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Biomedical subjects

J A Roach

Publications and source records attributed to J A Roach.

At least 37 records · Page 2Linked to original sources
PubMed1984

Phenotypic characterization of human T lymphocyte populations producing macrophage-activating factor (MAF) lymphokines.

Human T lymphocytes, which are known to produce lymphokines that can activate monocytes and macrophages, can be subdivided into two functionally relevant subsets, as indicated by the expression of the T4 and T8 antigens. To determine whether one or both of these T cell subsets is capable of generating macrophage activating factor(s) (MAF) after stimulation with lectin, soluble antigen, or cell surface alloantigen, highly purified populations of T4 or T8 cells were cultured in medium containing PHA, tetanus toxoid-soluble antigen, or allogeneic B lymphoblastoid cells. The resultant culture supernatants were tested for the presence of MAF activity, as manifested by the activation of human peripheral blood monocytes to perform enhanced cytotoxicity and cytostasis against a murine tumor cell line, or to perform antibody-dependent cytotoxicity against anti-RhD-coated human erythrocytes. Both isolated T4 or T8 cells were able to produce MAF activity after stimulation with either PHA or alloantigens, but only the T4 subset generated MAF in response to stimulation with tetanus toxoid. These results coincide with the proliferative capacity of the isolated T subsets to respond to the same stimulators, and demonstrate that the ability to generate MAF lymphokines is not subset restricted.

Cell Line↗
PubMed1980

Field desorption mass spectrometry of cyanogenic glycosides.

The field desorption mass spectra of several underivatized cyanogenic glycosides exhibit molecular ions or ions derived from the parent compound by protonation and alkali metal cationization. Abundant fragment ions are present and can be readily related to structure. Significant deviations from established fragmentation pathways are observed due to the nature of the aglycone. The ability to successfully determine the presence of cyanogenic glycosides by field desorption is demonstrated in crude extracts isolated from Vicia sativa, a food-contaminating plant material.

Crystallization↗
PubMed1980

Container-derived contamination of maple sirup with methyl methacrylate, toluene, and styrene as determined by headspace gas-liquid chromatography.

Samples of maple sirup and associated plastic packaging were examined for the presence of methyl methacrylate, toluene, and styrene by a head space gas chromatographic procedure. The volatile components common to the sirup and the plastic container were identified by gas chromatography-mass spectrometry. The quantities of these contaminants in the sirup were determined at ppb levels by the standard additions technique and repetitive headspace analysis.

Chromatography, Gas↗
PubMed1978

Gas-liquid chromatographic determination of chlorinated norbornene derivatives in fish.

1,2,3,4,7,7-Hexachloro-2,5-norbornadiene (I), 1,2,3,4,5-endo,7,7-heptachloro-2-norbornene (II), and 1,2,3,4,7,7-hexachloro-5,6-endo-epoxy-2-norbornene (III) have been identified as contaminants in Mississippi River fish by combined gas-liquid chromatography (GLC)-mass spectrometry. The method used to determine residues of these compounds, which are associated with production of the pesticide endrin, is similar to the AOAC multiresidue method for chlorinated pesticides. The residues are extracted from the sample with acetonitrile, transferred to petroleum ether, and chromatographed on a Florisil column. Compounds I and II are eluted from the Florisil with petroleum ether and compound III is eluted with ethyl ether-petroleum ether (6 + 94). The concentrated eluates are analyzed by using electron capture GLC. The method provides adequate recoveries of all 3 chlorinated norbornene derivatives and allows quantitation at or below the 0.05 ppm level in fish with a 20 mg sample equivalent injection.

Animals↗
PubMed1978

Headspace sampling and gas-solid chromatographic determination and confirmation of greater than or equal to 1 ppb vinyl chloride residues in polyvinyl chloride food packaging.

The determination and confirmation of residual vinyl chloride (VC) in polyvinyl chloride (PVC) food packaging materials are described. PVC packaging materials are dissolved in dimethylacetamide (DMAC). VC is sparged from solution with helium gas and collected in sealed vials of ethanol. VC is detected and quantitated by using a headspace sampling technique and standard gas-solid chromatography (GSC) with flame ionization detection. GSC peak heights of about 5% full scale deflection are obtained for samples of PVC containing 1 ppb VC. Polymer samples taken from tubing, blood bags, food packaging films, bottles, and unprocessed resin were analyzed. Residual VC levels ranged from 0.3 to 913 ppb. VC was confirmed by GSC-mass spectrometry, using selected ion recording of m/z 62 and 64 in conjunction with full mass scans to identify components eluting near VC.

Chromatography, Gas↗
PubMed1977

Determination of urethane in wines by gas-liquid chromatography and its confirmation by mass spectrometry.

A gas-liquid chromatographic (GLC)-mass spectral (MS) method for the determination and confirmation of urethane in wines has been developed. Analyses of domestic and imported wines indicated urethane to be present at levels ranging from 1 to 20 microng/L. Recoveries of urethane from wines fortified at 10 ppb (microng/L) ranged from 50 to 100% with an average value of 71%. GLC-MS was used to confirm the identity of urethane in wine extracts in which GLC indicated the presence of urethane.

Chromatography, Gas↗
PubMed1977

Mass spectral coding technique for identification of drugs and related compounds in reference compendia.

A modification of the spectral abbreviation technique originally described by Hites and Biemann is proposed for identifying compounds through a coding of mass spectral data. Data from 2 closely related compounds (trimethadione and paramethadione), acquired by using 3 instruments, are presented. The technique appears to overcome observed differences in low resolution spectra when the same compound is analyzed by electron impact on mass spectrometers differing in design, manufacturer, principle of ion separation,, and operator. A list of spectra coded by this technique could constitute a rapid manual system of reproducing mass spectral data, using the significant high mass ions of low abundance as well as the frequently more abundant lower mass ions. This system is compared with existing systems.

Formularies as Topic↗
PubMed1977

Determination of vinylidene chloride in Saran films by electron capture gas-solid chromatography and confirmation by mass spectrometry.

A method is presented for determining vinylidene chloride (VdC) in Saran food packaging films by using electron capture gas-solid chromatography. The VdC present was confirmed by combined gas-solid chromatography-mass spectrometry, employing selected ion recording. The method is capable of detecting larger than or equal to 5 ppm VdC in films. Production lots of Saran film were analyzed and found to contain 6-30 ppm VdC.

Chromatography, Gas↗
PubMed1976

Excretion of hydroxylated polychlorinated biphenyl metabolites in cows' milk.

Four lactating Holstein cows were each given a single oral dose of either 0.5 g 2,5,2',5'-tetrachlorobiphenyl, 0.5 g 2,5,2',4',5'-pentachlorobiphenyl, 1.5 g Aroclor 1242, or 1.5 g Aroclor 1254 in gelatin capsules. Milk samples were collected twice daily at the am and pm milkings and were analyzed for polychlorinated biphenyl (PCB) metabolites and PCBs. Excretion of metabolites in the milk paralleled excretion of the parent PCBs, with maximum amounts eliminated 1 day after dosing. Less than 0.06% of the initial doses of the 2 single components appeared as metabolites in milk over a period of 10 days. Most of the metabolites occurred as conjugates. Only the 4-hydroxy metabolites were found in the milk of cows given single components. Milk samples from cows given Aroclor 1242 or Aroclor 1254 contained 10 and 4 monohydroxy metabolites, respectively. Using the same methodology, no monohydroxy metabolites were detected in whole milk samples from herds accidentally contaminated with a polybrominated biphenyl mixture.

Animals↗