Factors influencing pathogenicity of three isolates of colletotrichum graminicola on wheat

Summary Factors such as varieties of wheat, hydrogen ion and various mineral salts concentrations of soil having possible influence on the pathogenicity of certain isolates ofColletotrichum graminicola (Ces.)Wils. on wheat were studied. Of the six varieties of wheat studied, the variety Dual was highly susceptible, and the variety Knox highly resistant. The percentage seedling blight was greatest in soil at the highest pH values, 7.0–9.0. Concentrations of potassium nitrate, ammonium nitrate and magnesium sulfate in soil greatly influenced disease development.Portion of a Ph. D. thesis, Department of Botany and Plant Pathology, The Ohio State University, Columbus-10, Ohio, U.S.A.     

Factors influencing ascorbate free radical formation

Several constituents of serum and related substances were examined in order to find factors influencing ascorbate radical formation. Human ceruloplasmin and albumin catalyzed singly ascorbate oxidation and caused a remarkable increase in ESR intensity of the ascorbate radical. Although, however, the combination of these two factors showed synergic effects on catalysis of ascorbate oxidation, the radical intensity significantly decreased. Fibrinogen and fetuin showed inhibitory effects on catalysis of ascorbate oxidation, whereas transferrin, citric acid, or other related substances exhibited no effect. A new factor which inhibited ascorbate oxidation was found in a serum fraction. These results indicate there is a counterbalanced equilibrium in the redox process of ascorbate in serum and the intensity of ascorbate radical is influenced by the summation of the complicated effects of many factors.     

Vacuolar system of ungerminated Colletotrichum graminicola conidia: convergence of autophagic and endocytic pathways

Vacuoles of ungerminated Colletotrichum graminicola conidia engulf cytoplasmic structures by a process analogous to microautophagy, demonstrated by using a vacuolar membrane acid phosphatase marker. Fusion of vesicles with vacuoles, without deposition of the acid phosphatase reaction product has been observed, suggesting other pathways of material delivery to vacuoles than microautophagy. Plasma membrane invaginations, multivesicular bodies and retention of neutral red into small vesicles, which were internalized by the vacuole, were verified. These results provided evidence for endocytosis and an active endosomal system. Together, our findings with C. graminicola demonstrated that vacuoles are very dynamic compartments, playing roles in autophagy and endocytic processes.     

Factors influencing Giemsa band formation of human chromosomes

Summary Factors influencing a Giemsa banding method in which slides are treated with NaOH and then incubated in phosphate buffer were investigated. The study indicated that the removal of chromosomal proteins during fixation in acetic methanol is important for band formation. When fixatives containing formalin were used no banding occurred. Histones do not appear to be involved in band formation as neither of the two histone staining methods tested gave banding patterns. The age of the slide preparations was important, the best banding occurring on slides a week old. Romanovsky stains were the only stains to give banding, other stains resulted in distorted chromosomes. The composition of the incubation buffer had little effect on the quality of the banding. However liquid scintillation analysis of the phosphate buffer in which ³H-thymidine labelled preparations had been treated, revealed that thymidine is removed during incubation in buffer, and suggests that the degradation of thymidine is an important factor in band formation.This work was supported by the W. H. Travis Trust and the Canterbury and Westland Division of the Cancer Society of New Zealand.     

Adhesive knob formation by conidia of the nematophagous fungusDrechmeria coniospora

We studied conidiogenesis and adhesive knob formation (maturation) by newly developed conidia of the nematophagous fungusDrechmeria coniospora. Upon conidiogenesis on infected nematodes or during saprophytic growth of the fungus in axenic cultures compact clusters of conidia developed. Less than 10% of such clustered conidia matured; mature conidia were invariably located on the periphery of the clusters.The kinetics and rate of maturation of conidia were studied inin vitro systems and in soil. In both cases adhesive knobs were formed; the rate at which knobs were formed appeared to be determined by the age of the conidia, the temperature and the soil moisture. In addition, knob formation was suppressed at increasing conidial densities. Under favorable conditions, however, over 90% of the conidia matured within a period of 3 days. The rate of knob formation was neither influenced by the presence of nematodes nor by that of exogenous nutrients, which suggests that maturation is an autonomous process. Electron-microscopical analysis indicated that budding of the conidia at the initial stage of maturation occurred simultaneously with the deposition of the sticky, adhesive layer around the wall of the developing knob.The ecological significance of the time- and spatially separated maturation of conidia after conidiogenesis is discussed with respect to survival of the conidia.     

Factors influencing lesion formation during radiofrequency catheter ablation

In radiofrequency (RF) ablation, the heating of cardiac tissue is mainly resistive. RF current heats cardiac tissue and in turn the catheter electrode is being heated. Consequently, the catheter tip temperature is always lower--or ideally equal--than the superficial tissue temperature. The lesion size is influenced by many parameters such as delivered RF power, electrode length, electrode orientation, blood flow and tissue contact. This review describes the influence of these different parameters on lesion formation and provides recommendations for different catheter types on selectable parameters such as target temperatures, power limits and RF durations.     

中国被毛孢分生孢子形成过程显微结构的研究

分生孢子是中国被毛孢(H sinensis)生活史中极为重要的一个环节,其在冬虫夏草侵染和形成过程中有着十分关键的作用.本实验以中国被毛孢纯培养菌种为实验材料,采用显微镜观察了其菌丝体经营养生长产分生孢子过程中显微结构变化,结果表明:中国被毛孢在固体培养条件下,可以形成分生孢子,其形态和产生方式与微循环产孢过程中形成的分生孢子一致,同时,在产孢过程中,还存在瓶梗结构纵裂形成对生分生孢子的现象.     

Factors influencing odour production by actinomycetes

Odour production by actinomycete (Streptomyces spp.) strains isolated from hypereutrophic natural waters in which muddy odours in fish have occurred, were studied by the ISP (International Streptomyces Project) carbon utilization method. The streptomycete strains were isolated from water, bottom mud and aquatic plants. Nine different carbon sources were used. Odour character was determined by sniffing the cultures. Odour production varied depending on the strain and the carbon source used. Some of the strains produced similar odours in all media regardless of the carbon source. In other strains, the odour varied depending on the carbohydrate used. The total colony counts of actinomycetes may not necessarily indicate the role of actinomycetes in odour problems in the aquatic environment because the odour production by actinomycetes depends on environmental factors.     

Factors influencing the degradation of garbage in methanogenic bioreactors and impacts on biogas formation

Anaerobic digestion of garbage is attracting much attention because of its application in waste volume reduction and the recovery of biogas for use as an energy source. In this review, various factors influencing the degradation of garbage and the production of biogas are discussed. The surface hydrophobicity and porosity of supporting materials are important factors in retaining microorganisms such as aceticlastic methanogens and in attaining a higher degradation of garbage and a higher production of biogas. Ammonia concentration, changes in environmental parameters such as temperature and pH, and adaptation of microbial community to ammonia have been related to ammonia inhibition. The effects of drawing electrons from the methanogenic community and donating electrons into the methanogenic community on methane production have been shown in microbial fuel cells and bioelectrochemical reactors. The influences of trace elements, phase separation, and co-digestion are also summarized in this review.