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T Lan

Publications and source records attributed to T Lan.

At least 19 recordsLinked to original sources
PubMed2006

Toroidal symmetry of the geodesic acoustic mode zonal flow in a tokamak plasma.

The toroidal symmetry of the geodesic acoustic mode (GAM) zonal flows is identified with toroidally distributed three step Langmuir probes at the edge of the HuanLiuqi-2A (commonly referred to as HL-2A) tokamak plasmas for the first time. High coherence of both the GAM and the ambient turbulence for the toroidally displaced measurements along a magnetic field line is observed, in contrast with the high coherence of the GAM but low coherence of the ambient turbulence when the toroidally displaced measurements are not along the same field line. The radial and poloidal features of the flows are also simultaneously determined. The nonlinear three wave coupling between the high frequency turbulent fluctuations and the flows is demonstrated to be a plausible formation mechanism of the flows.

Journal Article↗
PubMed2006

Differentiating sex chromosomes of the dioecious Spinacia oleracea L. (spinach) by FISH of 45S rDNA.

Spinacia oleracea L. (spinach) is a dioecious species with both male and female plants having 2n = 2x = 12 chromosomes, consisting of two large metacentrics, two long subtelocentrics, two short subtelocentrics, two acrocentrics, and four submetacentrics. The location of 45S rDNA was investigated on metaphase chromosomes using fluorescence in situ hybridization (FISH). The numbers of 45S rDNA foci in diploid sets of chromosomes from females was six and from males was five. All the fluorescent foci lay in secondary constrictions and the satellites. Our results indicate that an XY-type sex chromosome system could be present in spinach where the Y chromosome lacks a 45S RNA focus.

Chromosomes, Plant↗
PubMed2005

Polycyclic aromatic hydrocarbons in dustfall in Tianjin, China.

Atmospheric dustfall samples from 23 locations in Tianjin, China, were collected and analyzed for 16 polycyclic aromatic hydrocarbons (PAHs) classified by the Environmental Protection Agency as priority pollutants from March 2002 to March 2003. SigmaPAH16 (sum of 16 PAH compounds) concentrations in the dustfall collected during heating season ranged from 2.5 to 85.5 mug/g, while that during the non-heating season varied from 1.0 to 48.2 microg/g dry weight. The dominant components in the heating season included naphthalene, phenanthrene, fluoranthene, and chrysene, while naphthalene, fluorene, phenanthrene, and fluoranthene were dominant during the non-heating season. Compared with the non-heating season, the heating season was characterized by a higher fraction of high-molecular-weight PAHs with four to six rings with exception of the samples from the east industrial area. The east industrial area had more significant correlations between individual PAH compounds, and more discrete triangular components of three-, four-, five- and six-ring PAHs. No significant correlations were observed between the PAHs concentrations and total organic carbon (TOC) in the dustfall samples. The deposition fluxes of sigmaPAH15 (sum of 15 PAHs except naphthalene), sigmaPAH6 (sum of 6 carcinogenic PAHs recommended by IARC) and benzo[a]pyrene (BaP) from atmospheric deposition to the whole area were estimated as 1911, 196, and 53 microg/m2/year, respectively. The deposition rates for PAH compounds in the east industrial area were higher than those in the urban and rural areas. Furthermore, the deposition contribution of PAHs during domestic heating season in winter was not significant relative to the annual inputs.

Air Pollution, Indoor↗
PubMed2001

Minor groove functional groups are critical for the B-form conformation of duplex DNA.

Two analogue bases are described: 3-deazaadenine is a derivative of adenine from which N3 has been deleted and 3-methyl-2-pyridone is a C-nucleoside that mimics thymine but lacks the O2 carbonyl. The dc(3)A-dm(3)2P base pair is similar to dA-dT but eliminates the polar functional groups in the minor groove. The presence of this base pair in dA-dT rich sequences results in destabilized duplexes or conformational preferences for monomolecular hairpins rather than bimolecular duplexes. When present in dG-dC rich sequences, no significant differences in helix stability are observed. These differences are explained on the basis of hydration effects, most notably, the elimination of the minor groove spine of hydration normally present in dA-dT rich sequences. CD spectra suggest that sequences with a fully modified core (four analogue base pairs) are more A-like helices than B-like helices. Sequences containing two analogue base pairs can be transformed to A-like helices under conditions of high salt, or 65% trifluoroethanol. These conformational changes are also explained in terms of a loss of hydration in the minor groove that normally stabilizes the B-form conformation. In the absence of such hydration, the helices are conformationally mobile and adopt a more A-like helix form.

Adenine↗
PubMed2001

Synthesis of a dA-dT base pair analogue and its effects on DNA-ligand binding.

