Biomedical subjects

Bin Lin

Publications and source records attributed to Bin Lin.

36 records · Page 2Linked to original sources

PubMed2004

Retinal ganglion cell type, size, and spacing can be specified independent of homotypic dendritic contacts.

In Brn3b(-/-) mice, where 80% of retinal ganglion cells degenerate early in development, the remaining 20% include most or all ganglion cell types. Cells of the same type cover the retinal surface evenly but tile it incompletely, indicating that a regular mosaic and normal dendritic field size can be maintained in the absence of contact among homotypic cells. In Math5(-/-) mice, where only approximately 5% of ganglion cells are formed, the dendritic arbors of at least two types among the residual ganglion cells are indistinguishable from normal in shape and size, even though throughout development they are separated by millimeters from the nearest neighboring ganglion cell of the same type. It appears that the primary phenotype of retinal ganglion cells can develop without homotypic contact; dendritic repulsion may be an end-stage mechanism that fine-tunes the dendritic arbors for more efficient coverage of the retinal surface.

Animals↗

PubMed2004

A novel mechanism for the facilitation of theta-induced long-term potentiation by brain-derived neurotrophic factor.

Brain-derived neurotrophic factor (BDNF) contributes to the induction of long-term potentiation (LTP) by theta-pattern stimulation, but the specific processes underlying this effect are not known. Experiments described here, using BDNF concentrations that have minor effects on baseline responses, show that the neurotrophin both reduces the threshold for LTP induction and elevates the ceiling on maximal potentiation. The enhanced LTP proved to be as stable and resistant to reversal as that recorded under control conditions. BDNF markedly increased the facilitation of burst responses that occurs within a theta train. This suggests that the neurotrophin acts on long-lasting events that (1) are set in motion by the first burst in a train and (2) regulate the amplitude of subsequent bursts. Whole-cell recordings established that BDNF causes a rapid reduction in the size of the long-lasting afterhyperpolarization (AHP) that follows individual theta bursts. Apamin, an antagonist of type 2 small-conductance Ca2+-activated potassium (SK2) channels, also reduced hippocampal AHPs and closely reproduced the effects of BDNF on theta-burst responses and LTP. The latter results were replicated with a newly introduced, highly selective inhibitor of SK2 channels. Immunoblot analyses indicated that BDNF increases SK2 serine phosphorylation in hippocampal slices. These findings point to the conclusion that BDNF-driven protein kinase cascades serve to depress the SK2 component, and possibly other constituents, of the AHP. It is likely that this mechanism, acting with other factors, promotes the formation and increases the magnitude of LTP.

Animals↗

PubMed2004

Catalog of 162 single nucleotide polymorphisms (SNPs) in a 4.7-kb region of the HLA-DP loci in southern Chinese ethnic groups.

HLA class-II proteins are cell-surface molecules that present antigens to T cells, and their expressional regulation is crucial to the immune reaction. Sequence variation at the regulatory region can directly affect the gene expression level. We cloned and sequenced a 4.7-kb region containing the regulatory region, exon1, and partial intron1 of both HLA-DPA1 and DPB1 genes in 25 variable sequences from southern Chinese ethnic groups and got a high-density map of 162 single nucleotide polymorphisms (SNPs): seven in 5'-flanking regions, four in 5'-untranslated regions, and four in the coding regions. By comparing these data with SNPs in dbSNP database in the NCBI, 145 SNPs (89.5%) were novel. In addition, eight genetic variations of insertion-deletion polymorphisms (INDELs) were discovered within the 4.7-kb region. These high-resolution maps can be used as resources of markers for association studies of complex diseases, assessment of individuals' predisposition to diseases, and tailoring of therapies, as well as research markers for population genetics and evolution.

Base Sequence↗

PubMed2004

Effect of partial shading on photoproduction of hydrogen by Chlorella.

The photoproduction of hydrogen by the green alga Chlorella pyrenoidosa was studied in 650-ml bubble columns made of glass with 7 cm diameter. Hydrogen was produced by adding sodium dithionite as an oxygen scavenger directly to an algal suspension. When a part of the wall of the bubble column was shaded with a sheet of plastic film impervious to light, the production rate and total volume of hydrogen increased as compared to those in the columns without partial shading. This relationship between the hydrogen photoevolution rate and the proportion of lighted region is contrary to normal photochemical reactions. This phenomenon is considered to be related to the regulation by light of the activity of the enzymes and/or the photosynthetic electron transport systems, which was examined by measuring fluorescence induction curves of dark-adapted Chlorella cells and also the distribution of light intensity within the bubble column bioreactors.

