PubMed Health⌕ Search

Biomedical subjects

F Rieders

Publications and source records attributed to F Rieders.

At least 19 recordsLinked to original sources
PubMed1999

Filtration capture immunoassay for bacteria: optimization and potential for urinalysis.

A novel assay utilizing immuno-labeling, filtration, and electrochemistry for the rapid detection of bacteria has been optimized for the detection of Escherichia coli O157:H7. Bacteria were specifically labeled with alkaline phosphatase conjugated polyclonal antibodies and captured on a polycarbonate track-etched membrane filter (0.2 microm pore size). The filter was then placed directly against a glassy carbon electrode, incubated with enzyme substrate, and the product detected by square wave voltammetry. The high speed and capture efficiency of membrane filtration and inherent sensitivity of electrochemical detection produced a 25-min assay with a detection limit of 5 x 10(3) E. coli O157:H7 per ml using a filtration volume of 100 microl (i.e. 500 cells filtered). The labeling, filtration, and electrochemical steps were optimized, and the assay performance using electrochemical and colorimetric detection methods was compared. The assay was used to detect E. coli O157:H7 that was spiked into filter-sterilized urine at clinically relevant concentrations.

Bacteriological Techniques↗
PubMed1995

The determination of cocaine in hair: a review.

The explosion of literature related to the analysis of hair for cocaine and its products is reviewed. In the commonly accepted applications of hair testing for cocaine, those related to criminal or civil investigations and pharmacotoxicologic studies occupy most of the relevant published work. This review uses detailed, 'binary' (yes/no) tables to demonstrate trends in the literature, and allows researchers and caseworkers quick access to the literature most important for answering a variety of questions.

Cocaine↗
PubMed1993

Applications of biological monitoring in occupational health practice: practical application of urinary 2-ethoxyacetic acid to assess exposure to 2-ethoxyethyl acetate in large format silk-screening operations.

A practical application of urinary 2-ethoxyacetic acid (EAA) to assess occupational exposure to 2-ethoxyethyl acetate (EGEE-Ac) during a large format silk-screening operation is described. Industrial hygiene air monitoring of employees of a silk-screen shop producing large aircraft interior panel coverings revealed a broad range of exposures to EGEE-Ac. Time weighted exposures averaged 12 ppm (range 2.9-34 ppm) in press operators during production press runs, exceeding the 5 ppm Washington State permissible exposure limit. Employees were instructed to use organic vapor respirators until engineering controls could be developed. Urinary monitoring of EAA was conducted on 30 employees by the company medical department to aid in exposure risk assessment and to assess compliance. Results obtained ranged from 1.1-27 mg EAA/g creatinine which compares favorably with the proposed Biological Exposure Index (BEI) of 100 mg EAA/g creatinine. Results of representative air and biological monitoring, and observations of work practices for different exposure groups indicated that inhalation exposure was the predominant route of exposure. Follow-up testing to assess the efficacy of a newly installed ventilation upgrade is planned.

Acetates↗
PubMed1990

Aspirin acetylates the tricyclic antidepressant amoxapine spontaneously to N-acetylamoxapine in vitro and in vivo.

1. N-Acetylamoxapine is formed nonenzymically in vitro, and in mice, from amoxapine, a tricyclic antidepressant, and aspirin. 2. Formation of acetylamoxapine from amoxapine and aspirin in vitro was maximal at pH 5.0 since this pH optimized reactant solubilities as well as decreasing aspirin hydrolysis. 3. Formation of aceylamoxapine from amoxapine and aspirin in mouse stomachs was rapid, and the pH study indicates that the intestinal pH would favour formation even more. 4. Acetylamoxapine administered to mice produced the same CNS-related signs, leading to death, as with amoxapine, but much larger doses and longer time periods were required to elicit these effects. As brain and liver levels of amoxapine in animals dying from acetylamoxapine administration were less than half those found in animals given lethal doses of amoxapine, the toxicity in mice of acetylamoxapine may not be due solely to deacetylation of acetylamoxapine to the parent compound.

Acetylation↗
PubMed1984

Determination of carboxyhemoglobin in the presence of other blood hemoglobin pigments by visible spectrophotometry.

The convenience of the spectrophotometric method for the determination of carboxyhemoglobin has been tempered by the observation that the analysis of postmortem bloods is often biased by the presence of pigments other than oxyhemoglobin, carboxyhemoglobin, and reduced hemoglobin. These other pigments include most prominently methemoglobin and sulfhemoglobin. Using a microprocessor-controlled spectrophotometer, a method was developed depending on absorbance difference measurements at isosbestic points for oxyhemoglobin, carboxyhemoglobin, and reduced hemoglobin that is accurate down to 2% carboxyhemoglobin in fresh blood. A correction for the error caused by methemoglobin is part of the method. Qualitative confirmation of carboxyhemoglobin by examination of spectra details, sodium dithionite reduction, and first derivative spectra is described. The analysis of denatured and autolyzed bloods is examined in the context of postmortem case reports. A number of spectra are shown in detail, including methemoglobin, sulfhemoglobin, alkaline hematin, acid hematin, and mixtures of blood pigments containing varying concentrations of carboxyhemoglobin. The method has been shown to be precise, accurate, and reliable for fresh bloods. While accuracy for denatured bloods is diminished, reliability of carboxyhemoglobin identification is maintained. The analysis time is about 5 min for routine blood samples and the method is easily implemented with a precise microprocessor-controlled spectrophotometer.

