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Biomedical subjects

H Liu

Publications and source records attributed to H Liu.

At least 523 records · Page 29Linked to original sources
PubMed2000

Anti-human platelet tetraspanin (CD9) monoclonal antibodies induce platelet integrin alphaIIbbeta3 activation in a Fc receptor-independent fashion.

OBJECTIVE: This study characterized the activation of platelet integrin alphaIIbbeta3 induced by two anti-human platelet tetraspanin monoclonal antibodies (mAbs), HI117 and SJ9A4. METHODS: Using 125I-labeled human fibrinogen(Fg), specific Fg binding to human platelets induced by HI117 and SJ9A4 was measured as indication of activation of platelet integrin alphaIIbbeta3 by the two mAbs. RESULTS: HI117 and SJ9A4 (10 microg/ml and 20 microg/ml) induced evident specific Fg binding to human platelets, suggesting that the two mAbs evoked activation of platelet integrin alphaIIbbeta3. Further study indicated that HI117 and SJ9A4 induced integrin alphaIIbbeta3 activation independent of platelet Fc-receptors, and that HI117 and SJ9A4-induced integrin alphaIIbbeta3 activation was inhibited by sphingosing, aspirin, apyrase, and/or PGI2. CONCLUSION: The anti-platelet tetraspanin (CD9) mAbs, HI117 and SJ9A4, can induce platelet integrin alphaIIbbeta3 activation independent of Fc-receptor. Three signaling pathways, i.e. thromboxane, secreted ADP, and cAMP pathways may be involved in the process, with protein kinase C activation presumably being the common step of the three pathways.

Antibodies, Monoclonal↗
PubMed2000

[The study of induced circular dichroism of phenylalanine bridged metal bis-porphyrin].

L- and D-phenylalanine bridged zinc bis-porphyrin with the connecting chain at ortho and para position of two phenyl rings [o,o-C2-Phe-C2-(TPP)2Zn2 and p,p-C2-Phe-C2-(TPP)2Zn2] have been synthesized and characterized. o,o-C2-Phe-C2-(TPP)2Zn2 exhibited strong induced circular dichroism (ICD). While p,p-C2-Phe-C2-(TPP)2Zn2 exhibited no significant ICD. The ICD of present complexes were mainly determined by the pi-pi interaction and chiral excition coupling between two porphyrin moieties of the molecules. Our results also indicated that the existence of chiral center in a porphyrin molecule does not mean it would surely exhibit ICD.

Chelating Agents↗
PubMed2000

[Studies on spectral interferences and correction in simultaneous determination of multi-elements in sediments with ICP-AES].

Spectral interferences in the simultaneous determination of multi-elements in sediments and soil by ICP-AES were investigated and the multicomponent spectral fitting (MSF) method was used for the correction. Several factors affecting the MSF method such as the signal integration time and the spectra shift were studied. The comparison between MSF and off-peak background correction were made by analyzing national standard reference material: sediment GBW07306. The detection limit and the precision could be improved by a factor of 1.3-9.0 and 1.1-4.9 respectively and the results agreed better with those of the certified values when using MSF correction.

Aluminum↗
PubMed2000

[An evaluation of human hair homogeneity by inductively coupled plasma mass spectrometry].

Human hair certified reference material(GBW09101) homogeneity was evaluated by determining 10(-6) quantity Cu, Zn, Mg, K, Pb, Fe, Ca, Na and S on sample weight from 100 mg to 300 mg by neutron activation analysis, atomic absorption spectrometry and X-ray fluorescence analysis. Using variance F test, the results(F < F alpha) is not differ significantly and this material could be considered homogeneous. In this paper, an evaluation of homogeneity was made by Inductively Coupled Plasma Mass Spectrometry through the determination of 10(9) quantity La, Sm, Y in 0.2000 g samples. Using t test and F test, the results (magnitude of t < t alpha, F < F alpha) were satisfactory.

Copper↗
PubMed2000

[Spectral study of the microenviroment change of aromatic amino-acid residues in BSA induced by pH].

The microenvironment change of aromatic amino-acid residues in BSA at various pH were studied by fluorescence spectra and ultraviolet absorption spectra. It suggested that the change of protein surface and surface hydrophobicity from result. Compared to neutral pH, the Trp microenvironment seemed to be more hydrophobic at lower pH indicating less local surface hydrophobicity of BSA. At higher pH, the protein undergo conformational changes and unhold, the more buried Phe exposed to solvents consistent with stronger surface hydrophobicity of BSA.

