In vitro release of dextran sulfate from silicone intravaginal rings

Abstract 02665

FASCIOLA-HEPATICA - ULTRASTRUCTURAL-CHANGES TO THE TEGUMENT OF JUVENILE FLUKES FOLLOWING INCUBATION IN-VITRO WITH THE DEACETYLATED (AMINE) METABOLITE OF DIAMPHENETHIDE

Ultrastructural changes to the tegument of 5-week-old, 3-week-old and freshly-excysted Fasciola hepatica following in vitro incubation with the deacetylated (amine) metabolite of diamphenethide (DAMD, 10 mu gml(-1)) were examined by transmission electron microscopy, A similar sequence of tegumental changes occurred in all three age groups of fluke, although, with increasing fluke age, the time before onset increased and the damage became more extensive. The 5-week-old flukes showed an initial stress response after 3 h, typified by blebbing of the apical plasma membrane, formation of microvilli and an accumulation and accelerated release of secretory bodies at the tegumental apex, as well as swelling of the basal infolds, The swelling increased in extent with progressively longer periods of incubation in DAMD, leading to extreme edema and sloughing of the tegument after 9 h. The 3-week-old flukes showed a stress response and swelling of the basal infolds after only 1.5 h, although sloughing of the tegument did not occur until after 9 h. In the freshly-excysted metacercaria, a stress response and some sloughing of the tegument were evident after only 0.5 h. At all stages of development, the ventral tegument was more severely affected than the dorsal, Changes also occurred to the tegumental cells which were indicative of a disruption in the synthesis and release of tegumental secretory bodies: the amount of GER became reduced, the cisternae became swollen and their ribosomal covering decreased, the Golgi complexes disappeared from the cells and the numbers of secretory bodies in the cells also decreased, The heterochromatin content of the nuclei increased and eventually the tegumental cells began to break down, Again, the changes became apparent more rapidly at the earlier stages of development. The ultrastructural changes to the tegument are linked to a possible mode of action for diamphenethide as an inhibitor of protein synthesis. In turn, the results may help to explain the drug's high efficacy against juvenile stages of F. hepatica.

MODULATORY ACTION OF HELICOBACTER-PYLORI ON HISTAMINE-RELEASE FROM MAST-CELLS AND BASOPHILS IN-VITRO

Helicobacter pylori is important in the aetiology of peptic ulceration. Despite inducing an inflammatory response in the mucosa, the organism persists, suggesting that it has efficient protective mechanisms. Some bacterial and viral products modulate histamine secretion from inflammatory cells. Therefore, this study examined the modulatory effects of H. pylori preparations on histamine release from rat peritoneal mast cells and human basophils. Eleven clinical isolates of H. pylori were prepared in different ways: as whole washed bacteria, washed sonicated bacteria, and formalin-killed bacteria, and as outer-membrane and lipopolysaccharide (LPS) extracts. Histamine release from mast cells or basophils was not elicited by any of these bacterial preparations alone. However, when mixed with various secretory stimulants, the bacterial preparations caused inhibition of histamine release from rat mast cells (calcium ionophore A23187, compound 48/80, concanavalin A, anti-rat IgE) and human basophils (A23187, N-formyl Met-Leu-Phe). The degree of inhibition ranged from 48 % to 97 %. These results indicate that H. pylori exerts an inhibitory effect on cells of the immune system that contributes to its persistence within the gastric mucosa.

Phosphoramidates of 2'-beta-D-arabinouridine (AraU) as phosphate prodrugs; design, synthesis, in vitro activity and metabolism

2'-Beta-D-arabinouridine (AraU), the uridine analogue of the anticancer agent AraC, was synthesized and evaluated for antiviral activity and cytotoxicity. In addition, a series of AraU monophosphate prodrugs in the form of triester phosphoramidates (ProTides) were also synthesized and tested against a range of viruses, leukaemia and solid tumour cell lines. Unfortunately, neither the parent compound (AraU) nor any of its ProTides showed antiviral activity, nor potent inhibitory activity against any of the cancer cell lines. Therefore, the metabolism of AraU phosphoramidates to release AraU monophosphate was investigated. The results showed carboxypeptidase Y, hog liver esterase and crude CEM tumor cell extracts to hydrolyse the ester motif of phosphoramidates with subsequent loss of the aryl group, while molecular modelling studies suggested that the AraU l-alanine aminoacyl phosphate derivative might not be a good substrate for the phosphoramidase enzyme Hint-1. These findings are in agreement with the observed disappearance of intact prodrug and concomitant appearance of the corresponding phosphoramidate intermediate derivative in CEM cell extracts without measurable formation of araU monophosphate. These findings may explain the poor antiviral/cytostatic potential of the prodrugs.