Changes in Antigenicity of Trypanosoma lewisi During the Course of Infection in Rats*

SYNOPSIS. In rats infected with T. lewisi, 2 morphologically distinct forms of the trypanosome occur. By means of the immunodiffusion technic several antigenic differences between the 2 forms were observed. The time course in the antigenic and morphologic changes is somewhat different. The antigenic change from young to adult forms is gradual. It starts 12 days after infection and is complete in 14 days, 3 to 5 days after the morphologic appearance of the trypanosomes is that of adult forms. In addition, there appear to be 2 separate stages of young forms when they are analyzed for antigenic composition.     

Modelling the effect of temperature on transmission of dengue

The main entomological parameters involved in the rate of dengue virus transmission include the longevity of female mosquitoes, the time interval between bites and the extrinsic incubation period of the virus. Field and laboratory data provide estimates for these parameters, but their interactions with other factors (e.g. host population density and environmental parameters) make their integration into a transmission model quite complex. To estimate the impact of these parameters on transmission, we developed a model of virus transmission by a vector population which predicts the number of potentially infective bites under a range of temperatures and entomological parameters, including the daily survival rate of females, the interval between bites and the extrinsic incubation period. Results show that in a stable population, an increase in mosquito longevity disproportionately enhances the number of potential transmissions (e.g. by as much as five times when the survival rate rises from 0.80 to 0.95). Halving the length of the biting interval with a 10-°C rise in temperature increases the transmission rate by at least 2.4 times. Accordingly, the model can predict changes in dengue transmission associated with short-term variation in seasonal temperature and also with potentially long-lasting increases in global temperatures.     

NADH diaphorase polymorphism in goat erythrocytes

This paper describes for the first time polymorphism of the erythrocyte diaphorase in goats. Three diaphorase 1 phenotypes were observed in the red cells of goats. Breeding data indicated that polymorphism was controlled by two autosomal codominant alleles, DiaF and DiaS, the frequencies of which were determined in 14 different Spanish breeds of goat.     

Epidemiology of bluetongue in Central America and the Caribbean: initial entomological findings

Abstract. Forty-four species of Culicoides (Diptera: Ceratopogonidae) were caught in insect light traps during the first 2 years of studies on the epidemiology of bluetongue virus in the Caribbean and Central America. Traps were operated near sentinel ruminants which were bled monthly for serologic evaluation and then virus isolation. More than 570,000 individuals were identified. Culicoides insignis Lutz accounted for 90% of the catch, C.filarifer Hoffman/C.ocumarensis Ortiz 5%, C.furens Poey 3% and C.pusillus Lutz 2%. Other species accounted for less than 1% of the total catch. Sentinel ruminants became seropositive when C.insignis populations were high at many study sites. At a few sites C.pusillus and C.filarifer I C.ocumarensis were predominant or were present in large numbers during seroconversions of sentinels. Virus isolations were obtained from sentinel ruminants during times when these same species were present in large populations.     

Comments on the taxonomic treatment of Arenaria section Plinthine (Caryophyllaceae)

Comments on the taxonomic treatment of Arenaria section Plinthine (Caryophyllaceae) by D. J.Goyder. Comments are given on the taxonomic treatment of Arenaria section Plinthine presented by D. J.Goyder in a revision of this group recently published in the Botanical Journal of the Linnean Society, 97(1): 9–32.     

Influence of pollination systems on fruit set and fruit quality in kiwifruit (Actinidia deliciosa)

Kiwifruit (Actinidia deliciosa (Chev.) Liang and Ferguson) is a dioecious species highly pollination dependent, since fruit size is directly correlated with seed number. To evaluate the best pollination system for this species a study of two natural and two artificial pollination systems was carried out and their effect on fruit set and fruit quality was determined. While anemophilous pollination produced few and small fruits, that were not commercially acceptable, high fruit set percentages and good quality fruits were obtained when insects participated in the pollination process. Artificial pollination, performed as hand pollination, improved yield quantity and quality. When environmental conditions impair insect activity this method can be an useful agricultural practice in order to assure a good yield.     

Erythrocyte potassium polymorphism in 14 Spanish goat breeds

Summary. The existence of polymorphism for erythrocyte potassium (Ke) is confirmed in certain Spanish breeds of goat. A statistical boundary is established between two caprine populations: low (LK) and high (HK) red cell potassium, the dividing line being set at 45 m-equiv/l of Ke. Both types are shown to be controlled genetically by an autosomal locus with two alleles K ^L and K ^h, being K ^L dominant over K ^h. The gene frequencies of K ^L and K ^h are determined in 14 native Spanish breeds of goat.