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Biomedical subjects

J H Lin

Publications and source records attributed to J H Lin.

At least 109 records · Page 6Linked to original sources
PubMed2000

Intracellular delivery of membrane-impermeable hydrophilic molecules to a hepatoblastoma cell line by asialoglycoprotein-labeled liposomes.

BACKGROUND AND PURPOSE: Mammalian hepatic receptors are specific for the terminal D-galactose of desialylated glycoproteins. This study used asialofetuin-labeled liposomes (AF-liposomes) to target hepatoma cells using this receptor mechanism, and investigated their efficiency in intracellular delivery of membrane-impermeable hydrophilic molecules to a hepatoblastoma cell line (HepG2). METHODS: Inulin was used as a model molecule. Blank liposomes consisting of phosphatidylcholine:phosphatidic acid:cholesterol in 6:1:6 molar ratio were prepared. Palmitoyl-asialofetuin was anchored onto the blank liposomes using a detergent dialysis method. 3H-inulin was entrapped in the AF-liposomes by dehydration (freeze-drying) and rehydration followed by freeze-thaw sonication. Plain liposomes (N-liposomes) were prepared by the same process but without AF. HepG2 cells were incubated for 3 hours with free 3H-inulin, N-liposomal 3H-inulin, AF-liposomal 3H-inulin, or free AF. The cellular uptake of 3H-inulin and the cell viability were then determined. Uptake of AF-liposomes in a non-hepatoma cell line, NIH3T3, was also studied for comparison. RESULTS: Cellular uptake of free inulin was negligible while uptake of liposomal inulin, either in N-liposomes or in AF-liposomes, was significant (p < 0.01). The uptake of AF-liposomal inulin was significantly higher than that of N-liposomal inulin in HepG2 cells but not in NIH3T3 cells. Free AF and blank AF-liposomes inhibited the HepG2 cell uptake of AF-liposomal inulin. CONCLUSIONS: These results indicate that AF-liposomes enhanced intracellular delivery of a membrane-impermeable hydrophilic drug into hepatoma cells by a receptor mechanism. AF-liposomes are a potential drug carrier for intracellular delivery of membrane-impermeable hydrophilic drugs to HepG2 cells.

3T3 Cells↗
PubMed1999

Immersion behavior of RF magnetron-assisted sputtered hydroxyapatite/titanium coatings in simulated body fluid.

The focus of the present study was on the dissolution/degradation behavior of a series of magnetron-sputtered, single-layered HA/Ti coatings on Ti-6Al-4V substrate immersed in SBF. Changes in coating morphology, crystal structure, and adhesion strength with immersion time are characterized. XRD, FTIR, and LVSEM results consistently indicate that highly crystalline monolithic HA coating is very dissolvable in SBF. The monolithic HA coating is largely delaminated in 3 weeks and entirely peeled off the substrate in 7 weeks. The dissolution is even greater for 95HA/5Ti coating, which severely disintegrated in only 1 week. The amorphous-like coatings sputtered from targets comprising 10 vol % or more Ti, however, appeared almost intact, and their adhesion strengths, which were all higher than 60 MPa, did not change much (within 10%) even after 14 weeks of immersion. The coatings from targets comprising roughly 10-50 vol % Ti combine advantages of high and nondeclining adhesion strength, high resistance to SBF attack, and possibly much higher bioactivity (with large amounts of Ca, P, etc., dissolved in the coatings) than that of Ti.

Biocompatible Materials↗
PubMed1999

Induction of apoptosis by penta-O-galloyl-beta-D-glucose through activation of caspase-3 in human leukemia HL-60 cells.

