Effect of soy-based breakfast cereal on blood lipids and oxidized low-density lipoprotein.

Consumption of soy protein may reduce the risk of cardiovascular disease both through reduction in serum lipids and by the antioxidant properties of protein-associated soy isoflavones. However, the effect that processing required for the manufacture of breakfast cereals may have on the lipid lowering and antioxidant activities of soy has not been studied. We have therefore assessed the health benefits of soy incorporation into breakfast cereals. Twenty-five hyperlipidemic men and women took soy (providing 36 g/d soy protein and 168 mg/d isoflavones) and control breakfast cereals, each for 3 weeks in a randomized crossover study with a 2-week washout period between treatments. Fasting blood samples were obtained pretreatment and at weeks 2 and 3 of each treatment. No significant difference was seen in serum lipids between treatments at week 3 apart from a 3.8% +/- 1.5% higher apolipoprotein A-1 level on control versus soy (P = .021). However, oxidized low-density lipoprotein (LDL) was reduced on the test compared with the control both as total dienes in LDL and as the ratio of conjugated dienes to cholesterol in the LDL fraction by 9.2% +/- 4.3% (P = .042) and 8.7% +/- 4.2% (P = .050), respectively. High isoflavone intakes in soy breakfast cereals may decrease the risk of cardiovascular disease by reducing oxidized LDL, while having no significant effect on the absolute concentration of LDL cholesterol.

Protein metabolism in leaves and developing grains of rices differing in grain protein content.

Four semi-dwarf rices (Oryza sativa L.) differing in percentage of grain protein, grown in a flooded field receiving basal N fertilization, had a peak activity of root glutamate dehydrogenase 4 weeks after transplanting. A lower peak occurred during panicle formation 10 weeks after transplanting. The percentage of N of the active leaf blades was also highest 4 weeks after transplanting. The activity of nitrate reductase in the leaf blades was low and decreased after transplanting.Among the three rices with similar grain yield, the rice with high percentage of protein tended to translocate more leaf N to the developing grains than the rices with average grain protein content. The leaf blades of the former also had lower rates of leucine incorporation during grain development but higher protease activity than leaves of the rices with average protein content. Developing grains of the rices with high percentage of protein tended to have higher levels of soluble protein, free amino N, and protease, and a faster rate of leucine incorporation than grains of the IR3 rice with average percentage of protein, regardless of grain yield.

Biochemical factors affecting protein accumulation in the rice grain.

Rice grains (Oryza sativa L.) from three varieties and three pairs of lines with different protein content were collected at 4-day intervals from 4 to 32 days after flowering. The samples were analyzed for protein, free amino nitrogen, ribonucleic acid, protease activity, and ribonuclease activity. In addition, the capacity of the intact grain to incorporate amino acids was determined for the three pairs of lines. The maximal level of free amino nitrogen and the capacity of the developing grain to incorporate amino acids were consistently found to be higher in the samples with the high protein content in the mature grain. The ribonucleic acid content of the grain tended to be higher in the high protein samples.

Ribonuclease Activity in Normal, opaque-2, and floury-2 Maize Endosperm during Development.

The elevated ribonuclease activity produced in the endosperm of a maize (Zea mays L.) inbred, W64A, by homozygous opaque-2, results from a more than doubled rate of ribonuclease accumulation occurring prior to 16 days post-pollination; after 16 days the rates in opaque-2 and normal are the same, suggesting that opaque-2 is no longer active. The pattern of ribonuclease increase in the opaque-2 dosage series indicates that opaque-2 is not fully recessive. Ribonuclease accumulation is not affected by floury-2 in a second inbred, B14. The results are discussed with reference to other proteins, notably zein, the net synthesis of which is affected by opaque-2.