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Biomedical subjects

Q Zhao

Publications and source records attributed to Q Zhao.

At least 91 records · Page 5Linked to original sources
PubMed2000

Hazard identification and dose response of inhaled nickel-soluble salts.

A substantial body of occupational epidemiology data has shown that exposure to mixed soluble and insoluble nickel causes the development of lung and nasal cancer. However, due to coexposure of these populations to soluble and insoluble forms of nickel, and limitations in exposure measurements, the contribution of soluble nickel is difficult to determine. Soluble nickel was negative in an NTP inhalation bioassay, while there was some evidence for tumorigenicity in rats for less soluble nickel oxide, and there was clear evidence for tumorigenicity of insoluble nickel subsulfide in rats. Results of parenteral assays follow a similar pattern, but provide evidence of weak carcinogenicity of soluble nickel. Kinetic factors also indicate that exposure to soluble nickel alone has a low carcinogenic potential. Overall, we conclude that the carcinogenic activity of insoluble nickel compounds should not be used to predict the carcinogenic potential of water-soluble nickel salts. The overall data suggest a nonlinear dose-response relationship for carcinogenicity, but the data are insufficient to determine the doses at which such nonlinearities occur. Under the U.S. EPA's 1996 proposed "Guidelines for Carcinogen Risk Assessment," inhaled soluble nickel compounds would be classified as "cannot be determined," because the existing evidence is composed of conflicting data. A reference concentration of 2 x 10(-4) mg Ni/cu x m was calculated, based on lung fibrosis in male rats observed in the NTP study.

Administration, Inhalation↗
PubMed2000

Hazard identification and dose response of ingested nickel-soluble salts.

People can ingest soluble nickel compounds as a normal constituent of food or as a contaminant in drinking water. This paper presents an assessment of the noncancer and cancer human health risks from ingestion of soluble nickel compounds. A reference dose (RfD) of 8 x 10(-3) mg Ni/kg/day in addition to the amount in food was calculated, based on albuminuria in female rats exposed to nickel sulfate in drinking water for 6 months (A. Vyskocil et al., 1994, Hum. Exp. Toxicol. 13, 689-693). This RfD is comparable to the current RfD based on decreased body weight in a chronic feeding study in rats (A. M. Ambrose et al., 1976, J. Food Sci. Technol. 13, 181-187). The potential for nickel-induced reproductive toxicity was also taken into account in the derivation of the RfD. There are a number of negative animal bioassays with soluble nickel salts, but all of them have deficiencies that preclude a definitive conclusion. According to EPA's 1996 draft cancer guidelines, the carcinogenic potential of oral exposure to soluble nickel "cannot be determined because there are inadequate data to perform an assessment."

Administration, Oral↗
PubMed2000

Stereo-enriched phosphorothioate oligodeoxynucleotides: synthesis, biophysical and biological properties.

Stereo-enriched [Rp] and [Sp]-phosphorothioate oligodeoxynucleotides are synthesized using oxazaphospholidine derivatized monomers. Three different designs of phosphorothioate oligodeoxynucleotides (PS-oligos), (i) stereo-enriched all-[Rp] or all-[Sp] PS-linkages, (ii) stereo-random mixture of PS-linkages, and (iii) segments containing certain number of stereo-enriched [Rp] and [Sp] PS-linkages ([Sp-Rp-Sp] or [Rp-Sp-Rp]), have been studied. Thermal melting studies of these PS-oligos with RNA complementary strands showed that the binding affinities are in the order [Rp] > [Sp-Rp-Sp]-[Rp-Sp-Rp] > stereo-random > [Sp]. Circular dichroism (CD) studies suggest that the stereochemistry of the PS-oligo does not affect the global conformation of the duplex. The in vitro nuclease stability of these PS-oligos is in the order [Sp] > [Sp-Rp-Sp] > stereo-random > [Rp]. The RNase H activation is in the order [Rp] > stereo-random > [Rp-Sp-Rp] > [Sp] > [Sp-Rp-Sp]. Studies in a cancer cell line of PS-oligos targeted to MDM2 mRNA showed that all oligos had similar biological activity under the experimental conditions employed. Protein- and enzyme-binding studies showed insignificant stereo-dependent binding to proteins. The [Sp] and [Sp-Rp-Sp] chimeric and stereo-random PS-oligos that contained a CpG motif showed higher cell proliferation than [Rp] PS-oligo of the same sequence.