Penta-O-galloyl-beta-D-glucose is structurally related to (-)-epigallocatechin gallate and is isolated from hydrolyzed tannin. Penta-O-galloyl-beta-D-glucose can inhibit tumor promotion by teleocidin. We investigated the effects of penta-O-galloyl-beta-D-glucose and various tea polyphenols on cell viability in human leukemia HL-60 cells. In this study, we demonstrated that penta-O-galloyl-beta-D-glucose was able to induce apoptosis in a concentration- and time-dependent manner; however, other polyphenols were less effective. We further investigated the molecular mechanisms of penta-O-galloyl-beta-D-glucose-induced apoptosis. Treatment with penta-O-galloyl-beta-D-glucose caused induction of caspase-3/CPP32 activity in dose- and time-dependent manner, but not caspase-1 activity, and induced the degradation of poly-(ADP-ribose) polymerase. Pretreatment with acetyl-Asp-Glu-Val-Asp-aldehyde (Ac-DEVD-CHO) and Z-Val-Ala-Asp-fluoromethyl-ketone (Z-VAD-FMK) inhibited penta-O-galloyl-beta-D-glucose-induced DNA fragmentation. Furthermore, treatment with penta-O-galloyl-beta-D-glucose (50 microM) caused a rapid loss of mitochondrial transmembrane potential, release of mitochondrial cytochrome c into cytosol, and subsequent induction of procaspase-9 processing. Our results indicate that penta-O-galloyl-beta-D-glucose allows caspase-activated deoxyribonuclease to enter the nucleus and degrade chromosomal DNA, and induces DFF-45 (DNA fragmentation factor) degradation. These results lead to a working hypothesis that penta-O-galloyl-beta-D-glucose-induced apoptosis is triggered by the release of cytochrome c into the cytosol, procaspase-9 processing, activation of caspase-3, degradation of poly-(ADP-ribose) polymerase, and DNA fragmentation caused by the caspase-activated deoxyribonuclease through the digestion of DFF-45. The induction of apoptosis by penta-O-galloyl-beta-D-glucose may provide a pivotal mechanism for its cancer chemopreventive action.

Acridine Orange↗
PubMed1999

Macrocurrents of voltage gated Na+ and K+ channels from the crayfish stretch receptor neuronal soma.

Currents from the slowly adapting stretch receptor neuron of the crayfish (Pacifastacus leniusculus) were studied in a cell attached configuration using patch pipettes with an opening diameter of 2-10 microm. The neuronal membrane was enzymatically freed from the glial layer. The voltage gated Na+ and K+ channels seemed to be more concentrated in the lower part of soma close to the axon hillock. The Na+ and K+ currents could be analysed by fitting the currents to a fourth-order exponential function for Na+ current and a second-order exponential function for the K+ current. The macropatch recordings of enzymatically treated neurons are superior to two electrode voltage clamp recordings when analyzing voltage gated Na+ and K+ currents.

Animals↗
PubMed1999

CLAP, a novel caspase recruitment domain-containing protein in the tumor necrosis factor receptor pathway, regulates NF-kappaB activation and apoptosis.

Molecules that regulate NF-kappaB activation play critical roles in apoptosis and inflammation. We describe the cloning of the cellular homolog of the equine herpesvirus-2 protein E10 and show that both proteins regulate apoptosis and NF-kappaB activation. These proteins were found to contain N-terminal caspase-recruitment domains (CARDs) and novel C-terminal domains (CTDs) and were therefore named CLAPs (CARD-like apoptotic proteins). The cellular and viral CLAPs induce apoptosis downstream of caspase-8 by activating the Apaf-1-caspase-9 pathway and activate NF-kappaB by acting upstream of the NF-kappaB-inducing kinase, NIK, and the IkB kinase, IKKalpha. Deletion of either the CARD or the CTD domain inhibits both activities. The CARD domain was found to be important for homo- and heterodimerization of CLAPs. Substitution of the CARD domain with an inducible FKBP12 oligomerization domain produced a molecule that can induce NF-kappaB activation, suggesting that the CARD domain functions as an oligomerization domain, whereas the CTD domain functions as the effector domain in the NF-kappaB activation pathway. Expression of the CARD domain of human CLAP abrogates tumor necrosis factor-alpha-induced NF-kappaB activation, suggesting that cellular CLAP plays an essential role in this pathway of NF-kappaB activation.

Adaptor Proteins, Signal Transducing↗
PubMed1999

Different spatial distributions of sodium channels in the slowly and rapidly adapting stretch receptor neuron of the crayfish.

Inward Na+ currents were studied, using a two-microelectrode intracellular voltage-clamp technique, in the slowly adapting (SA) and rapidly adapting (RA) stretch receptor neurons of the crayfish after the axons were cut at different distances from the soma. In the SA neuron, inward Na+ currents were recorded in the soma even when the axon was cut as close as 100 microm from the center of the soma, indicating the presence of Na+ channels in these parts. Also, two populations of Na+ channels seem to exist in the SA neuron. In the RA neuron, only minute Na+ currents were observed if the axon was shorter than 250 microm. The results strongly indicate that the voltage-gated Na+ channels in the SA and RA neurons have different distributions and that the difference in the spatial distribution of Na+ channel types may be important for the difference in firing properties in the two types of neurons.

