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Biomedical subjects

G Y Sun

Publications and source records attributed to G Y Sun.

At least 163 records · Page 9Linked to original sources
PubMed1976

Changes in phospholipids and acyl group composition of rat mammary gland during pregnant, lactating, and post-weaning periods.

The distribution of phospholipids as well as their fatty acid compositions of rat mammary tissues were examined during pregnant, lactating, and post-weaning periods. There was no apparent change in phospholipids and their acyl groups during the early and late pregnant periods. However, tissue phospholipid composition was different during pregnant, early, and late lactating periods. After parturition, there was a marked increase in the proportion of diacyl-glycerophosphorylcholine in the phospholipids of mammary tissue, but this proportion decreased gradually during lactation. The decrease in diacyl-glycerophosphorylcholine during lactation was marked by a corresponding increase in diacyl-glycerophosphorylethanolamie. Although the shorter chain fatty acids of triglycerides were increased during lactation, only a small proportion of these fatty acids was found in the phosphoglycerides. Marked changes in acyl group composition of individual phospholipids are found during these different physiological stages. In general, there was a rapid decrease in 20:4 and an increase in 18:2 in the major phosphoglycerides during parturition. The proportion of 20:4 in the phosphoglycerides remained low throughout the entire lactating period, while that of 18:2 continued to increase 2-3 fold. Most of the changes in acyl group of the phosphoglycerides during lactation returned to normal ca. 10 days after weaning. A possible relationship of the variation of phospholipid and acyl group compositions in mammary tissue to changes in hormonal pattern during different physiological stages is discussed.

Animals↗
PubMed1976

Acyl group composition of membrane phospholipids in mammary tissues and carcinoma induced by dimethylbenz(a)anthracene.

Phospholipids and their acyl group composition in mammary adenocarcinomas and mammary tissue of the same tumor-bearing animals were investigated. Breast adenocarcinoma induced by dimethybenz(a)anthracene exhibited a phospholipid pattern which was different from that of the mammary tissue. Tumor phospholipids had higher proportions of diacyl-GPI, diacyl-GPE, and alkenylacyl-GPE and a lower proportion of diacyl-GPC than the controls. The acyl groups of most phospholipids in tumors showed a marked increase in the proportion of 18:1 and a decrease in the proportion of 18:2. The fatty acid composition of plasmalogen and triglyceride, however, remained unchanged. In spite of the decrease in the proportion of 18:2, there was no apparent difference in the proportion of 20:4 in most of the phosphoglycerides; however, a significant decrease in this fatty acid was noted in diacyl-GPI. Results of this study demonstrated that the membrane phospholipids of mammary adenocarcinoma were altered in respect to acyl group composition. Changes in physical properties of the cell membrane, in turn, could lead to abnormal manifestation of membrane regulated events in tumor cells.

Adenocarcinoma↗
PubMed1974

Phospholipids and acyl groups of subcellular membrane fractions from human intracranial tumors.

The phospholipids from subcellular fractions of human intracranial tumors were examined. For comparison, microsomes were isolated from a fetal human brain and from the gray matter of adult human brains. The subcellular membranes of tumors had a higher protein-to-phospholipid ratio than the normal brain membranes. The microsomes from tumors had a lower proportion of diacylglycerophosphorylethanolamine and higher proportions of alkenylacylglycerophosphorylcholine and sphingomyelin (plus diacylglycerophosphorylinositol) than microsomes from the gray matter. Also, the ratios of alkenylacylglycerophosphorylethanolamine to diacylglycerophosphorylethanolamine were higher in the tumors than in the normal controls. The acyl groups of ethanolamine phosphoglycerides in tumor microsomes had relatively more 18:1, 18:2, and 20:4(n - 6) and less 18:0, 22:4(n - 6), and 22:6(n - 3) than the adult brain gray matter. Except for the increase in 18:2, acyl group changes in choline phosphoglycerides between tumors and controls were not as extensive as in the ethanolamine phosphoglycerides. The characteristic features of phospholipids and their constituent acyl groups of tumors were often present in all the subcellular fractions. Although the acyl group profiles of the tumor phosphoglycerides were in closer resemblance to the fetal brain than to the adult brain, other differences were observed. Results indicate that neoplastic brain cells are unique in their cellular composition, and consequently they deviate from the normal neurons and glials in metabolism and functions.

