Sulphadoxine and trimethoprim in goats and cows: absorption fraction, half-lives and the degrading effect of the ruminal flora

Oral administration of sulphadoxine to adult goats (100 mg/kg body weight) resulted in absorption of about two thirds from the gastrointestinal tract. The absorption rate was lowest in newborn kids and increased with increasing age. Following administration of sulphadoxine (40 mg/kg body weight) through a rumen fistula about 80% was absorbed in cows. Also the elimination rate for sulphadoxine was lower in newborn kids than in adult goats and increased with the age. Oral administration of the trimethorpim (TMP) to kids, goats (20 mg/kg body weight) and cows (8 mg/kg body weight) resulted in higher plasma concentrations in newborn kids than in the older age groups and the maximal concentration of TMP in the blood of adult goats and cows was lower than 0.2 μg/ml. In vitro experiments showed that trimethoprim may be degraded by ruminal microorganisms, but from experiments with oral administration of trimethoprim to cows it is concluded that metabolism in the cow's liver is at least as important as ruminal degradation.     

Percutaneous absorption of organophosphorus insecticides in pigs – the influence of different vehicles

In 40 experiments on 20 pigs three different organophosphorus insecticides (OPs), parathion ( n = 6), phoxim ( n = 7) and phosmet ( n = 7), were administered both intravenously (i.v.) and dermally (d.) as 'pour-ons' in a crossover design in order to determine the dermal bioavailability of the OPs. As percutaneous absorption of drugs may be affected by the vehicle used, three chemically different vehicles – DMSO, 1-octanol and macrogol 400 – were used for the dermal administration of each of the OPs. The pharmacokinetic parameters measured showed that 15–30% of dermally applied parathion is absorbed when administered in DMSO or octanol, but only 4–5% when administered in macrogol. Absorption was fastest with DMSO and slowest with macrogol. For the two ectoparasiticides, phoxim and phosmet, only between 0.5 and 3% of the dermal dose was absorbed with little difference in the absorption rate between the three vehicles. On the basis of the very limited dermal bioavailability for these two OPs it seems doubtful whether sufficient concentrations can reach the ectoparasites through the systemic route.     

Straying of Atlantic salmon, Salmo salar, from delayed and coastal releases in the Baltic Sea, with special focus on the Swedish west coast

Abstract  Atlantic salmon, Salmo salar L., reared from two Baltic strains were released around the islands Bornholm and Møn in the Baltic Sea between 1995 and 1999. A total 600 000 reared salmon were released from net pens using the delayed release technique, keeping the salmon in net pens for approximately 3 months after smolting, and 208 000 were released directly from the hatchery. Of these, 15 958 were tagged with Carlin tags. Additionally, 65 300 coded wire tagged salmon were released as delayed release salmon close to Bornholm in 2000. Recaptures from the five years of Carlin tagged releases varied between 2.8% and 21.2% (average 13.1%). Most recaptures were from within the Baltic Sea (average 98%), but some were recaptured outside the Baltic Sea, either in the sea (1%) or in fresh water (1%). Recaptures outside the Baltic Sea and in fresh water were higher for releases at Møn in the western part of the Baltic, than releases at Bornholm. Straying rates from the releases into six rivers on the Swedish west coast were estimated using information from capture in traps and sport and broodstock fisheries. The proportion of straying salmon in rivers on the Swedish west coast was about 3.8% of the salmon run, but with large variations between rivers. Releases were discontinued because of possible deleterious effect on the local wild salmon populations.     

Disposition of parathion after dermal application in pigs*

Pharmacokinetic parameters of parathion were studied in pigs after intravenous (i.v,) and dermal administration of unlabelled and ‘“C-parathion. Plasma concentration-time data were subjected to non-compartmental analysis. Intravenous injection studies showed a mean residence time (MRT) of 2.15 h, a body clearance (Cl_B) of 4.4 l/kg/h and a volume of distribution (V_ss) of 9.8 l/kg. Dermal application led to a mean absorption time (MAT) of 78 h. and a bioavailability of 9.9%. Plasma levels of ¹⁴C-parathion (parathion + metabolites) were much higher and more persistent than those of parathion itself. After i.v. administration, recovery of ¹⁴C-parathion from urine plus faeces was almost 100% within 3 d, while it was less than 20% after dermal application. Ten days after dermal application high I4C concentrations remained in the back skin, i.e. the application area. In skin samples from areas where contamination from the application area could not have occurred, the ¹⁴C-parathion concentration was as low as 2 μg/g. It is concluded that in view of the low dermal bioavailability for organophosphorus insecticides it is unlikely that pour-on preparations containing these insecticides reach the ectoparasites through absorption and systemic distribution, but rather that this happens after spreading on the surface of the skin.     

