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Biomedical subjects

D T Williams

Publications and source records attributed to D T Williams.

At least 55 records · Page 3Linked to original sources
PubMed1983

Determination of organic phosphate triesters in human adipose tissue.

A method of analysis has been developed for the determination of organic phosphate triesters in human adipose fat at low ng/g levels. After fat extraction from the tissue with benzene (or acetone-hexane, 15 + 85, v/v), phosphates were fractionated from fat by gel permeation chromatography with methylene chloride-cyclohexane (5 + 95, v/v) as solvent. After Florisil column cleanup, the GPC extract was analyzed by capillary column gas chromatography using a nitrogen-phosphorus selective detector. Recoveries at the 2.5, 10, and 25 ng/g levels were greater than 75% except for tri(2,4-xylenyl) phosphate (ca 65%). Of 16 human adipose tissue samples analyzed, 5 contained tris(1,3-dichloropropyl) phosphate in the range of 0.5 to 110 ng/g, 4 contained tributoxyethyl phosphate in the range of 4.0 to 26.8 ng/g, and one contained tributyl phosphate at 9.0 ng/g.

Adipose Tissue↗
PubMed1981

Mutagenicity of paint removers containing dichloromethane.

A volatile component of commercially available paint and varnish removers was mutagenic in strains of Salmonella typhimurium TA1535, TA100 and TA98. Levels of dichloromethane in exposure chambers were determined by gas chromatography and were related directly to mutational dose-effect curves observed for the products.

Environmental Exposure↗
PubMed1980

On site determination of Sulfotep air levels in a fumigating greenhouse.

Sulfotep air levels in a greenhouse were monitored continuously in real time, for 4-40 hours after fumigation, using a trace atmospheric gas analyzer system. Sulfotep air levels were below the threshold limit value of 15 ppb following overnight ventilation but, when ventilation was stopped to conserve heat, the Sulfotep air levels exceeded the threshold limit value. This study also showed that worker activity in the greenhouse significantly increased Sulfotep air levels. It is recommended, therefore, that ventilation of a greenhouse following Sulfotep fumigation should continue during the entire day and workers exposed to such conditions should wear appropriate protective equipment.

Air Pollutants↗
PubMed1979

Mutagenicity of organic extracts from Canadian drinking water in the Salmonella/mammalian-microsome assay.

Organic extracts of chlorinated Ontario drinking water samples have been found to induce mutation and lethality in the Salmonella/mammalian-microsome histadine reversion assay. Collections of water were made at water treatment plants in five municipalities in June 1978. To determine the reproducibility of the positive mutagenic effects found, a second sampling at the same plants was performed in September 1978. Preparation of extracts involved passing 200 liter samples through XAD-2 resin columns which were eluted with a mixture of hexane and acetone, and the eluent was evaporated to dryness. For those extracts with sufficient organic matter, dose-related increases in mutagenicity were observed. Extracts of untreated water from a river and a well were weakly mutagenic.

Dose-Response Relationship, Drug↗
PubMed1979

The determination of polycyclic aromatic hydrocarbons at the ng/L level in Ottawa tap water.

Samples of Ottawa drinking water, collected in January and February 1978 were analysed by Gas Chromatography/Mass Spectrometry (GC/MS) for fifty polycyclic aromatic hydrocarbons (PAH) and five oxygenated polycyclic aromatic hydrocarbons (O-PAH), following extraction of the organic species using Amberlite XAD-2 macroreticular resin. In the January sample, thirty PAHs, ranging in concentration from 0.05 to 14 ng/L with a mean value of 3.8 ng/L and a total weight of 114 ng/L and four O-PAHs, ranging in concentration from 0.10 to 1.8 ng/L with a mean value of 0.91 ng/L and a total weight of 3.7 ng/L, were detected. In the February sample, thirty-six PAHs, ranging in concentration from 0.05 to 8.1 ng/L with a mean value of 1.4 ng/L and a total weight of 50.4 ng/L and five O-PAHs, ranging in concentration from 0.20 to 2.4 ng/L with a mean value of 1.0 ng/L and a total weight of 5.2 ng/L, were detected. Twenty-eight PAHs and four O-pahs were common to the two samples. The use of Amberlite XAD-2 macroreticular resin to extract PAHs from drinking water is shown to be effective, although the recovery of individual PAHs from artificially loaded XAD-2 resin varied from 57 to 100%.

Chromatography, Gas↗
PubMed1979

The impact of psychiatric intervention on patients with uncontrolled seizures.

There is much evidence that emotional stess can trigger both neurogenic and hysterical seizures in susceptible patients. We reviewed out experience with 37 patients whose seizures appeared to be precipitated at times by emotional stress and had not been controlled by anticonvulsant medication alone. Approximately 70 per cent of patients demonstrated substantial improvement in seizure control after psychiatric treatment and maintained this improvement during follow-up. The findings of this study suggest that patient characteristics associated with better prognosis include normal intelligence, partial (as opposed to generalized) neurogenic seizures, a diagnosis of hysterical seizures, a less severely abnormal EEG, and being hypnotizable. After psychiatric treatment, 32 per cent of patients had their anticonvulsant medication reduced and another 16 per cent had it discontinued.

Adolescent↗