Journal Article↗

PubMed2004

The Caulobacter crescentus CgtAC protein cosediments with the free 50S ribosomal subunit.

The Obg family of GTPases is widely conserved and predicted to play an as-yet-unknown role in translation. Recent reports provide circumstantial evidence that both eukaryotic and prokaryotic Obg proteins are associated with the large ribosomal subunit. Here we provide direct evidence that the Caulobacter crescentus CgtA(C) protein is associated with the free large (50S) ribosomal subunit but not with 70S monosomes or with translating ribosomes. In contrast to the Bacillus subtilis and Escherichia coli proteins, CgtA(C) does not fractionate in a large complex by gel filtration, indicating a moderately weak association with the 50S subunit. Moreover, binding of CgtA(C) to the 50S particle is sensitive to salt concentration and buffer composition but not guanine nucleotide occupancy of CgtA(C). Assays of epitope-tagged wild-type and mutant variants of CgtA(C) indicate that the C terminus of CgtA(C) is critical for 50S association. Interestingly, the addition of a C-terminal epitope tag also affected the ability of various cgtA(C) alleles to function in vivo. Depletion of CgtA(C) led to perturbations in the polysome profile, raising the possibility that CgtA(C) is involved in ribosome assembly or stability.

Ammonium Chloride↗

PubMed2004

Comparative study on treating complete dislocation of acromioclavicular joint with three different methods.

OBJECTIVE: To comparatively study complete dislocation of acromioclavicular joint treated with three different methods. METHODS: A total of 96 patients (81 males and 15 females, aged 16-59 years, mean=45 years) with complete dislocation of acromioclavicular joint were treated with Dewar's operation (Group A, n=32), internal fixation with Kirschner tension band wires (Group B, n=44), or internal fixation with Wolter plates (Group C, n=20), respectively, in this study. Eighty-five patients suffered from acute dislocations and eleven from chronic dislocations. RESULTS: The patients were followed up for 50 months on an average. According to Karlsson's standard, in Group A, 26 patients were assessed as good, 5 as fair and 1 as poor. In Group B, 20 patients were assessed as good, 13 as fair and 11 as poor. In Group C, 15 patients were assessed as good, 4 as fair and 1 as poor. The good and fair rates were significantly different between Group A and Group B, and between Group C and Group B, but no statistical difference was found between Group A and Group C. The operating time was (52.36+/-7.24) minutes, (67.43+/-8.11) minutes and (69.73+/-8.04) minutes in Groups A, B and C, respectively. And the hospitalizing fees were (2400+/-270) yuan, (2100+/-190) yuan and (8450+/-360) yuan in Groups A, B and C, respectively. CONCLUSIONS: Dewar's operation is a good and safe method with shorter operating time and lower hospitalizing fee for treating complete dislocation of acromioclavicular joint. The method is simple without the need of a second operation to remove the implants and with few complications.

Acromioclavicular Joint↗

PubMed2004

[Determination of free chlorine with spectrophotometric method using N,N-diethyl-1,4-phenylenediamine].

In this paper, the absorption spectra of free chlorine in the visible region has been measured after free chlorine in the solution had reacted with N,N-diethyl-1,4-phenylenediamine (DPD). The relation between the absorption spectra and peak wavelength has been discussed. From the experiment of liquor with different concentration, the error of spectral measurement is less than 0.04%. By nonlinear data fitting, the relation between the concentration of free chlorine and the transmittivity has been given.

Absorption↗

PubMed2003

2-ammonio-6-(3-oxidopyridinium-1-yl)hexanoate (OP-lysine) is a newly identified advanced glycation end product in cataractous and aged human lenses.

