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Biomedical subjects

G Lin

Publications and source records attributed to G Lin.

At least 55 records · Page 3Linked to original sources
PubMed2000

Simultaneous determination of seven major isosteroidal alkaloids in bulbs of Fritillaria by gas chromatography.

The present paper describes the development of a most simple, sensitive, and specific gas chromatographic method to date, for the direct determination of seven major bioactive isosteroidal alkaloids, namely ebeiedine, ebeiedinone, ebeienine, hupehenine, isoverticine, verticine, verticinone and imperialine, in Fritillaria species, a commonly used antitussive traditional Chinese medicinal (TCM) herb. In the present study, a commercially available Supelco SAC-5 capillary column (30 m x 0.25 mm, 0.25 microm) specifically designed for the analysis of steroids was utilized for the direct determination of Fritillaria alkaloids. Calibration curves were obtained by spiking authentic compounds and the internal standard (solanidine) into herbal samples prior to extraction. Extraction was conducted simply by shaking the pre-alkalized diethyl ether solution (5.0 ml) containing dried herb (0.1 g) for 2 h. All calibration curves showed good linear regressions (r2>0.995) within test ranges. The assay was reproducible and accurate with the overall intra- and inter-day variation and accuracy of less than 10% and more than 90%, respectively. The developed GC method was successfully utilized to analyze seven major bioactive alkaloids in seven Fritillaria species, and the results demonstrate that this direct GC analytical method is suitable for the quality control of this commonly used antitussive TCM herb.

Alkaloids↗
PubMed2000

t(1) noise and sensitivity in pulsed field gradient experiments.

In this paper, a calculation routine based on product operator formalism and coherence pathway is presented, which describes t(1) noise and sensitivity in pulsed field gradient experiments. Several examples including the absolute value mode pulsed field gradient COSY, MQF-COSY, MQC, HMQC, and NOESY sequences are investigated to study the t(1) noise stemming from the phase errors of radiofrequency (RF) pulses and the sensitivity affected by RF pulse rotation angles. Our theoretical results indicate that the t(1) noises in P-type COSY, multiple-quantum-filtered (MQF)-COSY, and multiple-quantum coherence (MQC) are lower than those in the N-type corresponding experiments, while in HMQC and NOESY there is no difference in t(1) noise effects between P-type and N-type spectra. Meanwhile, from the calculations, we obtained the optimized RF pulse rotation angles in those sequences. In MQF-COSY, an increase in sensitivity of about 4(cos(2)θ sin(q-1)2θ)(2) - 1 (θ = arc cot can be achieved by using the optimized angles. In MQC, the increase is 2 cos(2)θ sin(q-1)2θ - 1 (θ = arc cot. MQF-COSY experiments are also carried out to support our corresponding theoretical results.

Magnetic Resonance Spectroscopy↗
PubMed2000

Apolipoprotein binding to protruding membrane domains during removal of excess cellular cholesterol.

High-density lipoproteins (HDL) are believed to protect against cardiovascular disease by removing excess cholesterol from cells. Lipid-free HDL apolipoproteins remove cellular cholesterol and phospholipids by an active, Golgi-dependent process that is still poorly understood. Here we characterized the morphology of apolipoprotein binding sites on cultured cells by immunogold electron microscopy. After 6 h incubations with lipid-free apoA-I or apoE, immunogold-labeled apolipoproteins were distributed sparsely along the planar surface of human fibroblasts and THP-1 macrophages. Overloading these cells with cholesterol led to a several-fold increase in the concentration of immunogold-labeled apoA-I and apoE on the cell surface, and over 80% of these gold particles were associated with novel electron-opaque structures protruding from the plasma membrane. Protrusions binding apoE were larger (100-200 nm) than those binding apoA-I (10-60 nm), and similar apoA-I-binding structures appeared when cells were incubated with either purified apoA-I or HDL particles. These structures were formed and enlarged by a time-dependent process inhibited by the Golgi disruptor brefledin A, the energy poison NaF, and low temperature. Moreover, formation of these structures was nearly absent in fibroblasts from a subject with Tangier disease, cells that lack a functioning apolipoprotein-mediated lipid removal pathway. Thus, formation of novel apolipoprotein binding structures protruding from the cell surface is an intermediate step in the cellular pathway by which apolipoproteins remove excess cholesterol.