Animals↗
PubMed2000

Affinity adsorbents for the vancomycin group of antibiotics.

The vancomycin group of antibiotics kill Gram-positive bacteria by binding to nascent bacterial cell-wall peptidoglycan bearing the C-terminal sequence-D-Ala-D-Ala. In this paper, affinity adsorbents for the vancomycin group of antibiotics were prepared by immobilizing the peptidoglycan analogues -D-Ala-D-Ala, -succinyl-D-Ala and -succinyl-Gly on to crosslinked poly(N, N-dimethylacrylamide). The adsorption capacities of the three adsorbents for demethylvancomycin were 0.59, 0.35 and 0.29 mmol/g, respectively. The adsorption capacity of the adsorbent with-D-Ala-D-Ala for vancomycin was 0.53 mmol/g. In contrast, the adsorbent bearing -succinyl-L-Ala hardly adsorbed demethylvancomycin. Aqueous sodium carbonate (0.4 M)/acetonitrile (7/3, v/v) completely desorbed demethylvancomycin adsorbed on the adsorbents.

Adsorption↗
PubMed2000

Psychosocial predictors of smoking among secondary school students in Henan, China.

The objective of this study was to measure the risk factors associated with tobacco use among secondary school students in Henan, China. Self-reported questionnaires were administered to four secondary schools; 3519 students were studied including 1799 boys and 1720 girls aged 10-19. Demographic, behavioral, attitudinal/belief, knowledge and interpersonal variables were investigated. Overall, 15.1% of boys and 1.4% girls reported smoking at least occasionally. Smoking onset is most prevalent from the ages of 10-14. The smoking rate increased with age. The likelihood of tobacco use was significantly higher among those having peers, teachers or mother who smoked. Positive smoking-related attitudes among students had a significant association with their smoking status. The results suggest that effective smoking prevention interventions need to be comprehensive and implemented in the early teen years.

Adolescent↗
PubMed2000

Comparative toxicokinetics of manganese chloride and methylcyclopentadienyl manganese tricarbonyl (MMT) in Sprague-Dawley rats.

The toxicokinetics of manganese (Mn) was investigated in male and female rats either following a single intravenous (iv) or oral dose of MnCl2 (6.0 mg Mn/kg), or following a single oral dose of methylcyclopentadienyl manganese tricarbonyl (MMT) (20 mg MMT/kg or 5.6 mg Mn/kg). The plasma concentrations of manganese were quantified by atomic absorption spectrophotometry (AAS). Upon iv administration of MnCl2, manganese rapidly disappeared from blood with a terminal elimination t1/2 of 1.83 h and CL8 of 0.43 L/h/kg. The plasma concentration-time profiles of manganese could be described by C = 41.9e(-424t) + 2.1e(-0.44t). Following oral administration of MnCl2, manganese rapidly entered the systemic circulation (Tmax = 0.25 h). The absolute oral bioavailability was about 13%. Oral dose of MMT resulted in a delayed Tmax(7.6 h), elevated Cmax (0.93 microg/ml), and prolonged terminal t1/2 (55.1 h). The rats receiving MMT had an apparent clearance (CL/F = 0.09 L/h x kg) about 37-fold less than did those who were dosed with MnCl2. Accordingly, the area under the plasma concentration-time curves (AUC) of manganese in MMT-treated rats was about 37-fold greater than that in MnCl2-treated rats. A gender-dependent difference in toxicokinetic profiles of plasma manganese was also observed. Female rats displayed a greater AUC than that of male rats. Although the apparent volume of distribution of manganese was similar in both sexes, the apparent clearance in males was about twice that observed in females. The results indicated that after oral administration, the MMT-derived manganese displayed higher and more prolonged plasma concentration-time profiles than MnCl2-derived manganese. Thus, MMT-derived manganese appeared likely to accumulate in the body following repeated exposure.

Administration, Oral↗
PubMed2000

Ketamine modulates the stimulated adhesion molecule expression on human neutrophils in vitro.

