Search Results

You are looking at 1 - 10 of 16 items for

  • Author or Editor: T. Cheng x
  • Refine by Access: All Content x
Clear All Modify Search

Abstract  

Toenail samples were collected from 129 carpenters (average age 47). The bone and blood lead data for these carpenters have shown a broad range of lead-level exposure in this population. A total of 28 elements were measured in the sample set by a combination of instrumental neutron activation analysis (INAA) and graphite furnace atomic absorption spectrometry (GFAAS) methods. Of the elements measured, only Co, Cr, Fe, Na, Cd, Cu, F, and Ni were significantly correlated with lead. A statistical treatment of the overall data set, including principal component analysis, was further applied in an attempt to correlate the elements in the samples.

Restricted access

Abstract  

Iodine is an essential nutrient in the human diet. Its primary role is expressed as a component of thyroxine (T4) and the corresponding deiodinated triiodothyronine (T3) hormones produced by the thyroid as part of the system that regulates growth, mental development and metabolism. The recommended daily allowance (RDA) for iodine ranges from 50 μg/day for infants to 150 μg/day for adults. Reports over the last 15 years have indicated that the U.S. diet provides 2 to 7 times the iodine RDA and that dairy products typically provide 20 to 60 percent of the dietary iodine intake. Measurements of iodine in dietary components and composites reported in FDA studies have been done calorimetrically. These studies have, according to the authors, both under reports (by up to −50%) and over reports (by up to +80%) the iodine, depending on food type, compared to a radiochemical NAA reference method. Milk is typically under reported by −20%. The objective of this study was to utilize epiboron neutron activation analysis (EBNAA) to study the iodine concentrations, and seasonal variations of iodine, and market milk and infant formula, collected 15 years apart, in comparison with the Food and Drug Administration (FDA) market-basket reports.

Restricted access

Abstract  

Chronic dietary deficiency of selenium has been shown to be associated with degenerative heart disease in production animals in the U.S. and in the human in parts of China. In the latter, subjects in the endemic areas suffer high rates of a cardiomyopathy known as Keshan's Disease which is normally fatal in early adulthood and can be prevented, or reversed in its early stages, via selenium supplementation. Selenium, as the active moiety in the enzyme glutathione peroxidase, protects against oxidative attack of cell membranes by peroxides formed during normal metabolism. In this study, we investigated the distribution of selenium in healthy porcine and bovine heart tissue freshly collected at slaughter. The whole heart was perfused with DI water and carefully de-fatted. Representative samples of left and right atria and ventricles and the interventricular septum were collected, lyophilized and homogenized prior to preparing replicate samples for analysis. Replicates were analyzed for selenium via an INAA scheme employing a 5, 15 and 25 second irradiation (φth = 8·1013 n·cm−2·s−1), decay and real-time count (77mSe,T 1/2=17.4 s), respectively, using high-resolution gamma-ray spectroscopy with Westphal pulse pile-up correction. Selenium distribution will be discussed relative to differentiated function and oxygenation of the specific tissues.

Restricted access

Summary

Harmaline and harmine accounted for more than 70% in composition in extracts of P. harmala. More attention, however, should be paid to the other alkaloids which would be favorable or unfavorable to the efficacy and safety of the products. It was necessary to determine these trace alkaloids in the extracts; thereafter, most of them have been characterized. Diglycoside vasicine, vasicine, vasicinone, harmalol, harmol, tetrahydroharmine, 8-hydroxy-harmine, ruine, harmaline, and harmine were separated and identified with reference substances and characteristic MS spectra in extracts by liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) and high-performance liquid chromatography (HPLC). Three trace alkaloids, vasicine, harmalol, and harmol were determined using the developed chromatographic separation method subsequently. The average contents of vasicine, harmalol, and harmol in extracts of ten batches were 2.53 ± 0.73, 0.54 ± 0.19, and 0.077 ± 0.03%, respectively. The total content of the three alkaloids was 3.23 ± 0.90% (from 1.81 to 4.48%). For rough estimation of all the relative alkaloids except of harmaline and harmine, the average total areas of all peaks in extracts varied from 4.35 to 26.64% detected at 220, 254, 265, 280, and 380 nm, respectively. The results indicated that area normalization method was powerless for the quality evaluation for traditional herb medicine consisting of numerous compounds with highly differential features. It might be concluded that LC-MS or HPLC could be utilized as a qualitative and quantitative analytical method for quality control of the extracts from seeds of P. harmala L.

Full access
Journal of Radioanalytical and Nuclear Chemistry
Authors: C. Baskett, J. Morris, V. Spate, M. Mason, T. Cheng, T. Nichols, H. Anderson, C. Tharp, T. Horsman, and R. Dowdy

Abstract  

The objective of this study was to determine if a stable enriched tracer of Se-76 could be used to establish the delay time between a dietary intake of selenium and its appearance in various matrices. Selenium, an essential trace element, has been investigated at the Missouri University Research Reactor (MURR) for several years. Several matrices have been studied to determine selenium status in humans; these include fingernails, toenails, blood, hair, and urine. A cohort of five women and seven men was utilized for this study. Each subject ingested selenium supplements which were enriched in Se-76 (96.48%). Fingernails, toenails, whole blood, and blood sera were collected as biochemical indicators. Selenium concentrations and glutathione peroxidase activities were determined in blood sera and whole blood to monitor the effect of the selenium supplement in these matrices. Selenium concentrations were determined in fingernails and toenails prior to supplementation and for several months afterward to determine the delay time for the appearance of selenium. The effects of the selenium supplement on the selenium concentrations of the fingernails, toenails, whole blood, and blood sera and the effect of the supplement on glutathione peroxidase activity will be reported.

