π-Stacking Stopper-Macrocycle Stabilized Dynamically Interlocked [2]Rotaxanes.

The synthesis of mechanically interlocked molecules is valuable due to their unique topologies. With π-stacking intercomponent interaction, e.g., phenanthroline and anthracene, novel [2]rotaxanes have been synthesized by dynamic imine clipping reaction. Their X-ray crystal structures indicate the π-stackings between the anthracene moiety (stopper) on the thread and the (hetero)aromatic rings at the macrocycle of the rotaxanes. Moreover, the length of glycol chains affects the extra π-stacking intercomponent interactions between the phenyl groups and the dimethoxy phenyl groups on the thread. Dynamic combinatorial library has shown at best 84% distribution of anthracene-threaded phenanthroline-based rotaxane, coinciding with the crystallography in that the additional π-stacking intercomponent interactions could increase the thermodynamic stability and selectivity of the rotaxanes.

Assembly of high-symmetry silver(i) alkyl-1,3-diynyl cluster complexes via core transformation.

New tetranuclear supramolecular precursors [(R-C[triple bond, length as m-dash]C-C[triple bond, length as m-dash]C)Ag(PPh3)]4 (R = iPr and chx) are employed to construct three polynuclear silver(i) alkyl-1,3-diynyl cluster complexes (1-3) that bear the same novel trigonal bipyramidal Ag5 core consolidated by silver-ethynide and argentophilic interactions. The present results strongly suggest that the assembly of high-symmetry medium-nuclearity clusters 1-3 is initiated by the accretion of additional Ag(i) ions by the Ag4 template of the precursors through argentophilic (<3.4 Å) interaction, and demonstrate that core transformation is an effective synthetic route to high-symmetry metal clusters.

Assembly of Heterometallic Silver(I)-Copper(I) Alkyl-1,3-diynyl Clusters via Inner-Core Expansion.

New tetranuclear supramolecular precursors [(R-C≡C-C≡C)Ag]4 (R = iPr, tBu, and chx) are employed to construct a series of heterometallic silver(I)-copper(I) alkyl-1,3-diynyl cluster complexes (1-9) that bear a common CuAg3 core (normally trigonal-planar, but can be distorted to pyramidal) consolidated by cupro-argentophilic interaction under 3.12 Å, as found in 1 and 2. The photophysical properties of the multinuclear supramolecular precursors and selected complexes have been investigated. The present results strongly suggest that the assembly of medium-nuclearity clusters 3 to 9 is initiated by accretion of additional Ag(I) ions by the ubiquitous CuAg3 template through argentophilic (<3.4 Å) interaction, with cooperative cuprophilic enhancement (<2.76 Å) in the case of compound 9. To our knowledge, the present study provides the first report of conversion of a Group 11 homonuclear cluster into a heteronuclear one of higher nuclearity via inner-core expansion.

Synthesis of unstable carbides Ag2C(2n) (n = 3, 4) and characterization via crystallographic analysis of their double salts with silver(I) trifluoroacetate.

Two new silver(I) carbides, Ag2C6 and Ag2C8, have been synthesized, and single-crystal X-ray analysis of their crystalline silver(I) trifluoroacetate complexes, Ag2C6·8AgCF3CO2·6H2O, 4(Ag2C6)·16AgCF3CO2·14.5DMSO, and 2.5(Ag2C8)·10AgCF3CO2·10DMSO, provides detailed information on the influence of ligand disposition and orientation of the all-carbon anionic ligands in the construction of multidimensional supramolecular structures, which are consolidated by argentophilic and weak inter-/intramolecular interactions.

Organosilver(I) framework assembly with trifluoroacetate and enediyne-functionalized alicycles.

Eight new silver(I) trifluoroacetate complexes based on a series of designed ligands, each featuring an alicyclic ring with enediyne functionality, have been synthesized and characterized by single-crystal X-ray diffraction. Each ethynide terminal is inserted into an Agn (n = 4-5) basket, leading to the generation of coordination chain or layer structures, but the well shielded ethenyl group does not take part in silver-olefin bonding. Variation in ring size of the alicycles is shown to influence the construction of the organosilver(I) coordination networks, which are consolidated by weak intermolecular interactions in the crystal structures. The effect of adding ancillary N-donor ligands to the reaction system on the coordination and supramolecular network assembly is also investigated.

