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Biomedical subjects

C Lu

Publications and source records attributed to C Lu.

At least 109 records · Page 6Linked to original sources
PubMed2000

Saliva biomonitoring of atrazine exposure among herbicide applicators.

A field study was conducted in which saliva samples were collected from a cohort of herbicide applicators during the pre-emergent spray season in Ohio in 1996. Atrazine concentrations were detected in human saliva samples using an enzyme-linked immunosorbent assay (ELISA) method. Trend due to atrazine exposure and subsequent elimination in the body were evidenced by the temporal pattern of decreasing atrazine concentrations in saliva over time. Median salivary concentrations of atrazine on non-spray days were significantly lower than on spray days for each sampling time (Mann-Whitney U-Wilcoxon rank sum test, P < 0.01). Within spray days, median salivary atrazine concentrations were significantly higher on days atrazine was sprayed than on days herbicides other than atrazine were sprayed for each sampling time (Mann-Whitney U-Wilcoxon rank sum test, P = 0.02 for 4 6 p.m. samples, P = 0.04 for bedtime samples, P = 0.03 for next-morning samples). Median salivary atrazine concentrations on days atrazine was sprayed were higher than the median concentration for the corresponding sampling time on non-spray days and on days when other herbicides were sprayed. Salivary concentration of atrazine is a plausible indicator of those days in which atrazine spraying was likely to have occurred. Salivary concentrations of atrazine not only reflect exposures resulting from spraying atrazine, but also exposures from other field activities where applicators may come in contact with atrazine. The results of this study confirmed data from animal experiments that atrazine is able to cross the cell membranes of salivary glands, and can be measured in human saliva with high sensitivity. The sampling method itself is convenient and easy to use in the field, with a high compliance rate, and analytical procedures are rapid and inexpensive. It is, therefore, concluded that saliva sampling of atrazine exposure among herbicide applicators is a feasible biomonitoring method.

Adult↗
PubMed2000

Reengineering a database for clinical trials management: lessons for system architects.

This paper describes the process of enhancing Trial/DB, a database system for clinical studies management. The system's enhancements have been driven by the need to maximize the effectiveness of developer personnel in supporting numerous and diverse users, of study designers in setting up new studies, and of administrators in managing ongoing studies. Trial/DB was originally designed to work over a local area network within a single institution, and basic architectural changes were necessary to make it work over the Internet efficiently as well as securely. Further, as its use spread to diverse communities of users, changes were made to let the processes of study design and project management adapt to the working styles of the principal investigators and administrators for each study. The lessons learned in the process should prove instructive for system architects as well as managers of electronic patient record systems.

Clinical Trials as Topic↗
PubMed2000

Effect of freezing on the activity of catalase in apple flesh tissue.

Catalase (CAT, EC 1.11.1.6) activity was measured in flesh tissue of six apple cultivars (Malus domestica Borkh. cvs. Braeburn, Gala, Jonagold, McIntosh, Red Delicious, and Spartan). Activity of CAT was determined for fresh and frozen tissue of the same fruit. Freezing resulted in reductions of 50 to 90% in CAT activity compared with the activity measured in crude extracts from fresh tissues. The rate of freezing had an impact on the level of reduction of CAT activity, with slower freezing procedures leading to greater losses in activity. Six additives to the extraction buffer were tested to evaluate their potential to reduce the inactivation of CAT from frozen tissue, but only EDTA and Tween 20 showed any benefit. However, EDTA and Tween 20 provided only partial recovery in CAT activity. In contrast, crude extracts prepared from fresh tissue showed no appreciable loss in CAT activity after frozen storage for two weeks at -80 degrees C. Gel electrophoresis and immunological analysis indicated that the loss in CAT activity from tissue freezing could be attributed to loss of both the tetrameric CAT enzyme structure and total CAT protein. The implications of using freezing to preserve apple tissue samples prior to catalase activity analysis is discussed.

Catalase↗
PubMed2000

Canine distemper virus causes apoptosis of Vero cells.

