lethal toxin, a mixture of lethal factor and protective antigen. Structure-function studies indicated that the cyclic backbone, intramolecular tri-disulfide ladder, and arginine residues of theta-defensins contributed substantially to these protective effects. Surface plasmon resonance studies showed that retrocyclins bound the lethal factor rapidly and with high affinity. Retrocyclin-mediated inhibition of the enzymatic activity of lethal factor increased substantially if the enzyme and peptide were preincubated before substrate was added. The temporal discrepancy between the rapidity of binding and the slowly progressive extent of lethal factor inhibition suggest that post-binding events, perhaps in situ oligomerization, contribute to the antitoxic properties of retrocyclins. Overall, these findings suggest that theta-defensins provide molecular templates that could be used to create novel agents effective against B. anthracis and its toxins.     

Physical signals and solute transport in human intervertebral disc during compressive stress relaxation: 3D finite element analysis

A 3D finite element model for charged hydrated soft tissues containing charged/uncharged solutes was developed based on the multi-phasic mechano-electrochemical mixture theory (Lai et al., J. Biomech. Eng. 113 (1991), 245-258; Gu et al., J. Biomech. Eng. 120 (1998), 169-180). This model was applied to analyze the mechanical, chemical and electrical signals within the human intervertebral disc during an unconfined compressive stress relaxation test. The effects of tissue composition [e.g., water content and fixed charge density (FCD)] on the physical signals and the transport rate of fluid, ions and nutrients were investigated. The numerical simulation showed that, during disc compression, the fluid pressurization was more pronounced at the center (nucleus) region of the disc while the effective (von Mises) stress was higher at the outer (annulus) region. Parametric analyses revealed that the decrease in initial tissue water content (0.7-0.8) increased the peak stress and relaxation time due to the reduction of permeability, causing greater fluid pressurization effect. The electrical signals within the disc were more sensitive to FCD than tissue porosity, and mechanical loading affected the large solute (e.g., growth factor) transport significantly, but not for small solute (e.g., glucose). Moreover, this study confirmed that the interstitial fluid pressurization plays an important role in the load support mechanism of IVD by sharing more than 40% of the total load during disc compression. This study is important for understanding disc biomechanics, disc nutrition and disc mechanobiology.     

Differential response of photosynthesis in greenhouse- and field-ecotypes of tomato to long-term chilling under low light

Three greenhouse- and four field-ecotype varieties of domestic tomato (Lycopersicon esculentum) were compared for the sensitivity of their photosynthetic apparatus to chilling under low light intensity. After chilling at 12/7 degrees C under 100 micromolm(-2)s(-1) of light for 10 days, they were allowed to recover at 25/18 degrees C and 600 micromolm(-2)s(-1) of light for 10 days. For both pre-chilling and recovered plants, greenhouse-ecotype varieties did not necessarily show higher net CO(2) assimilation rate (A), quantum yield of electron transport at PSII (Phi(PSII)) and photochemical quenching (q(P)) than field-ecotype varieties. However for the post-chilling period, greenhouse-ecotype varieties, exhibited higher A, and Phi(PSII) values than field-ecotype varieties. The difference in Phi(PSII) was found to be largely due to q(P). The absence of ecotypic differences in pre-chilling plants indicates that the trait was not expressed constitutively, but relied mainly on adaptation/acclimation mechanisms. Greenhouse-ecotype varieties were able to adapt to low temperature and low light more quickly, and then exhibited higher A, Phi(PSII), q(P) values and greater re-growth capacity after chilling than field-ecotype varieties. Plant re-growth capacity after chilling was highly correlated with Phi(PSII) and q(P) measured in chilled plants, suggesting the usefulness of Phi(PSII) and q(P) measured at low temperature after defined chilling stresses as screening indexes for chilling tolerance in breeding programs.     

