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Biomedical subjects

H F Li

Publications and source records attributed to H F Li.

At least 19 recordsLinked to original sources
PubMed2007

Flow and particle deposition patterns in a realistic human double bifurcation airway model.

Velocity profiles, local deposition efficiencies (DE), and deposition patterns of aerosol particles in the first three generations (i.e., double bifurcations) of an airway model have been simulated numerically, in which the airway model was constructed from computed tomography (CT) scan data of real human tracheobronchial airways. Three steady inhalation conditions, 15, 30, and 60 L/min, were simulated and a range of micrometer particle sizes (1-20 mum diameter) were injected into the model. Results were then compared with experimental and other numerical results which had employed either similar model geometry or test conditions. The effects of inhalation conditions on velocity profiles and particle deposition were studied. The data indicated that the local deposition efficiencies in the first bifurcation increased with a rise in the Stokes number (St) within St range from 0.0004 to 0.7. Within the same St range, DE in the second bifurcations (both left and right) was dropped dramatically after St increased to 0.17. Also, the second bifurcation in the right side (B2.1, closer to first bifurcation than left side, B2.2) was found to show a much higher (almost double) DE than the left side. This may be due to the fact that the left main bronchus is longer and has greater angulation than the right main bronchus. Generally, the present simulation using a computational fluid dynamic (CFD) technique obtained concurrent results with subtle differences compared to other works. However, due to omission of larynx in the model, which is known to significantly modify airflow and hence particle deposition, the present model may only serve as the "stepping stone" to simulating and analyzing dose-response or inhalation risk assessment visually for clinical researchers.

Aerosols↗
PubMed2006

Screening and analysis of bioactive compounds in traditional Chinese medicines using cell extract and gas chromatography-mass spectrometry.

As the cost of drug development is always many times more than that of drug discovery, predictive methods aiding in the screening of bioavailable drug candidates are of profound significance. In this paper, a novel method for screening bioactive compounds from traditional Chinese medicines (TCMs) was developed by using living cell extract and gas chromatography (GC)-mass spectrometer (MS). The method was validated by using elemene emulsion injection (EEI), a typical TCM with known active compound, to interact with murine ascites hepatocarcinoma cell strain with high metastatic potential (HCa-F). Finally, the method was applied to screen the bioactive compounds from multi-component zedoary turmeric oil and glucose injection (ZTOGI). After HCa-F cells was incubated in ZTOGI, ethyl acetate (EtOAc) was used to extract the compounds in the cells for GC-MS analysis. Fourteen compounds were detected in the desorption eluate of HCa-F cell extract of ZTOGI, and further identified by MS. Curzerene and beta-elemene were found to be two major bioactive compounds in ZTOGI. These results show that the method developed may be applied to quickly screen the potential bioactive components in TCMs interacting with the target cells.

Animals↗
PubMed2006

The genomic sequence of Wisteria vein mosaic virus and its similarities with other potyviruses.

The complete nucleotide sequence of a Beijing isolate of Wisteria vein mosaic virus was determined to be 9695 nucleotides in length excluding the poly(A) tail. Sequence analysis predicted a single large open reading frame of 9279 nucleotides potentially encodes a polyprotein of 3092 amino acids. Phylogenetic analysis based on the genomic and deduced amino acid sequences support the current status of Wisteria vein mosaic virus (WVMV) as a distinct virus of the genus Potyvirus and a member of the Bean common mosaic virus (BCMV) subgroup. Sequence comparisons of WVMV and other members of the BCMV subgroup showed that WVMV is most closely related to both soybean mosaic virus and watermelon mosaic virus.

Amino Acid Sequence↗
PubMed2006

Optimization of medium and cultivation conditions for alkaline protease production by the marine yeast Aureobasidium pullulans.

A yeast strain, Aureobasidium pullulans, which could produce the high yield of protease was isolated from sediment of saltern in Qingdao, China. Maximum production of enzyme (623.1 U/mg protein; 7.2 U/ml) was obtained in a medium containing 2.5 g soluble starch and 2.0 g NaNO(3), 100ml seawater, initial pH 6.0, after fermentation at 24.5 degrees C for 30 h. The protease had the highest activity at pH 9.0 and 45 degrees C.

Ascomycota↗
PubMed2006

Molecular cloning and expression of the duplicated thyroid hormone responsive spot 14 (THRSP) genes in ducks.

