The major determinant of exendin-4/glucagon-like peptide 1 differential affinity at the rat glucagon-like peptide 1 receptor N-terminal domain is a hydrogen bond from SER-32 of exendin-4

BACKGROUND AND PURPOSE

Exendin-4 (exenatide, Ex4) is a high-affinity peptide agonist at the glucagon-like peptide-1 receptor (GLP-1R), which has been approved as a treatment for type 2 diabetes. Part of the drug/hormone binding site was described in the crystal structures of both GLP-1 and Ex4 bound to the isolated N-terminal domain (NTD) of GLP-1R. However, these structures do not account for the large difference in affinity between GLP-1 and Ex4 at this isolated domain, or for the published role of the C-terminal extension of Ex4. Our aim was to clarify the pharmacology of GLP-1R in the context of these new structural data.

EXPERIMENTAL APPROACH

The affinities of GLP-1, Ex4 and various analogues were measured at human and rat GLP-1R (hGLP-1R and rGLP-1R, respectively) and various receptor variants. Molecular dynamics coupled with in silico mutagenesis were used to model and interpret the data.

KEY RESULTS

The membrane-tethered NTD of hGLP-1R displayed similar affinity for GLP-1 and Ex4 in sharp contrast to previous studies using the soluble isolated domain. The selectivity at rGLP-1R for Ex4(9–39) over Ex4(9–30) was due to Ser-32 in the ligand. While this selectivity was not observed at hGLP-1R, it was regained when Glu-68 of hGLP-1R was mutated to Asp.

CONCLUSIONS AND IMPLICATIONS

GLP-1 and Ex4 bind to the NTD of hGLP-1R with similar affinity. A hydrogen bond between Ser32 of Ex4 and Asp-68 of rGLP-1R, which is not formed with Glu-68 of hGLP-1R, is responsible for the improved affinity of Ex4 at the rat receptor.     

Malignant jejunal strictures after Whipple procedure: stenting with large-bore tubes and use of combined transhepatic and peroral approach

Malignant strictures of the afferent jejunal limbs are difficult to treat. Surgical revision and chronic external drainage, two commonly used palliative procedures, have significant associated morbidity. A combined transhepatic and peroral approach was used to stent malignant jejunal strictures in two patients, allowing antegrade internal drainage of biliary and pancreatic secretions. Excellent palliation was achieved, and there were no associated complications.     

超声和微泡造影剂介导细胞基因转染的实验研究

目的 探讨低频超声对细胞基因转染的作用。方法 超声治疗仪频率1MHz，脉冲重复频率100Hz，占空系数20％。质粒DNA为含编码绿荧光蛋白的pEGFP。应用荧光显微镜和流式细胞仪评价细胞基因转染率，台盼蓝染色计算细胞成活率。选用C2C12、3T3-MDEI和CHO3种细胞系为研究对象，加入DNA后辐照不同声强、时间或加入超声造影剂，观察各条件下的细胞基因转染率和成活率。结果 ①超声介导的基因转染与声强和辐射时间有关，最佳剂量为1w／cm^2 20s；②同样超声剂量，较高的声强较早达到最大基因转染率；③较低剂量时，微泡造影剂可使超声介导的基因转染提高2～3倍并可显著提高最高基因转染率。结论 低频超声可介导细胞基因转染，基因转染率不但与超声辐射剂量有关，而且同样剂量时，高声强较早达到最大基因转染率，最佳剂量是1w／cm^2 20s。同时，微泡造影剂可提高超声介导基因转染的最高转染率。     

Histogram analysis of MR imaging-derived cerebral blood volume maps： combined glioma grading and identification of low-grade oligodendroglial subtypes

BACKGROUND AND PURPOSE： Inclusion of oligodendroglial tumors may confound the utility of MR based glioma grading. Our aim was, first, to assess retrospectively whether a histogram-analysis method of MR peifusion images may both grade gliomas and differentiate between low-grade oligodendroglial tumors with or without loss of heterozygosity （LOH） on 1p/19q and, second, to assess retrospectively whether low-grade oligodendroglial subtypes can be identified in a population of patients with high-grade and low-grade astrocytic and oligodendroglial tumors.     

