颈髓损伤的常规MRI表现与DTI技术临床应用

目的：比较不同时期颈髓损伤的MRI表现及DTI的应用价值。方法：收集急性颈髓压迫病例15例、慢性颈髓压迫病例23例、颈髓慢性压迫合并急性压迫病例12例。15例健康志愿者作为对照组。进行常规MRI检查,应用DTI检查测量表现扩散系数（ADC）值和各向异性分数（FA）。比较各组间ADC值和FA值,并进行统计学分析。结果：急性颈髓迫病例,常规MRI显示颈髓增粗,呈等T1长T2信号;慢性颈髓压迫病例,9例呈长T1长T2信号,14例呈等T1长T2信号;慢性颈髓压迫并急性压迫病例颈髓明显增粗,呈等、长T1明显长T2信号。与对照组比较：急性颈髓压迫组的ADC值和FA值均明显降低,两组的差异有显著性;慢性颈髓压迫组的FA值降低,ADC值增高,两组的差异有显著性;慢性脊髓压迫合并急性脊髓压迫组ADC值与对照组比较无差异,FA值低于对照组。颈髓压迫各组间ADC值及FA值比较差异显著。结论：不同时期颈髓损伤常规MRI图像缺乏特异性,根据ADC值及FA值可判断颈髓损伤的时期。     

Retrograde tracing and toe spreading after experimental autologous nerve transplantation and crush injury of the sciatic nerve: a descriptive methodological study

ABSTRACT: Evaluation of functional and structural recovery after peripheral nerve injury is crucial to determine the therapeutic effect of a nerve repair strategy. In the present study, we examined the relationship between the structural evaluation of regeneration by means of retrograde tracing and the functional evaluation analysis of toe spreading. Two standardized rat sciatic nerve injury models were used to address this relationship. As such, animals received either a 2 cm sciatic nerve defect (neurotmesis) followed by autologous nerve transplantation (ANT animals) or a crush injury with spontaneous recovery (axonotmesis; CI animals). Functional recovery of toe spreading was observed over an observation period of 84 days. In contrast to CI animals, ANT animals did not reach pre-surgical levels of toe spreading. After the observation period, the lipophilic dye DiI was applied to label sensory and motor neurons in dorsal root ganglia (DRG; sensory neurons) and spinal cord (motor neurons), respectively. No statistical difference in motor or sensory neuron counts could be detected between ANT and CI animals. In the present study we could indicate that there was no direct relationship between functional recovery (toe spreading) measured by SSI and the number of labelled (motor and sensory) neurons evaluated by retrograde tracing. The present findings demonstrate that a multimodal approach with a variety of independent evaluation tools is essential to understand and estimate the therapeutic benefit of a nerve repair strategy.     

Intra‐ and interspecific differences in nutrient recycling by European freshwater fish

1. We measured N and P excretion rates of 470 individuals belonging to 18 freshwater fish species widespread in Western Europe. We assessed the effect of body mass on excretion rates at both the intra‐ and interspecific levels. 2. The high variability in per capita N and P excretion rates was mainly determined by differences in body mass. The scaling coefficients of allometric relationships for both N and P excretion rates were significantly lower than 1 (mean ± SE, 0.95 ± 0.04 and 0.81 ± 0.05, respectively). 3. The slope of the allometric relationship between fish mass and nutrient excretion rate was significantly different among species. We did not detect any influence of phylogenetic conservatism on fish mass and on excretion rates. Further investigations are needed to understand the biological determinants of these differences. 4. This high intra‐ and interspecific variability in per capita excretion rates, coupled with differences in fish body mass, produce marked differences in biomass‐standardised excretion rates. These results thus indicate the necessity for further experimental and in situ investigations on the consequences of nutrient recycling by fish in freshwater ecosystems.     

Dibasic benzo[b]thiophene derivatives as a novel class of active site directed thrombin inhibitors: 2. Sidechain optimization and demonstration of in vivo efficacy

Potent, subnanomolar thrombin inhibitors 4, 5, and 6 are developed through side chain optimization of novel, benzo[b]thiophene-based small organic entities 2 and 3 and through SAR additivity studies of the new structural elements identified. X-ray crystallographic studies of 4b-thrombin complex revealed a hydrophobic and an electrostatic interaction of these new elements with thrombin at the S2 and S3 binding sites. In vitro and in vivo pharmacological studies showed that 4, 5, and 6 are potent anticoagulants in human plasma with demonstrated antithrombotic efficacy in a rat model of thrombosis.     

Association of a bovine prion gene haplotype with atypical BSE

Background

Atypical bovine spongiform encephalopathies (BSEs) are recently recognized prion diseases of cattle. Atypical BSEs are rare; approximately 30 cases have been identified worldwide. We tested prion gene (PRNP) haplotypes for an association with atypical BSE.

Methodology/Principle Findings

Haplotype tagging polymorphisms that characterize PRNP haplotypes from the promoter region through the three prime untranslated region of exon 3 (25.2 kb) were used to determine PRNP haplotypes of six available atypical BSE cases from Canada, France and the United States. One or two copies of a distinct PRNP haplotype were identified in five of the six cases (p = 1.3×10⁻⁴, two-tailed Fisher''s exact test; CI_95% 0.263–0.901, difference between proportions). The haplotype spans a portion of PRNP that includes part of intron 2, the entire coding region of exon 3 and part of the three prime untranslated region of exon 3 (13 kb).

