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Biomedical subjects

J C Phillips

Publications and source records attributed to J C Phillips.

At least 73 records · Page 4Linked to original sources
PubMed1980

Substrates and inhibitors of hepatic amine oxidase inhibit dimethylnitrosamine-induced mutagenesis in Salmonella typhimurium.

The mutagenic effect of dimethylnitrosamine in Salmonella typhimurium TA100, in the presence of a rat-liver homogenate derived from animals treated with Aroclor 1254, was inhibited by substrates and inhibitors of monoamine oxidase. Substrates of diamine oxidase did not inhibit dimethylnitrosamine mutagenesis and, furthermore, monoamine oxidase inhibitors had no effect on mutagenesis by benzo[a]pyrene or aflatoxin B1. The results suggest that monoamine oxidase participates in the activation of dimethylnitrosamine to a mutagen.

Animals↗
PubMed1980

White lines in L-edge x-ray absorption spectra and their implications for anomalous diffraction studies of biological materials.

We have measured high-resolution x-ray absorption spectra of lanthanide (Ln) and heavy transition metal complexes that display prominent narrow absorption peaks near the L2 and L3 absorption edges. The anomalous scattering factors (f' and f"), which are mathematically related to the absorption cross section, have correspondingly sharp changes in their magnitude within 5-10 eV of the absorption edge. Calculations of the magnitude of the change in f' and f" demonstrate that significant changes (on the order of 20 electrons in f') can be expected for these materials. These substantial changes in the anomalous scattering factors have applications to deriving structural information for macromolecules from x-ray diffraction studies. The magnitude of the changes indicate that the anomalous scattering technique is a powerful means of obtaining structural characteristics for macromolecules in single crystals, in solution, and in biological membranes.

Crystallography↗
PubMed1980

Problems in radioimmunoassay of human lutropin with commercially available reagents.

To evaluate five commercially available reagent sets supplied for the radioimmunoassay of lutropin, we determined whether there was parallelism between the curve given by dilutions of the standards supplied by the manufacturers, by dilutions of a serum pool, and by dilutions of a standard preparation from human pituitaries, LER-907. These studies demonstrated significant analytical problems with three of the five sets. We conclude that each user should carefully evaluate all commercially available radioimmunoassays for lutropin (and, by inference, for other peptide hormones) before use.

Humans↗
PubMed1978

Studies on the gastrointestinal absorption of N-nitrosamines: effect of dietary constituents.

Studies on the intestinal absorption of N-nitrosodimethylamine (DMN) in the rat have shown that the presence of dietary constituents such as fat markedly reduced the rate of disappearance of this nitrosamine whereas the presence of protein and carbohydrate had little effect on the absorption rate. Fat was also found to reduce the absorption rate of N-nitrosodiethylamine (DEN), N-nitrosopyrrolidine (NPY) and N-nitrosopiperidine (NPIP). Further it was confirmed that the small-intestinal tract of the rat has the ability to degrade DMN. The implications of these findings are discussed in terms of the biological fate of orally ingested nitrosamines.

Animals↗
PubMed1978

Evaluation of an aqueous fluorometric continuous-flow method for measurement of total urinary estrogens.

Measurement of urinary estrogen excretion is used extensively to monitor fetal welfare in utero, allowing the fetus at risk to be identified. We evaluated a direct all-aqueous fluorometric method adapted to a continous-flow (AutoAnalyzer I) system, using a spectrofluorophotometer for detection. In this method, which is based on a modified Kober reaction, NaBH4 is used to eliminate the known negative interference of glucose. The mean analytical recovery was 98%. Urines from 15 men showed no blank fluorescence. Comparison studies of the fluorometric method (x) and a manual method based on the Kober/Ittrich reaction (y) yielded the equation y = 1.53x + 4.38 (r = 0.9235). The incomplete correlation can be explained by erratic extraction in the manual Kober/Ittrich procedure (mean recoveries were 57%). A day-to-day precision (CV) of 5.2% can be achieved with the automated method. Samples are analyzed at a rate of 20 per hour, but this rate can be doubled, if necessary, without significant carryover problems. We conclude that the automated fluorometric method is accurate, precise, and inexpensive and therefore the method of choice for measuring urinary estrogens.

Autoanalysis↗
PubMed1977

Epidural analgesia and its effects on the "normal" progress of labor.

The effects of epidural analgesia on the duration of labor have been a controversal subject since its increased use in recent years. A total of 598 patients receiving this form of analgesia were studied as to progress in labor and eventual outcome. The mean cervical changes during epidural analgesia with a single drug, bupivacaine, 0.125%, with epinephrine, 1:200,000, have been calculated. The labor curves are characterized by constant acceleration in dilatation without deceleration at approximately the same rate for nulliparous and multiparous patients after dilatation of 5 cm. has been reached. Examination of maternal and fetal profiles failed to demonstrate any consistent variables that produce abnormal labor.

Anesthesia, Epidural↗
PubMed1977

Studies of the metabolic fate of p-hydroxybenzoic acid in male and female cats.

Metabolic studies conducted on p-hydroxybenzoic acid orally administered at dose levels of 13 and 26 mg/kg to male and female cats have shown that the compound is rapidly excreted in the urine exclusively in the form of the glycine conjugate p-hydroxyhippuric acid. Similar results were obtained following either single administration or 7-day treatment. The metabolite in the urine was characterised by thin-layer chromatography, amino acid analysis and mass spectrometry.

Amino Acids↗