Possible role of plant phenolics in the production of trichothecenes by Fusarium graminearum strains on different fractions of maize kernels

Four trichothecene-producing strains of Fusarium graminearum were grown on three maize grain fractions, whole grain, degermed grain, and the germ, to determine the effect of natural substrates on mycotoxin production. Monitoring the ergosterol content after 25 days of incubation indicated that fungal growth on all grain fractions was comparable. Trichothecene (TCT) production was highest on degermed grain, less on whole grain, and very low or nondetectable on the germ; similar results were found with four different strains. It was concluded that inhibitor(s) of TCT biosynthesis were present in maize germ. The presence of phenolic compounds was investigated in the different fractions. The hydroxamate 4-acetylbenzoxazolin-2-one (4-ABOA), a known inhibitor of mycotoxin production, was found in the degermed and whole grain fractions but not in the germ. Therefore, the TCT inhibition observed on the maize germ fraction used in our study is clearly not linked to 4-ABOA. Other soluble phenolic compounds were found at a much higher concentration in the germ than in the two other fractions. The inhibition property of the soluble ester-bound extracts was tested in liquid culture. A possible role for these compounds is discussed.     

The origin of the A genome donor of wheats (Triticum: Poaceae) – a perspective based on the sequence variation of the 5S DNA gene units

In a prior study on the haplomes of wheat using the 5S rRNA gene we assigned the long A1 and short A1 unit classes to the A haplome in the diploid T. monococcum. The short A1 unit class is absent in the tetraploids T. turgidum and T. timopheevii and in the hexaploid T. aestivum, although present in the hexaploid T. zhukovskyi. Both T. turgidum and T. aestivum contained a different 5S DNA unit class labeled the short A2.The purpose of this paper was to study the short A2 units in the two diploid species to shed light on the theory that the A haplome donor of T. turgidum and T. aestivum was T. urartu. Fifty eight clones were obtained from 12 accessions, sequenced and analyzed. As expected T. baeoticum, which is often classified as a subspecies of T. monococcum, contained the long A1 and the short A1 5S DNA units. Unexpectedly, T. urartu had the long A1 and the short G1 unit classes instead and other units not found so far in Triticum. These findings support the hypothesis that the donor of the A genome in T. zhukovskyi was T. monococcum, as identified by the short A1 units. However, the short A1 units are absent in T. timopheevii, also a carrier of the A genome. The short G1 units found in T. urartu also identify it as a possible donor of the G genome to T. timopheevii. The short G1 units were also found in T. aestivum in our prior study. The long G1 unit class was not found in T. urartu but reported from T. timopheevii and T. zhukovskyi. The implications of these and related findings on the evolution of wheats are discussed.     

Modelling of sorption experiments and seepage data of an Amazonian Ultisol subsoil under cropping fallow

The results of physico-chemical investigations of an Ultisol subsoil under a 2-year old fallow in eastern Amazonia are presented. Subsoil chemistry was studied using 4 different approaches: i) concentrations of H, Na, K, Ca, Mg, Mn, Al, and Fe in seepage water were measured under field conditions, ii) the equilibrium soil chemistry was studied in sequential batch experiments where the soil was treated with different solutions, iii) results of batch experiments were simulated with a chemical equilibrium model, and iv) the seepage data were calculated using selectivity coefficients obtained by modelling the batch experiments. The model included multiple cation exchange, precipitation/dissolution of Al(OH)₃ and inorganic complexation. Cation selectivity coefficients were pK_x/Ca^sel: X = Na: 0.3, K: 0.8, Mg: ?0.1, and Al: 0.4. The amount of cations sorbed ranged from ?0.2 to 2.0 (K), ?0.7 to 2.3 (Mg), ?1.6 to 1.8 (Ca), ?4.8 to 3.6 (Al) and 0.0 to 8.5 (Na) mmol_c kg^?1. The model predictions were good with values lying within 0.3 pH units (for the pH range 3.7 to 7.2), and 3% of CEC for individual cations. The most important proton buffer reaction seemed to be the dissolution of gibbsite and a large release of Al into the soil solution. When selectivity coefficients obtained by the modelling procedure were used to predict the field data for cation concentrations in the seepage water, they decreased in the following order: Na > K > Ca > Mg > Al. These calculated values were similar to the measured order: Na > Ca > K ≈ Mg > Al. Thus the options for managing these soils should be carefully chosen to avoid soil acidification which may result from inappropriate use of fertilizer during the cropping period.     

