Enhanced Lacto-Tri-Peptide Bio-Availability by Co-Ingestion of Macronutrients

Some food-derived peptides possess bioactive properties, and may affect health positively. For example, the C-terminal lacto-tri-peptides Ile-Pro-Pro (IPP), Leu-Pro-Pro (LPP) and Val-Pro-Pro (VPP) (together named here XPP) are described to lower blood pressure. The bioactivity depends on their availability at the site of action. Quantitative trans-organ availability/kinetic measurements will provide more insight in C-terminal tri-peptides behavior in the body. We hypothesize that the composition of the meal will modify their systemic availability. We studied trans-organ XPP fluxes in catheterized pigs (25 kg; n=10) to determine systemic and portal availability, as well as renal and hepatic uptake of a water-based single dose of synthetic XPP and a XPP containing protein matrix (casein hydrolyte, CasH). In a second experiment (n=10), we compared the CasH-containing protein matrix with a CasH-containing meal matrix and the modifying effects of macronutrients in a meal on the availability (high carbohydrates, low quality protein, high fat, and fiber). Portal availability of synthetic XPP was 0.08 ± 0.01% of intake and increased when a protein matrix was present (respectively 3.1, 1.8 and 83 times for IPP, LPP and VPP). Difference between individual XPP was probably due to release from longer peptides. CasH prolonged portal bioavailability with 18 min (absorption half-life, synthetic XPP: 15 ± 2 min, CasH: 33 ± 3 min, p<0.0001) and increased systemic elimination with 20 min (synthetic XPP: 12 ± 2 min; CasH: 32 ± 3 min, p<0.0001). Subsequent renal and hepatic uptake is about 75% of the portal release. A meal containing CasH, increased portal 1.8 and systemic bioavailability 1.2 times. Low protein quality and fiber increased XPP systemic bioavailability further (respectively 1.5 and 1.4 times). We conclude that the amount and quality of the protein, and the presence of fiber in a meal, are the main factors that increase the systemic bioavailability of food-derived XPP.     

Optimization of the dilute maleic acid pretreatment of wheat straw

Background  

In this study, the dilute maleic acid pretreatment of wheat straw is optimized, using pretreatment time, temperature and maleic acid concentration as design variables. A central composite design was applied to the experimental set up. The response factors used in this study are: (1) glucose benefits from improved enzymatic digestibility of wheat straw solids; (2) xylose benefits from the solubilization of xylan to the liquid phase during the pretreatment; (3) maleic acid replenishment costs; (4) neutralization costs of pretreated material; (5) costs due to furfural production; and (6) heating costs of the input materials. For each response factor, experimental data were fitted mathematically. After data translation to €/Mg dry straw, determining the relative contribution of each response factor, an economic optimization was calculated within the limits of the design variables.     

Elektronenmikroskopische Untersuchungen über Bildung und Struktur der Zygotenwand beiMicrasterias papillifera (Desmidiaceae)

Zusammenfassung Ungefähr 30 Minuten nach Abrundung der verschmolzenen Gameten zur kugelförmigen Zygote wird ein der Anordnung der später entstehenden Zygotenstacheln entsprechendes Muster in der Verteilung von Zellorganellen und Vesikeln im peripheren Cytoplasma sichtbar (Initialmuster der Stachelbildung). Dem korrespondiert ein Muster in der Ausbildung der schon vor der Stachelbildung angelegten äußersten Schicht der Zygotenwand, des primären Exospors, einer Primärwand mit Streutextur. Im Bereich der Stachelinitialen ist das primäre Exospor dünner und reicher an Pektinen als zwischen ihnen und zeigt vorwiegend konzentrische Anordnung der Mikrofibrillen. Die Stachelinitialen sind Orte bevorzugter Anlagerung von Wandmaterial. Die vom primären Exospor umgebenen Zygotenstacheln weisen Spitzenwachstum auf. Sie zeigen im Längsschnitt eine zonenmäßige Verteilung der Zellorganellen und Vesikel.Nachdem die Stacheln ihre endgültige Größe erreicht haben, wird eine weitere Schicht der Zygotenwand, das sekundäre Exospor, angelagert. Es ist ebenfalls eine Zellulosewand, zeigt aber im Gegensatz zur Primärwand des primären Exospors einen Aufbau aus sich überkreuzenden Bändern von Mikrofibrillen. Während seiner Bildung treten bisher nicht beschriebene, scheibenförmige Gebilde mit fibrillärer oder tubulärer Innenstruktur auf. Es wird vermutet, daß sie an der Wandbildung beteiligt sind. Primäres und sekundäres Exospor der Zygote vonMicrasterias papillifera haben grundsätzlich dieselbe Textur wie Primär- und Sekundärwand der vegetativen Zelle. Das primäre Exospor löst sich innerhalb weniger Tage vom sekundären Exospor ab und verquillt. Die Ablösung wird durch eine dünne amorphe Zwischenschicht aus globulären Elementen, wahrscheinlich Matrixmaterial des sekundären Exospors, vermittelt.Die Dicke der fertig ausgebildeten Schichten des Exospors beträgt: primäres Exospor zwischen den Stacheln 170–200 nm; primäres Exospor auf halber Höhe eines Zygotenstachels 70–90 nm. Zwischenschicht ca. 60 nm. Sekundäres Exospor 1,4–1,6 m.

