Polarization‐dependent second‐harmonic generation for collagen‐based differentiation of breast cancer samples

Nonlinear optical imaging techniques have been widely used to reveal biological structures for accurate diagnosis at the cellular as well as the tissue level. In the present study, polarization‐dependent second‐harmonic generation (PSHG) was used to determine collagen orientation in breast cancer biopsy tissues (grades 0, I, II and III). The obtained data were processed using fast Fourier transform (FFT) analysis, while second‐harmonic generation (SHG) anisotropy and the “ratio parameter” values were also calculated. Such measurements were shown to be able to distinguish collagen structure modifications in different cancer grades tested. The analysis presented herein suggests that PSHG imaging could provide a quantitative evaluation of the tumor state and the distinction of malignant from benign breast tissues. The obtained results also allowed the development of a biophysical model, which can explain the aforementioned differentiations and is in agreement with the simulations relating the SHG anisotropy values with the mechanical tension applied to the collagen during cancer progression. The current approach could be a step forward for the development of new, nondestructive, label free optical diagnostic tools for cancer reducing the need of recalls and unnecessary biopsies, while potentially improving cancer detection rates.     

Monitoring aging-associated structural alterations in Caenorhabditis elegans striated muscles via polarization-dependent second-harmonic generation measurements

The in-vivo elucidation of the molecular mechanisms underlying muscles dysfunction due to aging via non-invasive label free imaging techniques is an important issue with high biological significance. In this study, polarization-dependent second-harmonic generation (PSHG) was used to evaluate structural alterations in the striated muscles during Caenorhabditis elegans lifespan. Young and old wild-type animals were irradiated. The obtained results showed that it was not feasible to detect differences in the structure of myosin that could be correlated with the aging of the worms, via the implementation of the classical, widely used, cylindrical symmetry model and the calculation of the SHG anisotropy values. A trigonal symmetry model improved the extracted results; however, the best outcome was originated from the application of a general model. Myosin structural modifications were monitored via the estimation of the difference in spectral phases derived from discrete Fourier transform analysis. Age classification of the nematodes was achieved by employing both models, proving the usefulness of the usage of PSHG microscopy as a potential diagnostic tool for the investigation of muscle diseases.     

More is less: Inactivation and deletion events and the search for tumor suppressor genes

Tumor suppressor genes are frequently inactivated in cancer by large‐scale deletion events or epigenetic silencing, and experimental demonstration of such inactivation has historically been considered as support for assigning tumor suppressive function to a given gene. However, the discovery of a number of chromosomal domains wherein large deletions naturally occur at frequencies up to 100 times the average for the genome as a whole leads us to reevaluate the significance of sporadic deletions found within genes associated with these hotspots. Similarly, our recent demonstration that epigenetic chromatin silencing frequently spreads in cancer cells from gene‐poor into gene‐rich regions with apparent indifference to the gene content of the affected domain raises questions about the pertinence of inactivation as a criterion for ascribing tumor suppressor function to a given gene. We suggest that a number of putative suppressor genes for which inactivation and/or deletion events have been documented may simply be victims of collateral damage when these events occur, and the implication that these genes are being selected against during cancer progression should in some cases be reassessed. J. Cell. Biochem. 110: 281–287, 2010. © 2010 Wiley‐Liss, Inc.     

Clustering transfers the translocated Escherichia coli receptor into lipid rafts to stimulate reversible activation of c-Fyn

Enteropathogenic Escherichia coli (EPEC) mimic a ligand–receptor interaction to induce 'pedestal-like' pseudopodia on mammalian cells, providing a tractable system to study tyrosine kinase signalling to the actin cytoskeleton. EPEC delivers its own receptor (Tir), which is engaged by a bacterial surface ligand (intimin). When Tir delivery and activity are uncoupled, intimin-induced Tir clustering stimulates Tir^Y474 phosphorylation by the Src-family kinase (SFK) c-Fyn, triggering actin polymerization and pedestal formation. How c-Fyn specifically targets Tir and is regulated remains unknown. We show that clustering transfers Tir into cholesterol-rich detergent-resistant microdomains (DRMs), a signal prompting transient c-Fyn accumulation at bacterial adhesion sites. Co-clustering of Tir^Y474 and c-Fyn in DRMs rapidly stimulates robust kinase activation both by induced c-Fyn^Y531 dephosphorylation to unlock the inactive state and by reciprocal c-Fyn^Y417 autophosphorylation to promote activity. After signal induction, c-Fyn dissipates and the resting state restored by Csk-dependent phosphorylation of c-Fyn^Y531. These data illustrate a sophisticated mechanism evolved by a pathogen effector to reversibly regulate SFKs, and resolve early interactions at a model receptor initiating tyrosine kinase signalling.     

