Biomedical subjects

L Dong

Publications and source records attributed to L Dong.

At least 109 records · Page 6Linked to original sources

PubMed1997

[Research on the reproducibility and selection of experimental conditions of capillary electrochromatography].

In this work, we prepared the packed columns for capillary electrochromatography (CEC) with 75microm and 100microm i.d., both of coupled mode and uncoupled mode. A mixture of thiourea and other three aromatic compounds was employed to evaluate the efficiency of the CEC columns. RSD values of retention times smaller than 2.12% was obtained on the home-made CEC system. The influence of pH value and the concentration of the organic solvent in the buffer on the retention behavior was investigated, giving a guide to the selection of experimental conditions. High speed analysis can be achieved by using high pH value buffers. Higher concentration of acetonitrile will improve the elution ability, while lower ocncentration of acetonitrile would improve the resolution. Seven kinds of neutral molecules were separated efficiently within 25 minutes. The results from the two modes of CEC columns were compared.

English Abstract↗

PubMed1997

Characteristics of risk-taking behaviors, HIV and AIDS knowledge, and risk perception among young males in southwest China.

A cross-sectional survey was undertaken to describe risk-taking behaviors and to assess the knowledge and risk perception of HIV and AIDS among young males aged 18 to 29 years in 82 villages in Longchuan, Yunnan, China, in 1994. Information on demographic, behavioral, and drug-using factors, and knowledge of HIV transmission and prevention, and risk perception was collected using an interviewer-administered anonymous questionnaire. A total of 1,548 individuals were interviewed and 433 drug users, including 52 nonsharing injectors and 140 sharing injectors, were identified. Over half the individuals scored 0 on HIV knowledge, but knowledge was greater among nonsharing drug injectors. Most drug injectors had initiated drug injection after 1990. The reported incidence continues to increase in all three major ethnic groups. Sharing of equipment was common (73%) among injectors. Drug users were four times more likely to have had premarital or extramarital sex, but condoms were used by only 2.5%. Thus, factors promoting spreading of HIV are common in this area. We recommend that a community-based intervention program, targeting both young men and women, be implemented and evaluated in Longchuan as soon as possible.

Acquired Immunodeficiency Syndrome↗

PubMed1997

[Effects of low pH and nicotine on carotid body chemoreceptor activity in the rabbit].

The unit discharges of carotid chemosensory afferent fibers were recorded in the in vitro carotid body (CB)--sinus nerve preparations (n = 55) from 29 rabbits. The results were as follows: (1) The discharge of all the units increased from 0.86 +/- 0.21 to 1.75 +/- 0.40 imp/s (P < 0.001) upon lowering the pH of modified Locke solution. (2) Addition of nicotine at doses of 1, 3, 6, 10 and 15 micrograms/ml to the solution led to a dose-dependent increase in the discharge from 0.60 +/- 0.21 to 0.96 +/- 0.21, 1.19 +/- 0.30. 1.24 +/- 0.29, 1.48 +/- 0.41 and 1.82 +/- 0.39 imp/s, respectively (r = 0.94, P < 0.001, n = 10). Nicotinic stimulation was antagonized by D-tubocurarine but the basal discharge was not significantly affected. (3) Superfusion of the CB with acid solution increased the discharge from 0.95 +/- 0.34 to 1.84 +/- 0.55 imp/s (P < 0.01, n = 19); After injections of nicotine 1-5 micrograms/ml to acid perfusate the unit discharge showed an increase from 0.96 +/- 0.25 to 1.53 +/- 0.24 imp/s. The degree of increase was less as compared with that due to mere acidification (P < 0.05). (4) D-tubocurarine did not alter the action of acid solution on chemosensory discharge (P > 0.05, n = 17). The present results suggest that ACh might act only as a modulator on carotid chemosensory activity without involving N-cholinergic receptor directly as did by low pH perfusion of CB.

Animals↗

PubMed1996

Enzyme-triggered formation of electrochemiluminescent ruthenium complexes.

