Mechanical injury and fungal infection induce acquired resistance in Norway spruce

Norway spruce trees (Picea abies (L.) Karst.) pretreated by wounding and fungal infection showed highly enhanced resistance to a subsequent challenge inoculation with the pathogenic bluestain fungus Ceratocystis polonica (Siem.) C. Moreau. This is the first time the effectiveness of the constitutive and inducible defenses has been shown to depend on prior wounding and infection in conifers, although such acquired resistance has previously been found in several angiosperms. Trees that were pretreated with a combination of 12 bark wounds (1.6 x 10 cm), four fungal inoculations and four sterile inoculations 1-15 days before mass inoculation with C. polonica at 400 inoculations per square meter over a 0.8 m stem section had significantly shorter necroses in the phloem, less bluestained sapwood, and less dead cambium than untreated control trees. Pretreatment with four fungal or sterile inoculations alone did not lead to enhanced resistance. Pretreatment by bark wounding alone seemed to provide an intermediate degree of resistance compared to bark wounding, fungal inoculations and sterile inoculations combined. All trees had a marked increase in the number of resin ducts in the year of inoculation compared with previous years, suggesting that formation of traumatic resin ducts play an important role in the development and maintainance of enhanced resistance.     

Metabolism of 15N-14C-acetylurea in the sheep]

3 male sheep (phi 48.3 kg) were fed a semisynthetic diet containing acetyl urea as sole protein source and 15N-14C labelled acetyl urea (urea-C labelled) by intraruminal tube. A half life period of 4 hrs was established for the removal of labelled acetyl urea from the TCE-soluble portion of the ruminal fluid. The degree of 14C labelling in ruminal proteins was very low whereas the extent of 15N labelled protein synthesis was quite marked reaching a maximum between the 18th and 24th hour of experiment. The steepest rise of 15N incorporation into ruminal proteins was found to occur between 8 to 12 hrs after start of the experiment, i.e. at the time of peak level of 15N returned from 15N urea via the rumino-hepatic circulation. 23.3% of the amount of 14C activity administered (mean of all 3 experimental animals) was excreted through respiration. The curve patterns of both isotopes in the TCE soluble portion of the ruminal fluid were similar to that of the degasified TCE soluble portion of the blood blasma. At the peak time (8 hrs) a concentration of the nitrogen isotope of about 4 atom% excess of 15N was observed. The level of 14C labeling in blood plasma proteins was insignificant when compared with that of 15N labelling. The ratio at the peak time was 1:10; the same ratio was found for ruminal proteins. From this it can be concluded that the process of labelling of blood plasma proteins proceeds mainly through microbial protein synthesis. Sheep I and III excreted an average of 60.6% of 14C activity and 57.0% of the administered excess of 15N in the urine. 6 hrs after the beginning of the experiment 81% of the amount of urinary 14C activity was found to occur as acetyl urea; after 48 hrs this amount had decreased to 50%. All experimental sheep excreted a urinary sediment consisting mainly of acetyl urea. The level of faecal 14C excretion (1.4%-2.9% of the amount administered) was considerably lower than that of 15N excretion (9.1%--15.6% of the administered dose). The TCE soluble fraction of the faeces contained up to 2% of the 14C dose and 3% of the 15N dose. The true digestibility data of 15N from 15N acetyl urea varied between 96.4% and 98.2%. An average of 40.9% was obtained for the 15N balance over the 7-day trial period.     

The molecular basis of the sparse fur mouse mutation

The ornithine transcarbamylase-deficient sparse fur mouse is an excellent model to study the most common human urea cycle disorder. The mutation has been well characterized by both biochemical and enzymological methods, but its exact nature has not been revealed. A single base substitution in the complementary DNA for ornithine transcarbamylase from the sparse fur mouse has been identified by means of a combination of two recently described techniques for rapid mutational analysis. This strategy is simpler than conventional complementary DNA library construction, screening, and sequencing, which has often been used to find a new mutation. The ornithine transcarbamylase gene in the sparse fur mouse contains a C to A transversion that alters a histidine residue to an asparagine residue at amino acid 117.     

Primary orthostatic tremor in Great Danes

Two Great Danes were presented for an investigation of 6-month histories of incessant tremor of all 4 limbs and trunk occurring only when the dogs were standing at rest. Dog 1 was a 2-year-old intact female harlequin Great Dane living in the UK, and dog 2 was a 2-year-old castrated male fawn Great Dane living in the United States. The owners described both dogs as having constant quivering of the limbs while standing, suggestive of an involuntary dance, since the age of 18 months. The intensity of the tremors was reported in both dogs to have steadily increased since onset. In dog 1, tremors were noticed to be more pronounced in the fore limbs when she was eating and more pronounced in the hind limbs when she was trying to sit. The owner of dog 1 also reported that the dog could no longer assume a position of recumbency without manual assistance because of the severity of the tremors. Intermittently, tremors were reported to involve the facial musculature of dog 2. Vaccinations were current, and the owners of both dogs did not report any previous medical history, exposure to natural or manufactured toxins, or concurrent treatment. No familial relationship was identified between these 2 dogs.     