Prevalence of myopia-related retinal changes among 12-18 year old Hong Kong Chinese high myopes.

PURPOSE: To determine the prevalence and risk factors of myopia-related retinal changes in Hong Kong Chinese adolescents with high myopia. METHODS: A cross-sectional study on Hong Kong Chinese teenage subjects with high myopia was conducted between January 2005 and June 2009. Subjects were recruited via newspaper advertisements, invitation letters to schools, leaflets and posters. Data collected included history related to myopia progression and retinal characteristics. RESULTS: In total, 120 subjects (61 boys and 59 girls) were recruited. The mean age was 14.8 ± 1.6 years (range: 12-18 years). The mean SER of the eyes was -8.41 ± 1.60 D. Ninety four of the 120 adolescents were found to have a retinal change of which 0.8% were sight-threatening, 2.5% were posterior pole changes, and 61.7% were peripheral retinal changes. The five most frequent retinal changes found were optic nerve crescents (52.5%), white-without-pressure (51.7%), lattice degeneration (5.8%), microcystoid degeneration (5%) and pigmentary degeneration (4.2%). After adjusting for myopia over -8 D, age, gender, duration of myopia, family retinal history and intraocular pressure (IOP), binary logistic regressions showed that an axial length longer than 26.5 mm was a significant risk factor for peripheral retinal changes, optic nerve crescents and white-without-pressure. CONCLUSIONS: Peripheral retinal degenerative changes and optic nerve crescent were found in a significant proportion of high myopic teenage subjects. There is increased risk of retinal changes in eyes with an axial length >26.5 mm in 12-18 year-olds.

Systematic investigation of silver-carbon bonding in coordination frameworks with aryl ligands that contain ethynyl and ethenyl substituents.

Single-crystal X-ray diffraction of a series of ten crystalline silver(I)-trifluoroacetate complexes that contained designed ligands, each of which was composed of an aromatic system that was functionalized with terminal and internal ethynyl groups and a vinyl substituent, provided detailed information on the influence of ligand disposition and orientation, coordination preferences, and the co-existence of different types of silver(I)-carbon bonding interactions (silver-ethynide, silver-ethynyl, silver-ethenyl, and silver-aromatic) on the construction of coordination networks that were consolidated by argentophilic and weak inter/intramolecular interactions. The complex AgL10⋅6 AgCF3CO2⋅H2O⋅ MeOH (HL10 = 1-{[4-(prop-2-ynyloxy)-3-vinylphenyl]ethynyl}naphthalene) is the first reported example that exhibits all four kinds of silver(I)-carbon bonding interactions in the solid state.

Enlargement of globular silver alkynide cluster via core transformation.

The multinuclear metal-ligand supramolecular synthon R-C≡C⊃Ag(n) (R = alkyl, cycloalkyl; n = 3, 4, 5) has been employed to construct two high-nuclearity silver ethynide cluster compounds, [Cl(6)Ag(8)@Ag(30)((t)BuC≡C)(20)(ClO(4))(12)]·Et(2)O (1) and [Cl(6)Ag(8)@Ag(30)(chxC≡C)(20)(ClO(4))(10)](ClO(4))(2)·1.5Et(2)O (chx = cyclohexyl) (2), that bear the same novel Cl(6)Ag(8) central core. The synthesis of 1 made use of [Cl@Ag(14)((t)BuC≡C)(12)]OH as a precursor, and its reaction with AgClO(4) in CH(2)Cl(2) resulted in an increase in nuclearity from 14 to 38. The results presented here strongly suggest that the formation of multinuclear silver ethynide cage complexes 1 and 2 proceeds by a reassembly process in solution that involves transformation of the encapsulated chloride template within a Ag(14) cage into a cationic pseudo-O(h) Cl(6)Ag(8) inner core, leading to the generation of a much enlarged Cl(6)Ag(8)@Ag(30) cluster within a cluster. To our knowledge, this provides the first example of the conversion of a silver cluster into one of higher nuclearity via inner-core transformation.

Retinal thickness in myopic and non-myopic eyes.

