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Biomedical subjects

H Li

Publications and source records attributed to H Li.

At least 991 records · Page 55Linked to original sources
PubMed1999

[Studies on polysaccharides from Holothuria leucospilota].

A powder was obtained from the dried body of Holothuria leucosilota (Brandt). According to IR and UV spectra, paper chromatography and the physical and chemical data, it is showed a sulfated mucopoly-saccharide consisted of galactosamine, glucouronic acid, fucose and sulfate with the molar ratio of 1:0.96:0.78:1.98 respectively. The specific rotation, intrinsic viscoslty and molecular weight of this polysaccharide were all presented.

Animals↗
PubMed1999

Effect of liposome-encapsulated total alkaloid of harmaline on rabbit lens epithelial cells: experimental study on the prevention of posterior capsule opacification.

PURPOSE: To investigate whether liposome encapsulated total alkaloid of Harmaline (TAH) as a therapeutic agent is beneficial to prevention of posterior capsular opacification (PCO). METHODS: Liposome-encapsulated TAH was prepared by modified freeze-thawing method. 0.1 ml of liposome-encapsulated TAH (0.2 mg/ml) was injected into the capsular bag during extracapsular lens extraction (ECLE) of each eye in total 10 rabbit eyes. Blank liposome or balance salt solution (BSS) was used as control. Slit-lamp examination and histopathological examination was used to evaluated capsule opacification. Intraocular pressure (IOP), density and morphology of corneal endothelia cells, the amplitude and latency of b wave of ERG were measured. RESULTS: The inflammatory response was mild both in TAH treated and the control group. PCO formation occurred in the control group 2 weeks postoperatively, but the posterior capsule was clear in TAH treated eyes. 4 weeks and 8 weeks after operation, PCO occurred both in TAH treated and control eyes. However, it was milder in the TAH treated eyes. IOP remained at the normal level in all eyes. There was no difference in the density of corneal endothelial cells, and the amplitude and latency of b wave of ERG between TAH treated and control eyes. Histopathological study revealed that lens epithelial proliferation occurred 4 weeks and the Soemmerings ring developed 8 weeks postoperatively in the control eyes. However, only mild vacuolization and pkynotic changes of lens epithelial cells were found in TAH treated eyes. Transmmission electronic microscopy demonstrated that there were mild cytoplasm vacuolization and mitochondria swelling of lens epithelial cells in TAH treated eyes. CONCLUSION: The results suggest that liposome encapsulated TAH can inhibit metaplasia and proliferation of lens epithelial cells in the rabbit eye without obvious toxicity to the eye tissue. It may be used as a potential agent to prevent the development of PCO.

Alkaloids↗
PubMed1999

[The study of the control system of new generation EECP].

A new algorithm for the inflation and deflation timing of the Enhanced External Counterpulsation (EECP) have been developed, A pentium PC and 16 bit microcontroller with parallel interrupt communication were used for developing a new kind of EECP system. The 16 bit microcontroller was used to collect and pre-process the ECG and EECP signals. The pre-processing data is transmitted to PC by the parallel communication interface. According to the new algorithm, PC sent out the sequential control signals and monitor the state of EECP. It is necessary to synchronize the time of aortic valve closure and diastolic augmentation during EECP, under the condition of the patients' safety, the effect of therapy have been extremely improved.

Algorithms↗
PubMed1999

[Determination of mercury in food by microwave oven digestion-hydride generation atomic absorption spectrometry].

Mercury in food was determined by microwave oven digestion-hydride generation atomic absorption spectrometry. The best condition of digestion was also studied. Furthermore, the way of doing digestion was compared to standard method with satisfactory results. The method is rapid and simple, and of good precision and high accuracy. The sensitivity is 0.43 microg/L. The detection limit is 0.35 microg/L. The relative standard deviation is 2.8% and the recovery is 93.5%-103.0%.

Food Analysis↗
PubMed1999

[Vibration studies of amphetamine and methamphetamine by micro Raman].

For the first time, we obtained and investigated the Raman spectra of amphetamine and methamphetamine by micro Raman with incidence excitation light 514.5 nm under the ambient environment. According to the fact that both molecules belong to single substituted benzene which has the symmetry of Cy2v, the attribution of Raman vibration modes in amphetamine and methamphetamine molecules was carried out by studying the spectral lines in the two spectra. The Raman line that only appeared in methamphetamine but could not be seen in any other drugs we have investigated was most possibly attributed to the stretching vibration between C-N(+)-C.

