Acyl group composition of lipids and the activities of (Na+ + K+)-ATPase, 5′-nucleotidase and γ-glutamyltranspeptidase in salivary glands and kidneys of rats fed diets containing different dietary fats

Two nutritional models, an essential fatty acid deficiency model and the feeding of saturated versus unsaturated fats, were used in a feeding study in order to assess the relationship between tissue fatty acid composition and the activities of some membrane-associated enzymes. Purified diets containing 7% hydrogenated coconut, oil, 7% corn oil, 10% safflower oil or butter were fed to rats for a total of 49 weeks (1 week of pregnancy, 3 weeks of lactation and 45 weeks post-weaning). Tissue homogenates from submandibular salivary glands and kidneys were analyzed for fatty acid composition of total lipids and phospholipids. Changes in fatty acid patterns typical of essential fatty acid deficiency such as an increase in the levels of 16:1 and 18:1, a decrease in 18:2 and 20:4 and an accumulation of 20:3ω9 were observed in salivary glands and kidneys of rats fedd the deficient diet. Tissues of rats fed 10% butter also showed fatty acid compositional changes which were somewhat similar to those in essential fatty acid deficiency, but to a lesser degree. The activities of ouabain-sensitive (Na⁺ + K⁺)-ATPase were higher in homogenates of salivary glands and kidneys of the deficient rats and those fed butter as compared with their controls. The results suggest a relationship between the double bond index of fatty acids as an indication of membrane lipid fluidity and allosteric modification of (Na⁺ + K⁺)-ATPase activity. However, other explanations for the observed changes in (Na⁺ + K⁺-ATPase activity cannot be ruled out. There were no diet-related differences in the activities of γ-glutamytranspeptidase or 5′-nucleotidase.     

Application of neural networks to automated assignment of NMR spectra of proteins

Summary Simulated neural networks are described which aid the assignment of protein NMR spectra. A network trained to recognize amino acid type from TOCSY data was trained on 148 assigned spin systems from E. coli acyl carrier proteins (ACPs) and tested on spin systems from spinach ACP, which has a 37% sequence homology with E. coli ACP and a similar secondary structure. The output unit corresponding to the correct amino acid is one of the four most activated units in 83% of the spin systems tested. The utility of this information is illustrated by a second network which uses a constraint satisfaction algorithm to find the best fit of the spin systems to the amino acid sequence. Application to a stretch of 20 amino acids in spinach ACP results in 75% correct sequential assignment. Since the output of the amino acid type identification network can be coupled with a variety of sequential assignment strategies, the approach offers substantial potential for expediting assignment of protein NMR spectra.     

Triglyceride Interesterification by Lipases: 2. Reaction parameters for the reduction of trisaturated impurities and diglycerides in batch reactions

A model system consisting of pure triolein and palmitic acid and LipozymeTM, an immobilized lipase (E.C. 3.1.1.3.). has been used to determine the effects of various reaction parameters on the reaction rate and the formation of by-products in the interesterification reaction. The goal was to minimize the level of diglycerides and eliminate trisaturated triglycerides at an endpoint chosen so that the results could be applied to the production of cocoa butter substitutes. The levels of diglycerides, which are essential reaction intermediates, and trisaturated glycerides, which are believed to be formed as a result of spontaneous acyl migration of mono- and diglyceride intermediates, were determined at a defined endpoint. A lag period was observed in which no tripalmitate was formed. The content of Lipozyme used was the most powerful factor in eliminating tripalmitate formation and reducing diglycerides; by using large quantities of Lipozyme, the reaction reached the endpoint before the tripalmitate formation became measurable and low levels of diglycerides were formed. The effects of varying the ratio of palmitic acid to triolein were investigated. A complex relationship between the ratio of substrate components emerged in which the diglyceride content increased with increasing triolein concentration and the tripalmitate content was lowest at a molar ratio of palmitic acid to triolein of 3.5. The reaction was run at 70, 80, and 90°C; best results were obtained at 70°. The water activity of the reaction was adjusted prior to catalysis and maintained during the reaction by equilibrating the reaction mixture and enzyme and running the reaction in an atmosphere of controlled water activity. A direct relationship between diglycerides and water activity was observed, and the level of tripalmitate formed corresponded to the time required to reach the endpoint. The reaction system was tested using ethyl palmitate instead of palmitic acid as acyl donor; the diglyceride content again increased with increasing water activity, but larger amounts of diglycerides were formed. Much shorter reaction times were required, with small quantities of tripalmitate formed.     

