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Biomedical subjects

J M Mitchell

Publications and source records attributed to J M Mitchell.

At least 91 records · Page 5Linked to original sources
PubMed1981

Periodic alternating skew deviation.

A 78-year-old hypertensive woman suddenly developed blurred vision, followed shortly by dizziness, difficulty walking with a tendency to veer to the left, and vertical diplopia. Examination 3 weeks later revealed a unique neuro-ophthalmologic motility pattern, which may be described as periodic alternating skew deviation. This previously unreported motility disturbance was associated with downbeat nystagmus in our patient, and a focal lesion at the level of the interstitial nucleus of Cajal was demonstrated on computed tomography. The spectrum of physiologically related motility patterns--including periodic alternating nystagmus, cyclic oculomotor paralysis, see-saw nystagmus, periodic alternating gaze deviation, "ping-pong" gaze, and intermittent aperiodic alternating skew deviation--has been considered and is helpful in topical neuro-ophthalmologic diagnosis.

Aged↗
PubMed1979

Eye malformations in rats: induction by prenatal exposure to nickel carbonyl.

Exposure of pregnant rats to inhalation of nickel carbonyl on days 7 or 8 of gestation frequently causes the progeny to develop ocular anomalies, including anophthalmia and microphthalmia. The incidence of extraocular anomalies is very low. The specificity of nickel carbonyl for induction of ocular anomalies in rats appears to be unique among known teratogenic agents.

Abnormalities, Drug-Induced↗
PubMed1978

Induction of testicular sarcomas in Fischer rats by intratesticular injection of nickel subsulfide.

Nickel subsulfide (Ni3S2) was injected in various amounts into the testis of adult Fischer rats for the study of the acute and chronic effects of Ni3S2 on testicular cells. Rats given injections of 0.6 to 10 mg of Ni3S2 developed an immediate inflammatory response at the site of injection, followed by a delayed, slowly evolving coagulation necrosis of seminiferous tubules and interstitial cells. The extent of testicular necrosis was dose dependent, but at doses of 5 or 10 mg of Ni3S2 the rats invariably developed subtotal destruction of the testis. The testis became atrophic, without regeneration of seminiferous tubules. No damage was seen in the other testis, and no systemic effects were noted. Malignant testicular neoplasms developed in 16 of 19 rats within 20 months after an injection of 10 mg of Ni3S2. These neoplasms were classified by light and electron microscopy as fibrosarcomas, malignant fibrous histiocytomas, and rhabdomyosarcomas. None of the testicular neoplasms was derived from germ cells or genital cord cells. The occurrence of rhabdomyosarcomas in the testis, an organ normally devoid of striated muscle, suggests that Ni3S2 induces malignant transformation of undifferentiated, pluripotential mesenchymal cells.

Animals↗
PubMed1977

Carcinogenicity of nickel subsulfide in Fischer rats and Syrian hamsters after administration by various routes.

In an endeavor to expand the variety of experimental models for study of nickel carcinogenesis, nickel subsulfide (Ni3S2) was administered to rodents by five previously untested routes. In two groups of Syrian hamsters, Ni3S2 induced multiple sarcomas at the sites of single im injections (5 or 10 mg of Ni3S2). In contrast, Ni3S2 did not induce any malignant tumors of the cheek pouches, oral cavity or gastrointestinal tract, despite multiple local applications to the cheek pouches of several groups of hamsters in total dosages as large as 1.1 g of Ni3S2. In a group of Fischer rats, single intratesticular injections of Ni3S2 (10 mg) induced many testicular sarcomas. In contrast, no malignant tumors developed in two groups of rats that received single injections into the submaxillary gland (2.5 mg of Ni3S2) or into the liver (5 mg of Ni3S2 via the portal venous system).

Animals↗
PubMedDate not supplied

The use of military antishock trousers in trauma--a reevaluation.

The military antishock trousers (MAST) continue to be used widely. The physiologic mechanisms of action have been further elucidated. There are many potential complications associated with their use, some of which are serious. While most observations in the past were based on dog studies or human volunteers, clinical studies are now providing new information that questions the usefulness of the MAST.

Evaluation Studies as Topic↗
PubMedDate not supplied

Detection and quantitation of urinary 11-nor-delta-9-tetrahydrocannabinol-9-carboxylic acid, a metabolite of tetrahydrocannabinol, by capillary gas chromatography and electron impact mass fragmentography.