Thyroid hormone responsive Spot 14 (THRSP) is suggested as a transcription factor involved in the regulation of adipogenic enzymes by 3 thyroid response elements in the promoter region. In the chicken genome, THRSP gene was identified to duplicate into 2 paralogs, THRSPalpha and THRSPbeta. In the current study, cDNA sequences of the duplicated duck THRSP genes were cloned by real-time PCR and rapid amplification of cDNA ends. Duck THRSPalpha and THRSPbeta were predicted to encode peptides with 133 amino acids, which had 74 and 68% sequence identity at cDNA level, 78 and 74% identity at amino acid level to the chicken counterparts, respectively. A high percentage (73.1%) of G and C nucleotides were found in the 3' untranslated region of duck THRSPbeta cDNA. Although a low similarity of peptide composition was shared between ducks and mammals, and a moderate similarity was shared between ducks and chickens, many predicted properties of THRSP, including the pI, subcellular localization and functional domains seemed to be highly conserved. The present study demonstrated that the duck THRSP gene duplicates into the 2 paralogs as in chickens. Phylogenetic analysis indicated that the duplication for THRSP paralogs appeared to have taken place preceding the chicken-duck split, and the diverging rate between THRSP paralogs seemed faster in the chicken genome than that in the duck genome. Expression analysis by real-time quantitative PCR showed that THRSP paralogs in ducks were more actively transcribed in fat tissues (i.e., s.c. fat and abdominal fat) than in liver, and the mRNA concentrations of THRSPbeta were higher than that of THRSPalpha in liver and s.c. fat.

Amino Acid Sequence↗
PubMed2006

Hibiscus chlorotic ringspot virus p27 and its isoforms affect symptom expression and potentiate virus movement in kenaf (Hibiscus cannabinus L.).

Hibiscus chlorotic ringspot virus (HCRSV), a member of the genus Carmovirus, encodes p27 (27-kDa protein) and two other in-frame isoforms (p25 and p22.5) that are coterminal at the carboxyl end. Only p27, which initiates at the 2570CUG codon, was detected in transfected kenaf (Hibiscus cannabinus L.) protoplasts through fusion to a Flag tag at either its N or C terminus. Subcellular localization of a p27-green fluorescent fusion protein in kenaf epidermal cells showed that it was localized to membrane structures close to cell walls. To study the functions of these proteins, a number of start codon mutants and premature translation termination mutants were constructed. Phenotypic differences were observed between the wild-type virus and these mutants during infection. Infectivity assays on plants indicated that p27 is a determinant of symptom severity. Without p25, appearance of symptoms on systemically infected kenaf leaves was delayed by 4 to 8 days. In a timecourse analysis, Western blot assays revealed that the delay corresponded to retardation in virus systemic movement, which suggested that p25 is probably involved in virus systemic movement. Mutations disrupting expression of p22.5 did not affect symptoms or virus movement.

3' Untranslated Regions↗
PubMed2005

[Ischemic cardiovascular disease risks in among public servants in China].

OBJECTIVE: To examine ischemic cardiovascular disease risks (ICVD) over 10 years among china middle class (public servants) in China. METHODS: Evaluation of 10-year risks of ICVD for 2287 people with the simplified method of prediction of the cardiovascular disease risks worked out by the Collaborative Research Group of the National 10th Five Year Plan. RESULTS: (1) 98,16% of the men and 99,39% of the women have a low risk of ICVD (lower than 10%); 0,19% of the men and 0,15% of the women have a significant risk of ICVD (over 20%). (2) the average of the absolute risk of the examined subjects is higher than that of the corresponding ages of the national population. The variation is significant between men and women (p<0,001). The number of the people having an absolute risk higher than the national average increases with the age. (3) Among people with high risks (absolute risk > or =10%), the rate of SBP, FBG, TC, BMI abnormal is respectively 100%, 20,8%, 75%, 87,5%. Among the population of low risk (absolute risk<10%), those with abnormal SBP, FBG, TC, BMI are respectively 7,31%, 3,4%, 37,74%, 59,26%. The difference between the two groups is significant on all the points (p<0,001). CONCLUSION: If the average of the risks of the ICVD remains acceptable, it is nevertheless high than the national average, especially for men and older women.

Adult↗
PubMed2004

Expression of recombinant vitellogenin in the yeast Pichia pastoris.

