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  • 1
    Electronic Resource
    Electronic Resource
    Desensitization of Pituitary Cells by Gonadotrophin-Releasing Hormone or its Analogues in the Superfusion System: Different Pattern for Males and Females (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neuroendocrinology 4 (1992), S. 0 
    Details
    ISSN: 1365-2826
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The effect of a 6-h infusion of gonadotrophin-releasing hormone (GnRH) or its analogues on dispersed anterior pituitary cells from male or female rats was investigated. The cells were stimulated with 3-min pulses of K+ and GnRH. Thereafter GnRH (1 nM) or GnRH analogues ([D-Trp6]GnRH-ethylamide ([D-Trp6]GnRH, 50 pM), [D-Phe6, Gln8]GnRH-ethylamide (Folligen, 100 pM) and [Asu6]GnRH-ethylamide ([Asu6]GnRH, 33 pM)) were applied for 6 h. In cells from female rats this treatment resulted in a 20-fold increase in luteinizing hormone (LH) secretion during the first 90-min period of the 6-h incubation. Following this a gradual decrease in LH release occurred, and during the fourth 90-min period the amount of LH secreted was only one-third or less of the initial value. The pituitary cells of male rats responded to the same treatment with only a 7-fold rise of LH secretion during the first period. In the second 90-min of the 6-h incubation a 20% to 30% increase was observed. Even in the fourth 90-min period the amount of LH secreted was two-thirds or more greater than that of the first 90-min period. When using 10-fold greater concentrations of the same peptides in males, the increase in hormone secretion in the second 90-min was not seen and the hormone release decreased to around 50%. We found definite differences in the responses of male and female rat pituitary cells to the 6-h infusion of GnRH or its analogues: the initial amplitude of the response in females was higher but desensitization was stronger. In males, the initial response was weaker; however, even using doses one magnitude greater, the level of desensitization did not reach the values obtained in females. The results were similar both with GnRH and the analogues. The responses to 3-min K+ and GnRH stimuli given after the 6-h incubation were strongly reduced in cells from female rats compared to the initial responses; however, in cells from male rats the reaction was higher or unchanged. The ratio of LH released by the final K+ stimulus relative to the actual LH content of the cells decreased in females but increased in males. Our data show that the differences between the pattern of desensitization in cells from male and female rats may be caused by the differences in the amount and ratio of immediately releasable hormone and the hormone replenishment into these pools.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2826.1992.tb00205.x
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  • 2
    Electronic Resource
    Electronic Resource
    New antitumor leads from a peptidomimetic library (1999)
    Springer
    International journal of peptide research and therapeutics 6 (1999), S. 325-333 
    Details
    ISSN: 1573-3904
    Keywords: antiproliferative effect ; apoptosis ; combinatorial library ; isosteric structures ; oxaniloyl hydrazides ; peptidomimetics ; substrate-binding site ; tyrosine kinase inhibition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A parallel combinatorial library of over 1600 compounds has been designed and synthesized for the development of new potential peptidomimetic protein tyrosine kinase (PTK) inhibitor leads. These peptidomimetic molecules are aimed at intervening with the substrate binding site of the pp60c-src enzyme. The new structures were based on known PTK inhibitors with at least two variously substituted aromatic moieties attached by spacer groups of different length and flexibility. Eleven bis-aryl-type inhibitory compounds were found in the range of 18–100 μM IC50 concentrations from combinations of 12 different substituents. Molecular modeling of the active compounds showed a characteristic distance of 12–14 Å between the farthest sp2 carbon atoms of the two aromatic rings. Conformational analysis of several peptide substrates recently found for pp60c-src PTK showed that the energy-minimized conformers had the same distance between the two aromatic moieties. Several compounds in the library not only showed remarkable PTK inhibitory activity but also a significant apoptosis-inducing effect on HT-29 human colon tumor cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008994116275
