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Biomedical subjects

W Fiddler

Publications and source records attributed to W Fiddler.

At least 19 recordsLinked to original sources
PubMed2001

Method for the analysis of thyreostats in meat tissue using gas chromatography with nitrogen phosphorus detection and tandem mass spectrometric confirmation.

An analytical method not requiring a mercury column cleanup step is described for the isolation and detection of four thyreostatic agents in meat tissue. The use of these growth promotants in livestock has been banned by regulatory agencies. The meat tissue is homogenized with acetonitrile-water, centrifuged, and the supernatant is partitioned with petroleum ether. The acetonitrile-water is concentrated and then passed through a silica-gel column. The solvent is then removed and the residue derivatized with N-methyl-N-(trimethylsilyl)-trifluoroacetamide. The total amount of organic solvent used for the analysis is merely 35 mL. The derivatized thyreostats are detected and quantitated by gas chromatography (GC) equipped with a nitrogen-phosphorus detector. Percent recoveries from fortified meat tissue (n = 6) at the 0.1-microg/g (parts per million) level are 93.5 +/- 2.9 for 2-thiouracil, 90.3 +/- 3.0 for tapazole, 87.5 +/- 2.9 for 6-methyl-2-thiouracil, and 85.1 +/- 5.8 for 6-n-propyl-2-thiouracil. For the confirmation of analyte identities, GC-tandem mass spectrometry with an ion-trap instrument is used. The estimated minimum level for a reliable measurement is 0.050 microg/g in meat tissue.

Animals↗
PubMed2000

Potential artifact formation of dioxins in ball clay during supercritical fluid extraction.

Earlier surveys indicate that meat, fish and dairy products are the principal source of polychlorinated dibenzo-p-dioxin (PCDD) exposure in the diet. A recent finding by others of PCDDs in chickens that consumed a feed containing PCDD led to the finding of ball clay, an anti-caking agent, as the source. Supercritical fluid extraction (SFE) was studied as a means to isolate PCDDs from commercial ball clays using GC-electron capture detection (muECD) as a means to screen for these contaminants. The finding of ng/g amounts and recoveries >100% in several samples of ball clay containing octachlorodibenzo-p-dioxin (OCDD) suggested that PCDD may form artifactually as a result of analysis. Studies on pentachlorophenol (PCP) fortified ball clay were carried out by SFE and soxhlet extraction and the results compared. The values obtained by SFE were considered more problematic. The results obtained from ball clay suggest that precautions need to be exercised when using SFE to analyze for dioxins in solid samples containing chlorophenols.

Animal Feed↗
PubMed2000

Supercritical fluid extraction of atrazine and other triazine herbicides from fortified and incurred eggs.

Triazines are a class of important pre-emergent weed herbicides. Some members of this class of herbicides exhibit carcinogenic and immunotoxicity properties, which make their use controversial in areas where animal feed crops are grown. It is therefore important to determine if triazine residues are transported to animal food products in order to ascertain the extent of human exposure. Most of the current herbicide residue extraction methods are time-consuming and solvent intensive. Supercritical fluid extraction (SFE) using CO(2) has been used as a alternative for other residue extraction methods as a replacement for hazardous organic solvents. In this study, 10 triazines were extracted from eggs fortified at 100 ppb using unmodified supercritical CO(2) at a pressure of 10000 psi and a temperature of 50 degrees C with off-line collection on a solid phase extraction cartridge containing Florisil. Atrazine recovery averaged 90.4% with an RSD of 3.3%. The other triazines were recovered at mean levels >73%. In a separate feeding study, atrazine and two of its dealkyl metabolites were detected in the egg. The results indicate that SFE is a viable technique for isolating triazine residues from eggs, requiring only 8 mL of solvent for each analysis.

Atrazine↗
PubMed1999

Supercritical fluid extraction of organochlorine pesticides in eggs.

