Biomedical subjects
Publications and source records attributed to H Liu.
A series of 1-(N-ethoxycarbonylamino)alkylphosphonic monoesters were synthesized via three-component Mannich-type condensation of ethyl carbamate, aldehydes and dichlorophosphites in benzene, followed by hydrolysis.
A wedge-shaped structure made of split-ring resonators (SRR) and wires is numerically simulated to evaluate its refraction behavior. Four frequency bands, namely, the stop band, left-handed band, ultralow-index band, and positive-index band, are distinguished according to the refracted field distributions. Negative phase velocity inside the wedge is demonstrated in the left-handed band and the Snell's Law is conformed in terms of its refraction behaviors in different frequency bands. Our results confirmed that negative index of refraction indeed exists in such a composite metamaterial and also provided a convincing support to the results of previous Snell's Law experiments.
HCHs and DDTs in sediment-dwelling animals including mollusks and crabs from the Yangtze Estuary were determined by GC-ECD. Levels of t-HCH were in the range of 1.2-5.5 ng g(-1) and averaged 3.5 ng g(-1) in mollusks, while t-DDT concentrations ranged from 26.0 to 68.8 ng g(-1), with a mean of 34.5 ng g(-1). In crabs t-HCH concentrations varied from 2.0 to 25.7 ng g(-1) and averaged 13.8 ng g(-1), whereas the concentrations of t-DDT were in the range of 1.5-24.8 ng g(-1) with a mean value of 5.9 ng g(-1). The HCHs and DDTs levels depend on geographical position and sources, showing the high levels at fresh water area in the estuary, such as XP, CM and LHK sites, and lower at brackish water area, such as FX site, and little difference between species. Results also indicate there was no significant relationship between t-HCH (t-DDT) concentrations and lipid contents both in mollusks and crabs because of non-equilibrium state under a specific estuarine dynamics; smaller individuals accumulated more HCHs and DDTs than larger individuals of mollusks at LHK site, showing different uptake rate for these pesticides; moreover, HCHs and DDTs levels were lower in female crab bodies than male crab bodies suggesting that the release of spawning. BSAFs (Biota- Sediment Accumulation Factors) from sediment-dwelling animals for HCHs and DDTs show a significant "one high with two low" and "one low with two high" effect in the Yangtze Estuary.
HCHs and DDTs in salt marsh plants taken from intertidal flats in the Yangtze estuary and coastal area in April and July 2002 were determined by GC-ECD. A significant seasonal effect was observed for HCHs and DDTs in sources and concentration levels in different sample types including above-ground tissues and roots as well as the whole plants and rhizospheric sediments. The results indicated that the concentration of t-HCH was higher in the above-ground tissues than in their roots in April; however, the partitioning of DDTs between contaminated sediments and the roots showed the higher concentrations of t-DDT in their roots. HCHs and DDTs concentration levels were higher in above-ground tissues than in roots in July. BCFs of HCHs and DDTs exhibited lower values with higher levels of contaminants in sediments, and higher values with lower levels in sediments.
A carbon dioxide (CO(2))-based microencapsulation technique was used to impregnate indomethacin, a model drug, into biodegradable polymer nanoparticles. Compressed CO(2) was emulsified into aqueous suspensions of biodegradable particles. The CO(2) plasticizes the biodegradable polymers, increasing the drug diffusion rate in the particles so that drug loading is enhanced. Four types of biodegradable polymers were investigated, including poly(d,l-lactic acid) (PLA), poly(d,l-lactic acid-co-glycolic acid) (PLGA) with two different molar ratios of LA to GA, and a poly(d,l-lactic acid-b-ethylene glycol) (PLA-PEG) block copolymer. Biodegradable nanoparticles were prepared from polymer solutions through nonsolvent-induced precipitation in the presence of surfactants. Indomethacin was incorporated into biodegradable nanoparticles with no change of the particle size and morphology. The effects of a variety of experimental variables on the drug loadings were investigated. It was found that the drug loading was the highest for PLA homopolymer and decreased in PLGA copolymers as the fraction of glycolic acid increased. Indomethacin was predicted to have higher solubility in PLA than in PLGA based on the calculated solubility parameters. The drug loading in PLA increased markedly as the temperature for impregnation was increased from 35 to 45 degrees C. Drug release from the particles is a diffusion-controlled process, and sustained release can be maintained over 10 h. A simple Fickian diffusion model was used to estimate the diffusion coefficients of indomethacin in the biodegradable polymers. The diffusion coefficients are consistent with previous studies, suggesting that the polymer properties are unchanged by supercritical fluid processing. Supercritical CO(2) is nontoxic, easily separated from the polymers, can extract residual organic solvent, and can sterilize biodegradable polymers. The CO(2)-based microencapsulation technique is promising for the production of drug delivery devices without the use of harmful solvents.
