Receptor-mediated regulation of calcium mobilization and cyclic GMP synthesis in neuroblastoma cells

In neuroblastoma N1E 115 cells, carbachol, histamine and PGE1 elevated cyclic GMP content and, induced the efflux of preloaded 45Ca2+, the release of membrane-bound Ca2+ measured by fluorescent CTC, and the increase in [Ca2+]i as measured by Quin 2 fluorescence. The time course of the responses, the absolute requirement of extracellular Ca2+, the inhibition by receptor blockers, and the concentration dependency on histamine were all similar between these responses. The observation indicates that the mobilization of Ca2+, especially the increase of [Ca2+]i, may be intimately linked to the synthesis of cyclic GMP in the cells.     

Condensed tannins: co-occurrence of procyanidins,prodelphinidins and profisetinidins in the heartwood of Acacia baileyana

The flavonoids and condensed tannins of the heartwood of Acacia baileyana var. purpurea are described. In conformity with other Acacia species, the hydroxylation pattern of the flavonoids is of the resorcinol type but, in sharp contrast, the tannins are heterogeneous consisting of a mixture of the resorcinol and phtoroglucinol series. Dimeric proanthocyanidins of the phloroglucinol type were absent and this exception to the general observation that they invariably co-occur with the polymers may be explained by the relative nucleophilicity of the aromatic A-rings.     

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.     

Interaction of coupled nonlinear oscillators having different intrinsic resting levels

The interaction among coupled oscillators is governed by oscillator properties (intrinsic frequency and amplitude) and coupling mechanisms. This study considers another oscillator property, the intrinsic resting level, and evaluates its role in governing oscillator interactions. The results of computer experiments on a chain of either three or five bidirectionally coupled nonlinear oscillators, suggest that an intrinsic resting level gradient, if present, is one of the factors governing the interaction between coupled oscillators. If there is no intrinsic frequency gradient, then an intrinsic resting level gradient is sufficient to produce many features of interaction among coupled oscillators. If both intrinsic frequency and intrinsic resting level gradients are present, then both of them determine the manner in which the coupled oscillators interact with each other.     

氨基酰化酶中金属锌离子的功能作用

 氨基酰化酶是含锌金属酶。该酶每摩尔蛋白中含2摩尔Zn(Ⅱ)离子。金属鳌合剂与酶作用,通过竞争螯合Zn(Ⅱ)离子使酶活力下降。残余活力与残留金属含量呈正相关。竞争螯合的结果,生成不含金属的脱辅基酶蛋白,并导致酶活力的丧失。脱辅基酶由于加入Zn(Ⅱ)离子而恢复其活力。实验表明金属锌离子是氨基酰化酶催化活力所必需。与Zn(Ⅱ)离子相似,Co(Ⅱ)离子也可与脱辅基酶相结合并使之复活。 在190—240nm区域内对比了天然酶、脱辅基酶蛋白与Co(Ⅱ)置换氨基酰化酶的圆二色谱。远紫外圆二色谱表明,与天然酶相比,在脱辅基酶中由于金属离子的丧失导致主链构象发生变化,其中α螺旋增加约7％。因而锌离子(钴离子)对蛋白主链的反应最适构象有一定的稳定作用。脱辅基酶与Co(Ⅱ)离子结合,酶的主链构象恢复至与天然酶几近相同。可认为这是促使酶复活的内在因素。     

Phenolic acid effects on peanut growth and oil production

Plants of peanut (Arachis hypogaea L. var. PG No. 1) were given two foliar sprays of phenolic compounds (H-acid, 1, 2, 4-acid, resorcinol and RD-Brown) at 100 and 200 ppm, 35 and 50 days after sowing. In treated plants, shelling %, yield (kg/ha), number of gynophores per plant and number of pods per plant were significantly greater than in the control. Oil content of kernels also showed a significant increase with all the phenolic compounds applied. These compounds increased the linoleic acid concentration so improving nutritional quality. The number of gynophores was significantly correlated with the number of pods per plant and yield per hectare. The effect of phenolic compounds on growth and development was independent of their structural configuration.     

Distribution and characterization of the opioid octapeptide met5-enkephalin-arg6-gly7-leu8 in the gastrointestinal tract of the rat

Summary The distribution and characterization of the opioid octapeptide met⁵-enkephalin-arg⁶-gly⁷-leu⁸ (met⁵-enk-arg⁶-gly⁷-leu⁸) within the gastrointestinal tract of the rat has been determined by immunohistochemistry and radioimmunoassay by use of a newly developed antibody to met⁵-enk-arg⁶-gly⁷-leu⁸. With both techniques, met⁵-enk-arg⁶-gly⁷-leu⁸-immunoreactivity (met⁵-enk-arg⁶-gly⁷-leu⁸IR) was detected in all regions of the gastrointestinal (GI) tract except the esophagus. The highest concentration of immunoreactive met⁵-enk-arg⁶-gly⁷-leu⁸ was observed in the colon, while intermediate concentrations were found in the stomach, duodenum, jejunum, and ileum. Immunostained somata were observed chiefly in the myenteric plexus; immunostained processes were present primarily in the myenteric plexus and the circular muscle layer. This distribution pattern is similar to that previously observed with antiserum to met⁵-enkephalin-arg⁶-phe⁷ (met⁵-enk-arg⁶phe⁷). Chromatographic analysis of met⁵-enk-arg⁶-gly⁷leu⁸-immunoreactive peptides extracted from the GI tract revealed the presence of an immunoreactive peptide of high molecular weight which accounted for approximately three-quarters of met⁵-enk-arg⁶-gly⁷-leu⁸-IR in both stomach and colon. These findings suggest a role for peptides related to the octapeptide met⁵-enk-arg⁶-gly⁷-leu⁸ in the regulation of GI function.     

Molecular cloning of the F8 fimbrial antigen from Escherichia coli

Abstract The genetic determinant coding for the P-specific F8 fimbriae was cloned from the chromosome of the Escherichia coli wild-type strain 2980 (O18:K5:H5:F1C, F8). The F8 determinant was further subcloned into the Pst I site of pBR322 and a restriction map was established. In a Southern hybridization experiment identity between the chromosomally encoded F8 determinant of 2980 and its cloned counterpart was demonstrated. The cloned F8 fimbriae and those of the wild type strain consist of a protein subunit of nearly 20 kDa. F8 fimbriated strains were agglutinated by an F8 polyclonal antiserum, caused mannose-resistant hemagglutination and attached to human uroepithelial cells. The cloned F8 determinant was well expressed in a variety of host strains.     

Binding of 8-bromoguanylic acid to ribonuclease T1 as studied by absorption and circular dichroism spectroscopy

8-Bromoguanosine 2'- and 3'-phosphates have been shown to bind to RNase T1 with the same affinity as the corresponding guanosine phosphates, inducing difference absorption and circular dichroism spectra similar to those induced by the guanosine phosphates. Since the brominated ligands have reduced electron density on N-7 of the guanine ring and syn-fixed conformation due to a bulky, electron-withdrawing Br substituent on C-8, the difference spectra are not attributable to the protonation on N-7 and to the restriction of the ligand to syn-conformation as proposed previously.     

Capacitance--voltage relationship in phospholipid bilayers containing gangliosides

Changes in the position of the minimum of the parabolic capacitance-voltage curve allow the measurement of the amount of ganglioside present in artificial bilayers made with phosphatidylcholine-ganglioside mixtures and asymmetrically shielded with Ca2+. The screening effect of the ionic solution must be considered. With ganglioside/phospholipid molar ratios of up to 15%, all glycolipids can be found at the membrane surfaces.