Apolipoproteins A↗
PubMed2000

Simultaneous analysis of clivorine and its four microsomal metabolites by high-performance liquid chromatography.

A specific high-performance liquid chromatographic assay was developed for a simultaneously qualitative and quantitative determination of clivorine, a hepatotoxic otonecine-type pyrrolizidine alkaloid, and its four putative hepatotoxicity-related metabolites, namely dehydroretronecine, 7-glutathionyldehydroretronecine, 7,9-diglutathionyldehydroretronecine, and clivoric acid, generated in rat microsomal incubation. This simultaneous determination was conducted by a direct analysis of aliquots of the supernatant of incubates using a specific two-column set-up. Impurities in the supernatant were firstly eluted out from the first PRP-1 guard column (50x4.1 mm) during an initial 5 min washing period with isocratic elution by mobile phase A (0.2% formic acid at pH 3.4 adjusted by ammonia). Subsequently, the guard column was then connected to the second PRP-1 analytical column (250x4.6 mm) and analytes were separated by a gradient elution with mobile phases A and B (acetonitrile). The assay provided good reproducibility and accuracy for all analytes tested with less than 12% of overall intra- and inter-day variations and higher than 87% of overall accuracy. This developed method was successfully applied to determine the intact clivorine and its four metabolites generated in rat microsomal incubation.

Animals↗
PubMed2000

Regional assessment of elderly disability in the U.S.

This study examines regional variation of elderly disability in the United States. Elderly disability measurements are derived from two newly available questions on mobility and self-care limitations in the 1990 census. Substantial regional differences in elderly disability rates exist, with a higher prevalence of disability in the Southeast. These differences persist after controlling for age and socioeconomic status (SES). The study findings suggest that some public health policy should be regionally formulated and some government actions should be devoted to reduce the excessive elderly disability in the South.

Aged↗
PubMed2000

Quantitative structure-activity relationships for the pre-steady-state inhibition of cholesterol esterase by 4-nitrophenyl-N-substituted carbamates.

4-Nitrophenyl-N-substituted carbamates (1-6) are the pseudo-substrate inhibitors of porcine pancreatic cholesterol esterase. Thus, the first step of the inhibition (Ki step) is the formation of the enzyme inhibitor tetrahedral adduct and the second step of the inhibition (kc) is the formation of the carbamyl enzyme. The formation of the enzyme inhibitor tetrahedral adduct is further divided into two steps, the formation of the enzyme-inhibitor complex with the dissociation constant, KS, at the first step and the formation of the enzyme-inhibitor tetrahedral adduct from the complex at the second step. The two-step mechanism for the formation of the enzyme-inhibitor tetrahedral adduct is confirmed by the pre-steady-state kinetics. The results of quantitative structure-activity relationships for the pre-steady-state inhibitions of cholesterol esterase by carbamates 1-6 indicate that values of -logKs and logk2/k-2 are correlated with the Taft substituent constant, sigma*, and the rho* values from these correlations are -0.33 and 0.1, respectively. The negative rho* value for the -logKS-sigma*-correlation indicates that the first step of the two-step formation of the enzyme-inhibitor tetrahedral adduct (KS step) is the formation of the positive enzyme inhibitor complex. The positive rho* value for the logk2/k-2 -sigma*-correlation indicates that the enzyme inhibitor tetrahedral adduct is more negative than the enzyme inhibitor complex. Finally, the two-step mechanism for the formation of the enzyme inhibitor tetrahedral adduct is proposed according to these results. Thus, the partially positive charge is developed at nitrogen of carbamates 1-6 in the enzyme-inhibitor complex probably due to the hydrogen bonding between the lone pair of nitrogen of carbamates 1-6 and the amide hydrogen of the oxyanion hole of the enzyme. The second step of the two-step formation of the enzyme-inhibitor tetrahedral adduct is the nucleophilic attack of the serine of the enzyme to the carbonyl group of carbamates 1-6 in the enzyme-inhibitor complex and develops the negative-charged oxygen in the adduct.

Animals↗
PubMed2000

Characterization of two structural forms of otonecine-type pyrrolizidine alkaloids from Ligularia hodgsonii by NMR spectroscopy.

