Biomedical subjects

H H Yang

Publications and source records attributed to H H Yang.

At least 19 recordsLinked to original sources

PubMed2005

Macro- and nanoscale observations of adhesive behavior for several E. coli strains (O157:H7 and environmental isolates) on mineral surfaces.

Subsurface biobarriers can be conceived to attenuate the migration of pathogens by adhesion to mineral surfaces. Candidate biobarrier materials of varied surface characteristics (dolomite, alpha-alumina, silica, pyrophyllite, and Pyrax (a composite form of pyrophyllite, mica, and silica)) were tested for Escherichia coli adhesive capacity in macroscale continuous-flow columns. Atomic force microscopy (AFM) was used to determine nanoscale interaction energies. Predicted attractive interaction energies correlated well with macroscale adhesive behavior for tested E. coli strains. AFM measurements confirmed ExDLVO model predictions of attachment in the primary minima for E. coli O157:H7 and two environmental isolates E. coli (UCFL339 and UCFL-348) with MOPS conditioned Pyrax. In macroscale column experiments, pyrophyllite and Pyrax demonstrated significantly higher bacterial retention, higher deposition coefficients and lower initial cell breakthrough values for E. coli O157:H7 than did alpha-alumina, silica, or dolomite (pyrophyllite, 0.93, 3.56 h(-1), 3.2% ODo; Pyrax, 0.95, 3.73 h(-1), 2.8% ODo; alpha-alumina, 0.74, 1.60 h(-1), 33% ODo; silica, 0.63, 0.43 h(-1), 73% ODo; and dolomite, 0.33, 0.17 h(-1), 89% ODo, respectively). Bacterial hydrophilicity impacted cell retention in Pyrax columns with the relatively hydrophobic E. coli isolate UCFL-339 (0.99, 6.13 h(-1), 0.4% ODo) retained better than the more hydrophilic E. coli isolate UCFL348 (0.94, 3.70 h(-1), 3.6% ODo). The strong adhesive behavior of Pyrax was attributed to the hydrophobic (deltaGiwi = -32.4 mJ/m2) pyrophyllite component of the mineral. Vicinal water appears poised between the bacterial and the mineral surface during initial attachment. Overall, observed behavior of the various E. coli strains and the selected mineral surfaces was consistent with surface analyses, conducted at both the macro- and nanoscale.

Aluminum Oxide↗

PubMed2005

Safety and immunogenicity of an oral, inactivated, whole-cell vaccine for Shigella sonnei: preclinical studies and a Phase I trial.

Orally delivered, inactivated whole-cell vaccines are safe methods of inducing local and systemic immunity. To increase surface proteins associated with adherence and invasion, Shigella sonnei were grown in BHI broth containing deoxycholate. A whole-cell vaccine (SsWC) was then produced by formalin inactivation. In pre-clinical studies, the SsWC vaccine was immunogenic and protected against S. sonnei-induced keratoconjunctivitis in the guinea pig model. In a randomized, double-blind, placebo-controlled, Phase I study, 10 evaluable subjects received either three doses of SsWC on Days 0, 14, and 28 (N = 3); five doses of SsWC on Days 0, 2, 4, 6, and 28 (N = 4); or placebo (N = 3). Each dose contained 2.0 x 10(10) inactivated cells. Serum and fecal antibodies against SsWC, LPS, and IpaC were measured by ELISA. A > or = 4-fold increase in titer was considered significant. Both SsWC dosing regimens were well tolerated. No fever or severe gastrointestinal symptoms were noted by any of the vaccinated subjects. Antibody responses were similar in the two dosing groups. Serum IgG or IgA responses to SsWC were seen in six of seven vaccinees (86%), to LPS in four of seven (57%), and to IpaC in five of seven (61%). Fecal IgA responses to these three antigens developed in five of five, three of five, and three of five subjects, respectively. Among the seven vaccinees, geometric mean rises in serum IgA levels to all three immunogens were significant; IgG increases trended toward significance (paired one-tailed t-test). We conclude that SsWC was immunogenic and protective in animal studies and well tolerated and immunogenic in a Phase I trial.