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  • 3
    Electronic Resource
    Electronic Resource
    New antitumor leads from a peptidomimetic library (1999)
    Springer
    International journal of peptide research and therapeutics 6 (1999), S. 325-333 
    Details
    ISSN: 1573-3904
    Keywords: antiproliferative effect ; apoptosis ; combinatorial library ; isosteric structures ; oxaniloyl hydrazides ; peptidomimetics ; substrate-binding site ; tyrosine kinase inhibition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A parallel combinatorial library of over 1600 compounds has been designed and synthesized for the development of new potential peptidomimetic protein tyrosine kinase (PTK) inhibitor leads. These peptidomimetic molecules are aimed at intervening with the substrate binding site of the pp60c−src enzyme. The new structures were based on kown PTK inhibtors with at least two variously substituted aromatic moieties attached by spacer groups of different length and flexibility. Eleven bis-aryl-type inhibitory compounds were found in the range of 18–100 μM IC50 concentrations from combinations of 12 different substituents. Molecular modeling of the active compounds showed a characteristic distance of 12–14 Å between the farthest sp2 carbon atoms of the two aromatic rings. Conformational analysis of several peptide substrates recently found for pp60c−src PTK showed that the energyminimized conformers had the same distance between the two aromatic moieties. Several compounds in the library not only showed remarkable PTK inhibitory activity but also a significant apoptosis-inducing effect on HT-29 human colon tumor cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02443428
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  • 4
    Electronic Resource
    Electronic Resource
    Analysis of macromolecular branched chain polypeptides by capillary electrophoresis and micellar electrokinetic chromatography (1996)
    Weinheim : Wiley-Blackwell
    Electrophoresis 17 (1996), S. 1357-1360 
    Details
    ISSN: 0173-0835
    Keywords: Capillary electrophoresis ; Micellar electrokinetic chromatography ; Macromolecular branched chain polypeptides ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Amphoteric poly(Lys-[Glu1.0-DL-Ala4.1]), (EAK) and anionic poly(Lys-Ac-Glu0.98-DL-Ala3.98]), (AcEAK) branched chain polypeptides were analyzed by capillary electrophoresis (CE) and micellar elektrokinetic chromatography (MEKC) in the following buffers. A1: 0.25 N triethyl ammonium phosphate (TEAP) buffer (pH 2.25); A2: 100 mM sodium dodecyl sulfate (SDS) in buffer A1; B1: Na-borate buffer (pH 7.7); B2: 100 mM SDS in buffer B1; C1: Na-borate buffer (pH 11.0); C2: 100 mM SDS in buffer C1. Both EAK and AcEAK could be separated by a CE mechanism at pH 2.25 and by an MEKC mechanism at pH 11.0. Optimum results were achieved with CE in buffer A1 and with MEKC in buffer C2.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.1150170813
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  • 5
    Electronic Resource
    Electronic Resource
    Analysis of polyanionic macromolecular carrier poly-(N-vinylpyrrolidone-co-maleic acid) and its bioconjugates by capillary electrophoresis (1998)
    Weinheim : Wiley-Blackwell
    Electrophoresis 19 (1998), S. 295-299 
    Details
    ISSN: 0173-0835
    Keywords: Capillary zone electrophoresis ; Micellar electrokinetic chromatography ; Polyanionic macromolecular carrier ; Conjugate ; Tyrosine kinase molecule ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Aninonic carrier poly(N-vinylpyrrolidone-co-maleic acid) and its conjugates, prepared with coupling of 2-cyano-3-hydroxy-5-amino-2-pentenoyc(4-trifluoromethyl anilide) or (6′,7′-dimethyl-1′-quinoxalinyl)-4-(2′ amino) acetanilide to the carrier, were analyzed by capillary zone electrophoresis (CZE) and micellar electrokinetic chromatography (MEKC) in the following buffers: 0.25N triethylammonium phosphate (TEAP); sodium dodecyl sulfate (SDS; 25-150 mM) in TEAP (pH 2.25-6.30); 0.1 M Na-borate buffer (pH range 7-11) and SDS (25-150 mM) in Na-borate buffer (pH range 7-11). The presence of strong carboxyl groups (dissociated even at pH 2.25) on the polymer chain was proved by the CZE method. It was also proved by potentometric titration that carboxyls with a wide range of acidity were on the polymer chain. CZE was able to differentiate among the analytes possessing carboxyl groups of different acidic strengths at pH 2.25. These components were not distinguished by CZE at high pH va use (11.0). Interaction between the analyte and SDS affected the separation at this pH, and hence good resolution was obtained by MEKC. Informative separations were achieved both for the carrier and the conjugates in TEAP buffer at pH 2.25 by the CZE method. Optimal separation was achieved in borate buffer containign 75 mM SDS at pH 11.0 for the carrier and at pH 7.7 for the conjugates in MEKC.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.1150190225