Adaptation, Physiological↗
PubMed1999

The ankyrin repeat-containing adaptor protein Tvl-1 is a novel substrate and regulator of Raf-1.

Tvl-1 is a 269-amino acid ankyrin repeat protein expressed primarily in thymus, lung, and testes that was identified by screening a murine T-cell two-hybrid cDNA library for proteins that associate with the serine-threonine kinase Raf-1. The interaction of Tvl-1 with Raf-1 was confirmed by co-immunoprecipitation of the two proteins from COS-1 cells transiently transfected with Tvl-1 and Raf-1 expression constructs as well as by co-immunoprecipitation of the endogenous proteins from CV-1 and NB2 cells. Tvl-1 interacts with Raf-1 via its carboxyl-terminal ankyrin repeat domain. The same domain also mediates Tvl-1 homodimerization. Tvl-1 was detected by immunofluorescence in both the cytoplasm and the nucleus suggesting that in addition to Raf-1 it may also interact with nuclear proteins. Activated Raf-1 phosphorylates Tvl-1 both in vitro and in vivo. In baculovirus-infected Sf9 insect cells, Tvl-1 potentiates the activation of Raf-1 by Src and Ras while in COS-1 cells it potentiates the activation of Raf-1 by EGF. These data suggest that Tvl-1 is both a target as well as a regulator of Raf-1. The human homologue of Tvl-1 maps to chromosome 19p12, upstream of MEF2B with the two genes in a head to head arrangement.

Adaptor Proteins, Signal Transducing↗
PubMed1999

Direct gap junction communication between malignant glioma cells and astrocytes.

Gap junctions are intercellular channels that connect the interiors of coupled cells. We sought to determine the extent to which malignant glioma cells form gap junction channels with astrocytes from either adult human brain or rat forebrain. The astrocytic gap junction protein, connexin 43 (Cx43), was identified in immunoreactive plaques at areas of cell-to-cell contact between cocultured glioma cells and astrocytes. These gap junction plaques were composed of functional channels, because extensive dye coupling was evident between the glioma cells and astrocytes from both human and rat brain. Calcium signaling was also readily transmitted from glioma cells to astrocytes and vice versa. In live rat brain, injection of glioma cells prelabeled with the gap junction tracer, dicarboxy-dichlorofluorescein, revealed extensive dye transfer to host cells, demonstrating that malignant glioma cells directly couple with normal brain cells. These observations suggest that intercellular communication via gap junctions may play a role in regulating cellular interactions during tumor invasion. In fact, the presence of gap junctions between astrocytes and glioma cells was sufficient to induce a transformation of astrocytic phenotype. Astrocytes cocultured with C6 glioma cells overexpressing Cx43 were significantly smaller and expressed a lower level of glial fibrillary acidic protein than astrocytes cocultured with otherwise identical mock-transfected, gap junction-deficient C6 cells. Thus, direct cellular coupling with glioma cells result in a phenotypic transformation of astrocytes that may contribute to the susceptibility of surrounding tissue to glioma invasion.

Adult↗
PubMed1999

Characterization of hydroxyapatite and titanium coatings sputtered on Ti-6Al-4V substrate.

A series of thin (<10 microm), single-layered HA/Ti coatings were deposited on Ti-6Al-4V substrate using a radio frequency magnetron-assisted sputtering system. The adhesion strength, microstructure, and chemistry of the coatings were characterized. Experimental results showed that higher Ti contents in targets or coatings resulted in higher deposition rates. When Ti was added the highly crystalline structure of monolithic HA coating was largely disrupted and the coating became amorphous-like. The highly crystalline structure of the monolithic Ti coating was also disrupted by introducing small amounts of Ca, P, and O into the coating. The HA/Ti coatings had quite uniform thicknesses and appeared smooth, dense, and well bonded to the substrate. A scanning electron microscope with an energy dispersive spectroscopy system showed that monolithic HA, 95HA/5Ti, 25HA/75Ti, and 50HA/50Ti coatings had the lowest Ca/P ratios while the 75HA/25Ti coating had the highest. The adhesion strengths of all coatings were between 60 and 80 MPa.

Alloys↗
PubMed1999

Molecular cloning and characterization of porcine cDNA encoding a 90-kDa heat shock protein and its expression following hyperthermia.

