The kinetics of insecticide action. Part IV: the in-vivo distribution of pyrethroid insecticides during insect poisoning

The distribution of pyrethroids in insects has been studied using a combination of mathematical modelling and experimental observation. This approach has resulted in the formulation of a physiological model of the pharmaco-kinetics of cypermethrin applied topically to larvae of Spodoptera littoralis. Development of this model from simpler two- and three-compartment models is described. Simple models, whilst capable of complex behaviour, consider only the average rates and magnitudes of pharmaco-kinetic processes over whole animals, and cannot account for differences in concentration of insecticide between individual tissues. This can be achieved by using physiological models, but these require more experimental information for their validation. Moreover, unless simplifying assumptions are made, analytical solutions are not feasible for the large number of equations necessary to define such models. The modelling studies prompted an investigation of (1) in-vivo binding of insecticide to insect tissues, (2) the sizes of body compartments, and (3) the factors which affect the distribution of toxicant between these compartments. Binding has a marked effect on pharmacokinetic profiles and may result in oscillatory behaviour. During poisoning, the total bound cypermethrin increases proportionally to the cube root of the elapsed time. This results in a rapid rate of increase over early elapsed times (< 3h) which slows to approach a more linear form thereafter. Average sizes for the body compartments of larvae of Spodoptera littoralis Boisd, and the steady-state distribution of cypermethrin in these compartments are described. Although the haemolymph, which acts as the main distributive phase during poisoning, forms the largest compartment by volume, it has a low affinity for cypermethrin and distribution reaches steady state within 5 min after topical application. The nerve cord (the target tissue), which is the smallest compartment, has the highest steady-state concentration of cypermethrin. The distribution of cypermethrin in larval tissues is related to the ratios of tissue dry matter to water content.     

A genetic map of macadamia based on randomly amplified DNA fingerprinting (RAF) markers

The first genetic linkage map of macadamia (Macadamia integrifolia and M. tetraphylla) is presented. The map is based on 56 F₁ progeny of cultivars ‘Keauhou’ and ‘A16’. Eighty-four percent of the 382 markers analysed segregated as Mendelian loci. The two-way pseudo-testcross mapping strategy allowed construction of separate parental cultivar maps. Ninety bridging loci enabled merging of these maps to produce a detailed genetic map of macadamia, 1100 cm in length and spanning 70–80% of the genome. The combined map comprised 24 linkage groups with 265 framework markers: 259 markers from randomly amplified DNA fingerprinting (RAF), five random amplified polymorphic DNA (RAPD), and one sequence-tagged microsatellite site (STMS). The RAF marker system unexpectedly revealed 16 codominant markers, one of them a putative microsatellite locus and exhibiting four distinct alleles in the cross. This molecular study is the most comprehensive examination to date of genetic loci of macadamia, and is a major step towards developing marker-assisted selection for this crop. This revised version was published online in July 2006 with corrections to the Cover Date.     

Relationship between amino acid scores and protein quality indices based on rat growth

Protein efficiency ratio (PER), relative PER (RPER), net protein ratio (NPR) and relative NPR (RNPR) values, and amino acid scores were calculated for 20 food products (casein, casein + Met, beef salami, skim milk, tuna, chicken frankfurters, sausage, heated skim milk, peanut butter, rolled oats, soy isolate, chick peas, pea concentrate, kidney beans, wheat cereal, pinto bean, lentils, rice-wheat gluten cereal, macaroni-cheese, and beef stew). In most cases, PER, RPER, NPR or RNPR ranked the products in the same order and positive correlations among the protein quality methods were highly significant (r=0.98–0.99). Amino acid scores (based on the first limiting amino acid, Lys-Met-Cys, Lys-Met-Cys-Trp or lys-Met-Cys-Trp-Thr) were positively correlated to the PER, RPER, NPR or RNPR data (r=0.61–0.75). Inclusion of the correction for true digestibility of protein improved the correlations between amino acid scores and the indices based on rat growth. The correlations were especially high between Lys-Met-Cys scores (corrected for true digestibility of protein) and PER, RPER, NPR or RNPR (r=0.86–0.91). Inclusion of the correction for true digestibility of individual amino acids did not result in further improvements of the correlations in most cases. It is concluded that adjusting amino acid scores for true digestibility of protein would be sufficient and further correction for digestibility of amino acids would be unnecessary in mixed diets.This paper was presented in part at the 71st annual FASAB meeting, Washington, DC, March 29–April 2, 1987.     

