N-terminal glycation of cholecystokinin-8 abolishes its insulinotropic action on clonal pancreatic B-cells.

Monoglycated cholecystokinin octapeptide (Asp(1)-glucitol CCK-8) was prepared under hyperglycaemic reducing conditions and purified by reverse phase-high performance liquid chromatography. Electrospray ionisation mass spectrometry and automated Edman degradation demonstrated that CCK-8 was glycated specifically at the amino-terminal Asp(1) residue. Effects of Asp(1)-glucitol CCK-8 and CCK-8 on insulin secretion were examined using glucose-responsive clonal BRIN-BD11 cells. In acute (20 min) incubations, 10(-10) mol/l CCK-8 enhanced insulin release by 1.2-1.5-fold at 5.6-11.1 mmol/l glucose. The stimulatory effect induced by 10(-10) mol/l CCK-8 was abolished following glycation. At 5.6 mmol/l glucose, CCK-8 at concentrations ranging from 10(-11) to 10(-7) mol/l induced a significant 1.6-1.9-fold increase in insulin secretion. Insulin output in the presence of Asp(1)-glucitol CCK-8 over the concentration range 10(-11)-10(-7) mol/l was decreased by 21-35% compared with CCK-8, and its insulinotropic action was effectively abolished. Asp(1)-glucitol CCK-8 at 10(-8) mol/l also completely blocked the stimulatory effects of 10(-11)-10(-8) mol/l CCK-8. These data indicate that structural modification by glycation at the amino-terminal Asp(1) residue effectively abolishes and/or antagonises the insulinotropic activity of CCK-8.     

Initiating Events in Direct Cardiomyocyte Reprogramming

1. Download high-res image (165KB)
2. Download full-size image

     

Tachykinins (Substance P, Neurokinin A and Neuropeptide γ) and Neurotensin from the Intestine of the Burmese Python, Python molurus

Conlon, J. M., T. E. Adrian and S. M. Secor. Tachykinins (substance P, neurokinin A and neuropeptide γ,) and neurotensin from the intestine of the burmese python, Python molurus. Peptides 18(10) 1505–1510, 1997.—Peptides with substance P-like immunoreactivity, neurokinin A-like immunoreactivity and neurotensin-like immunoreactivity were isolated in pure form from an extract of the intestine of the Burmese python (Python molurus). The primary structure of python substance P (Arg-Pro-Arg-Pro-Gln-Gln-Phe-Tyr-Gly-Leu-Met-NH₂) shows one amino acid substitution (Phe⁸ → Tyr) compared with chicken/alligator substance P and an additional substitution (Lys³ → Arg) as compared with mammalian substance P. The neurokinin A-like immunoreactivity was separated into two components. Python neuropeptide γ (Asp-Ala-Gly-Tyr-Ser-Pro-Leu-Ser-His-Lys-Arg-His-Lys-Thr-Asp-Ser-Phe-Val-Gly-Leu-Met-NH₂ shows three substitutions (Gly⁵ → Ser, Gln⁶ → Pro and Ile⁷ → Leu) compared with alligator neuropeptide γ and an additional substitution (His⁴ → Tyr) compared with mammalian neuropeptide γ. Python neurokinin A (His-Lys-Thr-Asp-Ser-Phe-Val-Gly-Leu-Met.NH₂) is identical to human/chicken/alligator neurokinin A. Python neurotensin (pGlu-Leu-Val-His-Asn-Lys-Ala-Arg-Pro-Tyr-Ile-Leu) is identical to chicken/alligator neurotensin. The data are indicative of differential evolutionary pressure to conserve the amino acid sequences of reptilian gastrointestinal peptides.     

Epidemiology of Infection with Epstein-Barr Virus Types 1 and 2: Lessons from the Study of a T-Cell-Immunocompromised Hemophilic Cohort

In apparent contrast to earlier work on Epstein-Barr virus (EBV) carriage in the general Caucasian population, in vitro virus isolations from human immunodeficiency virus (HIV)-positive male homosexual cohorts have shown frequent examples of multiple EBV infection and an overall prevalence of type 2 EBV strains exceeding 30%. Here we ask to what extent these findings might hold true in another T-cell-immunocompromised cohort, HIV-positive hemophilic patients. Resident EBV strains were rescued within lymphoblastoid cell lines derived from the blood and throat washings of 39 such individuals, using the same in vitro protocols of virus isolation as for the homosexual cohort. A mean of 19 independent cell lines was made per patient, and in each case the resident virus was characterized by PCR-based viral genomic analysis and by immunoblotting to reveal the viral “EBNAprint.” By these criteria a significant proportion (14 of 39) of the hemophilic cohort carried more than one EBV strain, suggesting that T-cell impairment does indeed sensitize virus carriers to reinfection with new strains of exogenously transmitted virus. However, the overall incidence of type 2 EBV infection was 10%, which is close to that observed in the earlier work with healthy carriers and substantially lower than that seen in HIV-positive homosexuals. We infer that type 2 EBV is relatively rare in the general Caucasian population but has become endemic in the homosexual community.     

Novel 2-imidazoles as potent and selective alpha1A adrenoceptor partial agonists

Novel 2-imidazoles have been identified as potent partial agonists of the α_1A adrenergic receptor, with good selectivity over the α_1B, α_1D and α_2A receptor sub-types. Sulfonamide 23 possessed attractive drug-like properties with respect to physicochemical and ADME properties and wide ligand selectivity.     

Novel 2-imidazoles as potent, selective and CNS penetrant alpha1A adrenoceptor partial agonists

A novel series of central nervous system (CNS) penetrant indane 2-imidazoles have been identified as potent, partial agonists of the alpha(1A) adrenergic receptor, having good selectivity over the alpha(1B), alpha(1D) and alpha(2) sub-types. A key structural motif to impart selectivity is a methylene spacer between the indane and a pendant substituent, which includes heterocycles, sulphones and ethers. Introduction of an ortho-halogen to this group led to a lowering of intrinsic efficacy (E(max)).