UNLABELLED: Cytokine production, neutrophil adhesion to endothelial cells, and release of reactive oxygen species are thought to be critical events in sepsis or ischemia/reperfusion. Modulation of leukocyte responses by anesthetics may have an important role in limiting tissue injury under these conditions. Therefore, we investigated the effect of ketamine on the expression of CD18, CD62L, and oxygen radical production of human neutrophils in vitro and on interleukin-6 production in endotoxin-stimulated human whole blood. Ketamine inhibited both the N-formyl-methionyl-leucyl-phenylalanine- and phorbol 12-myristate 13-acetate-induced up-regulation of CD18 and shedding of CD62L, determined by flow cytometry, in a concentration-dependent manner. Ketamine also caused a significant suppression of oxygen radical generation of isolated human neutrophils. In addition, there was a significant decrease in endotoxin-stimulated interleukin-6 production in human whole blood. The inhibitory effects were similar for racemic ketamine and its isomers S(+)-ketamine and R(-)-ketamine, suggesting that the inhibition of stimulated neutrophil function is most likely not mediated through specific receptor interactions. IMPLICATIONS: Modulation of leukocyte responses by anesthetics may have an important role in limiting tissue injury in sepsis or ischemia/reperfusion. Therefore, we examined the effect of ketamine on stimulated neutrophil functions in vitro. These neutrophil functions were significantly inhibited by ketamine, independent of whether the racemic mixture or isomers were tested.

Anesthetics, Dissociative↗
PubMed2000

Additive noise properties of active matrix flat-panel imagers.

A detailed theoretical and empirical investigation of additive noise for indirect detection, active matrix flat-panel imagers (AMFPIs) has been performed. Such imagers comprise a pixelated array, incorporating photodiodes and thin-film transistors (TFTs), and an associated electronic acquisition system. A theoretical model of additive noise, defined as the noise of an imaging system in the absence of radiation, has been developed. This model is based upon an equivalent-noise-circuit representation of an AMFPI. The model contains a number of uncorrelated noise components which have been designated as pixel noise, data line thermal noise, externally coupled noise, preamplifier noise and digitization noise. Pixel noise is further divided into the following components: TFT thermal noise, shot and 1/f noise associated with the TFT and photodiode leakage currents, and TFT transient noise. Measurements of various additive noise components were carried out on a prototype imaging system based on a 508 microm pitch, 26 x 26 cm2 array. Other measurements were performed in the absence of the array, involving discrete components connected to the preamplifier input. Overall, model predictions of total additive noise as well as of pixel, preamplifier, and data line thermal noise components were in agreement with results of their measured counterparts. For the imaging system examined, the model predicts that pixel noise is dominated by shot and 1/f noise components of the photodiode and TFT at frame times above approximately 1 s. As frame time decreases, pixel noise is increasingly dominated by TFT thermal noise. Under these conditions, the reasonable degree of agreement observed between measurements and model predictions provides strong evidence that the role of TFT thermal noise has been properly incorporated into the model. Finally, the role of the resistance and capacitance of array data lines in the model was investigated using discrete component circuits at the preamplifier input. Measurements of preamplifier noise and data line thermal noise components as a function of input capacitance and resistance were found to be in reasonable agreement with model predictions.

Electronics↗
PubMed2000

A quantitative investigation of additive noise reduction for active matrix flat-panel imagers using compensation lines.

A quantitative investigation of a technique for reducing correlated noise in indirect detection active matrix flat-panel imagers has been reported. Correlated noise in such systems arises from the coupling of electronic noise, originating from fluctuations in external sources such as power supplies and ambient electromagnetic sources, to the imaging array via its address lines. The noise reduction technique involves the use of signals from columns of compensation line pixels located in relatively close proximity to the columns of normal imaging pixels on the array. Compensation line pixels are designed to be as sensitive to externally-coupled noise as columns of normal imaging pixels but are insensitive to incident radiation. For each imaging pixel, correlated noise is removed by subtracting from the imaging pixel signal a signal derived from compensation line pixels located on the same row. The effectiveness of various implementations of this correction has been examined through measurements of signal and noise from individual pixels as well as of noise power spectra. These measurements were performed both in the absence of radiation as well as with x rays. The effectiveness of the correction was also demonstrated qualitatively by means of an image of a hand phantom. It was found that the use of a single compensation line dramatically reduces external noise through removal of the correlated noise component. While this form of the correction increases non-radiation-related uncorrelated noise, the effect can be largely reduced through the introduction of multiple compensation lines. Finally, a position-dependent correction based on compensation lines on both sides of the array was found to be effective when the magnitude of the correlated noise varied linearly across the array.

