Effects of a carotene-deficient diet on measures of oxidative susceptibility and superoxide dismutase activity in adult women

The effect of consuming a low carotene diet (≈60 μg carotene/day) on oxidative susceptibility and superoxide dismutase (SOD) activity in women living in a metabolic research unit was evaluated. The diet had sufficient vitamins A, E, and C. The women ate the diet supplemented with 1500 μg/day β-carotene for 4 days (baseline), then the unsupplemented diet for 68 days (depletion), followed by the diet supplemented with > 15,000 μg/day carotene for 28 days (repletion). Production of hexanal, pentanal, and pentane by copper-oxidased plasma low density lipoproteins from carotene-depleted women was greater than their production of these compounds when repleted with carotene. Erythrocyte SOD activity was depressed in carotene-depleted women; it recovered with repletion. Thiobarbituric acid reactive substances in plasma of carotene-depleted women were elevated and diminished with repletion. Dietary carotene seems to be needed, not only as a precursor of vitamin A, but also to inhibit oxidative damage and decrease oxidation susceptibility.     

A rapid and sensitive method to measure the enzymatic activity of ribosome-inactivating proteins.

A method is described in which the adenosine- N -glycosidase activity of ribosome-inactivating proteins (RIPs) is measured using as substrate a 2251 bp [3H]DNA obtained by PCR amplification of the 731-2981 region of the pBR322 plasmid. The DNA, labelled in the purine ring of adenine, proved a good substrate for all three RIPs tested (PAP-S, ricin and shiga-like toxin I). The method, which measures directly the [3H]adenine released, is highly specific, extremely rapid and quantitative in a wide range of RIP concentrations.     

Effects of plant ribosome-inactivating proteins on ribosomes from Musca domestica.

1. Ribosomes from M. domestica larvae were isolated and their susceptibility to the action of several ribosome-inactivating proteins (RIPs) from plants was tested. 2. Ribosome-inactivating proteins inhibited, to different extents, phenylalanine polymerization by ribosomes. 3. Analysis of RNA from RIP-treated ribosomes showed the appearance of an aniline-cleavable rRNA fragment resulting from the N-glycosidase activity of the RIPs. 4. The release of adenine from saporin 6-treated M. domestica ribosomes was demonstrated by h.p.l.c. analysis.     

Effects of chorda tympani nerve anesthesia on taste responses in the NST

Human clinical and psychophysical observations suggest that the taste system is able to compensate for losses in peripheral nerve input, since patients do not commonly report decrements in whole mouth taste following chorda tympani nerve damage or anesthesia. Indeed, neurophysiological data from the rat nucleus of the solitary tract (NST) suggests that a release of inhibition (disinhibition) may occur centrally following chorda tympani nerve anesthesia. Our purpose was to study this possibility further. We recorded from 59 multi- and single- unit taste-responsive sites in the rat NST before, during and after recovery from chorda tympani nerve anesthesia. During anesthesia, average anterior tongue responses were eliminated but no compensatory increases in palatal or posterior tongue responses were observed. However, six individual sites displayed increased taste responsiveness during anesthesia. The average increase was 32.9%. Therefore, disinhibition of taste responses was observed, but infrequently and to a small degree in the NST At a subset of sites, chorda tympani-mediated responses decreased while greater superficial petrosal-mediated responses remained the same during anesthesia. Since this effect was accompanied by a decrease in spontaneous activity, we propose that taste compensation may result in part by a change in signal-to-noise ratio at a subset of sites.