Pharmacokinetics of sulphadoxine and trimethoprim in horses. Half-life and volume of distribution of sulphadoxine and trimethoprim and cumulative excretion of [14C]-trimethoprim

A proprietary combination product containing sulphadoxine and trimethoprim was administered to horses by intravenous injection. Protein-binding of sulphadoxine was dependent on the concentration in plasma and decreased from 72% at 50 μg/ml to 14% at 450 μg/ml. Sulphadoxine is eliminated from plasma in accordance with a three compartment open model. The elimination half-life was on average 14 h while the volume of distribution was found to be 0.39 1/kg. Trimethoprim was eliminated from plasma in accordance with a two compartment open model. The elimination half-life was on an average 3 h. Experiments in which trimethoprim was administered alone showed that the elimination half-life was not dependent on the simultaneous administration of sulphadoxine. About 50% of trimethoprim was bound to plasma proteins, but in contrast to sulphadoxine there was no dependence between plasma concentration and protein binding. The protein binding of trimethoprim was independent of the presence of sulphadoxine and vice versa. Experiments with ¹⁴C-labelled trimethoprim showed that it was excreted in almost equal amounts in urine and faeces. 97% of the administered dose was recovered in urine and faeces during the course of the first 4 days after administration.     

Yield response models for mechanical weed control by harrowing at early crop growth stages in peas (Pisum sativum L.)

A modelling procedure for prediction of the optimum intensity of harrowing on crop yield is developed. The models are applicable when harrowing is carried out to control annual weed seedlings at early crop growth stages without assessment of associated crop damage. The opti-mum intensity of harrowing is expressed either as number of harrowings or percentage weed con-trol calculated on weed densities or weed dry matter. To verify the modelling approach field experiments in peas were conducted during 1991. Harrowings at progressive intensities were carried out at different growth stages of peas. The optimum yield responses varied between 0% to 5% corresponding to 0% to 70% weed control in terms of weed dry matter reductions. Significant crop damage was associated with harrowing, and yield increases of 13% to 18% were recorded from herbicide application corresponding to 96% to 100% weed control. Modelisation des rendements apres desherbage mecanique par hersage a des stades precoces en cultures de pois (Pisum sativum L.) Un schéma de modélisaation pour prévoir l'optimum d'intensité de hersage pour le rendement de la culture a été développé. Les modèles sont applicables quand le hersage est conduit pourdétruire les plantules d'adventices annuelles à des stades précoces de la culture sans estimation du dégât à la culture associée. L'intensité optimale de hersage est exprimé soil par le nombre de hersages ou le pourcentage d'adventices détruites calculé sur la densité en adventices ou le poids de matiàre sàche. Pour vérifier l'approche par modélisation, des essais de plein champ sur pois ont été conduits en 1991. Des hersages a des intensités progressives ont été conduits à différents stades des pois. Les optima de gain de rendement ont varié entre 0 et 5% correspondant à des destructions d'adventice de 0 à 70% en terme de réductions de matiére sèche. Des dégâts aux cultures ont été associés au hersage et des augmentations de rendements de 13 à 18% ont été observées après des applications herbicides correspondant à 96–100% d'effica-cité. Ertragsmodelle für die mechanische Unkraut bekämpfung durch Eggen in frühen Entwick-lungsstadien der Erbse (Pisum sativum L.) Es wird ein Modell für die Vorhersage der optimalen Intensität des Eggens auf den Ertrag entwickelt, das angewendet werden kann, wenn das Eggen zur Bekämpfung von annuellen Unkräutern in frühen Entwicklungsstadien eingesetzt wird, ohne dabei Kulturpflanzenschaden zu berücksichtigen. Die optimale Intensität des Eggens wird entweder als Anzahl der Eggen striche als Grad der Unkrautbekämpfung, berechnet aus Unkrautdichten oder Unkraut-trockenmasse, ausgedrückt. Zur Überprüfung des Models wurden 1991 Feldversuche durchge-führt, wobei die Erbsen in verschiedenen Entwicklungsstadien mit zunehmender Inten-sität geeggt wurden. Die Ertragsreaktionvariierte zwischen 0 und 5% entsprechend 0 bis 70% Wirkungsgrad, bestimmt als Abnahtne der Unkrauttrockenmasse. Mit dem Eggen waren signifikante Schaden an der Kulturpflanze verbunden. Bei chemischer Unkrautbekämpfung mit 96 bis 100% Wirkunggrad nahmen die Enräge urn 13 bis 18% zu.     