Vitellogenin (Vtg) plays vital roles as precursor to the yolk proteins and as carrier for lipids, carbohydrates, phosphates, metal ions, vitamins, and hormones into the oocytes during the massive deposition of yolk nutrients for subsequent nourishment of the developing embryos. Reproductive success is highly sensitive to the nutritional quality of the broodstock diet, which greatly affects the egg and larval viability. We present a novel strategy for genetically engineering a Pichia pastoris yeast strain that constitutively produces recombinant Vtg (rVtg), for application as an enriched feed. The tilapia Oreochromis aureus Vtg (OaVtg) cDNA (5.3 kb) was cloned into a nonsecretory pGAPZA vector. Clones containing up to 31 copies of glyceraldehyde-3-phosphate dehydrogenase (GAP)-promoter-driven Vtg expression cassettes were isolated. These clones expressed a membrane-associated intracellular rVtg protein of 194 kDa, constituting up to 1.16% of total protein. To facilitate future purification of rVtg, we explored the possibility of secreting rVtg using the native Vtg secretion signal and the alpha-factor secretion signal of Saccharomyces cerevisiae. However, neither signal promoted the secretion of rVtg. The clones maximally expressed rVtg at 23 degrees C, reaching a peak at 22 h in shake flasks and 16 h in a fermentor. The clones exhibited a significant increase in essential amino acids and long-chain polyunsaturated fatty acids, which are important for its application as a high-quality nutrient feed.

Amino Acids, Essential↗
PubMed2004

Compost stability assessment using a secondary metabolite: geosmin.

Composting is a process involved not only in transformation of organic matter (OM), but also for transition of the microbial community. Microorganisms can directly provide important information on the stages and characteristics of composting. This paper was aimed at characterizing compost stability by a microbial secondary metabolite, geosmin, which is a volatile compound presenting an earthy smell. Since secondary metabolite production is dependent on the nutrient state of microorganisms, its production in association with physical and chemical parameters was monitored in the laboratory-scale and plant-scale composting processes. The results showed that the peaked geosmin liberation was consistent with stable state of composting indicated by the ambient temperature achieved, a slightly alkaline product and steady states of dissolved organic carbon (DOC), N and P contents and OM degradation in the laboratory-scale experiment. It was also in accordance with the stability identified by the facilities and CO2 respiration rate in the plant-scale composting. In addition, the production of geosmin was correlated with the C/N ratio for the solid sample. These results demonstrated that geosmin levels could be used as an index for the compost stability assessment in different composting processes with various organic solid wastes.

Bacteria↗
PubMed2003

Complete sequence of the genomic RNA of the prevalent strain of a potyvirus infecting maize in China.

The complete nucleotide sequence of the prevalent strain of a potyvirus isolated from maize in Beijing, China was determined and compared with other closely related potyviruses. The viral genome comprises 9595 nucleotides, excluding the poly (A) tail, and encodes a putative polyprotein of 3063 amino acid residues. Sequence comparison of the coat proteins showed that this isolate was most closely related to most other potyviral isolates infecting maize across China with identities of about 99% and thus represented the prevalent strain. It was also closely related to most isolates of Sugarcane mosaic virus (SCMV) infecting maize in Europe with maximum identity of about 95% at the amino acid level. The polyprotein sequence of the Beijing isolate shares identities of 98% with those of two other Chinese maize isolates and shares identity of 69% with Maize dwarf mosaic virus-Bulgarian isolate, respectively. Phylogenetic analyses of the sequences indicated that the Beijing isolate can be tentatively referred to as a prevalent strain of SCMV.

Binding Sites↗
PubMed2001

Functional coupling of voltage-dependent L-type Ca2+ current to Ca2+-activated K+ current in pituitary GH3 cells.

Ca2+-activated K+ currents (I(K(Ca)) can contribute to action potential repolarization and after-hyperpolarization in GH3 cells. In this study, we examined how the activation of I(K(Ca) at the cellular level could be functionally coupled to Ca2+ influx through L-type Ca2+ channels. A 30-msec Ca2+ influx step to 0 mV was found to exhibit substantial contribution of Ca2+ influx through the activation of I(Ca,L) to the activation of I(K(Ca)). A bell-shaped relationship between the conditioning potentials and the integrated I(K(Ca)) was observed, suggesting that the magnitude of integrated I(Ca,L) correlates well with that of integrated I(K(Ca)) in the same cell. A linear relationship of integrated I(Ca,L) and integrated I(K(Ca)) was found with a coupling ratio of 69+/-7. The value of the coupling ratio was unaffected by the presence of Bay K 8644 or nimodipine, although these compounds could effectively affect the amplitudes of both I(K(Ca)) and I(Ca,L). However, tetrandrine could decrease the coupling ratio. Paxilline or intracellular Ca2+ buffer with EGTA decreased the coupling ratio, while apamin had no effect on it. Interestingly, phorbol 12-myristate 13-acetate also reduced the coupling ratio significantly, whereas thapsigargin increased this value. Thus, the present study indicates that the activation of I(K(Ca)) during brief Ca2+ influx, which is inhibited by paxilline, is coupled to Ca2+ influx primarily through the L-type channels. The selective modulation of I(K(Ca)) by second messengers or Ca2+ release from internal stores may affect the coupling efficiency and hence cellular excitability.

