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.
A physiological study on the toxicity of culture filtrate of helminthosporium sativum P.K. & P.
When symptoms of the leaf-spot disease of barley caused byHelminthosporium sativum could be reproduced by dipping host plants in fungal filtrate, it was thought to trace any correlation that may exist between nitrogenous constituents of the filtrate and its wilt-inducing capacity to test plants (lupin seedlings). The fungus was grown on a modified Fries' No 3 medium with sodium nitrate or ammonium chloride or an equivalent mixture of both as nitrogen source. The nitrogen content of the culture medium and its wilt-inducing capacity were traced over 34 days. The nitrogen content, after reaching a minimum, was found to rise again; the rise being more rapid and bigger in nitrate and ammonium-nitrate media than in ammonium media. Only a partial apparent correlation could be noted between the trend in the wilt-inducing capacity of filtrates obtained at different periods of incubation, and the trend in the change in their nitrogen content. It is suggested that the toxicity of the culture filtrate may be attributed to more than one substance, one of them being a nitrogenous product (possibly of peptide nature). The observed degree of toxicity would therefore depend on the relative amounts of the nitrogenous product and other substances.
Community refinement of glaucoma referrals
AbstractAim To describe a Manchester-based glaucoma referral refinement scheme designed to reduce the number of false-positive referrals to the hospital eye service. To report on the first years results of this scheme and its financial costs to the NHS.Methods Patients with suspected glaucoma, instead of being referred to their GP and then on to the hospital eye service, were referred to a group of specially trained community optometrists working to an agreed set of referral criteria. Those patients who did not meet the referral criteria were returned to the referring optometrist, while those who met the referral criteria were referred directly to Manchester Royal Eye Hospital. The patient's GP was informed in all cases.Results The number of suspect glaucoma cases referred to the Manchester Royal Eye Hospital was reduced by 40%. This figure is close to the percentage of false-positive referrals measured at Manchester Royal Eye Hospital prior to the onset of this study. The information accompanying referral has been improved and the scheme produces a small financial cost saving to the NHS of approximately £17 per patient.Conclusion Community refinement of suspect glaucoma offers some important benefits over the current referral pathway.