Effect of sulphanilamide on citric acid production by Aspergillus niger

It has been shown that the mechanism of resistance to sulphanilamide toxicity in E. coli involves the enhanced formation of coenzyme A which is required for the acetylation of the drug. A similar increase in the coenzyme A levels of the cells has been observed in S. cerevisiae subjected to sulphanilamide toxicity. An interesting observation made in the experiments with S. cerevisiae was that, concomitant with the increase in the coenzyme A levels of the cells, there was an enhancement in the levels of ergosterol as well. In view of the known role of coenzyme A in sterol biosynthesis, it was considered of interest to investigate the effect of sulphanilamide toxicity on other biosynthetic processes involving the action of coenzyme A. Accordingly the effect of the drug on citric acid production by a citric acid-accumulating strain of Aspergillus niger was investigated. The results presented here show that the production of citric acid by the mould is markedly inhibited by sulphanilamide

Biomimetic Regeneration of Elastin Matrices Using Hyaluronan and Copper Ion Cues

Current efforts to tissue engineer elastin-rich vascular constructs and grafts are limited because of the poor elastogenesis of adult vascular smooth muscle cells (SMCs) and the unavailability of appropriate cues to upregulate and enhance cross-linking of elastin precursors (tropoelastin) into organized, mature elastin fibers. We earlier showed that hyaluronan (HA) fragments greatly enhance tropo- and matrix-elastin synthesis by SMCs, although the yield of matrix elastin is low. To improve matrix yields, here we investigate the benefits of adding copper (Cu2+) ions (0.01 M and 0.1 M), concurrent with HA (756–2000 kDa), to enhance lysyl oxidase (LOX)-mediated elastin cross-linking machinery. Although absolute elastin amounts in test groups were not different from those in controls, on a per-cell basis, 0.1 M of Cu2+ ions slowed cell proliferation (5.6 ± 2.3–fold increase over 21 days vs 22.9 ± 4.2–fold for non-additive controls), stimulated synthesis of collagen (4.1 ± 0.4–fold), tropoelastin (4.1 ± 0.05–fold) and cross-linked matrix elastin (4.2 ± 0.7–fold). LOX protein synthesis increased 2.5 times in the presence of 0.1 M of Cu2+ ions, and these trends were maintained even in the presence of HA fragments, although LOX functional activity remained unchanged in all cases. The abundance of elastin and LOX in cell layers cultured with 0.1 M of Cu2+ ions and HA fragments was qualitatively confirmed using immunoflourescence. Scanning electron microscopy images showed that SMC cultures supplemented with 0.1 M of Cu2+ ions and HA oligomers and large fragments exhibited better deposition of mature elastic fibers (∼1 μm diameter). However, 0.01 M of Cu2+ ions did not have any beneficial effect on elastin regeneration. In conclusion, the results suggest that supplying 0.1 M of Cu2+ ions to SMCs to concurrently (a) enhance per-cell yield of elastin matrix while allowing cells to remain viable and synthetic and not density-arrested in long-term culture because of their moderating effects on otherwise rapid cell proliferation and (b) provide additional benefits of enhanced elastin fiber formation and cross-linking within these tissue-engineered constructs