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Biomedical subjects

N P Thompson

Publications and source records attributed to N P Thompson.

At least 37 records · Page 2Linked to original sources
PubMed1994

Reversible jaundice in primary biliary cirrhosis due to hyperthyroidism.

A patient with primary biliary cirrhosis had a dramatic deterioration in liver function with jaundice over 2 months as a result of development of Graves' disease. Clinical examination and radiological and cardiovascular investigations excluded heart failure and biliary obstruction as the cause of this deterioration. The patient's jaundice entirely reversed with treatment of hyperthyroidism, with bilirubin levels decreasing from 244 to 16 mumol/L (14.35 to 0.94 mg/dL). Deterioration in liver function in a patient with primary biliary cirrhosis as a result of hyperthyroidism has not previously been described.

Bilirubin↗
PubMed1986

Residues of chlorinated hydrocarbons in tissues of raptors in Florida.

Dead or moribund raptors (n = 75) representing 11 species were collected between 1971 and 1981 from various locations in Florida. Samples of bran, muscle, liver and adipose tissue were analyzed for DDT, DDE, DDD, dieldrin, and PCB's. Detectable concentrations of DDT or its metabolites were found in 100% of all samples of muscle and liver, and 77% all samples of brain. Dieldrin was determined to be present in 91%, 93%, 87% and 78% of all samples of brain, muscle, liver and adipose tissue, respectively. Lethal or hazardous concentrations of dieldrin were found in brain samples from three birds, but DDT and PCB's were present at sublethal concentrations. When species were grouped according to their dietary habits, it was not possible to identify any trends in pesticide concentrations.

Adipose Tissue↗
PubMed1982

Simultaneous electron capture detection of chlorpyrifos and 3, 5, 6-trichloro-2-pyridinol residues in peach and bahia grass field samples following gel permeation cleanup.

A recently published method involving the simultaneous extraction, gel permeation cleanup, and electron capture gas chromatographic detection of residues of the insecticide and acaricide chlorpyrifos and its principal metabolite 3,5,6-trichloro-2-pyridinol is successfully applied to Lorsban-treated peach and Bahia samples. Previous quantitation of these compounds has required 2 separate analytical procedures. Multilevel temperature programming and manipulation of the gel permeation column effluent rate are the only adjustments of experimental parameters necessary to avoid large amounts of gas chromatographic interferences. Chromatographic peaks are more clearly defined and easier to integrate with the multilevel program than they are with 2-step or linear programs. This is one reason that recovery data are improved over those reported for the method as applied in the pea vine work. Residue analysis conducted on field-treated peaches and Bahia grass show the newly published procedure to be sensitive and effective.

Chlorpyrifos↗
PubMed1982

Influence of various solvent-water mixtures on the extraction of dieldrin and methomyl residues from radishes.

The effect of organic solvent/water ratios on the extraction of field-incurred residues of dieldrin and methomyl from radishes was determined. 14C-Dieldrin and 14C-methomyl were applied separately to radishes in commercial formulations at rates of 0.2 and 0.9 kg/ha, respectively. Fourteen days post-application, the radishes were harvested and fresh root tissues were extracted using a Polytron homogenizer. Acetone, acetonitrile, and methanol containing 0, 10, 20, 30, 40, and 50% water were used as extraction solvents. For methomyl residues, the optimum water content of acetonitrile-water extraction mixtures was 40-50%; less than 40% water reduced the ability of acetonitrile to extract carbon-14. Methanol and acetone were nearly as efficient as 50% acetonitrile-water and were apparently not influenced by solvent/water ratios. For dieldrin, low water content slightly reduced the extraction efficiency of acetonitrile, with the optimum water content also being 40-50%. Percentage of water appeared to have little overall effect on methanol extraction efficiency. The extraction efficiency of acetone was lower than that of the other 2 solvents, and this effect was independent of the acetone/water ratio. Approximately 20% of the 14C-dieldrin residue was bound to radish roots 14 days post-application.

Acetone↗
PubMed1981

Degradation of methomyl residues in frozen strawberries.