Post-translational modifications of proteins take place during the aging of human lens. The present study describes a newly isolated glycation product of lysine, which was found in the human lens. Cataractous and aged human lenses were hydrolyzed and fractionated using reverse-phase and ion-exchange high performance liquid chromatography (HPLC). One of the nonproteinogenic amino acid components of the hydrolysates was identified as a 3-hydroxypyridinium derivative of lysine, 2-ammonio-6-(3-oxidopyridinium-1-yl)hexanoate (OP-lysine). The compound was synthesized independently from 3-hydroxypyridine and methyl 2-[(tert-butoxycarbonyl)amino]-6-iodohexanoate. The spectral and chromatographic properties of the synthetic OP-lysine and the substance isolated from hydrolyzed lenses were identical. HPLC analysis showed that the amounts of OP-lysine were higher in water-insoluble compared with water-soluble proteins and was higher in a pool of cataractous lenses compared with normal aged lenses, reaching 500 pmol/mg protein. The model incubations showed that an anaerobic reaction mixture of Nalpha-tert-butoxycarbonyllysine, glycolaldehyde, and glyceraldehyde could produce the Nalpha-t-butoxycarbonyl derivative of OP-lysine. The irradiation of OP-lysine with UVA under anaerobic conditions in the presence of ascorbate led to a photochemical bleaching of this compound. Our results argue that OP-lysine is a newly identified glycation product of lysine in the lens. It is a marker of aging and pathology of the lens, and its formation could be considered as a potential cataract risk-factor based on its concentration and its photochemical properties.

Aged↗

PubMed2003

Glutamate receptors at bipolar synapses in the inner plexiform layer of primate retina: light microscopic analysis.

At least 10 different types of bipolar cells have been distinguished in the primate retina. The axon terminals of these cells stratify in distinct strata in the inner plexiform layer and are involved in parallel pathways to distinct types of ganglion cells. Ionotropic glutamate receptor (GluR) subunits also show a stratified distribution in the inner plexiform layer. Here, we investigated whether different types of bipolar cells are associated with different types of ionotropic glutamate receptors in the inner retina of a New World primate, the common marmoset Callithrix jacchus. Vertical cryostat sections through central retina were double labeled with immunohistochemical markers for bipolar cell types and with antibodies to alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptor subunits GluR1 to 4, kainate receptor subunits GluR6/7, and the NR1C2' subunit of the N-methyl-D-aspartate (NMDA) receptor. The axon terminals of bipolar cell types were reconstructed from confocal sections, and the colocalized immunoreactive puncta were quantified. For all bipolar cell types, immunoreactive puncta for the AMPA receptor subunits GluR2, 2/3, and 4 were colocalized at highest densities, whereas GluR1-immunoreactive puncta were expressed at very low densities. The kainate receptor subunits GluR6/7 were predominantly associated with diffuse bipolar (DB6) and rod bipolar cells. The NMDA receptor subunit NR1C2' was specifically colocalized with flat midget and DB3 axons. These findings suggest that rod and cone bipolar cell types contribute to multiple but distinct glutamate receptor pathways in primate retina.

Animals↗

PubMed2003

Isolation and characterization of a new advanced glycation endproduct of dehydroascorbic acid and lysine.

Proteins are subject of posttranslational modification by sugars and their degradation products in vivo. The process is often referred as glycation. L-Dehydroascorbic acid (DHA), an oxidation product of L-ascorbic acid (vitamin C), is known as a potent glycation agent. A new product of modification of lysine epsilon -amino group by DHA was discovered as a result of the interaction between Boc-Lys and dehydroascorbic acid. The chromatographic and spectral analyses revealed that the structure of the product was 1-(5-ammonio-5-carboxypentyl)-3-oxido-4-(hydroxymethyl)pyridinium. The same compound was isolated from DHA modified calf lens protein after hydrolysis and chromatographic separation. The study confirmed that L-erythrulose is an important intermediate of modification of proteins by DHA. The structure of the reported product and in vitro experiments suggested that L-erythrulose could further transform to L-threose, L-erythrose and glycolaldehyde under conditions similar to physiological. The present study revealed that the modification of epsilon -amino groups of lysine residues by DHA is a complex process and could involve a number of reactive carbonyl species.

Acetaldehyde↗

PubMed2003

Separation of the yellow chromophores in individual brunescent cataracts.

