On the performance of single-layered neural networks

This paper studies the performance of single-layered neural networks. This study begins with the performance of single-layered neural networks trained using the outer-product rule. The outer-product rule is a suboptimal learning scheme, resulting under certain assumptions from optimal least-squares training of single-layered neural networks with respect to their analog output. Extensive analysis reveals the improvement on the network performance caused by its optimal least-squares training. The effect of the training scheme on the performance of single-layered neural networks with binary output is exhibited by experimentally comparing the performance of single-layered neural networks trained with respect to their analog and binary output.     

Comparison of C-erbB2 (HER-2/Neu) immunohistochemistry results on invasive breast carcinomas. Experience of 2 Pathology departments in Turkey and Greece

OBJECTIVE: To compare c-erbB2 (HER-2/Neu) immunohistochemical staining results obtained in 2 pathology departments and evaluate the reproducibility of staining and assessments. STUDY DESIGN: Ninety primary invasive ductal carcinoma cases constituted the material of this study. For concordant assessment, serial sections from the same tissue blocks were prepared in both Turkey and Greece and were sent to each other. Evaluation of c-erbB2 (HER-2/Neu) staining was done independently in 2 departments by experienced pathologists. Stained slides were evaluated semiquantitatively in Turkey and both semiquantitatively and automatically in Greece. RESULTS: There was complete agreement on staining density in 58 (64.4%) cases in both centers. In 15 cases there were major discordances in staining degrees, and in 17 cases there was a major discordance. Hypothetical treatment decisions based on these results showed that 82% of patients would have been handled the same way. CONCLUSION: Comparison of immunostaining patterns performed at 2 centers provided valuable data that may be used in the development of quality assurance policies. The present study showed the usefulness of multicenter comparative studies in initiating the development of guidelines.     

Reconfiguring gene traps for new tasks using iTRAC

We recently developed integrase-mediated trap conversion (iTRAC) as a means of exploiting gene traps to create new genetic tools, such as new markers for imaging, drivers for gene expression and landing sites for gene and chromosome engineering. The principle of iTRAC is simple: primary gene traps are generated with transposon vectors carrying ϕC31 integrase docking sites, which are subsequently utilized to integrate different constructs into trapped loci. Thus, iTRAC allows us to reconfigure selected traps for new purposes. Two features make iTRAC an attractive approach for Drosophila research. First, its versatility permits the exploitation of gene traps in an open-ended way, for applications that were not envisaged during the primary trapping screen. Second, iTRAC is readily transferable to new species and provides a means for developing complex genetic tools in Drosophilids that lack the facility of Drosophila melanogaster genetics.     

The differential proliferative response of fetal and adult human skin fibroblasts to TGF-β is retained when cultured in the presence of fibronectin or collagen

Background

Transforming growth factor-β is a multifunctional and pleiotropic factor with decisive role in tissue repair. In this context, we have shown previously that TGF-β inhibits the proliferation of fetal human skin fibroblasts but stimulates that of adult ones. Given the dynamic reciprocity between fibroblasts, growth factors and extracellular matrix (ECM) in tissue homeostasis, the present study aims to investigate the role of fibronectin and collagen in the proliferative effects of TGF-β on fetal and adult cells.

Methods

Human fetal and adult skin fibroblasts were grown either on plastic surfaces or on surfaces coated with fibronectin or collagen type-I, as well as, on top or within three-dimensional matrices of polymerized collagen. Their proliferative response to TGF-β was studied using tritiated thymidine incorporation, while the signaling pathways involved were investigated by Western analysis and using specific kinase inhibitors.

Results

Fetal skin fibroblast-proliferation was inhibited by TGF-β, while that of adult cells was stimulated by this factor, irrespective of the presence of fibronectin or collagen. Both inhibitory and stimulatory activities of TGF-β on the proliferation of fetal and adult fibroblasts, respectively, were abrogated when the Smad pathway was blocked. Moreover, inhibition of fetal fibroblasts was mediated by PKA activation, while stimulation of adult ones was effected through the autocrine activation of FGF receptor and the MEK–ERK pathway.

Conclusions

Fetal and adult human skin fibroblasts retain their differential proliferative response to TGF-β when cultured in the presence of fibronectin and unpolymerized or polymerized collagen.

General significance

The interplay between TGF-β and ECM supports the pleiotropic nature of this growth factor, in concordance with the different repair strategies between fetuses and adults. This article is part of a Special Issue entitled Matrix-mediated cell behaviour and properties.     