The efficacy of supercritical fluid extraction (SFE) for the recovery of 16 common organochlorine pesticides (OCPs) from liquid whole eggs was investigated by employing supercritical carbon dioxide (SC-CO(2)) without the use of a solvent modifier to minimize interfering coextractives. The OCPs tested included aldrin; alpha-, beta-, delta-, and gamma-BHCs; p,p'-DDD, -DDE, and -DDT; dieldrin; endosulfans I, II, and sulfate; endrin; endrin aldehyde; heptachlor; and heptachlor epoxide. The SFE conditions were as follows: 10000 psi (680 bar), 40 degrees C, SC-CO(2) flow rate of 3.0 L/min with an extraction time of 40 min for a total of 120 L of CO(2). The OCPs were trapped off-line in an SPE cartridge containing Florisil and then eluted by an acetone/hexane mixture and analyzed by gas chromatography-electron capture detection (GC-ECD). Recovery studies were carried out on homogenized eggs fortified at the 0.05, 0.10, and 0.20 ppm levels. At the lowest level, 0.05 ppm, recoveries ranged from 81.8 to 108.3%, with CVs < 9.8%. All recoveries were significantly higher than those obtained by an AOAC/FDA solvent extraction method. Eggs containing incurred endosulfan I were also effectively extracted by SFE. This study suggests that the application of SFE for the extraction of OCPs from eggs will result in significant savings in analysis time and lower solvent use and disposal costs compared to conventional solvent extraction procedures.

Animals↗
PubMed1994

Kinetic study on the nitrosation of dibenzylamine in a model system.

A kinetic study of the formation of N-nitrosodibenzylamine (NDBzA), from the nitrosation of dibenzylamine (DBzA) by sodium nitrite, was performed in a model system under conditions (temperature, pH) that are similar to those encountered in the industrial production of hams processed in elastic rubber nettings. The nitrosation reaction was carried out in a KH2PO4 buffer (0.5 M) at pH 5.8 and at a temperature of 69 degrees C. Since DBzA is insoluble in an aqueous buffer system, a non-ionic surfactant, Tween 20, was used as a solubilizing agent. The nitrosation reaction exhibited first-order kinetics with respect to DBzA and second-order kinetics with respect to nitrite. The calculated rate constant was 4.7 +/- 0.5 M-2/min. The pH profile of NDBzA formation was also determined. The optimal pH of NDBzA formation, 3.12, was close to the pKa of nitrous acid (HNO2, pKa = 3.1).

Benzylamines↗
PubMed1993

Multiresidue recovery at PPB levels of 10 nitrosamines from frankfurters by supercritical fluid extraction.

The design of a laboratory-assembled supercritical fluid extractor is described for the efficient recovery of volatile nitrosamines from a common-cured meat product, frankfurters. The principal feature of the apparatus was a newly designed restrictor-collector interface where a commercial solid-phase extraction cartridge was directly attached to the micrometering valve. This reduced the path length between the discharge tube and the 1 g silica gel sorbent bed. The elapsed time for each 2.5 g sample extraction with supercritical CO2 was 17 min. The nitrosamines were separated and detected using a gas-chromatographic chemiluminescence (Thermal Energy Analyzer, Thermedics, Inc.; Woburn, MA) system. Recovery of 10 volatile aliphatic and alicyclic nitrosamines from frankfurters, fortified at the 20 ppb level, ranged from 84.3 to 104.8% with relative standard deviation of 2.34 to 6.13%.

Carbon Dioxide↗
PubMed1992

Nitrosamines in rubber bands used for orthodontic purposes.

Fourteen samples from eight brands of elastic-rubber bands used in orthodontics were tested for their nitrosamine content. The presence of N-nitrosodibutylamine and N-nitrosopiperidine was confirmed. The potential for nitrosamine formation from accelerating agents used for vulcanization and from other nitrosatable amines, which may be present in rubber exposed to salivary nitrite, justifies further investigations.

Nitrosamines↗
PubMed1990

N-nitrosodimethylamine blood levels in patients with chronic renal failure: modulation of levels by ethanol and ascorbic acid.

We measured levels of N-nitrosodimethylamine (NDMA) in peripheral blood from 13 fasting male patients, 30-74 years old, who had chronic renal failure, and in five healthy control subjects (four males and one female) 31-50 years old. In the patients, we found significant (P less than .01) levels of NDMA (mean +/- SD; 201 +/- 111 ng/kg of blood), which is known to be carcinogenic in animals. Five minutes after oral administration of ethanol (0.4 g/kg of body weight), all patients exhibited a significant (P less than .01) rise in blood NDMA levels (338 +/- 125 ng/kg), suggesting continuous endogenous formation of NDMA that was unmasked by ethanol's ability to inhibit first-pass hepatic metabolism of NDMA. In five of six patients, pretreatment with oral ascorbic acid resulted in a blunting, but not statistically significant, effect on maximum blood NDMA levels after consumption of ethanol. Mean levels were 340 +/- 100 ng/kg before treatment with ascorbic acid and 237 +/- 127 ng/kg during treatment. Ethanol administration unmasks increased gastrointestinal formation of NDMA in patients with chronic renal failure. Further studies are required to confirm a possible link between endogenous NDMA formation and the increased incidence of cancer in these patients.