A sensitive enzyme assay is described using substrates derivatized with metal-binding ligands. Enzymes catalyzed changes in the abilities of substrates to bind to the nonelectrochemiluminescent complex ruthenium (II) bis(bipyridyl), Ru(bpy)2(2+), to form electrochemiluminescent mixed-ligand complexes. A highly electrochemiluminescent complex was formed between Ru(bpy)2(2+) and picolinic acid (1) but not picolinic acid ethyl ester (4), permitting the detection of 4 hydrolysis by pig liver esterase (PLE). Electrochemiluminescence (ECL) differences between Ru(bpy)2(2+) mixtures of 1 and 4 were detected to a lower concentration limit of 65pM. Under the conditions used in actual enzyme assays, it was possible to detect 4.4 pM PLE and the hydrolysis of 1.3 microM 4. In a second assay, leucine aminopeptidase (LAP) hydrolyzed 8-(L)-leucylaminoquinoline (9) to leucine and aminoquinoline (10). A mixed-ligand complex formed between (9) and Ru(bpy)2 (2+) was substantially more electrochemiluminescent than a complex of Ru(bpy)2(2+) and 10. ECL differences between Ru(bpy)2(2+) mixtures of 9 and 10 were detectable to 65 nM. Under actual enzyme assay conditions, 375 pM LAP could be detected as well as the hydrolysis of 1.3 microM 9.

2,2'-Dipyridyl↗

PubMed1996

DNA binding by the heterodimeric Ah receptor. Relationship to dioxin-induced CYP1A1 transcription in vivo.

The environmental contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin induces the microsomal enzyme cytochrome P4501A1 by increasing the transcription rate of the CYP1A1 gene. Induction requires two basic helix-loop-helix proteins, the ligand-binding aromatic hydrocarbon receptor (AhR) and its heterodimerization partner, the AhR nuclear translocator (Arnt). The AhR/Arnt heterodimer induces transcription by binding to dioxin-responsive elements (DREs) within an enhancer upstream of the CYP1A1 gene. The basic regions of AhR and Arnt are crucial for DRE binding. We have mutated these regions in order to analyze the relationship between DRE binding (determined in vitro using an electrophoretic mobility shift assay) and induction of CYP1A1 transcription (determined in vivo by genetic complementation of AhR-defective and Arnt-defective mouse hepatoma cells, using an RNase protection assay to measure mRNA accumulation). Our findings reveal the amino acids in the basic regions of AhR/Arnt that are important for both DRE binding and induction of transcription. This information provides biological background for the interpretation of structural (e.g. crystallographic) studies of the interactions between AhR/Arnt and the DRE. Our findings also indicate that the in vitro behavior of the mutants does not consistently predict their functional activity in vivo. Thus, genetic complementation constitutes an important and stringent test for analyzing the effects of mutations on AhR/Arnt function.

Amino Acid Sequence↗

PubMed1996

Risk factors for initiation of drug use among young males in southwest China.

To identify risk factors for drug use among young males in southwest China a cross-sectional survey and a non-concurrent cohort study were conducted. Demographic, behavioral and drug-use information was collected from young males aged 18-29 years. The non-concurrent cohort included the period 1 January 1991 to 1 August 1994. A total of 1548 subjects were interviewed. The cumulative incidence increased between 1991 and 1993. Multivariate analysis identified the following significant risk factors for drug use: being divorced/widowed/separated, having been encouraged by friends/others to try drugs, smoking cigarettes, belonging to the Jingpo ethnic group, and having a family member who used drugs in 1991. More than 6 years of education was a protective factor for drug use. Drug use in the community was associated with having been encouraged by friends or others to try drugs (71%), to smoking cigarettes (50%), and to belonging to the Jingpo group (24%). The results are consistent with community based prevention approaches which should be studied carefully because of the unique cultural and epidemiological situation in China.

Adolescent↗

PubMed1996

A portal image alignment and patient setup verification procedure using moments and correlation techniques.

