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Biomedical subjects

Y Hu

Publications and source records attributed to Y Hu.

679 records · Page 38Linked to original sources
PubMedDate not supplied

The swelling behavior and wet morphology of water-absorbable polymer materials.

In this research work, a low-temperature examination method for scanning electron microscopy (SEM) is introduced. A water-absorbable polymer material, the sulfonated polyethylene (SPE) ion-exchange hollow fiber membrane, was used for the experiments. With this low-temperature technique, the wet morphology of the water-absorbable sulfonated polyethylene hollow fiber membrane was revealed. The results obtained from this investigation offer some important information to explain the behavior of the SPE hollow fiber membranes when they are applied in pervaporation separation of water/organic solvent mixtures, such as water/ethylene glycol, water/ethanol, and so forth.

Membranes, Artificial↗
PubMedDate not supplied

Resistance to trimethoprim in Haemophilus influenzae.

The mechanisms of resistance to trimethoprim in eleven U.K. clinical isolates of Haemophilus influenzae were studied. The levels of dihydrofolate reductase (DHFR) activities in crude extracts from four resistant wild-types were similar to those in susceptible controls. However, activities in extracts from the other seven resistant wild-type isolates, and transformants of two of these, were at least triple those in the sensitive strains. Resistance to trimethoprim was also selected for in vitro during prolonged exposure to the drug and was associated with increased levels of DHFR specific activity in the mutants. DHFR enzymes were, however, still very susceptible to inhibition by trimethoprim. Activities in four extracts, including one from a transformant of a resistant mutant, were reduced by at least 45% following incubation with 10(-8) M trimethoprim. The results suggested that overproduction of the chromosomal DHFR enzyme may be the resistance mechanism in some organisms. The much lower DHFR activities measured in extracts from other resistant isolates may reflect synthesis of chromosomal enzymes that have reduced susceptibility to trimethoprim.

Folic Acid Antagonists↗
PubMedDate not supplied

2-Amino-3-(methylamino)propanoic acid (BMAA) bioavailability in the primate.

2-Amino-3-(methylamino)-propanoic acid (BMAA) is a low potency excitatory amino acid present in the cycad plant that has been proposed as a factor in the high incidence of amyotrophic lateral sclerosis-parkinsonism dementia (ALS-PD) in the western Pacific region. We employed stable isotopic forms of BMAA to assess the oral bioavailability of this compound in cynomolgous monkeys (n = 3). The stable isotope labeled BMAA ([15N]-BMAA) was injected i.v. at the same time that the unlabeled compound was administered orally. Both forms of BMAA were then quantified in a 48h urine sample by gas chromatography-mass spectrometry (GC/MS). Following oral dosing, 80% of the administered BMAA was absorbed into the systemic circulation; thus, oral bioavailability was high and other routes of administration could not result in significantly higher circulating levels of BMAA for a given administered dose.

Administration, Oral↗
PubMedDate not supplied

An interaction between type 1 and type 2 programmed cell death and clonogenic survival.

UNLABELLED: We suggest two additional reasons why current, non-surgical therapies for most solid, epithelial-derived cancers can lack effectiveness. Studies with panc-1 human pancreatic cancer cells cultured with actinomycin D and/or MK 886 indicate firstly, that type 2 (intrinsic, autophagic, mitochondrial-dependent, MK 886-induced) programmed cell death is less effective than the type 1 (apoptotic, extrinsic, ligand-dependent, actinomycin D-induced) form in reducing the number of residual clonogenic cells, and secondly, that activation of cellular suicide during their combined culture results in a greater number of residual clonogenic cells compared with either agent alone. HYPOTHESIS: Based on results from the culture of panc-1 cells with MK 886 and/or actinomycin D, we suggest that in this system, and possibly in others: (a) type 2 programmed cell death is a less effective inhibitor of residual cells with clonogenic potential, and (b) activation together of both forms of PCD increases the number of residual clonogenic cells.

Antibiotics, Antineoplastic↗
PubMedDate not supplied

Factors influencing total dietary exposures of young children.

A deterministic model was developed to identify the critical input parameters needed to assess dietary intakes of young children. The model was used as a framework for understanding the important factors in data collection and data analysis. Factors incorporated into the model included transfer efficiencies of pesticide from surfaces to food, transfer efficiencies of pesticide from surfaces to hands to food, and more accurate microactivity data related to contact frequency for the three variables of interest--hands, surfaces, and food. Results from range-finding measurements of transfer efficiencies using an aqueous pesticide solution of a mixture of malathion, diazinon, and chlorpyrifos sprayed on the surfaces indicate that a higher pesticide transfer occurred from hard surfaces to food (hardwood, plastic), with low transfer from soft surfaces (carpet, cloth). Six children, all less than 4 years old, were videotaped to obtain realistic contact frequency and times for the interaction of hands, surfaces, and foods during eating meals and snacks while in their homes or day care centers. The time range of eating events varied from about 2 to 55 min, with an average of about 20 min. The average number of contact frequencies between food and hands was 19 times for each eating event, with a range of 10-40. Contacts between the surface and hand were about the same as the food and hands. Contacts between foods and surfaces ranged from 0 to 32, but only five or less of the contacts per eating event were associated with surfaces other than eating utensil. The children's microactivity data collected during the eating events, together with the laboratory results from the transfer studies, were provided as input into a Monte Carlo simulation of the dietary ingestion model. Simulation results indicate that children's handling of the food could contribute 20-80% of the total dietary intake of pesticides. Dietary exposure due to residues in the food before handling accounted for 16% and 47%, respectively, of the total mean intake from simulations for a child's consumption of an apple or banana. These results indicated that transfer efficiencies for foods on various surfaces typically found in homes as well as children's hand contacts with the food and surfaces are important as determinants of dietary exposure.