Restricted access

Abstract  

An instrumental neutron activation analysis (INAA) technique, based on the19F(n,)20F reaction, has been development for the determination of fluoride in bone. The purpose was to study fluoride distribution in different kinds of bone samples using a rabbit model. The rationale for the study stems from the posible correlation between fluoride in bone and osteoporosis. The sodium concentration in the bone was used to correct the20F peak area for the23F(n,)20F contribution. Two secondary standards, teflon tape and teflon coated dacron line, were used to quantify fluoride concentration. They proved to be stable and consistent with respect to their fluoride concentration. Bone specimens from 10 sites and two tooth samples were analyzed for fluoride. Fluoride concentration ranged from 305 ppm in the tibia long bone to 585 ppm in the humerus trochanter end and the magnitude of fluoride concentration levels is age depdentent. The detection limit of the fluoride is approximately 5 ppm using a 100 mg bone sample.

Restricted access

Abstract  

The inclusion complex of benzaldehyde (BA) with β-cyclodextrin (β-CD) was prepared and was studied by thermal analysis and X-ray diffractometry. The composition of the complex was identified by TG and elemental analysis as β-CDBA9H2O. TG and DSC studies showed that the thermal dissociation of β-CDBA9H2O took place in three stages: dehydration in the range 70-120C; dissociation of β-CDBA in the range 235-270C; and decomposition of β-CD above 280C. The kinetics of dissociation of β-CDBA in flowing dry nitrogen was studied by means of TG both at constant temperature and at linearly increasing temperature. The results showed that the dissociation of β-CDBA was dominated by a one-dimensional random nucleation and subsequent growth process (A2). The activation energy E was 124. 8 kJ mol-1, and the pre-exponential factor A 5.041011 min-1.

Restricted access
Journal of Radioanalytical and Nuclear Chemistry
Authors: T. Nichols, J. Morris, M. Mason, V. Spate, C. Baskett, T. Cheng, C. Tharp, J. Scott, T. Horsman, J. Colbert, A. Rawson, M. Karagas, and V. Stannard

Abstract  

Arsenic is toxic to humans with the lethal dose being approximately 1 mg/kg/day. At much lower long-term exposures, arsenic is hypothesized to increase the risk of certain cancers. We have developed an irradiation position for the neutron activation analysis (NAA) of nail specimens for arsenic, in support of a case-control study involving New Hampshire residents consuming well water above the EPA Safe Drinking Water Standard of 0.050 ppm. Arsenic is bound to nail keratin through sulfhydryl groups proportional to intake providing a convenient means of integrating arsenic intake in population-based studies. Our objective was to develop the necessary facilities and procedures by which relatively small samples (i.e. 20 to 100 mg) could be accurately analyzed for arsenic, so that affordable nutritional epidemiology investigations, requiring large numbers of samples (>1000 in this case), could be undertaken. A high-flux reflector position, with minimal axial variation throughout the fuel cycle, suitable for pneumatic-tube irradiations, was characterized by measurement of the neutron flux distribution (thermal and epithermal) within the irradiation capsule over time. Results from application of the method to a case-control study of basal and squamous cell skin cancer will be presented.

Restricted access
Journal of Radioanalytical and Nuclear Chemistry
Authors: C. Baskett, V. Spate, J. Morris, H. Anderson, M. Mason, C. Reams, T. Cheng, K. Zinn, G. Hill, and R. Dowdy

Abstract  

The principal objective of this study was to determine if the use of a stable enriched tracer of Se-76 could be used to determine the delay time between a dietary intake of selenium and its appearance in fingernails and toenails. Selenium is an essential trace element in human nutrition. It has been studied at the Missouri University Research Reactor (MURR) for the past 15 years using an Instrumental Neutron Activation Analysis (INAA) technique. The principal route of human exposure to selenium is through the diet. Selenium concentrations of nails, blood, hair, and urine have been used as indicators of dietary selenium intake. In this study, a cohort consisting of seven men and five women ingested three selenium supplements of 150 g each over a three day period. The selenium was enriched in Se-76 (96.48%) and ingested as selenite in orange juice following an overnight fast. Fingernails and toenails were collected prior to the selenium supplementation and for several months afterward to be used as biochemical indicators. The peak76Se concentration in the fingernails and toenails occurred at 19–23 and 16–32 weeks after supplementation, respectively.

Restricted access

Abstract  

There is currently great interest in iodine as a micro nutrient. Both high and low intakes have been associated with thyroid cancer incidence. Development of dietary iodine monitors is needed to supplement the use of dietary recall methods which have not been well validated for iodine. In this study, 30 pooled urine samples, from ethnic groups on various islands in the South Pacific, were analyzed for iodine using epithermal instrumental neutron activation analysis (EINAA).

Restricted access