Amino Acids, Aromatic↗
PubMed2000

[Progress in charge-coupled device and its applications].

Charge-coupled device (CCD) is a photosensitive element based on the metal-oxidesemiconductor technology. Currently, it has a number of benefits; broad spectral range response, low detection limit, wide dynamic range, minimal dark current and readout noise as well as abilities of signal integration, simultaneous multichannel detection and real-time detection. In this paper, the operational principle, features and performance characterization of CCD are introduced and its applicaton in spectral detection and spectral imaging are veiwed. The development of CCD technique has brought a revolutionary progress in the spectroscopic areas. Its future developments are also outlooked.

Electrochemistry↗
PubMed2000

[Studies on the gas phase reaction of ablated Ni+ with molecular flows of alcohols in the time-of-flight mass spectrometer].

A apparatus combining molecular flows, laser ablation and time-of-flight mass spectrometer was first designed, in which the gas phase reactions of metal ions with organic compounds were realized. In a small quartz cell of it, laser ablated Ni+ meet and react with molecular flows of alcohols, and their product ions were detected by the time-of-flight mass spectrometer. The gas phase reactions of Ni+ with C2-C6 alcohols were studied. All of which can be explained by the following mechanism: (1) Insertion of Ni+ into bonds of alcohols; (2)Following each insertion, a beta-hydrogen shift onto Ni+ to produce intermediate; (3) Dessociation of each intermediate by loss of neutral molecular to give product ion.

English Abstract↗
PubMed1999

Selection of a human anti-progesterone antibody fragment from a transgenic mouse library by ARM ribosome display.

In antibody-ribosome-mRNA complex (ARM) ribosome display, stable complexes of nascent protein, mRNA and ribosomes are produced in a eukaryotic in vitro expression system, through coupled transcription and translation of DNA lacking a 3' stop codon. Selection of the protein simultaneously captures the relevant mRNA, which is recovered as DNA by coupled reverse transcription-polymerase chain reaction (RT-PCR) performed on the intact complexes. Here, we describe the use of ARM display to select a specific human antibody fragment from a transgenic mouse library. The mice carry unrearranged gene segments of the human heavy (H) and kappa light (L) chain loci, while the endogenous murine H and kappa loci are functionally silenced; they respond to immunisation by production of fully human IgM antibodies. A library encoding human single-chain (sc) antibody (V(H)/K) fragments, in which V(H) domains and kappa light chains were combined at random by PCR, was prepared from spleen cells of transgenic mice immunised with progesterone-bovine serum albumin (BSA). Library diversity was demonstrated by sequencing. Progesterone-binding fragments were selected over five cycles of ARM display and the selected DNA cloned and expressed in Escherichia coli. Soluble V(H)/K fragments obtained in periplasmic extracts had the same specificity as ribosome-bound V(H)/K, supporting the view that folding and specificity of the displayed and soluble proteins are equivalent. The affinity of the expressed V(H)/K was approximately 10(-8) M. Sequencing showed that ARM display selected a single V(H)/V(L) combination (V(H)1-2, Vkappa4-1) and rearrangement, with a few mutational differences between clones. Monoclonal antibodies against progesterone-BSA obtained from hybridomas were encoded by the same V(H) and V(L) segments and had similar properties to the fragments obtained in vitro. The combination of ribosome display and transgenic mouse technologies is a rapid means of generating fully human antibody fragments in vitro for expression and further manipulation.

Amino Acid Sequence↗
PubMed1999

Resistance to excitotoxin-induced seizures and neuronal death in mice lacking the preprotachykinin A gene.

