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Biomedical subjects

J Bitman

Publications and source records attributed to J Bitman.

At least 19 recordsLinked to original sources
PubMed1992

Human milk in disease: lipid composition.

Differences in the lipid composition of human milk have been described in maternal diseases known to affect fat metabolism. Diseases such as diabetes, cystic fibrosis, hypobetalipoproteinemia and Type I hyperlipoproteinemia affect the quantity and quality of human milk fat. Increased fatty acid chain elongation and changes in desaturation (especially delta 6 desaturase), as well as changes in lipid class composition, have been shown in diabetes and cystic fibrosis, whereas compensatory increases in medium-chain fatty acids have been described in hypobetalipoproteinemia and Type I hyperlipoproteinemia. It is important to realize that these observations were made either on single women or on very small groups of women. In infant diseases, such as breast milk jaundice and ectopic eczema, changes in polyunsaturated fatty acids in maternal milk have been described.

Cystic Fibrosis↗
PubMed1992

Human mammary gland function at the onset of lactation: medium-chain fatty acid synthesis.

The onset of medium-chain fatty acid synthesis in the human mammary gland was investigated. Colostrum and serum were collected from 31 healthy women and the fatty acid composition of total lipid was analyzed by gas-liquid chromatography. Although colostrum/serum ratios for most fatty acids range from 0.7-2.4, very low levels of 10:0 and 12:0 were present in serum lipids as compared to much higher concentrations of these fatty acids in colostrum lipids (colostrum/serum ratio 16.23 and 17.11 for 10:0 and 12:0, respectively). We have previously found that medium-chain fatty acid levels are very low in prepartum mammary secretions (6-10 wk before term delivery) but are higher and similar in colostrum of women who deliver preterm (3-14 wk) or at full term. The data indicate that parturition, irrespective of length of pregnancy, is the trigger for medium-chain fatty acid synthesis in the human mammary gland.

Breast↗
PubMed1992

Milk and blood fatty acid composition during two lactations in the same woman.

Fatty acid composition of colostrum, milk, and serum was studied during two consecutive lactations in the same woman. There were marked differences between milk and serum: medium chain fatty acids (C6:0-C14:0) were higher in milk (8.36-21.37%) than in serum (1.59-9.6%) throughout lactation. The high milk-serum ratio of medium chain fatty acids (up to 28.4, 30.2, and 6.2 for 10:0, 12:0, and 14:0, respectively) indicates synthesis in the mammary gland. Long-chain polyunsaturated fatty acids (C20:1-C22:6) of the n - 3 and n - 6 series were higher in serum (6.76-12.53%) than in milk (1.57-4.42%). With the exception of colostrum, the fatty acid composition of milk and serum changed little during lactation and was similar in two consecutive lactations in the same woman. Comparison of milk and serum fatty acids provides a noninvasive approach for the assessment of the synthetic activity of the human mammary gland.

Adult↗
PubMed1992

Changes in the lipid composition of the secretions of the bovine mammary gland during the dry period.

To study initiation of milk fat synthesis, lipid composition of mammary secretions at -60, -40, and -10 d prepartum was studied in lactating and nonlactating Holstein cows. Eleven cows were dried off, and 13 cows were milked twice per day throughout the normal dry period. Total neutral lipid was similar in late lactation milk (-60 d) from lactating cows, 2.1 g/dl, and in milk from the dry group, 2.2 g/dl. Neutral lipids decreased to 1.3 and .9 g/dl in quarters from dry cows at -40 and -10 d prepartum. In secretions from dry quarters, triglycerides were 97% of total lipids at -60 d and decreased to 85 and 91% at -40 and -10 d, respectively. Conversely, FFA and monoglycerides increased during the dry period. Lipids associated with fat globule membrane components increased during the dry period. These increases were 10 times for cholesterol, 20 times for cholesteryl esters, and twice for phospholipids. In general, the content of fat globule core lipids (triglycerides) exhibited a pattern opposite that of membrane lipids (cholesterol, cholesteryl esters, phospholipids) during the prepartum period. Proportions of core lipids tended to decrease, whereas proportions of membrane lipids increased in prepartum mammary secretions. Lipid composition of prepartum secretions may be influenced by blood lipids, somatic cells, and alterations in mammary lipid synthesis.

