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Background: Cardiac hypertrophy is a major risk factor for morbidity and mortality in a number of cardiovascular diseases. Consequently, the signaling pathways that inhibit cardiac hypertrophy are currently receiving much interest. Among them, nitric oxide (NO), signaling via cGMP and cGMP-dependent protein kinase I, has been recognized as a negative regulator of cardiac hypertrophy. The present study investigated the in-vivo effect of sildenafil as a phosphodiestrase-5A (PDE-5A) inhibitor on the hypertrophic response of rat heart to isoproterenol and the relation of this effect to the level of myocardial cGMP and integrity of the constitutive nitric oxide synthase (cNOS) activity.

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Abstract:The influence of pH on kojic acid fermentation by Aspergillus flavus Link 44-1 in submerged fermentation and resuspended cell system was investigated separately. Although the highest growth in submerged fermentation was obtained at initial culture pH between 6 to 7, the optimum kojic acid production was achieved at initial culture pH 3. At initial culture pH 2, growth was greatly inhibited and kojic acid was not produced. In resuspended cell system using buffered glucose solution, in which the production of cell material was carried out at initial culture pH 3, the optimum kojic acid production was also obtained at pH 3. Kojic acid production in fermentation using 50 L stirred tank fermenter with pH control strategy (fermentation was started with pH 3 and without pH control during growth phase and culture pH was controlled at 3 during the production phase) was improved by about 20% as compared to fermentation without pH control. The maximum kojic acid concentration in fermentation with pH control strategy was 62.00 g/L and this gave yield and productivity of 0.516 g/g and 0.22 G/L h, respectively.