The influence of antibiotics on the immune system: immuno-pharmokinetic investigations on the primary anti-SRBC response in carp, Cyprinus carpio L., after oxytetracycline injection

Abstract. The present study was performed to obtain further details on the immuno-modulating effects of oxytetracycline (OTC) in carp, Cyprinus carpio L. The immuno-logical study was extended by investigating the pharmacokinetic behaviour of OTC. Oxytetracycline, at a dosage of 60 mg/kg, was administered five times intra-peritoneally at 3-day intervals; the first injection was given 1 day before immunization. The kinetics of the primary anti-sheep red blood cell (SRBC) response, during a short-term OTC treatment revealed that the kinetics of the plaque-forming cell (PFC) response was not significantly affected by OTC nor its solvent. In contrast, the number of plaque-forming cells was significantly decreased. The anti-SRBC antibody production was delayed by 2–4 days in both experimental groups (OTC and solvent). However, within 12–14 days post-immunization, the same antibody levels were detected as in the control group. High OTC plasma levels (>50 μg/ml) were detected about 10 h after a single i. p. injection. A mean plasma elimination half-life (T¹/₂) of 34·5 h was calculated.     

Soil Test,Aerial Image and Yield Data as Inputs for Site-specific Fertility and Hybrid Management Under Maize

Several potential sources of information exist to support precision management of crop inputs. This study evaluated soil test data, bare-soil remote sensing imagery and yield monitor information for their potential contributions to precision management of maize (Zea mays L.). Data were collected from five farmer-managed fields in Central New York in 1999, 2000, and 2001. Geostatistical techniques were used to analyze the spatial structure of soil fertility (pH, P, K, NO₃ and organic matter content) and yield variables (yield, hybrid response and N fertilization response), while remote sensing imagery was processed using principal component analysis. Geographic information system (GIS) spatial data processing and correlation analyses were used to evaluate relationships in the data. Organic matter content, pH, P, and K were highly consistent over time and showed high to moderate levels of spatial autocorrelation, suggesting that grid soil sampling at 2.5–5.5ha scale may be used as a basis for defining fertility management zones. Soil nitrate levels were strongly influenced by seasonal weather conditions and showed low potential for site-specific N management. Aerial image data were correlated to soil organic matter content and in some cases to yield, mainly through the effect of drainage patterns. Aerial image data were not well correlated with soil fertility indicators, and therefore were not useful for defining fertility management zones. Yield response to hybrid selection and nitrogen fertilization rates were highly variable among years, and showed little justification for site-specific management. In conclusion, we recommend grid-based management of lime, P, and K, but no justification existed within our limited study area for site-specific N or hybrid management.     

Germination of Chromolaena odorata (L.) K. & R. achenes: effect of storage, harvest locality and the pericarp

The percentage germination of achenes of Chromolaena odorata (L.) K. & R. stored dry in the dark at 25°C for 7 months was markedly higher than that of freshly harvested achenes. This is indicative of an after-ripening requirement that may be of benefit to the species by ensuring temporal distribution of germination. Germination of freshly harvested achenes from various sites differed. However, after 7 months of dry, dark storage at 25°C no differences were present, thus, confirming the after-ripening requirement. Although the total number of achenes per capitulum did not vary from site to site, there were distinctive differences in the number of filled (presumably viable) achenes. It is suggested that this is a reflection of the environmental conditions prevailing at the sites. Puncturing of the achene pericarp did not influence dark germination but its removal increased percentage germination significantly. Natural degradation of the pericarp in the field may, therefore, permit germination of buried achenes in the absence of a suitable light stimulus.     

Effect of crop age on primary gradients of late leaf spot (Cercosporidium personatum) on groundnut

Artificial sources of late leaf spot were established by inoculation of one plant at the centre of several groundnut plots differing in age. First-generation dispersal and resulting primary gradients of disease were then compared. The gradients were corrected for source strength, spontaneous infection (primary gradient), and interplot interference (first-generation dispersal). The shapes of the gradients for spore dispersal and of the gradients of disease corresponded for each age of groundnut plot, but differed between the ages. The slopes of gradients were steeper in the older plots. Spore dispersal and the resulting disease gradients were not isodiametric, gradients being most protracted in a north-to-north westerly direction. The results suggest that the strength of the sources was reduced by abscission of infected leaves in the sources of the younger plots, whereas accessibility of the canopy to the transported spores was reduced by increasing canopy density in the older ones.     

Determination of red blood cell potassium content in horses with diarrhoea: A practical approach for therapy

The concentration of potassium in the red blood cells in 15 horses with severe diarrhoea was determined. The red blood cell potassium content (RBCK⁺) was low compared with levels obtained in normal horses. The decrease in the RBCK⁺ was used to evaluate the total body potassium deficit. This calculated amount was administered orally, following each RBCK⁺ determination. In those horses which recovered, RBCK⁺ content returned to normal levels. During treatment, refilling of the red blood cells with potassium occurred only gradually as long as the diarrhoea persisted. In each case, oral loading with the calculated dose resulted in an improvement of the general condition and no side effects were observed. The importance of using RBCK⁺ levels as a diagnostic and therapeutic parameter is discussed.