PURPOSE: To investigate the retinal thickness profile in myopic and non-myopic eyes. METHODS: The retinal thickness profile of 30 myopic eyes [spherical equivalent error (SER) between -6.00 and -13.63 D] and 31 non-myopic eyes (SER between +2.75 and -0.50 D) were measured using the Stratus OCT (Carl Zeiss Meditec, Dublin, CA, USA). Two scan types were used: the Macular Thickness Map and the Customized Line Scan for a central 80° horizontal retinal thickness profile. RESULTS: At foveal center and fovea, myopic eyes had a thicker retina than the non-myopic group (p = 0.002 and 0.044, respectively). At other zones of the macula, the retina was significantly thinner in myopic eyes compared to non-myopic eyes (p < 0.01, unpaired t-test). From 40° nasal to 40° temporal retina, a general reduction of retinal thickness was observed across the myopic retina compared to the non-myopic retina except at 20° nasal to fixation. CONCLUSIONS: There was general reduction in retinal thickness within the horizontal central 80° in myopic eyes compared with non-myopic eyes.

MECP2 mutations in Malaysian Rett syndrome patients.

INTRODUCTION: Rett syndrome (RS) is a severe neurodevelopmental disorder characterised by normal neurological development followed by progressive developmental regression. The X-linked dominant inheritance of RS has been mapped to the gene that encodes the methyl-CpG-binding protein-2 (MECP2) at Xq28. In the present study, denaturing high-performance liquid chromatography (DHPLC) was used to detect mutations in the MECP2 gene in 20 Malaysian RS patients. METHODS: Polymerase chain reaction (PCR) was carried out to amplify the MECP2 coding exons 2, 3, and 4 in a total of eight reactions (exons 2, 3a, 3b, 4a, 4b, 4c, 4d and 4e). Subsequently, PCR products were analysed by DHPLC. RESULTS: Mutations in the MECP2 gene were detected in 13 of the 20 (65 percent) RS patients. 11 patients had mutations in exons 3b and 4a and six patients had mutations in exon 4c. These mutations were mainly concentrated in the methyl-CpG-binding domain and the transcriptional-repression domain. CONCLUSION: Through the use of post-PCR high-performance liquid chromatography, 65 percent of 20 RS patients were found to have mutation(s) in the MECP2.

Use of the Optomap with lid retraction and its sensitivity and specificity.

BACKGROUND: Optomap uses the ultra-wide field scanning laser ophthalmoscopy to provide retinal examination. It permits fundus examination without the use of a mydriatic, which is more comfortable for the patients. This paper determines the sensitivity and specificity of the Optomap for detecting retinal signs under non-mydriatic conditions. METHODS: Fifty-four eyes identified with retinal/choroidal signs and eight normal eyes were recruited from 31 Hong Kong Chinese subjects. Photo-documentation of fundal changes was obtained with the Optomap under non-mydriatic conditions before a dilated fundus examination by a clinician using standard procedures. The eyelid was retracted using a cotton bud when necessary. Dilated fundus examinations were performed by another clinician using binocular indirect ophthalmoscopy and slitlamp biomicroscopy with a fundus lens. The Optomap images were evaluated by four other investigators under masked condition. The International Classification of Disease, Ninth Revision (ICD-9-CM) was adopted for recording retinal features. Screening results were compared with those obtained using the dilated fundus examination as the gold standard. RESULTS: The cotton bud method for eyelid retraction showed an improvement in the area of retina that could be visualised. The sensitivity and specificity of the Optomap averaged 76.4 and 71.9 per cent, respectively. Some fundal signs were missed by all observers in the Optomap but not with the biomicroscope. These included white-without-pressure, lattice degeneration, paramacular drusen and pigmentary changes at central fundus. CONCLUSION: Optomap serves as a reliable screening tool for fundus examination especially because it covers a much wider area of the peripheral retina than other digital instruments for fundus photography.

Biological properties of TW01 cells expressing latent membrane protein-1 gene of EBV-derived from nasopharyngeal carcinoma cells at different stages of malignancy.

