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Biomedical subjects

S Hong

Publications and source records attributed to S Hong.

At least 19 recordsLinked to original sources
PubMed2006

Dual reporter genes enabling cell tracing with viable and reliable selection of various cell types.

Dual reporter genes driven by either a ubiquitous cytomegalovirus (CMV) or a neuro-specific tubulin alpha1 promoter (Talpha1) were constructed. The new genes, CMV (pCMV-GL) or Talpha1 promoter-driven GFP-LacZ (pTalpha1-GL), robustly expressed the fused GFP-LacZ protein reporting constitutive expressions in various cell types including CHO cells, loach and chicken embryos, and neuro-specific expression in differentiating mouse embryonic stem cells, respectively. The dual reporter genes thus provide a versatile tool for the studies of gene expression, cell lineage within the embryo and possibly the fate of stem cells in transplantation experiment, thus facilitating different analyses depending on the experimental purposes.

Animals↗
PubMed2005

Parametric amplification of matter waves in periodically translated optical lattices.

We observe the sudden growth of small classes of Bloch waves from atomic Bose-Einstein condensates held in periodically translated optical lattices. The effect is explained by narrowband parametric amplification of Bloch waves from noise, due to phase-matched scattering of atom pairs out of the condensate. Amplification occurs above a well-defined modulation threshold, described by dynamic shaping of single-particle band structure.

Journal Article↗
PubMed2005

Essential role of extracellular matrix (ECM) overlay in establishing the functional integrity of primary neonatal rat Sertoli cell/gonocyte co-cultures: an improved in vitro model for assessment of male reproductive toxicity.

The development of in vitro models for testicular toxicity may provide important tools for investigating specific mechanisms of toxicity in the testis. Although various systems have been reported, their application in toxicological studies has been limited by the poor ability to replicate the complex biochemical, molecular, and functional interactions observed in the testis. In the present study, we evaluated a significantly improved Sertoli cell/gonocyte co-culture (SGC) system that employs a 3-dimensional extracellular matrix Matrigel (ECM) applied as an overlay instead of a substratum. We explored the dose- and time-dependent effects of the addition of such an ECM overlay on cytoskeletal and morphological changes in the SGC system, and the resulting effects on cellular integrity. Furthermore, we correlated the latter effects with the ECM-dependent modulation of stress and survival signaling pathways and, most critically, the expression levels of the spermatogonia-specific protein, c-Kit. Finally, we applied this co-culture system to investigate the dose- and time-dependent effects on the morphology and induction of apoptosis of cadmium. We observed that the dose-dependent addition of an ECM overlay led to an enhanced attachment of Sertoli cells and facilitated the establishment of SGC communication and cytoskeletal structure, with a dramatic improvement in cell viability. The latter was consistent with the observed dose- and time-dependent modulation of both stress signaling pathways (SAPK/JNK) and survival signaling pathways (ERK and AKT) in the presence of the ECM overlay. Furthermore, the dose-dependent stabilization of c-Kit protein expression confirmed the functional integrity of this co-culture system. We conclude that this modified SGC system will provide investigators with a simple, efficient, and highly reproducible alternative in the screen for testicular cell-specific cytotoxicity and the assessment of molecular mechanisms associated with both normal development and reproductive toxicity induced by environmental toxicants.

Actins↗
PubMed2005

Multinucleation of koilocytes is in fact multilobation and is related to aberration of the G2 checkpoint.

AIMS: To clarify the fine structure of koilocytes and correlate this with genetic aberration of the G2 checkpoint. METHODS: Three dimensional reconstruction from confocal fluorescent images, together with functional assays for key molecules of the G2 checkpoint-cdc2 and cyclin B1-was performed in human uterine cervical samples. After confirming 22 human papillomavirus (HPV) types using a DNA chip from 30 cervical swabs, previously confirmed as 15 cervical low grade and 15 high grade intraepithelial lesions, the activity of molecules involved in the G2 checkpoint was evaluated using western blotting for cyclin B1, cdc2, and phospho-cdc2 (Y15 and T161), a nuclear extraction fractional assay, and a reverse transcription polymerase chain reaction assay. In addition, three dimensional confocal image restoration was performed on confirmed cervical intraepithelial neoplasia tissue samples. RESULTS: T161 phospho-cdc2 and cyclin B1 expression was higher in HPV infected cervical lesions than in normal samples. Immunofluorescence, revealed that cyclin B1 was present predominantly in the nuclei of HPV infected cells, confirming the results of the nuclear fractional assay. On restoration of three dimensional confocal images, the multinucleation of koilocytes was revealed to be multilobation of a single nucleus, rather than true multinucleation. This multilobation appeared to be associated with chromosomal instability and aberration of the G2 checkpoint. CONCLUSIONS: The multiple nuclei of koilocytes are in fact multilobation of a single nucleus, and this phenomenon is associated with upregulation of gene products related to the G2 checkpoint.

