Assessment of micronucleus frequency in normal oral mucosa of patients exposed to carcinogens

OBJECTIVE: To assess the presence of micronuclei in exfoliated oral mucosal cells collected from 3 anatomic sites in patients exposed to tobacco and alcohol. STUDY DESIGN: Smears were prepared with normal oral mucosal cells obtained from the lower lip, tongue border and floor of the mouth of 21 controls, 28 tobacco users and 19 tobacco/alcohol users. Slides were stained with Feulgen stain for quantification of micronucleated cells, karyorrhexis and "broken eggs." RESULTS: The groups were similar in terms of the mean number of micronucleated cells and cells undergoing karyorrhexis. In the comparison of anatomic sites, the mean number of cells undergoing karyorrhexis was higher on the lower lip than on the tongue border or floor of the mouth (all groups). A significantly higher number of broken eggs was observed in the control group when compared to the tobacco and tobacco/alcohol groups at all anatomic sites. CONCLUSION: The higher number of broken eggs in patients not exposed to tobacco and/or alcohol suggests that this nuclear alteration may be associated with DNA repair or a healthy mucosa. A trend toward an increased number of micronucleated cells was observed for tobacco and/or alcohol users at all anatomic sites.     

Functional characterization of an insulin-responsive glucose transporter (GLUT4) from fish adipose tissue

Glucose transport across the plasma membrane is mediated by a family of glucose transporter proteins (GLUTs), several of which have been identified in mammalian, avian, and, more recently, in fish species. Here, we report on the cloning of a salmon GLUT from adipose tissue with a high sequence homology to mammalian GLUT4 that has been named okGLUT4. Kinetic analysis of glucose transport following expression in Xenopus laevis oocytes demonstrated a 7.6 +/- 1.4 mM K(m) for 2-deoxyglucose (2-DG) transport measured under zero-trans conditions and 14.4 +/- 1.5 mM by equilibrium exchange of 3-O-methylglucose. Transport of 2-DG by okGLUT4-injected oocytes was stereospecific and was competed by D-glucose, D-mannose, and, to a lesser extent, D-galactose and D-fructose. In addition, 2-DG uptake was inhibited by cytochalasin B and ethylidene glucose. Moreover, insulin stimulated glucose uptake in Xenopus oocytes expressing okGLUT4 and in isolated trout adipocytes, which contain the native form of okGLUT4. Despite differences in protein motifs important for insulin-stimulated translocation of mammalian GLUT4, okGLUT4 was able to translocate to the plasma membrane from intracellular localization sites in response to insulin when expressed in 3T3-L1 adipocytes. These data demonstrate that okGLUT4 is a structural and functional fish homolog of mammalian GLUT4 but with a lower affinity for glucose, which could in part explain the lower ability of fish to clear a glucose load.     

Immunodetection of pectin and arabinogalactan protein epitopes during pollen exine formation of Beta vulgaris L.

Summary. We present the results of ultrastructural and immunocytochemical studies of sugar beet microsporocytes during the developmental phase that begins with the first meiotic metaphase and ends with the formation of young tetrads. The most prominent feature noted during this period of microsporogenesis was the presence of numerous cisternae of endoplasmic reticulum which frequently lie perpendicular to the surface of the plasma membrane and eventually fuse to it. Microscopic observations have been combined with the detection of several carbohydrate epitopes representing pectins and arabinogalactan proteins in the primexine and incipient exine. Pectin domains that possess both low and highly methylesterified epitopes, as well as pectin side chains enriched in (1→4)-β-D-galactose residues, are deposited in this young microspore wall. The epitopes of arabinogalactan protein that bind to JIM13, JIM8, and LM2 antibodies are localised within the callose wall surrounding posttelophase tetrads. The possibility of endoplasmic-reticulum involvement in the synthesis, transport, or metabolism of several microspore wall compounds is discussed. Correspondence and reprints: Institute of Plant Breeding and Acclimatization, Powstańców Wielkopolskich 10, 85-090 Bydgoszcz, Poland.     

The crystal structure of the carboxy-terminal domain of human translation initiation factor eIF5

The carboxy-terminal domain (CTD) of eukaryotic initiation factor 5 (eIF5) plays a central role in the formation of the multifactor complex (MFC), an important intermediate for the 43 S pre-initiation complex assembly. The IF5-CTD interacts directly with the translation initiation factors eIF1, eIF2-beta, and eIF3c, thus forming together with eIF2 bound Met-tRNA(i)(Met) the MFC. In this work we present the high resolution crystal structure of eIF5-CTD. This domain of the protein is exclusively composed out of alpha-helices and is homologous to the carboxy-terminal domain of eIF2B-epsilon (eIF2Bepsilon-CTD). The most striking difference in the two structures is an additional carboxy-terminal helix in eIF5. The binding sites of eIF2-beta, eIF3 and eIF1 were mapped onto the structure. eIF2-beta and eIF3 bind to non-overlapping patches of negative and positive electrostatic potential, respectively.     