Variation in Occurrence of Dematiaceous Hyphomycetes on Forage Bermudagrass over Years, Sampling Times, and Locations

ABSTRACT Leaf samples of forage bermudagrass with symptoms of infection by species of Bipolaris, Curvularia, and Exserohilum (dematiaceous hyphomycetes) were collected from three swine waste application sites in Mississippi at eight sampling times during each of 3 years. Samples were assayed for pathogens by observing sporulation on plated leaf tissue. Among 3,600 leaves assayed, eight species of the three genera were observed. Features and criteria for the practical identification of species on plated leaf samples are described. Sporulation by dematiaceous hyphomycetes was observed on 97% of leaves; a single pathogen was observed on 20% and two to five pathogens were observed on 77% of leaves. Distributions of leaves among classes with one to five pathogens per leaf, for sites within years, always differed significantly (P = 0.01) from a Poisson distribution and usually included fewer leaves than expected with four or five pathogens. Significant (P = 0.05) variation in frequencies of occurrence of pathogens among 72 samples of 50 leaves each was attributed to pathogen species, sampling times, and species-time interactions. Exserohilum rostratum, Curvularia lunata, and Bipolaris cynodontis were the most frequent pathogens across years and sites; B. spicifera and C. geniculata were intermediate; and B. hawaiiensis, B. sorokiniana, and B. stenospila were least frequent. For the five most common pathogens, significant differences in frequency among locations were commonplace. Six pathogens exhibited significant (P = 0.05) positive and negative correlations with others in overall frequencies of occurrence across years, sampling times, and sites. However, chi(2) tests of dual occurrence indicated that interactions between specific pairs of pathogens in or on leaves are not likely to be major causes for overall frequency correlations. Results indicate that dematiaceous hyphomycetes typically infect forage bermudagrass on swine waste application sites in complexes rather than as individual species; that E. rostratum, C. lunata, and B. cynodontis are the predominant pathogens; and that frequencies of pathogens often differ significantly between locations.     

Resistance to benzimidazole and macrocyclic lactone anthelmintics in cattle nematodes in Argentina

In April 2003, persistent scouring and ill-thrift that was reported in calves form an intensive beef rearing operation in central Argentina despite treatments with benzimidazole and ivermectin. In order to conduct a controlled faecal egg count reduction test on this herd, 40 calves 5-8-months-old were selected on the basis that they had a nematode eggs per gram (epg) of faeces count greater than 150. Animals were divided into four groups (1-4) of 10 calves. Calves of groups 1-3 were treated, respectively, with subcutaneous injection of ivermectin (200 mcg/kg), ricobendazole (4 mg/kg) and levamisole (7.5 mg/kg), while calves of group 4 remained as untreated controls. The egg count reductions carried out 10 days later were lower than 15% in calves treated with ivermectin and ricobendazole, but 100% in animals receiving levamisole. Pooled post-treatment faecal cultures showed larval percentages of 92 and 95 for Haemonchus and 8 and 5 for Cooperia in the faeces of calves treated with ivermectin and ricobendazole, respectively. This is the first reported case of Haemonchus parasiting cattle showing simultaneous resistance to avermectins and benzimidazole type anthelmintics.     

Toxoplasmosis in two cats with inflammatory intestinal disease

Lymphocytic-plasmacytic enteritis, a chronic inflammatory intestinal disease, was diagnosed in 2 cats. In 1 cat, recurrence of clinical signs after initiating treatment was attributed to relapse of the inflammatory intestinal disease, but was found to be attributable to relapsing toxoplasmosis secondary to immunosuppressive drug therapy. Treatment with clindamycin resolved the recurrent toxoplasmosis. In the second cat, clinical signs of toxoplasmosis did not develop, but serologic testing yielded evidence of active toxoplasmosis. Treatment with clindamycin caused the titers to decrease. Relapsing toxoplasmosis may be responsible for apparent resistance to treatment in cats for inflammatory intestinal disease being treated with immunosuppressive drugs.     

Genetic characterization by fluorescent AFLP of Pseudomonas savastanoi pv. savastanoi strains isolated from different host species

The genetic diversity of 71 Pseudomonas savastanoi pv. savastanoi strains isolated from different host species and from diverse geographical regions was determined by fluorescent amplified fragment length polymorphism (f-AFLP) analysis. The study was carried out using three different selective primer combinations. Strains of P. syringae pv. syringae , P. syringae pv. phaseolicola , P. syringae pv. glycinea , P. syringae pv. tagetis and P. amygdali were also included as outgroups. Based on cluster analysis of f-AFLP data, all P. savastanoi pv. savastanoi strains showed a high degree of similarity, grouping in a cluster and forming a taxon clearly separate from outgroup strains. AFLP analyses failed to support placing strains of P. savastanoi pv. savastanoi , P. syringae pv. phaseolicola and P. syringae pv. glycinea in the same species. Strains of P. savastanoi pv. savastanoi formed subclusters that correlated with the host species. Strains identified within these subclusters were related to the geographical region where the strains were isolated. Strains of P. savastanoi pv. savastanoi from olive were divided into two subclusters. Strains from oleander were differentiated from those from ash and were divided into two additional subclusters, distinct from olive strains. Three strains isolated from jasmine showed a high level of similarity among them but, at a lower Dice similarity coefficient, were linked to a subcluster including olive strains. Finally, two strains isolated from privet were similar to strains from olive and were included in the same subcluster.