Amphetamine↗
PubMed1999

[Studies of narcotics by micro Raman spectroscopy].

For the first time, the Raman spectra of eight kinds of narcotics were obtained and investigated by micro Raman. The results indicated that the Raman spectra were affected by the numbers and position of methyl in substituent groups. Under incidence light 514.5 nm and appropriate measurement condition, high quality Raman spectra of drugs with low fluorescence background were obtained. In addition, we discovered that narcotine and thedaine were very sensitive to strong light radiation. Finally, by comparing Raman spectra carefully for all drugs we measured the specific Raman peaks were given for the purpose of distinguishing different kinds of drugs.

Illicit Drugs↗
PubMed1999

Effect of cocaine on testicular blood flow in rats: evaluation by percutaneous injection of xenon-133.

PURPOSE: Cocaine abuse has reached epidemic proportions in the United States. Our recent study has shown that cocaine has adverse action on spermatogenesis and fertility in male rats. The indirect action of cocaine occurs by blocking the reuptake of neurotransmitter, which causes local vasoconstriction. In this study we evaluate blood flow to the testes after subcutaneous injection of cocaine to male rats. METHODS: Male Sprague-Dawley rats were divided into two main groups. The treatment group received subcutaneous cocaine (30 mg/kg body weight) and the control animals received normal saline. Xenon-133 wash out experiments were carried out on testes at 5, 10, 15, 20, 30, 45, 60, 90 min and 4.5 hours after injection of cocaine or normal saline. Statistical analysis was done by SPSS V. 7.S for windows. P < 0.05 was considered statistically significant. RESULTS: There was a reduction in testicular blood flow after cocaine administration to male rats. This vasoconstrictor effect was most pronounced at 15 min after injection of cocaine and persisted up to 60 min. At 90 min, the early restitution of blood flow to ischemic tissue occurred. There was a significant increase in testicular blood flow in cocaine-treated groups than in the control group during restitution phases at 90 min. At 4.5 hours, there was no difference in blood flow in both groups. CONCLUSION: This study demonstrates that cocaine, when given subcutaneously at a 30 mg/kg body weight dose, results in prolonged vasoconstriction of the blood vessels to the testes. Adverse effects of cocaine on the testes may be in part due to ischemic and postischemic reperfusion injury to the organ.

Administration, Cutaneous↗
PubMed1998

Crystal structure of constitutive endothelial nitric oxide synthase: a paradigm for pterin function involving a novel metal center.

Nitric oxide, a key signaling molecule, is produced by a family of enzymes collectively called nitric oxide synthases (NOS). Here, we report the crystal structure of the heme domain of endothelial NOS in tetrahydrobiopterin (H4B)-free and -bound forms at 1.95 A and 1.9 A resolution, respectively. In both structures a zinc ion is tetrahedrally coordinated to pairs of symmetry-related cysteine residues at the dimer interface. The phylogenetically conserved Cys-(X)4-Cys motif and its strategic location establish a structural role for the metal center in maintaining the integrity of the H4B-binding site. The unexpected recognition of the substrate, L-arginine, at the H4B site indicates that this site is poised to stabilize a positively charged pterin ring and suggests a model involving a cationic pterin radical in the catalytic cycle.

Amino Acid Sequence↗
PubMed1998

Conformational changes between the active-site and regulatory light chain of myosin as determined by luminescence resonance energy transfer: the effect of nucleotides and actin.

Myosin is thought to generate movement of actin filaments via a conformational change between its light-chain domain and its catalytic domain that is driven by the binding of nucleotides and actin. To monitor this change, we have measured distances between a gizzard regulatory light chain (Cys 108) and the active site (near or at Trp 130) of skeletal myosin subfragment 1 (S1) by using luminescence resonance energy transfer and a photoaffinity ATP-lanthanide analog. The technique allows relatively long distances to be measured, and the label enables site-specific attachment at the active-site with only modest affect on myosin's enzymology. The distance between these sites is 66.8 +/- 2.3 A when the nucleotide is ADP and is unchanged on binding to actin. The distance decreases slightly with ADP-BeF3, (-1.6 +/- 0.3 A) and more significantly with ADP-AlF4 (-4.6 +/- 0.2 A). During steady-state hydrolysis of ATP, the distance is temperature-dependent, becoming shorter as temperature increases and the complex with ADP.Pi is favored over that with ATP. We conclude that the distance between the active site and the light chain varies as Acto-S1-ADP approximately S1-ADP > S1-ADP-BeF3 > S1-ADP-AlF4 approximately S1-ADP-Pi and that S1-ATP > S1-ADP-Pi. The changes in distance are consistent with a substantial rotation of the light-chain binding domain of skeletal S1 between the prepowerstroke state, simulated by S1-ADP-AlF4, and the post-powerstroke state, simulated by acto-S1-ADP.