Animals↗
PubMed1992

Effect of clinical and subclinical mastitis on lipid composition of teat canal keratin.

Two experiments were conducted to investigate lipid composition of teat canal keratin when different conditions of bacterial colonization and quarter inflammation were present. In Experiment 1, 11 multiparous cows with subclinical mastitis (bacteria present but no visible inflammation) in at least one quarter were selected for study. Quarters that were sampled and found negative for bacterial growth were classified as control. In Experiment 2, 10 multiparous cows with clinical mastitis in one or more quarters were selected. Milk samples from inflamed quarters were cultured to identify mastitis pathogens; these quarters were classified as clinical; all other quarters were classified as control. Teat canal keratin was collected from all quarters just before an a.m. milking, samples were weighed, and lipid determinations were conducted by TLC. Keratin from subclinical quarters compared with keratin from control quarters did not differ in either neutral lipid or fatty acid composition. Total lipid was significantly higher in keratin from teats of clinical quarters than in keratin from control quarters (27.8 vs. 21.5 microgram/mg). Neutral lipid composition of keratin was similar between teats from clinical quarters and teats from control quarters. In Experiment 2, quarter foremilk samples were also obtained to determine lipid composition. The FFA in milk from clinical quarters contained fewer short-chain fatty acids, whereas polyunsaturated fatty acids were significantly higher in milk from clinical quarters.

Animals↗
PubMed1992

Increased susceptibility to intramammary infection following removal of teat canal keratin.

Influence of teat canal keratin on susceptibility to intramammary infection was investigated in lactating Jersey cows. In each of two replicate trials, keratin was removed from the left teats of 20 cows immediately before milking. Immediately after milking, all teats were exposed to bacterial challenge by immersion in a suspension of Streptococcus agalactiae (5 x 10(7) cfu/ml). Bacterial challenge was repeated after the next four milkings. Foremilk samples were obtained for 8 d after keratin removal to determine infection status. A mammary quarter was classified as infected based solely upon the bacteriological criteria outlined by the National Mastitis Council. The rate of infection in quarters from which keratin was removed was greater than that in control quarters. Infection rates were 26.3% for keratin-removed quarters and 8.3% for control quarters in trial 1 and 13.5 and 0%, respectively, in trial 2. When more stringent criteria (recovery of greater than 100 cfu of S. agalactiae/ml in three or more successive milk samples and a SCC of greater than 10(6)) were used to identify a subset of infections that were clearly intramammary, infection rates were 9.3% for keratin-removed quarters and 1.4% for control quarters. Thus, partial removal of keratin from the teat canal compromised the ability of the teat to prevent passage of bacterial pathogens from the external environment into the mammary gland.

Animals↗
PubMed1991

Adherence of medium-chain fatty acids to feeding tubes of premature infants fed formula fortified with medium-chain triglyceride.

Adherence of medium-chain triglyceride (MCT) oil to feeding tubes during gavage feeding of Enfamil formula was quantitated. Infants were fed similar volumes of either unfortified formula (n = 11) or MCT oil-fortified formula (0.5 ml/oz); either the MCT oil was mixed with the formula before feeding (n = 11) or the MCT oil was delivered into the feeding tube and then was followed by formula (n = 11). The fat residue in the feeding sets was quantitated by gravimetry, and individual fatty acids were characterized by gas-liquid chromatography. The data show that only trace amounts of lipid (0.23 +/- 0.04%) adhered to feeding sets during feeding of unfortified formula. Significantly more lipid (p less than 0.0005) adhered when formula was fortified with MCT oil, and the method of feeding greatly affected lipid adherence, i.e., 1.52 +/- 0.21% when the MCT oil was followed by formula versus 10.20 +/- 1.76% when the MCT oil was mixed with formula before feeding. Analysis of the fat residue of fortified formula showed that greater than 90% was composed of C8:0 and C10:0, the major fatty acid components of MCT oil. We suggest that care be exercised when fortifying infant formula with MCT oil.