Conclusions/Significance

This result suggests that a genetic determinant in or near PRNP may influence susceptibility of cattle to atypical BSE.     

Minimal primer and primer-free SELEX protocols for selection of aptamers from random DNA libraries

Standard systematic evolution of ligands by exponential enrichment (SELEX) protocols require libraries that contain two primers, one on each side of a central random domain, which allow amplification of target-bound sequences via PCR or RT-PCR. However, these primer sequences cause nonspecific binding by their nature (generally adding about 20 nt on each end of the random sequence of about 30-40 nt), and can result in large numbers of false-positive binding sequences and/or interfere with good binding random sequences. Here, we have developed two DNA-based methods that reduce and/or eliminate the primer sequences from the target-binding step, thus reducing or eliminating the interference caused by the primer sequences. In these methods, the starting selection libraries contain a central random sequence that is: (i) flanked by only 2 nt on each side (minimal primer); or (ii) flanked only by either a 2- or 0-nt overhand on the 3' end (primer-free). These methods allow primer regeneration and re-elimination after and before selection, are fast and simple, and don't require any chemical modifications for selection in a variety of conditions. Further, the selection rounds are performed with DNA oligomers, which are generally employed as end product aptamers.     

Variability in responses to thermal stress in parasitoids

Abstract 1. To study phenotypic effects of stress, a stress is applied to cohorts of organisms with an increasing intensity. In the absence of mortality the response of traits will be a decreasing function of stress intensity because of increasing physiological costs. We call such decreasing functions type A responses. 2. However, when stress caused mortality, some studies have found that for high stress intensities, survivors performed as well as control individuals (type B responses). We proposed that type A responses are caused by the physiological cost of stress whereas type B responses are caused by a mixture of physiological costs and selection. 3. The present study exposed Aphidius picipes wasps to an increasing duration of cold storage (cold stress), and obtained variable responses as predicted when both physiological costs and selection of resistant individuals determine the outcome. 4. When cold storage of parasitoids for biological control is desirable, research should be carried out to find (i) the temperature regime and duration of storage and (ii) the least sensitive stage for storage to minimise losses from mortality and reduction of fitness of survivors. 5. Selection by cold stress as observed in the present study could result in rapid adaptation of populations exposed to such stress.     

腺嘌呤与氢化可的松大鼠肾阳虚模型造模方法比较

目的比较腺嘌呤诱导与氢化可的松诱导的SD大鼠肾阳虚模型的优劣,从而得到临床症状、生化指标更符合中医“肾阳虚”型的动物模型,以供科研、教学使用。方法雄性SD大鼠100只,随机分成正常组、腺嘌呤造模组及氢化可的松低剂量组、中剂量组、高剂量组各20只,造模成功后检测血肌酐（Scr）、尿素氮（BUN）、尿液中17-羟皮质类固醇（17-OH）和血浆中甲状腺激素（13、T4）、睾丸酮（T）、雌二醇（E2）及模型大鼠骨密度。结果无论从症状主证方面,还是客观指标方面（除骨密度外）,腺嘌呤诱导的SD大鼠肾阳虚型动物模型在生化指标研究方面均优于氢化可的松诱导组。结论腺嘌呤诱导的肾阳虚证SD大鼠模型在症状主证方面及其相关的生化研究方面优于氢化可的松组。     

Major surface protein 1a effects tick infection and transmission of Anaplasma marginale.

Anaplasma marginale, an ehrlichial pathogen of cattle and wild ruminants, is transmitted biologically by ticks. A developmental cycle of A. marginale occurs in a tick that begins in gut cells followed by infection of salivary glands, which are the site of transmission to cattle. Geographic isolates of A. marginale vary in their ability to be transmitted by ticks. In these experiments we studied transmission of two recent field isolates of A. marginale, an Oklahoma isolate from Wetumka, OK, and a Florida isolate from Okeechobee, FL, by two populations of Dermacentor variabilis males obtained from the same regions. The Florida and Oklahoma tick populations transmitted the Oklahoma isolate, while both tick populations failed to transmit the Florida isolate. Gut and salivary gland infections of A. marginale, as determined by quantitative PCR and microscopy, were detected in ticks exposed to the Oklahoma isolate, while these tissues were not infected in ticks exposed to the Florida isolate. An adhesion-recovery assay was used to study adhesion of the A. marginale major surface protein (MSP) 1a to gut cells from both tick populations and cultured tick cells. We demonstrated that recombinant Escherichia coli expressing Oklahoma MSP1a adhered to cultured and native D. variabilis gut cells, while recombinant E. coli expressing the Florida MSP1a were not adherent to either tick cell population. The MSP1a of the Florida isolate of A. marginale, therefore, was unable to mediate attachment to tick gut cells, thus inhibiting salivary gland infection and transmission to cattle. This is the first report of MSP1a being responsible for effecting infection and transmission of A. marginale by Dermacentor spp. ticks. The mechanism of tick infection and transmission of A. marginale is important in formulating control strategies and development of improved vaccines for anaplasmosis.