REP27, a tetratricopeptide repeat nuclear-encoded and chloroplast-localized protein, functions in D1/32-kD reaction center protein turnover and photosystem II repair from photodamage

The goal of this research is elucidation of the molecular mechanism for the unique photosystem II (PSII) damage and repair cycle in chloroplasts. A frequently occurring, irreversible photooxidative damage inhibits the PSII charge separation reaction and stops photosynthesis. The chloroplast PSII repair process rectifies this adverse effect by selectively removing and replacing the photoinactivated D1/32-kD reaction center protein (the chloroplast-encoded psbA gene product) from the massive (>1,000 kD) water-oxidizing and O2-evolving PSII holocomplex. DNA insertional mutagenesis in the model organism Chlamydomonas reinhardtii was applied for the isolation and characterization of rep27, a repair-aberrant mutant. Gene cloning and biochemical analyses in this mutant resulted in the identification of REP27, a nuclear gene encoding a putative chloroplast-targeted protein, which is specifically required for the completion of the D1 turnover process but is not essential for the de novo biogenesis and assembly of the PSII holocomplex in this model green alga. The REP27 protein contains two highly conserved tetratricopeptide repeats, postulated to facilitate the psbA mRNA cotranslational insertion of the nascent D1 protein in the existing PSII core template. Elucidation of the PSII repair mechanism may reveal the occurrence of hitherto unknown regulatory and catalytic reactions for the selective in situ replacement of specific proteins from within multiprotein complexes.     

Mitochondrial fission in endothelial cells after simulated ischemia/reperfusion: role of nitric oxide and reactive oxygen species

Ischemia (I)/reperfusion (RP)-induced endothelial cell (EC) injury is thought to be due to mitochondrial reactive oxygen species (mtROS) production. MtROS have been implicated in mitochondrial fission. We determined whether cultured EC exposure to simulated I/RP causes morphological changes in the mitochondrial network and the mechanisms behind those changes. Because shear stress results in nitric oxide (NO)-mediated endothelial mtROS generation, we simulated I/RP as hypoxia (H) followed by oxygenated flow over the ECs (shear stress of 10dyn/cm(2)). By exposing ECs to shear stress, H, H/reoxygenation (RO), or simulated I/RP and employing MitoTracker staining, we assessed the differential effects of changes in mechanical forces and/or O(2) levels on the mitochondrial network. Static or sheared ECs maintained their mitochondrial network. H- or H/RO-exposed ECs underwent changes, but mitochondrial fission was significantly less compared to that in ECs exposed to I/RP. I/RP-induced fission was partially inhibited by antioxidants, a NO synthase inhibitor, or an inhibitor of the fission protein dynamin-related protein 1 (Drp1) and was accompanied by Drp1 oligomerization and phosphorylation (Ser616). Hence, shear-induced NO, ROS (including mtROS), and Drp1 activation are responsible for mitochondrial fission in I/RP-exposed ECs, and excessive fission may be an underlying cause of EC dysfunction in postischemic hearts.     

Heterozygous loss of epilepsy gene KCNQ2 alters social,repetitive and exploratory behaviors

KCNQ/K_v7 channels conduct voltage‐dependent outward potassium currents that potently decrease neuronal excitability. Heterozygous inherited mutations in their principle subunits K_v7.2/KCNQ2 and K_v7.3/KCNQ3 cause benign familial neonatal epilepsy whereas patients with de novo heterozygous K_v7.2 mutations are associated with early‐onset epileptic encephalopathy and neurodevelopmental disorders characterized by intellectual disability, developmental delay and autism. However, the role of K_v7.2‐containing K_v7 channels in behaviors especially autism‐associated behaviors has not been described. Because pathogenic K_v7.2 mutations in patients are typically heterozygous loss‐of‐function mutations, we investigated the contributions of K_v7.2 to exploratory, social, repetitive and compulsive‐like behaviors by behavioral phenotyping of both male and female KCNQ2^+/? mice that were heterozygous null for the KCNQ2 gene. Compared with their wild‐type littermates, male and female KCNQ2^+/? mice displayed increased locomotor activity in their home cage during the light phase but not the dark phase and showed no difference in motor coordination, suggesting hyperactivity during the inactive light phase. In the dark phase, KCNQ2^+/? group showed enhanced exploratory behaviors, and repetitive grooming but decreased sociability with sex differences in the degree of these behaviors. While male KCNQ2^+/? mice displayed enhanced compulsive‐like behavior and social dominance, female KCNQ2^+/? mice did not. In addition to elevated seizure susceptibility, our findings together indicate that heterozygous loss of K_v7.2 induces behavioral abnormalities including autism‐associated behaviors such as reduced sociability and enhanced repetitive behaviors. Therefore, our study is the first to provide a tangible link between loss‐of‐function K_v7.2 mutations and the behavioral comorbidities of K_v7.2‐associated epilepsy.