Alkaloids↗
PubMed2001

2-Methyl-1-(4-nitrobenzyl)pyridinium bis(maleonitriledithiolato)nickelate(III).

In the title complex, 2-methyl-1-(4-nitrobenzyl)pyridinium bis(1,2-dicyanoethene-1,2-dithiolato)nickelate(III), (C(13)H(13)N(2)O(2))[Ni(C(4)N(2)S(2))(2)], the most prominent general structural feature of the complex is the completely segregated columnar stacks of anions and cations. Within the cation column, there may be stacking interactions between adjacent nitro groups and benzene rings.

Journal Article↗
PubMed2001

Vinpocetine-induced stimulation of calcium-activated potassium currents in rat pituitary GH3 cells.

The effects of vinpocetine, an inhibitor of cyclic GMP phosphodiesterase, on ionic currents were examined in rat pituitary GH3 lactotrophs with the aid of the patch-clamp technique. In GH3 cells bathed in normal Tyrode's solution, vinpocetine (10 microM) reversibly increased the amplitude of Ca2+-activated K+ current (I(K)Ca) with an EC50 value of 4 microM. When the recording pipettes were filled with 10 mM EGTA, vinpocetine also stimulated I(K)Ca. In the cell-attached configuration, application of vinpocetine to the bath increased the activity of large-conductance Ca2+-activated K+ (BK(Ca)) channels. In excised membrane patches, application of vinpocetine (10 microM) to the bath did not change the single-channel conductance of BK(Ca) channels; however, it did increase channel activity. In the inside-out configuration, neither 8-bromo cyclic GMP nor YC-1 applied intracellularly affected BK(Ca) channel activity. The vinpocetine-induced change in the kinetic behavior of BK(Ca) channels was due to an increase in mean open time and a decrease in mean closed time. Vinpocetine (10 microM) caused a leftward shift in the midpoint for the voltage-dependent opening. Under the current-clamp mode, vinpocetine (10 microM) decreased the firing rate of spontaneous action potentials induced by thyrotropin-releasing hormone (10 microM) in GH3 cells. In pheochromocytoma PC12 cells, vinpocetine (10 microM) applied intracellularly also enhanced the activity of BK(Ca) channels without altering single-channel conductance. Thus, the present study suggests that vinpocetine-mediated stimulation of I(K)Ca may result from the direct activation of BK(Ca) channels and indirectly from elevated cytosolic Ca2+.

Animals↗
PubMed2001

Characterization of action potential waveform-evoked L-type calcium currents in pituitary GH3 cells.

The response of the L-type Ca2+ current (ICa,L) in pituitary GH3 cells to variations in the action potential (AP) waveform was examined using the whole-cell configuration of the patch-clamp technique. ICa,L evoked during an AP waveform exhibited an early and a late component. The early component occurred on the rising phase of the AP; the late component coincided with the falling phase. Prolonging the falling phase of the AP increased the Ca2+ charge carried by ICa,L, although the amplitude of the late ICa,L was reduced. Prolonging the peak voltage of the AP waveform, however, increased the amplitude of the late component. ICa,L inactivated during a train of AP waveforms. When Ba2+ was used as the charge carrier, current inactivation during a train of APs decreased. Likewise, ICa,L evoked by the AP templates with irregular bursting pattern was inactivated. When the repetitive firing of APs with depolarizing potentials was replayed to cells, Ca2+ entry was not only spread over the entire AP, but also occurred during the interspike voltage trajectory. After application of thyrotropin releasing hormone (TRH; 10 microM), ICa,L in response to rectangular pulses was increased and the current/voltage relation shifted slightly to more negative values. TRH (10 microM), thapsigargin (10 microM) or cyclopiazonic acid (30 microM) enhanced the late component of the AP-evoked ICa,L. TRH also attenuated the inactivation of ICa,L during a train of APs. These results indicate that in pituitary GH3 cells, the time course and kinetics of ICa,L during the AP waveforms is distinct from that evoked by rectangular voltage clamp. Changes in the shape and firing pattern of APs in GH3 cells can modulate Ca2+ influx through L-type Ca2+ channels. Ca2+ release from internal stores may affect the magnitude of AP-evoked ICa,L in these cells.