Visceral leishmaniasis in a dog: clinical, hematological and pathological observations.

Visceral leishmaniasis was diagnosed in a dog that had been living with his owners in Spain for two years. Clinical diagnosis was somewhat delayed as the disease is largely unknown to Canada and was manifested by a nonresponsive anemia which was not easily explained on peripheral blood evaluation alone, and concomitant interstitial nephritis. On post mortem examination splenomegaly was the main gross pathological finding. Light microscopic examination of bone marrow aspirates and subsequent electron microscopic examination of splenic and hepatic tissues revealed numerous Leishman-Donovan bodies in cells of the reticuloendothelial system. Parasitized reticuloendothelial cells were seen singly or forming granulomata. These latter did not contain giant cells and were confined mainly to the liver and spleen, being sparse and single in the first but extremely numerous and coalescing in the latter. Accumulation of intrafollicular hyaline material was seen in a small number of splenic follicles. Leishman-Donovan bodies on electron microscopic examination had a trilaminar periplast, a large round nucleus with heavy blocks of marginated chromatin and two nucleoli, a short flagellum and a kinetoplast. Lymph nodes and bone marrow had numerous parasitized macrophages but no granulomata. Leishman-Donovan bodies were not detected in the lungs and kidneys both of which exhibited a chronic intersitital reaction. The comparative hematological profile as well as the importance of bone marrow and electron microscopic examinations of the spleen and liver in diagnosis are discussed. The potential public health hazard of leishmaniasis to North America and particularly to Canada is considered.     

Efficacy and Toxicity of Doxorubicin/Cyclophosphamide Maintenance Therapy in Dogs with Multicentric Lymphosarcoma

Doxorubicin/cyclophosphamide were evaluated as maintenance drugs for dogs with multicentric lymphosarcoma (n = 28). Median remission time of all dogs was 173 days. Remission duration was shorter, however, in dogs with stage IV/V disease, in dogs with pretreatment hypoalbuminemia, and in dogs that had received glucocorticoids before initiation of chemotherapy (P less than 0.04). Nineteen dogs were evaluable for toxicity. Dose-limiting gastrointestinal toxicosis was observed in three dogs, neutropenia was observed in three dogs, and cardiomyopathy was observed in three dogs. The doxorubicin/cyclophosphamide protocol described in this report is safe and effective in treating canine multicentric lymphosarcoma. Clinical stage, pretreatment steroid therapy, and hypoalbuminemia are prognostic factors for response to this protocol.     

Surface temperature variability patterns within irrigated fields

During 1981, an experiment was conducted to examine the spatial variability of surface temperature within differentially irrigated grain sorghum fields. The measurements were performed at the University of California-Davis in 85 m long transects measured with an infrared thermometer reading at 1.0 m intervals. These measurements were made repeatedly throughout the season. When the data were analyzed to evaluate the spatial variability along each transect, it was found that along the transects the readings at 1 m intervals were not correlated. This lack of structure or spatial dependence within a given field suggests that a random sampling in a field would be adequate for infrared thermometer measurements. During a drying cycle from one irrigation to the next, the variance of surface temperature along a transect increased. However, there was not a statistically significant relationship between the amount of water extracted from the upper 150 cm of the profile when more than 40% of the available water remained. When more than 60% of the available water had been removed, the variance increased above 0.5°C² but below this amount the variances did not exhibit any significant pattern. These data suggest that the variance of surface temperature within a field may not be a sensitive indicator of the soil water status. Utilizing the fact that the surface temperatures along the transects were random and normally distributed, we calculated that the number of samples needed to achieve a confidence limit of 1.0°C about the mean was 10 samples for a field with more than 40% available soil water and increased to 20 samples as the field dried below the 60% extraction level. These data suggest that the spatial variability techniques could be utilized to evaluate agricultural fields for their distribution efficiencies and problems. In application the samples required per field are a manageable number and could be analyzed with classical statistical methods.