Apoptosis of Vero cells infected with two canine distemper virus (CDV) vaccine strains was detected using TdT (terminal deoxynucleotidyl transferase)-mediated dUTP nick end-labelling (TUNEL), flow cytometric analysis, agarose gel electrophoresis and electron microscopy (EM). By TUNEL, apoptotic cells were found in CDV-Onderstepoort (CDV-Ond)-infected cells. DNA fragments isolated from infected cells were separated by agarose gel electrophoresis and a 'ladder' pattern appeared. EM observations demonstrated that the cells undergoing cytopathic effect (CPE) possessed morphological characteristics of apoptotic cells. Flow cytometric analysis indicated that CDV could induce apoptosis of Vero cells, but the percentages of the apoptotic cells were correlated with the CPE types. The strain showing the cell-rounding type of CPE produced a much higher percentage of apoptotic cells than CDV-Ond with the syncytium type of CPE (P < 0.01). It was concluded that CDV vaccine strains could induce apoptosis of Vero cells and the apoptosis was virus strain-dependent and cell-dependent. The mechanism remains to be studied.

Animals↗
PubMed2000

Potential of wheat-based breakfast cereals as a source of dietary antioxidants.

Whole wheat- and wheat bran-based ready-to-eat breakfast cereals could be important sources of dietary antioxidants. Of the antioxidants in wheat, free and esterified phenolic acids seem to have the greatest potential to be beneficial to health. Phenolic acids from breakfast cereals possess strong antioxidant activity in vitro at concentrations that would be obtained from a normal serving of whole wheat cereal. In addition, acid conditions and enzymic hydrolysis increase the solubility and activity of wheat phenolics suggesting that the digestive process could be important in altering the antioxidant potential of wheat-based foods. Current research on the antioxidant activity of wheat phenolics suggests that further research is warranted to determine the potential benefits of these dietary antioxidants. In addition, identification of both biological (e.g. digestion) and food processing conditions that impact the distribution, stability and activity of wheat antioxidants is needed in order to be able to produce food products with maximum health benefits.

Antioxidants↗
PubMed2000

Removal of BTEX vapor from waste gases by a trickle bed biofilter.

The system performance of a trickle bed biofilter for treating single and mixed benzene, toluene, ethylbenzene, and o-xylene (BTEX) vapors from waste gases was investigated under different gas flow rates and influent BTEX concentrations. When a single substrate was fed, removal efficiencies of greater than 90% could be achieved for the loads below 64 g benzene/m3/hr, 110 g toluene/m3/hr, 53 g ethylbenzene/m3/hr, and 55 g o-xylene/m3/hr. When a mixed substrate was fed, removal efficiencies of each compound could be above 90% at BTEX loads below 96 g/m3/hr. The trickle bed biofilter appears to be an effective treatment process for removing both single and mixed BTEX vapors with low to high loads. Under similar substrate loads, BTEX vapors were preferentially biodegraded in the order of toluene, benzene, o-xylene, and ethylbenzene. The volumetric removal rates (elimination capacities) of BTEX vapors for a single-substrate feed were higher than those for a mixed-substrate feed under similar substrate loads; these differences were enhanced at higher substrate loads and less significant for a preferred substrate.

Air Pollutants, Occupational↗
PubMed2000

A mutation in the Arabidopsis HYL1 gene encoding a dsRNA binding protein affects responses to abscisic acid, auxin, and cytokinin.

Both physiological and genetic evidence indicate interconnections among plant responses to different hormones. We describe a pleiotropic recessive Arabidopsis transposon insertion mutation, designated hyponastic leaves (hyl1), that alters the plant's responses to several hormones. The mutant is characterized by shorter stature, delayed flowering, leaf hyponasty, reduced fertility, decreased rate of root growth, and an altered root gravitropic response. It also exhibits less sensitivity to auxin and cytokinin and hypersensitivity to abscisic acid (ABA). The auxin transport inhibitor 2,3,5-triiodobenzoic acid normalizes the mutant phenotype somewhat, whereas another auxin transport inhibitor, N-(1-naph-thyl)phthalamic acid, exacerbates the phenotype. The gene, designated HYL1, encodes a 419-amino acid protein that contains two double-stranded RNA (dsRNA) binding motifs, a nuclear localization motif, and a C-terminal repeat structure suggestive of a protein-protein interaction domain. We present evidence that the HYL1 gene is ABA-regulated and encodes a nuclear dsRNA binding protein. We hypothesize that the HYL1 protein is a regulatory protein functioning at the transcriptional or post-transcriptional level.

