Investigation of the effects of histamine inhalation on the tracheobronchial tree of calves by the forced oscillation technique

Gustin, P., Dhem, A.R., Lekeux, P., Lomba, F., Lándsér, F.J. & Van de Woestijne, K.P. Investigation of the effects of histamine inhalation on the tracheobronchial tree of calves by the forced oscillation technique. J. vet. Pharmacol. Therap. 11 , 374–380.
Effects of histamine inhalation were investigated with two different techniques in nine conscious, healthy calves. The oesophageal balloon technique was used to measure the dynamic respiratory compliance (C_dyn) and the pulmonary resistance (RL). The reactance (X_rs) and the resistance (R_rs) of the respiratory system were measured at high frequencies by the forced oscillation technique. These parameters were recorded before and after histamine inhalation. Three histamine dihydrochloride solution concentrations were used (16 mg/ml; 32 mg/ml; 64 mg/ml). Histamine inhalation induced a decrease in Cd_yn and X_rs an increase in R_rs, RL and of the resonant frequency and a negative frequency dependence of R_rs. Some of these changes were satisfactorily correlated with the histamine solution concentrations. The resonant frequency was well correlated with C_dvn. It was concluded that histamine inhalation induces a decrease of the calibre of small and large airways and a non-homogeneous behaviour of the pulmonary ventilation in awake calves. The forced oscillation technique can be used to perform an inhalation provocation test in unsedated animals.     

Interaction between phyllosphere yeasts, aphid honeydew and fungicide effectiveness in wheat under field conditions

Aphid honeydew can reduce fungicide effectiveness against necrotrophic pathogens of wheat under controlled conditions. In 1988 and 1989, field experiments were carried out at different locations in The Netherlands, to assess the interference of honeydew with fungicide effectiveness under field conditions, and to establish whether honeydew consumption by naturally occurring saprophytes could prevent this effect. Different combinations of chemicals were used to create differences in saprophytic population densities and aphid populations, which were expected to result in differences in the amount of honeydew and other nutrients on the leaves. In two of the experiments, Septoria nodorum was the only necrotrophic pathogen present; in the other two the only necrotroph was S. tritici . On several sampling dates, the effect of the fungicides was significantly enhanced by addition of insecticide, most often when the saprophytes were reduced by maneb/anilazine. This effect of insecticide is ascribed to prevention of interference of honeydew with fungicide activity, and not to a direct effect of insecticide, as insecticide alone had no effect on necrosis. On the basis of the fact that interference of honeydew with fungicide activity was most apparent when saprophytic population densities were reduced, it is concluded that the naturally occurring saprophytes can generally prevent the effect of honeydew. The same interactions are likely to occur between other nutrients and fungicides, and it is therefore argued that the naturally occurring saprophytes should be protected by elimination of harmful chemicals.     

Interference of nutrients with fungicide activity against Septoria nodorum on wheat leaves

The effect of nutrients on reduction of the germination and mycelial growth of Septoria nodorum by the fungicides propiconazole, fenpropimorph and prochloraz, and on the reduction of S. nodorum infection by prochloraz, was tested on wheat plants in a controlled environment. The nutrients tested were aphid honeydew, sucrose, a mixture of amino acids and combinations of sucrose with yeast extract and amino acids, all in different concentrations. All nutrients could stimulate S. nodorum infection in combination with the tested prochloraz concentrations (4.5–45 mg a.i./1), but amino acids did not significantly stimulate infection in the fungicide-free treatments. The stimulating effect of the nutrients was generally stronger with higher nutrient/fungicide ratios. Aphid honeydew had more effect than its main components sucrose and amino acids separately. Antagonism between nutrients and prochloraz was determined with the Colby method and from dose-response curves by comparing ED₅₀ S and drawing antagonism isoboles. Aphid honeydew, sucrose and amino acids caused an up to 10-fold increase of the ED₅₀ and can be considered antagonistic to prochloraz.     

Reduction of growth and reproduction of Cyperus esculentus by specific crops

To assess the potential contribution of growing highly competitive crops to control Cyperus esculentus in the Netherlands, the influence of silage maize, hemp, winter barley and silage winter rye on emergence, growth and reproduction of this weed was studied in two field experiments. Growth and reproduction of C. esculentus (determined both as tuber production per plant and density of the weed in the subseuent crop maize) was reduced by each crop, compared to plots in which no crop was grown. In hemp, hardly any tuber production was observed. By growing a green manure crop after harvest of the winter barley the tuber production of the weed was reduced to about 40% of that in winter barley followed by fallow. Decreasing the light regime in a greenhouse experiment in the same order as was observed in the crops winter barley, maize and hemp, caused a similar reduction of tuber production to that found in the field. Therefore, it is suggested that competition for light is the main factor explaining the observed crop effects on the population dynamics of the weed. It is concluded that growing competitive crops as hemp in rotation may effectively complement chemical control of C. esculentus.     

AN ASSEMBLY FOR THE CONTINUOUS RECORDING OF CO2 EXCHANGE AND TRANSPIRATION OF WHOLE PLANTS

Summary. Photosynthesis, respiration and transpiration of whole platns are continuously recorded with the assembly described. An infra-red gas analyser is used for photosynthesis and respiration measurements, while for transpiration data psychrometers are employed, Air and leaf temperatures as well as light intensity are recorded. The assimilation chamber is constructed in such a way that whole platns of various plant species can be investigated under constant conditions of CO₂ content of the air and air humidity. Some experiments with simazine and monuron are described.
Un appareil pour enregistrer continuellement l'échange de CO₂ et la transpiration des plantes entiéres     

Morphology of alpaca (Vicugna pacos) embryos in the first third of pregnancy

The breeding of South American camelids is the main economic activity of the high Andean region of South America and it, is potentially, the most profitable resource in of the Puna environmental conditions of the Puna. The duration of the gestation in alpaca is 339.7 ± 12 days. The objective of the present work was to macroscopically and microscopically describe the ontogenic development of the splanchnic cavities of the alpaca and to determine the gestational time in which the post‐cranial ossification centers are observed in the embryos/fetuses of this species, from day 21 to 107 of gestation. The documentation of normal ontogenic development, which is vacant for this period, is of the utmost importance to understand the consequences of the alterations at the different gestational times, as well as for the estimation of the gestational age in the case of abortions. Forty‐seven alpaca specimens of both sexes, at different times of their gestational development, collected during slaughter at local slaughterhouses of the Department of Huancavelica, Peru, were evaluated. Specimens were assigned to seven groups according to their morphological characteristics. The embryogenesis in the alpaca was characterized by a series of changes comparable to those occurring in other mammals with similar gestational periods. Despite these similarities, species differences were found in some organs as stomach, which are observed too in adult individuals.