The objective of this study was to develop an integrated field shape and patient setup verification procedure for portal images. The proposed procedure used one of the approved portal images as the reference image for automated comparison with subsequent portal images. The first step of the procedure used a moments method to align treatment field boundaries. This step was necessary to compensate for the repositioning error of an image detector and to create a common frame of reference for comparing anatomical shifts relative to the field boundary. At the end of the moments alignment, a moments figure of merit was computed and compared with a pre-established threshold. This verified whether there was a potential shape change in the treatment field. To measure anatomical misalignment, the last step in the procedure was to use a grey-scale image correlation method to align translations and in-plane rotations relative to the anatomy of the reference image. The procedure was shown in phantom studies to err by less than 1 mm when detecting translational shifts and less than 1 degree when detection in-plane rotations. The moments verification method showed a sensitivity of detecting a placement error of 6 mm for a single leaf in a controlled experiment where a multileaf collimator was used for field shaping. The alignment procedure was fast and could be done in less than 12 s on an IBM-compatible 486 personal computer.

Humans↗

PubMed1996

Cytochromes P450 5: induction of cytochrome P4501A1: a model for analyzing mammalian gene transcription.

The induction of microsomal cytochrome P4501A1 by polycyclic aromatic hydrocarbons represents an interesting response by which mammalian cells adapt to xenobiotic exposure. Enzyme induction reflects increased transcription of the corresponding CYP1A1 gene. Analyses of the induction mechanism using genetic, biochemical, and molecular biological approaches have revealed a novel transcriptional regulatory pathway that involves ligand-dependent heterodimerization between two basic helix-loop-helix proteins (the Ah receptor and Arnt), interaction of the heterodimer with a xenobiotic-responsive enhancer, transmission of the induction signal from the enhancer to the CYP1A1 promoter, and alterations in chromatin structure. Current techniques permit examination of the induction mechanism in intact cells and analyses of the CYP1A1 gene in its native chromosomal configuration. Such experiments generate new insights into the control of mammalian transcription that are of relatively broad interest.

Animals↗

PubMed1996

Risk factors for intravenous drug use and sharing equipment among young male drug users in Longchuan County, south-west China.

OBJECTIVES: To identify the risk factors for intravenous drug use and sharing of equipment in Longchuan County in south-west China. METHODS: Demographic information and sexual and drug-use-related behavior between 1 January 1991 and 1 August 1994 were collected retrospectively from a cohort of young male drug users aged 18-29 years in 82 villages. RESULTS: A total of 433 drug users were identified. The cumulative incidence of intravenous drug use was 40.0% during the 3.7-year study period. The annual incidence increased from 10% in 1991 to over 30% in 1994. Risk factors for intravenous drug use among drug users, according to the multivariate model, included having had premarital/extramarital sex [odds ratio (OR), 1.5; 95% confidence interval (CI), 1.01-2.3], having a family member who used drugs in 1991 (OR, 1.8; 95% CI, 1.1-2.9), and currently not married (OR, 1.6; 95% CI, 0.98-2.7). Being Buddhist protected against intravenous drug use (OR, 0.4; 95% CI, 0.2-0.9). The population attributable fraction was 30% for not being currently married, 17% for having had premarital/extramarital sex and 14% for having a family member who used drugs. The risk factor for sharing of equipment was being of Jingpo ethnicity (OR, 5.8; 95% CI, 2.5-13.8). The average incidence of sharing equipment was 19.6% per year. The population attributable fraction for sharing equipment was 58.5% for being Jingpo. CONCLUSIONS: The incidence of intravenous drug use and sharing equipment is increasing. Therefore, it is urgent that vigorous, effective intervention programs be initiated in southern Yunnan. Unmarried, sexually promiscuous Jingpo drug users with a family history of drug use should be especially targeted. Given the problems of transport and communication in this remote area of China, intervention programs which use existing social, governmental and community networks should be implemented.

