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Biomedical subjects

G Nelson

Publications and source records attributed to G Nelson.

At least 127 records · Page 7Linked to original sources
PubMedDate not supplied

Ultraviolet mutagenesis of radiation-sensitive (rad) mutants of the nematode Caenorhabditis elegans.

A mutational tester strain (JP10) of the nematode C. elegans was used to capture recessive lethal mutations in a balanced 300 essential gene autosomal region. The probability of converting a radiation interaction into a lethal mutation was measured in young gravid adults after exposure to fluences of 254-nm ultraviolet radiation (UV) ranging from 0 to 300 Jm-2. Mutation frequencies as high as 5% were observed. In addition, three different radiation-hypersensitive mutations, rad-1, rad-3 and rad-7 were incorporated into the JP10 background genotype, which allowed us to measure mutation frequencies in radiation-sensitive animals. The strain homozygous for rad-3 was hypermutable to UV while strains homozygous for rad-1 and rad-7 were hypomutable. Data showing the effects of UV on larval development and fertility for the rad mutants is also shown and compared for wild-type and JP10 backgrounds.

Animals↗
PubMedDate not supplied

An application of an effective interdisciplinary health-focused cross-cultural collaboration.

The phenomenon of cross-cultural collaboration is not new. What is lacking in the literature, however, is a discussion of how health professionals from various cultures, collaborating together, have addressed their patients' health care needs to improve their quality of life. Because of increased interest in global health issues, it seems logical that health professionals from various countries form collaborative partnerships to investigate and address these health issues. Although treatments to health problems are offered, it is not generally communicated in the literature how cross-cultural collaboration played a role in managing the process to solve the problem. By applying the concepts for global managers outlined by P. R. Harris and R. T. Moran (1996), this article describes how the investigators established a successful cross-cultural collaboration for conducting health research between teams in the United States and Russia.

Communication↗
PubMedDate not supplied

Mechanistically identified suitable biomarkers of exposure, effect, and susceptibility for silicosis and coal-worker's pneumoconiosis: a comprehensive review.

Clinical detection of silicosis is currently dependent on radiological and lung function abnormalities, both late manifestations of disease. Markers of prediction and early detection of pneumoconiosis are imperative for the implementation of timely intervention strategies. Understanding the underlying mechanisms of the etiology of coal workers pneumoconiosis (CWP) and silicosis was essential in proposing numerous biomarkers that have been evaluated to assess effects following exposure to crystalline silica and/or coal mine dust. Human validation studies have substantiated some of these proposed biomarkers and argued in favor of their use as biomarkers for crystalline silica- and CWP-induced pneumoconiosis. A number of "ideal" biological markers of effect were identified, namely, Clara cell protein-16 (CC16) (serum), tumor necrosis factor-alpha (TNF-alpha) (monocyte release), interleukin-8 (IL-8) (monocyte release), reactive oxygen species (ROS) measurement by chemiluminescence (neutrophil release), 8-isoprostanes (serum), total antioxidant levels measured by total equivalent antioxidant capacity (TEAC), glutathione, glutathione peroxidase activity, glutathione S-transferase activity, and platelet-derived growth factor (PDGF) (serum). TNF-alpha polymorphism (blood cellular DNA) was identified as a biomarker of susceptibility. Further studies are planned to test the validity and feasibility of these biomarkers to detect either high exposure to crystalline silica and early silicosis or susceptibility to silicosis in gold miners in South Africa.

Air Pollutants, Occupational↗
PubMedDate not supplied

The quantitative conversion of morphine 3-beta-D glucuronide to morphine using beta-glucuronidase obtained from Patella vulgata as compared to acid hydrolysis.

Methods to confirm morphine in urine require hydrolysis to liberate morphine from its 3-beta-D glucuronide (M-3G) conjugate. Lengthy enzyme hydrolysis procedures prolong testing turnaround time whereas rapid enzyme methods may produce a low conversion of M-3G to morphine. The purpose of this study was to evaluate the quantitative conversion of M-3G to morphine in human urine using a thermally stable beta-glucuronidase isolated from Patella vulgata; to compare these findings with those obtained from acid hydrolysis; and to compare between-run imprecision for both hydrolysis methods. We found both enzyme and acid hydrolysis techniques to be efficient, giving 90.4% and 92.8% conversion of M-3G to morphine, respectively. Also, both methods were found to be reproducible. Over a 14 week period, 20 opiate confirmation batches were analyzed by each hydrolysis method; the coefficient of variation for morphine liberated from M-3G was 5.5% for enzyme hydrolysis and 2.7% for acid hydrolysis.

Animals↗
PubMedDate not supplied

Improving ion mass ratio performance at low concentrations in methamphetamine GC-MS assay through internal standard selection.

