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A study of the lactating dairy cows maintained under stringently regulated environmental conditions through radioimmunoassay of sequential CS-minute blood samples obtained over 48 hours reveals the presence of sinusoidal and ultradian rhythms in peripheral prolactin levels. Lights on or lights off conditions do not influence the rhythms. Any variation in the circadian rhythm phase is accompanied by an alteration in the estradian rhythm duration.

Thyroid hormones T3 and T4 show circadian patterns in lactating dairy cows. The sinusoidal wave patterns reach their peak during morning and minimum points at night for T3 and T4, respectively. The circadian T4 rhythm resembles the circadian pattern, also exhibiting 90-min ultradian rhythms.

Abstract. The extent of gastric lipolysis, fat absorption, and infant weight gain was studied in 12 preterm infants (gestational age 28.75 +/- 0.50 weeks, postnatal age 6.08 +/- 0.81 weeks) fed medium-chain triglyceride or long-chain triglyceride formula for I week in a crossover design. The former formula contained 42% of 8:0 and 10:0 and 19% of 12:0, 14:0, and 16:0; the latter formula contained only 7% of 8:0 and 10:0 and 46% of 12:0, 14:0, and 16:0. Gastric aspirates were obtained on the second and third day of formula feeding for quantitation of lipase activity and of the extent of gastric lipolysis. Fat, balance studies were conducted during the last three days of each feeding regimen. The study showed that (1) there was marked hydrolysis of formula fat in the stomach during feeding of either medium-chain triglyceride formula or long-chain triglyceride formula (20% and 16%, respectively); (2) lipase activity in the gastric aspirates was less during feeding of medium-chain triglyceride formula than before the meal, which suggested stimulation of lipase secretion by long-chain fatty acid released from long-chain triglyceride formula fat or more rapid binding of lipase to ingested lipid in the medium-chain triglyceride formula; (3) fatty acid distribution in glycerides and free fatty acids showed preferential release of medium-chain (8:0, 10:0) and long-chain unsaturated (18:1, 18:2) fatty acids in the stomach. The low content of 8:0 and 10:0 in gastric triglyceride and free fatty acids suggested that medium-chain fatty acids were absorbed directly in the stomach. (4) fat balance studies showed almost identical absorption rates (84.6% +/- 3.1% and 82.8% [ABSTRACT FROM AUTHOR]

Abstract. Milk lipids from six mothers with cystic fibrosis were compared with milk lipids from six mothers without cystic fibrosis. Mean neutral lipids (in g/dL) were colostrum, 2.4; transitional, 2.9; mature milk, 2.9, suggesting that milk fat content was sufficient to support energy needs of the infant. Lipid class composition was normal, 98% being present as triglyceride. Cholesterol and cholesteryl ester concentrations were similar in the milk of both groups of lactating women. Phospholipid class distribution of cystic fibrosis milk was different from that in control milk. Approximately 85% of the lipids were present in six major fatty acids from 12:0 to 18:2 in both groups, indicating that the profile of most of the lipid was similar. The linoleic acid content of cystic fibrosis milk was decreased significantly to 75% of normal values. Other polyunsaturated fatty acids were elevated in cystic fibrosis milk. Concentrations of 16:2, 18:3, and several longer chain polyunsaturated fatty acids were twice that in the milk of the control women, suggesting increased change 6-desaturation. Elevated proportions of several other polyunsaturated fatty acid metabolites suggested increased chain elongation to C20 and C22 polyunsaturated fatty acids. These differences in fatty acid patterns in cystic fibrosis milk were similar to differences found in blood lipid patterns of children with cystic fibrosis. These results suggest abnormal polyunsaturated fatty acid nutrition or metabolism in cystic fibrosis. [ABSTRACT FROM AUTHOR]

Abstract. Human milk contains 3.0% to 4.5% fat. The fat is contained within membrane-enclosed milk fat globules. The core of the globules consists of triglycerides (98% to 99% of total milk fat) whereas the globule membrane (which originates from the mammary secretory cell's Golgi and cell membranes) is composed mainly of phospholipids, cholesterol, and proteins. Milk fat content and composition change during lactation. Whereas the triglyceride level rises, the phospholipid and cholesterol concentrations decrease during the transition from colostrum to mature milk, resulting in an increase in the size of the milk fat globules. Digestion of milk fat depends on the consecutive action of several lipases. The first step is the partial hydrolysis of the milk fat globule core by lingual and gastric lipases in the stomach. Hydrolysis continues in the duodenum, where the bile salt-stimulated lipase of human milk and pancreatic lipase complete the process initiated in the stomach. Pediatrics 1984; 75(suppl):146-150; triglyceride, fat globule, gastric lipase, lingual lipase. [ABSTRACT FROM AUTHOR]