BACKGROUND: Monitoring of iodine nutrition depends chiefly on the urinary iodine concentration in representative samples from the population. International groups have recommended school-age children as a convenient group for surveys, because of their accessibility and young age, but the relevance of this group to others, especially pregnant women, is not well established. OBJECTIVE: The purpose was to compare different approaches to assessing iodine nutrition within communities, especially for pregnant and lactating women. DESIGN: In an urban and a rural site from each of the 11 Chinese provinces, covering a wide geographic and socioeconomic range, we measured the iodine content of household salt and drinking water, the thyroid volume in school children, and the urinary iodine concentration in five population subsets; in some sites we also assessed iodine in breast milk and thyroid size in adult women. RESULTS: The median urinary iodine concentrations for pregnant and lactating women were well below those of the schoolchildren from the same community in most study sites, the difference between medians, at overall level, being about 50 microg/l for the pregnant and 40 microg/l for the lactating, respectively. When ranked by median urinary iodine concentrations at overall level, the order of the groups was: all infants, schoolchildren, women of childbearing age, lactating women and pregnant women in both urban and rural sites. This relative distribution was constant among the study sites. From it, we derived a relationship to predict the median values for other groups, based on the data of schoolchildren. The median iodine content of salt was 30.9 ppm in urban sites and 31.3 ppm in rural sites, respectively, close to the nationally mandated 35 mg/kg. Water had low iodine content (3.7 microg/l) in both urban and rural sites except in a rural site from Tianjin. Ultrasonography showed that 6.5% of 1329 children in urban sites and 5.3% of 1431 children in rural sites had thyroid enlargement. Breast milk had a median iodine content of 135.9 microg/l in the urban and 157.5 microg/l in the rural. The goiter prevalence by palpation was low (2.0%) among all women examined (3367), but higher in pregnant women (2.7%) than in lactating women or other adult women. CONCLUSIONS: An effective iodized salt program has brought iodine sufficiency to most of China, but pregnant women in some areas may still risk deficiency and need further supplements. We suggest other countries and international agencies pay more attention to pregnancy, where iodine deficiency has its worst consequences.
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In recent years, much interest has been generated over the potential of human embryonic stem cells in transplantation medicine. The ground-breaking study of Fraidenraich and colleagues conclusively demonstrated that rescue of lethal cardiac defects in Id knockout mutant mouse embryos was not due to transplanted embryonic stem cells giving rise to functional new tissues within the defective embryonic heart. Instead, there is indirect evidence that the observed therapeutic effect was due to various secreted factors emanating from the transplanted cells. This therefore introduces the exciting prospect of utilizing human embryonic stem cells as "catalysts" to promote biological repair and regeneration in transplantation therapy. Nevertheless, the immunological barrier against allogenic transplantation, as well as the teratogenic potential of human embryonic stem cells poses major technical challenges. A possible strategy to overcome the immunological barrier may be to impose a temporary regimen of immunosuppressive drugs followed by their gradual withdrawal, once adequate tissue regeneration has been achieved. Other more novel alternatives include the use of microencapsulation to block interaction with the transplant recipient's immune system, and co-transplantation with bone marrow-derived mesenchymal stem cells, which have been demonstrated to possess immuno-suppressive properties. The teratogenic potential of human embryonic stem cells could possibly be alleviated by directing the differentiation of these cells to specific lineages prior to transplantation, or through mitotic inactivation. Co-transplantation with autologous adult stem cells may represent a novel strategy to further enhance the "catalytic" effects of human embryonic stem cells. The various factors secreted by human embryonic stem cells could then have a concentrated localized effect on relatively large numbers of co-transplanted autologous adult stem cells, which may in turn lead to enhanced repair and regeneration of the damaged tissue or organ. This new therapeutic strategy needs to rigorously investigated, in view of its potentially important clinical applications.
3-Hydroxybenzoate 6-hydroxylase from Klebsiella pneumoniae M5a1 is an enzyme that utilizes 3-hydroxybenzoate (3-HBA) as substrate yielding gentisate. Site-directed mutagenesis was carried out to define which residues may be involved in catalytic reaction. Substitution of arginine to glutamate at position 169 of the enzyme resulted in the complete loss of catalytic activity. This indicated Arg169 may play an important role in 3-HBA 6-hydroxylase catalysis.
