Polyethylenes Having Well‐Defined Bimodal Molecular Weight Distributions Formed with Bis(phenoxy‐imine) Zr Complexes

Summary: Bis(phenoxy‐imine) Zr complexes with MAO activation can produce polyethylenes with well‐defined bimodal molecular weight distributions. Polymerization behavior indicates that minor changes in the ligand structures can have a significant effect on the modality of the resulting polyethylenes. Although there is no direct relationship between the bimodal catalytic behavior and the structure of a precatalyst complex in solution, a precatalyst complex having a methyl or methoxy group para to the phenoxy‐oxygen inclined to exhibit bimodal behavior whereas that with a pentafluorophenyl group on the imine‐nitrogen displayed unimodal behavior. Polymerization results suggest that bimodal behavior is linked to the presence of two kinds of cationic active species, which arise from different modes of ligand coordination. A qualitative correlation was found between the calculated amounts of possible cationic active species and the uni‐ and bimodal catalytic behavior. Based on the results obtained, we concluded that the bimodal polyethylenes are produced by two kinds of cationic active species having two available cis‐located sites with cis‐N, trans‐O and cis‐N, cis‐O arrangements. The results introduced herein are rare examples of the production of well‐defined bimodal polyethylenes using a single precatalyst.

Bis(phenoxy imine) Zr complexes can produce well‐defined bimodal polyethylenes.     

Priming effect of RANTES on eosinophil oxidative metabolism

Background RANTES has been shown to possess chemotactic activity for eosinophils, which have also been considered to play a role in allergic inflammation through reactive oxygen species. Thus, in this study, we examined the effect of RANTES on radical oxygen products from eosinophils.
Methods Purified eosinophils by CD16-negative selection or an eosinophilic cell line (EoL-1) were incubated with or without RANTES (2.5 x 10⁻⁶). To the mixture of eosinophils and luminol, calcium ionophore (A23187) or opsonized zymosan (OZ) was added, and radical oxygen products were determined by luminol-dependent chemiluminescence for 600 s.
Results Eosinophil-mediated radical oxygen products of untreated eosinophils produced with A23187 gave a peak value of 14.09 + 2.40 (mean±SE, n = 12) relative light units (RLU) and an integrated value of 3232.20 + 513.09 RLU. However, with treatment with RANTES, a peak value of 18.66 + 2.40 RLU and an integrated value of 5301.05 ±561.02 RLU were obtained. Eosinophil oxidative metabolism-induced A23187 or OZ was apparently augmented by the preincubation with RANTES. In addition, the radical oxygen products of EoL-1 showed similar results.
Conclusions Thus, we concluded that RANTES may play an important role the pathogenesis of allergic inflammation through its involvement in eosinophil activation, as evidenced by oxygen products, as well as in selective eosinophil infiltration as selective eosinophil chemoattractant.     

Molecular epidemiology of adenoviruses isolated from hospitalized children with severe lower acute respiratory infection in Santiago, Chile

Genome analysis was performed on 69 adenovirus isolates from pharyngeal secretions of young children hospitalized with severe lower acute respiratory disease in Santiago, Chile, between 1984 and 1986. As expected, most isolated strains belonged to subgenus B (68.1%). Among the isolates of 1984, Ad7c was the dominant genotype (12 out of 23). The majority of isolates of 1986 were of the recently described genomic variant 3f.     

Genomic characterization of KIR2DL4 in families and unrelated individuals reveals extensive diversity in exon and intron sequences including a common frameshift variation occurring in several alleles

The KIR2DL4 gene including a portion of exon 1 through exon 9 was sequenced from two families and eight cell lines from the International Histocompatibility Workshop (IHWS). Two known alleles and eight variants were detected. Overall, there were five synonymous and three non-synonymous changes when the variants were compared to the coding sequences of the most closely related known alleles plus a common frameshift change in five of the variant alleles. Alignment of the new variants with all known alleles showed that the regions encoding the extracellular region and the cytoplasmic tail were the most polymorphic. Two non-synonymous changes, P146H and L161V, occurred in an extracellular immunoglobulin-like domain. Five of the eight variants had a single adenine deletion in the exon encoding the transmembrane region, potentially resulting in a truncated protein lacking the cytoplasmic tail. The distribution of the deletion variant among many KIR2DL4 alleles may explain the high frequency of this variation in the population. Four of the eight consanguineous IHWS cell lines were found to be heterozygous for KIR2DL4 carrying two alleles that differed from one another by a few nucleotide substitutions. Analysis of intron sequences in the families revealed the nature and distribution of interspersed repeat elements which comprise 46% of the KIR2DL4 nucleotide sequence and consist of 12 elements including six SINEs (13.73% of the total length), one LINE (12.41%), and five LTR elements (19.51%). The results revealed the presence of extensive diversity in the KIR2DL4 gene. This is the first extensive report providing both exon and intron data in related individuals.     

“Smart” Materials for Biosensing Devices: Cell-Mimicking Supramolecular Assemblies and Colorimetric Detection of Pathogenic Agents

Mimicking cell membrane and the biomolecular recognition associated with membranes represents a great technical challenge, yet it has opened doors to innovative diagnostic and therapeutic methods. Our work has focused on design and synthesis of a class of smart materials exploiting biological principals for use in biosensors: these materials are functional polymeric assemblies that mimic the cell membrane and conveniently report the presence of pathogens with a color change. Biologically active cell membrane components are incorporated into conjugated polymers with desirable optical properties and the binding of the target molecules onto the material triggers conformational and electronic shifts that are reflected in a chromatic change (a so-called biochromic shift) that is conveniently observed and recorded. Langmuir–Blodgett thin films and vesicle bilayers provide ideal configurations for precise delivery of the biological binding entity to the sensing interface, and for control of molecular orientation for effective biomolecular interaction. Polydiacetylenic membrane-mimicking materials containing cell surface receptor gangliosides and sialic acid residues, respectively were formulated into these architectures and used for colorimetric detection of bacterial toxins and influenza virus. One advantage of these biochromic conjugated polymer (BCP) sensors is that their molecular recognition and signal transduction functionalities are resident in a single functional unit, making them amenable to convenient microfabrication and use.     

Bronchopulmonary Dysplasia: A Correlative Study by Light, Scanning, and Transmission Electron Microscopy

The sequential stages of bronchopulmonary dysplasia occurring in 18 infants after intensive respiratory therapy supplemented by oxygen in high concentrations were studied by correlative light, scanning, and transmission electron microscopy. Infant survival ranged from 3 to 225 days. The earliest stage was an exudative reaction with a predominance of hyaline membranes. This merged with a subacute reparative response that was replaced by a chronic fibroproliferative stage in infants of longest survival; this stage was complicated by pulmonary fibrosis and emphysema. Correlative scanning and transmission electron microscopy demonstrated that type 2 pneumocytes contributed significantly to the reparative fibroproliferative response by organization of hyaline membranes and reepithelialization of damaged septal walls.     

The Origin and Evolution of Human T-Cell Lymphotropic Virus Types I and II

Studies on human T-cell lymphotropic virus types I (HTLV-I) and II (HTLV-II) are briefly reviewed from the viewpoint of molecular evolution, with special reference to the evolutionary rate and evolutionary relationships among these viruses. In particular, it appears that, in contrast to the low level of variability of HTLV-I among different isolates, individual isolates form quasispecies structures. Elucidating the mechanisms connecting these two phenomena will be one of the future problems in the study of the molecular evolution of HTLV-I and HTLV-II.