消旋棉酚拆分的研究——Ⅳ.苏(-)或(+)-1-(对硝基苯基)-1,3-二羟基丙胺-2为拆分剂

本文介绍以光学活性苏-1-(对硝基苯基)-1,3-二羟基丙胺-2为拆分剂,与消旋棉酚缩合,用常压柱色谱或溶剂结晶法分离得到两个光学纯的非对映体,然后分别水解得(+)和(-)-棉酚。     

Uroscopy in the 21st century: high-field NMR spectroscopy

From the experiments described, it can be seen that there are different research approaches that can be taken and these are summarized in Table 1. Whereas much scientific research is principally hypothesis led, there remains, nevertheless, an important place for exploratory research. High resolution NMR can measure, directly and simultaneously, a wide range of endogenous metabolites in biological fluids and has the unique capability of providing structural information on the metabolites detected. It has proved to be a powerful research tool with which to study inherited metabolic diseases, renal disease, drug metabolism, and toxicity, and can be used to monitor the effects of drug therapy. For instance, by using a library of experimental toxins one can map the metabolic profile of site-specific nephron injury. With this approach in man one could eventually take an unknown disease such as Balkan nephropathy and predict the initial site of tubular injury, the mode of injury and therefore the kind of toxin capable of producing that injury. NMR spectroscopic techniques are still advancing rapidly, with ever increasing sensitivity and sophistication of NMR pulse sequences to enhance structural elucidation in complex mixtures. Given the advances in directly coupled HPLC-NMR and even HPLC-NMR-mass spectroscopy it is likely that these technologies in conjunction with pattern recognition will make major contribution to our understanding of renal processes and provide new diagnostic insights in the 21st century.      

Factors predictive of response and survival in patients with metastatic colorectal cancer in Taiwan

5-Fluorouracil in combination with leucovorin has been shown to be active in therapeutic trials of metastatic colorectal carcinoma. In this study, we administered these drugs to 72 patients with metastatic colorectal carcinoma. Thirty-six of them without previous exposure to 5-fluorouracil were treated with weekly bolus injections of 5-fluorouracil (425 mg/m2) and leucovorin (25 mg/m2) supplemented with oral levamisole. Another 36 patients with or without prior 5-fluorouracil treatment received 5-fluorouracil 3,000 mg/m2 and leucovorin 300 mg/m2 in a 48-hour continuous infusion every two weeks. Clinical efficacy and toxicity were assessed by WHO criteria. Variables were tested for relations to response and survival by univariate and multivariate analysis. The response rate was 19.4% in weekly bolus arm and 13.9% in biweekly high-dose infusion arm (P = 0.527). Median survivals in the two arms were 18.4 months (weekly) and 21 months (biweekly) respectively (P = 0.708). Gastrointestinal side effects including nausea, vomiting, diarrhea and mucositia were the major toxicities of these regimens. By multivariate analysis, the only factor to influence response rate was the site of metastases (P = 0.009). The only factor to affect survival was performance status of the patient (P = 0.0001). We concluded that the two 5-fluorouracil based regimens are well-tolerated and shown to have a response rate comparable with previous reports of similar regimens in patients with metastatic colorectal cancer. Only liver metastases seemed to have a better response to therapy. Performance status is the most important prognostic factor in patients with metastatic colorectal cancer.      

Household air pollution and the sustainable development goals

Globally, 41% of households, over 2.8 billion people, rely on solid fuels (coal and biomass) for cooking and heating. In developing countries in Asia and sub-Saharan Africa where these fuels are predominantly used, women who are customarily responsible for cooking, and their young children, are most exposed to the resulting air pollution. Solid fuels are still in widespread use and it appears that intervention efforts are not keeping pace with population growth in developing countries. Here we pinpoint the challenges and identify opportunities for addressing household air pollution while mitigating global climate change and promoting the sustainable development goals. We recommend the following actions: implementation of the WHO indoor air quality guidelines on household fuel combustion; effective promotion and dissemination of improved cookstoves through formation of country alliances for clean cookstoves; expansion of liquefied petroleum gas production facilities and distribution networks; harnessing renewable energy potential; promotion of biogas production at both household and community level; ensuring improved ventilation of homes through education and enforcement of building standards; and exploiting opportunities in the health and other sectors for changing health-damaging cooking behaviour.     

Molecular basis of familial cleft lip and palate

Cleft lip and palate (CLP) is one of the commonest congenital malformations and although the aetiology is still very unclear, a familial genetic component is considered to be an important factor in certain individuals. Molecular biology techniques are being used to identify the genes involved and this paper reviews current knowledge and the advances that have already been made. Recent evidence suggests a potential major gene on 6p, and a modifying role for transforming growth factor alpha (TGFA). Moreover retinoic acid receptor alpha (RARA) (17q), MSXl (4p), 4q and BCL3 (19q) could all be implicated in certain CLP families. In addition, the potential modifying role of various genes with the environment are considered to be important areas of research in the future. The identification of a genetic locus associated with this disease would be an important advance in CLP genetic counselling and lead to a better understanding of the genetic basis of CLP.