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45 results on '"Pradhan, Tapas K."'

4. Identification of CCK-A receptors on chief cells with use of a novel, highly selective ligand

Author

Pradhan, Tapas K., Qian, Jia-Ming, Sutliff, Vincent E., Mantey, Samuel A., and Jensen, Robert T.

Subjects
cholecystokinin -- Analysis, Cell receptors -- Research, Ligands -- Methods, Biological sciences
Abstract

Ligands of (D-TYR-Gly)A-71378 have, on synthesis, identified CCK-A and indicated CCK-B receptors in the guinea pig chief cells. These highly CCK-A-selective agonist ligands can be used to actually describe the specific CCK-A receptors since they employ binding. They can identify CCK-A receptors, even when the concentration of CCK-A is as low as 0.2% of the total CCK receptor number.

Published
1995

5. Smooth muscle cells from guinea pig stomach possess high-affinity galanin receptors that mediate relaxation

Author

Gu, Zeng-Fa, Pradhan, Tapas K., Coy, David H., and Jensen, Robert T.

Subjects
Muscle contraction -- Analysis, Neuropeptides -- Physiological aspects, Carrier proteins -- Physiological aspects, Biological sciences
Abstract

Gastric smooth muscle cells of guinea pig possess high affinity receptors, which mediate the biological activity of galanin. The binding of these receptors by galanin results in adenosine 35-cyclic monophosphate (cAMP) generation and muscle relaxation. The galanin receptor affinity is regulated by activation of guanine nucleotide-binding protein-G8. Galanine inhibits carbachol-induced contraction and causes relaxation.

Published
1994

8. 8-Methoxypsoralen Levels in Blood

Author

Chakrabarti, Siba G., Halder, Rebat M., Johnson, Beverly A., Minus, Harold R., Pradhan, Tapas K., and Kenney, John A., Jr.

Published
1987

27. Pharmacology and cell biology of the bombesin receptor subtype 4 (BB4-R)

Author

Katsuno, Tasuro, Pradhan, Tapas K., Ryan, Richard R., Mantey, Samuel A., Hou, Wei, Donohue, Patrick J., Akeson, Mark A., Spindel, Eliot R., Battey, James F., Coy, David H., and Jensen, Robert T.

Subjects
Bombesin -- Research, Peptides -- Research, Cell receptors -- Research, Structure-activity relationship (Pharmacology) -- Case studies, Cytology -- Case studies, Biological sciences, Chemistry
Abstract

A study was conducted to investigate the pharmacology and cellular basis of action of the bombesin receptor subtype four isolated from a Bombina orientalis brain cNA library. Three different approaches were used to attempt to produce cell lines expressing bombesin receptor subtype four whose pharmacology and coupling would likely resemble that of the native bombesin receptor subtype four. Experimental results of the study are discussed.

Published
1999

28. Identification of a unique ligand which has high affinity for all four bombesin receptor subtypes

Author

Pradhan, Tapas K., primary, Katsuno, Tatsuro, additional, Taylor, John E., additional, Kim, Sun H., additional, Ryan, Richard R., additional, Mantey, Samuel A., additional, Donohue, Patrick J., additional, Weber, H.Christian, additional, Sainz, Eduardo, additional, Battey, James F., additional, Coy, David H., additional, and Jensen, Robert T., additional

Published
1998
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29. Discovery of a High Affinity Radioligand for the Human Orphan Receptor, Bombesin Receptor Subtype 3, Which Demonstrates That It Has a Unique Pharmacology Compared with Other Mammalian Bombesin Receptors

Author

Mantey, Samuel A., primary, Weber, H. Christian, additional, Sainz, Eduardo, additional, Akeson, Mark, additional, Ryan, Richard R., additional, Pradhan, Tapas K., additional, Searles, Robert P., additional, Spindel, Eliot R., additional, Battey, James F., additional, Coy, David H., additional, and Jensen, Robert T., additional

Published
1997
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35. Identification of bombesin receptor subtype-specific ligands: effect of N-methyl scanning, truncation, substitution, and evaluation of putative reported selective ligands.

Author

Mantey, Samuel A, Gonzalez, Nieves, Schumann, Michael, Pradhan, Tapas K, Shen, Lin, Coy, David H, and Jensen, Robert T