Actins↗
PubMed1998

LIM homeodomain factors Lhx3 and Lhx4 assign subtype identities for motor neurons.

The circuits that control movement are comprised of discrete subtypes of motor neurons. How motor neuron subclasses develop and extend axons to their correct targets is still poorly understood. We show that LIM homeodomain factors Lhx3 and Lhx4 are expressed transiently in motor neurons whose axons emerge ventrally from the neural tube (v-MN). Motor neurons develop in embryos deficient in both Lhx3 and Lhx4, but v-MN cells switch their subclass identity to become motor neurons that extend axons dorsally from the neural tube (d-MN). Conversely, the misexpression of Lhx3 in dorsal-exiting motor neurons is sufficient to reorient their axonal projections ventrally. Thus, Lhx3 and Lhx4 act in a binary fashion during a brief period in development to specify the trajectory of motor axons from the neural tube.

Animals↗
PubMed1998

Telomerase is controlled by protein kinase Calpha in human breast cancer cells.

Telomerase, a specialized RNA-directed DNA polymerase that extends telomeres of eukaryotic chromosomes, is repressed in human somatic tissues and becomes activated during tumor progression in most human cancers. To date, little is known about how telomerase is activated and controlled in cancer, although activation is thought to be involved in cancer cell immortalization. Here, we report that human telomerase-associated protein 1 (hTEP1) and the telomerase catalytic subunit (human telomerase reverse transcriptase (hTERT)) are phosphoproteins and that their phosphorylation is a prerequisite for the activation of telomerase in intact human breast cancer cells. Identified by hTEP1 peptide affinity chromatography, protein kinase Calpha mediates the phosphorylation of hTEP1 and hTERT and induces a marked increase in telomerase activity. Thus, phosphorylation of hTEP1 and hTERT by protein kinase Calpha represents an essential step in the generation of a functional telomerase complex in the initiation and maintenance of telomerase activity in human cancer.

Amino Acid Sequence↗
PubMed1998

Human 12(R)-lipoxygenase and the mouse ortholog. Molecular cloning, expression, and gene chromosomal assignment.

Expressed sequence tag information was used to clone the full-length sequence for a new human lipoxygenase from the B cell line CCL-156. A related mouse sequence with 83% nucleotide identity to the human sequence was also cloned. The human lipoxygenase, when expressed via the baculovirus/insect cell system produced an approximately 80-kDa protein capable of metabolizing arachidonic acid to a product identified as 12-hydroxyeicosatetraenoic acid by mass spectrometry. Using chiral phase-high performance liquid chromatography, the product was identified as >98% 12(R)-hydroxyeicosatetraenoic acid as opposed to the S-stereoisomer formed by all other known mammalian lipoxygenases. The single copy human 12(R)-lipoxygenase gene was localized to the chromosome 17p13 region, the locus where most other lipoxygenase genes are known to reside. By reverse transcription-polymerase chain reaction, but not by Northern blot, analysis the 12(R)-lipoxygenase mRNA was detected in B cells and adult skin. However, the related mouse lipoxygenase mRNA was highly expressed in epidermis of newborn mice and to a lesser extent in adult brain cortex. By in situ hybridization the mouse lipoxygenase gene was demonstrated to be temporally and spatially regulated during embryogenesis. Expression was induced at embryonic day 15.5 in epidermis, nasal epithelium, and surface of the tongue. These results broaden the mammalian lipoxygenase family to include a 12(R)-lipoxygenase whose biological function remains to be determined.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1998

[Use of the primed in situ labeling technique for a rapid detection of chromosomes X, 18].

