Systematic investigations on the reactivity of oxazolinium salts

The termination reaction of the cationic polymerization of 2-phenyl- and 2-nonyl-2-oxazolines was examined by reacting the corresponding model oxazolinium salts having tosylate and trifluoromethansulfonate counterions with various nucleophiles. The reaction was monitored by ¹H NMR spectroscopy. Piperidine and KOH react with the oxazolinium salts very fast and quantitatively. In the case of piperidine, the use of a double molar amount of piperidine is necessary to achieve complete conversion. The addition of piperidine, pyridine, 4-dimethylaminopyridine and morpholine takes place in position 5 of the oxazolinium ring, whereas water and KOH add in position 2. The rate of the termination reaction depends on the electron density of the nucleophile which can be correlated with the pK_a value. With CF₃SO as counterion the addition of nucleophiles in position 5 is distinctly faster, whereas the addition of water in position 2 is much slower than with TsO^? as counterion. The ring-opening of the nonyl oxazolinium ion is slower than that of the phenyl oxazolinium ion.     

Solution properties of ultrahigh-molecular-weight polymers, 16. Unperturbed dimensions of poly(isobutyl methacrylate)

Three techniques, i. e., the Lenka extrapolation method, the Stockmayer-Fixman method, and the extrapolation of the Mark-Houwink constants to a = 0,5 were applied to determine the unperturbed dimensions of ultrahigh-molecular-weight poly(isobutyl methacrylate). A correction term, depending on the exponent a of the Mark-Houwink relation, is suggested to be introduced into the Stockmayer-Fixman-Burchard equation.     

The ex-vivo-shunt-model: novel approach for assessing the thrombogenicity of vascular implants

OBJECTIVE: Disadvantages associated with commercially available vascular implants necessitate alternative strategies to develop new vascular prostheses. Although many tissue characterizing strategies have been defined, no valid test for thrombogenicity exists. Here we introduce a novel concept for thrombogenicity testing of vascular implants METHODS: Silastic tubes were implanted into the carotid arteries of 12 sheep. After placing these shunts, tc99m-labeled platelets were administered and test-vessels were put in between the shunts. Native autologous (n=6), as well as native/acellularized allogeneic (n=6/n=6), and xenogeneic (n=6/n=6) carotid arteries and allogeneic (n=6/n=6) and xenogeneic (n=6/n=6) carotid arteries reseeded with allogeneic endothelial-cells, fibroblasts and myocytes were evaluated. Number and time course of intra-operatively deposited platelets were evaluated with a Geiger-counter; certain areas of platelet deposition located, envisioned and characterized by a gamma-camera and scanning electron-microscopy afterwards. RESULTS: Counter results revealed no significant different platelet depositions when comparing silastic tubes with either autologous or allogeneic native carotid arteries. However, starting 5 minutes after placement, acellularized/reseeded allogeneic (p=0.001/p=0.00004), and xenogeneic (p=0.0001/p=0.01) carotid arteries showed significantly more platelet depositions than native autologous carotides. Moreover, it was possible to show that almost no platelets adhere to native vessels or silastic tubes, thus proving the test method itself. CONCLUSION: The Ex-Vivo-Shunt-Model is a valid method to measure and envision the intrinsic thrombogenicity of vascular implants.     

包甲素类似物的绝对构型研究

目的　建立手性包甲素类似物绝对构型的简便方法。方法　以外消旋６β－羟基莨菪烷－３－酮为原料,通过拆分、酰化和还原制备手性包甲素类似物。结果　合成了手性包甲素类似物,通过物理常数、光谱数据鉴定其结构并与已知构型的化合物Ｉｓ进行化学关联确定其绝对构型。结论　本文建立的方法可用于确定某些活性手性包甲素类似物的绝对构型,从而有助于此类化合物构效关系的进一步研究。     

Endothelin-like immunoreactivity in aqueous humor of patients with primary open-angle glaucoma and cataract

