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Biomedical subjects

T Y Toribara

Publications and source records attributed to T Y Toribara.

14 recordsLinked to original sources
PubMed2001

Analysis of single hair by XRF discloses mercury intake.

Utilizing information obtained from the X-ray fluorescence linear scanning along a single strand of hair in a recent fatal exposure to dimethylmercury, it was possible to determine the circumstances leading to the fatal result. When the Dartmouth chemistry professor displayed symptoms of mercury toxicity, samples of her urine and blood were found to have considerable amounts of mercury by a commercial laboratory. The Dartmouth medical people immediately started treatment with a chelator on January 29, 1997 to remove the mercury, and sent the first samples of blood, urine and hair taken on January 31, 1997 to our laboratory. Our X-ray fluorescence analysis of a single strand of hair shown in Figure 1 shows a single large peak of intake of mercury confirming the information revealed by examination of her laboratory notebook that she had spilled some dimethylmercury about 5 months previous to the date the hair sample was taken. Figure 2 shows two peaks, the peak closest to the scalp end of the hair shows the effect of the large amount of mercury released by the chelator, part of which appeared in the blood. Utilizing the start of the first increase in the blood level as August 14, 1996, and the second as caused by the chelator on January 29, 1997, a count of the number of 2-mm points measured between the two dates gives an accurate growth of the hair during that time. A close examination of Figure 1 indicates that it required five points, each of 2 mm, along the hair to reach the maximum. This indicates a time period of 10 mm of growth equal to 23 days during which a large concentration of methylmercury was entering the blood as evidenced by the hair concentration. The professor died on June 11, 1997.

Chelating Agents↗
PubMed1995

The biological monitoring of mercury in the Seychelles study.

The concentration of total mercury in maternal hair during pregnancy was used as a measure of fetal exposure to methylmercury in a study of a fish-eating population in the Seychelles islands. A segment of scalp hair approximately 10 centimeters in length, that grew during pregnancy, was selected for measurement. Total and inorganic mercury were measured by cold vapor atomic absorption (CVAA) using the Magos reagents (Magos, 1971). For comparative purposes, total mercury was measured by X-ray Fluorescent Spectrometry (XRF) and methylmercury by gas chromatography/atomic fluorescence detection (GC/AFD) in a subset of hair samples. A limited number of fish samples were also analyzed. Extensive interlaboratory testing was conducted to ensure accuracy of the mercury measurements. Concentrations of organic mercury calculated as the difference between total and inorganic mercury as measured by CVAA agreed with those of methylmercury measured on the same samples of hair by GC/AFD. Methylmercury measured by GC/AFD and organic mercury measured by CVAA accounted for over 80% of the total mercury in hair and over 90% of the total mercury in fish muscle. To test the accuracy of recapitulation by hair sampling, hair samples were collected from mothers at the time of delivery and 6 months later. The segment corresponding to the pregnancy term was selected for measurement assuming a hair growth rate of 1.1 cm/month. Results from both samples were in close agreement. As part of both a pilot investigation followed by the main study, maternal hair samples were collected each year from 1986 to 1989 for a total of 1604 samples. The median and mean values for each year's collection fell in the range of 5.9 to 8.2 ppm and exhibited no statistically significant trend with time. The highest recorded concentration was 36 ppm. In hair samples from 654 mothers, the mean concentration of total mercury was compared with the mean concentrations in segments corresponding to each trimester, approximately 3.3 centimeters in length. A high degree of correlation was found between mean levels in each trimester versus the entire pregnancy segment.

Child Development↗
PubMed1987

Arsenic speciation by capillary gas-liquid chromatography.

Specific environmentally significant arsenic compounds are determined by capillary gas-liquid chromatography. Inorganic (arsenite, arsenate) and organic (monomethylarsonate, dimethylarsinate) arsenicals are measured as the corresponding methylthioglycolate derivatives, which are simultaneously separated on wide-bore borosilicate glass and fused-silica columns under conditions of temperature programming. Inorganic arsenate and arsenite cannot be differentiated by the derivatization technique. Flame-ionization and electron-capture detection are evaluated. A simple and rapid sample preparation procedure is used for water, urine, blood, and tissue.

Arsenic↗
PubMed1985

Preparation of CH3 203HgCl of high specific activity.

In order to have a methylmercury compound of much higher specific activity than was obtainable from commercial suppliers of the compound, a procedure for the methylation of radioactive mercuric chloride with no addition of non-radioactive mercury has been developed. Methylation is accomplished by reacting the mercuric chloride with tetramethyl tin. Extractions into and out of benzene twice produces a methylmercury compound which is finally dissolved in a dilute sodium carbonate solution suitable for biological experiments. The entire procedure to produce a batch of the compound may be accomplished within a single day.

Indicators and Reagents↗
PubMed1982

X-Ray fluorescence measurement of the zinc profile of a single hair.

Many trace elements appear in hair in concentrations related to those in the blood, but the relationship for zinc is complicated by disorders that probably affect its state in the blood. A built-to-order x-ray fluorescence spectrometer was used to measure, nondestructively, the concentrations of 16 elements in a 1-mm interval of a single hair. A scan along a hair strand, together with the known growth rate, enables the zinc concentration in the hair to be correlated with the time the hair was formed. A comparison with the blood concentration at the same time may reveal possible bodily disorders that affect the availability of zinc to incorporation in the hair. The instrument has been carefully calibrated for zinc, and we studied the conditions under which there can be losses or gains in the hair after sampling. The sample chamber will accommodate 16 separate holders, and each sample may be automatically measured according to a program pre-selected for it. The average zinc content of hair samples from foreign countries, some ancient specimens, and an interesting profile of a strand from an Iraqi woman are shown.

Female↗
PubMed1982

Are the original Donnan assumptions applicable to serum?

Analyses of the diffusible fraction of serum for sodium, potassium, and chloride have indicated that the ratios of the levels of the protein solution to those of the filtrate do not follow the predicted Donnan values. Specifically, measurements by sodium glass electrode showed that sodium activities are the same for both protein solution and filtrate in contradiction to the Donnan model which predicts greater activity for the sodium in the protein solution because of its greater analyzed content. An alternative model that fits the experimental findings is discussed, and calculations made possible by this model are presented that give reasonable values for bound sodium, bound water, and a radius for an assumed spherical albumin molecule. A review of Donnan's original data discloses discrepancies in his assumptions.

Biophysical Phenomena↗