Abscisic Acid↗
PubMed2000

Straight and curved conformations of FtsZ are regulated by GTP hydrolysis.

FtsZ assembles in vitro into protofilaments that can adopt two conformations-the straight conformation, which can assemble further into two-dimensional protofilament sheets, and the curved conformation, which forms minirings about 23 nm in diameter. Here, we describe the structure of FtsZ tubes, which are a variation of the curved conformation. In the tube the curved protofilament forms a shallow helix with a diameter of 23 nm and a pitch of 18 or 24 degrees. We suggest that this shallow helix is the relaxed structure of the curved protofilament in solution. We provide evidence that GTP favors the straight conformation while GDP favors the curved conformation. In particular, exclusively straight protofilaments and protofilament sheets are assembled in GMPCPP, a nonhydrolyzable GTP analog, or in GTP following chelation of Mg, which blocks GTP hydrolysis. Assembly in GDP produces exclusively tubes. The transition from straight protofilaments to the curved conformation may provide a mechanism whereby the energy of GTP hydrolysis is used to generate force for the constriction of the FtsZ ring in cell division.

Actin Cytoskeleton↗
PubMed2000

GAP-43 mediates retinal axon interaction with lateral diencephalon cells during optic tract formation.

GAP-43 is an abundant intracellular growth cone protein that can serve as a PKC substrate and regulate calmodulin availability. In mice with targeted disruption of the GAP-43 gene, retinal ganglion cell (RGC) axons fail to progress normally from the optic chiasm into the optic tracts. The underlying cause is unknown but, in principle, can result from either the disruption of guidance mechanisms that mediate axon exit from the midline chiasm region or defects in growth cone signaling required for entry into the lateral diencephalic wall to form the optic tracts. Results here show that, compared to wild-type RGC axons, GAP-43-deficient axons exhibit reduced growth in the presence of lateral diencephalon cell membranes. Reduced growth is not observed when GAP-43-deficient axons are cultured with optic chiasm, cortical, or dorsal midbrain cells. Lateral diencephalon cell conditioned medium inhibits growth of both wild-type and GAP-43-deficient axons to a similar extent and does not affect GAP-43-deficient axons more so. Removal or transplant replacement of the lateral diencephalon optic tract entry zone in GAP-43-deficient embryo preparations results in robust RGC axon exit from the chiasm. Together these data show that RGC axon exit from the midline region does not require GAP-43 function. Instead, GAP-43 appears to mediate RGC axon interaction with guidance cues in the lateral diencephalic wall, suggesting possible involvement of PKC and calmodulin signaling during optic tract formation.

Animals↗
PubMed2000

Biologically based pesticide dose estimates for children in an agricultural community.

Current pesticide health risk assessments in the United States require the characterization of aggregate exposure and cumulative risk in the setting of food tolerances. Biologic monitoring can aggregate exposures from all sources and routes, and can integrate exposures for chemicals with a common mechanism of action. Its value was demonstrated in a recent study of organophosphorus (OP) pesticide exposure among 109 children in an agricultural community in Washington State; 91 of the children had parents working in agriculture. We estimated individual OP pesticide doses from urinary metabolite concentrations with a deterministic steady state model, and compared them to toxicologic reference values. We evaluated doses by assuming that metabolites were attributable entirely to either azinphos-methyl or phosmet, the two OP pesticides used most frequently in the region. Creatinine-adjusted average dose estimates during the 6- to 8-week spraying season ranged from 0 to 36 microg/kg/day. For children whose parents worked in agriculture as either orchard applicators or as fieldworkers, 56% of the doses estimated for the spray season exceeded the U.S. Environmental Protection Agency (EPA) chronic dietary reference dose, and 19% exceeded the World Health Organization acceptable daily intake values for azinphos-methyl. The corresponding values for children whose parents did not work in agriculture were 44 and 22%, respectively. The percentage of children exceeding the relevant reference values for phosmet was substantially lower (< 10%). Single-day dose estimates ranged from 0 to 72 microg/kg/day, and 26% of these exceeded the EPA acute reference dose for azinphos-methyl. We also generated dose estimates by adjustment for total daily urine volume, and these estimates were consistently higher than the creatinine-adjusted estimates. None of the dose estimates exceeded the empirically derived no-observable-adverse-effect levels for these compounds. The study took place in an agricultural region during a period of active spraying, so the dose estimates for this population should not be considered representative of exposures in the general population. The findings indicate that children living in agricultural regions represent an important subpopulation for public health evaluation, and that their exposures fall within a range of regulatory concern. They also demonstrate that biologically based exposure measures can provide data for health risk evaluations in such populations.