Clivorine (1) and ligularine (2), two hepatotoxic otonecine-type pyrrolizidine alkaloids isolated from Ligularia hodgsonii, an antitussive traditional Chinese medicine, were investigated in CDCl(3) and D(2)O by various NMR techniques to delineate why this type of alkaloid displays uncharacteristic solubility properties by dissolving in both nonpolar organic and aqueous solutions. The results demonstrated that both alkaloids exist in a non-ionized form in CDCl(3), but in an ionized form in D(2)O, suggesting that this unique dual solubility may play a role in the intoxication resultant from consumption of water extracts of herbs, including herbal teas, containing otonecine-type pyrrolizidine alkaloids.

Antitussive Agents↗
PubMed2000

Heme oxygenase-1 and ferritin are increased in cerebral arteries after subarachnoid hemorrhage in monkeys.

Hemoglobin is a key factor in the production of cerebral vasospasm. Metabolism of hemoglobin involves breakdown of heme by heme oxygenase (HO) and sequestration of the released iron in ferritin. We determined whether subarachnoid hemorrhage induces these proteins in cerebral arteries and, if so, in which cells they are produced. Whether the changes correlated with vasospasm also was investigated. Subarachnoid hemorrhage was created in monkeys, and vasospasm was assessed by angiography in cohorts of animals killed 3, 7, or 14 days after the hemorrhage. Ferritin and HO-1 messenger ribonucleic acid (mRNA) and protein were measured by competitive reverse transcription-polymerase chain reaction and Western blotting in hemorrhage-side and control-side cerebral arteries and brain tissue. The location of these proteins was determined by immunohistochemistry. There was significant vasospasm 3 and 7 days but not 14 days after subarachnoid hemorrhage. There were no significant changes in mRNA for HO-1 or ferritin in cerebral arteries or brain tissue at any time. There was a significant increase in HO-1 and ferritin protein in hemorrhage-side compared with control-side cerebral arteries at 3, 7, and 14 days. The increase in HO-1 protein was maximal at 3 days, whereas the increase in ferritin protein was maximal at 7 days. There was no detectable increase in HO-1 or ferritin protein in brain tissue at any time. Immunohistochemistry localized HO-1 protein and ferritin to cells in the adventitia of the arterial wall. We show that subarachnoid hemorrhage is associated with a significant increase in HO-1 and ferritin proteins in cerebral arteries that begins at least as early as 3 days after the hemorrhage and that persists for up to 14 days.

Animals↗
PubMed2000

Effect of adenovirus-mediated nitric oxide synthase gene transfer on vasospasm after experimental subarachnoid hemorrhage.

OBJECTIVE: Evidence indicates that vasospasm after subarachnoid hemorrhage (SAH) is caused in part by a decrease in the vasodilator nitric oxide (NO), which is produced mainly in endothelial cells. This study tested whether intracisternal injection of adenovirus-expressing endothelial NO synthase (eNOS) would decrease vasospasm in dogs. METHODS: In 12 dogs, baseline cerebral angiography was performed, and then SAH was produced by two injections of blood into the cisterna magna. The dogs were randomized (n = 6/group) to intracisternal injection of adenovirus-expressing lacZ (Ad327beta-Gal) or eNOS (AdCD8-NOS), administered immediately after the first blood injection. Angiography was repeated on Day 7, and then L-arginine (50 mg) was administered intracisternally, and angiography was repeated. Cerebrospinal fluid aspirated from the cisterna magna on Days 2 and 7 was analyzed for levels of NO metabolites. The dogs were killed, and their basilar arteries were removed and studied pharmacologically. Four control dogs underwent angiography on Day 0, followed by virus injection (n = 2/group). Angiography was repeated on Day 7, and the control dogs were killed. Transgene expression was detected in tissue removed on Day 7 by histochemical staining for lacZ, by polymerase chain reaction for messenger ribonucleic acid for eNOS, and by measurement of NO metabolites in cerebrospinal fluid. RESULTS: Angiography showed significant vasospasm in each group (Ad327beta-Gal, -54 +/- 7% reduction in basilar artery diameter; AdCD8-NOS, -53 +/- 7%), with no significant difference between groups. Injection of L-arginine caused an insignificant increase in arterial diameter in each group. In dogs without SAH, Ad327beta-Gal caused a reduction in basilar artery diameter (-13 +/- 10%, P = 0.42; paired t test), whereas injection of AdCD8-NOS caused an increase in diameter (14 +/- 16%, P = 0.77; paired t test). Histological examination and beta-galactosidase staining of dogs given injections of Ad327beta-Gal showed staining in inflammatory cells in the subarachnoid space, in the adventitia of the cerebral vessels, and in the liver and lungs. Messenger ribonucleic acid for eNOS was detected in the leptomeninges of dogs given injections of AdCD8-NOS. Under isometric tension, basilar arteries from each group demonstrated similar relaxation to L-arginine, but arteries exposed to eNOS demonstrated significantly greater relaxation to L-arginine plus tetrahydrobiopterin than arteries exposed to lacZ. Cerebrospinal fluid levels of NO and its metabolites were significantly higher in dogs treated with AdCD8-NOS than those treated with Ad327beta-Gal 2 days after SAH. CONCLUSION: These results demonstrate that adenovirus vectors can be used to transfer genes to cells in the subarachnoid space of dogs. Enough NO can be produced in the absence of SAH to dilate the basilar artery. After SAH, however, NO plus a cofactor can dilate arteries in vitro, but not enough NO is generated in the subarachnoid space to prevent vasospasm, perhaps owing to the scavenging of NO by hemoglobin.