In federally regulated drug testing, laboratories must identify and quantitate drugs and their breakdown products by gas chromatography-mass spectrometry (GC-MS) to a concentration that is at least 60% below the cutoff concentration for reconfirmation purposes. Use of methamphetamine-d5 as an internal standard in routine testing with derivatization by HFBA was found to contribute m/z 91 and 118 ions to the same ions from the nondeuterated methamphetamine in the specimen. This resulted in poor chromatography and occasionally caused the 91/254 and 118/254 ion mass ratios to exceed the +20% acceptance limit established in the calibration process at low concentrations. The analogues methamphetamine-d8 and -d11 were evaluated for contributions to the nondeuterated methamphetamine ion fragments. Methamphetamine-d8 produced m/z 91 and 118 ions, but in less abundance than methamphetamine-d5. Methamphetamine-d11 was found to produce little or no detectable m/z 91 or 118. Replacing methamphetamine-d5 with methamphetamine-d11 eliminates this problem and allows the assay to consistently produce ion mass ratios and acceptable chromatography sufficient for identifying and quantitating methamphetamine at 60% below the 500-ng/mL cutoff concentration.

Gas Chromatography-Mass Spectrometry↗
PubMedDate not supplied

A positive cannabinoids workplace drug test following the ingestion of commercially available hemp seed oil.

A commercially available health food product of cold-pressed hemp seed oil ingested by one volunteer twice a day for 4 1/2 days (135 mL total). Urine specimens collected from the volunteer were subjected to standard workplace urine drug testing procedures, and the following concentrations of 11-nor-delta9- tetrahydrocannabinol carboxylic acid (9-THCA) were detected: 41 ng/mL 9-THCA at 45 h, 49 ng/mL at 69 h, and 55 ng/mL at 93 h. Ingestion was discontinued after 93 h, and the following concentrations were detected: 68 ng/mL at 108 h, 57 ng/mL at 117 h, 31 ng/mL at 126 h, and 20 ng/mL at 142 h. The first specimen that tested negative (50 ng/mL initial immunoassay test, 15 ng/mL confirmatory gas chromatographic-mass spectrometric test) was at 146 h, which was 53 h after the last hemp seed oil ingestion. Four subsequent specimens taken to 177 h were also negative. This study indicates that a workplace urine drug test positive for cannabinoids may arise from the consumption of commercially available cold-pressed hemp seed oil.

Artifacts↗
PubMedDate not supplied

Nitrite adulteration of workplace urine drug-testing specimens. I. Sources and associated concentrations of nitrite in urine and distinction between natural sources and adulteration.

The active ingredient in the commercial workplace urine drug-testing adulterant, Klear, was previously determined to be nitrite ion. Nitrite adulteration compromises the confirmation of some drugs, notably the marijuana metabolite. A previously reported bisulfite step overcomes some nitrite adulteration, but it cannot do so in every case, which leaves the laboratory to report the specimen as not suitable for testing. Unlike many other adulterants, nitrite is found in normal urine at low concentrations. In order to defend a report of nitrite adulteration, it is necessary to provide evidence that the amount of nitrite in a workplace urine specimen could not arise by normal means. The objectives of this study were to identify all sources of nitrite in urine and the range of concentrations associated with these sources and to determine if nitrite adulteration can be supported based upon a quantitative result. The scientific literature was reviewed for internal and external sources of nitrite and their concentration ranges and are reported. The following specimens were obtained and nitrite concentrations measured by a spectrophotometric method: clinical specimens nitrite positive by test strip (< 15 micrograms/mL); specimens culture positive for nitrate-reducing microorganisms (< 36 micrograms/mL); specimens from patients on medications that may metabolize to nitrite (< 6 micrograms/mL); and drug-test specimens, both negative (< 130 micrograms/mL) and others that appeared to be adulterated with nitrite (range 1910-12,200 micrograms/mL, mean 5910). The literature and the nitrite measurements of this study indicate a substantial difference between concentrations from natural sources compared with adulteration. A quantitative measurement of nitrite by a well-structured assay can provide scientifically valid and forensically defensible proof of adulteration with a nitrite-containing substance.

Drug Contamination↗
PubMedDate not supplied

Comparison of four derivatizing reagents for 6-acetylmorphine GC-MS analysis.

The propionyl, trimethylsilyl, trifluroacetyl, and heptafluoroacyl derivatives of 6-acetylmorphine (6-AM) were evaluated with respect to optimal method performance, derivative stability, and methods characterization for use in gas chromatographic-mass spectrometric (GC-MS) analysis with electron ionization mode and selected ion monitoring. The most common potential interferences and compatibility with other derivatives when used on the same GC-MS were determined for the derivatizing reagents. The propionyl, trimethylsilyl, and trifluroacetyl derivatives produced adequate stability, accuracy, and precision for the method. The 6-AM derivatization with commercially available propionic anhydride generated a relatively small amount of 6-AM-propionyl derivative from the free morphine present in a specimen. The trimethylsilyl derivative obtained by the reaction with MSTFA did not require incubation, was the easiest to prepare, and had the highest potential for use on an automated sample-preparation device. An important advantage of derivatization with MSTFA is elimination of the possibility of heroin decomposition to 6-AM that is due to incubation at elevated temperature.

Gas Chromatography-Mass Spectrometry↗
PubMedDate not supplied

Solid-phase extraction of 11-nor-delta9-tetrahydrocannabinol-9-carboxylic acid from urine drug-testing specimens with the cerex polycrom-THC column.