Quantitative changes in the 330 nm absorbing chromophores and 350/450 nm fluorophores of water-soluble (WS) and water-insoluble (WI) proteins of individual human cataract lenses were characterized and compared with aged normal human lens. Twenty-five brunescent cataract lenses from India were selected from five different stages (types I-V) based upon the color of the lens. The WS and WI proteins from each lens were collected and subjected to an extensive enzymatic digestion procedure under argon. The lens protein digests were separated by Bio-Gel P-2 size-exclusion chromatography and individual peaks were analyzed further by reversed-phase HPLC. The total WI proteins increased and the total WS protein decreased with the development of cataract, especially in the late stages of cataract (III-V). The total 330 nm absorbance and 350/450 nm fluorescence of the WI fraction also increased, however, the A(330) and fluorescence per mg lens protein were constant except for type V (black) lenses. Bio-Gel P-2 chromatography separated the chromophores and fluorophores into four fractions. The main fraction (designated as peak 2+3) from the cataract WI proteins was several times higher than that present in aged normal human lens WI proteins. A significant increase of this fraction was observed in WI proteins, but not in WS proteins with cataract development. Similarly, fractions 1 and 4 in the WI proteins also increased gradually but fraction 5 did not. Reversed-phase HPLC resolved fraction (2+3) of the water-insoluble sonicate supernatant proteins into four 330 nm absorbing peaks and eight fluorescent peaks. Among these peaks, a late-eluting peak (peak 8) increased 10 to 15-fold with the progress of cataract, and accounted for 80% of the total chromophores in type V lenses. This peak may represent limit digests of advanced glycation end-products (AGEs) derived protein cross-links. HPLC profiles of fraction 5 from both WS and WI proteins showed numerous new peaks which were not observed in either WS protein from cataract or WI proteins from aged normal human. The severe coloration and the higher levels of numerous novel chromophores and fluorophores in brunescent cataractous lenses reveal the possibility that a different chemistry occurs during cataract development.

Aged↗

PubMed2003

Integrins regulate NMDA receptor-mediated synaptic currents.

Synapses contain high concentrations of integrins, adhesion receptors known to influence the operation of neighboring transmembrane proteins. Evidence that integrins are important for consolidation of long-term potentiation suggests that these adhesion proteins may modulate activities of synaptic glutamate receptors. The present study provides a first test of the possibility that integrins modulate synaptic N-methyl-d-aspartate (NMDA)-type glutamate receptor activities. Excitatory postsynaptic currents (EPSCs) were recorded with whole cell clamp from hippocampal slices in which AMPA-type glutamate receptors and GABA(A) receptors were pharmacologically blocked. Microperfusion of the peptide integrin ligand gly-arg-gly-asp-ser-pro (GRGDSP) caused an approximately twofold increase in the amplitude and duration of NMDA receptor-gated synaptic currents. Control peptides had no effect. Paired-pulse facilitation was unchanged, indicating that the ligand did not modify neurotransmitter release probabilities. Infusion of the Src kinase antagonist PP2 but not the control drug 4-amino-7-phenylpyrazolo[3,4-d]pyrimidine eliminated the enhancing effect of GRGDSP. Integrins regulate Src kinases that are known to phosphorylate NMDA receptors. It is concluded that integrins act through this route to exert potent modulatory effects on the operation of NMDA receptors.

Animals↗

PubMed2002

Interactions between recording technique and AMPA receptor modulators.

Whole cell recording (EPSCs) and extracellular recording (field EPSPs) were compared in hippocampal field CA1 with regard to the effects of experimental treatments that increase AMPA receptor gated currents. Cyclothiazide, which maintains AMPA receptors in the sensitized state, caused a rapid and pronounced increase in EPSCs but only minor changes in field EPSPs. This difference was evident in recordings carried out at 22 and 32 degrees C and with different solutions in the clamp pipette. The larger effect of cyclothiazide on EPSCs was unaffected by blockade of GABA and NMDA receptors. Two-dimensional current source density analyses derived from 64 recording sites were used to provide extracellular estimates of AMPA receptor mediated synaptic currents. With this method, cyclothiazide again had much smaller effects than were obtained with whole cell clamp. Differences between whole cell and extracellular recordings were present, although not as pronounced, for the ampakines, a class of drugs that slow both deactivation and desensitization of AMPA receptors. Additionally, increases in synaptic responses produced by frequency facilitation, a manipulation that enhances the number of bound receptors, were not qualitatively different between recording techniques. These results support the conclusion that the whole cell clamp technique may alter AMPA receptors in such a way as to increase the relative importance of desensitization.