Adenoviridae↗
PubMed2000

Adenoviral gene transfer of nitric oxide synthase increases cerebral blood flow in rats.

OBJECTIVE: Depletion of nitric oxide may play a role in the development of vasospasm after aneurysmal subarachnoid hemorrhage. Replenishment of nitric oxide might be a useful treatment for vasospasm. Using rats, we performed intracisternal injections of replication-defective adenovirus containing the endothelial nitric oxide synthase (eNOS) gene and determined the localization of and effect on cerebral blood flow of transgene expression. METHODS: Rats underwent baseline measurement of cortical cerebral blood flow using laser Doppler flowmetry. Replication-defective adenovirus containing the Escherichia coli LacZ gene (Ad327beta-Gal, n = 2/time point) or the bovine eNOS gene (AdCD8-NOS, n = 4/time point) or physiological saline solution was injected into the cisterna magna. Cerebral blood flow was measured 1, 2, 4, 7, or 14 days later, and the animals were killed. Expression of beta-galactosidase activity from the LacZ gene was examined by histochemical staining and that of eNOS was examined by polymerase chain reaction assays of messenger ribonucleic acid. Brains were histopathologically examined for inflammation. RESULTS: Beta-galactosidase activity was observed throughout the leptomeninges and in some cells in the adventitia of small subarachnoid blood vessels in the Ad327beta-Gal-injected rats. Messenger ribonucleic acid for eNOS was detected in the leptomeninges and brainstem 1 and 2 days after injection of AdCD8-NOS. Rats injected with Ad327beta-Gal or physiological saline solution exhibited decreased cerebral blood flow beginning 2 days after virus injection and lasting up to 14 days after injection. Rats injected with AdCD8-NOS developed significant transient increases in cerebral blood flow 2 days after virus injection, followed by slight decreases in blood flow. There was inflammation in the subarachnoid space of all animals; the inflammation was qualitatively worse in animals injected with Ad327beta-Gal, compared with rats injected with AdCD8-NOS or saline solution. CONCLUSION: Intracisternal injection of replication-defective adenovirus containing the eNOS gene can transiently increase cerebral blood flow.

Animals↗
PubMed2000

Characterization of rat liver microsomal metabolites of clivorine, an hepatotoxic otonecine-type pyrrolizidine alkaloid.