Carboxyhemoglobin↗
PubMedDate not supplied

The medical and scientific evidence in alleged tubocurarine poisonings. A review of the so-called Dr. X case.

The problem of proving the presence or absence of a poison in a buried cadaver is the central theme of this presentation. Certain general questions are posed which may serve to guide those seeking to determine the cause of death in buried cadavers and allegedly due to a poison. Medicolegal and scientific evidence is presented from the court records of five deaths which were alleged homicides due to intravenous tubocurarine. As to the medical evidence: The prosecution claimed absence of adequate medical causes but full congruence with intravenous tubocurarine as the cause of death. The defense claimed and presented its evidence, including history, clinical picture, gross and microscopic pathological findings--for the deaths having occurred from competent natural causes in all but one case. In that one case the cause was undetermined. In two of the four cases evidence was presented for the mechanism of death and why they died at the time that they did. As to the forensic toxicological evidence: The prosecution claimed qualitative identification but with no particular quantitative detection or identification limits of tubocurarine in the remains based on results of combinations of HPLC followed by RIA and of some selected ion direct inlet mass spectrometry. The defense corroborated--along with a quantitative estimate--the presence of a substantial concentration of tubocurarine in the liver specimen of one case. However the chain of custody of this particular specimen was compromised for a period of several days between post-exhumation autopsy and submission to the prosecution toxicologists. With respect to all the other specimens examined by the defense, direct inlet mass spectrometry failed to show ions which are critical for establishing the identity of tubocurarine. The defense also presented results of experiments which showed that the tissues of the cases in question destroyed tubocurarine at such a rate that no reasonably conceivable administered amount could have survived the 10 years of burial of these cases. In each of the five cases exhumation and re-autopsy would have been found to be neither justified nor even indicated had an objective examination of the available record been made and supplemented by a similarly objective review of the literature and the simple stability experiments used by the defense. After an 8-month trial, the jury brought in a not guilty verdict on all counts after less than 2 h of deliberations.

Adult↗
PubMedDate not supplied

Oleandrin distribution in a fatality from rectal and oral Nerium oleander extract administration.

In a fatal (cardiotoxic) case of oleander extract poisoning of a young female, ethanol extracts of blood and tissue homogenates were purified by lead acetate. After removal of excess lead by ammonium sulfate, oleandrin was extracted into chloroform. Oleandrin in the extract concentrates was detected by thin-layer chromatography, with location by fluorescence and chromogenically by means of p-anisaldehyde. Quantitation was performed on dried extracts reconstituted in water/methanol, reacted with hydrogen peroxide, ascorbic acid, and hydrochloric acid, and analyzed by fluorescence spectrophotometry. Excitation was at 355 nm, and fluorescence scanning from 340 to 580 nm. The fluorescence peak at 460 nm was used for the quantitative measurement. The concentrations of oleandrin measured in blood, stomach wall, colon tissue, liver, heart, lung, brain, spleen, and kidney ranged from 10 to 39 micrograms/g, with 200 micrograms/mL in the total gastric content residue submitted for analysis.

Adult↗
PubMedDate not supplied

Quantitative determination of phenelzine in human fluids by gas chromatography with nitrogen specific detection.

A quantitative gas chromatographic assay for the determination of phenelzine in plasma or other fluids is presented. A stable derivative is formed by cyclization with acetylacetone, and the derivative is separated, purified, and concentrated by liquid-liquid solvent extraction. Analysis of the extracts is by capillary gas chromatography with nitrogen specific detection. Detection limits of less than 1 ng/mL and CVs of 5% at the 10-ng/mL level are attainable with a 2-mL sample and benzylhydrazine as the internal standard.

Body Fluids↗
PubMedDate not supplied

Direct automated EMIT d.a.u. analysis of N,N-dimethylformamide-modified serum, plasma, and postmortem blood for benzodiazepines, benzoylecgonine, cannabinoids, and opiates.

Serum, plasma, and postmortem blood treated with two volumes of N,N-dimethylformamide (DMF) and centrifuged, were directly analyzable by means of the EMIT d.a.u. reagents on the Syva Autocarousel in the same manner as urine. Cutoff values in milligrams (immunochemically cross-reactive analyte equivalents)/L are 0.05 for morphine (MOR), 0.15 for benzoylecgonine (BZE), 0.20 for oxazepam (OX), and 0.02 for 11-nor-delta 9-tetrahydrocannabinol carboxylic acid (THCC). The relationship of concentrations (micrograms/mL serum) to absorbance changes (delta A) were S-shaped up to greater than 3.0 for MOR, 4.0 for BZE, greater than 5.0 for OX, and 0.2 for THCC. Beyond these maximal concentrations, delta A values declined. Thus, negatives should be repeated on substantially diluted aliquots to avoid missing extraordinarily high positives. "False" quantitative negative/positive noncongruence between total EMIT cross-reactives and free-drug analyses by gas chromatography/mass spectrometry (GC/MS) were 0/17 (N = 75) for opiates, 8/0 (N = 119) for cocaine products, and 19/5 (N = 103) for cannabinoids. For benzodiazepines (N = 58) the "false" negative/"false" positive ratio of EMIT (total)/high performance liquid chromatography (HPLC) (free) was 4/4. Within-day precision as coefficient of variation (CV) of quantitative estimates was 8-18%. For between-day precision, quantitative estimates varied by 8% for MOR, 15% for BZE, 18% for OX, and 34% for THCC.

Benzodiazepines↗