A procedure for detection and quantitation of 11-nor-delta-9-tetrahydrocannabinol-9-carboxylic acid, a major metabolite of delta-9-tetrahydrocannabinol in urine, has been described. Since the metabolite is present in both conjugated and unconjugated forms, hydrolysis of urine was carried out to increase the sensitivity of detection. The acidic metabolite was isolated by strongly basic anion exchange resin, and subsequently derivatized to methyl 1-dehydroxy-1-methoxy-11-nor-delta-9-tetrahydrocannabinol-9-carbox ylate (1a) by methyliodide in the presence of tetramethylammonium hydroxide. The derivatized product was separated in a capillary column gas chromatograph, and finally detected by a mass spectrometer under electron impact mode. Confirmation of the product was carried out by monitoring three ions that represent the major portions of the molecule and comparing their relative abundances to that of a standard. Quantitation was based on 5'-2H3-11-nor-delta-9-tetrahydrocannabinol-9-carboxylic acid as internal standard. Excellent linearity was obtained over the range of 2 to 1000 ng/mL. The overall yield of extraction using the anion exchange resin was 50 to 60%. This extraction process is rapid and suitable for a large number of sample analyses. The methylated product (1a) is stable for at least 72 hr at room temperature.

Chromatography, Gas↗
PubMedDate not supplied

GC/MS analysis of phencyclidine acid metabolite in human urine.

Available methods for determining PCP use are based on the presence of the parent drug in urine. PCP, however, is very potent and is extensively metabolized; it is therefore present in urine in only small quantities. This work was undertaken to determine whether an amino acid metabolite of PCP, 5-(N-(1'-phenylcyclohexyl)amino)pentanoic acid, can be used to determine PCP use. A solid phase adsorption technique was developed to extract the amino acid metabolite from urine. Recovery averaged 93%, and subsequent GC/MS analysis was free from interference. Analysis of 67 urine samples demonstrated that the amino acid metabolite exists in human urine in significant quantities.

Gas Chromatography-Mass Spectrometry↗
PubMedDate not supplied

Gas chromatography/electron impact mass fragmentometric determination of urinary 6-acetylmorphine, a metabolite of heroin.

A procedure for detection and quantification of urinary 6-acetylmorphine (6-AM), a metabolite of heroin, is described. After initial solvent extraction from urine, the 6-AM was purified either by acid-base liquid-liquid extraction or by solid-phase extraction techniques. The 6-AM was then derivatized to its propionyl ester, which was characterized by gas chromatography/mass spectrometry in the electron impact mode. Confirmation of 6-AM was accomplished by comparing retention times and relative abundances of selected ions with that of a standard. Quantification was based on 6-[2H3]acetyl-N-[2H3]methylnormophine (6-[2H6]AM) as internal standard. Excellent linearity was obtained in the concentration range 1-100 ng/mL. The overall yield after solvent extraction and acid-base purification ranged from 79 to 82%; for solvent extraction and solid-phase purification, it was 92 to 95%. The limit of detection was 810 pg/mL. Within-run and between-run CVs for 6-AM at concentrations in the range 1-100 ng/mL were generally less than 5% and less than 10%, respectively.

Gas Chromatography-Mass Spectrometry↗
PubMedDate not supplied

Forensic drug testing for opiates: I. Detection of 6-acetylmorphine in urine as an indicator of recent heroin exposure; drug and assay considerations and detection times.

The urinary excretion patterns of 6-acetylmorphine (6-AM), free morphine, and total morphine were determined by GC/MS assay for six human subjects who received single doses of 3.0 and 6.0 mg of heroin hydrochloride. Clinical specimens were collected and combined with standardized drug urines into a 400 specimen/standard set. The urines were coded, randomized, and analyzed under blind conditions. The GC/MS assay had a limit of sensitivity of 0.81 ng/mL for 6-AM and displayed a linear response across a concentration range of 1-100 ng/mL. Following heroin administration, 6-AM was excreted rapidly with an average half-life of 0.6 h. This resulted in a very short detection time for 6-AM with a range of 2-8 h at the most sensitive cutoff limit. This short detection time limits the usefulness of 6-AM as a marker for identification of heroin abusers to a period immediately after drug use. In contrast, free morphine and total morphine were detectable up to approximately 24 h after heroin administration. The average half-life for free morphine was 3.6 h and for total morphine was 7.9 h. After morphine and codeine administration, no 6-AM was detected by GC/MS above the 0.81-ng/mL detection limit of the assay. It is concluded that the presence of 6-AM in urine can be interpreted with confidence to mean that heroin, or 6-AM, was administered within 24 h of specimen collection and that the presence of 6-AM in urine is not caused by morphine or codeine administration.

Gas Chromatography-Mass Spectrometry↗
PubMedDate not supplied

Forensic drug testing for opiates. II. Metabolism and excretion rate of morphine in humans after morphine administration.