The metabolism of the hepatotoxic otonecine-type pyrrolizidine alkaloid (PA), clivorine, was investigated using rat liver microsomes. The metabolites dehydroretronecine (DHR), 7-glutathionyldehydroretronecine (7-GSH-DHR), 7, 9-diglutathionyldehydroretronecine (7,9-diGSH-DHR), and clivoric acid were identified using chromatographic and mass spectrometric analyses. NMR characterizations were also performed on the isolated clivoric acid and the synthetic 7-GSH-DHR and 7,9-diGSH-DHR. The results indicated that the two glutathione (GSH) conjugates were formed by reaction of the unstable toxic pyrrolic ester with GSH added in the microsomal incubation system, whereas DHR was generated from hydrolysis of the unstable pyrrolic ester, and that clivoric acid was produced from all these further conversions of the unstable pyrrolic ester. Furthermore, tissue-bound pyrroles were also determined to be present after microsomal incubation of clivorine. Clivoric acid has not been previously identified, and DHR and 7, 9-diGSH-DHR were found, for the first time, as metabolites of an otonecine-type PA, while 7-GSH-DHR was previously reported by us to be a microsomal metabolite of clivorine. The in vitro metabolic pathway of clivorine was delineated to be the initial formation of the unstable pyrrolic ester, which then may undergo hydrolysis, GSH conjugations, or covalent binding with hepatic tissues that may lead to hepatotoxicity. The present definitive identification of four pyrrolic ester-related metabolites of clivorine and indirect determination of bound pyrroles provide the strongest evidence to date to support the hypothesis that the formation of an unstable pyrrolic ester plays a key role in otonecine-type PA-induced hepatotoxicity.

Animals↗
PubMed2000

[Retrospective cohort study on the prognosis of chronic myeloid leukemia].

OBJECTIVE: To evaluate the prognostic factors of chronic myeloid leukemia (CML). METHODS: Survival curves were plotted according to the Kaplan-Meier method. Variables associated with prognosis were analyzed by Logrank test. A multivariate analysis of prognostic factors was performed using stepwise Cox model. RESULTS: Of the total 158 patients, the median survival time was 1,480 days. 5 years survival rate was 47.1% (95% CI, 36.7% - 56.9%). 10 years was 24.8% (95% CI, 15.0% - 35.8%). The predominant blastic crisis type is myeloblastic, myelomonocytic or monocytic(77.5%). The period from chronic phase to blastic phase was equal in myelosuppressive therapy group, non- myelosuppressive therapy group or altretamine (HMM) group. After evaluated by stepwise Cox's regression model, age>or=50 years, bone marrow blasts>or=0.05, bone marrow basophilic>or=0.05, Ph chromosome negative and HMM treatment were associated with poor prognosis. Hydroxyurea was always associated with longer survival. CONCLUSION: Age, Ph chromosome, bone marrow blasts and basophilic, and various treatment affected the survival of CML.

Adult↗
PubMed2000

[Assessment of erythrocyte pyrimidine 5'-nucleotidase test for screening of occupational lead poisoning].

OBJECTIVE: To determine the diagnostic value of red cell P5'-N for detecting occupational lead poisoning. METHODS: Red cell pyrimidine 5;-nucleotidase, blood lead and urine lead levels, free erythrocyte protoporphyrin (FEP), zinc protoporphyrin (ZPP) and urine delta-aminolevulinic acid levels were determined in 157 lead exposed workers and 30 non-exposed healthy people. According to the golden standard; i.e. blood lead >/= 1.93 micromol/L and >/= 2.90 micromol/L, the diagnostic value of red cell P5'N and other indicators for detecting blood lead >/= 1.93 micromol/L and >/= 2.90 micromol/L was compared by receiver operative characteristic curve (ROC) software. After determining the optimal cut-points of the above indicators for detecting the blood lead >/= 1.93 micromol/L and >/= 2.90 micromol/L, the sensitivity of the parallel tests for detecting the blood lead >/= 1.93 micromol/L and >/= 2.90 micromol/L was calculated and compared by EPINFOR software. RESULTS: For detecting blood lead level >/= 1.93 micromol/L, the areas under ROC curve (AUC(ROC)) of P5'N was significantly larger than that of urinary lead and urinary delta-ALA (P < 0.05). The sensitivity of parallel tests with ZPP and P5'N was significantly larger than that of parallel tests with Upb and Udelta-ALA. For detecting blood lead level >/= 2.90 micromol/L, the areas under ROC curve (AUC(ROC))of P5'N was significantly larger than that of urinary lead, FEP and urinary delta-ALA (P < 0.05). The sensitivity of parallel tests with P5'N and ZPP was significantly larger than that of parallel tests with Upb and Udelta-ALA, and that of parallel tests with ZPP and FEP (P < 0.05). CONCLUSION: For detecting blood lead >/= 1.93 micromol/L and >/= 2.90 micromol/L, red cell P5'N is more accurate. It is worth being applied in detecting occupational lead poisoning. For detecting blood lead >/= 1.93 micromol/L and >/= 2.90 micromol/L, the parallel tests with P5'N and ZPP are more accurate.