Two nucleoside derivatives containing the base analogues 3-deazaadenine and 3-methyl-2-pyridone have been prepared as analogues of dA and dT, respectively. After conversion into the appropriately protected phosphoramidites, DNA sequences were prepared with site-specifically placed analogues. When present in a duplex DNA sequence, the analogues result in the deletion of one or both of the hydrogen bonding functional groups (the N3-nitrogen of dA and the O2-carbonyl of dT) present in the minor groove. Binding by two ligands, 4',6-diamidine-2-phenyl indole (DAPI) and Hoechst 33258 in the minor groove has been probed using a variety of DNA sequences. These sequences contain a d(GAATTC)2 core with analogue nucleosides substituted for one or more of the dA and dT residues. DAPI bound strongly to any sequence that contained both O2-carbonyls of the central two dT residues. The presence of a dc3A residue did in some cases enhance binding. With one of the central O2-carbonyls deleted, the binding was noticeably reduced, and with both absent, no significant binding could be detected. Similar although less dramatic results were observed with Hoechst 33258 binding to analogue sequences.

Adenine↗
PubMed2001

[Protective effect of berberine on isolated perfused heart in heart failure].

OBJECTIVE: To examine the protective action of berberine against the development of heart failure. METHODS: Wister rats were divided into two groups. The Langendorff perfusion of isolated heart was performed and Verapamil was used to bring about acute heart failure. The experiment group was given berberine (10(-6) mol/L) before the use of Verapamil, but the control group was not given the berberine. A comparison was made on the degree of heart failure between the two group. RESULTS: The degree of heart failure in the experiment group was significantly less severe than that in the control group (P < 0.001). CONCLUSION: Berberine has the protective action against to the development of heart failure.

Animals↗
PubMed2000

Complex segregation analysis provides compelling evidence for a major gene underlying obsessive-compulsive disorder and for heterogeneity by sex.

Evidence from twin and family studies supports a genetic etiology for obsessive-compulsive disorder (OCD). The purpose of this study was to test whether a major gene is implicated in a proportion of families with OCD. Complex segregation analyses of 153 families (80 case and 73 control), ascertained in the Johns Hopkins OCD Family Study, provided strong evidence for a major gene. A Mendelian-dominant model, with significant sex effects and with residual familial effects, best explained the observed data. Stratification of the sample by the sex of probands provided further evidence of heterogeneity with respect to familial aggregation. Segregation analyses of 86 families with a female proband and of the 67 families with a male proband suggested that a Mendelian-dominant model with familial residual effects was the most parsimonious model explaining the inheritance of OCD in both subgroups.

Adolescent↗
PubMed2000

Nucleoside analogue substitutions in the trinucleotide DNA template recognition sequence 3'-(CTG)-5' and their effects on the activity of bacteriophage T7 primase.

Bacteriophage T7 primase catalyzes the synthesis of the oligoribonucleotides pppACC(C/A) and pppACAC from the single-stranded DNA template sites 3'-d[CTGG(G/T)]-5' and 3'-(CTGTG)-5', respectively. The 3'-terminal deoxycytidine residue is conserved but noncoding. A series of nucleoside analogues have been prepared and incorporated into the conserved 3'-d(CTG)-5' site, and the effects of these analogue templates on T7 primase activity have been examined. The nucleosides employed include a novel pyrimidine derivative, 2-amino-5-(beta-2-deoxy-D-erythro-pentofuranosyl)pyridine (d2APy), whose synthesis is described. Template sites containing d2APy in place of the cryptic dC support oligoribonucleotide synthesis whereas those containing 3-deaza-2'-deoxycytidine (dc(3)C) and 5-methyl-6-oxo-2'-deoxycytidine (dm(5ox)C) substitutions do not, suggesting that the N3 nitrogen of cytidine is used for a critical interaction by the enzyme. Recognition sites containing 4-amino-1-(beta-2-deoxy-D-erythro-pentofuranosyl)-5-methyl-2,6[1H, 3H]-pyrimidione (dm(3)2P) or 2'-deoxyuridine (dU) substitutions for dT support oligoribonucleotide synthesis whereas those containing 5-methyl-4-pyrimidinone 2'-deoxyriboside (d(2H)T) substitutions do not, suggesting the importance of Watson-Crick interactions at this template residue. Template sites containing 7-deaza-2'-deoxyguanosine (dc(7)G) or 2'-deoxyinosine (dI) in place of dG support oligoribonucleotide synthesis. The reduced extent to which dc(7)G is successful within the template suggests a primase-DNA interaction. Inhibition studies suggest that the primase enzyme binds "null" substrates but cannot initiate RNA synthesis.

Bacteriophage T7↗
PubMed2000

Karyotypic analysis of intersexuality in Chinese from Taiyuan.

