Do pollen beetles need pollen? The effect of pollen on oviposition,survival, and development of a flower‐feeding herbivore

Abstract.  1. Pollen is considered to be an important dietary component for many species of flower-feeding herbivores. Its influence on oviposition site selection by the pollen beetle Meligethes aeneus , and on the development of its larvae was investigated.
2. The effects of pollen presence and absence on adult, egg, and larval incidence in the field, and on larval development in the laboratory were compared through the use of Synergy, a composite hybrid oilseed rape Brassica napus variety comprising male-fertile (with pollen) and male-sterile (without pollen) plants.
3. In the field, adult females were more abundant on male-fertile plants during flowering, and a greater proportion of male-fertile than male-sterile buds were accepted for oviposition. These data indicate a possible role of pollen in oviposition site selection by female pollen beetles.
4. The numbers of first instar larvae on the two plant lines did not differ; however, more second instars were found on male-fertile than on male-sterile flowers. This suggests a greater larval survival on male-fertile plants, possibly due to the more readily available food resources and better nutrition afforded by the presence of pollen.
5. Laboratory experiments confirmed that a diet which included pollen improved survival to adulthood and resulted in heavier pupae and adults; however, pollen was not obligatory for larval survival and development.
6. The pollen beetle, previously thought to be an obligate pollen feeder, is therefore more generalist in its requirements for development. These findings may relate to the nutritional and behavioural ecology of other flower-feeding herbivores.     

Thermal properties of chemically modified cytochrome c

Differential scanning calorimetry was used as a probe to follow structural disturbances in cytochrome c with electrostatic modification. At 51.7% maleylation, the Td decreased 14.1 degrees C; however, relatively stable delta H values reflected minor structural variations. With 77.5 and 96.4% modification, a significant decrease in delta H was more indicative of major conformational change. On this basis, a critical labelling point was considered. Extensive maleylation (96.4%) did not result in complete cytochrome denaturation. In general, assessment of cytochrome thermal parameters by DSC provided a conformational perspective for the influence of specific electrostatic parameters on molecular integrity.     

5-Amino-4-imidazolecarboxamide is a mutagen in E. coli

5-Amino-4-imidazolecarboxamide (5A4IC), the base moiety of a common intermediate in de novo purine biosynthesis, was found to be mutagenic in E. coli. Using a series of mutants in the tryptophan synthetase A gene, 5A4IC was observed to cause transition and transversion mutations at similar levels. At 400 micrograms/ml in the growth medium, it stimulates the base substitution GC----AT 4.8-fold; AT----GC 20-fold; AT----CG (2 sites) an average of 6.0-fold; AT----TA 7.8-fold; and GC----CG 6.1-fold. The transversion GC----TA was not tested. In contrast to the base, 5-amino-4-imidazolecarboxamide riboside is not mutagenic at a similar molar concentration.     

Metabolism of the mutagen MeIQx in vivo: metabolite screening by liquid chromatography-thermospray mass spectrometry

2-Amino-3,8-dimethylimidazo(4,5-f)quinoxaline (MeIQx) is a potent mutagen found in cooked food. MeIQx and its isotopically labelled (13C, 15N2 and 14C) analogues were synthesised and used for metabolic studies in vivo. An equimolar mixture of MeIQx and its 13C, 15N2 stable isotope labelled analogue (containing tracer amounts of 14C-MeIQx) was given intraperitoneally to mice. Some 67% of the radioactivity was eliminated in urine and faeces within 24h. Four radiolabelled species were observed when urine was analysed by HPLC, corresponding to unchanged MeIQx and three more polar metabolites. Urine was analysed directly by HPLC-thermospray mass spectrometry. Four signals were observed containing the characteristic 1:1 isotopic doublet, corresponding to unchanged MeIQx, an MeIQx glucuronide, and two uncharacterized metabolites.     

Mucosal epithelial cells and Langerhans cells are targets for infection by the immunosuppressive type D retrovirus simian AIDS retrovirus serotype 1

Simian acquired immune deficiency syndrome (SAIDS) caused by the type D retrovirus SRV-1 results in opportunistic infections and a spectrum of oral lesions similar to those seen in humans with AIDS. To better understand the pathogenesis of these oral lesions we have retrospectively examined the oral mucosa from ten rhesus monkeys that died with SAIDS and prospectively examined the oral mucosa of ten additional animals inoculated with SRV-1 to determine at what time, and in what cells SRV-1 infection of the oral mucosa occurs. Using single and double label immunohistologic techniques, and electron microscopy we detected SRV-1 in clusters of oral epithelial cells and rare Langerhans cells as early as 1 month postinoculation.     

Models of epidermal wound healing

The spreading of cells across the surface of an epidermal wound enables epidermal migration to be studied independently of the wound contraction that occurs in deeper wounds. In particular, the stimulus for the increase in epidermal mitosis during would healing is uncertain. Our modelling suggests that biochemical regulation of mitosis is fundamental to the process, and that a single chemical with a simple regulatory effect can account for the healing of circular epidermal wounds. The model results compare well with experimental data.     

Sequence specificity of 125I-labelled Hoechst 33258 in intact human cells

Using polyacrylamide/urea DNA sequencing gels, the DNA sequence selectivity of 125I-labelled Hoechst 33258 damage has been determined in intact human cells to the exact base-pair. This was accomplished using a novel procedure with human alpha RI-DNA as the target DNA sequence. In this procedure, after size fractionation, the alpha RI-DNA is selectively purified by hybridization to a single-stranded M13 clone containing an alpha RI-DNA insert. The sequence specificity of [125I]Hoechst 33258 was indistinguishable in intact cells from purified high molecular weight DNA; and this is surprising considering the more complex environment of DNA in the nucleus where DNA is bound to nucleosomes and other DNA binding proteins. The ligand preferentially binds to DNA sequences which have four or more consecutive A.T base-pairs. The extent of damage was measured with a densitometer and, relative to the damage hotspot at base-pair 94, the extent of damage was similar in both purified high molecular weight DNA and intact cells. [125I]Hoechst 33258 causes only double-strand breaks, since single-strand breaks or base damage were not detected. These experiments represent the first occasion that the sequence specificity of a DNA damaging agent, which causes only double-strand breaks, has been determined to the exact base-pair in intact cells.