Administration, Oral↗

PubMed2005

Morphometric studies on the testis of Korean ring-necked pheasant (Phasianus colchicus karpowi) during the breeding and non-breeding seasons.

The purpose of this study was to obtain detailed quantitative information on all cell types in the testis interstitium of Korean ring-necked pheasants and to combine these data with changes in the steroidogenic function of the testis during the breeding and non-breeding seasons. For animals collected during the breeding season, their testis weights, sperm production, serum testosterone levels and leuteinizing hormone (LH)-stimulated testosterone secretion were significantly (p < 0.01) increased compared to the non-breeding season. Testes of the pheasants during the non-breeding season displayed a 98% reduction in testis volume that was associated with a decrease in the absolute volume of seminiferous tubules (98% reduction), tubular lumen (100%), interstitium (90%), blood vessels (84%), lymphatic spaces (97%), Leydig cells (79%), mesenchymal cells (51%) and myoid cells (61%) compared to the breeding season. The numbers of Leydig cells, mesenchymal cells and myoid cells per testis in the breeding season were much higher than in the non-breeding season. Although the mean volume of a Leydig cell was 74% lower in the non-breeding season, the mean volumes of myoid and mesenchymal cells remained unchanged. These results demonstrate that there are striking differences in the testicular structure of the Korean ring-necked pheasant during the breeding and non-breeding seasons. Every structural parameter of the Leydig cell was positively correlated with both testosterone serum levels and LH-stimulated testosterone secretion. The correlation of changes in hormonal status with the morphometric alterations of Leydig cells suggests that the Korean-ring necked pheasant may be used as a model to study structure-function relationships in the avian testis.

Animals↗

PubMed2001

Fluorescence immunoassay system based on the use of a pH-sensitive phase-separating polymer.

Poly(N-isopropylacrylamide-co-methacrylic acid) [P(NIPAAm-co-MAA)], a linear water-soluble pH-sensitive phase-separating polymer, was synthesized and used as a novel separation carrier for the reactants in immunoassay. This polymer precipitates out of water below a critical pH 5.8 at 37 degrees C and redissolves when the pH of solution is above 6.2. The characteristic of this polymer makes it possible to carry out the immunochemical steps of an immunoassay in a true solution and then to quickly separate the resulting product from the reaction mixture. The above approach was applied to determination of alpha-fetoprotein with the competitive immunoassay format. Compared with traditional ELISA using the same reactants, the proposed method was much faster (the assay time decreased from 100-120 to 30 min) and showed similar sensitivity, i.e., 0.04 ng/mL. In addition, a sandwich immunoassay method for the determination of hepatitis B surface antigen was also studied, and the results showed that the pH phase-separating immunoassay could be carried out through a sandwich or a competitive method. This general technique may also be used for a wide variety of separation processes in addition to immunoassay, in which a specific component is to be isolated for analysis, recovery, or disposal.

Acrylamides↗

PubMed2001

An outbreak of typhoid fever, Xing-An County, People's Republic of China, 1999: estimation of the field effectiveness of Vi polysaccharide typhoid vaccine.

To evaluate the effectiveness of Vi polysaccharide vaccine (Vi vaccine) in preventing typhoid fever, an analysis was done of an outbreak of typhoid fever among students attending a middle school in the People's Republic of China, where Vi vaccine is licensed for use. Vi vaccine effectiveness was analyzed by using Cox proportional hazards modeling to account for the time-dependent nature of vaccination and illness status during the outbreak. Among 1260 students who had been immunized before the outbreak, receipt of Vi vaccine was associated with 73% (95% confidence interval [CI], 32%-89%) protection. Among the additional 441 students immunized during the outbreak, receipt of Vi vaccine was associated with 71% (95% CI, -9% to 92%) protection. These results provide the first evidence about the effectiveness of Vi vaccine when deployed routinely in a typhoid-endemic area and support the use of Vi vaccine as a public health tool to control typhoid fever.