Epileptic seizures are associated with increases in hippocampal excitability, but the mechanisms that render the hippocampus hyperexcitable chronically (in epilepsy) or acutely (in status epilepticus) are poorly understood. Recent evidence suggests that substance P (SP), a peptide that has been implicated in cardiovascular function, inflammatory responses, and nociception, also contributes to hippocampal excitability and status epilepticus, in part by enhancing glutamate release. Here we report that mice with disruption of the preprotachykinin A gene, which encodes SP and neurokinin A, are resistant to kainate excitoxicity. The mice show a reduction in the duration and severity of seizures induced by kainate or pentylenetetrazole, and both necrosis and apoptosis of hippocampal neurons are prevented. Although kainate induced the expression of bax and caspase 3 in the hippocampus of wild-type mice, these critical intracellular mediators of cell death pathways were not altered by kainate injection in the mutant mice. These results indicate that the reduction of seizure activity and the neuroprotection observed in preprotachykinin A null mice are caused by the extinction of a SP/neurokinin A-mediated signaling pathway that is activated by seizures. They suggest that these neurokinins are critical to the control of hippocampal excitability, hippocampal seizures, and hippocampal vulnerability.

Animals↗
PubMed1999

Childhood-onset schizophrenia: progressive brain changes during adolescence.

BACKGROUND: Previous NIMH childhood onset schizophrenia (COS) anatomic brain MRI studies found progression of ventricular volume and other structural brain anomalies at 2-year follow up across mean ages 14 to 16 years. However, studies in adult patients generally do not show progression of ventricular volume or correlation of ventricular volume with duration of illness. To address issues of progression of brain anomalies in schizophrenia, this report extends previous studies to include a third longitudinal scan, uses a larger sample size, and includes measures of the amygdala and hippocampus. METHODS: Volumes of the total cerebrum, lateral ventricles, hippocampus, and amygdala were quantified on 208 brain magnetic resonance imaging scans from 42 adolescents with COS (23 with one or more repeat scan) and 74 age- and gender-matched controls (36 with one or more repeat scan). A statistical technique permitting combined use of cross-sectional and longitudinal data was used to assess age-related changes, linearity, and diagnostic group differences. RESULTS: Differential nonlinear progression of brain anomalies was seen during adolescence with the total cerebrum and hippocampus decreasing and lateral ventricles increasing in the COS group. The developmental curves for these structures reached an asymptote by early adulthood for the COS group and did not significantly change with age in the control group. CONCLUSIONS: These findings reconcile less striking progression of anatomic brain images usually seen for adult schizophrenia and complement other data consistent with time-limited, diagnostic-specific decreases in brain tissue. Adolescence appears to be a unique period of differential brain development in schizophrenia.

Adolescent↗
PubMed1999

Cigarettes, alcohol, marijuana, other risk behaviors, and American youth.

Increases in adolescent marijuana and other drug use have created widespread concern. One theory argues that increased use of cigarettes and alcohol among younger adolescents leads to greater use of marijuana which, in turn, leads to subsequent use of other drugs (e.g. cocaine, heroin, hallucinogens). Detractors of this theory claim that use of these substances is a symptom of a larger set of destructive behaviors (e.g. violence, suicide, promiscuous sex), and marijuana has no independent effect on the use of other more serious drugs. The authors examined whether, for high school seniors, early use of cigarettes, alcohol and marijuana has an independent effect on more serious drug use even when other behaviors are considered. Using the 1995 Youth Risk Behavior Survey (n = 2871) and logistic analysis, after accounting for selected other behaviors, seniors using cigarettes before age 13 were 3.3 (95% C.I. 2.3,4.6) times likelier to have used marijuana than ones who never smoked; for alcohol, the odds ratio was 4.5 (2.6,7.7). Seniors using marijuana before the age of 14 were 7.4 times (4.0,13.6) likelier to have used other drugs. Though no causal effect is demonstrated, cigarette and alcohol use was associated with the likelihood of marijuana use; marijuana use was associated with the likelihood of other drug use, even after selected other risk and protective behaviors were considered.

Adolescent↗
PubMed1999

Dissociation of CH4 at high pressures and temperatures: diamond formation in giant planet interiors?

Experiments using laser-heated diamond anvil cells show that methane (CH4) breaks down to form diamond at pressures between 10 and 50 gigapascals and temperatures of about 2000 to 3000 kelvin. Infrared absorption and Raman spectroscopy, along with x-ray diffraction, indicate the presence of polymeric hydrocarbons in addition to the diamond, which is in agreement with theoretical predictions. Dissociation of CH4 at high pressures and temperatures can influence the energy budgets of planets containing substantial amounts of CH4, water, and ammonia, such as Uranus and Neptune.

Diamond↗
PubMed1999

Thromboxane A2 is a mediator of cyclooxygenase-2-dependent endothelial migration and angiogenesis.