Agriculture↗
PubMed2000

[Construction of silkworm RAPD molecular linkage map].

In this research, a RAPD linkage map of Bombyx mori was constructed with Dazao/C108 and their F2 generation. The map consists of 182 RAPD loci, of which 103 loci come from Dazao and from the first 23 linkage groups and the other 79 loci come from C108 and form the second 16 linkage groups. This map covered a total genetic distance of over 1,148.3 cM (centimorgan). It could be integrated with the SADF map of the same materials constructed in our laboratory and the corresponding RFLP linkage map.

Animals↗
PubMed2000

Role of light in the response of PSII photochemistry to salt stress in the cyanobacterium Spirulina platensis.

The role of light in the effect of salt stress on PSII photochemistry in the cyanobacterium Spirulina platensis grown at 50 micromol m(-2) s(-1) was investigated. The time-course of changes in PSII photochemistry in response to high salinity (0.8 M NaCl) incubated in the dark and at 30, 50 and 100 micromol m(-2) s(-1) was composed of two phases. The first phase, which was independent of light, was characterized by a rapid decrease (20-50%) in the maximal efficiency of PSII photochemistry (F:(v)/F:(m)), the efficiency of excitation energy capture by open PSII reaction centres (F(1)(v)/F(1)(m)), photochemical quenching (q(P)), and the quantum yield of PSII electron transport (Phi(PSII)) in the first 15 min, followed by a recovery of up to about 86-92% of their initial levels after 4 h of incubation. The second phase took place after 4 h, in which a further decline in the above parameters occurred only in the light but not in the dark, reaching levels as low as 32-56% of their initial levels after 12 h. Moreover, the higher incubation light intensity, the greater the decrease in the above parameters. At the same time, Q(B)-non-reducing PSII reaction centres increased significantly in the first 15 min and then recovered to the initial level during the first phase, but increased again in the light in the second phase. Photosynthetic oxygen evolution activity decreased sharply by 70% in the first 5 min, and then kept largely constant until 12 h. The changes in oxygen evolution activity were independent of light intensity during both phases.

Cyanobacteria↗
PubMed2000

[Population density of Eucalyptus urophylla plantation].

This paper dealt with the relationships and correlation models of the population density of 5.6 years old Eucalyptus urophylla plantation with its crown width, diamter at breast height(DBH), tree height, individual standing volume, stand volume, wood properties and survital rate. The results showed that the population density remarkably affected DBH, individual standing volume, crown width, live branch height, stand volume and wood fiber width; but not affect tree height, basic density of wood, and length of wood fibers. It had a positive relationship with stand volume, live branch height and wood fibers width, and a negative relationship with DBH, individual standing volume and crown width. In addition, E. urophylla had a wide range of reasonable density. For short-rotation puplwoods, the optimum planting density of E. urophylla is 2000 individuals per hectare.

Ecology↗
PubMed2000

[Judgement of gross type and local invasion of advanced gastric carcinoma by spiral computed tomography].