Data from 1,543 female migrants working in eight occupational clusters in Beijing and Nanjing, China were analysed to examine the association of workplace with HIV-related behaviours and perceptions. For sexually experienced women (n = 666, 43.2%), those working in entertainment establishments or personal service (e.g., nightclubs, dancing halls, barbershops, beauty salons, massage parlours, etc.) engaged in risky sexual practices twice as frequently as those working in non-entertainment establishments (e.g. restaurants, stalls, domestic service, factories, etc.). About 10% of women in the entertainment establishments reported having sold sex, 30% having multiple sexual partners and 40% having sex with men with multiple sexual partners. The rate of consistent condom use was less than 15%. They also tended to have a higher level of perceptions of both peer risk involvement and positive expectancy of risk behaviours, and lower perceptions of severity of STDs and HIV. For women who were not sexually experienced, those working in 'stalls' or 'domestic service' tended to perceive higher peer risk involvement, less severity of HIV infection, and less effectiveness of protective behaviour. The occupational pattern of sexual risk behaviours and perceptions observed in the current study indicates employment conditions are associated with HIV risk. Intervention strategies should be tailored to address occupational-related factors.
Microarrays derived from Solanum tuberosum expressed sequence tags were used to test the hypothesis that genetically distinct enveloped viruses elicit unique changes in Nicotiana benthamiana gene expression. The results of our study, which included Sonchus yellow net virus (SYNV), a plant rhabdovirus that replicates in the nucleus of infected cells, and Impatiens necrotic spot virus (INSV), a plant bunyavirus that replicates in the cytoplasm, were consistent with this hypothesis. Statistically significant changes (P< or =0.01) in the expression of 275, 2646 and 4165 genes were detected in response to INSV at 2, 4 and 5 days post-inoculation (d.p.i.), respectively. In contrast, 35, 665 and 1458 genes were expressed differentially in response to SYNV at 5, 11 and 14 d.p.i., respectively. The microarray results were verified by Northern hybridization using a subset of these genes as probes. Notably, INSV, but not SYNV, induced expression of small heat-shock protein genes to high levels. In contrast to SYNV, infection by INSV resulted in downregulation of all histone genes, of which the downregulation of histone 2b expression to very low levels was confirmed by Northern hybridization. The expression of a putative WRKY transcription factor at 11 d.p.i., but not at 5 or 14 d.p.i., in SYNV-infected tissue suggested that the temporal response to virus infection was identified readily using our experimental design. Overall, infection by INSV resulted in larger fold changes in host gene expression relative to infection by SYNV. Taken together, the present data demonstrate differential responses of a common host to two genetically distinct viruses.
We report a rare case of idiopathic acquired factor VIII inhibitor in an 80-year old Chinese man presented as sudden onset of monocular blindness because of macular haemorrhage. This was complicated by painful glaucoma that did not respond to medical treatment. The patient died of cerebral haemorrhage shortly afterwards. Most cases of reported intraocular bleeding in acquired haemophiliacs are iatrogenic because of intraocular operations in undiagnosed cases, and spontaneous intraocular haemorrhage has never been reported. The literature reports of intraocular bleeding in hereditary and acquired haemophilia cases are summarized.
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Microscale liquid droplets could act as the SARS carriers in air when released from an infected person through breathing, coughing, or sneezing. In this study, a dynamic model has been built to quantitatively investigate the effect of the relative humidity on the transport of liquid-droplets in air using coupled mass transfer and momentum equations. Under higher relative humidity, the exhaled liquid droplets evaporate slowly. Larger droplets fall faster, which could reduce the probability of the droplets inhalation. This may be one of the most important factors that influence the SARS transmission in air.
OBJECTIVE: To investigate how an individual's stigmatising beliefs towards people living with HIV are related to his or her own sexual risk and protective behaviours. METHODS: A cross sectional survey was conducted to assess HIV related stigmatising beliefs, risk sexual behaviours, and preventive practices among sexually experienced rural to urban migrants aged 18-30 years in 2002 in Beijing and Nanjing, two large Chinese cities. RESULTS: Among 2153 migrants, 7.2% reported having had more than one sexual partner in the previous month, 9.9% had commercial sex partners, and 12.5% had an episode of a sexually transmitted disease (STD). Only 18% reported frequently or always using condoms, with 20% sometimes or occasionally using them. 57% of the Chinese migrants were willing to take a voluntary HIV test, and 65% had HIV related stigmatising beliefs towards people living with HIV. Multiple logistic regression analysis depicts that individual's stigmatising beliefs towards people with HIV were positively associated with having had an episode of an STD, having multiple sex partners, or having had commercial sex partners, and were negatively associated with condom use and the willingness to accept an HIV test. CONCLUSION: The finding that one's own stigmatising belief is a potential barrier to HIV related preventive practices highlights the difficulties and challenges in implementing behavioural interventions.