AIM: To analyze the kayrotypic patterns of 33 cases of intersexuality in Chinese from Taiyuan, China in order to further clarify its mechanism of development and the interrelationship between karyotype and phenotypic sex. METHODS: High-resolution GTG-banding chromosome technique was used to analyze the karyotype patterns. RESULTS: In these patients, 57.58% were male pseudohermaphrodites (46,XY), 18.18%, female pseudohermaphrodites (46, XX), 12.12%, true hemaphrodites, and 12.12%, other karyotypes. Although testes can be seen in 88.8% of karyotypes with Y chromosome, 73.68% of the patients were of female social sex. In 42.82% of patients the social sex is in conformity with their karyotypes. There were 2 cases of male pseudohermaphrodites, where the sex chromosome was normal, but abnormalities were found in chromosomes 9, 13, or 14. CONCLUSION: Sex chromosomes determine the direction of gonadal and sex differentiation, while the development of the normal gonad and external genitalia should have the participation of many autosomal chromosomes as well.

Adolescent↗
PubMed1998

[Protective effects of flunarizine and vitamin C on isolated rat heart subjected to ischemia-reperfusion injury].

Isolated rat heart was subjected to Langendorff perfusion for 10 minutes of total global ischemia, and reperfusion for 15 minutes. The content of myocardial intracellular calcium, content of oxygen free radical induced lipid peroxide mitabolite-malondialdehyde (MDA), content of Lactic dehydrogenase (LDH) in coronary effluent, and the change of myocardial morphology were studied. The effects of flunarizine(FNZ) and/or vitamin C(Vit C) on the above parameters were observed. The results showed that, at 15 minutes of reperfusion, the contents of myocardial intracellular calcium, of MDA in myocaredium and of LDH in coronary effluent in the FNZ + Vit C group, Vit C group and FNZ group were all lower than those in the control group, and the change of morphology in the three groups was also slighter than that in the control group. When FNZ and Vit C were administered together, the effect was more marked and equivalent to the sum total of the effects of the two drugs. These suggest that both FNZ and Vit C reduce reperfusion injury through suppression of myocardium calcium overload and oxygen free radical damage.

Animals↗
PubMed1998

[Effects of flunarizine and vitamin C on hemodynamics in rat heart subjected to ischemia-reperfusion].

Langendorff perfusion isolated rat heart was subjected to total global ischemia (coronary flow rate is equal to zero) for 10 minutes and reperfusion for 15 minutes. The heart rate (HR), left ventricular developed pressure (LVDP), coronary flow rate (CFR), electrocardiogram (ECG) and the effects of calcium antagonist-flunarizine (FNZ) and/or oxygen free radical scavenger--vitamine C on the above parameters were observed. The results showed that FNZ dilated coronary vessel (P < 0.01) and had a slight negative chronotropic effect, but it had no effect on LVP. Vitamine C did not affect HR, LVP and CFR. The recovery of the product of HR and LVDP-Rate Pressure Product (RPP) in the FNZ + Vit. C group, Vit. C group and FNZ group was significantly higher than that in the control group (P < 0.05) at ten minutes reperfusion. All the results suggest that FNZ and Vit. C may improve the recovery of heart function after reperfusion.

Animals↗
PubMed1995

[Effects of berberine on single Ca2+ channel current in cultured embryonic chick ventricular myocytes].

On cultured embryonic chick ventricular myocytes, we investigated the influence of berberine (BR) on single Ca2+ channel current using patch clamp technique with cell-attached configuration. The results showed that BR could increase the single Ca2+ channel current significantly and the increases of open availability (Ps) and open probability (Po) caused by BR were 114.2% (P < 0.001) and 75.3% (P < 0.05), respectively. The beta-receptor antagonist propranolol and Ca2+ channel blocker ispotin could reverse the effects of BR on single Ca2+ channel, suggesting that (1) BR works as a Ca2+ channel agonist; (2) the regulating effects of BR on single Ca2+ channel is depending upon the phosphorylation process induced by beta-receptor activity.

Adrenergic beta-Antagonists↗
PubMed1995

[Inward rectifier potassium current in cultured embryonic chick ventricular myocytes and effect of culture time].

The single channel features of inward rectifier potassium current (IK1) in primary cultured embryonic chick ventricular myocytes and the effect of culture time on it were studied by using cell-attached patch clamp technique. The results showed that inward current fluctuation could be recorded at membrane potential negative to the potassium equilibrium potential (EK) and [K+] o = [K+]i = 140 mmol/L. The single channel current-voltage (I-V) relation was linear. The slope conductance was 35 pS (1-3 day culture). But at membrane potential positive to the EK, strong inward rectification was evident. The analysis of open and close time distribution indicated that a close-close-open three state model was appropriate to describe the gating processes of IK1 channel. No significant effect of culture time was observed. The channel density and slope conductance of IK1 were 0.64, 0.76, 0.77 channels/microns and 35, 28, 37 pS corresponding to 1-3, 4-6, and 7-11 day culture period, respectively. This result could partially explain why action potential of cardiomyocytes did not change with culture time.