Blotting, Western↗
PubMed2005

Impact of RO-desalted water on distribution water qualities.

A large-scale pilot distribution study was conducted to investigate the impacts of blending different source waters on distribution water qualities, with an emphasis on metal release (i.e. corrosion). The principal source waters investigated were conventionally treated ground water (G1), surface water processed by enhanced treatment (S1), and desalted seawater by reverse osmosis membranes (RO). Due to the nature of raw water quality and associated treatment processes, G1 water had high alkalinity, while S1 and RO sources were characterized as high sulfate and high chloride waters, respectively. The blending ratio of different treated waters determined the quality of finished waters. Iron release from aged cast iron pipes increased significantly when exposed to RO and S1 waters: that is, the greater iron release was experienced with alkalinity reduced below the background of G1 water. Copper release to drinking water, however, increased with increasing alkalinity and decreasing pH. Lead release, on the other hand, increased with increasing chloride and decreasing sulfate. The effect of pH and alkalinity on lead release was not clearly observed from pilot blending study. The flat and compact corrosion scales observed for lead surface exposed to S1 water may be attributable to lead concentration less than that of RO water blends.

Calcium Carbonate↗
PubMed2004

Insulin-like growth factor-1 receptor signaling in 3T3-L1 adipocyte differentiation requires lipid rafts but not caveolae.

Previously, we have found that lipid rafts/caveolae were essential for insulin-like growth factor-1 (IGF-1) receptor signaling during 3T3-L1 preadipocytes differentiation induction. However, it was not identified as to which of the membrane lipid-ordered microdomains mediates the receptor signal. Using small double-stranded RNA-mediated interference (RNAi), we successfully suppressed the caveolin-1 protein expression. In cells stably transfected with vector expressing small interfering RNA (siRNA) fragment, no caveolin-1 protein or caveola was detected. On the other hand, removal of caveolin-1 did not affect the caveolinless lipid rafts or the localization of IGF-1 receptor in lipid rafts on plasma membrane. IGF-1 receptor signal transduction and induced cellular differentiation were normal in RNAi cells with only lipid rafts. Furthermore, these IGF-1 receptor signaling events were still sensitive to the cholesterol-binding reagents. Thus, our results suggest that lipid rafts are sufficient for IGF-1 receptor signaling and the recruitment of signal molecules by caveolin-1 is not essential for IGF-1 receptor signaling.

3T3-L1 Cells↗
PubMed2004

Diabetic autonomic neuropathy: evidence for apoptosis in situ in the rat.

We examined the hypothesis that activation of the apoptosis cascade occurs relatively early in diabetes mellitus affecting three distinct neuronal populations that are involved in regulating gut function: (i) dorsal root ganglion (DRG), (ii) vagus nodose ganglion and (iii) colon myenteric plexus. A validated streptozotocin-induced diabetic rat model and age-matched healthy controls were studied. After 4-8 weeks of diabetes the animals were anaesthetized, fixed in situ and the relevant tissues removed. After 1 month of diabetes some animals were treated with insulin for 2 weeks to restore euglycaemia. Apoptosis was measured using immunohistochemical detection of activated caspase-3 and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling (TUNEL)-positive cells in adjacent sections in neurones (PGP 9.5-positive cells). The level of apoptosis was confirmed using double-label assessment of caspase-3 and TUNEL in DRG preparations. Caspase-3 immunoreactive neurones demonstrated a range in staining intensity. When all grades of staining were included, 6-8% of the DRG, nodose ganglia and myenteric neurones were immunoreactive in the preparations from diabetic rats compared with 0.2-0.5% in controls. Neurones staining positive for both caspase-3 and TUNEL accounted for 1-2% of the total neuronal population in all three preparations in diabetic rats compared with 0.1-0.2% in controls (P < 0.05). Insulin treatment reversed the percentage of TUNEL-positive neurones in diabetic rats to control levels. Activation of the apoptosis cascade occurs relatively early in diabetic autonomic neuropathy and may contribute to the pathophysiology of this disorder.

Animals↗
PubMed2003

Effect of methylmercury on midbrain cell proliferation during organogenesis: potential cross-species differences and implications for risk assessment.