Adolescent↗

PubMed1996

Systemic uptake and clearance of chloroform by hairless rats following dermal exposure. I. Brief exposure to aqueous solutions.

The systemic uptake of chloroform from dilute aqueous solutions into live hairless rats under conditions simulating dermal environmental exposure was studied. Whole blood was sampled during a 30-min immersion of an animal within water containing a known concentration of chloroform and then for 5.5 h following its removal from the bath. The amount of chloroform systemically absorbed was determined by comparing the AUCs of the blood concentration vs. time plots from dermal exposure to that obtained after i.v. infusion (for a period of 30 min) of an aqueous solution containing a known amount of chloroform (positive control). Although dermal data implied two-compartment disposition characteristics, i.v. infusion data fit best to a three-compartment disposition. Linear pharmacokinetics was observed both by i.v. administration and percutaneous absorption at the dose levels studied. Chloroform was detected in the rat blood as early as 4 min following exposure. Our findings suggest that about 10.2 mg of chloroform was systemically absorbed after dermal exposure of a rat to an aqueous solution of 0.44 mg/ml. This amount is substantially higher than the predictions of mathematical risk-models put forth by some investigators. However, when expressed as the "effective" permeability coefficient (Kpeff), close agreement was noticed between our value and those estimated by others using physiologically based pharmacokinetic (PBPK) models. Also, in terms of Kpeff, reasonable agreement existed between our and another investigator's past estimates of uptake based on depletion of bath level of chloroform and the actual uptake measured in our current experiments. The estimated onset of systemic entry seen here is entirely consistent with our estimate of how long it takes to establish the diffusion gradient across the stratum corneum based on tape stripping.

Animals↗

PubMed1996

Role of intracardiac angiotensin II in cardiac dysfunction of rat during septic shock.

OBJECTIVE: To observe changes in the content of myocardial angiotensin II and its role in cardiac dysfunction of rat during septic shock. METHODS: Septic shock model was produced by cecal ligation and puncture (CLP) operation on rats. Experimental rats were given captopril 15 mg.kg-1/d per os for 3 days before CLP operation. Mean blood pressure and left ventricular pressure were recorded. Myocardial angiotensin converting enzyme (ACE) activities were determined by a fluorometric assay and myocardial angiotensin II content was measured by radioimmunoassay. Highly purified membrane of sarcoplasmic reticulum (SR) was prepared from rat hearts. Assays were made of ATP-dependent Ca2+ uptake by cardiac SR and (3H) ryanodine binding to SR. RESULTS: Myocardial angiotensin II content increased by 51.5% (P < 0.01) at the 18th hour post CLP, meanwhile there was a decrease in left ventricular +/- dp/dtmax value and the impairment in Ca2+ uptake and (3H) ryanodine binding to cardiac SR. Preliminary administration of captopril reduced myocardial ACE activity and angiotensin II content, but increased left ventricular +/- dp/dtmax value. In comparison to shock group, the initial rate and the capacity of SR Ca2+ uptake were increased by 120% (P < 0.01) and 33.9% (P < 0.05), the Bmax value of (3H) ryanodine binding to SR was also elevated, while the Kd value remained unchanged. CONCLUSIONS: The elevated intracardiac angiotensin II, resulting from the activation of myocardial ACE during sepsis, probably serves as one of the important mediators participating in the pathogenesis of heart failure: the effects of angiotensin II may be associated with the disturbance of Ca2+ transport function of cardiac SR.

Angiotensin II↗

PubMed1996

[Effect of HE-NE laser acupuncture on the spleen in rats].

