The incidence of virus diseases in the honey bee

Chronic bee-paralysis virus and sacbrood virus occur commonly in apparently normal honey-bee colonies in Britain. Most sick adult bees not affected by Nosema apis, Malpighamoeba mellificae or Acarapis woodi have chronic paralysis and most dead larvae not affected by micro-organisms have sacbrood. Both virus diseases are probably limited by hereditary factors, but unknown environmental factors also seem to influence disease. Paralysed bees from Australia, Canada, Eire, Germany and Mexico were found to be infected with chronic paralysis virus.     

Complete Development of Caryospora bigenetica (Apicomplexa: Eimeriidae) In Vitro1

The development of Caryospora bigenetica in vitro is described by light microscopy. Sporozoites from snake-derived oocysts were purified and inoculated onto cultures of primary testicle cells of the cotton rat, cotton rat kidney cells, and human fetal lung cells. Intracellular sporozoites were observed one and two days postinoculation (DPI). Motile, extracellular first-generation merozoites were present 3 DPI, and second-generation merozoites were present 5 DPI. Mature gamonts were observed 9 DPI and developed into unsporulated oocysts by 10 DPI. Oocysts sporulated in vitro, and excystation was observed. Cells that were penetrated by in vitro-produced sporozoites formed caryocysts by 16 DPI. To test infectivity of in vitro-derived stages, merozoites were removed from cultured cells 5 DPI and inoculated intraperitoneally into a mouse; infection resulted. Sporulated oocysts removed from cell cultures 12 DPI produced facial swelling in an orally inoculated cotton rat.     

Phytoalexin production by leaves of Pisum sativum in relation to senescence

A sterile culture nitrate of Penicillium expansum was shown to induce pisatin synthesis in pea leaf discs. The amount of pisatin produced by pea leaves was shown to decrease as they underwent senescence. N⁶-benzyladenine delayed senescence, and at the same time maintained the production of pisatin at a high level. In darkness, leaf discs maintained on either benzyl-adenine solution or distilled water produced greater amounts of pisatin than leaf discs which were not treated in this way. Benzyladenine also increased pisatin production by leaf discs kept in the light. The relevance of these results to disease resistance and possible mechanisms involved are discussed.     

The effect of water temperature on the functional response of the water stick insect Ranatra dispar (Heteroptera: Nepidae)

Functional response curves were constructed for adult Ranatra dispar feeding on four different densities of notonectid prey at 15, 20, 25 and 30°C. Values for the attack-rate and handling time were estimated from Roger's random predator equation. The most generally applicable response was the type II, with the mean number of prey eaten increasing with increase in temperature. The attack-rate was linearly related to temperature while handling time decreased exponentially with increase in temperature, although values changed very little between 20 and 30°C. It is suggested that changes in metabolic activity and related ‘hunger’ effects on various components of predatory behaviour account for the observed number of prey eaten up to 25°C, however, an increase in the level of prey activity at 30°C may influence the observed number of prey caught (and eaten) at this higher temperature.     

Big flies, small repeats: the "Thr-Gly" region of the period gene in Diptera

The region of the clock gene period (per) that encodes a repetitive tract of threonine-glycine (Thr-Gly) pairs has been compared between Dipteran species both within and outside the Drosophilidae. All the non- Drosophilidae sequences in this region are short and present a remarkably stable picture compared to the Drosophilidae, in which the region is much larger and extremely variable, both in size and composition. The accelerated evolution in the repetitive region of the Drosophilidae appears to be mainly due to an expansion of two ancestral repeats, one encoding a Thr-Gly dipeptide and the other a pentapeptide rich in serine, glycine, and asparagine or threonine. In some drosophilids the expansion involves a duplication of the pentapeptide sequence, but in Drosophila pseudoobscura both the dipeptide and the pentapeptide repeats are present in larger numbers. In the nondrosophilids, however, the pentapeptide sequence is represented by one copy and the dipeptide by two copies. These observations fulfill some of the predictions of recent theoretical models that have simulated the evolution of repetitive sequences.      

Site directed chromosomal marking of a fluorescent pseudomonad isolated from the phytosphere of sugar beet; stability and potential for marker gene transfer.

A plasmid-free, non-pathogenic, ribosomal RNA group 1 fluorescent pseudomonad, Pseudomonas fluorescens SBW25, was selected from the microflora of sugar beet (Beta vulgaris) and modified to contain constitutively expressed marker genes. By site directed homologous recombination a KX cassette [kanamycin resistance (kanτ) and catechol 2,3 dioxygenase (xylE)] and a ZY cassette [lactose utilization (lacZY, β-galactosidase, lactose permease)] were introduced at least 1 Mbp apart on the 6.6 Mbp bacterial chromosome. Separate sites were selected to provide sensitive detection methods and allow assessments of marker gene stability of the genetically modified micro-organism (GMM), SBW25EeZY6KX, when it colonized the leaves and roots of sugar beet plants following seed inoculation.