Adult↗
PubMed1988

Carcinogenesis in rats by cyclic N-nitrosamines containing sulphur.

The effects of chronic exposure to three sulphur-containing heterocyclic N-nitrosamines were determined after repeated oral administration to female Fischer 344 rats. Nitrosothiazolidine did not significantly affect the survival of the rats or the incidence of tumours at a total dose of 3.5 mmol. Nitrosodithiazine, an analogue of nitrosothiazolidine which contains an extra sulphur atom inserted between the carbons of its CH2-CH2 moiety, produced only three tumours (two of the nasal mucosa) in a group of 20 rats at a total dose of 1.75 mmol/rat. Nitrosothialdine, the all-cis 2,4,6-trimethyl analogue of nitrosodithiazine, was a potent carcinogen that significantly shortened the lifespan and produced oesophageal tumours in 70% of treated rats as well as numerous tumours of the tongue and liver; this outcome was unexpected because alpha-methyl substitution in other heterocyclic nitrosamines usually reduces or eliminates tumorigenicity. The results extend the data base on the carcinogenic activity of molecules containing both divalent sulphur and the nitrosamino function. The lack of significant carcinogenicity of nitrosothiazolidine in this study suggests that its presence in the human food supply presents a relatively minor risk.

Animals↗
PubMed1987

Inhibitory effects of thiols on a mutagenic contaminant from the synthesis of N-nitrosothiazolidine.

The effect of S9 and various thiols were studied for potential modifying effects on a mutagenic trace artifact ('NTHZ') formed during the synthesis of N-nitrosothiazolidine (NTHZ) from cysteamine, formaldehyde and nitrite. Induced and uninduced S9 prepared from Syrian hamster livers reduced mutagenic activity in Salmonella TA100. Incorporation of boiled S9 into the preincubation medium produced similar effects, indicating a non-enzymatic mechanism for the detoxification reaction. Thiols alone also lowered revertant yields, and inhibitory efficacy was, in general, related to the pKa of the compound. At equimolar concentrations mutagenic activity was reduced in the following order (pKa values in parentheses): Thioglycolate (10.7) greater than mercaptoethanol (9.6) greater than reduced glutathione (8.8) greater than cysteine (8.35) greater than cystine (8.2). N-Acetylcysteine (9.52) and cysteamine (8.35), however, did not fit this pattern. The results of this study suggest that normal hepatic mechanisms may minimize 'NTHZ' genotoxicity thereby reducing potential health risks associated with its exposure.

Animals↗
PubMed1987

Observations of the use of 137caesium radiation to control N-nitrosopyrrolidine formation in bacon.

Several alternatives to the use of nitrite, including irradiation, have been developed to reduce the nitrosamine content in bacon and still retain its microbiological safety and desirable sensory characteristics. This paper presents results obtained from experiments in which 137Cs was used at +5 degrees C. Bacon prepared with 120 or 40 mg/kg sodium nitrite (NaNO2) yielded lower residual nitrite before frying and lower levels of N-nitrosopyrrolidine (NPYR) after frying when irradiated at 3.0 Mrad, compared to doses of 0, 0.75 and 1.50 Mrad. Also, a slight increase in the level of NPYR in fried bacon over the 0 control was noted with 0.75 Mrad. In bacon irradiated with 0-1.5 Mrad in 0.25-Mrad increments, a marked increase was observed at 0.5 Mrad. Bacon from pork bellies irradiated prior to processing had more NPYR after frying than bacon irradiated after processing, suggesting the formation of an additional precursor or some catalytic agent.

Animals↗
PubMed1985

Investigation of volatile nitrosamines in disposable protective gloves.

Laboratory personnel of Eastern Regional Research Center, USDA, are required to wear disposable latex or vinyl gloves for certain analyses involving nitrosamines. In order to assess possible exposure of the wearers of these gloves, a limited survey was carried out on the volatile nitrosamine content in disposable protective gloves. Six latex gloves, nonsterile and sterile, surgical and nonsurgical, from four companies, and four vinyl gloves from three companies were analyzed. N-nitrosodimethylamine (NDMA) and N-nitrosopiperidine (NPIP) were the primary nitrosamines detected. Five of the six latex gloves contained 37-329 ppb NDMA and 115-1879 ppb NPIP, all confirmed by gas chromatography-mass spectrometry (GC-MS); one glove contained no detectable trace of NDMA or NPIP. Of the four vinyl gloves, one contained 19 ppb NDMA and 759 ppb NPIP, both confirmed by GC-MS, one contained 6 ppb apparent NDMA and no detectable level of NPIP, and the remaining two contained no detectable levels of NDMA and NPIP.

