14 beta-O-cinnamoylnaltrexone and related dihydrocodeinones are mu opioid receptor partial agonists with predominant antagonist activity.

14-O-Cinnamoyl esters of naltrexone (6) were synthesized and evaluated in isolated tissue assays in vitro and in vivo in mouse antinociceptive assays. Their predominant opioid receptor activity was mu receptor (MOR) antagonism, but the unsubstituted cinnamoyl derivative (6a) had partial MOR agonist activity in vitro and in vivo. When compared to the equivalent 14-cinnamoylaminomorphinones (5), the cinnamoyloxy morphinones (6) as MOR antagonists had a shorter duration of action and were less effective as pseudoirreversible antagonists. The antinociceptive activity of the cinnamoyloxycodeinones (7) was not significantly greater than that of the morphinones (6), but they exhibited no evidence of any pseudoirreversible MOR antagonism. In both respects, these profiles differed from those of the equivalent 14-cinnamoylaminocodeinones (4).

Synthesis and hydrolytic behaviour of glycerol-1,2-diibuprofenate-3-nitrate, a putative pro-drug of ibuprofen and glycerol-1-nitrate.

Nitroxylated derivatives of non-steroidal anti-inflammatory drugs appear to offer protection against the gastrotoxicity normally associated with non-steroidal anti-inflammatory drugs, ostensibly via local production of nitric oxide. A diester of ibuprofen and glycerol-1-mononitrate has been prepared via the condensation of ibuprofen with 3-bromopropan-1,2-diol, followed by silver-(I)-nitrate-mediated nitroxylation. The release of ibuprofen from this diester has been studied in a simulated gastric fluid model with direct analysis by reverse-phase HPLC, using an acetonitrile-water (80%:20%) mobile phase containing trifluoroacetic acid (0.005%). n-Propyl ibuprofen was found to undergo pH-dependent hydrolysis, ranging from negligible hydrolysis at pH 5 to 52% hydrolysis at pH 3, over a 2-h period in this model. The ibuprofen-glycerol mononitrate diester was subjected to the most vigorous model hydrolytic conditions and was found to undergo 50 % hydrolysis during the study period. This study shows that pro-drugs of ibuprofen and glycerol mononitrate can be obtained, and can undergo degradation to the parent drugs under conditions simulating those likely to be encountered in the stomach.

"Spin-labelling" with the second hydrogen radioisotope: radicals formed from squalene by muonium addition.

By radio-labelling with muonium (the second hydrogen radioisotope), a free radical species has been clearly identified in squalene (2,6,10,15,19,23-hexamethyl-2,6,10,14,18,22-tetracosahexaene ) with a muon-electron hyperfine coupling of 240.7 MHz, as measured by the muon spin rotation (MuSR) technique. The radical is undetectable in pure squalene due to its high viscosity and the large molecular size which leads to extreme line broadening, but its signals may be resolved on reducing the viscosity of the medium by dilution with diethyl ether. The potential of the MuSR method is thus demonstrated as a means for spin-labelling radical species such as are formed from cellular antioxidants; ESR spectroscopy is unsuitable for studies of radicals formed from this molecule, due to extreme line-broadening and spectral complexity.

Potential irreversible ligands for opioid receptors. Cinnamoyl derivatives of beta-naltrexamine.

Cinnamoyl derivatives of beta-naltrexamine (beta-NTA) have been prepared and evaluated as potential irreversible opioid antagonists. In receptor binding assays, isolated tissue preparations and mouse antinociception assays the p-methylcinnamoyl derivative BU42 was similar to the standard opioid ligand beta-funaltrexamine (beta-FNA). The main features were reversible kappa agonism and irreversible mu antagonism. Surprisingly the p-chlorocinnamoyl derivative BU59 showed only modest competitive antagonist activity in-vivo despite appearing to bind irreversibly to mu receptors in the guinea-pig ileum (GPI) preparation. BU60, the dihydrocinnamoyl analogue of BU59, like BU59 displayed reversible kappa agonism in GPI but in mouse antinociception assays its agonism was mediated by mu and delta receptors rather than kappa. The surprising changes of profile attributable to substitution in the aromatic ring of the cinnamoylamido group in this small series suggests that a larger range of substituted cinnamoylamido derivatives should be studied to further elucidate the effects of Michael acceptor activity and other factors.

Effect of cyclosporin therapy in controlling the rejection of ileal versus jejunal allografts.