The effect of some oligo-amines and -guanidines on membrane permeability in higher plants

The effect of a series of oligo-amines and -guanidines on the membranes of higher plants has been tested by measuring the efflux of betacyanin from beet root discs, and the loss of total ions from beet root and swede discs, beet and spinach leaf discs and apple cells in suspension culture. All of the naturally occurring di- and polyamines tested showed relatively little toxicity. Betacyanin efflux from beet root discs was reduced by diamines [NH₂(CH₂)_xNH₂] up to x = 10 or less. Ion efflux was minimal at x = 7. Within the triamine series [NH₂(CH₂)_xNH(CH₂)₃NH₂] for x = 8 or less, betacyanin efflux was reduced or unaffected, although total ion loss was increased by the triamines when x = 4 or more and especially by the longer chain amines (to x = 10). Similar behaviour was found in the tetra-amine series [NH₂(CH₂)₃NH(CH₂)_xNH(CH₂)₃NH₂] with betacyanin efflux reduced for x = 2–4 (spermine). Although spermine potentiated the toxicity effects of Guazatine {[NH₂C(NH)NH(CH₂)₈]₂NH} and Dodine [NH₂C(NH)NH(CH₂)₁₁,Me] in beet root discs, spermine and calcium ions reduced the ion efflux caused by these toxic guanidines and also by Synthalin B [NH₂C(NH)NH(CH₂)₁₂NHC(NH)NH₂] in swede discs, spinach leaves and apple cells. No significant reversal of ion loss was detected with putrescine, cadaverine or spermidine in swede discs. In the homologous series of monoguanidines [NH₂C(NH)NH(CH₂)_x?1Me] for x up to 18, greatest toxicity was shown for x = 10 and 11 in both betacyanin loss and total ion efflux in beet root discs. Greatest ion efflux from the apple cell suspension was found with x = 11 and 12. In the homologous series of diguanidines [NH₂C(NH)NH(CH₂),NHC(NH)NH₂] for x = 2–12 greatest toxicity was shown for x = 12 (the longest chain tested) in beet root and in the efflux of ions from apple cell suspension. Technical Guazatine was considerably more phytotoxic than pure Guazatine in all systems tested. p-Chloromercuribenzoate (p-CMB) potentiates the loss of betacyanin and total ions caused by Guazatine, Synthalin B, and Dodine in beet root discs. This effect of p-CMB is reversed by subsequent incubation in cysteine or mercaptoethanol, prior to treatment with the guanidines.     

Calcium modifies Cd effect on runner bean plants

The effect of different Ca concentrations in the growth medium on the toxicity of 25 μM CdSO₄ was studied in runner bean plants (var. Pi kny Ja ) at two different growth stages of primary leaves. In young plants growing in a medium with low level of Ca a treatment with Cd for 12 days resulted in Ca accumulation in roots, a strong reduction of the leaf area, a decreased monogalactosyl diacylglycerol/digalactosyl diacylglycerol ratio and efficiency of the photosynthetic apparatus. In leaves of older plants growing under the same conditions, and surviving Cd treatment, a high accumulation of Ca but a low one of Cd, chlorosis of leaves, a decrease of the ratio monogalactosyl diacylglycerol/digalactosyl diacylglycerol and photosynthetic activity were shown. At a high level of Ca in the nutrient medium plant roots showed a remarkably high specificity to accumulate Cd but the toxic effect of the metal on plant growth parameters and content of pigments was decreased. No changes were observed in the level of galactolipids, but changes in fluorescence quenching were recorded. Calcium deficit enhanced the effect of Cd toxicity, including primary photochemistry, whereas excess Ca reduced toxic effects, while it is increasing the nonphotochemical quenching of excitation energy.