Adhesiveness↗
PubMed1991

Lipid composition of teat canal keratin collected before and after milking from Holstein and Jersey cows.

In three experiments, keratin was collected from individual teats of 40 Holstein and 20 Jersey cows immediately before and after milking. In Experiments 1 and 2, keratin collected from teats of 20 Holstein cows before milking was compared with keratin collected after milking. In Experiment 3, keratin was collected from two teats of 20 Jersey and 20 Holstein cows before milking and compared to the other two teats of the same cows after milking. All three experiments yielded similar results. In Holsteins, keratin weight before milking was 1.6 times greater than keratin weight after milking (3.1 vs. 1.9 mg). In Jerseys, only small amounts of keratin were removed during milking (3.5 mg before vs. 3.1 mg after) In Holsteins and Jerseys, neutral lipid concentration was 1.6 times greater after milking than before, suggesting that when keratin was removed during milking, only moderate amounts of lipid were removed. In Holsteins, total lipid collected per teat was similar before or after milking (59.2 vs. 48.5 micrograms). Results demonstrate that keratin collected after milking had a different lipid composition than keratin collected before milking.

Animals↗
PubMed1991

Effect of lactational intensity on extrathyroidal 5'-deiodinase activity in rats.

Concentrations of thyroxine and triiodothyronine in serum and 5'-monodeiodination activity in liver and kidney were studied in lactating Sprague-Dawley rats with different litter sizes. Litter sizes were adjusted at birth to 0 (postpartum nonlactating group), 4, 8, 12, and 16 pups per lactating rat. Serum and tissue samples were collected from lactating rats and pups on d 12 of lactation and from 6 nulliparous females. Nulliparous and postpartum nonlactating rats did not differ in serum thyroxine, triiodothyronine concentrations, or in 5'-deiodinase activity in liver and kidney. As litter size increased, maternal serum thyroxine, triiodothyronine concentrations, and 5'-deiodinase activity in liver and kidney decreased. Growth rate of pups was inversely correlated with litter size and positively correlated with concentration of serum thyroxine and liver 5'-deiodinase in mothers. In pups, serum triiodothyronine concentrations decreased as litter size increased, but serum thyroxine concentrations were not affected. Results suggest a relationship between the hypothyroid status of lactating rats and suckling intensity. The thyroid status of the dam may influence thyroid status and growth of offspring.

Animals↗
PubMed1990

Evidence that bovine growth hormone treatment increases the rate of extrathyroidal 5'-monodeiodinase activity in cattle.

This study examined the influence of bovine growth hormone (bGH) on liver and kidney thyroxine-5'-monodeiodinase activity (TMA) in growing beef cattle. In a preliminary trial (trial 1), tissue samples were obtained at slaughter from two placebo-injected and two bGH-injected (29.2 IU/day for 14 days before slaughter) Hereford heifers (398 kg avg slaughter wt), with one heifer on each treatment fed at either 1.0 or 2.0 times maintenance energy requirement. In a second trial, tissue and plasma samples were obtained from six placebo-injected and six bGH-injected (29.2 IU/day for 19 days) Hereford steers (331 kg avg slaughter wt) fed at 1.8 times maintenance energy requirement. In a third trial, liver tissue and plasma samples were obtained from 14 Angus X Hereford steers (270 kg avg wt) fed either an 8% protein, 1.96 Mcal-metabolizable energy/kg diet (8 steers) or a 14% protein, 2.67 Mcal-metabolizable energy/kg diet (6 steers) in association with acute administration of bGH. Half the steers in each group were given two injections per steer of either placebo or 37.8 IU bGH at 24-hr intervals and slaughtered 24 hr after the second injection. Units of tissue TMA in all trials were measured at slaughter; one unit defined as 1 ng T3 generated/hr/mg protein during incubation with T4 (1.3 fM). In trial 1, TMA in liver and kidney was 2.86 and 1.21 times greater, respectively, for bGH than for placebo treatments. In trial 2, units of TMA in liver homogenates were higher (P less than .05) for bGH (4.14) than for placebo (2.83) treatments and higher (P less than .02) in liver microsomal preparations for bGH (32.7) than for placebo (27.3) treatments. Units of TMA in kidney homogenates were also higher (P less than .10) for bGH (1.48) than for placebo (.87) treatments and higher (P less than .02) in kidney microsomal preparations for bGH (23.0) than for placebo (16.4) treatments. Following acute injection of bGH (trial 3), units of TMA in liver homogenates were higher (P less than .01) for bGH (2.5) than for placebo (1.8) treatments. Plasma T4 (70.0 vs 73.5 ng/ml) and T3 (1.08 vs 1.18 ng/ml) concentrations appeared slightly higher in bGH-treated steers (trial 2) and increased by 20 and .5 ng/ml, respectively, (P less than .01) within 6 to 12 h after acute injection of bGH (trial 3). Concurrently, plasma TSH concentration increased following acute GH injection (trial 3).(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1990