Adolescent↗

PubMed2001

Fluorescence immunoassay of alpha-fetoprotein with iron(III) tetrasulfonatophthalocyanine as a mimetic enzyme labeling reagent.

A new fluorimetric immunoassay for alpha-fetoprotein (AFP) has been developed using a novel promising mimetic peroxidase, iron(III) tetrasulfonatophthalocyanine (FeTSPc), as a labeling reagent to catalyze the fluorescence reaction of P- hydroxyphenylacetic acid (P-HPA) and hydrogen peroxide (H2O2). In the competitive immunoassay, anti-AFP antibody was coated on a 96-well plate (polystyrene) and a constant amount of FeTSPc-labeled AFP and a known amount of test solution were added. Non-labeled and FeTSPc-labeled AFP compete for binding to the plate-bound antibody. After the immunoreaction, the immunochemically adsorbed FeTSPc-AFP conjugate moiety was determined by measuring the fluorescence produced in a solution containing P-HPA and H2O2. AFP can be determined in the concentration range of 1-300 ng mL(-1) with a detection limit of 0.5 ng mL(-1).

Antibodies↗

PubMed2001

A new red-region substrate, tetra-substituted amino aluminium phthalocyanine, for the fluorimetric determination of H2O2 catalyzed by mimetic peroxidases.

A new red-region fluorogenic substrate, tetra-substituted amino aluminium pthalocyanine, was developed for the selective determination of H2O2 based on the catalytic effect of mimetic peroxidases, viz., hemin or iron tetrasulfonatophthalocyanine (FeTSPc). Under the optimum conditions, the linearity of the calibration graph for the determination of H2O2 with hemin (or FeTSPc) as the catalyst was in the range from 0.0 to 3.0 x 10(-7) mol L-1 (or from 0.0 to 2.0 x 10(-6) mol L-1). The detection limits were 3.7 x 10(-9) and 4.9 x 10(-9) mol L-1 H2O2, respectively. The relative standard deviation (n = 7) was within 1.5% in the middle of the linear range. The peroxidase activity of the mimetic enzymes hemin and FeTSPc, the effects of some experimental conditions and the influence of foreign substances were investigated. With this substrate, 0.0-7.5 x 10(-8) mol L-1 hemin and 0.0-2.0 x 10(-6) mol L-1 FeTSPc can be determined with an accuracy and precision of about 1.3%. The potential application of the reagent was tested by the determination of H2O2 in rainwater.

Hemin↗

PubMed2001

The effect of hydration on adsorption and desorption of heavy metals in soils.

Cr, Ni, and Cd adsorption-desorption on five characterized Taiwan soils was studied. The potential for toxicity and the fate of metals in the soils is dependent upon the ability of the metals to desorb into the aqueous phase. To simulate field conditions, the soils were subjected to wet-dry cycles. The amount and rate of desorption was found to decrease with increasing number of cycles. The wet-dry cycle effect in the desorption of metals from soils is related to the soil composition, with desorption being easiest from sandy soil with low organic content. The desorption process is much slower than adsorption process. More than 95% of each metal adsorption takes place within one hour, and the amount of metal adsorbed from solution reached equilibrium in one day. In contrast, less than 20% metal desorption could be attained after 3 days each of four wet-dry cycles for Cr, Ni, and Cd.

Adsorption↗

PubMed2001

Human papillomavirus type 16 is an important infectious factor in the high incidence of esophageal cancer in Anyang area of China.

