An Improved Liquid Chromatographic Method for the Quantitative Determination of Free Fatty Acids in Milk Products

Elliott, Jerry M.; Haan, Betty de; Parkin, Kirk L.

doi:10.3168/jds.s0022-0302(89)79388-7

Cited by 22 publications

(10 citation statements)

References 6 publications

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“…(1957). Fatty acids were analyzed as 4‐bromophenacyl ester derivatives by a gradient‐elution HPLC method as described by Elliott and Parkin (1989). Phospholipid species were separated by an isocratic HPLC method as described (Bolaños and Medina 1993; Tabernero et al .…”

Section: Methodsmentioning

confidence: 99%

Neuronal differentiation is triggered by oleic acid synthesized and released by astrocytes

Tabernero

Lavado

Granda

et al. 2001

Journal of Neurochemistry

108

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Unlike in the adult brain, the newborn brain speci®cally takes up serum albumin during the postnatal period, coinciding with the stage of maximal brain development. Here we report that albumin stimulates oleic acid synthesis by astrocytes from the main metabolic substrates available during brain development. Oleic acid released by astrocytes is used by neurons for the synthesis of phospholipids and is speci®cally incorporated into growth cones. Oleic acid promotes axonal growth, neuronal clustering, and expression of the axonal growth-associated protein-43, GAP-43; all these observations indicating neuronal differentiation. The effect of oleic acid on GAP-43 synthesis is brought about by the activation of protein kinase C, since it was prevented by inhibitors of this kinase, such as H-7, polymyxin or sphingosine. The expression of GAP-43 was signi®cantly increased in neurons co-cultured with astrocytes by the presence of albumin indicating that neuronal differentiation takes place in the presence of oleic acid synthesized and released by astrocytes in situ. In conclusion, during brain development the presence of albumin could play an important role by triggering the synthesis and release of oleic acid by astrocytes, which induces neuronal differentiation.

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Section: Methodsmentioning

confidence: 99%

Neuronal differentiation is triggered by oleic acid synthesized and released by astrocytes

Tabernero

Lavado

Granda

et al. 2001

Journal of Neurochemistry

108

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“…Reaction rates and yields were determined on the basis of the disappearance of specific substrates (Le., FA, FAOH and triC8:0) or the appearance of specific products (esterified FA). FA were determined as their p-bromophenacyl ester derivatives by HPLC with a reverse-phase column at 10°C, as previously described (16). To follow the esterification of FA substrates to butteroil acylglycerols (AG), esterified FA were analyzed after conversion to their FAME derivatives by reaction with 0.5 N KOH in anhydrous methanol for 15 min at 55°C.…”

Section: Methodsmentioning

confidence: 99%

Substrate preferences for lipase‐mediated acyl‐exchange reactions with butteroil are concentration‐dependent

Kuo

Parkin

1993

J Americ Oil Chem Soc

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Substrate preferences for pancreatic lipase~mediated acylexchange reactions with butteroil were concentrationdependent for the series of acyl donors and alcohol acceptors evaluated. For acidolysis reactions, the initial reao tion rates and percent reaction yields after 18 h at 50 pmol acyl donor per gram substrate mixture were similar for nfatty acids and their methyl and glycerol esters. At 400-500 pmol g-1 (and greater), order of initial reaction rates and percent reaction yield was fatty acid glycerol esters > fatty acid methyl esters > fatty acids. At concentrations above 300-500 ~nol g-X, reaction inhibition was observed for fatty acid substrates, and inhibition took place at lower concentrations for the shorter-chainlength fatty acids of those evaluated (5-17 carbons}. Inhibition was primarily attributed to acidification of the microaqueous environment of the lipase. Desorption of water by the fatty acid substrate may be a secondary mode of inhibition. The concentration dependence of initial reaction rates and percent reaction yield was similar for the n-alcohol substrates evaluated (2-15 carbons} for alcoholysis reactions with butteroil. Optimum alcohol concentration was 375-500 pmol g-1 (except for butanol, which was 1 mmol g-l), above which reaction inhibition was observed. Inhibition was attributed to desorption of water from the enzyme by the alcohol substrate. Relative reactivity of classes of alcohols for this reaction system was primary alcohols > secondary alcohols > tertiary alcohols. Generally, alcoholysis reactions were faster than acidolysis reactions, and triacylglycerols were the best substrates for acidolys'rs reactions with butteroil at high levels (up to 2 mmol g-l) of acyl donor substrate.

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“…Lipids were extracted from the medium recovered after the incubation with a mixture of chloroform/methanol (2:1, v/v) as described by Folch et al (23). Oleic acid was analyzed as 4-bromophenacyl ester derivatives by a gradient-elution HPLC method as described (24). 0.5-ml fractions of the eluate were collected, and the radioactivity was measured by liquid scintillation counting.…”

Section: Methodsmentioning

confidence: 99%

Transcytosis of Albumin in Astrocytes Activates the Sterol Regulatory Element-binding Protein-1, Which Promotes the Synthesis of the Neurotrophic Factor Oleic Acid

Tabernero

Velasco

Granda

et al. 2002

Journal of Biological Chemistry

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We have recently reported that albumin, a serum protein present in the developing brain, stimulates the synthesis of oleic acid by astrocytes, which promotes neuronal differentiation. In this work, we gain insight into the mechanism by which albumin induces the synthesis of this neurotrophic factor. Our results show that astrocytes internalize albumin in vesicle-like structures by receptor-mediated endocytosis. Albumin uptake was followed by transcytosis, including passage through the endoplasmic reticulum, which was required to induce the synthesis of oleic acid. Oleic acid synthesis is feedback-regulated by the sterol regulatory element-binding protein-1, which induces the transcription of stearoylCoA 9-desaturase, the key rate-limiting enzyme for oleic acid synthesis. In our research, the presence of albumin activated the sterol regulatory element-binding protein-1 and increased stearoyl-CoA 9-desaturase mRNA. Moreover, when the activity of sterol regulatory element-binding protein-1 was inhibited by overexpression of a truncated form of this protein, albumin did not affect stearoyl-CoA 9-desaturase mRNA, indicating that the effect of albumin is mediated by this transcription factor. The effect of albumin was abolished when traffic to the endoplasmic reticulum was prevented or when albumin was accompanied with oleic acid. In conclusion, our results suggest that the transcytosis of albumin includes passage through the endoplasmic reticulum, where oleic acid is sequestrated, initiating the signal cascade leading to an increase in its own synthesis.Astrocytes, the main glial cell population in the central nervous system, play a major role in supporting the development of neurons. In fact, astrocytes synthesize and release extracellular matrix proteins and adhesion molecules, which participate not only in the migration of neurons but also in the formation of neuronal aggregates. In addition, astrocytes produce a broad spectrum of growth factors and cytokines, which can regulate the morphology, proliferation, differentiation, and survival of neurons (for a review, see Ref.

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An Improved Liquid Chromatographic Method for the Quantitative Determination of Free Fatty Acids in Milk Products

Cited by 22 publications

References 6 publications

Neuronal differentiation is triggered by oleic acid synthesized and released by astrocytes

Neuronal differentiation is triggered by oleic acid synthesized and released by astrocytes

Substrate preferences for lipase‐mediated acyl‐exchange reactions with butteroil are concentration‐dependent

Transcytosis of Albumin in Astrocytes Activates the Sterol Regulatory Element-binding Protein-1, Which Promotes the Synthesis of the Neurotrophic Factor Oleic Acid

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