Adult↗
PubMed1973

Metabolism of palmitic acid in the subcellular fractions of mouse brain.

After an intracerebral injection of [(14)C]palmitic acid to C57BL/10J mice, the radioactivity in the brains decreased rapidly with time. The incorporated radioactivity was primarily in the 16:0 acyl groups of the diacyl phosphoglycerides at 1 and 3 days after injection. At longer times, increasing proportions of the radioactivity were found in cerebrosides, alkenyl groups, and other acyl groups. The specific radioactivities of the phosphoglycerides were highest in the microsomal fraction at 1 day after injection. The exchange of the diacyl glycerophosphorylcholines and diacyl glycerophosphorylethanolamines between the microsomes and the myelin required 8-14 days. When calculated on the basis of the radioactivity in the 16:0 acyl groups, the half-lives for both of these phosphoglycerides were 6-8 days in all subcellular fractions during the period from 14 to 30 days after injection. The radioactivity in the total lipids from the purified myelin fraction did not decline until more than 14 days after injection because of the reutilization of labeled 16:0 acyl groups for lipid biosynthesis. Recycling of the acyl groups explains the long half-lives reported for myelin phosphoglycerides after injection of [(14)C]acetic acid. Lipids with a relatively high specific radioactivity were lost from the myelin fraction during the purification procedure. The most likely source of these lipids is the most recently formed myelin that is not consolidated into the myelin sheath.

Acylation↗
PubMed1973

Phospholipids and acyl groups in subcellular fractions from human cerebral cortex.

Subcellular fractionation of human brain cortex obtained at autopsy yielded microsomal and synaptosome-rich fractions from the gray matter and microsomal and purified myelin fractions from the white matter. The phospholipids of myelin were high in plasmalogens, and the molar ratio of alkenyl acyl sn-glycero-3-phosphorylethanolamine to diacyl sn-glycero-3-phosphorylethanolamine was 4. The acyl groups of the myelin phosphoglycerides were enriched in monoenes (mainly 18:1 and 20:1) and a tetraene, 22:4(n - 6). The phospholipids in the synaptosome-rich fraction were high in diacyl sn-glycero-3-phosphorylcholine, and the molar ratio of the alkenyl acyl sn-glycero-3-phosphorylethanolamine to diacyl sn-glycero-3-phosphorylethanolamine was 0.88. The acyl groups of synaptosomal ethanolamine phosphoglycerides were rich in 22:6(n - 3) but contained a very low amount of 20:1. The lipid composition of microsomes from the gray matter was different from that of microsomes from the white matter but was nearly identical with that of the synaptosome-rich fraction. Except for a slightly lower proportion of alkenyl acyl sn-glycero-3-phosphorylethanolamine and sphingomyelin, the lipid composition of microsomes from the white matter was also similar to that of the myelin. There were also species-related differences between the brain lipid composition of human and subhuman primates and that of the rodents. Furthermore, the brain lipid composition in normal human subjects is rather constant and does not seem to be affected much by individual variations.

Aged↗
PubMed1972

Effects of a fatty acid deficiency on lipids of whole brain, microsomes, and myelin in the rat.

The lipid compositions of whole brain homogenates and microsomal and myelin fractions isolated from the brains of 6-month-old rats raised on a lab chow diet, a fatty acid-deficient diet, and a deficient diet supplemented with 5% (w/w) corn oil were determined. Brain and body weights were significantly lower in the fatty acid-deficient group. The compositions of alk-1-enyl groups and phospholipids of whole brain homogenates of rats maintained on the three diets were not different. However, marked alterations were found in the acyl group compositions of the major phosphoglycerides from whole brain homogenates and from the myelin and microsomal fractions of rats maintained on the fatty acid-deficient diet. With the deficient diet, 20:3(n - 9) was found in the major phosphoglycerides as well as in the myelin and microsomal fractions. In addition, the levels of 20:4(n - 6) and 22:4(n - 6) were decreased. The levels of 20:4(n - 6), 22:4(n - 6), and 22:5(n - 6) were higher in the brain phosphoglycerides of rats maintained on the corn oil-supplemented diet than on the lab chow control diet, and the elevation in these acyl groups was more evident in the microsomal fraction than in the myelin fraction.

Alkenes↗