Abstract

Mammalian bombesin (Bn) receptors include the gastrin-releasing peptide receptor, neuromedin B receptor, and bombesin receptor subtype 3 (BRS-3). These receptors are involved in a variety of physiological/pathologic processes, including thermoregulation, secretion, motility, chemotaxis, and mitogenic effects on both normal and malignant cells. Tumors frequently overexpress these receptors, and their presence is now used for imaging and receptor-mediated cytotoxicity. For these reasons, there is an increased need to develop synthetic, selective receptor subtype-specific ligands, especially agonists for these receptors. In this study, we used a number of strategies to identify useful receptor subtype-selective ligands, including synthesizing new analogs (N-methyl-substituted constrained analogs, truncations, and substitutions) in [d-Tyr(6),betaAla(11),Phe(13),Nle(14)]Bn(6-14), which has high affinity for all Bn receptors and is metabolically stable, as well as completely pharmacologically characterized analogs recently reported to be selective for these receptors in [Ca(2+)](i) assays. Affinities and potencies of each analog were determined for each human Bn receptor subtype. N-Methyl substitutions in positions 14, 12, 11, 10, 9, and 8 did not result in selective analogs, with the exception of position 11, which markedly decreased affinity/potency. N-Terminal truncations or position 12 substitutions did not increase selectivity as previously reported by others. Of the four shortened analogs of [d-Phe(6),betaAla(11),Phe(13),Nle(14)]Bn(6-14) reported to be potent selective BRS-3 ligands on [Ca(2+)](i) assays, only AcPhe,Trp,Ala,His(tauBzl),Nip,Gly,Arg-NH(2) had moderate selectivity for hBRS-3; however, it was less selective than previously reported Apa(11) analogs, demonstrating these are still the most selective BRS-3 analogs available. However, both of these analogs should be useful templates to develop more selective BRS-3 ligands.

Published
2006
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38. Reply

Author

Chakrabarti, Siba G., primary, Halder, Rebat M., additional, Johnson, Beverly A., additional, Minus, Harold R., additional, Pradhan, Tapas K., additional, and Kenney, John A., additional

Published
1987
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44. REPLY.

Author

Chakrabarti, Siba G., Grimes, Pearl E., Minus, Harold R., Kenney Jr., John A., and Pradhan, Tapas K.

Subjects
*LETTERS to the editor, *BODY fluids
Abstract

Presents a response by S.G. Chakrabarty to a letter to the editor about his article "Determination of Trimethyipsoralen in Blood, Ophthalmic Fluids, and Skin," in the April 1982 issue.

Published
1983
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45. Elucidation of vasoactive intestinal peptide pharmacophore for VPAC(1) receptors in human, rat, and guinea pig.

Author

Igarashi H, Ito T, Hou W, Mantey SA, Pradhan TK, Ulrich CD 2nd, Hocart SJ, Coy DH, and Jensen RT

Subjects
Alanine chemistry, Amino Acid Sequence, Amino Acid Substitution, Amylases metabolism, Animals, Blotting, Southern, CHO Cells, Cells, Cultured, Cricetinae, Guinea Pigs, Humans, Male, Molecular Sequence Data, Pancreas enzymology, Pancreas metabolism, Peptides chemical synthesis, Peptides pharmacology, Rats, Receptors, Vasoactive Intestinal Peptide biosynthesis, Receptors, Vasoactive Intestinal Peptide genetics, Receptors, Vasoactive Intestinal Polypeptide, Type I, Reverse Transcriptase Polymerase Chain Reaction, Species Specificity, Transfection, Tumor Cells, Cultured, Receptors, Vasoactive Intestinal Peptide drug effects, Vasoactive Intestinal Peptide chemistry
Abstract

Vasoactive intestinal peptide (VIP) is a neurotransmitter involved in a number of pathological and physiological processes. VIP is rapidly degraded and simplified stable analogs are needed. VIP's action was extensively studied in rat and guinea pig. However, it is largely unknown whether its pharmacophore in these species resembles human. To address this issue we investigated the VIP pharmacophore for VPAC(1) (the predominant receptor subtype in cancers and widely distributed in normal tissues) by using alanine and D-amino acid scanning. Interaction with rat, guinea pig, and human VPAC(1) was assessed using transfected Chinese hamster ovary (CHO) and PANC1 cells and cells possessing native VPAC(1). Important species differences existed in the VIP pharmacophore. The human VPAC(1) expressed in CHO cells, which were used almost exclusively in previous studies, differed markedly from the native VPAC(1) in T47D cells. The most important amino acids for determining affinity are His(1), Asp(3), Phe(6), Arg(12), Arg(14), and Leu(23). Ser(2), Asp(8), Asn(9), Thr(11), Val(19), Asn(24), Ser(25), Leu(27), and Asn(28) are not essential for high-affinity interaction/activation. [Ala(2,8,9,11,19,24,25,27,28)]VIP, which contained 11 alanines, was synthesized and it was equipotent to VIP at VPAC(1) receptors in all species and was metabolically stable. Our results show in any design of simplified VIP analogs for VPAC(1) it will be important to consider species differences and it is essential to use transfected systems that reflect the native receptor's pharmacophore. Last, with our results a simplified, metabolically stable VIP analog was identified that should be useful as a prototype for design of selective agonists/antagonists that could be useful therapeutically.

Published
2002
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