Cyclooxygenase-2 (COX-2) inhibitors reduce angiogenic responses to a variety of stimuli, suggesting that products of COX-2 may mediate critical steps. Here, we show that thromboxane A2 (TXA2) is one of several eicosanoid products generated by activated human microvascular endothelial cells. Selective COX-2 antagonists inhibit TXA2 production, endothelial migration, and fibroblast growth factor-induced corneal angiogenesis. Endothelial migration and corneal angiogenesis are similarly inhibited by a TXA2 receptor antagonist, SQ29548. A TXA2 agonist, U46619, reconstitutes both migration and angiogenesis responses under COX-2-inhibited conditions. These findings identify TXA2 as a COX-2 product that functions as a critical intermediary of angiogenesis.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1999

Tert-butylsulfonamide. A new nitrogen source for catalytic aminohydroxylation and aziridination of olefins.

[reaction: see text] The N-chloramine salt of tert-butylsulfonamide has been shown to be an efficient nitrogen source and the terminal oxidant for catalytic aminohydroxylation and aziridination of olefins, resembling closely Chloramine-T by its behavior in these catalytic reactions. The sulfonyl-nitrogen bond in the product or its derivatives is easily cleaved under mild acidic conditions, allowing for facile liberation of the amino group.

Alkenes↗
PubMed1999

Molecular cloning and characterization of AtTERT, a telomerase reverse transcriptase homolog in Arabidopsis thaliana.

On the basis of its predicted homology to human telomerase reverse transcriptase (hTERT), a cDNA for Arabidopsis thaliana TERT (AtTERT) has now been isolated from cultured cells. The cDNA contains an open reading frame of 3372 bp, encoding a protein with a predicted size of 131 kDa and isoelectric point of 9.9. The AtTERT protein contains the conserved reverse transcriptase motifs 1, 2 and A-E as well as the TERT-specific T motif. Reverse transcription-polymerase chain reaction analysis and an assay of telomerase activity revealed that both AtTERT mRNA and telomerase activity are abundant in shoot apical meristems but are not detectable in rosette leaves.

Amino Acid Sequence↗
PubMed1999

Molecular cloning and sequencing of two 'short chain' and two 'long chain' K(+) channel-blocking peptides from the Chinese scorpion Buthus martensii Karsch.

Five full-length cDNAs encoding the precursors of two 'short chain' scorpion non-toxic peptides active on Ca(2+)-activated K(+) channels (BmP02 and BmP03) and two novel putative long chain K(+) channel-blocking peptides (named BmTXKbeta and BmTXKbeta2) were first isolated from the venom gland cDNA library of the Chinese scorpion Buthus martensii Karsch (BmK). BmTXKbeta2 showed a high similarity with AaTXKbeta, while BmTXKbeta was completely different in the deduced primary structure from the long chain and short chain scorpion toxins already characterized. Thus, BmTXKbeta expands the scorpion long chain K(+) channel-blocking peptide family. Although little sequence similarity exists between the above two short and two long peptides, they are similar at the positions of six cysteines, suggesting that they should all share a similar scaffold composed of an alpha-helix and a three-stranded beta-sheet.

3' Untranslated Regions↗
PubMed1999

Selective and transient expression of a native chondroitin sulfate epitope in Deiters' cells, pillar cells, and the developing tectorial membrane.

The tectorial membrane (TM) is an acellular connective tissue overlying the sensory hair cells of the organ of Corti. Association of the tectorial membrane with the stereocilia of the sensory hair cells is necessary for proper auditory function. During development, the mature tectorial membrane is thought to arise by fusion of a "major" and "minor" tectorial membrane (Lim, Hear Res 1986;22:117-146). Several proteins and glycoconjugates have been detected in the developing TM; however, the specific molecules which mediate fusion of the two components of the TM have not been identified. In the present study, a novel monoclonal antibody (TC2) that recognizes a native epitope on glycosaminoglycans enriched in chondroitin-4-sulfate revealed a transient and restricted expression in the developing gerbil TM. The localization patterns suggest that Deiters' and pillar cells secrete a TC2-positive matrix prior to birth that later becomes incorporated into the marginal band and superior layer (cover net) of the TM. The developmental timecourse and patterns of TC2 reactivity suggest that this molecule may play a critical role in the fusion of the minor TM with the major TM.

Animals↗