BACKGROUND AND AIM: Epstein-Barr virus (EBV), a human gammaherpesvirus is intimately associated with nasopharyngeal carcinoma (NPC), with the incidence of the virus detected in malignant tissues being close to 100% in NPC endemic areas. The viral latent gene, latent membrane protein 1 (LMP1), has all the typical characteristics of an oncogene and extensive studies have shown beyond doubt its abilities in cellular transformation giving rise to malignant phenotypes. The present study compares the gene sequence and biological properties of LMP1 gene derived from two patients with different stages of NPC--one presented with dysplastic, pre-malignant lesion and the other with malignant lesion. METHODS: The sequences of the LMP1 genes derived from pre-malignant (NORLMP1) and malignant (NPCLMP1) tissues were compared. NORLMP1 and NPCLMP1 were expressed in TW01 cells and their biological properties conferred were assessed in terms of in vitro invasion capability, ability to resist apoptosis and regulation of E-cadherin (CDH1) expression. RESULTS: NORLMP1 and NPCLMP1, possessed numerous amino acid changes with respect to the wild-type B95.8 LMP1. Both LMP1 variants demonstrated distinct biological properties when expressed in TW01 cells. NORLMP1-expressing TW01 cells exhibited more aggressive phenotypes than the NPCLMP1-expressing counterpart in terms of invasive ability, resistance to stimuli-induces apoptosis and regulation of CDH1 expression. CONCLUSION: It could be inferred from the present study that LMP1 genes derived from two patients with different stages of NPC differed in their gene sequences that manifested in distinct biological properties.

Human leukocyte class I antigen alleles A2 and A11 are not associated with nasopharyngeal carcinoma in West Malaysia.

INTRODUCTION: Nasopharyngeal carcinoma (NPC) is the second most common cancer among Malaysian Chinese males. We determined the frequencies of 17 human leukocyte antigens (HLA), HLA-A and HLA-B, alleles in 88 Malaysian Chinese with NPC. METHODS: Using polymerase chain reaction sequence-specific primers, the frequencies of 17 HLA-A and HLA-B alleles were analysed. They were A1, A2, A11, A31, A32, A33, B8, B13, B27, B38, B39, B44, B46, B55, B58, B61 and B71. RESULTS: Three of the 17 alleles were detected in NPC patients. They were A1 (0.6 percent), A2 (56.3 percent) and A11 (43.2 percent). Three of the 17 alleles were detected in age- and sex-matched healthy individuals. They were A2 (50.0 percent), A11 (50.0 percent) and B27 (4.7 percent). The A2 and A11 alleles were evenly distributed in both groups, while A1 was only found in one NPC patient and B27 exclusively in healthy individuals. CONCLUSION: We conclude that A1 is very rare, and A2, A11, A31, A32, A33, B8, B13, B38, B39, B44, B46, B55, B58, B61 and B71 alleles have no associations with the occurrence of NPC in Malaysia, while allele B27 is negatively associated.

Evaluation of plasma Epstein-Barr virus DNA load as a prognostic marker for nasopharyngeal carcinoma.

INTRODUCTION: Nasopharyngeal carcinoma (NPC) is an important cancer in Malaysia and is one of the major causes of cancer mortality in this country. This study evaluates the diagnostic and prognostic values in the quantitative relationship between the cell-free Epstein-Barr virus (EBV) deoxyribonucleic acid (DNA) load and the tumour burden. METHODS: Blood plasma from 18 untreated NPC patients, 20 NPC patients who had been treated with radiotherapy, and 12 healthy individuals were evaluated. EBV copy number was determined following DNA extraction using real-time quantitative polymerase chain reaction. RESULTS: The cell-free EBV DNA load was shown to be proportionately related to the presence of malignant disease. While the EBV copy number in untreated NPC patients had a median of 2,043 copies/ml, viral load in plasma of healthy controls was significantly lower (median of 0 copy/ml). A significant decrease in EBV load was observed in patients who had undergone radiotherapy while a high viral load indicated in one patient correlated to tumour relapse and presence of distant metastasis upon clinical investigation. CONCLUSION: The blood plasma EBV DNA load was shown to be proportionately related to the presence of malignant disease. This preliminary study underscores the prognostic value of cell-free EBV DNA quantification.

Cypris habitat selection facilitated by microbial films influences the vertical distribution of subtidal barnacle Balanus trigonus.