Experimental evidence suggests that jejunal allografts are rejected as rapidly as are ileal grafts, despite their lesser content of lymphoid tissue as an immunologic stimulus. However, it may be possible to postpone the rejection of jejunal grafts more readily than that of ileal grafts by means of immunosuppressive therapy with cyclosporin (CyA). To test this, we used the rat model (BN-LEW) of orthotopic small-bowel transplantation. The proximal third of the small-bowel with one-third of the mesenteric lymph nodes (n = 20), or the distal ileal third with all of the mesenteric lymph nodes (n = 22), or the entire small-bowel (n = 23) was interposed after resection of an equivalent type and length of recipient bowel. CyA (15 mg/kg) was given to all of these rats for 5 days. Three additional control groups were not given CyA. The difference in graft/recipient survival among the groups receiving CyA and among those not on CyA therapy was not statistically significant. Antidonor hemagglutinin titers, the mixed lymphocyte culture (MLC) assay, and histologic examination of the allograft failed to show a mitigated rejection reaction for the recipients of jejunal grafts. The data show that short-term treatment with CyA prolongs graft survival. Equal doses of CyA, however, did not lead to prolonged survival of jejunal grafts or alter the course of rejection in comparison with that for ileal or whole-bowel transplants.

Urea hydrolysis by immobilized urease in a fixed-bed reactor: analysis and kinetic parameter estimation.

Urea hydrolysis by urease immobilized onto ion exchange resins in a fixed-bed reactor has been studied. A modified Michaelis-Menten rate expression is used to describe the pH-dependent, substrate- and product-inhibited kinetics. Ionic equilibria of product and buffer species are included to account for pH changes generated by reaction. An isothermal, heterogeneous plug-flow reactor model has been developed. An effectiveness factor is used to describe the reaction-diffusion process within the particle phase. The procedure for covalent immobilization of urease onto macroporous cation exchangers is described. Urea conversion data are used to estimate kinetic parameters by a simplex optimization method. The best-fitted parameters are then used to predict the outlet conversions and pH values for systems with various inlet pH values, inlet urea and ammonia concentrations, buffers, particle sizes, and spacetimes. Very good agreement is obtained between experimental data and model predictions. This immobilized urease system exhibits quite different kinetic behavior from soluble urease because the pH near the enzyme active sites is different from that of the pore fluid. This effect results in a shift of the optimal pH value of the V(max) (pH) curve from 6.6 (soluble urease) to ca. 7.6 in dialysate solution, and ca. pH 8.0 in 20mM phosphate buffer. The reactor model is especially useful for estimating intrinsic kinetic parameters of immobilized enzymes and for designing urea removal columns.

Rejection of ileal versus jejunal allografts.

Small-bowel allografts are replete with lymphocytes, which may be the main stimulus for the recipient's immune system, thereby inducing rejection. Since most of the lymphoid tissue is located in the ileum, one would expect ileal grafts to be rejected more rapidly than are jejunal grafts. To test this theory, we transplanted a jejunal (n = 13) or an ileal segment (n = 9) or the entire small bowel (n = 6) orthotopically in the BN----LEW rat strain combination. Jejunal grafts included a short segment of the mesentery, whereas ileal and whole small-bowel grafts included the entire mesentery with its lymph nodes. Segmental as well as entire-bowel grafts induced peak anti-BN titers on the 6th to 7th postoperative day. In rats with entire-bowel grafts, rejection culminated in the recipient's death after an average of 9.5 +/- 1 days from graft necrosis and peritonitis; the rejection of jejunal (13.1 +/- 2.1 days) and ileal grafts (12.9 +/- 1.3 days) was less rapid. Segmental grafts were often encapsulated, and the causes of death were inanition and intestinal obstruction. Thus, despite their high lymphocyte content, ileal grafts were not rejected more quickly than were jejunal grafts; they should, therefore, be preferred because of their greater specialized absorptive capacity. Histologically, entire-bowel grafts were found to be rejected as rapidly as were segmental grafts; however, the toxic effects of the larger grafts that are undergoing rejection lead to earlier death of the recipient.

The structure of highly crosslinked poly(2-hydroxyethyl methacrylate) hydrogels.

Films were prepared by reaction of HEMA monomer with the crosslinking agent ethyleneglycol dimethacrylate (EGDMA) at crosslinking ratios, X, of 0.005, 0.01, 0.0128, 0.025, and 0.050 mol EGDMA/mol HEMA in the presence of 40 wt.% water at 60 degrees C for 12 h. These membranes were subsequently swollen in water at 37 degrees C and their structure analyzed using a modified Gaussian distribution equation of equilibrium swelling. The calculated values of Mc varied between 800 and 3700 daltons, which corresponded to a correlation length of the mesh size xi of 16.2 to 35.6 A. The structural analysis and diffusive studies of PHEMA membranes indicate that the recent determinations of Mc for PHEMA by Migliaresi et al. (C. Migliaresi, L. Nicodemo, L. Nicolais, and P. Passerini, "Physical characterization of PHEMA gels," J. Biomed. Mater. Res., 15, 307 (1981). and others are not accurate. The methods presented can also be used for analysis of any highly crosslinked polymer network produced by simultaneous polymerization and crosslinking reactions.