The effect of pH value on the toxicity of culture filtrates ofHelminthosporium Sativum and on its possible correlation to extracellular nitrogen accumulation
Helminthosporium sativum P.K. & B. was grown on modified Fries No. 3 medium buffered at pH 4.7, 5.5, 6.7, and 7.8. The nitrogen content of the culture filtrate, mycelial growth and the toxicity of the filtrate (as measured by its wilt inducing capacity to lupin seedlings) were traced over 24 days. The correlation between nitrogen accumulation and the toxicity of the filtrates was clear in case of media originally buffered at 4.7, 5.5 and 7.8. On the other hand, there was no correlation between growth of the mycelial mats and toxin production. The toxicity of the filtrate was attributed to two substances at least, one of unknown composition produced during the accelerated growth phase, while the other is nitrogenous and produced during the decline growth phase i.e. autolytic in nature. Acidity of the medium favoured toxin production during the first two weeks of incubation. The toxicity of the filtrate remained stable within a wide range of pH between pH 3–9.4.
THE pH FACTOR IN THE METABOLISM OF FUSARIUM MONILIFORME SHELDON ON SUCROSE
A study has been made of the effects of varying the pH value of the culture media on sucrose inversion and absorption, on respiration, and on growth of Fusarium moniliforme Sheldon. The study was carried out on 1-week-old fungal mats that were then subjected to experimentation for 48 hours. Sucrose inversion was almost unaffected by pH values higher than 5.4 but was inhibited at pH 4.0. Sugar uptake was influenced more by lowering than by raising pH beyond 5.4. Carbon dioxide output per unit dry weight of mycelial mat was lowest at the pH optimum for growth, as measured by mat dry weight. At the same optimum pH there was also the highest rate of sucrose inversion and uptake. It seemed, therefore, that the effect of pH on growth was the additive effects on the different enzymatic processes operating in the metabolism of the fungus. It is also suggested that the external pH of the medium might act by the invasion of hydrogen or hydroxyl ions into the mycelial cells, thus changing the internal pH.
The costs of identifying undiagnosed prostate cancer in asymptomatic men in New Zealand general practice
Background. Screening for prostate cancer (PCa) using the prostate-specific antigen (PSA) test is widespread in New Zealand. 3 informed testing history in 2007–09 were NZ$8887 compared to NZ$13 870 if the men had PSA tests in 2007–09. If we assumed a PSA test involved a full 15-minute general practice consultation, the estimated costs increased to NZ$26 877 per PCa identified. Conclusions. Screening of asymptomatic men for PCa is widely practiced. Most of the costs of screening were incurred in general practice. Calls for men to receive increased information on the harms and benefits of screening will substantially increase the costs. The current costs could be reduced by better targeting of screening.