To investigate the potential role of human papillomavirus (HPV) infection in the pathogenesis of esophageal carcinomas in the Anyang area of China, we have evaluated specimens collected by balloon cytology examination from volunteers in two regions with significantly different incidences of esophageal carcinoma. 138 donors were from a village in a county with an esophageal carcinoma (EC) age-adjusted mortality rate of 132x10(5), the remaining 68 were resident in a second village from another county with an EC mortality rate of 52x10(5). Specimens were evaluated using both polymerase chain reaction (PCR) amplification and in situ hybridization (ISH) protocols. PCR results showed that the prevalence of the human papillomavirus type 16 (HPV-16) E6 gene in the high incidence area was 1.9-fold higher than that of the low incidence area (72 and 37%, respectively, P < 0.01). Moreover, the positive rate corresponded with pathology grade. Similar results were obtained with the HPV-16 E7 gene. As the cells undergoing cytopathological progress, the HPV-16 E6 positive rate was increased, in both villages. In contrast to HPV-16 E6 and E7, detection of the HPV L1 gene was consistently lower, and its prevalence decreased with increasing dysplasia grades (P < 0.05). By ISH analyses, the expression rate of HPV-16 E6 in the specimens collected from the high incidence area was 2.2-fold higher than those from the low incidence area (49 versus 22%, respectively; P < 0.05), and transcription of the E6 gene paralleled cytopathology. HPV-18 was also detected in 17 and 15% of the specimens from the high and low incidence areas, respectively, but most of these samples were also simultaneously HVP-16 positive. These results suggest that HVP-16 plays a causative role in the high incidence of esophageal cancer in the Anyang region of CHINA:

China↗

PubMed2001

Seasonal changes of testicular weight, sperm production, serum testosterone, and in vitro testosterone release in Korean ring-necked pheasants (Phasianus colchicus karpowi).

To study the biology of reproduction of male Korean ring-necked pheasants kept under natural conditions of temperature and photoperiod, testicular weight, serum testosterone concentrations, testosterone release from the luteinizing hormone (LH)-stimulated testis in vitro and sperm production were measured. Significant changes associated with seasonal cycles were found. Testis weight decreased dramatically in August, remained low until February, rapidly increased from March to high levels to June, and decreased subsequently. Serum testosterone concentrations remained little from August until February, but increased sharply in March to reach the highest levels in April. Thereafter, the concentrations decreased significantly from June. The testosterone release was low from August to February, increased abruptly in March to reach the highest levels in May, and showed rapid decrease thereafter. Sperm production decreased to nondetectable levels from August to February, increased markedly in March, reached a peak in May, and sharply decreased thereafter. Thus, the pheasants breed from late March to late June. These results indicate that the Korean ring-necked pheasant, under natural conditions, exhibits characteristics of a seasonal cycle in reproduction.

Animals↗

PubMed2001

Efficacy trial of Vi polysaccharide vaccine against typhoid fever in south-western China.

OBJECTIVE: To test the efficacy of locally produced Vi vaccine over a time period of longer than one year. METHODS: A double-blinded, randomized field trial was performed in Guangxi Zhuang Autonomous Region in south-western China, using 30 micrograms doses of locally produced Vi. Enrolled subjects were 3-50 years of age, although the majority (92%) were school-aged children, who have the highest rate of typhoid fever in this setting. A total of 131,271 people were systematically allocated a single dose of 30 micrograms of Vi polysaccharide or saline placebo. The study population was followed for 19 months, with passive surveillance conducted in the Ministry of Health and the Regional Health and Anti-epidemic Centre (HAEC). Clinically suspected cases of typhoid fever were confirmed by blood culture, or by serological reaction with O-antigen (Widal tests). FINDINGS: After 19 months, there were 23 culture-confirmed cases of typhoid fever in the placebo group versus 7 cases in the Vi group (Protective efficacy (PE) = 69%; 95% CI = 28%, 87%). Most of the isolates were from school-aged children: 22 cases in the placebo group versus 6 in the Vi group (PE = 72%; 95% CI = 32%, 82%). No serious post-injection reactions were observed. The locally produced Vi polysaccharide vaccine showed levels of protective efficacy similar to those for Vi vaccine produced in industrial countries. CONCLUSION: The slightly higher dose of vaccine did not seem to alter efficacy significantly in China.