OBJECTIVE: To develop a rapid method for detection of chromosomes. METHODS: Chromosomes X, 18 were detected by the primed in situ labeling(PRINS) in eight samples of female peripheral blood cultures. RESULTS: Specific chromosomes were obtained on both metaphase and interphase nuclei. The efficiency of labeling was 84%-92%(mean=89%) in chromosome 18, and 73%-87%(mean=84%) in chromosome X. The pretreatment of slides by proteinase K markedly raised the efficiency of labeling and increased the intensity of signals. PRINS reaction could be performed automatically with a programmable thermocycler in less than one hour. CONCLUSION: The results suggest that PRINS is a fast and specific method for identifying chromosomes. It may be a reliable technique for detecting aneuploid in prenatal diagnosis.

Chromosomes, Human, Pair 18↗
PubMed1998

Cytokine and chemokine mRNA expressing cells in muscle tissues of experimental autoimmune myasthenia gravis.

In-situ hybridization with labeled oligonucleotide probes was applied to explore cytokine and chemokine mRNA expression in sections of striated muscle, the target organ in experimental autoimmune myasthenia gravis (EAMG), induced in Lewis rats by immunization with acetylcholine receptor (AChR) and complete Freund's adjuvant (CFA). A transient burst of TNF-alpha, IL-1beta and IL-6 mRNA expressing cells was detected during the early phase of EAMG. This cytokine pattern was related to muscular infiltration of macrophages. Levels of IL-4, IL-10, IFN-gamma, cytolysin and TGF-beta mRNA expressing cells were low and observed mainly during the early phase of EAMG. C-C chemokine RANTES, MCP, MIP-1alpha and MIP-2 mRNA expressing cells were not detected over the course of EAMG. The low and transient expression of cytokines in EAMG muscle tissues suggests that the immune effector responses are unlikely operated by infiltrating cells in muscle. Muscular infiltrations in EAMG are unlikely due to local accumulation of C-C chemokines.

Animals↗
PubMed1998

Identification of two major F2 isoprostanes, 8,12-iso- and 5-epi-8, 12-iso-isoprostane F2alpha-VI, in human urine.

Isoprostanes (iPs) are nonenzymatic, free radical-derived compounds isomeric with enzymatically formed eicosanoids such as prostaglandins, leukotrienes, and thromboxanes. One group formed by the auto-oxidation of arachidonic acid, the F2-iPs, consists of four classes of isomers of prostaglandin F2alpha (PGF2alpha). They are relatively abundant in human urine. This fact, along with their chemical stability and excellent characteristics for quantitation by gas chromatography/mass spectrometry, has made them attractive indices of oxidative stress in humans. We developed a specific assay using gas chromatography/mass spectrometry for the first identified F2-iP, iPF2alpha-III (previously called 8-iso-PGF2alpha or 8-epi-PGF2alpha), which demonstrated the utility of monitoring a specific isomer. Recently, we described an assay for another isomer, iPF2alpha-VI, which is present in urine in greater concentration than iPF2alpha-III and which is particularly amenable to quantitation. We now describe the identification in human urine of two more isomers, 8,12-iso-iPF2alpha-VI and 5-epi-8, 12-iso-iPF2alpha-VI, using high performance liquid chromatography/tandem mass spectrometry and gas chromatography/mass spectrometry. These compounds are each present in approximately 5-fold greater concentrations than iPF2alpha-VI (approximately 20-fold greater than iPF2alpha-III). They share the unique chemical characteristics of class VI compounds, which make them attractive targets for quantitation by gas chromatography/mass spectrometry and immunoassay development.

Chromatography, High Pressure Liquid↗
PubMed1998

Regulation of anti-DNA B cells in recombination-activating gene-deficient mice.

Anti-DNA antibodies are regulated in normal individuals but are found in high concentration in the serum of systemic lupus erythematosus (SLE) patients and the MRL lpr/lpr mouse model of SLE. We previously studied the regulation of anti-double-stranded (ds)DNA and anti-single-stranded (ss)DNA B cells in a nonautoimmune background by generating mice carrying immunoglobulin transgenes coding for anti-DNAs derived from MRL lpr/lpr. Anti-dsDNA B cells undergo receptor editing, but anti-ssDNA B cells seem to be functionally silenced. Here we have investigated how anti-DNA B cells are regulated in recombination- activating gene (RAG)-2-/- mice. In this setting, anti-dsDNA B cells are eliminated by apoptosis in the bone marrow and anti-ssDNA B cells are partially activated.

Animals↗