Background: Experimental evidence suggests a role of endothelin-1 (ET) in the regulation of intraocular pressure (IOP). Method: Therefore, inpatients undergoing cataract surgery, ET-like immunoreactivity (STIR) was measured by radioimmunoassay in pooled samples of aqueous humor of eyes with primary open-angle glaucoma (POAG) and normotensive eyes with cataract only. Results: ETIR was significantly (P < 0.05) higher in patients with cataract and POAG (20.5 ± 1.8 pg/ml,n = 12; preoperative IOP 21.4 ± I.1 mmHg,n = 33) than in patients with cataract only (15.8 ± 1.6 pg/m1,n = 15; preoperative IOP 16.0 ± 0.6 mmHg,n = 77). Conclusion: This finding may indicate a role of ET in POAG or ocular antihypertensive treatment, and its relevance should be further investigated.     

Expression of the ELAV-like protein HuR is associated with higher tumor grade and increased cyclooxygenase-2 expression in human breast carcinoma.

PURPOSE: The human ELAV (embryonic lethal abnormal vision)-like protein HuR stabilizes a certain group of cellular mRNAs that contain AU-rich elements in their 3'-untranslated region. Cell culture studies have shown that the mRNA of cyclooxygenase (COX)-2 can be stabilized by HuR. EXPERIMENTAL DESIGN: To investigate a possible contribution of dysregulation of mRNA stability to the progression of cancer and to overexpression of COX-2, we studied expression of HuR in 208 primary breast carcinomas by immunohistochemistry. RESULTS: There were two different staining patterns of HuR in tumor tissue of breast carcinomas: nuclear expression was seen in 61% of cases; and an additional cytoplasmic expression was seen in 30% of cases. Expression of HuR was significantly associated with increased COX-2 expression; this association was particularly significant for cytoplasmic HuR expression (P < 0.0005). We further observed a significant association of cytoplasmic (P = 0.002) or nuclear HuR (P = 0.027) expression with increased tumor grade. Only 13% of the grade 1 carcinomas showed cytoplasmic expression of HuR, compared with 46% of the grade 3 carcinomas. There was no significant correlation between HuR expression and other clinicopathological parameters such as histological type, tumor size, or nodal status as well as patient survival. CONCLUSIONS: Our results suggest that overexpression of HuR in tumor tissue may be part of a regulatory pathway that controls the mRNA stability of several important targets in tumor biology, such as COX-2. Based on our results, additional studies are necessary to investigate whether HuR might be a potential target for molecular tumor therapy.     

Anti-adaptors provide multiple modes for regulation of the RssB adaptor protein

RpoS, an RNA polymerase σ factor, controls the response of Escherichia coli and related bacteria to multiple stress responses. During nonstress conditions, RpoS is rapidly degraded by ClpXP, mediated by the adaptor protein RssB, a member of the response regulator family. In response to stress, RpoS degradation ceases. Small anti-adaptor proteins—IraP, IraM, and IraD, each made under a different stress condition—block RpoS degradation. RssB mutants resistant to either IraP or IraM were isolated and analyzed in vivo and in vitro. Each of the anti-adaptors is unique in its interaction with RssB and sensitivity to RssB mutants. One class of mutants defined an RssB N-terminal region close to the phosphorylation site and critical for interaction with IraP but unnecessary for IraM and IraD function. A second class, in the RssB C-terminal PP2C-like domain, led to activation of RssB function. These mutants allowed the response regulator to act in the absence of phosphorylation but did not abolish interaction with anti-adaptors. This class of mutants is broadly resistant to the anti-adaptors and bears similarity to constitutively activated mutants found in a very different PP2C protein. The mutants provide insight into how the anti-adaptors perturb RssB response regulator function and activation.     

Left superior pulmonary vein connected to superior vena cava vein in a patient with situs inversus totalis: A challenging diagnosis

We herein describe the previously unreported combination of partial anomalous venous connection to the superior vena cava combined with situs inversus totalis. Following peripheral contrast injection, bubbles appeared initially in the left atrium allowing the diagnosis of a supra‐atrial connection to be made using transthoracic echocardiography, but this timing was not anymore reproduced during transesophageal echocardiography performed minutes later. Cardiac computed tomography allowed the final diagnosis to be made. This case emphasizes the importance of performing bubble studies both during transesophageal and transthoracic echocardiography.