Animals↗
PubMed1995

[Effects of vesnarinone on L-type single Ca2+ channel current in cultured ventricular myocytes of embryonic chick].

The effects of vesnarinone on L-type Ca2+ channel current of embryonic chick ventricular myocytes were studied with cell-attached patch clamp technique. Vesnarinone was used in the concentrations of 10(-5), 2 x 10(-5) and 10(-4) mol/L; the availability (P8) of Ca2+ channel activity was increased (P < 0.001) markedly (about 2-3 fold). The increasing of the open probability (Po) of Ca2+ channel by vesnarinone showed concentration-dependence. The increase was 2.25 (10(-5)mol/L), 3(2 x 10(-5)mol/L) and 4.3(10(-4)mol/L) fold. The open time rate constant (tau 0) and close time rate constant (tau 1 and tau 2) of Ca2+ channel were not changed in the concentrations of 10(-5) and 2 x 10(-5) mol/L, but the tau 0 was slightly decreased in the concentration of 10(-4) mol/L. The actions of vesnarinone on single Ca2+ current were compared with those of milrinone (it is known as an PDE inhibitor which had inotropic effect associated with an increase in cytoplasmic cAMP level.) The effects of milrinone on P8, tau 0 and tau 1 were similar with those of vesnarinone (10(-4) mol/L), but the increase of Po was 2 fold less than that of vesnarinone. The results showed that apart from the role of PDE inhibitor, vesnarinone has other effects on myocytes.

Animals↗
PubMed1994

[Effect of nitrendipine on hypoxic myocardial energy preservation].

To investigate the relationship between post-hypoxic myocardial dysfunction and myocardial energy reserve and the effect of nitrendipine on hypoxic myocardial energy preservation, we submitted the Langendorff isolated perfused rat hearts to 30 minutes of hypoxia and then 20 minutes of reoxygenation. Nitrendipine was infused continuously 10 minutes before hypoxia and throughout the following perfusion. The high energy phosphate contents of isolated perfused rat hearts before and 30 minutes after hypoxia were measured by using reverse high performance liquid chromatography. The results showed that nitrendipine, when administered prophylactically, enhanced myocardial energy reserve and relieved high energy phosphates' depletion during 30 minutes of hypoxia insult. It is suggested that nitrendipine has an effect on hypoxic myocardial energy preservation.

Adenine Nucleotides↗
PubMed1993

[Synchronous investigation of the effects of vesnarinone on action potential and muscle tension of isolated rabbit's ventricular papillary muscle].

This study adopted intracellular microelectrode technique to observe synchronously the effects of vesnarinone on intracellular potential and muscle tension of isolated rabbit's ventricular papillary muscle and analysed their variation. The results showed that vesnarinone increased the Tmax (P < 0.01) and Tdv/dt (P < 0.01) of isolated rabbit's ventricular papillary muscle and prolonged the action potential time (APT) without obvious effects on RP, APA and Vmax of papillary muscle. The relationship between them (r = 0.994, P < 0.05), suggesting that their changes be of the same mechanism and probably relate to the increase of inward calcium current.

Action Potentials↗
PubMed1992

[Comparative studies on LH/CG receptor from rat testes and hCG-binding protein from Pseudomonas maltophilia by antibodies against the hCG-binding protein].

An indirect immunoprecipitation experiment was developed to characterize the antigenic determinants of the hCG-binding protein and the rat testicular LH/CG receptor. The hCG-binding protein preincubated with 125I iodo hCG was immunologically precipitated by the antibodies against the hCG-binding protein in the presence of goat anti-rabbit IgG. Similarly, the LH/CG receptor solubilized with 1% triton X-100 from the rat testes was also immunoprecipitated by the antibodies. Furthermore, the antibodies did not inhibit the binding of 125I iodo hCG to the hCG-binding protein or to the solubilized rat testicular LH/CG receptor. From these results it can be concluded that there exists the sharing of antigenic determinants between the hCG-binding protein from Pseudomonas maltophilia and the LH/CG receptor from the rat testes and that the antibodies specifically recognize the antigenic determinants outside the hCG-binding sites on the rat testicular LH/CG receptor. Therefore, the antibodies against the hCG-binding protein are of potential applications to studies on structure and function of the mammalian LH/CG receptors.

Animals↗