5'-Nucleotidase↗
PubMed2000

[Expression of T cell factor 4 in renal cell carcinoma].

OBJECTIVE: To investigate of the transduction of Wnt/Frizzled pathway in nuclei and the function of TCF4 (T Cell Factor) in renal cell carcinoma. METHODS: TCF4 mRNA are tested through RT-PCR and Northern Blot in renal cancer tissue and renal cancer cell strain (GRC-I). RESULTS: It has been certificated that TCF4 are expressed in renal cell carcinoma, at the same time, there are some different splice of TCF4 in renal cancer. A new 300bp mutant gene are found. CONCLUSION: TCF4, an important molecular of Wnt/Frizzled pathway, takes part in the formation and progression of renal cell carcinoma, different splice of TCF4 is one of the mechanism.

Blotting, Northern↗
PubMed2000

[Proliferation inhibition and apoptosis induction of K562 cells by fatty acid synthase inhibitor--cerulenin].

OBJECTIVE: To investigate the effect of fatty acid synthase (FAS) inhibitor--cerulenin on K562 leukemia cells and its mechanism. METHODS: Inhibition rate of cerulenin on K562 leukemia cells was assayed by MTT method, cell apoptosis by flow cytometry (FCM) and agarose gel electrophoresis. RESULTS: When treated with 10(-9) - 10(-5) mol/L of cerulenin for 24 h, the proliferation of K562 cells was obviously inhibited with dose related effect. At the same concentrations, the inhibition rates of human skin fibroblasts were all lower than 30%. When K562 cells were treated for 12 h with 50 microg/ml and 60 microg/ml of cerulenin, the apoptosis rate revealed by FCM was 42.30% and 38.8%, respectively, and DNA agarose gel electrophoresis showed the typical DNA ladder of apoptosis. CONCLUSION: Fatty acid synthase inhibitor--cerulenin inhibits proliferation of K562 cells but not of human fibroblasts. Cerulenin mediated cytotoxity is due to apoptosis induction. Fatty acid synthase might be a potential target for anti-leukemia.

Apoptosis↗
PubMed2000

[Nitric oxide and cytokines in otitis media with effusion].

OBJECTIVE: To study the role of cytokines and nitric oxide (NO) in the pathogenesis of secretory otitis media (SOM). METHODS: The content of NO, interleukin-8 (IL-8) and tumor necrosis factor alpha (TNF-alpha) in blood plasma and middle ear effusion (MEE) were measured in 58 (80 ears) patients with secretory otitis media and in 23 normal subjects, respectively. RESULTS: NO, IL-8 and TNF-alpha were found in 100%, 82.2% and 71.4% of MEE respectively. NO, IL-8 or TNF-alpha of blood plasma in the SOM group was higher than those in the normal control group (P < 0.05). The concentration of NO, IL-8 or TNF-alpha in MEE was remarkably higher than those in blood plasma (P < 0.01). It revealed that the shorter the course, the higher the concentration of IL-8 in MEE (P < 0.01), and the longer the course, the higher the concentration of NO or TNF-alpha in MEE (P < 0.05). IL-8 concentration of MEE in serous fluid group was remarkably higher than that in the mucous fluid group (P < 0.01), and the concentration of NO or TNF-alpha of MEE in the mucous fluid group was higher than that in the serous fluid group (P < 0.05). NO level of MEE was positively correlated with TNF-alpha (r = 0.696 P < 0.01). CONCLUSION: NO IL-8 and TNF-alpha might be important mediators in MEE secretion in SOM. IL-8 might participate in the defensive reaction of organism during the early stages of SOM, and play a role in serous effusion secretion. NO and TNF-alpha might be closely related to the persistence of SOM, and might be a mediator of mucin secretion in SOM.

Adolescent↗