Methods of collection and lipid composition of teat canal keratin in dry and lactating cows.

Methods for collecting keratin from the teat canal were examined to select a procedure to obtain representative samples for lipid analysis. Data obtained by solvent extraction of excised teats were compared with those obtained by scraping keratin from dissected teats of lactating and dry cows. Solvent extraction with petroleum ether or 2:1 chloroform-methanol yielded similar dry weights of material. However, both solvents removed large amounts of material other than keratin from the teat canal. The lipid class and fatty acid profiles of the material extracted by solvent flushing were not similar to profiles obtained by scraping keratin from the teat canal. A metal tapestry needle was suitable for collection of keratin from the teat canal of living cows. About 78% of the keratin present in the teat was collected with the needle. Lipid composition of keratin collected with the needle was the same as in keratin scraped from excised teats. The tapestry needle was suitable as a tool for collecting repeatable, representative samples of keratin for analysis from single teat canals of living cows.

Alkanes↗
PubMed1990

Rhythms in cholesterol, cholesteryl esters, free fatty acids, and triglycerides in blood of lactating dairy cows.

Blood samples from six lactating dairy cows were analyzed to determine whether circulating neutral lipids exhibit rhythmic variations. Plasma neutral lipids were measured by quantitative TLC on every fourth integrated 15-min blood sample taken over 48-h periods. Cows were housed in an environmental chamber at 20 degrees C with 16 h light:8 h dark (lights on at 0700 h), fed daily at 0900 h, and milked at 0830 and 2000 h. Other variables monitored included: body temperature, ammonia nitrogen, urea nitrogen, glucose, triiodothyronine, thyroxine, somatotropin, insulin, cortisol, and prolactin. Mean concentrations of cholesterol, cholesteryl esters, free fatty acids, and triglycerides were 21.4, 175.4, 3.1, and 6.3 mg/dl, respectively. Visual and power spectral analysis of the pulsatile fluctuations in lipids indicated rhythms with periods of 2 to 3 h. Amplitudes of rhythms for free fatty acids and triglycerides were 60% of mean concentrations and for cholesterol and cholesteryl esters were 20% of mean concentrations. The presence of these rhythms was conserved when data were averaged across time by cow. However, because of nonstationary conditions, rhythms identified by spectral analysis were not statistically significant. There was no evidence of circadian patterns in circulating neutral lipid components. All other metabolic and hormonal variables except cortisol exhibited distinct circadian rhythms.

Animals↗
PubMed1990

Changes in milk fat phospholipids during lactation.

Changes in lipid composition were studied in milk obtained on postpartum d 3 (colostrum), 7, 42, and 180 from 12 Holstein cows. Triglycerides, 96 to 97% of total lipids, were relatively constant during lactation. Phospholipids and cholesterol declined with advancing lactation. Concentrations of the fatty acids synthesized within the mammary gland, C10:0 to C16:0, increased about 50% from 7 to 42 d of lactation. During this period, compensatory decreases were observed in C18:1. The phospholipids were separated into five major classes: sphingomyelin, phosphatidyl choline, serine, inositol, and ethanolamine for fatty acid analysis. The changes that occurred in milk total fatty acids were reflected in phosphatidyl phospholipid fatty acid composition: an increase in medium-chain fatty acids and a decrease in polyunsaturated fatty acids of 18, 20, and 22 carbon atom chain length as lactation progressed. These changes are consistent with the theory that milk phospholipids are synthesized de novo entirely in the mammary gland.