14C-Methomyl (S-methyl N-[(methylcarbamoyl)-oxy]thioacetimidate) suspended in a commercial formulation was sprayed on strawberries. At 7 and 14 days post-application, mature berries were harvested in chopped. Fresh chopped berries were extracted with methanol using a Polytron homogenizer, and the crop marc was subsequently leached with methanol, freeze-dried, and re-extracted. Portions of the fresh chopped fruit were also frozen at-20 degrees C for 1, 30, and 102 days before extraction with methanol using a Polytron homogenizer, followed by subsequent leaching of the crop marc. For fresh berries, 93.7 and 88.9% of the 14C present at harvest was extractable at 7 and 14 days post-application, respectively. Based on thin layer chromatographic analysis, methomyl represented 83.5 and 68.2% of the 14C extracted from fresh berries at 7 and 14 days, respectively. Freezing of strawberries reduced extraction efficiency and appeared to degrade methomyl. At 7 and 14 days post-application, averages of 80.9 and 77.1%, respectively, of the 14C present were extractable after frozen storage regardless of storage time. Furthermore, only about 10% of the extracted 14C was methomyl; the remainder was of unknown composition.

Chromatography, Thin Layer↗
PubMed1980

Sensitive gas-liquid chromatographic method for asulam residues in peaches.

The current analytical method for determining residues of the herbicide asulam (methyl (4-amino-benzenesulfonyl) carbamate) is the nonspecific colorimetric procedure based on the coupling reaction of N-1-naphthylethylenediamine with the diazotized amine. A new analytical method for determining the residues of this herbicide and its 2 known major metabolites, acetylasulam and sulfanilamide, in peaches has been developed and evaluated using gas chromatography with an N-P detector. The method is based on the hydrolytic conversion of the parent compound and the known metabolites to the common product sulfanilamide which is then analyzed by gas-liquid chromatography as its per N-methylated derivative. The identity of the derivative has been confirmed by chemical ionization mass spectrometry. The method was tested by using fortified crop extracts and also be analyzing crop treated by post-emergent application of the method is 5 ng and the detection limit in the crop is 0.1 ppm. Recoveries ranged from 70 to 80% from peaches at fortification levels of 1, 5, and 10 ppm. At a fortification level of 0.1 ppm the recovery is 50-60%.

Carbamates↗
PubMed1980

Extraction efficiencies for pesticides in crops: 14C-benomyl extraction from mustard green and radishes.

14C-labeled benomyl [methyl 1-(butylcarbamoyl)-2-benzimidazolecarbamate] suspended in a commercial benomyl formulation was sprayed on mustard greens and radishes. At 3 intervals after application, the crops were extracted with methanol, acetonitrile, or acetone. Crops were either blended and leached or repetitively blended followed by Soxhlet extraction. Essentially all of the extractable radioactivity was removed by blending. The 14C was more difficult to extract from radishes than from mustard greens as time increased. Respective percentages of 14C extracted at 1, 7, and 14 days were 99, 98, and 97 from mustard greens and 96, 88, and 79 from radishes. Methanol exhibited the highest extraction efficiency, and the blend-Soxhlet process was better than the blend-leach process. Thin layer chromatography of the organic-soluble extracts indicated that the majority of 14C was recovered as methyl 2-benzimidazole carbamate (MBC), a breakdown product of benomyl. Acid hydrolysis of the extracted tissues released 30--50% of the residual 14C.

Benomyl↗
PubMed1977

Starvation-pesticide unteraetions in juvenile brown pelicans.

Nineteen 9-week-old brown pelicans (Pelecanus occidentalis), obtained from a colony in Vero Beach, Florida, containing environmentally acquired p,p'-DDE residues, were subjected to a food deprivation experiment. Samples of brain, liver, muscle, and fat taken after one and two week periods of starvation indicated that starved birds contained significantly greated residue levels in fat compared to non-starved controls. Such differences were not observed in residues in the other tissues. The significance of these findings is discussed in relation to the biology of brown pelicans.

Animals↗
PubMed1977

Dislodgeable residues of ethion in Florida citrus and relationships to weather variables.

Five different treatments of ethion on Valencia orange trees were compared for decay rates and for ethion monoxon and ethion dioxon production under different environmental conditions. The oxon metabolite levels observed were low and always below the residue level of ethion itself. There were no significant differences in the decay rates of ethion between treatments. A model of ethion decay utilizing environmental variables as a time base is presented. This model explains 94% of the variation observed in ethion decay during very wet and very dry periods in Florida. The application of these results and general experimental approach to worker safety reentry standards is discussed.

Chromatography, Gas↗