5'-bromodeoxyuridine (BrdU) labeling was employed to explore the effects of methylmercury (MeHg) on cell cycle kinetics in the developing rat midbrain during gestational days (GDs) 11 to 14. Contrary to what has been previously reported in mice, no effects of MeHg on cell cycle kinetics were observed up to embryonic brain concentrations of 3-4 microg/g. The absence of an effect was confirmed using stereology and counts of midbrain cell number. Treatment with colchicine, the positive control, resulted in significant effects on cell cycle kinetics in the developing rat midbrain. The parallelogram method, borrowed from genetic toxicology, was subsequently used to place the data obtained in the present study in the context of previously collected in vitroand in vivo data on MeHg developmental neurotoxicity. This required developing a common dose metric (microg Hg/g cellular material) to allow in vitro and in vivo study comparisons. Evaluation suggested that MeHg's effects on neuronal cell proliferation show a reasonable degree of concordance across mice, rats, and humans, spanning approximately an order of magnitude. Comparisons among the in vivo data suggest that humans are at least or more sensitive than the rodent and that mice may be a slightly better model for MeHg human developmental neurotoxicity than the rat. Such comparisons can provide both a quantitative and a qualitative framework for utilizing both in vivo and in vitro data in human health risk assessment.

Animals↗
PubMed2003

Anomalous surface diffusion in nanoscale direct deposition processes.

We report the first observation of anomalous diffusion in nanometer scale direct deposition processes utilizing dip-pen nanolithography (DPN). DPN permits quite general nanostructure patterns to be drawn on flat surfaces. Here we demonstrate experimentally, and discuss theoretically, the situation in which the molecular ink in DPN binds weakly to the surface. We observe, for the weak-binding case of 1-dodecylamine on mica, that anomalous diffusion occurs, leading to nearly fractal deposition patterns.

Journal Article↗
PubMed2002

Methylmercury distribution in the pregnant rat and embryo during early midbrain organogenesis.

BACKGROUND: The period of neurogenesis represents a window of susceptibility for in utero methylmercury (MeHg) exposure. This study examined the toxicokinetics of potentially neurotoxic doses of MeHg during neurogenesis in the developing rat to provide additional information in the areas of mercury speciation and inter-study variability. METHODS: Pregnant Sprague-Dawley rats were dosed s.c. with 5-22 mg/kg MeHg on Day 11 of gestation to target rapidly dividing cells of the developing midbrain. Maternal liver, kidney, skin, blood, placenta, and the embryonic body and brain were evaluated for total and inorganic mercury content at 24, 48, and 72 hr after dosing. Tissue Hg partitioning ratios derived from our data were then compared to those derived from previous studies. RESULTS: Mercury was present in all tissues examined by 24 hr after dosing, and levels remained relatively stable over the subsequent 2 days in most tissues. The exceptions were the maternal blood and kidney, in which total mercury decreased significantly over the three days after dosing. Inorganic mercury concentrations were similarly stable over time. At maternal MeHg doses above 12 mg/kg, non-linearities were observed in mercury accumulation in the embryo, placenta and maternal liver. The mercury tissue partitioning coefficients ranged from 0.09 for maternal blood:embryo to 1.97 for maternal blood:kidney. CONCLUSIONS: Our observations at the 5 mg/kg dose were consistent with those of previous studies that involved evaluations at slightly later gestational times. The estimates of tissue partitioning coefficients we derived using multiple studies provide valuable insight into the effects of inter-study variability.

Animals↗
PubMed2002

Use of natural zeolite to enhance nitrification in biofilter.

To enhance nitrification, natural zeolite and activated carbon were tested as a media in a biofilter to treat wastewater containing relatively high concentrations of TKN. Using those media, the adsorption isotherms for ammonium ion were compared; the K values for natural zeolite and activated carbon were found to be 0.5117 and 0.0006, respectively. In comparison of the performance of the two media, two identical, lab-scale biofilters were then operated for 4 months. The effect of NH3-N loading rates on the performance was investigated. The results showed that higher NH3-N removal efficiency and faster nitrification were achieved in the biofilter with natural zeolite throughout the experimental period. Nitrosomonas and Nitrobacter, two principal nitrifiers, in biofilm grown on two different media were counted and compared. Nitrobacter which is the more fragile of the two principal nitrifiers was outgrown in the biofilm on natural zeolite media. The reason for this may be due to the ammonium ion exchanging capacity of natural zeolite which provided the favorable environment for Nitrobacter.

Biodegradation, Environmental↗
PubMed2002

Genotype associations of factor VII gene with plasma factor VII coagulant activity and antigen levels in healthy Chinese.