Certain hemocyte proteins of the medfly,Ceratitis capitata,are responsible for nonself recognition and immobilization of Escherichia coli in vitro

The results indicate that certain hemocyte proteins of the medfly, Ceratitis capitata, are responsible for the recognition of foreignness, since they are able to bind to the surface of Escherichia coli in vitro. Furthermore, when the E. Coli-hemocyte protein complex was incubated in the presence of tyrosine and phenoloxidase, the bacteria were immobilized, forming large aggregates. The formation of aggregates seems to be due to reactive tyrosine intermediate (quinone) generated by the action of phenoloxidase. © 1992 Wiley-Liss, Inc.     

On the occurrence of the Lesser White-fronted GooseAnser erythropus in Greece

Summary Since 1859, wintering Lesser White-fronted Geese have been recorded 25 times in Greece. Of the records obtained in the second half of the 19th century only two, based on museum specimens, are valid. There were four records in the first half of the present century, while all the others come from the second half due to increased coverage mostly during IWRB midwinter censuses. Their distribution had been more southerly in the past, but in recent years only northern Greek wetlands hold the bulk of the wintering population, with the Evros Delta being the most important area (12, or 48% of all records). The wintering population of the species in the Evros Delta is threatened by habitat destruction and shooting.

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Zum Vorkommen der Zwerggans in Griechenland

Zusammenfassung Seit 1859 wurden in Griechenland 25mal Zwerggänse festgestellt; aus dem 19. Jh. liegen nur 2 sichere Nachweise vor. 4 Nachweise fallen in die erste Hälfte des 20. Jh., die restlichen alle in die zweite Hälfte, Die Verteilung der Funde scheint in der Vergangenheit weiter nach Süden gereicht zu haben; heute liegen nur aus dem Norden Beobachtungen vor. Der wichtigste Platz ist das Evros-Delta (12 von 25 Nachweisen; einmal 1630 Ind. im Februar 1963). Die Winterpopulation ist durch Biotopzerstörung und Abschuß bedroht.

     

Effects of substituents on the rates of deacylation of substituted benzoyl papains. Role of a carboxylate residue in the catalytic mechanism.

The effect of ring substituents on the rates of deacylation of 8 meta- and para-substituted benzoyl papains was evaluated. The rate constants were found to depend upon a single ionizing group of pKa = 4.2--4.3, and to decrease by a factor of approximately 2.2 when measured in 94% D2O/H2O. The rates of deacylation are increased greatly by electron-withdrawing groups on the benzene ring. The Hammett rho value is 2.74 +/- 0.32. A plot of the rate constants for deacylation of the benzoyl papains against the corresponding constants for substituted benzoyl chymotrypsins generates a straight line of slope 1.0. This result suggests a very similar distribution of charge on the benzoyl moiety in the transition state for the two enzymes, which is interpreted in terms of the net charge of the transition state for the deacylation of nonspecific acyl papains being equal to--1 with the general base catalyzed assistance to the attack of water on the acyl enzyme being provided by the negatively charged Asp-158 rather than by the neutral Asn-175-His-159 hydrogen bond network. This result together with a survey of literature data suggests that the role of Asp-158 in papain catalysis has been underestimated. The evidence advanced to date in support of the proposition that an imidazolium-159-cysteine-25 thiolate ion pair exists in native papain is evaluated and considered to be insufficient to decide the issue.     

DNA binding specificity and transactivation properties of SREBP-2 bound to multiple sites on the human apoA-II promoter.

DNase I footprinting of the apoA-II promoter using sterol regulatory element binding protein-2 [(SREBP-2 (1-458)] expressed in bacteria identified four protected regions, designated AIIAB (-64 to -48), AIICD (-178 to -154), AIIDE (-352 to -332) and AIIK (-760 to -743), which bind SREBP-2 and contain either palindromic or direct repeat motifs. Potassium permanganate and dimethyl sulfate interference experiments using the AIIAB region as probe showed that the nucleotides of a decameric palindromic repeat RTCAMVTGMY and two 5' T residues participate in DNA-protein interactions. SREBP-2 transactivated the intact (-911/+29) apoA-II promoter 1.7-fold and truncated apoA-II promoter segments which contain one, two or three SREBP-2 sites 11- to 17-fold in HepG2 cells. Transactivation of a promoter construct containing the binding site AIIAB and the apoA-II enhancer, which includes the binding site AIIK, was abolished by mutations in element AIIAB. An SREBP-2 mutant defective in DNA binding caused a dose-dependent repression of the apoA-II promoter activity. Repression was also caused by an SREBP-2 mutant which lacks the N-terminal activation domain (residues 1-93) but binds normally to its cognate sites. In contrast, a double SREBP-2 mutant which lacks both the DNA binding and the activation domains has no effect on the apoA-II promoter activity. Overall, the findings suggest that SREBP-2 can transactivate the apoA-II promoter by binding to multiple sites. Furthermore, the repression caused by the DNA binding deficient mutants results from squelching of positive activator(s) which appear to recognize the activation domain of SREBP-2.