Changes in chemical composition of Alxa bactrian camels reared in Inner Mongolia (China) during lactation were investigated. Colostrum and milk samples from 10 nomadic female camels in their first season of lactation were collected periodically from parturition until 90 d postpartum (PP). The average contents of gross composition were 14.23% protein, 4.44% lactose, 0.27% fat, 0.77% ash, and 20.16% total solids in colostrum at 2 h PP, and the respective mean values were 3.55, 4.24, 5.65, 0.87, and 14.31% for regular milk on d 90. A 15-fold increase was shown in fat content during the first 24 h, whereas a sharp decrease was shown during the first 12 h of lactation in protein, ash, and total solids contents. Variation in lactose content was small (4.24 to 4.71%) throughout the study period. Total N, nonprotein N, casein N, and whey protein N were found to be 2.23, 0.06, 0.86, and 1.31 g/100 mL for the colostrum at 2 h PP; and 0.56, 0.04, 0.45, and 0.07 g/100 mL for the milk at 90 d PP. Percentages of caseins increased steadily, whereas whey proteins declined gradually until 3 mo of lactation. Gas liquid chromatography analysis of milk fat showed that the content of even-numbered saturated fatty acids (C12:0-C18:0) in camel colostrum (2 h to 7 d PP) was lower than that of regular milk (15 to 90 d PP). The predominant saturated fatty acids were C14:0, C16:0, and C18:0, regardless of the stage of lactation. There was a considerable level of polyunsaturated fatty acids (mainly C18:1) in Alxa camel's milk fat. The levels of Ca, P, Na, K, and Cl were 222.58, 153.74, 65.0, 136.5, and 141.1 mg/100 g, respectively, at 2 h PP; the values of the minerals were 154.57, 116.82, 72.0, 191.0, and 152.0 mg/100 g, respectively, for the regular milk on d 90. The levels of vitamins A, C, E, B1, B2, B6, and D were 0.97, 29.60, 1.45, 0.12, 1.24, 0.54 mg/L, and 640 IU/L, respectively, in Alxa camel milk at 90 d PP. Vitamin A and C contents were higher and vitamins E and B1 were lower than those in colostrum. Sodium dodecyl sulfate-PAGE and densitometry results demonstrated that Alxa camel colostrum is rich in immunoglobulins, serum albumin, and 2 unknown fractions, which are reduced in amount (%) within 2 d of lactation. It seems that there is lack of beta-lactoglobulin in Alxa camel milk, whereas casein and -lactalbumin start at a low level and increase gradually until they reach their regular levels in the milk.
The aim of the present investigation was to evaluate the effects of physical properties of the carrier on the in vitro deposition performance of dry powder inhalations (DPIs) of recombination human interferon a2b (IFN a2b). Recrystallized lactose was used as the carrier. Inverse gas chromatography (IGC) was used to assess the surface energy, and atomic force microscopy (AFM) was used to assess the roughness and topography of the carrier. In vitro performance of the powder blends was strongly correlated to the physical properties of the carrier. Plotting emitted dose (%) vs. flow rate and fine particle fraction vs. surface energy, yielded an R2 value of 0.9621 and 0.9146, respectively.
We have studied isotropic-to-nematic pretransitional fluctuations in an aqueous solution of disodium cromoglycate (cromolyn) by static and dynamic light scattering. Cromolyn is a representative of lyotropic chromonic liquid crystals with building units being elongated rods formed by aggregates of disk-like molecules. By combining light-scattering and viscosity measurements we have determined the correlation length and relaxation time of the orientational order-parameter fluctuations and estimated the size of the cromolyn aggregates. The pretransitional behavior of light scattering does not completely follow the classic Landau-de Gennes model. This feature is most probably associated with the variable length of cromolyn aggregates. We have observed a dramatic increase of the shear viscosity near the transition to the nematic phase, the fact which correlates with the idea of growing supramolecular aggregates. The steep temperature dependence of the viscosity is accompanied by a practically temperature-independent translational diffusion coefficient.