Action Potentials↗
PubMed2001

Rutaecarpine-induced block of delayed rectifier K+ current in NG108-15 neuronal cells.

The effects of rutaecarpine on ionic currents of NG108-15 neuronal cells were investigated in this study. Rutaecarpine (2-100 microM) suppressed the amplitude of delayed rectifier K+ current (I(K(DR))) in a concentration-dependent manner. The IC50 value for rutaecarpine-induced inhibition of I(K(DR)) was 11 microM. I(K(DR)) present in these cells is sensitive to the inhibition by quinidine and dendrotoxin, yet not by E-4031. The presence of rutaecarpine enhanced the rate and extent of I(K(DR)) inactivation, although it had no effect on the initial activation phase of I(K(DR)). Recovery from block by rutaecarpine (5 microM) was fitted by a single exponential with a value of 2.87 s. Crossover of tail currents in the presence of rutaecarpine was also observed. Cell-attached single-channel recordings revealed that rutaecarpine decreased channel activity, but it did not alter single-channel amplitude. With the aid of the binding scheme, a quantitative description of the rutaecarpine actions on I(K(DR)) was provided. However, rutaecarpine (20 microM) had no effect on L-type Ca2+ current. Under current-clamp configuration, rutaecarpine prolonged action potential duration in NG108-15 cells. These results show that rutaecarpine is a blocker of the K(DR) channel. The increase in action potential duration induced by rutaecarpine can be explained mainly by its blocking actions on I(K(DR)).

Action Potentials↗
PubMed2001

Effect of enforced aeration on in-vessel food waste composting.

A laboratory composting was conducted to determine the effect of the continuously enforced aeration on the composting performance. The mixture of dog food, excess sludge, and woodchip was used as raw composting materials. The temperature changes in the decomposition process, and pH, weight loss, ash, and extract composition from the final product after 17 days composting were investigated. The results demonstrated that flow rate of enforced aeration indeed influenced the composting performance. Composting under 0.05-0.1 1 min(-1) condition seemed better than that under 0.2-0.41 min(-1) condition. Higher flow rate of air not only cooled the composting mixture significantly, further adversely affected temperature rise, but also evaporated moisture mostly. Thermophilic composting can occur under 0.05-0.11 min(-1) air flow rate condition, while composting in cases of 0.2-0.4 l min(-1) air flow rate mainly resulted in a mesophilic process. Microbial activity was considered to be significantly inhibited at 0.4 1 min(-1) air flow rate condition based on the analyses of total organic carbon and volatile fatty acids from water extraction of composting products.

Air Movements↗
PubMed2001

Effect of progesterone on the contractile response of isolated pulmonary artery in rabbits.

The purpose of this study was to assess the direct effect of progesterone on rabbit pulmonary arteries and to examine the mechanism of its action. Rings of pulmonary artery from male rabbits were suspended in organ baths containing Krebs solution, and isometric tension was measured. The response to progesterone was investigated in arterial rings contracted with noradrenaline (NA), KCl, and CaCl2. The effects of endothelium, nitric oxide (NO), prostaglandins, cyclic GMP (cGMP), and the adrenergic beta-receptor on progesterone-induced relaxation were also assessed. Progesterone inhibited the vasocontractivity to NA, KCl, and CaCl2, and relaxed rabbit pulmonary artery. The relaxing response of progesterone in pulmonary artery was significantly reduced by removal of endothelium, inhibitors of nitric oxide synthase and guanylate cyclase, but not by prostaglandin synthase inhibitor and blockage of the adrenergic beta-receptor. In Ca2+-free (0.1 mM EGTA) Krebs solution, progesterone inhibited NA-induced contraction that was intracellular Ca2+-dependent, but didn't affect the contraction of extracellular Ca2+-dependent component. Our results suggest that progesterone induces relaxation of isolated rabbit pulmonary arteries partially via NO and cGMP. Progesterone may also inhibit Ca2+ influx through potential-dependent calcium channels (PDCs) and Ca2+ release from intracellular stores.

Animals↗