Herbivore pressure increases toward the equator

Increases in species diversity and density from higher to lower latitudes are well documented. Nevertheless, the consequences of these changes in diversity for structuring ecological communities and influencing biotic evolution are largely unknown. It is widely believed that this increase in species diversity is associated with increased intensity of ecological interactions closer to the equator. For plant-herbivore interactions in particular, the predictions are that, at lower latitudes, plants will be attacked by more individual herbivores, more herbivore species, and more specialized herbivores and, therefore, will suffer greater damage. We used a large-scale latitudinal transect from Mexico to Bolivia to quantify changes in leaf damage, diversity, and abundance of lepidopteran larvae on two widely distributed host species of the genus Piper (Piperaceae). We show that both density and species richness of herbivores were highest at the equator and decreased with increasing latitude, both northward and southward. Contrary to expectation, however, this increase in herbivore diversity was attributable to the addition of generalist not specialist species. Finally, and again contrary to expectation, the increase in herbivore density with decreasing latitude did not produce a corresponding damage gradient. We propose that the lack of a latitudinal concordance between increases in herbivore density and diversity with decreasing latitude, and the resulting herbivore damage, supports the hypothesis of better plant antiherbivore defenses at lower latitudes. Furthermore, the changes in the relative abundance of generalist vs. specialist species suggest that the nature of the selective pressure is intrinsically different between higher and lower latitudes.     

nHA/BG涂层与Bio-Oss骨粉修复种植体骨缺损的实验研究

目的:评价生物玻璃/纳米羟基磷灰石(nHA/BG)涂层与Bio-Oss骨粉在种植体骨缺损中引导骨再生的效果。方法:选取6只Beagle犬,拔除两侧下颌前磨牙。3个月后预备种植窝,同时颊侧制造裂隙状骨缺损(2.25 mm×3 mm×4 mm)。按照分组植入种植体和骨粉,A组为nHA/BG+Bio-Oss,B组为nHA/BG+血凝块愈合,C组为微米级HA+Bio-Oss。术后2周、处死前2周和3 d分别进行四环素、钙黄绿素和茜素红荧光标记。术后8周和16周处死动物,行大体观察和组织学测量。采用SPSS13.0软件包对数据进行统计学分析。结果:3组骨-种植体结合率(BIC)在8周时分别为30%、18%、21%,16周时分别为61%、53%、46%;缺损区新骨面积(RA)在8周时分别为(2.1±0.6)mm3、(1.4±1.0)mm3、(0.6±0.1)mm3,16周时分别为(4.2±0.7)mm3、(2.2±1.2)mm3、(1.2±0.6)mm3。各组8周与16周的BIC和RA相比均有显著差异(P<0.05);8周时,A、C 2组的BIC和RA相比有显著差异(P<0.05),16周时,A、B 2组的RA相比有显著差异(P<0.05)。结论:在种植体周围2.25 mm骨缺损区,nHA/BG涂层能促进种植体-Bio-Oss替代骨-骨的骨结合。     

PCR-DGGE检测早期儿童龋治疗前后口腔菌群多样性的初步研究

目的:应用PCR-变性梯度凝胶电泳技术(denaturing gradient gel electrophoresis,DGGE)技术检测早期儿童龋治疗前后唾液中微生物多样性的变化。方法:选取北京大学燕东幼儿园22名3～5岁儿童进行口腔检查,在龋齿治疗前和治疗后2周分别取样,采用PCR-DGGE技术检测受试儿童唾液样本,分析治疗前后唾液微生物多样性的变化。结果:治疗前唾液样本DGGE条带数为23±2.9,治疗后唾液样本DGGE条带数为28±4.1,差异有显著性(P<0.01);在同一时期内各唾液样本DGGE图谱的相似性高于不同时期样本之间。结论:PCR-DGGE技术可用于与龋病相关细菌的生物多样性的研究以及监测微生物群落组成的动态变化。     

3.0T磁共振成像定量分析正常胰腺T2*值

目的定量分析正常胰腺头、体、尾T2’值。方法选取51名胰腺正常者,利用16回波GRE-T2’序列分别测量胰腺头、体、尾的T2。值,比较胰腺头、体、尾的T2＊值的差异及其在不同性别和年龄组间的差异,并分析三者T2＊值间的相关性。结果正常胰腺头、体、尾T2’值分别为（22．74±3．45）ms、（20．51±3．40）ms、（19．92±3．90）ms,在男性与女性间以及不同年龄组间的差异均无统计学意义（P均〉O．05）。胰头与胰体（t=3．59,P=0．001;r=0．19,P=0．18）、胰头与胰尾（t=4.30,P〈0.05;r=0．15,P=0．32）的T2。值差异有统计学意义,但无相关性;而胰体与胰尾的T2’值差异无统计学意义,但存在相关性（t=1．30,P=0．20;r=0．50,P〈0．01）。结论利用MR多回波GRE-T2序列成像初步界定了正常胰腺头、体、尾的T2＊值,可为临床胰腺疾病的诊断和研究提供参考。     

The Role of EC-IC in the Treatment of Giant Intracranial Aneurysms

Abstract

Extracranial to intracranial bypass surgery was used in 27 cases of intracranial giant aneurysm to prevent ischemic complications. In 19 of 21 patients the aneurysm was considered unfit for a direct clipping or ligation, and an EC-IC bypass was done in conjunction with staged clipping of the internal carotid artery or occlusion of the middle cerebral artery. All bypass grafts have remained patent postoperatively. None of the patients have developed ischemic complications in the 6-41 month period of follow-up.     

Validity and reliability of measurements of aponeurosis dimensions from magnetic resonance images

Muscle performance is closely related to the structure and function of tendons and aponeuroses, the sheet‐like, intramuscular parts of tendons. The architecture of aponeuroses has been difficult to study with magnetic resonance imaging (MRI) because these thin, collagen‐rich connective tissues have very short transverse relaxation (T2) times and therefore provide a weak signal with conventional MRI sequences. Here, we validated measurements of aponeurosis dimensions from two MRI sequences commonly used in muscle‐tendon research (mDixon and T1‐weighted images), and an ultrashort echo time (UTE) sequence designed for imaging tissues with short T2 times. MRI‐based measurements of aponeurosis width, length, and area of 20 sheep leg muscles were compared to direct measurements made with three‐dimensional (3D) quantitative microdissection. The errors in measurement of aponeurosis width relative to the mean width were 1.8% for UTE, 3.7% for T1, and 18.8% for mDixon. For aponeurosis length, the errors were 7.6% for UTE, 1.9% for T1, and 21.0% for mDixon. Measurements from T1 and UTE scans were unbiased, but mDixon scans systematically underestimated widths, lengths, and areas of the aponeuroses. Using the same methods, we then found high inter‐rater reliability (intraclass correlation coefficients >0.92 for all measures) of measurements of the dimensions of the central aponeurosis of the human tibialis anterior muscle from T1‐weighted scans. We conclude that valid and reliable measurements of aponeurosis dimensions can be obtained from UTE and from T1‐weighted scans. When the goal is to study the macroscopic architecture of aponeuroses, UTE does not hold an advantage over T1‐weighted imaging.