Adolescent↗

PubMed2000

Similar potency of the enantiomers of huperzine A in inhibition of [(3)H]dizocilpine (MK-801) binding in rat cerebral cortex.

The inhibition of huperzine A, a potential therapeutic agent to treat Alzheimer's disease, on rat cortical acetylcholinesterase was found to be highly stereospecific. In the present study the effect of the enantiomers of huperzine A on [(3)H]dizocilpine (MK-801) binding to synaptic membrane of rat cerebral cortex was compared. The natural (-)-huperzine A and the synthetic (+)-huperzine A inhibited the specific binding of [(3)H]MK-801 with a similar potency. The IC(50) values were 65+/-7 and 82+/-12 microM (n=5 for each enantiomer, P=0.248), respectively. The result indicates that huperzine A inhibits N-methyl-D-aspartate (NMDA) receptor in rat cerebral cortex without stereoselectivity.

Alkaloids↗

PubMed2000

A novel method for the determination of total protein in human serum by near infrared fluorescence recovery.

A novel fluorometric method has been developed for the determination of total protein in human serum with a new near-IR reagent as a fluorescence probe, based on the fluorescence recovery of the cyanine-CTAB system in the presence of protein. Maximum fluorescence is produced with maximum excitation and emission wave-lengths at 765 and 812 nm, respectively. Under optimal conditions, the calibration graphs are linear over the range 0.4-12.0 microg/mL for protein. The detection limit is 70 ng/mL, and the relative standard deviation of six replicate measurements is 1.14% for 6.0 microg/mL protein. The results are satisfactory.

Animals↗

PubMed2000

Application of magdala red as a fluorescence probe in the determination of nucleic acids.

A fluorescence quenching method was developed for the rapid determination of DNA and RNA using magdala red as fluorescence probe. In weakly acidic medium, the fluorescence of magdala red (lambdaex/lambdaem = 540/555 nm) can be largely quenched by DNA or RNA. The calibration graphs are linear over the range 0.01-1.2 microg/mL for both calf thymus DNA (CT DNA) and salmon DNA (SM DNA), and 0.015-1.0 microg/mL for yeast RNA, respectively. The corresponding detection limits are 6.0 ng/mL for CT DNA, 7.0 ng/mL for SM DNA and 15.0 ng/mL for yeast RNA, respectively. CT DNA could be determined in the presence of 20% (w/w) yeast RNA, and the relative standard deviation of six replicate measurements is 3.18% for 400 ng/mL of CT DNA. Interference from coexisting substances in the determination of DNA was also examined. Real samples were determined with satisfactory results.

Adenine↗

PubMed2000

Determination of proteins at nanogram levels by their quenching effect on large particle scattering of colloidal silver chloride.

A novel quantitative method for the determination of proteins in aqueous solutions has been based on the quenching of the resonance scattering light of colloidal silver chloride in the presence of proteins. The detection limits for eight kinds of proteins (BSA, HSA, egg albumin, human gamma-IgG,alpha-chymotrypsin, E. Coli. alpsase, myoglobin, alpha-casein) were at about 8 ng/mL; the linear ranges of the calibration curves were 10-400 ng/mL under optimal conditions,except for human gamma-IgG (20-400 ng/mL), myoglobin (10-300 ng/mL), and alpha-casein (10-300 ng/mL). Three wavelengths (398 nm, 475 nm, 499 nm) were all suitable for the determination and any acidity from pH 3.0 to pH 9.0 could be chosen. A few non-protein substances at high concentration levels interfered with this method, but this problem could simply be overcome by diluting the samples before the assay. Mechanism studies showed that the quenching effect of proteins on the scattering light of colloidal silver chloride was mainly due to the coagulation of AgCl particles retarded by protein. The method was employed for the determination of total protein in human serum with satisfactory results.

