6-O-β-d-Xylopyranosylaucubin from Verbascum sinuatum

Verbascum sinuatum contains, in addition to aucubin and harpagide, four new highly polar iridoid glycosides one of which has been identified as 6-O-β-d-xylopyranosylaucubin on the basis of spectral data and chemical modifications.     

Uptake of Amino Acids by Brain Microvessels Isolated from Rats after Portacaval Anastomosis

Abstract: The uptake of amino acids by microvessels isolated from brains of rats was studied. Previous studies have demonstrated alterations in blood-brain amino acid transport after portacaval shunt in rats. In order to elucidate whether such changes in the blood-brain barrier were located in the microvessels, brain microvessels were isolated from both rats with portacaval shunt and controls. Brain microvessels from rats 2 weeks after shunt operations took up significantly greater amounts of ¹⁴C-labeled neutral amino acids, but not of glutamic acid. lysine, or α-methylaminoisobutyric acid than microvessels from sham-operated controls. Measurement of uptake kinetics showed a higher V _max for phenylalanine and leucine uptake and a lower V _max for lysine uptake in microvessels from shunted rats compared with control, whereas the respective K _m's of uptake were similar in both preparations. The results suggest that changes in brain microvessel transport activity account for altered brain neutral amino acid concentrations after portacaval shunt and that such changes can be studied in vitro in isolated microvessels.     

6-O-α-Sinuatosylaucubin from Verbascum sinuatum

From Verbascum sinuatum, besides aucubin, harpagide, 6-O-β-d-xylopyranosylaucubin and sinuatol (6-O- α-l-rhamnopyranosylaucubin), a new iridoid glycoside, sinuatoside, has been isolated and its structure elucidated as 6-O-(3-O-β-d-xylopyranosyl)α-d-galactopyranosyl aucubin on the basis of spectral data and chemical modifications. For the new disaccharide unit of the latter compound the name sinuatose is proposed.     

Presence of specific prolactin binding sites in the rabbit hypothalamus

The presence of specific prolactin binding sites in membranes obtained from rabbit brain was investigated. Among the different brain areas studied (hypothalamus, cerebral cortex, cerebellum, olfactory bulbi and ponsmedulla) only the hypothalamus showed an evident specific binding (5.34% in male and 6.64% in female rabbits), whereas in the other brain regions the binding was lower or negligible. Scatchard analysis of the binding revealed the presence of high-affinity saturable binding sites. The study on hormonal specificity showed that the binding in the hypothalamus was inhibited by ovine and rat prolactin and by human GH, but not by many other polypeptide hormones.     

Conformational studies of peptides: Crystal and molecular structures of L-3,4-dehydroproline and its t-butoxycarbonyl and acetyl amide derivatives

The crystal structures of L -3,4-dehydroproline, t-butoxycarbonyl-L -3,4-dehydroproline amide, and acetyl-L -3,4-dehydroproline amide have been determined. L -3,4-Dehydroproline is orthorhombic with a = 16.756, b = 5.870, c = 5.275 Å, and Z = 4; t-butoxycarbonyl-L -3,4-dehydroproline amide is orthorhombic with a = 6.448, b = 8.602, c = 21.710 Å, and Z = 4; acetyl-L -3,4-dehydroproline amide is monoclinic with a = 4.788, b = 10.880, c = 7.785 Å, β = 105.25°, and Z = 2. The final R value for the L -3,4-dehydroproline is 0.046 based on 529 reflections; for t-butoxycarbonyl-L -3,4-dehydroproline amide, 0.050 based on 792 reflections; and for acetyl-L -3,4-dehydroproline amide, 0.058 based on 632 reflections. The structures clearly establish that the free amino acid exists in the zwitterionic form in the crystalline state. The molecular conformations of the t-Boc and acetyl derivatives consist of two planes: one involving the primary amide and the other the remaining atoms of the molecule. The acetyl-L -3,4-dehydroproline amide contains a tertiary amide bond in the cis conformation. To the best of our knowledge, this is the first example of a cis bond in an acetyl derivative of an amino acid or peptide. At variance with the previously reported proline amides, which present ? and ψ values corresponding to those of a right-handed α-helical conformation (conformation A), the t-Boc and acetyl derivatives both have ? and ψ values corresponding to a collagenlike conformation (conformation F).     

Structural analysis of winter phytoplankton in the Gulf of Naples

Quantitative and qualitative distribution of surface phytoplankton,as related to hydrographic conditions, was studied in the Gulfof Naples in February 1979. Previous work has shown that the Gulf of Naples is a diversifiedecosystem, due to geographic and hydrographic features as wellas man made eutrophication, that can be subdivided into twomajor parts: a coastal subsystem and an open water one. Hydrographic analysis of the winter situation at the surfacefully confirms this picture, as it identifies two distinct watermasses corresponding respectively to surfaced Tyrrhenian IntermediateWater and to Coastal Surface Water. The structural analysisof phytoplankton reveals three assemblages of species characterizingdifferent water types: 1 - the Ischia and Procida channels affectedby the advection of Volturno river and Cuma outfall plumes;2 - the coastal area of the Gulf proper, namely the bays ofPozzuoli, Naples and Castellammare; 3 - the open waterhemislocated beyond the 100 m isobath. The channel area assemblage is dominated by diatoms, particularlyby fast growing species, such as Asterionella japonica, severalspecies of Chaetoceros and Rhizosolenia hebetata f. semispina.The coastal assemblage is identified, among others, by the diatomsCerataulina bergonii, Hemiaulus sinensis; the dinoflagellatesGlenodinium lenticula, Exuviaella compressa and Porella perforata.The open water assemblage is characterized by the diatoms Coscinodiscuscurvatulus and Hemidiscus cuneiformis, the dinoflagellate Amphidiniumacutissimum and the coccolithophore Coccolithus haeckelii.     

Acylation of aspartate aminotransferase

1. Acetylation of aspartate aminotransferase from pig heart inhibits completely the enzymic activity when the coenzyme is in the amino form (pyridoxamine phosphate) or when the coenzyme has been removed, but not when the coenzyme is in the aldehyde form (pyridoxal phosphate). 2. The group the acylation of which is responsible for the inhibition has been identified with the in-amino group of a lysine residue at the coenzyme-binding site. Moreover, in the pyridoxamine-enzyme the amino group of the coenzyme is also acetylated. 3. The reactivity of the coenzyme-binding lysine residue is greatly different in the pyridoxamine-enzyme and in the apoenzyme, suggesting the possibility of an interaction of its in-amino group with pyridoxamine or with other groups on the protein.