Evolution of Cooperation Patterns in Psoriasis Research: Co-Authorship Network Analysis of Papers in Medline (1942–2013)

Background

Although researchers have worked in collaboration since the origins of modern science and the publication of the first scientific journals in the eighteenth century, this phenomenon has acquired exceptional importance in the last several decades. Since the mid-twentieth century, new knowledge has been generated from within an ever-growing network of investigators, working cooperatively in research groups across countries and institutions. Cooperation is a crucial determinant of academic success.

Objective

The aim of the present paper is to analyze the evolution of scientific collaboration at the micro level, with regard to the scientific production generated on psoriasis research.

Methods

A bibliographic search in the Medline database containing the MeSH terms “psoriasis” or “psoriatic arthritis” was carried out. The search results were limited to articles, reviews and letters. After identifying the co-authorships of documents on psoriasis indexed in the Medline database (1942–2013), various bibliometric indicators were obtained, including the average number of authors per document and degree of multi-authorship over time. In addition, we performed a network analysis to study the evolution of certain features of the co-authorship network as a whole: average degree, size of the largest component, clustering coefficient, density and average distance. We also analyzed the evolution of the giant component to characterize the changing research patterns in the field, and we calculated social network indicators for the nodes, namely betweenness and closeness.

Results

The main active research clusters in the area were identified, along with their authors of reference. Our analysis of 28,670 documents sheds light on different aspects related to the evolution of scientific collaboration in the field, including the progressive increase in the mean number of co-authors (which stood at 5.17 in the 2004–2013 decade), and the rise in multi-authored papers signed by many different authors (in the same decade, 25.77% of the documents had between 6 and 9 co-authors, and 10.28% had 10 or more). With regard to the network indicators, the average degree gradually increased up to 10.97 in the study period. The percentage of authors pertaining to the largest component also rose to 73.02% of the authors. The clustering coefficient, on the other hand, remained stable throughout the entire 70-year period, with values hovering around 0.9. Finally, the average distance peaked in the decades 1974–1983 (8.29) and 1984–2003 (8.12) then fell over the next two decades, down to 5.25 in 2004–2013. The construction of the co-authorship network (threshold of collaboration ≥ 10 co-authored works) revealed a giant component of 161 researchers, containing 6 highly cohesive sub-components.

Conclusions

Our study reveals the existence of a growing research community in which collaboration is increasingly important. We can highlight an essential feature associated with scientific collaboration: multi-authored papers, with growing numbers of collaborators contributing to them, are becoming more and more common, therefore the formation of research groups of increasing depth (specialization) and breadth (multidisciplinarity) is now a cornerstone of research success.     

A novel mutation in the mitochondrial tRNAAla gene (m.5636T>C) in a patient with progressive external ophthalmoplegia

We report a heteroplasmic novel mutation m.5636T>C in the mt-tRNA^Ala in a patient with bilateral ptosis and ophthalmoparesis in whom a muscle biopsy showed cytochrome c oxdidase (COX) negative and ragged red fibers. Using laser capture microdissection we have isolated COX negative fibers and COX positive fibers from the muscle of the patient and determined that the mutation load was clearly increased in COX negative muscle fibers. Additionally, the mutated m.5636T nucleotide is conserved in all the mammal and non-mammal species analyzed and might be structurally relevant as it is located in a position involved in the formation of tertiary structure of canonical mitochondrial tRNAs.     

The C-terminal polyproline-containing region of ELMO contributes to an increase in the life-time of the ELMO-DOCK complex

The eukaryotic Engulfment and CellMotility (ELMO) proteins form an evolutionary conserved family of key regulators which play a central role in Rho-dependent biological processes such as engulfment and cell motility/migration. ELMO proteins interact with a subset of Downstream of Crk (DOCK) family members, a new type of guanine exchange factors (GEF) for Rac and cdc42 GTPases. The physiological function of DOCK is to facilitate actin remodeling, a process which occurs only in presence of ELMO. Several studies have determined that the last 200 C-terminal residues of ELMO1 and the first 180 N-terminal residues of DOCK180 are responsible for the ELMO-DOCK interaction. However, the precise role of the different domains and motifs identified in these regions has remained elusive. Divergent functional, biochemical and structural data have been reported regarding the contribution of the C-terminal end of ELMO, comprising its polyproline motif, and of the DOCK SH3 domain. In the present study, we have investigated the contribution of the C-terminal end of ELMO1 to the interaction between ELMO1 and the SH3 domain of DOCK180 using nuclear magnetic resonance spectroscopy and surface plasmon resonance. Our data presented here demonstrate the ability of the SH3 domain of DOCK180 to interact with ELMO1, regardless of the presence of the polyproline-containing C-terminal end. However, the presence of the polyproline region leads to a significant increase in the half-life of the ELMO1-DOCK180 complex, along with a moderate increase on the affinity.