Field weed population dynamics: a review of model approaches and applications

Mathematical modelling is a commonly used tool for studying the long-term dynamics of weed populations in agriculture. This was reflected in our review by the large number of scientific papers (134 original publications) and the continuing need to gain an overview over this fast developing field (20 previous review papers were found). In this article, we provide a more comprehensive review than earlier seen, striving to include all relevant publications. Thus, we cover models of the population dynamics of 60 weed species in 40 crops. An online, accompanying database provides an indexed bibliography. Despite the large variation in crops, weeds and geography, the models were surprisingly similar in their approach: structured around the weed life cycle, excluding environmental factors and giving little attention to validation or even documentation of model construction. In addition, their application was similar, limited mostly to strategic decision making. We hope that the overview provided by this review will inspire weed modellers and that it will serve as a basis for discussion and as a frame of reference when we proceed to advance the modelling of weed populations to a new level, developing new approaches and tackling new application domains.     

Effect of oxidation and reduction upon the biological activity of parathyroid hormone

Parathyroid hormone loses biological activity upon oxidation with hydrogen peroxide. Part or all of this lost activity can be regained by subsequent reduction with cysteine. The extent and reversibility of this oxidation is dependent upon pH.     

Multiple epiphyseal dysplasia in a litter of Beagle puppies

Out of a litter of eight (five male, three female) Beagle puppies, four (three male, one female) showed hind leg dysfunction at birth. One of them was killed at the age of 3 weeks because its condition had deteriorated. The other three were subjected to periodic radiographical examination. Punctate calcification or stippled epiphyses were found bilaterally in the tarsal and carpal bones, in the femoral, humeral, metacarpal and meta-tarsal epiphyses, and in the bodies of the sixth and seventh lumbar vertebrae. No anomalies were seen in the antebrachial, crural, phalangeal and flat bones. Seventeen radiographs showed characteristic ‘stippled epiphyses’ in the puppies and arthritic changes in the adult dog. Furthermore, the radiographs gave two examples of separate subsidiary ossification centres. Résumé. Dans une portée de 8 chiots beagle (cinq mâles et trois femelles) quatre (trois mâles et une femelle) présentaient des troubles de la mobilité des membres postérieurs à la naissance. Un de ces chiots à été sacrifié à l‘âge de trois semaines à cause de l'aggravation de son état, les trois autres ont été soumis périodiquernent à des examens radiologiques. On a trouvé des calcifications ponctiformes ou des épiphyses ponctuées bilatérales dans les os du carpe et du tarse, ainsi que des ponctuations dans les épiphyses fémorales, humérales, métacarpiennes et métatar-siennes et dans les corps des vertèbres lombaired (L 6 et L 7). Aucune anomalie n'a été constatée dans les os de l'avant-bras, de la jambe et des phalanges, pas plus que dans les os plats. Dix-sept radiographies ont montré des “épiphyses ponctuées” typiques chez les chiots et des lésions des articulations chez les chiens adultes. De plus, les radiographies révélèrent deux images de centres supplémentaires d'ossification. Zusammenfassung. Aus einem Wurf von acht (fünf männlichen, drei weiblichen) Beagles zeigten vier (drei männliche, ein weiblicher) eine angeborene Dysfunktion des Hinterbeins. Von diesen wurde ein Tier im Alter von drei Wochen getötet, weil sich der Zustand verschlimmert hatte. Die drei anderen wurden in Abständen radiographisch untersucht. Punktförmige Calci-ficationen oder Epiphysosen wurden bilateral an den Tarsal- und Carpalknochen, in den Femoral-, Humeral-, Metacarpal- und Metatarsalepiphysen und in den Körpern des sechsten und siebenten Lendenwirbels gefunden. Keine Anomalien wurden an den Antebrachial-, Crural-, Phalangeal- und Flachknochen beobachtet. Siebzehn Röntgenaufnahmen zeigten charakteristische Epiphysosen bei den jungen Hunden und arthritische Veränderungen bei erwachsenen Hunden. Ausserdem enthielten die Röntgenaufnahmen zwei Beispiele getrennter subsidiärer Ossifikationszentren.