Electronics↗
PubMed2000

Strategies to improve the signal and noise performance of active matrix, flat-panel imagers for diagnostic x-ray applications.

A theoretical investigation of factors limiting the detective quantum efficiency (DQE) of active matrix flat-panel imagers (AMFPIs), and of methods to overcome these limitations, is reported. At the higher exposure levels associated with radiography, the present generation of AMFPIs is capable of exhibiting DQE performance equivalent, or superior, to that of existing film-screen and computed radiography systems. However, at exposure levels commonly encountered in fluoroscopy, AMFPIs exhibit significantly reduced DQE and this problem is accentuated at higher spatial frequencies. The problem applies both to AMFPIs that rely on indirect detection as well as direct detection of the incident radiation. This reduced performance derives from the relatively large magnitude of the square of the total additive noise compared to the system gain for existing AMFPIs. In order to circumvent these restrictions, a variety of strategies to decrease additive noise and enhance system gain are proposed. Additive noise could be reduced through improved preamplifier, pixel and array design, including the incorporation of compensation lines to sample external line noise. System gain could be enhanced through the use of continuous photodiodes, pixel amplifiers, or higher gain x-ray converters such as lead iodide. The feasibility of these and other strategies is discussed and potential improvements to DQE performance are quantified through a theoretical investigation of a variety of hypothetical 200 microm pitch designs. At low exposures, such improvements could greatly increase the magnitude of the low spatial frequency component of the DQE, rendering it practically independent of exposure while simultaneously reducing the falloff in DQE at higher spatial frequencies. Furthermore, such noise reduction and gain enhancement could lead to the development of AMFPIs with high DQE performance which are capable of providing both high resolution radiographic images, at approximately 100 microm pixel resolution, as well as variable resolution fluoroscopic images at 30 fps.

Feasibility Studies↗
PubMed2000

Divergent N-terminal sequences target an inducible testis deubiquitinating enzyme to distinct subcellular structures.

Ubiquitin-specific processing proteases (UBPs) presently form the largest enzyme family in the ubiquitin system, characterized by a core region containing conserved motifs surrounded by divergent sequences, most commonly at the N-terminal end. The functions of these divergent sequences remain unclear. We identified two isoforms of a novel testis-specific UBP, UBP-t1 and UBP-t2, which contain identical core regions but distinct N termini, thereby permitting dissection of the functions of these two regions. Both isoforms were germ cell specific and developmentally regulated. Immunocytochemistry revealed that UBP-t1 was induced in step 16 to 19 spermatids while UBP-t2 was expressed in step 18 to 19 spermatids. Immunoelectron microscopy showed that UBP-t1 was found in the nucleus while UBP-t2 was extranuclear and was found in residual bodies. For the first time, we show that the differential subcellular localization was due to the distinct N-terminal sequences. When transfected into COS-7 cells, the core region was expressed throughout the cell but the UBP-t1 and UBP-t2 isoforms were concentrated in the nucleus and the perinuclear region, respectively. Fusions of each N-terminal end with green fluorescent protein yielded the same subcellular localization as the native proteins, indicating that the N-terminal ends were sufficient for determining differential localization. Interestingly, UBP-t2 colocalized with anti-gamma-tubulin immunoreactivity, indicating that like several other components of the ubiquitin system, a deubiquitinating enzyme is associated with the centrosome. Regulated expression and alternative N termini can confer specificity of UBP function by restricting its temporal and spatial loci of action.

Age Factors↗
PubMed2000

Stereotactic biopsy for intracranial space-occupying lesions: clinical analysis of 550 cases.

