Numerical Analysis of Dynamic Properties of an Auxetic Structure with Rotating Squares with Holes

In this paper, a novel auxetic structure with rotating squares with holes is investigated. The unit cell of the structure consists of four units in the shape of a square with cut corners and holes. Finally, the structure represents a kind of modified auxetic structure made of rotating squares with holes or sheets of material with regularly arranged diamond and square cuts. Effective and dynamic properties of these structures depend on geometrical properties of the structure. The structures are characterized by an effective Poisson's ratio from negative to positive values (from about minus one to about plus one). Numerical analysis is made for different geometrical features of the unit cells. The simulations enabled the determination of the dynamic characteristic of the analyzed structures using vibration transmission loss, transmissibility, and mechanical impedance. Numerical calculations were conducted using the finite element method. In the analyzed cases of cellular auxetic structures, a linear elasticity model of the material is assumed. The dynamic characteristic of modified rotating square structures is strongly dependent not only on frequency. The dynamic behavior could also be enhanced by adjusting the geometric parameter of the structure. Auxetic and non-auxetic structures show different static and dynamic properties. The dynamic properties of the analyzed structures were examined in order to determine the frequency ranges of dynamic loads for which the values of mechanical impedance and transmissibility are appropriate.

[Gastrointestinal stromal tumors (GIST)]

The vast majority of mesenchymal tumors originating from the GI tract consists of gastrointestinal stromal tumors (GIST), an entity just recently defined. The incidence is estimated to be around 10 - 20/1000000, the median age at diagnosis has been reported to be 55 to 65 years. GISTs most commonly occur in the stomach or duodenum, followed by the small intestine. About half of the patients present with metastatic disease at first diagnosis, predominantly in the liver or periteneum. GISTs are strongly and uniformly positive for CD117 (c-kit), a type III receptor-tyrosine kinase. Kit mutations, mostly in exon 11, leading to ligand independent constitutive activation are supposed to play a major role in the pathogenesis of GIST. Until recently no active systemic treatment was available for advanced gastrointestinal stromal tumors. Imatinib (STI571 = Glivec) is a rationally designed, orally available phenylaminopyrimidin analogue. The mechanism of action consists of a competitive interaction with the ATP-binding pocket of specific tyrosine kinases. Early results from clinical trials with response rates around 60 % and progression arrest in more than 80 % of patients resulting in fast relief of symptoms, confirm the high activity of this novel treatment. The role of adjuvant treatment after potentially curative resection of GIST is currently evaluated in ongoing clinical trials. Patients with progressive disease while under treatment with Imatinib should be enrolled in studies testing novel treatment strategies as RAD001, PKC412 or SU11 248.

Crystal structure of 1,1,5,5-tetramethyl-1,2,5,6-tetrahydro-3a,4,7a,8-tetraaza- s-indacene-3,7-dione, C12H16N4O2

C12H16N4O2, monoclinic, P121/c1 (No. 14), a = 9.306(2) Å, b = 5.755(1) Å, c = 11.499(2) Å, β = 98.15(3)°, V = 609.6 Å3, Z = 2, Rgt(F) = 0.045, wRref(F2) = 0.075, T = 294 K.

Bax expression in benign and malignant thyroid tumours: Dysregulation of wild-type P53 is associated with a high Bax and P21 expression in thyroid carcinoma

The purpose of our study was to determine the expression of the pro-apoptotic BAX protein in relation to the mutational status of BAX and p53 (as transcriptional activator of the BAX gene) in benign and malignant thyroid tissue. In 47 patients with thyroid tumours (14 follicular and 3 papillary carcinomas, 14 adenomas and 16 goitres), the DNA was screened for mutations of BAX (exon 1-6) and p53 (exon 5-8) by single-strand conformation polymorphism polymerase chain reaction (SSCP-PCR). Furthermore, the protein expression of BAX, p53 and p21 (which is also increased transcriptionally by p53) was investigated by immunohistochemistry. Surprisingly, we observed elevated BAX levels in patients with thyroid carcinomas compared with patients with adenomas (unpaired t-test: p<0.05) or with goitres (p<0.02). This is in clear contrast to other carcinomas where BAX is frequently inactivated which correlates to a poor prognosis (Sturm et al. J. Clin. Oncol. 1999;17:1364-74.). There were no significant differences of the BAX levels between goitres or the adenomas. In the SSCP-PCR analysis, no BAX mutations were detectable. P53 mutation analysis by SSCP-PCR did not reveal any functional p53 mutations in the patients with carcinomas, adenomas or goitres. Nevertheless, patients with carcinomas showed an overexpression (preferentially cytoplasmic) of p53 protein compared with patients with benign tumours (p<0.05). The absence of p53 mutations suggests that the overexpressed p53 is wild type. This is in line with the expression profile of BAX and p21, which showed a higher protein expression in these p53 positive tumours (p<0.05 in the carcinomas compared with the non-malignant lesions). Consequently, the overexpressed p53 might be a correlate for dysregulation without loss of function. This, in turn, might be a reason for the good outcome of some patients with thyroid cancer.

Quantitative analysis of structure-activity relationship in the acridine series. Part 2: Antitumor 9-thiadiazolo-acridine derivatives

Synthesis and activity, vs. leukaemia cells of new 9-thiadiazolo acridine derivatives are reported. In addition, electronic properties and molecular structure are correlated with biological activity of these molecules. Results are in agreement with the capability of drugs to intercalate into DNA.

Quantitative analysis of structure-activity relationship in the acridine serie. Part 1: Antiparasitic 9-thioaryl-acridine derivatives

Synthesis and antiparasitic activity vs T. cruzi and L. donovani of a series of 9-thioaryl acridines are reported. A convenient correlation between molecular structure and biological activity is proposed. Results not only agree with the classical interactions of acridines with DNA but also suggest possible role of charge transfer complexes.

Identification of transplanted pancreatic islet cells by radioactive dithizone-[131I]-histamine conjugate. Preliminary report

BACKGROUND

The unique mechanism of dithizone action in the interior of the viable pancreatic islet suggests the possible development of a specific radiopharmaceutical that may have a potential clinical application in the diagnosis of the pancreatic organ allografts or islets rejection. The radiodiagnostic properties of the newly developed radioactive analogue of dithizone, i.e. Dithizone-[(131)I]-Histamine conjugate have been evaluated in the present study.

METHODS

The four islet cells transplantation models were chosen for this purpose. The most important feature of the Dithizone-[(131)I]-Histamine conjugate is its possessed ability of zinc chelation. As was presented in the recent study, the conjugate stains pink-reddish the isolated pancreatic islets in vitro. Among the studied transplantation models, only the islets grafting under testis capsule enabled determination of the pancreatic islets in rats by radioactive Dithizone-[(131)I]-Histamine conjugate. The level of the radioactivity in the recipient testis (right) was almost two times higher compared to the controls (0.24 vs. 0.13% ID/g, respectively).

CONCLUSIONS

These preliminary data demonstrate the ability of the developed radioactive analogue of dithizone for in vivo identification of transplanted pancreatic islets, and suggests a potential clinical application of the radiodithizone in the diagnosis of the pancreatic islet rejection.