Large granular lymphocytosis in a cynomolgus macaque (Macaca fascicularis) with a subclinical Trypanosoma cruzi infection

A 5.25-year-old cynomolgus macaque (Macaca fascicularis) was found to have a marked leukocytosis due to a lymphocytosis on routine quarantine laboratory data prior to inclusion in a preclinical research study. The majority of lymphocytes were characterized as intermediate to large with round to convoluted nuclei, coarse to clumped chromatin, rare prominent nucleoli, and moderate amounts of lightly basophilic cytoplasm that frequently contained small magenta granules and/or clear vacuoles. The animal had tested negative for several viruses and other etiologic agents found in nonhuman primates 1 week prior to shipment to the research facility. However, further evaluation of the blood smear revealed rare hemoflagellates, and later testing using real-time PCR and ELISA was confirmatory for Trypanosoma cruzi (T cruzi). Trypanosoma cruzi is a zoonotic pathogen responsible for Chagas disease in people and can have negative consequences on study results when positive animals are inadvertently used for preclinical research. This case report describes a marked large granular lymphocytosis in an otherwise healthy macaque as the only indication of infection with T cruzi in an animal believed to be negative for the infection. Additionally, it highlights the diagnostic limitations of screening tests to rule out diseases in animals intended to be used in preclinical studies.     

Annual and spatial variation in coning shown by the Forest Condition Monitoring programme data for Norway spruce, Sitka spruce and Scots pine in Britain

Conifer seed is a valuable forest resource; as well as beingreproductive material, it is an important foodstuff for manywoodland species. Information on cone and therefore seed productionof the main forest species are useful in the fields of bothforest management and forest ecology. Coning has been recordedsince 1989 in plots of Norway spruce, Sitka spruce and Scotspine across Britain as part of the Forestry Commission's ForestCondition Monitoring programme. An 11-year period of these recordswas analysed and a summary of annual cone production by speciesand coning synchrony is presented. Both Norway spruce and Sitkaspruce coned sporadically, with a 4-year period between mastcrops during which cone density was very low or cone productionabsent, whereas Scots pine produced a good cone crop in mostyears throughout Britain. Coning was synchronous within andbetween Norway and Sitka spruce across the whole of Britain(at distances >600 km) but coning within Scots pine was insynchrony only over distances of up to 200 km. Synchrony ofcone production was not evident between the spruce species andScots pine. These findings have implications when planning andinterpreting monitoring used to predict cone crops and in thedesign of forests for wildlife conservation.     

Resistance of Phytophthora porri to metalaxyl

Metalaxyl resistance has been identified in the Phytophthora porri population in the UK. In field experiments the presence of such resistant strains reduced the level of control of leek white tip given by applications of phenylamide-containing fungicides. The level of control achieved by fungicides with alternative modes of action to the phenylamides was not affected. ©1997 SCI     

Participatory development of decision support systems: which features of the process lead to improved uptake and better outcomes?

Decision support systems (DSSs) are important in decision-making environments with conflicting interests. Many DSSs developed have not been used in practice. Experts argue that these tools do not respond to real user needs and that the inclusion of stakeholders in the development process is the solution. However, it is not clear which features of participatory development of DSSs result in improved uptake and better outcomes. A review of papers, reporting on case studies where DSSs and other decision tools (information systems, software and scenario tools) were developed with elements of participation, was carried out. The cases were analysed according to a framework created as part of this research; it includes criteria to evaluate the development process and the outcomes. Relevant aspects to consider in the participatory development processes include establishing clear objectives, timing and location of the process; keeping discussions on track; favouring participation and interaction of individuals and groups; and challenging creative thinking of the tool and future scenarios. The case studies that address these issues show better outcomes; however, there is a large degree of uncertainty concerning them because developers have typically neither asked participants about their perceptions of the processes and resultant tools nor have they monitored the use and legacy of the tools over the long term.     

Complete amino acid analysis in hydrolysates of foods and feces by liquid chromatography of precolumn phenylisothiocyanate derivatives

The amino acid analysis method using precolumn phenylisothiocyanate (PITC) derivatization and liquid chromatography was modified for accurate determination of methionine (as methionine sulfone), cysteine/cystine (as cysteic acid), and all other amino acids, except tryptophan, in hydrolyzed samples of foods and feces. A simple liquid chromatographic method (requiring no derivatization) for the determination of tryptophan in alkaline hydrolysates of foods and feces was also developed. Separation of all amino acids by liquid chromatography was completed in 12 min compared with 60-90 min by ion-exchange chromatography. Variation expressed as coefficients of variation (CV) for the determination of most amino acids in the food and feces samples was not more than 4%, which compared favorably with the reproducibility of ion-exchange methods. Data for amino acids and recoveries of amino acid nitrogen obtained by liquid chromatographic methods were also similar to those obtained by conventional ion-exchange procedures.