OBJECT: To investigate the role of stereotactic biopsy in planning the optimal management of intracranial space-occupying lesions. PATIENTS AND METHODS: Between December 1989 and December 1999, stereotactic biopsy was performed in 550 patients with intracranial mass lesions that were deep-seated or located in the functional area. There were 340 males and 210 females, and their ages ranged from 4 to 75 years. All the procedures were done under local anesthesia with a Leksell stereotactic system. A CT scan was used to determine the coordinates in the first 420 cases and the Aero Tech Stereotactic Surgical Plan System in the subsequent 130 patients. RESULTS: Brain tumors were diagnosed pathologically in 475 patients (86.4%), inflammatory process in 44 (8.0%), other lesions in 12 (2.2%) and no conclusive diagnosis was found in 19 (3.4%). The overall positive rate of biopsy was 96.6%, and the positive rate for brain tumor was 86.4%. Intracranial hematomas after biopsy were found in 13 cases (2.4%). Seizures occurred during the operation in 7 cases (1.2%), and slight and transient neurological deficits were found in 23 cases (4.2%). There were no deaths or other serious complications. CONCLUSIONS: The results suggest that the stereotactic biopsy is a reliable method to obtain histopathological diagnosis of intracranial mass lesions, and it is also of great help in selecting the appropriate management.

Adolescent↗
PubMed2000

Detecting hormesis using a non-parametric rank test.

When a dose-response experiment is conducted, the enhanced responses can be observed at low doses. This phenomenon is often called hormesis. The enhanced responses at low doses does not necessarily mean the existence of hormesis. It is important to conduct statistical analyses to determine whether a departure from monotonic relationships is significantly different from the chance occurrence. This paper introduces a non-parametric rank test to detect hormesis. To illustrate the use of this method, we apply it to the data from a Whole Effluent Toxicity test. We demonstrate that the occurrence of hormesis can be statistically evaluated by using this non-parametric rank test.

Animals↗
PubMed2000

Interaction of alcohol and the G to a substitution at the promoter region of the apolipoprotein AI gene in determining plasma apolipoprotein AI levels in Yi and Han Chinese.

OBJECTIVE: To investigate the influence on plasma lipid levels of alcohol and a common polymorphism in the human apolipoprotein AI gene promoter at a position 75 bp upstream of the transcription start site. METHODS: For this study, 742 healthy Yi and Han subjects all above 15 years old formed the total population which was divided into three groups: the Yi-farmer group, the Yi-emigrant group and the Han-resident group. All estimates of plasma lipids and apolipoproteins were performed using an auto-analyzer. Genetic DNA was prepared from the blood clots using the Triton X-100 lysis technique. Amplification of a 432 bp fragment of the apoAI gene promoter was performed using PCR followed by restriction digestion, electrophoresis and identification of the genotypes involved. RESULTS: The samples were divided on the basis of alcohol consumption: non-drinkers, 1-25 g/day, 26-75 g/day and > 75 g/day. Comparing the four alcohol consumption groups, plasma HDLC and apoAI levels were increased as the alcohol consumption increased with no evidence of threshold effects in the Yi-farmers and the Han people groups. A similar association was found in the Yi-emigrant group, but was not statistically significant. The frequencies of the A allele in the three populations were similar, and no significant difference of lipid and apolipoprotein levels was found between subjects with and without the A allele in the three populations. But, in Han and Yi-emigrant samples, the drinkers with the GG genotype had higher plasma HDLC and apoAI levels than non-drinkers with the same genotype, while the drinkers with the A allele had lower plasma HDLC and apoAI levels than drinkers without the A allele. Non-drinkers with the A allele had higher levels of apoAI than non-drinkers with GG genotypes. It was estimated that 18% of the variability of plasma apoAI level could be explained by the G to A polymorphism in non-drinkers of Yi-emigrants (F = 8.94, P < 0.01). CONCLUSIONS: The present data suggest that moderate alcohol consumption and the G to A substitution could lower the risk of coronary heart disease (CHD), but the beneficial effects of one will be negated by the other.

Adolescent↗
PubMed2000

[Effect of adenovirus type 5 E1A gene on proliferation and metastasis of human lung adenocarcinoma cells].

