A proform of secretin with high secretin-like bioactivity

A variant form of the heptacosapeptide amide secretin, with C-terminal -Val-Gly-Lys-Arg instead of valine amide, has been isolated from porcine upper intestinal tissue. Unexpectedly, this triacontapeptide exhibited a substantially higher bioactivity than the heptacosapeptide amide.     

Isolation of a brain peptide identical to the intestinal PHI (peptide HI)

The isolation of a brain peptide identical to the intestinal peptide PHI (peptide HI) is described. The peptide was isolated from porcine brain extract using a chemical assay method based on its C-terminal isoleucine amide structure. The complete amino acid sequence of the peptide was found to be: His-Ala-Asp-Gly-Val-Phe-Thr-Ser-Asp-Phe-Ser-Arg-Leu-Leu-Gly-Gln-Leu-Ser-Ala- Lys-Lys-Tyr-Leu-Glu-Ser-Leu-Ile-NH2. This sequence is identical to the intestinal peptide thus demonstrating PHI to be a brain-gut peptide. The role of PHI in the central nervous system as a neurotransmitter or neuromodulator is discussed.     

Über die chromotropen Zellen der Nebenniere vom Wasserfrosch

Zusammenfassung Aus dieser neuerlichen Untersuchung der zuerst von Stilling beschriebenen Sommerzellen ergibt sich somit als einzige Übereinstimmung in den sonst widerspruchsvollen Angaben des Schrifttums, daß sie in ihrem Vorkommen nicht auf den Sommer beschränkt sind, weshalb sie von mir nach ihrer färberischen Eigentümlichkeit als chromotrope Zellen bezeichnet werden. Da ihr isoelektrischer Punkt bei etwa p_H 5 liegt, verhalten sie sich gegenüber Farbstoffen nicht ausschließlich (acido-) oxyphil, doch sind sie auch keine Mastzellen oder überhaupt während der Entwicklung veränderte Wanderzellen, sondern eine besondere Art autochthon entstandener Nebennieren-Epithelzellen, deren Körnchen saure Polysaccharide enthalten. Ihre funktionelle Bedeutung muß erst geklärt werden. Dabei ist es besonders bemerkenswert, daß sich das Vorkommen dieser Zellen auf Rana esculenta und eine Abart von ihr sowie exotische Verwandte beschränkt, während sie bei Rana temporaria und deren nächsten Verwandten immer fehlen. Die gegenteiligen Angaben der Literatur beruhen wahrscheinlich teilweise auf unzutreffender Bestimmung der Art und im übrigen wohl auf Verwechslung mit gekörnten Wanderzellen, was besonders bei der Entwicklung zu falschen Vorstellungen führen kann.Herrn Professor Alfred Kohn in dankbarer Erinnerung gewidmet.     

NK-lysin, a novel effector peptide of cytotoxic T and NK cells. Structure and cDNA cloning of the porcine form, induction by interleukin 2, antibacterial and antitumour activity.

A 78 residue antimicrobial, basic peptide, NK-lysin, with three intrachain disulfide bonds was purified from pig small intestine and characterized. A corresponding clone was isolated from a porcine bone marrow cDNA library. The 780 bp DNA sequence had a reading frame of 129 amino acids which corresponded to NK-lysin. The clone was used to show that stimulation with human interleukin-2 induced synthesis of NK-lysin-specific mRNA in a lymphocyte fraction enriched for T and NK cells. Lower levels of mRNA were detected in tissues known to contain T and NK cells, such as small intestine, spleen and colon. Interleukin-2 also induced both proliferation of the lymphocyte fraction and cytolytic function in these cells. Immunostaining showed that NK-lysin was present in cells positive for CD8, CD2 and CD4. NK-lysin showed high anti-bacterial activity against Escherichia coli and Bacillus megaterium and moderate activity against Acinetobacter calcoaceticus and Streptococcus pyogenes. The peptide showed a marked lytic activity against an NK-sensitive mouse tumour cell line, YAC-1, but it did not lyse red blood cells. The amino acid sequence of NK-lysin exhibits 33% identity with a putative human preproprotein, NKG5, of unknown function but derived from a cDNA clone of activated NK cells. We suggest that NK-lysin is a new effector molecule of cytotoxic T and NK cells.     