OBJECTIVE: To evaluate the value of spiral computed tomography(sCT) in the judgement of gross type, invasion to serosa and adjacent organs of advanced gastric carcinoma. METHODS: The sCT results of 53 cases of advanced gastric carcinoma undergone gastrectomy were compared with surgical pathologic findings. RESULTS: The accuracy of judging gross type, location and size of gastric carcinoma was 92.5%, 88.7%, 81.1% respectively; 80.5% of serosal invasion was correctly judged by extraluminal fat sign, while 63.4% by serosal contour sign (P < 0.05). Different serosal types could be differentiated by CT features. The accuracy of judging invasion to pancreas, spleen and transverse colon was 87.8%, 87.8%, and 90.2%; and the specificity was 96.7%, 97.0% and 96.7%, respectively. CONCLUSION: Spiral computed tomography is of help in the identification of the gross type, invasion to serosa and adjacent organs of gastric cancer in its stage of progression.

Adult↗
PubMed2000

[Study on beta-adrenoceptors mechanism of cadmium immunotoxicity].

OBJECTIVE: To study if the beta-adrenoceptors mechanism plays important role in the immunotoxicity of cadmium. METHODS: The beta-adrenoceptor density, cellular cyclic adenosine 3',5' monophosphate (cAMP) levels, and DNA damage of rat spleen lymphocytes were studied. Beta-antagonist propranolol was used to block the beta-adrenoceptor. RESULTS: In the single Cd administration group: beta-adrenoceptor density of spleen lymphocytes in the middle and high Cd concentration groups was higher than that in the non-Cd treated control group (P < 0.05), the levels of cAMP increased with the increase of Cd doses, and the result of the high Cd group was higher than that of the control group (P < 0.05). The proliferation function of T lymphocytes was lower in each Cd group than that in the control group (P < 0.05). Single cell gel electrophoresis (SCGE) detected that DNA damage of spleen lymphocytes in each Cd group were more severe than the control (P < 0.05). Pretreated with Pro group: After blocked with propranolol, beta-adrenoceptor density increased in the Pro control group and the density in all Cd treated groups was higher than the control group (P < 0.05), but all Cd treated groups showed no statistical significance than the Pro control group (P > 0.05). The cAMP levels, MTT and the subsets of T lymphocytes showed no statistical significance among all the groups (P > 0.05). The results of SCGE showed that DNA damage was most severe only in the high Cd group than other groups (P < 0.05). CONCLUSION: The results suggest that the nerve-internal secretion system plays an important role in the immunotoxicity of cadmium, and the beta-adrenoceptor mechanism is important in the immunotoxic mechanism of cadmium.

Adrenergic beta-Antagonists↗
PubMed2000

[A study on apoptosis and activity of SAPK/JNK in adrenocortical cells induced by cadmium chloride].

OBJECTIVE: To study apoptosis induced by cadmium chloride and the alteration in activity of stress activated protein kinase (SAPK) in adrenocortical cells. METHODS: Fasciculata-glomerulosa (FG) cells of male guinea pigs were dispersed and primarily cultured in vitro. Features of apoptotic cells were observed using combined labeling with annexin-V and propidium iodide (PI) and flow cytometry, and activity of SAPK was determined with immunoprecipitation and chemiluminescence assay. RESULTS: Apoptosis rate of FG cells increased with dose of cadmium chloride (CdCl(2)) two hours after treatment with 6.25 - 200.00 micromol/L of it. The average percentages of apoptotic cells ranged from 9.90% to 82.35%, with significant difference in the groups treated with 25, 50, 100 and 200 micromol/L of CdCl(2), as compared with the control group (P < 0.01). Regression analysis showed that occurrence of apoptosis correlated with the dose of cadmium chloride in a dose-response pattern. In the meanwhile, there were obviously elevated percentages of apoptotic cells as the increase in duration of incubation, ranging from 5.58% to 73.08% for incubating cells with 50.00 micromol/L of CdCl(2), from 15 minutes to four hours. Duration of incubating cells with cadmium chloride correlated to occurrence of apoptosis in a time-effect manner. There were no remarkable changes in the activity of SAPK in adrenocortical cells two hours after incubation with 25.00 - 100.00 micromol/L of CdCl(2). CONCLUSIONS: Apoptosis can be induced by cadmium chloride in adrenocortical cells and its mechanism should be studied further.

Adrenal Cortex↗