Animals↗

PubMed2002

Rate of formation of AGEs during ascorbate glycation and during aging in human lens tissue.

The similarity of the yellow chromophores isolated from human cataracts with those from ascorbic acid modified calf lens proteins was recently published [Biochim. Biophys. Acta 1537 (2001) 14]. The data presented here additionally quantify age-dependent increases in individual yellow chromophores and fluorophores in the water-insoluble fraction of normal human lens. The water-insoluble fraction of individual normal human lens was isolated, solubilized by sonication and digested with a battery of proteolytic enzymes under argon to prevent oxidation. The level of A(330)-absorbing yellow chromophores, 350/450 nm fluorophores and total water-insoluble (WI) protein were quantified in each lens. The total yellow chromophores and fluorophores accumulated in parallel with the increase in the water-insoluble protein fraction during aging. The digest from each single human lens was then subjected to Bio-Gel P-2 size-exclusion chromatography. The fractions obtained were further separated by a semi-preparative prodigy C-18 high-performance liquid chromatography (RP-HPLC). Bio-Gel P-2 chromatography showed four major fractions, each of which increased with age. RP-HPLC of the amino acid peak resolved five major A(330)-absorbing peaks and eight fluorescent peaks, and each peak increased coordinately with age. A late-eluting peak, which contained hydrophobic amino acids increased significantly after age 60. Aliquots from an in vitro glycation of calf lens proteins by ascorbic acid were removed and subjected to the same enzymatic digestion. Ascorbic acid-modified calf lens protein digests showed an almost identical profile of chromophores, which also increased in a time-dependent manner. The late-eluting peak, however, did not increase with the time of glycation and may not be an advanced glycation endproduct (AGE) product. The data indicate that the total water-insoluble proteins, individual yellow chromophores and fluorophores increased equally both with aging in normal human lens and during ascorbate glycation in vitro. The major protein modifications, which accumulate during aging, therefore, appear to be AGEs. Whereas the late-eluting peak, which showed poor correlation to ascorbylation, may represent UV filter compounds bound to lens proteins.

Adult↗

PubMed2002

Stratification and seasonal stability of diverse bacterial communities in a Pinus merkusii (pine) forest soil in central Java, Indonesia.

In Java, Indonesia, many nutrient-poor soils are intensively reforested with Pinus merkusii (pine). Information on nutrient cycles and microorganisms involved in these cycles will benefit the management of these important forests. Here, seasonal effects on the stratification of bacterial community structure in the soil profile of a tropical pine forest are described, and differences in bacterial communities are related to chemical and physical soil parameters. Culture-independent community profiles of litter, fragmented litter and mineral soil layers were made by denaturing gradient gel electrophoresis (DGGE) of 16S rDNA-specific polymerase chain reaction (PCR) fragments. The community profiles of the different soil layers clustered separately, correlating with significant differences in organic matter content between the three layers. The bacterial communities appeared to be stable during the wet season of 1998. The drought in 1997, caused by the El Niño climatic effect, did not influence the bacterial communities in fragmentation and mineral soil, although moisture content and other soil parameters were markedly lower than in the wet season. However, communities in litter were influenced by drought. In the litter layer, the moisture content was significantly lower than in the fragmentation and mineral layers during the dry season. A clone library was made from a litter sample taken during the wet season. Partial sequencing of 74 clones and linking the DGGE banding positions of these clones to bands in the DGGE profile of the sample from which the clone library was derived showed considerable bacterial diversity. Alpha-proteobacteria (40.5% of the clones, of which 57% belonged to the Rhizobium-Agrobacterium group) and high-G+C content, Gram-positive bacteria (36.5%) dominated the clone library.

Bacteria↗

PubMed2002

Long-term potentiation alters the modulator pharmacology of AMPA-type glutamate receptors.