Child, Preschool↗
PubMedDate not supplied

Sensitive biomarker of polycyclic aromatic hydrocarbons (PAHs): urinary 1-hydroxyprene glucuronide in relation to smoking and low ambient levels of exposure.

The study was conducted in a Chinese population with occupational or environmental exposures to polycyclic aromatic hydrocarbons (PAHs). A total of 106 subjects were recruited from coke-oven workers (workers), residents in a metropolitan area (residents) and suburban gardeners (gardeners). All subjects were monitored twice for their personal exposures to PAHs. The biological samples were collected for measurements of 1-hydroxypyrene (1-OHP) and cotinine in urine. The geometric means of personal exposure levels of pyrene, benz(a)anthracene (BaA) and benzo(a)pyrene (BaP) in workers were 1.470, 0.978 and 0.805 microg m-3, respectively. The corresponding levels in residents were 0.050, 0.034 and 0.025 microg m-3; and those in gardeners were 0.011, 0.020 and 0.008 microg m-3, respectively. The conjugate of 1-OHP with glucuronide (1-OHP-G) is the predominant form of pyrene metabolite in urine and it showed strong associations with exposures not only to pyrene, but also to BaA, BaP and total PAHs. Most importantly, a significant difference in 1-OHP-G was even detected between the subgroups with exposures to BaP at < 0.010 and > 0.010 but < 0.020 microg m-3, suggesting that 1-OHP-G is a good marker that can be used for the risk assessment of BaP exposure at levels currently encountered in ambient air. Furthermore, multiple regression analyses of 1-OHP-G on PAHs exposure indicated that cigarette smoke was a major confounding factor and should be considered and adjusted for while using 1-OHP to estimate PAHs exposure.

Air Pollutants↗
PubMedDate not supplied

Mitochondrial polymorphisms as risk factors for endometrial cancer in southwest China.

It is just in recent years that mitochondrial DNA (mtDNA) mutations have been found in solid tumors. Although a direct link between the presence of mtDNA mutations and the development of tumors has not been made, mtDNA mutations might prove significant in the detection of tumor recurrence and possibly in the detection of genotoxic damage. To investigate the relationship between mtDNA variation and endometrial cancer, we collected blood samples from subjects with Han native background in Yunnan province in China, 49 of them with pathologically conformed endometrial cancer and 31 as controls with no cancer disease and sequenced two hypervariable segments of control region, part of 16sRNA gene, tRNA(leu) (tRNA is transfer RNA) gene and ND1 gene of mtDNA and identified some diagnostic polymorphisms by restriction fragment length polymorphism of coding region of mtDNA. We could not identify the suspected mutations that are related to diabetes and obesity from our endometrial cancer patients. However, our data showed that patients with endometrial cancers clustered in haplogroup D in a significantly higher frequency when compared with controls, implicating a possible association of haplogroup D to endometrial cancer. We concluded that mitochondrial polymorphisms in haplogroup D might play a genetic role in predisposing to endometrial cancer.

Case-Control Studies↗
PubMedDate not supplied

The swelling behavior and wet morphology of water-absorbable polymer materials.

In this research work, a low-temperature examination method for scanning electron microscopy (SEM) is introduced. A water-absorbable polymer material, the sulfonated polyethylene (SPE) ion-exchange hollow fiber membrane, was used for the experiments. With this low-temperature technique, the wet morphology of the water-absorbable sulfonated polyethylene hollow fiber membrane was revealed. The results obtained from this investigation offer some important information to explain the behavior of the SPE hollow fiber membranes when they are applied in pervaporation separation of water/organic solvent mixtures, such as water/ethylene glycol, water/ethanol, and so forth.

Journal Article↗
PubMedDate not supplied

Altered immunoendocrine dialogue in autoimmune disease.

Autoimmune diseases have a multifactorial pathogenesis including essential genetic and nonessential modulatory factors. Among the essential factors, not only should genes coding for an abnormal reactivity of the immune system be considered, but we have, in addition, provided experimental evidence for the existence of genes responsible for a susceptibility of the target organ/structure for the autoimmune attack. Only when both sets of essential genes are present does an autoimmune disease develop at all. The modulatory factors then determine the final outcome in each case. The present contribution discusses the immunomodulating role of glucocorticoid and sex steroids focussing on the Obese Strain (OS) of chickens, a model for Hashimoto thyroiditis.

Animals↗