Animals↗

PubMed2000

Effect of fuel aromatic content on PAH emission from a heavy-duty diesel engine.

Polycyclic aromatic hydrocarbons (PAHs) emission tests for a heavy-duty diesel engine fueled with blend base diesel fuel by adding batch fractions of poly-aromatic and mono-aromatic hydrocarbons, Fluorene and Toluene, respectively, were simulated to five steady-state modes by a DC-current dynamometer with fully automatic control system. The main objective of this study is to investigate the effect of total aromatic content and poly-aromatic content in diesel fuels on PAH emission from the HDD engine exhaust under these steady-state modes. The results of this study revealed that adding 3% and 5% (fuel vol%) Fluorene in the diesel fuel increases the amount of total-PAH emission by 2.6 and 5.7 times, respectively and increases the amount of Fluorene emission by 52.9 and 152 times, respectively, than no additives. However, there was no significant variation of PAH emission by adding 10% (vol%) of Toluene. To regulate the content of poly-aromatic content in diesel fuel, in contrast to the total aromatic content, will be more suitable for the management of PAH emission.

Fluorenes↗

PubMed2000

A novel mimetic enzymatic fluorescence immunoassay for hepatitis B surface antigen by using a thermal phase separating polymer.

Iron tetrasulfonatophthalocyanine (FeTSPc), a peroxidase mimic, was used as a labeling reagent and poly(N-isopropylacrylamide) (PNIP) as the separation support of the immune complex for the mimetic-enzymatic immunoassay of hepatitis B surface antigen (HBsAg). PNIP was precipitated from aqueous solution when the ambient temperature was higher than its lower critical solution temperature of 31 degrees C. In a sandwich immunoassay, the antigen (HBsAg) first reacted with mouse anti-human HBsAg antibody immobilized on PNIP (PNIP-antibody) and then further reacted with FeTSPc-labeled mouse anti-HBsAg antibody (antibody-FeTSPc) at room temperature in a homogeneous format. After changing the temperature to separate the PNIP-antibody-HBsAg-antibody-FeTSPc conjugate moiety, it was re-dissolved and determined by coupling with the fluorogenic reaction of hydrogen peroxide and p-hydroxyphenylpropionic acid. The sensitivity of this method (3 ng mL-1) was close to that of the traditional ELISA using the same reactants. However, the assay was much faster (the assay time decreased from 100-120 to 45 min). This method was applied to determine HBsAg in human serum with satisfactory results.

Hepatitis B Surface Antigens↗

PubMed1999

Comparison of the effects of cholinesterase inhibitors on [3H]MK-801 binding in rat cerebral cortex.

Huperzine A, a selective inhibitor of acetylcholinesterase, was recently demonstrated to exert an antagonist effect on N-methyl-D-aspartate (NMDA) receptor in rat cerebral cortex. In the present study, the effects of six cholinesterase inhibitors, e.g. huperzine A, huperzine B, tacrine, donepezil (E2020), physostigmine and galanthamine on [3H]dizocilpine (MK-801) binding to synaptic membrane of rat cerebral cortex were compared. Their IC50 values (mean +/- SD) were 36.9 +/- 12.1, 316.8 +/- 93.2, 33.2 +/- 3.7, 135.0 +/- 15.1, 50.4 +/- 7.4, and 3344 +/- 295 microM, respectively. The rank order of potency is tacrine approximately huperzine A > physostigmine > donepezil > huperzine B >> galanthamine. There is no correlation between their activities to inhibit [3H]MK-801 binding and to inhibit acetylcholinesterase (r = +0.563, P = 0.245). The results suggest that most cholinesterase inhibitors available exhibit an antagonist effect on NMDA receptor in rat cerebral cortex in addition to their inhibitory effect on acetylcholinesterase.

Alzheimer Disease↗