The splenic sinuses, lymphocytes and antigen presenting cells in the spleen of rat stimulated by He-Ne laser acupuncture were observed by using TEM to investigate the ultrastructural changes of them. The width of endothelial interstice was increased, hence a lot of blood cells oozed out of the splenic sinuses. There were numerous activated T cells which contained abundant mitochondria and ribosome in the periarterial lymphatic sheaths. The B cells were gradually differentiated into large lymphocytes, immature and mature plasmatic cells with a lot of endoplasmic reticula. They were prominently increased in the splenic nodules. The macrophages had short processes with numerous folds and microvilli and tended to neighboring lymphocytes. The nucleus pores were increased. There were a lot of vacuoles, phagosome and mitochondria were closed to macrophages and lymphocytes. In conclusion the activities of the cellular immunity and humoral immunity were enhanced by laser.

Acupuncture Points↗

PubMed1996

[Effects of different natural stimulants on the activity of the rabbits' carotid chemoreceptor].

The effects of different natural stimulants on the afferent unit discharge of rabbit carotid chemoreceptors were studied in the in vitro carotid body- sinus nerve preparation. A total of 32 chemoreceptive units were recorded. The results were as follows: (1) Of the 32 units, 10 (31%) showed chemosensory responses only to PO2 decrease; 9 (28%) to all stimulants (PO2 decrease, PCO2 increase and pH decrease); 9 (28%) to PO2 decrease and PCO2 increase; 3 (9%) to PO2 decrease and pH decrease; only one to pH decrease. (2) The potency of the three natural stimulants in eliciting the changes in intensity of discharge showed a decreasing order as follows: PO2 decrease > PCO2 increase > pH decrease. The above results suggest that the carotid body may contain only one or a combination of 2 or 3 kinds of chemoreceptors respectively sensitive to decrease PO2 to increase PCO2 or decrease pH.

Afferent Pathways↗

PubMed1995

An image correlation procedure for digitally reconstructed radiographs and electronic portal images.

PURPOSE: To study a procedure that uses megavoltage digitally reconstructed radiographs (DRRs) calculated from patient's three-dimensional (3D) computed tomography (CT) data as a reference image for correlation with on-line electronic portal images (EPIs) to detect patient setup errors. METHODS AND MATERIALS: Megavoltage DRRs were generated by ray tracing through a modified volumetric CT data set in which CT numbers were converted into linear attenuation coefficients for the therapeutic beam energy. The DRR transmission image was transformed to the grayscale window of the EPI by a histogram-matching technique. An alternative approach was to calibrate the transmission DRR using a measured response curve of the electronic portal imaging device (EPID). This forces the calculated transmission fluence values to be distributed in the same range as that of the EPID image. A cross-correlation technique was used to determine the degree of alignment of the patient anatomy found in the EPID image relative to the reference DRR. RESULTS: Phantom studies demonstrated that the correlation procedure had a standard deviation of 0.5 mm and 0.5 degrees in aligning translational shifts and in-plane rotations. Systematic errors were found between a reference DRR and a reference EPID image. The automated grayscale image-correlation process was completed within 3 s on a workstation computer or 12 s on a PC. CONCLUSION: The alignment procedure allows the direct comparison of a patient's treatment portal designed with a 3D planning computer with a patient's on-line portal image acquired at the treatment unit. The image registration process is automated to the extent that it requires minimal user intervention, and it is fast and accurate enough for on-line clinical applications.

Dose-Response Relationship, Radiation↗

PubMed1995

35H, a sequence isolated as a protein kinase C binding protein, is a novel member of the adducin family.