宽体金线蛭嗜水气单胞菌感染的病原检验

对河北某宽体金线蛭（Whitmania pigra Whitman）养殖场所养殖的宽体会线蛭发生的病害,进行了发病情况、临床表现、病理变化等方面的枪验。同时,择代表菌株进行了16S rRNA基因的分子鉴定,测定了16S rRNA基因序列、分析了相关细菌相应序列的同源性、构建了系统发生树。结果表明所检病例为由嗜水气单胞菌（Aeronmnas hydrophila）所引起的感染。分离后做纯培养的10株嗜水气申胞菌均为同种血清型菌株;代表菌株对健康宽体金线蛭的人工感染试验表明了相应的原发病原学意义;药敏试验结果显示,对供试37种抗菌药物中的头孢噻肟等高度敏感、对链霉素等敏感、对苯唑青霉素等耐药。     

Design and mechanism of action of a novel bacteria-selective antimicrobial peptide from the cell-penetrating peptide Pep-1

Here, we report the successful design of a novel bacteria-selective antimicrobial peptide, Pep-1-K (KKTWWKTWWTKWSQPKKKRKV). Pep-1-K was designed by replacing Glu-2, Glu-6, and Glu-11 in the cell-penetrating peptide Pep-1 with Lys. Pep-1-K showed strong antibacterial activity against reference strains (MIC = 1-2 microM) of Gram-positive and Gram-negative bacteria as well as against clinical isolates (MIC = 1-8 microM) of methicillin-resistant Staphylococcus aureus and multidrug-resistant Pseudomonas aeruginosa. In contrast, Pep-1-K did not cause hemolysis of human erythrocytes even at 200 microM. These results indicate that Pep-1-K may be a good candidate for antimicrobial drug development, especially as a topical agent against antibiotic-resistant microorganisms. Tryptophan fluorescence studies indicated that the lack of hemolytic activity of Pep-1-K correlated with its weak ability to penetrate zwitterionic phosphatidylcholine/cholesterol (10:1, w/w) vesicles, which mimic eukaryotic membranes. Furthermore, Pep-1-K caused little or no dye leakage from negatively charged phosphatidylethanolamine/phosphatidylglycerol (7:3, w/w) vesicles, which mimic bacterial membranes but had a potent ability to cause depolarization of the cytoplasmic membrane potential of intact S. aureus cells. These results suggested that Pep-1-K kills microorganisms by not the membrane-disrupting mode but the formation of small channels that permit transit of ions or protons but not molecules as large as calcein.     

Myometrial cells induce angiogenesis and salvage damaged myocardium

Characteristically, uterine myometrial cells (MCs) are proliferative, inducing angiogenesis within the female reproductive organ. We evaluated whether MCs implanted into myocardium could also induce angiogenesis and restore heart function after injury. MCs were isolated from the adult rat uterus and cultured for three studies: 1) Intracellular VEGF levels were measured in MCs cultured with progesterone (10(-11), 10(-9), and 10(-7) M) (n = 6 tests per group). 2) Blood vessel density was evaluated 8 days after MCs (3 x 10(6) or 6 x 10(6)), smooth muscle cells (SMCs), or endothelial cells (n = 6 rats per group) were injected with matrigel into the subcutaneous tissue of adult rats. 3) MCs, SMCs (5 x 10(6)/rat), or media were injected into a transmural scar 3 wk after cryoinjury in rat hearts (n = 12 rats per group), and heart function, blood vessel density, and myocardial scar size and thickness were evaluated 5 wk later. In study 1, cultured MCs expressed VEGF, with levels significantly (P < 0.05) upregulated by progesterone at an optimal dose of 10(-11) M. In study 2, MCs injected into the subcutaneous tissue with matrigel induced significantly more blood vessels, especially large-diameter vessels, than did SMCs or endothelial cells (P < 0.01 for all groups). This angiogenic effect was greatest (P < 0.01) at higher doses of MCs and was enhanced by progesterone (10(-11) M). In study 3, MCs implanted into the injured myocardium increased blood vessel density at the implant area, reduced scar size, and improved cardiac function relative to SMCs and media. Overall, MCs induced angiogenesis in vitro and in vivo, prevented cardiac remodeling, and improved heart functional recovery after cardiac injury.