Disposable Equipment↗
PubMed1984

Comparison of the acute toxicities of N-nitrosothiazolidine and N-nitrosomorpholine.

The effects of N-nitrosothiazolidine (NNT) and N-nitrosomorpholine (NNM) on different biological parameters were investigated and compared. The oral LD50 value of NNT (1950 +/- 85 mg/kg) showed that it was about 6 times less toxic than NNM (LD50 = 320 mg/kg, po; Druckrey et al., 1967). Lethal and near-lethal doses (greater than or equal to 1500 mg/kg, po) of NNT caused central nervous system depression (reduced spontaneous motor activity, loss of righting and pain reflexes, without loss of consciousness), stereotypical behavior such as, purposeless chewing jaw movements lasting more than one hour, muscular rigidity, and in some rats, rare and brief clonic convulsions, 3 to 24 h after dosing. These neurotoxic signs, as a whole, were reminiscent of opioid intoxication. Rats that died after NNT-treatment had kidney necrosis in the distal tubules, but all survivors had normal kidneys. NNT (500 and 1000 mg/kg, sc) had no effect on the relative liver weights, but it inhibited liver mitosis at 24, 48, and 72 h after treatment. NNM (100 mg/kg, sc) decreased the relative liver weights on 3 posttreatment days; it inhibited liver mitosis after 24 h and enhanced it after 48 h in male rats. Both NNT and NNM increased the relative adrenal weights, but only NNM enhanced adrenocortical mitosis. In general, NNT had no effect on serum enzymes (SGOT, SGPT, LDH, HBDH), but it increased blood urea nitrogen (BUN) and serum creatinine 24 h after administration. Pretreatment of rats with 3 doses of NNT (150 mg/kg X d, po) increased the pentobarbital-induced sleep (PST) by 26% (not significant), while 3 doses of NNM (50 mg/kg X d, po) increased PST by 188%. In addition, NNM caused a severe centrilobular liver necrosis and glycogen depletion, associated with a marked rise in serum enzymes (SGOT, SGPT, LDH, HBDH) and fall in serum glucose. Compared with NNM, NNT, which was found in fried bacon (Kimoto et al., 1982; Gray et al., 1982), seemed to be a relatively nontoxic nitrosamine.

Adrenal Cortex↗
PubMed1983

Generation of dimethylnitrosamine in water purification systems. Detection in human blood samples during hemodialysis.

Dimethylnitrosamine (DMNA), a carcinogen, was detected at levels up to 32 micrograms/L in dialysate from five of 16 dialysis units surveyed. Blood drawn from patients at one of these units in which DMNA was raised in the dialysate showed a significant increase in the amount of DMNA in the patient's blood when predialysis levels were compared with 15-minute intradialysis levels. The presence of a mixed-bed deionizer without an antecedent carbon filter appeared to be necessary for DMNA production. These data suggest that DMNA is generated in certain water purification systems and may then diffuse into the patient's blood. Guidelines for deionizer-treated water should be revised to include an activated carbon filter.

Adolescent↗
PubMed1983

Evidence for generation of the precarcinogen nitrosodimethylamine in the small intestine in chronic renal failure.

We have previously reported raised concentrations of dimethylamine and also bacterial overgrowth in the small intestine in CRF. Evidence for in vivo NDMA formation in the same site in CRF is now presented. Gastroduodenal intubation was performed in 9 healthy volunteers and 7 patients with advanced chronic renal failure. Blood, gastric, and duodenal aspirates were analyzed for NDMA. NDMA levels in control and CRF patients for blood were normal, but for gastric aspirate they were 67 +/- 13 and 312 +/- 68 (P less than 0.001) and for duodenal aspirate they were 70 +/- 21 and 319 +/- 47 (P less than 0.001), respectively. The results of bacterial cultures confirmed small intestinal bacterial overgrowth. We thus demonstrated statistically significant differences between NDMA concentrations in the control subjects and patients for both gastric and duodenal aspirates. This suggests that there is increased intestinal generation of NDMA in uremia. The presence of this precarcinogen may be linked with the reported increase in the incidence of cancer in CRF.

Bacteria↗