We have isolated and sequenced cDNA clones encoding a 90-kDa heat shock protein (HSP90) from a porcine brain cDNA library. The sequence of the 2202-nucleotide coding region showed 88.6% homology with that of the human homologue. Moreover, the deduced amino acid sequence of the porcine hsp90 cDNA was 99.7% identical to that of the human counterpart, with a difference of only three amino acids in a total of 733 residues. Expression of the gene was greatly increased in cultured cells during recovery from heat shock treatment at 45 degrees C for 60 min. Three major transcripts 2.2, 3.0, and 4.1kb in size were detected by Northern blot hybridization. These transcripts were further identified in a whole-pig hyperthermia experiment. These three hsp90 transcripts were constitutively expressed in porcine tissues including kidney, liver, brain, and heart, and their levels were markedly enhanced during recovery from 30-min hyperthermia treatment at 43 degrees C. Furthermore, we found that HSP90 was preferentially expressed in pituitary gland, brain, adrenal gland, and testis, in comparison to the other tissues.

Amino Acid Sequence↗
PubMed1999

Renal handling of biphosphonate alendronate in rats.

Alendronate is a bisphosphonate that is secreted via a saturable pathway in rat kidney. This study is designed to discover if the rate-determining step in its net renal secretion is uptake into the renal tubule. The tissue uptake clearance of alendronate by the kidney, estimated from an integration plot analysis and normalized with respect to plasma protein binding, was 4.2 times higher at a tracer dose than that of inulin, indicating uptake of alendronate by the renal tubules. The uptake clearance is comparable with the net secretion clearance obtained from an infusion study, indicating that the rate-determining step in the net secretion is uptake under the tracer conditions. When the dose was increased, however, there was no reduction in uptake clearance while the net secretion clearance fell to almost zero. The urinary excretion clearance defined with respect to the steady state concentration in the kidney also fell to almost zero. This result suggests that saturation of the net secretion of alendronate is caused by saturation of membrane transport through the brush-border membrane. Thus, it would seem that there is a transport mechanism for alendronate on the brush-border membrane of kidney epithelial cells.

Alendronate↗
PubMed1999

Markov chain Monte Carlo linkage analysis of a complex qualitative phenotype.

We tested a new computer program, LOKI, that implements a reversible jump Markov chain Monte Carlo (MCMC) technique for segregation and linkage analysis. Our objective was to determine whether this software, designed for use with continuously distributed phenotypes, has any efficacy when applied to the discrete disease states of the simulated data from the Mordor data from GAW Problem 1. Although we were able to identify the genomic location for two of the three quantitative trait loci by repeated application of the software, the MCMC sampler experienced significant mixing problems indicating that the method, as currently formulated in LOKI, was not suitable for the discrete phenotypes in this data set.

Chromosome Mapping↗
PubMed1999

Genetic dissection of a complex trait.

A number of genetic and statistical tools were applied to various partitions of the simulated data to identify susceptibility loci, relevant environmental factors, and their interaction(s). The distribution of genotypes at D1G24 among affected children in the first population was found to differ significantly from Hardy-Weinberg expectation. Two transmission/disequilibrium tests identified the preferential transmission of allele 1 as the source of the disequilibrium. Simple contingency table analysis revealed a positive association between exposure to environmental factor E1 and disease phenotype. Multipoint linkage analyses on various subsets of the data identified three "signal" regions (in addition to the aforementioned D1G24) localized at D1G9-10, D3G45, and D5G38. The even numbered chromosomes appeared to be devoid of susceptibility loci. Further analyses of subsamples of affected sib pairs, selected according to their disease phenotype and their exposure to E1, clarified some linkage relationships, particularly for D3G45, thereby suggesting the presence of a specific gene x environment interaction. Logistic analysis designed to clarify the relationship between disease phenotype and two risk factors (E1 exposure and the presence of allele 1 at D1G24) in the first population, revealed a significantly negative interaction which, upon learning the details of the generating model, we now attribute to the presence of heterogeneity.

Environment↗
PubMed1999

Low-density lipoprotein augments interleukin-1-induced vascular adhesion molecule expression in human endothelial cells.