OBJECTIVE: To investigate the effects of E1A gene on proliferation and metastasis of human lung adenocarcinoma cells. METHODS: A mammalian E1A-expressing recombinant constructed in our laboratory, named pcDNA3-E1A, was introduced into human lung adenocarcinoma cell line(Anip 973) by lipofectamine. The cells resistant to G418 were selected. The characteristics of the E1A-expressing Anip 973(Anip 973-E1A) cells were studied in vitro and in vivo, including cell growth rate and doubling-time, colony-forming efficiency on soft agarose, tumorigenicity and metastasis. RESULTS: The growth rate of E1A-Anip 973 cells was diminished and their colony-forming efficiency was inhibited significantly. The tumorigenicity in nude mice of the E1A-expressing Anip 973 was markedly suppressed. CONCLUSION: E1A suppresses the malignant phenotype of human lung adenocarcinoma cell line. This study provides experimental data for gene therapy of lung cancer with E1A.

Adenocarcinoma↗
PubMed2000

[The significance of detecting tumor necrosis factor-alpha and its receptors in serum and pleural effusion in differentiating tuberculosis and malignant pleural effusions].

OBJECTIVE: To investigate the significance of TNF-alpha and its soluble receptors (sTNFR-I and sTNFR-II) in differentiating benign and malignant pleural disease. METHODS: TNF-alpha and its soluble receptors (sTNFR-I and sTNFR-II) were detected using ELISA method in the serum and pleural effusion of 25 cases of tuberculosis pleural effusion and 28 cases of malignant pleural effusion, and in the serum of 32 cases of normal control. RESULTS: TNF-alpha level in the serum of tuberculosis patients with pleural effusion is (16.4 +/- 6.2) ng/L, lower than that in the serum of malignant pleural effusion patients (20.5 +/- 10.9) ng/L (P < 0.01), but higher than that in the serum of normal control (11.0 +/- 2.9) ng/L (P < 0.01). TNF-alpha level in the pleural effusion of tuberculosis patients is (29.4 +/- 10.3) ng/L, significantly higher than that of malignant pleural effusion (11.7 +/- 2.0) ng/L (P < 0.01). The sTNFR-I and sTNFR-II level in the serum of malignant pleural effusion is (1,132 +/- 303) ng/L and (1,548 +/- 489) ng/L respectively, significantly higher than that in tuberculosis pleural effusion which is (979 +/- 146) ng/L and (977 +/- 93) ng/L (P < 0.01) respectively. The sTNFR-I and sTNFR-II level in malignant pleural effusion is (1,404 +/- 306) ng/L and (2,195 +/- 418) ng/L respectively, markedly higher than those in tuberculosis pleural effusion which is (1,185 +/- 215) ng/L and (1,195 +/- 300) ng/L (P < 0.01). CONCLUSION: There are highly elevated TNF-alpha in tuberculosis pleural effusion; The sTNFR-I and sTNFR-II level in the serum and pleural effusion of malignant pleural effusion patients are significantly higher than those in tuberculosis pleural effusion patients, suggesting they may play some role in differentiating benign and malignant pleural diseases.

Adult↗
PubMed2000

[Tissue engineered neo-cartilage using polymer substrates and chondrocytes: experimental study].

OBJECTIVE: To investigate the possibility of using poly beta-hydroxybutyrate (PHB) as a scaffold for chondrocytes and the feasibility of generating tissue engineered cartilage in rabbit animal model. METHODS: The articular cartilage from 4-week-old rabbits was enzymatically dissolved by type II collagenase, and chondrocytes were harvested and seeded into foams of PHB. After incubation for 1 week in vitro, chondrocyte-polymer constructs were implanted subcutaneously into rabbits. Two respective control groups were established by subcutaneous implantation of PHB foams and chondrocytes alone. The rabbits were killed at 4, 8, 12 weeks postoperatively, and the specimens were dissected and examined macroscopically, histologically and immunohistochemically. RESULTS: Specimens harvested from chondrocyte-polymer constructs and subjected to gross morphologic and histologic analysis demonstrated new cartilage formation, and those from control groups showed no cartilage formation. CONCLUSION: These findings demonstrate that the foam of PHB is not only a good "matrix" for cartilage tissue engineering, but also optimal scalffold for the seeding of chondrocytes to generate new cartilage that would be useful in plastic and reconstructive surgery.

Animals↗