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Electron microscopical investigations on the structure and formation of the zygote wall inMicrasterias papillifera (Desmidiaceae) I. The exospore

Summary Approximately 30 minutes after formation of the globular zygote, a patterned arrangement of cell organelles and vesicles becomes visible in the peripheral cytoplasm of the zygote. The pattern corresponds to that of the arrangement of the spines in the fully grown zygote. It is called initial pattern of spine formation. This cytoplasmic pattern leads to the patterned secretion of the outermost layer of the zygote wall, called primary exospore. It is a primary wall, displaying disperse texture. The primary exospore (up to 200 nm thick) is thinner and contains more matrix material in the areas of the spine initials where the cellulose microfibrils are arranged more or less concentrically, than between them. The spines develop from the spine initials under assistance of the turgor pressure. They grow apically. In median longitudinal sections of a growing spine, a zonal arrangement of vesicles and cell organelles is apparent.When the spines have reached their ultimate length, the secondary exospore is laid down. This 1,4–1,6 m thick secondary wall consists of crossed bands of parallel microfibrils. The bands are dispersely arranged between the spines whereas in the secondary exospore of the spines they have a helical arrangement. During the secretion of the secondary exospore, still undescribed disc-shaped membrane-bounded bodies occur which contain fibrillar or tubular structures. They probably participate in wall formation. The primary and secondary exospore of the zygote wall show fundamentally the same texture as the primary and secondary wall of vegetative cells ofMicrasterias. Two to three days after its formation the primary exospore is shed and disintegrates. The shedding is mediated by a 60 nm thick amorphous layer between primary and secondary exospore, probably matrix material of the secondary exospore.

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Herrn Prof. Dr. H. Drawert zum 60. Geburtstag gewidmet.

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Frl. Dr. M.Mix, Frl. E.Manshard und Frl. B.Zapf danke ich für die Einführung in die Elektronenmikroskopie, der Deutschen Forschungsgemeinschaft für Sachbeihilfe.     

Sequence of Guinea Pig Myelin Basic Protein

This paper proposes a tentative amino acid sequence of guinea pig myelin basic protein obtained by comparison of peptide fragments of the guinea pig and bovine proteins. Analyses of the tryptic peptides confirmed the known sequence differences in the NH2-terminal half of the molecule and showed that in the COOH-terminal half of the guinea pig protein Ser131 was missing, Ala136 - His137 was deleted, Leu140 was replaced by Phe, and an extra Ala was inserted somewhere within sequence 142-151 (tryptic peptide T23 ). Sequence determination of guinea pig tryptic peptides corresponding to residues 130-134 ( T20 ), 135-138 ( T21 ), and 142-151 ( T23 ) of the bovine protein confirmed the above sequence changes and placed the extra Ala between Gly142 and His143 . The sequence of the region corresponding to bovine residues 130-143 is thus Ala-Asp-Tyr-Lys-Ser-Lys-Gly-Phe-Lys-Gly-Ala-His. No species differences were observed in the amino acid compositions of the remaining tryptic peptides obtained from the COOH-terminal half of the molecule. Based upon these results, the guinea pig basic protein contains 167 amino acid residues and has a molecular weight of 18,256.