Neuropeptide Y receptor in the rat brain

The specific binding of the chloramine-T iodinated neuropeptide Y (125I-NPY) to membranes from rat cerebral cortex was investigated using equilibrium binding and kinetic methods. The equilibrium binding of 125I-NPY at 37 degrees C was characterized by a Kd value of 0.38 nM. The receptor densities in the cerebral cortex, hypothalamus and cerebellum were 0.45 pmol/mg, 0.47 pmol/mg and 0.04 pmol/mg protein respectively. The binding site for 125I-NPY was sensitive to treatment with proteolytic enzymes and thiol reagents. The binding showed a sharp optimum at pH 7-7.7 and was inhibited by increasing concentrations of Mg2+.     

15N nmr spectroscopy. I. Polysarcosine and related sequence polypeptides

The natural abundance ¹⁵N nmr spectra of linear polysarcosine (DP = 35) has been recorded in Me₂SO and H₂O solution. Because of cis/trans isomerization at the peptide bond, a broad signal with several splittings was observed. These splittings appear to reflect the influence of three peptide bonds on a single N atom. The ¹⁵N signals from the sequence polypeptides (β-Ala-Sar-Gly)_n and (β-Ala-Sar-D ,L -Ala)_n also show a cis/trans splitting, as well as chemical shifts which are dependent on the peptide sequence. The tertiary nitrogen of the sarcosyl residue has a T₁ relaxation time which is longer than the T₁ for secondary nitrogens of the other amino acids. The nuclear Overhauser effect is also discussed.     

The preparation of biotinyl-epsilon-aminocaproylated forms of the vasoactive intestinal polypeptide (VIP) as probes for the VIP receptor.

Vasoactive intestinal polypeptide (VIP) was biotinyl-epsilon-aminocaproylated using sulfosuccinimidyl-6-(biotinamido) hexanoate thereby producing a series of products that were separated by high performance liquid chromatography (HPLC). Seven VIP-derivatives were isolated and the number and location of biotinyl-epsilon-aminocaproylation was determined by a combination of enzymatic degradation and plasma desorption mass spectrometry (PDMS). Receptor binding experiments with the VIP biotinyl-epsilon-aminocaproylated derivatives revealed IC50 values for the monobiotinyl-epsilon-aminocaproylated peptides that were 1.3-3.2 times higher than for natural VIP. All isolated biotinyl-epsilon-aminocaproylated derivatives possess VIP-like bioactivity as shown by an assay measuring pancreatic juice secretion in cat, VIP biotinyl-epsilon-aminocaproylated in position lysine being almost equipotent with natural VIP.     

Cysteine restriction‐specific effects of sulfur amino acid restriction on lipid metabolism

Decreasing the dietary intake of methionine exerts robust anti‐adiposity effects in rodents but modest effects in humans. Since cysteine can be synthesized from methionine, animal diets are formulated by decreasing methionine and eliminating cysteine. Such diets exert both methionine restriction (MR) and cysteine restriction (CR), that is, sulfur amino acid restriction (SAAR). Contrarily, SAAR diets formulated for human consumption included cysteine, and thus might have exerted only MR. Epidemiological studies positively correlate body adiposity with plasma cysteine but not methionine, suggesting that CR, but not MR, is responsible for the anti‐adiposity effects of SAAR. Whether this is true, and, if so, the underlying mechanisms are unknown. Using methionine‐ and cysteine‐titrated diets, we demonstrate that the anti‐adiposity effects of SAAR are due to CR. Data indicate that CR increases serinogenesis (serine biosynthesis from non‐glucose substrates) by diverting substrates from glyceroneogenesis, which is essential for fatty acid reesterification and triglyceride synthesis. Molecular data suggest that CR depletes hepatic glutathione and induces Nrf2 and its downstream targets Phgdh (the serine biosynthetic enzyme) and Pepck‐M. In mice, the magnitude of SAAR‐induced changes in molecular markers depended on dietary fat concentration (60% fat >10% fat), sex (males > females), and age‐at‐onset (young > adult). Our findings are translationally relevant as we found negative and positive correlations of plasma serine and cysteine, respectively, with triglycerides and metabolic syndrome criteria in a cross‐sectional epidemiological study. Controlled feeding of low‐SAA, high‐polyunsaturated fatty acid diets increased plasma serine in humans. Serinogenesis might be a target for treating hypertriglyceridemia.