Urine levels of free and total morphine were determined by GC/MS for four male subjects who received single doses of 20 mg of morphine sulfate intramuscularly. Peak concentrations were observed within 10 h for both conjugated and free morphine; thereafter, levels declined rapidly. Initially, free morphine represented from 25 to 34% of the total amount of morphine present, but this ratio declined after 12 h to an average of only 5.9% of total morphine. Free morphine accounted for an overall mean of 6.8% of the dose excreted in urine and conjugated morphine for 58.6%. The mean excretion half-life for free morphine was 6.6 h and for conjugated morphine was 8.2 h. The lower concentration and shorter half-life of free morphine resulted in a shorter detection time for free morphine versus total morphine at a 300-ng/mL cutoff. An equivalent detection time for free morphine was obtained when its cutoff was lowered to 25 ng/mL. The possibility that morphine is metabolized to codeine was unequivocally ruled out by the finding of an absence of codeine at or above the LOD of the GC/MS assay in all clinical specimens collected after morphine administration.

Adult↗
PubMedDate not supplied

Forensic drug testing for opiates, III. Urinary excretion rates of morphine and codeine following codeine administration.

The urinary excretion profile of free and conjugated codeine and morphine was determined by GC/MS for four healthy male subjects after intramuscular administration of 60- and 120-mg doses of codeine. Codeine and metabolites were rapidly excreted with the majority of drug appearing in the first 24 h. No dose-related differences in metabolism were observed. The initial ratio of total codeine to total morphine was substantially greater than 1.0 but declined over time. For two of the four subjects, the codeine-morphine ratio declined below 1.0 late in the elimination phase. With a 300-ng/mL cutoff, one subject tested positive on more than one occasion for total morphine and negative for codeine during the terminal elimination phase. The data indicate that urine codeine-morphine ratios are not reliable indices of the type of opiate exposure.

Codeine↗
PubMedDate not supplied

Forensic drug testing for opiates. IV. Analytical sensitivity, specificity, and accuracy of commercial urine opiate immunoassays.

Four commercial immunoassays, TDx Opiates (TDx), Coat-A-Count Morphine in Urine (CAC), Abuscreen Radioimmunoassay for Morphine (ABUS) and Emit d.a.u. Opiate Assay (EMIT), were tested for sensitivity, specificity, and accuracy with urine specimens containing known amounts of opiates and opiate metabolites. The immunoassays were evaluated in a semiquantitative mode by comparison of morphine equivalents to GC/MS assay of free and total morphine and codeine or to target concentrations. In all cases, the apparent sensitivities of the assays were higher than those required for detection of morphine at cutoffs mandated by the Health and Human Services guidelines for testing of Federal workers. The apparent specificities of the immunoassays varied considerably. The CAC assay was found to be highly selective for free morphine, whereas TDx, ABUS, and EMIT demonstrated broad cross-reactivity with other opiates. Comparison of semiquantitative results from the immunoassays with GC/MS data indicated a high degree of accuracy for determination of morphine levels. Generally, the patterns of sensitivity and cross-reactivity were unique for each assay, indicating that a detailed knowledge of assay performance characteristics is necessary for accurate interpretation of forensic urine testing data.

Forensic Medicine↗
PubMedDate not supplied

Forensic drug testing for opiates. V. Urine testing for heroin, morphine, and codeine with commercial opiate immunoassays.

Urine specimens collected after heroin, morphine, and codeine administration were tested by four commercial opiate immunoassays (TDx, CAC, ABUS, and EMIT) and GC/MS. Quantitative immunoassay results (morphine equivalents) were compared with results by GC/MS for total morphine, free morphine, or total codeine. Mean detection times for the broadly cross-reacting immunoassays (TDx, ABUS, and EMIT, 300 ng/mL cutoff) ranged from 15-44 hours following heroin and morphine administration and 33-54 hours following codeine administration. Detection times obtained with CAC (25 ng/mL cutoff) tended to be somewhat shorter as a result of the high selectivity of the antibody for free morphine. High correlations over a wide concentration range were obtained for TDx, CAC, and ABUS versus GC/MS, with specimens collected after heroin and morphine administration. EMIT showed a high correlation over a narrow concentration range (0-1000 ng/mL) with heroin and morphine specimens, but responses plateaued at higher concentrations. There was substantial variability in immunoassay responses with specimens collected after codeine administration. Generally, this study demonstrated that immunoassay responses for opiate urine testing can be used as a semi-quantitative guide for GC/MS confirmation; however, the presence of codeine increased variability and diminished the accuracy of the immunoassay response.

Codeine↗