Transcranial Doppler estimation of cerebral blood flow and cerebrovascular conductance during modified rebreathing.

Clinical transcranial Doppler assessment of cerebral vasomotor reactivity (CVMR) uses linear regression of cerebral blood flow velocity (CBFV) vs. end-tidal CO(2) (Pet(CO(2))) under steady-state conditions. However, the cerebral blood flow (CBF)-Pet(CO(2)) relationship is nonlinear, even for moderate changes in CO(2). Moreover, CBF is increased by increases in arterial blood pressure (ABP) during hypercapnia. We used a modified rebreathing protocol to estimate CVMR during transient breath-by-breath changes in CBFV and Pet(CO(2)). Ten healthy subjects (6 men) performed 15 s of hyperventilation followed by 5 min of rebreathing, with supplemental O(2) to maintain arterial oxygen saturation constant. To minimize effects of changes in ABP on CVMR estimation, cerebrovascular conductance index (CVCi) was calculated. CBFV-Pet(CO(2)) and CVCi-Pet(CO(2)) relationships were quantified by both linear and nonlinear logistic regression. In three subjects, muscle sympathetic nerve activity was recorded. From hyperventilation to rebreathing, robust changes occurred in Pet(CO(2)) (20-61 Torr), CBFV (-44 to +104% of baseline), CVCi (-39 to +64%), and ABP (-19 to +23%) (all P < 0.01). Muscle sympathetic nerve activity increased by 446% during hypercapnia. The linear regression slope of CVCi vs. Pet(CO(2)) was less steep than that of CBFV (3 vs. 5%/Torr; P = 0.01). Logistic regression of CBF-Pet(CO(2)) (r(2) = 0.97) and CVCi-Pet(CO(2)) (r(2) = 0.93) was superior to linear regression (r(2) = 0.91, r(2) = 0.85; P = 0.01). CVMR was maximal (6-8%/Torr) for Pet(CO(2)) of 40-50 Torr. In conclusion, CBFV and CVCi responses to transient changes in Pet(CO(2)) can be described by a nonlinear logistic function, indicating that CVMR estimation varies within the range from hypocapnia to hypercapnia. Furthermore, quantification of the CVCi-Pet(CO(2)) relationship may minimize the effects of changes in ABP on the estimation of CVMR. The method developed provides insight into CVMR under transient breath-by-breath changes in CO(2).     

Distribution of endoglin in early human development reveals high levels on endocardial cushion tissue mesenchyme during valve formation

Endoglin is a component of the receptor complex for transforming growth factor (TGF)-β1 and TGF-β3. We analysed its expression by immunohistochemistry in human embryos at 4–8 weeks of gestation and in hearts ranging from 4–13 weeks old. We compared endoglin distribution with that of TGF-β receptors type I (TβR-I), type II (TβR-II) and betaglycan. Endoglin was found on endothelial cells in all tissues examined, consistent with its expression in adult blood vessels. TβR-I, TβR-II and betaglycan were observed on most cell types and had an overall similar pattern of distribution. Endoglin was detected on the endocardium as early as 4 weeks, but was absent from myocardium. It was present at high levels on the endocardial cushion tissue mesenchyme from 5–8 weeks’ gestation, during heart septation and valve formation, and subsequently decreased as the valves matured. Endoglin expression in heart extracts was confirmed by Western blot analysis. TβR-I, TβR-II and betaglycan were mostly found on cardiac myocytes, but were detectable at low levels on endocardium. They were expressed transiently on cushion mesenchyme, albeit at much lower levels than endoglin. All four components of the TGF-β receptor complex were detected by RT-PCR in embryonic heart. Thus transient up-regulation of the components of the TGF-β receptor complex, and particulartly of endoglin, is associated with heart septation and valve formation during early human development.     

转录激活因子样效应物核酸酶介导的山羊β-乳球蛋白基因敲除和人乳铁蛋白基因定点整合

为了敲除山羊乳中致敏源β-乳球蛋白(BLG)基因,同时在BLG基因座定点整合人乳铁蛋白(hLF)基因。首先针对山羊BLG第3外显子识别位点设计了1对特异性TALEN-3-L/R质粒对;同时,构建了含有1个HSV-TK负筛选基因的hLF基因打靶载体BLC14-TK。TALENs质粒对转染山羊胎儿成纤维细胞,2μg/m L嘌呤霉素筛选3 d,PCR扩增产物测序来验证其切割DNA活性。打靶载体BLC14-TK与TALEN-3-L/R质粒对共转染山羊胎儿成纤维细胞,经700μg/m L G418和2μg/m L GCV共筛选药物抗性细胞株;通过整合检测和同源重组检测来筛选hLF基因打靶细胞株;BLG~–/hLF~+打靶细胞株作为供核细胞进行山羊体细胞核移植。结果为:TALEN-3-L/R致突变率为25%-30%;获得BLG~–/hLF~+打靶细胞6株;共制作重构胚胎335枚,移植受体山羊23只,B超检测到30-35 d的妊娠受体9只(妊娠率39.1%),其中1只50日龄克隆胎儿验证为BLG~–/hLF~+基因型。以上结果表明获得BLG基因座定点整合hLF基因的基因打靶山羊是可行的,为培育羊乳中含低致敏原和富含hLF的山羊新品系奠定了基础。     

Hemagglutinin Stalk Immunity Reduces Influenza Virus Replication and Transmission in Ferrets

We assessed whether influenza virus hemagglutinin stalk-based immunity protects ferrets against aerosol-transmitted H1N1 influenza virus infection. Immunization of ferrets by a universal influenza virus vaccine strategy based on viral vectors expressing chimeric hemagglutinin constructs induced stalk-specific antibody responses. Stalk-immunized ferrets were cohoused with H1N1-infected ferrets under conditions that permitted virus transmission. Hemagglutinin stalk-immunized ferrets had lower viral titers and delayed or no virus replication at all following natural exposure to influenza virus.     

Responses of arbuscular mycorrhizal symbionts to contrasting environments: field evidence along a Tibetan elevation gradient

Plant adaptation to alpine ecosystems is not fully explained by plant physiological and morphological traits. Arbuscular mycorrhizal (AM) associations may be involved in mediating plant performance in response to environmental differences. Little is known, however, as to whether or not a close relationship exists between plant performance and arbuscular mycorrhizal fungus status across environmental gradients. We conducted a field investigation of the performance of six plant species and their associated AM fungi along higher and lower elevation gradients on Mount Segrila in Tibet. In most of our species, we observed higher shoot and inflorescence biomass production and a lower root-to-shoot ratio in the populations at those sites where the species was dominant (intermediate elevation sites) than in populations sampled at the limits of the distribution. The elevation pattern of root colonization differed with plant species on both gradients, and the extraradical hypha development of most species showed a unimodal pattern as did plant growth. The relationship between plant and fungus traits shows that AM fungus development generally matched host plant performance on the lower elevation gradient but not on the higher elevation gradient. This study provides evidence that plant distribution and productivity were significantly related to root and soil colonization by AM fungi, especially under less physically stressful conditions.