A raised plasma factor VII (FVII) level is one of the risk factors for coronary artery disease. The R353Q polymorphism at codon 353 and the 10 base pair (bp) insertion (0/10 bp) polymorphism of the FVII gene have been reported to be associated with plasma FVII levels in several populations. We investigated these two polymorphisms in 209 male and 214 female healthy Chinese. The allele frequencies of 10 bp and Q were 0.036 and 0.045, respectively. Strong linkage disequilibrium was observed between these two sites (Delta = 0.85, P < 0.001). There were significant genotype associations of these two loci with FVII coagulant activity (FVIIc) and antigen (FVIIAg) levels. Heterozygous individuals had lower FVIIc and FVIIAg levels than those homozygous for the common alleles. When analyzed separately by gender, the 0/10 bp polymorphism was strongly associated with FVIIAg levels in males and females. However, both polymorphisms were significantly associated with FVIIc levels only in the females. The effect of 0/10 bp polymorphism predominated over that of the R353Q polymorphism in a two-way analysis of variance procedure. In the Chinese, the 10 bp insertion may reduce transcription of the FVII gene, leading to the decreased synthesis of FVII protein and thus FVIIc.

Adult↗
PubMed2001

Natural killer T cell activation protects mice against experimental autoimmune encephalomyelitis.

Experimental autoimmune encephalomyelitis (EAE) serves as a prototypic model for T cell-mediated autoimmunity. V(alpha)14 natural killer T (NKT) cells are a subset of T lymphocytes that recognize glycolipid antigens presented by the nonpolymorphic major histocompatibility complex (MHC) class I-like protein CD1d. Here, we show that activation of V(alpha)14 NKT cells by the glycosphingolipid alpha-galactosylceramide (alpha-GalCer) protects susceptible mice against EAE. beta-GalCer, which binds CD1d but is not recognized by NKT cells, failed to protect mice against EAE. Furthermore, alpha-GalCer was unable to protect CD1d knockout (KO) mice against EAE, indicating the requirement for an intact CD1d antigen presentation pathway. Protection of disease conferred by alpha-GalCer correlated with its ability to suppress myelin antigen-specific Th1 responses and/or to promote myelin antigen-specific Th2 cell responses. alpha-GalCer was unable to protect IL-4 KO and IL-10 KO mice against EAE, indicating a critical role for both of these cytokines. Because recognition of alpha-GalCer by NKT cells is phylogenetically conserved, our findings have identified NKT cells as novel target cells for treatment of inflammatory diseases of the central nervous system.

Animals↗
PubMed2001

Surface organization and nanopatterning of collagen by dip-pen nanolithography.

Collagen is a key fibrous protein in biological systems, characterized by a complex structural hierarchy as well as the ability to self-assemble into liquid crystalline mesophases. The structural features of collagen influence cellular responses and material properties, with importance for a wide range of biomaterials and tissue architectures. The mechanism by which fibrillar collagen structures form from liquid crystalline mesophases is not well characterized. We report positive printing of collagen and a collagen-like peptide down to 30-50-nm line widths, using the atomic force microscopy technique of dip-pen nanolithography. The method preserved the triple-helical structure and biological activity of collagen and even fostered the formation of characteristic higher levels of structural organization. The "direct-write" capability of biologically relevant molecules, while preserving their structure and functionality, provides tremendous flexibility in future biological device applications and in proteomics arrays, as well as a new strategy to study the important hierarchical assembly processes of biological systems.

Collagen↗
PubMed2001

Post-World War II uranium changes in dated Mont Blanc ice and snow.

Recent controversies concerning the possibility of environmental contamination due to the use of uranium in classical weaponry have led us to realize that there is a lack of time series for this metal from environmental archives. We have therefore performed analysis of a dated 140 m-long ice/snow core that was drilled in 1994 at a cold high altitude site (4250 m) near the summit of Mont Blanc in the French-Italian Alps. Ultraclean analytical procedures were employed in our analyses. Uranium concentrations were determined by inductively coupled plasma sector field mass spectrometry. In ice dating from before the 1940s, uranium concentrations are found to have remained fairly constant and can be explained simply by a crustal contribution. For the post-World War II layers, on the other hand, the data show large excesses above crustal contributions. These uranium excesses are attributed to tropospheric transport of dust emitted during extensive mining and milling operations which took place in the GDR and to a smaller extent in France at that time. There is no enhancement in uranium concentrations in the ice layer in which fallout from the 1986 Chernobyl accident was previously identified from a gross beta activity vs depth profile.

Altitude↗