Changes in the biophysical properties of AMPA-type glutamate receptors have been proposed to mediate the expression of long-term potentiation (LTP). The present study tested if, as predicted from this hypothesis, AMPA receptor modulators differentially affect potentiated versus control synaptic currents. Whole cell recordings were collected from CA1 pyramidal neurons in hippocampal slices from adult rats. Within-neuron comparisons were made of the excitatory postsynaptic currents (EPSCs) elicited by two separate groups of Schaffer-collateral/commissural synapses. LTP was induced by theta burst stimulation in one set of inputs; cyclothiazide (CTZ), a drug that acts on the desensitization kinetics of AMPA receptors, was infused 30 min later. The decay time constants of the potentiated EPSCs prior to drug infusion were slightly, but significantly, shorter than those of control EPSCs. CTZ slowed the decay of the EPSCs, as reported in prior studies, and did so to a significantly greater degree in the potentiated synapses. Additionally, infusion of CTZ resulted in significantly greater effects on amplitude in potentiated pathways as compared with control pathways. The interaction between LTP and CTZ was also obtained in a separate set of experiments in which GABA receptor antagonists were used to block inhibitory postsynaptic currents. Additionally, there was no significant change in paired-pulse facilitation in the presence of CTZ, indicating that presynaptic effects of the drug were negligible. These findings provide new evidence that LTP modifies AMPA receptor kinetics. Candidates for the changes responsible for the observed effects of LTP were evaluated using a model of AMPA receptor kinetics; a simple increase in the channel opening rate provided the most satisfactory match with the LTP data.

6-Cyano-7-nitroquinoxaline-2,3-dione↗

PubMed2002

Microbial aspects of anaerobic BTEX degradation.

Combined with conventional methods, developments in both geochemical (delineation of redox processes) and molecular microbial methods (analysis of 16S rDNA genes and functional genes) have allowed us to study in details microorganisms and genes involved in the anaerobic degradation of benzene, toluene, ethylbenzene and xylene (BTEX) under specific redox conditions. This review summarizes recent research in this field. The potential for anaerobic BTEX degradation is widely spread. Specific groups of microorganisms appear to be involved in degradation under different redox conditions. Members of the Azoarcus/Thauera cluster perform BTEX degradation under denitrifying conditions, Geobacteraceae under Fe (III) reducing conditions and Desulfobacteriaceae under sulfate reducing conditions. The information so far obtained on biochemistry and molecular genetics of BTEX degradation indicates that each BTEX compound is funneled into the central benzyol-CoA pathway by a different peripheral pathway. The peripheral pathways of per BTEX compound show similarities among different physiological groups of microorganisms. We also describe how knowledge obtained on the microbial aspects of BTEX degradation can be used to enhance and monitor anaerobic BTEX degradation.

Bacteria, Anaerobic↗

PubMedDate not supplied

Expression and distribution of ionotropic glutamate receptor subunits on parasol ganglion cells in the primate retina.

The response properties of postreceptoral sensory neurones are determined by the properties of their input neurones, by intrinsic membrane properties, and by the properties of neurotransmitter receptors on the soma and dendritic tree. We previously showed that inhibitory neurotransmitter (GABA(A) and glycine) receptors on a well-characterised sensory neurone, the parasol ganglion cell in the primate retina, are segregated towards the distal part of the dendritic tree. Here we studied the distribution of excitatory ionotropic glutamate receptor subunits on the dendrites of parasol cells in the retina of a New World monkey, the marmoset, Callithrix jacchus. Individual ganglion cells were intracellularly injected in an in vitro retinal wholemount preparation. Ionotropic glutamate receptor subunits. including AMPA (GluR1-4), kainate (GluR6/7), NMDA (NR1C2') subunits, and the orphan receptors delta1 and delta2 were visualized with immunocytochemical methods. Immunoreactive puncta that colocalized with the dendrites of ganglion cells were analyzed using standard and/or confocal light microscopy. Colocalized puncta were present on parasol dendrites for all subunits studied, but their density was much lower (approximately 1/5) than previously reported for inhibitory (GABA and glycine) receptors. Segregation of the glutamate receptor clusters (GluR1, GluR6/7 subunits) to the peripheral dendrites was less marked than that shown for GABA and glycine receptor clusters. No sign of segregation of colocalized puncta to the peripheral part of the dendritic field was seen with antibodies to the GluR2, GluR2/3, GluR4, delta1/2, or NR1C2' subunits. The results suggest that although there is diverse expression of glutamate receptor subtypes, the glutamatergic synapses form only a small proportion of the total synaptic input to primate ganglion cells. They further suggest that the processes which control distribution of excitatory and inhibitory synapses on the dendritic field of ganglion cells are, at least to some extent, independent.

Animals↗