Animals↗
PubMed1990

Regeneration of teat canal keratin in lactating dairy cows.

This study was designed to determine the regeneration rate of teat canal keratin in two groups of 10 lactating Holstein cows. The weight of keratin obtained upon successive collections of keratin was determined. Intervals between successive collections were varied between 8 and 72 h. Following initial collection, the quantity of keratin removed was regenerated within 1 to 2.5 d. The rate of keratin regeneration per teat was approximately 1.5 mg of wet weight or .6 mg of dry weight per 24 h. The concentration (microgram lipid/mg keratin, wet weight) of lipid in keratin samples collected during regeneration was almost twice that present initially or after regeneration was complete. With the exception of free cholesterol, composition (%) of lipid components of keratin did not differ between samples collected initially, those collected early in the process of regeneration, and those collected after the mass of keratin removed had been replaced. Although data suggest that keratin matures during the process of regeneration, maturation appears complete by the time mass of keratin is fully regenerated. Additionally, the quantity of keratin recovered at initial sampling was inversely correlated with milk production. We hypothesize that as milk production increases, more keratin is lost during milking.

Animals↗
PubMed1989

Effect of bovine growth hormone on incorporation of [14C]acetate into lipids by co-cultures of bovine mammary, liver, and adipose tissue explants.

Incorporation of [14C]acetate into lipids was measured in 24 hr co-cultures of mammary, liver and adipose tissue from Holstein cows at 53, 210 and 318 d of lactation in the presence or absence of bovine growth hormone. Little (less than 1%) of the labeled lipids appeared in the media relative to that incorporated into the tissue. In mammary tissue, incorporation of [14C]acetate was highest into triglycerides (16,298 cpm/mg mammary tissue), followed by phospholipids (1,887 cpm), free fatty acids (1,252 cpm), diglycerides (708 cpm), free cholesterol (360 cpm) and monoglycerides (93 cpm). Bovine growth hormone did not increase incorporation of [14C]acetate when mammary or adipose tissue were incubated separately. However, in the presence of liver and adipose tissue, bovine growth hormone significantly increased the incorporation of [14C]acetate into triglycerides, diglycerides, free fatty acids and free cholesterol by mammary tissue. These results suggest that bovine growth hormone acts on mammary tissue indirectly through liver and adipose tissue to increase lipid synthesis. This mechanism may play a role in the action of bovine growth hormone in vivo to increase milk and milk fat production.

Acetates↗
PubMed1989

Milk composition and volume during the onset of lactation in a diabetic mother.

Milk volume and composition were examined in a diabetic mother on days 3-7 postpartum. By day 5 milk volume produced and concentrations of sodium, potassium, chloride, lactose, protein, calcium, magnesium, and citrate were within limits of a reference population. Fat content of the milk was slightly lower. Free fatty acids were 2% of total lipid on day 3 but increased to 23% on days 4-7, suggesting impaired esterification in the mammary gland. Total milk lipoprotein lipase increased approximately fourfold during days 4-5. Other changes were 1) low cholesterol content, only one-fifth of normal milk; 2) decreased medium-chain fatty acids, suggesting impairment of fatty acid synthesis in the mammary gland; 3) increased oleic acid; and 4) high concentrations of polyunsaturated fatty acids, suggesting increased chain elongation. These results suggest that diabetes produces changes in lipid metabolism in the mammary gland that alter the composition of milk produced by the diabetic mother.

Adult↗
PubMed1989

Gastric lipolysis and fat absorption in preterm infants: effect of medium-chain triglyceride or long-chain triglyceride-containing formulas.

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 1 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.(ABSTRACT TRUNCATED AT 250 WORDS)

Body Weight↗