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  • 6
    Electronic Resource
    Electronic Resource
    Calculation of modified capacity factor in micellar electrokinetic chromatography (1996)
    Weinheim : Wiley-Blackwell
    Electrophoresis 17 (1996), S. 762-765 
    Details
    ISSN: 0173-0835
    Keywords: Micellar elektrokinetic chromatography ; Modified capacity factor ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: In addition to the expression, k′ = (tm-to)/to (1-tm/tmc), we propose the expression k″ = (tm-to)/(tmc-to) to calculate the capacity factor in micellar electrokinetic chromatography (MEKC), where tm, to, and tmc are the migration time of the analyte, the flow marker, and the micelles, respectively. The k′ and k″ values that were obtained from simulated data as well as from MEKC analysis of different peptides (in 100 mM sodium dodecyl sulfate/0.1 N sodium borate buffer at pH 11.0) were calculated and compared. The k″ value is equal to zero for an analyte remaining in the aqueous phase whereas it is equal to one for an analyte always staying in the micellar phase. By applying k″ a finite capacity factor can be obtained for an analyte, indicating its partition between the two moving phases (aqueous and micellar) even in those cases when tm equals tmc. The slope of the curve k″ as a function of tm is constant through the whole migration window and therefore peak compression does not occur when applying k″ to calculate the capacity factor. A given difference in k″ corresponds the same difference in migration times and this value does not depend on the position within the migration window. Since k″ is a normalized paramete it is easy to evaluate the significance of a given difference in capacity factor or to estimate the relative position of an analyte with a given capacity factor in the migration window by applying k″. Therefore, k″ seems to be an adequate parameter to calculate the capacity factor in MEKC and, similar to k′, it also refers to the hydrophobicity of the analyte.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.1150170423
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  • 7
    Electronic Resource
    Electronic Resource
    Comparative analysis of somatostatin analog peptides by capillary electrophoresis and micellar elektrokinetic chromatography (1996)
    Weinheim : Wiley-Blackwell
    Electrophoresis 17 (1996), S. 758-761 
    Details
    ISSN: 0173-0835
    Keywords: Capillary electrophoresis ; Micellar electrokinetic chromatography ; Somatostatin analog peptides ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Capillary electrophoresis (CE) and micellar electrokinetic chromatography (MEKC) methods, utilizing uncoated silica capillary and triethyl ammonium phosphate or sodium borate buffers in the pH range of 2.25-11.0, containing sodium dodecyl sulfate (SDS) (0-100 mM) for analysis of somatostatin-analog peptides were developed. The method presented here was compared with the reversed-phase high performance liquid chromatographic (RP-HPLC) and CE methods developed for analysis of peptides. The peptides investigated in this work can be separated by CE on the basis of their electrophoretic mobility in aqueous buffer of low pH value (pH 2.25) or by MEKC on the basis of their hydrophobicity in SDS containing buffer of high pH value (pH 11.0). Optimal MEKC separation of the investigated peptides has been achieved at pH 11.0 in an Na-borate buffer containig 100 mM SDS. CE at pH 2.25 proved insensitive to the hydrophobicity of the peptides investigated. By contrast, results obtained with MEKC at pH 11.0 proved to be anologous to those obtained by RP-HPLC, with highly hydrophobic peptides - migrating slower than peptides without hydrophobic moieties.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.1150170422
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