We recently cloned a partial cDNA (35H) for a protein kinase C (PKC) binding protein from a rat kidney cDNA library and demonstrated that it is a PKC substrate in vitro (Chapline, C., Ramsay, K., Klauck, T., and Jaken, S. (1993) J. Biol. Chem. 268, 6858-6861). Additional library screening and 5' rapid amplification of cDNA ends were used to obtain the complete open reading frame. Amino acid sequence analysis, DNA sequence analysis, and Northern analysis indicate that 35H is a unique cDNA related to alpha-and beta-adducins. Antisera prepared to the 35H bacterial fusion protein recognized two polypeptides of 80 and 90 kDa on immunoblots of kidney homogenates and cultured renal proximal tubule epithelial cell extracts. The 35H-related proteins were similar to alpha- and beta-adducins in that they were preferentially recovered in the Triton X-100-insoluble (cytoskeletal, CSK) fraction of cell extracts and were predominantly localized to cell borders. Phorbol esters stimulated phosphorylation of CSK 35H proteins, thus emphasizing that sequences isolated according to PKC binding activity in vitro are also PKC substrates in vivo. The phosphorylated forms of the 35H proteins were preferentially recovered in the soluble fraction, thus demonstrating that phosphorylation regulates their CSK association and, thereby, their function in regulating cytoskeletal assemblies. We have isolated another PKC binding protein partial cDNA (clone 45) from a rat fibroblast library with substantial homology to alpha-adducin. Antisera raised against this expressed sequence recognized a protein of 120 kDa, the reported size of alpha-adducin, on immunoblots of renal proximal tubule epithelial cell extracts. A 120-kDa protein that cross-reacts with the clone 45 (alpha-adducin) antisera coprecipitated with 35H immunecomplexes, indicating that alpha-adducin associates with 35H proteins in vivo. Taken together, these results indicate that 35H is a new, widely expressed form of adducin capable of forming heterodimers with alpha-adducin. We propose naming this adducin homologue gamma-adducin.

Amino Acid Sequence↗

PubMed1995

Transcriptional activation by the mouse Ah receptor. Interplay between multiple stimulatory and inhibitory functions.

The aromatic hydrocarbon receptor (AhR) is a ligand-dependent transcription factor that mediates cellular responses to the environmental contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). We cloned AhR cDNA from C57BL/6 mouse liver and verified by transfection that it encodes a functional protein. Analyses of deletion mutants indicate that the carboxyl half of AhR contains several types of transactivation domain, which function independently of domains that mediate TCDD recognition, DNA binding, and heterodimerization with the Ah receptor nuclear translocator (Arnt) protein. The transactivation domains function independently of each other, display different levels of activity, and act synergistically when linked. In addition, AhR contains an 82-amino acid domain that inhibits transactivation. The inhibitory domain displays specificity, in that it blocks the transactivating functions of AhR and Arnt, but not that of the herpes simplex protein VP16. The inhibitory activity depends upon the cell type in which AhR is expressed, implying that a cell-specific protein mediates the effect.

Animals↗

PubMed1995

[Study of H(+)-Ca2+ exchange in cultured heart cells after hypoxia and reoxygenation].

Reoxygenation is more serious for hypoxic myocardial cells because of the subsequent calcium overload. The calcium overload is known due to augmentation of H(+)-Na+, Na(+)-Ca2+, exchange during pH paradox. But the present experiment showed that, when H(+)-Na+, Na(+)-Ca2+ exchange was inhibited, calcium could still enter myocardial cells after hypoxia or reoxygenation. Similar result was observed after using Na(+)-Free solution, suggesting that calcium entrance into the cell was unrelated to Na+ channel. It was further shown that calcium accumulation was related to pH gradient across the myocardial cell membrane, i.e., being increased with increase of H+ concentration in the cell. Therefore, it appears that, besides H(+)-Na+, Na(+)-Ca2+ exchange, H(+)-Ca2+ exchange is one of the reasons of calcium overload during intracellular pH paradox.

Animals↗

PubMed1995

Analysis of heterogeneity of gene products (interferon) expressed in yeast.

FPLC, SDS-PAGE and Western blot techniques are used to analyse the heterogeneity of interferon alpha A (IFN-alpha A) expressed in yeast. The heterogeneity consists of (i) the presence of IFN polymer, (ii) partial processing of signal leader peptide and (iii) internal degradation. The reasons for heterogeneity of gene products in expression system of yeast are analysed. The methods of avoiding heterogeneity, such as depolymerization, adding inhibitors of protease to the culture supernatant, the oligonucleotide-directed deletion mutagenesis and improvements of fermentation, are discussed.

Gene Expression↗