Transient Nature of a (1 --> 3), (1 --> 4)-beta-d-Glucan in Zea mays Coleoptile Cell Walls.

Excised Zea mays L. embryos were cultured on Linsmaier and Skoog medium. Coleoptiles were sampled at regular intervals and the length, fresh weight, cell wall weight, and cell wall neutral sugar composition were determined. A specific beta-d-glucanase from Bacillus subtilis was used to determine the content of a (1 --> 3),(1 --> 4)-beta-d-glucan.Coleoptiles elongated through the 5th day following imbibition with the most rapid elongation occurring between days 3 and 4. The greatest net rate of incorporation of cell wall per coleoptile occurred between the 2nd and 3rd days when deposition of approximately one-third of the maximum net glucan level was observed. By day 5, the amount of glucan present had increased 34-fold from the 6 micrograms per coleoptile on day 1 and accounted for about 14% of the cell wall (w/w). Thereafter, the glucan content declined until only 3.3% (w/w) remained by day 10. In this 10-day interval, xylose increased 32% and cellulose content doubled, while proportions of other neutral sugars changed less dramatically.These results are consistent with a possible role for the beta-d-glucan in elongation of the Zea coleoptile. Moreover, changes in the quantity of this wall component clearly reflect the dynamic nature of plant cell wall polysaccharides. An evaluation of glucan dynamics in vivo suggests that in vitro autolysis studies employing Zea coleoptile walls may overestimate the actual rate of glucan turnover in the intact tissue.

Selectivity in modification of the fatty acid composition of normal mouse tissues and membranes in vivo.

The fatty acid composition of five normal tissues and purified liver plasma membranes of the mouse was modified by feeding diets rich in either coconut or sunflower oil. The phospholipids from the animals fed the coconut oil diets were enriched in monoenoics, and those from the mice fed the sunflower oil diet contained large percentages of polyenoics. Most importantly, there were differences in the extent and type of modification in each tissue. For example, the phospholipids of the heart from animals fed the sunflower oil diet contained 21% docosapentaenoate compared to less than 6% in other tissues. The bone marrow from animals fed the coconut oil diets contained a high proportion of saturates, including those of medium chain length. The fatty acyl composition of the neutral lipids was also modified, but in some cases the degree of alteration differed from that occurring in the phospholipids. Purified liver plasma membranes demonstrated diet-induced changes but contained smaller amounts of arachidonate, and those from the animals fed sunflower oil diets were less polyunsaturated compared to whole liver phospholipids. We conclude that the modification of fatty acid composition of normal tissues induced by experimental diets differs in extent and type. Furthermore, the liver plasma membrane composition is different from that of liver phospholipids. The differences in the extent and type of modification demonstrate selectivity amongst normal tissues.

Fatty acid positional specificity in phospholipids of L1210 leukemia and normal mouse lymphocytes.

The positional distribution of fatty acids in the choline and ethanolamine phosphoglycerides of the L1210 murine leukemia cells was determined and compared to that of normal mouse lymphocytes. The major phospholipids of both cell types had appreciable degrees of positional specificity as evident from the higher percentage of saturated fatty acids in position 1 and of polyunsaturated fatty acids in position 2. The L1210 cells had less arachidonate and more linoleate in position 2 of choline and ethanolamine phosphoglycerides as compared to the normal lymphocytes. However, there were similar proportions of saturated, monoenoic and polyenoic fatty acids in positions 1 and 2 of the phospholipids of the L1210 leukemia cells and the lymphocytes, These data demonstrate that fatty acid positional specificity is retained in the major phospholipids of this rapidly growing tumor.

Effect of dietary fat saturation on survival of mice with L1210 leukemia.

We examined L1210 murine leukemia growth rate and survival of host male DBA/2J mice fed a diet rich in either polyunsaturated fat (16% sunflower oil) or saturated fat (16% coconut oil). The survival of mice that received transplants of L1210 leukemia cells was longer among the animals that had ingested a diet rich in the saturated fat as compared to those fed the more unsaturated fat. In duplicate experiments, the mean survivals of mice fed coconut oil were 200.9 +/- 1.6 and 202.5 +/- 3.4 hours compared to 188.7 +/- 5.3 and 187.6 +/- 3.5 hours for those fed sunflower oil. Tumor growth rate or the rate of DNA synthesis by the leukemia cells did not differ between the two experimental groups. Therefore, the alteration in survival was apparently due to an effect of the diets on the responses of the hosts rather than their effect on tumor size or growth rate.