Confirmation of drugs of abuse by gas chromatography-mass spectrometry (GC-MS) is the most time-consuming process used by drug-testing laboratories. Cost effectiveness and competitive turnaround times for testing results demand fast, efficient, and reliable extraction methods. We applied the Cerex Polycrom-THC solid-phase extraction (SPE) column to the extraction of 11-nor-delta9-tetrahydrocannabinol carboxylic acid (9-THCA) from urine. This column uses an anion exchange divinyl-benzene copolymer, which requires no pH adjustment after hydrolysis of the THC-glucuronide with base, as is necessary with many other SPE columns. With urine, no preconditioning of the SPE column was necessary. After extraction, trimethylsilation derivatization was performed with N-methyl-N-(trimethylsilyl) trifluoroacetamide. This further improved efficiency because no heated incubation was required. A method correlation to an existing liquid-liquid extraction was performed. Analysis was on a Finnigan Voyager GC-MS with a 2.5-min run time per injection. Using 9-THCA-d9 deuterated internal standard, the assay was linear from 2 to 2000 ng/mL. Total precision at the 15-ng/mL cutoff concentration was 4.4%. The Cerex column was also evaluated for interference using two common drug-test adulterants, Klear and Urine Luck. Considerably less interference was observed when compared to an existing liquid-liquid method.

Cost-Benefit Analysis↗
PubMedDate not supplied

Insensible water loss during extracorporeal membrane oxygenation: an in vitro study.

To measure insensible fluid loss from silicone membrane oxygenators during extracorporeal membrane oxygenation (ECMO), an in vitro system was used. A standard neonatal ECMO circuit (Avecor) was connected to a noncompliant reservoir, which was then primed with normal saline. The experiment was conducted by using two silicone oxygenators (Avecor 0.4 and 0.8 m2), three gas flow rates (0.5, 1.0, and 2.0 L/min) (sweep), and two fluid flow rates (200 and 400 ml/min). Two methods were used to measure the water loss. One method was to replace the water to the noncompliant circuit by using a calibrated burette, and the other method was to collect condensed water after cooling the postmembrane sweep gas to 0 degrees C. The influence of the amount of sweep, fluid flow rate, size of membrane, and inlet and outlet sweep gas temperatures on measured water loss was statistically determined. The amount of water loss correlated with sweep (r2 = 0.81; p<0.00001) but was not related to the fluid flow rate, membrane size, or inlet and outlet sweep gas temperature. The average daily fluid loss measured with replacement and collection methods for each liter of sweep per minute were 72.0+/-12.6 and 62.3+/-10.0 ml, respectively. This information may be applied to clinical practice to accurately manage fluid balance in the sick neonate on ECMO.

Extracorporeal Membrane Oxygenation↗
PubMedDate not supplied

Microencapsulation in yeast cells.

A method for encapsulating high concentrations of essential oils into bakers' yeast (Saccharomyces cerevisiae) is described. The process involves mixing an aqueous suspension of yeast and an essential oil, which allows the oil to pass freely through the cell wall and membrane and remain passively within the cell. Oil droplets sequestered within the cell were clearly visible using confocal microscopy. Transmission electron microscopy demonstrated that the cell wall and membrane remain intact during the process. Cells quickly lost viability during the process and it appeared unnecessary for the cells to be viable for the process to occur. Encapsulated oil was recovered from the cells using a water/ethanol extraction procedure and analysed by gas chromatography. No significant differences were noted between encapsulated and unencapsulated oil profiles. The rate of permeation of oil into the yeast cells was found to increase significantly at higher temperatures due to the phase transition of the lipid membrane. The rates at which different essential oils permeated the cell varied considerably due to variations in terpene chemistry. The encapsulation of straight chain hydrocarbons highlighted the effects of molecular size, shape and the presence of hydroxl groups on the process. The process occurs by passive diffusion as a result of hydrophobic flavour components partitioning into the cell membrane and intracellular lipid. This paper briefly reviews the patented literature and reports some of the initial observations of the transport mechanisms involved during the accumulation of essential oils by yeast cells.

Capsules↗
PubMedDate not supplied

Comparative studies of bone marrow from the United States and Japan.

Two hundred and eighty four bone marrow sections obtained at autopsy from the United States and 304 from Japan were evaluated. Patients who died of malignancy were excluded from the study. There was a significant increase in the incidence of lymphoid aggregates in the bone marrow with increasing age. After the age of 40, the incidence increased to 26.5 percent and 13.8 percent in the USA and Japan, respectively. After age 70, the frequencies reached 45.2 percent (USA) and 18.9 percent (Japan). There was a significant difference in the frequency of lymphoid aggregates between Americans and Japanese, and between females and males. The frequencies are 41.5 percent (females) and 35.1 percent (males) in the USA, and 18.7 percent (females) and 15.2 percent (males) in Japan. Bone marrow necrosis is more frequent in the old age group. The average frequency of marrow necrosis is 38 percent (USA) and 43.1 percent (Japan). Bone marrow fibrosis also increased with increasing age, reaching 16.1 percent (USA) and 19.5 percent (Japan) after the age of 70.

Adolescent↗