Solution-structure of a Peptide Designed to Mimic the C-terminal Hexapeptide of Endothelin

The peptide: Ac-cyclo(Cys-His-Leu-Asp-Cys)-Ile-Trp-OH, has been designed by computer-aided molecular-modelling techniques to mimic the proposed α-helical conformation of the C-terminal hexapeptide of endothelin. Two-dimensional proton nuclear magnetic resonance spectra were acquired for the peptide dissolved in d₆-DMSO or D₂O-H₂O and the distance and angle constraints incorporated into simulated annealing experiments. Conformers generated from the D₂O-H₂O data superposed on the corresponding main-chain atoms in the crystal structure of endothelin 1 and the solution structure of BQ-123 with root mean square co-ordinate differences of 0·9 Å and 0·77 Å, respectively. The peptide did not elicit antagonism of endothelin-induced in-vitro contractions of rabbit aorta (endothelin A receptor) or rabbit bronchus (endothelin B receptor) preparations. Because the peptide can adopt a conformer which closely matches the equivalent residues in the endothelin 1 crystal structure and in BQ-123, we suggest BQ-123 does not necessarily mimic the endothelin C-terminal region to achieve its antagonism, and that a helical conformation of the endothelin C-terminal hexapeptide does not favour its interaction at the endothelin B receptor.     

Modified polyalkenoate (glass-ionomer) cement – a study

summary Conventional glass-ionomer cements with varying amounts (5–15%) of borax (Na₂B₄O₇.10H₂O) as modifier were prepared. These mixtures were spatulated with an aqueous solution of polyacrylic acid with a powder to liquid (P/L) ratio of 1.5:1. Properties such as working time, setting time, compressive strength, diametral tensile stength, solubility and fluoride release of these cements were determined. It was observed that the working time and setting time of the resultant cements shortened with the addition of borax. Certain physical properties such as compressive and diametral tensile strength, solubility and disintegration of these glass-ionomer cements deteriorated with borax addition but fluoride release from them was unaffected.     

COMPARATIVE ANTI-NOCICEPTIVE, ANTI-INFLAMMATORY AND TOXICITY PROFILE OF NIMESULIDE vs NIMESULIDE AND PIPERINE COMBINATION

Piperine is an inhibitor of various hepatic and other enzymes involved in the biotransformation of drugs. Preliminary pharmacokinetic studies conducted by us suggested the increased bioavailability of nimesulide co-administered with piperine. The present study was, thus, conducted to evaluate the antinociceptive, anti-inflammatory and toxicity profile of a new nimesulide-piperine combination administered orally as compared with nimesulide alone. Antinociceptive efficacy was tested using an acetic acid writhing test and tail flick latency test (TFL). The ED50 value of a nimesulide-piperine combination in writhing test was calculated to be significantly lower (1.5 mg kg(-1)) as compared to (11.2 mg kg(-1)) of nimesulide alone. The antinociceptive effect was lesser in the tail flick latency test as compared to what was observed in the writhing test indicating the peripheral action of the Non-Steriodal Anti-Inflammatory Drug (NSAID). In carrageenan-induced inflammatory tests, the nimesulide-piperine combination was found to be dose-to-dose superior than nimesulide alone. Acute toxicity studies on mice revealed a reduction in lethal dose (LD50) of the combination (980 mg kg(-1)) as compared to nimesulide (1500 mg kg(-1)) alone. Results from the present study suggest a better therapeutic index for the nimesulide-piperine combination indicating that this combination would further reduce the frequency of adverse effects associated with nimesulide alone.     

Reduced IL-4 and interferon-gamma (IFN-γ) expression by CD4 T cells in patients with chronic lymphocytic leukaemia

CD7 co-expression by CD4 T cells has been reported to be higher in the Th1 compared with the Th2 functional subset. Clinical immunodeficiency and immune dysregulation are more prevalent in the advanced stages of B cell chronic lymphocytic leukaemia (B-CLL). To analyse this further 25 patients with B-CLL and 11 healthy subjects were examined for cell surface CD7 and intracellular IFN-γ and IL-4 expression in the peripheral blood CD4⁺ T helper cell population. Significantly decreased CD7, IFN-γ and IL-4 expression was observed in the patients with B-CLL (P < 0.001). While CD7 negativity and IL-4 expression were more frequent in the later stages of the disease, this did not attain statistical significance. These results suggest a possible explanation for the reduced cellular and humoral immunity in B-CLL.