The potential driving force(s) of the vertical distribution of subtidal barnacle Balanus trigonus Darwin were investigated using both field and laboratory experiments. Early juveniles (approximately 24 h old) placed in intertidal [approximately 0.5 m above mean low water level (MLWL)] and subtidal (approximately 3 m below MLWL) habitats survived equally well, indicating that the intertidal absence of B. trigonus in Hong Kong waters was not determined by differential mortality. However, enhanced attachment of cyprids in subtidal habitats indicated the importance of differential larval choice in determining their vertical distribution. In the laboratory, cyprids preferred to attach in response to subtidal microbial films, which may implicate microbial films as a primary cue in driving the adult vertical distribution. Microbial films developed in these two habitats differed in their biomass (= total organic carbon), abundance of bacteria and diatoms (determined by fluorescence microscopy), and bacterial diversity (determined by DNA fingerprinting analysis). For example, 6-day films in subtidal habitat had a significantly higher biomass than in films from intertidal habitat (P < 0.05). There was no difference in the biomass of films from these two habitats in 9-day films (P > 0.05); however, bacterial abundance was greater in subtidal films than in intertidal films, irrespective of the age of the film, although there was no difference in diatom abundance in films from these two habitats. Neither the abundance of bacteria and diatoms nor the biomass correlated with the attachment preferences of cyprids. This study has not provided any data to prove the existence of inductive and inhibitive (to cyprid attachment) bacterial species in subtidal and intertidal films, respectively; however, results indicate that bacterial community provided qualitative information that might explain the preferential attachment of B. trigonus cyprids in subtidal habitat.

Mutational analysis of p53 and RB2/p130 genes in Malaysian nasopharyngeal carcinoma samples: a preliminary report.

This study reports the results of mutation detection of tumour suppressor genes, p53 and RB2/p130 genes in Malaysian nasopharyngeal carcinoma (NPC) studied by PCR-CSGE analysis and direct DNA sequencing method. Frequent sites of mutation in both genes (exons 5-8 of p53 and exons 19-21 of RB2/p130) were examined. Thirty-six NPC blood samples and three NPC cell lines were investigated for the presence of mutations. No mutation of p53 and RB2/p130 genes was identified in any of the blood samples. Nonetheless, there was an identical G-->4 C nucleotide change at codon 280 of p53 gene in all the cell lines. A larger study that includes biopsy tissues should be carried out to provide a more in-depth look into the pathogenesis of NPC in Malaysia.

Sensitization profiles of Malaysian and Singaporean subjects to allergens from Dermatophagoides pteronyssinus and Blomia tropicalis.

BACKGROUND: The house dust mites Dermatophagoides pteronyssinus (Der p) and Blomia tropicalis (Blo t) are the most common house dust mite species in Southeast Asia. To date, there have only been a few studies on the sensitization profile of the general populations in Southeast Asia to house dust mites. The aim of this study was to determine the profiles of Der p and Blo t sensitization among Singaporean and Malaysian subjects. METHODS: Enzyme-linked immunosorbent assay was used to detect specific IgE to Der p and Blo t mite crude extracts as well as purified Der p 1, Der p 2 and Blo t 5 allergens. Sera used were from 229 Singaporean subjects (124 with rhinitis, 105 without rhinitis) and 143 Malaysian subjects (94 adults and 49 children with asthma). RESULTS: The sensitization profile of rhinitis subjects to the dust mite allergens used in this study was as follows: Blo t extract positive: 91/124 (73%); Blo t 5 positive: 62/124 (50%); Der p extract positive: 61/124 (49%); Der p 1 positive: 53/124 (43%); Der p 2 positive: 45/124 (36%). The nonrhinitis subjects' sensitization profile was as follows: Blo t extract positive: 60/105 (57%); Blo t 5 positive: 24/105 (23%); Der p extract positive: 38/105 (36%); Der p 1 positive: 14/105 (13%); Der p 2 positive: 17/105 (16%). The study of Malaysian asthmatic adults showed that 39% of them were sensitized to Der p 1, 32% to Der p 2 and 37% to Blo t 5. Among the asthmatic children, sensitization to Blo t 5, Der p 1 and Der p 2 was 90, 57 and 39%, respectively. CONCLUSION: This study clearly revealed that dual sensitization to B. tropicalis and D. pteronyssinus is common in the general populations of Singapore and Malaysia. Sensitization to Blo t 5 is more prevalent than to Der p 1 and Der p 2.