In this study, the effect of low density lipoproteins (LDL) on the ability of the vascular endothelium to respond to vascular cell adhesion molecule 1 (VCAM-1) activation by a cytokine was investigated. After a 4-day pre-exposure to 240 mg/dl of LDL, human umbilical vein endothelial cells (HUVECs) were hyperresponsive to minute amounts of interleukin 1 alpha (IL-1 alpha) as demonstrated by an augmentation of VCAM-1 gene expression. Furthermore, in response to LDL exposure, endothelial recruitment of monocytes induced by minute amounts of IL-1 alpha was increased. This enhancing effect was blocked by an anti-VCAM antibody. The increased response appears not to be due to changes in IL-1 binding affinity or induction of endogenous IL-1 alpha. Transient transfection of HUVECs with a reporter driven by the VCAM promoter showed that LDL increased cellular response to IL-1 alpha by 46%. LDL itself does not increase NF-kappa B binding in endothelial cells (ECs). However, after a 2-day LDL incubation, NF-kappa B binding could be induced by over 63% with a very low dose of IL-1 alpha. IL-1 alpha at this dose (which activates NF-kappa B, but not AP-1) also enhanced LDL-activated AP-1 binding. This cross-enhanced effect may be an important intracellular signaling mechanism for EC activation. The results from this study provide new clues to understanding the mechanisms governing combined risk factors for atherosclerosis.

Cells, Cultured↗
PubMed1999

Effect of particle configuration on structure and properties of dispersed Pd-containing dental amalgam.

The present work investigates the effect of particle configuration on the structure and properties of four dispersed type Pd-containing amalgams with the same chemical composition. The results indicate that particle configuration plays an important role not only in the structure and chemistry, but also in such properties as compressive strength, creep and mercury release rate. Compromises among the various properties of the present Pd amalgams are needed, when a decision on particle configuration is to be made. As mechanical properties or corrosion resistance is concerned, the amalgam should comprise at least one spherical alloy (matrix or dispersant). As far as mercury release is concerned, the amalgam should comprise irregular dispersant alloy. The amalgam fabricated from irregular dispersant and spherical matrix particles seems to serve all well.

Compressive Strength↗
PubMed1999

Structure and properties of cast binary Ti-Mo alloys.

Structure and properties of a series of binary Ti-Mo alloys with molybdenum contents ranging from 6 to 20 wt% have been investigated. Experimental results indicated that crystal structure and morphology of the cast alloys were sensitive to their molybdenum contents. The hexagonal alpha' phase c.p. Ti exhibited a feather-like morphology. When Mo content was 6 wt%, a fine, acicular martensitic structure of orthorhombic alpha" phase was observed. When Mo content was 7.5 wt%, the entire alloy was dominated by the martensitic alpha" structure. When Mo content was increased to 10 wt% or higher, the retained beta phase became the only dominant phase. Among all Ti-Mo alloys, the alpha" phase Ti-7.5Mo alloy had the lowest hardness. The bending strength of Ti-7.5Mo was similar to that of Ti-15Mo and Ti-13Nb-13Zr, and higher than c.p. Ti by nearly 60%. The bending modulus of the alpha"-dominated Ti-7.5Mo alloy was lower than that of Ti-15Mo by 22%, of Ti-6A1-4V by 47%, of Ti-13Nb-13Zr by 17%, and of c.p. Ti by 40%.

Alloys↗
PubMed1999

3-D power Doppler cerebral angiography in neonates and young infants: comparison with 2-D power Doppler angiography.

The aims of this study were to evaluate the ability of 3-dimensional (3-D) power Doppler angiography (3DPDA) to depict the intracranial vasculature in infants, to compare with 2-D power Doppler ultrasonography (2DPDU), and to explore the potential clinical applications of this procedure in young infants with brain disorders. We performed 3DPDA in 27 infants. 2DPDU were completed in both sagittal and coronal directions in 12 of these patients. In the other 15, only right sagittal plane images were available for comparison. Using a grading system and with only vessels with more than half of the length demonstrated included for comparison, we compared the Doppler signals of major vessels. 3DPDA could have good visualization in more than 60% of the internal carotid artery, ophthalmic artery, pericallosal artery, callosomarginal artery, internal cerebral vein, vein of Galen, and straight sinus in the sagittal plane. 3DPDA also could have good demonstration in about 50% of basilar artery in coronal plane, and posterior communicating artery, posterior cerebral artery, and lenticulostriate artery in sagittal plane. 3DPDA was better than 2DPDU in demonstrating all the major intracranial vessels in different planes, except the anterior communicating artery. In the anterior communicating artery, neither can demonstrate more than 30%.

Brain Diseases↗